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IAUC 6539: GRB 970111

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                                                 Circular No. 6539
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 970111
     R. C. Butler, Agenzia Spaziale Italiana, Rome; L. Piro, E.
Costa, and M. Feroci (cf. IAUC 6533); F. Frontera and D. Dal Fiume,
TESRE, CNR, Bologna; J. Heise and R. Jager; B. Sacco, IFCAI, CNR,
Palermo; L. Chiappetti, IFCTR, CNR, Milan; A. Parmar, Space Science
Department, ESTEC; L. A. Antonelli and D. Ricci, BeppoSAX, Rome; J.
M. Muller, BeppoSAX, Rome, and SRON, Utrecht; and A. Coletta, C. De
Libero, and L. Salotti, BeppoSAX, Rome, write:  "BeppoSAX pointed
its Narrow Field Instruments on the estimated position of GRB
970111 (IAUC 6533) during Jan. 12.09-13.38 UT.  A quick analysis of
the data shows two sources within the BeppoSAX WFC error box:  (a)
R.A. = 15h28m46s.3, Decl. = +19o44'50" (equinox 2000.0), with a
MECS 2-10-keV flux of 0.0025 counts/s (corresponding to 3.8 x
10E-13 erg cmE-2 sE-1) and a LECS flux 0.1-10-keV of 0.0037
counts/s (about 4.4 x 10E-13 erg cmE-2 sE-1); (b) R.A. =
15h28m48s.3, Decl. = +19o38'34", with a MECS flux (2-10 keV) of
0.0013 counts/s (about 1.9 x 10E-13 erg cmE-2 sE-1).  The spectrum
of source 'a' is considerably softer than that of source 'b'.  As
some systematic effects can still be present, an error radius of 1'
must still be assumed.  Though the detection is highly significant,
the countrates can have an uncertainty of 30 percent, due to
systematic effects and to the application of a spectrum-independent
correction for rough flux estimation."
     W. Voges and T. Boller, Max-Planck-Institut fur
Extraterrestrische Physik, Garching; and J. Greiner,
Astrophysikalisches Institut, Potsdam, report:  "Within the 10'
error box centered on the BeppoSAX position of the gamma-ray burst
970111 (IAUC 6533), we have found three faint x-ray sources in the
ROSAT all-sky survey data from 1991 Aug. 5-7, with the following
positions (equinox 2000.0; estimated 1-sigma error 45"), PSPC
countrates and fluxes (assuming a power-law model with photon index
of 2.0 but not corrected for any galactic absorption):  source 1,
R.A. = 15h28m40s, Decl. = +19o44'.5, 0.045 +/- 0.015 counts/s (0.1-
2.0 keV) or 2.5 x 10E-13  erg cmE-2 sE-1; source 2, R.A. =
15h28m59s, Decl. = +19o43'.8, 0.012 +/- 0.06 counts/s (0.5-2.0 keV)
or 3.1 x 10E-14 erg cmE-2 sE-1; source 3, R.A. = 15h28m43s, Decl. =
+19o38'.5, 0.026 +/- 0.011 counts/s (0.5-2.0 keV) or 6.6 x 10E-14
erg cmE-2 sE-1.  The BeppoSAX source 'a' appears to be resolved
into ROSAT sources 1 and 2; the BeppoSAX source 'b' coincides well
with ROSAT source 3.  ROSAT sources 1 and 2 are softer than source
3.  Within the error circle of each ROSAT source, there is more
than one optical object."

                      (C) Copyright 1997 CBAT
1997 January 16                (6539)            Daniel W. E. Green

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