56 research outputs found
Mode Switching and Subpulse Drifting in PSR B0826-34
We present high-quality observations of PSR B0826-34 at 1374 MHz. The
emission from this pulsar exhibits strong bursts of pulses followed by long
periods of `null' pulses. When it is strong, the radiation extends through the
whole pulse period. We show for the first time that there is weak emission
during the `null' phases, which should therefore be considered to be a
different mode rather than a null. During this weak mode the profile is similar
to that observed in the strong mode at low radio frequency. Using a
phase-tracking method, the pattern of drifting subpulses during the strong mode
is seen to be coherent across the whole profile. The drift rate is variable and
includes positive and negative values. Thirteen subpulse bands have been
directly observed, covering the whole longitude range. The subpulses and their
spacings () are wider in one half of the profile than those in the other
half. This difference, and the variation of observed within the two
regions, can be accounted for if the magnetic pole is inclined to the rotation
axis by about 0.5 degrees. These two regions appear to represent radiation from
outer and inner cones. The intensity modulation of subpulses in all longitude
ranges is related to the magnitude of the drift rate.Comment: 8 pages, 10 figures. Accepted for publication in MNRA
Strong pulses detected from a rotating radio transient J18191458
We analyze individual pulses detected from RRAT J18191458. From April 2007
to April 2010, we carried out observations using the Nanshan 25-m radio
telescope of Urumqi Observatory at a central frequency of 1541.25 MHz. We
obtain a dispersion measure pc cm^{-3} by analyzing all the
423 detected bursts. The tri-band pattern of arrival time residuals is
confirmed by a single pulse timing analysis. Twenty-seven bimodal bursts
located in the middle residual band are detected, and, profiles of two typical
bimodal bursts and two individual single-peak pulses are presented. We
determine the statistical properties of SNR and W of bursts in different
residual bands. The W variation with SNR shows that the shapes of bursts
are quite different from each other. The cumulative probability distribution of
intensity for a possible power law with index is inferred
from the number of those bursts with and high intensities.Comment: 6 pages, 8 figures, 1 table, accepted for publication in A&
Radiation properties of extreme nulling pulsar J1502-5653
We report on radiation properties of extreme nulling pulsar J1502-5653, by
analyzing the data acquired from the Parkes 64-m telescope at 1374 MHz. The
radio emission from this pulsar exhibits sequences of several tens to several
hundreds consecutive burst pulses, separated by null pulses, and the appearance
of the emission seems quasi-periodic. The null fraction from the data is
estimated to be 93.6%. No emission is detected in the integrated profile of all
null pulses. Systematic modulations of pulse intensity and phase are found at
the beginning of burst-pulse sequences just after null. The intensity usually
rises to a maximum for the first few pulses, then declines exponentially
afterwards, and becomes stable after few tens of pulse periods. The peak phase
appears at later longitudes for the first pulse, then drifts to earlier
longitudes rapidly, and then systematic drifting gradually vanishes while the
intensity becomes stable. In this pulsar, the intensity variation and phase
modulation of pulses are correlated in a short duration after the emission
starts following a null. Observed properties of the pulsar are compared with
other nulling pulsars published previously, and the possible explanation for
phase modulation is discussed.Comment: 5 pages, 7 figures. Accepted by MNRA
Microlensing pulsars
We investigate the possibilities that pulsars act as the lens in
gravitational microlensing events towards the galactic bulge or a spiral arm.
Our estimation is based on expectant survey and observations of FAST (Five
hundred meter Aperture Spherical Telescope) and SKA (Square Kilometer Array),
and two different models of pulsar distribution are used. We find that the
lensing rate is > 1 event/decade, being high enough to search the real events.
Therefore, the microlensing observations focusing on pulsars identified by FAST
or SKA in the future are meaningful. As an independent determination of pulsar
mass, a future detection of microlensing pulsars should be significant in the
history of studying pulsars, especially in constraining the state of matter
(either hadronic or quark matter) at supra-nuclear densities. The observations
of such events by using advanced optical facilities (e.g., the James Webb Space
Telescope and the Thirty Meter Telescope) in future are highly suggested.Comment: 5pages, 2figure
Precise determination of stellar parameters of the ZZ Ceti and DAZ white dwarf GD 133 through asteroseismology
An increasing number of white dwarf stars show atmospheric chemical
composition polluted by heavy elements accreted from debris disk material. The
existence of such debris disks strongly suggests the presence of one or more
planet(s) whose gravitational interaction with rocky planetesimals is
responsible for their disruption by tidal effect. The ZZ Ceti pulsator and
polluted DAZ white dwarf GD 133 is a good candidate for searching for such a
potential planet. We started in 2011 a photometric follow-up of its pulsations.
As a result of this work in progress, we used the data gathered from 2011 to
2015 to make an asteroseismological analysis of GD 133, providing the star
parameters from a best fit model with / = 0.630 0.002,
= 12400 K 70 K, log() = -2.00 0.02,
log() = -4.50 0.02 and determining a rotation period of
7 days.Comment: 10 pages, 13 figures, accepted by MNRA
Unusual glitch activity in the RRAT J1819-1458: an exhausted magnetar?
We present an analysis of regular timing observations of the
high-magnetic-field Rotating Radio Transient (RRAT) J18191458 obtained using
the 64-m Parkes and 76-m Lovell radio telescopes over the past five years.
During this time, the RRAT has suffered two significant glitches with
fractional frequency changes of and .
Glitches of this magnitude are a phenomenon displayed by both radio pulsars and
magnetars. However, the behaviour of J18191458 following these glitches is
quite different to that which follows glitches in other neutron stars, since
the glitch activity resulted in a significant long-term net decrease in the
slow-down rate. If such glitches occur every 30 years, the spin-down rate, and
by inference the magnetic dipole moment, will drop to zero on a timescale of a
few thousand years. There are also significant increases in the rate of pulse
detection and in the radio pulse energy immediately following the glitches.Comment: accepted for publication in MNRAS, 7 pages, 7 figures, 1 tabl
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