Resonance potassium and sodium lines in the spectra of ultracool dwarfs

Pavlenko, Ya. V.; Zhukovskaya, S. V.; Volobuev, M.

doi:10.1134/s106377290704004x

Cited by 10 publications

(10 citation statements)

References 19 publications

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“…atoms He and molecules H 2 computed by gamess (Granovsky et al 1999). Our procedure is described in more detail in Pavlenko, Zhukovska & Volobuyev (2007). Here we point out that in computations of K i profiles we used a combined profile: cores of these lines were computed in the frame of the collisional approach, and their wings (δλ > 40 Å) were treated by quasi‐stationary theory.…”

Section: Standard Spectral Modellingmentioning

confidence: 99%

Lithium in LP 944−20★

Pavlenko

Jones

Martín

et al. 2007

Monthly Notices of the Royal Astronomical Society

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We present a new estimate of the lithium abundance in the atmosphere of the brown dwarf LP 944−20. Our analysis is based on a self‐consistent analysis of low‐, intermediate‐ and high‐resolution optical and near‐infrared spectra. We obtain log N(Li) = 3.25 ± 0.25 using fits of our synthetic spectra to the Li i resonance line doublet profiles observed with Very Large Telescope/Ultraviolet–Visual Echelle Spectrograph (VLT/UVES) and Anglo‐Australian Telescope/Segmented Pupil/Image Reformatting Array of Lenslets (AAT/SPIRAL). This lithium abundance is over two orders of magnitude larger than previous estimates in the literature. In order to obtain good fits of the resonance lines of K i and Rb i and better fits to the TiO molecular absorption around the Li i resonance line, we invoke a semi‐empirical model atmosphere with the dusty clouds located above the photosphere. The lithium abundance, however, is not changed by the effects of the dusty clouds. We discuss the implications of our estimate of the lithium abundance in LP 944−20 for the understanding of the properties of this benchmark brown dwarf.

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Section: Standard Spectral Modellingmentioning

confidence: 99%

Lithium in LP 944−20★

Pavlenko

Jones

Martín

et al. 2007

Monthly Notices of the Royal Astronomical Society

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“…Then, we computed partial pressures of some molecules and atoms that exceeded the pressures of the gas-dust phase transitions and decreased their gas phase abundances to the corresponding equilibrium values (see Pavlenko 1998). We computed the profiles of the NaI and KI resonance doublets in the framework of a quasi-static approach described in Pavlenko et al (2007b) with an upgraded approach from Burrows et al (2003). We computed the CrH and FeH line lists from the work of Burrows et al (2002b) and Dulick et al (2003), respectively, while the water vapour line list was taken from Tennyson et al (2007).…”

Section: Comparison With Theoretical Modelsmentioning

confidence: 99%

VLT X-Shooter spectroscopy of the nearest brown dwarf binary

Lodieu

Osorio

Rebolo

et al. 2015

A&A

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Aims. The aim of the project is to characterise the two components of the brown dwarf system nearest to the Sun, WISE J104915.57−531906.1 (also called Luhman 16AB) at optical and near-infrared wavelengths. Methods. We obtained high signal-to-noise intermediate-resolution (R ∼ 6000−11 000) optical (600−1000 nm) and near-infrared (1000−2480 nm) spectra of each component of Luhman 16AB with the X-Shooter instrument on the Very Large Telescope. Results. We classify the primary and secondary of the Luhman 16 system as L6−L7.5 and T0 ± 1, respectively, in agreement with previous measurements published in the literature. We present measurements of the lithium pseudo-equivalent widths, which appear of similar strength in both components (8.2 ± 1.0 Å for the L and 8.4 ± 1.5 Å for the T component). The presence of lithium ( 7 Li) in both components implies masses lower than 0.06 M , while the comparison with models suggests lower limits of 0.04 M . The detection of lithium in the T component is the first of its kind. Similarly, we assess the strength of other alkali lines (e.g. pseudoequivalent widths of 6−7 Å for RbI and 4−7 Å for CsI) present in the optical and near-infrared regions and compare with estimates for L and T dwarfs. We also derive effective temperatures and luminosities of each component of the binary: −4.66 ± 0.08 dex and 1305K for the L dwarf and −4.68 ± 0.13 dex and 1320K for the T dwarf. According to our radial velocity determinations, the binary does not appear to belong to any of the well-known moving group. Our preliminary theoretical analysis of the optical and J-band spectra indicates that the L-and T-type spectra can be reproduced with a single temperature and gravity but different relative chemical abundances, which strongly affects the spectral energy distribution of L/T transition objects.

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“…The spectroscopic data for atomic absorption VALD3 come from the Vienna Atomic Line Database Kupka et al (1999) 7 . The profiles of the NaI and KI resonance doublets were computed here in the framework of a quasi-static approach described in Pavlenko et al (2007) with an upgraded approach from Burrows & Volobuyev (2003). More Table 2.…”

Section: G 224-58 B Spectrum Analysismentioning

confidence: 99%

Probing M subdwarf metallicity with an esdK5+esdM5.5 binary

Pavlenko

Zhang

Gálvez-Ortiz

et al. 2015

A&A

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Context. We present a spectral analysis of the binary G 224-58 AB, which consists of the coolest M extreme subdwarf (esdM5.5) and a brighter primary (esdK5). This binary may serve as a benchmark for metallicity measurement calibrations and as a test bed for atmospheric and evolutionary models for esdM objects. Aims. We perform the analysis of optical and infrared spectra of both components to determine their parameters. Methods. We determine abundances primarily using high-resolution optical spectra of the primary. Other parameters were determined from the fits of synthetic spectra computed with these abundances to the observed spectra from 0.4 to 2.5 microns for both components. Results. We determine T eff = 4625 ± 100 K, log g = 4.5 ± 0.5 for the A component and T eff = 3200 ± 100 K, log g = 5.0 ± 0. We find consistent abundances with fits to the secondary albeit at lower signal to noise. Conclusions. Abundances of different elements in G 224-58 A and G 224-58 B atmospheres cannot be described by one metallicity parameter. The offset of ∼0.4 dex between the abundances derived from alpha element and iron group elements corresponds with our expectation for metal-deficient stars. We thus clarify that some indices used to date to measure metallicities for establishing esdM stars, based on CaH, MgH, and TiO band system strength ratios in the optical and H 2 O in the infrared, relate to abundances of alpha-element group rather than to iron peak elements. For metal deficient M dwarfs with [Fe/H] < −1.0, this provides a ready explanation for apparently inconsistent metallicities derived with different methods.

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Resonance potassium and sodium lines in the spectra of ultracool dwarfs

Cited by 10 publications

References 19 publications

Lithium in LP 944−20★

Lithium in LP 944−20★

VLT X-Shooter spectroscopy of the nearest brown dwarf binary

Probing M subdwarf metallicity with an esdK5+esdM5.5 binary

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