Issue |
A&A
Volume 388, Number 3, June IV 2002
|
|
---|---|---|
Page(s) | 936 - 939 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20020610 | |
Published online | 10 June 2002 |
Mass transfer from the donor of GRS 1915+105
Observatory, Box 14, 00014 University of Helsinki, Finland
Corresponding author: osmi.vilhu@helsinki.fi
Accepted: 21 February 2002
A scenario for a periodic filling and emptying of the accretion disc of
the microquasar GRS1915+105 is proposed, by estimating the mass transfer rate
from the donor and comparing it with the observed accretion rate
onto the primary black hole.
The mass of the Roche-lobe-filling donor (),
the primary black hole mass (
) and the binary orbital
period of 33.5 d (Greiner et al. 2001b)
predict for the donor spectral type
and K-magnitude around K6 III and -2.6, respectively.
The He-core of 0.28
of such a giant leads to evolutionary expansion along the
giant branch with a conservative mass transfer rate of
/year. On the other hand, the average observed
accretion rate onto the primary
is ten times larger:
(
kpc)
/y,
where η is the efficiency of converting
accretion into radiation.
We propose a duty cycle with (5–10)(η/0.1) per cent
active ON-state. The timescale of the (recurrent) OFF-state
is identified as the viscosity
time scale at the circularization radius (14
) and equals
/0.001)-4/5 years,
where α is the viscosity parameter in the α-prescription
of a classical disc.
If the viscosity at the outer edge of the disc is small and η is close to the maximum available
potential energy (per rest mass energy) at the innermost stable orbit,
the present activity phase may still last another 10–20 years. We also
discuss other solutions allowing a broader range of donor masses
(0.6–2.4
).
Key words: stars: binaries: close / stars: individual: GRS 1915+105
© ESO, 2002
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