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IAUC 5707: GRB 930131; RE J0751+14

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                                                  Circular No. 5707
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


GRB 930131
     The Compton Observatory EGRET Team (M. Sommer, K. Brazier,
G. Kanbach, H. A. Mayer-Hasselwander and C. von Montigny,
Max-Planck-Institut fur Extraterrestrische Physik; D. L. Bertsch, B. L.
Dingus, C. E. Fichtel, R. C. Hartman, S. D. Hunter, J. R.
Mattox, P. Sreekumar and D. J. Thompson, NASA Goddard Space Flight
Center; D. A. Kniffen, Hampden-Sydney College; J. Chiang, J.
Fierro, Y. C. Lin, P. F. Michelson and P. L. Nolan, Stanford
University; and E. Schneid, Grumman Aerospace Corporation), together with
coinvestigator K. Hurley, University of California, report that the
EGRET detector on the Gamma Ray Observatory imaged the Jan. 31
gamma-ray burst at energies above 30 MeV.  The highest event energies
are significantly greater than have been observed in any previous burst.
The location is R.A = 12h11m, Decl = -10.7 (equinox 2000.0;
68-percent-confidence radius 40'; 95-percent-confidence radius 66'), near
the edge of the error box reported on IAUC 5702; see also IAUC 5704.


RE J0751+14
     V. Piirola and P. Hakala, University of Helsinki and Vatican
Observatory communicate: "We report the discovery of variable circular
and linear polarization over the 13.9-min spin period of the intermediate
polar RE J0751+14 (R.A. = 7h51m17s.3, Decl. = +14 44'23", equinox 2000.0;
V = 14.1) from observations with the Nordic 2.5-m telescope on 1992 Oct. 26.
The total (peak-to-peak) circular polarization variation was 4.2 +/- 0.6
percent in the I band (830 nm) and 2.2 +/- 0.3 percent in the R band (690
nm), with slightly stronger negative extremes and a faster transition from
the negative to the positive values.  The linear polarization
reached about 2 percent in I and 0.8 percent in R.  A preliminary analysis
suggests cyclotron emission from two regions near the opposite magnetic
poles of the white dwarf and field strength in the range 5-10 MG.
The position-angle variability could be tentatively explained with an
inclination of the magnetic white dwarf rotation axis 45-70 deg and the two
cyclotron-emission regions 35-60 deg from the rotation poles.  The intensity
modulation was 0.18 mag in I and 0.10 mag in R, with a double-peaked
structure, but in the UBV bands the lightcurve was nearly sinusoidal over
the spin period, and the amplitude decreased to about 0.07 mag.  The UBV
power spectra peak at 14.5 min, which could be the beat period corresponding
to a binary period of about 5 hr.  Further polarimetric, spectroscopic
and photometric observations are encouraged."


1993 February 5                (5707)              Brian G. Marsden

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