M-dwarf metallicities. A high-resolution spectroscopic study in the near infrared

Önehag, Anna; Heiter, U.; Gustafsson, B.; Piskunov, Nikolai; Plez, B.; Reiners, A.

doi:10.1051/0004-6361/201118101

Cited by 80 publications

(50 citation statements)

References 87 publications

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“…However, the densely lined and essentially continuum-less optical spectra of M dwarfs are notoriously difficult to analyze, and they are fainter at optical wavelengths than in the IR. Thus, IR spectroscopy has become the state-of-the-art tool for measuring the dynamics and chemistry of these stellar tracers (e.g., Önehag et al 2012;Schmidt et al 2016;Souto et al 2017).…”

Section: Dwarfsmentioning

confidence: 99%

Target Selection for the SDSS-IV APOGEE-2 Survey

et al. 2017

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APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing ∼3×10 5 stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding on APOGEE's goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch and red clump stars, RR Lyrae, lowmass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.

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Section: Dwarfsmentioning

confidence: 99%

Target Selection for the SDSS-IV APOGEE-2 Survey

et al. 2017

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“…Owing to the difficulty in deriving precise values for the effective temperature and metallicity based on spectral fitting procedures (e.g. Valenti et al 1998;Woolf & Wallerstein 2005;Bean et al 2006;Önehag et al 2012), most determinations of their values are based on calibrations using colors (Bonfils et al 2005a;Johnson & Apps 2009;Casagrande et al 2008;Schlaufman & Laughlin 2010;Neves et al 2012) or spectroscopic indices (e.g. Terrien et al 2012;Rojas-Ayala et al 2012;Mann et al 2013;Neves et al 2013).…”

Section: M-dwarfs Starsmentioning

confidence: 99%

SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs

Santos

Sousa

Mortier

et al. 2013

A&A

293

255

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Context. Thanks to the importance that the star-planet relation has to our understanding of the planet formation process, the precise determination of stellar parameters for the ever increasing number of discovered extra-solar planets is of great relevance. Furthermore, precise stellar parameters are needed to fully characterize the planet properties. It is thus important to continue the efforts to determine, in the most uniform way possible, the parameters for stars with planets as new discoveries are announced. Aims. In this paper we present new precise atmospheric parameters for a sample of 48 stars with planets. We then take the opportunity to present a new catalogue of stellar parameters for FGK and M stars with planets detected by radial velocity, transit, and astrometry programs. Methods. Stellar atmospheric parameters and masses for the 48 stars were derived assuming local thermodynamic equilibrium (LTE) and using high-resolution and high signal-to-noise spectra. The methodology used is based on the measurement of equivalent widths for a list of iron lines and making use of iron ionization and excitation equilibrium principles. For the catalogue, and whenever possible, we used parameters derived in previous works published by our team, using well-defined methodologies for the derivation of stellar atmospheric parameters. This set of parameters amounts to over 65% of all planet host stars known, including more than 90% of all stars with planets discovered through radial velocity surveys. For the remaining targets, stellar parameters were collected from the literature. Results. The stellar parameters for the 48 stars are presented and compared with previously determined literature values. For the catalogue, we compile values for the effective temperature, surface gravity, metallicity, and stellar mass for almost all the planet host stars listed in the Extrasolar Planets Encyclopaedia. This data will be updated on a continuous basis. The compiled catalogue is available online. The data can be used for statistical studies of the star-planet correlation, as well as for the derivation of consistent properties for known planets.

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“…Large samples of M dwarfs have been characterised by means of near-infrared indices in the recent works by Newton et al (2014) and Gaidos et al (2014). On the other hand, spectral synthesis has been tested in several works, usually on small numbers of stars and mainly focusing on strong atomic lines or on spectral windows known to be less affected by molecular lines (Woolf & Wallerstein 2005;Bean et al 2006;Maness et al 2007;Önehag et al 2012;Rajpurohit et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

Maldonado

Affer

Micela

et al. 2015

A&A

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Context. Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. As a consequence, Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are providing huge quantities of optical spectra of M dwarfs. However, determining the stellar parameters of M dwarfs using optical spectra has proven to be challenging. Aims. We aim to calibrate empirical relationships to determine accurate stellar parameters for early-M dwarfs (spectral types M0-M4.5) using the same spectra as those that are used for radial velocity determinations, without the necessity of acquiring IR spectra or relying on atmospheric models and/or photometric calibrations. Methods. Our methodology consists of using ratios of pseudo-equivalent widths of spectral features as a temperature diagnostic, a technique frequently used in solar-type stars. Stars with effective temperatures obtained from interferometric estimates of their radii are used as calibrators. Empirical calibrations for the spectral type are also provided. Combinations of features and ratios of features are used to derive calibrations for the stellar metallicity. Our methods are then applied to a large sample of M dwarfs that are currently being observed in the framework of the HARPS GTO search for extrasolar planets. The derived temperatures and metallicities are used together with photometric estimates of mass, radius, and surface gravity to calibrate empirical relationships for these parameters. Results. A long list of spectral features in the optical spectra of early-M dwarfs was identified. This list shows that the pseudoequivalent width of roughly 43% of the features is strongly anticorrelated with the effective temperature. The correlation with the stellar metallicity is weaker. A total of 112 temperature sensitive ratios were identified and calibrated over the range 3100−3950 K, providing effective temperatures with typical uncertainties of about 70 K. Eighty-two ratios of pseudo-equivalent widths of features were calibrated to derive spectral types within 0.5 subtypes for stars with spectral types between K7V and M4.5V. We calibrated 696 combinations of the pseudo-equivalent widths of individual features and temperature-sensitive ratios for the stellar metallicity over a metallicity range from −0.54 to +0.24 dex, with estimated uncertainties in the range of 0.07−0.10 dex. We provide our own empirical calibrations for stellar mass, radius, and surface gravity. These parameters depend on the stellar metallicity. For a given effective temperature, lower metallicities predict lower masses and radii as well as higher gravities.

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M-dwarf metallicities. A high-resolution spectroscopic study in the near infrared

Cited by 80 publications

References 87 publications

Target Selection for the SDSS-IV APOGEE-2 Survey

Target Selection for the SDSS-IV APOGEE-2 Survey

SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

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