128 research outputs found
Mass and p-factor of the type II cepheid OGLE-LMC-T2CEP-098 in a Binary System
No full textWe present the results of a study of the type II Cepheid (P-puls = 4.974 days) in the eclipsing binary system OGLELMC- T2CEP-098 (P-orb = 397.2 days). The Cepheid belongs to the peculiar W Vir group, for which the evolutionary status is virtually unknown. It is the first single-lined system with a pulsating component analyzed using the method developed by Pilecki et al. We show that the presence of a pulsator makes it possible to derive accurate physical parameters of the stars even if radial velocities can be measured for only one of the components. We have used four different methods to limit and estimate the physical parameters, eventually obtaining precise results by combining pulsation theory with the spectroscopic and photometric solutions. The Cepheid radius, mass, and temperature are 25.3 +/- 0.2 R-circle dot, 1.51 +/- 0.09 M-circle dot, and 5300 +/- 100 K, respectively, while its companion has a similar size (26.3 R-circle dot), but is more massive (6.8 M-circle dot) and hotter (9500 K). Our best estimate for the p-factor of the Cepheid is 1.30 +/- 0.03. The mass, position on the period-luminosity diagram, and pulsation amplitude indicate that the pulsating component is very similar to the Anomalous Cepheids, although it has a much longer period and is redder in color. The very unusual combination of the components suggest that the system has passed through a mass-transfer phase in its evolution. More complicated internal structure would then explain its peculiarity.Polish National Science Center, SONATA 2014/15/D/ST9/02248 / BASAL Centro de Astrofisica y Tecnologias Afines,
CATA PFB-06/2007 /
Chilean Ministry of Economy, Development and Tourism's Millennium Science Initiative, IC120009 / French Agence Nationale de la Recherche (ANR), ANR-15-CE31-0012-01 /
European Research Council (ERC) under the European Union's Horizon research and innovation program, 695099 /
European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs, 096.D-0425(A),
097.D-0400(A), 098.D-0263(A
The villa designed by Rudolf Fränkel, in Smolec near Wrocław
No full textTa dotąd zupełnie nieznana w polskiej literaturze willa powstała w latach 1931–1932. Reprezentuje koncepcję budowania organicznego, sformułowaną w 1925 r. przez Hugona Häringa. Projekt wykonał Rudolf Fränkel będący wówczas wschodzącą gwiazdą berlińskiej architektury, autor kilku luksusowych willi, ale przede wszystkim berlińskich osiedli mieszkaniowych, m.in. osiedla Atlantic z pięciuset mieszkaniami, zapleczem rekreacyjnym i kinem „Lichtburg”. Jego znakomicie zapowiadająca się kariera architektoniczna została jednak w 1933 r., ze względu na żydowskie pochodzenie, w dramatycznych okolicznościach przerwana. Zleceniodawcą podwrocławskiej willi był Robert Stern, ogrodnik o wyrobionym guście artystycznym i dużych aspiracjach, który w Brochowie (obecnie dzielnica Wrocławia) prowadził ogrodnictwo, uczestniczył w wystawach ogrodniczych, zbierając doświadczenie i nagrody. Około 1930 r. swoje przedsiębiorstwo przeniósł na obrzeża Smolca, a nad stawem, na dużej posesji wzniósł willę. Villa rustica o znakomitych, niemalże palladiańskich proporcjach i luksusowych, indywidualnie aranżowanych wnętrzach została zaprojektowana od wnętrza na zewnątrz, jej pomieszczenia powiązano z ukształtowaniem terenu i roztaczającym się z dwóch tarasów szerokim widokiem na staw i zieloną okolicę. Bardzo dobrej jakości zdjęcia willi wykonane przez fotografa Maxa Krajewskiego, stale współpracującego z architektem, zamieszczone w ówczesnej fachowej prasie dają wyobrażenie o jej pierwotnym kształcie i komforcie, dostosowanym do oczekiwań właścicieli. Dom, choć bardzo przebudowany, nadal jest zamieszkany. Artykuł przedstawia wszystkie dostępne informacje o kształcie i detalach architektonicznych willi, jej projektancie oraz pierwszych właścicielach.This, to date completely unknown in Polish literature, villa was built in 1931–1932, representing the concept of organic building (organhaftes Bauen), formulated in 1925 by Hugo Häring. The design was created by an architect, being then a rising star of the Berlin architecture, the designer of several luxury villas, but above all Berlin housing estates, including the Atlantic estate with five hundred apartments, leisure facilities and the “Lichtburg” cinema. The very promising architectural career of Fränkl was interrupted in dramatic circumstances in 1933 due to his Jewish ancestors. Fränkl’s employer and the villa’s owner was Robert Stern, a horticulturist with refined taste and high artistic aspirations, who in Brochów (now a quarter of Wrocław) ran a horticulture enterprise and who participated in horticultural exhibitions collecting both experience and awards. Around 1930 he moved his company to the outskirts of Smolec and at the pond, within a large estate he built the villa, designed by Fränkl. This villa rustica with excellent, almost Palladian, proportions and luxurious, individually decorated interiors was designed from the inside to the outside, its spaces were linked with the landscape and a panoramic view of the pond and the nature from two large terraces. Photographs of very good quality taken by the photographer Max Krajewski constantly cooperating with the architect, published in the contemporary architecture magazines give an idea of its original shape and comfort, adapted to the expectations of the owners. The house, although strongly rebuilt, still exists. The article presents all available information about the shape and architectural details of the villa, its designer and oryginal owners
Survey of hydrodynamic RR Lyrae models
No full textWe present a grid of hydrodynamic RR Lyrae-type models covering a large range of physical parameters. These models were computed with the aim to analyse the mode selection in these stars and to search for the Blazhko-type modulation. Initial results of the survey are reported
The Eclipsing Binary Cepheid OGLE-LMC-CEP-0227 in the Large Magellanic Cloud: Pulsation Modeling of Light and Radial Velocity Curves
No full textUnstable standard candles. Periodic light-curve modulation in fundamental mode classical Cepheids
No full textMultimode Radiative beta Cephei and delta Cephei Models
No full textAs a by-product of β Cephei and δ Cephei radiative model surveys we have found interesting cases of multimode pulsation. In case of β Cephei stars, we found two multimode domains with two or three modes being involved. The origin of the multimode pulsation can be traced to one of the two different mechanisms: either to the non-resonant coupling of the two excited modes (double-mode pulsation) or to the 2ω1 ω0 + ω2 parametric resonance (triple-mode pulsation). In case of δ Cephei models, a triple-mode pulsation domain, connected with the 2:1 resonance,
2ω0 ω2, is found. These models are of theoretical interest only, since they do not obey a proper mass-luminosity relation
Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227
No full textA novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating-eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 (P-puls = 3.80 d, P-orb = 309 d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V-band, I-band and Spitzer 3.6 mu m photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M-1 = 4.165 +/- 0.032 M-circle dot and R-1 = 34.92 +/- 0.34 R-circle dot, respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p = 1.21 +/- 0.03(stat.) +/- 0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for delta Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity
Amplitude Saturation in β Cephei Models - Preliminary Results. Veröffentlichungen der Kommission für Astronomie|Communications in Asteroseismology|Communications in Asteroseismology 150 150|
No full textThe census of non-radial pulsation in first-overtone RRLyrae stars of the OGLE Galactic bulge collection
No full textWe analysed photometry for the up-to-date collection of the first-overtone RRLyrae stars (RRc; 11415 stars) and double-mode RRLyrae stars (RRd; 148 stars) towards the Galactic bulge from the Optical Gravitational Lensing Experiment (OGLE). We analysed frequency spectra of these stars in search for additional, low-amplitude signals, beyond the radial modes. We focused on stars from two groups: RR0.61 and RR0.68. In the first group, additional low-amplitude signals have periods shorter than the first-overtone period; period ratios fall in the 0.60-0.64 range. In the second group, additional low-amplitude signals have periods longer than the first-overtone period; period ratios tightly cluster around 0.68. Altogether we have detected 960 and 147 RRLyrae stars that belong to RR0.61 and RR0.68 groups, respectively, which yield the incidence rates of 8.3 and 1.3percent of the considered sample. We discuss statistical properties of RRLyrae stars with additional periodicities. For RR0.61 group we provide strong arguments that additional periodicities are connected to non-radial pulsation modes of degrees l=8 and l=9, as proposed by Dziembowski. We have also detected two double-periodic variables, with two close periodicities, similar to RRLyrae variable V37 in NGC6362. Properties of these peculiar variables, which may form a new group of double-mode pulsators, are discussed
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