THE RADIO PULSAR GEMINGA

We report the results of our search for pulsed radio emission from Gem inga carried out in 1992, 1993 and 1996-1997 at 102.5 MHz using the BS A radiotelescope of the Pushchino Radioastronomy Observatory. The Gemi nga radio pulsar (PSR J0633+1746) was detected in all three observatio n periods. With the best signal to noise ratio Geminga was detected in records taken in 1993, when the maximum passband of the radiotelescop e was used for the searches. The main criterion for radio pulsar detec tion was the presence of records containing the dominant spectral line at the rotation frequency of the pulsar Omega=4.22 Hz in the amplitud e spectra. The method of averaging the amplitude spectra, obtained for many days in February-June 1993, was used for the determination of th e mean flux density of the Geminga radio emission at 102.5 MHz. We rep ort the main parameters of the pulsar PSR J0633+1746, obtained from ou r observations. The mean flux S-102= 8((+3)(-2))mJy. The average pulse profile is very wide and has a shape like in X-rays (Halpern and Holt , 1992 [Natur, 357, 222]). The profile width on the 0.5 level W-0.5 si milar or equal to 120ms, i. e. about 180 degrees. The dispersion measu re DM=3.2+/-0.3pc.cm(-3). A timing analysis, which was performed for t he best profiles, obtained from 1992 to 1997, yields values for the pe riod P and derivative P, which are, within error limits, in agreement with the data published by Mayer-Hasselwander et al. (1994)[ApJ, 421, 276]. We discuss possible reasons for the extremely low radio luminosi ty of the Geminga pulsar. (C) 1998 Elsevier Science B. V.