Circular No. 6617
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 970402
     L. Piro, M. Feroci, and E. Costa, Istituto di Astrofisica
Spaziale, CNR, Frascati; L. A. Antonelli, F. Fiore, and P. Giommi,
BeppoSAX, Rome; A. Owens and A. Parmar, Space Science Department,
ESTEC; S. Molendi, Istituto di Fisica Cosmica e Tecnologie Relative,
CNR, Milano; G. Cusumano, Istituto di Fisica Cosmica e Applicazioni
Informatica, CNR, Palermo; J. in 't Zand, J. Heise, and R. Jager,
Space Research Organization of the Netherlands, Utrecht; F.
Frontera and G. Zavattini, Universita di Ferrara; L. Nicastro and
E. Palazzi, Istituto Tecnologie e Studio Radiazioni Extraterrestri,
CNR, Bologna; L. Salotti, OCC, Nuova Telespazio, Rome; L. Di Ciolo,
G. D'Andreta, R. Ricci, G. Spoliti, A. Coletta, M. Capalbi, and M.
R. Daniele, BeppoSAX, Rome; and R. C. Butler, Agenzia Spaziale
Italiana, Rome, report:  "The BeppoSAX GRBM/WFC error box of GRB
970402 (IAUC 6610) was observed with the BeppoSAX Narrow Field
Instruments on Apr. 3.280 UT for 25 000 s (8 hr after the gamma-ray
burst).  A previously unknown x-ray source, SAX J1450.1-6920, has
been detected by the MECS and LECS at the same position (R.A. =
14h50m06s, Decl. = -69o20'.0, equinox 2000.0; estimated error
radius 50").  This position lies at the center of the reported
BeppoSAX WFC error box (IAUC 6610).  The source countrate was (3.0
+/- 0.7) x 10E-3 counts sE-1, corresponding to a flux of (1.5 +/-
0.5) x 10E-13 erg cmE-2 sE-1 in the MECS (2-10 keV), and (2.0 +/-
0.6) x 10E-3 counts sE-1 in the LECS (0.5-5 keV), corresponding to
(2.0 +/- 0.6) x 10E-13 erg cmE-2 sE-1 in the range 0.5-5 keV.  The
flux conversion has been derived assuming the galactic column
density and a power law with photon index 2.  The source showed a
decreasing trend during the observation.  The field was observed
again on Apr. 4.634 for 50 000 s.  No source was detected in the
position of SAX J1450.1-6920.  The 3-sigma upper limit on the
source flux implies a decrease by a factor of 3 or more.  Given the
similarity with the behavior of the x-ray transient associated with
GRB 970228 (IAUC 6576), we conclude that BeppoSAX has detected the
x-ray afterglow of GRB 970402."


SUPERNOVA 1997bp IN NGC 4680
    G. V. Williams, Smithsonian Astrophysical Observatory, provides
the following measurement of SN 1997bp from the image by N. Grogin
(cf. IAUC 6613): R.A. = 12h46m53s.75, Decl. = -11o38'33".2 (equinox
2000.0), which is 14".1 west and 19".8 south of the nucleus of NGC
4680.

                      (C) Copyright 1997 CBAT
1997 April 8                   (6617)            Daniel W. E. Green