Photometric observations of SN 2017egm and peculiar transient AT 2018cow

Abstract

. We present 57 photometric epochs of superluminous SN 2017egm in NGC3191, covering the period of 285 days, and 36 epochs of peculiar object AT 2018cow, for which observations lasted 69 days. UBV RI photometry was carried out with 7 telescopes at 5 locations, including the 2.5-m telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute. The light and color curves of SN 2017egm were compared to several well-studied objects of similar type. The light curves of SN 2017egm show definite undulations: a shoulder at phase 114 days past maximum and a plateau lasting for a phase interval 155–235 days. We determined the basic parameters of the light curves for SN 2017egm and AT 2018cow: dates and magnitudes of maximum light, rates of decline at different stages of evolution in different bands.