Hydrogen-poor Disks in Compact X-Ray Binaries

We present a comprehensive description of the population synthesis code StarTrack. The original code has been significantly modified and updated. Special emphasis is placed here on processes leading to the formation and further evolution of compact objects (white dwarfs, neutron stars, and black holes). Both single and binary star populations are considered. The code now incorporates detailed calculations of all mass transfer phases, a full implementation of orbital evolution due to tides, as well as the most recent estimates of magnetic braking. This updated version of StarTrack can be used for a wide variety of problems, with relevance to observations with many current and planned observatories, e.g., studies of X-ray binaries (Chandra, XMM-Newton), gravitational radiation sources (LIGO, LISA), and gamma-ray burst progenitors (HETE-II, Swift). The code has already been used in studies of Galactic and extragalactic X-ray binary populations, black holes in young star clusters, Type Ia supernova progenitors, and double compact object populations. Here we describe in detail the input physics, we present the code calibration and tests, and we outline our current studies in the context of X-ray binary populations.

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“…We use the work of Dubus et al (1999) for H-rich disks (see their eq. [30]) and the study of Menou et al (2002) …”

Section: X-ray Luminosity Calculationsmentioning

confidence: 99%

Compact Object Modeling with the StarTrack Population Synthesis Code

Belczyński

Kalogera

Rasio

et al. 2008

ASTROPHYS J SUPPL S

772

1,099

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“…In the example given above, the system becomes a transient X-ray source, when the MT rate falls below a certain critical value (see Menou, Perna, & Hernquist 2002; marked on Fig. 2).…”

Section: Evolution At Ultracompact Phasementioning

confidence: 99%

Galactic Populations of Ultracompact Binaries

Belczyński

Taam

2004

ApJ

110

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Recent RXTE and Chandra discoveries of low-mass X-ray binaries with ultrashort orbital periods have initiated theoretical work on the origins of these peculiar systems. Using the StarTrack population synthesis code, we analyze the formation and evolution of X-ray ultracompact binaries (UCBs) in the Galactic field. The relative number of UCBs with a neutron star or a black hole accretor populating our Galaxy is predicted. Our results demonstrate that standard evolutionary scenarios involving primordial binaries can be sufficient to produce the UCBs in the Galactic field without requiring additional processes associated with the dense stellar environments in the cores of globular clusters. In contrast to previous studies, we find that the majority of the immediate progenitors of these systems consist of a hydrogen-exhausted donor with an ONeMg white dwarf. The evolution of these systems leads to the accretion-induced collapse of the white dwarf to a neutron star, which can play an important role in the formation of a majority of Galactic UCBs. We predict that with an increase in the number of X-rayactive UCBs hosting neutron stars by an order of magnitude, a system with a black hole accretor may be found.

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“…Since some AM CVn binaries (in which matter is accreted onto a white dwarf) show dwarf-nova type outbursts and several Ultra Compact X-ray Binaries (UCXBsbinaries with a neutron-star accreting primary) are transient (see it seems that the thermal-viscous instability is operating also in these systems. Stability criteria for hydrogen-deficient discs were first obtained by Smak (1983) and later by Cannizzo (1984), Tsugawa & Osaki (1997), El-Khoury & Wickramasinghe (2000) and Menou et al (2002). However, since they did not include effects of irradiation, they were not applicable to UCXBs in which irradiation is important (Deloye & Bildsten 2003;, but they are of course relevant to AM CVn stars).…”

Section: Introductionmentioning

confidence: 99%

Stability of helium accretion discs in ultracompact binaries

Lasota

Dubus

Kruk

2008

A&A

156

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Context. Stellar companions of accreting neutron stars in ultra compact X-ray binaries (UCXBs) are hydrogen-deficient. Their helium or C/O accretion discs are strongly X-ray irradiated. Both the chemical composition and irradiation determine the disc stability with respect to thermal and viscous perturbations. At shorter periods, UCXBs are persistent, whereas longer-period systems are mostly transient. Aims. To understand this behaviour one has to derive the stability criteria for X-ray irradiated hydrogen-poor accretion discs. Methods. We use a modified and updated version of the Dubus et al. code describing time-dependent irradiated accretion discs around compact objects. Results. We obtained the relevant stability criteria and compared the results to observed properties of UCXBs Conclusions. Although the general trend in the stability behaviour of UCXBs is consistent with the prediction of the disc instability model, in a few cases the inconsistency of theoretical predictions with the system observed properties is weak enough to be attributed to observational and/or theoretical uncertainties. Two systems might require the presence of some amount of hydrogen in the donor star.

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Hydrogen-poor Disks in Compact X-Ray Binaries

Cited by 44 publications

References 33 publications

Compact Object Modeling with the StarTrack Population Synthesis Code

Compact Object Modeling with the StarTrack Population Synthesis Code

Galactic Populations of Ultracompact Binaries

Stability of helium accretion discs in ultracompact binaries

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