SIMBAD references

M. Ganeshalingam, B. J. Swift, and A. V. Filippenko, University of California, Berkeley, report that inspection of CCD spectra (range 330-1060 nm), obtained on Dec. 18 UT with the Shane 3-m reflector at Lick Observatory, reveals that SN 2004gt (IAUC 8454) is of type Ib/Ic, not far from maximum brightness. The He I/Na I absorption near 570 nm is strong, but the only clear He I line is an absorption trough near 1040 nm attributed to He I 1083-nm. Other type-Ic supernovae have shown evidence for a small quantity of He (e.g., SN 1994I; Filippenko et al. 1995, Ap.J. 450, L11). The substantial strength of the O I 777.4-nm trough in SN 2004gt is more consistent with a type-Ic than a type-Ib classification (Matheson et al. 2001, A.J. 121, 1648), though type Ib is still a possibility. It is difficult to distinguish unambiguously between the Ib and Ic subclasses with a single optical spectrum obtained near maximum brightness; further observations are thus encouraged.