The first spectroscopically identified L dwarf in Praesepe

Abstract

We have obtained a low-resolution optical spectrum for one of the faintest cluster member candidates in Praesepe with the Optical System for Imaging and low Resolution Integrated Spectroscopy mounted on the 10.4m Gran Telescopio de Canarias. We confirm spectroscopically the first L dwarf member in Praesepe, UGCS J084510.66+214817.1. We derived an optical spectral type of L0.3+/-0.4 and estimated its effective temperature to Teff=2279+/-371 K and a mass of 71.1+/-23.0M_Jup, according to state-of-the-art models, placing it at the hydrogen-burning boundary. We measured the equivalent width of the gravity-sensitive sodium doublet at 8182/8194 A, which adds credit to the membership of this new L dwarf to Praesepe. We also derived a probability of ~20.5% that our candidate would be a field L0 dwarf. We conclude that this object is likely to be a true member of Praesepe, with evidence of being a binary system.

6 pages, 3 figures, accepted for publication in MNRAS

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• A 5D view of the Alpha Per, Pleiades, and Praesepe clusters
• Spectroscopy of Hyades L dwarf candidates
• Probing the Upper Scorpius mass function in the planetary-mass regime
• Characterization of the Praesepe Star Cluster by Photometry and Proper Motions with 2MASS, PPMXL, and Pan-STARRS
• Spectral library of age-benchmark low-mass stars and brown dwarfs
• Hunting for Brown Dwarfs in the Globular Cluster M4: 2nd epoch HST NIR observations
• Deep near-IR observations of the Globular Cluster M4: Hunting for Brown Dwarfs
• Two close binaries across the hydrogen-burning limit in the Praesepe open cluster