Pulsar studies with COMPTEL

Abstract

The Compton Gamma-Ray Observatory (C-GRO) has completed a full-sky survey during which the number of known 7-ray pulsars has more than doubled. COMPTEL has observed the classical pulsars Crab and Vela on several occasions and has derived detailed pulse patterns and spectral parameters in the 0.7-30 MeV energy interval. The new C-GRO 7-ray pulsars have different properties in terms of energy spectra and light-curve shapes, and, in fact, only the Crab is seen by all four C-GRO instruments. This raises intriguing questions about the particle acceleration processes and beaming taking place in the neutron magnetosphere. We have examined the COMPTEL data to add information on these objects in the 0.7-30 MeV energy interval and present evidence for the detection of one of them, PSR B1509-58. We have also undertaken a search for candidate radio pulsars whose ephemerides are well denned. The results of these analyses are presented.

First results from the Australia Telescope Compact Array 18-GHz pilot survey

“…Our counts are in good agreement with those by Waldram et al (2003, 9C survey) at 15 GHz (Fig. 7), and with the preliminary VSA , DASI (Leitch et al 2002), and WMAP counts (Bennett et al 2003) if we assume a radio spectral index α = 0.…”

“…Although this pilot survey is not extremely uniform we know the sensitivity map and can estimate the 18-GHz counts of extragalactic sources down to 100 mJy. The results are in good agreement with the 15-GHz counts by Taylor et al (2001), with the preliminary VSA and DASI (Leitch et al 2002) counts, with the WMAP counts at 41 GHz (Bennett et al 2003) and with the 9C survey at 15 GHz by Waldram et al (2003). We determine the source counts particularly well in the crucial 200-800 mJy flux range, bridging the gap between the 9C and the WMAP surveys.…”

“…This is mainly because large radio telescopes typically have fields of view of a few arcmin at high frequencies, making it extremely time-consuming to carry out large-area surveys. Measuring the high-frequency properties of extragalactic radio sources is also crucial for interpreting the high-sensitivity and high-resolution maps of the cosmic microwave background (CMB) provided by the Wilkinson Microwave Anisotropy Probe (WMAP; Bennett et al 2003) and forthcoming missions such as the European Space Agency (ESA) Planck satellite (Tauber 2001). Current analyses (De Zotti et al 1999a) indicate that the best regions for high-E-mail: ricci@sissa.it resolution CMB mapping lie near 100 GHz, and that the main contaminant is likely to be the fluctuations caused by individual foreground radio sources.…”

“…Preliminary radio source counts at 30 GHz have been measured by the DASI (Leitch et al 2002), VSA ) and CBI (Mason et al 2003) groups, and a catalogue of 208 point source candidates stronger than approximately 1 Jy from the first year of WMAP data (five frequency bands from 23 to 94 GHz) has recently been published by Bennett et al (2003).…”

OSSE Observations of the Vela and Geminga Pulsars

“…An observation of 0.3-30 MeV pulsed emission was reported by T umer et al 1984 31 days after a major pulsar period glitch, but negative results have been reported by Ulmer et al 1991 using data from the gamma-ray spectrometer aboard HEAO 3, and by Sacco et al 1990 using the FIGARO II balloon-borne experiment. However, with the launch of the Compton Gamma Ray Observatory, a positive detection in the 1-30 MeV range has been reported by the COMPTEL instrument team Bennett et al 1994;Sch onfelder et al 1994.…”