1,286 research outputs found
Discovery of Five New Pulsars in Archival Data
Reprocessing of the Parkes Multibeam Pulsar Survey has resulted in the
discovery of five previously unknown pulsars and several as-yet-unconfirmed
candidates. PSR J0922-52 has a period of 9.68 ms and a DM of 122.4 pc cm^-3.
PSR J1147-66 has a period of 3.72 ms and a DM of 133.8 pc cm^-3. PSR J1227-6208
has a period of 34.53 ms, a DM of 362.6 pc cm^-3, is in a 6.7 day binary orbit,
and was independently detected in an ongoing high-resolution Parkes survey by
Thornton et al. and also in independent processing by Einstein@Home volunteers.
PSR J1546-59 has a period of 7.80 ms and a DM of 168.3 pc cm^-3. PSR J1725-3853
is an isolated 4.79-ms pulsar with a DM of 158.2 pc cm^-3. These pulsars were
likely missed in earlier processing efforts due to their high DMs and short
periods and the large number of candidates that needed to be looked through.
These discoveries suggest that further pulsars are awaiting discovery in the
multibeam survey data.Comment: 12 pages, 2 figures, 2 tables, accepted to Ap
Observations of 20 millisecond pulsars in 47 Tucanae at 20 cm
We have used a new observing system on the Parkes radio telescope to carry
out a series of pulsar observations of the globular cluster 47 Tucanae at 20-cm
wavelength. We detected all 11 previously known pulsars, and have discovered
nine others, all of which are millisecond pulsars in binary systems. We have
searched the data for relatively short orbital period systems, and found one
pulsar with an orbital period of 96 min, the shortest of any known radio
pulsar.
The increased rate of detections with the new system resulted in improved
estimates of the flux density of the previously known pulsars, determination of
the orbital parameters of one of them, and a coherent timing solution for
another one. Five of the pulsars now known in 47 Tucanae have orbital periods
of a few hours and implied companion masses of only ~ 0.03 Msun. Two of these
are eclipsed at some orbital phases, while three are seen at all phases at 20
cm but not always at lower frequencies. Four and possibly six of the other
binary systems have longer orbital periods and companion masses ~ 0.2 Msun,
with at least two of them having relatively large orbital eccentricities. All
20 pulsars have rotation periods in the range 2-8 ms.Comment: 15 pages, 6 embedded EPS figures, to be published in The
Astrophysical Journa
Heartbeat of the Mouse: a young radio pulsar associated with the axisymmetric nebula G359.23-0.82
We report the discovery of PSR J1747-2958, a radio pulsar with period P = 98
ms and dispersion measure DM = 101 pc/cc, in a deep observation with the Parkes
telescope of the axially-symmetric "Mouse" radio nebula (G359.23-0.82). Timing
measurements of the newly discovered pulsar reveal a characteristic age Pdt/2dP
= 25 kyr and spin-down luminosity dE/dt = 2.5e36 erg/s. The pulsar (timing)
position is consistent with that of the Mouse's "head". The distance derived
from the DM, ~2 kpc, is consistent with the Mouse's distance limit from HI
absorption, < 5.5 kpc. Also, the X-ray energetics of the Mouse are compatible
with being powered by the pulsar. Therefore we argue that PSR J1747-2958,
moving at supersonic speed through the local interstellar medium, powers this
unusual non-thermal nebula. The pulsar is a weak radio source, with
period-averaged flux density at 1374 MHz of 0.25 mJy and luminosity ~1 mJy
kpc^2.Comment: 6 pages, 2 figures, accepted for publication in ApJ Letter
Constraining phases of quark matter with studies of r-mode damping in neutron stars
The r-mode instability in rotating compact stars is used to constrain the
phase of matter at high density. The color-flavor-locked phase with kaon
condensation (CFL-K0) and without (CFL) is considered in the temperature range
10^8K < T <10^{11} K. While the bulk viscosity in either phase is only
effective at damping the r-mode at temperatures T > 10^{11} K, the shear
viscosity in the CFL-K0 phase is the only effective damping agent all the way
down to temperatures T > 10^8 K characteristic of cooling neutron stars.
However, it cannot keep the star from becoming unstable to gravitational wave
emission for rotation frequencies f ~ 56-11 Hz at T ~ 10^8-10^9 K. Stars
composed almost entirely of CFL or CFL-K0 matter are ruled out by observation
of rapidly rotating neutron stars, indicating that dissipation at the
quark-hadron interface or nuclear crust interface must play a key role in
damping the instability.Comment: 8 pages, 2 figure
Timing the millisecond pulsars in 47 Tucanae
In the last 10 years 20 millisecond pulsars have been discovered in the
globular cluster 47 Tucanae. Hitherto, only 3 of these had published timing
solutions. Here we improve upon these 3 and present 12 new solutions. These
measurements can be used to determine a variety of physical properties of the
pulsars and of the cluster. The 15 pulsars have positions determined with
typical uncertianties of only a few milliarcsec and they are all located within
1.2 arcmin of the cluster centre. We have also measured the proper motions of 5
of the pulsars, which are consistent with the proper motion of 47 Tuc based on
Hipparcos data. The period derivatives measured for many of the pulsars are
dominated by the dynamical effects of the cluster gravitational field, and are
used to constrain the surface mass density of the cluster. All pulsars have
characteristic ages T > 170 Myr and magnetic fields B < 2.4e9 Gauss, and the
average T > 1 Gyr. We have measured the rate of advance of periastron for the
binary pulsar J0024-7204H, implying a total system mass 1.4+-0.8 solar masses.Comment: 17 pages, 11 included figures, accepted for publication in MNRA
A search for rotating radio transients and fast radio bursts in the Parkes high-latitude pulsar survey
Discoveries of rotating radio transients and fast radio bursts (FRBs) in
pulsar surveys suggest that more of such transient sources await discovery in
archival data sets. Here we report on a single-pulse search for dispersed radio
bursts over a wide range of Galactic latitudes (|b| < ) in data
previously searched for periodic sources by Burgay et al. We re-detected 20 of
the 42 pulsars reported by Burgay et al. and one rotating radio transient
reported by Burke-Spolaor. No FRBs were discovered in this survey. Taking into
account this result, and other recent surveys at Parkes, we corrected for
detection sensitivities based on the search software used in the analyses and
the different backends used in these surveys and find that the all-sky FRB
event rate for sources with a fluence above 4.0 Jy ms at 1.4 GHz to be FRBs day sky, where the
uncertainties represent a confidence interval. While this rate is lower
than inferred from previous studies, as we demonstrate, this combined event
rate is consistent with the results of all systematic FRB searches at Parkes to
date and does not require the need to postulate a dearth of FRBs at
intermediate latitudes.Comment: Accepted, 10 pages, 6 figure
Estimating the sensitivity of wide-parameter-space searches for gravitational-wave pulsars
This paper presents an in-depth study of how to estimate the sensitivity of
searches for gravitational-wave pulsars -- rapidly-rotating neutron stars which
emit quasi-sinusoidal gravitational waves. It is particularly concerned with
searches over a wide range of possible source parameters, such as searches over
the entire sky and broad frequency bands. Traditional approaches to estimating
the sensitivity of such searches use either computationally-expensive Monte
Carlo simulations, or analytic methods which sacrifice accuracy by making an
unphysical assumption about the population of sources being searched for. This
paper develops a new, analytic method of estimating search sensitivity which
does not rely upon this unphysical assumption. Unlike previous analytic
methods, the new method accurately predicts the sensitivity obtained using
Monte Carlo simulations, while avoiding their computational expense. The change
in estimated sensitivity due to properties of the search template bank, and the
geographic configuration of the gravitational wave detector network, are also
investigated.Comment: 16 figures, 2 tables, REVTeX 4.1; minor typos corrected from v2,
updated reference
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