Central Bureau for Astronomical Telegrams
IAUC 4703: 1989c; GALACTIC CENTER ANNIHILATION RADIATION; (3908)
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Read IAUC 4704
Circular No. 4703
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
COMET BRADFIELD (1989c)
A. Beresford, Adelaide, reports that W. A. Bradfield,
Dernancourt, has discovered a new comet (his fourteenth). The
object is diffuse and uncondensed and moving very rapidly.
1989 UT R.A. (1950) Decl. m1
Jan. 6.514 21 09.5 -56 23 12
6.583 21 10.2 -56 20
GALACTIC CENTER ANNIHILATION RADIATION
The GRIS collaboration (S. Barthelmy, N. Gehrels, B. J. Teegarden
and J. Tueller, Goddard Space Flight Center; M. Leventhal, AT&T/Bell
Laboratories; and C. J. MacCallum, Sandia National Laboratories) reports
the detection of 511-keV gamma-ray radiation from the galactic center
(R.A. = 17h45m, Decl.= -28 54'). The observations were made with a
high-resolution germanium spectrometer having a 20 deg FWHM field of
view flown on high-altitude balloons over Alice Springs. Twelve hours
of data were obtained on 1988 May 1 and again on Oct. 29. An additional
eight hours of data were obtained from a point in the galactic plane 25
deg west of the center (l = 335 deg, b = 0 deg) on Oct. 30. The
experiment alternated between source and background pointings every
20 min. Preliminary results for the line fluxes (in units of 10**-4
photons cm**-2 s**-1) are 11.4 +/- 1.2 from the galactic center (average
of the two measurements) and 2.4 +/- 1.6 from the off-center pointing.
(The quoted errors are 1 sigma statistical errors only). Previous
measurements made with similar balloon and satellite instruments during
the period 1980-1984 indicated that the compact 511-keV source had gone
into a quiescent state. Apparently it reemerged some time during 1984-1988
at a flux level indistinguishable from those reported during the 1970s.
(3908) 1980 PA
Continuation to the ephemeris on IAUC 4673:
1989 ET R.A. (1950) Decl. Delta r V
Jan. 14 5 55.61 +20 36.5 0.441 1.397 17.4
24 5 59.49 +20 27.5
Feb. 3 6 06.58 +20 25.6 0.643 1.524 18.7
13 6 16.34 +20 26.0
23 6 28.22 +20 25.1 0.891 1.652 19.7
1989 January 7 (4703) Brian G. Marsden
Read IAUC 4704
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