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# Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?

Buisson, D. J. K., Altamirano, D., Trigo, M. Díaz, Mendez, M., Padilla, M. Armas, Segura, N. Castro, Degenaar, N. D., Eijnden, J. van den, Fogantini, F. A., Gandhi, P., Knigge, C., Muñoz-Darias, T., Arabacı, M. Özbey and Vincentelli, F. M. (2020) Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind? Monthly Notices of the Royal Astronomical Society: Letters.

Record type: Article

## Abstract

We find soft X-ray emission lines from the X-ray binary Swift J1858.6-0814 in data from XMM-Newton-RGS: N VII, O VII and O VIII, as well as notable residuals short of a detection at Ne IX and other higher ionisation transitions. These could be associated with the disc atmosphere, as in accretion disc corona sources, or with a wind, as has been detected in Swift J1858.6-0814 in emission lines at optical wavelengths. Indeed, the N VII line is redshifted, consistent with being the emitting component of a P-Cygni profile. We find that the emitting plasma has an ionisation parameter $\log(\xi)=1.35\pm0.2$ and a density $n>1.5\times10^{11}$ cm$^{-3}$. From this, we infer that the emitting plasma must be within $10^{13}$ cm of the ionising source, $\sim5\times10^{7}r_{\rm g}$ for a $1.4M_{\odot}$ neutron star, and from the line width that it is at least $10^4r_{\rm g}$ away ($2\times10^{9}(M/1.4M_{\odot})$ cm). We compare this with known classes of emission line regions in other X-ray binaries and active galactic nuclei.

Text
Soft X-ray emission lines in the X-ray binary Swift - Version of Record

Published date: 28 July 2020
Additional Information: 10 pages, 7 figures, MNRAS accepted
Keywords: astro-ph.HE

## Identifiers

Local EPrints ID: 443650
URI: http://eprints.soton.ac.uk/id/eprint/443650
ISSN: 1745-3925
PURE UUID: aae85fbc-9b77-4b2c-befb-e576a2df2be8
ORCID for D. Altamirano: orcid.org/0000-0002-3422-0074
ORCID for P. Gandhi: orcid.org/0000-0003-3105-2615

## Catalogue record

Date deposited: 07 Sep 2020 16:30

## Contributors

Author: D. J. K. Buisson
Author: D. Altamirano
Author: M. Díaz Trigo
Author: M. Mendez
Author: N. D. Degenaar
Author: J. van den Eijnden
Author: F. A. Fogantini
Author: P. Gandhi
Author: C. Knigge
Author: T. Muñoz-Darias
Author: M. Özbey Arabacı

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