Central Bureau for Astronomical Telegrams
IAUC 3399: MXB1636-53; HR 8752
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Read IAUC 3400
Circular No. 3399
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 617-864-5758
MXB1636-53
H. Pedersen, European Southern Observatory; the Hakucho Team
of the University of Tokyo (principal investigator M. Oda); and L.
Cominsky, J. Doty, G. Jernigan, J. van Paradijs and W. H. G. Lewin,
Massachusetts Institute of Technology, report the detection of simultaneous
x-ray/optical bursts from MXB1636-53 (McClintock et al.
1977, Nature 270, 320). The optical observations were made with
the 1.5-m Danish telescope at E.S.O., the x-ray observations with
the Japanese satellite Hakucho, in the periods June 20-July 2 and
July 20-Aug. 2. A total of 15 optical bursts were observed. The
largest observed increase in the stellar brightness was a factor of
4, and the duration of the tail of the longest optical bursts was
2 min. During the times that simultaneous optical and x-ray observations
were made, five bursts were detected simultaneously by both
observatories. In one case an optical burst was observed but no x-ray
burst, but the reverse was never the case. Though unlikely,
the possibility that the optical event not accompanied by an x-ray
burst was caused by a passing moonlit cloud cannot be excluded.
The integrated x-ray burst fluxes show a range of size that differ
by a factor of ~ 3. If the upper limit for the event where an optical
but not an x-ray burst was observed is included, this range
is at least a factor of 8. The optical bursts show a range of
sizes by a factor of ~ 4. The risetimes were about 1 s in most optical
and x-ray bursts. However, in at least one case the risetimes
for both x-ray and optical bursts were ~ 5 s. In the case that has
so far been analyzed in some detail, the optical burst is delayed
by ~ 2.5 s. This delay is comparable to those observed for MXB
1735-44 (McClintock et al. 1979, Nature 279, 47) and MXB1837+05
(Hackwell et al. 1979, Ap. J. Lett. in press).
HR 8752
R. Barbier and J. P. Swings, Institut d'Astrophysique, Universite
de Liege, communicate: "A well exposed blue spectrogram (dispersion
1.2 x 10**-6) of HR 8752 = V509 Cas (IAUC 3382, 3390) was obtained
on July 31 at the coude focus of the Haute Provence 1.5-m
reflector. No conspicuous emission is present, either at H-beta or at
other wavelengths. No search was made for filling in of absorption
lines in this spectral region, which is known to be very crowded.
A print and/or tracing of the plate is available on request for
detailed study of our material."
1979 September 4 (3399) Brian G. Marsden
Read IAUC 3400
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