Martin Román Ciro
GAIA photometry for four open clusters
As part of the course ”Astrofísica General” (FaMAF, UNC), the age, distance, reddening, and metallicity of four open clusters in the Galaxy are presented. The determination of these astrophysical parameters was carried out using GAIA data, through the detailed fitting of theoretical isochrones to their respective color-magnitude diagrams (G_BP − G_RP , G). The results obtained are compared with those derived by other authors, and a discussion on the findings is presented.
Krilich Tomás
Spectroscopic characterization of Wolf-Rayet Stars within Open Cluster Danks 1 (Undergrad)
Wolf-Rayet (WR) stars are evolved, massive stars that play a key role in stellar evolution and feedback in galaxies. However, their physical properties remain poorly constrained, particularly in open clusters, where environmental effects can be assessed. In this work, we present the first results of our study on WR stars in open clusters, based on CASLEO spectroscopic observations.
Macaroff Tadeo, Hormaeche Camila, Ferreira Guido Javier
GAIA photometry for four open clusters (Undergrad)
As a continuation of Callen et al. (2024), in the context of the course “Astrofísica General” (FaMAF, UNC), the age, metallicity, distance and color excess E [G-GRP] were determined for four galactic open clusters (OC) (Fig. 1). These astrophysical parameters were obtained through the photometric data of GAIA’s DR3 and adjusting theoretical isochrones to each OC’s Color-Magnitude Diagram (G-GRP, G) .
Macaroff Tadeo, Hormaeche Camila, Ferreira Guido Javier
Direct imaging from EABA
As part of the course ‘Astrometría General’ (FAMAF-UNC), three astronomical objects were imaged from Estación Astrofísica de Bosque Alegre (EABA): NGC 6522 (globular cluster), CD-2410977 (symbiotic star) y PKS 1510-08 (radio quasar), with the V, R and I filters. The purpose of this work is to carry out a complete observational technique, from the planning, the observation time proposal, the acquisition of the images, their processing, the determination of instrumental magnitudes, their transformation to a standard system and ultimately the comparison of the results with existing literature.
Colazo Agustina
Evolution of central galaxy alignments in IllustrisTNG simulations
Previous studies indicate that the alignment between the central galaxies’ shape and the distribution of matter in their surroundings strongly depends on their color. Also, these alignments evolve very differently when considering the stellar component of the central galaxy or its dark matter halo. Motivated by these results, we aim to deepen the analysis of how various astrophysical processes influence central galaxy alignments with the matter distribution. In this context, we concentrate on the role of mergers in the alignment between the baryonic component and the dark matter. In this work, we use the brightest central galaxies in groups selected at z = 0 in the IllustrisTNG 300 hydrodynamic simulation then we follow the main branch of the central galaxies’ merger tree to study the evolution of the alignment between the shape of the stellar component and the shape of the halo, as well as how the angle between the semi-axes of the central galaxy’s shape tensor and its angular momentum changes over time.
Baracchi Marcos
From Hot Jupiters to Earth-like Planets: Characterizing Exoplanetary Atmospheres with JWST and POSEIDON (PhD)
In this work, we studied and characterized the chemical composition of the atmosphere of five exoplanets: WASP-39b, WASP-107b, HD 189733b, K2-18b, and GJ 1132b. These planets cover a wide range of masses, from 1.13 Jupiter masses in the case of HD 189733b to less than 2 Earth masses for GJ 1132b. The five planets were observed, some on multiple occasions, with the James Webb Space Telescope, which provides the highest-quality transmission spectra currently available for the study of exoplanetary atmospheres. These spectra were analyzed using the POSEIDON code, which allows us to study the atmosphere under different scenarios: isoquimic abundance, thermochemical equilibrium, and tidal locking. We determined the scenario that best reproduces the observed spectrum and, from there, derived the atmospheric chemical composition, the detection significance of each molecule and/or atomic element, and their relative abundances.
Martinez-Bezoky Alejandra
Exploring NGC 6316: Spectral Synthesis with CASLEO and WAGGS spectra (Undergrad)
This work presents an analysis based on optical spectra of the galactic globular cluster NGC 6316. Observations were carried out at CASLEO using integrated spectroscopy and data reduction was performed to subsequently determine the cluster’s age, metallicity, and possible multiple stellar populations through spectral synthesis. The obtained results are analyzed and compared with a study we previously carried out, in which these parameters were derived by means of spectral synthesis from the spectrum of NGC 6316 from WAGGS.
Dominguez Feldman Juan Ignacio
Relation between CMB and filamentary structures (Undergrad)
We study the relation between the CMB, in particular the temperature map of the 2018 planck release (PR3) and one of the main constituents of the cosmic web, the cosmic filaments. In particular we aim at analysing foregrounds associated to these structures in this universe and the CMB. We consider subsamples of filaments, taking into account different properties such as length and mass per unit length.
Colombo Priscila Daiana
Activity cycles in fast rotating solar-type stars (PhD)
Systematic observational studies carried out so far, mainly dedicated to solar-type stars in the F to early K range, have detected magnetic activity cycles similar to the solar cycle. By analysing the length of the activity cycles in these stars as a function of stellar parameters such as the star’s rotation rate, it has been detected that this relationship is not univocal but that the activity periods are distributed discreetly in a series of branches (inactive and active). Even been discovered that some solar-type stars, with rotation periods shorter than the solar one, present two coexisting activity cycles distributed in the two branches simultaneously. In this work, we analyse the activity records of a set of 29 stars, with rotation periods between 3 and 20 days, with the ultimate goal of detecting single or double activity cycles. Of the set of stars analyzed, we detected activity cycles in 14 stars, of which 5 presented double activity cycles.
Gómez Mercedes
Physical Properties of Open Galactic Clusters with Planets (Researcher)
In this contribution we present an analysis of the physical properties of a simple of ten open stellar clusters harboring planets. In particular, we consider parameters such as stellar density, age, metallicity in order to search for correlation with the presence of exoplanets. We also inspect physical characteristics (mass, temperature, luminosity, etc.) of cluster stellar members with confirmed planets and properties of planets.
Callen Ailen
Brown dwarfs: characterizing the bridge between stars and planets (PhD)
Brown dwarfs are compact objects that do not reach a high enough internal temperature to produce sustained hydrogen fusion over time. This means that their interior is dominated by degenerate electron gas, which makes them peculiar objects, different from both planets and stars. However, in terms of their mass, brown dwarfs are in the range between 13 − 80Mjup, placing them between both groups.
In this context, the complex relationship between color indices and spectral type of brown dwarfs is explored, and two machine learning algorithms are proposed to estimate the spectral type using only photometric data. With these algorithms, it was possible to determine an approximation of the spectral type for 21 brown dwarfs that did not have a previous classification in the literature.
Gramajo Luciana
The interplay between binary systems and stellar clusters (Researcher)
Binary stars play a fundamental role in understanding stellar populations, formation, and evolution within star clusters. In this study, we investigate eclipsing binary (EB) candidates detected in a near-infrared window of the VVV Survey, focusing on their potential membership in nearby young star clusters. Using Gaia DR3 and VVV data, we analyzed the kinematics and photometry of two open clusters, associated with EBs identified in the VVV and ASAS-SN datasets. Additionally, we modeled the light curves of the newly identified ASAS-SN binaries using the PHOEBE code in the V-band. Our analysis aims to assess the physical connection between these EBs and their host clusters, contributing to a better understanding of cluster dynamics and binary system evolution. In this contribution we present our preliminary findings on cluster membership and characterization, providing valuable insights into the interplay between binary systems and stellar environments.
Parisi Celeste
The VISCACHA Survey: The SMC Southern Bridge in 8D and its comparison with the Northern Bridge (Researcher)
The structure of the Small Magellanic Cloud (SMC) outside its main body is characterized by tidal branches resulting primarily from its interactions with the Large Magellanic Cloud (LMC). Characterizing the stellar populations in these tidal components helps to understand the dynamical history of this galaxy and the Magellanic system in general. We provide full phase-space vector information for clusters in one of these tidal branches, the Southern Bridge. We performed a photometric and spectroscopic analysis of 12 SMC clusters, doubling the number of SMC clusters with full phase-space vector information known to date. Our analysis reveals that Southern Bridge clusters are moving towards the LMC and share the kinematics of the Northern Bridge (another SMC outer tidal structure). Adding clusters from the literature with CaT metallicity determinations to our sample, we compare the age–metallicity relation of the Southern Bridge with that of the Northern Bridge. We reinforce the idea that both regions do not seem to have experienced the same chemical enrichment history and that there is a clear absence of clusters in the Northern Bridge older than 3 Gyr and more metal-poor than −1.1, suggesting that these clusters have been removed from the main body of the SMC by tidal forces.
Parisi Celeste
Infrared Photometry and CaT Spectroscopy of the Most Metal-Poor Bulge Globular Cluster VVV-CL001
Globular Clusters (GCs) are among the oldest structures in the Universe, with ages ranging from 10 to 13 Gyr, and are considered key tracers of the formation and evolution of galaxies. The study of GCs provides valuable information about the age, metallicity, kinematics, and dynamics of their host galaxies. The total number of GCs in the Milky Way remains uncertain, with estimates exceeding 200. This uncertainty arises from the fact that GCs are distributed throughout the halo, bulge, and disk of the galaxy and are often obscured by interstellar dust and gas. As a result, many well-studied GCs are located in the halo, where extinction is lower and observations are more straightforward. In contrast, GCs in dust- and gas-rich regions, such as the bulge and disk, are more difficult to observe in the optical spectrum, so it is necessary to resort to wavelengths that can penetrate dust and gas, such as near-infrared (NIR). In this work, we present a detailed analysis of the GC VVV-CL001 using NIR spectroscopic data from the FORS2 instrument on the VLT (Very Large Telescope), astrometric data from Gaia EDR3 (Gaia Early Data Release 3), and photometric data from the VVV survey, 2MASS, and the FourStar instrument on the Magellan Baade Telescope. We will present our main results concerning the analysis of this bulge GC.
Oviedo Carla
Stellar cycles in HD 147379 and HD 095735 with SOPHIE (PhD)
Stellar variability poses a challenge for the detection and characterization of exoplanets, particularly in radial velocity (RV) studies. In this study, we analyze stellar activity in HD 147379 and HD 095735 using high-resolution spectra from the SOPHIE spectrograph. To characterize their stellar cycles, we apply the GLS and Lingls methods to the Mount Wilson and Hα activity indices. We complement this analysis with TESS photometry, enabling the determination of rotation periods and the detection of flares, key factors for correctly interpreting RV signals.
Saker Leila
Timescale for gas dissipation in white dwarfs debris disks (Researcher)
In the late 80s, infrared (IR) excesses were detected around a white dwarf star (WD) which was attributed to the presence of a circumstellar disk of dust. In recent years, the number of WDs with excesses has increased significantly: about 60 WDs are now known to have confirmed IR excesses. Additionally, disks of gas have been found in about 1/3 of WDs with debris disks. However, it is not certain the duration of the gas in the disk. In this contribution we determine the total ages of both white dwarfs with only dusty disks and with dust and gas disks. Constraining the duration of gas in the disk is relevant to confront current scenarios for the origin of gas and also dust in WD disks. We also explore the implications of these findings for our understanding of the late stages of stellar evolution of planetary systems around WDs.
Saker Leila
Searching for signals of transiting planets in the TESS light curves of white dwarfs with dust disks
Around 97% of stars are expected to end their life cycle as white dwarfs, making them the most prevalent type of stellar remnants in our Galaxy. A small fraction, about 1-3%, of these white dwarfs exhibit an infrared excess due to the presence of a circumstellar dust disk, which is being accreted by the star. This debris disk is the result of tidal disruption caused by rocky planetesimals that once formed part of a planetary system. In this work, we present a photometric analysis using data from the TESS space mission of a small sample of white dwarfs with dust disks, aiming to detect potential transit events of rocky bodies that have endured through the star’s evolution.
Lopez Claudio
Clustering of Obscured and Unobscured IR-selected AGN at z~1 with Subaru HSC-SSP (PhD)
Recent studies using data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) have reported surprising evidence that unobscured active galactic nuclei (AGN) at z~1 reside in denser environments and more massive dark matter halos than their obscured counterparts. To further investigate this discrepancy, we employ an independent AGN selection and a novel set of tools for cross-matching, masking, and efficient spatial correlation analysis. Using photometric redshifts, we measure the cross-correlation of type 1 and type 2 AGN with luminous red galaxies in HSC-SSP. Our findings confirm the striking difference in clustering between the two AGN populations and provide new constraints on the 1-halo term to potentially improve the halo occupation distribution (HOD) modeling. This will help refine our understanding of AGN distribution within dark matter halos.
Garcia Ana Laura
Photometric analysis of 10 galactic open clusters (Undergrad)
We present preliminary astrophysical parameters for 10 galactic open clusters. Age, reddening, distance, and chemical abundance, were derived from fitting theoretical isochrones to colour-magnitude diagrams made with photometric data from the GAIA mission. We discuss the results obtained in relation to the location of these aggregates in the Galaxy and to those determined by other authors.
Diaz Margionet
Statistical characterization of the wake generated by the Magellanic Clouds on the stellar halo of the Milky Way (PhD)
When a massive body moves through a field of particles (such as dark matter or stars), its gravity perturbs the medium. The particles in the field are attracted to the moving body, creating a concentration of matter, or “wake,” behind it.
In the case of the Magellanic Clouds’ infall into the Milky Way, this wake has been detected in stars of the stellar halo of our Galaxy using Gaia DR2 (Conroy et al., 2020; Peñarrubia, 2022) and DR3 (Fushimi et al., 2024). The shape and intensity of this wake are strongly influenced by the nature of dark matter in both the halo and subhalo of the Milky Way (Foote et al., 2021), and its properties can be characterized through the angular power spectrum (Cunningham et al., 2020).
In this work, we determine the angular power spectra of the density and velocity distributions for stars in the halo associated with the Magellanic Clouds’ wake. We then compare our results with simulations of cold dark matter to evaluate their consistency with different dark matter models.
Perez Noelía Rocío, Coldwell Georgina
Obtaining HOD parameters using genetic algorithms (PhD – Researcher)
The Halo Occupation Distribution (HOD) describes the galaxy bias with a fixed characteristic through the probability function that a halo of mass M contains N galaxies (Peacock & Smith, 2000; Berlind & Weinberg, 2002; Berlind et al., 2003).Zheng et al. (2005) proposed a HOD parameterisation with five free parameters to describe the contribution of central and satellite galaxies to the HOD.
Throughout history, organisms have evolved through natural selection, where those that do not adapt to the environment disappear (Darwin, 1859; Goodwin, 1982). This idea inspired the development of evolutionary algorithms, such as genetic algorithms, to solve optimisation problems (Baeck et al., 1997). These algorithms work with a population of possible solutions and, through biological processes such as crossover and mutation, generate new populations to find better solutions to the problem.
Genetic algorithms have proven to be effective tools to address and solve various problems in the field of astronomy (Mokiem et al., 2005; Rajpaul, 2012; De Geyter et al., 2013; Macdonald et al., 2017; Carpintero and Melita, 2018; McWhirter et al., 2018) which evidences the versatility and effectiveness of this methodology.
In the present work, we search for the five parameters that describe the HOD by means of genetic algorithms.
Gianuzzi Emmanuel
Analysis of Triple Stellar Systems Catalogue (PhD)
This study investigates the properties of triple star systems using the latest version of the Multiple Star Systems Catalogue (MSC) as of January 1, 2024. The analysis involves data cleansing and exploration to derive distributions of mass, orbital periods, semimajor axes, and eccentricities. The findings contribute to a better understanding of the statistical properties of hierarchical triple systems. We also discuss the potential for some of these systems to host a circumbinary planet, considering their orbital configurations and dynamical stability.
Quijano Vodniza Alberto
THE COMET C/2023 A3 (TSUCHINSHAN-ATLAS)
Introduction: The comet, scientifically named C/2023 A3-(Tsuchinshan-ATLAS), likely originates from the Ort cloud due to its highly elongated orbit. It was discovered in 2023 as it approached the inner solar system, and was simultaneously recorded by astronomers at the Tsuchinshan Observatory in China and the ATLAS system in South Africa. The comet had its closest approach to the Sun on September 27/2024, at a distance of 0.391 A.U , and passed 0.938472 A.U from Earth on October 12/2024. Initially some astronomers thought that the comet would not survive the encounter with the Sun, as happened with Comet ISON in 2013, but fortunately these predictions did not come true . The comet acquired greater brightness than estimated by some astronomers, and could be observed with the naked eye. The physical-chemical activity of the comet when it approached the sun was great, which is why it was dubbed by some media as the “Comet of the Century”. On October 10, when the comet was located between the Earth and the Sun, its brightness increased considerably, and it had a total apparent magnitude m=-4.9. Unfortunately on that date, in Colombia it was below the horizon. The comet is currently moving away from the sun and its orbit is open, as can be seen in the orbital parameters that I calculated based on several astrometric observations.
Methodology: I observed the comet from September 23/2024 to November 25/2024. Stages of observation of the comet: a) I took several photos at dawn with a professional Canon camera from my house located in the city of Pasto -Nariño-Colombia (1.213611° N, 77.281111° W, 2527 meters above sea level). Date: September 23/2024. b) At dawn and from the Astronomical Observatory of the University of Nariño (located in the same city), when the height of the comet with respect to the horizon increased. Dates: September 24 to 27/2024. c) At dusk ,from the town of Chachaguí, near Pasto, (1.4269° N, 77.2891° W, 1900 meters above sea level ), since the comet was at low altitude in the area “covered” by the Galeras – Pasto volcano. I took photos with a professional Canon camera. Dates: October 13 and 14/2024. d) At dusk from the Astronomical Observatory of the University of Nariño, when the height of the comet was already adequate. Dates: October 15 to November 25/2024. Some of my images are published on the SPACE-WEATHER webpage.
From our Observatory, located in Pasto-Colombia, I captured several pictures and videos during two months. I made photometry and astrometry measurements of the comet. The images of the asteroid were captured with the following equipment: CGE PRO 1400 CELESTRON (f/11 Schmidt-Cassegrain Telescope) and STL-1001 SBIG camera. I also used a professional Canon EOS 20D camera.
Conclusions: I obtained the following orbital parameters of the comet: eccentricity = 1.0009999, orbital inclination = 139.1204°, longitude of the ascending node = 21.56338°, argument of perihelion = 308.48555°, perihelion distance = 0.39098645 A.U. The parameters were calculated with RMS error = 0.210 arc seconds. The light curve of the comet was also designed.
Machuca Yasmin
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Simondi Romero Federico
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Caporaso Franco
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Ahumada Andrea – (Researcher)
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Event Timeslots (1)
Wednesday
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