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IAUC 6580: GRB 970228

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                                                 Circular No. 6580
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 970228
     T. Boller and W. Voges, Max-Planck-Institut fur
Extraterrestrische Physik, Garching; F. Frontera, Universita di
Ferrara and Instituto Tecnologie e Studio delle Radiazioni
Extraterrestri, CNR, Bologna; and E. Costa and L. Piro, Istituto
Astrofisica Spaziale, Frascati, report: "Within the 3'-radius error
box of the BeppoSAX/WFC position for this gamma-ray burst (IAUC
6572), no source is detected in the ROSAT all-sky-survey data
between 1990 Aug. 26 and 28.  The survey exposure time at the
BeppoSAX/WFC position is 435 s.  The ROSAT 1.7-sigma upper limit in
this error box is 0.0272 count/s (0.1-2.4 keV), which corresponds
to 9.2 x 10E-13 erg cmE-2 sE-1, assuming a column density of
hydrogen NH = 1.6 x 10E21 cmE-2 and a power-law model with energy
index 0.8.  The distance to the nearest ROSAT all-sky-survey source
from the GRB centroid is 12'.7.  Within the 50" error box of the
BeppoSAX Narrow Field Instruments centered on R.A. = 5h01m44s, Decl.
= 11o46'.7 (IAUC 6576), the ROSAT all-sky-survey 2.5-sigma upper
limit is 0.0056 count/s (0.1-2.4 keV), which corresponds to 1.9 x
10E-13 erg cmE-2 sE-1; this is compatible with the BeppoSAX flux
level reported for GRB 970228 on Mar. 3.734 UT (IAUC 6576)."
     H. Pedersen, Copenhagen University Observatory; S. Benetti and
M. Turatto, European Southern Observatory (ESO); P. Goudfrooij and
A. Marconi, Space Telescope Science Institute, Baltimore; P.
Jablonka, Departement d'Astrophysique Extragalactique et de
Cosmologie, Observatoire de Paris; E. Costa, Istituto Astrofisica
Spaziale, CNR, Frascati; F. Frontera, Universita di Ferrara; E.
Palazzi, Istituto Tecnologie e Studio Radiazioni Extraterrestri,
CNR, Bologna; J. Heise, Space Research Organization of the
Netherlands, Utrecht; J. Studt, Hamburg Observatory; and A. J.
Castro-Tirado, LAEFF, Madrid, report:  "We have observed the
position of the VLA source (IAUC 6576) using the ESO 3.6-m
telescope (+ EFOSC1 instrument).  On the sharpest and deepest
exposure (R, 3 min, Mar. 8), the optical object reported by Margon
et al. (IAUC 6577) has the appearance of a centrally condensed
galaxy.  Integrated within a 5" diaphragm, we find B > 22, R =
21.06 (Mar. 8); and V = 22.27, R = 21.05 (Mar. 9).  The measurement
errors are 0.1-0.2 mag.  Several fainter galaxies are close by; one
is 2".5 east, another 5" west.  Low-dispersion, noisy spectra
(range 380-700 and 600-1000 nm) obtained on Mar. 9 show no evident
emission or absorption lines present in the red continuum."

                      (C) Copyright 1997 CBAT
1997 March 10                  (6580)            Daniel W. E. Green

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