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Gamma Rays from the Geminga Pulsar: Variations with time and Phase

Published online by Cambridge University Press:  12 April 2016

I. A. Grenier ,
K. Bennett ,
R. Buccheri ,
M. Gros ,
R. N. Henriksen ,
W. Hermsen ,
G. Kanbach  and
B. Sacco
I. A. Grenier
Affiliation:
EUROPA, Université Paris 7, Observatoire de Paris, 92190 Meudon, France DAPNIA/SAp, Centre d’Etudes de Saclay, 91191 Gif-sur-Yvette Cedex, France
K. Bennett
Affiliation:
Space Science Department of ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
R. Buccheri
Affiliation:
IFCAI/CNR, Via M. Stabile 172, 90139 Palermo, Italy
M. Gros
Affiliation:
DAPNIA/SAp, Centre d’Etudes de Saclay, 91191 Gif-sur-Yvette Cedex, France
R. N. Henriksen
Affiliation:
Queen’s University, Physics Department, Kingston, Ontario, Canada K7L3N6
W. Hermsen
Affiliation:
SRON/Leiden, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands
G. Kanbach
Affiliation:
MPI für Extraterrestrische Physik, Karl Schwarzschild Str. 1, 8046 Garching, Germany
B. Sacco
Affiliation:
IFCAI/CNR, Via M. Stabile 172, 90139 Palermo, Italy

Abstract

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Pulsed γ radiation from the Geminga pulsar was recorded by the COS B satellite from 50 MeV to 5 GeV between 1975 and 1982. It has been analysed to derive the source spectral properties as a function of time and phase. The two main peaks are separated by 0.50 ± 0.01 in phase. Significant pulsed emission has also been detected in both phase regions between the two main peaks. Significant spectral differences with phase have been found; the emission from the first peak is slightly softer than from the second one and the Interpeak 2 radiation is extremely soft. The first peak emission remained stable within the statistics over 7 years while the flux from the other phase intervals changed significantly with time. The phase dependence of the variability implies that all the observed source emission should be pulsed and that it consists of four discrete beams with different apertures and spectra. The beams characteristics are strikingly similar to those of four γ-ray beams generated by the Vela pulsar.

Subject headings: gamma rays: observations — pulsars: individual (Geminga, Vela)

Type
Pulsars, Supernovae, and Supernova Remnants
Information
International Astronomical Union Colloquium , Volume 142: Particle Acceleration Phenomena in Astrophysical Plasmas , 1994 , pp. 813 - 816
Copyright
Copyright © The American Astronomical Society 1994

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