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IAUC 5365: 1991bb; VENUS

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                                                  Circular No. 5365
Central Bureau for Astronomical Telegrams
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

SUPERNOVA 1991bb IN UGC 2892
     J. Mueller reports her discovery of a supernova (mag about 18)
in UGC 2892 (R.A. = 3h50m.7, Decl. = +18 57', equinox 1950.0), found
on a red plate taken by J. D. Mendenhall and Mueller on Oct. 13 with
the 1.2-m Oschin Telescope in the course of the second Palomar Sky
Survey.  SN 1991bb is located 9".4 east and 2" north of the galaxy
nucleus.  A. V. Filippenko and T. Matheson, University of California
at Berkeley, report that broadband CCD images of UGC 2892 obtained
on Oct. 14 UT with the Nickel 1-m reflector at Lick Observatory
confirm the presence of the candidate.  The object appears bluer than
the nearby galactic nucleus, and it may be brighter than reported by
Mueller.  At their request, R. Cohen, R. Lyons, and E. M. Burbidge
(University of California at San Diego) obtained a CCD spectrum
(range 310-870 nm, resolution 1 nm) with the Shane 3-m reflector at
Lick.  Preliminary inspection of the uncalibrated spectrum shows
that the object is indeed a supernova, probably of type Ia; a
reasonably deep absorption trough near 620 nm is present.

     J. Lecacheux, Observatoire de Meudon; F. Colas, Bureau des
Longitudes, Paris; P. Laques, F. Deladerriere, OMP, Observatoire du
Pic-du-Midi; and P. Drossart, Observatoire de Meudon, communicate:
"We have succeeded in detecting thermal emission on the night side
of Venus, on Sept. 20-22 and Oct. 12-13, through the 0.99- to 1.03-
micrometer spectral window of the cytherean atmosphere.  The CCD
camera on the Pic-du-Midi 1.05-m reflector was equipped with a
coronagraph-like device masking the bright crescent of Venus.  We
observed dark markings on the night side of Venus, such that the
corresponding longitude and latitude are correlated with the high-
altitude regions as mapped by Pioneer Venus radar.  The thick CO2
atmosphere and the clouds of Venus at 1 micron are transparent enough in
the near-infrared to allow thermal emission from the hot surface to
be seen.  The contrasts are interpreted as due to lower temperatures
in the high-altitude regions, as first observed by Galileo/NIMS at
1.18 microns on Maxwell Montes (Carlson et al. 1991, Science 253,
1541).  Aphrodite Terra, up to about 5000 m above surroundings, is
currently approaching the terminator.  Its photometric contrast is
about 40 percent, according to preliminary measurements, and its
quasi-equatorial latitude make it an easy target for CCD-equipped
ground-based telescopes."

1991 October 14                (5365)             Daniel W. E. Green

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