Examinando por Autor "Montesinos Comino, B."

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Acceso Abierto
Exocomets: A spectroscopic survey
(EDP Sciences, 2020-07-01) Rebollido, I.; Eiroa, C.; Montesinos Comino, B.; Maldonado, J.; Villaver, E.; Absil, O.; Bayo, A.; Canovas, H.; Carmona, A.; Chen, Ch.; Ertel, E.; Henning, T.; Iglesias, D. P.; Launhardt, R.; Liseau, R.; Meeus, G.; Moór, A.; Mora, A.; Olofsson, J.; Rauw, Gregor; Rivière Marichalar, P.; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Ministerio de Economía y Competitividad (MINECO); 0000-0002-4388-6417; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around β Pic in the early 1980s, only ∼20 stars have been reported to host exocomet-like events. Aims. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. Methods. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the Ca II K&H and Na I D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. Results. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the Ca II and/or Na I lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the Ca II K line are similar to those observed in β Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger v sin i is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.
Acceso Abierto
H2S observations in young stellar disks in Taurus
(EDP Sciences, 2021-08-09) Rivière Marichalar, P.; Fuente, A.; Le Gal, R.; Arabhavi, A. M.; Cazaux, S.; Navarro Almaida, D.; Ribas, Álvaro; Mendigutía, I.; Barrado, D.; Montesinos Comino, B.; Agencia Estatal de Investigación (AEI); Rivière Marichalar, P. [0000-0003-0969-8137]
Context. Studying gas chemistry in protoplanetary disks is key to understanding the process of planet formation. Sulfur chemistry in particular is poorly understood in interstellar environments, and the location of the main reservoirs remains unknown. Protoplanetary disks in Taurus are ideal targets for studying the evolution of the composition of planet forming systems. Aims. We aim to elucidate the chemical origin of sulfur-bearing molecular emission in protoplanetary disks, with a special focus on H2S emission, and to identify candidate species that could become the main molecular sulfur reservoirs in protoplanetary systems. Methods. We used IRAM 30 m observations of nine gas-rich young stellar objects (YSOs) in Taurus to perform a survey of sulfur-bearing and oxygen-bearing molecular species. In this paper we present our results for the CS 3–2 (ν0 = 146.969 GHz), H2CO 21,1−11,0 (ν0 = 150.498 GHz), and H2S 11,0−10,1 (ν0 = 168.763 GHz) emission lines. Results. We detected H2S emission in four sources out of the nine observed, significantly increasing the number of detections toward YSOs. We also detected H2CO and CS in six out of the nine. We identify a tentative correlation between H2S 11,0−10,1 and H2CO 21,1−11,0 as well as a tentative correlation between H2S 11,0−10,1 and H2O 818−707. By assuming local thermodynamical equilibrium, we computed column densities for the sources in the sample, with N(o-H2S) values ranging between 2.6 × 1012 cm−2 and 1.5 × 1013 cm−2.
Acceso Abierto
Homogeneous study of Herbig Ae/Be stars from spectral energy distributions and Gaia EDR3
(EDP Sciences, 2021-06-25) Guzmán Díaz, J.; Mendigutía, I.; Montesinos Comino, B.; Oudmaijer, R. D.; Vioque, M.; Rodrigo, C.; Solano, Enrique; Meeus, G.; Marcos Arenal, P.; Comunidad de Madrid; Agencia Estatal de Investigación (AEI); European Research Council (ERC)
Context. Herbig Ae/Be stars (HAeBes) have so far been studied based on relatively small samples that are scattered throughout the sky. Their fundamental stellar and circumstellar parameters and statistical properties were derived with heterogeneous approaches before Gaia. Aims. Our main goal is to contribute to the study of HAeBes from the largest sample of such sources to date, for which stellar and circumstellar properties have been determined homogeneously from the analysis of the spectral energy distributions (SEDs) and Gaia EDR3 parallaxes and photometry. Methods. Multiwavelength photometry was compiled for 209 bona fide HAeBes for which Gaia EDR3 distances were estimated. Using the Virtual Observatory SED Analyser (VOSA), photospheric models were fit to the optical SEDs to derive stellar parameters, and the excesses at infrared (IR) and longer wavelengths were characterized to derive several circumstellar properties. A statistical analysis was carried out to show the potential use of such a large dataset. Results. The stellar temperature, luminosity, radius, mass, and age were derived for each star based on optical photometry. In addition, their IR SEDs were classified according to two different schemes, and their mass accretion rates, disk masses, and the sizes of the inner dust holes were also estimated uniformly. The initial mass function fits the stellar mass distribution of the sample within 2 < M*∕M⊙ < 12. In this aspect, the sample is therefore representative of the HAeBe regime and can be used for statistical purposes when it is taken into account that the boundaries are not well probed. Our statistical study does not reveal any connection between the SED shape from the Meeus et al. (2001, A&A, 365, 476) classification and the presence of transitional disks, which are identified here based on the SEDs that show an IR excess starting at the K band or longer wavelengths. In contrast, only ~28% of the HAeBes have transitional disks, and the related dust disk holes are more frequent in HBes than in HAes (~34% vs. 15%). The relatively small inner disk holes and old stellar ages estimated for most transitional HAes indicate that photoevaporation cannot be the main mechanism driving disk dissipation in these sources. In contrast, the inner disk holes and ages of most transitional HBes are consistent with the photoevaporation scenario, although these results alone do not unambiguously discard other disk dissipation mechanisms.Conclusions. The complete dataset is available online through a Virtual Observatory-compliant archive, representing the most recent reference for statistical studies on the HAeBe regime. VOSA is a complementary tool for the future characterization of newly identified HAeBes.
Acceso Abierto
K-band GRAVITY/VLTI interferometry of “extreme” Herbig Be stars. The size–luminosity relation revisited
(EDP Sciences, 2021-08-11) Marcos Arenal, P.; Mendigutía, I.; Koumpia, E.; Oudmaijer, R. D.; Vioque, M.; Guzmán Díaz, J.; Wichittanakom, C.; De Wit, W. J.; Montesinos Comino, B.; Ilee, J. D.; Agencia Estatal de Investigación (AEI), European Research Council; Comunidad de Madrid; Science and Technology Facilities Council (STFC); European Research Council (ERC); Marcos Arenal, P. [0000-0003-1549-9396]
Context. It has been hypothesized that the location of Herbig Ae/Be stars (HAeBes) within the empirical relation between the inner disk radius (rin), inferred from K-band interferometry, and the stellar luminosity (L*), is related to the presence of the innermost gas, the disk-to-star accretion mechanism, the dust disk properties inferred from the spectral energy distributions (SEDs), or a combination of these effects. However, no general observational confirmation has been provided to date. Aims. This work aims to test whether the previously proposed hypotheses do, in fact, serve as a general explanation for the distribution of HAeBes in the size–luminosity diagram. Methods. GRAVITY/VLTI spectro-interferometric observations at ~2.2 μm have been obtained for five HBes representing two extreme cases concerning the presence of innermost gas and accretion modes. V590 Mon, PDS 281, and HD 94509 show no excess in the near-ultraviolet, Balmer region of the spectra (ΔDB), indicative of a negligible amount of inner gas and disk-to-star accretion, whereas DG Cir and HD 141926 show such strong ΔDB values that cannot be reproduced from magnetospheric accretion, but probably come from the alternative boundary layer mechanism. In turn, the sample includes three Group I and two Group II stars based on the Meeus et al. SED classification scheme. Additional data for these and all HAeBes resolved through K-band interferometry have been compiled from the literature and updated using Gaia EDR3 distances, almost doubling previous samples used to analyze the size–luminosity relation. Results. We find no general trend linking the presence of gas inside the dust destruction radius or the accretion mechanism with the location of HAeBes in the size–luminosity diagram. Similarly, our data do not support the more recent hypothesis linking such a location and the SED groups. Underlying trends are present and must be taken into account when interpreting the size–luminosity correlation. In particular, it cannot be statistically ruled out that this correlation is affected by dependencies of both L* and rin on the wide range of distances to the sources. Still, it is argued that the size–luminosity correlation is most likely to be physically relevant in spite of the previous statistical warning concerning dependencies on distance. Conclusions. Different observational approaches have been used to test the main scenarios proposed to explain the scatter of locations of HAeBes in the size–luminosity diagram. However, none of these scenarios have been confirmed as a fitting general explanation and this issue remains an open question.
Acceso Abierto
The A-shell star ϕ Leo revisited: its photospheric and circumstellar spectra
(EDP Sciences, 2021-09-21) Eiroa, C.; Montesinos Comino, B.; Rebollido, I.; Henning, T.; Launhardt, R.; Maldonado, J.; Meeus, G.; Mora, A.; Rivière Marichalar, P.; Villaver, E.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Istituto Nazionale di Astrofisica (INAF); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. We previously suggested that variable red- and blueshifted absorption features observed in the Ca II K line towards the A-type shell star ϕ Leo are likely due to solid, comet-like bodies in the circumstellar (CS) environment. Aims. Our aim is to expand our observational study of ϕ Leo to other characteristic spectral lines of A-type photospheres as well as to lines arising in their CS shells. Methods. We obtained more than 500 high-resolution optical spectra collected at different telescopes over 37 nights in several observing runs from December 2015 to January 2019. Consecutive time-series spectra were taken, covering intervals of up to ~9 h on some nights. We analysed some photospheric lines, in particular Ca I 4226 Å and Mg II 4481 Å, as well as the circumstellar shell lines Ca II H and K, the Ca II IR triplet, Fe II 4924, 5018, and 5169 Å, Ti II 3685, 3759, and 3761 Å, and the Balmer lines Hα and Hβ. Results. Our observational study reveals that ϕ Leo is a variable δ Scuti star whose spectra show remarkable dumps and bumps superimposed on the photospheric line profiles, which vary in strength and sharpness, propagate from blue- to more redshifted radial velocities, and persist for a few hours. Similarly to other δ Scuti stars, these features are likely produced by non-radial pulsations. At the same time, all shell lines present emission at ~3 km s−1 centred at the core of the CS features, and two variable absorption minima at both sides of the emission; those absorption minima occur at almost the same velocity for each line, that is, no apparent dynamical evolution is observed. The variations observed in the Ca II H and K, Fe II, and Ti II lines occur on a range of timescales from minutes to days and between observing runs, but without any clear correlation or recognisable temporal pattern among the different lines. In the case of Hα, the CS contribution is also variable in just one of the observing runs. Conclusions. We suggest that ϕ Leo is a rapidly rotating δ Scuti star surrounded by a variable, (nearly) edge-on CS disk possibly re-supplied by the δ Scuti pulsations. The behaviour of the CS shell lines is reminiscent of that of rapidly rotating Be shell stars with an edge-on CS disk, and is clear evidence that the variations observed in the CS features of ϕ Leo are highly unlikely to be produced by exocomets. In addition, the observational results presented in this work, together with some recent results concerning the shell star HR 10, highlight the need for critical revision of the Ca II K features, which have been attributed to exocomets in other shell stars.
Acceso Abierto
Zoé
(Gobierno de España: Ministerio de Defensa, 2011-05-15) Cuesta Crespo, L.; Ruiz Zelmanovitch, B.; Vaquerizo Gallego, J. A.; Montesinos Comino, B.; Cuevas Manrubia, S.; Gómez Gómez, F.; Martín Torres, Javier; Martín Soler, J.; Gómez Elvira, J.; Cernicharo, J.; Mas Hesse, J. M.; Parro García, V.; Amils Pibernat, R.; Rodríguez Manfredi, J. A.
La pregunta “¿Hay vida en otros lugares del Universo?” tenía, hasta hace poco, únicamente implicaciones filosóficas. Pero, actualmente se está empezando a abordar desde otros campos de la Ciencia. Precisamente, la Astrobiología aglutina todos los esfuerzos dirigidos a encontrar su respuesta, tratando de entender cómo son los procesos por los que una nube de polvo interestelar llega a transformarse en un sistema planetario en el que alguno de sus cuerpos se desarrolla de tal forma que aparecen microorganismos que lo pueblan y evolucionan. El reto de la Astrobiología es fabuloso y, embarcarse en esa misión, es realmente una aventura: la “aventura de la vida”. “La divulgación es una obligación que tiene la comunidad científica y tecnológica con la sociedad”: ésta es una frase que, desgraciadamente, todavía no ha calado lo suficiente en nuestra comunidad. Quizás el problema esté en nuestra formación: nadie nos ha enseñado a hacerlo y muchos no sabemos cómo se hace, pero nuestra obligación es intentarlo, porque es realmente una obligación para con la sociedad. No cabe duda de que la divulgación en Astrobiología es muy atractiva para el gran público por el interés del tema que aborda y porque su multidisciplinariedad atrae a “curiosos” de muchas áreas. Desde su creación, de la mano de Juan Pérez-Mercader, el Centro de Astrobiología (CSIC-INTA) ha considerado la divulgación como una de sus actividades básicas: esta revista es un intento más en esa dirección. Con ella, no sólo se quiere informar a la sociedad de sus actividades más relevantes, sino que pretende ser un “imán” para atraer hacia la ciencia y la tecnología a todo aquel que sienta curiosidad y quiera satisfacerla. D. Jaime Denís Zambrana – Director General del Instituto Nacional de Técnica Aeroespacial (INTA)