K2 observations of type Ia supernova SN 2018oh

These data are supplemented by multi-color Panoramic Survey Telescope (Pan-STARRS1) and Rapid Response System 1 and Cerro Tololo Inter-American Observatory 4m Dark Energy Camera (CTIO 4-m DECam) observations obtained within hours of explosion.

The K2 light curve has an unusual two-component shape, where the flux rises with a steep linear gradient for the first few days, followed by a quadratic rise as seen for typical supernovae (SNe) Ia. This "flux excess" relative to canonical SNIa behavior is confirmed in our i-band light curve, and furthermore, SN2018oh is especially blue during the early epochs. The flux excess peaks 2.14{+/-}0.04 days after explosion, has a full width at half maximum (FWHM) of 3.12{+/-}0.04 days, a blackbody temperature of T=17500_-9000_^+11500^K, a peak luminosity of 4.3{+/-}0.2x10^37^erg/s, and a total integrated energy of 1.27{+/-}0.01x10^43^erg.