scholarly journals Globular Cluster Luminosity Functions

1988 ◽  
Vol 126 ◽  
pp. 121-131
Author(s):  
Pierre Demarque
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Structure ◽  
Structure Theory ◽  
Initial Mass ◽  
Helium Content ◽  
Luminosity Functions

The use of luminosity functions in the following areas is reviewed: (a) the determination of the helium content and ages of the globular clusters; (b) the testing of stellar structure theory; and (c) the determination of the initial mass function of globular clusters.

scholarly journals The Globular Cluster Population of X-ray Binaries

1987 ◽  
Vol 125 ◽  
pp. 187-197 ◽  
Author(s):  
Frank Verbunt ◽  
Piet Hut
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Encounter Rate ◽  
Formation Mechanisms ◽  
Main Sequence Stars ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

We discuss formation mechanisms for low-mass X-ray binaries in globular clusters. We apply the most efficient mechanism, tidal capture in close two-body encounters between neutron and main-sequence stars, to the clusters of our galaxy. The observed number of X-ray sources in these can be explained if the birth velocities of neutron stars are higher than estimated from velocity measurements of radiopulsars, or if the initial mass function steepens at high masses. We perform a statistical test on the distribution of X-ray sources with respect to the number of close encounters in globular clusters, and find satisfactory agreement between the tidal capture theory and observation, apart from the presence of low-mass X-ray binaries in four clusters with a very low encounter rate: Ter 1, Ter 2, Gr 1 and NGC 6712.EXOSAT observations indicate that some dim globular cluster sources may be less luminous than hitherto assumed, and support the view that the brighter dim sources may be soft X-ray transients in quiescence.

scholarly journals The uncertain masses of progenitors of core-collapse supernovae and direct-collapse black holes

2020 ◽  
Vol 494 (1) ◽  
pp. L53-L58 ◽  
Author(s):  
Eoin J Farrell ◽  
Jose H Groh ◽  
Georges Meynet ◽  
J J Eldridge
Keyword(s):  
Black Holes ◽  
Probability Distribution ◽  
Evolutionary History ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Core Collapse ◽  
Core Mass ◽  
Individual Determination

ABSTRACT We show that it is not possible to determine the final mass Mfin of a red supergiant (RSG) at the pre-supernova (SN) stage from its luminosity L and effective temperature Teff alone. Using a grid of stellar models, we demonstrate that for a given value of L and Teff, an RSG can have a range of Mfin as wide as 3 to 45 M⊙. While the probability distribution within these limits is not flat, any individual determination of Mfin for an RSG will be degenerate. This makes it difficult to determine its evolutionary history and to map Mfin to an initial mass. Single stars produce a narrower range that is difficult to accurately determine without making strong assumptions about mass-loss, convection, and rotation. Binaries would produce a wider range of RSG Mfin. However, the final Helium core mass $M_{\operatorname{He-core}}$ is well determined by the final luminosity and we find $\log (M_{\operatorname{He-core}}/\mathrm{M}_{\odot }) = 0.659 \log (L/\mathrm{L}_{\odot }) -2.630$. Using this relationship, we derive $M_{\operatorname{He-core}}$ for directly imaged SN progenitors and one failed SN candidate. The value of Mfin for stripped star progenitors of SNe IIb is better constrained by L and Teff due to the dependence of Teff on the envelope mass Menv for Menv ≲ 1 M⊙. Given the initial mass function, our results apply to the majority of progenitors of core-collapse SNe, failed SNe, and direct-collapse black holes.

scholarly journals A spatially-resolved study of initial mass function in the outer Galaxy

2016 ◽  
Vol 11 (S321) ◽  
pp. 34-36
Author(s):  
Chikako Yasui ◽  
Natsuko Izumi ◽  
Masao Saito ◽  
Naoto Kobayashi
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Solar Neighborhood ◽  
High Mass ◽  
Initial Mass ◽  
Mass Detection ◽  
Spatially Resolved ◽  
Luminosity Functions ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

AbstractOutskirts of spiral galaxies, including our own, and dwarf irregular galaxies are known to have a different environment from the solar neighborhood, e.g., low metallicities ( ~ − 1 dex). Among them, the outer Galaxy is the closest and hence is so far the only site suitable for population studies of resolved stars on the same basis as solar neighborhood. We have obtained NIR images of young clusters in the outer Galaxy, using the Subaru 8.2-m telescope, and clearly resolved cluster members with mass detection limits of ~ 0.1 M⊙. Based on the fitting of K-band luminosity functions (KLFs) for four clusters, we found that the initial mass function (IMF) in the outer Galaxy is consistent with that in the solar neighborhood in terms of the high-mass slope and IMF peak. Upcoming observations with a higher spatial resolution and sensitivity, using JWST, TMT, etc., will allow us to extend spatially-resolved studies of the IMF to Local Group galaxies.

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