Decline of Type Ia Supernova Light Curves
Harvard Smithsonian Center for Astrophysics | 2019 Oct 07
Scientists at the Center for Astrophysics | Harvard & Smithsonian have announced the discovery that, contrary to previously accepted knowledge, Type Ia supernovae experience light curve decline plateaus, and lengthy ones at that, lasting up to a year.
CfA scientist Or Graur first noticed strange light curve behaviors while studying late-time Type Ia supernovae in 2015, and this year confirmed light curve plateaus in Type Ia supernovae. "Most supernova research is conducted in the weeks or months immediately following an explosion, but we wanted to see how light curves behave at late times, around 500 to 1000 days after explosion," said Graur. "Optical observations of SN2012cg in 2015 revealed a slowdown in the light curve as expected, but as we studied additional supernovae over time, it became apparent that other mechanisms were at play, so we started looking for patterns to explain what was going on."
To better understand the strange behavior, Graur teamed up with Adam Riess of The Johns Hopkins University and the Space Telescope Science Institute, and 2011 winner of the Nobel Prize in Physics, to study nearby supernovae using Riess's already-set HST programs. "Even though these were all nearby supernovae, at these late times they were very faint. We needed Hubble's resolving power to be able to tell them apart from other stars in their respective galaxies," said Graur. "But what made the difference to our observations was that Adam's programs on Hubble also had near-infrared data in the H-band. What started as a fishing expedition revealed a portion of time where the light curve is flat, and that period lasts for up to a year. That was a surprise. I didn't expect to see that." ...
A year-long plateau in the late-time near-infrared light curves of type Ia supernovae ~ Or Graur et al
- Nature Astronomy (online 07 Oct 2019) DOI: 10.1038/s41550-019-0901-1