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Session 6 - Novae and Supernovae.
Display session, Monday, June 08
Atlas Ballroom,

[6.09] Observations of Unusual Type Ia Supernova SN1997ej

A. T. Steffen (University of Wisconsin - Eau Claire), N. Suntzeff, M. M. Phillips, R. Covarrubias (CTIO)

We report photometric and spectroscopic observations for the Type Ia supernova SN1997ej located in the lenticular galaxy IC2060. Data were obtained using the 0.9, 1.5, and 4m telescopes at Cerro Tololo Inter-American Observatory (CTIO). A spectrum taken on 1997 DEC 31.1 UT by A. Clocchiatti (P. Universidad Catolica de Chile) and M. M. Phillips (CTIO) displayed very high expansion velocities of the Si II and Ca II lines, initially suggesting that the supernova had been discovered significantly before maximum light. However, the UBVRI photometry obtained over the next month showed that the spectrum was obtained just after maximum. Thus, SN1997ej appears to be related to the Type Ia SN1984A which formed unusually high-velocity matter in the ejecta. We fit BVI light curves of SN1997ej to Type Ia templates using the method described in Hamuy et al. (1996, AJ, 112, 2408). The best fits give B_max=15.85\pm0.05 on \mboxJD=2450808.3 with a decline rate of \Delta m_15(B)=1.43\pm0.05. For an assumed Hubble constant of 65 km s^-1 Mpc^-1, we derive absolute magnitudes of M_B=-19.19\pm0.21, M_V=-19.20\pm, and M_I=-18.66\pm0.20, and show that SN1997ej had a normal Type Ia photometric evolution despite the unusually high ejection velocities.

Program listing for Monday