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IAUC 6600: C/1995 O1; GRB 920501

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                                                  Circular No. 6600
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)


COMET C/1995 O1 (HALE-BOPP)
     J. Sarmecanic, University of California at San Diego (UCSD);
D. J. Osip, University of Florida; and M. Fomenkova and B. Jones, UCSD,
report: "Imaging of comet C/1995 O1 has been obtained using the UCSD
mid-infrared camera at the 1.5-m telescope on Mt. Lemmon, Arizona.
The inner coma (40 000 km across) was continuously observed for 11.5 hr
at 8.7, 10.3, 11.7 and 12.5 microns during Mar. 3.51-4.00 and 5.52-6.00 UT.
A bright jet, initially directed to the southwest, appears in all filters;
over time, it rotates clockwise and reappears in the southwest 11.3 hr
later, consistent with previously reported rotation periods of between
11.2 and 11.65 hr (IAUC 6560, 6583).  There are also two arcs on the
sunward side (southwest) at 15 and 30 arcsec from the nucleus.
Photometric magnitudes in a 10-arcsec circular aperture on Mar. 5.53,
5.77 and 5.97 are, respectively (uncertainties 0.10-0.15 mag):
[8.7 microns] = -4.6, -4.4, -4.4; [10.3 microns] = -6.0, -5.6, -5.6;
[11.7 microns] = -5.7, -5.6, -5.8; [12.5 microns] = -5.2, -5.0, -5.1.
The strong silicate feature, as observed at 10.3 microns, is a factor of
2.5 +/- 0.3 higher than the continuum, which is estimated to be 390 K."


GRB 920501
     M. J. Drinkwater and L. A. Jones, University of New South Wales;
O. M. Blaes, T. Hurt and R. Antonucci, University of California at Santa
Barbara; and K. Hurley, University of California at Berkeley, report: "We
have measured the optical spectrum of the galaxy in the HRI error circle of
the possible x-ray counterpart to GRB 920501 with the Australian National
University 2.3 m telescope at Siding Spring Observatory.  The galaxy is
labelled source 7 in Fig. 1 of Blaes et al. (1997, Ap.J., in press).  This
figure is available on the World Wide Web at
http://vela.physics.ucsb.edu/people/jkeck.html.  The HRI error circle
depicted there has 6" radius and center at R.A. = 8h15m18s.06,
Decl. = -32d44'27".0 (equinox 2000.0).  The spectrum shows H-beta, [O III]
(495.9 and 500.7 nm), H-alpha and the [S II] doublet in emission at a
redshift of 0.315.  The H-alpha line has an equivalent width of
approximately 40 nm and an FWHM of 2300 km/s.  This strongly suggests
that the galaxy is a type 1 Seyfert and that it is the x-ray source.
Given the possible association with the gamma-ray burst, we encourage
further observations of this Seyfert."

                      (C) Copyright 1997 CBAT
1997 March 21                  (6600)              Brian G. Marsden

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