The X-ray Binary GX 339–4/V821 Ara: the Distance, Inclination, Evolutionary Status, and Mass Transfer

We consider constraints on the distance, inclination, and component masses in the X-ray binary GX 339–4 resulting from published works, and then construct detailed evolutionary models for the donor. From both considerations, and assuming the black hole nature for the compact object (i.e. its mass ${\gt} 3\, \rm {M}_{\odot }$), the possible donor mass is ≈0.5–$1.4\, \rm {M}_{\odot }$, the inclination is ≈40°–60°, and the distance is ≈8–12 kpc. The corresponding mass of the compact object is ≈4–$11\, \rm {M}_{\odot }$. We then confirm a previous estimate that the theoretical conservative mass transfer rate in GX 339–4 is ${\lesssim} {10^{-9}}\, {\rm M}_{{\odot} }$ yr−1. This is ≳10 times lower than the average mass accretion rate estimated from the long-term X-ray light curve. We show that this discrepancy can be solved in two ways. One solution invokes irradiation of the donor by X-rays from accretion, which can temporarily enhance the mass transfer rate. We found that absorption of a ∼1 per cent of the irradiating luminosity results in the transfer rate equal to the accretion rate. The time-scale at which the transfer rate will vary is estimated to be ∼10 yr, which appears consistent with the observations. The other solution invokes non-conservative mass transfer. This requires that ≈70 per cent of the transferred mass escapes as a strong outflow and carries away the specific angular momentum comparable to that of the donor.