Outbursts in ultracompact X-ray binaries

Abstract

Very faint X-ray binaries appear to be transient in many cases with peak luminosities much fainter than that of usual soft X-ray transients, but their nature still remains elusive. We investigate the possibility that this transient behaviour is due to the same thermal/viscous instability which is responsible for outbursts of bright soft X-ray transients, occurring in ultracompact binaries for adequately low mass-transfer rates. More generally, we investigate the observational consequences of this instability when it occurs in ultracompact binaries. We use our code for modelling the thermal-viscous instability of the accretion disc, assumed here to be hydrogen poor. We also take into account the effects of disc X-ray irradiation, and consider the impact of the mass-transfer rate on the outburst brightness. We find that one can reproduce the observed properties of both the very faint and the brighter short transients (peak luminosity, duration, recurrence times), provided that the viscosity parameter in quiescence is slightly smaller (typically a factor of between two and four) than in bright soft X-ray transients and normal dwarf nova outbursts, the viscosity in outburst being unchanged. This possibly reflects the impact of chemical composition on non-ideal MHD effects affecting magnetically driven turbulence in poorly ionized discs.

arXiv comment9 pages, 7 figures, Astronomy and Astrophysics, in press

References in corpus (44)

• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• The Properties of X-Ray and Optical Light Curves of X-Ray Novae
• The disc instability model for X-ray transients: evidence for truncation and irradiation
• Thanatology in Protoplanetary Discs: the combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones
• Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305
• An Overabundance of Transient X-ray Binaries within 1 pc of the Galactic Center
• Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: I. Wind Solutions at the Inner Disk
• Further Constraints on Thermal Quiescent X-ray Emission from SAX J1808.4-3658
• Revisiting a fundamental test of the disc instability model for X-ray binaries
• The XMM-Newton/Chandra monitoring campaign of the Galactic center region: Description of the program and preliminary results
• X-ray coherent pulsations during a sub-luminous accretion disk state of the transitional millisecond pulsar XSS J12270-4859
• Stability of helium accretion discs in ultracompact binaries
• Ultra-compact (X-ray) binaries
• The evolution of ultracompact X-ray binaries
• The behavior of subluminous X-ray transients near the Galactic center as observed using the X-ray telescope aboard Swift
• Stability and Evolution of Supernova Fallback Disks
• Spectral analysis of the XMM-Newton data of GX 339-4 in the low/hard state: disc truncation and reflection
• X-ray source populations in the Galactic Plane
• X-ray outbursts of low-mass X-ray binary transients observed in the RXTE era
• The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
• A four-year baseline Swift study of enigmatic X-ray transients located near the Galactic center
• The faintest accretors
• The Thermal State of the Accreting White Dwarf in AM Canum Venaticorum Binaries
• Rapid Cooling of the Neutron Star in the Quiescent Super-Eddington Transient XTE J1701-462
• Disc instability models for X-ray transients: evidence for evaporation and low alpha-viscosity ?
• Models of AM CVn star outbursts
• The nature of very faint X-ray binaries; hints from light curves
• The X-ray spectral properties of very-faint persistent neutron star X-ray binaries
• XMMU J174716.1-281048: a "quasi-persistent" very faint X-ray transient?
• A Population of Faint Non-Transient Low Mass Black Hole Binaries
• The first low-mass black hole X-ray binary identified in quiescence outside of a globular cluster
• A model for WZ Sge with "standard" values of alpha
• Unusual X-ray transients in the Galactic Centre
• On the nature of two low M-dot X-ray bursters: 1RXS J170854.4-321857 and 1RXS J171824.2-402934
• The Population of Faint Transients in the Galactic Centre
• Are the very faint X-ray transients period gap systems?
• A year in the life of the low-mass X-ray transient Aql X-1
• Long-term luminosity behavior of 14 ultracompact X-ray binaries
• Anomalous Z Cam stars: a response to mass-transfer outbursts
• The peculiar Galactic center neutron star X-ray binary XMM J174457-2850.3
• Discovery of a bright X-ray transient in the Galactic Center with XMM-Newton
• A low-level accretion flare during the quiescent state of the neutron-star X-ray transient SAX J1750.8-2900
• Mass transfer variation in the outburst model of dwarf novae and soft X-ray transients
• Hydrodynamic simulations of irradiated secondaries in dwarf novae

Cited by in corpus (12)

• A review of the disc instability model for dwarf novae, soft X-ray transients and related objects
• Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays
• New insights on the puzzling LMXB 1RXS J180408.9-342058: the intermediate state, the clocked type-I X-ray bursts and much more
• Multiwavelength characterisation of the accreting millisecond X-ray pulsar and ultra-compact binary IGR J17062-6143
• The Swift Bulge Survey: optical and near-IR follow-up featuring a likely symbiotic X-ray binary & a focused wind CV
• Near-infrared counterparts of three transient very faint neutron star X-ray binaries
• MAXI J1957+032: an accreting neutron star possibly in a triple system
• Constraining the duty cycle of transient low-mass X-ray binaries through simulations
• Multi-band observations of Swift J0840.7-3516: a new transient ultra-compact X-ray binary candidate
• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras
• Optical spectroscopy of 4U 1812-12: an ultra-compact X-ray binary seen through an H II region
• The very faint X-ray transient Swift J174610-290018 at the Galactic center