Central Bureau for Astronomical Telegrams
IAUC 5229: V1223 Sgr; N Her 1991
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Circular No. 5229
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
V1223 SAGITTARII
M. Briggs, J. Matteson, D. Gruber and L. Peterson, University
of California at San Diego, report: "Analysis of the HEAO-1/A-4
database has uncovered a point source of positron annihilation. The
evidence for the positron annihilation radiation is a broad excess
flux between about 333 and 635 keV. In late 1977 the flux from 333
to 635 keV was (1.80 +/- 0.32) x 10E-5 photon sE-1 cmE-2 keVE-1,
while the flux from 207 to 333 keV was only (0.44 +/- 0.33) x 10E-5
and from 635 to 1000 keV was only (-0.20 +/- 0.34) x 10E-5 photon
sE-1 cmE-2 keVE-1. The flux between 333 and 635 keV for epochs in
late 1977, early 1978, and late 1978 was (1.80 +/- 0.32), (0.56 +/-
0.36), and (1.17 +/- 0.39) x 10E-5 photon sE-1 cmE-2 keVE-1. The
statistical confidence of the detection, including allowance for
multiple possible locations in the search region of abs(b) < 36 deg,
is > 99.999 percent. The emission is likely due to Compton scattered
annihilation radiation, or annihilation radiation from a pair
plasma, or annihilation after positronium formation. The best-fit
location of the emission is l = +1.6 deg, b = -16.0 deg. The 90-
percent confidence error box is approximately elliptical, with
dimensions +/- 4.0 deg in galactic longitude and +/- 5.0 deg in
latitude. The only HEAO-1/A-1 catalogue source in this error box is
1H 1853-312, the cataclysmic variable V1223 Sgr. No other HEAO-1/
A-1 catalogue source is within the 99-percent confidence error box.
The HEAO-1/A-2 instrument observed the about 2- to 10-keV flux of
1H 1853-312 for each of the above three epochs to be 4.5 +/- 0.25,
0.0 +/- 0.3, and 3.7 +/- 0.34 total counts/s (K. Jahoda, Goddard
Space Flight Center). On the basis that V1223 Sgr is the only known
x-ray source with flux > about 1 UFU in the 90-percent confidence
error box, and that its soft x-ray flux variability correlates with
the positron annihilation radiation, it is probable that V1223 Sgr
is the source of the positron annihilation radiation seen by the
HEAO-1/A-4 instrument."
NOVA HERCULIS 1991
Visual magnitude estimates: Mar. 31.79 UT, 9.6 (R. H. McNaught,
Siding Spring Observatory); Apr. 1.08, 10.1 (P. Schmeer, Bischmisheim,
Germany); 1.78, 10.2 (McNaught); 2.135, 10.3 (Schmeer); 2.14,
10.4 (A. Pereira, Cabo da Roca, Portugal); 2.79, 10.4 (McNaught).
1991 April 2 (5229) Daniel W. E. Green
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