80,270 research outputs found
Pulsars identified from the NRAO VLA Sky Survey
We identified 97 strong pulsars from the NRAO VLA Sky Survey (NVSS) at 1.4
GHz north of Dec(J2000) >-40\degr. The total flux density, linear
polarization intensity and polarization angle (PA) of all pulsars are extracted
from the NVSS catalog. The well-calibrated PA measurement of 5 pulsars can be
used for absolute PA calibrations in other observations. Comparing the source
positions with those in the pulsar catalog, we got the first measurement of the
proper motion upper limit of PSR B0031-07, which is and .Comment: 7 pages; 3 figures; one big table; To appear in A&A Supplement
Helium star evolutionary channel to super-Chandrasekhar mass type Ia supernovae
Recent discovery of several overluminous type Ia supernovae (SNe Ia)
indicates that the explosive masses of white dwarfs may significantly exceed
the canonical Chandrasekhar mass limit. Rapid differential rotation may support
these massive white dwarfs. Based on the single-degenerate scenario, and
assuming that the white dwarfs would differentially rotate when the accretion
rate , employing Eggleton's
stellar evolution code we have performed the numerical calculations for
1000 binary systems consisting of a He star and a CO white dwarf (WD). We
present the initial parameters in the orbital period - helium star mass plane
(for WD masses of and , respectively), which
lead to super-Chandrasekhar mass SNe Ia. Our results indicate that, for an
initial massive WD of , a large number of SNe Ia may result from
super-Chandrasekhar mass WDs, and the highest mass of the WD at the moment of
SNe Ia explosion is 1.81 , but very massive () WDs
cannot be formed. However, when the initial mass of WDs is , the
explosive masses of SNe Ia are nearly uniform, which is consistent with the
rareness of super-Chandrasekhar mass SNe Ia in observations.Comment: 6 pages, 7 figures, accepted for publication in Astronomy and
Astrophysic
Tidal deformability with sharp phase transitions in (binary) neutron stars
The neutron star tidal deformability is a critical parameter which determines
the pre-merger gravitational-wave signal in a neutron star merger. In this
article, we show how neutron star tidal deformabilities behave in the presence
of one or two sharp phase transition(s). We characterize how the tidal
deformability changes when the properties of these phase transitions are
modified in dense matter equation of state (EoS). Sharp phase transitions lead
to the smallest possible tidal deformabilities and also induce discontinuities
in the relation between tidal deformability and gravitational mass. These
results are qualitatively unmodified by a modest softening of the phase
transition. Finally, we test two universal relations involving the tidal
deformability and show that their accuracy is limited by sharp phase
transitions.Comment: 20 pages, 18 figures; accepted for publication in PR
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