Constraining the Mapping Between Initial Stellar Masses and Compact Remnants

There is currently little observational guidance as to the masses of stars thatleave behind neutron stars and black holes. Three of the four best constraintscome from Xray pulsars that are associated with young star clusters.Remarkably, all three of these limits suggests that the progenitors weremassive, with lower limits between 20 and 50 Msun. Moreover, the neutron starsthemselves appear to be highlymagnetized, with Bvirgul1e14 G, compared to Bvirgul1e12 Gfor an ordinary radio pulsar. More constraints on the masses of progenitors areclearly needed, so we are proposing a pilot study of 2 candidate young clustersof massive stars to search for Xray pulsars. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]