Neutral hydrogen absorption in the spectra of four low-latitude pulsars.
Abstract
Summary. The Arecibo 305-m telescope was used to measure the absorption of four pulsars' signals by intervening neutral hydrogen. Distance limits (in kpc) based on the Schmidt (1965) rotation model for three low-latitude objects are: PSR 1859+ 03,6< d<: 18;PSR1900+01,3 <: d< 5;andPSR2002+31, 8 < d <: 13. These distance estimates, when combined with known dispersion measures, lead to mean free-electron densities (in cm-3) of 0.02 <: ne> < 0.07 in the direction of PSR 1859 + 03; 0.045 <: <n6> < 0.08 toward PSR 1900+01; and 0.018 <: n6 < 0.03 toward PSR 2002+31. Independent evidence from Seacord and Gottesman (1977) supports the close distance and high electron density limits for PSR 1859 + 03. Absorption by the local arm was also seen in the spectrum of PSR 1946+35, but no distance limits could be derived. The electron density measured in the direction of pulsar 2002+31 is quite typical of the value found toward most pulsars (0.02-0.03 cm-3), while the higher electron densities measured along the lines of sight to pulsars 1859+03 and 1900+01 are similar to the values measured toward other pulsars in the inner parts of the Galaxy. The harmonic mean spin temperature of neutral hydrogen in the local arm in the direction of pulsar 2002+31 is found to be about 2000K. Key words: pulsar distances - H I absorption - electron density
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1979
- Bibcode:
- 1979A&A....77..204W
- Keywords:
-
- Absorption Spectra;
- Hydrogen Clouds;
- Neutral Gases;
- Pulsars;
- Electron Density (Concentration);
- Free Electrons;
- Milky Way Galaxy;
- Astrophysics;
- Distances:Pulsars;
- Interstellar Absorption:Pulsars;
- Neutral Hydrogen:Pulsars;
- Pulsars:Radio Spectra