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971.
972.
As a neutron star spins down, the nuclear matter is continuously converted into quark matter due to the core density increase, and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of changed rate of deconfinement baryon number. The numerical solutions to the cooling equation are seen to be very different from those without the heating effect. The results show that neutron stars may be heated to higher temperatures which is well matched with pulsar's data despite the onset of fast cooling in neutron stars with quark matter cores. It is also found that the heating effect has a magnetic field strength dependence. This feature could be particularly interesting for high temperatures of low-field millisecond pulsars at a later stage. The high temperature could fit the observed temperature for PSR J0437−4715. 相似文献
973.
974.
A. De Luca P. A. Caraveo S. Mereghetti A. Tiengo G. F. Bignami 《Astrophysics and Space Science》2007,308(1-4):231-238
1E 161348-5055 (1E) is a compact object lying at the center of the 2000 year old Supernova Remnant (SNR) RCW103. Its original
identification as an isolated, radio-quiet neutron star has been questioned in recent years by the observation of a significant
long-term variability, as well as by reports of a possible periodicity at ∼6 hours. Here we report conclusive evidence for
a strong (nearly 50%) periodic modulation of 1E at 6.67±0.03 hours, discovered during a long (90 ks) XMM-Newton observation
performed in August 2005, when the source was in a “low state”. The source spectrum varies along the 6.67 hr cycle. No fast
pulsations are seen. 1E could be a very young binary system, possibly composed of a compact object and a low-mass star in
an eccentric orbit. This would be the first example of a low-mass X-ray binary (LMXB) associated with a SNR, and thus the
first LMXB for which we know the precise birth date, just 2000 years ago. Alternatively, if it is an isolated neutron star,
the unprecedented combination of age, period and variability may only fit in a very unusual scenario, featuring a peculiar
magnetar, dramatically slowed-down over 2000 years, possibly by a supernova debris disc.
相似文献
975.
A. E. Chukwude 《中国天文和天体物理学报》2007,7(4):521-530
We present an analysis of the timing observations on 27 radio pulsars, collected at Hartebeesthoek Radio Astronomy Observatory (HartRAO), with time spans ranging between ～ 9 and 14yr. Our results show that the measured pulsar frequency second derivatives are non-stationary. Both the magnitude and the sign of the ■ values depend upon the choice of epoch and data span. A simple statistical analysis of the observed second time derivative of the pulse frequency (■obs) of a large sample of 391 (25 HartRAO and 366 Jodrell Bank Observatory) pulsars reveals that ■ is only marginally correlated with both the pulsar spin-d own rate ( ■) and the characteristic age (τc). We find correlation coefficients of ～ 0.20a nd-0.30 between the measured braking indices and, respectively, ■ and τc. This result reaffirms earlier conclusions that the braking indices of most radio pulsars, obtained through the standard timing technique, are strongly dominated by sustained random fluctuations in the observed pulse phase. 相似文献
976.
977.
RX J1856.5-3754 has been proposed as a strange star candidate due to its very small apparent radius measured from its X-ray
thermal spectrum. However, its optical emission requires a much larger radius and thus most of the stellar surface must be
cold and undetectable in X-rays. In the case the star is a neutron star such a surface temperature distribution can be explained
by the presence of a strong toroidal field in the crust (Pérez-Azorín et al.: Astron. Astrophys. 451, 1009 (2006); Geppert
et al.: Astron. Astrophys. 457, 937 (2006)) We consider a similar scenario for a strange star with a thin baryonic crust to
determine if such a magnetic field induced effect is still possible.
This work was partially supported by PAPIIT, UNAM, grant IN119306. J.A.H. studies at UNAM and travel to London are covered
by fellowships from UNAM’s Dirección General de Estudios de Posgrado. 相似文献
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979.
980.