1,671 research outputs found
Proper Motions of PSRs B1757-24 and B1951+32: Implications for Ages and Associations
Over the last decade, considerable effort has been made to measure the proper
motions of the pulsars B1757-24 and B1951+32 in order to establish or refute
associations with nearby supernova remnants and to understand better the
complicated geometries of their surrounding nebulae. We present proper motion
measurements of both pulsars with the Very Large Array, increasing the time
baselines of the measurements from 3.9 yr to 6.5 yr and from 12.0 yr to 14.5
yr, respectively, compared to previous observations. We confirm the
non-detection of proper motion of PSR B1757-24, and our measurement of (mu_a,
mu_d) = (-11 +/- 9, -1 +/- 15) mas yr^{-1} confirms that the association of PSR
B1757-24 with SNR G5.4-1.2 is unlikely for the pulsar characteristic age of
15.5 kyr, although an association can not be excluded for a significantly
larger age. For PSR B1951+32, we measure a proper motion of (mu_a, mu_d) =
(-28.8 +/- 0.9, -14.7 +/- 0.9) mas yr^{-1}, reducing the uncertainty in the
proper motion by a factor of two compared to previous results. After correcting
to the local standard of rest, the proper motion indicates a kinetic age of ~51
kyr for the pulsar, assuming it was born near the geometric center of the
supernova remnant. The radio-bright arc of emission along the pulsar proper
motion vector shows time-variable structure, but moves with the pulsar at an
approximately constant separation ~2.5", lending weight to its interpretation
as a shock structure driven by the pulsar.Comment: LaTeX file uses emulateapj.cls; 7 pages, 4 figures, to be published
ApJ February 10, 2008, v674 p271-278. Revision reflects journal formatting;
there are no substantial revision
Timing models for the long-orbital period binary pulsar PSR B1259-63
The pulsar PSR B1259-63 is in a highly eccentric 3.4-yr orbit with the Be
star SS 2883. Timing observations of this pulsar, made over a 7-yr period using
the Parkes 64-m radio telescope, cover two periastron passages, in 1990 August
and 1994 January. The timing data cannot be fitted by the normal pulsar and
Keplerian binary parameters. A timing solution including a (non-precessing)
Keplerian orbit and timing noise (represented as a polynomial of fifth order in
time) provide a satisfactory fit to the data. However, because the Be star
probably has a significant quadrupole moment, we prefer to interpret the data
by a combination of timing noise, dominated by a cubic phase term, and
and terms. We show that the and are
likely to be a result of a precessing orbit caused by the quadrupole moment of
the tilted companion star. We further rule out a number of possible physical
effects which could contribute to the timing data of PSR B1259-63 on a
measurable level.Comment: LaTeX, 9 pages, 8 figures, accepted for publication in MNRA
The 69 ms Radio Pulsar Near the Supernova Remnant RCW 103
We report the detection of the radio pulsar counterpart to the 69 ms X-ray
pulsar discovered near the supernova remnant RCW 103 (G332.4-0.4). Our
detection confirms that the pulsations arise from a rotation-powered neutron
star, which we name PSR J1617-5055. The observed barycentric period derivative
confirms that the pulsar has a characteristic age of only 8 kyr, the sixth
smallest of all known pulsars. The unusual apparent youth of the pulsar and its
proximity to a young remnant requires that an association be considered.
Although the respective ages and distances are consistent within substantial
uncertainties, the large inferred pulsar transverse velocity is difficult to
explain given the observed pulsar velocity distribution, the absence of
evidence for a pulsar wind nebula, and the symmetry of the remnant. Rather, we
argue that the objects are likely superposed on the sky; this is reasonable
given the complex area. Without an association, the question of where is the
supernova remnant left behind following the birth of PSR J1617-5055 remains
open. We also discuss a possible association between PSR J1617-5055 and the
gamma-ray source 2CG 333+01. Though an association is energetically plausible,
it is unlikely given that EGRET did not detect 2CG 333+01.Comment: 18 pages, 2 encapsulated Postscript figures, uses AAS LaTeX style
files. Accepted for publication in The Astrophysical Journal Letter
Radio Emission Signatures in the Crab Pulsar
Our high time resolution observations of individual pulses from the Crab
pulsar show that both the time and frequency signatures of the interpulse are
distinctly different from those of the main pulse. Main pulses can occasionally
be resolved into short-lived, relatively narrow-band nanoshots. We believe
these nanoshots are produced by soliton collapse in strong plasma turbulence.
Interpulses at centimeter wavelengths are very different. Their dynamic
spectrum contains regular, microsecond-long emission bands. We have detected
these bands, proportionately spaced in frequency, from 4.5 to 10.5 GHz. The
bands cannot easily be explained by any current theory of pulsar radio
emission; we speculate on possible new models.Comment: 26 pages, 10 figures, to appear in Ap
Magnetic Effects Change Our View of the Heliosheath
There is currently a controversy as to whether Voyager 1 has already crossed
the Termination Shock, the first boundary of the Heliosphere. The region
between the Termination Shock and the Heliopause, the Helisheath, is one of the
most unknown regions theoretically. In the Heliosheath magnetic effects are
crucial, as the solar magnetic field is compressed at the Termination Shock by
the slowing flow. Recently, our simulations showed that the Heliosheath
presents remarkable dynamics, with turbulent flows and the presence of a jet
flow at the current sheet that is unstable due to magnetohydrodynamic
instabilities \cite{opher,opher1}. In this paper we review these recent
results, and present an additional simulation with constant neutral atom
background. In this case the jet is still present but with reduced intensity.
Further study, e.g., including neutrals and the tilt of the solar rotation from
the magnetic axis, is required before we can definitively address how the
Heliosheath behaves. Already we can say that this region presents remarkable
dynamics, with turbulent flows, indicating that the Heliosheath might be very
different from what we previously thought.Comment: 6 pages, 5 figures, to appear in IGPP 3rd Annual International
Astrophysics Conference, "PHYSICS OF THE OUTER HELIOSPHERE
Glitches in Southern Pulsars
Timing observations of 40 mostly young pulsars using the ATNF Parkes radio
telescope between 1990 January and 1998 December are reported. In total, 20
previously unreported glitches and ten other glitches were detected in 11
pulsars. These included 12 glitches in PSR J13416220, corresponding to a
glitch rate of 1.5 glitches per year. We also detected the largest known
glitch, in PSR J16145047, with
where is the pulse frequency. Glitch parameters were determined
both by extrapolating timing solutions to inter-glitch intervals and by
phase-coherent timing fits across the glitch(es). Analysis of glitch
parameters, both from this work and from previously published results, shows
that most glitches have a fractional amplitude of between
and . There is no consistent relationship between glitch
amplitude and the time since the previous glitch or the time to the following
glitch, either for the ensemble or for individual pulsars. As previously
recognised, the largest glitch activity is seen in pulsars with ages of order
10 years, but for about 30 per cent of such pulsars, no glitches were
detected in the 8-year data span. There is some evidence for a new type of
timing irregularity in which there is a significant increase in pulse frequency
over a few days, accompanied by a decrease in the magnitude of the slowdown
rate. Fits of an exponential recovery to post-glitch data show that for most
older pulsars, only a small fraction of the glitch decays. In some younger
pulsars, a large fraction of the glitch decays, but in others, there is very
little decay.Comment: 19 pages, 20 figures. Accepted for publication in MNRA
X-ray Observations of High-B Radio Pulsars
The study of high-magnetic-field pulsars is important for examining the
relationships between radio pulsars, magnetars, and X-ray-isolated neutron
stars (XINSs). Here we report on X-ray observations of three such
high-magnetic-field radio pulsars. We first present the results of a deep
XMM-Newton observation of PSR J1734-3333, taken to follow up on its initial
detection in 2009. The pulsar's spectrum is well fit by a blackbody with a
temperature of 300 +/- 60 eV, with bolometric luminosity L_bb = 2.0(+2.2
-0.7)e+32 erg/s = 0.0036E_dot for a distance of 6.1 kpc. We detect no X-ray
pulsations from the source, setting a 1 sigma upper limit on the pulsed
fraction of 60% in the 0.5-3 keV band. We compare PSR J1734-3333 to other
rotation-powered pulsars of similar age and find that it is significantly
hotter, supporting the hypothesis that the magnetic field affects the observed
thermal properties of pulsars. We also report on XMM-Newton and Chandra
observations of PSRs B1845-19 and J1001-5939. We do not detect either pulsar,
setting 3 sigma upper limits on their blackbody temperatures of 48 and 56 eV,
respectively. Despite the similarities in rotational properties, these sources
are significantly cooler than all but one of the XINSs, which we attribute to
the two groups having been born with different magnetic fields and hence
evolving differently.Comment: 18 pages, 2 tables, 5 figures, accepted for publication in the
Astrophysical Journa
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