[IAUC] CBET 1710: 20090301 : SUPERNOVAE 2009am AND 2009an

[IAUC mailing list]

                                                  Electronic Telegram No. 1710
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS en CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT en CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVAE 2009am AND 2009an
     M. Yamanaka and A. Arai, Hiroshima University, report that they obtained
optical spectra (range 480-950 nm) of 2009an (cf. CBETs 1707, 1709) on Mar.
1.6 UT with the KANATA 1.5-m telescope (+ TRISPEC) at Higashi-Hiroshima
Astronomical Observatory.  SN 2009an exhibits a strong Si II 635.5-nm
absorption feature that is blueshifted by about 14000 km/s.  The spectrum
shows the W-feature profile of sulfur at 520-550 nm, and the deep O I
777.4-nm feature is seen at 750 nm.  The high-velocity feature of the Ca II
infrared triplet clearly reaches about 22500 km/s.  The spectrum is similar
to that of the normal type-Ia supernova 2003du at around a week before
maximum.
     J. Vinko, H. Marion, and J. C. Wheeler, University of Texas; P.
Garnavich, University of Notre Dame; and C. Gerardy, Florida State University,
report that a spectrum (range 430-1000 nm) of 2009am (cf. CBET 1707),
obtained on Mar. 1.34 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario
Low-Resolution Spectrograph) by J. Caldwell, shows it to be a type II-P
supernova at least one month after the explosion.  The spectrum shows strong
Balmer-alpha and Ca II infrared-triplet lines with P-Cyg profiles.  Na I
(590 nm) and other metallic lines (mostly Fe II) appear toward the blue end
of the spectrum.  Comparison of the spectrum of SN 2009am to other supernovae
spectra using SNID (Blondin and Tonry 2007, Ap.J. 666, 1024) provides a close
match for two spectra:  that of SN 2005cs at 27 +/- 3 days after maximum and
1999em at about 60 days after maximum.  Spectra of SN 2009an were obtained on
Mar. 1.37 with the Hobby-Eberly Telescope (HET), using the same configuration
as above, and on Mar. 1.52 with the Infrared Telescope Facility (+ SpeX in
low-dispersion mode, range 0.7-2.4 microns); the data show it to be a young
type-Ia supernova.  SNID finds the best match for the HET spectrum to be to
that of SN 2002bo at 6 +/- 2 days before maximum.  Adopting the host-galaxy
(NGC 4332) recession velocity of 2768 km/s listed in NED, the Si II (635.5
nm) feature is blueshifted by 14000 +/- 2000 km/s.  The near-infrared spectrum
reveals a strong high-velocity component for the Ca II infrared triplet and
lines from O I and Mg II, consistent with the age above.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2009 CBAT
2009 March 1                     (CBET 1710)              Daniel W. E. Green