CHARACTERIZATION OF THE BENCHMARK BINARY NLTT 33370^,

Abstract

We confirm the binary nature of the nearby, very low mass (VLM) system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show significant orbital motion between 2013 February and 2013 April. Optical spectra reveal weak, gravity-sensitive alkali lines and strong lithium 6708 Å absorption that indicate the system is younger than field age. VLT-SINFONI near-IR spectra also show weak, gravity-sensitive features and spectral morphology that is consistent with other young VLM dwarfs. We combine the constraints from all age diagnostics to estimate a system age of ∼30-200 Myr. The 1.2-4.7 μm spectral energy distribution of the components point toward T eff = 3200 ± 500 K and T eff = 3100 ± 500 K for NLTT 33370 A and B, respectively. The observed spectra, derived temperatures, and estimated age combine to constrain the component spectral types to the range M6-M8. Evolutionary models predict masses of 97 +41 −48 M Jup and 91 +41 −44 M Jup from the estimated luminosities of the components. KPNO-Phoenix spectra allow us to estimate the systemic radial velocity of the binary. The Galactic kinematics of NLTT 33370AB are broadly consistent with other young stars in the solar neighborhood. However, definitive membership in a young, kinematic group cannot be assigned at this time and further follow-up observations are necessary to fully constrain the system's kinematics. The proximity, age, and late-spectral type of this binary make it very novel and an ideal target for rapid, complete orbit determination. The system is one of only a few model calibration benchmarks at young ages and VLMs.

High-Precision Radio and Infrared Astrometry of LSPM J1314+1320ab. Ii. Testing Pre-Main-Sequence Models at the Lithium Depletion Boundary With Dynamical Masses

“…Of the four features used in the alkali score, the K I line at 1.169 μm was consistently indicative of low gravity. Figure 6 shows all four alkali lines, and in fact all of them appear visually weaker than the field gravity M6 standard, consistent with the findings of Schlieder et al (2014) from an independent spectrum. The other three are simply not weak enough to qualify as low gravity on the Allers & Liu (2013a) system.…”

“…The detection of lithium by Schlieder et al (2014) in the combined light spectrum of these ≈0.09 M ☉ objects further supports the pre-main-sequence nature of this binary, as models predict lithium will be destroyed in objects of this mass hundreds of megayears before they reach the main sequence.…”

“…The first definitive evidence for the youth of LSPMJ1314 +1320AB came from the analysis by Schlieder et al (2014) of its published optical spectra and Schlieder et al's own nearinfrared (NIR) spectrum, all spatially unresolved. These spectra display weak alkali lines, which are indicative of low surface gravity, and strong Li I absorption.…”

“…These spectra display weak alkali lines, which are indicative of low surface gravity, and strong Li I absorption. Although Schlieder et al (2012) had previously identified LSPMJ1314+1320AB as a likely new member of the AB Doradus moving group (∼150 Myr), subsequent analysis and updated proper motion data has led to the conclusion that it cannot be confidently associated with any known group (Gagné et al 2014;Schlieder et al 2014). McLean et al (2011) has also identified LSPMJ1314+1320AB as a source of bright (∼1 mJy), persistent radio emission with a flat spectrum across a wide range of frequencies (1.43-22.5 GHz), suggesting high levels of magnetic activity and a stable, large-scale magnetosphere (Williams et al 2014(Williams et al , 2015.…”

Characterization of close visual binaries from the AstraLux Large M Dwarf Survey

“…Detailed studies of orbital elements of individual low mass binaries, and dynamical masses, are needed for empirical calibration of models for low-mass stars, and significant effort has therefore been made in recent years to better characterise in particular ultracool dwarfs (e.g. Bouy et al 2008;Bonnefoy et al 2009;Konopacky et al 2010;Dupuy et al 2010;Schlieder et al 2014;Zhou et al 2014). In addition, the recent discoveries and dedicated surveys for M dwarf planets require accurate stellar physical properties in order to derive reliable planetary parameters, furthering the interest for characterising M dwarfs (e.g., Johnson et al 2012;Mann et al 2012Mann, Gaidos & Ansdell 2013;Muirhead et al 2012Muirhead et al , 2014Dressing & Charbonneau 2013;Newton et al 2014Newton et al , 2015Gaidos et al 2014;Alonso-Floriano et al 2015;Bowler et al 2015).…”