This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction).
Massive stars are central objects to Astrophysics. Born with at least 8 solar masses, their evolution proceeds very fast, yielding large amounts of nuclear processed material by means of strong stellar winds (loosing up to 90% of their initial mass before facing a violent death as Supernova) and emitting intense radiation fields. Despite their scarcity, massive stars play a decisive role in many aspects of the evolution of the Cosmos (e.g. they are primary agents of the chemical and dynamical evolution of galaxies and have been proposed as key agents in the reionization of the Universe). Along their complex evolution, they are associated with the most extreme stellar objects (O-type and WR stars; blue and red supergiants; luminous blue variables; massive stellar black holes, neutron stars and magnetars; massive X- and gamma-ray binaries). They are also the origin of newly studied phenomena such as long-duration GRBs or the recently detected gravitational waves produced by a merger of two massive black holes or neutron stars. From a practical perspective, massive stars have become invaluable indicators of present-day abundances and distances in external galaxies, even beyond the Local Group. In addition, the interpretation of the light emitted by H II regions and starburst galaxies relies on our knowledge of the effect that the strong ionizing radiation emitted by these hot stellar objects produces on the surrounding interstellar medium.
This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction). In this endeavour, the project benefits from best quality observations obtained with the last generation of facilities available at the Canary and the ESO observatories, as well as other observations of interest provided from space missions such as Gaia, HST, IUE and TESS. Samples with a few to several hundreds of individual massive stars in different evolutionary stages and metallicity environments are then analyzed with the last generation of stellar atmosphere codes and optimized tools for the quantitative spectroscopic analysis of massive stars to extract as much empirical information as possible about stellar+wind parameters, surface abundances and spectroscopic variability.
The main research lines presently active in the project are:
- the observation and analysis of large samples of massive OB stars in the Milky Way;
- the exploration of the hidden population of massive stars in the Milky Way;
- the searching, observation and analysis of massive extragalactic stars, with special emphasis in those found in low metallicity galaxies;
- the development and use of model atmospheres, model atoms and numerical tools for the analysis of massive stars.
Members of the project
Highlights and results
- S. R. Berlanas has published a series of three papers in which she studies in detail several topics related with the massive star population of the Cygnus OB2 association by using high quality spectra obtained with INT and data about paralaxes provided by Gaia DR2.
- G. Holgado has finished his PhD, including the a spectroscopic and physical caracterization of the largest sample of Galactic O-type stars investigated to date.
- We have investigated the spectroscopic and photometric variability of two blue supergiant stars (rho Leo and kappa Cas) using HERMES/FIES/SONG multiepoch spectroscopy and photometric data provided by the Hipparcos and K2 mission. Our analysis point towards the confirmation of the existence of internal gravity waves in this type of stars.
- We have found a rare alignment of two massive stars populations in the Milky Way, that we have called MASGOMAS-6A+B. Located at a Galactic longitude of 38 degrees, the first population contains two Wolf-Rayet stars and O dwarfs at 3.9 kpc, whereas the second one hosts a Luminous Blue Variable and an evolved population of blue supergiants at a distance of 9.6 kpc.
- We have contributed to present an updated census of the massive star popullation of the quintuplet cluster, one of the most massive young clusters in the Galaxy.
A peculiar Of star in the Local Group galaxy IC 1613
Context. Results from the theory of radiatively driven winds are nowadays incorporated in stellar evolutionary and population synthesis models, and are used in our interpretation of the observations of the deep Universe. Yet, the theory has been confirmed only until Small Magellanic Cloud metallicities. Observations and analyses of O-stars at lowerHerrero, A. et al.
The young stellar population of IC 1613. I. A new catalogue of OB associations
Context: Determining the parameters of massive stars is crucial to understand many processes in galaxies and the Universe, since these objects are important sources of ionization, chemical enrichment and momentum. 10m class telescopes enable us to perform detailed quantitative spectroscopic analyses of massive stars in other galaxies, samplingGarcia, M. et al.
The VLT-FLAMES Tarantula Survey. XII. Rotational velocities of the single O-type stars
Context. The 30 Doradus (30 Dor) region of the Large Magellanic Cloud, also known as the Tarantula nebula, is the nearest starburst region. It contains the richest population of massive stars in the Local Group, and it is thus the best possible laboratory to investigate open questions on the formation and evolution of massive stars. Aims: UsingSana, H. et al.