SIMBAD references

2018MNRAS.474.1922L - Mon. Not. R. Astron. Soc., 474, 1922-1934 (2018/February-3)

State transitions in ultracompact neutron star LMXBs: towards the low-luminosity limit.

LIN J. and YU W.

Abstract (from CDS):

Luminosity of X-ray spectral state transitions in black hole and neutron star X-ray binaries can put constraint on the critical mass accretion rate between accretion regimes. Previous studies indicate that the hard-to-soft spectral state transitions in some ultracompact neutron star LMXBs have the lowest luminosity. With X-ray monitoring observations in the past decade, we were able to identify state transitions towards the lowest luminosity limit in 4U 0614+091, 2S 0918-549 and 4U 1246-588. By analysing corresponding X-ray pointed observations with the Swift/XRT and the RXTE/PCA, we found no hysteresis of state transitions in these sources, and determined the critical mass accretion rate in the range of 0.002-0.04{dot}M_ Edd_ and 0.003-0.05{dot}M_ Edd_ for the hard-to-soft and the soft-to-hard transition, respectively, by assuming a neutron star mass of 1.4 solar masses. This range is comparable to the lowest transition luminosity measured in black hole X-ray binaries, indicating the critical mass accretion rate is not affected by the nature of the surface of the compact stars. Our result does not support the advection-dominated accretion flow (ADAF) model, which predicts that the critical mass accretion rate in neutron star systems is an order of magnitude lower if same viscosity parameters are taken. The low transition luminosity and insignificant hysteresis in these ultracompact X-ray binaries provide further evidence that the transition luminosity is likely related to the mass in the disc.

Abstract Copyright: © 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): stars: low-mass - stars: neutron - X-rays: binaries

CDS comments: 2S 0914-549 is a misprint for 2S 0918-549.

Simbad objects: 42

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2020.01.19-15:10:40

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