A near-infrared variability study in the cloud IC1396W: low star-forming efficiency and two new eclipsing binaries

Abstract

Identifying the population of young stellar objects (YSOs) in high extinction regions is a prerequisite for studies of star formation. This task is not trivial, as reddened background objects can be indistinguishable from YSOs in near-infrared colour-colour diagrams. Here we combine deep JHK photometry with J- and K-band lightcurves, obtained with UKIRT/WFCAM, to explore the YSO population in the dark cloud IC1396W. We demonstrate that a colour-variability criterion can provide useful constraints on the star forming activity in embedded regions. For IC1396W we find that a near-infrared colour analysis alone vastly overestimates the number of YSOs. In total, the globule probably harbours not more than ten YSOs, among them a system of two young stars embedded in a small (~10000 AU) reflection nebula. This translates into a star forming efficiency SFE of ~1%, which is low compared with nearby more massive star forming regions, but similar to less massive globules. We confirm that IC1396W is likely associated with the IC1396 HII region. One possible explanation for the low SFE is the relatively large distance to the ionizing O-star in the central part of IC1396. Serendipitously, our variability campaign yields two new eclipsing binaries, and eight periodic variables, most of them with the characteristics of contact binaries.

13 pages, 10 figures, MNRAS, in press

References in corpus (11)

• The UKIRT Infrared Deep Sky Survey Early Data Release
• An Infrared/X-ray Survey for New Members of the Taurus Star-Forming Region
• Lithium Depletion of Nearby Young Stellar Associations
• Rotation and accretion of very low mass objects in the SigmaOri cluster
• A Large-Area Search for Low-Mass Objects in Upper Scorpius II: Age and Mass Distributions
• A General Catalogue of Molecular Hydrogen Emission-Line Objects (MHOs) in Outflows from Young Stars
• A Spitzer Census of Star Formation Activity in the Pipe Nebula
• Deep near-IR variability survey of pre-main-sequence stars in Rho Ophiuchi
• Hot spots and a clumpy disk: Variability of brown dwarfs and stars in the young Sigma Ori cluster
• Exploring pre-main sequence variables of ONC: The new variables
• Extinction techniques and impact on dust property determination

Cited by in corpus (3)

• UWISH2 -- The UKIRT Widefield Infrared Survey for H2
• About the nature of Mercer14
• Near-Infrared Variability of Low Mass Stars in IC 1396A and TR 37