T. Muñoz-Darias

On the masses and evolutionary status of the black hole binary GX 339‐4: a twin system of XTE J1550‐564?

We apply the K-correction to the black hole low-mass X-ray binary (LMXB) GX 339-4 which implies MX? 6 M? by only assuming that the companion is more massive than ?0.17 M?, the lower limit allowed by applying a ‘stripped-giant’ model. This evolutionary model successfully reproduces the observed properties of the system. We obtain a maximum mass for the companion of M2? 1.1 M? and an upper limit to the mass ratio of q(=M2/MX) ? 0.125. The high X-ray activity displayed by the source suggests a relatively large mass transfer rate which, according to the model, results in M2? 0.3 M? and MX? 7 M?. We have also applied this scenario to the black hole binary XTE J1550-564, which has a similar orbital period but the donor is detected spectroscopically. The model successfully reproduces the observed stellar parameters

The “K-Correction” for Irradiated Emission Lines in LMXBs: Evidence for a Massive Neutron Star in X1822–371 (V691 CrA)

We study the K-correction for the case of emission lines formed in the X-ray illuminated atmosphere of a Roche lobe filling star. We compute the K-correction as function of the mass ratio q and the disc flaring angleusing a compact binary code where the companions Roche lobe is divided into 10 5 resolution elements. We also study the effect of the inclination angle in the results. We apply our model to the case of the neutron star low-mass X-ray binary X1822-371 (V691 CrA), where a K-emission velocity Kem = 300±8 km s −1 has been measured by Casares et al. (2003). Our numerical results, combined with previous determination of system parameters, yields 1.61M⊙ ≤ MNS ≤ 2.32M⊙ and 0.44M⊙ ≤ M2 ≤ 0.56M⊙ for the two binary components(i. e. 0.24 ≤q≤ 0.27), which provide a compelling evidence for a massive neutron star in this system. We also discuss the implications of these masses into the evolutionary history of the binary. Subject headings: accretion, accretion disks - binaries: close - stars: individual: X1822-371 - X- rays:stars

Regulation of black-hole accretion by a disk wind during a violent outburst of V404 Cygni

Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black-hole transients have outflows whose properties are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk. Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10(-8) solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.

A late jet rebrightening revealed from multiwavelength monitoring of the black hole candidate XTE J1752−223

We present optical monitoring of the black hole candidate XTE J1752−223 during its 2009–10 outburst and decay to quiescence. The optical light curve can be described by an exponential decay followed by a plateau, then a more rapid fade towards quiescence. The plateau appears to be due to an extra component of optical emission that brightens and then fades over ∼40 days. We show evidence for the origin of this optical ‘flare’ to be the synchrotron jet during the decaying hard state, and we identify and isolate both disc and jet components in the spectral energy distributions. The optical flare has the same morphology and amplitude as a contemporaneous X-ray rebrightening. This suggests a common origin, but no firm conclusions can be made favouring or disfavouring the jet producing the X-ray flare. The quiescent optical magnitudes are B ≥ 20.6,V ≥ 21.1,R ≥ 19.5,i � ≥ 19.2. From the optical outburst amplitude we estimate a likely orbital period of <22 h. We also present near-infrared (NIR) photometry and polarimetry and rare mid-IR imaging (8–12 µm) when the source is nearing quiescence. The fading jet component, and possibly the companion star, may contribute to the NIR flux. We derive deep mid-IR flux upper limits and NIR linear polarization upper limits. With the inclusion of radio data, we measure an almost flat jet spectral index between radio and optical; Fν ∝ ν ∼+0.05 . The data favour the jet break to optically thin emission to

Swift J1357.2−0933: a massive black hole in the Galactic thick disc

Swift J1357.2-0933 is one of the shortest orbital period black hole X-ray transients (BHTs). It exhibited deep optical dips together with an extremely broad H

Echoes from the companion star in Sco X-1

\alpha

Searching for flickering statistics in T CrB

line during outburst. We present 10.4-m GTC time-resolved spectroscopy during quiescence searching for donor star absorption features. The large contribution of the accretion flow to the total luminosity prevents the direct detection of the companion. Nevertheless, we constrain the non-stellar contribution to be larger than

The puzzling orbital period evolution of the LMXB AX J1745.6−2901

\sim 80\%

Links between quasi-periodic oscillations and accretion states in neutron star low-mass X-ray binaries

of the total optical light, which sets new lower limits to the distance (

The donor of Aquila X-1 revealed by high-angular resolution near-infrared spectroscopy

d > 2.29\, \rm{kpc}