We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1 ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry and X-ray variability information. We found 41 variable sources, 14 of which have a flare-like light curve, and 2 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 3 Myr. -2et al. (2002) have found a good correlation between disk indicators and report lower limits for the disk fraction ranging from 21% to 56%. They also found a typical value for mass accretion rates of ∼ 10 −8 M ⊙ yr −1 , comparable to the values derived for Orion and Taurus-Auriga.NGC 2264 provides a laboratory for studying the interrelationships of rotation, mass accretion, disk indicators and X-ray luminosity of PMS stars. The question of how exactly these things are related is still an open problem in star formation phenomenology. There is a clear relationship between rotation rate (period) and X-ray luminosity (L x ) found in late-type stars in clusters as old as NGC 2547 (15-40 Myrs, Jeffries et al. 2000) through the Hyades (∼500 Myrs, Stauffer et al. 1997). The ratio between the X-ray and bolometric luminosity, L x /L bol , increases with increasing rotation rate, until the most rapidly rotating stars reach a maximum X-ray luminosity (or saturation level) such that L x /L bol ∼ 10 −3 (see Pizzolato et al. 2003, and references within). It is much less clear that rotation and L x /L bol are related in younger clusters (e.g. Gagne et al. 1995). Feigelson et al. (2003) see no obvious correlation between rotation and L x /L bol for their Orion (∼ 1 Myr old; Hillenbrand 1997) sample, and conclude that the X-ray generation mechanism for young PMS stars must be different from that responsible in young main sequence stars. Flaccomio et al. (2003) analyze data for a number of young associations and clusters (including Orion), and agree that there is little correlation between L x /L bol and rotation at very young ages, but conclude that the data are consistent with a single physical mechanism, where the Orion-age stars are simply all at or near the saturation level (and that level and the critical velocity for it are a function of gravity/age). We want to study at what age the relationship between rotation and L x /L bol emerges. NGC 2264 (∼ 3 Myrs old; Sung et al. 1997;Park et al. 2000), being slightly older than Orion, is at an ideal age to probe the relationship between these parameters.Chandra observations provide a unique tool to improve the X-ray sample of PMS stars in NGC 2264. The high spatial resolution provided by the ACIS camera allows us to resolve the source confusion present in previous ROSAT data samples. The Chandra sensitivity extends the X-ray flux limit from the ROSAT value of lo...

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Approximately one-half of the L1551 bipolar outflow was mapped in the J = 1-0 transition of 12CO using the FCRAO 14 m telescope. The data were obtained by heavily oversampling over the beam area and then were reconstructed using a maximum entropy algorithm to obtain images of the high-velocity gas with an angular resolution of approximately 20". The outflow exhibits a striking shell-like structure with the lowest velocity out-flowing gas found along the limb of the outflow, and the highest velocity outflowing gas found along the axis of the outflow. A smooth transition is found between low-velocity emission on the periphery and high-velocity gas in the center. Our data can be modeled by molecular material located in a thin expanding shell which is accelerating away from IRS 5.