Infrared Spectra of Supernovae

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Session 37 -- Supernovae and Their Remnants
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

[37.04] Infrared Spectra of Supernovae

P.M.Garnavich (CfA)

The infrared spectral region of supernovae is relatively unexplored. Here, I present spectra of five supernovae in the wavelength range of 1.2$\mu$m to 2.4$\mu$m. The data were obtained in March 1995 with the Rieke `F-Spec' IR spectrometer mounted on the MMT. The most spectacular spectrum is that of 1994Y, a peculiar SN~II with narrow optical emission lines. In the infrared, Br$\gamma$ and P$\beta$ emission is very strong and higher level Brackett series lines are also visible. The Br$\gamma$ line has a width of 2000 kms$^{-1}$ FWHM, while the Balmer lines are broader with a FWHM of 3400 kms$^{-1}$. A strong line at a rest wavelength of 2.206$\mu$m is tentatively identified as NaI emission and, along with the permitted FeII lines seen in the optical, suggest the presence of cool and rather dense gas.

Late-time optical spectra of 1993J show broad H$\alpha$ emission thought to be due to an ongoing interaction with its circumstellar environment. The K band spectrum contains no evidence of Br$\gamma$, but an intense HeI line at 2.058$\mu$m implies emission from a thin shell expanding at nearly 10000 kms$^{-1}$. The progenitor's hydrogen layer was severely depleted in this `SN~IIb', and the strength of the HeI relative to Br$\gamma$ is consistant with interaction models which predict that most of the emission comes from the SN ejecta behind the reverse shock.

The type~Ia supernovae 1995D and 1995E were observed about 30 days past maximum light. The mysterious `1.2$\mu$m' feature is seen to extend well into the H band. The IR flux from 1995E confirms that it is highly obscured at optical wavelengths by dust in its host galaxy. Supernova 1994AE (Ia) reached a maximum of V=13.0, but was only marginally detected in the H band spectra four months after peak brightness.

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