The DIM Inner Accretion Disk of the Quiescent Black Hole A0620-00
Abstract
We observed the X-ray nova A0620-00 with the Hubble Space Telescope (HST) Faint object Spectrograph 16 yr after its 1975 outburst. We present a single spectrum (1250-4750 A), which is approximately an average over a full 7.8 hr orbital cycle of the source. The continuum can be fitted approximately by a blackbody model with T = 9000 K and a small projected source area, which is approximately 1 % of the expected area of the accretion disk. AS0620-00 is faint in the far-UV band; its luminosity is comparable to the luminosity of the quiescent dwarf-nova accretion disk (i.e., excluding the white dwarf). By analogy with dwarf novae, the optical luminosity of the disk (Mnu approximately = 7) and the orbital period of A0620-00 imply that the rate of mass transfer onto the outer disk in Md approximately 10-10 solar mass/yr. We also observed A0620-00 with the ROSAT PSPC X-ray detector for 3 x 104 s and detected a faint source (5 sigma) at the location of the X-ray nova. For an assumed blackbody spectrum the source temperature and luminosity are approximately 0.16 keV and 6 x 1030 ergs/s, respectively (d = 1 kpc). This luminosity implies that the rate of mass transfer into the black hole is extraordinarily small: MBH less than 5 x 10-15 solar mass/yr. The much larger mass transfer rate onto the outer disk, and the UV/X-ray faintness of the inner disk confirm key predictions of the disk instability model for the nova outburst of A0620-00 published by Huang and Wheeler and by Mineshige and Wheeler.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/175445
- Bibcode:
- 1995ApJ...442..358M
- Keywords:
-
- Accretion Disks;
- Black Body Radiation;
- Black Holes (Astronomy);
- Stellar Luminosity;
- Stellar Spectra;
- Ultraviolet Spectra;
- X Ray Binaries;
- X Ray Spectra;
- Light Curve;
- Mass Flow Rate;
- Mass Transfer;
- Spectrum Analysis;
- Stellar Spectrophotometry;
- Astronomy;
- ACCRETION;
- ACCRETION DISKS;
- BLACK HOLE PHYSICS;
- STARS: BINARIES: CLOSE;
- STARS: INDIVIDUAL ALPHANUMERIC: A0620-00;
- X-RAYS: STARS