Abstract
As part of our comprehensive, ongoing characterisation of the low-mass end of the main
sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Tele-
scopio Canarias to acquire low- and mid-resolution (R≈300 and R≈2500) optical spectroscopy
of 53 late-M and L ultracool dwarfs. Most of these objects are known but poorly investigated
and lacking complete kinematics. We measured spectral indices, determined spectral types
(six of which are new) and inferred effective temperature and surface gravity from BT-Settl
synthetic spectra fits for all objects. We were able to measure radial velocities via line centre
fitting and cross correlation for 46 objects, 29 of which lacked previous radial velocity mea-
surements. Using these radial velocities in combination with the latest Gaia DR3 data, we also
calculated Galactocentric space velocities. From their kinematics, we identified two candidates
outside of the thin disc and four in young stellar kinematic groups. Two further ultracool dwarfs
are apparently young field objects: 2MASSW J1246467+402715 (L4ß), which has a potential,
weak lithium absorption line, and G 196–3B (L3ß), which was already known as young due
to its well-studied primary companion.
sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Tele-
scopio Canarias to acquire low- and mid-resolution (R≈300 and R≈2500) optical spectroscopy
of 53 late-M and L ultracool dwarfs. Most of these objects are known but poorly investigated
and lacking complete kinematics. We measured spectral indices, determined spectral types
(six of which are new) and inferred effective temperature and surface gravity from BT-Settl
synthetic spectra fits for all objects. We were able to measure radial velocities via line centre
fitting and cross correlation for 46 objects, 29 of which lacked previous radial velocity mea-
surements. Using these radial velocities in combination with the latest Gaia DR3 data, we also
calculated Galactocentric space velocities. From their kinematics, we identified two candidates
outside of the thin disc and four in young stellar kinematic groups. Two further ultracool dwarfs
are apparently young field objects: 2MASSW J1246467+402715 (L4ß), which has a potential,
weak lithium absorption line, and G 196–3B (L3ß), which was already known as young due
to its well-studied primary companion.
Original language | English |
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Number of pages | 33 |
Journal | Monthly Notices of the Royal Astronomical Society |
Publication status | Accepted/In press - 5 Sept 2024 |