Gullstrand’s Optical Schematic System of the Eye – Modified by Vojniković & Tamajo

According to early examination (Vojnikovi}, 1978) estimated, that the index of refraction for aqueous and vitreous is not the sum (1.33 or 1.66), than is for aqueous n = 1.334, and for vitreous N = 1.336. This measurements are made with Abbe’s refractometer, by temperature of 33 °C for aqueous, and 36 °C for vitreous, as it’s in human eye. In the principle of these results, the authors calculated the new values of cardinal points for the eye, and compared with Gullstrand’s optical schematic eye. So, the refractive power for the eye F= 59.98 D, first focal length f1= – 16.67 mm and second focal length f2 = + 22.27 m

Physical properties and CNO abundances for high-mass stars in four main-sequence detached eclipsing binaries: V478 Cyg, AH Cep, V453 Cyg, and V578 Mon

We present ten high-precision light curves of four transits in the XO-1 planetary system, obtained using u, g, r, redshifted Hα, I and z filters. We use these to measure the physical properties, orbital ephemeris, and a transmission spectrum of the planet covering the full optical wavelength range. We augment this with published HST/WFC3 observations to construct a transmission spectrum of the planet covering 0.37 to 1.65 μm. Our best-fitting model to this spectrum is for a H2/He-rich atmosphere containing water (3.05σ confidence), nitrogen-bearing molecules NH3 and HCN (1.5σ) and patchy cloud (1.3σ). We find that adding the optical to the near-infrared data does not lead to more precise constraints on the planetary atmosphere in this case. We conduct a detailed investigation into the effect of stellar limb darkening on our results, concluding that the choice of limb darkening law and coefficients is unimportant; such conclusions may not hold for other systems so should be reassessed for all high-quality datasets. The planet radius we measure in the g-band is anomalously low and should be investigated with future observations at a higher spectral resolution. From the measured times of transit we determine an improved orbital ephemeris, calculate a lower limit on the modified stellar tidal quality factor of Q′⋆>105.6, and rule out a previously postulated sinusoidal variation in the transit times

Chemical evolution of binary stars

U posljednjem su desetljeću značajno napredovali teorijski modeli zvijezda. Pokazalo se da uvođenje rotacijski potpomognutog miješanja zvjezdanog materijala i/ili magnetskog polja, može znatno promijeniti unutrašnju gradu zvijezda, što ima kao posljedicu promjene globalnih svojstava zvijezda i tijeka njihovog razvoja. Rotacijski evolucijski modeli zvijezda također predviđaju promjene u kemijskoj građi zvjezdanih atmosfera. Cilj je ove disertacije upravo bilo testiranje predviđanja novih teorijskih modela. Dvojne su zvijezde glavni izvor temeljnih zvjezdanih veličina (mase, polumjera i efektivnih temperatura) i kao takve služe za baždarenje teorijskih evolucijskih modela. Standardni postupci analize pažačkih podataka, naročito spektroskopskih, na granici su mogućnosti ovakvih testova. U ovom radu opisani su algoritmi i postupci kojima su postavljeni novi standardi u analizi opservabli, a otvoren je i novi kanal koji omogućava detaljnu analizu zastupljenosti elemenata u atmosferama komponenata dvojnih sustava zvijezda. Odabrana su tri dvojna sustava sa zvijezdama velikih masa, V380 Cyg, V621 Per i V615 Per, od kojih prva dva imaju primarne komponente sa svojstvima divova, i nalaze se u naprednijoj fazi zvjezdanog razvoja. Komponente ovih sustava u idealnom su evolucijskom stanju za testiranje novih rotacijskih modela. Napredna analiza pokazala je neslaganje empirijskih podataka s teorijskim predviđanjima. Zastupljenost elemenata u atmosferama evolucijski naprednijih komponenata ne razlikuje se sa zastupljenosti elemenata u B zvijezdama iz Sunčeve okoline. Otvoreno je važno pitanje vjerodostojnosti usporedbe svojstava jednostrukih zvijezda i zvijezda u dvojnim sustavima. Istraživanja u ovom radu pokazuju da su svojstva i razvoj zvijezda u dvojnim sustavima različiti od jednostrukih zvijezda već u ranim fazama razvoja.The last decade was characterized by a significant improvement of stellar theoretical models. It was shown that the involving of rotationally induced mixing of stellar material and/or magnetic field, can significantly change the internal stellar structure which then consequently implicates changes in global stellar features and their evolution. Rotational evolutionary stellar models also predict changes regarding the chemical structure of stellar atmospheres. The goal of this doctoral thesis was to test the predictions of new theoretical models. Binary stars are the main source of fundamental stellar parameters (masses, radii and effective temperatures) and therefore are used to calibrate theoretical evolutionary models. Standard procedures of empirical data analysis, especially the spectroscopic ones, are at the limit of possibilities of such tests. This thesis illustrates algorithms and procedures which are to establish new standards of observable analysis and at the same time sets a new way to analyze in detail the abundance of elements in the component atmospheres of binary stellar systems. Three binary systems were chosen with high-mass components, V380 Cyg, V621 Per and V615 Per, of which the first two systems contain the primary component with the nature of giants, and are in an evolved evolutionary phase. The components of these stellar systems are in an ideal evolutionary phase to test new rotational models. An advanced analysis has shown a discrepancy between empirical data and theoretical predictions. The abundance of elements in atmospheres of evolved stellar components has confirmed no difference to the abundances of elements of B stars in the solar neighbourhood. A very important question has been opened regarding the consistency of the comparison of features between single and binary stars. The conclusions of research in this thesis implicates that the properties and evolution of binary stars are different comparing to the ones of single stars already in the early phases of evolution

BF Cyg during ITS current outburst

We are intensively monitoring the current outburst on BF Cyg, both spectroscopically (high and low resolution modes) and photometrically (so far 450 BVRCRIC measurements have been collected). The outburst is photometrically reminiscent of the major event BF Cyg experienced in 1890 when it rose by 4 mag in the blue. In this contribution we present the data and describe the plans to investigate this object