scholarly journals Zooming into Eta Carinae with interferometry

2014 ◽  
Vol 9 (S307) ◽  
pp. 267-272
Author(s):  
Jose H. Groh
Keyword(s):  
Mass Loss ◽  
High Spatial Resolution ◽  
Massive Stars ◽  
Spatial Scales ◽  
Large Telescope ◽  
Rapid Rotation ◽  
Eta Carinae ◽  
Very Large Telescope ◽  
Effects Of Rotation ◽  
Circumstellar Environment

AbstractShaped by strong mass loss, rapid rotation, and/or the presence of a close companion, the circumstellar environment around the most massive stars is complex and anything but spherical. Here we provide a brief overview of the high spatial resolution observations of Eta Carinae performed with the Very Large Telescope Interferometer (VLTI). Special emphasis is given to discuss VLTI/AMBER and VLTI/VINCI observations, which directly resolve spatial scales comparable to those where mass loss originates. Studying scales as small as a few milli-arcseconds allows us to investigate kinematical effects of rotation and binarity in more detail than ever before.

scholarly journals Episodic Mass Loss and Pre-SN Circumstellar Envelopes

2007 ◽  
Vol 3 (S250) ◽  
pp. 193-200 ◽  
Author(s):  
Nathan Smith
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Supernova Explosion ◽  
Circumstellar Envelopes ◽  
Observational Fact ◽  
Solar Metallicity ◽  
The 19Th Century ◽  
Very High ◽  
Circumstellar Environment

AbstractI discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 102 AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.

scholarly journals Emploi de la caméra électronique grand champ avec les très grands télescopes - Extrapolation des résultats obtenus avec le télescope C.F.H.

1984 ◽  
Vol 79 ◽  
pp. 639-657 ◽  
Author(s):  
G. Wlérick ◽  
L. Renard ◽  
D. Horville ◽  
F. Gex ◽  
J.M. Munier ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Large Field ◽  
Nearby Galaxy ◽  
Gravitational Lenses ◽  
Large Telescope ◽  
Very Large Telescope

Abstractthe large field Lallemand electronographic camera has proved to be an ideal receptor for bidimensional photometry with the C.F.H. 3.6 m. Telescope. It permits to measure faint stars up to about B = 25. Plates of a large variety of objects have been obtained ; for example : crowded fields such as the nearby galaxy Messier 33 ; fields where one must recognize faint galaxies from stars; objects for which a high spatial resolution is needed, such as the optical jet of Messier 87 or gravitational lenses. It is possible to predict the limits of the receptor with a very large telescope.

scholarly journals MUSEing about the SHAPE of eta Car's outer ejecta

2016 ◽  
Vol 12 (S329) ◽  
pp. 423-423
Author(s):  
A. Mehner ◽  
W. Steffen ◽  
J. Groh ◽  
F. P. A. Vogt ◽  
D. Baade ◽  
...  
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Three Dimensional ◽  
Shape Modelling ◽  
Integral Field Spectroscopy ◽  
Spatial Cohesion ◽  
Integral Field ◽  
Circumstellar Environment ◽  
Η Car

AbstractThe role of episodic mass loss in evolved massive stars is one of the outstanding questions in stellar evolution theory. Integral field spectroscopy of nebulae around massive stars provide information on their recent mass-loss history. η Car is one of the most massive evolved stars and is surrounded by a complex circumstellar environment. We have conducted a three-dimensional morpho-kinematic analysis of η Car’s ejecta outside its famous Homunculus nebula. SHAPE modelling of VLT MUSE data establish unequivocally the spatial cohesion of the outer ejecta and the correlation of ejecta with the soft X-ray emission.

scholarly journals Resolving the mass loss from red supergiants by high angular resolution

2016 ◽  
Vol 12 (S329) ◽  
pp. 97-103
Author(s):  
Keiichi Ohnaka
Keyword(s):  
Mass Loss ◽  
Spatial Resolution ◽  
Angular Resolution ◽  
High Spatial Resolution ◽  
Spatial Scales ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Long Baseline ◽  
Red Supergiants ◽  
Late Stages

AbstractDespite its importance on late stages of the evolution of massive stars, the mass loss from red supergiants (RSGs) is a long-standing problem. To tackle this problem, it is essential to observe the wind acceleration region close to the star with high spatial resolution. While the mass loss from RSGs is often assumed to be spherically symmetric with a monotonically accelerating wind, there is mounting observational evidence that the reality is much more complex. I review the recent progress in high spatial resolution observations of RSGs, encompassing from the circumstellar envelope on rather large spatial scales (~100 stellar radii) to milliarcsecond-resolution aperture-synthesis imaging of the surface and the atmosphere of RSGs with optical and infrared long-baseline interferometers.

scholarly journals An ALMA 3 mm continuum census of Westerlund 1

2018 ◽  
Vol 617 ◽  
pp. A137 ◽  
Author(s):  
D. M. Fenech ◽  
J. S. Clark ◽  
R. K. Prinja ◽  
S. Dougherty ◽  
F. Najarro ◽  
...  
Keyword(s):  
Mass Loss ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Spatially Resolved ◽  
Wind Theory ◽  
Key Driver ◽  
Massive Clusters ◽  
Circumstellar Environment ◽  
Loss Rates

Massive stars play an important role in both cluster and galactic evolution and the rate at which they lose mass is a key driver of both their own evolution and their interaction with the environment up to and including their terminal SNe explosions. Young massive clusters provide an ideal opportunity to study a co-eval population of massive stars, where both their individual properties and the interaction with their environment can be studied in detail. We aim to study the constituent stars of the Galactic cluster Westerlund 1 in order to determine mass-loss rates for the diverse post-main sequence population of massive stars. To accomplish this we made 3mm continuum observations with the Atacama Large Millimetre/submillimetre Array. We detected emission from 50 stars in Westerlund 1, comprising all 21 Wolf-Rayets within the field of view, plus eight cool and 21 OB super-/hypergiants. Emission nebulae were associated with a number of the cool hypergiants while, unexpectedly, a number of hot stars also appear spatially resolved. We were able to measure the mass-loss rates for a unique population of massive post-main sequence stars at every stage of evolution, confirming a significant increase as stars transitioned from OB supergiant to WR states via LBV and/or cool hypergiant phases. Fortuitously, the range of spectral types exhibited by the OB supergiants provides a critical test of radiatively-driven wind theory and in particular the reality of the bi-stability jump. The extreme mass-loss rate inferred for the interacting binary Wd1-9 in comparison to other cluster members confirmed the key role binarity plays in massive stellar evolution. The presence of compact nebulae around a number of OB and WR stars is unexpected; by analogy to the cool super-/hypergiants we attribute this to confinement and sculpting of the stellar wind via interaction with the intra-cluster medium/wind. Given the morphologies of core collapse SNe depend on the nature of the pre-explosion circumstellar environment, if this hypothesis is correct then the properties of the explosion depend not just on the progenitor, but also the environment in which it is located.

scholarly journals Interferometry of massive stars: the next step

2014 ◽  
Vol 9 (S307) ◽  
pp. 480-489
Author(s):  
Ph. Stee ◽  
A. Meilland ◽  
O. L. Creevey
Keyword(s):  
Differential Rotation ◽  
Angular Resolution ◽  
Massive Stars ◽  
High Angular Resolution ◽  
Third Generation ◽  
Optical Interferometer ◽  
Large Telescope ◽  
Very Large Telescope ◽  
Beam Combiner ◽  
Radial Pulsations

AbstractWe present some new and interesting results on the complementarity between asteroseismology and interferometry, the detection of non-radial pulsations in massive stars and the possibility for evidencing differential rotation on the surface of Bn stars. We also discuss the curretn interferometric facilities, namely the Very Large Telescope Interferometer (VLTI)/AMBER, VLTI/MIDI, VLTI/PIONIER within the European Southern Observatory (ESO) context and the Center for High Angular Resolution Astronomy (CHARA) array with their current limitations. The forthcoming second-generation VLTI instruments GRAVITY and MATISSE are presented as well as the FRIEND prototype in the visible spectral domain and an update of the Navy Precision Optical Interferometer (NPOI). A conclusion is presented with a special emphasis on the foreseen difficulties for a third generation of interferometric instruments within the (budget limited) Extremely Large Telescope framework and the need for strong science cases to push a future visible beam combiner.

scholarly journals Can Very Massive Stars Avoid Pair-Instability Supernovae?

2007 ◽  
Vol 3 (S250) ◽  
pp. 209-216 ◽  
Author(s):  
Sylvia Ekström ◽  
Georges Meynet ◽  
André Maeder
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Mass Loss ◽  
Massive Stars ◽  
Core Size ◽  
Metal Free ◽  
The Core ◽  
Low Metallicity ◽  
Effects Of Rotation ◽  
Population Iii

AbstractVery massive primordial stars (140 M⊙ < M < 260 M⊙) are supposed to end their lives as PISN. Such an event can be traced by a typical chemical signature in low metallicity stars, but at the present time, this signature is lacking in the extremely metal-poor stars we are able to observe. Does it mean that those very massive objects were not formed, contrarily to the primordial star formation scenarios ? Could it be possible that they avoided this tragic fate ?We explore the effects of rotation, anisotropical mass loss and magnetic field on the core size of very massive Population III models. We find that magnetic fields provide the strong coupling that is lacking in standard evolution metal-free models and our 150 M⊙ Population III model avoids indeed the pair-instability explosion.

scholarly journals Critical angular velocity and anisotropic mass loss of rotating stars with radiation-driven winds

2019 ◽  
Vol 625 ◽  
pp. A88 ◽  
Author(s):  
D. Gagnier ◽  
M. Rieutord ◽  
C. Charbonnel ◽  
B. Putigny ◽  
F. Espinosa Lara
Keyword(s):  
Angular Momentum ◽  
Angular Velocity ◽  
Mass Loss ◽  
Mass Flux ◽  
Rotation Rate ◽  
Massive Stars ◽  
Rotating Stars ◽  
Wind Regime ◽  
Rapid Rotation ◽  
Radiative Acceleration

Context. The understanding of the evolution of early-type stars is tightly related to that of the effects of rapid rotation. For massive stars, rapid rotation combines with their strong radiation-driven wind. Aims. The aim of this paper is to investigate two questions that are prerequisite to the study of the evolution of massive rapidly rotating stars: (i) What is the critical angular velocity of a star when radiative acceleration is significant in its atmosphere? (ii) How do mass and angular momentum loss depend on the rotation rate? Methods. To investigate fast rotation, which makes stars oblate, we used the 2D ESTER models and a simplified approach, the ω-model, which gives the latitudinal dependence of the radiative flux in a centrifugally flattened radiative envelope. Results. We find that radiative acceleration only mildly influences the critical angular velocity, at least for stars with masses lower than 40 M⊙. For instance, a 15 M⊙ star on the zero-age main sequence would reach criticality at a rotation rate equal to 0.997 the Keplerian equatorial rotation rate. We explain this mild reduction of the critical angular velocity compared to the classical Keplerian angular velocity by the combined effects of gravity darkening and a reduced equatorial opacity that is due to the centrifugal acceleration. To answer the second question, we first devised a model of the local surface mass flux, which we calibrated with previously developed 1D models. The discontinuity (the so-called bi-stability jump) included in the Ṁ − Teff relation of 1D models means that the mass flux of a fast-rotating star is controlled by either a single wind or a two-wind regime. Mass and angular momentum losses are strong around the equator if the star is in the two-wind regime. We also show that the difficulty of selecting massive stars that are viewed pole-on makes detecting the discontinuity in the relation between mass loss and effective temperature also quite challenging.

scholarly journals Physics of Mass Loss in Massive Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 25-36 ◽  
Author(s):  
Joachim Puls ◽  
Jon O. Sundqvist ◽  
Nevena Markova
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Massive Stars ◽  
Small Scale ◽  
Rapid Rotation ◽  
Luminous Blue Variables ◽  
Red Supergiants ◽  
The Impact ◽  
Eddington Limit ◽  
Loss Mechanisms

AbstractWe review potential mass-loss mechanisms in the various evolutionary stages of massive stars, from the well-known line-driven winds of O-stars and BA-supergiants to the less-understood winds of Red Supergiants. We discuss optically thick winds from Wolf-Rayet stars and Very Massive Stars, and the hypothesis of porosity-moderated, continuum-driven mass loss from stars formally exceeding the Eddington limit, which might explain the giant outbursts from Luminous Blue Variables. We finish this review with a glance on the impact of rapid rotation, magnetic fields and small-scale inhomogeneities in line-driven winds.

scholarly journals OB-stars as extreme condition test beds

2010 ◽  
Vol 6 (S272) ◽  
pp. 554-565 ◽  
Author(s):  
Joachim Puls ◽  
Jon O. Sundqvist ◽  
Jorge G. Rivero González
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Massive Stars ◽  
Extreme Condition ◽  
Rapid Rotation ◽  
Ob Stars ◽  
Test Beds

AbstractMassive stars are inherently extreme objects, in terms of radiation, mass loss, rotation, and sometimes also magnetic fields. Concentrating on a (personally biased) subset of processes related to pulsations, rapid rotation and its interplay with mass-loss, and the bi-stability mechanism, we will discuss how active (and normal) OB stars can serve as appropriate laboratories to provide further clues.

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