scholarly journals The evolution of stellar triples

2020 ◽  
Vol 640 ◽  
pp. A16 ◽  
Author(s):  
S. Toonen ◽  
S. Portegies Zwart ◽  
A. S. Hamers ◽  
D. Bandopadhyay
Keyword(s):  
Mass Transfer ◽  
Population Synthesis ◽  
Transfer Event ◽  
Term Evolution ◽  
Body Dynamics ◽  
Large Populations ◽  
Three Body ◽  
Synthesis Approach ◽  
Hubble Time

Context. Many stars do not live alone, but instead have one or more stellar companions. Observations show that these binaries, triples, and higher-order multiples are common. While the evolution of single stars and binaries have been studied extensively, the same is not true for the evolution of stellar triples. Aims. To fill in this gap in our general understanding of stellar lives, we aim to systematically explore the long-term evolution of triples and to map out the most common evolutionary pathways that triples go through. We quantitatively study how triples evolve, which processes are the most relevant, and how this differs from binary evoluion. Methods. We simulated the evolution of several large populations of triples with a population synthesis approach. We made use of the triple evolution code TRES to simulate the evolution of each triple in a consistent way, including three-body dynamics (based on the secular approach), stellar evolution, and their mutual influences. We simulated the evolution of the system up until mass transfer starts, the system becomes dynamically unstable, or a Hubble time has passed. Results. We find that stellar interactions are common in triples. Compared to a binary population, we find that the fraction of systems that can undergo mass transfer is ∼2−3 times larger in triples. Moreover, while orbits typically reach circularisation before Roche-lobe overflow in binaries, this is no longer true in triples. In our simulations, about 40% of systems retain an eccentric orbit. Additionally, we discuss various channels of triple evolution in detail, such as those where the secondary or the tertiary is the first star to initiate a mass transfer event.

scholarly journals Accretion and outflow in V404 Cyg

2019 ◽  
Vol 488 (1) ◽  
pp. 1356-1365 ◽  
Author(s):  
J Casares ◽  
T Muñoz-Darias ◽  
D Mata Sánchez ◽  
P A Charles ◽  
M A P Torres ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Black Hole ◽  
Radiation Pressure ◽  
Decay Time ◽  
Total Mass ◽  
Key Factors ◽  
X Ray ◽  
Term Evolution ◽  
Inner Parts

ABSTRACT We study the optical evolution of the 2015 outburst in V404 Cyg, with emphasis on the peculiar nebular phase and subsequent decay to quiescence. From the decay time-scale of the Balmer emission associated with the nebula, we measure an outflow mass Mwind ≃ 4 × 10−6 M⊙. Remarkably, this is ∼100 times larger than the accreted mass and ∼10 per cent of the total mass stored in the disc. The wind efficiency must therefore be significantly larger than previous estimates for black hole transients, suggesting that radiation pressure (in addition to other mechanisms such as Compton-heating) plays a key role in V404 Cyg. In addition, we compare the evolution of the 2015 and 1989 outbursts and find not only clear similarities (namely a large luminosity drop ∼10 d after the X-ray trigger, followed by a brief nebular phase) but also remarkable differences in decay time-scales and long-term evolution of the H α profile. In particular, we see evidence for a rapid disc contraction in 2015, consistent with a burst of mass transfer. This could be driven by the response of the companion to hard X-ray illumination, most notably during the last gigantic (super-Eddington) flare on 2015 June 25. We argue that irradiation and consequential disc wind are key factors to understand the different outburst histories in 1989 and 2015. In the latter case, radiation pressure may be responsible for the abrupt end of the outburst through depleting inner parts of the disc, thus quenching accretion and X-ray irradiation. We also present a refined orbital period and updated ephemeris.

scholarly journals Nova Outbursts and the Secular Evolution of Cataclysmic Variables

1996 ◽  
Vol 158 ◽  
pp. 447-448
Author(s):  
K. Schenker ◽  
U. Kolb ◽  
H. Ritter
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Secular Evolution ◽  
Term Evolution ◽  
Angular Momentum Loss ◽  
The Mean ◽  
Nova Outbursts

AbstractWe present calculations of the long-term evolution of CVs which include the influence of nova outbursts. In particular we investigate the consequences of the discontinuous mass loss due to recurring outburst events and the effects of frictional angular momentum loss (FAML), i.e. the interaction of the expanding nova envelope with the secondary. We show that a description assuming continuous mass loss – averaged over a complete nova cycle – is applicable for determining the mean mass transfer rate and the secular evolution both with and without FAML. Between two subsequent outbursts, deviations from the mean evolution depend on the strength of FAML and on the mass ejected during the outburst. Formally FAML is a consequential angular momentum loss [1] and therefore increases the mean mass transfer rate by pushing the systems closer to mass transfer instability. Depending on the actual strenghth of FAML the long-term evolution of CVs could be significantly different from the standard model predictions.

Link-Level Simulator for Wireless local Area Network

2018 ◽  
Vol 6 (7) ◽  
pp. 314
Author(s):  
Chaithra. H. U ◽  
Vani H.R
Keyword(s):  
Wireless Local Area Network ◽  
Local Area Network ◽  
Local Area Networks ◽  
Local Area ◽  
Long Term Evolution ◽  
Wireless Local Area Networks ◽  
Area Network ◽  
Network Simulator ◽  
Term Evolution

Now a days in Wireless Local Area Networks (WLANs) used in different fields because its well-suited simulator and higher flexibility. The concept of WLAN  with  advanced 5th Generation technologies, related to a Internet-of-Thing (IOT). In this project, representing the Network Simulator (NS-2) used linked-level simulators for Wireless Local Area Networks and still utilized IEEE 802.11g/n/ac with advanced IEEE 802.11ah/af technology. Realization of the whole Wireless Local Area Networking linked-level simulators inspired by the recognized Vienna Long Term Evolution- simulators. As a outcome, this is achieved to link together that simulator to detailed performances of Wireless Local Area Networking with Long Term Evolution, operated in the similar RF bands. From the advanced 5th Generation support cellular networking, such explore is main because different coexistences scenario can arise linking wireless communicating system to the ISM and UHF bands.

Simulación de cobertura del modelo de radio propagación 3GPP para un entorno urbano en una red 4G – LTE

2013 ◽  
Vol 8 (15) ◽  
pp. 33-40
Author(s):  
Javier Enrique Arévalo Peña
Keyword(s):  
Long Term Evolution ◽  
Term Evolution ◽  
Nuevas Tecnologías ◽  
4G Lte ◽  
3Rd Generation Partnership Project

En la planeación de las próximas generaciones de redes inalámbricas es importante contar con estudios de radio propagación que permitan establecer diseños adecuados para ofrecer los servicios proyectados por las nuevas tecnologías a los usuarios móviles. En este artículo se presentan aspectos relacionados con el comportamiento de cobertura de radio propagación del modelo propuesto por el 3GPP (3rd Generation Partnership Project) para un entorno urbano en una red LTE (Long Term Evolution) empleando sistemas de antenas convencionales y sistemas de antena adaptativas (AAS). Para ello se utiliza la herramienta de software ICS Designer y se establece como escenario los alrededores la Fundación Universidad Autónoma de Colombia ubicada en el centro urbano de la ciudad de Bogotá D. C.

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