Central Bureau for Astronomical Telegrams
IAUC 4054: GB 811016 AND EXO 0748-676; NGC 4051; AG Dra
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Read IAUC 4055
Circular No. 4054
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
GB 811016 AND EXO 0748-676
J. G. Laros, E. E. Fenimore, M. M. Fikani and R. W.
Klebesadel, Los Alamos National Laboratory, report: "Contrary to
what might be concluded from IAUC 4047, the transient x-ray source
EXO 0748-676 apparently is not associated with the gamma-ray burst
(GRB) GB 811016. In fact, EXO 0748-676 is not in the original
error box presented by Katoh et al. (1984, AIP Proc. 115, 390),
unless the Pioneer Venus Orbiter (PVO)-Hakucho time-of-arrival
annulus is arbitrarily ignored. A refined PVO-Hakucho annulus and
a new PVO-International Cometary Explorer annulus are both in
agreement with the earlier time-of-arrival work. The new annuli
miss EXO 0748-676 by more than ten times their half-widths. The
only conceivable systematic effect that would allow the two
sources to coincide is a 3-s PVO timing error. However, PVO has
demonstrated in other GRB analyses a timing accuracy better than
0.010 s, and several PVO clock correlations taken up to +/- 1 month
from GB 811016 showed no irregularities. Therefore, it seems
almost certain that we are dealing with a chance coincidence
involving only the 3 deg**2 Hakucho collimator-determined error box,
and not a real association between an x-ray source and a GRB."
NGC 4051
A. Lawrence, Queen Mary College, London; M. Elvis, Center for
Astrophysics; and K. Pounds and M. Watson, Leicester University;
telex: "EXOSAT will observe NGC 4051 during May 13.15-15.46 UT,
and we encourage simultaneous observations at all possible
wavelengths. When observed for 8 hr last April, the galaxy exhibited
quasiperiodic x-ray variations of factor two amplitude and 1-hr
period; clear spectral changes were also noted. We now intend to
monitor (in both soft and hard x-rays) the object for an unbroken
stretch of 56 hr. Partial coverage has been arranged using a CCD
at the Whipple Observatory, but observers at other longitudes and
who can give coverage at other wavelengths are urged to contact
us: A. Lawrence, telex U.K. 893750 QMCUOL G (Mathematics Dept.),
telephone 44-1-980-4811, X 3881; or M. Elvis, telex U.S. 921428
SATELLITE CAM, telephone 1-617-495-7442."
AG DRACONIS
Visual magnitude estimates by J. Bortle, Stormville, NY:
Mar. 16.0 UT, 9,3; 19.0, 9.3; 21.0, 9.3.
1985 April 25 (4054) Brian G. Marsden
Read IAUC 4055
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