Dynamical Masses of ε Indi B and C: Two Massive Brown Dwarfs at the Edge of the Stellar–substellar Boundary

Dieterich, Sergio; Weinberger, Alycia J.; Boss, Alan P.; Henry, Todd J.; Jao, Wei-Chun; Gagné, Jonathan; Astraatmadja, T.; Thompson, Maggie; Anglada-Escudé, G.

doi:10.3847/1538-4357/aadadc

Cited by 61 publications

(78 citation statements)

References 50 publications

(86 reference statements)

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“…However, for Indi Bb we now obtain a much lower value of 4.85 +0.17 −0.19 , which is still roughly consistent with the lower end of previously published values (see Table 2). Compared to the equilibrium chemistry retrieval, the inferred mass of Indi Bb is now much lower (≈ 15M J ) but also deviates strongly from the dynamical mass of ≈ 70M J predicted by Dieterich et al (2018).…”

Section: Free Chemistry Retrievalcontrasting

confidence: 64%

Helios-r2: A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres

Kitzmann

Heng

Oreshenko

et al. 2020

ApJ

123

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We present an improved, hybrid CPU-GPU atmospheric retrieval code, Helios-r.2, which is applicable to medium-resolution emission spectra of brown dwarfs, in preparation for precision atmospheric spectroscopy in the era of the James Webb Space Telescope. The model is available as open source code on the Exoclimes Simulation Platform. We subject Helios-r.2 to a battery of tests of varying difficulty. The simplest test involves a mock retrieval on a forward model generated using the same radiative transfer technique, the same implementation of opacities, and the same chemistry model. The least trivial test involves a mock retrieval on synthetic spectra from the Sonora model grid, which uses a different radiative transfer technique, a different implementation of opacities, and a different chemistry model. A calibration factor, which is included to capture uncertainties in the brown dwarf radius, distance to the brown dwarf and flux calibration of the spectrum, may compensate, sometimes erroneously, for discrepancies in modeling choices and implementation. We analyze spectra of the benchmark brown dwarf GJ 570 D and the binary brown dwarf companions in the Epsilon Indi system. The retrieved surface gravities are consistent with previous studies and/or values inferred from dynamical masses (for Epsilon Indi Ba and Bb only). There remains no clear criterion on how to reject unphysical values of the retrieved brown dwarf radii. The retrieved carbon-to-oxygen ratios and metallicity depend on whether chemical equilibrium is assumed.

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Section: Free Chemistry Retrievalcontrasting

confidence: 64%

Helios-r2: A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres

Kitzmann

Heng

Oreshenko

et al. 2020

ApJ

123

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“…This measurement joins a growing list of massive T dwarfs that are challenging evolutionary models (e.g. Bowler et al (2018); Dieterich et al (2018); Dupuy et al (2019)). We note, however, that the dynamical mass measurement of Gl 229 B should be considered with caution until confirmed unambiguously (the paper is only on ArXiv for now) (R. Oppenheimer priv.…”

Section: Comparison With Dynamical Massesmentioning

confidence: 75%

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

Phillips

Tremblin

Baraffe

et al. 2020

A&A

193

262

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We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D radiative-convective equilibrium code ATMO, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001 − 0.075 M objects. Our models include several key improvements to the input physics used in previous models available in the literature. Most notably, the use of a new H-He equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ∼ 1 − 2% at the stellar-substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. A second key improvement concerns updated molecular opacities in our atmosphere model ATMO, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. This leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. We present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. We generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. We show the impact of vertical mixing on emission spectra and in colourmagnitude diagrams, highlighting how the 3.5 − 5.5 µm flux window can be used to calibrate vertical mixing in cool T-Y spectral type objects.

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“…All three brown dwarfs have been subjects of previous characterization studies. For the Indi objects, dynamic masses have been reported by Dieterich et al (2018). A SpeX spectrum of GJ 570D has previously been analyzed by Line et al (2015) using a classical MCMC approach.…”

Section: Atmospheric Retrieval Of Measured Brown Dwarf Spectramentioning

confidence: 99%

“…Based on the measured dynamical masses (Dieterich et al 2018) and assuming R = (1±0.1)R J , the values for log(g) are: 5.269 ± 1.055 for Indi Ba and 5.240 ± 1.049 for Indi Bb. Since there is (approximate) "ground truth" for the surface gravities, we explicitly perform pairs of retrievals that include or exclude the calibration factor in order to investigate its effects.…”

Section: The Triple Star System Indimentioning

confidence: 99%

Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System

Oreshenko

Kitzmann

Márquez-Neila

et al. 2019

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Self-consistent model grids of brown dwarfs involve complex physics and chemistry, and are often computed using proprietary computer codes, making it challenging to identify the reasons for discrepancies between model and data as well as between the models produced by different research groups. In the current study, we demonstrate a novel method for analyzing brown dwarf spectra, which combines the use of the Sonora, AMES-cond and HELIOS model grids with the supervised machine learning method of the random forest. Besides performing atmospheric retrieval, the random forest enables information content analysis of the three model grids as a natural outcome of the method, both individually on each grid and by comparing the grids against one another, via computing large suites of mock retrievals. Our analysis reveals that the different choices made in modeling the alkali line shapes hinder the use of the alkali lines as gravity indicators. Nevertheless, the spectrum longward of 1.2 µm encodes enough information on the surface gravity to allow its inference from retrieval. Temperature may be accurately and precisely inferred independent of the choice of model grid, but not the surface gravity. We apply random forest retrieval to three objects: the benchmark T7.5 brown dwarf GJ 570D; and Indi Ba (T1.5 brown dwarf) and Bb (T6 brown dwarf), which are part of a binary system and have measured dynamical masses. For GJ 570D, the inferred effective temperature and surface gravity are consistent with previous studies. For Indi Ba and Bb, the inferred surface gravities are broadly consistent with the values informed by the dynamical masses.

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Dynamical Masses of ε Indi B and C: Two Massive Brown Dwarfs at the Edge of the Stellar–substellar Boundary

Cited by 61 publications

References 50 publications

Helios-r2: A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres

Helios-r2: A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System

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