Spectral Transitions of an Ultraluminous X-Ray Source, NGC 2403 Source 3
| Autor: | Hiromitsu Takahashi, Hiroshi Kobori, Atsushi Senda, Aya Kubota, Tsunefumi Mizuno, Poshak Gandhi, Kazuo Makishima, Ryouhei Miyawaki, Madoka Kawaharada, Naoki Isobe, Tessei Yoshida |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Physics
Ultraluminous X-ray source Photon Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) FOS: Physical sciences Astronomy and Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics Radius Spectral line Luminosity Black hole symbols.namesake Accretion disc Space and Planetary Science Eddington luminosity symbols Astrophysics::Earth and Planetary Astrophysics Astrophysics::Galaxy Astrophysics |
| Zdroj: | Publications of the Astronomical Society of Japan. 61:S279-S289 |
| ISSN: | 2053-051X 0004-6264 |
| DOI: | 10.1093/pasj/61.sp1.s279 |
| Popis: | Suzaku observation of an ultraluminous X-ray source, NGC 2403 Source 3, performed on 2006 March 16--17, is reported. The Suzaku XIS spectrum of Source 3 was described with a multi-color black-body-like emission from an optically thick accretion disk. The innermost temperature and radius of the accretion disk was measured to be $T_{\rm in} = 1.08_{-0.03}^{+0.02} $ keV and $R_{\rm in} = 122.1_{-6.8}^{+7.7} \alpha^{1/2}$ km, respectively, where $\alpha = (\cos 60^\circ /\cos i)$ with $i$ being the disk inclination. The bolometric luminosity of the source was estimated to be $L_{\rm bol} = 1.82 \times 10^{39} \alpha $ ergs s$^{-1}$. Archival Chandra and XMM-Newton data of the source were analyzed for long-term spectral variations. In almost all observations, the source showed multi-color black-body-like X-ray spectra with parameters similar to those in the Suzaku observation. In only one Chandra observation, however, Source 3 was found to exhibit a power-law-like spectrum, with a photon index of $\Gamma = 2.37 \pm 0.08$, when it was fainter by about $\sim 15 %$ than in the Suzaku observation. The spectral behavior is naturally explained in terms of a transition between the slim disk state and the "very high" states, both found in Galactic black hole binaries when their luminosity approach the Eddington limit. These results are utilized to argue that ultraluminous X-ray sources generally have significantly higher black-hole masses than ordinary stellar-mass black holes. Comment: Accepted for PASJ 3nd Suzaku special issue |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|