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IAUC 5750: 1993J; GRB 930309

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                                                  Circular No. 5750
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)


SUPERNOVA 1993J IN NGC 3031
     H. U. Zimmermann, Max-Planck-Institut fur Extraterrestrische
Physik (MPE); W. Lewin and E. Magnier, Massachusetts Institute of
Technology; P. Predehl, G. Hasinger, W. Pietsch, B. Aschenbach, and
J. Trumper, MPE; G. Fabbiano, Center for Astrophysics; J. van
Paradijs, University of Amsterdam; L. Lubin, Princeton University;
and R. Petre, Goddard Space Flight Center, communicate:  "We report
on the x-ray spectrum of SN 1993J obtained with ROSAT on Apr. 3.4
(IAUC 5747).  In total, 212 counts were collected.  The spectrum
appears to be very flat, consistent with either a power law having
a photon index of about -0.7 or a thermal spectrum with kT > 4 keV.
The NH column density is 3.4 x 10E20 cmE-2, slightly below the
galactic H I column density.  This corresponds to a luminosity of 1.6
x 10E39 erg/s in the range 0.1-2.4 keV for a distance of 3.25 Mpc.
The optical/x-ray luminosity ratio is therefore about 1000, similar
to SN 1980K but in strong contrast to SN 1987A.  This first x-ray
observation of a supernova (whose progenitor was a red supergiant)
near maximum optical light indicates a relatively hard spectrum in
the ROSAT x-ray band.  We plan to observe the source several times
during the next few weeks."
     U. Munari, Asiago Astrophysical Observatory, corrects the
photometry reported by Sostero et al. on IAUC 5741, using the
magnitudes provided by Hanzl for HD 86677 (IAUC 5742):  Mar. 31.972 UT,
V = 10.94, B-V = +0.37.  Further electronic photometry (Johnson
system unless denoted Cousins by subscript 'c'):  Apr. 1.020 UT, V
= 10.90, B-V = +0.40 (Munari); 1.660, V = 11.22 (M. Okyudo and T.
Ishida, Nishiharima Observatory, Hyogo, Japan); 3.16, Bc = 12.21,
Bc-Rc = +0.66 (P. Prugniel, Observatoire de Haute Provence); 5.00,
Bc = 12.46, Bc-Rc = +0.76 (Prugniel); 5.489, V = 11.88 (T. Kato,
Kyoto University); 5.549, B = 12.25 (Kato); 5.513, Ic = 11.24
(Kato); 5.614, V = 11.89 (Kato); 5.660, V = 11.98 (Okyudo and
Ishida); 5.93, V = 11.87 +/- 0.03, U-B = -0.47 +/- 0.10, B-V =
+0.50 +/- 0.05, V-R = +0.52 +/- 0.04, V-I = +0.38 +/- 0.10 (M.
Mikolajewski and K. Belczynski, N. Copernicus University, Torun;
reference star 24 UMa); 5.669, B = 12.25 (Kato); 5.713, Ic =
11.08: (Kato).


GRB 930309
Corrigendum.  On IAUC 5749, the apparent position of the radio
source was given; the J2000.0 position is R.A. = 21h32m52s.96,
Decl. = +54 40'15".94.


1993 April 6                   (5750)            Daniel W. E. Green

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