科研之友
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摘要
The neutron star low-mass X-ray binary and intermittent millisecond X-ray pulsar HETE J1900.1-2455 returned to quiescence in late 2015, after a prolonged accretion outburst of similar or equal to 10 yr. Using a Chandra observation taken similar or equal to 180 d into quiescence, we detect the source at a luminosity of similar or equal to 4.5 x 10(31) (D/4.7 kpc)(2) erg s(-1) (0.5-10 keV). The X-ray spectrum can be described by a neutron star atmosphere model with a temperature of similar or equal to 54 eV for an observer at infinity. We perform thermal evolution calculations based on the 2016 quiescent data and a less than or similar to 98 eV temperature upper limit inferred from a Swift observation taken during an unusually brief (less than or similar to 2 weeks) quiescent episode in 2007. We find no evidence in the present data that the thermal properties of the crust, such as the heating rate and thermal conductivity, are different than those of non-pulsating neutron stars. Finding this neutron star so cold after its long outburst imposes interesting constraints on the heat capacity of the stellar core; these become even stronger if further cooling were to occur.
- 出版日期2017-2
