Resumen:

To understand the processes involved in star formation, detailed studies at multiple frequencies are required. In particular, here we study the star$-$forming region G29.96$-$0.02, also known as W43$-$South, which has a young and massive stellar object called MYSO G29.862$-$0.0044 within, embedded in a hot molecular core. To investigate the physical processes involved in the formation of this object and its environment, we present in this work, an analysis of the emission of various molecular lines acquired with the Atacama Large Millimeter Array (ALMA) that aims to study the complex chemistry of the region. Additionally, we present new near$-$infrared and radio continuum observations obtained with the NIFS instrument at Gemini North and with the Jansky Very Large Array (JVLA), respectively, which complement the molecular observations.

Resumen:

The study of high-mass star formation involves the characterization of massive molecular clumps at different evolutionary stages. We present the preliminary results of a sub arcsec angular resolution study of two massive molecular clumps at different evolutionary stages based on ALMA data and own JVLA observations. The clumps show evidence of fragmentation harbouring several molecular cores, some of them active. We present estimations of temperatures and masses of the cores. The results are discussed in the context of the two main high-mass stars formation models.

Resumen:

We present a spectroscopic analysis of T Tauri stars (TTSs) observed mainly with the wide field Chinese multifiber spectrograph LAMOST in the Orion Star forming Complex. Based on GAIA DR3 data, we selected stars with proper motions and parallaxes expected for TTSs belonging to the young associations of the complex. We perform a spectroscopic analysis to obtain spectral types and measure the equivalent widths of Li I and Halpha to confirm the youth of the stars and estimate the accretion status. We also estimate extinctions, masses, and ages for the studied sample using different evolutionary models. These results are used for characterizing several stellar kinematic groups detected using clustering algorithms and the locations, proper motions, and parallaxes of the samples (HDBSCAN). Our study supports that the star forming scenario in the Orion OB1 association is more complex than the traditional spatial temporal scenario, in which a generation of stars triggers the formation of a new spatially differentiated generation of stars (Hernandez et al., 2023). Using machine learning methods, the TTSs confirmed spectroscopically in this study are used as a training sample of classifiers designed to automatically detect and characterize low-mass young stars in the entire LAMOST database. The derived stellar parameters are crucial in other ongoing studies related to the early evolution of protoplanetary disks, stellar rotation, and magnetic activity.

Resumen:

Accurate age and mass determinations for the youngest stars are crucial for understanding Pre-Main-Sequence star-disk evolution and planet formation. This most important task has proven difficult, as these systems are characterized by strong magnetic fields that lead to significant magnetically-driven phenomena like starspots, flares, and the channeling of both inflowing and outflowing material. Due to the fully convective interiors of the youngest stars and these strong magnetic fields, the large-scale suppression of convection is possible in low-mass stars, leading to starspots covering large fractions of their surfaces. A number of observed phenomena support this: spectral type mismatches between optically determined and infrared spectral types, color differences with main sequence stars, radius inflation, large age spreads for stars in the same cluster, and periodic photometric variability. In the context of these struggles, we present results from multi-epoch near-infrared spectroscopy to characterize the spot-behavior of 32 T-Tauri Stars in Taurus-Auriga. We constructed composite models of spotted stars by combining BTSettl-CIFIST atmospheres to represent the spots and the photosphere along with accretion and disk continua. Using a Markov-Chain Monte-Carlo algorithm, we find the best-fit spot and photospheric temperatures, spot filling factors, as well as disk and accretion filling factors. This methodology allowed us to reproduce the 0.75-2.40 micron stellar spectra for all of our targets, disentangling the complicated multi-component emission. For a subset of the targets, fitting multi-epoch data spanning an entire stellar rotation, we are able to correlate K2 photometry with spectral variability on rotational timescales. Combining spot-corrected effective temperatures and Gaia distances, we calculate luminosities and use the Stellar Parameters of Tracks with Starspots (SPOTS) models to derive corrected masses and ages for our sample of stars. A proper treatment of starspots in young stars will be crucial to further refine our understanding of the earliest stages of stellar evolution.

Resumen:

The initial mass function (IMF) is one of the main results of the star formation process and a fundamental quantity for many branches of astrophysics. The Orion complex is one of the most studied star-forming regions composed of several sub-regions including stars and brown dwarfs in a wide mass range, with ages spanning from $\sim1$ to $\sim10$ Myr and distances around 400 pc. Particularly, the slightly evolved populations such as 25 Ori in Orion OB1a, $\sigma$ Ori in Orion OB1b and Collinder 69 in $\lambda$ Ori also show low extinctions which makes them a perfect laboratory for robust determinations of the IMF from massive stars down to the planetary mass domain. In this work, we determine the system IMF of stellar and sub-stellar overdensities belonging to the Orion OB1b sub-region in a mass range from $0.05M_\odot$ to $8M_\odot$. The candidate members were selected independently for different stellar mass ranges according to their distribution in color-magnitude diagrams and/or kinematics diagrams made based on Pan-STARRS DR1 photometry and Gaia DR3 photometry, proper motions, parallaxes and radial velocities. Additionally, we corrected the resulting distributions by the expected contamination from field stars and the biases affecting the observable quantities, using spectroscopically confirmed members from literature as a control sample. We present the comparison of the resulting IMF with those previously known for other Orion sub-regions, focusing on the similarities of the IMF in the solar neighborhood and the predictions from low-mass stars and brown dwarf formation models.

Resumen:

Massive stars are those that are born with an initial mass greater than 8 solar masses. Due to their short lives, these stars die in massive explosions known as supernovae, thus becoming a major source of chemical enrichment in galaxies. The study of these stars plays a fundamental role in understanding cosmic history and is essential for modeling the evolution of primitive galaxies. However, the observation of massive stars with low metallicity presents difficulties, since galaxies with very low metal content are at a distance greater than 1 Mpc. In this study, we aim to provide insights into low metallicity stars, in order to interpret the first stars in the Universe. To achieve this, we will work with spectroscopic observations of massive stars located in Leo A. Leo A is an isolated, gas-rich, irregular dwarf galaxy with low stellar mass and metallicity ($\sim$ 1/20 $Z_{\odot}$) that lies on the outskirts of our Local Group. Through spectroscopic classification, we will be able to identify the observed stars as massive stars and obtain an initial estimate of their stellar parameters. In this poster, we present the data reduction process and the first results of the spectroscopic study of massive stars in the Leo A galaxy. The observations were carried out using the OSIRIS instrument of the Gran Telescopio Canarias (GTC) in multi-object mode.

Resumen:

Transition disks are a well-suited class of disks to witness the signatures of planet formation and evolution, particularly when observed at few-au resolution. At low-resolution, they appear as a single wide ring around a dust-depleted cavity. This ring indicates that mm-sized dust is trapped in the outer disk, but it is impossible to establish their complexity and the presence of substructure inside the cavity when transition disks are are barely resolved. Thus, the prevalence and properties of transition disk substructures, and of the potential planetary systems shaping them, is yet unknown. In the Taurus Star Forming Region (1-3 Myr) using ALMA data at 230 GHz and 12CO J = 2-1 spectral line emission we characterize substructures at few-au (~40mas) and constrain the type of planet(s) that shape the cavity in transition disks with planet-disk interaction models of the transitional disks around low mass pre-main sequence stars UX Tau, LkHa 330, CIDA 9, MHO6 and IP Tau.