A Physically Motivated and Empirically Calibrated Method to Measure the Effective Temperature, Metallicity, and Ti Abundance of M Dwarfs

Veyette, Mark; Muirhead, Philip S.; Mann, Andrew W.; Brewer, John M.; Homeier, D.

doi:10.3847/1538-4357/aa96aa

Cited by 52 publications

(59 citation statements)

References 95 publications

(137 reference statements)

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“…In the above analyses we assumed that the stellar models (for both the photosphere and spots) were accurate representations of a true contaminated stellar spectrum. However, model stellar spectra are not necessarily perfect in all situations (Veyette et al 2017). Here, we explore the impact of an inaccurate stellar model on our ability to remedy spot contamination.…”

Section: How Precisely Do We Need To Know the Stellar/spotmentioning

confidence: 99%

The Influence of Stellar Contamination on the Interpretation of Near-infrared Transmission Spectra of Sub-Neptune Worlds around M-dwarfs

Iyer

Line

2020

ApJ

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The impact of unocculted stellar surface heterogeneities in the form of cool spots and hot faculae on the spectrum of a transiting planet has been a daunting problem for the characterization of exoplanet atmospheres. The wavelength-dependent nature of stellar surface heterogeneities imprinting their signatures on planetary transmission spectra are of concern particularly for systems of sub-Neptunes orbiting M-dwarfs. Here we present a systematic exploration of the impact of this spot-contamination on simulated near infrared transmission spectra of sub-Neptune planets. From our analysis, we find that improper correction of stellar surface heterogeneities on transmission spectra can lead to significant bias when inferring planetary atmospheric properties. However, this bias is negligible for lower fractions of heterogeneities ( < 1%). Additionally, we find that acquiring a priori knowledge of stellar heterogeneities does not improve precision in constraining planetary parameters if the heterogeneities are appropriately marginalized within a retrieval-however these are conditional on our confidence of stellar atmospheric models being accurate representations of the true photosphere. In sum, to acquire unbiased constraints when characterizing planetary atmospheres with the James Webb Space Telescope, we recommend performing joint retrievals of both the disk-integrated spectrum of the star and the stellar contamination corrected transmission spectrum.

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Section: How Precisely Do We Need To Know the Stellar/spotmentioning

confidence: 99%

The Influence of Stellar Contamination on the Interpretation of Near-infrared Transmission Spectra of Sub-Neptune Worlds around M-dwarfs

Iyer

Line

2020

ApJ

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“…Those optical spectra include atomic (Ca i, Na i, K i), diatomic (MgH, TiO, VO, CaH) and even triatomic (CaOH) absorption features. Veyette et al (2017) also determined T eff , [Fe/H] and [Ti/Fe] for 29 M dwarfs, but using Y-band highresolution (R∼25,000) spectra and equivalent widths of several lines of Fe i, Ti i, and a FeH temperaturesensitive index.…”

Section: Introductionmentioning

confidence: 99%

Effective Temperatures of Low-mass Stars from High-resolution H-band Spectroscopy

López-Valdivia

Mace

Sokal

et al. 2019

ApJ

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High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earthlike planets around low-mass stars. Yet, the properties of exoplanets can not be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion GRating INfrared Spectrometer (IGRINS) simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine effective temperature for stars between 4000-3000 K (∼K8-M5) using absorption line depths of Fe i, OH, and Al i. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method with typical errors of about 140 K, and systematic uncertainties less than ∼120 K. For the broadest applicability, we present T eff -line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between ∼10,000-120,000. These ratios offer a simple but accurate measure of effective temperature in cool stars that is distance and reddening independent.

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“…For the combined 70 M dwarfs, we measured the equivalent widths of 10 Ti I lines originally identified by Veyette et al (2017) as tracers of Ti abundance in M dwarf stars. We used the analyze NIRSPEC1 software pipeline to measure equivalent widths, available on GitHub.…”

Section: Discussionmentioning

confidence: 99%

“…We used the analyze NIRSPEC1 software pipeline to measure equivalent widths, available on GitHub. See Veyette et al (2017) for a detailed description of the method for measuring equivalent widths, which we briefly summarize here. Spectra of M dwarf stars contain significant molecular features across all wavelengths, which result in a pseudocontinuum useful for measuring equivalent widths.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Inflation and Stellar Mass. V. Intensification and Saturation of M-dwarf Absorption Lines with Rossby Number

Muirhead

Veyette

Newton

et al. 2020

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In young sun-like stars and field M dwarf stars, chromospheric and coronal magnetic activity indicators such as Hα, X-ray and radio emission are known to saturate with low Rossby number (Ro 0.1), defined as the ratio of rotation period to convective turnover time. The mechanism for the saturation is unclear. In this paper, we use photospheric Ti I and Ca I absorption lines in Y band to investigate magnetic field strength in M dwarfs for Rossby numbers between 0.01 and 1.0. The equivalent widths of the lines are magnetically enhanced by photospheric spots, a global field or a combination of the two. The equivalent widths behave qualitatively similar to the chromospheric and coronal indicators: we see increasing equivalent widths (increasing absorption) with decreasing Ro and saturation of the equivalent widths for Ro 0.1. The majority of M dwarfs in this study are fully convective. The results add to mounting evidence that the magnetic saturation mechanism occurs at or beneath the stellar photosphere.

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A Physically Motivated and Empirically Calibrated Method to Measure the Effective Temperature, Metallicity, and Ti Abundance of M Dwarfs

Cited by 52 publications

References 95 publications

The Influence of Stellar Contamination on the Interpretation of Near-infrared Transmission Spectra of Sub-Neptune Worlds around M-dwarfs

The Influence of Stellar Contamination on the Interpretation of Near-infrared Transmission Spectra of Sub-Neptune Worlds around M-dwarfs

Effective Temperatures of Low-mass Stars from High-resolution H-band Spectroscopy

Magnetic Inflation and Stellar Mass. V. Intensification and Saturation of M-dwarf Absorption Lines with Rossby Number

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