Diffractive Scintillation of the pulsar PSR B1259-63
Naomi McClure-Griffiths (Oberlin College, Ohio, USA),
Simon Johnston (RCfTA, University of Sydney, Australia),
Dan Stinebring (Oberlin College, Ohio, USA),
L. Nicastro (I.Te.S.R.E. - CNR, Bologna, Italy)
Abstract
PSR B1259-63 is in a highly eccentric 3.4 yr orbit around the Be-star SS2883.
The system is located in the direction of the Sagittarius-Carina spiral arm at a
distance of ~1.5 kpc. We have made scintillation observations of the
pulsar far from periastron at 4.8 and 8.4 GHz, determining the diffractive
bandwidth and timescale at both frequencies. We find no
dependency on orbital phase until within 30 days of periastron. The data
indicate that the scintillation is caused, not by the circumstellar
environment, but by an HII region within the Sagittarius-Carina spiral arm
located at least three-quarters of the way to the pulsar. Close to
periastron, when the line-of-sight to the pulsar intersects the disk of the
Be star, the electron densities within the disk are sufficient to overcome
the `lever-arm effect' and produce a reduction in the scintillation
bandwidth by six orders of magnitude.
Key words: ISM: structure --- pulsars: individual (PSR~B1259-63)
Complete paper can be found at http://xxx.lanl.gov/abs/astro-ph/9711012