Circular No. 6666
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
     M. Morris, N. Mastrodemos, B. Zuckerman, C. McCarthy, E.
Becklin, P. Lowrance, and R. Chary, University of California at Los
Angeles; and C. Barnbaum, Space Telescope Science Institute, report:
"We imaged the optical transient associated with GRB 970508 (cf.
IAUC 6649, 6654, 6655) with the Keck I telescope (+ NIRC camera +
K_s filter).  The K_s magnitudes of the variable on May 13.25 and
16.25 UT were 18.43 +/- 0.05 and 19.21 +/- 0.06, respectively,
corresponding to fluxes of 28.3 +/- 1.3 and 13.8 +/- 1.7 microJy.
The gradient of the decline in this interval is similar to that
reported in the r band in the preceding 3-day interval (IAUC 6658,
6660).  The May 13.25 K_s flux is slightly above the contemporaneous
r-band flux, giving an r-K_s color of +2.3 +/- 0.2.  In these brief
(about 10-min) images, the limit on the K_s flux from any associated
galaxy within a 1".2-2".4 annulus around the transient is 5 microJy."
     M. Donahue, K. C. Sahu, M. Livio, and L. Petro, Space Telescope
Science Institute; J. T. Stocke, University of Colorado; P. Groot,
University of Amsterdam (UoA); and J. van Paradijs, UoA and
University of Alabama, write:  "A 15-min exposure in the I band
taken on May 9.15 UT at the Kitt Peak 4-m telescope was used to get
relative photometry of the optical counterpart of GRB 970508 (IAUC
6654, 6655, 6658), yielding I = 20.4 +/- 0.1, assuming the magnitude
of the 'standard' star of Schaefer et al. (IAUC 6658) to be I = 18.4
+/- 0.1."


V485 CENTAURI
     A. Olech, Warsaw University Observatory, writes:  "CCD
observations of the dwarf nova V485 Cen during its recent outburst,
collected with the 1.3-m Warsaw telescope at Las Campanas
Observatory as a subproject of the OGLE-2 project, indicate that
this star belongs to the SU UMa group of cataclysmic variables.  A
3-hr I-band observation on May 17.1 UT shows three well-developed
typical superhumps with an amplitude of 0.25 mag and period 57.7
min.  Thus, V485 Cen has the shortest known period among SU UMa-
type stars, with a period as much as 25 percent shorter than
previously known objects."


SUPERNOVA 1997bp IN NGC 4680
     Unfiltered CCD magnitude estimate by S. Moretti and S.
Tomaselli, Forli, Italy: May 14.92 UT, 15.6 (GSC comparison stars).

                      (C) Copyright 1997 CBAT
1997 May 21                    (6666)            Daniel W. E. Green