Chandra X-ray observations of Young Clusters II. Orion Flanking Fields   Data
  We present results of Chandra observations of two flanking fields (FF) in Orion, outside the Orion Nebula Cluster (ONC). The observations were taken with the ACIS-I camera with an exposure time of about 48 ks each field. We present a catalog of 417 sources, which includes X-ray luminosity, optical and infrared photometry and X-ray variability information. We have found 91 variable sources, 33 of which have a flare-like light curve, and 11 of which have a pattern of a steady increase or decrease over a 10 hour period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main sequence stars with ages younger than 10 Myr. We present evidence for an age difference among the X-ray selected samples of NGC 2264, Orion FF, and ONC, with NGC 2264 being the oldest, and ONC being the youngest. 
Solange V. Ramirez, Luisa Rebull, John Stauffer, Stephen Strom, Lynne   Hillenbrand, Thomas Hearty, Eugene L. Kopan, Steven ...