Browsing by Author "Valenzuela Navarro, Álvaro Enrique Hernán"

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    TARdYS: Design and prototype of an exoplanet hunter for TAO using a R6 Echelle grating
    (2019) Rukdee, Surangkhana; Vanzi, Leonardo; Schwab, C.; Flores Cabrales, Mauricio Fabián; Valenzuela Navarro, Álvaro Enrique Hernán; Pember, J.; Zapata, Abner; Motohara, K.; Yoshii, Y.; Tala Pinto, M.
    One limitation in characterizing exoplanet candidates is the availability of infrared, high-resolution spectrographs. An important factor in the scarcity of high precision IR spectrographs is the high cost of these instruments. We present a new optical design, which leads to a cost-effective solution. Our instrument is a high-resolution (R = 60,000) infrared spectrograph with a R6 Echelle grating and an image slicer. We compare the best possible performance of quasi-Littrow and White Pupil setups, and prefer the latter because it achieves higher image quality. The instrument is proposed for the University of Tokyo Atacama Observatory (TAO) 6.5 m telescope in Chile. The Tao Aiuc high Resolution (d) Y band Spectrograph (TARdYS) covers 0.843-1.117 mu m. To reduce the cost, we squeeze 42 spectral orders onto a 1K detector with a semi-cryogenic solution. We obtain excellent resolution even when taking realistic manufacturing and alignment tolerances as well as thermal variations into account. In this paper, we present early results from the prototype of this spectrograph at ambient temperature.
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    Unveiling VVV/WISE Mira variables on the far side of the Galactic disk: distances, kinematics, and a new extinction law
    (EDP Sciences, 2024) Albarracín Contreras, Ricardo Rogelio; Zoccali, Manuela; Olivares Carvajal, Julio Ariel; Rojas Arriagada, Alvaro; Minniti, Javier Horacio; Catelan, Márcio; De Leo, M.; Gran Merino, Felipe Eduardo; Contreras Ramos, Rodrigo Andrés; Valenzuela Navarro, Álvaro Enrique Hernán; Salvo Guajardo, Claudio Andrés
    Context. The structure and kinematics of the Milky Way disk are largely inferred from the solar vicinity. To gain a comprehensive understanding, it is essential to find reliable tracers in less explored regions such as the bulge and the far side of the disk. Mira variables, which are well studied and bright standard candles, offer an excellent opportunity to trace intermediate and old populations in these complex regions., Aims. We aim to isolate a clean sample of Miras in the VISTA Variables in the Via Lactea survey using Gaussian process algorithms. This sample will be used to study intermediate and old age populations in the Galactic bulge and far disk., Methods. Near- and mid-infrared time-series photometry were processed using Gaussian Process algorithms to identify Mira variables and model their light curves. We calibrated selection criteria with a visually inspected sample to create a high-purity sample of Miras, integrating multiband photometry and kinematic data from proper motions., Results. We present a catalog of 3602 Mira variables. By analyzing photometry, we classify them by O-rich or C-rich surface chemistry and derive selective-to-total extinction ratios of A(Ks)/E(J - K-s) = 0.471 +/- 0.01 and A(Ks)/E(H - K-s) = 1.320 +/- 0.020. Using the Mira period-age relation, we find evidence supporting the inside-out formation of the Milky Way disk. The distribution of proper motions and distances aligns with the Galactic rotation curve and disk kinematics. We extend the rotation curve up to R-GC similar to 17 kpc and find no strong evidence of the nuclear stellar disk in our Mira sample. This study constitutes the largest catalog of variable stars on the far side of the Galactic disk to date.