Reproducido con permiso de Astronomy & Astrophysics ; CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 fund. Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministerio de Ciencia, Innovacion y Universidades (under grants AYA2016-79425-C3-1/2/3-P, AYA2017-89121-P, AYA2018-84089). The Junta de Andalucía, and by the Principado de Asturias (under grant FC-15-GRUPIN14-017) ; Díez Alonso, E., Caballero, J.A., Montes, D., De Cos Juez, F.J., Dreizler, S., Dubois, F., Jeffers, S.V., Lalitha, S., Naves, R., Reiners, A., Ribas, I., Vanaverbeke, S., Amado, P.J., Béjar, V.J.S., Cortés-Contreras, M., Herrero, E., Hidalgo, D., Kürster, M., Logie, L., Quirrenbach, A., Rau, S., Seifert, W., Schöfer, P., Tal-Or, L.
With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (Teti, log g, 4, and [Fell I]) by means of the STEPAR code, a PYTHON implementation of the equivalent width method that employs the 2017 version of the MOOG code and a grid of MARCS model atmospheres. We compiled four Fe 1 and Fe tl line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5300 to 17 100 A, thus substantially increasing the number of identified Fe! and Felt lines up to 653 and 23, respectively, We examined the impact of the near-infrared Fe and Fen lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gala benchmark stars contained in our sample, Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fel and Feu lines when the near-infrared region is taken into account reveals a deeper Teff scale that might stem from a higher sensitivity of the near-infrared lines to Tff.C 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society ; CARMENES is an instrument for the Centro Astronomico Hispano en Andaluc ' ia at Calar Alto (CAHA). CARMENES is funded by the German Max-Plank Gesellschaft (MPG), the Spanish Consejo Superior de InvestigacionesCientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Plank-Institut fur Astronomie, Instituto de Astrofisica deAndalucia, LandessternwarteKonigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenberg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano en Andalucia), with additional contributions by the Ministerio de Asuntos Economicos y Transformacion Digital, the German Research Foundation (DFG) through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 Blue Planets around Red Stars', the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. The authors acknowledge financial support from the Fundacao para a Ciencia e a Tecnologia (FCT) through national funds (PTDC/FIS-AST/28953/2017) and by Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE2020 -Programa Operacional Competitividade e Internacionalizacao (POCI01-0145-FEDER-028953), the Ministerio de Ciencia e Innovacion through fellowship FPU15/01476, and projects AYA2016-79425C3-1/2/3-P, and the Universidad Complutense de Madrid. JIGH acknowledges financial support from the Ministerio de Ciencia e Innovacion under the 2013 Ramon y Cajal programme RYC-201314875, and from the project AYA2017-86389-P. This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. We thank Calar Alto Observatory for the allocation of director's discretionary time to this programme. EM would also like to warmly thank the staff at the Hamburger Sternwarte for their hospitality during his stay funded by project EST18/00162 from the Ministerio de Ciencia e Innovacion. Based on data from the CARMENES data archive at CAB (INTA-CSIC). ; Peer reviewed
Context. The relevance of M dwarfs in the search for potentially habitable Earth-sized planets has grown significantly in the last years. Aims. In our on-going effort to comprehensively and accurately characterise confirmed and potential planet-hosting M dwarfs, in particular for the CARMENES survey, we have carried out a comprehensive multi-band photometric analysis involving spectral energy distributions, luminosities, absolute magnitudes, colours, and spectral types, from which we have derived basic astrophysical parameters. Methods. We have carefully compiled photometry in 20 passbands from the ultraviolet to the mid-infrared, and combined it with the latest parallactic distances and close-multiplicity information, mostly from Gaia DR2, of a sample of 2479 K5 V to L8 stars and ultracool dwarfs, including 2210 nearby, bright M dwarfs. For this, we made extensive use of Virtual Observatory tools. Results. We have homogeneously computed accurate bolometric luminosities and effective temperatures of 1843 single stars, derived their radii and masses, studied the impact of metallicity, and compared our results with the literature. The over 40 000 individually inspected magnitudes, together with the basic data and derived parameters of the stars, individual and averaged by spectral type, have been made public to the astronomical community. In addition, we have reported 40 new close multiple systems and candidates (ρ < 3.3 arcsec) and 36 overluminous stars that are assigned to young Galactic populations. Conclusions. In the new era of exoplanet searches around M dwarfs via transit (e.g. TESS, PLATO) and radial velocity (e.g. CARMENES, NIRPS+HARPS), this work is of fundamental importance for stellar and therefore planetary parameter determination. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
arXiv:2003.04872v2 ; [Context]: HD 209458 b is an exoplanet with an upper atmosphere undergoing blow-off escape that has mainly been studied using measurements of the Lyα absorption. Recently, high-resolution measurements of absorption in the He I triplet line at 10 830 Å of several exoplanets (including HD 209458 b) have been reported, creating a new opportunity to probe escaping atmospheres. ; [Aims]: We aim to better understand the atmospheric regions of HD 209458 b from where the escape originates. ; [Methods]: We developed a 1D hydrodynamic model with spherical symmetry for the HD 209458 b thermosphere coupled with a non-local thermodynamic model for the population of the He I triplet state. In addition, we performed high-resolution radiative transfer calculations of synthetic spectra for the helium triplet lines and compared them with the measured absorption spectrum in order to retrieve information about the atmospheric parameters. ; [Results]: We find that the measured spectrum constrains the [H]/[H+] transition altitude occurring in the range of 1.2 RP–1.9 RP. Hydrogen is almost fully ionised at altitudes above 2.9 RP. We also find that the X-ray and extreme ultraviolet absorption takes place at effective radii from 1.16 to 1.30 RP, and that the He I triplet peak density occurs at altitudes from 1.04 to 1.60 RP. Additionally, the averaged mean molecular weight is confined to the 0.61–0.73 g mole−1 interval, and the thermospheric H/He ratio should be larger than 90/10, and most likely approximately 98/2. We also provide a one-to-one relationship between mass-loss rate and temperature. Based on the energy-limited escape approach and assuming heating efficiencies of 0.1–0.2, we find a mass-loss rate in the range of (0.42–1.00) ×1011 g s−1 and a corresponding temperature range of 7125–8125 K. ; [Conclusions]: The analysis of the measured He I triplet absorption spectrum significantly constrains the thermospheric structure of HD 209458 b and advances our knowledge of its escaping atmosphere. ; IAA authors acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award SEV-2017-0709. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max- Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l'Espai, Insitut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades, funds through projects: ESP2016–76076–R, ESP2017-87143-R, BES–2015–074542, BES– 2015–073500, PGC2018-098153-B-C31, AYA2016-79425-C3-1/2/3-P. ; Peer reviewed
Context. Relatively large radii of some hot Jupiters observed in the ultraviolet and blue-optical are generally interpreted to be due to Rayleigh scattering by high-altitude haze particles. However, the haze composition and its production mechanisms are not fully understood, and observational information is still limited. Aims. We aim to study the presence of hazes in the atmospheres of HD 209458 b and HD 189733 b with high spectral resolution spectra by analysing the strength of water vapour cross-correlation signals across the red optical and near-infrared wavelength ranges. Methods. A total of seven transits of the two planets were observed with the CARMENES spectrograph at the 3.5 m Calar Alto telescope. Their Doppler-shifted signals were disentangled from the telluric and stellar contributions using the detrending algorithm SYSREM. The residual spectra were subsequently cross-correlated with water vapour templates at 0.70-0.96 μm to measure the strength of the water vapour absorption bands. Results. The optical water vapour bands were detected at 5.2σ in HD 209458 b in one transit, whereas no evidence of them was found in four transits of HD 189733 b. Therefore, the relative strength of the optical water bands compared to those in the near-infrared were found to be larger in HD 209458 b than in HD 189733 b. Conclusions. We interpret the non-detection of optical water bands in the transmission spectra of HD 189733 b, compared to the detection in HD 209458 b, to be due to the presence of high-altitude hazes in the former planet, which are largely absent in the latter. This is consistent with previous measurements with the Hubble Space Telescope. We show that currently available CARMENES observations of hot Jupiters can be used to investigate the presence of haze extinction in their atmospheres. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
The He I infrared (IR) triplet at 10 830 Å is known as an activity indicator in solar-type stars and has become a primary diagnostic in exoplanetary transmission spectroscopy. He I IR lines are a tracer of the stellar extreme-ultraviolet irradiation from the transition region and corona. We study the variability of the He I triplet lines in a spectral time series of 319 M dwarf stars that was obtained with the CARMENES high-resolution optical and near-infrared spectrograph at Calar Alto. We detect He I IR line variability in 18% of our sample stars, all of which show Hα in emission. Therefore, we find detectable He I variability in 78% of the sub-sample of stars with Hα emission. Detectable variability is strongly concentrated in the latest spectral sub-types, where the He I lines during quiescence are typically weak. The fraction of stars with detectable He I variation remains lower than 10% for stars earlier than M3.0 V, while it exceeds 30% for the later spectral sub-types. Flares are accompanied by particularly pronounced line variations, including strongly broadened lines with red and blue asymmetries. However, we also find evidence for enhanced He I absorption, which is potentially associated with increased high-energy irradiation levels at flare onset. Generally, He I and Hα line variations tend to be correlated, with Hα being the most sensitive indicator in terms of pseudo-equivalent width variation. This makes the He I triplet a favourable target for planetary transmission spectroscopy. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
