Martinez, C.
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Variability in Active Binaries: the stellar metallicity and activity correlation
Observational studies suggest that elemental abundances measured from stellar spectra can correlate with magnetic stellar activity: the changes in the cool spots fraction that covers the stellar surface during the activity cycle, may play a role varying the equivalent widths from many spectral lines. Therefore, studying the effects of magnetic activity on stellar spectra is an important step to understand how the stellar activity level can affect the spectroscopic determination of stellar parameters and chemical abundances. Parameters such as effective temperature, metallicity, and surface gravity are not only important for the characterization of stars themselves, but also for characterizing exoplanets, as the planetary radius and mass depend on the adopted properties of its host star. In this sense, binary systems are excellent laboratories to explore the abundance and stellar activity correlation because its tidally locked rotation may induce significant transformations in the stellar structure originating much higher levels of magnetic activity. In this contribution, we will present preliminary results of the spectroscopic and long-term periodicity analysis of a RS Canum Venaticorum (RS CVn) type system, an active binary consisting of a red giant primary star and an unseen main sequence secondary star. The study over the primary star is based on spectroscopic observations obtained in the framework of the HKα Project initiated by IAFE in 1999 and currently in progress.
Menezes, F.
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Physical Characteristics Correlations of Starspots on GKM Stars
Starspots, along with magnetic fields, serve as indicators for estimating stellar ages, as older stars exhibit reduced magnetic activity and fewer, smaller starspots compared to younger counterparts. The Sun and other main sequence stars have magnetic fields that permeate their interior and surface, and extend through the interplanetary medium, and are the main driver of stellar activity. One way to better understand stellar magnetic fields and activity is through the characterization of starspots properties. Using modeling of planetary transits in stellar light curves, it is possible to estimate the size, intensity, and position of spots on the stellar photosphere. Furthermore, with the characterization of the spots, it is possible to estimate their magnetic field with a linear relation to the flux deficit established with sunspots that were previously characterized. For our analysis, we used spots that were previously mapped on the photosphere of CoRoT-2, Kepler-17, Kepler-45, Kepler-63, Kepler-71, Kepler-210, Kepler-411, and KOI-883. We could establish correlations between starspots properties for different stellar ages, rotation period, and spectral types.
Cécere, M.
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QPPs in stellar and coronal loops
Fast sausage and standing slow modes in coronal loops are the most studied oscillation modes because their compressibility makes them susceptible to being observed. By performing magnetohydrodynamic numerical simulations, we analyse the capability of different types of disturbances associated with typical fluctuations in solar corona energy to generate these modes.
We investigate the modulation depth of gyrosynchrotron emission produced by these fast sausage modes. We analysed the synthetic emission from coronal and stellar loops and found that finite-amplitude sausage modes have the potential to generate the observed deep modulation depths.
Soto Vicencio, M.
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Proper motions on the far side of Galactic Bulge
This work is part of a series of papers that attempts to observe a clear signature of the Galactic bar/bulge using kinematic observations of the bulge stellar populations in low foreground extinction windows. We report on the detection of ∼100 000 new proper motions in four fields covering the far side of the Galactic bar/bulge, at negative longitudes. Our proper motions have been obtained using observations from the Advance Camera for Surveys (ACS), on board of the Hubble Space Telescope (HST), with a time-baseline of 8–9 years, which has produced accuracies better than 0.5 mas yr−1 for a significant fraction of the stellar populations with F814W < 23 mag. Interestingly, as shown in previous works, the Hess diagrams show a strikingly similar proper motion distribution to fields closer to the Galactic center and consistent with an old stellar population. The observed kinematics point to a significant bulge rotation, which seems to predominate even in fields as far as l ≃ −8◦, and is also reflected in the changes of the velocity ellipsoid in the l, b plane as a function of distance.
Parisi, C.
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The VISCACHA Survey: the contribution of the GMOS Trinational project
The GMOS trinational project, between Argentina, Brazil and Chile, has been in charge of the VISCACHA Survey spectroscopic follow up for the last seven years. It has provided relevant information for the kinematic, dynamic and chemical analysis of the SMC, using star cluster as tracers. In this talk I will summarize the results we have obtained using that information. I will also present the current status of projects in progress, observations and future plans of the VISCACHA collaboration.
Tapia-Reina, M.
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Astrophysical parameters and template spectra of Magellanic Clouds’ star clusters
Flux-calibrated integrated spectra have been obtained for a sample of 10 Magellanic Clouds (MCs) star clusters (SCs) at the Complejo Astronómico El Leoncito (CASLEO, San Juan, Argentina). The astrophysical parameters (age, reddening values and metallicity) were simultaneously derived using methods like equivalent width measurements, the template matching method and through evolutionary synthesis models for simple stellar populations (SSPs) for each SC. No metallicity determinations have been previously performed for most of the SC’s sample here studied. Ages for two SCs are determined here for the first time too (NGC 1826 y SL 573). On the other hand, the SSPs for each SC is analyzed and the presence of multiple stellar populations (MPs) is found in NGC 1866 confirming previous reports, and MPs are found in other SCs too. Finally, new templates representing 20 Myr, (100-160) Myr and 3000 Myr stellar populations were created by SC's integrated spectra observed in this sample.
Lunch
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Muñoz Arancibia, A.
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Exploring the changing sky with the ALeRCE community broker
The Automatic Learning for the Rapid Classification of Events (ALeRCE) is a Chilean-led astronomical alert broker that currently ingests the public stream from the Zwicky Transient Facility, which contains hundreds of thousands of alerts per night, providing classifications and visualization for the astronomical objects detected. In this talk I describe the ALeRCE project and its different science cases and tools, highlighting how it has enabled the follow-up and study of young supernovae and other transient objects. The advent of new surveys like the Asteroid Terrestrial-impact Last Alert System, and soon the Rubin Observatory Legacy Survey of Space and Time, opens a promising future for continuing the collaborative study of the changing universe.
Toscano, F.
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A CMB lensing analysis of the extended mass distribution of clusters
This study focuses on investigating the anisotropic weak lensing signal associated with the mass distribution of massive galaxy clusters. To do so, we analyze the Cosmic Microwave Background (CMB) data obtained from the Planck Collaboration CMB lensing convergence map (2018). Specifically, we examine patches of it centered on SDSS DR8 redMaPPer clusters within the redshift range [0.4, 0.5]. Using mean radial profiles, we detect a statistically significant signal up to 40 Mpc/h for the κ convergence parameter. Furthermore, by aligning the clusters along their major axis, determined by the distribution of galaxy members, we observe a notable distinction between parallel and perpendicular convergence profiles. On the other hand, by employing a model that implies an anisotropic surface mass density, we obtain results that agree with the mass and ellipticities of the clusters derived by weak lensing shear estimates. These findings provide strong evidence for a correlation between the distribution of galaxy cluster membership and the large-scale mass distribution
Racker, J.
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Baryogenesis at very low temperatures
We will discuss the motivations and quite general aspects of models for baryogenesis at very low temperatures, even as low as a few MeV, just before Big Bang nucleosynthesis.
Celiz, B.
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Galactic Stellar Haloes in ΛCDM simulations
Using the cosmological hydrodynamic simulation TNG50-1 we characterize stellar haloes (SHs) of galaxies with stellar mass in the range 8.0 ≲ log M*/M☉ ≲ 11.0 in a ΛCDM Universe. Defined as the accreted stellar component of a galaxy, our SHs encompasses the stars born ex-situ that are bounded to the host galaxy at redshift z = 0, up to the virial radius. We analyze the stellar halo density profile from isolated central galaxies and their correlation with intrinsic properties of the host galaxy, like kinematics, age and accreted mass ratio. The logarithmic slope of density profile shows a large scatter ranging -12 ≲ α ≲ -3 and i) it does not correlate with the total stellar mass M* for dwarfs galaxies but systematically increases for normal galaxies; ii) is inversely proportional to the SH rotation; and iii) is proportional to the median stellar age of the SH. These results aim to predict and compare simulated and observed SHs properties for galaxies with mass lower than the Milky Way or Andromeda, suggesting that the analysis of outer regions of galaxies could be insightful to unveil intrinsic properties of stellar population and the assembly history of galaxies in a wide range of mass.