Central Bureau for Astronomical Telegrams
IAUC 7128: 1999as and 1999at
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Circular No. 7128
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)
SUPERNOVAE 1999as and 1999at IN ANONYMOUS GALAXIES
R. Knop, G. Aldering, S. Deustua, G. Goldhaber, M. Kim, and P.
Nugent, Lawrence Berkeley National Laboratory, on behalf of the
Supernova Cosmology Project (SCP), report the discovery of two
supernovae on Feb. 18 UT as part of a joint collaboration between
the SCP and E. Helin, S. Pravdo, D. Rabinowitz, and K. Lawrence
(Near-Earth Asteroid Tracking project, Jet Propulsion Laboratory):
SN 1999as is located at R.A. = 9h16m30s.86, Decl. =
+13o39'02".2 (equinox J2000.0), on the edge of a very faint galaxy.
A CCD spectrum (range 430-890 nm) taken by Aldering at the MDM
2.4-m telescope on Mar. 6, shows the supernova to be an unusually
blue object with broad absorption features. Further spectra,
obtained Mar. 16 by A. Goobar and T. Dahlen (Stockholm University)
and I. Hook (Royal Observatory, Edinburgh) using the Nordic Optical
Telescope, and by Aldering using the Cerro Tololo Interamerican
Observatory (CTIO) 4-m telescope, bear a resemblance to type-Ia
supernovae, 1-2 weeks after maximum light, at an approximate
redshift of 0.12, with the following caveats: several narrow
spectral features consistent with Fe II lines are present; the Si
II features are similar to those of SN 1991T; and a type-Ia
supernova at this redshift should show a significant emission
feature at 475 nm (yet these spectra show a large deficit of flux
in this region). Finally, it should be noted that, at this
redshift, the supernova is about 2 mag brighter than a typical
type-Ia supernova at maximum light. Currently SN 1999as is at V =
18.3.
SN 1999at (unfiltered mag 18.8) is located at R.A. =
10h23m11s.30, Decl. = +17o59'06".0 (equinox 2000.0). An R-band
image from the YALO 1-m telescope obtained Mar. 7 by D. G. Huerta
(CTIO), A. Mourao (Centro de Astrofisica, Instituto Superior
Tecnico, Lisbon), and Rui Agostinho, Joao Lin Yun, and F. D. Santos
(University of Lisbon), confirmed the presence of the supernova and
that the host was an elliptical galaxy. A CCD spectrum obtained at
the ARC 3.5-m telescope on Mar. 10 by G. Richards (University of
Chicago) and H. Newberg and S. Kent (Fermi National Accelerator
Laboratory) shows the host at a redshift of 8180 km/s and a
supernova consistent with a normal type-Ia event, < 10 days after
maximum light. Finding charts for the supernovae can be obtained
from http://panisse.lbl.gov/nearsearch/fcharts/index.html.
Supernovae and comparison images can be found in the SkyMorph
archive at http://skys.gsfc.nasa.gov/skymorph/skymorph.html.
(C) Copyright 1999 CBAT
1999 March 19 (7128) Daniel W. E. Green
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