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IAUC 5155: 1991a; BARIUM AND LITHIUM CLOUD RELEASES; 1991A

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                                                  Circular No. 5155
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 or GREEN@CFA.BITNET    MARSDEN or GREEN@CFAPS2.SPAN


COMET BREWINGTON (1991a)
     Howard J. Brewington reports his discovery of a comet, as
indicated below:

   1991 UT         R.A. (1950) Decl.        m1       Observer
   Jan.  7.18      0 05.9      - 6 17       9.8      Brewington
         7.24      0 02.5      - 6 40       9.3      Hale

H. J. Brewington (near Cloudcroft, NM).  0.41-m reflector.  Object
   diffuse but strongly condensed.
A. Hale (Kitt Peak, AZ).  0.20-m reflector.


BARIUM AND LITHIUM CLOUD RELEASES
     Corrigenda.  In the table on IAUC 5154, subtract 0.208 day (5
hr) from all of the times.  Updated status concerning releases may
be obtained by dialing the following telephone number:  205-544-5356.


SUPERNOVA 1991A IN IC 2973
     A. V. Filippenko, University of California at Berkeley, reports:
"I obtained CCD spectra (range 390-990 nm, resolution 1.5 nm and 0.3
nm) of SN 1991A (cf. IAUC 5153) on Jan. 6 UT with the Shane 3-m
reflector at Lick Observatory.  Inspection of the partially calibrated
data suggests that the object is of type Ic (helium-poor Ib).  The
deep 615-nm (found in type-Ia SNe) and 570-nm (type-Ib SNe) absorption
troughs are both absent, and there is no obvious broad H-alpha
(type-II SNe).  However, SN 1991A is peculiar.  A broad, very low-
contrast bump near rest wavelength 656 nm might be H-alpha, but the
spectrum also exhibits deep O I 777.4-nm absorption, unlike early-
time spectra of other type-II SNe.  Narrow (FWHM < 100 km/s),
strong H-alpha emission is present, together with weaker [O III] and
very weak H-beta.  These lines are likely to be produced in high-
density circumstellar gas that was previously expelled by the
progenitor star and ionized by the ultraviolet radiation released at
the time of shock breakout.  Interaction of the supernova ejecta
with the circumstellar material during the next year should steadily
enhance the H-alpha emission.  Thus, the classification of SN 1991A
might change from type Ic to type II as the object ages -- nearly
opposite the behavior of SN 1987K (Filippenko 1988, A.J. 96, 1941).
The redshift of the parent galaxy is 0.011, measured from emission
lines in H II regions."


1991 January 7                 (5155)             Daniel W. E. Green

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