Productive tea this morning! Productive in the sense of coming up with lots of interesting questions I don't have time to answer.
Spurred by Shri Kulkarni's colloquium on the Palomar Transient Factory yesterday, I wondered if anyone has estimated the signature of a 'death spiral' of a hot Jupiter/Neptune/(super-)Earth into its parent star. Apparently it is one idea for explaining luminous red novae: a hot Jupiter entering a giant star's atmosphere might heat up the atmosphere and create an artificial supergiant. Cool, and we know there are white dwarfs with metal in their atmospheres from disrupted asteroids. So could you detect an asteroid impact on a white dwarf? How about a neutron star? In fact, white dwarfs are fluid/gaseous, but neutron stars have a stiff equation of state... so could you get craters on neutron stars?