6 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
Studying Millisecond Pulsars in X-rays
Millisecond pulsars represent an evolutionarily distinct group among rotation-powered pulsars. Outside the radio band, the soft X-ray range (--10 keV) is most suitable for studying radiative mechanisms operating in these fascinating objects. X-ray observations revealed diverse properties of emission from millisecond pulsars. For the most of them, the bulk of radiation is of a thermal origin, emitted from small spots (polar caps) on the neutron star surface heated by relativistic particles produced in pulsar acceleration zones. On the other hand, a few other very fast rotating pulsars exhibit almost pure nonthermal emission generated, most probably, in pulsar magnetospheres. There are also examples of nonthermal emission detected from X-ray nebulae powered by millisecond pulsars, as well as from pulsar winds shocked in binary systems with millisecond pulsars as companions. These and other most important results obtained from X-ray observations of millisecond pulsars are reviewed in this paper, as well as results from the search for millisecond pulsations in X-ray flux of the radio-quite neutron star RX J1856.5-3754