Evidence for a black hole in the x-ray transient GRS 1009-45

Aya Kubota, Yasuo Tanaka, Kazuo Makishima, Yoshihiro Ueda, Tadayasu Dotani, Hajime Inoue, Kazutaka Yamaoka

Research output: Contribution to journalArticlepeer-review

218 Citations (Scopus)


We report on the result of an X-ray observation of the X-ray Nova Velorum 1993 (GRS 1009-45), made with ASCA on 1993 November 10-11. The energy spectrum was extremely soft and accompanied by a hard tail, characteristics of the Galactic black-hole binaries in the soft state. It is well represented by a two-component model consisting of a multicolor disk model or a general relativistic accretion disk model, both describing emission from an optically thick accretion disk, and a power-law component with a photon index of ∼ 2.5. A spectral analysis of the soft component allows an estimation of the mass of the central object. For the optically-estimated distance (> 1 kpc) and inclination (> 37°), the mass is estimated to be > 3.1 M. These results strongly support that the compact object is a black hole.

Original languageEnglish
Pages (from-to)667-673
Number of pages7
JournalPublications of the Astronomical Society of Japan
Issue number6
Publication statusPublished - 1998
Externally publishedYes


  • Accretion disks
  • Black hole
  • X-rays: Binaries
  • X-rays: Transients

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Evidence for a black hole in the x-ray transient GRS 1009-45'. Together they form a unique fingerprint.

Cite this