Using the Position and Proper Motion Extended-L (PPMXL) catalogue, we have used optical and near-infrared colour cuts together with a reduced proper motion cut to find bright M dwarfs for future exoplanet transit studies. PPMXL's low proper motion uncertainties allow us to probe down to smaller proper motions than previous similar studies. We have combined unique objects found with this method to that of previous work to produce 8479 K < 9 M dwarfs. Low resolution spectroscopy was obtained of a sample of the objects found using this selection method to gain statistics on their spectral type and physical properties. Results show a spectral type range of K7-M4V. This catalogue is the most complete collection of K < 9 M dwarfs currently available and is made available here.
Two newly identified magnetic cataclysmic variables discovered in the Sloan Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5, have spectra showing highly prominent, narrow, strongly polarized cyclotron humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs, respectively. In the former, the spacing of the humps indicates the 3rd and 4th harmonics in a magnetic field of ∼60MG. The narrowness of the cyclotron features and the lack of strong emission lines imply very low temperature plasmas and very low accretion rates, so that the 1 Based in part on observations obtained with the Sloan Digital Sky Survey and with the Apache Point Observatory (APO) 3.5m telescope, which are owned and operated by the Astrophysical Research Consortium (ARC). A portion of the observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.
We present the homogeneous analysis of a sample of Southern early-type M dwarfs in the solar neighborhood (d < 60 pc). We used the MCAL technique to derive the effective temperature T
eff, metallicity [Fe/H], and activity index i
a
(H
alpha) of 420 M stars using HARPS spectra. The effective temperature T
eff, surface gravity log g, metallicity [Fe/H], and projected rotational velocity V
rotsini of 153 M0-M6 dwarfs were determined by fitting the observed intermediate-resolution spectra from the VIS arm of VLT/X-shooter with a grid of BT-Settl stellar atmosphere models. We estimated the typical uncertainties of the fit with X-shooter spectra by varying region-to-region results by σT
eff ∼ 50 K, σlog g ∼ 0.2, and σ[Fe/H] ∼ 0.2 dex. Photometric verification of T
eff for the 295 stars from the HARPS sample and the 61 stars from the X-shooter sample is also provided. We compared our results from different methods to estimate absolute uncertainty in determining the physical properties of M dwarfs.
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