Examinando por Autor "Kirk, J."

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Acceso Abierto
Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone
(IOP Science Publishing, 2021-01-11) Alam, M. K.; López Morales, M.; MacDonald, R. J.; Nikolov, N.; Kirk, J.; Goyal, J. M.; Sing, D. K.; Wakeford, H. R.; Rathcke, A. D.; Deming, D. L.; Sanz Forcada, J.; Lewis, N. K.; Barstow, J. K.; Mikal Evans, T.; Buchhave, L. A.; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Agencia Estatal de Investigación (AEI); Alam, M. K. [0000-0003-4157-832X]; López Morales, M. [0000-0003-3204-8183]; MacDonald, R. J. [0000-0003-4816-3469]; Nikolov, N. [0000-0002-6500-3574]; Kirk, J. [0000-0002-4207-6615]; Goyal, J. M. [0000-0002-8515-7204]; Sing, D. K. [0000-0001-6050-7645]; Wakeford, H. R. [0000-0003-4328-3867]; Rathcke, A. D. [0000-0002-4227-4953]; Deming, D. L. [0000-0001-5727-4094]; Sanz Forcada, J. [0000-0002-1600-7835]; Lewis, N. K. [0000-0002-8507-1304]; Barstow, J. K. [0000-0003-3726-5419]; Mikal Evans, T. [0000-0001-5442-1300]; Buchhave, L. A. [0000-0003-1605-5666]
Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise chemical abundance constraints. We present the first optical to infrared (0.3−5 μm) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1σ detection of Na i absorption at 0.59 μm, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4 μm is tentatively attributed to SiH at 2.1σ confidence. Our retrieval analyses are consistent with a cloud-free atmosphere without significant contamination from stellar heterogeneities. We simulate James Webb Space Telescope (JWST) observations, for a combination of instrument modes, to assess the atmospheric characterization potential of WASP-62b. We demonstrate that JWST can conclusively detect Na, H2O, FeH, NH3, CO, CO2, CH4, and SiH within the scope of its Early Release Science (ERS) program. As the only transiting giant planet currently known in the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant exoplanet for detailed atmospheric characterization in the James Webb era.
Acceso Abierto
Gas phase Elemental abundances in Molecular cloudS (GEMS) III. Unlocking the CS chemistry: the CS+O reaction
(EDP Sciences, 2021-02-02) Bulut, N.; Roncero, O.; Aguado, A.; Loison, J. C.; Navarro Almaida, D.; Wakelam, V.; Fuente, A.; Roueff, E.; Le Gal, R.; Caselli, P.; Gerin, M.; Hickson, K. M.; Spezzano, S.; Riviére Marichalar, P.; Alonso Albi, T.; Bachiller, R.; Jiménez Serra, I.; Kramer, C.; Tercero, B.; Rodríguez Baras, M.; García Burillo, S.; Goicoechea, J. R.; Treviño Morales, S. P.; Esplugues, G.; Cazaux, S.; Commercon, B.; Laas, J. C.; Kirk, J.; Lattanzi, V.; Martín Doménech, R.; Muñoz Caro, G. M.; Pineda, J. E.; Ward Thompson, D.; Tafalla, M.; Marcelino, N.; Malinen, J.; Friesen, R.; Giuliano, B. M.; Agúndez, Marcelino; Hacar, A.; Agencia Estatal de Investigación (AEI); Marcelino, N. [0000-0001-7236-4047]; Roncero, O. [0000-0002-8871-4846]; Pineda, J. [0000-0002-3972-1978]; Agundez, M. [0000-0003-3248-3564]; Tafalla, M. [0000-0002-2569-1253]
Context. Carbon monosulphide (CS) is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. However, chemical models fail to account for the observed CS abundances when assuming the cosmic value for the elemental abundance of sulfur. Aims. The CS+O → CO + S reaction has been proposed as a relevant CS destruction mechanism at low temperatures, and could explain the discrepancy between models and observations. Its reaction rate has been experimentally measured at temperatures of 150−400 K, but the extrapolation to lower temperatures is doubtful. Our goal is to calculate the CS+O reaction rate at temperatures <150 K which are prevailing in the interstellar medium. Methods. We performed ab initio calculations to obtain the three lowest potential energy surfaces (PES) of the CS+O system. These PESs are used to study the reaction dynamics, using several methods (classical, quantum, and semiclassical) to eventually calculate the CS + O thermal reaction rates. In order to check the accuracy of our calculations, we compare the results of our theoretical calculations for T ~ 150−400 K with those obtained in the laboratory. Results. Our detailed theoretical study on the CS+O reaction, which is in agreement with the experimental data obtained at 150–400 K, demonstrates the reliability of our approach. After a careful analysis at lower temperatures, we find that the rate constant at 10 K is negligible, below 10−15 cm3 s−1, which is consistent with the extrapolation of experimental data using the Arrhenius expression. Conclusions. We use the updated chemical network to model the sulfur chemistry in Taurus Molecular Cloud 1 (TMC 1) based on molecular abundances determined from Gas phase Elemental abundances in Molecular CloudS (GEMS) project observations. In our model, we take into account the expected decrease of the cosmic ray ionization rate, ζH2, along the cloud. The abundance of CS is still overestimated when assuming the cosmic value for the sulfur abundance.