229 research outputs found
Time Variability in the X-ray Nebula Powered by Pulsar B1509-58
We use new and archival Chandra and ROSAT data to study the time variability
of the X-ray emission from the pulsar wind nebula (PWN) powered by PSR B1509-58
on timescales of one week to twelve years. There is variability in the size,
number, and brightness of compact knots appearing within 20" of the pulsar,
with at least one knot showing a possible outflow velocity of ~0.6c (assuming a
distance to the source of 5.2 kpc). The transient nature of these knots may
indicate that they are produced by turbulence in the flows surrounding the
pulsar. A previously identified prominent jet extending 12 pc to the southeast
of the pulsar increased in brightness by 30% over 9 years; apparent outflow of
material along this jet is observed with a velocity of ~0.5c. However, outflow
alone cannot account for the changes in the jet on such short timescales.
Magnetohydrodynamic sausage or kink instabilities are feasible explanations for
the jet variability with timescale of ~1.3-2 years. An arc structure, located
30"-45" north of the pulsar, shows transverse structural variations and appears
to have moved inward with a velocity of ~0.03c over three years. The overall
structure and brightness of the diffuse PWN exterior to this arc and excluding
the jet has remained the same over the twelve year span. The photon indices of
the diffuse PWN and possibly the jet steepen with increasing radius, likely
indicating synchrotron cooling at X-ray energies.Comment: accepted to ApJ, 14 pages, 8 figure
ASCA observations of the young rotation-powered pulsars PSR B1046-58 and PSR B1610-50
We present X-ray observations of two young energetic radio pulsars, PSRs
B1046-58 and B1610-50, and their surroundings, using archival data from the
Advanced Satellite for Cosmology and Astrophysics (ASCA).
The energetic pulsar PSR B1046-58 is detected in X-rays with a significance
of 4.5 sigma. The unabsorbed flux, estimated assuming a power-law spectrum and
a neutral hydrogen column density N_H of 5E21 cm^-2 is (2.5 +/- 0.3) x 10E-13
ergs/cm^2/s in the 2-10 keV band. Pulsed emission is not detected; the pulsed
fraction is less than 31% at the 90% confidence level for a 50% duty cycle. We
argue that the emission is best explained as originating from a pulsar-powered
synchrotron nebula. The X-ray counterpart of the pulsar is the only hard source
within the 95% error region of the previously unidentified gamma-ray source 3EG
J1048-5840. This evidence supports the results of Kaspi et al. (1999), who in a
companion paper, suggest that PSR B1046-58 is the counterpart to 3EG
J1048-5840.
X-ray emission from PSR B1610-50 is not detected. Using similar assumptions
as above, the derived 3 sigma upper limit for the unabsorbed 2-10 keV X-ray
flux is 1.5E-13 ergs/cm^2/s. We use the flux limit to estimate the pulsar's
velocity to be less than ~170 km/s, casting doubt on a previously reported
association between PSR B1610-50 and supernova remnant Kes 32. Kes 32 is
detected, as is evident from the correlation between X-ray and radio emission.
The ASCA images of PSR B1610-50 are dominated by mirror-scattered emission from
the X-ray-bright supernova remnant RCW 103, located 33' away.
We find no evidence for extended emission around either pulsar, in contrast
to previous reports of large nebulae surrounding both pulsars.Comment: Accepted for publication in the ApJ (v.528, pp.436-444) Correcting
typo in abstract of .tex fil
Chandra and XMM-Newton Observations of the Vela-like Pulsar B1046-58
We present results from Chandra and XMM-Newton observations of the radio
pulsar B1046-58. A high-resolution spatial analysis reveals an asymmetric
pulsar wind nebula (PWN) ~6"x11" in size. The combined emission from the pulsar
and its PWN is faint, with a best-fit power-law photon index of =1.7
and unabsorbed luminosity of ~10^32 ergs/s in the 0.5-10.0 keV range (assuming
a distance of 2.7 kpc). A spatially resolved imaging analysis suggests the
presence of softer emission from the pulsar. No pulsations are detected from
PSR B1046-58; assuming a worst-case sinusoidal pulse profile, we derive a
3 upper limit for the pulsed fraction in the 0.5-10.0 keV range of 53%.
Extended PWN emission is seen within 2" of the pulsar; the additional
structures are highly asymmetric and extend predominantly to the south-east. We
discuss the emission from the PWN as resulting from material downstream of the
wind termination shock, as outflow from the pulsar or as structures confined by
a high space velocity. The first two interpretations imply equipartition fields
in the observed structures of ~40-100 uG, while the latter case implies a
velocity for the pulsar of ~ 190 n^-1/2 km/s (where n is the ambient number
density in units of cm^-3). No emission from an associated supernova remnant is
detected.Comment: 8 pages, 4 figures. Accepted to Ap
X-ray Observations of the New Pulsar-Supernova Remnant System PSR J1119-6127 and Supernova Remnant G292.2-0.5
PSR J1119-6127 is a recently discovered 1600-yr-old radio pulsar that has a very high inferred surface dipolar magnetic field. We present a detailed analysis of a pointed ASCA observation and archival ROSAT data of PSR J1119-6127 and its surroundings. Both data sets reveal extended emission coincident with the newly discovered radio supernova remnant G292.2-0.5, which is reported in a companion paper by Crawford et al. A hard point source, offset ~15 from the position of the radio pulsar, is seen with the ASCA Gas Imaging Spectrometer (GIS). No pulsations are detected at the radio period with a pulsed fraction upper limit of 61% (95% confidence). The limited statistics prevent a detailed spectral analysis, although a power-law model with photon index Î â 1-2 describes the data well. Both the spectral model and derived X-ray luminosity are consistent with those measured for other young radio pulsars, although the spatial offset renders an identification of the source as the X-ray counterpart of the pulsar uncertain
Chandra observations of the pulsar wind nebula in SNR G0.9+0.1
We present observations with the Chandra X-ray Observatory of the pulsar wind
nebula (PWN) within the supernova remnant G0.9+0.1. At Chandra's high
resolution, the PWN has a clear axial symmetry; a faint X-ray point source
lying along the symmetry axis possibly corresponds to the pulsar itself. We
argue that the nebular morphology can be explained in terms of a torus of
emission in the pulsar's equatorial plane and a jet directed along the pulsar
spin axis, as is seen in the X-ray nebulae powered by other young pulsars. A
bright clump of emission within the PWN breaks the axisymmetry and may
correspond to an intermediate-latitude feature in the pulsar wind.Comment: 5 pages, 2 embedded EPS figures, uses emulateapj.sty . Accepted to
ApJ Letter
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