HI Line Measurements of Eight Southern Pulsars
Bärbel Koribalski ( ATNF ),
Simon Johnston
( RCfTA ),
Joel Weisberg ( Carlton College ,
USA), and Warrick Wilson (ATNF)
Abstract. To derive their kinematic distances and to study the interstellar medium, we have measured 21-cm absorption and emission spectra in the direction of eight southern pulsars with the Parkes telescope . For the first time we have successfully obtained HI absorption measurements for PSRs J0908-4913 , J1453-6413 , J1456-6843 and J1709-4429 . We have also significantly improved the sensitivity and resolution on PSRs J0742-2822 , J1001-5507 , and J1056-6258 , whose spectra have previously been measured. Furthermore, we obtained a high-quality absorption spectrum on an eighth pulsar, PSR J1559-4438 , whose previously determined spectrum was not usable for kinematic distance determinations due to frequency structure imposed by interstellar scintillation.
We present our absorption and emission spectra for these eight pulsars, derive kinematic distances and electron densities along their lines of sight where possible, and compare our results with previous work. For PSRs J1001-5507 and J1056-6258 we see HI in emission and absorption at velocities which cannot be explained by a simple rotation curve model. We present evidence to suggest that PSR J1056-6258 may be located behind the HII region BBW328. We discuss the gamma-ray efficiency of PSR J1709-4429 and its association with a supernova remnant in light of our kinematic distance estimate.
Additionally, we briefly examine the optical depths and inferred spin temperatures of the interstellar gas clouds in the direction of some of the observed pulsars.
headings: general - radio lines: stars - stars: distances