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Transit photometry is a dependable method for detecting and characterizing exoplanets. However, the usual transit detection method requires a substantial amount of signal processing since the dip in the signal detected, an indication that there is a planet in transit, is minuscule compared to the overall background signal due mainly to its host star. In this paper, we discuss how to achieve higher planetary signals and lower noises by subtracting the flux of the equal halves of a host star — a split differential detection. We derive an expression of the split differential light curve and investigate the effect of two common noises: the white Gaussian background noise and the noise due to the occurrences of sunspots. We show that in separate simulations and derivation of analytical expression, the split differential transit doubles the signal and reduces the effective noise by a factor of 1 / 2 . While our idea may be simple, a split differential detection can be realizable and can provide a more precise estimation of planetary parameters. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the problem of clustering 1318 new variable stars found in the Milky way. Our recent work distinguishes these stars based on their light curves which are univariate series of brightness from the stars observed at discrete time points. This work proposes a new approach to look at these discrete series as continuous curves over time by transforming them into functional data. Then, functional principal component analysis is performed using these functional light curves. Clustering based on the significant functional principal components reveals two distinct groups of eclipsing binaries with consistency and superiority compared to our previous results. This method is established as a new powerful light curve-based classifier, where implementation of a simple clustering algorithm is effective enough to uncover the true clusters based merely on the first few relevant functional principal components. Simultaneously we discard the noise from the data study involving the higher order functional principal components. Thus the suggested method is very useful for clustering big light curve data sets which is also verified by our simulation study. [ABSTRACT FROM AUTHOR]

Many astronomers have discussed the property of BL Lacertae objects, including the variation of spectrum, the correlation of multi-wave bands and the property of polarization, which could give good information for studying intrinsic correlation of components and position of BL Lacertae objects. In the paper, we investigated the properties of RBLs and XBLs and RBLs/XBLs (these objects can also be found by radio survey as by X-ray survey). Firstly, we collected the light curve of 28 BL Lacertae objects, and gained their short timescales by Structure Function (SF). Secondly, we analyzed the distribution of the short timescales of some BL Lacertae objects, including 28 objects’ timescales calculated by SF, as well as the distribution of the redshift and the black hole mass and the flux densities of the multi-wavebands (radio, near-infrared, optical and Gamma-ray). Based on statistical analysis, the result of the paper support the unification model of RBLs and XBLs. [ABSTRACT FROM AUTHOR]

Due to its extreme mass ratio, the system AW UMa is considered as one of the most interesting contact binaries. In the present paper, a total of 1289 observations in VRI band were carried out from on 2006 March 7, 8, and 9 at Piszkesteto, Mountain Station of the Konkoly observatory (Hungary). VRI light curves were constructed and a photometric solution of these light curves was obtained by means of Willson-Devinney code. The results show that the primary component is more massive and hotter than the primary component by ∼140 K. A secular period decrease with a rate dP/ dE=2.436×10 day/cycle was detected. Based on the physical parameters of the system, we investigate the evolutionary state of the components. The primary component is above the zero age main sequence (ZAMS) track, while the secondary component has a larger radius and luminosity than expected from its ZAMS mass. [ABSTRACT FROM AUTHOR]

Interstellar and atmospheric extinctions redden the observational photometric data and they should be handled rigorously. This paper simulates the effect of reddening for the modest case of two main sequenceT1 = 6500 K andT2 = 5500 K components of a detached eclipsing binary system. It is shown that simply subtracting a constant from measured magnitudes (the approach often used in the field of eclipsing binaries) to account for reddening should be avoided. Simplified treatment of the reddening introduces systematics that reaches ~0.01 mag for the simulated case, but can be as high as ~0.2 mag for, e.g., B8 V-K4 III systems. With rigorous treatment, it is possible touniquelydetermine the colour excess valueE(B-V) from multi-colour photometric light curves of eclipsing binaries. [ABSTRACT FROM AUTHOR]

New BV light curves and photometric solutions of the W UMa-type contact binary CU Tau are presented in this paper. From the observations, four times of minimum light were determined and from the present times of minimum light and those collected from the references, a new ephemeris was formed. The O-C diagram of the period change suggests that the orbital period of the system seems to vary. While the B light curve seems to be symmetric, the V light curve appears to exhibit an O'Connell effect, with Maximum I being 0.015 mag. brighter than Maximum II. The light curves are analyzed by means of the latest version of the Wilson-Devinney code. The results show that CU Tau is A-subtype W UMa contact binary with a small mass ratio q = 0.180. The asymmetry of the light curve is explained by star spot models. [ABSTRACT FROM AUTHOR]

The present paper aims to study the previously unstudied Chandra observed X-ray point sources of NGC 3384. While most of the point sources in NGC 3384 are hard X-ray binaries, we report here the discovery of a candidate Ultra-luminous X-ray source (ULX), X-8 in NGC 3384 during an effective 28.67 ks Chandra observation. ULX, X-8 is found to have its 0.3-10.0 keV luminosity ∼1.52×10 ergs s and a bolometric luminosity ∼2.43×10 ergs s. The ULX is spectrally hard in X-rays, with Γ∼1.97 when fitted with an absorbed powerlaw. The spectral property of this object, when fitted with an absorbed disk blackbody, appears to be consistent with nearly a 30 M black hole accreting at ∼0.58 times its Eddington luminosity. The lightcurve of this ULX source, X-8 has shown no signature of short-term variability in kilo-seconds time scales in the present available Chandra observation. [ABSTRACT FROM AUTHOR]

Evidence is presented indicating that the bursting component of the X-ray radiation detected in the nuclear region of the active radio galaxy 3C 111 comes from the blobs ejected in the pc-scale jet and not from the accretion disc. After each new outburst the radio flux density associated with it increases to a peak in ∼1 year and then subsides over a period of 1-2 years with the flux falling off exponentially as the blob moves outward and dissipates. Similar peaks (bursts) are seen in the X-ray light curve and a cross-correlation between the two shows a very high correlation with the X-ray peaks leading the radio peaks by ∼100 days. A second cross-correlation, this time between the radio event start times and the X-ray light curve, also shows a significant correlation. When this is taken together with the long (∼1 yr) delay between the start of each ejection event and its associated X-ray peak it indicates that this bursting component of the X-ray flux must be associated with the ejected blobs in the pc-scale jet and not with the accretion disc. Because X-ray telescopes do not have the resolution required to resolve the accretion disc area from the pc-scale jet, this paper is the first to present observational evidence that can pinpoint the point of origin of at least those long-timescale X-ray bursts with durations of 1-3 yrs. [ABSTRACT FROM AUTHOR]

3C 66A was monitored by the BATC (Beijing-Arizona-Taipei-Connecticut) telescope from 2005 to 2008, 1994 observations were obtained on 89 nights. Detailed research and analysis was performed on these observations in this paper. A long term burst occurred in the whole light curve. No intra-day variability was claimed in our campaign by intra-night light curve analysis. Time lag of shorter wavelenth preceding longer wavelength was shown by correlation analysis. The results showed that the optical spectral shape turned flatter when the source brightened, and the spectral variability indicator was bigger on shorter time-scale as determined by the color indices variation analysis. [ABSTRACT FROM AUTHOR]

In this paper we analyze the behavior of the unusual dwarf nova EM Cyg using the data obtained in April–October, 2007, at the Vyhorlat observatory (Slovak Republic) and in September, 2006, at the Crimean Astrophysical Observatory (Ukraine). During our observations, EM Cyg has shown outbursts in every 15–40 days. Because on the light curves of EM Cyg a partial eclipse of the accretion disc is observed, we applied the eclipse mapping technique to a reconstruction of the temperature distribution in the eclipsed parts of the disc. Calculations of the accretion rate for the system were made for the quiescent and the outburst states of activity for various distances. [ABSTRACT FROM AUTHOR]

In this paper we investigate the variability of the gamma ray burst light curve. It is generally known that this fluctuation arise in the second phase of a GRB event, when two shock waves of different Lorentz factors collide. This is so called internal shock scenario. We have developed a simple model which includes dynamical and radiating part, to simulate shock wave evolution and collision. By specifying the model parameters, we show that this scenario could be used to describe variability of GRB light curve. We then use the model to simulate peeks in several different long GRB events from the BATSE database, which show us that some of the basic parameters have a very narrow range of values. [ABSTRACT FROM AUTHOR]

An analytically tractable method of transforming the problem of light curve analysis of eclipsing binaries from the time domain into the frequency domain was introduced by Kopal (1975, 1979, 1990). This method uses a new general formulation of eclipse functions a, the so-called momentsA2m, and their combinations asg2m =A2m+2/(A2mA2m+4) functions for the basic spherical model. In this paper, I will review the use of these functions in the light curve analysis of eclipsing binaries. [ABSTRACT FROM AUTHOR]

In this paper we parameterize the photoelectric waves in the light curves of BH Vir in B and λ 5125Å bands by Hoffmann (1982) by using the Wilson-Devinney program. The principal results are as follows: (1) The mass ratio obtained from the photoelectric light curves is q = m2/m1 = 0.967. (2) The photosphere temperature of the primary is T1 = 5947 K. (3) The distortion waves in the light curves can be fitted satisfactorily with the spot model of two hot spot activities on the primary star. [ABSTRACT FROM AUTHOR]

We report the detection of a quasi-periodic oscillation (QPO) in the optical R -band light curve of the blazar S5 0716+714 spanning approximately 32 years. Using both the Weighted Wavelet Z-transform and Lomb-Scargle Periodogram methods, we identified a prominent QPO of 1060 ± 50 days at a 5 σ confidence level against the red noise background. Our findings align well with previous studies. We introduce a supermassive binary black hole (SMBBH) model to account for the observed QPO and estimate the binary system's Keplerian orbit to be 0.0053 parsec, indicating S5 0716+714 as a notable subject for upcoming nanohertz gravitational wave studies. [ABSTRACT FROM AUTHOR]

In this study, we present the results obtained from the analysis of KOI-7234's photometric data obtained by the Kepler satellite. For the first time in the literature, the light curve analysis of the system was carried out and it seems that the system was composed of two low mass components with the masses of 0.574 M ⊙ and 0.442 M ⊙ in radii of 0.598 R ⊙ and 0.529 R ⊙ with the semi-major axis of 17.390 R ⊙ . In total, 195 flares have been detected from the short cadence data. Over these parameters, two different OPEA models were obtained for the system, and P l a t e a u values were calculated as 1.578 ± 0.117 s for the first model and 1.735 ± 0.099 s for the second, while the half-time values were calculated as 1826.87 s and 1138.10 s. The general flare frequency of the system was calculated as 0.02345 h − 1 . [ABSTRACT FROM AUTHOR]

The photometric light modulation of ζ Andromedae originates from the distorted geometry of the primary, and additionally, from spots of which parameters (temperature, size, location) are variable in time. We present spot modelling results for six two-colour light curves which show that spots preferably appear on the stellar surface towards the companion star and opposite to it, where the distortion also causes dimming. Therefore, simple fitting of the measured data for the ellipticity effect does not yield correct result. Instead, ellipticity calculated from exact stellar parameters should be removed from the data to get reliable spotted light curves. [ABSTRACT FROM AUTHOR]

Observations of the electromagnetic signals originating from an accretion discs in the close vicinity of a compact object can be used to test spacetime in the strong field regime. More specifically, the so-called quasi-periodic oscillations, observed in the X-ray light curves of some pulsars, might carry features of the underlying theory of gravity making them a promising tool for testing the modifications of Einstein's theory. Although there are different ways of explaining the quasi-periodic oscillations, one thing most of the models have in common is that they incorporate in certain way the radius of the innermost stable circular orbit, and the orbital and the epicyclic frequencies of particles moving around the compact object. In this paper we study the aforementioned quantities in the context of massive scalar-tensor theory including self-interaction of the scalar field. Unlike the massless scalar field case, the neutron stars in these theories can have large deviations from pure general relativity for values of the free parameters that are in agreement with the observations. Thus the deviations in the orbital and epicyclic frequencies can reach large values. [ABSTRACT FROM AUTHOR]

In spite that the Crab supernova in 1054 A.D. was studied over the years, it is still not clear what type of event produced the explosion. The most detailed and reliable source of the observed light curve is recorded in the Chinese and Japanese chronicles, and suggests a quick dimming after a very bright initial peak. We shall show in this work that the Crab event can be well explained by a type of precursor, a phenomenon emerging from large supernova sampling and quite expected from Stellar Evolution considerations of low-mass progenitors. This very early bright transient is followed by the explosion itself, likely a low-luminosity supernova from "small iron core" type instead of an electron-capture event. The latter conclusion stems from recent simulation work, which predict that an electron-capture supernova would render the magnitude to be much brighter for ∼ 3 months, hence visible during daytime, and would not match the Chinese records. [ABSTRACT FROM AUTHOR]

We present the first evidence for the pulsations of primary components of four eclipsing binary systems. The TESS light curves of the targets are analyzed, the light and the absolute parameters are derived. Fourier analyses are applied to the residual data subtracted from the binary models to reveal the pulsational characteristics of the primaries. The components of the systems are compared to well-known binary systems of the same morphological type. The types of pulsational classes for the primaries are also discussed. Results show that CPD-30 740 and V1637 Ori are oscillating eclipsing Algol type binary stars, while HD 97329 and TYC 683-640-1 are found to be detached systems with pulsating primary components. We conclude that the primary components of the systems are pulsating stars. [ABSTRACT FROM AUTHOR]

We have assembled historical light curve data of the BL Lac object 4FGL J0112.1+2245 at radio, optical and γ -ray bands, spanning about a 12.5, 8.4, and 11.9 yr period, respectively. We used the Lomb-Scargle Periodogram (LSP), Weighted Wavelet Z-transform (WWZ) and epoch folding methods to search for periodicity in the light curves. The results indicate that there is a possible quasi-periodic oscillation (QPO) of 896 ± 32 days for γ -rays, 880 ± 54 days in the optical, and 830 ± 33 days in the radio band, respectively. In addition, the QPO signals evaluated by employing a red noise model were found to be above 3 σ (99.7%) in the three bands. Assuming that it originates from a jet in helical motion in a supermassive binary black hole system undergoing a merger, we estimate the primary black hole mass M ≃ 2.2 × 10 9 M ⊙ . Using the discrete correlation function (DCF) method, we investigated the correlation among multi-wavelength bands, and found that there is a significant correlation between the different bands from MJD 57670 to 59000. The results indicated that the optical flux in this source is originating from the same or vicinal emission region as the γ -ray and show a time lag of 73 days with radio band. Across the data as a whole, the DCF results show that the optical correlation with radio and γ -ray is significant, while the correlation between the γ -ray and radio bands are weak. [ABSTRACT FROM AUTHOR]

The wavelength-dependent transit depth indicates the atmosphere composition of an exoplanet. We analyze the transit depth of HATS-5b using the data from the Transiting Exoplanet Survey Satellite (TESS) and compare the radius ratio of the planet to the star with the different band result in previous work. We generate a photometric pipeline to obtain the TESS light curve. The fitting of the HATS-5b light curve derives similar bandpass independent parameters compared to the reference work, e.g., the differences in the inclination and the semi-major axis within 1 σ . We fix the bandpass-independent parameters to values from the previous work for comparison purposes. The wavelength-dependent R p / R ∗ obtained is 2.5% (1.9 σ ) smaller compared to the joint band result from the referenced work. The difference of R p / R ∗ suggests a haze-dominant model preferred by observation (with χ 2 = 1.68 ) when fitting with different atmospheric models. The opaque featureless atmospheric model has a χ 2 ∼ 4 , while the other models are ruled out with χ 2 > 7 . We also predict an R p / R ∗ difference of ∼1 % , correlating the presence of water at z -band observation. This difference is detectable at 3 σ if the photometry precision reaches 500 ppm with 2 minute exposure for one-night observation. [ABSTRACT FROM AUTHOR]

We present the results of a statistical investigation of the period-color and period-bolometric magnitude relations using a carefully selected sample of 120 contact systems with known physical parameters. [ABSTRACT FROM AUTHOR]

We have carried out an intensive study of photometric (Kepler Mission) and spectroscopic data on the system Kepler-2 (HAT-P-7A) using the dedicated software WinFitter 6.4. The mean individual data-point error of the normalized flux values for this system is 0.00015, leading to the model's specification for the mean reference flux to an accuracy of ∼0.5 ppm. This testifies to the remarkably high accuracy of the binned data-set, derived from over 1.8 million individual observations. Spectroscopic data are reported with the similarly high-accuracy radial velocity amplitude measure of ∼2 m s−1. The analysis includes discussion of the fitting quality and model adequacy. Our derived absolute parameters for Kepler-2 are as follows: M p (Jupiter) 1.80 ± 0.13; R ⋆ 1.46 ± 0.08 × 10 6 km; R p 1.15 ± 0.07 × 10 5 km. These values imply somewhat larger and less condensed bodies than previously catalogued, but within reasonable error estimates of such literature parameters. We find also tidal, reflection and Doppler effect parameters, showing that the optimal model specification differs slightly from a 'cleaned' model that reduces the standard deviation of the ∼3600 binned light curve points to less than 0.9 ppm. We consider these slight differences, making comparisons with the hot-Jupiter systems Kepler-1 (TrES-2) and 13. We confirm that the star's rotation axis must be shifted towards the line of sight, though how closely depends on what rotation velocity is adopted for the star. From joint analysis of the spectroscopic and photometric data we find an equatorial rotation speed of 11 ± 3 km s−1. A slightly brighter region of the photosphere that distorts the transit shape can be interpreted as an indication of the gravity effect at the rotation pole; however we note that the geometry for this does not match the spectroscopic result. We discuss this difference, rejecting the possibility that a real shift in the position of the rotation axis in the few years between the spectroscopic and photometric data-collection times. Alternative explanations are considered, but we conclude that renewed detailed observations are required to help settle these questions. [ABSTRACT FROM AUTHOR]

The V R I passbands light curves of V344 Lac were presented and analyzed by using the latest version of the W-D code. The observed spectrum reveals that V344 Lac is not an A3 type but would be a later F type star according to the yielded temperature. The results of solution show that V344 Lac is an A-subtype contact binary, with a moderate photometric mass ratio of 0.387 ± 0.003 and a moderate contact factor of 44.6 ± 3.0 % . Based on the parallax given by Gaia, the parameters of the components are estimated as: M 1 = 1.16 M ⊙ , M 2 = 0.45 M ⊙ , R 1 = 1.31 R ⊙ , R 2 = 0.88 R ⊙ , L 1 = 2.512 L ⊙ , L 2 = 1.057 L ⊙ . The period investigation indicates that V344 Lac may have an eccentric orbital oscillation, with P 3 = 12.4 ± 0.5 yr , A 3 = 0.0020 ± 0.0002 d , and e = 0.38 ± 0.16 . Analysis shows such oscillation would be caused by a magnetic activity which can be explained by the Applegate mechanism. Meanwhile, according to the value of l 3 and the estimated physical parameters of V344 Lac, the mass of the third companion may be 0.79 M ⊙ . This third body could be a wide company. [ABSTRACT FROM AUTHOR]

We carried out high-precision photometric observations of three eclipsing ultrashort-period contact binaries (USPCBs). Theoretical models were fitted to the light curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: (a) 1SWASP J030749.87−365201.7, $q=0.439\pm0.003$ , $f=0.0\pm3.6\%$ ; (b) 1SWASP J213252.93−441822.6, $q=0.560\pm0.003$ , $f=14.2\pm1.9\%$ ; (c) 1SWASP J200059.78+054408.9, $q=0.436\pm0.008$ , $f=58.4\pm1.8\%$ . The light curves show O'Connell effects, which can be modeled by the assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the $I$ -band light curves of 1SWASP J030749.87−365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with $P < 0.24$ day. Thus, we found that most of them (17 of 28) are in shallow contact (i.e. fill-out factors $f<20\%$ ). Only four USPCBs have deep fill-out factors (i.e. $f>50\%$ ). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP J030749.87−365201.7 is a zero contact binary in thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory. [ABSTRACT FROM AUTHOR]

Internal structure coefficients for zero age Main Sequence (ZAMS) model stars with different initial metallicities are presented. A series of (Eggleton) stellar models with masses between $1\mbox{--}40\,M_{\odot}$ and metallicities $Z=0.0001$ , $Z=0.001$ , $Z=0.004$ , $Z=0.01$ , $Z=0.02$ , and $Z=0.03$ were used. We have also calculated the same coefficients for a recommended solar metallicity value $Z=0.0134$ (Asplund et al. in Annu. Rev. Astron. Astrophys. 47:481, 2009). For each model, values of the internal structure constants $k_{2}$ , $k_{3}$ , $k_{4}$ and related coefficients have been derived by numerically integrating Radau's equation with the (FORTRAN) program RADAU. The (Eggleton) stellar models used come from the ' EZ-Web' compilation of the Dept. of Astronomy, University of Wisconsin, Madison. The calculations follow the procedure given by Inlek and Budding (Astrophys. Space Sci. 342:365, 2012). These new results were compared with others in the literature. We deduce that the current state of theoretical evaluation of structure coefficients is generally in sufficient agreement with data obtained from apsidal advance rates of selected well-observed eccentric eclipsing binary stars at the present time, given the probable errors of the latter. However, new results coming from more precise and extensive data sets in the wake of the Kepler Mission, or similar future surveys, may call for further theoretical specification or refinement. The derivation of structure coefficients from observations of apsidal motion in close eccentric binary systems requires specification of relevant parameters from light curve analysis. A self-consistent treatment then implies inclusion of the structure coefficients within the fitting function of such analysis. [ABSTRACT FROM AUTHOR]

It is the first time complete light curves have been acquired and a more thorough analysis has taken place for EA-type binaries FO Aur and V1025 Her. Our data set consists of 4-color imaging (BVRI) obtained at NOA (Kryoneri, 1.2 m telescope). The deduced light curves were acquired using GAIA Starlink software. [ABSTRACT FROM AUTHOR]

Cyclic period changes, which are usually explained as being caused by the magnetic activity of one or both components or the light travel time effect of a third body, are a typical phenomenon in the RS CVn-type binary. Combining the newly determined eclipsing times with others compiled from literature, we analyzed the cyclic period change in the RS CVn-type binary RT CrB. The result shows that the orbital period of the binary shows a period of 3.47 yr with an amplitude of 0.0084. The cyclic oscillation can be attributed to the existence of a third body with a lower limit mass of 1.71(±0.19) M. The third body is cycling the binary at a distance of no more than 2.30(±0.19) AU which would play an important role in the evolution of this system. No detected spectral lines of the third body may suggest that the third component may itself be a close binary of 0.86 M stars, or more likely a dark star such as a neutron star. [ABSTRACT FROM AUTHOR]

We present the first light curves and pulsation analysis results for V729 Aql and two newly discovered eclipsing binaries, namely USNO-A2.0 0975-17281677 and USNO-A2.0 1200-03937339. Frequency search was applied on the residuals of their light curves and the results showed that their primary components pulsate in multiperiodic modes and lie well inside the frequency and temperature range of δ Scuti stars. Moreover, for USNO-A2.0 1200-03937339 two frequencies inside the γ Dor frequency range were also detected, but their origin is discussed. The photometric models of USNO-A2.0 1200-03937339 and V729 Aql are also presented, while their absolute parameters as well as the evolutionary status of their components were roughly estimated. [ABSTRACT FROM AUTHOR]

Based on the light curves at 4.8, 8.0 and 14.5 GHz of Quasar 1156+295 from the University of Michigan Radio Astronomy Observatory, we analyze the variability property of total flux at the three radio bands during the time range from 1980 to 2012. With the structure function (SF) analysis we find a similar evolution trend with the characteristic variability timescale of 1.15±0.05 year for all the three radio bands, and a possible quasi-periodic variability period of ∼2.3±0.1 year. The Lomb-Scargle periodogram (LSP) analysis implies the existence of multiple periods in the radio light curves, one of them with a period similar to the one found using the SF at around 2.3 year. The structure function analysis of pre- and post-1997 suggests that the characteristic timescales become longer since 1997, confirmed by the result of Lomb-Scargle periodogram and auto-correlation function. In addition, the cross correlation analysis confirms that there is a strong correlation of flux variations at the three radio frequencies with the 14.5 GHz variation leading the other two bands by about 60-120 days. [ABSTRACT FROM AUTHOR]

We have modified the graphical user interfaced close binary system analysis program CurveFit to the form WinKepler and applied it to 16 representative planetary candidate light curves found in the NASA Exoplanet Archive (NEA) at the Caltech website , with an aim to compare different analytical approaches. WinKepler has parameter options for a realistic physical model, including gravity-brightening and structural parameters derived from the relevant Radau equation. We tested our best-fitting parameter-sets for formal determinacy and adequacy. A primary aim is to compare our parameters with those listed in the NEA. Although there are trends of agreement, small differences in the main parameter values are found in some cases, and there may be some relative bias towards a 90 value for the NEA inclinations. These are assessed against realistic error estimates. Photometric variability from causes other than planetary transits affects at least 6 of the data-sets studied; with small pulsational behaviour found in 3 of those. For the false positive KOI 4.01, we found that the eclipses could be modelled by a faint background classical Algol as effectively as by a transiting exoplanet. Our empirical checks of limb-darkening, in the cases of KOI 1.01 and 12.01, revealed that the assigned stellar temperatures are probably incorrect. For KOI 13.01, our empirical mass-ratio differs by about 7 % from that of Mislis and Hodgkin (Mon. Not. R. Astron. Soc. 422:1512, ), who neglected structural effects and higher order terms in the tidal distortion. Such detailed parameter evaluation, additional to the usual main geometric ones, provides an additional objective for this work. [ABSTRACT FROM AUTHOR]

BL Lac object AO 0235+164 is a well-known object. We collect a large number of effective observation in B, V, R and I band from historical literatures. The possible periods are analyzed by means of discrete correlation function (DCF) method, structure function (SF) method and Jurkevich (J-K) method. The results show that there are possible periodic variations of 2.63-2.66 years in B band, 2.79-2.84 years in V band, 2.57-2.87 years in R band, 2.62-2.88 years in I band, respectively. [ABSTRACT FROM AUTHOR]

Early physical cosmologies were based on interpretations of the cosmic redshift for which there was insufficient evidence and on theories of gravitation that appear to be falsified by galactic dynamics. Eventually, the big bang paradigm came to be guarded against refutation by ad hoc hypotheses (dark matter, cosmic inflation, dark energy) and free parameters. Presently available data allow a more satisfactory phenomenological approach. Using data on magnitude and redshift from 892 type Ia supernovae, it is first shown that these suggest that the redshift factor (1+ z) is simply an exponential function of distance and that, for 'standard candles', magnitude m=5log[(1+ z)ln(1+ z)]+const. While these functions are incompatible with a big bang, they characterize certain tired light models as well as exponential expansion models. However, the former are falsified by the stretched light curves of distant supernovae and the latter by the absence of a predicted 1+ z increase in the angular sizes of galaxies. Instead, the observations suggest that physical processes speed up and objects contract uniformly as an exponential function of time, standards of measurement not excluded, and only free waves being excepted. Distant events proceed, then, more slowly, while angular sizes remain unaffected, approximately as observed. Since all objects contract in proportion, the Universe retains a static appearance. A corresponding physical theory, which should also explain galactic dynamics, remains yet to be derived from first principles. A way to do this, satisfying also Mach's principle, is vaguely suggested. [ABSTRACT FROM AUTHOR]

New and complete multi-band light curves of the oEA stars QY Aql, BW Del, TZ Dra, BO Her and RR Lep were obtained and analysed with the Wilson-Devinney code. The light curves residuals were further analysed with the Fourier method in order to derive the pulsation characteristics of the oscillating components. All the reliable observed times of minimum light were used to examine orbital period irregularities. The orbital period analyses revealed secular changes for QY Aql and BW Del, while the Light-Time Effect seems to be the best explanation for the cyclic period changes in TZ Dra and BO Her. RR Lep has a rather steady orbital period. Light curve solutions provided the means to calculate the absolute parameters of the components of the systems, which subsequently were used to make an estimate of their present evolutionary status. [ABSTRACT FROM AUTHOR]

GRB 090618 was simultaneously detected by Swift-BAT and Fermi-GBM. Its light curve shows two emission episodes consisting of four prominent pulses. The pulse in the first episode (episode A) has a smoother morphology than the three pulses in the second episode (episode B). Using the pulse peak-fit method, we have performed a detailed analysis of the temporal and spectral characteristics of these four pulses and found out that the first pulse (pulse A) exhibits distinctly different properties than the others in episode B (pulses B1, B2 and B3) in the following aspects. (i) Both the pulse width ( w) and the rise-to-decay ratio of pulse ( r/ d, pulse asymmetry) in GRB 090618 are found to be energy-dependent. The indices of the power-law correlation between w and E for the pulses in episode B however are larger than that in episode A. Moreover the pulses B1, B2 and B3 tend to be more symmetric at the higher energy bands while the pulse A displays a reverse trend. (ii) Pulse A shows a hard-to-soft spectral evolution pattern, while the three pulses in the episode B follow the light curve trend. (iii) Pulse A has a longer lag than the pulses B1, B2 and B3. The mechanism which causes the different pulse characteristics within one single GRB is unclear. [ABSTRACT FROM AUTHOR]

CoRoT is a space telescope which aims at studying internal structure of stars and detecting extrasolar planets. We present here a list of transits detected in the light curves of stars observed by CoRoT in two fields in the anti-center direction: the LRa03 one observed during 148 days from 3 October 2009 to 1 March 2010 followed by the SRa03 one from the 5 March 2010 to the 29 March 2010 during 25 days. 5329 light curves for the LRa03 field and 4169 for the SRa03 field were analyzed by the detection team of CoRoT. Then some of the selected exoplanetary candidates have been followed up from the ground. In the LRa03 field, 19 exoplanet candidates have been found, 8 remain unsolved. No secured planet has been found yet. In the SRa03 field, there were 11 exoplanetary candidates among which 6 cases remain unsolved and 3 planets have been found: CoRoT-18b, CoRoT-19b, CoRoT-20b. [ABSTRACT FROM AUTHOR]

We present the analysis of the morphology of the light curves of WZ Sge based on simultaneous multicolour highspeed photometry durings the superoutburst in 2001. Observations started around the middle of the main superoutburst and continued for several nights in each of the subsequent phases of its evolution. For the first time for WZ Sge in a superoutburst a significant difference between the morphology of the U and BVRI light curves was detected. This is interpreted as a consequence of a substantial distinction of the structure and radiation between the inner and outer parts of the accretion disc. Using the space observatory WSO-UV for UV monitoring of the WZ Sge-stars throughout the entire superoutburst cycle one would have an opportunity to explore innermost regions of the accretion discs in these systems, which is important for understanding the physics of accretion processes and the nature of their activity. [ABSTRACT FROM AUTHOR]

The Einstein static model of the universe as a whole is considered in Euclidean space and absolute time of a privileged reference frame. The universe as a whole is stable that specifies observers at rest relative to the global space of the universe. An observer in the centre of the universe is assumed to experience downward inertial acceleration along a certain radius due to the kinetic energy of the universe, with the total acceleration over all radii being equal zero. This yields the Doppler effect for the photon coming from the distant source that may explain the Hubble law in the static universe. The predictions of the model are qualitatively in agreement with the observations in the cosmological tests of a standard candle and a standard rod. Explanation of stretching of the light curve of SN Ia is proposed within the model considered. [ABSTRACT FROM AUTHOR]

The interest in the study of the Algol binary system Y Leonis is justified not only by its light curve having a very deep primary minimum, and pulsating character of its primary component, but also by the complex behavior of its O- C curve which is featured by the presence of long and short time scale modulations. Taking into account the previously inferred K spectral type of the secondary component, one may expect that one of the involved periodicities could be related to magnetic cycles of this star. We gave the Wilson-Devinney solution of the eclipse light curve using our observational data obtained during 2009. The long- and short-term photometric variability of Y Leo is approached both through literature data and new CCD data. Even though these data are scarce, they revealed significant variability in the maximum and minimum brightness of this binary system at long time-scale. The nature of the rapid photometric variations during the deepest phase of primary minima can hardly be explained only by weak δ Scuti pulsations of the primary component which is still visible in partial eclipses. [ABSTRACT FROM AUTHOR]

New Photometric data in R and V passband filters of the classical Algol system U Cep were analyzed. The orbital and physical parameters of the system were obtained via light curve solutions, using Wilson-Devinney code. The absolute dimensions are also estimated. The O-C curve (only photometric data) is analyzed through Kalimeris method. Fourier analysis of P( E) function gave at least two modulation periods, i.e., P 1=16.38 yr and P 2=9.77 yr, the first was attributed to magnetic cycle effects and the second to mean time interval of occasional mass out bursts. [ABSTRACT FROM AUTHOR]

Photometric analysis of BVR C light curves of newly discovered eclipsing binary GSC 0008-00901 is presented. The orbital period is improved to 0.28948(11) days. Photometric parameters are determined as well. The analysis yielded to conclusion that system is an over-contact binary of W UMa type with components not in thermal contact. The light curves from 2005 show the presence of a spot on the surface of one of the components, while light curves from 2006 are not affected by maculation. [ABSTRACT FROM AUTHOR]

UBVRI photometry and spectroscopic observations around the Hα line of the cataclysmic star UX UMa are presented. The analysis of the 9-year photometry shows that the out-of-eclipse brightness of the system and the depth of the eclipse changes in different time scales while the width of the eclipse remains constant. The observed features of the light curves as well as the features of the two-peaked Hα profiles were attributed to an inhomogeneity of the accretion disk. “Spiral arm” model for a fitting of the light curves of UX UMa is proposed. It reproduces well the observational data. The obtained azimuthal extent of the spiral arms is of ∼90° and their light contribution is about 17–30of the total V flux of the disk. The obtained two dense structures at the outer disk covering partially the inner hot disk and the white dwarf at orbital phases ∼0.7 and ∼0.2 is in agreement with the predictions of the theoretical computations. [ABSTRACT FROM AUTHOR]

Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable. [ABSTRACT FROM AUTHOR]

We describe an automated method for assigning the most likely physical parameters to the components of an eclipsing binary (EB), using only its photometric light curve and combined color. In traditional methods (e.g. WD and EBOP) one attempts to optimize a multi-parameter model over many iterations, so as to minimize the chi-squared value. We suggest an alternative method, where one selects pairs of coeval stars from a set of theoretical stellar models, and compares their simulated light curves and combined colors with the observations. This approach greatly reduces the EB parameter-space over which one needs to search, and allows one to determine the components' masses, radii and absolute magnitudes, without spectroscopic data. We have implemented this method in an automated program using published theoretical isochrones and limb-darkening coefficients. Since it is easy to automate, this method lends itself to systematic analyses of datasets consisting of photometric time series of large numbers of stars, such as those produced by OGLE, MACHO, TrES, HAT, and many others surveys. [ABSTRACT FROM AUTHOR]

In order to explain pre-eclipse dips at phases ~0.7 in light curves of cataclysmic variables, the hypothesis of the thickening at the outer edge of the accretion disk is usually used. Shock-free nature of the interaction between the stream and the steady-state disk in the stationary solution poses the question on the cause of the of matter presence at significant height above the accretion disk in systems of this type. The results of 3D modeling have shown that in the absence of direct collision between the stream and the disk the formation of thickening of the halo above the disk is also possible. In the framework of the hot line model the significant part of the matter gets the acceleration in vertical direction. Gas movement in the vertical direction together with its movement along the outer edge of the disk leads to the gradual increase of the near-disk halo width. Maximum of the calculated thickening located above the outer part of the disk corresponds to the ~0.7 phase that is in agreement with the observed values for cataclysmic variables with steady-state disks. This fact confirms the hot line model suggested earlier for description of the flow structure in semi-detached binaries and gives new opportunities for the interpretation of the light curves of such systems. [ABSTRACT FROM AUTHOR]

Photometric observations of GO Cyg were performed during July–October 2002, in B and V filters (Johnson system). Using the Wilson's computer codes, the light curve analysis were carried out to find the photometric elements of the system. The O-C diagram which is based on the observed times of minima as well as those found in the literature, suggests a negative rate of period variation (i.e. $$\frac{dP}{dt} <0$$ ) for the system. [ABSTRACT FROM AUTHOR]

BVRlight curves of the recently discovered eclipsing binary V351 Peg were studied to derive the preliminary physical parameters of the system. The light curves were obtained at the TÜBITAK* - Turkish National Observatory (TUG) during three nights in August, 2003. The solutions were made using Djuraševic’s inverse problem method. V351 Peg is a system in an overcontact configuration (fover~ 21 %) with a relatively small temperature difference between the components ?T˜ 20 K. The results suggest a significant mass and energy transfer from the more massive primary onto the less massive secondary. The hot area on the less massive star, near the neck region, can be considered as a consequence of this mass and energy exchange between the components through the connecting neck of the common envelope. [ABSTRACT FROM AUTHOR]

We explain a complex behaviour of the light curves (LC) of symbiotic binaries on the basis of their spectral energy distribution (SED) in the optical domain. During quiescent phases we observe a wave-like variation of the optical light as a function of orbital phase. This is produced by the orbitally-related variation of the emission measure (EM) of the symbiotic nebula. During active phases this type of variability disappears, the continuum level increases by 2-3 magnitudes in U and, in the case of a highly inclined orbit, narrow minima - eclipses - in the LC can occur. These phenomena are connected with the creation of a cool pseudo-photosphere around the hot star, whose contribution is significant in the optical, while the nebula practically disappears. [ABSTRACT FROM AUTHOR]

We present the first light curve analysis for two newly discovered W UMa eclipsing binaries in the field of the globular cluster M15. As spectroscopic observations are not available, we used the FOTEL program to obtain the light curve solution of both systems. The fundamental properties of each system are obtained. Several tests concerning values of mass ratio and effective temperatures were carried out. Independent distance moduli for each system are obtained, and the membership to the parent cluster is discussed. It is shown that W2 is a member of M15, whereas W1 is not. [ABSTRACT FROM AUTHOR]

Following a brief history of measurement of eclipsing binary mass ratios from light curves, we show that photometric mass ratios for overcontact and semi-detached binaries are reliable because the relative stellar radii,R/a, are accurately measured and not, as commonly claimed, because of information in the light variation outside eclipse. We explore the accuracy of photometric mass ratios by solving synthetic data of typical precisions for a semi-detached and an overcontact binary for orbital inclinations from 89° down into the partial eclipse range. [ABSTRACT FROM AUTHOR]