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Astron. Astrophys. 359, 876-886 (2000)

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Epochs of maximum light and bolometric light curves of type Ia supernovae

G. Contardo 1,2, B. Leibundgut 1 and W.D. Vacca 3

1 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
2 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany
3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

Received 28 May 1999 / Accepted 12 May 2000

Abstract

We present empirical fits to the UBVRI light curves of type Ia supernovae. These fits are used to objectively evaluate light curve parameters. We find that the relative times of maximum light in the filter passbands are very similar for most objects. Surprisingly the maximum at longer wavelengths is reached earlier than in the B and V light curves. This clearly demonstrates the complicated nature of the supernova emission.

Bolometric light curves for a small sample of well-observed SNe Ia are constructed by integration over the optical filters. In most objects a plateau or inflection is observed in the light curve about 20-40 days after bolometric maximum. The strength of this plateau varies considerably among the individual objects in the sample. Furthermore the rise times show a range of several days for the few objects which have observations early enough for such an analysis. On the other hand, the decline rate between 50 and 80 days past maximum is remarkably similar for all objects, with the notable exception of SN 1991bg. The similar late decline rates for the supernovae indicate that the energy release at late times are very uniform; the differences at early times are likely due to the radiation diffusing out of the ejecta.

With the exception of SN 1991bg, the range of absolute bolometric luminosities of SNe Ia is found to be at least a factor of 2.5. The nickel masses derived from this estimate range from 0.4 to 1.1 [FORMULA]. It seems impossible to explain such a mass range by a single explosion mechanism, especially since the rate of [FORMULA]ray escape at late phases seems to be very uniform.

Key words: stars: supernovae: general – stars: fundamental parameters

Send offprint requests to: G. Contardo (contardo@mpa-garching.mpg.de)

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© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000
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