Low-Mass Companions of Cepheids: Fingerprints of Star Formation

Starformation theory should be able to reproduce the binary characteristics(separation, mass ratio, eccentricity) for high and intermediatemass stars;but first we have to define, through observations, what those characteristicsare. This project proposes XMM Xray observations of a sample of 8 possiblecompanions of 5 Msun Cepheids to confirm that they are young physicalcompanions, not chance alignments with field stars. The sample is a subset of 69Cepheids surveyed with the Hubble Space Telescope Wide Field Camera 3 (WFC3),identifying 35 possible lowmass companions. They have the surprisingcharacteristic that there are more FG dwarfs (compared to K dwarfs) thanpredicted by the Initial Mass Function, a fingerprint of binary star formation truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]