The low-mass stellar content of galaxies - Constraints through hybrid population synthesis near 1 micron

1993 ◽  
Vol 406 ◽  
pp. 142 ◽  
Author(s):  
Jean Couture ◽  
Eduardo Hardy
Keyword(s):  
Hybrid Population ◽  
Population Synthesis ◽  
Stellar Content ◽  
Low Mass ◽  
Stellar Content Of Galaxies

scholarly journals Very low-mass stellar content of the young supermassive Galactic star cluster Westerlund 1

2017 ◽  
Vol 602 ◽  
pp. A22 ◽  
Author(s):  
M. Andersen ◽  
M. Gennaro ◽  
W. Brandner ◽  
A. Stolte ◽  
G. de Marchi ◽  
...  
Keyword(s):  
Star Cluster ◽  
Stellar Content ◽  
Low Mass

Constraining Progenitors of Observed Low-mass X-ray Binaries Using Convection and Rotation-Boosted Magnetic Braking

2021 ◽  
Vol 922 (2) ◽  
pp. 174
Author(s):  
Kenny X. Van ◽  
Natalia Ivanova
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Formation Rate ◽  
Mass Transfer Rate ◽  
Population Synthesis ◽  
X Ray ◽  
Synthesis Technique ◽  
Low Mass ◽  
Magnetic Braking ◽  
X Ray Binaries

Abstract We present a new method for constraining the mass transfer evolution of low-mass X-ray binaries (LMXBs)—a reverse population synthesis technique. This is done using the detailed 1D stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics) to evolve a high-resolution grid of binary systems spanning a comprehensive range of initial donor masses and orbital periods. We use the recently developed convection and rotation-boosted (CARB) magnetic braking scheme. The CARB magnetic braking scheme is the only magnetic braking prescription capable of reproducing an entire sample of well-studied persistent LMXBs—those with mass ratios, periods, and mass transfer rates that have been observationally determined. Using the reverse population synthesis technique, where we follow any simulated system that successfully reproduces an observed LMXB backward, we have constrained possible progenitors for each observed well-studied persistent LMXB. We also determined that the minimum number of LMXB formations in the Milky Way is 1500 per Gyr if we exclude Cyg X-2. For Cyg X-2, the most likely formation rate is 9000 LMXB Gyr−1. The technique we describe can be applied to any observed LMXB with well-constrained mass ratio, period, and mass transfer rate. With the upcoming GAIA DR3 containing information on binary systems, this technique can be applied to the data release to search for progenitors of observed persistent LMXBs.

scholarly journals Photometric Models for Globular Clusters from Population Synthesis

1988 ◽  
Vol 126 ◽  
pp. 559-560
Author(s):  
R. Capuzzo Dolcetta
Keyword(s):  
Structural Properties ◽  
Globular Clusters ◽  
Magellanic Cloud ◽  
Stellar Systems ◽  
Population Synthesis ◽  
Stellar Content ◽  
Cloud Clusters ◽  
Metal Abundance ◽  
Theoretical Frame

Integral fluxes (Bolometric and U, B, V) are computed in a completely theoretical frame in order to investigate the structural properties and stellar content of coeval stellar systems of various ages and metal abundance. Some results concerning the problem of the color gap in the distribution of the sample of Magellanic Cloud clusters are discussed.

scholarly journals HST Far–UV Imaging of M 31, M 32 and NGC 205

1995 ◽  
Vol 164 ◽  
pp. 444-444
Author(s):  
F. Bertola ◽  
C. Chiosi ◽  
A. Bressan ◽  
L.M. Buson ◽  
D. Burstein ◽  
...  
Keyword(s):  
Broad Band ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stellar Content ◽  
Hot Stars ◽  
Uv Emission ◽  
Luminosity Functions ◽  
Scientific Goal ◽  
M 31 ◽  
Direct Measures

Direct measures of luminosity functions, UV fluxes and colors of the hot stars that produce the UV turn–up in the SED of ellipticals and spiral bulges is the scientific goal of the HST observations presented here (see Bertola et al. 1995 for details). We concentrated our analysis on the hot stellar content of the M31 bulge. HST/FOC f/48 images were analyzed as observed (before the repair mission) through the F150W broad-band UV filter. We find that both individual stars and unresolved objects contribute to about 50% of the UV (1200-2450 Å) flux. Making use of the isochrones calculated by Bertelli et al. (1994) and Chiosi et al. (1994) together with the models of population synthesis presented by Bressan et al. (1994), we constructed theoretical CMDs to be compared with the CMD obtained by combining our F150W observations with the F175W observations of King et al. (1992). We conclude that the stars we resolved in M31 are classical P-AGB stars belonging to an old standard metallicity population. However, the P-EAGB and AGB-manqué stages as well as H-HB stars could be the source of the diffuse UV emission.

scholarly journals Binary fraction indicators in resolved stellar populations and supernova-type ratios

2020 ◽  
Vol 497 (2) ◽  
pp. 2201-2212 ◽  
Author(s):  
E R Stanway ◽  
J J Eldridge ◽  
A A Chrimes
Keyword(s):  
Massive Star ◽  
Stellar Population ◽  
Stellar Populations ◽  
Initial Mass ◽  
Core Collapse ◽  
Population Synthesis ◽  
Large Samples ◽  
Low Mass ◽  
Galaxy Population ◽  
Number Counts

ABSTRACT The binary fraction of a stellar population can have pronounced effects on its properties, and, in particular, the number counts of different massive star types, and the relative subtype rates of the supernovae (SNe) that end their lives. Here we use binary population synthesis models with a binary fraction that varies with initial mass to test the effects on resolved stellar pops and SNe, and ask whether these can constrain the poorly-known binary fraction in different mass and metallicity regimes. We show that Wolf–Rayet (WR) star subtype ratios are valuable binary diagnostics, but require large samples to distinguish by models. Uncertainties in which stellar models would be spectroscopically classified as WR stars are explored. The ratio of thermonuclear, stripped-envelope, and other core-collapse SNe may prove a more accessible test and upcoming surveys will be sufficient to constrain both the high- and low-mass binary fraction in the z < 1 galaxy population.

scholarly journals Exploring the formation by core accretion and the luminosity evolution of directly imaged planets

2019 ◽  
Vol 624 ◽  
pp. A20 ◽  
Author(s):  
Gabriel-Dominique Marleau ◽  
Gavin A. L. Coleman ◽  
Adrien Leleu ◽  
Christoph Mordasini
Keyword(s):  
Mass Star ◽  
Population Synthesis ◽  
Direct Imaging ◽  
Solar Mass ◽  
High Eccentricity ◽  
Body Dynamics ◽  
Low Mass ◽  
Open Question ◽  
Core Accretion ◽  
First Time

Context. A low-mass companion to the two-solar mass star HIP 65426 has recently been detected by SPHERE at around 100 au from its host. Explaining the presence of super-Jovian planets at large separations, as revealed by direct imaging, is currently an open question. Aims. We want to derive statistical constraints on the mass and initial entropy of HIP 65426 b and to explore possible formation pathways of directly imaged objects within the core-accretion paradigm, focusing on HIP 65426 b. Methods. Constraints on the planet’s mass and post-formation entropy are derived from its age and luminosity combined with cooling models. For the first time, the results of population synthesis are also used to inform the results. Then a formation model that includes N-body dynamics with several embryos per disc is used to study possible formation histories and the properties of possible additional companions. Finally, the outcomes of two- and three-planet scattering in the post-disc phase are analysed, taking tides into account for small-pericentre orbits. Results. The mass of HIP 65426 b is found to be mp = 9.9−1.8+1.1 MJ using the hot population and mp = 10.9−2.0+1.4 MJ with the cold-nominal population. We find that core formation at small separations from the star followed by outward scattering and runaway accretion at a few hundred astronomical units succeeds in reproducing the mass and separation of HIP 65426 b. Alternatively, systems having two or more giant planets close enough to be on an unstable orbit at disc dispersal are likely to end up with one planet on a wide HIP 65426 b-like orbit with a relatively high eccentricity (≳ 0.5). Conclusions. If this scattering scenario explains its formation, HIP 65426 b is predicted to have a high eccentricity and to be accompanied by one or several roughly Jovian-mass planets at smaller semi-major axes, which also could have a high eccentricity. This could be tested by further direct-imaging as well as radial-velocity observations.

scholarly journals Contamination of RR Lyrae stars from Binary Evolution Pulsators

2015 ◽  
Vol 5 (1) ◽  
pp. 24-28
Author(s):  
P. Karczmarek
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
Synthesis Method ◽  
Population Synthesis ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Low Mass ◽  
Binary Evolution ◽  
Lyrae Stars ◽  
Range Of Values

A Binary Evolution Pulsator (BEP) is a low-mass (0.26 𝔐☉) member of a binary system, which pulsates as a result of a former mass transfer to its companion. The BEP mimics RR Lyrae-type pulsations, but has completely different internal structure and evolution history. Although there is only one known BEP (OGLE-BLG-RRLYR-02792), it has been estimated that approximately 0.2% of objects classified as RR Lyrae stars can be undetected Binary Evolution Pulsators. In the present work, this contamination value is re-evaluated using the population synthesis method. The output falls inside a range of values dependent on tuning the parameters in the StarTrack code, and varies from 0.06% to 0.43%.

scholarly journals No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations

2020 ◽  
Vol 498 (2) ◽  
pp. 2001-2017 ◽  
Author(s):  
Xiangcheng Ma ◽  
Eliot Quataert ◽  
Andrew Wetzel ◽  
Philip F Hopkins ◽  
Claude-André Faucher-Giguère ◽  
...  
Keyword(s):  
Large Fraction ◽  
High Mass ◽  
Population Synthesis ◽  
Single Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sample Average ◽  
Dense Shell ◽  
Low Mass ◽  
Dust Attenuation

ABSTRACT We present the escape fraction of hydrogen ionizing photons (fesc) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z ≥ 5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 haloes in Mvir ∼ 108–$10^{12}\, M_{\odot }$ (M* ∼ 104–$10^{10}\, M_{\odot }$) at z = 5–12. We find the sample average 〈fesc〉increases with halo mass for Mvir ∼ 108–$10^{9.5}\, M_{\odot }$, becomes nearly constant for 109.5–$10^{11}\, M_{\odot }$, and decreases at ${\gtrsim}10^{11}\, M_{\odot }$. Equivalently, 〈fesc〉 increases with stellar mass up to $M_{\ast }\sim 10^8\, M_{\odot }$ and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate 〈fesc〉 ∼ 0.2 for galaxies at $M_{\ast }\sim 10^8\, M_{\odot }$. Nearly half of the escaped ionizing photons come from stars 1–3 Myr old and the rest from stars 3–10 Myr old. Binaries only have a modest effect, boosting 〈fesc〉 by ∼25–35 per cent and the number of escaped photons by 60–80 per cent. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of 〈fesc〉 at the high-mass end is due to dust attenuation, while at the low-mass end, 〈fesc〉 decreases owing to inefficient star formation and hence feedback. At fixed mass, 〈fesc〉 tends to increase with redshift. Although the absolute 〈fesc〉does not fully converge with resolution in our simulations, the mass- and redshift-dependence of 〈fesc〉 is likely robust. Our simulations produce sufficient ionizing photons for cosmic reionization.

scholarly journals Population synthesis of accreting neutron stars emitting gravitational waves

2019 ◽  
Vol 488 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Fabian Gittins ◽  
Nils Andersson
Keyword(s):  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Population Synthesis ◽  
Spin Distribution ◽  
Synthetic Populations ◽  
Low Mass ◽  
Wave Emission ◽  
X Ray Binaries ◽  
Production Mechanisms

ABSTRACT The fastest-spinning neutron stars in low-mass X-ray binaries, despite having undergone millions of years of accretion, have been observed to spin well below the Keplerian break-up frequency. We simulate the spin evolution of synthetic populations of accreting neutron stars in order to assess whether gravitational waves can explain this behaviour and provide the distribution of spins that is observed. We model both persistent and transient accretion and consider two gravitational-wave-production mechanisms that could be present in these systems: thermal mountains and unstable rmodes. We consider the case of no gravitational-wave emission and observe that this does not match well with observation. We find evidence for gravitational waves being able to provide the observed spin distribution; the most promising mechanisms being a permanent quadrupole, thermal mountains, and unstable r modes. However, based on the resultant distributions alone, it is difficult to distinguish between the competing mechanisms.

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