Near-Infrared Variability of Low Mass Stars in IC 1396A and TR 37

Abstract

We have monitored nearly a square degree in IC 1396A/Tr 37 over 21 epochs extending over 2014 - 2016 for sources variable in the JHK bands. In our data, 65 +\- 8 % of previously identified cluster members show variations, compared with < 0.3% of field stars. We identify 119 members of Tr 37 on the basis of variability, forming an unbiased sample down to the brown dwarf regime. The K-band luminosity function in Tr 37 is similar to that of IC 348 but shifted to somewhat brighter values, implying that the K- and M-type members of Tr 37 are younger than those in IC 348. We introduce methods to classify the causes of variability, based on behavior in the color-color and color-magnitude diagrams. Accretion hot spots cause larger variations at J than at K with substantial scatter in the diagrams; there are at least a dozen, with the most active resembling EXors. Eleven sources are probably dominated by intervention of dust clumps in their circumstellar disks with color behavior indicating the presence of grains larger than for interstellar dust, presumably due to grain growth in their disks. Thirteen sources have larger variations at K than at J or H. For 11 of them, the temperature fitted to the variable component is very close to 2000K, suggesting that the changes in output are caused by turbulence at the inner rim of the circumstellar disk exposing previously protected populations of grains.

accepted by ApJ

References in corpus (20)

• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• The WFCAM Science Archive
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• The Second Data Release of the INT Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS DR2)
• High-Resolution Spectroscopy in Tr37: Gas Accretion Evolution in Evolved Dusty Disks
• Dust inflated accretion disc as the origin of the Broad Line Region in Active Galactic Nuclei
• 3D Radiation Non-ideal Magnetohydrodynamical Simulations Of The Inner Rim In Protoplanetary Disks
• Young Stellar Object Variability (YSOVAR): Long Timescale Variations in the Mid-Infrared
• CSI 2264: Characterizing Young Stars in NGC 2264 with Short-Duration, Periodic Flux Dips in their Light Curves
• The Monitor project: Data processing and lightcurve production
• The VLTI / PIONIER near-infrared interferometric survey of southern T Tauri stars. I. First results
• Deep near-IR variability survey of pre-main-sequence stars in Rho Ophiuchi
• Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry
• YSOVAR: Mid-IR variability in the star forming region Lynds 1688
• The first 40 million years of circumstellar disk evolution: the signature of terrestrial planet formation
• Spitzer Observations of Long Term Infrared Variability Among Young Stellar Objects in Chamaeleon I
• Star-disk interactions in multi-band photometric monitoring of the classical T Tauri star GI Tau
• Connecting X-ray and Infrared Variability among Young Stellar Objects: Ruling out potential sources of disk fluctuations
• The Herschel/PACS view of the Cep OB2 region: Global protoplanetary disk evolution and clumpy star formation
• IRAM and Gaia views of multi-episodic star formation in IC1396A: The origin and dynamics of the Class 0 protostar at the edge of an HII region

Cited by in corpus (5)

• EXORCISM: a spectroscopic survey of young eruptive variables (EXor and candidates)
• Star formation in IC1396: Kinematics and subcluster structure revealed by Gaia
• What's Behind the Elephant's Trunk? Identifying Young Stellar Objects on the Outskirts of IC1396
• Near-infrared time-series photometry in the field of Cygnus OB2 association II. Mapping the variability of candidate members
• Study of the long-term $BV{R}_c{I}_c$ photometric variability of eight PMS stars in the young open cluster Trumpler 37