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First direct detection of an RR Lyrae star conclusively associated with an intermediate-age cluster

2026-05-13T15:24:13Z

Título: First direct detection of an RR Lyrae star conclusively associated with an intermediate-age cluster Autor: Mateu, Cecilia; Cuevas-Otahola, Bolivia; Downes, José Resumen: Context. RR Lyrae stars have long been considered unequivocal tracers of old (>10 Gyr) and metal-poor ([Fe/H] < −0.5) stellar populations. First, because these populations is where they are readily found and because, according to canonical stellar evolution models for isolated stars, these are the only populations where RR Lyrae are expected to exist. However, recent independent results are challenging this view and pointing to the existence of intermediate-age RR Lyrae (i.e. only about 2-5 Gyr old). Aims. Our goal in this work is to provide direct evidence of the existence of intermediate-age RR Lyrae by searching for these stars in Milky Way open clusters, where the age association would be direct and robust. Methods. We searched a catalogue of over 3000 open clusters with published kinematically associated member stars by cross-matching it against a compilation of the largest publicly available RR Lyrae surveys (Gaia, ASAS-SN, Pan-STARRS1, Zwicky Transient Facility, and OGLE-IV). Results. We identified a star as a bona fide RR Lyrae variable and robust member of the 2-4 Gyr old Trumpler 5 cluster, based on its parallax and proper motions and their agreement with confirmed cluster members. We derived an extremely low probability (0.049 ± 0.013%) of the star being a background field RR Lyrae and we provide initial constraints on a possible binary companion based on its position in the colour-absolute-magnitude diagram. Conclusions. As a current source of debate, the Trumpler 5 RR Lyrae star provides the most direct evidence to date of the existence of RR Lyrae stars at much younger ages than traditionally expected, adding to the mounting evidence supporting their existence.

Evolution of extreme Madden-Julian Oscillation events and their impacts on South America.

2026-05-13T14:17:03Z

Título: Evolution of extreme Madden-Julian Oscillation events and their impacts on South America. Autor: Minjares, Mónica; Corral, Álvaro; Barreiro, Marcelo Resumen: This study examines the evolution of extreme Madden-Julian Oscillation (MJO) events and their impacts on South America during the austral summer. Furthermore, the study explores how the different ENSO phases modulate extreme MJO events, and how the combined effects impact South American climate. Extreme MJO events are defined as those exceeding a specific threshold based on the events distribution, distinguishing them from weak events. Our analysis shows that extreme MJO events most frequently initiate in phases 2-3 throughout the year, with similar distributions across phases 8-1, 6-7, and 4-5. This distribution is also characteristic of winter, while in summer, initiation is more balanced between phases 2-3 and 8-1. In contrast, weak events predominantly start in phases 4-5 year-round, followed by phases 2-3, with phases 8-1 and 6-7 occurring at similar frequencies. Seasonally, weak event initiation prevails in phases 4-5 during summer, while in winter, it is evenly distributed between phases 8-1 and 4-5. Additionally, during La Niña, extreme events tend to last longer than during El Niño, a pattern not observed in weak events. A composite analysis of outgoing longwave radiation (OLR), eddy streamfunction, and velocity potential was conducted, with particular focus on the initiation phases 2-3 and 6-7 to determine which phases result in the most significant impacts and how the associated anomalies evolve. The findings show that enhanced (suppressed) convection centers in the equatorial region during extreme events are more intense and exhibit a southeastern displacement compared to those during weak events. These extreme MJO events influence the South American rainfall Dipole (SAD), a key feature of regional climate variability and results show that extreme MJO events induce more intense rainfall anomalies of larger spatial extent compared to weak events. This is because extreme events are characterized by dominant tropical-extratropical teleconnections, whereas weak events primarily feature tropical-tropical teleconnections. Also, as extreme events last longer, events that start in phases 2-3 influence the evolution of the SAD during the following phases, suggesting increased predictability of rainfall over South America.

Code in motion: integrating computational thinking with kinematics exploration

2026-05-13T14:16:52Z

Título: Code in motion: integrating computational thinking with kinematics exploration Autor: Dutra, Mateo; Suárez, Álvaro; Martí, Arturo Resumen: Although physics has become increasingly computational, with computing even being considered the third pillar of physics [1], it is still not well integrated into physics education [2]. Research suggests that integrating Computational Thinking (CT) into physics enhances conceptual understanding and strengthens students' ability to model and analyze phenomena [3]. Building on this, we designed a didactic sequence for K9 students to foster specific CT practices while reinforcing fundamental kinematics concepts. The activity revealed students’ ability to apply CT skills and is well suited for use in introductory kinematics courses.

Enhancing kinematics understanding through a video game based on real- time motion graphs

2026-05-13T14:16:37Z

Título: Enhancing kinematics understanding through a video game based on real- time motion graphs Autor: Dutra, Mateo; Abreu, Marcos; Monteiro, Martín; Sguilla, Silvia; Stari, Cecilia; Suárez, Álvaro; Martí, Arturo Resumen: Interpreting kinematic graphs remains a significant challenge in physics education. The MissionMotion Project addresses this issue by providing a gamified physical-computational environment combining low-cost sensors, physical activity, computational thinking, and real-time visualization of motion graphs. This paper presents the design, development, and implementation of the project, with a particular focus on the pilot phase conducted with high school students in Uruguay. During this phase, we primarily used the MEEGA+ questionnaire to evaluate the gaming experience, usability, and motivation of the participants. Our analysis of the results shows high levels of satisfaction, perceived learning, and engagement, supporting the proposal's viability. Finally, we plan to conduct a large-scale conceptual evaluation to analyze how the proposal impacts understanding of kinematic graphs using standardized assessment tools.