339,724 research outputs found
The Radiation Structure of PSR B201628 Observed with FAST
With the largest dish Five-hundred-meter Aperture Spherical radio Telescope
(FAST), both the mean and single pulses of PSR B201628, especially including
the single-pulse structure, are investigated in detail in this study. The mean
pulse profiles at different frequencies can be well fitted in a conal model,
and the peak separation of intensity-dependent pulse profiles increases with
intensity. The integrated pulses are obviously frequency dependent (pulse width
decreases by as frequency increases from 300 MHz to 750 MHz), but
the structure of single pulses changes slightly (the corresponding correlation
scale decreases by only ). This disparity between mean and single
pulses provides independent evidence for the existence of the RS-type vacuum
inner gap, indicating a strong bond between particles on the pulsar surface.
Diffused drifting sub-pulses are analyzed. The results show that the modulation
period along pulse series () is positively correlated to the separation
between two adjacent sub-pulses (). This correlation may hint a rough
surface on the pulsar, eventually resulting in the irregular drift of sparks.
All the observational results may have significant implications in the dynamics
of pulsar magnetosphere and are discussed extensively in this paper.Comment: Sci. China-Phys. Mech. Astron. 62, 959505 (2019
A mathematical form of force-free magnetosphere equation around Kerr black holes and its application to Meissner effect
Based on the Lagrangian of the steady axisymmetric force-free magnetosphere
(FFM) equation around Kerr black holes(KBHs), we find that the FFM equation can
be rewritten in a new form as , where . By coordinate
transformation, the form of the above equation can be given by . Based on the form, we prove finally that the
Meissner effect is not possessed by a KBH-FFM with the condition where
and , here is the component of the vector potential ,
is the angular velocity of magnetic fields and
corresponds to twice the poloidal electric current
Phase transitions in a holographic s+p model with backreaction
In a previous paper (arXiv:1309.2204, JHEP 1311 (2013) 087), we present a
holographic s+p superconductor model with a scalar triplet charged under an
SU(2) gauge field in the bulk. We also study the competition and coexistence of
the s-wave and p-wave orders in the probe limit. In this work we continue to
study the model by considering the full back-reaction The model shows a rich
phase structure and various condensate behaviors such as the "n-type" and
"u-type" ones, which are also known as reentrant phase transitions in condensed
matter physics. The phase transitions to the p-wave phase or s+p coexisting
phase become first order in strong back-reaction cases. In these first order
phase transitions, the free energy curve always forms a swallow tail shape, in
which the unstable s+p solution can also play an important role. The phase
diagrams of this model are given in terms of the dimension of the scalar order
and the temperature in the cases of eight different values of the back reaction
parameter, which show that the region for the s+p coexisting phase is enlarged
with a small or medium back reaction parameter, but is reduced in the strong
back-reaction cases.Comment: 15 pages(two-column), 9 figure
ELUCID IV: Galaxy Quenching and its Relation to Halo Mass, Environment, and Assembly Bias
We examine the quenched fraction of central and satellite galaxies as a
function of galaxy stellar mass, halo mass, and the matter density of their
large scale environment. Matter densities are inferred from our ELUCID
simulation, a constrained simulation of local Universe sampled by SDSS, while
halo masses and central/satellite classification are taken from the galaxy
group catalog of Yang et al. The quenched fraction for the total population
increases systematically with the three quantities. We find that the
`environmental quenching efficiency', which quantifies the quenched fraction as
function of halo mass, is independent of stellar mass. And this independence is
the origin of the stellar mass-independence of density-based quenching
efficiency, found in previous studies. Considering centrals and satellites
separately, we find that the two populations follow similar correlations of
quenching efficiency with halo mass and stellar mass, suggesting that they have
experienced similar quenching processes in their host halo. We demonstrate that
satellite quenching alone cannot account for the environmental quenching
efficiency of the total galaxy population and the difference between the two
populations found previously mainly arises from the fact that centrals and
satellites of the same stellar mass reside, on average, in halos of different
mass. After removing these halo-mass and stellar-mass effects, there remains a
weak, but significant, residual dependence on environmental density, which is
eliminated when halo assembly bias is taken into account. Our results therefore
indicate that halo mass is the prime environmental parameter that regulates the
quenching of both centrals and satellites.Comment: 21 pages, 16 figures, submitted to Ap
Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time
Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model
under the Newton-Hooke contraction of the spacetime with respect to the
transformation group, algebra and geometry. It is shown that in Newton-Hooke
space-time, there are inertial-type coordinate systems and inertial-type
observers, which move along straight lines with uniform velocity. And they are
invariant under the Newton-Hooke group. In order to determine uniquely the
Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well
as the postulate on Newton-Hooke universal time. All results are readily
extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter
spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte
A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies
We have conducted a systematic search of low-mass black holes (BHs) in active
galactic nuclei (AGNs) with broad Halpha emission lines, aiming at building a
homogeneous sample that is more complete than previous ones for fainter, less
highly accreting sources. For this purpose, we developed a set of elaborate,
automated selection procedures and applied it uniformly to the Fourth Data
Release of the Sloan Digital Sky Survey. Special attention is given to
AGN--galaxy spectral decomposition and emission-line deblending. We define a
sample of 309 type 1 AGNs with BH masses in the range -- \msun (with a median of solar mass), using the
virial mass estimator based on the broad Halpha line. About half of our sample
of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered
here for the first time. Our new sample picks up more AGNs with low accretion
rates: the Eddington ratios of the present sample range from to ~1,
with 30% below 0.1. This suggests that a significant fraction of low-mass BHs
in the local Universe are accreting at low rates. The host galaxies of the
low-mass BHs have luminosities similar to those of field galaxies,
optical colors of Sbc spirals, and stellar spectral features consistent with a
continuous star formation history with a mean stellar age of less than 1 Gyr.Comment: Accepted for publication in Ap
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