THE SOLAR NEIGHBORHOOD. XXXII. THE HYDROGEN BURNING LIMIT^,

Abstract

We construct a Hertzsprung-Russell diagram for the stellar/substellar boundary based on a sample of 63 objects ranging in spectral type from M6V to L4. We report newly observed VRI photometry for all 63 objects and new trigonometric parallaxes for 37 objects. The remaining 26 objects have trigonometric parallaxes from the literature. We combine our optical photometry and trigonometric parallaxes with 2MASS and WISE photometry and employ a novel SED fitting algorithm to determine effective temperatures, bolometric luminosities, and radii. Our uncertainties range from ∼20K to ∼150K in temperature, ∼0.01 to ∼0.06 in log(L/L ⊙ ) and ∼3% to ∼10% in radius. We check our methodology by comparing our calculated radii to radii directly measured via long baseline optical interferometry. We find evidence for the local minimum in the radius−temperature and radius−luminosity trends that signals the end of the stellar main sequence and the start of the brown dwarf sequence at T ef f ∼ 2075K, log(L/L ⊙ ) ∼ −3.9, and (R/R ⊙ ) ∼ 0.086. The existence of this local minimum is predicted by evolutionary models, but at temperatures ∼400K cooler. The minimum radius happens near the locus of 2MASS J0523-1403, an L2.5 dwarf with V −K = 9.42. We make qualitative arguments as to why the effects of the recent revision in solar abundances accounts for the discrepancy between our findings and the evolutionary models. We also report new color-absolute magnitude relations for optical and -2infrared colors useful for estimating photometric distances. We study the optical variability of all 63 targets and find an overall variability fraction of 36 +9 −7 % at a threshold of 15 milli-magnitudes in the I band, in agreement with previous studies.

A Catalog of Galex Ultraviolet Emission From Spectroscopically Confirmed M Dwarfs*

“…This relation was created by fitting to the 8 pc stellar sample of Reid & Gizis (1997). Although most of the stars in this sample are inactive, and active stars may have higher bolometric luminosities, our derived values are ∼35% lower than those found for the inactive early-type dwarfs in Mann et al (2013) and agree well with the values of Dieterich et al (2014) for late-type dwarfs. We next calculated the Hα luminosity of the DR7 and PMSU samples following West et al (2011), which integrates over a line region of width 8 Å, and subtracts the nearby continuum (see Table 1 and Section 2.2 in West et al 2011).…”

Neighbours hiding in the Galactic plane, a new M/L dwarf candidate for the 8 pc sample

“…The new trigonometric parallax measured for LP 944-20 by Dieterich et al (2014) leads to d photom,1 = 6.3 ± 1.5 pc for WISE J0720−0846, which is in better agreement with d photom,2 and d trig and yields d adopted ≈ 6−8 pc.…”

CARMENES input catalogue of M dwarfs

“…(a) Some other publications and meta-archives that we have searched for potential CARMENES targets are Kirkpatrick et al (1991), Gizis (1997), Gizis & Reid (1997), Gizis et al (2000b), Henry et al (2002Henry et al ( , 2006, Mochnacki et al (2002), Gray et al (2003), Bochanski et al (2005), Crifo et al (2005), Lodieu et al (2005), Scholz et al (2005), Phan-Bao & Bessell (2006), Reylé et al (2006), Riaz et al (2006), Caballero (2007Caballero ( , 2009Caballero ( , 2012, Gatewood & Coban (2009), Shkolnik et al (2009, 2012, Bergfors et al (2010), Johnson et al (2010), Boyd et al (2011), Irwin et al (2011), West et al (2011, Avenhaus et al (2012), Deacon et al (2012), Janson et al (2012, 2014), Frith et al (2013, Jódar et al (2013), Malo et al (2013), Aberasturi et al (2014), Dieterich et al (2014), Riedel et al (2014), Yi et al (2014), , and the DwarfArchive at http://dwarfarchive.org. (b) PMSU: Reid et al (1995Reid et al ( , 2002; Hawley et al (1996); Gizis et al (2002).…”