Sarah J. Schmidt

Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field

We present a 20 pc, volume-limited sample of M7YL8 dwarfs created through spectroscopic follow-up of sources selected from the Two Micron All Sky Survey Second Incremental Release Point Source Catalog. In this paper we present optical spectroscopy of 198 candidate nearby ultracool dwarfs, including 12 late-M and L dwarfs likely to be within 20 pc of the Sun and 94 more distant late-type dwarfs. We have also identifiedfive ultracool dwarfs withspectral signatures of low gravity. Combining these data with previous results, we definea sample of 99ultracool dwarfs in 91 systems within 20 pc. These are used to estimate the J- and K-band luminosity functions for dwarfs with optical spectral types between M7 and L8 (10:5 < MJ < 15, 9:5 < MKS < 13). We find a space density of 4:9 ;10 � 3 pc � 3 for late-M dwarfs (M7YM9.5) and a lower limit of 3:8 ;10 � 3 pc � 3 for L dwarfs.

ACTIVITY AND KINEMATICS OF ULTRACOOL DWARFS, INCLUDING AN AMAZING FLARE OBSERVATION

We present the activity and kinematics of a representative volume-limited (20 pc) sample of 152 late-M and L dwarfs (M7-L8) photometrically selected from the Two Micron All Sky Survey (2MASS). Using new proper-motion measurements and spectrophotometric distance estimates, we calculate tangential velocities. The sample has a mean tangential velocity of Vtan = 31.5 km s-1, a velocity dispersion of σtan = 20.7 km s-1, and a maximum tangential velocity of Vtan = 138.8 km s-1. These kinematic results are in excellent agreement with previous studies of ultracool dwarfs in the local solar neighborhood. Hα emission, an indicator of chromospheric activity, was detected in 63 of 81 late-M dwarfs and in 16 of 69 L dwarfs examined. We find a lack of correlation between activity strength, measured by log(FHα/Fbol), and Vtan, although velocity distributions suggest that the active dwarfs in our sample are slightly younger than the inactive dwarfs. Consistent with previous studies of activity in ultracool dwarfs, we find that the fraction of Hα-emitting objects per spectral type peaks at spectral type M7 and declines through mid-L dwarfs. Activity strength is similarly correlated with spectral type for types later than M7. Eleven dwarfs out of 150 show evidence of variability, ranging from small fluctuations to large flare events. We estimate a flare cycle of ~5% for late-M dwarfs and ~2% for L dwarfs. Observations of strong, variable activity on the L1 dwarf 2MASS J10224821+5825453 and an amazing flare event on the M7 dwarf 2MASS J1028404-143843 are discussed.

Colors and Kinematics of L Dwarfs From the Sloan Digital Sky Survey

We present a sample of 484 L dwarfs, 210 of which are newly discovered from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic database. We combine this sample with known L dwarfs to investigate their izJHKS colors. Our spectroscopically selected sample has ~0.1 mag bluer median J – KS color at a given spectral type (for L0-L4) than previously known L dwarfs, which reflects a bias toward redder L dwarfs in past selection criteria. We present photometric distance relations based on i – z and i – J colors and derive distances to our L dwarf sample. We combine the distances with SDSS/2MASS proper motions in order to examine the tangential velocities. For the majority of our spectroscopic sample, we measured radial velocities and present three-dimensional kinematics. We also provide Hα detections for the fraction of our sample with sufficient quality spectra. Comparison of the velocities of our L dwarf sample to a kinematic model shows evidence for both cold and hot dynamical populations, consistent with young and old disk components. The dispersions of these components are similar to those found for M dwarfs. We also show that J – KS color is correlated with velocity dispersion, confirming a relationship between J – KS color and age.

BOSS Ultracool Dwarfs. I. Colors and Magnetic Activity of M and L Dwarfs

We present the colors and activity of ultracool (M7-L8) dwarfs from the Tenth Data Release of the Sloan Digital Sky Survey (SDSS). We combine previous samples of SDSS M and L dwarfs with new data obtained from the Baryon Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool Dwarf (BUD) sample of 11820 M7-L8 dwarfs. By combining SDSS data with photometry from the Two Micron All Sky Survey and the Wide-Field Infrared Sky Explorer mission, we present ultracool dwarf colors from

MULTI-WAVELENGTH CHARACTERIZATION OF STELLAR FLARES ON LOW-MASS STARS USING SDSS AND 2MASS TIME-DOMAIN SURVEYS

i-z

Spatially resolved measurements of H2O, HCl, CO, OCS, SO2, cloud opacity, and acid concentration in the Venus near‐infrared spectral windows

to

Discovery of an Unusually Blue L Dwarf Within 10 pc of the Sun

W2-W3

THE IMPLICATIONS OF M DWARF FLARES ON THE DETECTION AND CHARACTERIZATION OF EXOPLANETS AT INFRARED WAVELENGTHS

as a function of spectral type, and extend the SDSS-2MASS-WISE color locus to include ultracool dwarfs. The

PROBING THE FLARE ATMOSPHERES OF M DWARFS USING INFRARED EMISSION LINES

i-z

THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

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