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Astron. Astrophys. 335, L21-L24 (1998)

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Letter to the Editor

Possible pulsed optical emission from Geminga *

A. , Shearer 1, A. , Golden 2, S. , Harfst 2, R. , Butler 2, R.M. , Redfern 2, C.M.M. , O'Sullivan 2, G.M. , Beskin 3, S.I. , Neizvestny 3, V.V. , Neustroev 3, V.L. , Plokhotnichenko 3, M. , Cullum 4, A. and Danks 5

1 Information Technology Centre, National University of Ireland, Galway, Galway City, Ireland
2 Department of Physics, National University of Ireland, Galway, Galway City, Ireland
3 SAO, Nizhnij Arhyz, Karachai-Cherkessia, Russia
4 European Southern Observatory, Garching bei München, Germany
5 STX/Goddard Space Flight Centre, Greenbank, Maryland, USA

Received 20 January 1998 / Accepted 12 May 1998


We present optical data which suggests that G", the optical counterpart of the [FORMULA] -ray pulsar Geminga, possibly pulses in B with a period of 0.237 seconds. The similarity between the optical pulse shape and the [FORMULA] -ray light curve indicates that a large fraction of the optical emission is non-thermal in origin - contrary to recent suggestions based upon the total optical flux. The derived magnitude of the pulsed emission is [FORMULA]. Whilst it is not possible to give an accurate figure for the pulsed fraction (due to variations in the sky background) we can give an 1 [FORMULA] upper limit of [FORMULA] for the unpulsed fraction.

Key words: pulsars: individual (Geminga) techniques: 2-d photon-counting detectors

* Based on Observations taken at ESO, La Silla, Chile and SAO, Nizhnij Arhyz, Russia

Send offprint requests to: A. Shearer (e-mail: andy.shearer@ucg.ie)

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© European Southern Observatory (ESO) 1998

Online publication: June 12, 1998