Carbon Monoxide in low-mass dwarf stars

Abstract

We compare high resolution infrared observations of the CO 3-1 bands in the 2.297-2.310 micron region of M dwarfs and one L dwarf with theoretical expectations. We find a good match between the observational and synthetic spectra throughout the 2000-3500K temperature regime investigated. Nonetheless, for the 2500-3500 K temperature range the temperatures that we derive from synthetic spectral fits are higher than expected from more empirical methods by several hundred K. In order to reconcile our findings with the empirical temperature scale it is necessary to invoke warming of the model atmosphere used to construct the synthetic spectra. We consider that the most likely reason for the back-warming is missing high temperature opacity due to water vapour. We compare the water vapour opacity of the Partridge & Schwenke (1997) line list used for the model atmosphere with the output from a preliminary calculation by Barber & Tennyson (2004). While the Partridge & Schwenke line list is a reasonable spectroscopic match for the new line list at 2000 K, by 4000 K it is missing around 25% of the water vapour opacity. We thus consider that the offset between empirical and synthetic temperature scales is explained by the lack of hot water vapour used for computation of the synthetic spectra. For our coolest objects with temperatures below 2500 K we find best fits when using synthetic spectra which include dust emission. Our spectra also allow us to constrain the rotational velocities of our sources, and these velocities are consistent with the broad trend of rotational velocities increasing from M to L.

Accepted for publication in MNRAS (9 pages, 33 figures)

References in corpus (25)

• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• L' and M' Photometry of Ultracool Dwarfs
• Towards Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis
• Rotation and Activity in Mid-M to L Dwarfs
• Preliminary Parallaxes of 40 L and T Dwarfs from the U.S. Naval Observatory Infrared Astrometry Program
• The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared Spectra
• Brown Dwarfs and the TW Hya Association
• First radius measurements of very low mass stars with the VLTI
• TiO and H${}_2$O absorption lines in cool stellar atmospheres
• Near-Infrared Spectral Classification of late-M and L Dwarfs
• Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral Features
• Dust in the Photospheric Environment: Unified Cloudy Models of M, L, and T Dwarfs
• Infrared Colors at the Stellar/Substellar Boundary
• The orbit of the brown dwarf binary Gl 569B
• Spectroscopic rotation velocities of L dwarfs from VLT/UVES and their comparison with periods from photometric monitoring
• FeH Absorption in the Near-Infrared Spectra of Late M and L Dwarfs
• A probable planetary companion to HD 39091 from the Anglo-Australian Planet Search
• Dust in the Photospheric Environment II. Effect on the Near Infrared Spectra of L and T Dwarfs
• Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra
• The field brown dwarf LP 944-20 and the Castor moving group
• CO bands in V4334 Sgr (Sakurai's Object): the 12C/13C ratio
• Carbon Monoxide bands in M dwarfs
• Atomic lines in infrared spectra for ultracool dwarfs

Cited by in corpus (33)

• A high accuracy computed water line list
• Biosignatures from Earth-Like Planets Around M Dwarfs
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• Rotational quenching of CO due to H${}_2$ collisions
• Metallicity and Temperature Indicators in M dwarf K band Spectra: Testing New & Updated Calibrations With Observations of 133 Solar Neighborhood M dwarfs
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• A global cloud map of the nearest known brown dwarf
• M dwarfs: effective temperatures, radii and metallicities
• Rotation Velocities for M-dwarfs
• Spectroscopic rotational velocities of brown dwarfs
• Doppler Imaging of Exoplanets and Brown Dwarfs
• Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition
• A Survey for H-alpha Emission from Late L dwarfs and T dwarfs
• The ExoMol Atlas of Molecular Opacities
• Periodic Optical Variability of Radio Detected Ultracool Dwarfs
• Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. IV. The Active, Young Binary NLTT 33370 AB (=2MASS J13142039+1320011)
• A 3D Search for Companions to 12 Nearby M-Dwarfs
• Metallicity determination of M dwarfs - High-resolution IR spectroscopy
• The red dwarf pair GJ65AB: inflated, spinning twins of Proxima
• Physical parameters of T dwarfs derived from high-resolution near-infrared spectra
• A high-resolution line list for AlO
• Spectral energy distribution for GJ406
• Dynamical Mass of the M8+M8 Binary 2MASS J22062280-2047058AB
• Experimental Ti I oscillator strengths and their application to cool star analysis
• Lithium in LP 944-20
• Discovery of a widely separated UCD-WD binary
• Spectral analysis of high resolution near-infrared spectra of ultra cool dwarfs
• Photometric Calibrations of M-dwarf Metallicity with Markov Chain Monte Carlo and Bayesian Inference
• Dynamical Measurements of the Young Upper Scorpius Triple NTTS 155808-2219
• Astrophysics in 2005
• Vsini-s for late-type stars from spectral synthesis in K-band region
• A potential new method for determining the temperature of cool stars