Detection of Methane in the Closest Extreme Metal-poor T Dwarf WISEA J181006.18−101000.5*

Abstract WISEA J181006.18−101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as an extreme early-T subdwarf. However, methane, the characteristic molecule of the spectral class T, was not seen in the previous low-resolution spectrum. Using the 10.4 m Gran Telescopio Canarias, we collected a high-quality JHK -band intermediate-resolution R ≈ 5000 spectrum of WISE1810, in which 17 ± 6 ppm of methane is clearly detected, while carbon monoxide is absent. Based on a custom computed ATMO2020++ model, we estimated an effective temperature of 1000 ± 100 K, a high surface gravity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> <mml:mo>=</mml:mo> <mml:mn>5.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> </mml:math> dex, and a carbon abundance of [C/H] = −1.5 ± 0.2 dex, inferring [Fe/H] = −1.7 ± 0.2 dex. Potassium is not seen in our data, and the upper limits of the pseudoequivalent width of the J -band atomic lines are at least 25–60 times weaker than those measured from solar-metallicity early-T counterparts. We measured a heliocentric radial velocity of −83 ± 13 km s −1 , inferring that WISE1810 is more likely a thick-disk member.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-04-29
DOI
https://doi.org/10.3847/2041-8213/adc91f
Citations
2
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.31

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article

Detection of Methane in the Closest Extreme Metal-poor T Dwarf WISEA J181006.18−101000.5*

M. R. Zapatero Osorio, Pascal Tremblin, V. J. S. Béjar, Ya. V. Pavlenko et al.
2 citations
The Astrophysical Journal Letters
Stellar, planetary, and galactic studies
2.31
article

Detection of Methane in the Closest Extreme Metal-poor T Dwarf WISEA J181006.18−101000.5*

M. R. Zapatero Osorio, Pascal Tremblin, V. J. S. Béjar, Ya. V. Pavlenko, B. Gauza, J.-Y. Zhang, R. Rébolo, N. Vitas, N. Lodieu, E. L. Martı́n
article en
2 citations

Abstract

Abstract WISEA J181006.18−101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as an extreme early-T subdwarf. However, methane, the characteristic molecule of the spectral class T, was not seen in the previous low-resolution spectrum. Using the 10.4 m Gran Telescopio Canarias, we collected a high-quality JHK -band intermediate-resolution R ≈ 5000 spectrum of WISE1810, in which 17 ± 6 ppm of methane is clearly detected, while carbon monoxide is absent. Based on a custom computed ATMO2020++ model, we estimated an effective temperature of 1000 ± 100 K, a high surface gravity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> <mml:mo>=</mml:mo> <mml:mn>5.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> </mml:math> dex, and a carbon abundance of [C/H] = −1.5 ± 0.2 dex, inferring [Fe/H] = −1.7 ± 0.2 dex. Potassium is not seen in our data, and the upper limits of the pseudoequivalent width of the J -band atomic lines are at least 25–60 times weaker than those measured from solar-metallicity early-T counterparts. We measured a heliocentric radial velocity of −83 ± 13 km s −1 , inferring that WISE1810 is more likely a thick-disk member.

The Astrophysical Journal LettersVol. 984(1)
Centre National de la Recherche Scientifique (FR), Universidad de La Laguna (ES), Université de Versailles Saint-Quentin-en-Yvelines (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Maison de la Simulation (FR), CEA Paris-Saclay (FR), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), Main Astronomical Observatory (UA), University of Zielona Góra (PL)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Ministerio de Ciencia, Innovación y Universidades, European Commission, Agencia Canaria de Investigación, Innovación y Sociedad de la Información, Agencia Estatal de Investigación
Openalex Percentile: Top 12%
Stellar, planetary, and galactic studies
2.31
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