Six new candidate ultracompact X-ray binaries

By J. I. Zand, Peter G. Jonker, C. Markwardt. 2007

140 citations recorded by the source corpus.

Ultracompact X-ray binaries (UCXBs) appear able to sustain accretion onto the compact accretor at rates lower than in wider X-ray binaries. This may be understood by the smaller accretion disks in UCXBs: a lower X-ray luminosity suffices to keep a disk completely ionized through irradiation and, thus, keep the viscosity at a sufficiently high level to allow effective transport of matter to the compact object. We employ this distinguishing factor on data from RXTE and BeppoSAX to identify six new candidate UCXBs, thus increasing the population by one quarter. The candidates are drawn from the population of persistently accreting and type-I X-ray bursting lowmass X-ray binaries. The X-ray bursts establish the low-mass X-ray binary nature and provide a handle on the accretion rate. We find that the low accretion rates are supported by the long burst recurrence times and the hard X-ray spectra of the persistent emission as derived from the 2nd INTEGRAL catalog of soft γ-ray sources. We discuss the peculiar light curves of some new UCXB candidates.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4da12a5cb71407aefc213291f7c89ab454ef3fd2

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In Astronomy and Astrophysics

Citations in the corpus

Formation and evolution of compact binaries in globular clusters – II. Binaries with neutron stars (2007, background): “…et al. 1999) and the evolution of UCXBs (Deloye & Bildsten 2003),1036 ergs/s is roughly the criticalLX for maintaining persistent accretion. in’t Zand et al. (2007) present a table of 40 persistent X-ray bursters, which shows a striking lowLX pileup and cutoff atLX = 1.3 × 1036 ergs/s, or 0.5%…”