The first spectroscopically identified L dwarf in Praesepe

TL;DR

This paper reports the spectroscopic confirmation of the first L dwarf member in the Praesepe cluster, providing insights into its properties and membership status.

Contribution

It presents the first spectroscopic identification and characterization of an L dwarf in Praesepe, including spectral type, temperature, mass, and membership evidence.

Findings

Confirmed L0.3+/-0.4 spectral type

Estimated effective temperature of 2279+/-371 K

Mass near the hydrogen-burning limit

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.