2004IAUC.8430....2G

G. Gomez, Instituto de Astrofisica de Canarias (IAC); R. Lopez, Universidad de Barcelona; and J. A. Acosta-Pulido, and the LIRIS Team, IAC, report that an infrared image (yielding magnitude J about 16.6) and a spectrogram (range 0.89-1.53 microns; resolution about 700) were obtained of SN 2004ao (cf. IAUC 8299, 8304) on June 8.1 UT with the William Herschel Telescope (+ LIRIS). Preliminary reduction of the spectrum shows absorption and emission features superimposed on a nearly flat continuum, indicating that the supernova had then reached the nebular phase. The spectrum shows a P-Cyg feature at 1.08 microns (absorption at 1.0430 microns and emission at 1.0865 microns, at the rest wavelength of the host galaxy); this feature is identified as He I 1.0830-microns in other core-collapse supernovae (e.g., SN 1999ex, Hamuy et al. 2002, A.J. 124, 417; SN 1998bw, Patat et al. 2001, Ap.J. 555, 900). Adopting the NED host-galaxy recession velocity of 1691 km/s, the expansion velocity derived from the minimum of the He I line is 11000 km/s. Broad emissions at 0.924, 1.089, 1.1295, 1.130, and 1.190 microns and absorptions at 0.9095, 0.979 and 1.0035 microns (all at the host-galaxy rest wavelength), are also detected. Tentative identifications include the 1.1295-microns emission as O I 1.129- microns (e.g., SN 1998bw at phase +51 days, Patat et al. 2001, Ap.J. 555, 900; SN 1998S at phases +56 and +110 days, Fasia et al. 2001, MNRAS 325, 907) and the 0.924-microns emission as O I 0.9261-micron (e.g., SN 1998S at phase +72.3 days, Fasia et al., op.cit.).