A more accurate Parameterization based on cosmic Age (MAPAge)

Recently, several statistically significant tensions between different cosmological datasets have raised doubts about the standard Lambda cold dark matter (ΛCDM) model. A recent letter (Huang 2020) suggests to use “Parameterization based on cosmic Age” (PAge) to approximate a broad class of beyond-ΛCDM models, with a typical accuracy ∼1% in angular diameter distances at z ≲ 10. In this work, we extend PAge to a More Accurate Parameterization based on cosmic Age (MAPAge) by adding a new degree of freedom η 2. The parameter η 2 describes the difference between physically motivated models and their phenomenological PAge approximations. The accuracy of MAPAge, typically of order 10−3 in angular diameter distances at z ≲ 10, is significantly better than PAge. We compare PAge and MAPAge with current observational data and forecast data. The conjecture in Huang (2020), that PAge approximation is sufficiently good for current observations, is quantitatively confirmed in this work. We also show that the extension from PAge to MAPAge is important for future observations, which typically require sub-percent accuracy in theoretical predictions.

Роль эллиптических интегралов в расчете гравитационного линзирования заряженной черной дыры Вейля, окруженной плазмой

In this paper, we mainly aim at highlighting the importance of (hyper-)elliptic integrals in the study of gravitational effects caused by strongly gravitating systems. For this, we study the application of elliptic integrals in calculating the light deflection as it passes a plasmic medium, surrounding a charged Weyl black hole. To proceed with this, we consider two specific algebraic ansatzes for the plasmic refractive index, and we characterize the photon sphere for each of the cases. This will be used further to calculate the angular diameter of the corresponding black hole shadow. We show that the complexity of the refractive index expressions, can result in substantially different types of dependencies of the light behavior on the spacetime parameters. В этой статье мы в основном стремимся подчеркнуть важность (гипер) эллиптических интегралов в изучении гравитационных эффектов, вызванных сильно гравитирующими системами. Для этого мы изучаем применение эллиптических интегралов при вычислении отклонения света при его прохождении через плазменную среду, окружающую заряженную черную дыру Вейля. Чтобы продолжить это, мы рассмотрим два конкретных алгебраических анзаца для показателя преломления плазмы и охарактеризуем фотонную сферу для каждого из случаев. Это будет использоваться в дальнейшем для вычисления углового диаметра соответствующей тени черной дыры. Мы показываем, что сложность выражений показателя преломления может привести к существенно разным типам зависимостей поведения света от пространственно-временных параметров.

Cosmology

The main features of the universe and its history, and the application of GR to the universe as a whole are presented. The observed near-isotropy and homogeneity of the universe are described, along with a survey of its history. The Saha equation is applied to the recombination process. Cosmic proper time and comoving coordinates are defined, and the form of the metric (Friedmann-Lemaitre-Robertson-Walker) applicable to such a universe is obtained. The main features of the resulting geometry are discussed at length, with a view to both accurate calculation and sound intuition. Redshift and the cosmic expansion are described from several perspectives. Distance measures (luminosity, angular diameter) are defined and the main elements of the observational cosmic distance ladder are outlined.

The analysis of the 2019 annular solar eclipse with simple instruments for developing student worksheet

The annular solar eclipse occurred when the Earth-Moon-Sun position aligned in the same line where the angular diameter of the moon is smaller than the angular diameter of the sun due to the moon is on the farthest distance with respect to the earth. The event was observed on 26 December 2019 at Siak Regency, Province of Riau, Indonesia. Based on that event observation, the sun is gradually covered by the moon until the peak event where the sun is completely covered and showing “ring of fire”. All stages of eclipse are captured as images from DSLR camera that been attached into telescope with specific filter as well as illumination determination from observation location using lux meter during the event. This study explained how to get the information from solar eclipse images available by using image-processing software namely ImageJ so it can be used as a student worksheet. The plotting of both pixel area-time graph and illumination-time graph of this study shows a similar trend. Therefore, the data acquired in this study is obtained well so it can be used as a student worksheet in the Astronomical Position lecture based on the actual phenomenon with a simple instrument for observation.

Refined fundamental parameters of Canopus from combined near-IR interferometry and spectral energy distribution

Context. Canopus, the brightest and closest yellow supergiant to our Solar System, offers a unique laboratory for understanding the physics of evolved massive stars. Aims. We aim at quantitatively exploring a large space of fundamental parameters of Canopus based on the combined analysis of its spectral energy distribution (SED) and optical-IR long baseline interferometry. Methods. We use the most recent high resolution near-IR data from the VLTI focal beam combiners PIONIER (H and K bands) and AMBER (K band), together with precise spectrophotometric measures that cover the SED of Canopus, from the UV to the IR, taken from ground and space observatories. Results. The accurate and precise PIONIER data allowed us to simultaneously measure the angular diameter and the limb darkening (LD) profile using different analytical laws. We found that the power-law LD, being also in agreement with predictions from stellar atmosphere models, reproduces the interferometric data well. For this model we measured an angular diameter of 7.184 ± 0.0017 ± 0.029 mas and an LD coefficient of 0.1438 ± 0.0015, which are respectively ≳5 and ~15−25 more precise than in our previous A&A paper on Canopus from 2008. From a dedicated analysis of the interferometric data, we also provide new constraints on the putative presence of weak surface inhomogeneities. Additionally, we analyzed the SED in a innovative way by simultaneously fitting the reddening-related parameters and the stellar effective temperature and gravity. We find that a model based on two effective temperatures is much better at reproducing the whole SED, from which we derived several parameters, including a new bolometric flux estimate: fbol = (59.22 ± 2.45) × 10−6 erg cm−2 s−1. We were also able to estimate the stellar mass from these measurements, and it is shown to be in agreement with additional predictions from evolutionary models, from which we inferred the age of Canopus as well. Conclusions. The Canopus angular diameter and LD measured in this work with PIONIER are the most precise to date, with a direct impact on several related fundamental parameters. Moreover, thanks to our joint analysis, we were able to determine a set of fundamental parameters that simultaneously reproduces both high-precision interferometric data and a good quality SED and, at the same time, agrees with stellar evolution models. This refined set of fundamental parameters constitutes a careful balance between the different methodologies used, providing invaluable observationally based constraints to models of stellar structure and evolution, which still present difficulties in simulating stars such as Canopus in detail.

Cosmography using strong lensing systems and cosmic chronometers

Using a new sub-sample of observed strong gravitational lens systems, for the first time, we present the equation for the angular diameter distance in the y-redshift scenario for cosmography and use it to test the cosmographic parameters. In addition, we also use the observational Hubble data from cosmic chronometers and a Joint analysis of both data is performed. Among the most important conclusions are that this new analysis for cosmography using Strong Lensing Systems is equally competitive to constrain the cosmographic parameters as others presented in literature. Additionally, we present the reconstruction of the effective equation of state inferred from our samples, showing that at z = 0 those reconstructions from Strong Lensing Systems and Joint analysis are in concordance with the standard model of cosmology.

Ergosphere, Photon Region Structure, and the Shadow of a Rotating Charged Weyl Black Hole

In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric charge and the spin parameter, and its shadow changes from being oblate to being sharp by increasing in the spin parameter. Comparing the calculated vertical angular diameter of the shadow with that of M87*, we found that the latter may possess about 1036 protons as its source of electric charge, if it is a rotating charged Weyl black hole. A complete derivation of the ergosphere and the static limit is also presented.

Scalable photonic-based nulling interferometry with the dispersed multi-baseline GLINT instrument

Characterisation of exoplanets is key to understanding their formation, composition and potential for life. Nulling interferometry, combined with extreme adaptive optics, is among the most promising techniques to advance this goal. We present an integrated-optic nuller whose design is directly scalable to future science-ready interferometric nullers: the Guided-Light Interferometric Nulling Technology, deployed at the Subaru Telescope. It combines four beams and delivers spatial and spectral information. We demonstrate the capability of the instrument, achieving a null depth better than 10−3 with a precision of 10−4 for all baselines, in laboratory conditions with simulated seeing applied. On sky, the instrument delivered angular diameter measurements of stars that were 2.5 times smaller than the diffraction limit of the telescope. These successes pave the way for future design enhancements: scaling to more baselines, improved photonic component and handling low-order atmospheric aberration within the instrument, all of which will contribute to enhance sensitivity and precision.

Psychophysical study of the moon illusion in paintings and landscape photos

The moon illusion is a visual deception when people perceive the angular diameter of the Moon/Sun near the horizon larger than that of the one higher in the sky. Some theories have been proposed to explain this illusion, but not any is generally accepted. Although several psychophysical experiments have been performed to study different aspects of the moon illusion, their results have sometimes contradicted each other. Artists frequently display(ed) the Moon/Sun in their paintings. If the Moon/Sun appears near the horizon, its painted disc is often exaggeratedly large. How great is the magnitude of moon illusion of painters? How different are the size enlargements of depicted lunar/solar discs? To answer these questions, we measured these magnitudes on 100 paintings collected from the period of 1534–2017. In psychophysical experiments, we also investigated the moon illusion of 10 test persons who had to estimate the size of the lunar/solar disc on 100 paintings and 100 landscape photographs from which the Moon/Sun was retouched. Compared to the lunar/solar disc calculated from reference distances estimated by test persons in paintings, painters overestimated the Moon's size on average Q = 2.1 ± 1.6 times, while the Sun was painted Q = 1.8 ± 1.2 times larger than the real one, where Q = r painted / r real is the ratio of the radii of painted ( r painted ) and real ( r real ) Moons/Suns. In landscape photos, test persons overestimated the Moon's size Q = 1.6 ± 0.4 times and the Sun was assumed Q = 1.7 ± 0.5 times larger than in reality, where Q = r test / r real is the ratio of the radius r test estimated by the test persons and the real radius r real of Moons/Suns. The majority of the magnitude of moon illusion Q = 1.6, 1.7, 1.8, 2.1, 2.8, 2.9 measured by us are larger than the Q -values 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8 obtained in previous psychophysical experiments due to methodological differences.