The Pre–Main-Sequence Stars and Initial Mass Function of NGC 2264

2000 ◽  
Vol 120 (2) ◽  
pp. 894-908 ◽  
Author(s):  
Byeong-Gon Park ◽  
Hwankyung Sung ◽  
Michael S. Bessell ◽  
Yong Hee Kang
Keyword(s):  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Main Sequence Stars

scholarly journals Very massive binaries in R 136

2010 ◽  
Vol 6 (S272) ◽  
pp. 497-498 ◽  
Author(s):  
André-Nicolas Chené ◽  
Olivier Schnurr ◽  
Paul A. Crowther ◽  
Eduardo F. Lajus ◽  
Anthony F. J. Moffat
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Clear Picture ◽  
Main Sequence Stars ◽  
High Quality ◽  
Keplerian Orbits

AbstractAs recent observations have shown, luminous, hydrogen-rich WN5-7h stars (and their somewhat less extreme cousins, O3f/WN6 stars) are the most massive main-sequence stars known. However, not nearly enough very massive stars have been reliably weighed to yield a clear picture of the upper initial-mass function (IMF). We therefore have carried out repeated high-quality spectroscopy of four new O3f/WN6 and WN5-7h binaries in R136 in the LMC with GMOS at Gemini-South, to derive Keplerian orbits for both components, respectively, and thus to directly determine their masses. We also monitored binary candidates and other, previously unsurveyed stars, to increase the number of very massive stars that can be directly weighed.

scholarly journals The initial mass function in the extended ultraviolet disc of M83

2019 ◽  
Vol 491 (2) ◽  
pp. 2366-2390 ◽  
Author(s):  
S M Bruzzese ◽  
David A Thilker ◽  
G R Meurer ◽  
Luciana Bianchi ◽  
A B Watts ◽  
...  
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Initial Mass ◽  
Main Sequence Stars ◽  
Red Giant ◽  
The Imf

ABSTRACT Using Hubble Space Telescope ACS/WFC data we present the photometry and spatial distribution of resolved stellar populations of four fields within the extended ultraviolet disc (XUV disc) of M83. These observations show a clumpy distribution of main-sequence stars and a mostly smooth distribution of red giant branch stars. We constrain the upper end of the initial mass function (IMF) in the outer disc using the detected population of main-sequence stars and an assumed constant star formation rate (SFR) over the last 300 Myr. By comparing the observed main-sequence luminosity function to simulations, we determine the best-fitting IMF to have a power-law slope α = −2.35 ± 0.3 and an upper mass limit $M_{\rm u}=25_{-3}^{+17} \, \mathrm{M}_\odot$. This IMF is consistent with the observed H $\rm \alpha$ emission, which we use to provide additional constraints on the IMF. We explore the influence of deviations from the constant SFR assumption, finding that our IMF conclusions are robust against all but strong recent variations in SFR, but these are excluded by causality arguments. These results, along with our similar studies of other nearby galaxies, indicate that some XUV discs are deficient in high-mass stars compared to a Kroupa IMF. There are over one hundred galaxies within 5 Mpc, many already observed with HST, thus allowing a more comprehensive investigation of the IMF, and how it varies, using the techniques developed here.

scholarly journals Supernova Nucleosynthesis in Massive Stars

1996 ◽  
Vol 145 ◽  
pp. 157-164
Author(s):  
M. Hashimoto ◽  
K. Nomoto ◽  
T. Tsujimoto ◽  
F.-K. Thielemann
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Explosion Energy ◽  
Initial Mass ◽  
Explosive Nucleosynthesis ◽  
Solar Abundances

Presupernova evolution and explosive nucleosynthesis in massive stars for main-sequence masses from 13 Mʘ to 70 Mʘ are calculated. We examine the dependence of the supernova yields on the stellar mass, 12C(α, γ)16O rate, and explosion energy. The supernova yields integrated over the initial mass function are compared with the solar abundances.

scholarly journals The Initial Mass Function of Be Stars

2004 ◽  
Vol 215 ◽  
pp. 83-84
Author(s):  
J. Zorec ◽  
R. Levenhagen ◽  
J. Chauville ◽  
Y. Frémat ◽  
D. Ballereau ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Be Stars ◽  
Fast Rotation ◽  
Formation Conditions ◽  
The Imf

Allowing for systematic differences in the counting of Be Stars due to their overluminosity, changes produced by their fast rotation on spectral types and time spent in the main sequence, a difference between the IMF (Be) and IMF(B) appears, which indicates that the appearance of the Be phenomenon may relay on differences in the initial star formation conditions.

First galaxy SED: Contribution from pre-main-sequence stars

2019 ◽  
Vol 15 (S341) ◽  
pp. 287-288
Author(s):  
Hiroto Mitani ◽  
Naoki Yoshida ◽  
Kazuyuki Omukai ◽  
Takashi Hosokawa
Keyword(s):  
Energy Distribution ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Spectral Energy ◽  
Population Synthesis ◽  
Main Sequence Stars ◽  
The Galaxy ◽  
First Galaxies

AbstractWe calculate the spectral energy distribution of the first galaxies which contain pre-main-sequence stars by using the stellar evolution code Modules for Experiments in Stellar Astrophysics, the spectra model BT-Settl, and the stellar population synthesis code PEGASE. We calculate the galaxy spectral energy distribution for Salpeter Initial Mass Function. We find that very young first galaxies are bright also in mid-infrared, and the contribution of pre-main-sequence stars can be significant over 0.1 Myr after a star-formation episode.

scholarly journals On the Bulk Yields of Nucleosynthesis from Massive Stars

1977 ◽  
Vol 45 ◽  
pp. 161-164
Author(s):  
W. David Arnett
Keyword(s):  
Solar System ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Iron Group ◽  
Helium Stars ◽  
The Absolute ◽  
The Imf

Preliminary estimates are made of the absolute yields of abundant nuclei synthesized in observed stars. The compositions of helium stars of mass 3 ≤ Mα / Mʘ≤ 64 are presented, taken at the instant of instability. These stars of mass Mα are identified with stars of main sequence mass M. The amount of synthesized matter for each mass M ≥ MʘHe is estimated (Table 1). Using a variety of choices for the initial mass function (IMF) the yield per stellar generation is calculated. For standard choices of the IMF the absolute and relative yields of12C,16O,20Ne,24Mg, the Si to Ca group and the iron group agree with solar system values, to the accuracy of the calculations.

scholarly journals Effects of a stochastic initial mass function on the upper main sequence band

1981 ◽  
Vol 59 ◽  
pp. 293-296
Author(s):  
C. Chiosi ◽  
L. Greggio
Keyword(s):  
Mass Loss ◽  
Effective Temperature ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Initial Mass ◽  
Sequence Band ◽  
High Mass Loss

The theoretical (Mb versus Log Te) HR diagram for the brightest galactic OB stars shows an upper boundary for the luminosity, which is characterized by a decreasing luminosity with decreasing effective temperature (Humphreys and Davidson, 1979). The existence of this limit was interpreted by Chiosi et al. (1978) as due to the effect of mass loss by stellar wind on the evolution of most massive stars in core H-burning phase. In fact, evolutionary models calculated at constant mass cover a wider and wider range in effective temperature as the initial mass increases during the main sequence phase. On the contrary, sufficiently high mass-loss rates make the evolutionary sequences of most massive stars (M 60⩾Mʘ) shrink toward the zero age main sequence whenever, due to mass loss, CNO processed material is brought to the surface (Chiosi et al., 1978; de Loore et al., 1978; Maeder, 1980).

scholarly journals Estimating Stellar Parameters and Interstellar Extinction from Evolutionary Tracks

2016 ◽  
Vol 25 (1) ◽  
Author(s):  
S. Sichevsky ◽  
O. Malkov
Keyword(s):  
Main Sequence ◽  
Formation Rate ◽  
Interstellar Extinction ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Atmospheres ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Stellar Radius ◽  
Multicolor Photometry

AbstractDeveloping methods for analyzing and extracting information from modern sky surveys is a challenging task in astrophysical studies. We study possibilities of parameterizing stars and interstellar medium from multicolor photometry performed in three modern photometric surveys: GALEX, SDSS, and 2MASS. For this purpose, we have developed a method to estimate stellar radius from effective temperature and gravity with the help of evolutionary tracks and model stellar atmospheres. In accordance with the evolution rate at every point of the evolutionary track, star formation rate, and initial mass function, a weight is assigned to the resulting value of radius that allows us to estimate the radius more accurately. The method is verified for the most populated areas of the Hertzsprung-Russell diagram: main-sequence stars and red giants, and it was found to be rather precise (for main-sequence stars, the average relative error of radius and its standard deviation are 0.03% and 3.87%, respectively).

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