A CCCP study of the progenitor of SN 2004gt
A High-Resolution Search for the Progenitor of Type Ic Supernova SN 2005gt.
This paper has been submitted for publication in ApJL. The full-resolution manuscript is available
in PS and PDF formats.
You can also get it from
astro-ph with lower resolution figures.
(1) The spectroscopic classification of SN 2004gt:
This SN was first identified (Dec. 17, 2004) as a type Ib event by Kinugasa and Kawakita (IAUC 8456), based
on a single He line at 587.6 nm. Ganeshalingam, Swift and Filippenko (IAUC 8456) dispute this claim, and
prefer a type Ic classifiction, based on the absence of other He lines in their spectrum from Dec. 18, 2004.
A CCCP spectrum obtained on Jan 15, 2004 (UT) with the DBSP spectrograph mounted on the 200''
Hale telescope at Palomar Observatory, does not show
any of the typical He features of SNe Ib (around 587.6 or 706.5 nm), while the feature seen near 590 nm is
consistent in strength with that of the Na II 589 line often observed in SNe Ic. We thus confirm the
type Ic identification of this event.
(2) Estimating the line of sight extinction towards the SN using the
Turatto et al. 2003 sample of well observed SNe:
These authors give two possible correlations between the Na II D equivalent width W and the
line of sight extinction E(B-V), based on their sample of well observed SNe. Using our
measurement of W=0.6 Angstrom, we find two possible values: E(B-V)=0.086 (Av=0.27 mag) or E(B-V)=0.266
(Av=0.82 mag). Since the nearby bright cluster ("S" in Whitmore et al. 1999) has a measured extinction
of E(B-V)=0.01 +/- 0.04, the lower value of the two we got seems more plausible.