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The objective of this paper is to identify the illumination conditions that maximise the differences that can be measured between light curves of an object resulting from its attitude state. This is relevant to attitude determination techniques using light curve data, and is valuable for the design of observation strategies that maximise the information contained in light curves. For this purpose, synthetic light curves were generated for a number of attitude states, object geometries and illumination configurations. The light curves were generated through application of a Bidirectional Reflectance Distribution Function (BRDF) to a faceted object geometry. The differences between the light curves were quantified using a Root Mean Square Error (RMSE). Results showed that, depending on the reflection model, the object geometry and the attitude state, particular illumination conditions existed that led to the largest RMSE between different attitude states. In most cases, increasing the phase angle increased the RMSE between light curves arising from different attitude states. The maximum RMSE occurred when the illumination vector was either aligned with the rotation vector or offset from it by 90°. It is concluded that characterising the rotational motion of an object from its brightness data is best performed using multiple observations. These observations should be constructed in a way that maximises the difference in the illumination geometry. One way of achieving this would be to use observations from multiple observatories with a diverse range of geographical locations.

A late (t $\sim$ 1,500 days) multi-wavelength (UV, optical, IR, and X-ray) flare was found in PS1-10adi, a tidal disruption event (TDE) candidate that took place in an active galactic nucleus (AGN). TDEs usually involve super-Eddington accretion, which drives fast mass outflow (disk wind). So here we explore a possible scenario that such a flare might be produced by the interaction of the disk wind with a dusty torus for TDEs in AGN. Due to the high velocity of the disk wind, strong shocks will emerge and convert the bulk of the kinetic energy of the disk wind to radiation. We calculate the dynamics and then predict the associated radiation signatures, taking into account the widths of the wind and torus. We compare our model with the bolometric light curve of the late flare in PS1-10adi constructed from observations. We find from our modeling that the disk wind has a total kinetic energy of about $10^{51}$ erg and a velocity of 0.1 c (i.e., a mass of 0.3 $M_{\odot}$); the gas number density of the clouds in the torus is $3\times 10^{7}$ $\rm cm^{-3}$. Observation of such a late flare can be an evidence of the disk wind in TDEs and can be used as a tool to explore the nuclear environment of the host., Comment: 12 pages, 7 figures. Accepted for publication in Journal of High Energy Astrophysics

The multi-band observation, from radio to gamma-ray, plays a crucial role in constraining the emission physics and geometrical magnetospheric models of the pulsars. In this paper, We use three-dimensional magnetospheric model, with the joint of the annular gap (AG) and core gap (CG) model, to simulate the radio and gamma-ray light curves for two representative pulsars, a millisecond pulsar J2302+4442 and a young pulsar J0659+1414. It is found that for PSR J2302 + 4442, the simulated magnetic inclination angle α and viewing angle ζ are 34 ∘ and 46 ∘ , and for PSR J0659 + 1414 are 45 ∘ and 33 ∘ . This implies that the radio and gamma-ray pulse emission originates from different magnetospheric regions and the radiation geometry for millisecond and young pulsar is different. The studies show that the joint of the AG and CG model can describe the light curves not only for millisecond pulsars but also for young pulsars, and hence it can be used to explain the multi-wavelength observations of pulsars.

We study the machine learning method for classifying the basic shape of space debris in both simulated and observed data experiments, where light curves are used as the input features. In the dataset for training and testing, simulated light curves are derived from four types of debris within different shapes and materials. Observed light curves are extracted from Mini-Mega TORTORA (MMT) database which is a publicly accessible source of space object photometric records. The experiments employ the deep convolutional neural network, make comparisons with other machine learning algorithms, and the results show CNN (Convolutional Neural Network) is better. In simulational experiments, both types of cylinder can be distinguished perfectly, and two other types of satellite have around 90% probability to be classified. Rockets and defunct satellites can achieve 99% success rate in binary classification, but in further sub-classes classifications, the rate becomes relatively lower.

This paper presents a data driven approach to space object characterisation through the application of machine learning techniques to observational light curve data. One-dimensional convolutional neural networks are shown to be effective at classifying the shape of objects from both simulated and real light curve data. To the best of the authors’ knowledge this is the first generalised attempt to classify the shape of space objects using real observational light curve data. It is also demonstrated that transfer learning is successful in improving the overall classification accuracy on real light curve datasets. The authors develop a simulated light curve dataset using a high fidelity three-dimensional ray-tracing software. The simulator takes in a textured geometric model of a Resident Space Object as well as its ephemeris and uses ray-tracing software to generate photo-realistic images of the object that are then processed to extract the light curve. Models that are pre-trained on the simulated dataset and then fine-tuned on the real datasets are shown to outperform models purely trained on the real datasets. This result indicates that transfer learning will allow organisations to effectively utilise deep learning techniques without the requirement to build up large real light curve datasets for training.

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1 m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4 m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work.

We present a time-series analysis of the asynchronous polar CD Ind, using fast cadence TESS photometry. A similar analysis is performed using ground based photometry of BY Cam. These asynchronous polars show remarkably similar light curves and enigmatic timing characteristics. A pair of competing models for the assignment of the white dwarf spin period have been presented for both binaries. TESS allows for the breaking of this degeneracy by providing continuous coverage over several beat-cycles. The CD Ind light curve displays a super-orbital period of 7.2 days due to beat-phased modulation of the accretion rate onto a permanently visible spot. This (main) accretion region is active for 3/4 of the beat-cycle. The dominant photometric signal is at 109.654(4) min and is identified as a side-band related to the white dwarf spin and the binary orbit, analogous to that found in BY Cam. We obtain the white dwarf spin period of CD Ind as 110.820(5) min and an orbital period of 111.952(8) min. The TESS light curve supports a pole-switching scenario for CD Ind, with a total of 4 alternating, and oppositely positioned accretion regions. This inclination of CD Ind is estimated as i = 65 ° ± 10 ° . One accretion region remains in view of the observer at all times. In addition, two pulsed accretion spots each accrete for just less than 1/2 of the beat-cycle. These alternating spots are orthogonal to the main accretion region (which is always in view), and are found to be roughly 180 ° apart in longitude. Finally, since the mean flux drops by a factor of 2 for about 1/4 of the beat-cycle and the dominant accretion region turns off during this time, we hypothesize the existence of a fourth (permanently hidden) accretion region opposite to the one permanently in view. Photometric models for the 2- and 4-pole accretion configurations are developed and only the 4-pole model is consistent with the observed periodogram for CD Ind. We conclude that complex magnetic fields affect accretion flow onto these white dwarf stars. In particular, the magnetic field of the white dwarf in both of these binaries is inconsistent with either a centered or an offset dipole configuration.

In order to investigate the periodical properties of radio sources, we analyze the light curves of a sample of 78 blazars observed by OVRO (Owens Valley Radio Observatory) at 15 GHz using the Jurkevich method, and find that the radio sources display a significant light period in range of 0.83 to 2.55 years. In addition, we also estimate the modulation index of variability for each source, and find the Gauss distribution of the peak value of the modulation index in FSRQs (Flat Spectrum Radio Quasars) is smaller than the corresponding distribution peak in BL Lacs (BL Lacertae Objects).

The flat spectrum radio quasar 3C 279 was observed in an extremely high activity state on June 16, 2015 (MJD 57189). In this paper, we investigate the properties of this flaring episode in the high energy γ-ray and optical bands using data from the Fermi-LAT, SMARTS, and SPOL observations during the period June 1-30, 2015 (MJD 57174-57203). The highest emission state in the γ-ray band detected by the Fermi-LAT exhibits a peak flux of ∼ 2×10−7 erg cm−2 s−1 which is more than 25 times the flux level measured in the low activity state of the source. The temporal analysis of the daily Fermi-LAT light curve suggests that the giant flaring episode has characteristic rise and decay times less than one day. The optical daily light curves in B, V, R, and J bands also indicate the flaring activity from 3C 279 with flux levels peaking for two days on June 16-17, 2015 (MJD 57189-57190). The discrete correlation function analysis indicates a time lag of 1 day or longer between the γ-ray and optical peaks during the flaring episode. The γ-ray emission is also observed to show a harder-when-brighter behaviour whereas optical emission exhibits an opposite behaviour. The γ-ray emission region during the flare is observed to be very compact and is located close to the base of the jet. The degree of linear polarization in the wavelength range 500-700 nm measured using SPOL during this period is also highly variable with a peak of ∼ 30% one day after the γ-ray flare. Near simultaneous γ-ray flux points show a linear anti-correlation with the degree of polarization during the period of γ-ray flare. The significant drop in the degree of linear polarization suggests a sudden increase in the tangled magnetic field strength in the emission region.

The Galactic plane scanning survey is one of the main scientific objectives of the Hard X-ray Modulation Telescope (known as Insight-HXMT). During the two-year operation of Insight-HXMT, more than 1000 scanning observations have been performed and the whole Galactic plane ($\rm 0^{\circ}, Comment: 14 pages, 17 figures, accepted for publication in JHEAP

Attitude is the important parameter for active debris removal and collision avoidance. This paper deduced the spin axis orientation and spin period of the rocket body, CZ-3B R/B (NORAD ID 38253), using the satellite laser ranging and light curve data measured with single-photon detector at Graz station. The epoch method and LC & SLR residuals fitting were combined to determine these values. The derived right ascension angle was around 220°, the declination angle was near 64° and the sidereal period was calculated to be 117.724 s, for 2017-07-03. The results derived from the two distinct methods were mutually validated. Rocket bodies are a major contributor to space debris and this work provides a reference for attitude determination and attitude modelling.

Recent studies on the high-energy photons from gamma-ray bursts~(GRBs) suggested a light speed variation $v(E)=c(1-E/E_{\mathrm{LV}})$ with $E_\mathrm{LV}=3.6\times 10^{17}$ GeV. We check this speed variation from previous observations on light curves of three active galactic nuclei (AGNs), namely Markarian 421 (Mrk 421), Markarian 501 (Mrk 501) and PKS 2155-304. We show that several phenomena related to the light curves of these AGNs can serve as the supports for the light speed variation determined from GRBs., 10 latex pages, 3 figures

Many defunct satellites in geosynchronous earth orbit (GEO) spin rapidly or have highly evolving spin states, with some transitioning between uniform and non-principal axis rotation (tumbling). It is hypothesized that the observed evolution of some defunct GEO satellites is caused by the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect and internal energy dissipation. YORP torques are generated by the absorption, reflection, and thermal re-emission of solar radiation and are known to cause secular changes in asteroid spin rates and obliquities. The defunct GOES 8 satellite is particularly notable. This satellite's uniform spin rate rapidly decreased in 2014 and it began tumbling. In this paper, newly analyzed light curve observations of the five nearly identical defunct GOES 8-12 satellites obtained between 2014 and 2018 are presented. The observations show large diversity in evolutionary time histories, with several satellites in consistent slow tumbling, GOES 10 in fast uniform rotation, and GOES 8 transitioning between both. To better understand this diversity, YORP dynamical models are investigated. They reveal that YORP driven spin state evolution is strongly dictated by end of life appendage orientations, which differ among the five satellites. The known end of life configurations are consistent with the observed evolution of GOES 8 and GOES 10. This provides a plausible explanation for the observed spin state diversity. Implications of the observed and simulated evolution for GEO debris mitigation are discussed.

Using the vector magnetograms observed by SDO (Solar Dynamics Observatory)/HMI (Helioseismic and Magnetic Imager), the current distribution and evolution associated with an X9.3 flare occurred in the active region AR12673 on Sept. 6, 2017 are studied in detail. The results show that there is a pair of electric current ribbons with opposite directions and the magnitude of 0.4 A/m 2 , which can be called a pair of conjugate electric current ribbons. This pair of conjugate electric current ribbons exist before, during, and after the flare; their positions are almost coincident with the two bright ribbons of the flare, and their shapes are also extremely similar with them. The light curve of the total electric current intensity on Sept. 6 shows that the electric current intensity enhanced sharply during the strong X9.3 flare eruption, and this phenomenon persisted for several hours. The results of this study strongly support the model of QSL (Quasi-Separatrix Layer) 3D magnetic reconnection.

We study the central mass accretion rate and its variation with time during the outburst of X-ray transients using disk irradiation effect once the outer boundary of the disk is defined by the binary parameters. We show that the decay of the light curve and its characteristics time are well linked to the disk aspect ratio ( H / R ) and the binary parameters. For that we parametrize viscosity ( α ) parameter with H / R , assuming that there is a vertical height dependence on the energy dissipated in the disk. We derive the central accretion rate to check the sensitivity on H / R . Mass accretion rate changes notably with disk height, orbital period (P) and with binary mass function (q). For the consistency check, we apply the solution to a low mass X-ray binary (LMXRB) 4U 1543-47, whose binary parameters are dynamically measured. Finally, we estimate the unknown binary parameters of MAXI J1543-564. Using this solution for the first time we propose some predictability on P for the unknown system. The estimated value of P varies in a range from ∼10.5 to 15.5 h, when the companion mass is ∼ 0.66 M ⊙ . Our estimated decay time scale is ∼ 40 d with α ∼ 0.18.

We report new light curves of two eclipsing binaries of AV Crb and EK Aqr obtained in 2017 and 2018 using Holcomb and SARA telescopes. We obtain the updated ephemeris and find a continuous period decrease (AV Crb) and increase (EK Aqr), respectively. We used the 2015 version Wilson-Devinney method to analyze the light curves and asymmetries. The effective temperature of the primary components of the two eclipsing binaries are obtained from the Gaia DR2. We determine the orbital parameters of AV Crb and EK Aqr. The secular period decrease of -3.23(17) × 10 − 7 days/yr suggests that in AV Crb mass transfer takes place from the primary component to the secondary at a rate dM1/dt of -3.67(17) × 10 − 7 M ⊙ /yr. We find a hot spot on the secondary component. The orbital period increase 3.33(21) × 10 − 7 days/yr implies that EK Aqr is undergoing mass transfer from the secondary component to the primary at a rate of 3.33(21) × 10 − 7 M ⊙ /yr and we find a cool spot on the primary component. We conclude that AV Crb is a shallow contact eclipsing binary with a contact degree of 19.17(2.45)%, and EK Aqr is a deep contact binary with 56.86(1.13)% factor.

AST3-1 is the second-generation optical photometric telescope at Dome A in Antarctica. In this study, photometric solutions of three eclipsing binaries comprising AST19571, AST21541, and AST38503 were determined for the first time using the light curves obtained with AST3-1. The light curves for the three binaries in the Galactic disk field were analyzed with the Wilson–Devinney method. We found that AST19571 and AST21541 are intermediate-contact binary systems with fill-out factors of f = 39.9 ( ± 5.4 ) % and 36.4( ± 4.7) %, respectively, and their mass ratios were determined as q = 0.275 ( ± 0.0034 ) and 0.25( ± 0.0024). AST38503 was shown to be a deep-contact binary system with a degree of contact of f = 66 ( ± 33 ) % and a mass ratio of q = 0.314 ( ± 0.03 ) . Some light minimum times were derived for the three contact binary stars. The results showed that the period of AST19571 is increasing at a rate of d p / d t = + 4.71 × 10 − 7 . This increase in the period could be explained by mass transfer between the components. The absolute parameters were estimated for the components of the three binaries.

We present photometric observations of the W UMa binaries OT UMa and UG Leo. Our results from the light curve solutions are: (i) The two targets show partial eclipses; (ii) The components OT UMa and UG Leo are of G spectral type; (iii) Detailed q-search analysis was carried out for determination of the mass ratios; (iv) The two binaries are of W subtype with middle fillout factors. We estimated masses, radii and luminosities of the target components by our light curve solutions and using GAIAdistances. It turned out that their values are similar for the two targets. The paper presents a discussion on the determination of the temperatures and mass ratios of partially-eclipsing W UMa stars.

A methodology is introduced to optimize and extend the inference of pre-entry size, density, strength, and mass of asteroids based on observed light curves. In this development study, a genetic algorithm (GA) approach is coupled with the fragment-cloud model (FCM) to efficiently evaluate entry and breakup for numerous potential asteroid property combinations and determine which case best matches the observed data. FCM produces energy deposition curves based on assumed pre-entry conditions, and the GA finds values for these inputs that minimize an objective function characterizing the difference between the FCM curve and a target curve. We present an overview of the GA approach, and then demonstrate its capability to infer pre-entry properties for three well-characterized events: Chelyabinsk, Lost City, and Benesov. In all cases, our initial mass and size estimates were within the range of published values.

The calculation results of photographic and radar meteoroid mass of simultaneous radio - TV and radio-photographic observations of meteors in 1977–1980 in Hissar Astronomical Observatory of the Institute of Astrophysics, Academy of Sciences of Tajikistan. The analyses' results of the shape of light curves of meteors within the theory of evaporation and the theory of the quasi-continuous fragmentation are presented. The photographic meteoroid mass from the light curve were defined: a) by the value of maximum luminous intensity at a height h m and b) by the integration light curve. Based on analysis of the data of the photographic mass were obtained correction factor that takes into account the effect of fragmentation and other factors to determine the mass of meteoroids first method. Average value of the mass of meteoroids calculated from the light curve for meteors with magnitude M ≤ 1 is 19 ∗ 10 − 3 g , and the average value of the mass found on magnitude of the luminous intensity at the height the maximum brightness consist 18.2 ∗ 10 − 3 g , that is in satisfactory agreement between. Masses of the meteoroids was calculated also radio method by value of maximum linear electron density at the height of maximum ionization. In the framework of the classical theory and the theory quasi-continuous fragmentation, we analyzed the shape of the light curves of simultaneous radio - optical meteors. It is shown that the main mechanism of ablation approximately 60% of simultaneous radio - optical meteors is a quasi-continuous fragmentation. The bulk density and porosity of showers and sporadic meteoroids were determined. Found that the Geminids meteoroids and S.δ-Aquariids have the largest bulk densities ( δ 0 = 3.6 g / c m 3 ), and have not porosity (K = 0). A meteoroids of the showers Orionids and Leonids have the lowest bulk density ( δ 0 ≤ 0.6 g / c m 3 ), and the highest value of the porosity ( 60 ≤ K ≤ 80 % ) . The mass fragments of shower and sporadic meteoroids lie in the range of 5 ∗ 10 − 8 ÷ 10 − 5 g .

There is no consensus on the emission mechanism of $\gamma$-ray bursts (GRBs). A synchrotron model can produce $\gamma$-ray spectra with the empirical Band function form, from a piece-wise two-power-law electron energy distribution (2EPLS). This model predicts that for the same $\gamma$-ray spectrum, optical emission can be very different in $f_{\nu}$ log slope, and in flux relative to $\gamma$-rays,depending on model parameter values. The model only allows a small set of $f_{\nu}$ log slopes in the optical -thereby allowing a clear path to verification or falsification. Measurements of prompt GRB emission in the optical thus far give no useful information about the spectral shape within the band, and therefore cannot be used to evaluate such predictions. We describe an experiment that responds to GRB alerts with a fast-slewing telescope, with 3+ simultaneous, high-time resolution cameras. Three channels measure two slopes in order to evaluate the model. We propose cross-correlation of $\gamma$ and OIR light curves to verify that GRB are single-component dominated, or to quantify additional contributions. Previous CCD measurements have limited-time resolution due to read noise. Electron-multiplied CCDS (EMCCDs) can be used to greatly reduce read noise allowing exposure times of a few hundred ms. Our Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) utilizes a 70 cm telescope that can point in $\le$ 8 s, with 3 optical channels. The NUTTelA-TAO is expected to measure 3-8 GRB/yr, and verify/refute the 2EPLS model with just a few bright GRBs. A space-based experiment with an IR channel would make improved measurements of the self-absorption frequency and physical conditions within the GRB jet. Additional science includes detection of dust evaporation due to GRBs, a tool to study progenitor environment dust., Comment: 19 pages, 4 figures, abstract truncated for arxiv format

We present new CCD $VI$ photometry of the distant globular cluster Pal 13. Fourier decomposition of the light curves of the three cluster member RRab stars lead to estimations of [Fe/H]=-1.65, and a distance of 23.67$\pm$0.57 kpc. Light and colour near minimum phases for RRab stars leads to an estimate of $E(B-V)$=0.104 $\pm$ 0.001. A $V/(V-I)$ colour-magnitude diagram, built exclusively with likely star members, shows consistency with the above parameters and an age of 12 Gyrs. A search of variable stars in the field of view of our images revealed the variability of a red giant cluster member and of three probably non-member stars; two RRab stars and one W Virginis star or CW. The GAIA proper motions of member stars in Pal 13 show a significant scatter, consistent with the scenario of the cluster being tidally stripped., 13 pages, 5 Tables, 14 Figures, Accepted by New Astronomy Feb 19, 2019

NSVS 10441882 is a newly discovered eclipsing binary system with strong magnetic activity and an orbital period of ∼ 0.5166 days. In order to study this eclipsing binary system, we analyzed its first four-color (BVRcIc) light curves. The observed light curves were asymmetric, so we used the 2013 version of the Wilson–Devinney (W–D) program with cool star-spots to analyze these data. We discovered that NSVS 10441882 is a detached total eclipsing binary system with an orbit inclination of 85°.34 ± 0.07 and a mass ratio of q = 0.94 ± 0.03. Based on the CCD times of the light minima according to our observations and those reported previously, the orbital period changes of NSVS 10441882 were studied using the traditional O–C method for the first time. The O–C diagram of the target exhibited a cyclic oscillation with a period of 16.7 ± 0.20 years and an amplitude of 0.00349 ± 0.00029 days, probably due to the presence of an unseen third body. If we assume that the total mass of NSVS 10441882 is 1.3M⊙ (according to our calculated results for the average color index and mass ratio), then the mass of the third body is no less than 0.12 ± 0.01 M⊙. Moreover, the orbital evolution of the central system will be accelerated due to the presence of this additional component.

The observation of R Scuti star has a long history. This unique characteristic of light curve allows us to search for evidence of period evolution. The behavior of R Sct is complex and has not been understood well. In the present work, we reviewed and analyzed the time series of light curve observations to search for period evolution. The irregular behavior of the light curve was investigated by power spectral density (PSD) and fast Fourier transform (FFT) techniques. A time-frequency technique was performed to show frequency evolution. Additionally, we studied the amplitude and frequency variations of the main and the second mode. The characteristics of the amplitude variation of two modes as time progresses are presented. An estimated value of the seasonal variations is approximately 10 years. The results suggest a magnetic field cycle for this system.

The physical composition and structure of meteoroids gives us insight into the formation processes of their parent asteroids and comets. The strength of and fundamental grain sizes in meteoroids tell us about the environment in which small solar system bodies formed, and the processes which built up these basic planetary building blocks. The structure of meteorites can be studied directly, but the set of objects which survive entry through the atmosphere is biased toward large, strong objects with slow encounter speeds. Fragile objects, small objects and objects with high relative speeds are very unlikely to survive impact with the atmosphere. Objects between 100 microns and 1 meter, which are not strong enough to survive the ablation process, must be studied by radar or optical methods. Large meteoroids, which produce bright fireballs, are generally studied by investigating their compressive strength when they fragment, and their strength can also be inferred indirectly from their end heights. Fragmentation in faint meteors can be inferred from interference in radar observations, or observed directly with high-resolution optical systems. Meteor light curves, begin heights and time-evolving spectra can also be used to infer meteoroid structure. This paper presents a review of the meteor observation methods currently used to infer the structure and fragmentation of meteoroids in the millimeter to meter size range, and the current state of understanding these observations have given us., 30 pages, 6 figures

Photometric observations of the W UMa binaries PY Boo and NSVS 7328383 with periods of around 0.27 d are presented. The light curve solutions reveal that the components of both targets are stars of K type (temperatures T1=4770 K, T2=5080 K and T1=5146 K, T2=5056 K, respectively,) and undergo total eclipses (both orbital inclinations are ∼ 78°). The well-determined mass ratios of 0.20 and 0.22 put PY Boo and NSVS 7328383 in the list of binaries with the smallest mass ratio whose number is less than 50. Both target configurations have fillout factor 0.17. The light curve distortions were reproduced by cool spots on the side of their primaries with angular size of 15°. Our observations confirmed the period decrease of PY Boo and we estimated its rate as –7.186 × 10 − 7 d yr − 1 . The period of NSVS 7328383 was improved and the new value is smaller than the previous one by 0.19 s. The target global parameters were estimated by the empirical relation “period – total mass” of low mass-ratio binaries. The calculated distance d = 228 ± 21 pc of PY Boo is within the errors of the value determined by GAIA(DR2) of 209 ± 20 pc. PY Boo and NSVS 7328383 turned out similar W UMa binaries in period, orbital inclination, magnitude, temperature of the components, mass ratio, fillout factor, and even in size and location of the spots.

We analyzed high-precision Kepler photometry and high-resolution UVES and GIRAFFE spectroscopy from ESO Science Archieve for a double-lined eclipsing binary star in the field of the high metallicity old open cluster NGC 6791. Earlier measurements of the masses and radii of the detached system were not accurate enough for photometric and spectroscopic data to demonstrate that there are significant differences between current stellar models. Here we improved on the result and add follow-up measurements of the system. Data from the Kepler archive makes it clear that the system has an inclination that is close to 90 degrees. The combination of radial velocity and Kepler light curve of the system were analysed simultaneously, which allows us to determine a reliable mass for the primary and secondary star and radii for both stars, and to constrain the cluster age. The characteristics of the primary star at the cluster turnoff indicate an age of 8.5 +/- 0.12 Gyr, consistent with earlier analysis of the color magnitude diagram. The brighter star in the binary also produces a precision estimate of the distance modulus, independent of reddening estimates: (m-M)(V) (mag) =13.899 +/- 0.117. The secondary star is not expected to have evolved significantly, but its radius is more than 10% larger than predicted by models. The hallmark is useful for testing the idea that radius inflation can occur in short period binaries for stars with significant convective envelopes due to the inhibition of energy transport by magnetic fields.

Multicolor photometric observations of the W UMa binaries CSS J113505.5+332031, ASAS J142124+1813.1 and HR Boo are presented. They led to improvement of the orbital periods of CSS J113505.5+332031 and HR Boo. The light curve solutions revealed that all the targets are overcontact binaries with moderate fill-out factors whose components are of G and K spectral types. ASAS J142124+1813.1 and HR Boo undergo total eclipses and their mass ratios are well-determined. The small mass ratio of ASAS J142124+1813.1 puts this target in the list of W UMa binaries with extreme low mass ratios. The possible solutions for the partially-eclipsed binary CSS J113505.5+332031 and their precision are discussed in detail. Masses, radii and luminosities of the target components were estimated by our light curve solutions and GAIA distances.

SuperWASPJ222302.02+195031.8 is an eclipsing binary with an orbital period about 0.22517657 days that is close to the short-period limit of contact binaries. Multi-color photometric light curves of the short-period binary in B, V, Rc and Ic bands are presented and analyzed by using the Wilson–Devinney (W–D) method. It is discovered that the system is a semi-detached binary where the secondary component is already filling the critical Roche lobe, while the primary is filling just 77.1% of its Roche lobe. The temperature of the primary is about 4300 K, and the temperature difference between the two components is about 500 K. The asymmetries in the light curves are explained by the coverage of stellar dark spots on the less massive component via magnetic activity. An analysis of all available eclipse times suggests that there are no any changes in the O-C diagram. This may indicate that there are no mass transfers between the two components. The semi-detached configuration with the dark spot on the surface of the lobe-filling secondary and no variations in the orbital period make the binary an interesting target for further investigations.

We present simultaneous optical and radar observations of meteors observed over the Arecibo radar in Puerto Rico. These observations were obtained during ∼ 24 h of radar time over 3 different nights in May 2012. The radar was operating in a dual-frequency mode at 430 MHz (UHF) and 46.8 MHz (VHF). The optical observations were made at 41 frames per second with an Andor Electron Multiplying CCD camera with a field of view of ∼ 6°, enabling the determination of accurate horizontal meteor velocities and optical light curves. There are varying detection sensitivities of the 3 different techniques (2 radar, 1 optical). The UHF radar is the most sensitive, resulting in a total of 8710 detected meteors during that period, while the VHF radar is significantly less sensitive—resulting in only 278 detected meteors. The optical observations are the least sensitive, resulting in a total of 178 detections. Of all of these meteors, only 19 were simultaneously detected by the 3 instruments. This paper focuses on the analysis of these 19 common events. The meteoroid masses determined from the optical light curves were found to be in the range of 20 μg to 1.2 mg and did not correlate with the maximum Signal-to-Noise Ratio (SNR) of either radar. In addition, the UHF radar detected 5 out of these 19 meteors with far side-lobes, beyond the main-beam and first side-lobe. This indicates that a significant fraction of events detected by the UHF radar could be in far side lobes and therefore have significantly underestimated Radar Cross Sections (RCS), given the smaller backscattered powers received in the side lobes.

Variable stars in HLF 356 identified from plates taken at Harvard Observatory southern station in the 1930s are characterised using data from the ASAS, SuperWASP and Catalina Sky Survey databases. Very little work has been done on these variables since their discovery. Their periods are determined, and light curves for these stars are presented, from which their classification is determined.

KIC 10684673 (TYC 3562-805-1) was observed by the Kepler mission, which obtained nearly 50,000 data points in the short cadence mode from May through June of 2009 for a total of about 33 days. It has been added to the Kepler Eclipsing Binary Catalog as an eclipsing binary. However it is flagged as uncertain in nature. Upon visual inspection, it is found the light curve is not consistent with features present in light curves from typical eclipsing binary systems. Instead, it shows features more consistent with pulsation. In the present study, it is shown the light curve can be satisfactorily modeled by considering the target as single, multi-modal δ Scuti pulsator.

The potentially hazardous asteroid 2012 TC4 made an Earth close approach at a distance of 0.11 lunar distance on 12 October 2017. Photometric observations were carried out between October 11 and October 12 at the Lulin Observatory at short cadence. Data analysis of the light curves shows that this PHA has a fast rotation period of 12.25 min, a light curve variation amplitude of 1.2 ± 0.1 mag corresponding to an axial ratio of about 3.0. Our BVRI photometry also indicates that 2012 TC4 is a C-type asteroid. With the C-type albedo of 0.065 and an absolute magnitude of H = 26.613 ± 0.350, its effective diameter can be derived to be 24.8 − 8.0 + 19.1 m.

We present the software package APPHi (A utomated P hotometry P ipeline for Hi gh Cadence, Large Volume Data), developed to carry out in a computationally-efficient manner, the aperture and differential photometry of the large volume of data to be produced by the TAOS-II project. However, it can also be used to process other astronomical, wide field image data. The main features of the APPHi package are: its computational speed, the capacity to work with large volume data and to handle both FITS and HDF5 image formats. Due to the large number of stars (in excess of 10 4 ) that the software has to handle in a great number of frames (more than 10 5 for a typical TAOS-II visit), it is optimized to automatically find the best value for parameters to carry out the photometry, such as: mask size for aperture, size of the window for extraction of a single star and the number of counts for the threshold for faint star detection. Using images with similar features to those that will be collected in the TAOS-II project, we carry out a comparative performance study with the widely used software IRAF, and find that APPHi can obtain light curves of comparable quality, in terms of the Signal to Noise Ratio over the light curve ( S N R L C ), up to 300 times faster. In addition to its efficiency, the tests carried out prove that APPHi, although intended to work with TAOS-II data, can also be used to analyze other sets of astronomical images, being a robust and versatile tool to perform aperture and differential photometry of point sources.

New complete BVR light curves of the contact binary AR Bootis (AR Boo) are presented. They are analyzed through the 2013 version of the Wilson–Devinney (W–D) code. Our new photometric solution shows that AR Boo is a W-subtype W UMa contact binary system with a mass ratio of q = m 2 / m 1 = 1.865 and a fill-out factor of 12.7%. The changes in the orbital period of AR Boo are analyzed. It is found that the orbital period of this binary has a continuous increase at a rate of 2.04 × 10 − 7 days yr − 1 , together with a cyclic variation (with a period of 39.05 yr and an amplitude of 0.0154 days). We discussed the mechanism responsible for the changes in the orbital period of AR Boo. It is found that the long-term increase in its orbital period is caused by mass transfer from the less massive component to the more massive one, and the periodic variation in its orbital period might be a result of the light-travel-time effect owing to a third body or the magnetic activity in the more massive component of AR Boo.

In the light curve of the geostationary earth orbit satellite (GEOS), there are 3 abrupt changes (AC) that are commonly to be seen. One of the AC that appears a peak near zero phase angle has been proved the specular reflection of solar panels leading to the phenomenon. However, the reasons of another two AC produced in the light curve are still unknown. In this paper, we proposed an advanced light curve model of GEOS and theoretically explained these unknown abrupt changes. Through calculating the satellite TDRS-8's light curve and comparing its actual observation, the proposed model is verified and the causes of the unknown abrupt changes are illustrated. The importance and purpose of this discovery are also emphasized at the end of the paper.

The new BVRI photometric observations of the HW Vir-type eclipsing binary system V1828 Aql (P = 0.11037399 days) were presented. From these measurements, 16 new eclipse times have been obtained. The light curves in BVRI colors and the radial curves were simultaneously analyzed by using the Wilson–Devinney method for the system parameters. The system consists of a very hot primary component ( T 1 = 42000 K) and a cold secondary component ( T 2 = 3077 ± 250 K). The absolute dimensions were found as follows: ( M 1 = 0.351 ± 4 0.040 M ⊙ , M 2 = 0.095 ± 0.011 M ⊙ , R 1 = 0.176 ± 0.007 R ⊙ , R 2 = 0.140 ± 0.007 R ⊙ , L 1 =86.91 ± 6.76 L ⊙ and L 2 = 0.002 ± 0.001 L ⊙ ). The orbital period variation of V1828 Aql was made using all available light minimum times. From the (O - C) diagram, the orbital period shows a variation possibly attributable to the light travel time effect by the presence of the third body. The third body orbital period is P 3 = 3317 . 7 − 17 . 2 + 18 . 9 days, its minimal mass is M 3 = 13 . 2 4 − 0 . 14 + 0 . 13 M j . The mass value calculated for the third body shows, that this object is right at the border between the planets and the brown dwarfs.

We present an astrometric and photometric study of the young open star cluster NGC 2168 and its proposed member [NBN2015]77. NGC 2168 was investigated by combining data from both the Gaia-ESO DR2 and the 2MASS databases. The photometric analysis and light curve modeling of the W UMa star [NBN2015] 77 in V and R bands was performed using the Wilson-Devinney (W-D) program. The cluster's main parameters: its distance, color excess, and age are d = 862 ± 67 pc , E ( B − V ) = 0.290 ± 0.049 , and 126 Myr, respectively. Our results show that the system [NBN2015] 77 is a W UMA eclipsing binary of A-subtype, with a low mass ratio of 0.231 ± 0.023 , and two components are of spectral types A7 and A9. The physical parameters of both components of the binary were estimated. Using two independent means we discuss the membership of [NBN2015] 77 and find that [NBN2015] 77 is a background field star and not a member of NGC 2168.

Precise and frequent photometric follow-up studies of transit light curves are indispensable when accurately characterizing extrasolar planets. We present new multi-wavelength photometry of three transiting “Hot Jupiters” — TrES-3b, WASP-2b and HAT-P-30b (WASP-51b). Data were acquired from an 0.8 meter telescope at Tarleton State University. When combined with data from the literature, this allowed us to redetermine system parameters. GCX reduction pipeline and TAP - modeling and light curve fitting package was used to analyze the extracted light curves. Weighted mean values were used to estimate the parameters from BVRI filters for three exoplanetary systems and compared them with previous published results. From our study, TreS-3b with a mass of M p = 1.7730±0.02 M j u p and R p = 1.3047±0.04 R j u p , appears to be 0.2±0.03 M j u p less massive than previously published by O’donovan et al. (2007) and Sozzetti et al. (2009), while HAT-P-30b, which has a mass of M p = 0.7006±0.041 M j u p and R p = 1.5109±0.0557 R j u p appears to be a bloated “Hot Jupiter”. Additionally, we compared the results of our broadband photometric analysis with previous studies to search for transit depth wavelength dependence. We found a flat spectrum across optical wavelengths (except WASP-2b in R-band) for TrES-3b and WASP-2b, indicating the presence of clouds in their atmospheres. HAT-P-30b had a significantly larger radius in B filter with R p = 1.613±0.05 R j u p , resulting from R p / R ∗ = 0.1334±0.004, which was secondarily confirmed by the atmospheric scale height value, H = 1450±38km, indicating that HAT-P-30b is an inflated “Hot Jupiter”.

A novel artificial intelligence (AI) technique that uses machine learning (ML) methodologies combines several algorithms, which were developed by ThetaRay, Inc., is applied to NASA's Transiting Exoplanets Survey Satellite (TESS) dataset to identify exoplanetary candidates. The AI/ML ThetaRay system is trained initially with Kepler exoplanetary data and validated with confirmed exoplanets before its application to TESS data. Existing and new features of the data, based on various observational parameters, are constructed and used in the AI/ML analysis by employing semi-supervised and unsupervised machine learning techniques. By the application of ThetaRay system to 10,803 light curves of threshold crossing events (TCEs) produced by the TESS mission, obtained from the Mikulski Archive for Space Telescopes, the algorithm yields about 50 targets for further analysis, and we uncover three new exoplanetary candidates by further manual vetting. This study demonstrates for the first time the successful application of the particular combined multiple AI/ML-based methodologies to a large astrophysical dataset for rapid automated classification of TCEs., Accepted for publication in New Astronomy

We presented the first photometric and orbital period investigation for the W UMa-type binary V0339 Com. The multi-bands light curves were obtained and analyzed with the Wilson–Devinney Code. The photometric solutions suggested that V0339 Com is an A-subtype shallow contact binary with a degree of contact f = 12 . 0 % . The total eclipse of V0339 Com gives a reliable mass ratio of 0.304. The asymmetry light curves are well modeled by a cool spot on either the secondary or primary. With the empirical relation derived from a catalog of individually studied contact binaries and the photometric solutions, we determined the absolute parameters of V0339 Com. Combining the eclipse timings determined from our observations and several surveys’ data with those reported in the literature, we revealed that the orbital period of V0339 Com is undergoing a secular increase at a rate of P = 5 . 45 × 1 0 − 7 d ⋅ yr−1. The secular period increase implies a continuous mass transfer from the less massive secondary to the more massive primary. Based on the conservative mass transfer, the observed period increase and the Roche-lobe model, we analyzed the evolutionary status of V0339 Com and found that it may be just at the stage predicted by the thermal relaxation oscillation theory, and be involving from the current contact state to the broken-contact one.

Four-color CCD photometric light curves (LCs) of eclipsing binary (EB) NSVS 11868841 are presented in this paper. These LCs are analyzed by using the 2013 version of the Wilson–Devinney (W–D) code. We found that NSVS 11868841 is a late-type low-mass detached EB with an orbit inclination nearly 90 ° . The LCs are asymmetric, especially in its out-of-eclipse. Based on all available times of the light minimum, we analyzed the variations of the orbital period by using the ( O – C ) method. The O–C curve shows a cycle oscillation with a period of 11.83( ± 0 . 04 ) years and an amplitude of 0.0009 days ( ∼ 1.3 min). This cyclic change detected in NSVS 11868841 could be explained by the light-travel time effect (LTTE) via the presence of a third body. Subsequently, we calculated the mass of this third component as M 3 sin( i 3 )=0.047( ± 0 . 015 ) M ⊙ . If the third body is coplanar with the central system, it may be a brown dwarf. And this discovery will provide important insights on the formation and evolution of brown dwarf companions.

We describe the construction and analysis of simulated SPHEREx spectra of Main Belt and Trojan asteroids. SPHEREx will deliver the first all-sky spectral survey at 96 spectral channels between 0.75 μ m and 5.0 μ m. We have developed a method for correcting SPHEREx asteroid spectra for intrinsic rotational variability that does not require light curves and can enable studies before LSST light curves become available for this purpose. Using these spectra, we predict that SPHEREx will deliver meaningful flux measurements for about 100,000 asteroids, including close to 10,000 objects with high-quality spectra; this dataset will represent an increase over our current sample size by more than an order of magnitude. The main SPHEREx contribution to asteroid science will be derived from taxonomic classifications, detailed spectroscopic analyses involving a number of diagnostic spectral features associated with olivine, pyroxene, hydroxyl, water ice, and organics, and constraints on thermal properties. We argue that all asteroids with currently known orbits, about a million objects, should be included in the SPHEREx forced photometry object list to maximize its science impact. Our tools and the library of simulated spectra are made publicly available.

The observation of objects of the Atiras population is a challenge due to the narrow time-window in which observations are possible and, even so, at very low altitudes. This is due to the orbit of these objects, internal to that of the Earth. In this work we present the results of a photometric observational campaign of Atiras aiming to determine their physical parameters using the rotational light curve, the solar phase curve and the photometric spectrum. The period and amplitude have been determined for the asteroids (163693) Atira, (413563) 2005 TG45 and 2017 YH. In the case of (163693) Atira, we have determined a plausible rotational period P = 3 . 1532 ± 0 . 0001 , where the composite light curve presents structure usually related to the presence of a companion, as it has been suggested by radar observations of this asteroid. For asteroids (163693) Atira, (413563) 2005 TG45, (481817) 2008 UL90 and 2018 JB3 it was possible to derive the absolute magnitude and the phase coefficient. The obtained values are similar to those observed for asteroids with intermediate to low albedo. Finally, for asteroid (163693) Atira we have obtained a featureless photometric spectrum which is compatible in the Carvano taxonomic scheme with the Xp, Dp or Cp classes. No appreciable surface variations were observed for this object.

We use observations of the Luminous Blue Variable (LBV) P Cygni spanning seven decades, along with signal processing methods, to identify a periodicity in the stellar luminosity. We find a distinct period of $4.7 \pm 0.3$ years together with shorter periods. The periodicity is a possible indication of a binary companion passing in an eclipse-like event from the dense LBV wind, and if so it is the first observational indication that P Cygni is a binary system. This may support models that contribute giant LBV eruptions to interaction with a binary companion. We discuss other interpretations for the periodicity as well., Accepted to New Astronomy

This study presents the photometric solutions of six binary systems with circular orbits and low mass components. Solutions for the sum of radii fraction, radii ratio, orbital inclination, surface brightness ratio, orbital eccentricity parameters were obtained, as well as a new solution for the orbital period, using data from V-band photometry from the All-Sky Automated Survey for Supernovae. Based on the geometry of the light curve, the study samples were analyzed using JKTEBOP code. In addition, their global parameters were also estimated, by applying based calibrations for the late main-sequence stars and color index (J-K). Thus, mass, temperature, luminosity, and radius values for each stellar component are also provided.

New CCD photometric observations of the eclipsing binary V737 Per have been performed in 2015 and complete BV bands light curves are obtained. From the observations, four times of light minimum are determined. By combining these times of light minimum with those collected from literature, we derive a new linear ephemeris and investigate the orbital period variation. The result shows that no significant period variation can be found during the past twelve years. The present light curves are analyzed by using the Wilson–Devinney code. The photometric solutions indicate that the system is an A-type, shallow-contact binary with a mass ratio of 0.41 and a degree of contact of 8.73%. Also, the asymmetry of the light curves is observed. It can be explained by a cool spot on the secondary component. Finally, we estimate the absolute parameters of V737 Per and discuss its evolutionary status. The results suggest that the primary of V737 Per has evolved away from the zero age main sequence.

It has been questioned whether comet 1P/Halley that appeared on 1222 September 9 was bright enough to be observed in daylight, as recorded in the Korean account. We investigate the light curve of 1P/Halley in the 1222 apparition considering brightness enhancement of the comet by forward-scattering, in order to verify the Korean account. We first analyze the Korean accounts of 1P/Halley observed in 1222, and of Venus and Jupiter appearing in daylight generally. We then determine the absolute magnitude ( m 0 ) and heliocentric power-law exponent (n) using observations made around the perihelion in 1986 and a formula considering brightness enhancement by forward-scattering. We apply the results to estimate the light curve of 1P/Halley in the 1222 event. According to the accounts, 1P/Halley underwent a sudden change in brightness and the conditions were good on the day the daylight observation was recorded. We also find that Jupiter could have been visible in daylight at about −2.1 mag. Regarding the light curve, we find that if the m 0 and n values are similar to those in a previous study, 1P/Halley could have been reached a maximum near mag −2 in 1222. In conclusion, there is a strong possibility that 1P/Halley was actually observed in daylight, inferring from observations and the predicted total visual magnitude at that time.

We present the first BVRI bands CCD photometric light curves of ASAS J212234-4627.6 and ASAS J212319-4622.4 observed with the SARA 0.6-m telescope at the Cerro Telolo Inter-American Observatory (CTIO), Chile on August 16, and September 28, 2014. From our multi-band photometry data, we obtained three minimum light times of ASAS J212234-4627.6 and four minimum light times of ASAS J212319-4622.4. We used the least square method to fit the minimum light times and got the linear ephemeris for the two eclipsing binary systems. Using the WD program, we solved the photometric solutions of the two objects: The photometric solution of ASAS J212234-4627.6 indicates that it is a semi-contact eclipsing binary star, the secondary component accurately filling its limiting lobe, and the asymmetry of the light curves may be due to the presence of a dark spot on the primary component; the photometric solution of ASAS J212319-4622.4 shows that it is a contact eclipsing binary system with a contact factor f = 5.899 ( ± 0.003)%. In addition, we also estimated the global parameters and the evolution state of the two objects. The Log Teff - Log (L/Lsun) diagram shows that the primary and secondary components of ASAS J212234-4627.6 and ASAS J212319-4622.4 are all MS stars.

Multicolor photometric observations of the W UMa binaries CSS J015638.9+224640, CSS J073801.1+303139 and ROTSE1 J135749.66+361609.3 with periods of around 6 h are presented. The light curve solutions revealed that the components of each target are almost equal in temperature and are of G and K spectral types. CSS J015638.9+224640 and ROTSE1 J135749.66+361609.3 undergo total eclipses and correspondingly they are with well-determined photometric mass ratios. These targets have not only close periods but also close mass ratios (around 0.5), fill-out factors (around 0.2) and component radii. CSS J073801.1+303139 is a slightly overcontact binary with shallow partial eclipses. All three targets are of W subtype. Masses, radii and luminosities of their components were estimated by the empirical relation “period, orbital axis” for short- and ultrashort-period binaries.