LARIM 2023

#056 | Revised distances for blue horizontal-branch stars based on SDSS photometry

Fabrícia Barbosa ¹ ; Rafael Santucci ² ; Silvia Rossi ¹ ; Guilherme Limberg ¹

1 - Instituto de Astronomia, Geofísica e Ciências Atmosféricas - IAG/USP. 2 - Universidade Federal de Goiás - UFG.

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#058 | Metallicity and age effects on lithium depletion in solar analogues

Giulia Martos ¹ ; Jorge Meléndez ¹ ; Anne Rathsam ¹ ; Gabriela Carvalho Silva ¹

1 - Universidade de São Paulo.

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#074 | Precision spectroscopy in stellar astrophysics, the star-planet connection and Galactic archaeology

Jorge Meléndez ¹

1 - Instituto de Astronomia, Geofísica e Ciências Atmosféricas - Universidade de São Paulo.

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#088 | Correlation between the surface faculae to spot ratio coverage and the magnetic field activity in Sun-like stars

Eliana M. Amazo-Gomez ¹ ; Arjit S. Banerjee ² ; Katja Poppenhaeger ¹

1 - Leibniz Institute for Astrophysics AIP. 2 - Indian Institute of Science Education and Research.

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#106 | Is the oldest planetary nebula really a member of the open cluster M37?

Vasiliki Fragkou ¹ ; Quentin Parker ² ; Roberto Vazquez ³ ; Laurence Sabin ³ ; Jackeline Suzett Rechy-Garcia ¹ ; Denise R. Gonçalves ¹

1 - Valongo Observatory, Federal University of Rio de Janeiro. 2 - The University of Hong Kong. 3 - Universidad Nacional Autónoma de México.

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#125 | Metallicity effects on the Age-Chromospheric activity diagram

Gabriela Carvalho Silva ¹ ; Jorge Meléndez ¹ ; Giulia Martos ¹

1 - Universidade de São Paulo.

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#134 | Exploring the uncertainties in mixing processes of low-mass stars: Preliminary results

Martín Miguel Ocampo ¹ ; Marcelo Miguel Miller Bertolami ¹ ; Leandro Althaus ¹

1 - Instituto de Astrofísica de La Plata, CONICET-UNLP.

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#136 | The influence of the Zeeman effect on radial velocity variations in solar-type stars

Augusto de Paula Baldo ¹ ; Luan Ghezzi Ferreira Pinho ¹ ; Raphaelle Haywood ²

1 - UFRJ - Observatório do Valongo. 2 - Exeter University.

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#148 | Massive Stars in Low-Metallicity Environments: Observations vs. Models

Júlia Camões Alves ¹ ; Wagner Luiz Ferreira Marcolino ¹

1 - Observatório do Valongo - UFRJ.

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Abstract:

Massive stars are extremely rare compared to solar-type stars and, their evolutionary paths, are still not well understood. They are progenitors of supernovas, neutron stars, black holes, gamma-ray bursts and are possible future sources of gravitational waves. Therefore, the understanding of their physical properties is a fundamental question for stellar astrophysics. This project aims to investigate the correlation between the wind's strength with the environment's metallicity. We expect that the winds will be more intense in higher metallicities, as these stars have line-driven winds — driven by the transference of momentum from their UV radiation field to metal lines. Even though observations agree with the theory for high-luminosity stars, there is no clear correlation in the low-luminosity regime (log L/Lsun < 5.0). Therefore, we will explore the wind-luminosity relation to evaluate the strength of the wind for different metallicity environments, by comparing stars from the Milky Way, the Large Magellanic Cloud, and the Small Magellanic Cloud. We will use CMFGEN, a stellar atmosphere code that is able to model the spectra of OB stars allowing the determination of the wind's intensity. Our initial sample consists of 11 observed spectra from the Very Large Telescope/X-Shooter Spectrograph and the Hubble Space Telescope COS and STIS spectrographs, obtained from the XShootU collaboration. In our methodology, we (i) estimate the main photospheric parameters by using an algorithm that searches for the best fits to an observed spectrum from a grid of models; (ii) analyze the wind features from the observed UV/HST spectra and (iii) obtain the stellar luminosity from the SED fit. We will present the model fits to the observed optical and UV spectra from the stars. The physical properties derived from the atmospheric analysis will be discussed in the context of wind strengths at different metallicities and compared with recent literature results.

#153 | Fine Structure of the Age-Chromospheric Activity Relation in Solar-Type Stars

Paulo Vitor Souza dos Santos ¹ ; Gustavo Frederico Porto de Mello ¹ ; Diego Lorenzo de Oliveira ² ; Erica Costa Bhering ¹ ; Felipe Almeida Fernandes ³ ; Ignasi Ribas ⁴

1 - Observatorio do Valongo - UFRJ. 2 - Laboratorio Nacional de Astrofisica. 3 - Universidade de Sao Paulo. 4 - Institut de Ciencies de lEspai.

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#157 | Dynamos in partially convective M-dwarfs

Bárbara Toro Velásquez ¹ ; Petri Käpylä ² ; Carolina Ortiz Rodriguez ¹ ; Felipe Navarrete ³ ; Dominik Schleicher ¹ ; Juan Pablo Hidalgo ¹

1 - Universidad de Concepción. 2 - Leibniz-Institut für Sonnenphysik (KIS), Schöneckstr. 6. 3 - Nordita, KTH Royal Institute of Technology and Stockholm University.

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#160 | Core-dynamo simulations of A-type stars

Juan Pablo Hidalgo ¹ ; Petri Käpylä ² ; Carolina Ortiz-Rodriguez ¹ ; Felipe Navarrete ³ ; Dominik Schleicher ¹ ; Bárbara Toro-Velásquez ¹

1 - Universidad de Concepción. 2 - Leibniz-Institut für Sonnenphysik. 3 - Universität Hamburg.

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#169 | Abundances of Bioessential Elements on Solar-type Stars Using High Resolution Spectra

Ellen Costa-Almeida ¹ ; Luan Ghezzi ² ; Katia Cunha ³

1 - Observatório Nacional. 2 - Universidade Federal do Rio de Janeiro. 3 - University of Arizona.

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#181 | O Vz stars in low-metallicity environments in the Magellanic Clouds

Leidy Arango ¹ ;

Julia Arias ¹

1 - Universidad de La Serena.

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#205 | Detailed spectroscopic analysis of F G K stars in open clusters and field.

Angela Catalina Franco Becerra ¹ ; Orlando Jose Katime Santrich ² ; Nelson Vera Villamizar ¹

1 - Universidad Pedagogica y Tecnologica de Colombia. 2 - Universidade Estadual de Santa Cruz.

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#218 | Asteroseismic catalogue of \textit{Kepler} Red Giants

Francisca Espinoza-Rojas ¹ ; Saskia Hekker ¹ ; Quentin Coppée ¹ ; Jeong Yun Choi ¹

1 - Heidelberg Institute for Theoretical Studies (HITS gGmbh).

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#243 | Chromospheric and Coronal Activity and Its Dependence on Rotation in Praesepe and the Hyades

Alejandro Núñez ¹ ; Marcel Agüeros ¹ ; Jason Curtis ¹ ; Kevin Covey ² ; Stephanie Douglas ³ ; Stanislav DeLaurentiis ¹ ; Jeremy Drake ⁴ ; Minzhi Wang ¹ ; Sabine Chu ⁵

1 - Columbia University. 2 - Western Washington University. 3 - Lafayette College. 4 - Center for Astrophysics. 5 - Massachusetts Institute of Technology.

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Abstract:

Low-mass ($\lesssim 1.2 M_\odot$) main-sequence stars lose angular momentum over time, leading to a decrease in their magnetic activity. The details of this rotation--activity relation between remain poorly understood, however. Using observations of members of the $\approx$700 Myr-old Praesepe and Hyades open clusters, we aim to characterize the rotation--activity relation for different tracers of activity at this age. To complement published data, we obtain new optical spectra for 250 Praesepe stars, new X-ray detections for ten, and new rotation periods for 28. These numbers for Hyads are 131, 18, and 137, respectively. The latter increases the number of Hyads with periods by 50\%. We use these data to measure the fractional $\mathrm{H}\alpha$ and X-ray luminosities, $L_{\mathrm{H}\alpha}$/$L_{\mathrm{bol}}$ and $L_{\mathrm{X}}$/$L_{\mathrm{bol}}$, and to calculate Rossby numbers. We find that at $\approx$700 Myr almost all M dwarfs exhibit $\mathrm{H}\alpha$ emission, with binaries having the same overall color--$\mathrm{H}\alpha$ equivalent width distribution as single stars. In the Rossby--$L_{\mathrm{H}\alpha}$/$L_{\mathrm{bol}}$ plane, unsaturated single stars follow a power-law with index $\beta = -5.9$$\pm$$0.8$ for Rossby $>0.3$. In the Rossby--$L_{\mathrm{X}}$/$L_{\mathrm{bol}}$ plane, we see evidence for supersaturation for single stars with Rossby $\lesssim$ 0.01, following a power-law with index $\beta_\mathrm{sup} = 0.5^{+0.2}_{-0.1}$, supporting the hypothesis that the coronae of these stars are being centrifugally stripped. We find that the critical Rossby value at which activity saturates is smaller for $L_{\mathrm{X}}$/$L_{\mathrm{bol}}$ than for $L_{\mathrm{H}\alpha}$/$L_{\mathrm{bol}}$. Finally, we observe an almost 1:1 relation between $L_{\mathrm{H}\alpha}$/$L_{\mathrm{bol}}$ and $L_{\mathrm{X}}$/$L_{\mathrm{bol}}$, suggesting that both the corona and the chromosphere experience similar magnetic heating.

#252 | Detailed chemical composition of solar analogues with and without planets

Marilia Carlos ¹ ; Anish Amarsi ¹

1 - Uppsala University.

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#255 | Core-Collapse Supernova Progenitors from Light Curves and Stellar-Evolution Models

Melina Bersten ¹

1 - IALP-FCAGLP.

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#258 | Determination of Fundamental Parameters of Wolf-Rayet Stars in Eclipsing Binary Systems

Tomás Ansín ¹ ; Roberto Gamen ²

1 - Facultad de Ciencias Astronómicas y Geofísicas, UNLP. 2 - Instituto de Astrofísica de La Plata, CONICET-UNLP.

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#289 | Unveiling the evolutionary states of B supergiant stars

Julieta Paz Sánchez Arias ¹ ; Péter Németh ¹ ;

Elisson Saldanha da Gama de Almeida ² ; Matias Agustin Ruiz Diaz ³ ; Michaela Kraus ¹ ; Maximiliano Haucke ⁴

1 - Astronomical Institute of the Czech Academy of Sciences. 2 - Instituto de Física y Astronomía/Universidad de Valparaíso. 3 - Instituto de Astrofísica de La Plata (CONICET-UNLP). 4 - Universidad Nacional Arturo Jauretche.

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Abstract:

We analyzed three blue supergiants (BSG) in this study: HD\,42087 (PU\,Gem), HD\,52089 ($\epsilon$\,CMa) and HD\,58350 ($\eta$\,CMa). These stars show pulsations and were suspected to be in an evolutionary stage either preceding or succeding the red supergiant (RSG) stage. We used 2-min cadence TESS data to study the photometric variability and we obtained new spectroscopic observations at the CASLEO observatory (Argentina). We used non-LTE radiative transfer models calculated with the code CMFGEN to derive their stellar and wind parameters. For first time, CMFGEN was coupled with the automatic spectral fitting procedure {\sc XTgrid}. The spectral modeling was limited to changing only the $T_{\rm eff}$ , $\log g$, $\dot{M}$, and CNO abundances. The frequency spectra of all stars show stochastic oscillations and indications of one nonradial strange mode, $f_r=$ 0.09321 d$^{-1}$ in HD\,42087 and a rotational splitting centred in $f_2=$ 0.36366 d$^{-1}$ in HD\,52089. We conclude that the rather short sectoral observing windows of TESS prevent establishing a reliable mode identification of low frequencies connected to mass-loss variabilities. The spectral analysis confirmed gradual changes in the mass-loss rates and our derived CNO abundances are in line with values reported in the literature. We achieved a quantitative match with stellar evolution models for the stellar masses and luminosities. However, the spectroscopic surface abundances turned out to be inconsistent with the predictions from Geneva stellar evolution models. The stars show N enrichment, typical for CNO cycle processed material, but the abundance ratios are not reflecting the associated levels of C and O depletion. We found HD\,42087 (PU\,Gem) to be most consistent with a pre-RSG stage, and HD\,58350 ($\eta$\,CMa) is most likely in a post-RSG stage. We were unable to model HD\,52089 ($\epsilon$\,CMa) with any evolved BSG tracks and conclude its relatively low mass and high luminosity are most consistent with a rejuvenated merger scenario.

#300 | Atlas of Massive Galactic O-type Spectral Standards in the near-infrared

Federico Giudici Michilini ¹ ; Roberto Gamen ¹ ;

Gabriel A. Ferrero ¹ ; Nidia Morrell ²

1 - Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata. 2 - Carnegie Observatories, Las Campanas Observatory.

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#301 | Supernova Light Curves with the HSH telescope at CASLEO

Axel Nahuel Méndez Llorca ¹ ; Gastón Folatelli ¹ ; Laureano Martinez ¹ ; Lucía Ferrari ¹ ; Keila Ertini ¹

1 - Instituto de Astrofísica de La Plata, CONICET–UNLP, Argentina.

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#323 | Coronal Mass Ejection Trajectories from Solar-type Stars

Fabian Menezes ¹ ; Adriana Valio ¹ ; Yuri Netto ² ; Alexandre Araújo ³ ; Christina Kay ⁴ ; Merav Opher ⁵

1 - Centro de Rádio Astronomia e Astrofísica Mackenzie (CRAAM), Universidade Presbiteriana Mackenzie. 2 - Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Departamento de Astronomia, Universidade de São Paulo. 3 - Centro de Rádio Astronomia e Astrofísica Mackenzie (CRAAM). 4 - Heliophysics Science Division, NASA Goddard Space Flight Center. 5 - Department of Astronomy, Boston University.

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#338 | Project SOL (Solar Origin and Life): Detailed characterization of candidates at ZAMS and Subgiant stages

Carlos Eduardo Oliveira dos Santos ¹ ; Luan Ghezzi Ferreira Pinho ¹ ; Gustavo Frederico Porto de Mello ¹ ; Diego Lorenzo de Oliveira ²

1 - Observatório do Valongo - UFRJ. 2 - Laboratório Nacional de Astrofísica.

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Abstract:

The luminosities of the stars vary throughout their evolution, changing the position and extent of their habitable zones. Furthermore, the chromospheric activity of the host star can influence the amount and the type of radiation received by the present planets, possibly altering their habitability. Thereby, the study of stars that are similar to the Sun at different points of its evolutionary trajectory is essential to understand how terrestrial planets can maintain the necessary conditions for the emergence and evolution of life as we know. Therefore, in this work we identified and characterized stars that could represent the Sun at the ZAMS and subgiant stages. Thus, the sample of stars was selected using photometric boxes, which resulted in 8 candidates to represent it at the ZAMS stage and 10 at subgiant stage. We performed the analysis of the candidates using high resolution (R = 35000 - 115000) and signal-to-noise (S/N > 150) spectra obtained with modern instruments on different telescopes around the world. We adopted the classical spectroscopic method, which uses equivalent widths of Fe I and Fe II lines and is based on the excitation and ionization equilibria. Additionally, we derived evolutionary parameters (mass, radius, luminosity and age), using theoretical evolutionary tracks and isochrones, and kinematic parameters for all stars in our sample. We also performed age estimates through 2 additional independent methods and we present the chromospheric activity levels of our candidates. From these, our results show that we successfully identified 3 excellent candidates capable of representing the Sun at the ZAMS (2) and subgiant (1) stages. Moreover, 2 other candidates of our sample could be interesting for studying the Sun with 2 Gyr. These candidates can help us better understand how the properties of Sun-like stars vary over time and their influence on the habitability of possible exoplanets.

#367 | Measurement of the longitudinal magnetic field component in Herbig AeBe stars using the LSD technique

Daniel Ruiz Basante ¹ ; Giovanni Pinzón Estrada ¹ ; Julio Ramirez Velez ²

1 - Universidad Nacional de Colombia. 2 - UNAM.

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#037 | Magnetic field map of an Ap star: Deep learning applied to the synthesis of polarized Stokes parameters

Julio Ramirez Velez ¹ ; Joan Raygoza ² ; Irvin Lopez Nava ²

1 - UNAM. 2 - CICESE.

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#374 | Prebiotic molecules identification in young solar-type stellar objects: methanol

Juan José Maldonado Portilla ¹ ; Heidy Mayerly Quitian Lara ²

1 - Universidad Industrial de Santander. 2 - University of Kent.

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#589 | The XShootU Stellar Library - hot low metallicity stars

Lucimara Martins ¹ ; XshootU Collaboration ²

1 - Universidade Cidade de Sao Paulo. 2 - -.

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#597 | The morpho-kinematic structure of the Thor$^\prime$s Helmet Nebula

Gerardo Ramos-Larios ¹ ; J.A. Quino-Mendoza ¹ ; E. Santamaría ²

1 - Instituto de Astronomía y Meteorología Dpto. de Física, CUCEI, Universidad de Guadalajara. 2 - Instituto de Radioastronomía y Astrofísica, UNAM.

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#126 | Exploring variability in B supergiant stars: a theoretical and photometric approach to pulsation modes and detection of binary systems

Aldana Alberici Adam ¹ ; Michalis Kourniotis ² ; Lydia Cidale ¹ ; Alejandra Christen ³ ; Wolfgang Glatzel ⁴

1 - Instituto de Astrofísica de La Plata (IALP) - CONICET. 2 - Astronomical Institute of Czech Academy of Sciences. 3 - Instituto de Estadística, Universidad de Valparaíso. 4 - Institut für Astrophysik, Georg-August-Universität Göttingen.

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