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Astron. Astrophys. 325, 631-639 (1997)

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Unusual increase in the 325 MHz flux density of PSR B0655+64

T.J. Galama 1, A.G. de Bruyn 2, 3, J. van Paradijs 1, 4, L. Hanlon 5 and K. Bennett 6

1 Astronomical Institute `Anton Pannekoek'/ CHEAF, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands
2 NFRA, Radio Observatory, Postbus 2, 7990 AA, Dwingeloo, The Netherlands
3 Kapteyn Astronomical Institute, Postbus 800, 9700 AV, Groningen, The Netherlands
4 Physics Department, UAH, Huntsville, AL 35899, USA
5 Physics Department, University College Dublin, Belfield, Dublin 4, Ireland
6 Astrophysics Division, ESTEC, Noordwijk, The Netherlands

Received 19 July 1996 / Accepted 12 November 1996

Abstract

We report on the detection of a large amplification of the flux density of PSR B0655+64 at 325 MHz (a factor of [FORMULA] 43) that lasted about one hour. To the best of our knowledge such a large amplification has not been reported before. The phenomenon is restricted to a very narrow bandwidth (50 % decorrelation half-width of 3.6 [FORMULA] 0.4 MHz). The decorrelation bandwidth and characteristic time scale of the variation are in agreement with the values expected for diffractive interstellar scintillation. However, the observed amplification of the flux density of PSR B0655+64 is rather large. The observations suggest that amplifications of a factor up to 8 are not uncommon for PSR 0655+64 at 92 cm. The extreme flux density amplification of PSR 0655+64 might be explained in terms of caustics. We consider it unlikely that this event can be explained by intrinsic variability.

Key words: pulsars: individual: PSR B0655+64 – scattering – radio continuum: ISM

Send offprint requests to: titus@astro.uva.nl

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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