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A. Clocchiatti (Pontificia Universidad Catolica de Chile), N.B. Suntzeff, R. Covarrubias (Cerro Tololo Interamerican Observatory), M.M. Phillips (CARSO, Las Campanas Observatory), A. Filippenko (University of California at Berkeley), M. Turatto, E. Cappellaro (Osservatorio Astronomico di Padova), M. Della Valle (Osservatorio Astrofisico di Arcetri), A. Piemonte (Pontificia Universidad Catolica de Chile), T. Matheson (University of California at Berkeley)
A study of the Type Ic SN 1990B, which exploded in the Sc galaxy NGC 4568, is presented. The work is based on observations done at Cerro Tololo Interamerican Observatory, Lick Observatory, European Southern Observatory, and Asiago Observatory. The combined dataset comprises BV(RI)c CCD images at 20 epochs, spanning approximately 160 days after maximum light, and 15 spectra from 8 up to 150 days after maximum light.
The SN appeared on a complicated background, which was modeled and subtracted using images of NGC 4568 taken years after the explosion, when the SN light had faded beyond detection. The photometry done on the subtracted frames shows the light curves of SN 1990B to be of the slow Ic SN type, with a slope steeper than that of the Type Ib SN 1983N or the Type II-t SN 1993J.
Using two estimates of the foreground reddening, a bolometric light curve of SN 1990B is computed. The mass--to--energy ratio of SN 1990B, relative to those of other Type Ib/c SNe is computed indicating that, for a constant energy deposited by the explosion, the mass in the ejecta of SN 1990B was smaller than those of other slow Ic SN events.
Late-time light curves of SN 1998bw in ESO 184-G82, probably connected with GRB 980425 are presented. They are based on observations done at Cerro Tololo and, together with observations already in the literature, allow to follow the UBVRI evolution for more than 150 days after discovery. The light curves of SN 1998bw are found to be peculiar, even within the very heterogeneous variety of Type Ic SNe, revealing exciting dimensions in the possible outcomes of core-collapse explosions.
AC acknowledges the support of CONICYT, Chile, under FONDECYT grant 1980803; NBS and MMP acknowledge the support from NASA through grants GO-2563.01-87A and GO-6020 from STScI.