Central Bureau for Astronomical Telegrams
IAUC 6722: GRB 970815; GRB 970616
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Circular No. 6722
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)
GRB 970815
T. Murakami, Y. Ueda, M. Ishida, and R. Fujimoto, Institute of
Space and Astronautical Science; and A. Yoshida and N. Kawai,
Institute of Physical and Chemical Research (RIKEN), report on
behalf of the ASCA team: "ASCA observed the error box of GRB 970815
following the detection by ASM/RXTE (IAUC 6718) from Aug. 18.68 to
19.80 UT (net exposures of 40 000 s and 46 000 s for the SIS and
GIS detectors, respectively). Analysis of the whole data set
reveals no source above 1 x 10E-13 erg cmE-2 sE-1 (2-10 keV) within
the ASM/RXTE error box. A nearby x-ray source was seen in both the
SIS and GIS fields-of-view, slightly outside the ASM/RXTE error box,
at R.A. = 16h06m54s, Decl. = +81o30'34" (1' error radius); its flux
was 3 x 10E-13 erg cmE-2 sE-1 at 2-10 keV, and it seemed stable
during the ASCA observation."
GRB 970616
J. Greiner, Astrophysikalisches Institut Potsdam; J. van
Paradijs, University of Amsterdam and University of Alabama at
Huntsville; F. M. Marshall, Goddard Space Flight Center; K. Hurley,
University of California at Berkeley; C. Robinson, Marshall Space
Flight Center; and J. Siebert, Max-Planck-Institut fur
Extraterrestrische Physik, Garching, report: "A 22 000-s ROSAT
observation of the RXTE error box of GRB 970616 (IAUC 6683) during
June 23-25 reveals eleven faint x-ray sources within the HRI field-
of-view. None of these coincides with the two optical variables
reported on IAUC 6687 and 6690, and three are within the IPN/RXTE
error box (IAUC 6687): R.A. = 1h19m03s.0, Decl. = -5 31'35";
1h18m50s.3, -5 25'58"; 1h18m17s.3, -5 12'48" (equinox 2000.0). The
second of these sources coincides with the first ASCA variable
source (IAUC 6687). The unabsorbed ROSAT flux (using a power-law
model with photon index 2 and galactic absorbing column N_H = 4 x
10E20 cmE-2) is 1.4 x 10E-14 erg cmE-2 sE-1 in the range 0.5-2 keV
(i.e., a factor of 5 lower than the flux measured by ASCA on June
20-21, using the same model assumptions and energy range). The 3-
sigma upper limit of the flux at the position of the fourth ASCA
source is a factor of 7 lower than that of the ASCA detection.
With two fading x-ray sources within the RXTE/IPN error box, an
association to the GRB remains open (an image can be viewed at
http://www.aip.de:8080/~jcg/grb970616.html)."
(C) Copyright 1997 CBAT
1997 August 23 (6722) Daniel W. E. Green
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