| タイトル | ROSAT observations of the black hole candidate V404 Cygni in quiescence |
| 著者（英） | Hjellming, R. M.; Kreidl, T. J.; Howell, S. B.; Wagner, R. Mark; Starrfield, S. G. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 1994-07-01 |
| 言語 | eng |
| 内容記述 | V404 Cyg was detected with the ROSAT PSPC in a 16 ks observation 1265 days after the 1989 May outburst. This is the first unambiguous detection of a soft X-ray transient or X-ray nova black hole candidate in quiescence. The observed X-ray spectrum is extremely soft and can be described equally well by either a blackbody, power-law, or a thermal bremsstrahlung continuum. The best-fit blackbody spectrum is characterized by a temperature of 0.2 keV. A significant amount of absorption, both along the line of sight and intrinsic to the V404 Cyg system, is required to understand the observations. The 0.2-2.4 keV light curve of V404 Cyg exhibits substantial variability on timescales of less than a day. Assuming a distance of 3.5 kpc, the quiescent X-ray luminosity of V404 Cyg is 8 x 10(exp 33) ergs/s, nearly two orders of magnitude larger than the upper such as Cen X-4. The lack of a significant hard X-ray luminosity in quiescence, the presence of a large and cold neutral region in the accretion disk, and a low-mass accretion rate suggests that an accretion disk instability might account for the outburst of V404 Cyg. |
| NASA分類 | ASTRONOMY |
| レポートNO | 95A61284 |
| 権利 | Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/311131 |
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