SUPERNOVAE 2007gw, 2008S, 2008T, 2008al, 2008ao, AND 2008ap
T. N. Steele, J. M. Silverman, M. Ganeshalingam, N. Lee, W. Li, and A. V.
Filippenko, University of California, Berkeley, report that inspection of CCD
spectra (range 440-980 nm), obtained on Feb. 29 UT with the 3-m Shane
reflector (+ Kast) at Lick Observatory, shows that 2007gw (CBET 1042) is a
type-II supernova, probably 100-200 days after explosion. Removing a
recession velocity of 4970 km/s (from narrow emission lines), the minimum of
the H-alpha absorption is blueshifted by about 6100 km/s.
SN 2008T (CBET 1237) is also a type-II supernova. Removing a recession
velocity of 5400 km/s (from narrow emission lines), the minimum of the H-alpha
absorption is blueshifted by about 5200 km/s.
SN 2008al (CBET 1261) is also of type-II, with H-alpha emission (FWHM
about 9850 km/s) greatly dominating the almost non-existent absorption. The
spectrum is similar to those of some type-IIL supernovae.
SN 2008ao (CBET 1269) is a type-Ic supernova within one week past maximum
light, consistent with the classification by Blondin et al. (CBET 1274).
SN 2008ap (CBET 1270) is a type-II supernova. Removing a recession
velocity of 8262 km/s (de Vaucouleurs et al. 1991, Third Reference Catalogue
of Bright Galaxies), the minimum of the H-alpha absorption is blueshifted by
about 7750 km/s.
The spectrum of the type-IIn supernova 2008S (CBETs 1234, 1235, 1236) is
quite peculiar. In addition to the narrow (FWHM about 900 km/s) Balmer
emission lines, there are strong, comparably narrow emission lines of the [Ca
II] 730-nm doublet and the Ca II near-infrared triplet, as well as many weak
emission lines of Fe II and other species. Given these spectral properties,
and an absolute visual magnitude of about -13 (corrected for Galactic
extinction of 1 mag), the object is likely to be a "supernova impostor" such
as 1997bs (Van Dyk et al. 2000, PASP 112, 1532).
2008 February 29 (CBET 1275) Daniel W. E. Green
Тема: SN 2008S (Прочитано 85378 раз)