A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei

Abstract

GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an abrupt variable and to have a circumstellar disk with very active accretion. Our monitoring observations in 2009-2011 revealed the star to show sporadic flare events, each with brightening of < 0.5 mag lasting for days. These brightening events, associated with a color change toward the blue, should originate from an increased accretion activity. Moreover, the star also underwent a brightness drop of ~1 mag lasting for about a month, during which the star became bluer when fainter. Such brightness drops seem to have a recurrence time scale of a year, as evidenced in our data and the photometric behavior of GM Cep over a century. Between consecutive drops, the star brightened gradually by about 1 mag and became blue at peak luminosity. We propose that the drop is caused by obscuration of the central star by an orbiting dust concentration. The UX Orionis type of activity in GM Cep therefore exemplifies the disk inhomogeneity process in transition between grain coagulation and planetesimal formation in a young circumstellar disk.

arXiv commentIn submission to the Astrophysical Journal, 4 figures

References in corpus (16)

• Rapid planetesimal formation in turbulent circumstellar discs
• Magnetospheric accretion-ejection processes in the classical T Tauri star AA
• Eclipses by circumstellar material in the T Tauri star AA Tau. II. Evidence for non-stationary magnetospheric accretion
• High-Resolution Spectroscopy in Tr37: Gas Accretion Evolution in Evolved Dusty Disks
• Accretion dynamics and disk evolution in NGC 2264: a study based on the Corot photometric observations
• Explaining UXOR variability with self-shadowed disks
• 25 Orionis: A Kinematically Distinct 10 Myr Old Group in Orion OB1a
• Constraining the Lifetime of Circumstellar Disks in the Terrestrial Planet Zone: A Mid-IR Survey of the 30-Myr-old Tucana-Horologium Association
• On the Stability of Dust-Laden Protoplanetary Vortices
• The Rapid Outbursting Star GM Cep: An EX-or in Tr 37?
• Young Exoplanet Transit Initiative (YETI)
• STK: A new CCD camera at the University Observatory Jena
• CTK - A new CCD Camera at the University Observatory Jena
• Optical photometry of GM Cep: evidence for UXor type of variability
• Long-Term Light Curve of Highly-Variable Protostellar Star GM Cep
• Photometric Observations of the Young Cluster Variable GM Cephei

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• The unusual photometric variability of the PMS star GM Cep
• Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei
• Triple Range Imager and POLarimeter (TRIPOL) --- A Compact and Economical Optical Imaging Polarimeter for Small Telescopes