UV light curves of the entire shock breakout phase lasting several hours was reported for two Type IIP SNe $-$ SNLS-04D2dc and SNLS-06D1jd (@gezari08 [@schawinski08]). Observation of the earliest UV and optical light curves of IIP SNe is crucial to model the shock breakout light curves and constrain the properties of SN progenitors [@tominaga09]. The earliest SNe IIP optical light curves have been studied in the past for SN 2005cs by @pastorello09 and for SN 2006bp by @quimby07 and the optical rising phase is rarely observed.

![image](lightcurve_2008in.ps){width="15cm"}

We model the early optical (ROTSE-IIIb $R$-band) light curves of using a simple model and put an observational constraint on the epoch and duration of shock breakout. Following the formulation of @waxman07, it can be shown that just after the shock breakout, the intensity of the SN light at a fixed wavelength is proportional to the intensity of blackbody radiation at that wavelength (see Equation 1 of @cowen10), while for the plateau phase @arnett80 derived an analytical expression (Equation 39 of that paper) and hence by combining these two equations one can approximate the overall intensity profile of a Type II SN during the rising phase through the plateau with the following expression 