The peculiar type Ia supernova SN 1997br in ESO576-G40 was extensively observed at Beijing Astronomical Observatory (BAO) and Lick Observatory. In this paper, we present and discuss the BV RI photometry and the spectra collected over three months, starting from 9 days before maximum brightness. The light curves of SN 1997br are similar to those of SN 1991T, with slow decline rates after the B maximum. Well sampled data before the B maximum show unambiguously that SN 1997br rises more slowly and has a wider peak than normal type Ia supernovae. The optical color evolution of SN 1997br is also similar to that of SN 1991T. We estimate the extinction of SN 1997br to be E(B −V )=0.35±0.10 by comparing its BV RI light curves to those of SN 1991T and by measuring the equivalent width of interstellar Na I D absorption lines. We have conducted a thorough comparison of the spectroscopic evolution of SN 1997br, SN 1991T, and SN 1994D. Although SN 1997br is generally very similar to SN 1991T, it shows some interesting differences at various epochs. Spectra of SN 1997br seem to indicate an earlier transition to the dominant phase of Fe peak elements after the B maximum. Si II lines in SN 1997br show a very short duration after the B maximum. We discuss the implications of our observations of SN 1997br for models of type Ia supernovae. Specifically, we suggest that some SNe Ia may result from decelerated detonations of white dwarfs. (Refer to PDF file for exact formulas).

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This is a pre-print of an article published by The American Astronomical Society. © 1999 The American Astronomical Society. The final, published version is located here: https://doi.org/10.1086/300895

Also archived in: arXiv:astro-ph/9903466 v1 30 Mar 1999

This work is supported by NSF grant AST-9417213 to A.V.F. and by the National Science Foundation of China. We are grateful to Sun Microsystems Inc. (Academic Equipment Grant Program), Photometrics Ltd., the National Science Foundation, and the Sylvia and James Katzman Foundation for donations that made KAIT possible.ISSN:1538-3881

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Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus