Revista Mexicana de Astronomía y Astrofísica,
Accepted Papers for Volume 61 Number 1 (ADVANCE ACCESS)

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August 2024

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Abstract: A cyclic flat universe with quintom behavior and future big rip has been presented in the framework of Rastall gravity, which is an extension of the standard ΛCDM model. The Hubble parameter oscillates periodically between positive and negative values from one cycle to the next. Cosmic transit has been simulated through an oscillating time-dependent deceleration parameter, and is expected to occur at approximately 8.7 Gyr. The causality is satisfied all the time except near the initial singularity and the future Big Rip singularity.The apparent horizon, entropy and other thermodynamical quantities associated to the current model have been analyzed. Energy conditions have been investigated.

Abstract: We analyze the asymmetry and concentration parameters in a sample of late-type spiral galaxies using V and R broadband images. Asymmetry values were computed for different rotation angles and radii, revealing low asymmetry overall, with smaller values in inner regions. No preferred angle significantly affected asymmetry measurements. Concentration indices lie between those of large spirals and irregular galaxies. We compare our samples distribution in the C—A plane with other late-type systems (dwarfs and normal spirals). Additionally, we explore correlations between asymmetry and star formation rate, and between concentration and stellar mass, contrasting our results with prior studies.

Abstract: We present the Deep-learning Transient Astronomical Object (Deep-TAO), a dataset of 1,249,079 annotated images from the Catalina Real-time Transient Survey, including 3,807 transient and 12,500 non-transient sequences. Deep-TAO has been curated to provide a clean, open-access, and user-friendly resource for bench-marking deep learning models. Deep-TAO covers transient classes such as blazars, active galactic nuclei, cataclysmic variables, supernovae, and events of indeterminate nature. The dataset is publicly available in FITS format, with Python routines and Jupyter notebooks for easy data manipulation. Using Deep-TAO, a baseline Convolutional Neural Network outperformed traditional random forest classifiers trained on light curves, demonstrating its potential for advancing transient classification.

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April 2025

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Abstract: This study presents photometric analysis of the intermediate-age open cluster King 6, utilizing photometric data in UBV>(RI)_c passband and data from the 2MASS mission. The Gaia DR3 kinematic data were used to estimate the membership probabilities and TESS data is employed to search for variable stars within the cluster. The cluster's radius is estimated to be 9'.0 based on the stellar density profile, while optical and near-infrared color-color diagrams revealed color excesses of E(B − V) = 0.58 ± 0.03, E(J − K) = 0.24 ± 0.03, and E(V − K) = 1.53 ± 0.01 mag. Interstellar extinction law is normal in the direction of the cluster. The cluster's estimated age is ∼ 251 Myr and distance is 724 ± 5 pc. The mass function slope was found to be x = 0.57 ± 0.28 by considering stars ≥ 1 M_☉. Our analysis indicates that the cluster is dynamically relaxed. Furthermore, we identified three new variable stars for the first time in the cluster region using TESS data. These variables belong to the category of slow pulsating B-type variables, with periods of 46.70, 47.92, and 37.56 hours.

Abstract: We present a spectroscopic investigation of 25 objects previously reported as possible Planetary Nebulae (PNe) in recent catalogs to obtain their physical properties and to establish their true nature. We found 11 objects showing intense emission lines, 11 where it was not possible to measure Hβ, and three where no lines are present. We have used diagnostic diagrams to confirm the true PN nature for eight objects. We obtained elemental abundances for three objects whose values are in agreement with the PNe mean values for our Galaxy. Four objects show [N II] λ6583 more intense than Hα, and for two of them, this can be explained by the presence of shocks in the gas. Finally, we report angular sizes based on Hα and [O III] λ5007 emission.

Abstract: We present the construction and early results of ESPARTACO 2, the new stellar spectrograph built for research and education at the Astronomical Observatory of the Universidad de los Andes in Bogotá, Colombia. This instrument offers several resolutions from 20,000 in first order using a 50 μm fiber, to 100,000 in second order in the near infrared. Precise radial-velocity measurements are made possible by simultaneous wavelength calibration. Combined with the 40-cm Meade telescope located at our facilities, a limiting magnitude of 6 is reached. This instrument is a considerable improvement over its predecessor in throughput, reliability and ease.

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May 2025

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Abstract: Photometric data from TESS were analyzed to obtain the light curve, confirming that the orbital period (P = 11.307 ± 0.005 days) remains constant. A wavelet analysis was applied to detect temporal anomalies. The photometric effective temperature of HD 72968 was estimated through colorimetry, comparing it with main-sequence stars. UVES spectra were analyzed, Doppler-corrected, and normalized using Chebyshev functions. A theoretical spectral grid generated with SPECTRUM and ATLAS9 was fitted using the chi-squared method. A comparison with UVES-ESO spectra refined the temperature estimate of HD 72968. The analysis of the spectral energy distribution (SED) enabled the derivation of stellar parameters, validating the models employed. These results provide new insights into the atmosphere and variability of HD 72968 and motivate further spectral studies for improved stellar modeling.