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AM CVn - System Parameters and Gravitational Waves

Smak J.

Acta Astronomica

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2023

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Vol. 73, No. 3

227--232

EN

System parameters of AM CVn are re-determined: M1=0.86±0.18 M☉, M2=0.103±0.0022 M☉, A=1.508±0.100×1010 cm, and i=69±3°. The secondary component of the system is a semi-degenerate helium star loosing mass at a rate M=4.93±1.65×10-9 M☉/yr. The accretion disk is sufficiently hot to avoid thermal instability. The orbital light curve recovered from observations made in 1962 shows minimum shifted to phase φ=0.50, corresponding to O-C=0.0060 d. Together with mimima observed in the years 1992-1999 this implies that the orbital period is increasing at a rate of dP/dt≈8.5×10-13 - consistent with predictions involving the emission of gravitational waves.

2

Formation, propagation and detection of gravitational waves

Shaliq Mohamed Armoon, Prasanna R. Sharath

Journal of Mechanical and Energy Engineering

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2020

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Vol. 4, No 2

189--196

EN

Gravitational Waves are a new form of energy that is too sensitive to measure. The study of Gravitational Waves paves a unique way to approach the new era of universal science. It is quite interesting to note that experimental proof of the early theory of Einstein is successfully proven after many years. The manuscript depicts the concepts of Gravitational Waves, propagation of Gravitational Waves, its effect on objects on Earth and various factors that affect the measurements along with their method of approach to detect Gravitational Waves. Detecting Gravitational Waves is a tedious process and it requires a very highly sensitive experimental setup to carry out the detection as well as on considering the current trend of technology it is observed that detection faces massive limitations. Detection of Gravitational Waves opens up a new way for understanding supermassive binary systems such as neutron stars and black holes and also for studying on Early universe history.

3

How Li and Paczyński Model of Kilonova Fits GW170817 Optical Counterpart

Kruszewski A.

Acta Astronomica

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2018

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Vol. 68, No. 3

205--211

EN

The original Li and Paczyński model of kilonova was compared with the observed bolometric optical light curve of the GW170817 electromagnetic counterpart. Perfect agreement is obtained for early observations up to 1.5 d since the time of merger.

4

P13 an ULX that is a Potential Progenitor of Merging BH-NS System

Beldycki B., Belczynski K.

Acta Astronomica

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2016

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Vol. 66, No. 3

347--355

EN

We have studied the future evolution of a recently discovered ULX source P13 in NGC 7793. This source was shown to contain a 5-15 M⊙ black hole and a massive 18-23 M⊙ B9Ia companion on a 64 day orbit. For low black hole mass (5-10 M⊙) and high companion mass ≳20 M⊙ the binary is predicted to initiate a common envelope evolution in near future and significantly decrease the orbital separation (6 hr orbit). This leads to a high probability (≈70%) of the system surviving a supernova explosion that will form a neutron star out of the companion. About one third of the surviving BH-NS systems will merge within Hubble time and be a source of high frequency gravitational radiation. We estimate that the chances of detection of BH-NS systems with Advanced LIGO/Virgo that form via P13-evolutionary channel are at the level of 0.1 yr-1 with wide range of allowed probability 0÷0.6 yr-1. This is the fourth empirical estimate of BH-NS merger rate.

5

Schumann Resonance Frequencies Found within Quantitative Electroencephalographic Activity: Implications for Earth-Brain Interactions

Persinger M. A.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 11, iss. 1

24-32

EN

Recent measurements of cerebral quantitative electroencephalographic power densities within the first three harmonics of the earth-ionosphere Schumann resonances and the same order of magnitude for both systems electric and magnetic (pT) fields suggest the possibility of direct intercalation or interaction. The phase modulations of the Schumann propagations and those associated with consciousness are very similar. Quantitative solutions from contemporary values for the physical parameters of the human brain and the earth-ionospheric resonances suggest that electromagnetic information maintained during the first 30 min of experience could be also represented within a property of the (Hilbert) space occupied by the ionospheric wave guide within the earth’s magnetic field. Several astronomical phenomena, including gravitational waves and the neutral hydrogen line, display physical properties with magnitudes matching cerebral electromagnetic activity particularly during light sleep. The presence of Schumann frequencies within the human brain may have greater significance than hereto assumed for the human species.

6

Generation and Propagation of Internal Gravity Waves: Comparison between Two- and Three-Dimensional Models at Low Resolution

Kiraga M., Stępień K., Jahn K.

Acta Astronomica

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2005

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Vol. 55, No. 2

205--217

EN

Dynamics of a convectively unstable layer sandwiched between two stable layers was investigated using direct hydrodynamical simulations in two and three dimensions. Particular attention was paid to the problem of generation and propagation of internal gravity waves (IGW) in a lower stable zone. The results show that convective motions in a 3-D model are significantly less vigorous than in an equivalent 2-D model, resulting in a lower efficiency of IGW generation and a weaker energy flux carried downwards by the waves. The flux obtained in our 3-D models is of the same order as calculated from a simple parametric model based on MLT. However, the comparison of numerical models with different depths of the convective layer indicates that the efficiency of IGW generation increases with the increasing depth whereas the opposite is true in case of parametric model. Extrapolation of this trend to deeper convective zones, existing in solar type stars, suggests that the parametric formulae may severely underestimate the IGW flux generated in the stellar radiative cores. If it is true, IGW existing in real stars will play an important role in transport of angular momentum and trace elements across their internal radiative zones. Due to existence of a rigid lower boundary, the effect of wave reflection occurs in numerical simulations. A method of suppressing the reflected flux is discussed.

7

Direct Numerical Simulations of Penetrative Convection and Generation of Internal Gravity Waves

Kiraga M., Jahn K., Stępień K., Zahn J.-P.

Acta Astronomica

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2003

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Vol. 56, No. 4

321--339

EN

Two-dimensional, direct numerical simulations are used to investigate how thermal convection excites internal gravity waves in the stable layer beneath a convectively unstable zone. The mechanical energy flux carried downwards by the waves strongly depends on the viscosity coefficient. This flux is compared with the energy flux predicted by a simple parametric model of wave generation applied to two models of convection dynamics: one based on the mixing-length treatment and the other on a convective plume model. Numerical simulations always produce substantially larger energy fluxes than the parametric models. This difference may result from shortcomings of the parametric modeling but also from the fact that our simulations are two-dimensional.