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IAUC 6593: GRB 970228

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                                                 Circular No. 6593
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)


GRB 970228
     T. L. Cline, P. S. Butterworth, and D. E. Stilwell, Goddard
Space Flight Center, NASA; and E. P. Mazets, S. V. Golenetskii, R.
L. Aptekar, D. D. Frederiks, V. N. Il'inskii, and M. M. Terekhov,
Ioffe Politechnical Institute, St. Petersburg, for the Wind/Konus
Gamma-Ray-Burst Team; and K. Hurley, Space Sciences Laboratory,
Berkeley, for the Ulysses gamma-Ray-Burst Team, report:  "An
independent source locus of the Feb. 28 transient event, based on
observations from the interplanetary network (IPN) incorporating
GGS-Wind and Ulysses, and entirely independent of observations from
the BeppoSAX spacecraft, consists of a source annulus with half-
width < 30".  This gamma-ray burst, first localized by BeppoSAX,
has been speculated as being possibly associated with one or more
candidate sources in other wavelength regions, including a long-
lived x-ray component, a weak VLA radio component, and most
recently an optical transient.  The center of the IPN annulus is at
R.A. = 11h03m47s, Decl. = +36o27'.8 (equinox 2000.0) and its radius
is 83.4313 deg.  The discrepancy with the SAX LECS source is < 1',
within the combined error estimates, and the discrepancy with the
optical transient source is < 15", entirely consistent with the IPN
source accuracy."
     A. Yoshida, N. Kawai, C. Otani, and F. Tokanai, Institute of
Physical and Chemical Research (RIKEN); H. Inoue, T. Murakami, F.
Nagase, R. Shibata, and Y. Ueda, Institute of Space and
Astronautical Science; S. Holt, Goddard Space Flight Center, NASA,
on behalf of the ASCA team; L. Piro and E. Costa, Istituto di
Astrofisica Spaziale, CNR, Frascati; J. Heise, Space Research
Organization of the Netherlands, Utrecht, on behalf of the SAX team;
and J. Hughes, Rutgers University, report:  "ASCA observed the SAX
burst position of GRB 970228 (IAUC 6572) on Mar. 7.028-7.486 UT
with a net exposure time of 20 000 s.  The data displayed a weak
excess in both GIS and SIS images of the revised BeppoSAX error
region (IAUC 6576).  Image fitting was done to both the GIS and SIS
data sets, assuming a point source.  The source's location was
found to be consistent with that of SAX J0501.7+1146, considering
statistical errors and the attitude uncertainty of ASCA.  The 2-10-
keV flux and its 1-sigma statistical error are estimated to be (9.0
+/- 2.6) x 10E-14 erg cmE-2 sE-1 for the GIS and (7.2 +/- 2.1) x
10E-14 erg cmE-2 sE-1 for the SIS, assuming a power-law spectrum
with a photon index of 1.4."

                      (C) Copyright 1997 CBAT
1997 March 19                  (6593)            Daniel W. E. Green

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