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Optical spectra of the bright Type II-L supernova SN 1979C obtained in April 2008 with the 6.5 m MMT telescope are compared with archival late-time spectra to follow the evolution of its optical emission over the age range of 11 to 29 years. We estimate an Halpha flux decrease of around 35% from 1993 to 2008 but noticeable increases in the strength of blueshifted emission of forbidden oxygen lines. While the maximum expansion of the broad ~6700 km/s Halpha emission appears largely unchanged from 1993, we find a significant narrowing of the double-peaked emission profiles in the [O I] 6300, 6364 and [O II] 7319, 7330 lines. A comparison of late-time optical spectra of a few other Type II supernovae which, like SN 1979C, exhibit bright late-time X-ray, optical, and radio emissions, suggests that blueshifted double-peaked oxygen emission profiles may be a common phenomenon. Finally, detection of a faint, broad emission bump centered around 5800 Angstroms suggests the presence of WC type Wolf-Rayet stars in the supernovas host star cluster.
We present late-time optical images and spectra of the Type IIn supernova SN 1986J. HST ACS/WFC images obtained in February 2003 show it to be still relatively bright with m(F606W) = 21.4 and m(F814W) = 20.0 mag. Compared against December 1994 HST WF
We report the detection of broad, high-velocity oxygen emission lines from the site of SN 1941C nearly eight decades after outburst, making it the oldest optically detected core-collapse supernova/youngest core-collapse supernova remnant with a well
Ground-based optical spectra and Hubble Space Telescope images of ten core-collapse supernovae (CCSNe) obtained several years to decades after outburst are analyzed with the aim of understanding the general properties of their late-time emissions. Ne
The evolution of the shape and size of the ejecta of SN 1987A is analyzed over a period of ~ 8 years based on HST images and spectra taken between 1278 and 4336 days after the supernova outburst. We combine both proprietary and archival HST data obta
The Type IIn supernovae (SNe IIn) have been found to be associated with significant amounts of dust. These core-collapse events are generally expected to be the final stage in the evolution of highly-massive stars, either while in an extreme red supe