Observations of GRO J0422+32. III. A Low-Inclination Black Hole X-Ray Nova
Abstract
We present the results of our campaign of photometry of the X-ray nova GRO J0422 +32 in quiescence, the purpose of which was to confirm the proposed orbital period of ∼5.1 hr, and to search for the ellipsoidal variations which are a prerequisite for the mass determination of the primary. We find evidence for a weak ellipsoidal modulation corresponding to an orbital period of 5.1 hr, with a semi- amplitude of ∼0.03 mag the lowest known of any quiescent X-ray nova. With the assumption that the I-band contamination by the accretion disk is no greater than that observed in other quiescent X-ray novae, we estimate that the orbital inclination must be < 45°. Furthermore, a ZAMS secondary implies an upper limit on the distance of ∼2.2 kpc, and a quiescent accretion rate ∼3% that observed in A0620-00. The inclination estimate implies a mass of the compact object ≥3.4 Msun. ROSAT observations constrain the quiescent X-ray luminosity to be less than 2 x 1032 ergs s-1 (for a distance of 2 kpc). We speculate that the low quiescent accretion rate through the disk, inferred from the optical observations, may well be related to the large outburst amplitude of GRO J0422+32.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1996
- DOI:
- 10.1086/177062
- Bibcode:
- 1996ApJ...461..351C
- Keywords:
-
- STARS: BINARIES: CLOSE;
- STARS: NOVAE;
- CATACLYSMIC VARIABLES;
- STARS: INDIVIDUAL ALPHANUMERIC: GRO J0422+32;
- X-RAYS: STARS