(CAB) Artículos

URI permanente para esta colecciónhttps://inta.metricsalad.com/handle/123456789/7

Buscar

Mostrando 1 - 20 de 553

Restringido
Interplay between Fast Diffusion and Molecular Interaction in the Formation of Self-Assembled Nanostructures of S-Cysteine on Au(111)
(ACS Publications, 2010-01-21) Mateo Martí, Eva; Rogero, Celia; González, César; Sobrado, J. M.; De Andrés, Pedro L.; Martín Gago, J. A.
We have studied the first stages leading to the formation of self-assembled monolayers of S-cysteine molecules adsorbed on a Au(111) surface. Density functional theory (DFT) calculations for the adsorption of individual cysteine molecules on Au(111) at room temperature show low-energy barriers all over the 2D Au(111) unit cell. As a consequence, cysteine molecules diffuse freely on the Au(111) surface and they can be regarded as a 2D molecular gas. The balance between molecule−molecule and molecule−substrate interactions induces molecular condensation and evaporation from the morphological surface structures (steps, reconstruction edges, etc.) as revealed by scanning tunnelling microscopy (STM) images. These processes lead progressively to the formation of a number of stable arrangements, not previously reported, such as single-molecular rows, trimers, and 2D islands. The condensation of these structures is driven by the aggregation of new molecules, stabilized by the formation of electrostatic interactions between adjacent NH3+ and COO− groups, together with adsorption at a slightly more favorable quasi-top site of the herringbone Au reconstruction.
Acceso Abierto
New results on thermal and photodesorption of CO ice using the novel InterStellar Astrochemistry Chamber (ISAC)
(EDP Science, 2010-11-09) Muñoz Caro, G. M.; Jiménez Escobar, A.; Martín Gago, J. A.; Rogero, Celia; Atienza, C.; Puertas, S.; Sobrado, J. M.; Torres Redondo, J.; Ministerio de Ciencia e Innovación (MICINN); Instituto Nacional de Técnica Aeroespacial (INTA)
Aims. We present the novel InterStellar Astrochemistry Chamber (ISAC), designed for studying solids (ice mantles, organics, and silicates) in interstellar and circumstellar environments: characterizing their physico-chemical properties and monitoring their evolution as caused by (i) vacuum-UV irradiation; (ii) cosmic ray irradiation; and (iii) thermal processing. Experimental study of thermal and photodesorption of the CO ice reported here simulates the freeze-out and desorption of CO on grains, providing new information on these processes. Methods. ISAC is an UHV set-up, with base pressure down to P = 2.5 × 10-11 mbar, where an ice layer is deposited at 7 K and can be UV-irradiated. The evolution of the solid sample was monitored by in situ transmittance FTIR spectroscopy, while the volatile species were monitored by QMS. Results. The UHV conditions of ISAC allow experiments under extremely clean conditions. Transmittance FTIR spectroscopy coupled to QMS proved to be ideal for in situ monitoring of ice processes that include radiation and thermal annealing. Thermal desorption of CO starting at 15 K, induced by the release of H2 from the CO ice, was observed. We measured the photodesorption yield of CO ice per incident photon at 7, 8, and 15 K, respectively yielding 6.4 ± 0.5 × 10-2, 5.4 ± 0.5 × 10-2, and 3.5 ± 0.5 × 10-2 CO molecules photon (7.3–10.5 eV)-1. Our value of the photodesorption yield of CO ice at 15 K is about one order of magnitude higher than the previous estimate. We confirmed that the photodesorption yield is constant during irradiation and independent of the ice thickness. Only below ~ 5 monolayers ice thickness the photodesorption rate decreases, which suggests that only the UV photons absorbed in the top 5 monolayers led to photodesorption. The measured CO photodesorption quantum yield at 7 K per absorbed photon in the top 5 monolayers is 3.4 molecules photon-1. Conclusions. Experimental values were used as input for a simple model of a quiescent cloud interior. Photodesorption seems to explain the observations of CO in the gas phase for densities below 3–7 × 104 cm-3. For the same density of a cloud, 3 × 104 cm-3, thermal desorption of CO is not triggered until T = 14.5 K. This has important implications for CO ice mantle build up in dark clouds.
Restringido
Mimicking Mars: A vacuum simulation chamber for testing environmental instrumentation for Mars exploration
(AIP Publishing, 2014-03-25) Sobrado, J. M.; Martín Soler, J.; Martín Gago, J. A.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Economía y Competitividad (MINECO)
We have built a Mars environmental simulation chamber, designed to test new electromechanical devices and instruments that could be used in space missions. We have developed this environmental system aiming at validating the meteorological station Rover Environment Monitoring Station of NASA's Mars Science Laboratory mission currently installed on Curiosity rover. The vacuum chamber has been built following a modular configuration and operates at pressures ranging from 1000 to 10−6 mbars, and it is possible to control the gas composition (the atmosphere) within this pressure range. The device (or sample) under study can be irradiated by an ultraviolet source and its temperature can be controlled in the range from 108 to 423 K. As an important improvement with respect to other simulation chambers, the atmospheric gas into the experimental chamber is cooled at the walls by the use of liquid-nitrogen heat exchangers. This chamber incorporates a dust generation mechanism designed to study Martian-dust deposition while modifying the conditions of temperature, and UV irradiated.
Acceso Abierto
Using radio astronomical receivers for molecular spectroscopic characterization in astrochemical laboratory simulations: A proof of concept
(EDP Science, 2017-12-22) Tanarro, I.; Alemán, Belén; De Vicente, P.; Gallego, J. D.; Pardo, Juan R.; Santoro, G.; Lauwaet, K.; Tercero, Felix; Díaz Pulido, A.; Moreno, E.; Agúndez, Marcelino; Goicoechea, J. R.; Sobrado, J. M.; López, J. A.; Martínez, L.; Doménech, Jose Luis; Herrero, V. J.; Hernández, J. M.; Peláez, R. J.; López Pérez, Jose A.; Gómez González, J.; Alonso, J. L.; Jiménez, Elena; Teyssier, D.; Makasheva, Kremena; Castellanos, Marcelo; Joblin, C.; Martín Gago, J. A.; Cernicharo, J.; Ministerio de Economía y Competitividad (MINECO)
We present a proof of concept on the coupling of radio astronomical receivers and spectrometers with chemical reactors and the performances of the resulting setup for spectroscopy and chemical simulations in laboratory astrophysics. Several experiments including cold plasma generation and UV photochemistry were performed in a 40 cm long gas cell placed in the beam path of the Aries 40 m radio telescope receivers operating in the 41–49 GHz frequency range interfaced with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz resolution. The impedance matching of the cell windows has been studied using different materials. The choice of the material and its thickness was critical to obtain a sensitivity identical to that of standard radio astronomical observations. Spectroscopic signals arising from very low partial pressures of CH3OH, CH3CH2OH, HCOOH, OCS, CS, SO2 (<10-3 mbar) were detected in a few seconds. Fast data acquisition was achieved allowing for kinetic measurements in fragmentation experiments using electron impact or UV irradiation. Time evolution of chemical reactions involving OCS, O2 and CS2 was also observed demonstrating that reactive species, such as CS, can be maintained with high abundance in the gas phase during these experiments.
Acceso Abierto
Enantiopure distorted ribbon-shaped nanographene combining two-photon absorption-based upconversion and circularly polarized luminescence†
(Royal Society of Chemistry (RSC), 2018-03-14) Cruz, C. M.; Márquez, I. R.; Mariz, I. F. A.; Blanco, V.; Sánchez-Sánchez, C.; Sobrado, J. M.; Martín Gago, J. A.; Cuerva, J. M.; Maçôas, E.; Campaña, A. G.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN); European Research Council (ERC); Fundacao para a Ciencia e a Tecnologia (FCT)
Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push–pull geometry and the extended network of sp2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results.
Acceso Abierto
Precisely controlled fabrication, manipulation and in-situ analysis of Cu based nanoparticles
(Nature, 2018-05-08) Martínez, Lidia; Lauwaet, K.; Santoro, G.; Sobrado, J. M.; Peláez, R. J.; Herrero, V. J.; Tanarro, I.; Ellis, G. J.; Cernicharo, J.; Joblin, C.; Huttel, Y.; Martín-Gago, J. A.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Economía y Competitividad (MINECO); European Commission (EC); Agencia Estatal de Investigación (AEI)
The increasing demand for nanostructured materials is mainly motivated by their key role in a wide variety of technologically relevant fields such as biomedicine, green sustainable energy or catalysis. We have succeeded to scale-up a type of gas aggregation source, called a multiple ion cluster source, for the generation of complex, ultra-pure nanoparticles made of different materials. The high production rates achieved (tens of g/day) for this kind of gas aggregation sources, and the inherent ability to control the structure of the nanoparticles in a controlled environment, make this equipment appealing for industrial purposes, a highly coveted aspect since the introduction of this type of sources. Furthermore, our innovative UHV experimental station also includes in-flight manipulation and processing capabilities by annealing, acceleration, or interaction with background gases along with in-situ characterization of the clusters and nanoparticles fabricated. As an example to demonstrate some of the capabilities of this new equipment, herein we present the fabrication of copper nanoparticles and their processing, including the controlled oxidation (from Cu0 to CuO through Cu2O, and their mixtures) at different stages in the machine.
Restringido
Modelling the kinetics and structural property evolution of a versatile reaction: aqueous HCN polymerization
(Royal Society of Chemistry (RSC), 2018-05-29) Fernández, Amparo; Ruiz Bermejo, Marta; De la Fuente, J. L.; Ministerio de Economía y Competitividad (MINECO); Instituto Nacional de Técnica Aeroespacial (INTA)
The kinetics of the reaction of the synthesis of HCN polymers in aqueous medium at high temperatures have been analysed to ascertain a suitable model for this material, for which it was recently demonstrated that prebiotic chemistry may now be adapted in the development of a new generation of high performance coatings and adhesives with biomedical applications. These experimental conditions were chosen for the simplicity of the reagents, being particularly convenient in regard to potential industrial scale-up of coating technology, where these polymers have revealed an interesting field of application. The kinetics of the precipitation polymerization of HCN in water were studied under isothermal conditions at four different temperatures between 75 °C and 90 °C throughout gravimetric measurements. The use of the Kamal–Sourour autocatalytic kinetic model was proposed, properly describing the overall formation process of this insoluble HCN polymer. All of the kinetic parameters, including reaction orders, kinetic constants and activation energy, were determined for the cross-linking polymerization reaction under study, and a relevant autocatalysis effect was observed. An isoconversion method was also used to analyse the variation of the global activation energy with conversion; and characterization by means of elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) was carried out. This study demonstrates the autocatalytic, robust and straightforward character of this heterogeneous aqueous HCN polymerization, and to the best of our knowledge, this report describes the first time that a systematic and extended kinetic analysis has been conducted to obtain a more comprehensive and deeper understanding of this complex reaction, which is of great interest to the origin of life and, currently, to materials science.
Acceso Abierto
Lucky Spectroscopy, an equivalent technique to Lucky Imaging Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope
(EDP Sciences, 2018-07-01) Maíz Apellániz, J.; Barbá, R. H.; Simón Díaz, S.; Sota, A.; Trigueros Páez, E.; Caballero, J. A.; Alfaro, Emilio J.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Maíz Apellániz, J. [0000-0003-0825-3443]; Barbá, R. H. [0000-0003-1086-1579]; Simón Díaz, S. [0000-0003-1168-3524]; Trigueros Páez, E. [0000-0001-6770-1977]
Context. Many massive stars have nearby companions whose presence hamper their characterization through spectroscopy. Aims. We want to obtain spatially resolved spectroscopy of close massive visual binaries to derive their spectral types. Methods. We obtained a large number of short long-slit spectroscopic exposures of five close binaries under good seeing conditions. We selected those with the best characteristics, extracted the spectra using multiple-profile fitting, and combined the results to derive spatially separated spectra. Results. We demonstrate the usefulness of Lucky Spectroscopy by presenting the spatially resolved spectra of the components of each system, in two cases with separations of only ~0.′′3. Those are δ Ori Aa+Ab (resolved in the optical for the first time) and σ Ori AaAb+B (first time ever resolved). We also spatially resolve 15 Mon AaAb+B, ζ Ori AaAb+B (both previously resolved with GOSSS, the Galactic O-Star Spectroscopic Survey), and η Ori AaAb+B, a system with two spectroscopic B+B binaries and a fifth visual component. The systems have in common that they are composed of an inner pair of slow rotators orbited by one or more fast rotators, a characteristic that could have consequences for the theories of massive star formation.
Restringido
Observatory science with eXTP
(Springer Link, 2018-08-30) Zand, J. J. M.; Bozzo, E.; Qu, J.; Li, X. D.; Amati, L.; Chen, Y.; Donnarumma, I.; Doroshenko, V.; Drake, S. A.; Hernanz, M.; Jenke, P. A.; Baykal, A.; Cumming, A.; Miller, M. C.; Gendre, B.; McHardy, I.; Peretz, U.; Schatz, H.; Brown, E. F.; Neubert, T.; Gill, R.; Mikusincova, R.; Prescod Weinstein, C.; Shearer, A.; Campana, R.; Pacciani, L.; Götz, D.; Rodríguez, J.; Stappers, B. W.; Chambers, F.; Paul, B.; Gouiffès, C.; Rózanska, A.; Strohmayer, T. E.; Chenevez, J.; De Martino, D.; Malzac, J.; Suleimanov, V. F.; Ciolfi, R.; Tauris, T. M.; Méndez, M.; Svoboda, J.; D´aì, A.; Atteia, J. L.; Motch, C.; Thielemann, F. K.; D´Ammando, F.; Mahmoodifar, S.; Tombesi, F.; Degenaar, N.; Zingale, M.; Torres, D. F.; D´Elia, V.; Zhang, S.; Torresi, E.; Doyle, G.; Zhang, S. N.; Fan, X.; Zdziarski, A. A.; Malyshev, D.; Zane, S.; Maccarone, Thomas J.; Zampieri, L.; Zhang, X.; Yuan, F.; Stratta, G.; Yu, W.; Younes, G.; Yan, Z.; Xu, Y.; Xiong, S. L.; Sala, G.; Agudo, I.; Ballantyne, D. R.; Bianchi, S.; Brandt, S.; Cackett, E. M.; Grandi, P.; Granot, J.; Güdel, M.; Heger, A.; Heinke, C. O.; Homan, J.; Iaria, R.; Iwasawa, K.; Izzo, L.; Ji, L.; Del Santo, M.; De Pasquale, M.; Dai, Z. G.; Constantin, E.; Chernyakova, M.; Chen, L.; Casella, P.; Burderi, L.; Braga, J.; Belloni, T.; Andersson, N. A.; Osborne, Julian P.; Wilms, J.; Nardini, E.; De Rosa, A.; Behar, E.; Turriziani, S.; Altamirano, D.; Cavecchi, Y.; Di Salvo, T.; Papadakis, L. E.; Blay, P.; Vacchi, A.; Chen, Y. P.; Falanga, M.; Pérez Torres, M. A.; Bucciantini, N.; Vercellone, S.; Jin, C. C.; Ferdman, R. D.; Reig, P.; Campana, S.; Rowlinson, A.; Feroci, M.; Rodríguez Gil, P.; Lu., F.; Zhou, P.; Fraschetti, F.; Sakamoto, T.; Mehdipour, M.; Baglio, C.; Galloway, D. K.; Salvaterra, R.; Bhattacharyya, S.; Gambino, A. F.; Santagelo, A.; Longo, F.; Gandhi, P.; Schanne, S.; Liang, E. W.; Ge, M.; Shao, L.; Kunneriath, D.; Shore, S. N.; Kuiper, L.; Rossi, E. M.; Kreykenbohm, I.; Wu, X.; Komossa, S.; Linares, M.; Keek, L.; Li, G.; Kawai, N.; Kargaltsev, O.; Kalemci, E.; Kaastra, J. S.; José, J.; Jonker, P. G.; Manousakis, A.; Mignani, R. P.; Nättilä, J.; Orlandini, M.; Paolillo, M.; Vink, J. S.; Wang, J. J.; Wang, J. F.; Watts, A. L.; Weng, S.; Weinberg, N. N.; Wheatley, P. J.; Wijnands, R.; Woods, T. E.; Woosley, S. E.; Savolainen, T.; Sanna, A.; Salmi, T.; Romano, P.; Riggio, A.; Perinati, E.; Pellizzoni, A.; Paltani, Stéphane; O´Brien, P. T.; Miniutti, G.; Men, Y.; Bilous, A.; Lutovinov, A. A.; National Natural Science Foundation of China (NSFC); European Research Council (ERC); National Aeronautics and Space Administration (NASA); Agencia Estatal de Investigación (AEI); Royal Society; Strategic Priority Research Program of the Chinese Academy of Sciences; European Research Council (ERC); National Science Centre, Poland (NCN); Unidad de Excelencia Científica María de Maeztu Instituto de Ciencias del Cosmos (ICCUB), MDM-2014-0369
In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.
Restringido
Accretion in strong field gravity with eXTP
(Springer Link, 2018-12-07) De Rosa, A.; Uttley, P.; Gou, L.; Liu, Y.; Bambi, C.; Barret, Didier; Belloni, T.; Berti, E.; Bianchi, S.; Caiazzo, I.; Casella, P.; Cui, W. K.; D´Ammando, F.; Dauser, T.; Del Santo, M.; De Marco, B.; Di Salvo, T.; Done, C.; Dovciak, M.; Fabian, A. C.; Falanga, M.; Gambino, A. F.; Gendre, B.; Grinberg, V.; Heger, A.; Homan, J.; Iaria, R.; Jiang, J.; Jin, C. C.; Koerding, E.; Linares, M.; Liu, Z.; Maccarone, Thomas J.; Malzac, J.; Manousakis, A.; Marin, F.; Marinucci, A.; Mehdipour, M.; Méndez, M.; Migliari, S.; Miller, C.; Miniutti, G.; Nardini, E.; O´Brien, P. T.; Osborne, Julian P.; Petrucci, P. O.; Possenti, A.; Riggio, A.; Rodríguez, J.; Sanna, A.; Shao, L. J.; Sobolewska, M.; Sramkova, E.; Stevens, A. L.; Stiele, H.; Stratta, G.; Stuchlik, Z.; Svoboda, J.; Tamburini, F.; Tauris, T. M.; Tombesi, F.; Torok, G.; Urbanec, M.; Vicent, F.; Wu, Q. W.; Yuan, F.; Zand, J. J. M.; Zdziarski, A. A.; Zhou, X.; Feroci, M.; Ferrari, V.; Gualtieri, L.; Heyl, J.; Ingram, A.; Karas, V.; Lu, F. J.; Luo, B.; Matt, G.; Motta, S. E.; Neilsen, J.; Pani, P.; Santangelo, A.; Shu, X. W.; Wang, J. F.; Wang, J. M.; Xue, Y. Q.; Xu, Y. P.; Yuan, W. M.; Yuan, Y. F.; Zhang, S. N.; Zhang, S.; Agudo, I.; Amati, L.; Andersson, N. A.; Baglio, C.; Bakala, P.; Baykal, A.; Bhattacharyya, S.; Bombaci, I.; Bucciantini, N.; Capitanio, F.; Ciolfi, R.; Istituto Nazionale di Astrofisica (INAF); Chinese Academy of Sciences (CAS); National Science Centre, Poland (NCN)
In this paper we describe the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to accretion flows in the strong field gravity regime around both stellar-mass and supermassive black-holes. eXTP has the unique capability of using advanced “spectral-timing-polarimetry” techniques to analyze the rapid variations with three orthogonal diagnostics of the flow and its geometry, yielding unprecedented insight into the inner accreting regions, the effects of strong field gravity on the material within them and the powerful outflows which are driven by the accretion process. X-spinmeasurements
Acceso Abierto
A Catalog of Wide Binary and Multiple Systems of Bright Stars from Gaia-DR2 and the Virtual Observatory
(American Astronomical Society, 2019) Jiménez Esteban, F. M.; Rodrigo, C.; Solano, Enrique
Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations >20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core (∼5000-10,000 au). We mined the recently published Gaia-DR2 catalog to identify bright comoving systems in the five-dimensional space (sky position, parallax, and proper motion). We identified 3741 comoving binary and multiple stellar candidate systems, out of which 575 have compatible radial velocities for all the members of the system. The candidate systems have separations between ∼400 and 500,000 au. We used the analysis tools of the Virtual Observatory to characterize the comoving system members and to assess their reliability. The comparison with previous comoving systems catalogs obtained from TGAS showed that these catalogs contain a large number of false systems. In addition, we were not able to confirm the ultra-wide binary population presented in these catalogs. The robustness of our methodology is demonstrated by the identification of well known comoving star clusters and by the low contamination rate for comoving binary systems with projected physical separations <50,000 au. These last constitute a reliable sample for further studies. The catalog is available online at the Spanish Virtual Observatory portal (http://svo2.cab.inta-csic.es/vocats/v2/comovingGaiaDR2/).
Acceso Abierto
Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733 b
(EDP Sciences, 2019-01-10) Alonso Floriano, F. J.; Sánchez López, A.; Snellen, I. A. G.; López Puertas, M.; Nagel, E.; Amado, P. J.; Bauer, F. F.; Caballero, J. A.; Czesla, S.; Nortmann, L.; Pallé, E.; Salz, M.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Aceituno, J.; Anglada Escudé, G.; Béjar, V. J. S.; Guenther, E. W.; Henning, T.; Kaminski, A.; Kürster, M.; Lampón, M.; Lara, L. M.; Montes, D.; Morales, J. C.; Tal Or, L.; Schmitt, J. H. M. M.; Zapatero Osorio, M. R.; Zechmeister, M.; European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Zapatero Osorio, M. R. [0000-0001-5664-2852]; Ribas, I. [0000-0002-6689-0312]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Aims. We explore the capabilities of CARMENES for characterising hot-Jupiter atmospheres by targeting multiple water bands, in particular, those at 1.15 and 1.4 μm. Hubble Space Telescope observations suggest that this wavelength region is relevant for distinguishing between hazy and/or cloudy and clear atmospheres. Methods. We observed one transit of the hot Jupiter HD 189733 b with CARMENES. Telluric and stellar absorption lines were removed using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra were analysed for water absorption with cross-correlation techniques using synthetic atmospheric absorption models. Results. We report a cross-correlation peak at a signal-to-noise ratio (S/N) of 6.6, revealing the presence of water in the transmission spectrum of HD 189733 b. The absorption signal appeared slightly blueshifted at –3.9 ± 1.3 km s−1. We measured the individual cross-correlation signals of the water bands at 1.15 and 1.4 μm, finding cross-correlation peaks at S/N of 4.9 and 4.4, respectively. The 1.4 μm feature is consistent with that observed with the Hubble Space Telescope. Conclusions. The water bands studied in this work have been mainly observed in a handful of planets from space. Being able also to detect them individually from the ground at higher spectral resolution can provide insightful information to constrain the properties of exoplanet atmospheres. Although the current multi-band detections can not yet constrain atmospheric haze models for HD 189733 b, future observations at higher S/N could provide an alternative way to achieve this aim.
Acceso Abierto
Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
(EDP Sciences, 2019-01-17) Lara, L. M.; Rodrigo, Rafael; Moreno, R.; Lampón, M.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Lara, L. M. [0000-0002-7184-920X]; Moreno, R. [0000-0002-9171-2702]; Lampón, M. [0000-0002-0183-7158]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. We present here an analysis of the potential sources of oxygen species in the Uranus atmosphere. Aims. Our aim is to explain the current measurements of H2O, CO, and CO2 in the Uranus atmosphere, which would allow us to constrain the influx of oxygen-bearing species and its origin in this planet. Methods. We used a time-dependent photochemical model of the Uranus atmosphere to ascertain the origin of H2O, CO, and CO2. We thoroughly investigated the evolution of material delivered by a cometary impact, together with a combined source, i.e. cometary impact and a steady source of oxygen species from micrometeoroid ablation. Results. We find that an impactor in the size range ~1.2–3.5 km hitting the planet between 450 and 822 yr ago could have delivered the CO currently seen in the Uranus stratosphere. Given the current set of observations, an oxygen-bearing species supply from ice grain ablation cannot be ruled out. Our study also indicates that a cometary impact cannot be the only source for rendering the observed abundances of H2O and CO2. The scenarios in which CO originates by a cometary impact and H2O and CO2 result from ice grain sublimation can explain both the space telescope and ground-based data for H2O, CO, and CO2. Similarly, a steady influx of water, carbon monoxide, and carbon dioxide, and a cometary impact delivering carbon monoxide give rise to abundances matching the observations. The time evolution of HCN also delivered by a cometary impact (as 1% of the CO in mass), when discarding chemical recycling of HCN once it is lost by photolysis and condensation, produces a very low stratospheric abundance which could be likely non-detectable. Consideration of N2-initiated chemistry could represent a source of HCN allowing for a likely observable stratospheric mixing ratio. Conclusions. Our modelling strongly indicates that water in the Uranus atmosphere likely originates from micrometeroid ablation, whereas its cometary origin can be discarded with a very high level of confidence. Also, we cannot firmly constrain the origin of the detected carbon monoxide on Uranus as a cometary impact, ice grain ablation, or a combined source due to both processes can give rise to the atmospheric mixing ratio measured with the Herschel Space Observatory. To establish the origin of oxygen species in the Uranus atmosphere, observations have to allow the retrieval of vertical profiles or H2O, CO, and CO2. Measurements in narrow pressure ranges, i.e. basically one pressure level, can be reproduced by different models because it is not possible to break this degeneracy about these three oxygen species in the Uranian atmosphere.
Acceso Abierto
The backscattering ratio of comet 67P/Churyumov–Gerasimenko dust coma as seen by OSIRIS onboard Rosetta
(Oxford Academics: Oxford University Press, 2019-01-22) Bertini, I.; La Forgia, F.; Fulle, M.; Tubiana, C.; Güttler, C.; Moreno, F.; Agarwal, J.; Muñoz, O.; Mottola, S.; Ivanovsky, S.; Pajola, M.; Lucchetti, A.; Petropoulou, V.; Lazzarin, M.; Rotundi, A.; Bodewits, D.; Frattin, E.; Toth, I.; Masoumzadeh, N.; Kovács, G.; Rinaldi, G.; Guirado, D.; Sierks, H.; Naletto, G.; Lamy, Philippe; Rodrigo, Rafael; Koschny, D.; Davidsson, B. J. R.; Barbieri, C.; Barucci, M. A.; Bertaux, J. L.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Ferri, F.; Fornasier, S.; Gutiérrez, Pedro J.; Hasselmann, P. H.; Ip, W. H.; Keller, H. U.; Lara, L. M.; López Moreno, J. J.; Marzari, F.; Massironi, M.; Penasa, L.; Shi, X.; Fulle, M. [0000-0001-8435-5287]; Tubiana, C. [0000-0001-8475-9898]; Güttler, C. [0000-0003-4277-1738]; Pajola, M. [0000-0002-3144-1277]; Rinaldi, G. [0000-0002-2968-0455]; Naletto, G. [0000-0003-2007-3138]; Barucci, M. A. [0000-0002-1345-0890]; Bertaux, J. L. [0000-0003-0333-229X]; Deller, J. [0000-0001-8341-007X]; Fornasier, S. [0000-0001-7678-3310]; Penasa, L. [0000-0002-6394-3108]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Remote sensing observations of dust particles ejected from comets provide important hints on the intimate nature of the materials composing these primitive objects. The measurement of dust coma backscattering ratio, BSR, defined as the ratio of the reflectance at phase angle 0° and 30°, helps tuning theoretical models aimed at solving the inverse scattering problem deriving information on the nature of the ejected particles. The Rosetta/OSIRIS camera sampled the coma phase function of comet 67P, with four series acquired at low phase angles from 2015 January to 2016 May. We also added previously published data to our analysis to increase the temporal resolution of our findings. We measured a BSR in the range ∼ [1.7–3.6], broader than the range found in literature from ground-based observations of other comets. We found that during the post-perihelion phase, the BSR is systematically larger than the classical cometary dust values only for nucleocentric distances smaller than ∼100 km. We explain this trend in terms of a cloud of chunks orbiting the nucleus at distances <100 km ejected during perihelion and slowly collapsing on the nucleus over a few months because of the coma gas drag. This also implies that the threshold particle size for the dust phase function to become similar to the nucleus phase function is between 2.5 mm and 0.1 m, taking into account previous Rosetta findings.
Restringido
A Catalog of Wide Binary and Multiple Systems of Bright Stars from Gaia-DR2 and the Virtual Observatory
(The Institute of Physics (IOP), 2019-01-28) Jiménez Esteban, F. M.; Rodrigo, C.; Solano, Enrique; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); European Research Council (ERC); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations >20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core (~5000–10,000 au). We mined the recently published Gaia-DR2 catalog to identify bright comoving systems in the five-dimensional space (sky position, parallax, and proper motion). We identified 3741 comoving binary and multiple stellar candidate systems, out of which 575 have compatible radial velocities for all the members of the system. The candidate systems have separations between ~400 and 500,000 au. We used the analysis tools of the Virtual Observatory to characterize the comoving system members and to assess their reliability. The comparison with previous comoving systems catalogs obtained from TGAS showed that these catalogs contain a large number of false systems. In addition, we were not able to confirm the ultra-wide binary population presented in these catalogs. The robustness of our methodology is demonstrated by the identification of well known comoving star clusters and by the low contamination rate for comoving binary systems with projected physical separations <50,000 au. These last constitute a reliable sample for further studies. The catalog is available online at the Spanish Virtual Observatory portal (http://svo2.cab.inta-csic.es/vocats/v2/comovingGaiaDR2/).
Acceso Abierto
A morphological study of galaxies in ZwCl0024+1652, a galaxy cluster at redshift z ∼ 0.4
(Oxford Academics: Oxford University Press, 2019-02-11) Beyoro Amado, Z.; Povic, M.; Sánchez Portal, M.; Tessema, S. B.; Bongiovanni, Á.; Cepa, J.; Cerviño, M.; González Serrano, J. I.; Nadolny, J.; Pérez García, A. M.; Pérez Martínez, R.; Pintos Castro, I.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Bongiovanni, Á. [0000-0002-3557-3234]; Povic, M. [0000-0002-9766-6110]; Pérez García, A. M. [0000-0003-1634-3588]; Pérez Martínez, R. [0000-0002-9127-5522]; Pintos Castro, I. [0000-0002-9133-4457]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The well-known cluster of galaxies ZwCl0024+1652 at z ∼ 0.4 lacks an in-depth morphological classification of its central region. While previous studies provide a visual classification of a patched area, we used the public code called galaxy Support Vector Machine (GALSVM) and HST/ACS data as well as the WFP2 master catalogue to automatically classify all cluster members up to 1 Mpc. GALSVM analyses galaxy morphologies through support vector machine (SVM). From the 231 cluster galaxies, we classified 97 as early types (ETs) and 83 as late types (LTs). The remaining 51 stayed unclassified (or undecided). By cross-matching our results with the existing visual classification, we found an agreement of 81 per cent. In addition to previous Zwcl0024 morphological classifications, 121 of our galaxies were classified for the first time in this work. In addition, we tested the location of classified galaxies on the standard morphological diagrams, colour–colour and colour–magnitude diagrams. Out of all cluster members, ∼20 per cent are emission-line galaxies, taking into account previous GLACE results. We have verified that the ET fraction is slightly higher near the cluster core and decreases with the clustercentric distance, while the opposite trend has been observed for LT galaxies. We found a higher fraction of ETs (54 per cent) than LTs (46 per cent) throughout the analysed central region, as expected. In addition, we analysed the correlation between the five morphological parameters (Abraham concentration, Bershady–Concelice concentration, asymmetry, Gini, and M20 moment of light) and the clustercentric distance, without finding a clear trend. Finally, as a result of our work, the morphological catalogue of 231 galaxies containing all the measured parameters and the final classification is available in the electronic form of this paper.
Acceso Abierto
Prebiotic chemistry in neutral/reduced-alkaline gas-liquid interfaces
(Springer Nature, 2019-02-13) Mompeán, Cristina; Roig Marín-Yaseli, Margarita; Espigares, Patricia; González Toril, Elena; Zorzano, María Paz; Ruiz Bermejo, Marta; Ministerio de Economía y Competitividad (MINECO); Instituto Nacional de Técnica Aeroespacial (INTA)
The conditions for the potential abiotic formation of organic compounds from inorganic precursors have great implications for our understanding of the origin of life on Earth and for its possible detection in other environments of the Solar System. It is known that aerosol-interfaces are effective at enhancing prebiotic chemical reactions, but the roles of salinity and pH have been poorly investigated to date. Here, we experimentally demonstrate the uniqueness of alkaline aerosols as prebiotic reactors that produce an undifferentiated accumulation of a variety of multi-carbon biomolecules resulting from high-energy processes (in our case, electrical discharges). Using simulation experiments, we demonstrate that the detection of important biomolecules in tholins increases when plausible and particular local planetary environmental conditions are simulated. A greater diversity in amino acids, carboxylic acids, N-heterocycles, and ketoacids, such as glyoxylic and pyruvic acid, was identified in tholins synthetized from reduced and neutral atmospheres in the presence of alkaline aqueous aerosols than that from the same atmospheres but using neutral or acidic aqueous aerosols.
Acceso Abierto
Hierarchical Bayesian approach for estimating physical properties in nearby galaxies: Age Maps (Paper II)
(Oxford Academics: Oxford University Press, 2019-02-15) Sánchez Gil, M. C.; Alfaro, Emilio J.; Cerviño, M.; Pérez, E.; Bland Hawthorn, J.; Death Jones, D.; Ministerio de Economía y Competitividad (MINECO); Junta de Andalucia; Agencia Estatal de Investigación (AEI); 0000-0002-2234-7035; 0000-0001-8009-231X; 0000-0001-9737-4559; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
One of the fundamental goals of modern astrophysics is to estimate the physical parameters of galaxies. We present a hierarchical Bayesian model to compute age maps from images in the H α line (taken with Taurus tunable filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 μm). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The H α to FUV flux ratio is a good relative indicator of the very recent star formation history (SFH). As a nascent star-forming region evolves, the H α line emission declines earlier than the UV continuum, leading to a decrease in the H α/FUV ratio. Using star-forming galaxy models, sampled with a probabilistic formalism, and allowing for a variable fraction of ionizing photons in the clusters, we obtain the corresponding theoretical ratio H α/FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. We take into account the mean uncertainties and the interrelationships between parameters when computing H α/FUV. We propose a Bayesian hierarchical model where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF) from the observed data (the observed flux ratios H α/FUV). The joint distribution of the parameters is described through independent and identically distributed (i.i.d.) random variables generated through MCMC (Markov Chain Monte Carlo) techniques.
Acceso Abierto
J-PLUS: The Javalambre Photometric Local Universe Survey
(EDP Sciences, 2019-02-21) Cenarro, A. J.; Moles, M.; Cristóbal Hornillos, D.; Marín Franch, A.; Ederoclite, A.; Varela, J.; López Sanjuan, C.; Hernández Monteagudo, C.; Angulo, R. E.; Vázquez Ramió, H.; Viironen, K.; Reis, R. R. R.; Molino, A.; Roig, F.; Vilella-Rojo, G.; Sako, M.; Sánchez Blázquez, P.; Gurung López, S.; Santos, W. A.; Telles, E.; Allende Prieto, C.; Bonatto, C.; Vilchez, J. M.; San Roman, I.; Daflon, S.; Dupke, R. A.; Greisel, N.; Jiménez Teja, Y.; Placco, V. M.; Logroño García, R.; Spinoso, D.; Maícas, N.; Izquierdo Villalba, D.; Abril, J.; Aguerri, J. A. L.; Carvano, J. M.; Bielsa de Toledo, S.; Chies Santos, A. L.; Falcón Barroso, J.; Civera, T.; Gonçalves, D. R.; Hernández Fuertes, J.; Iglesias Marzoa, R.; Whitten, D. D.; Antón, J. L.; Kruuse, K.; Lamadrid, J. L.; Bello, R.; Castillo Ramírez, J.; López Sainz, A.; Moreno Signes, A.; Chueca, S.; Díaz Martín, M. C.; Beers, T. C.; Domínguez Martínez, M.; Rueda Teruel, F.; Garzarán Calderaro, J.; Iñiguez, C.; Tilve, V.; Jiménez Ruiz, J. M.; Lasso Cabrera, N.; Alcaniz, J. S.; López Alegre, G.; Muniesa, D. J.; Lopes de Oliveira, R.; Tamm, A.; Rodríguez Llano, S.; Rueda Teruel, S.; Akras, S.; Alfaro, E. J.; Soriano Laguía, I.; Valdivielso, L.; Beasley, M. A.; Borges Fernandes, M.; Yanes Díaz, A.; Mendes de Oliveira, Claudia L.; Lyman, J. D.; Sodré, L.; Carrasco, J. M.; Coelho, P. R. T.; Xavier, H. S.; Costa Duarte, M. V.; Abramo, L. R.; Álvarez Candal, A.; Galarza, A.; Ascaso, B.; Bruzual, G.; González Serrano, J. I.; Gutiérrez Soto, L. A.; Buzzo, M. L.; Cepa, J.; Kuncarayakti, H.; Landim, R. C. G.; Cortesi, A.; De Prá, M.; Lima Neto, G. B.; Maíz Apellániz, J.; Favole, G.; Galbany, L.; Orsi, Álvaro A.; García, K.; Nogueira Cavalcante, J. P.; González Delgado, R. M.; Hernández Jiménez, J. A.; Oteo, I.; Kanaan, A.; Laur, J.; Rebassa-Mansergas, A.; Lincandro, J.; Miralda Escudé, J.; Salvador Rusiñol, N.; Sampedro, L.; Morate, D.; Novais, P. M.; Schmidtobreick, L.; Siffert, B. B.; Oncins, M.; Overzier, R. A.; Bonoli, S.; Hurier, G.; Pereira, C. B.; Díaz García, Pedro; Solano, Enrique; Gobierno de Aragón; European Commission (EC); Conselho Nacional de Desenvolvimento Científico e Tecnológico; Financiadora de Estudos e Projetos (FINEP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); National Science Foundation (NSF); Ministerio de Economía y Competitividad (MINECO); 0000-0002-2573-2342; Jailson Souza de Alcaniz. [https://orcid.org/0000-0003-2441-1413]; Coelho, P. R. T. [0000-0003-1846-4826]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The Javalambre Photometric Local Universe Survey (J-PLUS ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern Hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). The T80Cam is a camera with a field of view of 2 deg2 mounted on a telescope with a diameter of 83 cm, and is equipped with a unique system of filters spanning the entire optical range (3500–10 000 Å). This filter system is a combination of broad-, medium-, and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700–4000 Å Balmer break region, Hδ, Ca H+K, the G band, and the Mg b and Ca triplets) that are key to characterizing stellar types and delivering a low-resolution photospectrum for each pixel of the observed sky. With a typical depth of AB ∼21.25 mag per band, this filter set thus allows for an unbiased and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photospectral information for all resolved galaxies in the local Universe, as well as accurate photo-z estimates (at the δ z/(1 + z)∼0.005–0.03 precision level) for moderately bright (up to r ∼ 20 mag) extragalactic sources. While some narrow-band filters are designed for the study of particular emission features ([O II]/λ3727, Hα/λ6563) up to z < 0.017, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby Universe (Milky Way structure, globular clusters, 2D IFU-like studies, stellar populations of nearby and moderate-redshift galaxies, clusters of galaxies) and at high redshifts (emission-line galaxies at z ≈ 0.77, 2.2, and 4.4, quasi-stellar objects, etc.). With this paper, we release the first ∼1000 deg2 of J-PLUS data, containing about 4.3 million stars and 3.0 million galaxies at r < 21 mag. With a goal of 8500 deg2 for the total J-PLUS footprint, these numbers are expected to rise to about 35 million stars and 24 million galaxies by the end of the survey.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs Period search in Hα, Na I D, and Ca II IRT lines
(EDP Sciences, 2019-02-27) Fuhrmeister, B.; Czesla, S.; Schmitt, J. H. M. M.; Johnson, E. N.; Schöfer, P.; Jeffers, S. V.; Caballero, J. A.; Zechmeister, M.; Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Bauer, F. F.; Béjar, V. J. S.; Cortés Contreras, M.; Díez Alonso, E.; Dreizler, S.; Galadí Enríquez, D.; Guenther, E. W.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Deutsche Forschungsgemeinschaft (DFG); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We use spectra from CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, to search for periods in chromospheric indices in 16 M0–M2 dwarfs. We measure spectral indices in the Hα, the Ca II infrared triplet (IRT), and the Na I D lines to study which of these indices are best-suited to finding rotation periods in these stars. Moreover, we test a number of different period-search algorithms, namely the string length method, the phase dispersion minimisation, the generalized Lomb–Scargle periodogram, and the Gaussian process regression with quasi-periodic kernel. We find periods in four stars using Hα and in five stars using the Ca II IRT, two of which have not been found before. Our results show that both Hα and the Ca II IRT lines are well suited for period searches, with the Ca II IRT index performing slightly better than Hα. Unfortunately, the Na I D lines are strongly affected by telluric airglow, and we could not find any rotation period using this index. Further, different definitions of the line indices have no major impact on the results. Comparing the different search methods, the string length method and the phase dispersion minimisation perform worst, while Gaussian process models produce the smallest numbers of false positives and non-detections.

Buscar

Examinando (CAB) Artículos por Fecha de publicación