Figure 13: Constraints on mass, effective temperature, radius and average density of the primary
star of SN 2011fe. The shaded red region is excluded by non-detection of an optical quiescent
counterpart in the Hubble Space Telescope imaging. The shaded green region is excluded from
considerations of the non-detection of a shock breakout at early times. The blue region is excluded
by the non-detection of a quiescent counterpart in the Chandra X-ray imaging. The location of the
H, He, and C main-sequence is shown, with the symbol size scaled for different primary masses.
Several observed WDs and NSs are shown. The primary radius in units of is shown for mass
. Image reproduced with permission from , copyright by AAS.