Central Bureau for Astronomical Telegrams
IAUC 5583: GEMINGA; N Sco 1992
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Circular No. 5583
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
GEMINGA
The Compton Observatory EGRET Team (J. R. Mattox, Computer
Sciences Corporation and Goddard Space Flight Center; D. L. Bertsch,
B. L. Dingus, C. E. Fichtel, R. C. Hartman, S. D. Hunter, P. W.
Kwok, P. Sreekumar, and D. J. Thompson, Goddard Space Flight Center,
NASA; D. A. Kniffen, Hampden-Sydney College; J. Chiang, J. Fierro,
Y. C. Lin, P. F. Michelson, and P. L. Nolan, Stanford University;
E. Schneid, Grumman Aerospace Corporation; and K. Brazier, G.
Kanbach, H. A. Mayer-Hasselwander, C. von Montigny, K. Pinkau, H.
Rothermel, and M. Sommer, Max-Planck-Institut fur Extraterrestrische
Physik) communicates: "In addition to the 5 weeks of Geminga
pulsar exposure in 1991, we have now analyzed 260 gamma-ray events
with energies between 0.07 and 30 GeV from a low-sensitivity
observation (33 deg off-axis) in the interval 1992 June 11-25. Using
first and second frequency derivatives obtained from the COS-B
ephemeris (IAUC 5541) and a frequency determined from the 1991
EGRET data, we predict a phase for 1992 June which differs from the
observed phase by 0.06 of a revolution (the uncertainty of the
prediction is 0.08 due to the limited precision of the frequency).
This result, combined with the COS-B finding (IAUC 5541) that the
timing residuals are 5 ms or less for a single ephemeris over 7
years, suggests that Geminga has not glitched between 1975 and 1992,
and that the rotation is very well fit by a quadratic ephemeris.
The frequency in the following ephemeris has been refined so that
the 1991 and 1992 phases are consistent; numbers in parentheses are
approximately the 1-sigma error of the last digit given: T0 = 1991
May 24.0 UT, f0 = 4.2176749957(6) sE-1, f1 = -1.9508(5) x 10E-13
sE-2, f2 = +4(1) x 10E-25 sE-3. The phase of peak 1 (preceding the
bridge of emission which links peak one and peak two; see Bertsch
et al. 1992, Nature 357, 306, for the light curve) at T0 is 0.64(1)
at the solar system barycenter, and 0.21(1) at the geocenter. We
expect that this ephemeris will give the phase to within 0.1 of a
revolution for the interval 1988.8-1994.0. The position used for
the barycenter correction is that of the G" star (Halpern and
Tytler 1988, Ap.J. 330, 201)."
NOVA SCORPII 1992
Visual magnitude estimates by H. Dahle, Crete, Greece: July
31.85 UT, 8.8; Aug. 1.83, 8.5; 2.83, 8.3; 3.85, 8.5; 4.83, 8.1;
5.84, 8.3:.
1992 August 11 (5583) Daniel W. E. Green
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