Inner Disk Structure of Dwarf Novae in the Light of X-Ray Observations
| Autor: | Solen Balman |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences Astronomy White dwarf Radius Astrophysics Cooling flow Light curve Accretion (astrophysics) Intermediate polar lcsh:TA1-2040 Thick disk Astrophysics::Solar and Stellar Astrophysics General Earth and Planetary Sciences Astrophysics::Earth and Planetary Astrophysics lcsh:Engineering (General). Civil engineering (General) Astrophysics - High Energy Astrophysical Phenomena Dwarf nova Astrophysics::Galaxy Astrophysics General Environmental Science |
| Zdroj: | Acta Polytechnica CTU Proceedings, Vol 2, Iss 1, Pp 116-122 (2015) |
| ISSN: | 2336-5382 |
| DOI: | 10.14311/app.2015.02.0116 |
| Popis: | Diversity of the X-ray observations of dwarf nova are still not fully understood. I review the X-ray spectral characteristics of dwarf novae during the quiescence in general explained by cooling flow models and the outburst spectra that show hard X-ray emission dominantly with few sources that reveal soft X-ray/EUV blackbody emission. The nature of aperiodic time variability of brightness of dwarf novae shows band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break (1-6 mHz) indicates inner disk truncation of the optically thick disk with a range of radii (3.0-10.0)$\times$10$^{9}$ cm. The RXTE and optical (RTT150) data of SS Cyg in outburst and quiescence reveal that the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. A preliminary analysis of SU UMa indicates a similar behaviour. In addition, I find that the outburst spectra of WZ Sge shows two component spectrum of only hard X-ray emission, one of which may be fitted with a power law suggesting thermal Comptonization occuring in the system. Cross-correlations between the simultaneous UV and X-ray light curves (XMM-Newton) of five DNe in quiescence show time lags in the X-rays of 96-181 sec consistent with travel time of matter from a truncated inner disk to the white dwarf surface. All this suggests that dwarf novae and other plausible nonmagnetic systems have truncated accretion disks indicating that the disks may be partially evaporated and the accretion may occur through hot (coronal) flows in the disk. Comment: 7 pages and 10 figures, accepted for publication in Acta Polytechnica as proceedings of the 2013 workshop on "The Golden Age of Cataclysmic Variables and Related Objects - II", Franco Giovannelli & Lola Sabau-Graziati (eds.) |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|