Central Bureau for Astronomical Telegrams
IAUC 7215: 1999da; 1998bw
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Circular No. 7215
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1999da IN NGC 6411
R. Johnson and W. D. Li, University of California at Berkeley,
on behalf of the Lick Observatory Supernova Search (cf. IAUC 6627,
7126), report the discovery of an apparent supernova with the 0.8-m
Katzman Automatic Imaging Telescope (KAIT). SN 1999da was
discovered on unfiltered images taken on July 5.4 UT (mag about
17.0) and confirmed on images taken on July 2.4 (mag about 17.6).
The new object is located at R.A. = 17h35m22s.96, Decl. =
+60o48'49".3 (equinox 2000.0), which is 71".3 west and 1".2 north
of the nucleus of NGC 6411. A KAIT image of the same field on June
29.4 (limiting mag about 19.5) showed nothing at the position of SN
1999da.
SUPERNOVA 1998bw IN ESO 184-G82
F. Patat, European Southern Observatory (ESO); E. Cappellaro,
L. Rizzi, and M. Turatto, Padua Observatory; and S. Benetti,
Telescopio Nazionale Galileo, report on behalf of the ESO Team (cf.
IAUC 6895): "We have obtained broadband BVRI photometry of SN
1998bw using the ESO/Dutch 0.9-m telescope and the ESO 3.6-m
telescope (+ EFOSC2) at La Silla on four dates between Mar. 16 and
June 17 (i.e., between 310 and 403 days after B maximum). The
lightcurve does not appear to deviate significantly from the
exponential decay already discussed by McKenzie and Schaefer
(http://xxx.lanl.gov/abs/astro-ph/?9904397) for the phase range
50-270 days. The decline rates in magnitudes per 100 days,
computed using our new data and the data by Galama et al. (1998,
Nature 395, 670) and McKenzie and Schaefer are 1.52 +/- 0.01 in B,
1.73 +/- 0.01 in V, 1.63 +/- 0.04 in R, and 1.64 +/- 0.03 in I.
With the exception of the B band, all decline rates appear to have
slightly decreased with respect to the values reported by McKenzie
and Schaefer. Only for the data taken on June 16 does there seem
to be a lightcurve flattening, especially in R and I, which could
be the first indication that the ejecta/circumstellar-matter
interaction has commenced. This seems to be confirmed by a
spectrum that we took at the ESO 3.6-m reflector (+ EFOSC2) on May
21.2 UT (range 335-1000 nm, resolution 1.7 nm). A preliminary
analysis of the data shows that the Mg I] line at 457.1 nm has an
asymmetric profile and at least two components, with FWHM about
8000 and 2000 km/s. Similar results are obtained for the [O I]
doublet at 630.0 and 636.4 nm. The narrow component could be
generated in a fast expanding wind shocked by the supernova ejecta.
The overall morphology of the spectrum is very similar to that of a
type-Ib supernova at a similar phase."
(C) Copyright 1999 CBAT
1999 July 6 (7215) Daniel W. E. Green
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