scholarly journals THE CLOSE BINARY PROPERTIES OF MASSIVE STARS IN THE MILKY WAY AND LOW-METALLICITY MAGELLANIC CLOUDS

2013 ◽  
Vol 778 (2) ◽  
pp. 95 ◽  
Author(s):  
Maxwell Moe ◽  
Rosanne Di Stefano
Keyword(s):  
Milky Way ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Close Binary ◽  
Low Metallicity

scholarly journals The effects of different Type Ia SN yields on Milky Way chemical evolution

2021 ◽  
Vol 503 (3) ◽  
pp. 3216-3231
Author(s):  
Marco Palla
Keyword(s):  
Chemical Evolution ◽  
White Dwarf ◽  
Time Distribution ◽  
Milky Way ◽  
Massive Stars ◽  
Abundance Patterns ◽  
Type Ia ◽  
Low Metallicity ◽  
Explosion Mechanism ◽  
Chemical Evolution Model

ABSTRACT We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe, in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contribution to chemical evolution of different Type Ia SN channels. The results of the models are compared with recent LTE and NLTE observational data. We find that ‘classical’ W7 and WDD2 models produce Fe masses and [α/Fe] abundance patterns similar to more recent and physical near-Chandrasekar and sub-Chandrasekar models. For Fe-peak elements, we find that the results strongly depend either on the white dwarf explosion mechanism (deflagration-to-detonation, pure deflagration, double detonation) or on the initial white dwarf conditions (central density, explosion pattern). The comparison of chemical evolution model results with observations suggests that a combination of near-Chandrasekar and sub-Chandrasekar yields is necessary to reproduce the data of V, Cr, Mn and Ni, with different fractions depending on the adopted massive stars stellar yields. This comparison also suggests that NLTE and singly ionized abundances should be definitely preferred when dealing with most of Fe-peak elements at low metallicity.

scholarly journals Mass loss and evolution of massive stars in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 480-482 ◽  
Author(s):  
Claus Leitherer ◽  
Norbert Langer
Keyword(s):  
Mass Loss ◽  
Iterative Procedure ◽  
Metal Content ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Magellanic Clouds ◽  
Evolutionary Models ◽  
Low Metallicity ◽  
Self Consistency

The structure and evolution of massive stars is significantly influenced by effects of chemical composition in a low-metallicity environment (as compared to the solar neighbourhood, SN), such as the Magellanic Clouds. A fundamental ingredient in evolutionary models is the stellar mass-loss rate M. Lower metal content decreases the mass-loss rates derived theoretically, which in turn affects the stellar evolution models. On the other hand, different evolutionary models predict different stellar parameters (especially L), which again influence M so that an iterative procedure is required to achieve self-consistency.

scholarly journals The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way

2019 ◽  
Author(s):  
F Rizzuti ◽  
G Cescutti ◽  
F Matteucci ◽  
A Chieffi ◽  
R Hirschi ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Milky Way ◽  
Massive Stars ◽  
Rotational Velocity ◽  
Stellar Rotation ◽  
Deep Impact ◽  
Low Metallicity ◽  
Group Rotation ◽  
R Process ◽  
Chemical Evolution Model

Abstract Most neutron capture elements have a double production by r- and s-processes, but the question of production sites is complex and still open. Recent studies show that including stellar rotation can have a deep impact on nucleosynthesis. We studied the evolution of Sr and Ba in the Milky Way. A chemical evolution model was employed to reproduce the Galactic enrichment. We tested two different nucleosynthesis prescriptions for s-process in massive stars, adopted from the Geneva group and the Rome group. Rotation was taken into account, studying the effects of stars without rotation or rotating with different velocities. We also tested different production sites for the r-process: magneto rotational driven supernovae and neutron star mergers. The evolution of the abundances of Sr and Ba is well reproduced. The comparison with the the most recent observations shows that stellar rotation is a good assumption, but excessive velocities result in overproduction of these elements. In particular, the predicted evolution of the [Sr/Ba] ratio at low metallicity does not explain the data at best if rotation is not included. Adopting different rotational velocities for different stellar mass and metallicity better explains the observed trends. Despite the differences between the two sets of adopted stellar models, both show a better agreement with the data assuming an increase of rotational velocity toward low metallicity. Assuming different r-process sources does not alter this conclusion.

29. Stellar Spectra (Spectres Stellaires)

1991 ◽  
Vol 21 (1) ◽  
pp. 309-326
Keyword(s):  
Milky Way ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Dynamical Interaction ◽  
Stellar Spectra ◽  
Luminous Blue Variables ◽  
Classical Novae ◽  
Giant Stars ◽  
Red Giant ◽  
Sydney Australia

In the triennium under review, from the late second half of 1987 to the early second half of 1990, Commission 29 has sponsored or cosponsored the following IAU Conferences: Coll. No. 106, “Evolution of Peculiar Red Giant Stars,” Bloomington, Indiana, July 1988; CoU. No. 114, “White Dwarfs,” Hanover, New Hamsphire, August 1988; Coll. No. 113, “Physics of Luminous Blue Variables,” Val Morin, Quebec, August 1988; Coll. No. 122, “Physics of Classical Novae,” Madrid, Spain, June 1989; Symp. No. 143, “Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies,” Denpasar, Indonesia, June 1990; Symp. No 148, “The Magellanic Clouds and their Dynamical Interaction with the Milky Way,” Sydney, Australia, July 1990; Symp. No. 145, “Evolution of Stars: the Photospheric Abundance Connection,” Druzba, Bulgaria. August 1990.

scholarly journals Ultraviolet spectral libraries of massive stars at low metallicity

1999 ◽  
Vol 193 ◽  
pp. 616-617
Author(s):  
Carmelle Robert
Keyword(s):  
Stellar Population ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Solar Neighbourhood ◽  
Hot Stars ◽  
Star Forming ◽  
Distant Star ◽  
Medium Resolution ◽  
Low Metallicity ◽  
Spectral Libraries

Three new ultraviolet spectral libraries of massive, hot stars using high and medium resolution spectra of objects located in the solar neighbourhood and the Magellanic Clouds are presented. Massive stars display unique wind signatures which are relatively easy to study in the ultraviolet. These libraries are crucial tools when investigating the massive stellar population of distant star-forming galaxies.

scholarly journals The quest for magnetic massive stars in the Magellanic Clouds

2016 ◽  
Vol 12 (S329) ◽  
pp. 430-430
Author(s):  
Y. Nazé ◽  
S. Bagnulo ◽  
N. R. Walborn ◽  
N. Morrell ◽  
G. A. Wade ◽  
...  
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
High Resolution Spectroscopy ◽  
X Ray ◽  
Low Metallicity

AbstractThe Of?p category was introduced more than 40 years ago to gather several Galactic stars with some odd properties. Since 2000, spectropolarimetry, high-resolution spectroscopy, long-term photometry, and X-ray observations have revealed their nature: magnetic oblique rotators - they all have magnetic fields that confine their winds. Several Of?p stars have now been detected in the Magellanic Clouds, likely the prototypes of magnetic massive stars at low metallicity. This contribution will present the most recent photometric, spectroscopic, and spectropolarimetric data, along with the first modeling of these objects.

scholarly journals The WFI Hα spectroscopic survey of the Magellanic Clouds: Be stars in SMC open clusters

2008 ◽  
Vol 4 (S256) ◽  
pp. 349-354
Author(s):  
Christophe Martayan ◽  
Dietrich Baade ◽  
Juan Fabregat
Keyword(s):  
Angular Momentum ◽  
Milky Way ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Photometric Data ◽  
Be Stars ◽  
First Results ◽  
Low Metallicity ◽  
Loss Of Mass ◽  
Lower Loss

AbstractAt low metallicity, B-type stars show lower loss of mass and, therefore, angular momentum so that it is expected that there are more Be stars in the Magellanic Clouds than in the Milky Way. However, till now, searches for Be stars were only performed in a very small number of open clusters in the Magellanic Clouds. Using the ESO/WFI in its slitless spectroscopic mode, we performed a Hα survey of the Large and Small Magellanic Cloud. Eight million low-resolution spectra centered on Hα were obtained. For their automatic analysis, we developed the ALBUM code. Here, we present the observations, the method to exploit the data and first results for 84 open clusters in the SMC. In particular, cross-correlating our catalogs with OGLE positional and photometric data, we classified more than 4000 stars and were able to find the B and Be stars in them. We show the evolution of the rates of Be stars as functions of area density, metallicity, spectral type, and age.

scholarly journals Massive stars in advanced evolutionary stages, and the progenitor of GW150914

2016 ◽  
Vol 12 (S329) ◽  
pp. 223-227 ◽  
Author(s):  
Wolf-Rainer Hamann ◽  
Lidia Oskinova ◽  
Helge Todt ◽  
Andreas Sander ◽  
Rainer Hainich ◽  
...  
Keyword(s):  
Binary Systems ◽  
Massive Stars ◽  
Empirical Studies ◽  
Stellar Atmosphere ◽  
Close Binary ◽  
Close Binaries ◽  
Stellar Winds ◽  
Internal Mixing ◽  
Imperfect Knowledge ◽  
Low Metallicity

AbstractThe recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution. Critical ingredients comprise mass-loss, rotation, magnetic fields, internal mixing, and mass transfer in close binary systems. The imperfect knowledge of these factors implies large uncertainties for models of stellar populations and their feedback. In this contribution we summarize our empirical studies of Wolf-Rayet populations at different metallicities by means of modern non-LTE stellar atmosphere models, and confront these results with the predictions of stellar evolution models. At the metallicity of our Galaxy, stellar winds are probably too strong to leave remnant masses as high as ~30 M⊙, but given the still poor agreement between evolutionary tracks and observation even this conclusion is debatable. At the low metallicity of the Small Magellanic Cloud, all WN stars which are (at least now) single are consistent with evolving quasi-homogeneously. O and B-type stars, in contrast, seem to comply with standard evolutionary models without strong internal mixing. Close binaries which avoided early merging could evolve quasi-homogeneously and lead to close compact remnants of relatively high masses that merge within a Hubble time.

scholarly journals What Ejected Nebulae around Evolved Massive Stars Tell us of the Rotation of their Central Star

2004 ◽  
Vol 215 ◽  
pp. 491-499
Author(s):  
Antonella Nota
Keyword(s):  
Chemical Composition ◽  
Fossil Record ◽  
Milky Way ◽  
Massive Stars ◽  
Central Star ◽  
Magellanic Clouds ◽  
Supporting Evidence ◽  
Deep Insight ◽  
The Moment ◽  
Previous Phase

Most LBVs and Ofpe/WN9 stars in the Milky Way and in the Magellanic Clouds are surrounded by associated circumstellar nebulae which have been ejected in some previous phase of their evolution. These nebulae are the fossil record of the interactions of previous winds and of the violent ejections in which the stars most likely have shed their outer layers. The study of the morphology, kinematics and chemical composition of the ejected material has allowed us to gain deep insight in the ejection and shaping mechanism, and in the properties of the central star at the moment of the ejection. In this review I will address how ejected nebulae are providing independent supporting evidence that rotation plays a major role in the evolution of massive stars.

scholarly journals Empirical evidence suggesting a stellar upper-mass limit

2006 ◽  
Vol 2 (14) ◽  
pp. 206-206
Author(s):  
M. Sally Oey
Keyword(s):  
Empirical Evidence ◽  
Milky Way ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Statistical Techniques ◽  
Mass Limit ◽  
Theoretical Understanding ◽  
Stellar Masses

AbstractWhile theoretical understanding remains to be clarified regarding the mechanisms that may or may not limit stellar masses, it is possible to empirically evaluate the existence of an upper-mass limit. ZAMS masses of the most massive stars have been estimated for a range of environments in our local Milky Way neighborhood and the Magellanic Clouds. Various statistical techniques demonstrate the existence of an upper-mass limit in this stellar sample.

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