Whimper of a Bang: Documenting the Final Days of the Nearby Type Ia Supernova 2011fe

Understand

Using the Hubble Space Telescope (HST) and the Large Binocular Telescope, we followed the evolution of the Type Ia supernova (SN Ia) 2011fe for an unprecedented 1840 days past $B$-band maximum light and over a factor of $7$ million in flux.

• At 1840 days, the 4000 - 17000 \AA{} quasi-bolometric luminosity is just ($420 \pm 20$) $L_{\odot}$.
• By measuring the late-time quasi-bolometric light curve, we present the first confident detection of $^{57}$Co decay in a SN Ia light curve and estimate a mass ratio of $\log (^{57}\mathrm{Co}/^{56}\mathrm{Co}) = -1.59^{+ 0.06 }_{- 0.07 }$.
• We do not have a clean detection of $^{55}\mathrm{Fe}$, but find a limit of $^{55}\mathrm{Fe}/^{57}\mathrm{Co} < 0.22$ with 99% confidence.