10,855 research outputs found
The jets of the Vela pulsar
Chandra observations of the Vela pulsar-wind nebula (PWN) have revealed a jet
in the direction of the pulsar's proper motion, and a counter-jet in the
opposite direction, embedded in diffuse nebular emission. The jet consists of a
bright, 8''-long inner jet, between the pulsar and the outer arc, and a dim,
curved outer jet that extends up to 100'' in approximately the same direction.
From the analysis of thirteen Chandra observations spread over about 2.5
years we found that this outer jet shows particularly strong variability,
changing its shape and brightness. We observed bright blobs in the outer jet
moving away from the pulsar with apparent speeds (0.3-0.6)c and fading on
time-scales of days to weeks. The spectrum of the outer jet fits a power-law
model with a photon index of 1.3\pm0.1. The X-ray emission of the outer jet can
be interpreted as synchrotron radiation of ultrarelativistic
electrons/positrons. This interpretation allows one to estimate the magnetic
field, ~100 microGauss, maximum energy of X-ray emitting electrons, ~2\times
10^{14} eV, and energy injection rate, ~8\times 10^{33} erg/s, for the outer
jet. In the summed PWN image we see a dim, 2'-long outer counter-jet, which
also shows a power-law spectrum with photon ined of 1.2-1.5. Southwest of the
jet/counter-jet an extended region of diffuse emission is seen. Relativistic
particles responsible for this radiation are apparently supplied by the outer
jet.Comment: 4 pages, including 1 figure, accepted for publication in New
Astronomy Reviews; proceedings of the conference "The Physics of Relativistic
Jets in the CHANDRA and XMM Era", 23-27 September 2002, Bologna. The full
resolution versions of the images shown in the fugure are avaliable at
http://www.astro.psu.edu/users/green/vela_jet_proc/vela_jet_proc.htm
Thermal Radiation from Neutron Stars: Chandra Results
The outstanding capabilities of the Chandra X-ray observatory have greatly
increased our potential to observe and analyze thermal radiation from the
surfaces of neutron stars (NSs). Such observations allow one to measure the
surface temperatures and confront them with the predictions of the NS cooling
models. Detection of gravitationally redshifted spectral lines can yield the NS
mass-to-radius ratio. In rare cases when the distance is known, one can measure
the NS radius, which is particularly important to constrain the equation of
state of the superdense matter in the NS interiors. Finally, one can infer the
chemical composition of the NS surface layers, which provides information about
formation of NSs and their interaction with the environment. We overview the
recent Chandra results on the thermal radiation from various types of NSs --
active pulsars, young radio-quiet neutron stars in supernova remnants, old
radio-silent ``dim'' neutron stars -- and discuss their implications.Comment: URL changed for Figures 1, 12 and 18:
ftp://ftp.xray.mpe.mpg.de/people/zavli
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