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

• Autores: Buisson, D. J. K.; Altamirano, Diego; Diaz Trigo, M.; Mendez, Mariano; Padilla, M. Armas; Castro Segura, N.; Degenaar, Nathalie; van den Eijnden, J.; Fogantini, Federico Adrián; Gandhi, Poshak; Knigge, Christian; Muñoz-Darias, T.; Arabaci, M. Ozbey; Vincentelli, F. M.
• Año de publicación: 2020
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Astronómicas; Accretion; Accretion discs; Black hole physics; Stars: neutron; X-rays: binaries
• Institución: Universidad Nacional de La Plata

We find soft X-ray emission lines from the X-ray binary Swift J1858.6–0814 in data from XMM–NewtonReflection Grating Spectrometer (RGS): N VII, O VII, and O VIII, as well as notable residuals short of a detection at Ne IX and other higher ionization 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 ionization parameter log (ξ) = 1.35 ± 0.2 and a density n > 1.5 × 10¹¹ cm⁻³. From this, we infer that the emitting plasma must be within 1013 cm of the ionizing source, ∼5 × 10⁷ rg for a 1.4 M⊙ neutron star, and from the line width that it is at least 10⁴ rg away [2 × 10⁹(M/1.4 M⊙) cm]. We compare this with known classes of emission-line regions in other X-ray binaries and active galactic nuclei.
Facultad de Ciencias Astronómicas y Geofísicas