Three spectral states of the disk X-ray emission of the black-hole candidate 4U 1630-47

Yukiko Abe, Yasushi Fukazawa, Aya Kubota, Daisuke Kasama, Kazuo Makishima

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

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 the Rossi X-Ray Timing Explorer over 1996-2004. These observations covered five outbursts of 4U 1630-47, and recorded typical features of the high/soft states. The spectra in the high/soft states can be classified into three states. The first state is explained by a concept of the standard accretion disk picture. The second appears in the very high state, where a dominant hard component is seen and the disk radius apparently becomes too small. These phenomena are explained by the effect of inverse Compton scattering of disk photons, as shown by Kubota, Makishima, and Ebisawa (2001, ApJ, 560, L147) for GRO J1655-40. The third shows that the disk luminosity varies in proportion to T in 2, rather than T in 4, where T in is the inner-disk temperature. This state suggests an optically-thick and advection-dominated slim disk, as given by Kubota and Makishima (2004, ApJ, 601, 428) for XTE J1550-564. The second and third states appear, with good reproducibility, when T in and the total X-ray luminosity are higher than 1.2 keV and ∼ 2.5 × 10 38(D/10 kpc) 2[cosθ/(1/√3)] -1 ergs -1, respectively, where D is the distance to the object and θ is the inclination angle to the disk. The results suggest that these spectral states commonly appear among black-hole binaries under high accretion rates.

Original languageEnglish
Pages (from-to)629-641
Number of pages13
JournalPublications of the Astronomical Society of Japan
Volume57
Issue number4
Publication statusPublished - 2005
Externally publishedYes

Fingerprint

accretion
x rays
outburst
erg
advection
luminosity
scattering
X Ray Timing Explorer
monitoring
history
accretion disks
inclination
proportion
temperature
histories
radii
photons
effect
rate

Keywords

  • Accretion, accretion disks
  • Black hole physics
  • Stars: individual (4U 1630-47)
  • X-rays: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Three spectral states of the disk X-ray emission of the black-hole candidate 4U 1630-47. / Abe, Yukiko; Fukazawa, Yasushi; Kubota, Aya; Kasama, Daisuke; Makishima, Kazuo.

In: Publications of the Astronomical Society of Japan, Vol. 57, No. 4, 2005, p. 629-641.

Research output: Contribution to journalArticle

Abe, Yukiko ; Fukazawa, Yasushi ; Kubota, Aya ; Kasama, Daisuke ; Makishima, Kazuo. / Three spectral states of the disk X-ray emission of the black-hole candidate 4U 1630-47. In: Publications of the Astronomical Society of Japan. 2005 ; Vol. 57, No. 4. pp. 629-641.
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abstract = "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 the Rossi X-Ray Timing Explorer over 1996-2004. These observations covered five outbursts of 4U 1630-47, and recorded typical features of the high/soft states. The spectra in the high/soft states can be classified into three states. The first state is explained by a concept of the standard accretion disk picture. The second appears in the very high state, where a dominant hard component is seen and the disk radius apparently becomes too small. These phenomena are explained by the effect of inverse Compton scattering of disk photons, as shown by Kubota, Makishima, and Ebisawa (2001, ApJ, 560, L147) for GRO J1655-40. The third shows that the disk luminosity varies in proportion to T in 2, rather than T in 4, where T in is the inner-disk temperature. This state suggests an optically-thick and advection-dominated slim disk, as given by Kubota and Makishima (2004, ApJ, 601, 428) for XTE J1550-564. The second and third states appear, with good reproducibility, when T in and the total X-ray luminosity are higher than 1.2 keV and ∼ 2.5 × 10 38(D/10 kpc) 2[cosθ/(1/√3)] -1 ergs -1, respectively, where D is the distance to the object and θ is the inclination angle to the disk. The results suggest that these spectral states commonly appear among black-hole binaries under high accretion rates.",
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