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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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Blue supergiants as a progenitor of intermediate-luminosity red transientsThe current perspective about the explosions of massive hydrogen-rich blue supergiants is that they resemble SN 1987A. These so-called peculiar Type II supernovae, however, are one of the rarest types of supernovae and may not hence be the fate of all blue supergiants. In this work, we explore other explosion scenarios for blue supergiants. WeMoriya, Takashi J. et al.
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122024 -
WEAVE First Light Observations: Origin and Dynamics of the Shock Front in Stephan's QuintetWe present a detailed study of the large-scale shock front in Stephan's Quintet, a by-product of past and ongoing interactions. Using integral-field spectroscopy from the new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE), recent 144 MHz observations from the LOFAR Two-metre Sky Survey, and archival data from the Very LargeArnaudova, M. I. et al.
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Constraining the overcontact phase in massive binary evolution: III. Period stability of known B+B and O+B overcontact systemsContext. Binary systems play a crucial role in massive star evolution. Systems composed of B-type and O-type stars are of particular interest due to their potential to lead to very energetic phenomena or the merging of exotic compact objects. Aims. We aim to determine the orbital period variations of a sample of B+B and O+B massive overcontactVrancken, Jasmine et al.
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112024 -
Exploring massive star early evolution: the case of the Herschel 36 A triple systemTheoretical models show that some massive stars have not yet arrived at the zero-age main sequence (ZAMS) at the end of the accretion phase. At that time, they have lost their thick envelopes and thus could be optically visible. Although some candidates to optically observable ZAMS stars have been reported, the evolutionary status of none of themArias, Julia I. et al.
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112024 -
Boron depletion in Galactic early B-type stars reveals two different main sequence star populationsContext. The evolution and fate of massive stars are thought to be affected by rotationally induced internal mixing. The surface boron abundance is a sensitive tracer of this in early B-type main sequence stars. Aims. We test current stellar evolution models of massive main sequence stars which include rotational mixing through a systematic studyProffitt, Charles R. et al.
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102024 -
Binarity at LOw Metallicity (BLOeM): A spectroscopic VLT monitoring survey of massive stars in the SMCSurveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOwWang, C. et al.
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102024 -
The IACOB project: XII. New grid of northern standards for the spectral classification of B-type starsContext. With the advent of large spectroscopic surveys, automated stellar parameter determination has become commonplace. Nevertheless, spectral classification still offers a quick and useful alternative for obtaining parameter estimates for large samples of spectra of varying quality. Aims. We present a new atlas of stellar spectra covering the BNegueruela, I. et al.
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102024 -
Empirical mass-loss rates and clumping properties of O-type stars in the Large Magellanic CloudContext. The nature of mass-loss in massive stars is one of the most important and difficult to constrain processes in the evolution of massive stars. The largest observational uncertainties are related to the influence of metallicity and wind structure with optically thick clumps. Aims. We aim to constrain the wind parameters of sample of 18 OHawcroft, C. et al.
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102024 -
X-Shooting ULLYSES: Massive stars at low metallicity: V. Effect of metallicity on surface abundances of O starsContext. Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. Aims. We aim to testMartins, F. et al.
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92024 -
X-Shooting ULLYSES: Massive stars at low metallicity: IV. Spectral analysis methods and exemplary results for O starsContext. The spectral analysis of hot, massive stars is a fundamental astrophysical method of determining their intrinsic properties and feedback. With their inherent, radiation-driven winds, the quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment in order to obtain theSander, A. A. C. et al.
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92024 -
X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive starsContext. The winds of massive stars have a significant impact on stellar evolution and on the surrounding medium. The maximum speed reached by these outflows, the terminal wind speed v ∞, is a global wind parameter and an essential input for models of stellar atmospheres and feedback. With the arrival of the ULLYSES programme, a legacy UVHawcroft, C. et al.
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82024 -
X-Shooting ULLYSES: Massive stars at low metallicity. II. DR1: Advanced optical data products for the Magellanic CloudsContext. The XShootU project aims to obtain ground-based optical to near-infrared spectroscopy of all targets observed by the Hubble Space Telescope (HST) under the Director's Discretionary program ULLYSES. Using the medium-resolution spectrograph X-shooter, spectra of 235 OB and Wolf-Rayet (WR) stars in subsolar metallicity environments have beenSana, H. et al.
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82024 -
Rotational synchronisation of B-type binaries in 30 DoradusThe spin evolution of stars in close binary systems can be strongly affected by tides. We investigate the rotational synchronisation of the stellar components for 69 SB1 systems and 14 SB2 B-type systems in the 30 Doradus region of the Large Magellanic Cloud using observations from the VFTS and BBC surveys. Their orbital periods range from a few toLennon, D. J. et al.
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82024 -
The IACOB project. X. Large-scale quantitative spectroscopic analysis of Galactic luminous blue starsContext. Blue supergiants (BSGs) are key objects for understanding the evolution of massive stars, which play a crucial role in the evolution of galaxies. However, discrepancies between theoretical predictions and empirical observations have opened up important questions yet to be answered. Studying statistically significant and unbiased samples ofde Burgos, A. et al.
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72024 -
The IACOB project. XI. No increase in mass-loss rates over the bistability regionThe properties of blue supergiants are key for constraining the end of the main sequence (MS) of massive stars. Whether the observed drop in the relative number of fast-rotating stars below ≈21 kK is due to enhanced mass-loss rates at the location of the bistability jump, or the result of the end of the MS is still debated. Here, we combine newlyde Burgos, A. et al.
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72024 -
Expanded Sample of Small Magellanic Cloud Ultraviolet Dust Extinction Curves: Correlations between the 2175 Å Bump, q <SUB>PAH</SUB>, Ultraviolet Extinction Shape, and N(H I)/A(V)The Small Magellanic Cloud (SMC) shows a large variation in ultraviolet (UV) dust extinction curves, ranging from Milky Way (MW) like to significantly steeper curves with no detectable 2175 Å bump. This result is based on a sample of only nine sight lines. From Hubble Space Telescope Space Telescope Imaging Spectrograph and IUE spectra of OB starsGordon, Karl D. et al.
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72024 -
The colliding-wind binary HD 168112Context. Radio surveys of early-type stars have revealed a number of non-thermal emitters. Most of these have been shown to be binaries, where the collision between the two stellar winds is responsible for the non-thermal emission. Aims: HD 168112 is a non-thermal radio emitter, whose binary nature has only recently been confirmed spectroscopicallyBlomme, R. et al.
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72024 -
Evidence for very massive stars in extremely UV-bright star-forming galaxies at z ∼ 2.2-3.6We present a comprehensive analysis of the presence of very massive stars (VMS > 100 M ⊙) in the integrated spectra of 13 UV-bright star-forming galaxies at 2.2 ≲ z ≲ 3.6 taken with the Gran Telescopio Canarias (GTC). These galaxies have very high UV absolute magnitudes (M UV ≃ −24), intense star formation (star formation rate ≃100 − 1000 M ⊙ yr −1Upadhyaya, A. et al.
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62024 -
Boron Abundances in Early B Dwarfs of the Galactic Open Cluster NGC 3293New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron measurements. Six of the newly observed stars haveProffitt, Charles R. et al.
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62024 -
Detection of extragalactic magnetic massive starsContext. Studies of the magnetic characteristics of massive stars have recently received significant attention because they are progenitors of highly magnetised compact objects. Stars initially more massive than about 8 M ⊙ leave behind neutron stars and black holes by the end of their evolution. The merging of binary compact remnant systemsHubrig, S. et al.
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