Person: Gómez Marfil, Emilio
Universidad Complutense de Madrid
Faculty / Institute
Física de la Tierra y Astrofísica
Now showing 1 - 10 of 12
PublicationCalibrating the metallicity of M dwarfs in wide physical binaries with F-, G-, and K-primaries -I: High-resolution spectroscopy with HERMES: stellar parameters, abundances, and kinematics(Oxford Univ Press, 2018-09) Montes Gutiérrez, David; González Peinado, R.; Tabernero, H. M.; Caballero, J. A.; Gómez Marfil, Emilio; Alonso Floriano, F. J.; Cortés Contreras, Miriam; González Hernández, J. I.; Klutsch, A.; Moreno Jodar, C.We investigated almost 500 stars distributed among 193 binary or multiple systems made of late-E, G-, or earl y-K-primaries and late-K- or M-dwarf companion candidates, For all of them, we compiled or measured coordinates, J-band magnitudes, spectral types, distances, and proper motions. With these data, we established a sample of 192 physically bound systems. In parallel, we carried out observations with HERMES/Mercator and obtained high-resolution spectra for the 192 primaries and five secondaries. We used these spectra and the automatic STEPAR code for deriving precise stellar atmospheric parameters: T-eff, log g, xi, and chemical abundances for 13 atomic species, including [Fe/H]. After computing Galactocentric space velocities for all the primary stars, we performed a kinematic analysis and classified them in different Galactic populations and stellar kinematic groups of very different ages, which match our own metallicity determinations and isochronal age estimations. In particular, we identified three systems in the halo and 33 systems in the young Local Association, Ursa Major and Castor moving groups, and IC 2391 and Hyades superclusters. We finally studied the exoplanet-metallicity relation in our 193 primaries and made a list 13 M-dwarf companions with very high metallicity that can be the targets of new dedicated exoplanet surveys. All in all, our dataset will be of great help for future works on the accurate determination of metallicity of M dwarfS. PublicationThe CARMENES search for exoplanets around M dwarfs: rubidium abundances in nearby cool stars(EDP Sciencies, 2020-10-23) Cortés Contreras, Miriam; Tabernero Guzmán, Hugo Martín; Montes Gutiérrez, David; Gómez Marfil, Emilio; López Gallifa, ÁlvaroDue to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutroncapture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range −0.5 <˷ [Fe/H] <˷ +0.3, an interval poorly explored for Rb abundances in previous analyses. To do this we use high-resolution, high-signal-to-noise-ratio, optical and near-infrared spectra of 57 M dwarfs observed with CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs are almost constant at about the solar value, and are identical to those found in GK dwarfs of the same metallicity. However, for Rb we find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on average. Furthermore, a tendency is found for Rb – but not for other heavy elements (Sr, Zr) – to increase with increasing metallicity such that [Rb/Fe] >˷ 0.0 is attained at metallicities higher than solar. These are surprising results, never seen for any other heavy element, and are difficult to understand within the formulation of the s- and r-processes, both contributing sources to the Galactic Rb abundance. We discuss the reliability of these findings for Rb in terms of non-LTE (local thermodynamic equilibrium) effects, stellar activity, or an anomalous Rb abundance in the Solar System, but no explanation is found. We then interpret the full observed [Rb/Fe] versus [Fe/H] trend within the framework of theoretical predictions from state-of-the-art chemical evolution models for heavy elements, but a simple interpretation is not found either. In particular, the possible secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities would require a much larger production of Rb than currently predicted in AGB stars through the s-process without overproducing Sr and Zr. Python libraries Matplotlib, NumPy, SciPy and collection of software packages AstroPy. PublicationThe Gaia-ESO survey: calibrating the lithium-age relation with open clusters and associations I. Cluster age range and initial membership selections(EDP Sciencies, 2020-11-05) Gutiérrez Albarrán, M.L.; Montes Gutiérrez, David; Gómez Garrido, Miguel; Tabernero Guzmán, Hugo Martín; Gómez Marfil, EmilioContext. Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. Aims. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters. Methods. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate members for each of the clusters in the sample by deriving radial velocity distributions and studying the position of the kinematic selections in the EW(Li)-versus-Teff plane to obtain lithium members. We used gravity indicators to discard field contaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made use of studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections. Results. We identified likely member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted a comparative study that allowed us to characterize the properties of these members as well as identify field contaminant stars, both lithium-rich giants and non-giant outliers. Conclusions. This work is the first step towards the calibration of the lithium–age relation and its dependence on other GES parameters. During this project we aim to use this relation to infer the ages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups of different ages. PublicationMetodologías docentes aplicadas a la Red internacional de Laboratorios de Proyectos de Emprendimiento Universitarios(UCM, 2022-12-26) Bel Durán, Paloma; Abril Barrie, María del Carmen; Arranz Torres, Héctor; Barrio Calvo, Bárbara María; Cubo Trenado, María Esther; García Csaky, Aurelio; García de Madariaga Miranda, Jesús; Gómez Marfil, Emilio; De la Iglesia Villasol, MA. Covadonga; Lara Cuenca, María del Pilar; Lejarriaga Pérez de las Vacas, Gustavo; López Herraiz, Joaquín; Martín Escudero, María del Pilar; Pascual Matallana, Alvaro; Pascual Ezama, David; Peinado Miguel, Fernando; Pérez-Urria Carril, Elena; Rodríguez Barba, María Dolores; Salas Paniagua, Alba; Sánchez Espada, Javier; Sandulli, Francesco Domenico; Serrano López, Dolores Remedios; Casado Pérez, JosefaEl emprendimiento como disciplina científica se asienta sobre dos pilares fundamentales: la transversalidad y la internacionalización. Son estos los que requieren una planificación para la aplicación de metodologías que fortalezcan el emprendimiento. PublicationMetallicities in M dwarfs: Investigating different determination techniques(EDP Sciencies, 2022-02-24) Gómez Marfil, Emilio; Duque Arribas, Christian; Montes Gutiérrez, David; otros, ...Deriving metallicities for solar-like stars follows well-established methods, but for cooler stars such as M dwarfs, the determination is much more complicated due to forests of molecular lines that are present. Several methods have been developed in recent years to determine accurate stellar parameters for these cool stars (T-eff less than or similar to 4000 K). However, significant differences can be found at times when comparing metallicities for the same star derived using different methods. In this work, we determine the effective temperatures, surface gravities, and metallicities of 18 well-studied M dwarfs observed with the CARMENES high-resolution spectrograph following different approaches, including synthetic spectral fitting, analysis of pseudo-equivalent widths, and machine learning. We analyzed the discrepancies in the derived stellar parameters, including metallicity, in several analysis runs. Our goal is to minimize these discrepancies and find stellar parameters that are more consistent with the literature values. We attempted to achieve this consistency by standardizing the most commonly used components, such as wavelength ranges, synthetic model spectra, continuum normalization methods, and stellar parameters. We conclude that although such modifications work quite well for hotter main-sequence stars, they do not improve the consistency in stellar parameters for M dwarfs, leading to mean deviations of around 50-200 K in temperature and 0.1-0.3 dex in metallicity. In particular, M dwarfs are much more complex and a standardization of the aforementioned components cannot be considered as a straightforward recipe for bringing consistency to the derived parameters. Further in-depth investigations of the employed methods would be necessary in order to identify and correct for the discrepancies that remain. PublicationThe CARMENES search for exoplanets around M dwarfs Stellar atmospheric parameters of target stars with STEPARSYN(EDP Sciencies, 2021-12-16) Gómez Marfil, Emilio; Montes Gutiérrez, David; Lázaro, F. J.; Duque Arribas, C.; López Gallifa, Álvaro; otros, ...We determined effective temperatures, surface gravities, and metallicities for a sample of 343 M dwarfs observed with CARMENES, the double-channel, high-resolution spectrograph installed at the 3.5 m telescope at Calar Alto Observatory. We employed STEPARSYN, a Bayesian spectral synthesis implementation particularly designed to infer the stellar atmospheric parameters of late-type stars following a Markov chain Monte Carlo approach. We made use of the BT-Settl model atmospheres and the radiative transfer code turbospectrum to compute a grid of synthetic spectra around 75 magnetically insensitive Fel and Til lines plus the TiO gamma and epsilon bands. To avoid any potential degeneracy in the parameter space, we imposed Bayesian priors on T-eff and log g based on the comprehensive, multi-band photometric data available for the sample. We find that this methodology is suitable down to M7.0 V, where refractory metals such as Ti are expected to condense in the stellar photospheres. The derived Teff, log g, and [Fe/H] range from 3000 to 4200 K, 4.5 to 5.3 dex, and -0.7 to 0.2 dex, respectively. Although our T (eff) scale is in good agreement with the literature, we report large discrepancies in the [Fe/H] scales, which might arise from the different methodologies and sets of lines considered. However, our [Fe/H] is in agreement with the metallicity distribution of FGK-type stars in the solar neighbourhood and correlates well with the kinematic membership of the targets in the Galactic populations. Lastly, excellent agreement in T (eff) is found for M dwarfs with interferometric angular diameter measurements, as well as in the [Fe/H] between the components in the wide physical FGK+M and M+M systems included in our sample. PublicationSpectroscopy of FGKM-type stars for the scientific exploitation of the CARMENES exoplanet search(Universidad Complutense de Madrid, 2022-11-30) Gómez Marfil, Emilio; Montes Gutiérrez, David; Tabernero Guzmán, Hugo MartínThe increased interest that sparks the search for exoplanets over the last few years has resulted in the design of high-resolution spectrographs such as CARMENES, installed at the 3.5m telescope in the Calar Alto Observatory in Almería (Spain), in order to improve the radial-velocity measurements and, thus, to help detect Earth-type planets around stars other than the Sun. Among these, M dwarfs constitute ideal candidates given their ubiquity in the solar neighbourhood, low temperatures, and low masses, which favours detections by both the radial-velocity and transit techniques. In this context, the determination of stellar atmospheric parameters is an essential step to characterise exoplanet systems and to shed light on their formation and evolution by means of compared planetology, which tries to link the properties of exoplanets with those of their host stars. In particular, the CARMENES instrument, by virtue of its high resolution and simultaneous spectral coverage in the optical and near-infrared wavelength regions, not only provides key information for the analysis of cool stars, but it also opens up the opportunity to revisit classical techniques, such as the equivalent width method and spectral synthesis, to assess the impact of the near-infrared region on the computation of stellar parameters... PublicationHabilidades técnicas (soft skills) de los alumnos de Astrofísica en Grado y Máster(2021-01-18) Montes Gutiérrez, David; Castro Rubio, Elisa de; Gómez de Castro, Ana Inés; Canet Varea, Ada; Beitia Antero, Leire; Gómez Marfil, EmilioEl objetivo principal del proyecto de innovación docente es reforzar las habilidades técnicas (soft skills) de los alumnos de astrofísica del Grado en Física y Matemáticas y del Máster en Astrofísica de la Facultad. De cara a los Trabajos Fin de Grado y a las asignaturas prácticas del Máster, consideramos necesario que los alumnos adquieran un dominio previo de ciertas herramientas para un mejor aprovechamiento de los contenidos y un desarrollo fructífero de los TFG y TFM. En particular, consideramos fundamental la familiarización con entornos UNIX, la capacidad de realizar programas básicos en Python para el tratamiento de datos astronómicos, el manejo de grandes bases de datos y la utilización de software libre para astronomía. PublicationSTEPARSYN: A Bayesian code to infer stellar atmospheric parameters using spectral synthesis(EDP Sciencies, 2022-01-11) Tabernero, H. M.; Gómez Marfil, Emilio; Montes Gutiérrez, David; González Hernández, J. I.Context. STEPARSYN is an automatic code written in Python 3.X designed to infer the stellar atmospheric parameters T-eff, log g, and [Fe/H] of FGKM-type stars following the spectral synthesis method. Aims. We present a description of the STEPARSYN code and test its performance against a sample of late-type stars that were observed with the HERMES spectrograph mounted at the 1.2-m Mercator Telescope. This sample contains 35 late-type targets with well-known stellar parameters determined independently from spectroscopy. The code is available to the astronomical community in a GitHub repository. Methods. STEPARSYN uses a Markov chain Monte Carlo sampler to explore the parameter space by comparing synthetic model spectra generated on the fly to the observations. The synthetic spectra are generated with an spectral emulator. Results. We computed T-eff, log g, and [Fe/H] for our sample stars and discussed the performance of the code. We calculated an internal scatter for these targets of -12 +/- 117 K in T-eff, 0.04 +/- 0.14 dex in log g, and 0.05 +/- 0.09 dex in [Fe/H]. In addition, we find that the log g values obtained with STEPARSYN are consistent with the trigonometric surface gravities to the 0.1 dex level. Finally, STEPARSYN can compute stellar parameters that are accurate down to 50 K, 0.1 dex, and 0.05 dex for T-eff, log g, and [Fe/H] for stars with v sin i <= 30 km s(-1). PublicationA detailed analysis of the Gl 486 planetary system(EDP Sciencies, 2022-09-20) Caballero, J. A.; Gómez Marfil, Emilio; Montes Gutiérrez, David; Tabernero Guzmán, Hugo Martín; otros, ...Context. The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R_(⊕) and 3.0 M_(⊕). It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. Aims. To prepare for future studies, we aim to thoroughly characterise the planetary system with new accurate and precise data collected with state-of-the-art photometers from space and spectrometers and interferometers from the ground. Methods. We collected light curves of seven new transits observed with the CHEOPS space mission and new radial velocities obtained with MAROON-X at the 8.1 m Gemini North telescope and CARMENES at the 3.5 m Calar Alto telescope, together with previously published spectroscopic and photometric data from the two spectrographs and TESS. We also performed near-infrared interferometric observations with the CHARA Array and new photometric monitoring with a suite of smaller telescopes (AstroLAB, LCOGT, OSN, TJO). This extraordinary and rich data set was the input for our comprehensive analysis. Results. From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at θ_(LDD) = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R_(*) = 0.339 ± 0.015 R_(ꙩ). We also measure a stellar rotation period at P_(rot) = 49.9 ± 5.5 days, an upper limit to its XUV (5–920 Å) flux informed by new Hubble/STIS data, and, for the first time, a variety of element abundances (Fe, Mg, Si, V, Sr, Zr, Rb) and C/O ratio. Moreover, we imposed restrictive constraints on the presence of additional components, either stellar or sub-stellar, in the system. With the input stellar parameters and the radial-velocity and transit data, we determine the radius and mass of the planet Gl 486 b at R_(p) = 1.343^(+0.063)_( −0.062) R_(⊕) and M_(p) = 3.00^(+0.13)_(−0.13) M_(⊕), with relative uncertainties of the planet radius and mass of 4.7% and 4.2%, respectively. From the planet parameters and the stellar element abundances, we infer the most probable models of planet internal structure and composition, which are consistent with a relatively small metallic core with respect to the Earth, a deep silicate mantle, and a thin volatile upper layer. With all these ingredients, we outline prospects for Gl 486 b atmospheric studies, especially with forthcoming James Webb Space Telescope (Webb) observations.