Circular No. 7235
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 990806
     F. Frontera, Istituto TESRE, CNR, Bologna and University of Ferrara;
M. Capalbi and M. R. Daniele, BeppoSAX SDC, Rome; E. Montanari, University
of Ferrara; A. Paolino and A. Tesseri, BeppoSAX SOC, Rome; C. Pastor,
SAX-OCC, Rome; and G. Gandolfi, IAS, CNR, Rome, on behalf of a larger
collaboration, report: "The BeppoSAX Wide Field Camera (WFC) error box of
GRB 990806 (R.A. = 3h10m.6, Decl. = -68o07', error radius = 3'; GCN 392)
was observed, beginning about 8 hours after the burst, with the BeppoSAX
Narrow Field Instruments in the period Aug. 6.9267-8.6563 UT.  Preliminary
analysis of MECS2+3 data shows a previously unknown X-ray source, 1SAX
J0310.6-6806, located at R.A. = 3h10m35s, Decl. = -68o06'35" (equinox 2000.0),
with an error radius of 1'.  This position is very close to the centroid of
the WFC error box.  During the observation, the 1.4-10-keV source flux
decreased from (8.6 +/- 2.4) x 10**3 cts s**-1, corresponding to
(5.5 +/- 1.5) x 10**-13 erg s**-1 cm**-2, to (2.3 +/- 0.6) x 10**-3 cts s**-1,
corresponding to (1.5 +/- 0.6) x 10**-13 erg s**-1 cm**-2.  For comparison,
a ROSAT source, 1RXS J031250.0-680915, out of the WFC error box but visible
in the same MECS image, does not show any statistically significant variation
during the entire observation.  We conclude that 1SAX J0310.6-6806 is likely
the x-ray afterglow of GRB 990806."


CATALOGUE OF COMETARY ORBITS 1999
     The thirteenth edition of the Catalogue of Cometary Orbits, complete
through the 1999 July 28 batch of Minor Planet Circulars, is now available.
It contains 1722 orbits for 1688 cometary apparitions referring to 1036
different comets.  A tabulation provides osculating elements for 133 of the
140 numbered periodic comets at the standard epochs 1999 Aug. 10,
2000 Feb. 26, 2000 Sept. 13 and 2001 Apr. 1.  In a departure from previous
practice, the single-apparition comets with calculated periods of less than
200 years are now divided into two groups, with an arbitrary boundary at 30
years separating them into 58 short-period comets and 13 intermediate-period
comets, the latter group henceforth retaining the C/ prefixes they would
have had when only parabolic orbits were available, rather than the D/
prefixes that have recently been causing undesirable confusion in connection
with three recent comets.  `Original' and `future' reciprocal semimajor axes
are given for 330 high-quality long-period orbits.  The 127-page Catalogue
sells for $30.00 ($40.00 for airmail delivery outside North America).  There
is also an e-mail edition (with just the basic orbital information) for
$50.00.

                      (C) Copyright 1999 CBAT
1999 August 10                 (7235)              Gareth V. Williams