Issue |
A&A
Volume 693, January 2025
|
|
---|---|---|
Article Number | A260 | |
Number of page(s) | 16 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202348708 | |
Published online | 23 January 2025 |
Multi-wavelength study of 1eRASS J085039.9−421151 with eROSITA, NuSTAR, and X-shooter
1
Dr. Karl-Remeis Sternwarte and Erlangen Centre for Astroparticle Physics, Friedrich-Alexander Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
2
Universität Tübingen, Institut für Astronomie und Astrophysik Tübingen, Sand 1, 72076 Tübingen, Germany
3
University of Maryland College Park, Department of Astronomy, College Park MD 20742, USA
4
NASA Goddard Space Flight Center, Astrophysics Science Division, Greenbelt, MD 20771, USA
5
European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
6
Center for Space Science and Technology, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
7
Embry Riddle Aeronautical University, Department of Physics, 3700 Willow Creek Road, Prescott, AZ 86301, USA
8
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
9
Department of Physics and Astronomy, Howard University, Washington, DC 20059, USA
10
Department of Astronomy and Astrophysics, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0424, USA
11
Praxis Inc., Alexandria, VA 22303, resident at Naval Research Laboratory, Washington, DC 20375, USA
12
ESICT, Valencian International University, Pintor Sorolla 21, 46002 Valencia, Spain
13
Telespazio UK for ESA, European Space Astronomy Center (ESAC), Camino bajo del castillo S/N, 28692 Villanueva de la Cañada, Spain
⋆ Corresponding author; aafiazainab.ansar@fau.de
Received:
22
November
2023
Accepted:
30
October
2024
The eROSITA instrument on board Spectrum-Roentgen-Gamma (SRG) has completed four scans of the X-ray sky, leading to the detection of almost one million X-ray sources in eRASS1 alone, including multiple new X-ray binary candidates. We report on analysis of the X-ray binary 1eRASS J085039.9−421151, using a ∼55 ks long NuSTAR observation, following its detection in each eROSITA scan. An analysis of the eROSITA and NuSTAR X-ray spectra in combination with X-shooter data of the optical counterpart provide evidence of an X-ray binary with a red supergiant (RSG) companion, confirming previous results. However, we did determine a cooler spectral type for M2–3, owing to the presence of TiO bands in the optical and near-infrared spectra. The X-ray spectrum is well-described by an absorbed power law with a high-energy cutoff typically applied for accreting high mass X-ray binaries. In addition, we detected a strong fluorescent neutral iron line with an equivalent width of ∼700 eV and an absorption edge, the latter indicating strong absorption by a partial covering component. It is unclear whether the partial absorber is ionised. There is no significant evidence of a cyclotron resonant scattering feature. We did not detect any pulsations in the NuSTAR light curves, possibly on account of a large spin period that has gone undetected due to insufficient statistics at low frequencies or potentially large absorption that causes pulsations to be smeared out. Even so, the low persistent luminosity, the spectral parameters observed (photon index, Γ < 1.0), and the minuscule likelihood of detection of RSG-black hole systems suggest that the compact object is a neutron star.
Key words: stars: emission-line / Be / stars: neutron / X-rays: binaries
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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