pith. sign in

arxiv: 2606.08752 · v1 · pith:XU5WWDH2new · submitted 2026-06-07 · 🌌 astro-ph.HE

On The Nature of Einstein Probe Transient EP250916a: Insights from X-ray, Optical, and Radio Observations

Gaurava K. Jaisawal , Giulia Illiano , Francesco Carotenuto , Astrid L. Bouquin , David M. Russell , Giorgos Leloudas , Andrea Sanna , Dalya Akl
show 2 more authors
Rob Fender Sara Motta
This is my paper

Pith reviewed 2026-06-27 17:45 UTC · model grok-4.3

classification 🌌 astro-ph.HE
keywords X-ray transientsblack hole X-ray binarieshard statequasi-periodic oscillationsmulti-wavelength observationscompact object transients
0
0 comments X

The pith

Multi-wavelength observations of EP250916a support classification as a low-luminosity hard-state black hole X-ray binary candidate.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reports X-ray, optical, and radio follow-up of the transient EP250916a detected by Einstein Probe. It shows a long outburst lasting over 40 days with a persistently hard nonthermal spectrum up to 70 keV, a weak 13 Hz QPO, no pulsations or bursts, no radio detection, and only faint optical sources. These traits together rule out stellar flares and extragalactic origins while matching known faint hard-state black hole systems. A reader would care because the result adds one more member to an emerging class of low-luminosity compact-object transients that wide-field monitors can now catch.

Core claim

The combination of a long-lasting outburst, a hard nonthermal X-ray spectrum, a weak QPO detection, the absence of coherent timing features, and faint potential optical counterparts disfavors a stellar-flare or extragalactic origin and supports an accreting compact-object scenario. Comparisons with similar faint, hard-state transients place EP250916a within a growing population of low-luminosity, hard-state black hole X-ray binary candidates.

What carries the argument

Broadband spectral modeling with a nonthermal power-law plus partial-covering absorption, together with timing analysis that isolates the weak QPO while excluding coherent pulsations or bursts.

If this is right

  • EP250916a joins a growing sample of faint hard-state transients that can be discovered by sensitive wide-field X-ray monitors.
  • The two-stage decay and persistent hardness imply accretion flow behavior that persists at low luminosities.
  • Absence of radio emission is consistent with the hard state at these faint levels.
  • Optical counterparts remain faint, suggesting the systems are either distant or have low-mass companions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Rapid multi-wavelength campaigns may become essential for classifying the increasing number of faint transients found by new monitors.
  • Distinguishing black holes from neutron stars in this low-luminosity regime could require deeper timing or infrared observations.
  • The source may represent a bridge between bright outbursting binaries and quiescent black hole systems.

Load-bearing premise

The observed hard spectrum without a thermal disk, weak QPO, and lack of radio or strong optical emission are distinctive enough to assign the source specifically to the black hole X-ray binary class rather than a neutron-star system or another transient type.

What would settle it

Detection of coherent pulsations or thermonuclear X-ray bursts in additional observations would indicate a neutron star accretor instead.

Figures

Figures reproduced from arXiv: 2606.08752 by Andrea Sanna, Astrid L. Bouquin, Dalya Akl, David M. Russell, Francesco Carotenuto, Gaurava K. Jaisawal, Giorgos Leloudas, Giulia Illiano, Rob Fender, Sara Motta.

Figure 1
Figure 1. Figure 1: The field of EP250916a observed with (a) Swift/XRT (0.5–10 keV). Panels (b), (c), and (d) display zoomed views of the Swift/UVOT (V-band), NOT/ALFOSC R-band, and LCO i′ -filter images, respectively, centered on the Swift/XRT position (marked by a plus sign). Each zoomed-in panel shows a ∼ 8 ′′ ×8 ′′ region centred on the X-ray position. Both Gaia DR3 sources within the 2 arcsec X-ray positional uncertainty… view at source ↗
Figure 2
Figure 2. Figure 2: Left: Swift/XRT light curves of EP250916a in the 0.5–1.5 keV (soft; blue circles), 1.5–10 keV (hard; red squares), and 0.5–10 keV (full; green diamonds) bands (top), with the corresponding hardness ratio (HR = 1.5–10 keV/0.5–1.5 keV) shown below. Each point represents a single Swift/XRT observation. Right: Hardness–intensity diagram illustrating the spectral evolution of EP250916a during the outburst, colo… view at source ↗
Figure 3
Figure 3. Figure 3: PDS (black) of EP250916a using XMM-Newton. The grey line shows the best-fit model with three Lorentzian components. Broad Lorentzians (red and green) describe the underlying noise, while the narrow Lorentzian (blue) in￾dicates a weak QPO at ≈ 13 Hz. noise arising from the corona of an accreting compact object. 3.3. NuSTAR timing study For the NuSTAR observation on 2025 September 24, we extracted light curv… view at source ↗
Figure 5
Figure 5. Figure 5: Flux evolution of EP250916a during the out￾burst in the 0.5-10 keV range. EP/WXT (green star), SVOM/MXT (blue square), XMM-Newton (magenta dia￾mond), and Swift/XRT (black circles) measurements are shown. The dotted red line shows the best-fit quadruple-bro￾ken power-law model; grey vertical lines mark the break times, with the model indices indicated. ble 2). The unabsorbed flux in the 3–80 keV range is (7… view at source ↗
Figure 4
Figure 4. Figure 4: Spectral evolution of EP250916a during the outburst from Swift/XRT observations, fitted with an ab￾sorbed power-law model. Top to bottom panels show the absorption column density NH (1022 cm−2 ), photon index Γ, normalization (ΓNorm), and the 0.5–10 keV unabsorbed flux (erg s−1 cm−2 ), respectively. Such a phenomenological approach has been used to model the outburst light curve of another X-ray tran￾sient… view at source ↗
Figure 6
Figure 6. Figure 6: The 0.5–79 keV broadband X-ray spec￾tra of EP250916a from XMM-Newton (blue) and NuS￾TAR (FPMA/FPMB; red/black) observations, fitted with an absorbed power-law model with a partial covering absorp￾tion and a Gaussian emission line (top). Spectral residuals are shown in the bottom panel. tbpcf × (cutoffpl + gaussian) (Model III). This provides a statistically comparable fit (χ 2 ν ≈ 1.11), with a photon inde… view at source ↗
Figure 7
Figure 7. Figure 7: The 1–10 keV X-ray versus 5 GHz radio lumi￾nosity (LR–LX) plane for accreting systems (see, e.g., A. Bahramian & A. Rushton 2022). Gray circles represent hard-state black hole LMXBs, blue squares denote hard-s￾tate neutron star LMXBs, pink stars indicate accreting mil￾lisecond X-ray pulsars (AMXPs), and light green upward triangles correspond to transitional millisecond pulsars (tM￾SPs). EP250916a is shown… view at source ↗
read the original abstract

We report multi-wavelength studies of the transient EP250916a, detected by the Einstein Probe on 2025 September 16. Located at low Galactic latitude, the source exhibited a rapid X-ray brightening, reaching an unabsorbed 0.5--10 keV flux of $(6.4 \pm 0.1) \times 10^{-10}$ erg cm$^{-2}$ s$^{-1}$, followed by a plateau and a two-stage decay lasting over 40 days. Swift/XRT monitoring shows a persistently hard spectrum ($\Gamma \approx 1.6$--2.2) with only modest softening during decay, while a NuSTAR observation confirms a hard-state continuum extending up to 70 keV. Timing analysis of XMM-Newton data reveals a weak quasi-periodic oscillation (QPO) at $\sim$13 Hz. No other coherent pulsations or thermonuclear bursts are detected. Broadband spectral modeling favors a nonthermal power-law continuum with partial-covering absorption, and shows no significant thermal disk component. Optical imaging obtained with NOT/ALFOSC, LCO, and GaiaDR3 identifies two faint sources within the 2 arcsec Swift/XRT positional uncertainty. A MeerKAT observation at 1.28 GHz yielded no radio counterpart, with a 3$\sigma$ upper limit of 60 $\mu$Jy beam$^{-1}$. The combination of a long-lasting outburst, a hard nonthermal X-ray spectrum, a weak QPO detection, the absence of coherent timing features, and faint potential optical counterparts disfavors a stellar-flare or extragalactic origin and supports an accreting compact-object scenario. Comparisons with similar faint, hard-state transients place EP250916a within a growing population of low-luminosity, hard-state black hole X-ray binary candidates.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript presents multi-wavelength observations of the Einstein Probe transient EP250916a, including Swift/XRT monitoring showing a long outburst (>40 days) with persistently hard spectrum (Γ ≈ 1.6–2.2), NuSTAR confirmation of hard continuum to 70 keV, XMM-Newton detection of a weak ~13 Hz QPO with no coherent pulsations or bursts, faint optical candidates from NOT/ALFOSC/LCO/Gaia, and a MeerKAT radio non-detection (3σ limit 60 μJy). The authors conclude these properties disfavor stellar-flare or extragalactic origins and support classification as a low-luminosity hard-state black hole X-ray binary candidate.

Significance. If the classification is robust, the work adds a well-observed member to the population of faint hard-state X-ray transients, providing constraints on accretion states at low luminosities and the observational distinction between compact-object classes. The multi-band coverage (X-ray timing/spectral, optical, radio) is a clear strength for future comparisons.

major comments (2)
  1. [Abstract] Abstract (final paragraph): The claim that the combination of properties 'disfavors' a neutron-star origin and supports a black-hole X-ray binary rests on qualitative similarity to 'similar faint, hard-state transients' without a control sample, overlap metrics, or quantitative likelihoods separating the observed Γ range, weak QPO, and non-detections from atoll-source or other NS hard-state properties. This is load-bearing for the central classification.
  2. [Abstract] Abstract (luminosity and comparisons): The source is placed in the 'low-luminosity' category and compared to known objects, yet the unabsorbed flux is given without a distance estimate, luminosity conversion, or justification for the Galactic-distance assumption despite the low Galactic latitude; this directly affects the luminosity class and population placement.
minor comments (1)
  1. [Abstract] The partial-covering absorption model and lack of thermal disk component are mentioned but would benefit from explicit parameter values or fit statistics in the main text for reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review of our manuscript. We address the two major comments point by point below, with revisions indicated where the manuscript will be updated.

read point-by-point responses

  1. Referee: [Abstract] Abstract (final paragraph): The claim that the combination of properties 'disfavors' a neutron-star origin and supports a black-hole X-ray binary rests on qualitative similarity to 'similar faint, hard-state transients' without a control sample, overlap metrics, or quantitative likelihoods separating the observed Γ range, weak QPO, and non-detections from atoll-source or other NS hard-state properties. This is load-bearing for the central classification.

    Authors: We agree that the classification argument is qualitative and relies on consistency with the properties of known faint hard-state black hole candidates rather than a statistical control sample or quantitative separation from neutron-star atoll sources. The combination of a >40-day hard-state outburst, persistently hard spectrum, weak ~13 Hz QPO without coherent pulsations or bursts, and radio non-detection is presented as more aligned with black hole systems, but we recognize the overlap possible with some neutron-star hard states. We have revised the abstract to emphasize the candidate nature of the classification and added a paragraph in the discussion section comparing the observed properties to both black hole and neutron star systems at low luminosities, while noting the absence of definitive discriminants such as dynamical mass measurements. revision: partial

  2. Referee: [Abstract] Abstract (luminosity and comparisons): The source is placed in the 'low-luminosity' category and compared to known objects, yet the unabsorbed flux is given without a distance estimate, luminosity conversion, or justification for the Galactic-distance assumption despite the low Galactic latitude; this directly affects the luminosity class and population placement.

    Authors: The reported value is the observed unabsorbed flux; the 'low-luminosity' descriptor and population comparison are based on the flux level matching that of known faint Galactic X-ray binaries. We have added explicit justification in the introduction and discussion for the Galactic-distance assumption: the low Galactic latitude, the transient X-ray behavior, and spectral/timing properties are characteristic of Galactic compact-object systems rather than extragalactic sources. No precise distance is available from the current data (no bright optical counterpart for spectroscopy and no Gaia parallax detection), so a numerical luminosity is not computed. We note that an extragalactic distance would yield an unrealistically high luminosity inconsistent with the observed flux and lack of other extragalactic indicators. revision: yes

Circularity Check

0 steps flagged

No circularity: classification rests on direct empirical comparison to external literature

full rationale

The paper reports multi-wavelength observations (X-ray spectra, timing, optical counterparts, radio non-detection) and classifies the transient by qualitative similarity to known faint hard-state sources in the published literature. No equations, fitted parameters, or derivations are present that reduce to the paper's own inputs by construction. No self-citation chains, uniqueness theorems, or ansatzes are invoked as load-bearing steps. The central claim is an interpretive comparison to independently observed objects and is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard domain assumptions about transient classification and a small number of fitted spectral parameters; no new entities are postulated.

free parameters (1)
  • Photon index Gamma = 1.6-2.2
    Fitted value range 1.6-2.2 from Swift/XRT and NuSTAR spectra; central to the hard-state classification.
axioms (2)
  • domain assumption Low Galactic latitude and lack of extragalactic signatures imply the source is Galactic.
    Invoked to exclude extragalactic origin.
  • domain assumption Absence of radio detection and specific timing features rules out alternative classes when compared to known objects.
    Used to support compact-object accretion scenario.

pith-pipeline@v0.9.1-grok · 5918 in / 1219 out tokens · 18190 ms · 2026-06-27T17:45:13.388525+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

65 extracted references · 60 canonical work pages · 4 internal anchors

  1. [1]

    Arnaud, K. A. 1996, in Astronomical Society of the Pacific Conference Series, Vol. 101, Astronomical Data Analysis Software and Systems V, ed. G. H. Jacoby & J. Barnes, 17 Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A, 558, A33, doi: 10.1051/0004-6361/201322068 Astropy Collaboration, Price-Whelan, A. M., Sip˝ ocz, B. M., et a...

    work page doi:10.1051/0004-6361/201322068 1996

  2. [2]

    International Journal of Modern Physics D , keywords =

    Atteia, J.-L., Cordier, B., & Wei, J. 2022, International Journal of Modern Physics D, 31, 2230008, doi: 10.1142/S0218271822300087

    work page doi:10.1142/s0218271822300087 2022

  3. [3]

    B., et al., 2009, @doi [ ] 10.1088/0004-637x/697/2/1071 , 697, 1071–1102

    Atwood, W. B., Abdo, A. A., Ackermann, M., et al. 2009, ApJ, 697, 1071, doi: 10.1088/0004-637X/697/2/1071

    work page doi:10.1088/0004-637x/697/2/1071 2009

  4. [5]

    2022, bersavosh/XRB-LrLx pub: update 20220908, v220908 Zenodo, doi: 10.5281/zenodo.7059313

    Bahramian, A., & Rushton, A. 2022, bersavosh/XRB-LrLx pub: update 20220908, v220908 Zenodo, doi: 10.5281/zenodo.7059313

    work page doi:10.5281/zenodo.7059313 2022

  5. [6]

    doi:10.1086/340290 , eprint =

    Belloni, T., Psaltis, D., & van der Klis, M. 2002, ApJ, 572, 392, doi: 10.1086/340290

    work page doi:10.1086/340290 2002

  6. [7]

    Belloni, T. M. 2010, in Lecture Notes in Physics, Berlin Springer Verlag, ed. T. Belloni, Vol. 794, 53, doi: 10.1007/978-3-540-76937-8 3

    work page doi:10.1007/978-3-540-76937-8 2010

  7. [8]

    2018, ApJ, 856, 180, doi: 10.3847/1538-4357/aab35a

    Camilo, F., Scholz, P., Serylak, M., et al. 2018, ApJ, 856, 180, doi: 10.3847/1538-4357/aab35a

    work page doi:10.3847/1538-4357/aab35a 2018

  8. [9]

    2022, PASP, 134, 114501, doi: 10.1088/1538-3873/ac9642

    Carroll, B. W., & Ostlie, D. A. 2006, An introduction to modern astrophysics and cosmology CASA Team, Bean, B., Bhatnagar, S., et al. 2022, PASP, 134, 114501, doi: 10.1088/1538-3873/ac9642

    work page internal anchor Pith review doi:10.1088/1538-3873/ac9642 2006

  9. [10]

    , keywords =

    Cash, W. 1979, ApJ, 228, 939, doi: 10.1086/156922

    work page doi:10.1086/156922 1979

  10. [11]

    R., & Livio, M

    Chen, W., Shrader, C. R., & Livio, M. 1997, ApJ, 491, 312, doi: 10.1086/304921

    work page doi:10.1086/304921 1997

  11. [12]

    Q., Zhao, Q

    Cheng, H. Q., Zhao, Q. C., Tao, L., et al. 2025, ApJL, 991, L41, doi: 10.3847/2041-8213/adf104

    work page doi:10.3847/2041-8213/adf104 2025

  12. [13]

    2025, The Astronomer’s Telegram, 17396, 1

    Coleiro, A., Maggi, P., Cangemi, F., & Lachaud, C. 2025, The Astronomer’s Telegram, 17396, 1

    2025

  13. [14]

    2013, MNRAS, 428, 2500, doi: 10.1093/mnras/sts215

    Corbel, S., Coriat, M., Brocksopp, C., et al. 2013, MNRAS, 428, 2500, doi: 10.1093/mnras/sts215

    work page doi:10.1093/mnras/sts215 2013

  14. [15]

    M., Casares, J., Mu˜ noz-Darias, T., et al

    Corral-Santana, J. M., Casares, J., Mu˜ noz-Darias, T., et al. 2016, A&A, 587, A61, doi: 10.1051/0004-6361/201527130

    work page doi:10.1051/0004-6361/201527130 2016

  15. [16]

    M., Casares, J., Mu˜ noz-Darias, T., et al

    Corral-Santana, J. M., Casares, J., Mu˜ noz-Darias, T., et al. 2013, Science, 339, 1048, doi: 10.1126/science.1228222

    work page doi:10.1126/science.1228222 2013

  16. [17]

    Y., Wu, Q

    Dai, C. Y., Wu, Q. Y., Li, D. Y., Pan, H. W., & Einstein Probe Team. 2025b, GRB Coordinates Network, 41861, 1 D’Avanzo, P. 2015, Journal of High Energy Astrophysics, 7, 73, doi: 10.1016/j.jheap.2015.07.002 Di Salvo, T., Papitto, A., Marino, A., Iaria, R., & Burderi, L. 2023, in Handbook of X-ray and Gamma-ray Astrophysics, 147, doi: 10.1007/978-981-16-454...

    work page doi:10.1016/j.jheap.2015.07.002 2015

  17. [18]

    2007, A&A Rv, 15, 1, doi: 10.1007/s00159-007-0006-1

    Done, C., Gierli´ nski, M., & Kubota, A. 2007, A&A Rv, 15, 1, doi: 10.1007/s00159-007-0006-1

    work page doi:10.1007/s00159-007-0006-1 2007

  18. [19]

    2001, A&A, 373, 251, doi: 10.1051/0004-6361:20010632

    Dubus, G., Hameury, J.-M., & Lasota, J.-P. 2001, A&A, 373, 251, doi: 10.1051/0004-6361:20010632

    work page doi:10.1051/0004-6361:20010632 2001

  19. [20]

    2025, The Open Journal of Astrophysics, 8, 62, doi: 10.33232/001c.138448

    El-Badry, K. 2025, The Open Journal of Astrophysics, 8, 62, doi: 10.33232/001c.138448

    work page doi:10.33232/001c.138448 2025

  20. [21]

    2009, MNRAS, 400, 1181, doi: 10.1111/j.1365-2966.2009.15528.x

    Evans, P. A., Beardmore, A. P., Page, K. L., et al. 2009, MNRAS, 397, 1177, doi: 10.1111/j.1365-2966.2009.14913.x Gaia Collaboration, Vallenari, A., Brown, A. G. A., et al. 2023, A&A, 674, A1, doi: 10.1051/0004-6361/202243940

    work page doi:10.1111/j.1365-2966.2009.14913.x 2009

  21. [22]

    , keywords =

    Gehrels, N., Chincarini, G., Giommi, P., et al. 2004, ApJ, 611, 1005, doi: 10.1086/422091

    work page doi:10.1086/422091 2004

  22. [23]

    R., Tyler, L

    Goad, M. R., Tyler, L. G., Beardmore, A. P., et al. 2007, A&A, 476, 1401, doi: 10.1051/0004-6361:20078436 G¨ unther, H. M., Pasham, D., Binks, A., et al. 2024, ApJ, 977, 6, doi: 10.3847/1538-4357/ad8b2c G¨ uver, T., &¨Ozel, F. 2009, MNRAS, 400, 2050, doi: 10.1111/j.1365-2966.2009.15598.x

    work page doi:10.1051/0004-6361:20078436 2007

  23. [24]

    A., Craig, W

    Harrison, F. A., Craig, W. W., Christensen, F. E., et al. 2013, ApJ, 770, 103, doi: 10.1088/0004-637X/770/2/103

    work page doi:10.1088/0004-637x/770/2/103 2013

  24. [25]

    2020, oxkat: Semi-automated imaging of MeerKAT observations,, Astrophysics Source Code Library, record ascl:2009.003 HI4PI Collaboration, Ben Bekhti, N., Fl¨ oer, L., et al

    Heywood, I. 2020, oxkat: Semi-automated imaging of MeerKAT observations,, Astrophysics Source Code Library, record ascl:2009.003 HI4PI Collaboration, Ben Bekhti, N., Fl¨ oer, L., et al. 2016, A&A, 594, A116, doi: 10.1051/0004-6361/201629178

    work page doi:10.1051/0004-6361/201629178 2020

  25. [26]

    2005, Ap&SS, 300, 107, doi: 10.1007/s10509-005-1197-4

    Homan, J., & Belloni, T. 2005, Ap&SS, 300, 107, doi: 10.1007/s10509-005-1197-4

    work page doi:10.1007/s10509-005-1197-4 2005

  26. [27]

    Astronomical Data Analysis Software and Systems XXX , year = 2022, editor =

    Hugo, B. V., Perkins, S., Merry, B., Mauch, T., & Smirnov, O. M. 2022, in Astronomical Society of the Pacific Conference Series, Vol. 532, Astronomical Society of the Pacific Conference Series, ed. J. E. Ruiz, F. Pierfedereci, & P. Teuben, 541, doi: 10.48550/arXiv.2206.09179

    work page doi:10.48550/arxiv.2206.09179 2022

  27. [28]

    M., Sbarufatti, B., et al

    Illiano, G., Zanon, A. M., Sbarufatti, B., et al. 2025, The Astronomer’s Telegram, 17397, 1

    2025

  28. [29]

    R., & Motta, S

    Ingram, A. R., & Motta, S. E. 2019, NewAR, 85, 101524, doi: 10.1016/j.newar.2020.101524

    work page doi:10.1016/j.newar.2020.101524 2019

  29. [30]

    K., & Naik, S

    Jaisawal, G. K., & Naik, S. 2015, MNRAS, 448, 620, doi: 10.1093/mnras/stv029

    work page doi:10.1093/mnras/stv029 2015

  30. [31]

    K., Naik, S., Ho, W

    Jaisawal, G. K., Naik, S., Ho, W. C. G., et al. 2020, MNRAS, 498, 4830, doi: 10.1093/mnras/staa2604

    work page doi:10.1093/mnras/staa2604 2020

  31. [32]

    K., Wilson-Hodge, C

    Jaisawal, G. K., Wilson-Hodge, C. A., Fabian, A. C., et al. 2019, ApJ, 885, 18, doi: 10.3847/1538-4357/ab4595

    work page doi:10.3847/1538-4357/ab4595 2019

  32. [33]

    K., Chenevez, J., Strohmayer, T

    Jaisawal, G. K., Chenevez, J., Strohmayer, T. E., et al. 2025b, ApJ, 986, 16, doi: 10.3847/1538-4357/adcc24

    work page doi:10.3847/1538-4357/adcc24

  33. [34]

    K., et al

    Jana, A., Naik, S., Jaisawal, G. K., et al. 2022, MNRAS, 511, 3922, doi: 10.1093/mnras/stac315

    work page doi:10.1093/mnras/stac315 2022

  34. [35]

    K., Naik, S., et al

    Jana, A., Jaisawal, G. K., Naik, S., et al. 2021, Research in Astronomy and Astrophysics, 21, 125, doi: 10.1088/1674-4527/21/5/125

    work page doi:10.1088/1674-4527/21/5/125 2021

  35. [36]

    2001, A&A, 365, L1, doi: 10.1051/0004-6361:20000036

    Jansen, F., Lumb, D., Altieri, B., et al. 2001, A&A, 365, L1, doi: 10.1051/0004-6361:20000036 16

    work page doi:10.1051/0004-6361:20000036 2001

  36. [37]

    MeerKAT Science: On the Pathway to the SKA , year = 2016, month = jan, eid =

    Jonas, J., & MeerKAT Team. 2016, in MeerKAT Science: On the Pathway to the SKA, 1, doi: 10.22323/1.277.0001

    work page doi:10.22323/1.277.0001 2016

  37. [38]

    MNRAS , eprint =

    King, A. R., & Ritter, H. 1998, MNRAS, 293, L42, doi: 10.1046/j.1365-8711.1998.01295.x

    work page doi:10.1046/j.1365-8711.1998.01295.x 1998

  38. [39]

    doi:10.1111/j.1745-3933.2005.00057.x , eprint =

    King, A. R., & Wijnands, R. 2006, MNRAS, 366, L31, doi: 10.1111/j.1745-3933.2005.00126.x

    work page doi:10.1111/j.1745-3933.2005.00126.x 2006

  39. [40]

    2015, Journal of High Energy Astrophysics, 7, 148, doi: 10.1016/j.jheap.2015.04.006

    Komossa, S. 2015, Journal of High Energy Astrophysics, 7, 148, doi: 10.1016/j.jheap.2015.04.006

    work page doi:10.1016/j.jheap.2015.04.006 2015

  40. [41]

    Kouveliotou, C., Wijers, R. A. M. J., & Woosley, S. 2012, Gamma-ray Bursts

    2012

  41. [42]

    W., Mierle, K., Blanton, M., & Roweis, S

    Lang, D., Hogg, D. W., Mierle, K., Blanton, M., & Roweis, S. 2010, AJ, 139, 1782, doi: 10.1088/0004-6256/139/5/1782

    work page doi:10.1088/0004-6256/139/5/1782 2010

  42. [43]

    Lewin, W. H. G., van Paradijs, J., & van den Heuvel, E. P. J. 1997, X-ray Binaries

    1997

  43. [44]

    2012, Nature, 485, 478, doi: 10.1038/nature11063

    Maehara, H., Shibayama, T., Notsu, S., et al. 2012, Nature, 485, 478, doi: 10.1038/nature11063

    work page doi:10.1038/nature11063 2012

  44. [45]

    2025, ApJ, 980, 268, doi: 10.3847/1538-4357/ada698

    Mao, X., Liu, H.-Y., Wang, S., et al. 2025, ApJ, 980, 268, doi: 10.3847/1538-4357/ada698

    work page doi:10.3847/1538-4357/ada698 2025

  45. [46]

    2009, PASJ, 61, 999, doi: 10.1093/pasj/61.5.999

    Matsuoka, M., Kawasaki, K., Ueno, S., et al. 2009, PASJ, 61, 999, doi: 10.1093/pasj/61.5.999

    work page doi:10.1093/pasj/61.5.999 2009

  46. [47]

    eROSITA Science Book: Mapping the Structure of the Energetic Universe

    Merloni, A., Predehl, P., Becker, W., et al. 2012, arXiv e-prints, arXiv:1209.3114, doi: 10.48550/arXiv.1209.3114

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.1209.3114 2012

  47. [48]

    Migliari, S., & Fender, R. P. 2006, MNRAS, 366, 79, doi: 10.1111/j.1365-2966.2005.09777.x

    work page doi:10.1111/j.1365-2966.2005.09777.x 2006

  48. [49]

    2017, MNRAS, 468, 981, doi: 10.1093/mnras/stx466 Nasa High Energy Astrophysics Science Archive Research Center (Heasarc)

    Giustini, M., & Kuulkers, E. 2017, MNRAS, 468, 981, doi: 10.1093/mnras/stx466 Nasa High Energy Astrophysics Science Archive Research Center (Heasarc). 2014, HEAsoft: Unified Release of FTOOLS and XANADU,, Astrophysics Source Code Library, record ascl:1408.004 http://ascl.net/1408.004

    work page doi:10.1093/mnras/stx466 2017

  49. [50]

    R., McKinley, B., Hurley-Walker, N., et al

    Offringa, A. R., McKinley, B., Hurley-Walker, N., et al. 2014, MNRAS, 444, 606, doi: 10.1093/mnras/stu1368

    work page doi:10.1093/mnras/stu1368 2014

  50. [51]

    2021, ApJ, 906, 72, doi: 10.3847/1538-4357/abc8f5

    Okamoto, S., Notsu, Y., Maehara, H., et al. 2021, ApJ, 906, 72, doi: 10.3847/1538-4357/abc8f5

    work page doi:10.3847/1538-4357/abc8f5 2021

  51. [52]

    2005, A&A, 430, L9, doi: 10.1051/0004-6361:200400117

    Porquet, D., Grosso, N., Burwitz, V., et al. 2005, A&A, 430, L9, doi: 10.1051/0004-6361:200400117

    work page doi:10.1051/0004-6361:200400117 2005

  52. [53]

    2004, A&A, 418, 927, doi: 10.1051/0004-6361:20035798

    Revnivtsev, M., Sazonov, S., Jahoda, K., & Gilfanov, M. 2004, A&A, 418, 927, doi: 10.1051/0004-6361:20035798

    work page doi:10.1051/0004-6361:20035798 2004

  53. [54]

    MNRAS , keywords =

    Russell, D. M., Fender, R. P., Hynes, R. I., et al. 2006, MNRAS, 371, 1334, doi: 10.1111/j.1365-2966.2006.10756.x

    work page doi:10.1111/j.1365-2966.2006.10756.x 2006

  54. [55]

    A., Vierdayanti, K., & Premadi, P

    Saraswati, T. A., Vierdayanti, K., & Premadi, P. W. 2025, MNRAS, 537, 1146, doi: 10.1093/mnras/staf042

    work page doi:10.1093/mnras/staf042 2025

  55. [56]

    W., Miller, J

    Shaw, A. W., Miller, J. M., Grinberg, V., et al. 2022, MNRAS, 516, 124, doi: 10.1093/mnras/stac2213 Str¨ uder, L., Briel, U., Dennerl, K., et al. 2001, A&A, 365, L18, doi: 10.1051/0004-6361:20000066

    work page doi:10.1093/mnras/stac2213 2022

  56. [57]

    Gladstone, J. C. 2016, ApJS, 222, 15, doi: 10.3847/0067-0049/222/2/15 van Hoof, P. A. M. 2018, Galaxies, 6, 63, doi: 10.3390/galaxies6020063

    work page doi:10.3847/0067-0049/222/2/15 2016

  57. [58]

    A., Ferland, G

    Verner, D. A., Ferland, G. J., Korista, K. T., & Yakovlev, D. G. 1996, ApJ, 465, 487, doi: 10.1086/177435

    work page internal anchor Pith review doi:10.1086/177435 1996

  58. [59]

    M., Foltz, C

    Wagner, R. M., Foltz, C. B., Shahbaz, T., et al. 2001, ApJ, 556, 42, doi: 10.1086/321572

    work page doi:10.1086/321572 2001

  59. [60]

    J., et al

    Walter, R., Bodaghee, A., Barlow, E. J., et al. 2004, The Astronomer’s Telegram, 229, 1

    2004

  60. [61]

    2019, ApJ, 877, 116, doi: 10.3847/1538-4357/ab1c61

    Wang, S., & Chen, X. 2019, ApJ, 877, 116, doi: 10.3847/1538-4357/ab1c61

    work page doi:10.3847/1538-4357/ab1c61 2019

  61. [62]

    E., Swank, J

    White, N. E., Swank, J. H., & Holt, S. S. 1983, ApJ, 270, 711, doi: 10.1086/161162

    work page doi:10.1086/161162 1983

  62. [63]

    , eprint =

    Wilms, J., Allen, A., & McCray, R. 2000, ApJ, 542, 914, doi: 10.1086/317016

    work page internal anchor Pith review doi:10.1086/317016 2000

  63. [64]

    J.-L., Di Cocco, G., et al

    Winkler, C., Courvoisier, T. J.-L., Di Cocco, G., et al. 2003, A&A, 411, L1, doi: 10.1051/0004-6361:20031288

    work page doi:10.1051/0004-6361:20031288 2003

  64. [65]

    2022, in Handbook of X-ray and Gamma-ray Astrophysics, ed

    Yuan, W., Zhang, C., Chen, Y., & Ling, Z. 2022, in Handbook of X-ray and Gamma-ray Astrophysics, ed. C. Bambi & A. Sangangelo, 86, doi: 10.1007/978-981-16-4544-0 151-1

    work page doi:10.1007/978-981-16-4544-0 2022

  65. [66]

    2025, Galaxies, 13, 111, doi: 10.3390/galaxies13050111

    Zhu, H., & Wang, W. 2025, Galaxies, 13, 111, doi: 10.3390/galaxies13050111

    work page doi:10.3390/galaxies13050111 2025