AAS 198th Meeting, June 2001
Session 27. Neutron Stars, Pulsars Gamma ray Bursts
Oral, Monday, June 4, 2001, 2:00-3:30pm, C107

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[27.04] Chandra Spectra of the Vela Pulsar and Cas A Point Source

M.D. Stage, H.L. Marshall (MIT Center for Space Research), P.C. Joss (MIT), J. Madej (Warsaw University)

We present Chandra spectra of two neutron stars, HETG/ACIS-S spectra from our Chandra observation of the Vela pulsar and its synchrotron nebula, and ACIS spectra of Cassiopeia A from a 50 ksec Chandra observation which has recently become public. The 40 ksec Vela observation was made using the ACIS-S in continuous clocking mode, which sacrifices one spatial dimension for more precise timing. We will show the one-dimensional profile of the nebula and pulsar. We will present the current results of analysis of pulse-phased ACIS and HETG spectra of the pulsar, as well as ACIS spectra of the nebula. We will examine the unpulsed emission from Vela to search for identifiable atmospheric effects from the neutron star surface and deviations from the blackbody curve and the new model described below.

We will also analyse an ACIS S3 spectrum of the central point source of Cas A. Similarly to Chakrabarty et al.'s (ApJ 548:800, 2001) analysis of earlier Chandra observations of Cas A, we present fits with several models including an entirely new, state-of-the-art radiative transfer code for neutron star atmospheres developed by Madej (unpublished). The code solves the equation of radiative transfer subject only to the approximation that the neutron-star atmosphere is geometrically thin (i.e., plane-parallel), and limited in accuracy only by the number of discrete spectral lines are included in the numerical calculations and by the number of iterations that are used in a given computation.

Portions of this work were supported under the contract SAO SV1-61010.

The author(s) of this abstract have provided an email address for comments about the abstract: mikstage@space.mit.edu

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