The spin and mass ratio affects the gravitational waveforms of binary black hole mergers with a total system mass of 12-130 M⊙\rm{M}_\odot

Analyzing the observations obtained by the LIGO and the Virgo Collaborations, a new era has begun in binary black hole (BBH) merger processes and black hole physics studies. The fact that very massive stars that will become black holes at the end of their evolution are in binary or multiple states adds particular importance to BBH studies. In this study, using the SEOBNRv4$\_opt$ gravitational waveform model developed for compact binary systems, many ($\sim 10^6$) models were produced under different initial conditions, and the pre- and post-merge parameters were compared. In the models, it is assumed that the initial total mass (M$_{\rm{tot}}$) of the binary systems varies between 12-130 $\rm{M}_\odot$ with step interval 1$\rm{M}_\odot$, the mass ratios ($q = \rm{m}_{1i}/\rm{m}_{2i}$) vary between 1 and 2 with step interval 0.004, and the initial spin (\abs{\rchi_{1i}} = \abs{\rchi_{2i}}) value varies between $-0.83$ and $+0.83$ with step interval 0.017. Final spin (\rchi_{f}), fractional mass loss (M$_{FL}$), and the maximum gravitational wave amplitude (h$_{\rm{max}}$) obtained during the merger were compared with appropriate tables and figures obtained from the results of the relativistic numeric model obtained according to the initial parameters. Our results show that M$_{\rm{FL}}$ in generated BBH coalescences varied about 2.7 to 9.2\%, and \rchi_{\rm{f}} between 0.29 and 0.91. In most of the BBHs we have modeled, we found that M$_{\rm{FL}}$ varies inversely with $q$. However, it has been found that M$_{\rm{FL}}$ values are not always inversely varied to the $q$ parameter in systems of opposite initial spin, where the large mass black hole component is positively oriented. Accordingly, it is understood that the values of M$_{\rm{FL}}$ decrease to a certain point of $q$ and then increase according to the increasing direction of $q$.Comment: 29 pages, 5 figure, 5 tables, submitted for publicatio

Photometric study of close binary stars in the M35, M67, and M71 Galactic clusters

We obtained new multicolour photometry of close binary stars in the young open cluster M35, the solar-age open cluster M67, and the globular cluster M71. New observations have been carried out at the T\"{U}B\.{I}TAK National Observatory (TUG) by using the 100cm (T100) telescope. We present observational results for eclipsing binary systems in the selected Galactic clusters. New accurate light curves for 2MASS J19532554 + 1851175, 2MASS J19533427 + 1844047, 2MASS J06092044 + 2415155, and AH Cnc were obtained. The light curves were analysed and we derived some of the orbital parameters of the systems.Comment: 5 pages, 4 figures, accepted for publication in CAOS

General Relativistic Simulations of High-Mass Binary Neutron Star Mergers: rapid formation of low-mass stellar black holes

Almost 100 compact binary mergers have been detected via gravitational waves by the LIGO-Virgo-KAGRA collaboration in the past few years providing us with a significant amount of new information on black holes and neutron stars. In addition to observations, numerical simulations using newly developed modern codes in the field of gravitational wave physics will guide us to understand the nature of single and binary degenerate systems and highly energetic astrophysical processes. We here present a set of new fully general relativistic hydrodynamic simulations of high-mass binary neutron star systems performed with the publicly available Einstein Toolkit and LORENE codes. We considered systems with a total baryonic mass between 2.8 $M_\odot$ and 4.0 $M_\odot$ and we adopted the SLy equation of state. For all models we analyzed the gravitational wave signal and we report potential indicators of the systems undergoing rapid collapse into a black hole that may be observed by future-planned detectors such as the Einstein Telescope and the Cosmic Explorer. We also extracted the properties of the post-merger black hole, the disk and ejecta masses and their dependence on the binary parameters. We also compare our numerical results with recent analytical fits presented in the literature and we also provide parameter-dependent semi-analytical relations between the total mass and mass ratio of the systems and the resulting black hole masses and spins, coalescence time scale, mass loss, and gravitational wave energy.Comment: 13 pages, 5 figure, 4 tables, submitted for publicatio

Absolute properties of the binary system BB pegasi

We present ground-based photometry of the low-temperature contact binary BB Peg. We collected all the times of mid-eclipse available in the literature and combined them with those obtained in this study. Analyses of the data indicate a period increase of (3.0 ± 0.1) × 10-8 days yr -1. This period increase of BB Peg can be interpreted in terms of the mass transfer 2.4 × 10-8 M⊙ yr-1 from the less massive to the more massive component. The physical parameters have been determined as Mc = 1.42M⊙, Mh = 0.53 M⊙, Rc = 1.29 R⊙, Rh, = 0.83 R⊙, Lc = 1.86 L⊙, and L h = 0.94 L⊙ through simultaneous solutions of light and of the radial velocity curves. The orbital parameters of the third body, which orbits the contact system in an eccentric orbit, were obtained from the period variation analysis. The system is compared to the similar binaries in the Hertzsprung-Russell and mass-radius diagrams.Ege University Research Fund and TÜBİTAK National Observator

Black holes, gravitational waves and fundamental physics: a roadmap

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'

Aktif bileşenli örten çiftlerin ışık eğrilerinin modellenmesi

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.VII ABSTRACT LIGHT CURVE MODELLING OF THE ECLIPSING BINARIES WITH ACTIVE COMPONENTS YAKUT, Kadri MSc in Astronomy and Space Sciences Supervisor: Prof. Dr. Cafer İBANO?LU 2001, 119 pages In this thesis, an introduction on the light curve modelling is given along with the descriptions of softwares developed for this purpose. Two seperate light curves of very active RS CVn type eclipsing binary RT And have been obtained within 15 nights. These data have been combined with the others obtained by several researchers during the last 60 years. With the aid of all these data an O-C analysis has been performed, and furthermore, the brightnesses of the maxima and the selected four special phases have been investigated as a function of time. 30 light curves which have been obtained up to now have been analyzed with the Wilson-Devinney method and the variation of the activity versus years has been investigated. The orbital period of the binary has been found to be variable due to at least two different causes. One of them is due the revolution of the binary around a third body with a period of about 350 yrs and the other is due to magnetic activity of the one of the component with a period of about 40 yrs. According to the light curve variations the period of the magnetic cycle is proposed to be about 20 yrs. By the analsis of the light curves it was found that the spots on the surface of the hotter component are distributed over the longitudes of 90° and 250°. Keywords: RT And, light curve modeling and software, magnetic activity, orbital period change.ÖZET AKTİF BİLEŞENLİ ÖRTEN ÇİFTLERİN IŞIK EĞRİLERİNİN MODELLENMESİ YAKUT, Kadri Yüksek Lisans Tezi, Astronomi ve Uzay Bilimleri Bölümü Tez Yöneticisi: Prof. Dr. Cafer İBANOĞLU 2001, 119 sayfa. Bu tezde, ışık eğrilerinin modellenmesine ilişkin ön bilgiler verildikten sonra, bu amaçla geliştirilen yazılımlar kısaca tanıtılmıştır. Çok aktif bir RS CVn türü örten çift olan RT Andromedae yıldızı Ege Üniversitesi Gözlemevi'nde 15 gece gözlenerek iki ayrı ışık eğrisi elde edilmiştir. Bu veriler ile son 60 yılda başka araştırmacılar tarafından elde edilen veriler biraraya getirilmiştir. Bu veriler yardımı ile RT And'a ilişkin O-C analizi, maksimum parlaklığın ve seçilmiş dört özel evredeki parlaklığın yıllara göre değişimi incelenmiştir. Bugüne değin elde edilen 30 adet ışık eğrisi Wilson-Devinney yöntemi ile çözülmüş, aktivitenin (leke) yıllara göre değişimi araştırılmıştır. Çiftin yörünge döneminin en azından farklı iki nedenle değişime uğradığı sonucuna varılmıştır. Bunlardan birincisi, üçüncü bir cismin çevresinde yaklaşık 350 yıllık bir dolanım, ikincisi de yıldızın manyetik etkinliği nedeni ile yaklaşık 40 yıllık değişimdir. Işık eğrisindeki değişimlerden giderek manyetik çevrimin 20 yıl dolayında olduğu önerilmiştir. Işık eğrisinin analizi ile sıcak yıldızın yüzeyindeki lekelerin genellikle 90° ve 250° boylamlarında toplandığı sonucuna varılmıştır