scholarly journals Stellar properties of Galactic Centre He I sources

1999 ◽  
Vol 193 ◽  
pp. 476-477
Author(s):  
Luc Dessart ◽  
Paul A. Crowther ◽  
Linda J. Smith ◽  
Bruce Bohannan
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Star Formation History ◽  
Galactic Centre ◽  
Star Evolution ◽  
Formation History ◽  
Central Parsec ◽  
Stellar Properties ◽  
Massive Star Evolution ◽  
High Metallicity

The Galactic Centre (GC) region has in recent years attracted a lot of attention from the hot star community following the discovery of numerous He I emission line sources (Krabbe et al. 1991). Recent studies (e.g., Najarro et al. 1994) revealed stellar properties reminiscent of cool Wolf-Rayet stars, providing clues to the origin of the Lyman and He+ ionizing fluxes, and the luminosity in the central parsec of our galaxy. They allow the recent star formation history to be unveiled, and assess the effect of high metallicity on massive star evolution.

scholarly journals Metallicity studies of the Galactic center: evidence for a top-heavy star formation history?

2013 ◽  
Vol 9 (S303) ◽  
pp. 252-253
Author(s):  
Francisco Najarro ◽  
Diego de la Fuente ◽  
Tom R. Geballe ◽  
Don F. Figer
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Local Group ◽  
Galactic Center ◽  
Massive Stars ◽  
Star Formation History ◽  
Test Bed ◽  
Formation History ◽  
History Of ◽  
Stellar Properties

AbstractThe Galactic center (GC) region hosts three of the most massive resolved young clusters in the Local Group and constitutes a test bed for studying the star formation history of the region and inferring the possibility of a top-heavy scenario. Further, recent detection of a large number of apparently isolated massive stars within the inner 80 pc of the Galactic center has raised fundamental questions regarding massive star formation in a such a dense and harsh environment. Noting that most of the isolated massive stars have spectral analogs in the Quintuplet cluster, we have undertaken a combined analysis of the infrared spectra of both selected Quintuplet stars and the isolated objects using Gemini spectroscopy. We present preliminary results, aiming at α-elements versus iron abundances, stellar properties, ages and radial velocities which will differentiate the top-heavy and star-formation scenarios.

scholarly journals DDO68-V1: an extremely metal-poor LBV in a void galaxy

2018 ◽  
Vol 14 (S344) ◽  
pp. 392-395
Author(s):  
Yulia Perepelitsyna ◽  
Simon Pustilnik
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Rare Event ◽  
Local Universe ◽  
Hii Region ◽  
V Band ◽  
Star Evolution ◽  
Low Metallicity ◽  
Massive Star Evolution

AbstractThe lowest metallicity massive stars in the Local Universe with $Z\sim \left( {{Z}_{\odot }}/50-{{Z}_{\odot }}/30 \right)$ are the crucial objects to test the validity of assumptions in the modern models of very low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. DDO68-V1 in a void galaxy DDO68 is a unique extremely metal-poor massive star. Discovered by us in 2008 in the HII region Knot3 with $Z={{Z}_{\odot }}/35\,\left[ 12+\log \left( \text{O/H} \right)\sim 7.14 \right]$, DDO68-V1 was identified as an LBV star. We present here the LBV lightcurve in V band, combining own new data and the last archive and/or literature data on the light of Knot3 over the 30 years. We find that during the years 2008-2011 the LBV have experienced a very rare event of ‘giant eruption’ with V-band amplitude of 4.5 mag ($V\sim {{24.5}^{m}}-{{20}^{m}}$).

scholarly journals The Massive stellar Population at the Galactic Center

2016 ◽  
Vol 12 (S329) ◽  
pp. 287-291
Author(s):  
Francisco Najarro ◽  
Diego de la Fuente ◽  
Tom R. Geballe ◽  
Don F. Figer ◽  
D. John Hillier
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Milky Way ◽  
Local Group ◽  
Galactic Center ◽  
Spectroscopic Studies ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History

AbstractWe present results from our ongoing infrared spectroscopic studies of the massive stellar content at the Center of the Milky Way. This region hosts a large number of apparently isolated massive stars as well as three of the most massive resolved young clusters in the Local Group. Our survey seeks to infer the presence of a possible top-heavy recent star formation history and to test massive star formation channels: clusters vs isolation.

scholarly journals Massive-star evolution at high metallicity

2011 ◽  
pp. 341-353
Author(s):  
G. Meynet ◽  
N. Mowlavi ◽  
A. Maeder
Keyword(s):  
Massive Star ◽  
Star Evolution ◽  
Massive Star Evolution ◽  
High Metallicity

scholarly journals The New 30 Doradus

1999 ◽  
Vol 190 ◽  
pp. 213-216
Author(s):  
Nolan R. Walborn ◽  
Rodolfo H. Barbá
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Global Structure ◽  
Star Formation History ◽  
Massive Star Formation ◽  
Formation History ◽  
Infrared Studies ◽  
New Generation ◽  
30 Doradus

Recent optical and infrared studies of 30 Doradus have revealed a more complex and diverse star-formation history than previously recognized. Five spatially and/or temporally distinct populations have been identified, including a new generation currently being triggered by the R136 cluster in its surroundings. HST/NICMOS observations of the latter provide insights into the phenomena of triggered massive-star formation, as well as the global structure and evolution of the starburst region.

scholarly journals Talks also presented at the Symposium

2016 ◽  
Vol 12 (S329) ◽  
pp. 346-351
Keyword(s):  
Massive Star ◽  
Gamma Ray ◽  
Low Mass Stars ◽  
Giant Stars ◽  
Star Evolution ◽  
Low Mass ◽  
Red Giant ◽  
Stellar Properties ◽  
Massive Star Evolution ◽  
The Impact

Internal rotation and magnetism are key ingredients that largely affect explosive stellar deaths (Supernovae and Gamma Ray Bursts) and the properties of stellar remnants (White Dwarfs, Neutron Stars and Black Holes). However, the study of these subtle internal stellar properties has been limited to very indirect proxies. In the last couple of years, exciting asteroseismic results have been obtained by the Kepler satellite. Among these results are 1) The direct measure of the degree of radial differential rotation in many evolved low-mass stars and in a few massive stars, and 2) The detection of strong (>105 G) internal magnetic fields in thousands of red giant stars that had convective cores during their main sequence. I will discuss the impact of these important findings for our understanding of massive star evolution.

scholarly journals The UV upturn phenomenon in the hierarchical universe

2011 ◽  
Vol 7 (S284) ◽  
pp. 56-58
Author(s):  
Jaehyun Lee ◽  
Sukyoung K. Yi
Keyword(s):  
Star Formation ◽  
Empirical Studies ◽  
Population Models ◽  
Star Formation History ◽  
Model Galaxy ◽  
Formation History ◽  
History Of ◽  
High Metallicity ◽  
Traditional Understanding ◽  
Uv Upturn

AbstractRecent studies show that an old stellar population with high metallicity in the monolithic paradigm can explain the UV upturn. Numerical simulations and empirical studies however point out that massive early-type galaxies have evolved hierarchically with an extended star formation history. This obviously has an impact on our traditional understanding on the UV upturn and requires a new investigation on its origin. We report on our investigation on the evolutionary history of model galaxy SEDs in the hierarchical scenario. The use of conventional population models (calibrated to the monolithic picture) in combination with merger trees and extended star formation fails to reproduce the observed UV upturn. If a hierarchical picture is thought to be more realistic than a monolithic one, new calibration on the population models is required.

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