3,386 research outputs found
Timing of pulsars found in a deep Parkes multibeam survey
We have carried out a sensitive radio pulsar survey along the northern
Galactic plane ( and |b| \lapp 2^{\circ}) using
the Parkes 20-cm multibeam system. We observed each position for 70-min on two
separate epochs. Our analyses to date have so far resulted in the detection of
32 pulsars, of which 17 were previously unknown. Here we summarize the
observations and analysis and present the timing observations of 11 pulsars and
discovery parameters for a further 6 pulsars. We also present a timing solution
for the 166-ms bursting pulsar, PSR~J1938+2213, previously discovered during an
Arecibo drift-scan survey. Our survey data for this pulsar show that the
emission can be described by a steady pulse component with bursting emission,
which lasts for typically 20--25 pulse periods, superposed. Other new
discoveries are the young 80.1-ms pulsar PSR~J1935+2025 which exhibits a
significant amount of unmodeled low-frequency noise in its timing residuals,
and the 4.2-ms pulsar PSR~J1935+1726 which is in a low-mass binary system with
a 90.7-day circular orbit.Comment: 6 pages, 2 figures, accepted for publication in MNRA
The Next Geminga: Deep Multiwavelength Observations of a Neutron Star Identified with 3EG J1835+5918
We describe Chandra, HST, and radio observations that reveal a radio-quiet
but magnetospherically active neutron star in the error circle of the
high-energy gamma-ray source 3EG J1835+5918, the brightest of the unidentified
EGRET sources at high Galactic latitude. A Chandra ACIS-S spectrum of the
ultrasoft X-ray source RX J1836.2+5925, suggested by Mirabal & Halpern as the
neutron star counterpart of 3EG J1835+5918, requires two components: a
blackbody of T~3x10^5 K and a hard tail that can be parameterized as a power
law of photon index Gamma~2. An upper limit of d < 800 pc can be derived from
the blackbody fit under an assumption of R = 10 km. Deep optical imaging with
the HST STIS CCD failed to detect this source to a limit of V > 28.5, thus
f_X/f_V > 6000 and d > 250 pc assuming the X-ray fitted temperature for the
full surface. Repeated observations with the 76 m Lovell telescope at Jodrell
Bank place an upper limit of < 0.1 mJy on the flux density at 1400 MHz for a
pulsar with P > 0.1 s, and < 0.25 mJy for a ~10 ms pulsar at the location of RX
J1836.2+5925. All of this evidence points to an older, possibly more distant
version of the highly efficient gamma-ray pulsar Geminga, as the origin of the
gamma-rays from 3EG J1835+5918.Comment: 4 pages, 4 figures, accepted for publication in ApJ Letter
The Parkes multibeam pulsar survey: IV. Discovery of 180 pulsars and parameters for 281 previously known pulsars
The Parkes multibeam pulsar survey has led to the discovery of more than 700
pulsars. In this paper, we provide timing solutions, flux densities and pulse
profiles for 180 of these new discoveries. Two pulsars, PSRs J1736-2843 and
J1847-0130 have rotational periods P > 6s and are therefore among the slowest
rotating radio pulsars known. Conversely, with P = 1.8ms, PSR J1843-1113 has
the third shortest period of pulsars currently known. This pulsar and PSR
J1905+0400 (P = 3.8ms) are both solitary. We also provide orbital parameters
for a new binary system, PSR J1420-5625, which has P = 34ms, an orbital period
of 40 days and a minimum companion mass of 0.4 solar masses. The 10 degree-wide
strip along the Galactic plane that was surveyed is known to contain 264 radio
pulsars that were discovered prior to the multibeam pulsar survey. We have
redetected almost all of these pulsars and provide new dispersion measure
values and flux densities at 20cm for the redetected pulsars.Comment: 35 pages, accepted for publication in MNRAS, a high quality image of
the figure on page 32 is available from
http://www.atnf.csiro.au/research/pulsar/images/pmsurvey_fig.p
Discovery of the Putative Pulsar and Wind Nebula Associated with the TeV Gamma-ray Source HESS J1813-178
We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio
supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We
resolve the X-ray emission from the co-located ASCA source into a point source
surrounded by structured diffuse emission that fills the interior of the radio
shell. The morphology of the diffuse emission strongly resembles that of a
pulsar wind nebula. The spectrum of the compact source is well-characterized by
a power-law with index Gamma approx 1.3, typical of young and energetic
rotation-powered pulsars. For a distance of 4.5 kpc, consistent with the X-ray
absorption and an association with the nearby star formation region W33, the
2-10 keV X-ray luminosities of the putative pulsar and nebula are L(PSR) =
3.2E33 ergs/s and L(PWN) = 1.4E34 ergs/s, respectively. Both the flux ratio of
L(PWN)/L(PSR) = 4.3 and the total luminosity of this system predict a pulsar
spin-down power of Edot > 1E37 ergs/s, placing it within the ten most energetic
young pulsars in the Galaxy. A deep search for radio pulsations using the
Parkes telescope sets an upper-limit of approx 0.07 mJy at 1.4 GHz for periods
>~ 50 ms. We discuss the energetics of this source, and consider briefly the
proximity of bright H2 regions to this and several other HESS sources, which
may produce their TeV emission via inverse Compton scattering.Comment: 7 pages, 6 figure, Latex, emulateapj style. To appear in the
Astrophysical Journa
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
Discovery of short-period binary millisecond pulsars in four globular clusters
We report the discovery using the Parkes radio telescope of binary
millisecond pulsars in four clusters for which no associated pulsars were
previously known. The four pulsars have pulse periods lying between 3 and 6 ms.
All are in circular orbits with low-mass companions and have orbital periods of
a few days or less. One is in a 1.7-hour orbit with a companion of planetary
mass. Another is eclipsed by a wind from its companion for 40% of the binary
period despite being in a relatively wide orbit. These discoveries result from
the use of improved technologies and prove that many millisecond pulsars remain
to be found in globular clusters.Comment: 4 pages, 2 figs, 1 table - Accepted by Astrophysical Journal Letter
Arecibo timing and single-pulse observations of 17 pulsars
We report on timing and single-pulse observations of 17 pulsars discovered at
the Arecibo observatory. The highlights of our sample are the recycled pulsars
J1829+2456, J1944+0907 and the drifting subpulses observed in PSR J0815+0939.
For the double neutron star binary J1829+2456, in addition to improving upon
our existing measurement of relativistic periastron advance, we have now
measured the pulsar's spin period derivative. This new result sets an upper
limit on the transverse speed of 120 km/s and a lower limit on the
characteristic age of 12.4 Gyr. From our measurement of proper motion of the
isolated 5.2-ms pulsar J1944+0907, we infer a transverse speed of 188 +/- 65
km/s. This is higher than that of any other isolated millisecond pulsar. An
estimate of the speed, using interstellar scintillation, of 235 +/- 45 km/s
indicates that the scattering medium along the line of sight is non-uniform. We
discuss the drifting subpulses detected from three pulsars in the sample, in
particular the remarkable drifting subpulse properties of the 645-ms pulsar
J0815+0939. Drifting is observed in all four components of the pulse profile,
with the sense of drift varying among the different components. This unusual
`bi-drifting'' behaviour challenges standard explanations of the drifting
subpulse phenomenon.Comment: 9 pages, 6 figures. Accepted for publication in MNRA
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