High Energy Astrophysical Phenomena

• New submissions
• Cross-lists
• Replacements

See recent articles

New submissions for Friday, 21 June 2024 (showing 27 of 27 entries )

[1] arXiv:2406.13029 [pdf, html, other]

Title: The giant outburst of EXO 2030+375 II: Broadband spectroscopy and evolution

R. Ballhausen, P. Thalhammer, P. Pradhan, E. Sokolova-Lapa, J. Stierhof, K. Pottschmidt, J. Wilms, J. B. Coley, P. Kretschmar, F. Fuerst, P. Becker, B. West, C. Malacaria, M. T. Wolff, R. Rothschild, R. Staubert

Comments: 12 pages, 8 figures, accepted in A&A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

In 2021, the high-mass X-ray binary EXO 2030+375 underwent a giant X-ray outburst, the first since 2006, that reached a peak flux of ${\sim}600\,\mathrm{mCrab}$ (3-50\,keV). The goal of this work is to study the spectral evolution over the course of the outburst, search for possible cyclotron resonance scattering features (CRSFs), and to associate spectral components with the emission pattern of the accretion column. We used broadband spectra taken with the Nuclear Spectroscopic Telescope Array (NuSTAR), the Neutron Star Interior Composition Explorer (NICER), and Chandra near the peak and during the decline phase of the outburst. We describe the data with established empirical continuum models and perform pulse-phase-resolved spectroscopy. We compare the spectral evolution with pulse phase using a proposed geometrical emission model. We find a significant spectral hardening toward lower luminosity, a behavior that is expected for super-critical sources. The continuum shape and evolution cannot be described by a simple power-law model with exponential cutoff; it requires additional absorption or emission components. We can confirm the presence of a narrow absorption feature at ${\sim}10\,\mathrm{keV}$ in both NuSTAR observations. The absence of harmonics puts into question the interpretation of this feature as a CRSF. The empirical spectral components cannot be directly associated with identified emission components from the accretion column.

[2] arXiv:2406.13043 [pdf, html, other]

Title: Inferring Neutron Star Properties via r-mode Gravitational Wave Signals

Dhanvarsh Annamalai, Rana Nandi

Comments: 29 pages, 8 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present two frameworks to infer some of the properties of neutron stars from their electromagnetic radiation and the emission of continuous gravitational waves due to r-mode oscillations. In the first framework, assuming a distance measurement via electromagnetic observations, we infer three neutron star properties: the moment of inertia, a parameter related to the r-mode saturation amplitude, and the component of magnetic dipole moment perpendicular to the rotation axis. Unlike signals from mountains, r-mode oscillations provide additional information through a parameter (\kappa) that satisfies a universal relation with the star's compactness. In the second framework, we utilize this and the relation between the moment of inertia and compactness, in addition to assuming an equation of state and utilizing pulsar frequency measurements, to directly measure the neutron star's distance along with the aforementioned parameters. We employ a Fisher information matrix-based approach for quantitative error estimation in both frameworks. We find that the error in the distance measurement dominates the errors in the first framework for any reasonable observation time. In contrast, due to the low errors in pulsar frequency measurements, parameters can be inferred accurately via the second framework but work only in a restricted parameter space. We finally address potential ways to overcome critical drawbacks of our analyses and discuss directions for future work.

[3] arXiv:2406.13072 [pdf, html, other]

Title: Supermassive black hole formation via collisions in black hole clusters

Benjamin Gaete, Dominik R.G. Schleicher, Alessandro Lupi, Bastian Reinoso, Michael Fellhauer, Marcelo C. Vergara

Comments: 15 pages, 11 figures, 1 table. Accepted for publication with A&A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

More than 300 supermassive black holes have been detected at redshifts larger than 6, and they are abundant in the centers of local galaxies. Their formation mechanisms, however, are still rather unconstrained. A possible origin of these supermassive black holes could be through mergers in dense black hole clusters, forming as a result of mass segregation within nuclear star clusters in the center of galaxies. In this study, we present the first systematic investigation of the evolution of such black hole clusters where the effect of an external potential is taken into account. Such a potential could be the result of gas inflows into the central region, for example as a result of galaxy mergers. We show here that the efficiency for the formation of a massive central object is mostly regulated by the ratio of cluster velocity dispersion divided by the speed of light, potentially reaching efficiencies of 0.05-0.08 in realistic systems. Our results show that this scenario is potentially feasible and may provide seeds black hole of at least 10^3 solar masses. We conclude that the formation of seed black holes via this channel should be taken into account in statistical assessments of the black hole population.

[4] arXiv:2406.13276 [pdf, html, other]

Title: Impacts of Black-Hole-Forming Supernova Explosions on the Diffuse Neutrino Background

Ken'ichiro Nakazato, Ryuichiro Akaho, Yosuke Ashida, Takuji Tsujimoto

Comments: 13 pages, 5 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Flux spectrum, event rate, and experimental sensitivity are investigated for the diffuse supernova neutrino background (DSNB), which is originated from past stellar collapses and also known as supernova relic neutrino background. For this purpose, the contribution of collapses that lead to successful supernova (SN) explosion and black hole (BH) formation simultaneously, which are suggested to be a non-negligible population from the perspective of Galactic chemical evolution, is taken into account. If the BH-forming SNe involve the matter fallback onto the protoneutron star for the long term, their total emitted neutrino energy becomes much larger than that of ordinary SNe and failed SNe (BH formation without explosion). The expected event rate according to the current DSNB model is enhanced by up to a factor of two due to the BH-forming SNe, depending on their fraction and the neutrino mass hierarchy. In any case, the operation time required to detect the DSNB at Hyper-Kamiokande would be reduced by such contribution.

[5] arXiv:2406.13336 [pdf, html, other]

Title: Berezinsky Hidden Sources: An Emergent Tension in the High-Energy Neutrino Sky?

Antonio Ambrosone

Comments: 17 pages, 1 Table, 6 Figures, 1 appendix

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The IceCube Collaboration has recently reported compelling evidence of high-energy neutrino emission from NGC~1068, and also mild excesses for NGC 4151 and CGCG420-015, local Seyfert galaxies. This has increased the interest along neutrino emission from hot-corona surrounding the super massive black holes of Seyfert Galaxies. In this paper, we revisit phenomenological constraints on the neutrino emission from hot-coronae of seyfert galaxies, using an assumption of equi-ripartition between cosmic-rays and magnetic energy densities. We show that not only these sources are consistent with such an assumption but also that the data point towards low beta plasma parameters inside Seyfert Galaxies. We exploit this finding to constrain the Seyfert diffuse neutrino flux and we obtain that, in order not to overproduce neutrinos, not all the sources can be in an equi-ripartition state. We conclude (along with previous findings) that seyfert galaxies cannot explain the diffuse neutrino spectrum above $\sim 100\, \rm TeV$, allowing space for other astrophysical sources.

[6] arXiv:2406.13426 [pdf, html, other]

Title: Multi-messenger modeling of the Monogem pulsar halo

Youyou Li, Oscar Macias, Shinichiro Ando, Jacco Vink

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The High-Altitude Water Cherenkov Telescope (HAWC) has detected TeV halos associated with two nearby pulsars/pulsar wind nebulae (PWN) -- Geminga and B0656+14. These TeV halos extend up to tens of pc from the central accelerators, indicating that the diffusion of ultrarelativistic electrons and positrons in the interstellar medium has been suppressed by two orders of magnitude. Although Geminga and B0656+14 are at similar distances and in the same field of view, they have distinct histories. Notably, B0656+14 probably still resides within its parent supernova remnant, the Monogem Ring, which can be observed in X-rays. In this work, we perform high-resolution simulations of the propagation and emission of relativistic lepton pairs around B0656+14 using a two-zone diffusion model using the GALPROP numerical code. We compared the predicted inverse-Compton spectrum to the observations made by HAWC and Fermi-LAT and found physically plausible model parameters that resulted in a good fit to the data. Additionally, we estimated the contribution of this TeV-halo to the positron flux observed on Earth and found it to be smaller than 10\% of the measured flux. We conclude that future observations of the TeV halo and its synchrotron emission counterpart in radio and X-ray frequencies will be crucial to distinguish between various possible models.

[7] arXiv:2406.13463 [pdf, html, other]

Title: Exploring pulsar timing precision: A comparative study of polarization calibration methods for NANOGrav data from the Green Bank Telescope

Lankeswar Dey, Maura A. McLaughlin, Haley M. Wahl, Paul B. Demorest, Zaven Arzoumanian, Harsha Blumer, Paul R. Brook, Sarah Burke-Spolaor, H. Thankful Cromartie, Megan E. DeCesar, Timothy Dolch, Justin A. Ellis, Robert D. Ferdman, Elizabeth C. Ferrara, William Fiore, Emmanuel Fonseca, Nate Garver-Daniels, Peter A. Gentile, Joseph Glaser, Deborah C. Good, Ross J. Jennings, Megan L. Jones, Michael T. Lam, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Cherry Ng, David J. Nice, Timothy T. Pennucci, Nihan S. Pol, Scott M. Ransom, Renée Spiewak, Ingrid H. Stairs, Kevin Stovall, Joseph K. Swiggum

Comments: 21 pages, 6 figures, 1 table, submitted to Astrophysical Journal

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Pulsar timing array experiments have recently uncovered evidence for a nanohertz gravitational wave background by precisely timing an ensemble of millisecond pulsars. The next significant milestones for these experiments include characterizing the detected background with greater precision, identifying its source(s), and detecting continuous gravitational waves from individual supermassive black hole binaries. To achieve these objectives, generating accurate and precise times of arrival of pulses from pulsar observations is crucial. Incorrect polarization calibration of the observed pulsar profiles may introduce errors in the measured times of arrival. Further, previous studies (e.g., van Straten 2013; Manchester et al. 2013) have demonstrated that robust polarization calibration of pulsar profiles can reduce noise in the pulsar timing data and improve timing solutions. In this paper, we investigate and compare the impact of different polarization calibration methods on pulsar timing precision using three distinct calibration techniques: the Ideal Feed Assumption (IFA), Measurement Equation Modeling (MEM), and Measurement Equation Template Matching (METM). Three NANOGrav pulsars-PSRs J1643$-$1224, J1744$-$1134, and J1909$-$3744-observed with the 800 MHz and 1.5 GHz receivers at the Green Bank Telescope (GBT) are utilized for our analysis. Our findings reveal that all three calibration methods enhance timing precision compared to scenarios where no polarization calibration is performed. Additionally, among the three calibration methods, the IFA approach generally provides the best results for timing analysis of pulsars observed with the GBT receiver system. We attribute the comparatively poorer performance of the MEM and METM methods to potential instabilities in the reference noise diode coupled to the receiver and temporal variations in the profile of the reference pulsar, respectively.

[8] arXiv:2406.13479 [pdf, html, other]

Title: Is Lensing Amplitude Anomaly in the Cosmic Microwave Background the Evidence of Extremely Low Frequency Primordial Gravitational Wave?

Wenshuai Liu

Comments: 3 pages, 2 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Trajectories of photons of cosmic microwave background (CMB) from the surface of last scattering to us could be deflected by extremely low frequency primordial gravitational wave (PGW). With large scale structure (LSS) producing a smoothing of the acoustic peaks in the power spectrum of the CMB anisotropies through weak lensing, the presence of extremely low frequency PGW could enhance the effect of weak lensing on CMB due to the coupling of extremely low frequency PGW and LSS, thus, give rise to much more smoothing of the spectrum. This may be an natural explanation for the lensing amplitude anomaly observed by Planck, meaning that lensing amplitude anomaly may be the evidence of extremely low frequency PGW.

[9] arXiv:2406.13623 [pdf, html, other]

Title: Revealing the burning and soft heart of the bright bare AGN ESO 141-G55: X-ray broadband and SED analysis

Delphine Porquet, James N. Reeves, Scott Hagen, Andrew Lobban, Valentina Braito, Nicolas Grosso, Frédéric Marin

Comments: 16 pages, 14 figures, 3 appendices; accepted for publication in Astronomy & Astrophysics

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

[Abridged] ESO 141-G55 is a nearby X-ray bright BLS1, which has been classified as a bare AGN due to the lack of warm absorption along its line-of-sight, providing an unhampered view into its disc-corona system. We aim to probe its disc-corona system thanks to the first simultaneous XMM-Newton and NuSTAR observation obtained on October 1-2, 2022. We carry out the X-ray broadband spectral analysis to determine the dominant process(es) at work, as well as the SED analysis to determine the disc-corona properties. The simultaneous broadband X-ray spectrum of ESO 141-G55 is characterised by the presence of a prominent smooth soft X-ray excess, a broad Fe K emission line and a significant Compton hump. The RGS spectra confirmed the lack of intrinsic warm-absorbing gas along our line of sight in the AGN rest frame, confirming that it is still in a bare state. However, soft X-ray emission lines are observed indicating substantial warm gas out of our line of sight. The intermediate inclination of the disc-corona system, ~43°, may offer us a favourable configuration to observe UFOs from the disc, but none is found in this 2022 observation, contrary to a previous 2007 XMM-Newton one. Relativistic reflection alone on a standard disc is ruled out from the X-ray broadband analysis, while a combination of soft and hard Comptonisation by a warm and hot corona (relagn), plus relativistic reflection (reflkerrd) reproduces its SED quite well. The hot corona temperature is very hot, ~140 keV, much higher than about 80% of the AGNs, whereas the warm corona temperature, ~0.3 keV, is similar to the values found in other sub-Eddington AGNs. ESO 141-G55 is accreting at a moderate Eddington accretion rate (~10--20%). Our analysis points to a significant contribution of an optically-thick warm corona to both the soft X-ray and UV emission in ESO 141-G55.

[10] arXiv:2406.13704 [pdf, html, other]

Title: The Curious Case of Twin Fast Radio Bursts: Evidence for Neutron Star Origin?

Apurba Bera, Clancy W. James, Adam T. Deller, Keith W. Bannister, Ryan M. Shannon, Danica R. Scott, Kelly Gourdji, Lachlan Marnoch, Marcin Glowacki, Ronald D. Ekers, Stuart D. Ryder, Tyson Dial

Comments: Accepted for publication in ApJ Letters

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Fast radio bursts (FRBs) are brilliant short-duration flashes of radio emission originating at cosmological distances. The vast diversity in the properties of currently known FRBs, and the fleeting nature of these events make it difficult to understand their progenitors and emission mechanism(s). Here we report high time resolution polarization properties of FRB 20210912A, a highly energetic event detected by the Australian Square Kilometre Array Pathfinder (ASKAP) in the Commensal Real-time ASKAP Fast Transients (CRAFT) survey, which show intra-burst PA variation similar to Galactic pulsars and unusual variation of Faraday Rotation Measure (RM) across its two sub-bursts. The observed intra-burst PA variation and apparent RM variation pattern in FRB 20210912A may be explained by a rapidly-spinning neutron star origin, with rest-frame spin periods of ~1.1 ms. This rotation timescale is comparable to the shortest known rotation period of a pulsar, and close to the shortest possible rotation period of a neutron star. Curiously, FRB 20210912A exhibits a remarkable resemblance with the previously reported FRB 20181112A, including similar rest-frame emission timescales and polarization profiles. These observations suggest that these two FRBs may have similar origins.

[11] arXiv:2406.13746 [pdf, html, other]

Title: Insights into the Production of $^{44}$Ti and Nickel Isotopes in Core-Collapse Supernovae

Tianshu Wang, Adam Burrows

Comments: 15 pages, 7 figures. Submitted to ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We report nucleosynthetic results for both $^{44}$Ti and nickel isotopes for eighteen three-dimensional (3D) core-collapse supernova (CCSN) simulations extended to $\sim$20 seconds after bounce. We find that many of our long-term models are able to achieve $^{44}$Ti/$^{56}$Ni ratios similar to that observed in Cassiopeia A, and modern supernova models can synthesize up to $2\times10^{-4}M_\odot$ of $^{44}$Ti. Neutrino-driven winds and the fact that there can be simultaneous accretion and explosion in 3D models of core-collapse supernovae play central roles in its production. We conclude that the $^{44}$Ti underproduction problem in previous CCSN models is no longer an issue. In addition, we discuss the production of both $^{57}$Ni and stable nickel/iron ratios and compare our results to observations of SN1987A and the Crab.

[12] arXiv:2406.13755 [pdf, html, other]

Title: A detailed time-resolved and energy-resolved spectro-polarimetric study of bright GRBs detected by AstroSat CZTI in its first year of operation

Rahul Gupta, S. B. Pandey, S. Gupta, T. Chattopadhayay, D. Bhattacharya, V. Bhalerao, A. J. Castro-Tirado, A. Valeev, A. K. Ror, V. Sharma, J. Racusin, A. Aryan, S. Iyyani, S. Vadawale

Comments: 36 pages, 11 figures, Accepted for publication in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The radiation mechanism underlying the prompt emission remains unresolved and can be resolved using a systematic and uniform time-resolved spectro-polarimetric study. In this paper, we investigated the spectral, temporal, and polarimetric characteristics of five bright GRBs using archival data from AstroSat CZTI, Swift BAT, and Fermi GBM. These bright GRBs were detected by CZTI in its first year of operation, and their average polarization characteristics have been published in Chattopadhyay et al. (2022). In the present work, we examined the time-resolved (in 100-600 keV) and energy-resolved polarization measurements of these GRBs with an improved polarimetric technique such as increasing the effective area and bandwidth (by using data from low-gain pixels), using an improved event selection logic to reduce noise in the double events and extend the spectral bandwidth. In addition, we also separately carried out detailed time-resolved spectral analyses of these GRBs using empirical and physical synchrotron models. By these improved time-resolved and energy-resolved spectral and polarimetric studies (not fully coupled spectro-polarimetric fitting), we could pin down the elusive prompt emission mechanism of these GRBs. Our spectro-polarimetric analysis reveals that GRB 160623A, GRB 160703A, and GRB 160821A have Poynting flux-dominated jets. On the other hand, GRB 160325A and GRB 160802A have baryonic-dominated jets with mild magnetization. Furthermore, we observe a rapid change in polarization angle by $\sim$ 90 degrees within the main pulse of very bright GRB 160821A, consistent with our previous results. Our study suggests that the jet composition of GRBs may exhibit a wide range of magnetization, which can be revealed by utilizing spectro-polarimetric investigations of the bright GRBs.

[13] arXiv:2406.13786 [pdf, html, other]

Title: Galaxy-group-associated distances to Very High Energy gamma-ray emitting BL Lacs KUV 00311-1938 and S2 0109+22

Karri I. I. Koljonen, Elina Lindfors, Kari Nilsson, Pekka Heinämäki, Jari Kotilainen

Comments: 11 pages, 8 figures, 3 tables. This article has been accepted for publication in MNRAS published by Oxford University Press on behalf of the Royal Astronomical Society

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

Blazars constitute the most numerous source class in the known extragalactic population of very high energy (VHE) gamma-ray sources. However, determining their redshifts is often challenging due to weak or non-existent emission lines in their spectra. This study focuses on two BL Lacs, KUV 00311-1938 and S2 0109+22, where previous attempts at redshift determination have faced difficulties. By combining spectroscopic observations with photometric redshift estimates, we tentatively assign a redshift of z = 0.634 to KUV 00311-1938 and a likely redshift of z = 0.49 to S2 0109+22. Establishing redshift estimates for high-redshift blazars is crucial for understanding extragalactic VHE gamma-ray sources and their interactions with the surrounding universe.

[14] arXiv:2406.13821 [pdf, html, other]

Title: Multi-wavelength observations of the Luminous Fast Blue Optical Transient AT2023fhn

A. A. Chrimes, D. L. Coppejans, P. G. Jonker, A. J. Levan, P. J. Groot, A. Mummery, E. R. Stanway

Comments: Submitted to A&A, comments welcome. 15 pages, 12 figures, 8 tables

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

Luminous Fast Blue Optical Transients (LFBOTs) are a class of extragalactic transients notable for their rapid rise and fade times, blue colour and accompanying luminous X-ray and radio emission. Only a handful have been studied in detail since the prototypical example AT2018cow. Their origins are currently unknown, but ongoing observations of previous and new events are placing ever stronger constraints on their progenitors. We aim to put further constraints on the LFBOT AT2023fhn, and LFBOTs as a class, using information from the multi-wavelength transient light-curve, its host galaxy and local environment. Our primary results are obtained by fitting galaxy models to the spectral energy distribution of AT2023fhn's host and local environment, and by modelling the radio light-curve of AT2023fhn as due to synchrotron self-absorbed emission from an expanding blast-wave in the circumstellar medium. We find that the neither the host galaxy nor circumstellar environment of AT2023fhn are unusual compared with previous LFBOTs, but that AT2023fhn has a much lower X-ray to ultraviolet luminosity ratio than previous events. We argue that the variety in ultraviolet-optical to X-ray luminosity ratios among LFBOTs is likely due to viewing angle differences, and that the diffuse, yet young local environment of AT2023fhn - combined with a similar circumstellar medium to previous events - favours a progenitor system containing a massive star with strong winds. Plausible progenitor models in this interpretation therefore include black hole/Wolf-Rayet mergers or failed supernovae.

[15] arXiv:2406.14001 [pdf, html, other]

Title: High-energy Neutrino Emission from NGC 1068 by Outflow-cloud Interactions

Yong-Han Huang, Kai Wang, Zhi-Peng Ma

Comments: 7 Pages, 4 figures, 1 table; submitted

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

As the hottest high-energy neutrino spot, NGC 1068 has received much attention in recent years. Here we focus on the central region of the active galactic nuclei (AGN) and propose an outflow-cloud interaction model that could probably explain the observed neutrino data. Considering the accretion process adjacent to the central supermassive black hole (SMBH) of NGC 1068, strong outflows will be generated, which will likely interact with surrounding clouds floating in the corona region. Particles carried by the outflow will be accelerated to very high energy by the shocks forming during the outflow-cloud interactions. For the accelerated high-energy protons, $p\gamma$ interactions with the background photon field of the corona and disk and $pp$ interaction with the surrounding gas will produce considerable high-energy $\gamma$-rays and neutrino. However, because of the extremely dense photon fields in the corona and disk, the newly generated $\gamma$-rays will be significantly attenuated through the $\gamma\gamma$ absorptions. In our scenario, the expected GeV-TeV $\gamma$-ray emission will be suppressed to a much lower level than the neutrino emission, consistent with the observational characteristics of NGC 1068, while the generated 1-30\,TeV neutrino flux can fit the IceCube data very well.

[16] arXiv:2406.14002 [pdf, html, other]

Title: A Collaborative Explanation of Cosmic Ray Spectrum Based on the Gluon Condensation Model

Jintao Wu, Jianhong Ruan

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

Based on the Gluon Condensation (GC) model, the relationship between the spectra of electrons, $\gamma$ rays, and neutrinos in cosmic rays can be deduced. It has been found that these particles share the same parameter, $\beta_p$, and have an identical GC threshold values. This paper explores the connection between the second excess spectra of electron and the spectra of gamma rays and neutrinos. According to the observed gamma-ray data, it is suggested that the source LHAASO J2108+5157 might contribute to the second excess of electron.

[17] arXiv:2406.14057 [pdf, html, other]

Title: Evidence for bipolar explosions in Type IIP supernovae

T. Nagao, K. Maeda, S. Mattila, H. Kuncarayakti, M. Kawabata, K. Taguchi, T. Nakaoka, A. Cikota, M. Bulla, S. Vasylyev, C. P. Gutierrez, M. Yamanaka, K. Isogai, K. Uno, M. Ogawa, S. Inutsuka, M. Tsurumi, R. Imazawa, K.S. Kawabata

Comments: 16 pages, 10 figures, accepted for publication in A&A letter

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

Recent observations of core-collapse supernovae (SNe) suggest aspherical explosions. Globally aspherical structures in SN explosions are regarded as the key for understanding their explosion mechanism. However, the exact explosion geometries from the inner cores to the outer envelopes are poorly understood. Here, we present photometric, spectroscopic and polarimetric observations of the Type IIP SN 2021yja and discuss its explosion geometry, in comparison to those of other Type IIP SNe that show large-scale aspherical structures in their hydrogen envelopes (SNe 2012aw, 2013ej and 2017gmr). During the plateau phase, SNe 2012aw and 2021yja exhibit high continuum polarization characterized by two components with perpendicular polarization angles. This behavior can be interpreted to be due to a bipolar explosion, composed of a polar (energetic) and an equatorial (bulk) components of the SN ejecta. In such a bipolar explosion, an aspherical axis created by the polar ejecta would be dominating at early phases, while the perpendicular axis along the equatorial ejecta would emerge at late phases after the receding of the photosphere in the polar ejecta. The interpretation of the bipolar explosions in SNe 2012aw and 2021yja is also supported by other observational properties, including the time evolution of the line velocities and the line shapes in the nebular spectra. The polarization of other Type IIP SNe that show large-scale aspherical structures in the hydrogen envelope (SNe 2013ej and 2017gmr) is also consistent with the bipolar-explosion scenario, although this is not conclusive.

[18] arXiv:2406.14128 [pdf, html, other]

Title: Identifying Three New AGNs Among Fermi Unidentified Gigaelectronvolt Sources

Shunhao Ji, Zhongxiang Wang, Qiangmeng Huang, Ruoheng Yang (Yunnan University)

Comments: 15 pages, 7 figures, 2 tables, accepted to be published in RAA

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report our identification of three gigaelectronvolt $\gamma$-ray sources, 4FGL J0502.6+0036, 4FGL J1055.9+6507, and 4FGL J1708.2+5519, as Active Galactic Nuclei (AGNs). They are listed in the latest Fermi-LAT source catalog as unidentified ones. We find that the sources all showed $\gamma$-ray flux variations in recent years. Using different survey catalogs, we are able to find a radio source within the error circle of each source's position. Further analysis of optical sources in the fields allows us to determine the optical counterparts, which showed similar variation patterns to those seen in $\gamma$-rays. The optical counterparts have reported redshifts of 0.6, 1.5, and 2.3, respectively, estimated from photometric measurements. In addition, we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data. The broadband spectral energy distributions of the three sources from radio to $\gamma$-rays are constructed. Comparing mainly the $\gamma$-ray properties of the three sources with those of different sub-classes of AGNs, we tentatively identify them as blazars. Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.

[19] arXiv:2406.14195 [pdf, html, other]

Title: Investigating the Role of Pre-supernova Massive Stars in the Acceleration of Galactic Cosmic Rays

Michael De Becker, Santiago del Palacio, Paula Benaglia, Anandmayee Tej, Benito Marcote, Gustavo Esteban Romero, Valenti Bosch-Ramon, C. H. Ishwara-Chandra

Comments: 8 pages, 1 figure, Published in the Proceedings of the 3rd BINA Workshop on the Scientific Potential of the Indo-Belgian Cooperation

Journal-ref: Bulletin de la Soci\'et\'e Royale des Sciences de Li\`ege, 2024, Volume 93, No 2, 536-543

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Galactic cosmic rays (GCRs) constitute a significant part of the energy budget of our Galaxy, and the study of their accelerators is of high importance in modern astrophysics. Their main sources are likely supernova remnants (SNRs). These objects are capable to convert a part of their mechanical energy into accelerated charged particles. However, even though the mechanical energy reservoir of SNRs is promising, a conversion rate into particle energy of 10 to 20% is necessary to feed the population of GCRs. Such an efficiency is however not guaranteed. Complementary sources deserve thus to be investigated. This communication aims to address the question of the contribution to the acceleration of GCRs by pre-supernova massive stars in binary or higher multiplicity systems

[20] arXiv:2406.14257 [pdf, html, other]

Title: Finding Black Holes: an Unconventional Multi-messenger

Laura E. Uronen, Tian Li, Justin Janquart, Hemantakumar Phurailatpam, Jason S. C. Poon, Ewoud Wempe, Léon V. E. Koopmans, Otto A. Hannuksela

Comments: 17 pages, 4 figures. Proceedings from the Royal Society Meeting for Multi-messenger Lensing (2024). Submitted to Phil. Trans. A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

A rather clear problem has remained in black hole physics: localizing black holes. One of the recent theoretical ways proposed to identify black hole mergers' hosts is through multi-messenger gravitational lensing: matching the properties of a lensed galactic host with those of a lensed gravitational wave. This paper reviews the most recent literature and introduces some of the ongoing work on the localization of binary black holes and their host galaxies through lensing of gravitational waves and their electromagnetically-bright hosts.

[21] arXiv:2406.14268 [pdf, html, other]

Title: A hierarchical Bayesian approach to point source analysis in high-energy neutrino telescopes

F. Capel, J. Kuhlmann, C. Haack, M. Ha Minh, H. Niederhausen, L. Schumacher

Comments: Submitted to ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We propose a novel approach to the detection of point-like sources of high-energy neutrinos. Motivated by evidence for emerging sources in existing data, we focus on the characterisation and interpretation of these sources. The hierarchical Bayesian model is implemented in the Stan platform, enabling computation of the posterior distribution with Hamiltonian Monte Carlo. We simulate a population of weak neutrino sources detected by the IceCube experiment and use the resulting data set to demonstrate and validate our framework. We show that even for the challenging case of sources at the threshold of detection and using limited prior information, it is possible to correctly infer the source properties. Additionally, we demonstrate how modelling flexible connections between similar sources can be used to recover the contribution of sources that would not be detectable individually, going beyond what is possible with existing stacking methods.

[22] arXiv:2406.14366 [pdf, html, other]

Title: GRB 211211A: The Case for Engine Powered over r-Process Powered Blue Kilonova

Hamid Hamidani, Masaomi Tanaka, Shigeo S. Kimura, Gavin P. Lamb, Kyohei Kawaguchi

Comments: 18 pages, 6 figures, and 2 tables. To be submitted to ApJ. Comments are welcome

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The recent Gamma-Ray Burst (GRB) GRB~211211A provides the earliest ($\sim 5$ h) data of a kilonova (KN) event, displaying bright ($\sim10^{42}$ erg s$^{-1}$) and blue early emission. Previously, this KN has been explained using simplistic multi-component fitting methods. Here, in order to understand the physical origin of the KN emission in GRB~211211A, we employ an analytic multi-zone model for r-process powered KN. We find that r-process powered KN models alone cannot explain the fast temporal evolution and the spectral energy distribution (SED) of the observed emission. Specifically, i) r-process models require high ejecta mass to match early luminosity, which overpredicts late-time emission, while ii) red KN models that reproduce late emission underpredict early luminosity. We propose an alternative scenario involving early contributions from the GRB central engine via a late low-power jet, consistent with plateau emission in short GRBs and GeV emission detected by Fermi-LAT at $\sim10^4$ s after GRB 211211A. Such late central engine activity, with an energy budget of $\sim \text{a few }\%$ of that of the prompt jet, combined with a single red-KN ejecta component, can naturally explain the light curve and SED of the observed emission; with the late-jet -- ejecta interaction reproducing the early blue emission and r-process heating reproducing the late red emission. This supports claims that late low-power engine activity after prompt emission may be common. We encourage very early follow-up observations of future nearby GRBs, and compact binary merger events, to reveal more about the central engine of GRBs and r-process events.

[23] arXiv:2406.14378 [pdf, other]

Title: X-ray view of Dissipative Warm Corona in AGN

B. Palit, A. Rozanska, P.O. Petrucci, D. Gronkiewicz, S. Barnier, S. Bianchi, D. R. Ballantyne, V. E. Gianolli, R. Middei, R. Belmont, F. Ursini

Comments: 25 pages, 13 figures; Submitted to A&A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

In the X-ray spectra of AGNs, a noticeable excess of soft X-rays is typically detected beyond the extrapolation of the power-law trend observed between 2-10 keV. In the scenario of warm Comptonization, observations propose a warm corona temperature ranging from 0.1-1 keV and an optical depth of approximately 10-20. Furthermore, according to radiative constraints derived from spectral analyses employing Comptonization models, it is suggested that the majority of the accretion power is released within the warm corona, while the disk beneath it is largely non-dissipative, emitting mainly the reprocessed radiation from the corona. We test the dissipative warm corona model using the radiative transfer code-TITAN/NOAR on a sample of 82 XMM-Newton observations of AGNs. Through spectral modeling of the X-ray data, we aim to estimate the total amount of internal heating inside the warm corona situated on top of the accretion disk. By modeling the 0.3-10 keV EPIC-pn spectra, we estimate the internal heating and optical depth of the warm corona and check their correlations with global parameters blackhole parameters. From model normalization, we compute the radial extent of warm corona on top of cold accretion disk. Our model infers the presence of dissipative warm corona, with optical depths distributed in the range 6-30 and total internal heating in the range 1-29 x 1e-23 erg/s-cm3. The extent of warm corona is spread across a large range from 7-408 gravitational radii, and we find that warm corona is more extended for larger accretion rates. Soft excess emission is ubiquitous in AGNs across wide mass range and accretion rate. We confirm that warm corona responsible for producing the soft-excess is highly dissipative in nature with larger optical depths being associated with lower internal heating and vice versa. The presence of cold standard accretion disk regulates the extent of warm corona.

[24] arXiv:2406.14466 [pdf, html, other]

Title: The Radius of the High Mass Pulsar PSR J0740+6620 With 3.6 Years of NICER Data

Tuomo Salmi, Devarshi Choudhury, Yves Kini, Thomas E. Riley, Serena Vinciguerra, Anna L. Watts, Michael T. Wolff, Zaven Arzoumanian, Slavko Bogdanov, Deepto Chakrabarty, Keith Gendreau, Sebastien Guillot, Wynn C. G. Ho, Daniela Huppenkothen, Renee M. Ludlam, Sharon M. Morsink, Paul S. Ray

Comments: 17 pages, 9 figures (2 of which are figure sets), 2 tables, accepted for publication in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)

We report an updated analysis of the radius, mass, and heated surface regions of the massive pulsar PSR J0740+6620 using NICER data from 2018 September 21 to 2022 April 21, a substantial increase in data set size compared to previous analyses. Using a tight mass prior from radio timing measurements and jointly modeling the new NICER data with XMM-Newton data, the inferred equatorial radius and gravitational mass are $12.49_{-0.88}^{+1.28}$ km and $2.073_{-0.069}^{+0.069}$ $M_\odot$ respectively, each reported as the posterior credible interval bounded by the $16\,\%$ and $84\,\%$ quantiles, with an estimated systematic error $\lesssim 0.1$ km. This result was obtained using the best computationally feasible sampler settings providing a strong radius lower limit but a slightly more uncertain radius upper limit. The inferred radius interval is also close to the $R=12.76_{-1.02}^{+1.49}$ km obtained by Dittmann et al. 2024, when they require the radius to be less than $16$ km as we do. The results continue to disfavor very soft equations of state for dense matter, with $R<11.15$ km for this high mass pulsar excluded at the $95\,\%$ probability. The results do not depend significantly on the assumed cross-calibration uncertainty between NICER and XMM-Newton. Using simulated data that resemble the actual observations, we also show that our pipeline is capable of recovering parameters for the inferred models reported in this paper.

[25] arXiv:2406.14467 [pdf, html, other]

Title: A More Precise Measurement of the Radius of PSR J0740+6620 Using Updated NICER Data

Alexander J. Dittmann, M. Coleman Miller, Frederick K. Lamb, Isiah Holt, Cecilia Chirenti, Michael T. Wolff, Slavko Bogdanov, Sebastien Guillot, Wynn C. G. Ho, Sharon M. Morsink, Zaven Arzoumanian, Keith C. Gendreau

Comments: 18 pages, 8 figures, +appendices. Accepted in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

PSR J0740+6620 is the neutron star with the highest precisely determined mass, inferred from radio observations to be $2.08\pm0.07\,\rm M_\odot$. Measurements of its radius therefore hold promise to constrain the properties of the cold, catalyzed, high-density matter in neutron star cores. Previously, Miller et al. (2021) and Riley et al. (2021) reported measurements of the radius of PSR J0740+6620 based on Neutron Star Interior Composition Explorer (NICER) observations accumulated through 17 April 2020, and an exploratory analysis utilizing NICER background estimates and a data set accumulated through 28 December 2021 was presented in Salmi et al. (2022). Here we report an updated radius measurement, derived by fitting models of X-ray emission from the neutron star surface to NICER data accumulated through 21 April 2022, totaling $\sim1.1$ Ms additional exposure compared to the data set analyzed in Miller et al. (2021) and Riley et al. (2021), and to data from X-ray Multi-Mirror (XMM-Newton) observations. We find that the equatorial circumferential radius of PSR J0740+6620 is $12.92_{-1.13}^{+2.09}$ km (68% credibility), a fractional uncertainty $\sim83\%$ the width of that reported in Miller et al. (2021), in line with statistical expectations given the additional data. If we were to require the radius to be less than 16 km, as was done in Salmi et al. (2024), then our 68% credible region would become $R=12.76^{+1.49}_{-1.02}$ km, which is close to the headline result of Salmi et al. (2024). Our updated measurements, along with other laboratory and astrophysical constraints, imply a slightly softer equation of state than that inferred from our previous measurements.

[26] arXiv:2406.14488 [pdf, html, other]

Title: Multi-epoch X-ray spectral analysis of Centaurus A: revealing new constraints on iron emission line origins

Toshiya Iwata, Atsushi Tanimoto, Hirokazu Odaka, Aya Bamba, Yoshiyuki Inoue, Kouichi Hagino

Comments: 19 pages, 13 figures, 7 tables, accepted for publication in PASJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We conduct X-ray reverberation mapping and spectral analysis of the radio galaxy Centaurus A to uncover its central structure. We compare the light curve of the hard X-ray continuum from Swift Burst Alert Telescope observations with that of the Fe K$\alpha$ fluorescence line, derived from the Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Swift X-ray Telescope observations. The analysis of the light curves suggests that a top-hat transfer function, commonly employed in reverberation mapping studies, is improbable. Instead, the relation between these light curves can be described by a transfer function featuring two components: one with a lag of $0.19_{- 0.02}^{+ 0.10}~\mathrm{pc}/c$, and another originating at $r > 1.7~\mathrm{pc}$ that produces an almost constant light curve. Further, we analyze the four-epoch NuSTAR and six-epoch Suzaku spectra, considering the time lag of the reflection component relative to the primary continuum. This spectral analysis supports that the reflecting material is Compton-thin, with $N_{\mathrm{H}} = 3.14_{-0.74}^{+0.44} \times 10^{23}~ \mathrm{cm}^{-2}$. These results suggest that the Fe K$\alpha$ emission may originate from Compton-thin circumnuclear material located at sub-parsec scale, likely a dust torus, and materials at a greater distance.

[27] arXiv:2406.14512 [pdf, html, other]

Title: Scaling up global kinetic models of pulsar magnetospheres using a hybrid force-free-PIC numerical approach

Adrien Soudais, Benoît Cerutti, Ioannis Contopoulos

Comments: 12 pages, 7 figures, accepted for publication in A&A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Computational Physics (physics.comp-ph); Plasma Physics (physics.plasm-ph)

The particle-in-cell approach has proven effective at modeling neutron star and black hole magnetospheres from first principles, but global simulations are plagued with an unrealistically small separation between the scales where microphysics operates and the system-size scales due to limited numerical resources. A legitimate concern is whether the scale separation currently achieved is large enough, such that results can be safely extrapolated to realistic scales. In this work, our aim is to explore the effect of scaling physical parameters up, and to check whether salient features uncovered by pure kinetic models at smaller scales are still valid, with a special emphasis on particle acceleration and high-energy radiation emitted beyond the light cylinder. To reach this objective, we develop a new hybrid numerical scheme coupling the ideal force-free and the particle-in-cell methods, to optimize the numerical cost of global models. We propose a domain decomposition of the magnetosphere based on the magnetic field topology using the flux function. The force-free model is enforced along open field lines while the particle-in-cell model is restricted to the reconnecting field line region. As a proof of concept, this new hybrid model is applied to simulate a weak millisecond pulsar magnetosphere with realistic scales using high-resolution axisymmetric simulations. Magnetospheric features reported by previous kinetic models are recovered, and strong synchrotron radiation above 100MeV consistent with the Fermi-LAT gamma-ray pulsar population is successfully reproduced. This work further consolidates the shining reconnecting current sheet scenario as the origin of the gamma-ray emission in pulsars, as well as firmly establishes pulsar magnetospheres as at least TeV particle accelerators.

Cross submissions for Friday, 21 June 2024 (showing 13 of 13 entries )

[28] arXiv:2406.12917 (cross-list from astro-ph.IM) [pdf, html, other]

Title: The Black Hole Explorer: Motivation and Vision

Michael D. Johnson, Kazunori Akiyama, Rebecca Baturin, Bryan Bilyeu, Lindy Blackburn, Don Boroson, Alejandro Cardenas-Avendano, Andrew Chael, Chi-kwan Chan, Dominic Chang, Peter Cheimets, Cathy Chou, Sheperd S. Doeleman, Joseph Farah, Peter Galison, Ronald Gamble, Charles F. Gammie, Zachary Gelles, Jose L. Gomez, Samuel E. Gralla, Paul Grimes, Leonid I. Gurvits, Shahar Hadar, Kari Haworth, Kazuhiro Hada, Michael H. Hecht, Mareki Honma, Janice Houston, Ben Hudson, Sara Issaoun, He Jia, Svetlana Jorstad, Jens Kauffmann, Yuri Y. Kovalev, Peter Kurczynski, Robert Lafon, Alexandru Lupsasca, Robert Lehmensiek, Chung-Pei Ma, Daniel P. Marrone, Alan P. Marscher, Gary J. Melnick, Ramesh Narayan, Kotaro Niinuma, Scott C. Noble, Eric J. Palmer, Daniel C. M. Palumbo, Lenny Paritsky, Eliad Peretz, Dominic Pesce, Alexander Plavin, Eliot Quataert, Hannah Rana, Angelo Ricarte, Freek Roelofs, Katia Shtyrkova, Laura C. Sinclair, Jeffrey Small, Sridharan Tirupati Kumara, Ranjani Srinivasan, Andrew Strominger, Paul Tiede, Edward Tong, Jade Wang, Jonathan Weintroub, Maciek Wielgus, George Wong, Xinyue Alice Zhang

Comments: Proceedings for SPIE Astronomical Telescopes and Instrumentation

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We present the Black Hole Explorer (BHEX), a mission that will produce the sharpest images in the history of astronomy by extending submillimeter Very-Long-Baseline Interferometry (VLBI) to space. BHEX will discover and measure the bright and narrow "photon ring" that is predicted to exist in images of black holes, produced from light that has orbited the black hole before escaping. This discovery will expose universal features of a black hole's spacetime that are distinct from the complex astrophysics of the emitting plasma, allowing the first direct measurements of a supermassive black hole's spin. In addition to studying the properties of the nearby supermassive black holes M87* and Sgr A*, BHEX will measure the properties of dozens of additional supermassive black holes, providing crucial insights into the processes that drive their creation and growth. BHEX will also connect these supermassive black holes to their relativistic jets, elucidating the power source for the brightest and most efficient engines in the universe. BHEX will address fundamental open questions in the physics and astrophysics of black holes that cannot be answered without submillimeter space VLBI. The mission is enabled by recent technological breakthroughs, including the development of ultra-high-speed downlink using laser communications, and it leverages billions of dollars of existing ground infrastructure. We present the motivation for BHEX, its science goals and associated requirements, and the pathway to launch within the next decade.

[29] arXiv:2406.12933 (cross-list from gr-qc) [pdf, html, other]

Title: Charged Quark Stars and Extreme Compact Objects in Regularized 4D Einstein-Gauss-Bonnet Gravity

Michael Gammon, Robert B. Mann, Sarah Rourke

Comments: arXiv admin note: substantial text overlap with arXiv:2309.00703

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

Since the derivation of a well-defined $D\rightarrow 4$ limit for 4 dimensional Einstein Gauss-Bonnet (4DEGB) gravity coupled to a scalar field, there has been interest in testing it as an alternative to Einstein's general theory of relativity. Using the Tolman-Oppenheimer-Volkoff (TOV) equations modified for charge and 4DEGB gravity, we model the stellar structure of charged, non-interacting quark stars. We find that increasing the Gauss-Bonnet coupling constant $\alpha$ or the charge $Q$ both tend to increase the mass-radius profiles of quark stars described by this theory, allowing a given central pressure to support larger quark stars in general. We also derive a generalization of the Buchdahl bound for charged stars in 4DEGB gravity. As in the uncharged case, we find that quark stars can exist below the general relativistic Buchdahl bound (BB) and Schwarzschild radius $R=2M$, due to the lack of a mass gap between black holes and compact stars in the 4DEGB theory. Even for $\alpha$ well within current observational constraints, we find that quark star solutions in this theory can describe Extreme Compact Charged Objects (ECCOs), objects whose radii are smaller than what is allowed by general relativity.

[30] arXiv:2406.13024 (cross-list from astro-ph.SR) [pdf, html, other]

Title: A Lack of Mass-Gap Compact Object Binaries in APOGEE

Meir Schochet, Jamie Tayar, Jeff J. Andrews

Comments: 4 pages, 6 figures, accepted for publication in RNAAS

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Depending principally on mass, the compact object remnant left behind after a star's life may be a white dwarf (WD), neutron star (NS), or black hole (BH). While we have large samples of each of these remnants, we lack knowledge of the exact conditions separating these outcomes. The boundary between low-mass BHs and massive NSs is particularly poorly understood, as few objects between 2-5 $M_\odot$ are known. To probe this regime, we search the APOGEE DR17 dataset of 657,000 unique stars for binary systems with one stellar component that exhibit large radial velocity shifts over multiple observations. We identify 4751 likely binary systems, and estimate a minimum mass for each system's "invisible companion" under the assumption of tidal synchronization. Two systems have companion masses $\gtrsim$ 2 $M_\odot$, although we conclude that neither are good candidates for possessing a mass-gap NS or BH companions.

[31] arXiv:2406.13056 (cross-list from astro-ph.CO) [pdf, html, other]

Title: Mildly boosted dark matter annihilation and reconciling indirect galactic signals

Steven J. Clark

Comments: 6 pages, 3 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

The galactic center excess is a possible non-gravitational observation of dark matter; however, the canonical dark matter model (thermal freeze-out) is in conflict with other gamma-ray observations, in particular those made of the Milky Way's satellite dwarf galaxies. Here we consider the effects of a two-component dark matter model which results in minimally boosted particles that must remain bound to their host galaxy in order to produce an observational signal. This leads to a signal that is heavily dependent on galactic scale and can help reconcile the differences in the galactic center and dwarf galaxy measurements under the dark matter paradigm.

[32] arXiv:2406.13169 (cross-list from astro-ph.GA) [pdf, html, other]

Title: A surprising excess of radio emission in extremely stable quasars: a unique clue to jet launching?

Wen-Yong Kang, Jun-Xian Wang, Zhen-Yi Cai, Hao-Chen Wang, Wen-Ke Ren, Mai Liao, Feng Yuan, Andrzej Zdziarski, Xinwu Cao

Comments: 11 pages, 16 figures, Accepted by ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Quasars are generally divided into jetted radio-loud and non-jetted radio-quiet ones, but why only 10% quasars are radio loud has been puzzling for decades. Other than jet-induced-phenomena, black hole mass, or Eddington ratio, prominent difference between jetted and non-jetted quasars has scarcely been detected. Here we show a unique distinction between them and the mystery of jet launching could be disclosed by a prominent excess of radio emission in extremely stable quasars (ESQs, i.e., type 1 quasars with extremely weak variability in UV/optical over 10 years). Specifically, we find that $>$ 25% of the ESQs are detected by the FIRST/VLASS radio survey, while only $\sim$ 6-8% of the control sample, matched in redshift, luminosity, and Eddington ratio, are radio-detected. The excess of radio detection in ESQs has a significance of 4.4 $\sigma$ (99.9995%), and dominantly occurs at intermediate radio loudness with R $\sim$ 10 - 60. The radio detection fraction of ESQs also tends to increase in the ESQ samples selected with more stringent thresholds. Our results are in contrast to the common view that RL quasars are likely more variable in UV/optical due to jet contribution. New clues/challenge posed by our findings highlight the importance of extensive follow-up observations to probe the nature of jets in ESQs, and theoretical studies on the link between jet launching and ESQs. Moreover, our results makes ESQs, an essential population which has never been explored, unique targets in the burgeoning era of time domain astronomy, like their opposite counterparts of quasars exhibiting extreme variability or changing-look features.

[33] arXiv:2406.13589 (cross-list from astro-ph.GA) [pdf, html, other]

Title: Hydrodynamic simulation of Cygnus OB2: the absence of a cluster wind termination shock

Thibault Vieu, Cormac J. K. Larkin, Lucia Härer, Brian Reville, Andreas A. C. Sander, Varsha Ramachandran

Comments: 15 pages, 12 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We perform a large-scale hydrodynamic simulation of a massive star cluster whose stellar population mimics that of the Cygnus OB2 association. The main-sequence stars are first simulated during 1.6 Myr, until a quasi-stationary state is reached. At this time the three Wolf-Rayet stars observed in Cygnus OB2 are added to the simulation, which continues to 2 Myr. Using a high-resolution grid in the centre of the domain, we can resolve the most massive stars individually, which allows us to probe the kinetic structures at small (parsec) scales. We find that, although the cluster excavates a spherical "superbubble" cavity, the stellar population is too loosely distributed to blow a large-scale cluster wind termination shock, and that collective effects from wind-wind interactions are much less efficient than usually assumed. This challenges our understanding of the ultra-high energy emission observed from the region.

[34] arXiv:2406.13673 (cross-list from astro-ph.IM) [pdf, html, other]

Title: The EUSO-SPB2 Fluorescence Telescope for the Detection of Ultra-High Energy Cosmic Rays

James H. Adams Jr., Denis Allard, Phillip Alldredge, Luis Anchordoqui, Anna Anzalone, Matteo Battisti, Alexander A. Belov, Mario Bertaina, Peter F. Bertone, Sylvie Blin-Bondil, Julia Burton, Francesco S. Cafagna, Marco Casolino, Karel Černý, Mark J. Christ, Roberta Colalillo, Hank J. Crawford, Alexandre Creusot, Austin Cummings, Rebecca Diesing, Alessandro Di Nola, Toshikazu Ebisuzaki, Johannes Eser, Silvia Ferrarese, George Filippatos, William W. Finch, Flavia Flaminio, Claudio Fornaro, Duncan Fuehne, Christer Fuglesang, Diksha Garg, Alessio Golzio, Fausto Guarino, Claire Guépin, Tobias Heibges, Eleanor G. Judd, Pavel A. Klimov, John F. Krizmanic, Viktoria Kungel, Luke Kupari, Evgeny Kuznetsov, Massimiliano Manfrin, Wlodzimierz Marszal, John N. Matthews, Marco Mese, Stephan S. Meyer, Marco Mignone, Hiroko Miyamoto, Alexey S. Murashov, Jane M. Nachtman, Angela V. Olinto, Yasar Onel, Giuseppe Osteria, Beatrice Panico, Ètienne Parizot, Tom Paul, Miroslav Pech, Francesco Perfetto, Lech W. Piotrowski, Zbigniew Plebaniak, Jonatan Posliguaaa, Guillaume Prévôtb, Marika Przybylakae, Patrick Reardona, Mary Hall Reno, Marco Ricci, Fred Sarazin, P. Schovánek, Valentina Scotti, Kenji Shinozaki, Jorge F. Soriano, Ben K. Stillwell, Jacek Szabelski, Yoshiyuki Takizawa, Daniil Trofimov, Fredrik Unel, Laura Valore, Tonia M. Venters, John Watts Jr., Lawrence Wiencke, Hannah Wistrand, Roy Young

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

The Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) flew on May 13$^{\text{th}}$ and 14$^{\text{th}}$ of 2023. Consisting of two novel optical telescopes, the payload utilized next-generation instrumentation for the observations of extensive air showers from near space. One instrument, the fluorescence telescope (FT) searched for Ultra-High Energy Cosmic Rays (UHECRs) by recording the atmosphere below the balloon in the near-UV with a 1~$\mu$s time resolution using 108 multi-anode photomultiplier tubes with a total of 6,912 channels. Validated by pre-flight measurements during a field campaign, the energy threshold was estimated around 2~EeV with an expected event rate of approximately 1 event per 10 hours of observation. Based on the limited time afloat, the expected number of UHECR observations throughout the flight is between 0 and 2. Consistent with this expectation, no UHECR candidate events have been found. The majority of events appear to be detector artifacts that were not rejected properly due to a shortened commissioning phase. Despite the earlier-than-expected termination of the flight, data were recorded which provide insights into the detectors stability in the near-space environment as well as the diffuse ultraviolet emissivity of the atmosphere, both of which are impactful to future experiments.

[35] arXiv:2406.13717 (cross-list from nucl-th) [pdf, html, other]

Title: Beyond modified Urca: the nucleon width approximation for flavor-changing processes in dense matter

Mark G. Alford, Alexander Haber, Ziyuan Zhang

Comments: 6 pages, 6 figures

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

Flavor-changing charged current ("Urca") processes are of central importance in the astrophysics of neutron stars. Standard calculations approximate the Urca rate as the sum of two contributions, direct Urca and modified Urca. Attempts to make modified Urca calculations more accurate have been impeded by an unphysical divergence at the direct Urca threshold density. In this paper we describe a systematically improvable approach where, in the simplest approximation, instead of modified Urca we include an imaginary part of the nucleon mass (nucleon width). The total Urca rate is then obtained via a straightforward generalization of the direct Urca calculation, yielding results that agree with both direct and modified Urca at the densities where those approximations are valid. At low densities, we observe an enhancement of the rate by more than an order of magnitude, with important ramifications for neutron star cooling and other transport properties.

[36] arXiv:2406.13756 (cross-list from hep-ph) [pdf, html, other]

Title: Multi-messenger Approach to Ultra-light Scalars

Indra Kumar Banerjee, Soumya Bonthu, Ujjal Kumar Dey

Comments: 16 pages, 5 figures, 1 table

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We propose a novel method to study the ultra-light scalars, where compact rotating objects undergo the phenomenon of superradiance to create gravitational waves and neutrino flux signals. The neutrino flux results from the 'right' coupling between the ultra-light scalars and the neutrinos. We study the intertwining of gravitational waves and neutrino flux signals produced from a single source and elaborate if and when the signals can be detected in existing and upcoming experiments in a direct manner. We also discuss an indirect way to test it by means of cosmic neutrino background which can be detected by upcoming PTOLEMY experiment.

[37] arXiv:2406.14134 (cross-list from astro-ph.GA) [pdf, html, other]

Title: Hypervelocity star observations constrain the Galactic Centre

Sill Verberne, Elena Maria Rossi, Sergey E. Koposov, Tommaso Marchetti, Konrad Kuijken, Zephyr Penoyre, Fraser A. Evans, Dimitris Souropanis, Clár-Bríd Tohill

Comments: 17 pages, 16 figures, submitted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Hypervelocity stars (HVSs) are stars which have been ejected from the Galactic Centre (GC) at velocities of up to a few thousand km/s. They are tracers of the Galactic potential and can be used to infer properties of the GC, such as the initial-mass function and assembly history. HVSs are rare, however, with only about a dozen promising candidates discovered so far. In this work we use a novel, highly efficient method to identify new HVS candidates in Gaia. This method uses the nearly radial trajectories of HVSs to infer their distances and velocities based on their position and Gaia proper motion alone. Through comparison of inferred distances with Gaia parallaxes and photometry we identified 600 HVS candidates with G<20 including the previously discovered S5-HVS1, out of which we obtained ground-based follow-up observations for 196 stars. As we found no new HVSs based on their radial velocity, we used detailed HVS ejection simulations to significantly improve previous HVS ejection rate constraints. In particular, the ejection rate of HVSs more massive than 1 M$_\odot$ cannot be higher than $10^{-5}$ yr$^{-1}$ at $2\sigma$ significance. Additionally, we predict that there are 5-45 unbound HVSs in the complete Gaia catalogue ($1\sigma$ interval), most of which will be main-sequence stars of a few M$_\odot$ at heliocentric distances of tens to hundreds of kpc. By comparing our results to literature HVS candidates, we find an indication of either a time-dependent ejection rate of HVSs or a non-GC origin of many previously identified HVS candidates.

[38] arXiv:2406.14158 (cross-list from cond-mat.quant-gas) [pdf, html, other]

Title: Quantum vortices in fermionic superfluids: from ultracold atoms to neutron stars

Piotr Magierski, Andrea Barresi, Andrzej Makowski, Daniel Pęcak, Gabriel Wlazłowski

Subjects: Quantum Gases (cond-mat.quant-gas); High Energy Astrophysical Phenomena (astro-ph.HE); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)

Superfluid dilute neutron matter and ultracold gas, close to the unitary regime, exhibit several similarities. Therefore, to a certain extent, fermionic ultracold gases may serve as emulators of dilute neutron matter, which forms the inner crust of neutron stars and is not directly accessed experimentally. Quantum vortices are one of the most significant properties of neutron superfluid, essential for comprehending neutron stars' dynamics. The structure and dynamics of quantum vortices as a function of pairing correlations' strength are being investigated experimentally and theoretically in ultracold gases. Certain aspects of these studies are relevant to neutron stars. We provide an overview of the characteristics of quantum vortices in s-wave-type fermionic and electrically neutral superfluids. The main focus is on the dynamics of fermionic vortices and their intrinsic structure.

[39] arXiv:2406.14396 (cross-list from astro-ph.SR) [pdf, html, other]

Title: A disc wind origin for the optical spectra of dwarf novae in outburst

Yusuke Tampo, Christian Knigge, Knox S. Long, James H. Matthews, Noel Castro Segura

Comments: 13 pages, 9 figures, 3 tables. Accepted for publication in MNRAS

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Many high-state cataclysmic variables (CVs) exhibit blue-shifted absorption features in their ultraviolet (UV) spectra -- a smoking-gun signature of outflows. However, the impact of these outflows on {\em optical} spectra remains much more uncertain. During its recent outburst, the eclipsing dwarf nova V455 And displayed strong optical emission lines whose cores were narrower than expected from a Keplerian disc. Here, we explore whether disc + wind models developed for matching UV observations of CVs can also account for these optical spectra. Importantly, V455~And was extremely bright at outburst maximum: the accretion rate implied by fitting the optical continuum with a standard disc model is $\dot{M}_{\rm acc} \simeq 10^{-7}~{\rm M}_\odot~{\rm yr^{-1}}$. Allowing for continuum reprocessing in the outflow helps to relax this constraint. A disk wind can also broadly reproduce the optical emission lines, but only if the wind is (i) highly mass-loaded, with a mass-loss rate reaching $\dot{M}_{\rm wind} \simeq 0.4 \dot{M}_{\rm acc}$, and/or (ii) clumpy, with a volume filling factor $f_V \simeq 0.1$. The same models can describe the spectral evolution across the outburst, simply by lowering $\dot{M}_{\rm acc}$ and $\dot{M}_{\rm wind}$. Extending these models to lower inclinations and into the UV produces spectra consistent with those observed in face-on high-state CVs. We also find, for the first time in simulations of this type, P-Cygni-like absorption features in the Balmer series, as have been observed in both CVs and X-ray binaries. Overall, dense disc winds provide a promising framework for explaining multiple observational signatures seen in high-state CVs, but theoretical challenges persist.

[40] arXiv:2406.14450 (cross-list from hep-th) [pdf, html, other]

Title: Hydrodynamics of Relativistic Superheated Bubbles

Yago Bea, Jorge Casalderrey-Solana, David Mateos, Mikel Sanchez-Garitaonandia

Comments: 18 pages, 8 figures, 1 appendix

Subjects: High Energy Physics - Theory (hep-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Relativistic, charged, superheated bubbles may play an important role in neutron star mergers if first-order phase transitions are present in the phase diagram of Quantum Chromodynamics. We describe the properties of these bubbles in the hydrodynamic regime. We find two qualitative differences with supercooled bubbles. First, the pressure inside an expanding superheated bubble can be higher or lower than the pressure outside the bubble. Second, some fluid flows develop metastable regions behind the bubble wall. We consider the possible role of a conserved charge akin to baryon number. The fluid flow profiles are unaffected by this charge if the speed of sound is constant in each phase, but they are modified for more general equations of state. We compute the efficiency factor relevant for gravitational wave production.

Replacement submissions for Friday, 21 June 2024 (showing 18 of 18 entries )

[41] arXiv:2403.09444 (replaced) [pdf, html, other]

Title: Expansion and Spectral Softening of the Dust Scattering Rings of GRB 221009A

Guoying Zhao, Rong-Feng Shen

Comments: 9 pages, 6 figures, 2 tables, Accepted for publication in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Expanding X-ray halo or rings appear when short pulses of X-ray radiation from a background source are scattered by clouds of dust in the Milky Way. We study the X-ray rings of the brightest gamma-ray burst (GRB) 221009A, detected by the {\it Swift} X-Ray Telescope. The rings center on the GRB position and their angular radii increase with time. We identify five major expanding rings, and our modeling of their expansion history suggests that they are scattered off, respectively, from five dusty clouds at distances of 0.4-13 kpc from the observer. Given an assumed prompt X-ray fluence of this GRB, the fluxes of those rings suggest that these clouds have dust grain column densities of $10^{7\sim8}~\mathrm{cm^{-2}}$. More interestingly, our time-dependent spectral analysis of these rings show that they all experience spectral softening, i.e., getting softer as they expand, with spectral indices ranging from 2.2 to 5, consistent with what the dust scattering model predicts.

[42] arXiv:2403.15305 (replaced) [pdf, html, other]

Title: X-ray emission spectrum for axion-photon conversion in magnetospheres of strongly magnetized neutron stars

Shubham Yadav, M. Mishra, Tapomoy Guha Sarkar

Comments: Accepted in European Physical Journal C (15 pages, 17 figures)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

Detecting axionic dark matter (DM) could be possible in an X-ray spectrum from strongly magnetized neutron stars (NSs). We examine the possibility of axion-photon conversion in the magnetospheres of strongly magnetized NSs. In the current work, we investigate how the modified Tolman Oppenheimer Volkoff (TOV) system of equations (in the presence of a magnetic field) affects the energy spectrum of axions and axions-converted-photon flux. We have considered the distance-dependent magnetic field in the modified TOV system of equations. We employ three different equations of states (EoSs), namely APR, FPS, and SLY, to solve these equations. We obtain the axions emission rate by including the Cooper-pair-breaking formation process and Bremsstrahlung process in the core of NSs using the NSCool code. We primarily focus on Magnificient seven (M7) star RXJ 1856.5-3754. We further investigate the impact of the magnetic field on the actual observables, such as axion energy spectrum and axion-converted-photon flux at an axion mass in meV range by assuming mass $M_{NS} \sim 1.4M_{\odot}$. We compare our calculated axion-converted-photon flux from all available archival data sets from PN+MOS+Chandra. We also study the variation of the energy spectrum at a fixed energy with varying central magnetic fields. Our predicted axion-converted-photon flux values as a function of axion energy closely follow the experimentally archival data, which allows us to put bounds on the axion mass for the three EoS.

[43] arXiv:2403.17799 (replaced) [pdf, html, other]

Title: Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5

P.V. Padmanabh, S.M. Ransom, P.C.C. Freire, A. Ridolfi, J.D. Taylor, C. Choza, C.J. Clark, F. Abbate, M. Bailes, E.D. Barr, S. Buchner, M. Burgay, M.E. DeCesar, W. Chen, A. Corongiu, D.J. Champion, A. Dutta, M. Geyer, J.W.T. Hessels, M. Kramer, A. Possenti, I.H. Stairs, B.W. Stappers, V. Venkatraman Krishnan, L. Vleeschower, L. Zhang

Comments: 23 pages, 11 figures, 5 tables, published in A&A

Journal-ref: A&A, 686, A166 (2024)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the discovery of ten new pulsars in the globular cluster Terzan 5 as part of the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. We observed Terzan 5 at L-band (856--1712 MHz) with the MeerKAT radio telescope for four hours on two epochs, and performed acceleration searches of 45 out of 288 tied-array beams covering the core of the cluster. We obtained phase-connected timing solutions for nine discoveries, covering nearly two decades of archival observations from the Green Bank Telescope for all but one. Highlights include PSR J1748$-$2446ao which is an eccentric ($e = 0.32$) wide-orbit (orbital period $P_{\rm b} = 57.55$ d) system. We were able to measure the rate of advance of periastron ($\dot{\omega}$) for this system allowing us to determine a total mass of $3.17 \pm \, 0.02\, \rm M_{\odot}$. With a minimum companion mass ($M_{\rm c}$) of $\sim 0.8\, \rm M_{\odot}$, PSR J1748$-$2446ao is a candidate double neutron star (DNS) system. If confirmed to be a DNS, it would be the fastest spinning pulsar ($P = 2.27$ ms) and the longest orbital period measured for any known DNS system. PSR J1748$-$2446ap has the second highest eccentricity for any recycled pulsar ($e \sim 0.905$) and for this system we can measure the total mass ($1.997 \pm 0.006\, \rm M_{\odot}$) and also estimate the individual pulsar and companion masses. PSR J1748$-$2446ar is an eclipsing redback (minimum $M_{\rm c} \sim 0.34\, \rm M_{\odot}$) system whose properties confirm it to be the counterpart to a previously published source identified in radio and X-ray imaging. With these discoveries, the total number of confirmed pulsars in Terzan 5 is 49, the highest for any globular cluster so far. These discoveries further enhance the rich set of pulsars known in Terzan 5 and provide scope for a deeper understanding of binary stellar evolution, cluster dynamics and ensemble population studies.

[44] arXiv:2404.05786 (replaced) [pdf, html, other]

Title: Repeating partial disruptions and two-body relaxation

Luca Broggi, Nicholas C. Stone, Taeho Ryu, Elisa Bortolas, Massimo Dotti, Matteo Bonetti, Alberto Sesana

Comments: Open Journal of Astrophysics, accepted for publication

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Two-body relaxation may drive stars onto near-radial orbits around a massive black hole, resulting in a tidal disruption event (TDE). In some circumstances, stars are unlikely to undergo a single terminal disruption, but rather to have a sequence of many grazing encounters with the black hole. It has long been unclear what is the physical outcome of this sequence: each of these encounters can only liberate a small amount of stellar mass, but may significantly alter the orbit of the star. We study the phenomenon of repeating partial tidal disruptions (pTDEs) by building a semi-analytical model that accounts for mass loss and tidal excitation. In the empty loss cone regime, where two-body relaxation is weak, we estimate the number of consecutive partial disruptions that a star can undergo, on average, before being significantly affected by two-body encounters. We find that in this empty loss cone regime, a star will be destroyed in a sequence of weak pTDEs, possibly explaining the tension between the low observed TDE rate and its higher theoretical estimates.

[45] arXiv:2404.10660 (replaced) [pdf, html, other]

Title: Discovery of the optical and radio counterpart to the fast X-ray transient EP240315a

J. H. Gillanders, L. Rhodes, S. Srivastav, F. Carotenuto, J. Bright, M. E. Huber, H. F. Stevance, S. J. Smartt, K. C. Chambers, T.-W. Chen, R. Fender, A. Andersson, A. J. Cooper, P. G. Jonker, F. J. Cowie, T. deBoer, N. Erasmus, M. D. Fulton, H. Gao, J. Herman, C.-C. Lin, T. Lowe, E. A. Magnier, H.-Y. Miao, P. Minguez, T. Moore, C.-C. Ngeow, M. Nicholl, Y.-C. Pan, G. Pignata, A. Rest, X. Sheng, I. A. Smith, K. W. Smith, J. L. Tonry, R. J. Wainscoat, J. Weston, S. Yang, D. R. Young

Comments: Updated to match version accepted for publication in ApJL (17 pages, 4 figures, 2 tables)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Fast X-ray Transients (FXTs) are extragalactic bursts of soft X-rays first identified >10 years ago. Since then, nearly 40 events have been discovered, although almost all of these have been recovered from archival Chandra and XMM-Newton data. To date, optical sky surveys and follow-up searches have not revealed any multi-wavelength counterparts. The Einstein Probe, launched in January 2024, has started surveying the sky in the soft X-ray regime (0.5-4 keV) and will rapidly increase the sample of FXTs discovered in real time. Here, we report the first discovery of both an optical and radio counterpart to a distant FXT, the fourth source publicly released by the Einstein Probe. We discovered a fast-fading optical transient within the 3 arcmin localisation radius of EP240315a with the all-sky optical survey ATLAS, and our follow-up Gemini spectrum provides a redshift, z=4.859+/-0.002. Furthermore, we uncovered a radio counterpart in the S-band (3.0 GHz) with the MeerKAT radio interferometer. The optical (rest-frame UV) and radio luminosities indicate the FXT most likely originates from either a long gamma-ray burst or a relativistic tidal disruption event. This may be a fortuitous early mission detection by the Einstein Probe or may signpost a mode of discovery for high-redshift, high-energy transients through soft X-ray surveys, combined with locating multi-wavelength counterparts.

[46] arXiv:2404.12976 (replaced) [pdf, html, other]

Title: Insights from the Gaussian Processes Method for the FRB-associated X-ray Burst of SGR 1935+2154

Ruijing Tang, Dahai Yan, Haiyun Zhang, Qingchang Zhao, Lian Tao, Chengkui Li, Mingyu Ge, Xiaobo Li, Qianqing Yin, Ce Cai

Comments: 13 pages,17 figures,1 table

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Gaussian processes method is employed to analyze the light curves of bursts detected by Insight-HXMT, NICER, and GECAM from SGR 1935+2154 between 2020 to 2022. It is found that a stochastically driven damped simple harmonic oscillator (SHO) is necessary to capture the characteristics of the X-ray bursts. Variability timescale of the X-ray bursts, corresponding to the broken frequencies in the SHO power spectral densities (PSDs), are extracted. In particular, a high broken frequency of 35 Hz where the index of the SHO PSD changes from -4 to -2 is constrained by the HXMT-HE burst associated with FRB 200428. It is suggested that the corresponding timescale of 0.03 s could be the retarding timescale of the system driven by some energy release, and the production of the HE photon should be quasi-simultaneous with the response. The other special event is a NICER burst with a retarding timescale of 1/39 Hz (0.02 s). In the normal X-ray bursts, no retarding timescale is constrained; a long relax/equilibrium timescale (corresponding to a broken frequency of 1-10 Hz where the index of the SHO PSD changing from -4/-2 to 0 in the SHO PSD) is obtained. The results indicate that the FRB-associated HXMT-HE X-ray burst could be produced immediately when the system is responding to the energy disturbance, far before the equilibrium state.

[47] arXiv:2406.12477 (replaced) [pdf, html, other]

Title: An atypical low-frequency QPO detected in the hard state of MAXI J1348-630 with $Insight$-HXMT

Xin-Lei Wang, Zhen Yan, Fu-Guo Xie, Jun-Feng Wang, Ren-Yi Ma

Comments: 20 pages, 6 figures. Accepted by ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Based on the $Insight$-HXMT archival data, we have detected a new atypical low-frequency quasi-periodic oscillation (LFQPO) in the black hole X-ray binary MAXI J1348$-$630. The new LFQPO is detected in all the three instruments of $Insight$-HXMT with a combined significance of 3--5 $\sigma$, covering a wide energy range of 1--100 keV. The fractional root-mean-square (RMS) seems decrease with energy. It exclusively appears in the hard state during both the main and mini outburst, spanning an X-ray intensity range by a factor of 10, and a very narrow hardness range. The frequency of this new type of LFQPO is moderately stable, in the range of 0.08--0.15 Hz. We discussed different models for the LFQPO, and found none is able to explain the observed properties of this new type of LFQPO.

[48] arXiv:2209.02741 (replaced) [pdf, html, other]

Title: Probing ultralight scalar, vector and tensor dark matter with pulsar timing arrays

Caner Unal, Federico R. Urban, Ely D. Kovetz

Comments: 6 pages, 3 figures, accepted by PLB

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

Pulsar timing arrays (PTAs) are sensitive to oscillations in the gravitational potential along the line-of-sight due to ultralight particle pressure. We calculate the probing power of PTAs for ultralight bosons across all frequencies, from those larger than the inverse observation time to those smaller than the inverse distance to the pulsar. We show that since the signal amplitude grows comparably to the degradation in PTA sensitivity at frequencies smaller than inverse observation time, the discovery potential can be extended towards lower masses by over three decades, maintaining high precision. We demonstrate that, in the mass range $10^{-26} -10^{-23}$ eV, existing 15-year PTA data can robustly detect or rule out an ultralight component down to $O(1 - 10)\%$ of the total dark matter. Non-detection, together with other bounds in different mass ranges, will imply that ultralight scalar/axion can comprise at most $1-10\%$ of dark matter in the $10^{-30}\!-\!10^{-17}$ eV range. With 30 years of observation, current PTAs can extend the reach down to $0.1-1 \%$, while next-generation PTAs such as SKA can attain the $0.01-0.1\%$ precision. We generalize the analysis and derive predictions for ultralight spin-1 vector (i.e. dark photon) and spin-2 tensor dark components.

[49] arXiv:2306.03327 (replaced) [pdf, html, other]

Title: Superfluid extension of the self-consistent time-dependent band theory for neutron star matter: Anti-entrainment versus superfluid effects in the slab phase

Kenta Yoshimura, Kazuyuki Sekizawa

Comments: 21 pages, 11 figures, 4 tables. v4 - Version accepted for publication in Physical Review C, selected as an Editors' Suggestion

Journal-ref: Phys. Rev. C 109, 065804 (2024)

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas)

Background: The inner crust of neutron stars consists of a Coulomb lattice of neutron-rich nuclei, immersed in a sea of superfluid neutrons with background relativistic electron gas. A proper quantum mechanical treatment for such a system under a periodic potential is the band theory of solids. The effect of band structure on the effective mass of dripped neutrons, the so-called \textit{entrainment effect}, is currently in a debatable situation, and it has been highly desired to develop a nuclear band theory taking into account neutron superfluidity in a fully self-consistent manner.
Purpose: The main purpose of the present work is twofold: 1) to develop a formalism of the time-dependent self-consistent band theory, taking full account of nuclear superfluidity, based on time-dependent density functional theory (TDDFT) extended for superfluid systems, and 2) to quantify the effects of band structure and superfluidity on crustal properties, applying the formalism to the slab phase of nuclear matter in the $\beta$ equilibrium.
Results: Static calculations have been performed for a range of baryon (nucleon) number density ($n_b=0.04-0.07$ fm$^{-3}$) under the $\beta$-equilibrium condition with and without superfluidity, for various inter-slab spacings. From a dynamic response to an external potential, we extract the collective mass of a slab and that of protons immersed in neutron superfluid. From the results, we find that the collective mass of a slab is substantially reduced by 57.5--82.5\% for $n_b=0.04-0.07$ fm$^{-3}$, which corresponds to an enhancement of conduction neutron number density and, thus, to a reduction of the neutron effective mass, which we call the anti-entrainment effect. We discuss novel phenomena associated with superfluidity, quasiparticle resonances in the inner crust, which are absent in normal systems.
*shortened due to the arXiv word limit.

[50] arXiv:2309.07316 (replaced) [pdf, html, other]

Title: Plasma modes in QED super-strong magnetic fields of magnetars and laser plasmas

Mikhail V. Medvedev

Comments: Invited paper for the PoP Special Collection on Relativistic Plasma in Supercritical Electromagnetic Fields. 17 pages, 8 figures

Subjects: Plasma Physics (physics.plasm-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

Ultra-magnetized plasmas, where the magnetic field strength exceeds the Schwinger field of about $B_{Q}\approx4\times10^{13}$~gauss, become of great scientific interest, thanks to the current advances in laser-plasma experiments and astrophysical observations of magnetar emission. These advances demand better understanding of how quantum electrodynamics (QED) effects influence collective plasma phenomena. In particular, Maxwell's equations become nonlinear in the strong-QED regime. Here we present the `QED plasma framework' which will allow one to {\em systematically} explore collective phenomena in a QED-plasma with arbitrarily strong magnetic field. Further, we illustrate the framework by exploring low-frequency modes in the ultra-magnetized, cold, electron-positron plasmas. We demonstrate that the classical picture of five branches holds in the QED regime; no new eigenmodes appear. The dispersion curves of all the modes are modified. The QED effects include the overall modification to the plasma frequency, which becomes field-dependent. They also modify resonances and cutoffs of the modes, which become both field- and angle-dependent. The strongest effects are (i) the {\em field-induced transparency of plasma} for the O-mode via the dramatic reduction of the low-frequency cutoff well below the plasma frequency, (ii) the {\em Alfven mode suppression} in the large-$k$ regime via the reduction of the Alfven mode resonance, and (iii) the {\em O-mode slowdown} via strong angle-dependent increase of the index of refraction. These results should be important for understanding of a magnetospheric pair plasma of a magnetar and for laboratory laser-plasma experiments in the QED regime.

[51] arXiv:2312.17393 (replaced) [pdf, html, other]

Title: Quintessence and the Higgs Portal in the Carroll limit

B. Avila, J. Gamboa, R. B. MacKenzie, F. Mendez, M. B. Paranjape

Comments: Several references were added. To appear in PLB

Subjects: High Energy Physics - Theory (hep-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

A cosmological model based on two scalar fields is proposed. The first of these, $\varphi$, has mass $\mu$, while the second, $\chi$, is massless. The pair are coupled through a ``Higgs portal''. First, we show how the model reproduces the Friedmann equations if the square of the mass of the $\varphi$ field is proportional to the cosmological constant and $\chi$ represents the quintessence field. Quantum corrections break the conformal symmetry, and the $\chi$ field acquires a mass equal to $\sqrt{3g\Lambda}$. The perturbative approach with $g\ll 1$ is consistent with the bounds for $m_\chi$; moreover, by using dimensional analysis, we estimate $m_\chi \ll H_0\approx 10^{-33}$ eV, which is in accordance with what is expected in the quintessence scenario. The acceleration of the universe is proportional to $\chi^2$, we conclude that for very long times, the solution of the equation of motion approaches $\langle \chi\rangle \sim {m_\chi}/{\sqrt\lambda}$ and the universe continues to accelerate, with a constant acceleration.

[52] arXiv:2401.14389 (replaced) [pdf, html, other]

Title: Magnetic braking below the cataclysmic variable period gap and the observed dearth of period bouncers

Arnab Sarkar, Antonio C. Rodriguez, Sivan Ginzburg, Lev Yungelson, Christopher A. Tout

Comments: Accepted for publication in A&A Letters. Significant revision from the original version

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Period bouncers are cataclysmic variables (CVs) that have evolved past their orbital period minimum. The strong disagreement between theory and observations of the relative fraction of period bouncers is a severe shortcoming in the understanding of CV evolution. We test the implications of the hypothesis that magnetic braking (MB), which is suggested to be an additional angular momentum loss (AML) mechanism for CVs below the period gap ($P_\mathrm{orb}\lesssim 120$ min), weakens around their period minimum. We compute the evolution of CV donors below the period gap using the MESA code, assuming that the evolution of the system is driven by AML by gravitational wave radiation (GWR) and MB. We parametrize the MB strength as $\mathrm{AML_{MB}}=\kappa\mathrm{AML_{GWR}}$. We compute two qualitatively different sets of models, one where $\kappa$ is a constant and the other where $\kappa$ depends on stellar parameters. We find that two crucial effects drive the latter set of models. (1) A decrease in $\kappa$ as CVs approach the period minimum stalls their evolution so that they spend a long time in the observed period minimum spike ($80\lesssim P_\mathrm{orb}/\,\mathrm{min}\lesssim 86$). Here, they become difficult to distinguish from pre-bounce systems in the spike. (2) A strong decrease in the mass-transfer rate makes them virtually undetectable as they evolve further. So, the CV stalls around the period minimum and then `disappears'. This reduces the number of detectable bouncers. Physical processes, such as dynamo action, white dwarf magnetism, and dead zones, may cause such a weakening of MB at short orbital periods. The weakening magnetic braking formalism provides a possible solution to the problem of the lack of period bouncers in CV observational surveys.

[53] arXiv:2404.02085 (replaced) [pdf, html, other]

Title: On the model uncertainties for the predicted muon content of extensive air showers

Sergey Ostapchenko, Günter Sigl

Comments: Version accepted for Astroparticle Physics

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

Motivated by the excess of the muon content of cosmic ray induced extensive air showers (EAS), relative to EAS modeling, observed by the Pierre Auger Observatory, and by the tension between Auger data and air shower simulations on the maximal muon production depth $X^{\mu}_{\max}$, we investigate the possibility to modify the corresponding EAS simulation results, within the Standard Model of particle physics. We start by specifying the kinematic range for secondary hadron production, which is of relevance for such predictions. We further investigate the impact on the predicted EAS muon number and on $X^{\mu}_{\max}$ of various modifications of the treatment of hadronic interactions, in the framework of the QGSJET-III model, in particular the model calibration to accelerator data, the amount of the "glue" in the pion, and the energy dependence of the pion exchange process. None of the considered modifications of the model allowed us to enhance the EAS muon content by more than 10\%. On the other hand, for the maximal muon production depth, some of the studied modifications of particle production give rise up to $\sim 10$ g/cm$^2$ larger $X^{\mu}_{\max}$ values, which increases the difference with Auger observations.

[54] arXiv:2404.03364 (replaced) [pdf, html, other]

Title: High energy head-on particle collisions near event horizons: classifcation of scenarios

H.V.Ovcharenko, O.B.Zaslavskii

Comments: 16 pages, substantial revision

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

We consider head-on collisions of two particles near the event horizon. Particle 1 is outgoing, particle 2 is ingoing. We elucidate, in which case the energy $E_{c.m.}$ in the center of mass frame can grow unbounded. If the proper time between the horizon and an arbitrary point outside it for particle 1 is finite, we deal with a white hole. If it is infinite, we deal with a black hole. Particles can be either free or experience the action of a finite force. Our results are complementary to those for the standard BSW effect when particles move in the same direction. The results rely on classification of particles developed in our previous work H.V. Ovcharenko, O.B. Zaslavskii, Phys. Rev. D 108, 064029 (2023).

[55] arXiv:2405.01977 (replaced) [pdf, html, other]

Title: PINT: Maximum-likelihood estimation of pulsar timing noise parameters

Abhimanyu Susobhanan, David Kaplan, Anne Archibald, Jing Luo, Paul Ray, Timothy Pennucci, Scott Ransom, Gabriella Agazie, William Fiore, Bjorn Larsen, Patrick O'Neill, Rutger van Haasteren, Akash Anumarlapudi, Matteo Bachetti, Deven Bhakta, Chloe Champagne, H. Thankful Cromartie, Paul Demorest, Ross Jennings, Matthew Kerr, Sasha Levina, Alexander McEwen, Brent Shapiro-Albert, Joseph Swiggum

Comments: Accepted for publication in ApJ

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

PINT is a pure-Python framework for high-precision pulsar timing developed on top of widely used and well-tested Python libraries, supporting both interactive and programmatic data analysis workflows. We present a new frequentist framework within PINT to characterize the single-pulsar noise processes present in pulsar timing datasets. This framework enables the parameter estimation for both uncorrelated and correlated noise processes as well as the model comparison between different timing and noise models in a computationally inexpensive way. We demonstrate the efficacy of the new framework by applying it to simulated datasets as well as a real dataset of PSR B1855+09. We also describe the new features implemented in PINT since it was first described in the literature.

[56] arXiv:2405.12243 (replaced) [pdf, html, other]

Title: The Kohn-Luttinger Effect in Dense Matter and its Implications for Neutron Stars

Mia Kumamoto, Sanjay Reddy

Comments: 34 pages, 11 figures

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Superconductivity (cond-mat.supr-con)

Repulsive short-range interactions can induce p-wave attraction between fermions in dense matter and lead to Cooper pairing at the Fermi surface. We investigate this phenomenon, well-known as the Kohn-Luttinger effect in condensed matter physics, in dense matter with strong short-range repulsive interactions. We find that repulsive interactions required to stabilize massive neutron stars can induce p-wave pairing in neutron and quark matter. When massive vector bosons mediate the interaction between fermions, the induced interaction favors Cooper pairing in the 3P2 channel. For the typical strength of the interaction favored by massive neutron stars, the associated pairing gaps in neutrons can be in the range of 10 keV to 10 MeV. Strong and attractive spin-orbit and tensor forces between neutrons can result in repulsive induced interactions that greatly suppress the 3P2 pairing gap in neutron matter. In quark matter, the induced interaction is too small to result in pairing gaps of phenomenological relevance.

[57] arXiv:2405.15999 (replaced) [pdf, html, other]

Title: Perturbative Frequency Expansion for Nearly Monochromatic Binary Black Holes Detectable with LISA

Naoki Seto

Comments: 11 pages, 6 figures, corrected Eq. (15) and related errors

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

The proposed space gravitational wave (GW) detector LISA has potential to detect stellar-mass black hole binaries (BBHs). The majority of the detected BBHs are expected to emit nearly monochromatic GWs, whose frequency evolution will be efficiently described by Taylor expansions. We study the measurability of the associated time derivative coefficients of the frequencies, by extending a recent work based on a simplified Fisher matrix analysis. Additionally, we provide qualitative discussions on how to extract astrophysical information, such as orbital eccentricity and tertiary perturbation, from the observed derivative coefficients.

[58] arXiv:2405.17772 (replaced) [pdf, html, other]

Title: A Contact Binary Mis-Classified as an Ellipsoidal Variable: Complications for Detached Black Hole Searches

Tyrone N. O'Doherty, Arash Bahramian, Adelle J. Goodwin, James C. A. Miller-Jones, Jerome A. Orosz, Jay Strader

Comments: Accepted for publication in AJ. 16 pages, 8 figures, 2 tables. Updated description of ASAS-SN ellipsoidal search in Section 4.4 and author affiliations

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Identifying sources exhibiting ellipsoidal variability in large photometric surveys is becoming a promising method to search for candidate detached black holes in binaries. This technique aims to exploit the orbital-phase dependent modulation in optical photometry caused by the black hole distorting the shape of the luminous star to constrain the mass ratio of the binary. Without understanding if, or how much, contamination is present in the candidate black hole samples produced by this new technique it is hard to leverage them for black hole discovery. Here, we follow up one of the best candidates identified from Gaia Data Release 3, Gaia DR3 4042390512917208960, with a radial velocity campaign. Combined photometric and radial velocity modelling, along with spectral disentangling, suggests that the true mass ratio (mass of the unseen object divided by the mass of the luminous star) is an order of magnitude smaller than that inferred assuming the modulations arise from ellipsoidal variability. We therefore infer that this system is likely a contact binary, or on the boundary of both stars nearly filling their Roche lobes, however, further observations are required to confidently detect the secondary. We find that the well-known problem of discriminating between ellipsoidal and contact binary light curves results in a larger contamination from contact binaries than previously suggested. Until ellipsoidal variables can be reliably distinguished from contact binaries, samples of black hole candidates selected based on ellipsoidal variability are likely to be highly contaminated by contact binaries or similar systems.