Brown Dwarfs

Near-infrared Spectroscopic Characterisation Of Gaia Ultra-cool Dwarf Candidates; Spectral Types And Peculiarities

By Keith Cowing
Status Report
February 16, 2024
Filed under , , , , , ,
Near-infrared Spectroscopic Characterisation Of Gaia Ultra-cool Dwarf Candidates; Spectral Types And Peculiarities
Observed UCD candidates on a zoomed Gaia MG – G − J and G − GRP diagrams: UCDs are coloured by their obtained spectral type, as explained in Sect. 3. The two circled UCDs have peculiar colours (see text). Subdwarfs candidates are represented by crosses (see Sect. 4.1). Peculiar objects are represented by triangles (Sect. 4.2). The UCDs with common parallaxes and proper motions with another system are represented by diamonds (see Sect. 4.3) and those in (potentially) unresolved binary systems by squares (Sect. 4.4). The grey points are the sources from the Gaia Catalogue of Nearby Stars, with a RUWE < 1.4. The insets illustrate the locus of our sample on entire GaiaCatalogue of Nearby stars colour-absolute magnitude diagrams. -- astro-ph.SR

Context: The local census of very low-mass stars and brown dwarfs is crucial to improving our understanding of the stellar-substellar transition and their formation history. These objects, known as ultra-cool dwarfs (UCDs), are essential targets for searches of potentially habitable planets. However, their detection poses a challenge because of their low luminosity. The Gaia survey has identified numerous new UCD candidates thanks to its large survey and precise astrometry.

Aims: We aim to characterise 60 UCD candidates detected by Gaia in the solar neighbourhood with a spectroscopic follow-up to confirm that they are UCDs, as well as to identify peculiarities.
Methods: We acquired the near-infrared (NIR) spectra of 60 objects using the SOFI spectrograph between 0.93 and 2.5 microns (R∼600). We identified their spectral types using a template-matching method. Their binarity is studied using astrometry and spectral features.

Results: We confirm that 60 objects in the sample have ultra-cool dwarf spectral types close to those expected from astrometry. Their NIR spectra reveal that seven objects could host an unresolved coolest companion and seven UCDs share the same proper motions as other stars. The characterisation of these UCDs is part of a coordinated effort to improve our understanding of the Solar neighbourhood.

T. Ravinet, C. Reylé, N. Lagarde, A. Burgasser, R. L. Smart, W. H. Moya, F. Marocco, R.-D. Scholz, W. J. Cooper, K. L. Cruz, J. G. Fernández-Trincado, D. Homeier, L. M. Sarro

Comments: Based on observations made with the ESO New Technology Telescope at the La Silla Observatory under programme 106.214E.001 and 108.22G4.001. Accepted by A&A on the 30/01/2024
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2402.09783 [astro-ph.SR] (or arXiv:2402.09783v1 [astro-ph.SR] for this version)
Submission history
From: Thomas Ravinet
[v1] Thu, 15 Feb 2024 08:31:13 UTC (3,001 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻