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IAUC 6572: GRB 970228; 1997aa

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                                                 Circular No. 6572
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
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GRB 970228
     E. Costa and M. Feroci, Istituto Astrofisica Spaziale, CNR,
Frascati; F. Frontera and G. Zavattini, Universita di Ferrara; L.
Nicastro and E. Palazzi, Istituto Tecnologie e Studio Radiazioni
Extraterrestri, CNR, Bologna; G. Spoliti, L. Di Ciolo, A. Coletta,
G. D'Andreta, and J. M. Muller, BeppoSAX, Rome; and R. Jager, J.
Heise, and J. in 't Zand, Space Research Organization of the
Netherlands, Utrecht, communicate:  "The BeppoSAX Gamma Ray Burst
Monitor (GRBM) was triggered on Feb. 28.123620 UT.  A quick-look
analysis of the GRBM light curve shows a moderately intense,
multi-peaked gamma-ray burst lasting about 80 s, with one major
structured peak followed by three minor peaks.  The first peak
intensity at maximum is about 3700 counts/s, while the trailing
peaks show a decreasing intensity from 600 to 150 counts/s.  The
gamma-ray burst was detected by the Wide Field Camera (WFC) number
1 with a similar time profile and a peak countrate of about 400
counts/s.  Taking into account the off-axis position, the peak flux
corresponds to about 0.23 Crab.  From the WFC image, we have
derived a preliminary position of R.A. = 5h01m57s, Decl. = +11 46'.4
(equinox 2000.0), with a 3' error radius.  A BeppoSAX TOO pointing
of the Narrow Field Instruments was performed starting on Feb.
28.458, just 8 hr after the GRB trigger time.  The relevant data
analysis is in progress.  Observations in all bands are solicited."

SUPERNOVA 1997aa IN IC 2102
     W.-d. Li, Y.-l. Qiu, Q.-y. Qiaom and J.-y. Hu, Beijing
Astronomical Observatory (BAO), on behalf of the BAO supernova
survey, report the discovery of a supernova on CCD images of IC
2102 taken on Mar. 1.5 UT with the BAO 0.60-m reflector.  SN 1997aa
is located at R.A. = 4h51m53s.6, Decl. = -4 57'36" (equinox 2000.0),
which is 25" west and 29" south of the center of IC 2102.
Available unfiltered CCD magnitudes:  Mar. 1.5, about 17.0; 2.5,
about 16.7.  A low-resolution spectrum (40 nm/mm, range 350-930 nm)
obtained by Q.-r. Yuan (Nanjing Normal University) and W. Liu and
W.-d. Li (BAO) on Mar. 2.5 with the BAO 2.16-m telescope at Xinglong
station shows that this is an type-II supernova prior to optical
maximum.  There are weak, yet conspicuous, H Balmer lines
superimposed on a very blue continuum.  The expansion velocity of
the photosphere is 15 000 km/s (as derived from the H-alpha line).
H-beta could be seen only marginally.

                      (C) Copyright 1997 CBAT
1997 March 2                   (6572)            Daniel W. E. Green

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