Tolga Guver, Feryal Ozel, Dimitrios Psaltis
Time resolved X-ray spectroscopy of thermonuclear bursts observed from low
mass X-ray binaries offer a unique tool to measure neutron star masses and
radii. In this paper, we continue our systematic analysis of all the X-ray
bursts observed with RXTE from X-ray binaries. We determine the events which
show clear evidence for photospheric radius expansion and measure the Eddington
limits for these accreting neutron stars using the bolometric fluxes attained
at the touchdown moments of each X-ray burst. We employ a Bayesian technique to
investigate the degree to which the Eddington limit for each source remains
constant between bursts. We find that for sources with a large number of radius
expansion bursts, systematic uncertainties are at a 5-10% level. Moreover, in
six sources with only pairs of Eddington-limited bursts, the distribution of
fluxes is consistent with a ~10% fractional dispersion. This indicates that the
spectroscopic measurements of neutron star masses and radii using thermonuclear
X-ray bursts can reach the level of accuracy required to distinguish between
different neutron star equations of state, provided that uncertainties related
to the overall flux calibration of X-ray detectors are of comparable magnitude.
View original:
http://arxiv.org/abs/1104.2602
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