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IAUC 6670: GRB 970508; P/1997 G1

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                                                  Circular No. 6670
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


GRB 970508
     G. Pooley and D. Green, Mullard Radio Astronomy Observatory,
University of Cambridge, report: "We obtained observations of the radio
source (IAUC 6662) associated with GRB 970508 with the Ryle Telescope at
15 GHz on seven successive days.  During May 16.45-16.58 UT the mean flux
density was 1.57 +/- 0.25 mJy (1 sigma), a result supporting the inverted
radio spectrum reported by Frail et al. (IAUC 6662).  On none of the other
six days was an individually significant detection made, but by averaging
the data obtained during May 17-22 we obtain a measurement significant at
the 3-sigma level, giving a flux density of 0.66 +/- 0.11 mJy (1 sigma)."

     G. B. Taylor, A. J. Beasley and D. A. Frail, National Radio Astronomy
Observatory; and S. R. Kulkarni, California Institute of Technology,
report: "Observations with the Very Long Baseline Array at 8.4 GHz have
detected the radio source (IAUC 6662) identified with Bond's optical variable
(IAUC 6654, 6655) within the error circle of GRB 970508.  During
May 17.17-17.40 UT an unresolved source (size < 0".0003) was found
at R.A. = 6h53m49s.4513, Decl. = +79d16'19".513 (equinox J2000.0).  This
position is consistent with the earlier VLA position (IAUC 6662, with
errors of +/- 0".1), but the current uncertainty in the position derived
from the VLBA observations is 0".001 in both coordinates.  The flux
density of the source was 0.48 +/- 0.06 mJy.  Phase referencing was
performed by cycling every 3 min between the target source and the
strong (0.75 Jy) compact source B0718+793 located 1.5 deg away.  A
preliminary reduction of observations during May 16.48-16.92 using the
VLBA, the 100-m radio telescope at Effelsberg and the phased VLA confirms
this detection and should yield an image with much lower thermal noise.
We are continuing to observe this source every few days with the VLBA."


COMET P/1997 G1 (MONTANI)
     As was suggested on IAUC 6624, further observations through May 19 have
shown this to be a short-period comet.  The following orbital elements
are taken from MPC 29880:

     T = 1997 Apr. 26.757 TT          Peri. = 216.527
     e = 0.45668                      Node  = 267.471   2000.0
     q = 4.24044 AU                   Incl. =   3.959
       a =  7.80461 AU     n = 0.045204     P =  21.80 years

                      (C) Copyright 1997 CBAT
1997 May 24                   (6670)              Brian G. Marsden

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