Rotation periods and photometric variability of rapidly rotating ultra-cool dwarfs

Abstract

We used the optical and near-infrared imagers located on the Liverpool, the IAC80, and the William Herschel telescopes to monitor 18 M7$-$L9.5 dwarfs with the objective of measuring their rotation periods. We achieved accuracies typically in the range $\pm$1.5$-$28 mmag by means of differential photometry, which allowed us to detect photometric variability at the 2$\sigma$ level in the 50\% of the sample. We also detected periodic modulation with periods in the interval 1.5$-$4.4 h in 9 out of 18 dwarfs that we attribute to rotation. Our variability detections were combined with data from the literature; we found that 65$\pm$18 $\%$ of M7$-$L3.5 dwarfs with $v$sin$i\ge 30$ km s${}^{-1}$ exhibit photometric variability with typical amplitudes $\le$20 mmag in the $I$-band. For those targets and field ultra-cool dwarfs with measurements of $v$sin$i$ and rotation period we derived the expected inclination angle of their rotation axis, and found that those with $v$sin$i\ge 30$ km s${}^{-1}$ are more likely to have inclinations $\gtrsim 40$ deg. In addition, we used these rotation periods and others from the literature to study the likely relationship between rotation and linear polarization in dusty ultra-cool dwarfs. We found a correlation between short rotation periods and large values of linear polarization at optical and near-infrared wavelengths.

19 pages, 12 figures, accepted for publication in MNRAS

References in corpus (18)

• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Activity and Kinematics of Ultracool Dwarfs Including An Amazing Flare Observation
• Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary?
• BGLS: A Bayesian formalism for the generalised Lomb-Scargle periodogram
• Bayesian Ages for Early-Type Stars from Isochrones Including Rotation, and a Possible Old Age for the Hyades
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• The Viewing Geometry of Brown Dwarfs Influences Their Observed Colours and Variability Properties
• An independent analysis of the brown dwarf atmosphere monitoring (BAM) data: large-amplitude variability is rare outside the L/T transition
• On the Radii of Brown Dwarfs Measured with AKARI Near-Infrared Spectroscopy
• Trigonometric parallaxes of young field L dwarfs
• Optical variability of the ultracool dwarf TVLM 513-46546: evidence for inhomogeneous dust clouds
• Timing Analysis of the Periodic Radio and Optical Brightness Variations of the Ultracool Dwarf, TVLM 513-46546
• Optical and near-infrared linear polarization of low and intermediate-gravity ultra-cool dwarfs
• M dwarf search for pulsations within Kepler GO program

Cited by in corpus (12)

• Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. II. Emergence and Sedimentation of Silicate Clouds in L Dwarfs, and Analysis of the Full M5--T9 Field Dwarf Spectroscopic Sample
• Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: effects of rotation
• Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: global and equatorial dynamics
• Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-Cool Dwarfs
• Measurements of pulse jitter and single-pulse variability in millisecond pulsars using MeerKAT
• The Rotation-Disk Connection in Young Brown Dwarfs: Strong Evidence for Early Rotational Braking
• Modeling Polarization Signals from Cloudy Brown Dwarfs: Luhman 16 A and B in Three Dimensions
• Radio Emission from Binary Ultracool Dwarf Systems
• The photometric periods of rapidly rotating field ultra-cool dwarfs
• Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer
• The Perkins INfrared Exosatellite Survey (PINES) II. Transit Candidates and Implications for Planet Occurrence around L and T Dwarfs