THE 1990 CALAN TOLOLO SUPERNOVA SEARCH

We have started a search for supernovae as a collaboration between the University of Chile and the Cerro Tololo Inter-American Observatory, with the aim of producing a moderately distant (0.01 < z < 0.10) sampl e of Type Ia and Type II supernovae suitable for cosmological studies. The project began in mid-1990 and continues to the present. This pape r reports on the Calan/Tololo discoveries in the course of 1990, and o n the spectroscopic and photometric observations gathered for these ob jects. All of these observations were obtained with CCDs, with the ext ensive collaboration of visiting astronomers. Great care was exercised in the reduction of the light curves in order to properly correct for the background light of the host galaxy of each supernova. Of the fou r supernovae found in 1990, one proved to be a SN II-n; the remaining three were members of the Type Ia class at redshifts that ranged betwe en z = 0.04-0.05. One of the Type Ia events, SN 1990af, was found in t he elusive premaximum phase at a redshift of z = 0.0503, and was obser ved through maximum light. Peak magnitudes for the other two SNe Ia, w hich were not observed at maximum light, were derived using a chi2 min imization technique to fit the data with various template curves that represent a broad range of SNe Ia light curves. In future papers we wi ll make use of these estimates in order to discuss the Hubble diagram of SNe Ia.