Multiwavelength Observations of Accretion in Low-Mass X-ray Binary Systems

Really short review of this paper (1/2 page!) for my PhD reading list

Multiwavelength Observations of Accretion in Low-Mass X-ray Binary Systems

Robert I.Hynes

Low-Mass X-ray binaries (LMXBs) stars are formed by a X-ray emmiter primary star that can

be a neutron star or a stellar mass black hole and a late type G-M donor star with masses

below 1,5M . In this systems, the compact star accretes material from the donor mostly by

Roche lobe overflow.

LMXBs transients are often ultra-soft spectra and in quiescence are often dominated by

the companion star. All transient systems are recurrent, but not at the same timescale. It is

believed that the outburst are as the disk instability modell, originally developed to explain

dwarf novae outbursts.

Spectral energy distributions of LMXBs have prouf to be persuasive evidence on Black

Holes Jets. About LMXBs light curves, we can say that the simplest optical curve comes from

ellipsoidal variations in quiescence, who take a near sinusoidal form with 2 cycles per binary

orbit and is mostly determined by the system inclination. Superhumps are observed as well,

due disk eccentricity and precession, most likely occurring in black holes systems as these

have more extreme mass ratios than most neutron star LMXBs. Quasi-periodic oscillations,

repeating signals not strictly periodic, are common in LMXB. A transient signal it will manifest as a quasi-periodic oscillation. In eclipsing systems, structure from disk axisymmetry can

be observed. Also, eclipses provides precise constraints on the system inclination with sub-

sequent more accurate parameters derived from it, but there are not known eclipsing black

hole in our Galaxy. It is believed that this might be a selection effect.

LMXBs observation is multiwavenength. The most usual lines present in a LMXB spectra

are the Balmer lines, HeI, HeII(optical and ultraviolet). Besides hydrogen and helium, other

lines seen are NIII, CIII around 4640Å, known as the Bowen blend. This donor star lines are

very useful in luminous systems, have prove being a good tool for mass determination. In

quiescent systems, the period and radial velocity of the secondary are enough to estimate

the mass since Kepler’s third law.

Finally, it is possible to say that for the fully understanding of LMXB not only X-ray obser-

vations are necessary, but also optical and spectroscopic.

Here is the link with the real paper
http://adsabs.harvard.edu/abs/2010arXiv1010.5770H