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Astrophysics

Title: The Variable Jet of the Vela Pulsar

Abstract: Observations of the Vela pulsar-wind nebula (PWN) with the Chandra X-ray Observatory have revealed a complex, variable PWN structure, including inner and outer arcs, a jet in the direction of the pulsar's proper motion, and a counter-jet in the opposite direction, embedded in diffuse nebular emission.
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. 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 faint, strongly bent, extension of the outer jet. The more extreme bends closer to the pulsar, as well as the apparent side motions of the outer jet, can be associated with kink instabilities of a magnetically confined, pinched jet flow. Another feature found in the summed image is a dim, 2'-long outer counter-jet, which also shows a power-law spectrum with photon index of 1.2-1.5. Southwest of the jet/counter-jet (i.e., approximately perpendicular to the direction of pulsar's proper motion), an extended region of diffuse emission is seen. Relativistic particles responsible for this radiation are apparently supplied by the outer jet.
Comments: 13 pages, including 10 figures and 2 tables, accepted for publication in ApJ. The Vela Pulsar Jet movie and full resolution images are avaliable at this http URL
Subjects: Astrophysics (astro-ph)
Journal reference: Astrophys.J.591:1157-1171,2003
DOI: 10.1086/375531
Cite as: arXiv:astro-ph/0305510
  (or arXiv:astro-ph/0305510v1 for this version)

Submission history

From: Oleg Kargaltsev [view email]
[v1] Tue, 27 May 2003 19:22:25 GMT (248kb)