Person:
Montes Gutiérrez, David

First Name

David

Last Name

Montes Gutiérrez

URI

https://hdl.handle.net/20.500.14352/75137

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física de la Tierra y Astrofísica

Area

Astronomía y Astrofísica

Identifiers

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Now showing 1 - 10 of 104

The behaviour of the excess Ca II H and K and H epsilon emissions in chromospherically active binaries
(Astronomy & Astrophysics, 1996) Montes Gutiérrez, David; Fernández Figueroa, María José; Cornide Castro-Piñeiro, Manuel; Castro Rubio, Elisa De
In this work we analyze the behaviour of the excess Ca II H & K and H emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of diferent activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fernández-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995c). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active chromosphere contribution to the Ca II H & K lines in these 73 systems. We have determined the excess Ca ii H & K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. We have found that the components of active binaries are generally stronger emitters than single active stars for a given effective temperature and rotation rate. A slight decline of the excess Ca II H & K emissions towards longer rotation periods_(1) P_(rot1) and larger Rossby numbers, R_(01) is found. When we use R_(0) instead of P_(rot) the scatter is reduced and a saturation at R_(0)≈ 0.3 is observed. A good correlation between the excess Ca II K and He chromospheric emission fluxes has been found. The correlations obtained between the excess Ca II K emission and other activity indicators, (C IV in the transition region, and X-rays in the corona) indicate that the exponents of the power-law relations increase with the formation temperature of the spectral features.
Post T Tauri stars in the solar neighborhood: isolated or members of young associations and moving groups
(AIP conference proceedings, 2009) Montes Gutiérrez, David; López Santiago, J.; Martínez Arnáiz, R. M.; Guillout, P.; Klutsch, A.; Freire Ferrero, R.; Frasca, A.; Marilli, E.
Post T Tauri stars (PTTS) are late-type stars in the age range between 10 and 100 Myr filling the gap between T Tauri (TTs) and zero-age: main sequence phases. This period of evolution remains ambiguous and until now different studies of young stars have failed to find the numbers of PTTS that are expected. In the last years, some PTTS have been identified among the X-ray detected pre-main sequence stars in some star-forming regions. More recently, additional PTTS have been identified in young associations and moving groups (β Pic, TW Hya, Tucana/Horologium, and the AB Dor). However, many isolated PTTS still remain undiscovered. In this contribution, we compiled the PTTS previously identified in the literature, and identified new candidates using the information provided by the high resolution spectra obtained during our surveys of late-type stars possible members to young moving groups, FGK stars in the solar neighborhood, and RasTyc sample. To identify PTTS we applied an age-oriented definition using relative age indicators (Li abundance, chromospheric and coronal emission and the kinematics) as well as color-magnitude diagrams and pre-main sequence isochrones.
Planetary system around the nearby M dwarf GJ 357 including a transiting, hot, Earth-sized planet optimal for atmospheric characterization
(Astronomy & astrophysics, 2019) Caballero, J. A.; Cortés Contreras, Miriam; Montes Gutiérrez, David
We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2.5 V star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot, Earth-sized planet (T_(eq) = 525 ± 11 K) with a radius of R_(b) = 1.217 ± 0.084 Rꚛ and an orbital period of P_(b) = 3.93 d. Precise stellar radial velocities from CARMENES and PFS, as well as archival data from HIRES, UVES, and HARPS also display a 3.93-day periodicity, confirming the planetary nature and leading to a planetary mass of M_(b) = 1.84 ± 0.31 Mꚛ. In addition to the radial velocity signal for GJ 357 b, more periodicities are present in the data indicating the presence of two further planets in the system: GJ 357 c, with a minimum mass of M_(c) = 3.40 ± 0.46 Mꚛ in a 9.12 d orbit, and GJ 357 d, with a minimum mass of M_(d) = 6.1 ± 1.0 Mꚛ in a 55.7 d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period of P_(rot) = 78 ± 2 d. GJ 357 b is to date the second closest transiting planet to the Sun, making it a prime target for further investigations such as transmission spectroscopy. Therefore, GJ 357 b represents one of the best terrestrial planets suitable for atmospheric characterization with the upcoming JWST and ground-based ELTs.
CARMENES input catalogue of M dwarfs II. High-resolution imaging with FastCam
(Astronomy & Astrophysics, 2017) Cortés Contreras, Miriam; Montes Gutiérrez, David; Alonso Floriano, F. J.; otros, ...
Aims. We search for low-mass companions of M dwarfs and characterize their multiplicity fraction with the purpose of helping in the selection of the most appropriate targets for the CARMENES exoplanet survey. Methods. We obtained high-resolution images in the I band with the lucky imaging instrument FastCam at the 1.5m Telescopio Carlos Sanchez for 490 mid-to late-M dwarfs. For all the detected binaries, we measured angular separations, position angles, and magnitude differences in the I band. We also calculated the masses of each individual component and estimated orbital periods, using the available magnitude and colour relations for M dwarfs and our own M-J-spectral type and mass-M-I relations. To avoid biases in our sample selection, we built a volume-limited sample of M0.0-M5.0 dwarfs that is complete up to 86% within 14 pc. Results. From the 490 observed stars, we detected 80 companions in 76 systems, of which 30 are new discoveries. Another six companion candidates require additional astrometry to confirm physical binding. The multiplicity fraction in our observed sample is 16.7 +/- 2.0%. The bias-corrected multiplicity fraction in our volume-limited sample is 19.5 +/- 2.3% for angular separations of 0.2 to 5.0 arcsec (1.4-65.6 au), with a peak in the distribution of the projected physical separations at 2.5-7.5 au. For M0.0-M3.5V primaries, our search is sensitive to mass ratios higher than 0.3 and there is a higher density of pairs with mass ratios over 0.8 compared to those at lower mass ratios. Binaries with projected physical separations shorter than 50 au also tend to be of equal mass. For 26 of our systems, we estimated orbital periods shorter than 50 a, 10 of which are presented here for the first time. We measured variations in angular separation and position angle that are due to orbital motions in 17 of these systems. The contribution of binaries and multiples with angular separations shorter than 0.2 arcsec, longer than 5.0 arcsec, and of spectroscopic binaries identified from previous searches, although not complete, may increase the multiplicity fraction of M dwarfs in our volume-limited sample to at least 36%.
Late-type stars members of young stellar kinematic groups
(Stellar clusters and associations: convection, rotation, and dynamos, 2000) Montes Gutiérrez, David; Latorre, A.; Fernández Figueroa, María José; Pallavicini, R.; Micela, G.; Sciortino, S.
We have compiled a catalog of late-type stars (F5-M) members of representative, young disk, stellar kinematic groups: the Local Association (20-150 Myr), Ursa Mayor group (300 Myr), Hyades supercluster (600 Myr), IC 2391 supercluster (35 Myr), and Castor moving group (200 Myr). Stars have been selected from previously established members of stellar kinematic groups based in photometric and kinematic properties as well as from candidates based in other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, and published radial velocity measurements are used to calculate Galactic space motions (U, V, W) in order to determine the membership of the selected stars to the different stellar kinematic groups.
Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups
(Astronomy and astrophysics, 2001) Montes Gutiérrez, David; López Santiago, Javier; Fernández Figueroa, María José; Galves, M. C.
We present here high resolution echelle spectra taken during three observing runs of 14 single late-type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20-150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correlation with radial velocity standard stars and used together with precise measurements of proper motions and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria. The chromospheric activity level of these stars have been analysed using the information provided for several optical spectroscopic features (from the CaII H & K toCaII IRT lines) that are formed at different heights in the chromosphere. The Li I λ6707.8 Å line equivalent width (EW) has been determined and compared in the EW(Li I) versus spectral type diagram with the EW(Li I) of stars members of well-known young open clusters of different ages, in order to obtain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the different young stellar kinematic groups. Using both, kinematic and spectroscopic criteria we have confirmed PW And, V368 Cep, V383 Lac, EP Eri, DX Leo, HD 77407, and EK Dra as members of the Local Association and V834 Tau, π^1 UMa, and GJ 503.2 as members of the Ursa Major group. A clear rotation-activity dependence has been found in these stars.
Reliable probabilistic determination of membership in stellar kinematic groups in the young disk
(Astronomy and astrophysics, 2014) Klutsch, Alexis; Freire Ferreros, R.; Guillout, P.; Frasca, A.; Marilli, E.; Montes Gutiérrez, David
Context. Over the last century, the overdensities in the velocity distributions of nearby stars were attributed to stellar kinematic groups or moving groups. Although their reality was initially questioned, their existence is now supported by a confluence of evidence. Aims. To pursue investigations, quantitative methods should be clearly defined to identify new stars belonging to these groups. Here, we present two probabilistic methods to determine the likelihood of kinematic membership for possible candidates in five of the known young stellar kinematic groups – namely, Pleiades, IC 2391, Castor, Ursa Major, and Hyades – in which all are younger than 650 Myr. Methods. We tried different methods to handle kinematic data of their known members.We succeeded in developing two independent procedures able to identify new candidates of these five stellar stream. We tested the robustness of our two approaches by means of extensive Monte Carlo simulations. Results. Our methods are consistent with one another in more than 90% of cases and for almost all the stellar kinematic groups under scrutiny. The IC2391 supercluster is an exception. Applying our statistical methods to a large sample of young low-mass stars, we confirmed almost all the likely members and good candidates of these stellar streams. We also proposed 39 additional candidates based on the agreement and the high likelihood of age and kinematic membership. Conclusions. These probabilistic methods are very powerful to reliably identify new candidate members of young stellar kinematic groups. However, the kinematic criteria alone are not sufficient to distinguish between coeval stars that are evaporated from open clusters and other field stars trapped by dynamical processes generated by galactic perturbations. The identification of stars belonging to the remnant of a past star-forming event can be possible with the help of additional information, such as indicators of chromospheric activity, age proxies (lithium abundance), and chemical composition.
The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18
(Astronomical journal, 2018) Montes Gutiérrez, David; otros, ...
K2-18 is a nearby M2.5 dwarf, located at 34 pc and hosting a transiting planet that was first discovered by the K2 mission and later confirmed with Spitzer Space Telescope observations. With a radius of similar to 2 R-circle plus and an orbital period of similar to 33 days, the planet lies in the temperate zone of its host star and receives stellar irradiation similar to that of Earth. Here we perform radial velocity follow-up observations with the visual channel of CARMENES with the goal of determining the mass and density of the planet. We measure a planetary semi-amplitude of K-b similar to 3.5 m s(-1). and a mass of M-b similar to 9 M-circle plus, yielding a bulk density around rho(b) similar to 4 g cm(-3). This indicates a low-mass planet with a composition consistent with a solid core and a volatile-rich envelope. A signal at 9 days was recently reported using radial velocity measurements taken with the HARPS spectrograph. This was interpreted as being due to a second planet. We see a weaker, time-and wavelength-dependent signal in the CARMENES data set and thus favor stellar activity for its origin. K2-18 b joins the growing group of low-mass planets detected in the temperate zone of M dwarfs. The brightness of the host star in the near-infrared makes the system a good target for detailed atmospheric studies with the James Webb Space Telescope.
Incidence of debris discs around FGK stars in the solar neighbourhood
(Astronomy & Astrophysics, 2016) Montes Gutiérrez, David; otros, ...
Context. Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their counterparts in the solar system are the asteroid and Edgeworth-Kuiper belts. Aims. The aim of this paper is to provide robust numbers for the incidence of debris discs around FGK stars in the solar neighbourhood. Methods. The full sample of 177 FGK stars with d ≤ 20 pc proposed for the DUst around NEarby Stars (DUNES) survey is presented. Herschel/PACS observations at 100 and 160 μm were obtained, and were complemented in some cases with data at 70 μm and at 250, 350, and 500 μm SPIRE photometry. The 123 objects observed by the DUNES collaboration were presented in a previous paper. The remaining 54 stars, shared with the Disc Emission via a Bias-free Reconnaissance in IR and Sub-mm (DEBRIS) consortium and observed by them, and the combined full sample are studied in this paper. The incidence of debris discs per spectral type is analysed and put into context together with other parameters of the sample, like metallicity, rotation and activity, and age. Results. The subsample of 105 stars with d ≤ 15 pc containing 23 F, 33 G, and 49 K stars is complete for F stars, almost complete for G stars, and contains a substantial number of K stars from which we draw solid conclusions on objects of this spectral type. The incidence rates of debris discs per spectral type are 0.26^+0.21_-0.14 (6 objects with excesses out of 23 F stars), 0.21^+0.17_-0.11 (7 out of 33 G stars), and 0.20^+0.14_-0.09 (10 out of 49 K stars); the fraction for all three spectral types together is 0.22^+0.08_-0.07 (23 out of 105 stars). The uncertainties correspond to a 95% confidence level. The medians of the upper limits of L_dust/L_∗ for each spectral type are 7.8 × 10^-7 (F), 1.4 × 10^-6 (G), and 2.2 × 10^-6 (K); the lowest values are around 4.0 × 10^-7. The incidence of debris discs is similar for active (young) and inactive (old) stars. The fractional luminosity tends to drop with increasing age, as expected from collisional erosion of the debris belts.
A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups
(Astronomy & Astrophysics, 2010) Maldonado, J.; Martínez Arnáiz, R. M.; Eiroa, C.; Montes Gutiérrez, David; Montesinos, B.
Context. Nearby late-type stars are excellent targets for seeking young objects in stellar associations and moving groups. The origin of these structures is still misunderstood, and lists of moving group members often change with time and also from author to author. Most members of these groups have been identified by means of kinematic criteria, leading to an important contamination of previous lists by old field stars. Aims. We attempt to identify unambiguous moving group members among a sample of nearby-late type stars by studying their kinematics, lithium abundance, chromospheric activity, and other age-related properties. Methods. High-resolution echelle spectra (R ~ 57 000) of a sample of nearby late-type stars are used to derive accurate radial velocities that are combined with the precise Hipparcos parallaxes and proper motions to compute galactic-spatial velocity components. Stars are classified as possible members of the classical moving groups according to their kinematics. The spectra are also used to study several age-related properties for young late-type stars, i.e., the equivalent width of the lithium Li i 6707.8 Å line or the R'_HK index. Additional information like X-ray fluxes from the ROSAT All-Sky Survey or the presence of debris discs is also taken into account. The different age estimators are compared and the moving group membership of the kinematically selected candidates are discussed. Results. From a total list of 405 nearby stars, 102 have been classified as moving group candidates according to their kinematics. i.e., only ~25.2% of the sample. The number reduces when age estimates are considered, and only 26 moving group candidates (25.5% of the 102 candidates) have ages in agreement with the star having the same age as an MG member.