AAS Meeting #193 - Austin, Texas, January 1999
Session 111. Supernovae and Atmospheric Phenomena in Binaries
Oral, Saturday, January 9, 1999, 10:00-11:30am, Room 6 (A and B)

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[111.02] Early lightcurve profile of Type Ia Supernovae

D.E. Groom (LBNL/CfPA, Berkeley), Supernova Cosmology Project Collaboration

Intensity measurements for 36 high-redshift supernovae, a subset of those discovered by the Supernova Cosmology Project, have been fitted using a standard template with an adjustable time of maximum light, amplitude, and a horizontal (time) axis scale expansion factor s(1+z). Here the redshift z has been determined spectroscopically, and s is usually within 15% of unity. Appropriate K-corrections have been made. When this is done and individual lightcurves are normalized to unit maximum brightness, and the more than 1400 experimental points are found to lie on a common curve. Our search technique produces several measurements at each of two epochs before maximum light for each supernovae. The composite curve thus contains hundreds of points at early epochs, mapping the shape of the lightcurve in this region for the first time. Most na\"ively, the early supernovae has an isothermal photosphere expanding with uniform velocity, so that the initial luminosity grows as t2. The data at times earlier than the time of half of maximum brightness are quite adequately described by this parabola. The explosion occurs at -17.6±.4~days before maximum light in the rest frame, and the product vT2 determined from the fit is within reasonable expectation.

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The author(s) of this abstract have provided an email address for comments about the abstract: deg@lbl.gov

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