Examinando por Autor "Bayo, Amelia"
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Ítem Alert Classification for the ALeRCE Broker System: The Anomaly Detector(American Astronomical Society, 2023-10-01) Perez-Carrasco, Manuel; Cabrera-Vives, Guillermo; Hernandez-García, Lorena; Förster, F.; Sanchez-Saez, Paula; Muñoz Arancibia, Alejandra M.; Arredondo, Javier; Astorga, Nicolás; Bauer, Franz E.; Bayo, Amelia; Catelan, M.; Dastidar, Raya; Estévez, P.A.; Lira, Paulina; Pignata, GiulianoAstronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis. © 2023. The Author(s). Published by the American Astronomical Society.Ítem DELIGHT: Deep Learning Identification of Galaxy Hosts of Transients using Multiresolution Images(American Astronomical Society, 2022-11) Förster, Francisco; Muñoz Arancibia, Alejandra M.; Reyes Jainaga, Ignacio; Gagliano, Alexander; Britt, Dylan; Cuellar Carrillo, Sara; Figueroa Tapia, Felipe; Polzin, Ava; Yousef, Yara; Arredondo, Javier; Rodríguez Mancini, Diego; Correa Orellana, Javier; Bayo, Amelia; Bauer, Franz E.; Catelan, Márcio; Cabrera Vives, Guillermo; Dastidar, Raya; Estévez, Pablo A.; Pignata, Giuliano; Hernández García, Lorena; Huijse, Pablo; Reyes, Esteban; Sánchez Sáez, Paula; Ramírez, Mauricio; Grandón, Daniela; Pineda García, Jonathan; Chabour Barra, Francisca; Silva Farfán, JavierWe present DELIGHT, or Deep Learning Identification of Galaxy Hosts of Transients, a new algorithm designed to automatically and in real time identify the host galaxies of extragalactic transients. The proposed algorithm receives as input compact, multiresolution images centered at the position of a transient candidate and outputs two-dimensional offset vectors that connect the transient with the center of its predicted host. The multiresolution input consists of a set of images with the same number of pixels, but with progressively larger pixel sizes and fields of view. A sample of 16,791 galaxies visually identified by the Automatic Learning for the Rapid Classification of Events broker team was used to train a convolutional neural network regression model. We show that this method is able to correctly identify both relatively large (10″ < r < 60″) and small (r ≤ 10″) apparent size host galaxies using much less information (32 kB) than with a large, single-resolution image (920 kB). The proposed method has fewer catastrophic errors in recovering the position and is more complete and has less contamination ([removed]Ítem Erratum: Accretion signatures in the X-shooter spectrum of the substellar companion to SR12 (Monthly Notices of the Royal Astronomical Society(Oxford University Press, 2018-04) Santamaría-Miranda, Alejandro; Cáceres, Claudio; Schreiber, Matthias R.; Hardy, Adam; Bayo, Amelia; Parsons, Steven G.; Gromadzki, Mariusz; Villegas, Aurora Belén AguayoAbout a dozen substellar companions orbiting young stellar objects or pre-main sequence stars at several hundred au have been identified in the last decade. These objects are interesting both due to the uncertainties surrounding their formation, and because their large separation from the host star offers the potential to study the atmospheres of young giant planets and brown dwarfs. Here, we present X-shooter spectroscopy of SR 12 C, a ~2Myr young brown dwarf orbiting SR 12 at an orbital separation of 1083 au. We determine the spectral type, gravity, and effective temperature via comparison with models and observational templates of young brown dwarfs. In addition, we detect and characterize accretion using several accretion tracers. We find SR 12C to be a brown dwarf of spectral type L0 ± 1, log g = 4 ± 0.5, an effective temperature of 2600 ± 100 K. Our spectra provide clear evidence for accretion at a rate of ~10-10M⊙ yr-1. This makes SR 12 one of the few sub-stellar companions with a reliable estimate for its accretion rate. A comparison of the ages and accretion rates of sub-stellar companions with young isolated brown dwarfs does not reveal any significant differences. If further accretion rate measurements of a large number of substellar companions can confirm this trend, this would hint towards a similar formation mechanism for substellar companions at large separations and isolated brown dwarfs. © 2017 The Author(s).Ítem Multiscale Stamps for Real-time Classification of Alert Streams(American Astronomical Society, 2023-08) Reyes-Jainaga, Ignacio; Förster, Francisco; Muñoz Arancibia, Alejandra M.; Cabrera-Vives, Guillermo; Bayo, Amelia; Bauer, Franz E.; Arredondo, Javier; Reyes, Esteban; Pignata, Giuliano; Mourão A.M.; Silva-Farfán, Javier; Galbany, Lluís; Álvarez, Alex; Astorga, Nicolás; Castellanos, Pablo; Gallardo, Pedro; Moya, Alberto; Rodríguez, DiegoIn recent years, automatic classifiers of image cutouts (also called “stamps”) have been shown to be key for fast supernova discovery. The Vera C. Rubin Observatory will distribute about ten million alerts with their respective stamps each night, enabling the discovery of approximately one million supernovae each year. A growing source of confusion for these classifiers is the presence of satellite glints, sequences of point-like sources produced by rotating satellites or debris. The currently planned Rubin stamps will have a size smaller than the typical separation between these point sources. Thus, a larger field-of-view stamp could enable the automatic identification of these sources. However, the distribution of larger stamps would be limited by network bandwidth restrictions. We evaluate the impact of using image stamps of different angular sizes and resolutions for the fast classification of events (active galactic nuclei, asteroids, bogus, satellites, supernovae, and variable stars), using data from the Zwicky Transient Facility. We compare four scenarios: three with the same number of pixels (small field of view with high resolution, large field of view with low resolution, and a multiscale proposal) and a scenario with the full stamp that has a larger field of view and higher resolution. Compared to small field-of-view stamps, our multiscale strategy reduces misclassifications of satellites as asteroids or supernovae, performing on par with high-resolution stamps that are 15 times heavier. We encourage Rubin and its Science Collaborations to consider the benefits of implementing multiscale stamps as a possible update to the alert specification. © 2023. The Author(s). Published by the American Astronomical Society.Ítem NaCo polarimetric observations of Sz 91 transitional disc: a remarkable case of dust filtering(Oxford University Press, 2020-02) Mauco, Karina; Olofsson, Johan; Canovas, Hector; . Schreiber, Matthias R; Christiaens, Valentin; Bayo, Amelia; Zurlo, Alice; Caceres, Claudio; Pinte, Christophe; Villaver, Eva; Girard, Julien H.; Cieza, Lucas; Montesinos, MatıasWe present polarized light observations of the transitional disc around Sz 91 acquired with VLT/NaCo at H (1.7μm) and Ks (2.2μm) bands. We resolve the disc and detect polarized emission up to ∼0.5 arcsec (∼80 au) along with a central cavity at both bands. We computed a radiative transfer model that accounts for the main characteristics of the polarized observations. We found that the emission is best explained by small, porous grains distributed in a disc with a ∼45 au cavity. Previous ALMA observations have revealed a large sub-mm cavity (∼83 au) and extended gas emission from the innermost (<16 au) regions up to almost 400 au from the star. Dynamical clearing by multiple low-mass planets arises as the most probable mechanism for the origin of Sz 91’s peculiar structure. Using new L - band ADI observations, we can rule out companions more massive than Mp ≥ 8 MJup beyond 45 au assuming hot-start models. The disc is clearly asymmetric in polarized light along the minor axis, with the north side brighter than the south side. Differences in position angle between the disc observed at sub-mm wavelengths with ALMA and our NaCo observations were found. This suggests that the disc around Sz 91 could be highly structured. Higher signal-to-noise near-IR and sub-mm observations are needed to confirm the existence of such structures and to improve the current understanding of the origin of transitional discs.Ítem Stellar Properties for a Comprehensive Collection of Star-forming Regions in the SDSS APOGEE-2 Survey* Based on SDSS Data Releases 16 and 17.(American Astronomical Society, 2023-02) Román-Zúñiga, Carlos G.; Kounkel, Marina; Hernández, Jesús; Peña Ramírez, Karla; López-Valdivia, Ricardo; Covey, Kevin R.; Stutz, Amelia M.; Roman-Lopes, Alexandre; Campbell, Hunter; Khilfeh, Elliott; Tapia, Mauricio; Stringfellow, Guy S.; Downes, Juan José; Stassun, Keivan G.; Minniti, Dante; Bayo, Amelia; Kim, Jinyoung Serena; Suárez, Genaro; Ybarra, Jason E.; Fernández-Trincado, José G.; Longa-Peña, Penélope; Ramírez-Preciado, Valeria; Serna, Javier; Lane, Richard R.; García-Hernández D.A.; Beaton, Rachael L.; Bizyaev, Dmitry; Pan, KaikeThe Sloan Digital Sky Survey IV APOGEE-2 primary science goal was to observe red giant stars throughout the Galaxy to study its dynamics, morphology, and chemical evolution. The APOGEE instrument, a high-resolution 300-fiber H-band (1.55-1.71 μm) spectrograph, is also ideal to study other stellar populations in the Galaxy, among which are a number of star-forming regions and young open clusters. We present the results of the determination of six stellar properties (T eff, log g , [Fe/H], L/L ⊙, M/M ⊙, and age) for a sample that is composed of 3360 young stars, of subsolar to supersolar types, in 16 Galactic star formation and young open cluster regions. Those sources were selected by using a clustering method that removes most of the field contamination. Samples were also refined by removing targets affected by various systematic effects of the parameter determination. The final samples are presented in a comprehensive catalog that includes all six estimated parameters. This overview study also includes parameter spatial distribution maps for all regions and Hertzsprung-Russell ( log L / L ⊙ vs. T eff) diagrams. This study serves as a guide for detailed studies on individual regions and paves the way for the future studies on the global properties of stars in the pre-main-sequence phase of stellar evolution using more robust samples. © 2023. The Author(s). Published by the American Astronomical Society.