Rapid spectral transition of the black hole binary V404 Cygni
During the June 2015 outburst of the black hole binary V404 Cyg, rapid changes in the X-ray brightness and spectra were common. The INTEGRAL monitoring campaign detected spectacular Eddington-limited X-ray flares, but also rapid variations at much lower flux levels. On 2015 June 21 at 20 h 50 min, t...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2020 |
| País: | España |
| Institución: | Instituto Nacional de Técnica Aeroespacial (INTA) |
| Repositorio: | DIGITAL.INTA Repositorio Digital del Instituto Nacional de Técnica Aeroespacial |
| OAI Identifier: | oai:digital.inta.es:20.500.12666/259 |
| Acceso en línea: | https://www.aanda.org/articles/aa/full_html/2020/02/aa37191-19/aa37191-19.html http://hdl.handle.net/20.500.12666/259 |
| Access Level: | acceso abierto |
| Palabra clave: | Accretion Accretion disks Black hole physics X rays: binaries X rays: individuals: V404 Cyg |
| Sumario: | During the June 2015 outburst of the black hole binary V404 Cyg, rapid changes in the X-ray brightness and spectra were common. The INTEGRAL monitoring campaign detected spectacular Eddington-limited X-ray flares, but also rapid variations at much lower flux levels. On 2015 June 21 at 20 h 50 min, the 3–10 keV JEM-X data as well as simultaneous optical data started to display a gradual brightening from one of these low-flux states. This was followed 15 min later by an order-of-magnitude increase of flux in the 20–40 keV IBIS/ISGRI light curve in just 15 s. The best-fitting model for both the pre- and post-transition spectra required a Compton-thick partially covering absorber. The absorber parameters remained constant, but the spectral slope varied significantly during the event, with the photon index decreasing from Γ ≈ 3.7 to Γ ≈ 2.3. We propose that the rapid 20–40 keV flux increase was either caused by a spectral state transition that was hidden from our direct view, or that there was a sudden reduction in the amount of Compton down-scattering of the primary X-ray emission in the disk outflow. |
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