Study on SN 2018agk and detectability of early flux excess in light curves of SNe Ia in high cadence survey

Despite their fundamental importance to cosmology, the exact progenitor systems of type Ia supernovae (SNe Ia) are not known. Theories suggest that signatures of some SNe Ia progenitors could be seen as bumps or flux excess in the early light curve, e.g. the collision of SN ejecta with the non-degenerate binary companion (Kasen 2009). With high cadence light curves from Kepler  and TESS, we can search for such signals to identify progenitor systems of SNe. We present the 30-min cadence Kepler/K2 light curve of SN 2018agk that is fully consistent with a single power-law rise, giving strong limits on any early excess flux features. Combined with early ground-based observations, SN 2018agk has similar color evolution with other SNe Ia without early bumps and is a prototypical example for future study in early color evolution. Using the high-S/N light curve of SN 2018agk, we also study the detectability and characterization of early excess flux with high cadence survey and it will have substantial implication to similar studies with TESS.