Person: Montes Gutiérrez, David
Universidad Complutense de Madrid
Faculty / Institute
Física de la Tierra y Astrofísica
Astronomía y Astrofísica
Now showing 1 - 10 of 73
PublicationThe CARMENES search for exoplanets around M dwarfs Mapping stellar activity indicators across the M dwarf domain(EDP Sciencies, 2021-08-04) Caballero, J. A.; Cortés Contreras, Miriam; Montes Gutiérrez, DavidContext. Stellar activity poses one of the main obstacles for the detection and characterisation of small exoplanets around cool stars, as it can induce radial velocity (RV) signals that can hide or mimic the presence of planetary companions. Several indicators of stellar activity are routinely used to identify activity-related signals in RVs, but not all indicators trace exactly the same activity effects, nor are any of them always effective in all stars. Aims. We evaluate the performance of a set of spectroscopic activity indicators for M dwarf stars with different masses and activity levels with the aim of finding a relation between the indicators and stellar properties. Methods. In a sample of 98 M dwarfs observed with CARMENES, we analyse the temporal behaviour of RVs and nine spectroscopic activity indicators: cross-correlation function (CCF) full-width-at-half-maximum (FWHM), CCF contrast, CCF bisector inverse slope (BIS), RV chromatic index (CRX), differential line width (dLW), and indices of the chromospheric lines Hα and calcium infrared triplet (IRT). Results. A total of 56 stars of the initial sample show periodic signals related to activity in at least one of these ten parameters. RV is the parameter for which most of the targets show an activity-related signal. CRX and BIS are effective activity tracers for the most active stars in the sample, especially stars with a relatively high mass, while for less active stars, chromospheric lines perform best. FWHM and dLW show a similar behaviour in all mass and activity regimes, with the highest number of activity detections in the low-mass, high-activity regime. Most of the targets for which we cannot identify any activity-related signals are stars at the low-mass end of the sample (i.e. with the latest spectral types). These low-mass stars also show the lowest RV scatter, which indicates that ultracool M dwarfs could be better candidates for planet searches than earlier types, which show larger RV jitter. Conclusions. Our results show that the spectroscopic activity indicators analysed behave differently, depending on the mass and activity level of the target star. This underlines the importance of considering different indicators of stellar activity when studying the variability of RV measurements. Therefore, when assessing the origin of an RV signal, it is critical to take into account a large set of indicators, or at least the most effective ones considering the characteristics of the star, as failing to do so may lead to false planet claims. PublicationCARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b(EDP Sciencies, 2021-10-27) Montes Gutiérrez, David; otros, ...Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 A and the He I triplet at 10 830 A. We present the discovery of the Ca II IRT at 7 sigma in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, H alpha, and K I. The upper limits reported here for these lines are consistent with previous studies. PublicationThe CARMENES search for exoplanets around M dwarfs: variability of the HeI line at 10 830 Å(EDP Sciencies, 2020-08-10) Cortés Contreras, Miriam; Montes Gutiérrez, DavidThe 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. PublicationThe CARMENES search for exoplanets around M dwarfs Diagnostic capabilities of strong K I lines for photosphere and chromosphere(EDP Sciencies, 2022-01-21) Montes Gutiérrez, David; López Gallifa, Álvaro; otros, ...There are several strong K I lines found in the spectra of M dwarfs, among them the doublet near 7700 angstrom and another doublet near 12 500 angstrom. We study these optical and near-infrared doublets in a sample of 324 M dwarfs, observed with CARMENES, the high-resolution optical and near-infrared spectrograph at Calar Alto, and investigate how well the lines can be used as photospheric and chromospheric diagnostics. Both doublets have a dominant photospheric component in inactive stars and can be used as tracers of effective temperature and gravity. For variability studies using the optical doublet, we concentrate on the red line component because this is less prone to artefacts from telluric correction in individual spectra. The optical doublet lines are sensitive to activity, especially for M dwarfs later than M5.0 V where the lines develop an emission core. For earlier type M dwarfs, the red component of the optical doublet lines is also correlated with Ha activity. We usually find positive correlation for stars with Ha in emission, while early-type M stars with Ha in absorption show anti-correlation. During flares, the optical doublet lines can exhibit strong fill-in or emission cores for our latest spectral types. On the other hand, the near-infrared doublet lines very rarely show correlation or anti-correlation to Ha and do not change line shape significantly even during the strongest observed flares. Nevertheless, the near-infrared doublet lines show notable resolved Zeeman splitting for about 20 active stars which allows to estimate the magnetic fields B. PublicationThe CARMENES search for exoplanets around M dwarfs: two Saturn-mass planets orbiting active stars(EDP Sciencies, 2022-07-14) Montes Gutiérrez, David; Caballero, J. A.; otros, ...The CARMENES radial-velocity survey is currently searching for planets in a sample of 387 M dwarfs. Here we report on two Saturn-mass planets orbiting TYC 2187-512-1 (M_*) = 0.50 Mꙩ) and TZ Ari ((M_*) = 0.15 Mꙩ), respectively. We obtained supplementary photometric time series, which we use along with spectroscopic information to determine the rotation periods of the two stars. In both cases, the radial velocities also show strong modulations at the respective rotation period. We thus modeled the radial velocities as a Keplerian orbit plus a Gaussian process representing the stellar variability. TYC 2187-512-1 is found to harbor a planet with a minimum mass of 0.33 M_(Jup) in a near-circular 692-day orbit. The companion of TZ Ari has a minimum mass of 0.21 M_(Jup), orbital period of 771 d, and orbital eccentricity of 0.46. We provide an overview of all known giant planets in the CARMENES sample, from which we infer an occurrence rate of giant planets orbiting M dwarfs with periods up to 2 yr in the range between 2 and 6%. TZ Ari b is only the second giant planet discovered orbiting a host with mass less than 0.3 Mꙩ. These objects occupy an extreme location in the planet mass versus host mass plane. It is difficult to explain their formation in core-accretion scenarios, so they may possibly have been formed through a disk fragmentation process. PublicationAtmospheric characterization of the ultra-hot Jupiter WASP-33b Detection of Ti and V emission lines and retrieval of a broadened line profile(EDP Sciencies, 2022-12-02) Caballero, J. A.; Montes Gutiérrez, David; otros, ...Ultra-hot Jupiters are highly irradiated gas giant exoplanets on close-in orbits around their host stars. The dayside atmospheres of these objects strongly emit thermal radiation due to their elevated temperatures, making them prime targets for characterization by emission spectroscopy. We analyzed high-resolution spectra from CARMENES, HARPS-N, and ESPaDOnS taken over eight observation nights to study the emission spectrum of WASP-33b and draw conclusions about its atmosphere. By applying the cross-correlation technique, we detected the spectral signatures of Ti I, V I, and a tentative signal of Ti II for the first time via emission spectroscopy. These detections are an important finding because of the fundamental role of Ti- and V-bearing species in the planetary energy balance. Moreover, we assessed and confirm the presence of OH, Fe I, and Si I from previous studies. The spectral lines are all detected in emission, which unambiguously proves the presence of an inverted temperature profile in the planetary atmosphere. By performing retrievals on the emission lines of all the detected species, we determined a relatively weak atmospheric thermal inversion extending from approximately 3400 to 4000 K. We infer a supersolar metallicity close to 1.5 dex in the planetary atmosphere, and find that its emission signature undergoes significant line broadening with a Gaussian full width at half maximum of about 4.5 km s^(−1) . Also, we find that the atmospheric temperature profile retrieved at orbital phases far from the secondary eclipse is about 300 to 700 K cooler than that measured close to the secondary eclipse, which is consistent with different day- and nightside temperatures. Moreover, retrievals performed on the emission lines of the individual chemical species lead to consistent results, which gives additional confidence to our retrieval method. Increasing the number of species included in the retrieval and expanding the set of retrieved atmospheric parameters will further advance our understanding of exoplanet atmospheres. PublicationThe Gaia-ESO survey: galactic evolution of lithium from iDR6(EDP Sciencies, 2021-09-09) Gutiérrez Albarrán, M.L.; Jiménez Esteban, F. M.; Montes Gutiérrez, DavidContext. After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various ^(7)Li sources in enriching the interstellar medium (ISM) with this fragile element. Aims. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a sample of open clusters (OCs) and field stars for which high-precision ^(7)Li abundances and stellar parameters are homogeneously derived by the Gaia-ESO Survey (GES). Methods. We derive possibly un-depleted ^(7)Li abundances for 26 OCs and star forming regions with ages from young (∼3 Myr) to old (∼4.5 Gyr), spanning a large range of galactocentric distances, 5 < R_(GC)/kpc < 15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain ^(7)Li evolution in other Galactic components. The data are then compared to theoretical tracks from chemical evolution models that implement different ^(7)Li forges. Results. Thanks to the homogeneity of the GES analysis, we can combine the maximum average ^(7)Li abundances derived for the clusters with ^(7)Li measurements in field stars. We find that the upper envelope of the 7Li abundances measured in field stars of nearly solar metallicities (−0.3 < [Fe/H]/dex < +0.3) traces very well the level of lithium enrichment attained by the ISM as inferred from observations of cluster stars in the same metallicity range. We confirm previous findings that the abundance of ^(7)Li in the solar neighbourhood does not decrease at super-solar metallicity. The comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the ^(7)Li abundance in meteorites comes from novae. Current data also seem to suggest that the nova rate flattens out at later times. This requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. Neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. This likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the ^(7)Li abundance in the ISM of low-metallicity systems that would counterbalance the astration processes. PublicationModelling the He I triplet absorption at 10 830 Å in the atmospheres of HD 189733 b and GJ 3470 b(EDP Sciencies, 2021-03-23) Lampón, M.; López-Puertas, M.; Sanz Forcada, J.; Sánchez-López, A.; Molaverdikhani, K.; Czesla, S.; Quirrenbach, A.; Pallé, E.; Caballero, J. A.; Henning, Th.; Salz, M.; Nortmann, L.; Aceituno, J.; Amado, P. J.; Bauer, F. F.; Montes Gutiérrez, David; Nagel, E.; Reiners, A.; Ribas, I.Characterising the atmospheres of exoplanets is key to understanding their nature and provides hints about their formation and evolution. High resolution measurements of the helium triplet absorption of highly irradiated planets have been recently reported, which provide a new means of studying their atmospheric escape. In this work we study the escape of the upper atmospheres of HD 189733 b and GJ 3470 b by analysing high resolution He i triplet absorption measurements and using a 1D hydrodynamic spherically symmetric model coupled with a non-local thermodynamic model for the He i triplet state. We also use the H density derived from Lyα observations to further constrain their temperatures, mass-loss rates, and H/He ratios. We have significantly improved our knowledge of the upper atmospheres of these planets. While HD 189733 b has a rather compressed atmosphere and small gas radial velocities, GJ 3470 b, on the other hand with a gravitational potential ten times smaller, exhibits a very extended atmosphere and large radial outflow velocities. Hence, although GJ 3470 b is much less irradiated in the X-ray and extreme ultraviolet radiation, and its upper atmosphere is much cooler, it evaporates at a comparable rate. In particular, we find that the upper atmosphere of HD 189733 b is compact and hot, with a maximum temperature of 12 400^(+400)_(−300) K, with a very low mean molecular mass (H/He=(99.2/0.8)±0.1), which is almost fully ionised above 1.1 R_(P), and with a mass-loss rate of (1.1±0.1) × 10^(11) g s^(−1). In contrast, the upper atmosphere of GJ 3470 b is highly extended and relatively cold, with a maximum temperature of 5100±900 K, also with a very low mean molecular mass (H/He=(98.5/1.5)^(+1.0)_(−1.5)), which is not strongly ionised, and with a mass-loss rate of (1.9±1.1) × 10^(11) gs^(−1). Furthermore, our results suggest that upper atmospheres of giant planets undergoing hydrodynamic escape tend to have a very low mean molecular mass (H/He ˃̰ 97/3). PublicationThe CARMENES search for exoplanets around M dwarfs: characterization of the nearby ultra-compact multiplanetary system YZ Ceti(EDP Sciencies, 2020-04-07) Caballero, J. A.; Cortés Contreras, Miriam; Díez Alonso, Enrique; Domínguez Fernández, A.J.; Montes Gutiérrez, DavidContext. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i_(min) = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of i_(max) = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters. PublicationPrecise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap?(EDP Sciencies, 2020-07-21) Cortés Contreras, Miriam; Montes Gutiérrez, DavidWe report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384–1735–1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of M_(p) = 5.9 ± 0.6 M_(⊕) and a radius of Rp = 1.69 ± 0.08 R_(⊕), which together result in a density of ρ_(p) = 6.7^(+1.3)_(−1.1) g cm^(−3) . When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R_(⊕) or larger at the insolation levels received by TOI-1235 b (∼60 S_(⊕)). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution.