γ-Rays from γ Geminorum?
Abstract
THE γ-ray source CG195+4 (Geminga) discovered by SAS 2 and further observed by COS B has a period of 59 s which is increasing at a rate P˙ = 2×10-9 (refs 1,2). If the periodicity is produced by a neutron star which is spinning down at the observed rate, then the rate at which rotational energy is being lost is L ~ 3×1032 erg s-1 (ref. 3). The observed γ-ray flux of 3×10-6 photon cm-2 s-1 with energy E>100 MeV implies that the distance, d, to the source is given by d ~= 73f1/2 pc where f(≳ 1) is the fraction of the total energy output which is emitted as γ-rays. Theoretical studies of the evolution of binary systems which give rise to the binary X-ray sources have led to the suggestion that, before the neutron star starts to accrete and spin up (that is, before the X-ray source turns on) it spends a comparatively long time being spun down in the weak stellar wind of its companion4. This leads us to seek a candidate companion for the γ-ray source which is an early type star at a distance of ≳= 70 pc. As we report here, the only object which satisfies these constraints is γ Geminorum.
- Publication:
-
Nature
- Pub Date:
- February 1978
- DOI:
- 10.1038/271634a0
- Bibcode:
- 1978Natur.271..634D
- Keywords:
-
- Companion Stars;
- Early Stars;
- Gamma Ray Astronomy;
- Neutron Stars;
- Stellar Rotation;
- Bolometers;
- Relativistic Particles;
- Satellite Observation;
- Spaceborne Astronomy;
- Spin Reduction;
- Stellar Atmospheres;
- Stellar Winds;
- Astrophysics