Dust discs around intermediate mass and Sun-like stars in the 16 Myr old
  NGC 1960 open cluster
  We present an analysis of Spitzer IRAC (3.6--8um) and MIPS (24um) imaging of
members of the 16(+10/-5)Myr old open cluster NGC 1960 (M36). Models of
terrestrial planet formation indicate that rocky planets are likely to achieve
their final masses at around 10-30Myr, and thus this cluster is at an
interesting epoch for planet formation. We find 21 B-F5 type stars and 14 F6-K9
type stars which have 24um excess emission, and thus determine that >30% of
B-F5 type stars and >23% of F6-K9 type stars in this cluster have 24um excess
emission. These excess frequencies are similar to those observed in other
clusters of similar age. Three early type stars have excesses at near-infrared
wavelengths. Analysis of their SEDs confirms that these are true debris discs
and not remnant primordial or transitional discs. None of the 61 sun-like stars
have confirmed near-infrared excess, and we can place a limit on the frequency
of 8um excess emission around sun-like stars of <7%. All of the detected
excesses are consistent with emission from debris discs and are not primordial.
