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Wyświetlanie 1-10 z 22
Tytuł:
Very high optical activity of blazar OJ287
Autorzy:
Stachowski, G.
Drozdz, M.
Kozieł-Wierzbowska, Dorota
Kuźmicz, Agnieszka
Zoła, Stanisław
Ogloza, W.
Provencal, J.
Liakos, A.
Winiarski, Maciej
Opis:
OJ287 is being monitored in the optical waveband with small telescopes at the Astronomical Observatory of the Jagiellonian University (KRK) and the Mt. Suhora Observatory of the Pedagogical University (SUH) in Poland, and at the University of Athens, Greece (ATH). On April 19th, Mt. Cuba Observatory, USA (MTC), performed additional observations of this target. We report an even higher optical state of OJ287 than that published in Atel #4020 and Atel #4021.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
The absolute parameters of the detached eclipsing binary V482 Per
Autorzy:
Yılmaz, M.
Zakrzewski, B.
Şenavcı, H. V.
Zoła, Stanisław
Özavcı, İ.
Gazeas, K.
Nelson, R. H.
Baştürk, Ö.
Liakos, A.
Opis:
We present the results of a spectroscopic, photometric and orbital period variation analysis of the detached eclipsing binary V482 Per. We derived the absolute parameters of the system $(M_{1} = 1.51 M_{\bigodot }, M_{2} = 1.29 M_{\bigodot }, R_{1} = 2.39 R_{\bigodot }, R_{2} = 1.45 R_{\bigodot }, L_{1} = 10.15 L_{\bigodot }, L_{2} = 3.01 L_{\bigodot })$ for the first time in literature, based on an analysis of our own photometric and spectroscopic observations. We confirm the nature of the variations observed in the system’s orbital period, suggested to be periodic by earlier works. A light time effect due to a physically bound, star-sized companion $(M_{3} = 2.14 M_{\bigodot })$ on a highly eccentric (e = 0.83) orbit, seems to be the most likely cause. We argue that the companion can not be a single star but another binary instead. We calculated the evolutionary states of the system’s components, and we found that the primary is slightly evolving after the main sequence, while the less massive secondary lies well inside it.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
CoBiToM project : I. Contact binaries towards merging
Autorzy:
Niarchos, P. G.
Loukaidou, G. A.
Hakala, P.
Palafouta, S.
Gazeas, K. D.
Liakos, A.
Zoła, Stanisław
Athanasopoulos, D.
Essam, A.
Opis:
Binary and multiple stellar systems are numerous in our solar neighbourhood with 80 per cent of the solar-type stars being members of systems with high order multiplicity. The Contact Binaries Towards Merging (CoBiToM) Project is a programme that focuses on contact binaries and multiple stellar systems, as a key for understanding stellar nature. The goal is to investigate stellar coalescence and merging processes, as the final state of stellar evolution of low-mass contact binary systems. Obtaining observational data of approximately 100 eclipsing binaries and multiple systems and more than 400 archival systems, the programme aspires to give insights for their physical and orbital parameters and their temporal variations, e.g. the orbital period modulation, spot activity etc. Gravitational phenomena in multiple-star environments will be linked with stellar evolution. A comprehensive analysis will be conducted, in order to investigate the possibility of contact binaries to host planets, as well as the link between inflated hot Jupiters and stellar mergers. The innovation of CoBiToM Project is based on a multimethod approach and a detailed investigation, that will shed light for the first time on the origin of stellar mergers and rapidly rotating stars. In this work, we describe the scientific rationale, the observing facilities to be used and the methods that will be followed to achieve the goals of CoBiToM Project and we present the first results as an example of the current research on evolution of contact binary systems.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Physical parameters of close binary systems : VIII
Autorzy:
Zakrzewski, B.
Stachowski, G.
Kreiner, J. M.
Kjurkchieva, D.
Baran, A.
Erdem, A.
Szalankiewicz, S.
Kozieł-Wierzbowska, Dorota
Drozdz, M.
Rucinski, S. M.
Ogloza, W.
Siwak, M.
Marchev, D.
Gazeas, K.
Zoła, Stanisław
Liakos, A.
Opis:
This paper presents the results of a combined spectroscopic and photometric study of 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT Cnc, EE Cet, RW Com, KR Com, V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 Oph, V2612 Oph, V1363 Ori, V351 Peg, V357 Peg, Y Sex, V1123 Tau, and W UMa, which was conducted in the frame of the W UMa Project. Together with 51 already covered by the project and an additional 67 in the existing literature, these systems bring the total number of contact binaries with known combined spectroscopic and photometric solutions to 138. It was found that mass, radius, and luminosity of the components follow certain relations along the MS and new empirical power relations are extracted. We found that 30 per cent of the systems in the current sample show extreme values in their parameters, expressed in their mass ratio or fill-out factor. This study shows that, among the contact binary systems studied, some have an extremely low mass ratio (q < 0.1) or an ultrashort orbital period (Porb < 0.25 d), which are expected to show evidence of mass transfer progress. The evolutionary status of these components is discussed with the aid of correlation diagrams and their physical and orbital parameters compared to those in the entire sample of known contact binaries. The existence of very short orbital periods confirms the very slow nature of the merging process, which seems to explain why their components still exist as MS stars in contact configurations even after several Gyr of evolution.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Precursor Flares in OJ 287
Autorzy:
Chandra, S.
Sillanpää, A.
Berdyugin, A.
Reinthal, R.
Takalo, L.
Gopakumar, A.
Coggins-Hill, S. A.
Baliyan, K. S.
Salo, H.
Ganesh, S.
Lindfors, E.
Liakos, A.
Drozdz, M.
Santangelo, M. M. M.
Pihajoki, P.
Kozieł-Wierzbowska, Dorota
Provencal, J.
Valtonen, M.
Winiarski, Maciej
Nilsson, K.
Zoła, Stanisław
Ogłoza, W.
Opis:
We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z_{c} = 4000 AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Wyświetlanie 1-10 z 22

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