Physical properties and evolution of Massive Stars

    General
    Description

    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.
    Principal investigator
    Project staff
    Dr.
    Gabriel Gómez Velarde

    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).

    Related publications

    • Young LMC clusters: the role of red supergiants and multiple stellar populations in their integrated light and CMDs

      The optical integrated spectra of three Large Magellanic Cloud young stellar clusters (NGC 1984, NGC 1994 and NGC 2011) exhibit concave continua and prominent molecular bands which deviate significantly from the predictions of single stellar population (SSP) models. In order to understand the appearance of these spectra, we create a set of young

      Asa'd, Randa S. et al.

      Advertised on:

      11
      2017
      Citations
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    • Gran Telescopio Canarias observations of an overdense region of Lyman α emitters at z = 6.5

      We present the results of our search near the end of the Reionization Epoch for faint galaxies. This has been done using very deep OSIRIS images obtained at the Gran Telescopio Canarias (GTC). Our observations focus around two close, massive Lyman α emitters (LAEs) at redshift 6.5, discovered in the SXDS field within a large-scale overdense region

      Chanchaiworawit, K. et al.

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      8
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    • The VLT-FLAMES Tarantula Survey. XXVI. Properties of the O-dwarf population in 30 Doradus

      Context. The VLT-FLAMES Tarantula Survey has observed hundreds of O-type stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Aims: We study the properties of a statistically significant sample of O-type dwarfs in the same star-forming region and test the latest atmospheric and evolutionary models of the early main-sequence phase of

      Sabín-Sanjulián, C. et al.

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      5
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    • Legacy ExtraGalactic UV Survey with The Hubble Space Telescope: Stellar Cluster Catalogs and First Insights Into Cluster Formation and Evolution in NGC 628

      We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry

      Adamo, A. et al.

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      6
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    • Physical properties of the first spectroscopically confirmed red supergiant stars in the Sculptor Group galaxy NGC 55

      We present K-band Multi-Object Spectrograph (KMOS) observations of 18 red supergiant (RSG) stars in the Sculptor Group galaxy NGC 55. Radial velocities are calculated and are shown to be in good agreement with previous estimates, confirming the supergiant nature of the targets and providing the first spectroscopically confirmed RSGs in NGC 55

      Patrick, L. et al.

      Advertised on:

      6
      2017
      Citations
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    • The VLT-FLAMES Tarantula Survey . XXIV. Stellar properties of the O-type giants and supergiants in 30 Doradus

      Context. The Tarantula region in the Large Magellanic Cloud (LMC) contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and mass-loss properties. Aims: Using ground-based optical spectroscopy obtained in the

      Ramírez-Agudelo, O. H. et al.

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      4
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    • The VLT-FLAMES Tarantula Survey. XXV. Surface nitrogen abundances of O-type giants and supergiants

      Context. Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Aims: Using a sample of 72 presumably single O-type giants to supergiants observed in the context of the VLT-FLAMES Tarantula

      Grin, N. J. et al.

      Advertised on:

      4
      2017
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    • Constraining the Epoch of Reionization from the Observed Properties of the High-z Universe

      We combine observational data on a dozen independent cosmic properties at high-z with the information on reionization drawn from the spectra of distant luminous sources and the cosmic microwave background (CMB) to constrain the interconnected evolution of galaxies and the intergalactic medium since the dark ages. The only acceptable solutions are

      Salvador-Solé, E. et al.

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      1
      2017
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    • The VLT-FLAMES Tarantula Survey. XXIII. Two massive double-lined binaries in 30 Doradus

      Aims: We investigate the characteristics of two newly discovered short-period, double-lined, massive binary systems in the Large Magellanic Cloud, VFTS 450 (O9.7 II-Ib + O7::) and VFTS 652 (B1 Ib + O9: III:). Methods: We perform model-atmosphere analyses to characterise the photospheric properties of both members of each binary (denoting the

      Howarth, I. D. et al.

      Advertised on:

      10
      2015
      Citations
      10
    • Discovery of the Massive Overcontact Binary VFTS352: Evidence for Enhanced Internal Mixing

      The contact phase expected to precede the coalescence of two massive stars is poorly characterized due to the paucity of observational constraints. Here we report on the discovery of VFTS 352, an O-type binary in the 30 Doradus region, as the most massive and earliest spectral type overcontact system known to date. We derived the 3D geometry of the

      Almeida, L. A. et al.

      Advertised on:

      10
      2015
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      51
    • The Brightest Young Star Clusters in NGC 5253.

      The nearby dwarf starburst galaxy NGC 5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the “radio nebula”). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC 5253

      Calzetti, D. et al.

      Advertised on:

      10
      2015
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    • The VLT-FLAMES Tarantula Survey. XXII. Multiplicity properties of the B-type stars

      We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects

      Dunstall, P. R. et al.

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      8
      2015
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    • LEGUS Discovery of a Light Echo Around Supernova 2012aw

      We have discovered a luminous light echo around the normal Type II-Plateau Supernova (SN) 2012aw in Messier 95 (M95; NGC 3351), detected in images obtained approximately two years after explosion with the Wide Field Channel 3 on board the Hubble Space Telescope by the Legacy ExtraGalactic Ultraviolet Survey. The multi-band observations span from

      Van Dyk, S. D. et al.

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      6
      2015
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    • The VLT-FLAMES Tarantula Survey. XIX. B-type supergiants: Atmospheric parameters and nitrogen abundances to investigate the role of binarity and the width of the main sequence

      Context. Model atmosphere analyses have been previously undertaken for both Galactic and extragalactic B-type supergiants. By contrast, little attention has been given to a comparison of the properties of single supergiants and those that are members of multiple systems. Aims: Atmospheric parameters and nitrogen abundances have been estimated for

      McEvoy, C. M. et al.

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      3
      2015
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    • The VLT-FLAMES Tarantula Survey. XVIII. Classifications and radial velocities of the B-type stars

      We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We

      Evans, C. J. et al.

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      2
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    • Legacy Extragalactic UV Survey (LEGUS) With the Hubble Space Telescope. I. Survey Description

      The Legacy ExtraGalactic UV Survey (LEGUS) is a Cycle 21 Treasury program on the Hubble Space Telescope aimed at the investigation of star formation and its relation with galactic environment in nearby galaxies, from the scales of individual stars to those of ˜kiloparsec-size clustered structures. Five-band imaging from the near-ultraviolet to the

      Calzetti, D. et al.

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      2
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    • Building galaxies, stars, planets and the ingredients for life between the stars. The science behind the European Ultraviolet-Visible Observatory

      This contribution gathers the contents of the white paper submitted by the UV community to the Call issued by the European Space Agency in March 2013, for the definition of the L2 and L3 missions in the ESA science program. We outlined the key science that a large UV facility would make possible and the instrumentation to be implemented. The growth

      Gómez de Castro, A. I. et al.

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      11
      2014
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    • The VLT-FLAMES Tarantula Survey. XVII. Physical and wind properties of massive stars at the top of the main sequence

      The evolution and fate of very massive stars (VMS) is tightly connected to their mass-loss properties. Their initial and final masses differ significantly as a result of mass loss. VMS have strong stellar winds and extremely high ionising fluxes, which are thought to be critical sources of both mechanical and radiative feedback in giant H ii

      Bestenlehner, J. M. et al.

      Advertised on:

      10
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    • Winds of Low-metallicity OB-type Stars: HST-COS Spectroscopy in IC 1613

      We present the first quantitative ultraviolet spectroscopic analysis of resolved OB stars in IC 1613. Because of its alleged very low metallicity (lsim1/10 Z ☉, from H II regions), studies in this Local Group dwarf galaxy could become a significant step forward from the Small Magellanic Cloud (SMC) toward the extremely metal-poor massive stars of

      Garcia, M. et al.

      Advertised on:

      6
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    • The VLT-FLAMES Tarantula Survey. XIII: On the nature of O Vz stars in 30 Doradus

      Context. O Vz stars, a subclass of O-type dwarfs characterized by having He ii λ4686 stronger in absorption than any other helium line in their blue-violet spectra, have been suggested to be on or near the zero-age main sequence (ZAMS). If their youth were confirmed, they would be key objects with which to advance our knowledge of the physical

      Sabín-Sanjulián, C. et al.

      Advertised on:

      4
      2014
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