English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We studied a time history of X-ray spectral states of a black-hole candidate,4U 1630-47, utilizing data from a number of monitoring observations with theRossi X-Ray Timing Explorer over 1996--2004. These observations covered fiveoutbursts of 4U 1630-47, and most of the data recorded typical features of thehigh/soft states. We found that the spectra in the high/soft states can befurther classified into three states. The first spectral state is explained bya concept of the standard accretion disk picture. The second state appears inthe so-called very high state, where a dominant hard component is seen and thedisk radius apparently becomes too small. These phenomena are explained by theeffect of inverse Compton scattering of disk photons, as shown by Kubota,Makishima, & Ebisawa (2001, ApJ, 560, L147) for GRO J1655-40. The third stateis characterized in such a way that the disk luminosity varies in proportion to$T_{\rm in}^2$, rather than $T_{\rm in}^4$, where $T_{\rm in}$ is theinner-disk temperature. This state is suggested to be an optically-thick andadvection-dominated slim disk, as suggested by Kubota & Makishima (2004, ApJ,601, 428) for XTE J1550-564. The second and third states appear, with goodreproducibility, when $T_{\rm in}$ and the total X-ray luminosity are higherthan 1.2 keV and $\sim2.5\times10^{38}(D/10\quad{\rm kpc})^2\left[\cos{\theta}/(1/\sqrt{3})]^{-1}$ erg s$^{-1}$, respectively, where $D$ isthe distance to the object and $\theta$ is the inclination angle to the disk.The present results suggest that these three spectral states commonly appearamong black-hole binaries under high accretion rates.Comment: 24 pages, 9 figures, to appear in PASJ 57 p.62

Three Spectral States of the Disk X-Ray Emission of the Black-Hole Candidate 4U 1630−47