XMM-Newton observations of the young open cluster around lambda Orionis

Abstract

We studied the X-ray properties of the young (~1-8 Myr) open cluster around the O8III star lambda Ori using XMM-Newton. We detected 167 X-ray sources, of which 58 are identified with known cluster members, from massive stars down to low-mass stars with spectral types M5.5. Another 23 sources were identified with new possible photometric candidates. Late-type stars have a median log LX/Lbol ~ -3.3, close to the saturation limit. Variability was observed in 35% of late-type members, including six flaring sources. The emission from the central hot star lambda Ori is dominated by plasma at 0.2-0.3 keV, with a weaker component at 0.7 keV, consistently with a wind origin. The coronae of late-type stars can be described by two plasma components with temperatures T1~0.3-0.8 keV and T2~0.8-3 keV, and subsolar abundances Z~0.1-0.3 Zsun, similar to what is found in other star-forming regions and associations. No significant difference was observed between stars with and without circumstellar discs, although the smallness of the sample of stars with discs and accretion does not allow us to draw definitive conclusions. The X-ray properties of lambda Ori late-type stars are comparable to those of the coeval sigma Ori cluster, suggesting that stellar activity in lambda Ori has not been significantly affected by the different ambient environment.

19 pages, 10 figures, 7 tables. Accepted by A&A

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• Spectroscopy of Very Low Mass Stars and Brown Dwarfs in the Lambda Orionis Star Forming Region
• The Gould's Belt Very Large Array Survey III. The Orion region
• A stellar census of the nearby, young 32 Orionis group
• The APOGEE-2 Survey of the Orion Star Forming Complex: I. Target Selection and Validation with early observations
• The NEMESIS Catalogue of Young Stellar Objects for the Orion Star Formation Complex. I. General description of data curation
• HH 175: A Giant HH Flow Emanating From A Multiple Protostar