259 research outputs found
ATCA radio detection of the new X-ray transient IGR J17591-2342 suggests a black hole candidate
The connection between the UV/optical and X-ray emission in the neutron star low-mass X-ray binary Aql X-1
Constraining the properties of dense neutron star cores:the case of the low-mass X-ray binary HETE J1900.1-2455
Measuring the time evolution of the effective surface temperature of neutron
stars can provide invaluable information on the properties of their dense
cores. Here, we report on a new Chandra observation of the transient neutron
star low-mass X-ray binary HETE J1900.1-2455, which was obtained ~2.5 yr after
the end of its ~10-yr long accretion outburst. The source is barely detected
during the observation, collecting only six net photons, all below 2 keV.
Assuming that the spectrum is shaped as a neutron star atmosphere model we
perform a statistical analysis to determine a 1-sigma confidence upper range
for the neutron star temperature of ~30-39 eV (for an observer at infinity),
depending on its mass, radius and distance. Given the heat injected into the
neutron star during the accretion outburst, estimated from data provided by
all-sky monitors, the inferred very low temperature suggests that either the
core has a very high heat capacity or undergoes very rapid neutrino cooling.
While the present data do not allow us to disentangle these two possibilities,
both suggest that a significant fraction of the dense core is not
superfluid/superconductor. Our modeling of the thermal evolution of the neutron
star predicts that it may still cool further, down to a temperature of ~15 eV.
Measuring such a low temperature with a future observation may provide
constraints on the fraction of baryons that is paired in the stellar core.Comment: 14 pages (12 main, 2 appendix), 10 figures, published in MNRA
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