The Transient Nature of GRO J1655-40 and its Evolutionary State

Abstract

We consider the evolutionary state of the black-hole X-ray source GRO J1655-40 in the context of its transient nature. Recent optical observations show that the donor in GRO J1655-40 is an intermediate-mass star (~ 2.3 solar masses) crossing the Hertzsprung gap. Usually in such systems the donor's radius expansion drives a near-Eddington or super-Eddington mass transfer rate which would sustain a persistently bright accretion disk. We show that GRO J1655-40 is close to a narrow parameter range where disk instabilities can occur. This range corresponds to a short-lived evolutionary stage where the secondary's radius expansion stalls (or reverses), with a correspondingly lower mass transfer rate. If GRO J1655-40 belongs to this class of transients the predicted accretion rates imply large populations of luminous persistent and transient sources, which are not seen in X-rays. The transient nature of the related system GRS 1915+105 may reflect spectral variations in a bolometrically persistent source rather than a genuine luminosity increase.

Accepted for publication in ApJ Letters. LaTeX, 10 pages, including 2 figures

References in corpus (3)

• An unstable central disk in the superluminal black-hole X-ray binary GRS 1915+105
• An Optical Precursor to the Recent X-ray Outburst of the Black Hole Binary GRO J1655-40
• The Formation of Low-Mass Transient X-Ray Binaries

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• Advection-Dominated Flows and the X-ray Delay in the Outburst of GRO J1655-40
• On different types of instabilities in black hole accretion discs. Implications for X-ray binaries and AGN
• Alignment Timescale of the Microquasar GRO J1655-40
• A search for possible interactions between ejections from GRS 1915+105 and the surrounding interstellar medium
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• Optical and near-infrared observations of the microquasar V4641 Sagittarii during the 1999 September outburst
• Resolved Jets and Long-Period Black Hole X-ray Novae
• Near Infrared Observations of Galactic Black Hole Candidates
• The minimum orbital period in thermal-timescale mass transfer
• Black-Hole Transients and the Eddington Limit
• Binary evolution with relativistic jets