Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 514, Issue 2, Pages 1706-1719Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stac1441
Keywords
binaries: spectroscopic; galaxies: kinematics and dynamics
Categories
Funding
- National Science Foundation (NSF) [AST-1813881, AST-1909584]
- NSF [AST-1847909, AST-1815767, AST-1812461, AST-1909022]
- U.S. NSF [AST-1312997, AST-1726457, AST-1815403]
- VIDI grant 'Pushing Galactic Archaeology to its limits' - Dutch Research Council (NWO) [VI.Vidi.193.093]
- Cottrell Scholar award
- Max Planck Institute for Astronomy, Heidelberg
- Max Planck Institute for Extraterrestrial Physics, Garching
- Johns Hopkins University
- Durham University
- University of Edinburgh
- Queen's University Belfast
- Harvard-Smithsonian Center for Astrophysics
- Las Cumbres Observatory Global Telescope Network Incorporated
- National Central University of Taiwan
- Space Telescope Science Institute
- National Aeronautics and Space Administration through the Planetary Science Division of the NASA Science Mission Directorate [NNX08AR22G]
- National Science Foundation [AST-1238877]
- University of Maryland
- Eotvos Lorand University (ELTE)
- Los Alamos National Laboratory
- Gordon and Betty Moore Foundation
- Science & Technology Facilities Council (STFC)
- European Research Council (ERC)
- W. M. Keck Foundation
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In this study, we present new spectroscopic measurements for 257 stars observed along the line of sight to the dwarf galaxy Triangulum II (Tri II) and develop a methodology to infer the binary orbital parameters of the stars. However, the current data is still insufficient to resolve the velocity dispersion of Tri II.
We present new MMT/Hectochelle spectroscopic measurements for 257 stars observed along the line of sight to the ultrafaint dwarf galaxy Triangulum II (Tri II). Combining results from previous Keck/DEIMOS spectroscopy, we obtain a sample that includes 16 likely members of Tri II, with up to 10 independent redshift measurements per star. To this multi-epoch kinematic data set, we apply methodology that we develop in order to infer binary orbital parameters from sparsely sampled radial velocity curves with as few as two epochs. For a previously identified (spatially unresolved) binary system in Tri II, we infer an orbital solution with period 296.0(-3.3)(+3.8) d, semimajor axis 1.12(-0.24)(+0.41) au, and systemic velocity -380.0 +/- 1.7 km s(-1) that we then use in the analysis of Tri II's internal kinematics. Despite this improvement in the modelling of binary star systems, the current data remain insufficient to resolve the velocity dispersion of Tri II. We instead find a 95 per cent confidence upper limit of sv similar to 3.4 km s(-1).
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