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IAUC 5642: 1992bf; PG 0824+289; N Sgr 1992 No. 3

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IAUC number

                                                  Circular No. 5642
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

     Jean Mueller reports her discovery, on a blue plate taken Oct.
2 by C. Brewer, J. D. Mendenhall, and herself with the Oschin
Schmidt Telescope in the course of the second Palomar Sky Survey,
of a supernova of mag about 17 in NGC 930 (R.A. = 2h25m.1, Decl. =
+20 06', equinox 1950.0).  SN 1992bf is located 9".4 east and 10".8
south of the galaxy's center, and is somewhat embedded in the galaxy
nucleus.  W. Sargent and T. Small obtained spectra of this object
using the 5-m Hale Telescope (+ double spectrograph) on Oct.
20 UT, showing this to be a type-I supernova.

PG 0824+289
     B. Margon and P. J. Green, University of Washington; A.
Klemola, Lick Observatory; and J. G. Hoessel, University of Wisconsin,
communicate:  "PG 0824+289 is unique as the only known dwarf
carbon (dC) star to show a composite spectrum, with a very hot DA
white dwarf companion also explicitly visible in the spectrum
(Heber et al., A.Ap., in press).  Here we report that the object is
resolved into a close pair.  Elongated images are evident on the
Palomar Sky Survey and archival Lick astrograph plate material.
CCD imagery with the Kitt Peak 2.1-m reflector and Gunn gri filters
on Oct. 17 UT reveals two objects of similar i magnitude, but quite
different color, separated by 3".3 at position angle 120 deg.  The
easternmost object is clearly the cooler one.  Although spectra of
the individual components are desirable, it seems reasonable to
infer that the east and west resolved objects are the dC and DA,
respectively. The very wide physical spacing then implied greatly
complicates the evolutionary history of the pair, indicating that
any recent interaction of the two stars is implausible.  As many
spectrograph slits are by default oriented east-west, accidentally
quite close to the alignment of the two components of this system,
considerable care will be needed to avoid confusion in future

      Photometry by A. C. Gilmore, Mount John University Observatory
(+/- 0.03 unless otherwise noted):  Oct. 15.42 UT, V = 7.49 +/-
0.02, B-V = +0.60 +/- 0.02, U-B = -0.09 +/- 0.08, V-R = +0.41, V-I
= +0.82; Oct. 16.40, 7.67, +0.78, +0.34 +/- 0.05, +0.44, +0.87; Oct.
17.40, 7.87 +/- 0.04, +0.59 +/- 0.04, -0.26 +/- 0.05, +0.49, +1.06.

1992 October 22                (5642)            Daniel W. E. Green

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