According to the general catalog of variable stars, AL Cas was classified as an EW-type eclipsing binary with a spectral type of B and an orbital period of P = 0.5005555 days. The first photometric ...light curves of the close binary in the B, V, R, and I bands are presented. New low-resolution spectra indicate that its spectral type is about F7 rather than B-type. A photometric analysis with the Wilson-Devinney method suggests that it is a contact binary (functionof = 39.3%) with a mass ratio of 0.61. Using 17 newly determined eclipse times together with those collected from the literature, we found that the observed-calculated (O - C) curve of AL Cas shows a cyclic change with a period of 86.6 yr and an amplitude of 0.0181 days. The periodic variation was analyzed for the light-travel time effect via the presence of a third body. The mass of the third body was determined to be M sub(3) sin i' = 0.29(+ or -0.05) M sub(middot in circle) when a total mass of 2.14 M sub(middot in circle) for AL Cas is adopted. It is expected that the cool companion star may have played an important role in the origin and evolution of the system by removing angular momentum from the central binary system during early dynamical interaction and/or late dynamical evolution. This causes the original detached system to have a low angular momentum and a short initial orbital period. Then it can evolve into the present contact configuration via a case A mass transfer.
In this work, we investigate the effect of the number of available adsorption sites for diffusing particles in a liquid confined between walls where the adsorption (desorption) phenomena occur. We ...formulate and numerically solve a model for particles governed by Fickian’s law of diffusion, where the dynamics at the surfaces obey the Langmuir kinetic equation. The ratio between the available number of adsorption sites and the number of total particles are used as a control parameter. The investigation is carried out in terms of characteristic times of the system for different initial configurations, as well as the cases of identical or non-identical surfaces. We calculate the bulk and surface densities dynamics, as well as the variance of the system, and demonstrate that the number of sites affects the bulk, surface distributions, and diffusive regimes.
ABSTRACT In this paper, we present a combined photometric, spectroscopic, and orbital period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and AT Peg. As a result, we have ...derived the absolute parameters of their components and, on that basis, we discuss their evolutionary states. Furthermore, we compare their parameters with those of other binary systems and with theoretical models. An analysis of all available up-to-date times of minima indicated that all three systems studied here show cyclic orbital changes; their origin is discussed in detail. Finally, we performed a frequency analysis for possible pulsational behavior, and as a result we suggest that XZ Aql hosts a δ Scuti component.
We study flux and spectral variability of the high energy peaked TeV blazar PG 1553 + 113 on diverse timescales using the data collected from 2005 to 2019 which also includes the intensive ...intra-night monitoring of the target. Additionally, we recorded the brightest flare of the blazar PG 1553 + 113 during April 2019 when the source attained an
R
-band magnitude of 13.2. Analyzing the spectral evolution of the source during the flare gave a clockwise spectral hysteresis loop and a time lag with
V
-band variations leading to the
R
-band ones. Various statistical tests, fitting procedures and cross-correlation techniques are applied to search for periodicity and examine the color-magnitude relationship. We find a median period of (2.21 ± 0.04) years along with the secondary period of about 210 days. Finally, we briefly discuss various physical mechanisms which are capable of explaining our findings.
We developed a method that allows to classify the light curves of eclipsing binaries of the W UMa type (EW) with respect to their intrinsic variability. The algorithm measures several features of ...light curves, such as the amplitude of the O’Connell effect, the separation and location of maxima brightness as well as depths of the minima in subsequent orbital periods. This method is capable of distinguishing systems with presumed magnetic activity present from these without it, as well as recognizing systems with starspots migration and those with other types of intrinsic variability manifestation. The classification is done in an automatic way without a time consuming, visual inspection of light curves.
The occurrence of low-amplitude flux variations in blazars on hourly timescales, commonly known as microvariability, is still a widely debated subject in high-energy astrophysics. Several competing ...scenarios have been proposed to explain such occurrences, including various jet plasma instabilities leading to the formation of shocks, magnetic reconnection sites, and turbulence. In this Letter, we present the results of our detailed investigation of a prominent, five-hour-long optical microflare detected during the recent WEBT campaign on 2014 March 2-6 targeting the blazar 0716+714. After separating the flaring component from the underlying base emission continuum of the blazar, we find that the microflare is highly polarized, with the polarization degree ~(40-60)% + or - (2-10)% and the electric vector position angle ~(10-20)degrees + or - (1-8)degrees slightly misaligned with respect to the position angle of the radio jet. The microflare evolution in the (Q,U) Stokes parameter space exhibits a looping behavior with a counterclockwise rotation, meaning the polarization degree decreases with the flux (but is higher in the flux decaying phase), and an approximately stable polarization angle. The overall very high polarization degree of the flare, its symmetric flux rise and decay profiles, and also its structured evolution in the Q-U plane all imply that the observed flux variation corresponds to a single emission region characterized by a highly ordered magnetic field. As discussed in the paper, a small-scale but strong shock propagating within the outflow, and compressing a disordered magnetic field component, provides a natural, though not unique, interpretation of our findings.
Our sample of giant radio-source candidates, published in Paper I, is updated and supplemented with further radio and optical data. In this paper we present: (i) newly detected host galaxies, their ...photometric magnitude, and redshift estimate for the sample sources not identified yet, (ii) optical spectra and spectroscopic redshift for the host galaxies fainter than about R approximately 18.5 mag taken with the Apache Point Observatory 3.5 m telescope, and (iii) the VLA 4.9 GHz total-intensity and polarised-intensity radio maps of the sample members. In a few cases they reveal extremely faint radio cores undetected before, which confirm the previously uncertain optical identifications. The radio maps are analysed and the polarisation properties of the sample sources summarised. A comparison of our updated sample with three samples published by other authors implies that all these four samples probe the same part of the population of extragalactic radio sources. There is no significant difference between the distributions of intrinsic size and radio power among these samples. The median redshift of 0.38 plus or minus 0.07 in our sample is the highest among the corresponding values in the four samples, indicating that the angular size and flux-density limits in our sample, lower than those for the other three samples, result in effective detections of more distant, giant-size galaxies compared to those detected in the other samples. This sample and a comparison sample of "normal"-size radio galaxies will be used in Paper III (this volume) to investigate of a number of trends and correlations in the entire data.
We announce the discovery of a unique combination of features in a radio source identified with the merger galaxy CGCG 292−057. The radio galaxy both exhibits a highly complex, X-like structure and ...shows signs of recurrent activity in the form of double-double morphology. The outer lobes of CGCG 292−057 are characterized by low radio power, P
1400 MHz≃ 2 × 1024 W Hz−1, placing this source below the FR II/FR I luminosity threshold, and are highly polarized (almost 20 per cent at 1400 MHz) as is typical of X-shaped radio sources. The host is a low-ionization nuclear emission-line region-type galaxy with a relatively low black hole mass and double-peaked narrow emission lines. These features make this galaxy a primary target for studies of merger-triggered radio activity.
By using 78 newly determined timings of light minima together with those collected from the literature, we analysed the changes in the observed minus calculated (O−C) diagram in HS 0705+6700, a ...short-period (2.3 h) eclipsing binary that consists of a very hot subdwarf B-type (sdB) star and a very cool fully convective red dwarf. We confirmed the cyclic variation in the O−C and refined the parameters of the circumbinary brown dwarf (reported to orbit the binary system in 2009) by analysing the changes for the light travel time effect that arises from the gravitational influence of the third body. Our results indicate the lower mass limit of the third body to be M
3 sin i
′ = 33.7(±1.6) M
Jup. This companion would be a brown dwarf if its orbital inclination is larger than 27
7 and it is orbiting the central eclipsing binary with an eccentricity e ∼ 0.2 at a separation of about 3.7(±0.1) au.
We present results from analysis of combined spectroscopic and photometric data for three eclipsing binary systems: AP And, VZ Cep and V881 Per. Based on new, multicolour photometric light curves and ...spectroscopically determined mass ratio values, we derived accurate physical parameters of the components. Two of the systems, namely VZ Cep and V881 Per, were found to be magnetically active. The variability of V881 Per was studied in several sets of data Northern Sky Variability Survey (NSVS), Wide Angle Search for Planets (WASP) and newly derived gathered at different epochs. We show that the huge differences in the shape of its light curve can be explained by just a single model differing only in number of spots and their location on the surface of the primary component.
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