scholarly journals Binary Evolutionary Models

2008 ◽  
Vol 4 (S252) ◽  
pp. 349-357
Author(s):  
Z. Han ◽  
Ph. Podsiadlowski
Keyword(s):  
Globular Clusters ◽  
A Priori ◽  
Elliptical Galaxies ◽  
Ultraviolet Excess ◽  
Sdb Stars ◽  
Binary Model ◽  
Type Ia ◽  
Binary Evolution ◽  
Ehb Stars ◽  
Uv Upturn

AbstractIn this talk, we present the general principles of binary evolution and give two examples. The first example is the formation of subdwarf B stars (sdBs) and their application to the long-standing problem of ultraviolet excess (also known as UV-upturn) in elliptical galaxies. The second is for the progenitors of type Ia supernovae (SNe Ia). We discuss the main binary interactions, i.e., stable Roche lobe overflow (RLOF) and common envelope (CE) evolution, and show evolutionary channels leading to the formation of various binary-related objects. In the first example, we show that the binary model of sdB stars of Han et al. (2002, 2003) can reproduce field sdB stars and their counterparts, extreme horizontal branch (EHB) stars, in globular clusters. By applying the binary model to the study of evolutionary population synthesis, we have obtained an “a priori” model for the UV-upturn of elliptical galaxies and showed that the UV-upturn is most likely resulted from binary interactions. This has major implications for understanding the evolution of the UV excess and elliptical galaxies in general. In the second example, we introduce the single degenerate channel and the double degenerate channel for the progenitors of SNe Ia. We give the birth rates and delay time distributions for each channel and the distributions of companion stars at the moment of SN explosion for the single degenerate channel, which would help to search for the remnant companion stars observationally.

scholarly journals A binary model for the UV-upturn of elliptical galaxies

2007 ◽  
Vol 380 (3) ◽  
pp. 1098-1118 ◽  
Author(s):  
Z. Han ◽  
Ph. Podsiadlowski ◽  
A. E. Lynas-Gray
Keyword(s):  
Elliptical Galaxies ◽  
Binary Model ◽  
Uv Upturn

To Be or Not to Be: EHB Stars and AGB Stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 357-359
Author(s):  
David A. Brown
Keyword(s):  
Globular Clusters ◽  
Agb Stars ◽  
Multiple Populations ◽  
Galactic Field ◽  
Sdb Stars ◽  
Strong Case ◽  
Binary Formation ◽  
Ehb Stars

AbstractThe formation of EHB stars is linked to the lives of AGB stars by indications that such EHB/sdB stars might form in globular clusters with multiple populations linked to AGB evolution. Observations of massive globular clusters, such as ω-Centauri (Bedin et al.2004, Piotto et al.2005) suggest that single EHB stars might form from He-enhanced progenitors (D’Antona et al.2005, D’Antona & Caloi 2008, Lee et al.2005) in environments enriched by AGB ejecta. The studies conducted by Han et al. (2002), Han et al. (2003), and Han et al. (2007) have been able to provide a strong case for the binary formation of EHB/sdB stars in the Galactic field, though binary formation channels in globular clusters is uncertain. Simulations presented here are an extension of the simulations of Han et al. (2002) and Han et al. (2003), for low metallicities to examine the binary EHB population in globular clusters.

scholarly journals The UV Upturn in Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 239-248
Author(s):  
H.C. Ferguson
Keyword(s):  
Galaxy Evolution ◽  
Open Cluster ◽  
Elliptical Galaxies ◽  
Asymptotic Giant Branch ◽  
Star Mass ◽  
Uv Emission ◽  
Stellar Component ◽  
Red Clump ◽  
Ehb Stars ◽  
Uv Upturn

The hot stellar component in elliptical galaxies offers clues to both stellar evolution and galaxy evolution. Current observations suggest that extreme horizontal branch (EHB) stars dominate the far-UV emission from galaxies with the strongest “UV upturns,” while post asymptotic giant branch (PAGB) stars are probably significant contributors for weaker galaxies. Spectra near the Lyman limit indicate that a rather narrow range of temperature (and hence EHB star mass) is required. However, other arguments suggest that most of the helium-burning stars in elliptical galaxies are in the red clump. The HB star mass distribution therefore appears to be strongly bimodal. Such bimodality is qualitatively reproduced by two radically different stellar population models, (those of Lee and Bressan et al.), both of which require that the galaxies be very old. However, the Galactic open cluster NGC 6791 also contains EHB stars and exhibits strong bimodality, indicating that old age may not necessarily be a requirement for the UV upturn phenomenon.

scholarly journals A Binary Model for the UV-upturn of Elliptical Galaxies

2006 ◽  
Vol 2 (S241) ◽  
Author(s):  
Z. Han ◽  
Ph. Podsiadlowski ◽  
A.E. Lynas-Gray ◽  
K. Schawinski
Keyword(s):  
Elliptical Galaxies ◽  
Binary Model ◽  
Uv Upturn

scholarly journals Outflows from ellipticals: the role of supernovae

2003 ◽  
Vol 212 ◽  
pp. 630-636
Author(s):  
Francesca Matteucci ◽  
Antonio Pipino
Keyword(s):  
Star Formation ◽  
Dominant Role ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Type Ii ◽  
Chemical Enrichment ◽  
Galactic Winds ◽  
Type Ia ◽  
Intense Burst

Models of supernova (SN) driven galactic winds for ellipticals are presented. We assume that ellipticals formed at high redshift and suffered an intense burst of star formation. The role of supernovae of Type II and Type Ia in the chemical enrichment and in triggering galactic winds is studied. In particular, several recipes for SN feed-back together with detailed nucleosynthesis prescriptions are considered. It is shown that SNe of Type II have a dominant role in enriching the interstellar medium of elliptical galaxies whereas Type Ia SNe dominate the enrichment and the energetics of the intracluster medium.

scholarly journals A Bright Ultraviolet Excess in the Transitional 02es-like Type Ia Supernova 2019yvq

2021 ◽  
Vol 919 (2) ◽  
pp. 142
Author(s):  
J. Burke ◽  
D. A. Howell ◽  
S. K. Sarbadhicary ◽  
D. J. Sand ◽  
R. C. Amaro ◽  
...  
Keyword(s):  
Ultraviolet Excess ◽  
Type Ia Supernova ◽  
Type Ia

scholarly journals Variable Stars in Dwarf Spheroidal Galaxies

1973 ◽  
Vol 21 ◽  
pp. 35-48
Author(s):  
Steven Van Agt
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Elliptical Galaxies ◽  
Variable Stars ◽  
Dwarf Spheroidal Galaxies ◽  
Theoretical Predictions ◽  
History Of ◽  
Set Up ◽  
Theoretical Considerations ◽  
Spheroidal Galaxies

Interest in dwarf spheroidal galaxies is motivated by a number of reasons; an important one on the occasion of this colloquium is the abundance of variable stars. The theory of stellar evolution and stellar pulsations is now able to predict from theoretical considerations characteristic properties of variable stars in the colour-magnitude diagram (Iben, 1971). By observing the variable stars in the field, and in as wide a selection of objects as possible, more insight can be obtained into the history of the oldest members of our Galaxy (the globular clusters) and of the dwarf spheroidal galaxies in the Local Group. It is worthwhile to explore the spheroidal galaxies as observational tests for the theoretical predictions of conditions in space away from our Galaxy. The numbers of variable stars in the dwarf spheroidal galaxies are such that we may expect well-defined relations to emerge once reliable magnitude sequences have been set up, the variable stars found, and their periods determined. Six dwarf spheroidal galaxies are presently known in the Local Group within a distance of 250 kpc. In Table I, which lists members of the Local Group, they are at the low-luminosity end of the sequence of elliptical galaxies (van den Bergh, 1968).

The Effect of Neutrinos on the Formation Time of Rich Clusters of Galaxies

1981 ◽  
Vol 4 (2) ◽  
pp. 181-182 ◽  
Author(s):  
B. M. Lewis
Keyword(s):  
Globular Clusters ◽  
Relaxation Mechanism ◽  
Elliptical Galaxies ◽  
Formation Time ◽  
Clusters Of Galaxies ◽  
Cluster Mass ◽  
Cluster Of Galaxies ◽  
Universal Expansion ◽  
Hubble Time

Both the radial and the velocity distributions of galaxies within rich clusters are well described by the isothermal distribution (e.g. Lewis 1978 and 1979). It is tempting to ascribe this apparently relaxed state to the operation of Lynden-BeU’s (1967) violent relaxation mechanism, during the initial coherent collapse on the proto-cluster, after it brakes itself against the universal expansion. This scenario explains the isothermal distribution observed in elliptical galaxies and globular clusters. When applied to a cluster of galaxies made up of baryons, however, the timescale for the scenario is comparable with the Hubble time H−1. The situation changes if most of the cluster mass is contributed by neutrinos.

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