Variability and periodicity of field M dwarfs revealed by multichannel monitoring

Abstract

We present simultaneous, multiband monitoring of 19 field M dwarfs (spectral types M2-M9). Significant variability was found in seven objects in at least one out of the three channels I, R and G. Two objects, LHS370 (M5V) and 2M1707+64 (M9V), show periods of 5.9+-2.0 and 3.65+-0.1 hours respectively. On account of the agreement with the typical values of v*sin(i) published for M dwarfs (Mohanty & Basri 2003), we claim these to be the objects' rotation periods. In the case of 2M1707+64 we furthermore find evidence for the presence of magnetically-induced cool spots as the reason for the observed variability (at a temperature contrast of 4-8 percent, with a projected surface coverage factor of less than 0.075) and can rule out the scenario of dust clouds (as represented by the COND or DUSTY models). Comparing the frequency of occurrence of variability in this and various L dwarf samples published over the past few years, we find that variability is more common in field L dwarfs than in field M dwarfs. This implies a change in the physical nature and/or extent of surface features when moving from M to L dwarfs.

arXiv comment15 pages, 14 figures, accepted for publication by A&A

References in corpus (22)

• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence
• Rotation and Activity in Mid-M to L Dwarfs
• Meeting the Cool New Neighbors V: A 2MASS-Selected Sample of Ultracool Dwarfs
• Spectroscopic Properties of Cool Stars in the SDSS: An Analysis of Magnetic Activity and a Search for Subdwarfs
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• Spectral Energy Distributions for Disk and Halo M--Dwarfs
• A rotational and variability study of a large sample of PMS stars in NGC 2264
• Variability in ultra cool dwarfs: evidence for the evolution of surface features
• Gravity Indicators in the Near-Infrared Spectra of Brown Dwarfs
• High resolution spectroscopy of ultracool M dwarfs
• L-dwarf variability: I-band observations
• The Solar Neighborhood X: New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs
• Rotation and accretion of very low mass objects in the SigmaOri cluster
• Spectroscopic rotation velocities of L dwarfs from VLT/UVES and their comparison with periods from photometric monitoring
• Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust Clouds
• Limits on the infrared photometric monitoring of brown dwarfs
• Rotation periods for very low mass stars in the Pleiades
• A mini-survey for variability in early L dwarfs
• Time resolved spectroscopy of the variable brown dwarf Kelu-1
• Dust clouds or magnetic spots? Exploring the atmospheres of L dwarfs with time-resolved spectrophotometry

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