AN IMPROVED DYNAMICAL MODEL FOR THE MICROQUASAR XTE J1550−564

By J. Orosz, J. Steiner, J. E. McClintock, M. Torres, Ronald A. Remillard, C. Bailyn, Jonathan M. Miller. 2011

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We present an improved dynamical model of the X-ray binary and microquasar XTE J1550−564 based on new moderate-resolution optical spectroscopy and near-infrared photometry obtained with the 6.5 m Magellan Telescopes at Las Campanas Observatory. Twelve spectra of the source were obtained using the Magellan Echellette Spectrograph between 2008 May 6 and August 4. In addition, several hundred images of the field were obtained between 2006 May and 2009 July in the J and KS filters using the PANIC camera. The agreement between the 2006/2007 and 2008 J and KS light curves is not perfect, and the differences can plausibly be attributed to a hot spot on the accretion disk during the 2006/2007 observations. By combining our new radial velocity measurements with previous measurements obtained in 2001 May at the 8.2 m Very Large Telescope and with light curves, we find an orbital period of P = 1.5420333 ± 0.0000024 days and a radial velocity semiamplitude of K2 = 363.14 ± 5.97 km s−1, which together imply an optical mass function of f(M) = 7.65 ± 0.38 M☉. We find that the projected rotational velocity of the secondary star is 55 ± 5 km s−1, which implies a very extreme mass ratio of Q ≡ M/M2 ≈ 30. Using a model of a Roche lobe-filling star and an azimuthally symmetric accretion disk, we fit simultaneously optical light curves from 2001, near-infrared light curves from 2008, and all of the radial velocity measurements to derive system parameters. We find an inclination of 74.°7 ± 3.°8 and component masses of M2 = 0.30 ± 0.07 M☉ and M = 9.10 ± 0.61 M☉ for the secondary star and black hole, respectively. We note that these results depend on the assumption that in 2008, the disk did not have a hot spot, and that the fraction of light contributed by the accretion disk did not change between the spectroscopic and photometric observations. By considering two measured values of the disk fraction and by modeling various combinations of NIR and optical light curves, we show that our adopted black hole mass is probably not seriously in error, where the black hole mass ranges between M = 8.91 ± 1.10 M☉ and M = 13.94 ± 1.64 M☉. The radius of the secondary star for the adopted model is 1.75 ± 0.12 R☉. Using this radius, the average KS magnitude, and an extinction of AK = 0.507 ± 0.050 mag, we find a distance of 4.38+0.58−0.41 kpc, which is in good agreement with a recent distance estimate based on H i absorption lines.

Subfields: Astronomy and Astrophysics, Biomedical Engineering

View Paper: https://www.semanticscholar.org/paper/dee5e1711a29a2c84ed6942854791f60b18a8116

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Citations in the corpus

MASS MEASUREMENTS OF BLACK HOLES IN X-RAY TRANSIENTS: IS THERE A MASS GAP? (2012, methodology): “Similar variability has been observed in many other sources, including XTE J1550-564, SAX J1819.”
The spin of the black hole microquasar XTE J1550−564 via the continuum-fitting and Fe-line methods (2010, methodology): “Of central importance to this paper, Orosz et al. (2011) report accurate values of the three key quantities that are essential for determining the spin of the BH via the continuumfitting (CF) method, namely the distance D = 4.38+0.58−0.41 kpc, BH mass M = 9.10 ± 0.61 M and orbital inclination angle…”
BlackCAT: A catalogue of stellar-mass black holes in X-ray transients (2015, background): “7 Iab donor star, Orosz et al. 2011a) is the only confirmed Galactic BH in a persistent X-ray binary.”
WATCHDOG: A COMPREHENSIVE ALL-SKY DATABASE OF GALACTIC BLACK HOLE X-RAY BINARIES (2015, methodology): “…(1995), [48] Filippenko et al. (1997), [49] Harlaftis et al. (1997),[50]Neil et al. (2007), [51] Orosz et al. (2001), [52] Gelino et al. (2006), [53] Orosz et al. (2011b), [54] Homan et al. (2006b), [55] Remillard & McClintock (2006), [56] Gies & Bolt n (1982), [57] Cowley et al. (1983), [58]…”
Measuring the spins of accreting black holes (2011, methodology): “Using our recently-determined estimates of D, M and i for A0620–00 and XTE J1550−564 (Cantrell et al 2010, Orosz et al 2011), we fitted the x-ray spectra of these black holes and determined their spins (table 1).”
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets (2013, background): “In determining the spins of eight of the ten black holes (see Section 6), it is assumed that the plane of the inner X-ray-emitting portion of the disk is aligned with the binary orbital plane, whose inclination angle i is determined from optical observations (e.g., Orosz et al. 2011a).”