Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

IAUC 6830: 1998T; 1998S; V854 Cen

The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).

Read IAUC 6829  SEARCH Read IAUC 6831

View IAUC 6830 in .dvi or .ps format.
IAUC number

                                                 Circular No. 6830
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)

     W.-d. Li, University of California at Berkeley (UCB), forwards
the report from C. Li that Zhou Wan has found an apparent supernova
(unfiltered CCD mag 15.4) on Mar. 3 UT as part of the Beijing
Astronomical Observatory Supernova Survey.  As with SN 1998S (cf.
IAUC 6829), this object was confirmed by the Lick Supernova Survey
at unfiltered mag about 14.5 on Mar. 4.3, with the corresponding
KAIT position given as R.A. = 11h28m32s, Decl. = +58o33'.7 (equinox
2000.0); SN 1998T appears in a dust lane of the irregular host
galaxy that has no apparent nucleus, so the relative offsets cannot
be accurately determined, and its close proximity to a knot makes
it difficult to measure (the magnitudes were derived from
subtracted images).  Observations of the same field prior to Mar. 3
do not show an object at the position of SN 1998T.
     A. V. Filippenko and E. C. Moran, UCB, report that on Mar. 5
they obtained a Keck-2 spectrogram (range 510--900 nm, resolution 1
nm) of the stellar-looking knot on the southern side of the dust
lane of IC 694 (the eastern part of the irregular galaxy Arp 299 =
Markarian 171, of which the western part is NGC 3690; see
Wynn-Williams et al. 1991, Ap.J. 377, 426).  SN 1998T is indeed a
supernova, of type Ib; strong P-Cyg profiles of He I lines are
visible.  Narrow nebular emission lines are very intense.

     Filippenko and Moran also report:  "A low-resolution Keck-2
spectrum, obtained as above, shows that the type-II SN 1998S (cf.
IAUC 6829) is peculiar; the spectrum contains prominent H and He
emission lines superposed on a featureless blue continuum.  In many
respects, the spectrum resembles that of the type-IIn SN 1997eg
(cf. IAUC 6794):  the lines have multiple components, including a
very narrow (unresolved) one that is probably produced by flash-
ionized circumstellar gas.  This object might become very luminous
at radio and x-ray wavelengths, due to strong interaction between
the ejecta and circumstellar material."

     This R CrB-type variable is fading, as indicated by the
following visual magnitude estimates, in part from the AAVSO:  Feb.
4.67 UT, 7.6 (F. Farrell, Christies Beach, Australia); 21.9, 8.4
(B. Monard, Pretoria, South Africa); 25.22, 8.3 (A. Pereira, Cabo
da Roca, Portugal); 26.96, 8.7 (Monard); Mar. 1.20, 9.1 (Pereira);
2.92, 9.0 (Monard); 3.85, 8.9 (Monard).

                      (C) Copyright 1998 CBAT
1998 March 5                   (6830)            Daniel W. E. Green

Read IAUC 6829  SEARCH Read IAUC 6831

View IAUC 6830 in .dvi or .ps format.

Our Web policy. Index to the CBAT/MPC/ICQ pages.

Valid HTML 4.01!