Grants related:
General
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
Results
Highlights 2020
1. The IACOB project presents empirical evidence of the scarcity of Galactic O-type stars with masses 40-80 Msol close to the theoretical zero age main sequence. Th reason of this result could be indicating that the accretion rate of mass during the stars formation process of massive stars could be lower than traditionally considered.
2. Presented empirical evidence of the existence of multiple star forming bursts in the Cygnus OB2 massive star formation region. The way is paved for the first in-depth study of the massive star population of the Cygus-X region in the Milky Way benefiting from the WEAVE survey.
3. Studied membership and kinematical properties in a sample of 80 blue and red supergiants in the PerOB1 association by using high resolution multi-epoch spectroscopy and Gaia astrometry data. A forthcoming spectroscopic study of this sample of star will provide new empirical clues to improve our understanding of massive stars evolution.
4. The MAMSIE-IACOB collaboration presents first in-depth study of the pulsational propeties of a large sample of massive Galactic OB-type stars by means of the combined study of high-resolution spectroscopic data from HERMES, FIES and SONG and high cadence photometric data provide by the TESS mission.
5. Estimated that the binarity fraction for evolved high-mass stars (red supergiants) should be at least 0.15±0.03.
6. Identified the first strong candidate to be a super-AGB star in the Galaxy (VX Sgr).
Scientific activity
Related publications
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Properties of OB star-black hole systems derived from detailed binary evolution modelsContext. The recent gravitational wave measurements have demonstrated the existence of stellar mass black hole binaries. It is essential for our understanding of massive star evolution to identify the contribution of binary evolution to the formation of double black holes. Aims: A promising way to progress is investigating the progenitors of doubleLanger, N. et al.
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62020 -
A new spectroscopic analysis of the massive O + O type binary HD 54662 ABHD 54662 AB is one of the three O + OB binaries known so far with orbital period longer than 1000 d, offering the opportunity to test scenarios of massive star formation and models of single stellar evolution. Here, we present a detailed study of this system based on new high-resolution spectra and data. A disentangling method is used to recoverBarbá, R. H. et al.
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42020 -
Cluster membership for the long-period Cepheid calibrator SV VulClassical Cepheids represent the first step of the distance scale ladder. Claims of tension between the locally calculated Hubble constant and the values deduced from Planck's results have sparked new interest in these distance calibrators. Cluster membership provides an independent distance measurement, as well as astrophysical context for studiesNegueruela, I. et al.
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42020 -
Analysis of absorption lines in the high-resolution spectra of five hot post-AGB candidatesFrom an analysis of absorption lines in the high-resolution spectra, we have derived the radial velocities, stellar parameters (T eff, log g, wind-strength parameter log Q, and projected rotational velocity), and abundances (C, N, O, and Si) of IRAS 17460-3114, IRAS 18131-3008, IRAS 19336-0400, LSE 45, and LSE 163. Abundances are found to be solarHerrero, A. et al.
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32020 -
An ionized superbubble powered by a protocluster at z = 6.5We show herein that a proto-cluster of Ly α emitting galaxies, spectroscopically confirmed at redshift 6.5, produces a remarkable number of ionizing continuum photons. We start from the Ly α fluxes measured in the spectra of the sources detected spectroscopically. From these fluxes, we derive the ionizing emissivity of continuum photons of theRodríguez Espinosa, J. M. et al.
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32020 -
Time-domain Study of the Young Massive Cluster Westerlund 2 with the Hubble Space Telescope. ITime-domain studies of pre-main-sequence (PMS) stars have long been used to investigate star properties during their early evolutionary phases and to trace the evolution of circumstellar environments. Historically these studies have been confined to the nearest, low-density, star-forming regions. We used the Wide Field Camera 3 on board the HubbleSabbi, E. et al.
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32020 -
Candidate LBV stars in galaxy NGC 7793 found via HST photometry + MUSE spectroscopyOnly about 19 Galactic and 25 extragalactic bonafide luminous blue variables (LBVs) are known to date. This incomplete census prevents our understanding of this crucial phase of massive star evolution which leads to the formation of heavy binary black holes via the classical channel. With large samples of LBVs one could better determine theWofford, Aida et al.
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42020 -
Multiplicity of the red supergiant population in the young massive cluster NGC 330Context. The multiplicity properties of massive stars are one of the important outstanding issues in stellar evolution. Quantifying the binary statistics of all evolutionary phases is essential to paint a complete picture of how and when massive stars interact with their companions, and to determine the consequences of these interactions. Aims: WePatrick, L. R. et al.
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32020 -
The young massive SMC cluster NGC 330 seen by MUSE. I. Observations and stellar contentContext. A majority of massive stars are part of binary systems, a large fraction of which will inevitably interact during their lives. Binary-interaction products (BiPs), that is, stars affected by such interaction, are expected to be commonly present in stellar populations. BiPs are thus a crucial ingredient in the understanding of stellarBodensteiner, J. et al.
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22020 -
The NGC 346 massive star census. Nitrogen abundances for apparently single, narrow lined, hydrogen core burning B-type starsPrevious analyses of two large spectroscopic surveys of early-type stars in the Large Magellanic Cloud (LMC) have found an excess of nitrogen enriched B-type targets with a v e sin i ≤ 40 km s -1 compared with the predictions of single star evolutionary models that incorporate rotational mixing. By contrast, the number of such targets with 40 < v eDufton, P. L. et al.
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22020 -
The VLT-FLAMES Tarantula Survey. XXXII. Low-luminosity late O-type stars: classification, main physical parameters, and silicon abundancesAnalysis of late O-type stars observed in the Large Magellanic Cloud (LMC) by the VLT-FLAMES Tarantula Survey revealed a discrepancy between the physical properties estimated from model-atmosphere analysis and those expected from their morphological classifications. Here we revisit the analysis of 32 of these puzzling objects using new hydrogenMarkova, N. et al.
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22020 -
A detailed non-LTE analysis of LB-1: Revised parameters and surface abundancesContext. It has recently been proposed that LB-1 is a binary system at 4 kpc consisting of a B-type star of 8 M ☉ and a massive stellar black hole (BH) of 70 M ☉. This finding challenges our current theories of massive star evolution and formation of BHs at solar metallicity. Aims: Our objective is to derive the effective temperature, surfaceSimón-Díaz, S. et al.
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22020 -
H α morphologies of star clusters: a LEGUS study of H II region evolution time-scales and stochasticity in low-mass clustersThe morphology of H II regions around young star clusters provides insight into the time-scales and physical processes that clear a cluster's natal gas. We study ̃700 young clusters (≤10 Myr) in three nearby spiral galaxies (NGC 7793, NGC 4395, and NGC 1313) using Hubble Space Telescope (HST) imaging from LEGUS (Legacy ExtraGalactic UltravioletHannon, Stephen et al.
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122019 -
Physical parameters of red supergiants in dwarf irregular galaxies in the Local GroupContext. Increasing the statistics of evolved massive stars in the Local Group enables investigating their evolution at different metallicities. During the late stages of stellar evolution, the physics of some phenomena, such as episodic and systematic mass loss, are not well constrained. For example, the physical properties of red supergiantsBritavskiy, N. E. et al.
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112019 -
The Hubble Catalog of Variables (HCV)Aims: Over its lifetime and despite not being a survey telescope, the Hubble Space Telescope (HST) has obtained multi-epoch observations by multiple, diverse observing programs, providing the opportunity for a comprehensive variability search aiming to uncover new variables. We have therefore undertaken the task of creating a catalog of variableBonanos, A. Z. et al.
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102019 -
A giant exoplanet orbiting a very-low-mass star challenges planet formation modelsSurveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planetMorales, J. C. et al.
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92019 -
MOS spectroscopy of protocluster candidate galaxies at z = 6.5The epoch corresponding to a redshift of z ̃ 6.5 is close to full re-ionization of the Universe, and early enough to provide an intriguing environment to observe the early stage of large-scale structure formation. It is also an epoch that can be used to verify the abundance of a large population of low luminosity star-forming galaxies that areCalvi, R. et al.
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112019 -
Low-frequency gravity waves in blue supergiants revealed by high-precision space photometryAlmost all massive stars explode as supernovae and form a black hole or neutron star. The remnant mass and the impact of the chemical yield on subsequent star formation and galactic evolution strongly depend on the internal physics of the progenitor star, which is currently not well understood. The theoretical uncertainties of stellar interiorsBowman, Dominic M. et al.
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52019 -
The Stellar Atmosphere Physical System II. An Operative Sequential Algorithm to Solve the Stellar Atmosphere ProblemIn this paper, the second and the last of the series, we present a sequential algorithm to solve the stellar atmosphere problem that may serve as a paradigm for the solution of more general non-linear and non-local problems. The Iteration Factors (IF) Method is applied to achieve a solution of the radiative transfer equations, consistent with theCrivellari, L.
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62019 -
The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegarden's StarContext. Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. Aims: As part of the CARMENES search for exoplanets around M dwarfs, weZechmeister, M. et al.
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72019
