Estimations of orbital parameters of exoplanets from transit photometry by using dynamical constraints

ABSTRACT We use direct N-body simulations to explore some possible scenarios for the future evolution of two massive clusters observed towards the centre of NGC 4654, a spiral galaxy with mass similar to that of the Milky Way. Using archival HST data, we obtain the photometric masses of the two clusters, M = 3 × 105 M⊙ and M = 1.7 × 106 M⊙, their half-light radii, Reff ∼ 4 pc and Reff ∼ 6 pc, and their projected distances from the photometric centre of the galaxy (both <22 pc). The knowledge of the structure and separation of these two clusters (∼24 pc) provides a unique view for studying the dynamics of a galactic central zone hosting massive clusters. Varying some of the unknown cluster orbital parameters, we carry out several N-body simulations showing that the future evolution of these clusters will inevitably result in their merger. We find that, mainly depending on the shape of their relative orbit, they will merge into the galactic centre in less than 82 Myr. In addition to the tidal interaction, a proper consideration of the dynamical friction braking would shorten the merging times up to few Myr. We also investigate the possibility to form a massive nuclear star cluster (NSC) in the centre of the galaxy by this process. Our analysis suggests that for low-eccentricity orbits, and relatively long merger times, the final merged cluster is spherical in shape, with an effective radius of few parsecs and a mass within the effective radius of the order of $10^5\, \mathrm{M_{\odot }}$. Because the central density of such a cluster is higher than that of the host galaxy, it is likely that this merger remnant could be the likely embryo of a future NSC.

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Twin stars as tracers of binary evolution in the Kepler era

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab343 ◽

2021 ◽

Author(s):

Sara Bulut ◽

Baris Hoyman ◽

Ahmet Dervisoglu ◽

Orkun Özdarcan ◽

Ömür Cakilrli

Keyword(s):

High Resolution ◽

Internal Structure ◽

Spectroscopic Analysis ◽

Independent Method ◽

Eclipsing Binaries ◽

Physical Parameters ◽

Evolutionary Status ◽

Mass Ratio ◽

Orbital Parameters ◽

Binary Evolution

Abstract We present results of the combined photometric and spectroscopic analysis of four systems, which are eclipsing binaries with a twin–component (mass ratio q ≃ 1). These are exceptional tools to provide information for probing the internal structure of stars. None of the systems were previously recognized as twin binaries. We used a number of high–resolution optical spectra to calculate the radial velocities and later combined them with photometry to derive orbital parameters. Temperatures and metallicities of systems were estimated from high-resolution spectra. For each binary, we obtained a full set of orbital and physical parameters, reaching precision below 3 per cent in masses and radii for whole pairs. By comparing our results with PARSEC and MIST isochrones, we assess the distance, age and evolutionary status of the researched objects. The primary and/or secondary stars of EPIC 216075815 and EPIC 202843107 are one of the cases where asteroseismic parameters of δ Sct and γ Dor pulsators were confirmed by an independent method and rare examples of the twin–eclipsing binaries, therefore the following analyses and results concern the pulsating nature of the components.

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Dynamical constraints on RG flows and cosmology

Journal of High Energy Physics ◽

10.1007/jhep12(2019)134 ◽

2019 ◽

Vol 2019 (12) ◽

Cited By ~ 3

Author(s):

Daniel Baumann ◽

Daniel Green ◽

Thomas Hartman

Keyword(s):

Dynamical Constraints

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The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100100028 ◽

1989 ◽

Vol 114 ◽

pp. 440-442

Author(s):

M. Politano ◽

R. F. Webbink

Keyword(s):

Star Formation ◽

White Dwarf ◽

Galactic Disk ◽

Orbital Energy ◽

Orbital Parameter ◽

Orbital Parameters ◽

Cataclysmic Binaries ◽

Magnetic Braking ◽

Orbital Periods ◽

The Individual

A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.

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Transmission of substituent effects in heterocyclic systems. Application of molecular orbital parameters to the solvolysis of 4-substituted 1-(2-furyl)ethyl systems

The Journal of Organic Chemistry ◽

10.1021/jo00981a023 ◽

1972 ◽

Vol 37 (16) ◽

pp. 2623-2625 ◽

Cited By ~ 4

Author(s):

Donald S. Noyce ◽

Hernan J. Pavez

Keyword(s):

Molecular Orbital ◽

Substituent Effects ◽

Orbital Parameters ◽

Substituted 1

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Dynamical Constraints on Using Precise Spike Timing to Compute in Recurrent Cortical Networks

Neural Computation ◽

10.1162/neco.2008.05-06-206 ◽

2008 ◽

Vol 20 (4) ◽

pp. 974-993 ◽

Cited By ~ 19

Author(s):

Arunava Banerjee ◽

Peggy Seriès ◽

Alexandre Pouget

Keyword(s):

Dynamical System ◽

Initial Conditions ◽

Internal State ◽

Spike Timing ◽

Spiking Neurons ◽

Spatiotemporal Patterns ◽

Cortical Networks ◽

Temporal Precision ◽

Cortical Areas ◽

Dynamical Constraints

Several recent models have proposed the use of precise timing of spikes for cortical computation. Such models rely on growing experimental evidence that neurons in the thalamus as well as many primary sensory cortical areas respond to stimuli with remarkable temporal precision. Models of computation based on spike timing, where the output of the network is a function not only of the input but also of an independently initializable internal state of the network, must, however, satisfy a critical constraint: the dynamics of the network should not be sensitive to initial conditions. We have previously developed an abstract dynamical system for networks of spiking neurons that has allowed us to identify the criterion for the stationary dynamics of a network to be sensitive to initial conditions. Guided by this criterion, we analyzed the dynamics of several recurrent cortical architectures, including one from the orientation selectivity literature. Based on the results, we conclude that under conditions of sustained, Poisson-like, weakly correlated, low to moderate levels of internal activity as found in the cortex, it is unlikely that recurrent cortical networks can robustly generate precise spike trajectories, that is, spatiotemporal patterns of spikes precise to the millisecond timescale.

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