Central Bureau for Astronomical Telegrams
IAUC 5111: 1990aa; 1990U; SATURN
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Circular No. 5111
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
SUPERNOVA 1990aa IN UGC 540
A. V. Filippenko and J. C. Shields, University of California at
Berkeley, write: "Fully-calibrated CCD spectra (range 390-980 nm,
resolution 1.2 nm), obtained on Sept. 27 UT with the Shane 3-m
reflector at Lick Observatory, reveal that SN 1990aa is of type Ib,
definitely not type Ia as deduced by others (cf. IAUC 5090). The
helium lines appear quite weak; thus, SN 1990aa might instead be
called a 'type Ic' supernova (see Harkness and Wheeler 1990, in
Supernovae, ed. by A. G. Petschek, Springer-Verlag). It is not yet
clear, however, whether there are sufficient observational differences
between types Ib and Ic to justify having two separate
subclasses."
SUPERNOVA 1990U IN NGC 7479
Filippenko and Shields also note: "Spectra of SN 1990U,
obtained as above, show that it is entering the supernebular phase;
emission lines of [O I] and [Ca II] are present. A full analysis
of the July 30 spectra (cf. IAUC 5069) reveals that SN 1990U is
actually a type-Ic (helium-poor Ib) supernova discovered about 3
weeks past maximum brightness, rather than a helium-rich Ib
discovered near maximum. The prominent He I 587.6-nm absorption line
mentioned in IAUC 5069 is better identified with Na I D, and other
He I lines are weak or absent. This object clearly illustrates the
observational difficulty in distinguishing between most type-Ib and
type-Ic supernovae."
SATURN
M. Kidger, Instituto de Astrofisica de Canarias, reports: "F.
Hernandez and V. Gonzalez (Santa Cruz, Tenerife) made independent
visual meridian crossing timings of the new white spot, both being
Oct. 2.8167 UT; third-contact timings (east edge of spot) were Oct.
2.8299 and 2.8278, respectively. The inferred spot size is 20 000
+/- 1000 km (i.e., a nearly 20-percent increase in 21 hr). It appears
that the period has increased considerably in one day; the
observations on Oct. 1 and 2 give an implied period of 10h23m. This
does not seem to be due to observational errors." I. Miyazaki,
Oriental Astronomical Association, reports that a photograph taken
Oct. 1.538 UT shows the white spot at longitude 335 deg (System I),
near +12 deg latitude. It spanned 18 deg of longitude,
and the northern end of the white spot was embedded in the north
equatorial belt.
1990 October 3 (5111) Daniel W. E. Green
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