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Journal ArticleDOI

Spectroscopy of $A0620-00$: the mass of the black hole and an image of its accretion disc

TL;DR: In this article, spectra of the black hole binary A0620-00 taken at Hα and Hβ were used to study the distribution of emission-line flux from its accretion disc.
Abstract: We present spectra of the black hole binary A0620-00 taken at Hα and Hβ to study the distribution of emission-line flux from its accretion disc. Using the spectra of Hα, we have measured the K-type companion star's radial velocity semi-amplitude and rotational broadening to be K 2 =433±3 km s −1 and v sin i=83±5 km s −1 . Accounting for the Roche-lobe geometry of the companion, the rotational broadening gives the mass ratio q=M 2 /M 1 =0.06 7±0.01. The disc contributes 6±3 per cent of the light at Hα and 17±3 per cent at Hβ, with the K star providing the rest. The masses of the compact object and K star derived from our values of K 2 and q are M 1 =(3.09±0.09)sin −3 i M ○. and M 2 =(0.21±0.04)sin −3 i M ○.

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01 Jan 1965

1,239 citations

Journal ArticleDOI
TL;DR: In this article, the authors reported photometric and spectroscopic observations of the black hole binary GRO J1655-40 in complete quiescence, which yielded an inclination of i = 6950? 008 and a mass ratio of Q = M1/M2 = 2.34? 0.08.
Abstract: We report photometric and spectroscopic observations of the black hole binary GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the light curves from 1996 are almost completely dominated by ellipsoidal modulations from the secondary star. Model fits to the light curves, which take into account the temperature profile of the accretion disk and eclipse effects, yield an inclination of i = 6950 ? 008 and a mass ratio of Q = M1/M2 = 2.99 ? 0.08. The precision of our determinations of i and Q allow us to determine the black hole mass to an accuracy of ? 4% (M1 = 7.02 ? 0.22 M?). The secondary star's mass is M2 = 2.34 ? 0.12 M?. The position of the secondary on the Hertzsprung-Russell diagram is consistent with that of a ? 2.3 M? star that has evolved off the main sequence and is halfway to the start of the giant branch. Using the new spectra, we present an improved value of the spectroscopic period (P = 262157 ? 000015), radial velocity semiamplitude (K = 228.2 ? 2.2 km s-1), and mass function [f(M) = 3.24 ? 0.09 M?]. Based on the new spectra of the source and spectra of several MK spectral type standards, we classify the secondary star as F3 IV-F6 IV. Evolutionary models suggest an average mass transfer rate for such a system of ${u{M}{"705F}}$ --> -->2=3.4?10 -->?9 M? yr-1 = 2.16 ? 1017 g s-1, which is much larger than the average mass transfer rates implied in the other six transient black hole systems but is still barely below the critical mass transfer rate required for stability.

338 citations

Journal ArticleDOI
TL;DR: In this article, the reported distances of the Galactic black hole (BH) and neutron star low-mass X-ray binaries (LMXBs) were investigated, and it was shown that the latter are smaller by approximately a factor of 1.5-2.
Abstract: We investigated the reported distances of Galactic black hole (BH) and neutron star low-mass X-ray binaries (LMXBs). Comparing the distances derived for the neutron stars Cyg X-2 and XTE J2123-058 using the observed Eddington limited photospheric radius expansion bursts with the distances derived using the observed radius and effective temperature of the companion star, we find that the latter are smaller by approximately a factor of 1.5-2. The latter method is often employed to determine the distance to BH LMXBs. A possible explanation for this discrepancy is that the stellar absorption lines in fast rotating companion stars are different from those in the slowly rotating template stars as was found before for early-type stars. This could lead to a systematic mis-classification of the spectral type of the companion star, which in turn would yield a systematic error in the distance. Further, we derive a distance of 4.0 +2.0 -1.2 ) kpc for V404 Cyg, using parameters available in the literature. The interstellar extinction seems to have been overestimated for XTE J1550-564 and possibly for two other BH sources (H 1705-25 and GS 2000+25) as well. As a result of this, the distance to XTE J1550-564 may have been underestimated by as much as a factor three. We find that, using the new distances for XTE J1550-564 and V404 Cyg, the maximum outburst luminosity for at least five, but perhaps even seven, of the 15 BH soft X-ray transients exceed the Eddington luminosity for a 10-M ○. BH - showing that these systems would be classified as ultra-luminous X-ray sources had we observed them in other Galaxies. This renders support for the idea that many ultra-luminous X-ray sources are stellar-mass rather than intermediate-mass BHs. We find that the rms-value of the distance to the Galactic plane for BHs is consistent with that of neutron star LMXBs. This suggests that BHs could also receive a kick-velocity during their formation, although this has to be investigated in more detail. We find that the Galactic neutron star and BH l- and b-distributions are consistent with being the same. The neutron star and BH distribution is asymmetric in l with an excess of systems between -30° < l < 0° over systems with 0° < l < 30°.

300 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a catalogue of low-mass X-ray binaries, which is an updated version of the catalogue of van Paradijs (1995) and contains 150 sources, 31 new lowmass Xray binaries in addition to the 119 sources listed in van paradijs' catalogue.
Abstract: We present a catalogue of low-mass X-ray binaries. The catalogue is an updated version of the catalogue of van Paradijs (1995). This new catalogue contains 150 sources, 31 new low-mass X-ray binaries in addition to the 119 sources listed in van Paradijs' catalogue. The aim of this catalogue is to help the reader gain easy access to the recent literature (up to about August 2000) on individual sources, and to provide of some basic information on the X-ray sources and their counterparts in other wavelength ranges (UV, optical, IR, and radio). In cases where there is some doubt about the low-mass nature of the X-ray binary, this is mentioned. In an appendix we list the Anomalous X-ray Pulsars (AXPs), which nowadays are no longer thought to be low-mass X-ray binaries.

260 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the estimated outer accretion rate of A0620-00 in quiescence to demonstrate that the outflow kinetic power must be energy comparable to the total accretion power associated with such rate, if it was to reach the black hole with the standard radiative efficiency of 10 per cent.
Abstract: Deep observations with the Very Large Array of A0620-00, performed in 2005 August, resulted in the first detection of radio emission from a black hole binary at X-ray luminosities as low as 10-8.5 times the Eddington limit. The measured radio flux density, of 51 +/- 7 ?Jy at 8.5 GHz, is the lowest reported for an X-ray binary system so far, and is interpreted in terms of partially self-absorbed synchrotron emission from outflowing plasma. Making use of the estimated outer accretion rate of A0620-00 in quiescence, we demonstrate that the outflow kinetic power must be energetically comparable to the total accretion power associated with such rate, if it was to reach the black hole with the standard radiative efficiency of 10 per cent. This favours a model for quiescence in which a radiatively inefficient outflow accounts for a sizable fraction of the missing energy, and, in turn, substantially affects the overall dynamics of the accretion flow. Simultaneous observations in the X-ray band, with Chandra, confirm the validity of a non-linear radio/X-ray correlation for hard state black hole binaries down to low quiescent luminosities, thereby contradicting some theoretical expectations. Taking the mass term into account, the A0620-00 data lie on the extrapolation of the so-called Fundamental Plane of black hole activity, which has thus been extended by more than two orders of magnitude in radio and X-ray luminosity. With the addition of the A0620-00 point, the plane relation provides an empirical proof for the scale invariance of the jet-accretion coupling in accreting black holes over the entire parameter space observable with current instrumentation.

254 citations