SPEAKERS &

Symbiotic stars (SySts) are interacting binary systems, typically consisting of a red giant (RG) and a white dwarf (WD). These systems exhibit long orbital periods, mass transfer, accretion disk formation, jet generation, and X-ray emission. They are also considered potential progenitors of Type Ia supernovae.

Dust is also present in some of these binary systems, namely the D-type and D'-type, and it plays a crucial role in their overall physical properties. Studying the dust component therefore provides insights into the chemical enrichment of the surrounding medium and the mass loss process for example.

The objective of my thesis is to determine the type, size distribution, and mass of dust in the dusty symbiotic star K 3-22, identified in the IPHAS survey. To achieve this, I will use a spectral energy distribution (SED) generated with VOSA as the observational data. Then, using synthetic models produced with Cloudy and the PyCloudy code, I will model its spectral characteristics.

Li Shen (PhD)

Pulsation Analyisis of the SPB Star HD 215573

Slowly Pulsating B-type (SPB) stars exhibit gravity-mode (g-mode) pulsations that provide valuable probes of the deep interiors of intermediate- and high-mass stars. Studying these pulsations offers important insights into stellar structure and the physical processes occurring near convective cores.

In this work, we present a pulsation analysis of the SPB star HD 215573 using photometric observations from the Transiting Exoplanet Survey Satellite (TESS). The TESS light curves from multiple sectors are analyzed to extract significant pulsation frequencies and to search for characteristic period spacing patterns associated with high-order g modes.

In addition, ground-based spectroscopy is used to estimate the fundamental atmospheric parameters of the star, including the effective temperature, providing important constraints for future seismic modeling. These results represent a first step toward a detailed asteroseismic investigation of HD 215573. Future work will combine the observed pulsation properties with spectroscopic information and stellar modeling to further constrain the internal structure and mixing processes in the near-core region of the star.

Esfandiar Jahangiri (PhD)

The Role of Binary Central Stars in Shaping Planetary Nebula

Planetary nebulae exhibit a wide variety of morphologies, many of which depart significantly from spherical symmetry. Among the mechanisms proposed to explain these aspherical structures, binary interactions have emerged as a key factor in the shaping process. In this presentation, I explore the relationship between aspherical symmetry in planetary nebulae and the presence of binary central stars. I discuss how binary evolution, including mass transfer, common-envelope evolution, and angular momentum redistribution, can influence the formation of bipolar, elliptical, and other complex morphologies. Observational evidence and recent studies suggest that binarity plays a fundamental role in the development of these structures, providing important insight into the late stages of stellar evolution. Understanding this connection is essential for constraining models of planetary nebula formation and for explaining the diversity of shapes observed in these systems.

Yilin Lu (MSc)

Optical Counterparts to Exotic Compact Binaries in NGC 6712 from HST Observation

Globular clusters (GCs) host rich populations of dynamically formed exotic binaries in their dense cores, including millisecond pulsars (MSPs), low-mass X-ray binaries (LMXBs), and cataclysmic variables (CVs), which provide key tracers of cluster dynamical evolution. We present an optical characterization of exotic systems in the core of NGC6712 using archival Hubble Space Telescope (HST)/WFC3 imaging. High-precision photometry and accurate astrometric registration allow us to build a deep source catalog in this crowded field and cross-match optical sources with Chandra detections to identify candidate counterparts and objects displaced from the main sequence in color magnitude diagrams. We report the first optical identification of the black widow MSP NGC6712A. Its counterpart is located between the white dwarf cooling sequence and the main sequence, consistent with an irradiated black widow companion, and thus provides new constraints on the nature of spider-pulsar companions in GCs. We also recover the known optical counterpart of the LMXB 4U1850-087 and identify likely counterparts to CX2 and CX5. Their photometric properties and X-ray-to-optical flux ratios suggest that CX2 is likely a magnetically active binary, whereas CX5 is consistent with a cataclysmic-variable candidate.

Ramón Caballero Villegas (PhD)

Membership Determination for Galactic Stellar Clusters

The study of stellar clusters within the Galaxy serves an important role in understanding the Galaxy’s physical and chemical distribution. Open stellar clusters are defined as gravitationally-bound groups of stars born from a single, homogeneous molecular cloud nearly at the same time, typically composed of a single stellar population. As a direct result from this simultaneous birth, important physical parameters such as a cluster’s age, metallicity, distance, and extinction can be determined through photometric analysis in multiple passbands. In order for such an analysis to be possible it is first necessary to discriminate between cluster members and contaminating field stars given a sample of observed stars whose astrometric properties are known.

I will talk about the development of a custom membership determination pipeline in order to efficiently automatically recover as many member stars as possible using HDBSCAN, a hierarchical clustering algorithm widely used in the literature. Vector field visualization tools such as line-integral convolution (LIC) are implemented to visually identify proper motion coherence for a given HDBSCAN solution, helping distinguish true solutions from false positives. These results are compared with both the Unified Cluster Catalog and the Hunt & Reffert (2024) catalog. These membership solutions are essential for the subsequent photometric analysis using photometry obtained from the OAN–SPM to constrain each cluster’s physical parameters, where having observations in the U filter will help break the degeneracy in other cluster solutions, resulting in a higher quality cluster characterization.

Sergio González Barron (MSc)

Identification of Young Moving Stellar Groups

Young Moving Groups (MGs) are stellar aggregates resulting from the disaggregation of a star forming region in the Milky Way (MW) with ages ≤ 100 Myr that share common chemical and kinematic properties.
MGs are crucial to understand the population of the Solar Neighborhood and MW disk. However, identifying MGs is challenging due to their wide distribution in the sky, and their low stellar density compared to more compact star clusters. We are studying the whole sky using a spectroscopic sample (SDSS/LAMOST/GALAH) and Gaia astrometry of the Solar Vicinity (d<250 pc). The sample provides radial velocities and also a set of spectral features (Hα; 6562 Å, Li I; 6708 Å, Ca II K;3968 Å), characteristic of chromospheric activity in young stars. To identify the MGs in that sample, we are using the Hierarchical Cone Method that generates a global stellar density map of the orientation of the velocity vector, highlighting the possible MGs candidates using a static significant test. Subsequently, we apply a clustering method to isolate the groups using a metric that combines Euclidean distance in 3D physical space and 2D angular separation in the space of velocity vector orientations.
Our methodology detected 89 MGs, a fraction of which were not previously reported, suggesting a possibly more complex kinematic structure in the Solar Neighborhood than expected. Furthermore, spectroscopic analyses reveal that ∼10% of the members of 17 groups show characteristic lines of youth, reinforcing the hypothesis of their recent origin in regions of star formation.

Sergio Sánchez-Sanjuán (PhD)

Young Stellar Clusters: From Observations to Simulations. How do They Dissolve

We present a study that combines observations and simulations of young stellar clusters across nearby environments, focusing on the Orion star-forming complex and the Scorpius-Centaurus association. Using Gaia DR3 astrometry and complementary radial velocities, we estimated present-day phase-space and structural parameters for kinematic substructures. We then constructed Monte Carlo realizations consistent with the observed global constraints and evolved them with N-body simulations in a Galactic potential to measure the stellar bound fraction and dissolution timescales. Across both regions, the present-day virial state emerged as a predictor of survivability: near-virial clusters retained bound remnants after one Galactic rotation, whereas highly supervirial, diffuse clusters dissolved into the field before 150 Myr. To interpret these trends in a controlled way, we also ran suites of idealized N-body experiments with King initial conditions spanning the observed parameter space, mapping the $\alpha_{vir}$--$T_{dis}$ plane. The relation was well described by an exponential form, but its detailed shape depends on the adopted King parameters, indicating sensitivity to internal structure. In this contribution, as my last participation at the EAS since its inception, I will present the final results and conclusions of my PhD project.

Yazmin Torres Montana (MSc)

Private Sector's Latest Steps Toward Sustained Space Operations

The rapid expansion of private industry is fundamentally reshaping space activities, with direct and growing implications for astronomy and space science. Key developments driven by companies such as SpaceX, Blue Origin, and others include reusable launch vehicles like Starship that dramatically reduce the cost and increase the frequency of access to orbit, alongside large-scale satellite constellations such as Starlink that provide enhanced broadband connectivity between space and Earth.These innovations enable more affordable deep-space missions, potential deployment of larger or more advanced telescopes, and improved data transmission that could support astronomical facilities. However, they also introduce substantial challenges for the field: pervasive light pollution from satellite streaks that contaminate ground-based and space telescope observations, radio frequency interference disrupting sensitive instruments, increased orbital debris threatening long-term sustainability, and broader concerns over the privatization of near-Earth and cislunar space, including equitable access and environmental impacts.

Recent studies highlight the severity of these issues. For instance, projections indicate that mega-constellations could affect up to 40% of Hubble Space Telescope images and over 96% of those from certain planned observatories if current expansion trends continue. Private entities now dominate launch infrastructure, satellite deployment, and even emerging private space-based observatories, profoundly influencing observation conditions, potential scientific collaborations, and conflicts over orbital resources.

Awareness of the motivations, technological capabilities, and limitations of private industry has become essential for astronomers. The sector's dominance determines the future accessibility, integrity, and scientific productivity of the night sky and beyond, making informed engagement critical to safeguarding astronomical research in an increasingly commercialized orbital environment.

Marina Ilian Torres Boehme (MSc)

Design and Construction of a 210 GHz Radiometer for Water Vapor Measurement at the National Astronomical Observatory, Sierra de San Pedro Mártir

We present the design, development, and construction of a 210 GHz heterodyne radiometer, whose purpose is the continuous measurement of precipitable water vapor (PWV) in the atmosphere above the National Astronomical Observatory (OAN), located in the Sierra de San Pedro Mártir, Baja California, Mexico. The instrument operates near the water vapor emission line at 183 GHz, using a frequency offset to 210 GHz to optimize the signal-to-noise ratio and minimize direct atmospheric absorption. The system incorporates a low-noise millimeter-wave heterodyne receiver, a filter and power detector optimized for long-term stability, a calibration system using ambient temperature, and real-time control and data acquisition with remote storage and transmission. The atmospheric opacity measurements obtained with this radiometer will provide a statistical characterization of the site’s atmospheric conditions, optimize the scheduling of infrared astronomical observations and future operation at millimetric wavelengths, and enable correlation of opacity data with other atmospheric monitoring instruments. This development strengthens the OAN-SPM’s instrumental infrastructure and contributes to the comparative evaluation of high-altitude astronomical sites.

Amairani León García (MSc)

A Comprehensive Characterization of the [WC] Planetary Nebula BD+30 3639: A Multi-Range and Photoionization Approach

This work presents a comprehensive characterization of the planetary nebula BD+30 3639 and its [WC]-type central star through the analysis of spectroscopic data and numerical modeling. The methodology combines optical spectroscopy from the ISIS (WHT) and FIES (NOT) instruments to leverage both flux sensitivity and high spectral resolution. From these data, physical conditions (Te,ne) and chemical abundances of the gas are determined using the PyNeb tool, while the stellar atmosphere and wind parameters are characterized through the PoWR code. To account for the dust component, we reconstruct the Spectral Energy Distribution (SED) using VOSA, providing constraints on the infrared excess. Furthermore, available X-ray data are incorporated to better characterize the ionizing source within the photoionization model . Finally, the set of observables is integrated into the Cloudy code to generate a self-consistent physical model of the nebula-star complex. This approach allows for a refined understanding of the interaction between the central star, gas, and dust in an object characterized by intense stellar winds and hydrogen deficiency.

Alberto Emiliano Montoya Olivo (MSc)

The Role of Binary Central Stars in Shaping Planetary Nebula

Marissa Krystal Botello Nava (PhD)

Python White Dwarf Exoplanet (Py-WEP): Pipeline for the Identification of Candidate Companions Orbiting White Dwarfs Using TESS Photometric Data

Since the Transiting Exoplanet Survey Satellite (TESS) mission began, numerous exoplanets have been discovered. However, only one exoplanet has been found orbiting a white dwarf (WD) via transit. To date, only a few exoplanets have been found around white dwarfs. Studying these systems can help us understand how planets survive the evolution of their host star after it leaves the main sequence. There is a need for software that can process light curves from space exoplanet missions around evolutionary stars to increase the amount of data available for studying exoplanet survival. For this project, we designed a pipeline to detect potential exoplanet candidates around white dwarfs. The pipeline recovered the transit of 1.4 days of the exoplanet orbitin the WD 1856+534.

Daniel Segura Piña (PhD)

Study of the Morphological Properties of the Accretion Disk in the YSO HD98922

The study focuses on the young stellar object HD 98922 (Herbig AeBe type) to understand the physical processes occurring in the inner region of its circumstellar disk. Near-infrared interferometric data (VLTI/PIONIER) were used, and three methods were applied: image reconstruction, Bayesian geometric modeling, and radiative transfer modeling. The results reveal a ring-like structure with asymmetries in the inner rim of the disk, interpreted as the dust sublimation region. The asymmetries could be due to vortices, a complex distribution of dust grains, or a substellar companion. This work highlights the importance of studying these regions to understand the physical processes in protoplanetary disks.

Corina Zepeda (MsC)

Extinction and Photoplanetary Disks on the Determination of Stellar Parameters

The determination of atmospheric parameters in young pre-main-sequence stars is challenging due to environmental effects that are not typically present in main-sequence stars. Two major sources of uncertainty are interstellar extinction and emission from circumstellar disks. Extinction, caused by dust in molecular clouds, can introduce systematic biases in the estimation of stellar properties if not properly corrected. Additionally, infrared excess emission from protoplanetary disks may produce veiling effects that potentially affect the spectral energy distributions (SEDs) and, then, the derivation of stellar parameters.

In this work, we investigated how extinction and disk emission influence the determination of atmospheric parameters in young stars within the Orion OB1 association, using APOGEE H-band (1.5–1.7 μm, R~22,500) spectroscopy and Gaia DR3 photometry and astrometry. We implemented a hybrid method to estimate photometric extinction and applied corrections prior to performing a spectroscopic analysis using the tonalli code, which determines stellar parameters using the H band through synthetic spectral interpolation with models. In a second stage, we selected stars hosting a circumstellar disk based on infrared excess and constructed multiwavelength SEDs using Gaia, 2MASS, WISE, and Spitzer data. Disk properties were inferred using a neural network trained on DIAD models.

Our results show that extinction does not significantly affect effective temperature estimates but introduces systematic biases in surface gravity, emphasizing the importance of proper extinction correction when characterizing young stars. Also, we find that, for our sample, the presence of protoplanetary disks does not systematically bias stellar parameters derived from APOGEE H-band spectra, suggesting minimal disk effects in this region.

Andrés Ledesma Ramírez (MSc)

The Determination of the Mass of the Cosmic Web Filaments

Cosmic web filaments contain a significant fraction of the Universe's matter, yet directly measuring their mass remains a major observational challenge. This work explores whether filament mass can be inferred from galaxy kinematics using a scaling relation between the transverse velocity dispersion and the linear mass density, as proposed by Eisenstein (1997).Using the IllustrisTNG (TNG100) simulation, we identify filaments via the SpineWeb algorithm. We select structures with at least 10 connected voxels and associate galaxies within a 500 kpc cylindrical radius. To accurately characterize the kinematics, we apply Principal Component Analysis (PCA) for reorientation and fit a third-degree polynomial to the filament spine. This allows for a precise calculation of the local normal vector and the transverse velocity components of nearby galaxies.Our results confirm a correlation between the velocity dispersion-derived theoretical density and the actual mass density measured directly from the simulation. This calibration validates the use of galaxy kinematics as a reliable proxy for the gravitational potential of filaments, offering a promising method to weigh the Cosmic Web in current and future redshift surveys such as SDSS, DESI, Euclid, and the Vera C. Rubin Observatory.

Joel Alberto García Parra (PhD)

A (very) Small Look at Constrained Simulations

In the world of computational simulations, the development of rare condensations of matter such as rich galaxy clusters are rather difficult to examine by n-body simulations techniques. In practice, studying a specific scenario would require rather an extended simulation volume; diminishing the resolution, or an extremely large number of realizations of a small volume; increasing computational cost.
One way to solve this problem is to use constrained initial conditions as the starting point of N-body simulations. These initial conditions are obtained using different statistical techniques such that, given different properties of the desired structure; mass distribution, velocity field, you can derive a random field that resembles the density fluctuations that originated such structure in the desired redshift. Doing so, it is possible to study the Local Group throughout time, where the long term goal is to study different origin and evolution scenarios within the context of the Large Scale Structure.

Vanessa Enríquez Hernández (PhD)

Gas Geometry and Star Formation Across Cosmic Scales

As my PhD project, we asses the role of geometry and morphology of star-forming regions in setting star formation rate and history at three different cosmic scales: molecular clouds, galactic flows and gas distribution at cosmic web. This study is enabled by a novel combination of artificial intelligence (AI) and advanced mathematical techniques.

Gravitational collapse plays a principal role in star formation and the morphological shapes of the gas it produces provide insight into the global description of star-forming regions.

In this talk, we present the first step toward connecting and understanding the link between larger and smaller scales. We select a sample of simulated massive galaxies (≤ 10^12 Mo) at z=2 from Illustris-TNG-50 and project only the denser and colder gas particles in order to identify the inflows that supply gas for star formation.

Ricardo Ruiz Hernández (MSc)

Advancing HII Region Photoionization models: A 3D Benchmark for the Magellanic Clouds

H II regions are key laboratories for studying stellar feedback and the physical conditions of the interstellar medium. Their interpretation has traditionally relied on one-dimensional photoionization models that assume spherical symmetry and a single central ionizing source. While these models have been highly successful in many applications, modern observations reveal that real nebulae often exhibit complex geometries and multiple ionizing sources. The advent of spatially resolved spectroscopic surveys such as SDSS‑V Local Volume Mapper provides detailed maps of emission lines across nearby galaxies, motivating the development and validation of modeling approaches capable of handling such complexity.

In this thesis we perform a systematic comparison between two photoionization modeling strategies: the pseudo-3D approach implemented in Cloudy_3D (via PyCloudy) and the fully three-dimensional Monte Carlo radiative transfer code MOCASSIN. Despite the use of both methods, a quantitative benchmark between them has not previously been presented.

The comparison has three stages. First, a spherically symmetric benchmark model is constructed to isolate differences in the underlying numerical implementations. Second, geometric asymmetry is introduced through an ellipsoidal nebular model to evaluate how each approach handles non-radial structures. Finally, a more realistic configuration motivated by LVM observations is explored. For each model we compare predicted emission line intensities, ionization structures, and spatial distributions of physical parameters. Synthetic emission line diagnostics are analyzed using PyNeb to derive electron temperatures and densities in a manner consistent with observational analyses.

This work provides a quantitative benchmark between pseudo-3D and fully 3D photoionization methods and offers guidance for interpreting spatially resolved observations of complex H II regions.

Mónica Alejandra Villa Durango (PhD)

Kinematic Structure of the Rosette Nebula

H II regions associated with young stellar associations are ideal laboratories for probing the interplay between stellar feedback, gas dynamics, and the early evolution of stellar clusters. We present a kinematic study of the Rosette Nebula, ionized by the OB association NGC 2244, focusing on the coupling between ionized gas, molecular gas, and young stars. Spatially resolved line-of-sight velocity fields of the ionized gas are obtained directly from SDSS-V Local Volume Mapper observations based on the Hα, [S II], and [N II] emission lines. These data are compared with the molecular gas kinematics traced by ¹²CO emission from the MWISP survey and with the radial velocities of the associated stellar population. This multi-phase comparison reveals signatures of expansion, velocity gradients, and feedback-driven flows, allowing us to assess the degree of dynamical decoupling between gas phases and stars. Our results provide information about the impact of massive-star feedback on gas removal processes, as well as on the current dynamical state and early evolution of the NGC 2244 cluster within the Rosette Nebula.

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