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We observed the Monoceros R2 molecular cloud with the ACIS-I array onboardthe Chandra X-ray Observatory. From the central 3.2' x 3.2' region, we detect154 sources above the detection limit of ~5x10^-16 ergs s^-1 cm^-2 with a 100ks-exposure. About 85% of the X-ray sources are identified with an infraredcounterpart, including four high mass stars in zero age main sequence (ZAMS)and/or pre main sequence (PMS) phase. The X-ray spectra of the high mass ZAMSand PMS stars are represented with a thin thermal plasma model of a temperatureabove 2 keV. The X-rays are time-variable and exhibit rapid flares. These hightemperature plasma and flaring activity are similar to those seen in low massPMS stars and contrary to the behavior observed in high mass main sequencestars. The X-ray luminosity increases as the intrinsic K-band flux increases.However, the X-ray luminosity saturates at a level of ~10^31 ergs s^-1. Weconclude that high mass ZAMS and PMS emit X-rays, possibly due to the magneticactivity like those of low mass stars.Comment: 12 pages, 10 figures, accepted for publication in Ap

ChandraObservations of High‐Mass Young Stellar Objects in the Monoceros R2 Molecular Cloud