The speaker will be Dovi Poznanski
Place: Holcblat Hall
Time: Wednesday, 08/Jan/2003, 14:00
Title: Not Color-Blind: Using Multiband Photometry to Classify Supernovae
Current supernova (SN) classification methods rely almost solely on the
analysis of SN spectra to determine their type. However, spectroscopy may
not be possible or practical when SNe are faint, very numerous, or
discovered in archival studies. We present a classification method for SNe
based on the comparison of their observed colors with synthetic ones,
calculated from a large database of multi-epoch optical spectra of nearby
events. The temporal coverage of our compilation allows us to draw paths
in color space which show the time evolution of each SN type. Inspecting
the resulting diagrams, one can then look for regions which are either
populated by a single type of SN, or that are avoided by various SN types.
The observed photometric colors of a candidate SN with a known redshift
can then be plotted on the relevant diagrams, and constraints on its type
and age may be drawn. Broad-band photometry through standard
Johnson-Cousins UBVRI filters can be useful to classify SNe up to z ~ 0.6.
At higher redshifts, the V band samples the restframe UV, not covered by
our spectral database. Thus, only one color (R-I) remains in the
Johnson-Cousins system. The use of Sloan Digital Sky Survey (SDSS) ugriz
filters allows extending our classification method to higher redshifts (z
= 0.75), and the use of infrared bands, to z = 2.5. Community access to
the tools developed is provided by a dedicated Web site
http://wise-obs.tau.ac.il/~dovip/typing/index.html.