Science.gov

Sample records for light curve patterns

  1. Light guide plate with curved V-groove patterns in edge-lit backlight

    NASA Astrophysics Data System (ADS)

    Park, Sohee; Shin, Yongjin

    2016-01-01

    We propose curved V-groove-based patterns for light guide plates (LGPs) and demonstrate their performance by calculating their uniformity and luminance. Instead of the linear V-groove patterns used in previous research, curved patterns with asymmetric V-groove cuts were applied to the LGPs. The feasibility of obtaining enhanced uniformity and luminance from LGPs with the proposed patterns was evaluated by varying the degree of asymmetry of the V-grooves themselves and the distance between the V-groove patterns. The suggested patterns provided more stable uniformity with a small number of patterns and a large distance between patterns. The number of V-grooves is directly related to the processing time, and the degree of asymmetry in the V-groove cuts corresponds to the processing error during fabrication. Therefore, the proposed patterns could be fabricated with a low tolerance and shorter processing time. Their use would contribute to the cost-effective fabrication of LGPs. Because LGPs using the proposed patterns exhibited uniform illumination, a small number of curved patterns composed of asymmetric V-grooves can improve the characteristics of edge-type backlighting.

  2. EMISSION PATTERNS AND LIGHT CURVES OF GAMMA RAYS IN THE PULSAR MAGNETOSPHERE WITH A CURRENT-INDUCED MAGNETIC FIELD

    SciTech Connect

    Li, X.; Zhang, L.

    2011-12-20

    We study the emission patterns and light curves of gamma rays in the pulsar magnetosphere with a current-induced magnetic field perturbation. Based on the solution of a static dipole with the magnetic field induced by some currents (perturbation field), we derive the solutions of a static as well as a retarded dipole with the perturbation field in the Cartesian coordinates. The static (retarded) magnetic field can be expressed as the sum of the pure static (retarded) dipolar magnetic field and the static (retarded) perturbation field. We use the solution of the retarded magnetic field to investigate the influence of the perturbation field on the emission patterns and light curves, and apply the perturbed solutions to calculate the gamma-ray light curves for the case of the Vela pulsar. We find that the perturbation field induced by the currents will change the emission patterns and then the light curves of gamma rays, especially for a larger perturbation field. Our results indicate that the perturbation field created by the outward-flowing (inward-flowing) electrons (positrons) can decrease the rotation effect on the magnetosphere and makes emission pattern appear to be smoother relative to that of the pure retarded dipole, but the perturbation field created by the outward-flowing (inward-flowing) positrons (electrons) can make the emission pattern less smooth.

  3. Light on curved backgrounds

    NASA Astrophysics Data System (ADS)

    Batic, D.; Nelson, S.; Nowakowski, M.

    2015-05-01

    We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other items, a general relativistic dark matter metric, a dirty black hole, and a worm hole metric, the last two inspired by noncommutative geometry. The lensing in a holographic screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behavior in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases, we improve the accuracy of the lensing results for the weak and strong regimes.

  4. Analysis of Exoplanet Light Curves

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Budding, E.; Rhodes, M. D.; Püsküllü, Ç.; Soydugan, F.; Soydugan, E.; Tüysüz, M.; Demircan, O.

    2015-07-01

    We have applied the close binary system analysis package WINFITTER to a variety of exoplanet transiting light curves taken both from the NASA Exoplanet Archive and our own ground-based observations. WINFitter has parameter options for a realistic physical model, including gravity brightening and structural parameters derived from Kopal's applications of the relevant Radau equation, and it includes appropriate tests for determinacy and adequacy of its best fitting parameter sets. We discuss a number of issues related to empirical checking of models for stellar limb darkening, surface maculation, Doppler beaming, microvariability, and transit time variation (TTV) effects. The Radau coefficients used in the light curve modeling, in principle, allow structural models of the component stars to be tested.

  5. DELightcurveSimulation: Light curve simulation code

    NASA Astrophysics Data System (ADS)

    Connolly, Samuel D.

    2016-02-01

    DELightcurveSimulation simulates light curves with any given power spectral density and any probability density function, following the algorithm described in Emmanoulopoulos et al. (2013). The simulated products have exactly the same variability and statistical properties as the observed light curves. The code is a Python implementation of the Mathematica code provided by Emmanoulopoulos et al.

  6. Aq Psc Analysis of New Light Curves

    NASA Astrophysics Data System (ADS)

    Yamasaki, Atsuma

    2005-04-01

    New BV light curves of the A-type W UMa star AQ Psc (P = 0.476d) have been observed and are described. A few times of minimum light are obtained and the ephemeris is improved. The light curves are analyzed for the binary parameters with a light curve synthesis method. Combining the results with Lu and Rucinski’s spectroscopic mass ratio we determined the masses and radii of the components: M 1 = 1.69M ⊙, M 2 = 0.38M ⊙, R 1 = 1.77R ⊙, and R 2 = 0.89R ⊙.

  7. Light extraction block with curved surface

    DOEpatents

    Levermore, Peter; Krall, Emory; Silvernail, Jeffrey; Rajan, Kamala; Brown, Julia J.

    2016-03-22

    Light extraction blocks, and OLED lighting panels using light extraction blocks, are described, in which the light extraction blocks include various curved shapes that provide improved light extraction properties compared to parallel emissive surface, and a thinner form factor and better light extraction than a hemisphere. Lighting systems described herein may include a light source with an OLED panel. A light extraction block with a three-dimensional light emitting surface may be optically coupled to the light source. The three-dimensional light emitting surface of the block may includes a substantially curved surface, with further characteristics related to the curvature of the surface at given points. A first radius of curvature corresponding to a maximum principal curvature k.sub.1 at a point p on the substantially curved surface may be greater than a maximum height of the light extraction block. A maximum height of the light extraction block may be less than 50% of a maximum width of the light extraction block. Surfaces with cross sections made up of line segments and inflection points may also be fit to approximated curves for calculating the radius of curvature.

  8. Phenomenological modelling of eclipsing system light curves

    NASA Astrophysics Data System (ADS)

    Mikulášek, Zdeněk

    2015-12-01

    Context. The observed light curves of most eclipsing binaries and stars with transiting planets can be described well and interpreted by current advanced physical models that also allow for determining many of the physical parameters of eclipsing systems. However, for several common practical tasks, there is no need to know the detailed physics of a variable star, but only the shapes of their light curves or other phase curves. Aims: We present a set of phenomenological models for the light curves of eclipsing systems. Methods: We express the observed light curves of eclipsing binaries and stars, which are transited by their exoplanets orbiting in circular trajectories, by a sum of special, analytical, few-parameter functions that enable fitting their light curves with an accuracy of better than 1%. The proposed set of phenomenological models of eclipsing variable light curves were then tested on several real systems. For XY Bootis, we also give a detailed comparison of the results obtained using our phenomenological modelling with those found using available physical models. Results: We demonstrate that the proposed phenomenological models of transiting exoplanet and eclipsing binary light curves applied to ground-based photometric observations yield results compatible with those obtained by applying more complex physical models. Conclusions: The suggested phenomenological modelling appears useful for solving a number of common tasks in the field of eclipsing variable research.

  9. Modeling Type IIn Supernova Light Curves

    NASA Astrophysics Data System (ADS)

    De La Rosa, Janie; Roming, Peter; Fryer, Chris

    2016-01-01

    We present near-by Type IIn supernovae observed with Swift's Ultraviolet/Optical Telescope (UVOT). Based on the diversity of optical light curve properties, this Type II subclass is commonly referred to as heterogeneous. At the time of discovery, our IIn sample is ~ 2 magnitudes brighter at ultraviolet wavelengths than at optical wavelengths, and ultraviolet brightness decays faster than the optical brightness. We use a semi-analytical supernova (SN) model to better understand our IIn observations, and focus on matching specific observed light curves features, i.e peak luminosity and decay rate. The SN models are used to study the effects of initial SN conditions on early light curves, and to show the extent of the "uniqueness" problem in SN light curves. We gratefully acknowledge the contributions from members of the Swift UVOT team, the NASA astrophysics archival data analysis program, and the NASA Swift guest investigator program.

  10. Classification of ASKAP Vast Radio Light Curves

    NASA Technical Reports Server (NTRS)

    Rebbapragada, Umaa; Lo, Kitty; Wagstaff, Kiri L.; Reed, Colorado; Murphy, Tara; Thompson, David R.

    2012-01-01

    The VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light curve characterization and classification algorithms that are best suited for archival VAST light curve classification. We perform our experiments on light curve simulations of eight source types and achieve best case performance of approximately 90% accuracy. We note that classification performance is most influenced by light curve characterization rather than classifier algorithm.

  11. NONPARAMETRIC BAYESIAN ESTIMATION OF PERIODIC LIGHT CURVES

    SciTech Connect

    Wang Yuyang; Khardon, Roni; Protopapas, Pavlos

    2012-09-01

    Many astronomical phenomena exhibit patterns that have periodic behavior. An important step when analyzing data from such processes is the problem of identifying the period: estimating the period of a periodic function based on noisy observations made at irregularly spaced time points. This problem is still a difficult challenge despite extensive study in different disciplines. This paper makes several contributions toward solving this problem. First, we present a nonparametric Bayesian model for period finding, based on Gaussian Processes (GPs), that does not make assumptions on the shape of the periodic function. As our experiments demonstrate, the new model leads to significantly better results in period estimation especially when the light curve does not exhibit sinusoidal shape. Second, we develop a new algorithm for parameter optimization for GP which is useful when the likelihood function is very sensitive to the parameters with numerous local minima, as in the case of period estimation. The algorithm combines gradient optimization with grid search and incorporates several mechanisms to overcome the high computational complexity of GP. Third, we develop a novel approach for using domain knowledge, in the form of a probabilistic generative model, and incorporate it into the period estimation algorithm. Experimental results validate our approach showing significant improvement over existing methods.

  12. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  13. An Atlas for Interpreting γ-Ray Pulsar Light Curves

    NASA Astrophysics Data System (ADS)

    Watters, Kyle P.; Romani, Roger W.; Weltevrede, Patrick; Johnston, Simon

    2009-04-01

    We have simulated a population of young spin-powered pulsars and computed the beaming pattern and light curves for the three main geometrical models: polar-cap emission, two-pole caustic ("slot gap") emission and outer-magnetosphere emission. The light curve shapes depend sensitively on the magnetic inclination α and viewing angle ζ. We present the results as maps of observables such as peak multiplicity and γ-ray peak separation in the (α, ζ) plane. These diagrams can be used to locate allowed regions for radio-loud and radio-quiet pulsars and to convert observed fluxes to true all-sky emission.

  14. Modeling and Fitting Exoplanet Transit Light Curves

    NASA Astrophysics Data System (ADS)

    Millholland, Sarah; Ruch, G. T.

    2013-01-01

    We present a numerical model along with an original fitting routine for the analysis of transiting extra-solar planet light curves. Our light curve model is unique in several ways from other available transit models, such as the analytic eclipse formulae of Mandel & Agol (2002) and Giménez (2006), the modified Eclipsing Binary Orbit Program (EBOP) model implemented in Southworth’s JKTEBOP code (Popper & Etzel 1981; Southworth et al. 2004), or the transit model developed as a part of the EXOFAST fitting suite (Eastman et al. in prep.). Our model employs Keplerian orbital dynamics about the system’s center of mass to properly account for stellar wobble and orbital eccentricity, uses a unique analytic solution derived from Kepler’s Second Law to calculate the projected distance between the centers of the star and planet, and calculates the effect of limb darkening using a simple technique that is different from the commonly used eclipse formulae. We have also devised a unique Monte Carlo style optimization routine for fitting the light curve model to observed transits. We demonstrate that, while the effect of stellar wobble on transit light curves is generally small, it becomes significant as the planet to stellar mass ratio increases and the semi-major axes of the orbits decrease. We also illustrate the appreciable effects of orbital ellipticity on the light curve and the necessity of accounting for its impacts for accurate modeling. We show that our simple limb darkening calculations are as accurate as the analytic equations of Mandel & Agol (2002). Although our Monte Carlo fitting algorithm is not as mathematically rigorous as the Markov Chain Monte Carlo based algorithms most often used to determine exoplanetary system parameters, we show that it is straightforward and returns reliable results. Finally, we show that analyses performed with our model and optimization routine compare favorably with exoplanet characterizations published by groups such as the

  15. Stability of patterns on thin curved surfaces

    NASA Astrophysics Data System (ADS)

    Nampoothiri, Sankaran

    2016-08-01

    We consider reaction-diffusion equations on a thin curved surface and obtain a set of effective reaction-diffusion (R-D) equations to O (ɛ2) , where ɛ is the surface thickness. We observe that the R-D systems on these curved surfaces can have space-dependent reaction kinetics. Further, we use linear stability analysis to study the Schnakenberg model on spherical and cylindrical geometries. The dependence of the steady state on the thickness is determined for both cases, and we find that a change in the thickness can stabilize the unstable modes, and vice versa. The combined effect of thickness and curvature can play an important role in the rearrangement of spatial patterns on thin curved surfaces.

  16. Stability of patterns on thin curved surfaces.

    PubMed

    Nampoothiri, Sankaran

    2016-08-01

    We consider reaction-diffusion equations on a thin curved surface and obtain a set of effective reaction-diffusion (R-D) equations to O(ε^{2}), where ε is the surface thickness. We observe that the R-D systems on these curved surfaces can have space-dependent reaction kinetics. Further, we use linear stability analysis to study the Schnakenberg model on spherical and cylindrical geometries. The dependence of the steady state on the thickness is determined for both cases, and we find that a change in the thickness can stabilize the unstable modes, and vice versa. The combined effect of thickness and curvature can play an important role in the rearrangement of spatial patterns on thin curved surfaces. PMID:27627331

  17. PyTransit: Transit light curve modeling

    NASA Astrophysics Data System (ADS)

    Parviainen, Hannu

    2015-05-01

    PyTransit implements optimized versions of the Giménez and Mandel & Agol transit models for exoplanet transit light-curves. The two models are implemented natively in Fortran with OpenMP parallelization, and are accessed by an object-oriented python interface. PyTransit facilitates the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations. It offers efficient model evaluation for multicolour observations and transmission spectroscopy, built-in supersampling to account for extended exposure times, and routines to calculate the projected planet-to-star distance for circular and eccentric orbits, transit durations, and more.

  18. Analysis of light curve of LP Camelopardalis

    NASA Astrophysics Data System (ADS)

    Prudil, Z.; Skarka, M.; Zejda, M.

    2016-05-01

    We present photometric analysis of the RRab type pulsating star LP Cam. The star was observed at Brno Observatory and Planetarium during nine nights. Measurements were calibrated to the Johnson photometric system. Four captured and thirteen previously published maxima timings allowed us to refine the pulsation period and the zero epoch. The light curve was Fourier decomposed to estimate physical parameters using empirical relations. Our results suggest that LP Cam is a common RR Lyrae star with high, almost solar metallicity.

  19. Atlas of Secular Light Curves of Comets

    NASA Astrophysics Data System (ADS)

    Ferrin, Ignacio

    2007-12-01

    We have completed work on the secular light curves of 30 periodic and non-periodic comets. The objectives and approach of this project has been explained in Ferrin (Icarus, 178, 493-516, 2005). Each comet requires 2 plots. The time plot shows the reduced (to Δ = 1 AU) magnitude of the comet as a function of time, thus displaying the brightness history of the object. The log plot is a reflected double log plot. The reflection takes place at R=1 AU, to allow the determination of the absolute magnitude by extrapolation. 22 photometric parameters are measured from the plots, most of them new. The plots have been collected in a document that constitutes "The Atlas". We have defined a photometric age, P-AGE, that attempts to measure the age of a comet based on its activity. P-AGE has been scaled to human ages to help in its interpretation. We find that comets Hale-Bopp and 29P/SW 1, are baby comets (P-AGE < 3 comet years), while 107P, 162P and 169P are methuselah comets (P-AGE > 100 cy). The secular light curve of 9P/Tempel 1 exhibits sublimation due to H2O and due to CO. Comet 67P/Churyumov-Gerasimento to be visited by the Rossetta spacecraft in 2014 exhibits a photometric anomaly. Comet 65P/Gunn exhibits a lag in maximum brightness of LAG = + 254 days after perihelion. We suggest that the pole is pointing to the sun at that time. The secular light curves will be presented and a preliminary interpretation will be advanced. The secular light curves present complexity beyond current understanding. The observations described in this work were carried out at the National Observatory of Venezuela (ONV), managed by the Center for Research in Astronomy (CIDA), for the Ministry of Science and Technology (MinCyT).

  20. Atlas of secular light curves of comets

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio

    2010-02-01

    In this work we have compiled 37,692 observations of 27 periodic and non-periodic comets to create the secular light curves (SLCs), using two plots per comet. The data have been reduced homogeneously. Our overriding goal is to learn the properties of the ensemble of comets. More than 30 parameters are listed, of which over ˜20 are new and measured from the plots. We define two ages for a comet using activity as a proxy, the photometric age P-AGE, and the time-age, T-AGE. It is shown that these parameters are robust, implying that the input data can have significant errors but P-AGE and T-AGE come out with small errors. This is due to their mathematical definition. It is shown that P-AGE classifies comets by shape of their light curve. The value of this Atlas is twofold: The SLCs not only show what we know, but also show what we do not know, thus pointing the way to meaningful observations. Besides their scientific value, these plots are useful for planning observations. The SLCs have not been modeled, and there is no cometary light curve standard model as there is for some variable stars (i.e. eclipsing binaries). Comets are classified by age and size. In this way it is found that 29P/Schwassmann-Wachmann 1 is a baby goliath comet, while C/1983 J1 Sugano-Saigusa-Fujikawa is a middle age dwarf. There are new classes of comets based on their photometric properties. The secular light curves presented in this Atlas exhibit complexity beyond current understanding.

  1. Light Curve Models for Type IA Supernovae

    NASA Astrophysics Data System (ADS)

    Dominguez, Inmaculada

    1993-05-01

    The most widely accepted scenario for Type Ia supernovae is the thermonuclear explosion of a C+O white dwarf which, by accretion from a companion, approaches the Chandrasekhar mass. Whilst this scenario can account for most of the observed properties of SNe Ia, the exact nature of the explosion mechanism remains uncertain. This thesis presents the results obtained from hydrodynamical model calculations of post-explosion envelope expansion. The hydrodynamics are followed in spherical symmetry using a Lagrangean code, the energy equation being solved in the diffusion approximation. The conversion of decay gamma-rays into thermal energy is treated as an absorption process, while the time-dependent opacity is calculated as a function of composition, density, temperature and velocity gradient. The results of these models--light-curve shape, maximum luminosities, and expansion velocity profiles---are compared with the bolometric observational data (SN1981B, SN1972E and the composite light curve obtained by Leibundgut for 9 SNe Ia in Virgo) and current theoretical models of the explosion mechanism. Delayed detonation and deflagration models (Bravo 1990), adopting different C ignition densities, have been investigated. In all cases, the resulting light curve is in satisfactory agreement with observations. As the ignition density varies, the maximum of light remains nearly constant and the dispersion in the rates of decline of the light curve is compatible with observations. Moreover, variation in the ignition density readily accounts for the dispersion of 1000 km s^-1 in the observed expansion velocities. Delayed detonation models yield high kinetic energies, that result in (especially for the highest ignition densities) high expansion velocities, steep post-peak declines of the light curves and velocity distribution of intermediate-mass elements that are higher than that inferred from observations. Conversely, deflagration models provide less energetic explosions. However

  2. X-Ray Nova Light Curves

    NASA Astrophysics Data System (ADS)

    Shrader, Chris; Titarchuk, Lev

    2002-04-01

    We describe recent work in which we revisit the database of historical X-Ray nova (XRN) light curves compiled by Chen, Shrader & Livio (1997, ApJ 491, 312), augmented by subsequent events recorded by RXTE, in an attempt to gain a better understanding of the outburst phenomenon. Previously, we demonstrated that, given the occurrence of an instability in the mass transfer rate from the secondary, a model based on viscous diffusion of matter through the disk (Wood et al, 2001, astro-ph/0108189) we could reproduce a large number of fast-rise exponential decay (FRED) type XRN light curves. We augment this effort by considering deviations from the FRED form, such as plateaus and power-law decay forms are also considered within this framework. More complex structures are, in a number of instances, successfully modeled as a superposition of mass- injection, diffusive propagation events. In addition, for a large number of cases, we perform a joint analysis of optical light curve data. In particular, we will attempt to characterize empirical characteristics such as possible tie lags, and relative decay time scales, and then interpret such effects withing the context of diffusive propagation in the disk.

  3. A light synthesis program for binary stars. II - Light curve and color curve effects in a contact system

    NASA Astrophysics Data System (ADS)

    Linnell, A. P.

    1986-01-01

    This paper studies various models which attempt to explain light curves and color curves for eclipsing W Ursae Majoris stars of type W. Observed color curves for VW Cephei are in disagreement with the Mullan starspot model to explain W-type light curves. An alternative starspot model, with starspots located on the averted hemisphere of the larger star, represents the light curves and color curves for 1980 August 21 with good accuracy. The observed light curves and color curves of VW Cephei agree with theoretical curves for a Rucinski hot secondary model. A single spot, added to the underlying hot secondary model, provides a reasonably accurate representation of UBVRI photometric data.

  4. Creating A Light Curve Using Gathered Data

    NASA Astrophysics Data System (ADS)

    Wiggs, Joseph; Stolarz, S. A.; DePorto, R. W.; Shake, W. J.; Piper, M.; Linder, T. R.; Holmes, R.; Conwell, J.

    2012-01-01

    Our group of students with the support of educators and astronomers carried out a program to do astrometric and photometric analysis on the asteroid 2000 SO1 with the objective of obtaining a more in depth analysis of this asteroid and publishing light curve data describing the period of the asteroid. We chose our target asteroid using the minor planet center database, choosing an object that would have an acceptable Right Ascension, Declination, magnitude, and air mass for the ARO (Astronomical Research Observatory)-30 inch telescope operated by the SKYNET program. Our journey began with using Astrometrica for the IASC/WISE Program to identify and find new asteroids in the sky and add data to the Minor Planet Center Database. We then used MPO (Minor Planet Observatory) Canopus to form a light curve and conduct a fourier analysis on an example asteroid to familiarize ourselves with the program and used the program again to conduct fourier analysis on asteroid 2000 SO1. The educational goal in mind was to (a) learn the process of collecting and analyzing data using Astrometrica, MPO Canopus, the Minor Planet Center, and SKYNET and (b) create a poster to display the steps used in the process of surveying taken images and the production of a light curve. We collected 300 images a night, while discarding all the corrupted images, until we had enough data to accurately represent the object.Our work was successful due to resources from; Eastern Illinois University's Physics Department, the Astronomical Research Observatory, the University of Chicago's Yerkes Observatory, the SKYNET network, NASA's IASC/WISE (International Astronomical Search Collaboration/ Wide-Field Infrared Survey Explorer), NITARP (NASA/IPAC Teacher Archive Research Program) and Lincoln-Way North High School.

  5. SPECTRA AND LIGHT CURVES OF FAILED SUPERNOVAE

    SciTech Connect

    Fryer, Chris L.; Dahl, Jon A.; Fontes, Christopher J. E-mail: dahl@lanl.go

    2009-12-10

    Astronomers have proposed a number of mechanisms to produce supernova explosions. Although many of these mechanisms are now not considered primary engines behind supernovae (SNe), they do produce transients that will be observed by upcoming ground-based surveys and NASA satellites. Here, we present the first radiation-hydrodynamics calculations of the spectra and light curves from three of these 'failed' SNe: SNe with considerable fallback, accretion-induced collapse of white dwarfs, and energetic helium flashes (also known as type Ia SNe).

  6. Peranso - Light curve and period analysis software

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Vanmunster, T.

    2016-03-01

    A time series is a sample of observations of well-defined data points obtained through repeated measurements over a certain time range. The analysis of such data samples has become increasingly important not only in natural science but also in many other fields of research. Peranso offers a complete set of powerful light curve and period analysis functions to work with large astronomical data sets. Substantial attention has been given to ease-of-use and data accuracy, making it one of the most productive time series analysis software available. In this paper, we give an introduction to Peranso and its functionality.

  7. Template Reproduction of GRB Pulse Light Curves

    NASA Astrophysics Data System (ADS)

    Hakkila, Jon E.; Preece, R. D.; Loredo, T. J.; Wolpert, R. L.; Broadbent, M. E.

    2014-01-01

    A study of well-isolated pulses in gamma ray burst light curves indicates that simple models having smooth and monotonic pulse rises and decays are inadequate. Departures from the Norris et al. (2005) pulse shape are in the form of a wave-like pre-peak residual that is mirrored and stretched following the peak. Pulse shape departures are present in GRB pulses of all durations, but placement of the departures relative to pulse peaks correlates with asymmetry. This establishes an additional link between temporal structure and spectral evolution, as pulse asymmetry is related to initial hardness while pulse duration indicates the rate of hard-to-soft pulse evolution.

  8. Light-curve Analysis of Neon Novae

    NASA Astrophysics Data System (ADS)

    Hachisu, Izumi; Kato, Mariko

    2016-01-01

    We analyzed light curves of five neon novae, QU Vul, V351 Pup, V382 Vel, V693 CrA, and V1974 Cyg, and determined their white dwarf (WD) masses and distance moduli on the basis of theoretical light curves composed of free-free and photospheric emission. For QU Vul, we obtained a distance of d ˜ 2.4 kpc, reddening of E(B - V) ˜ 0.55, and WD mass of MWD = 0.82-0.96 {M}⊙ . This suggests that an oxygen-neon WD lost a mass of more than ˜ 0.1 {M}⊙ since its birth. For V351 Pup, we obtained d˜ 5.5 {{kpc}}, E(B-V)˜ 0.45, and {M}{{WD}}=0.98-1.1 {M}⊙ . For V382 Vel, we obtained d˜ 1.6 {{kpc}}, E(B-V)˜ 0.15, and {M}{{WD}}=1.13-1.28 {M}⊙ . For V693 CrA, we obtained d˜ 7.1 {{kpc}}, E(B-V)˜ 0.05, and {M}{{WD}}=1.15-1.25 {M}⊙ . For V1974 Cyg, we obtained d˜ 1.8 {{kpc}}, E(B-V)˜ 0.30, and {M}{{WD}}=0.95-1.1 {M}⊙ . For comparison, we added the carbon-oxygen nova V1668 Cyg to our analysis and obtained d˜ 5.4 {{kpc}}, E(B-V)˜ 0.30, and {M}{{WD}}=0.98-1.1 {M}⊙ . In QU Vul, photospheric emission contributes 0.4-0.8 mag at most to the optical light curve compared with free-free emission only. In V351 Pup and V1974 Cyg, photospheric emission contributes very little (0.2-0.4 mag at most) to the optical light curve. In V382 Vel and V693 CrA, free-free emission dominates the continuum spectra, and photospheric emission does not contribute to the optical magnitudes. We also discuss the maximum magnitude versus rate of decline relation for these novae based on the universal decline law.

  9. X-Ray Nova Light Curves

    NASA Astrophysics Data System (ADS)

    Shrader, C. R.; Titarchuk, L.

    2001-12-01

    We describe recent work in which we revisit the database of historical X-Ray nova (XRN) light curves compiled by Chen, Shrader & Livio (1997, ApJ 491, 312), augmented by subsequent events recorded by RXTE, in an attempt to gain a better understanding of the outburst phenomenon. In this presentation, we demonstrate that, given the occurrence of an instability in the mass transfer rate from the secondary, a model based on viscous diffusion of matter through the disk (Wood et al, 2001, astro-ph/0108189) can reproduce a large number of fast-rise exponential decay (FRED) type XRN light curves. Deviations from the FRED form, such as plateaus and power-law decay forms are also considered within this framework. More complex structures are, in a number of instances, successfully modeled as a superposition of mass-injection, diffusive propagation events. Limitations to this approach are considered. For example, recent concerns regarding the ability of viscous diffusion scenarios to reproduce the typical XRN rise and time scales (e.g. Cannizzo, ApJ, astro-ph/0110117) are discussed, as are possible time-dependent viscosity effects.

  10. The light curve of HD 200925

    NASA Astrophysics Data System (ADS)

    DuPuy, D. L.

    1981-02-01

    The light curve of the star HD 200925 is investigated based on an analysis of published photoelectric observations. A preliminary search of the data for periodicities using the Jurkevich period search method indicates a period of 0.267 days, although the observations reported by Bedolla and Pe a (1979) for the night of September 26-27, 1978 are systematically brighter by about 0.08 magnitudes than the other observations. A nonlinear least squares fit of the values of the period, approximate amplitude (0.4 magnitude) and phase angle of the periodicity (0.9 radian) derived to a sinusoid is shown to differ significantly from the data obtained on the nights of September 24-25, 25-26 and 27-28, 1978, although confirming the period of 0.2672 days. Data also suggest the presence of a secondary period of 0.36 days, which, however, may rather be due to the asymmetry of the observed light curve.

  11. Thermonuclear supernova light curves: Progenitors and cosmology

    NASA Astrophysics Data System (ADS)

    Rodney, Steven A.

    Thermonuclear Supernovae (TN SNe) are an extremely important tool in modern astronomy. In their role as cosmological distance probes, they have revealed the accelerated expansion of the universe and have begun to constrain the nature of the dark energy that may be driving that expansion. The next decade will see a succession of wide-field surveys producing thousands of TNSN detections each year. Traditional methods of SN analysis, rooted in time-intensive spectroscopic follow-up, will become completely impractical. To realize the potential of this coming tide of massive data sets, we will need to extract cosmographic parameters (redshift and luminosity distance) from SN photometry without any spectroscopic support. In this dissertation, I present the Supernova Ontology with Fuzzy Templates (SOFT) method, an innovative new approach to the analysis of SN light curves. SOFT uses the framework of fuzzy set theory to perform direct comparisons of SN candidates against template light curves, simultaneously producing both classifications and cosmological parameter estimates. The SOFT method allows us to shed new light on two rich archival data sets. I revisit the IfA Deep Survey and HST GOODS to extract new and improved measurements of the TNSN rate from z=0.2 out to z=1.6. Our new analysis shows a steady increase in the TNSN rate out to z˜1, and adds support for a decrease in the rate at z=1.5. Comparing these rate measurements to theoretical models, I conclude that the progenitor scenario most favored by the collective observational data is a single degenerate model, regulated by a strong wind from the accreting white dwarf. Using a compilation of SN light curves from five recent surveys, I demonstrate that SOFT is able to derive useful constraints on cosmological models from a data set with no spectroscopic information at all. Looking ahead to the near future, I find that photometric analysis of data sets containing 2,000 SNe will be able to improve our constraints on

  12. Light Curve of Minor Planet 1026 Ingrid

    NASA Astrophysics Data System (ADS)

    Delos, S.; Ahrendts, G.; Barker, T.

    2012-06-01

    (Abstract only) We have imaged minor planet 1026 Ingrid over the time period of July 29, 2011, to late September 2011, using the Wheaton College 0.25m telescope at Grove Creek Observatory in Australia via internet access. This telescope is equipped with a Santa Barbara Instrument Group STL-1001E CCD Camera, used with a clear filter. Over 1,000 30-second images were obtained and imported into the MPO Canopus software package for light curve analysis. Our preliminary estimate of the rotation period of 1026 Ingrid is 5.390 ± 0.001 hours, which is consistent with the previous estimate of 5.3 ± 0.3 hours (Székely, P., et al. 2005, Planet. Space Sci., 53, 925).

  13. Supernova Light Curves Powered by Fallback Accretion

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Kasen, Daniel

    2013-07-01

    Some fraction of the material ejected in a core collapse supernova explosion may remain bound to the compact remnant, and eventually turn around and fall back. We show that the late time (gsimdays) power potentially associated with the accretion of this "fallback" material could significantly affect the optical light curve, in some cases producing super-luminous or otherwise peculiar supernovae. We use spherically symmetric hydrodynamical models to estimate the accretion rate at late times for a range of progenitor masses and radii and explosion energies. The accretion rate onto the proto-neutron star or black hole decreases as \\dot{M} \\propto t^{-5/3} at late times, but its normalization can be significantly enhanced at low explosion energies, in very massive stars, or if a strong reverse shock wave forms at the helium/hydrogen interface in the progenitor. If the resulting super-Eddington accretion drives an outflow which thermalizes in the outgoing ejecta, the supernova debris will be re-energized at a time when photons can diffuse out efficiently. The resulting light curves are different and more diverse than previous fallback supernova models which ignored the input of accretion power and produced short-lived, dim transients. The possible outcomes when fallback accretion power is significant include super-luminous (gsim 1044 erg s-1) Type II events of both short and long durations, as well as luminous Type I events from compact stars that may have experienced significant mass loss. Accretion power may unbind the remaining infalling material, causing a sudden decrease in the brightness of some long duration Type II events. This scenario may be relevant for explaining some of the recently discovered classes of peculiar and rare supernovae.

  14. SUPERNOVA LIGHT CURVES POWERED BY FALLBACK ACCRETION

    SciTech Connect

    Dexter, Jason; Kasen, Daniel

    2013-07-20

    Some fraction of the material ejected in a core collapse supernova explosion may remain bound to the compact remnant, and eventually turn around and fall back. We show that the late time ({approx}>days) power potentially associated with the accretion of this 'fallback' material could significantly affect the optical light curve, in some cases producing super-luminous or otherwise peculiar supernovae. We use spherically symmetric hydrodynamical models to estimate the accretion rate at late times for a range of progenitor masses and radii and explosion energies. The accretion rate onto the proto-neutron star or black hole decreases as M-dot {proportional_to}t{sup -5/3} at late times, but its normalization can be significantly enhanced at low explosion energies, in very massive stars, or if a strong reverse shock wave forms at the helium/hydrogen interface in the progenitor. If the resulting super-Eddington accretion drives an outflow which thermalizes in the outgoing ejecta, the supernova debris will be re-energized at a time when photons can diffuse out efficiently. The resulting light curves are different and more diverse than previous fallback supernova models which ignored the input of accretion power and produced short-lived, dim transients. The possible outcomes when fallback accretion power is significant include super-luminous ({approx}> 10{sup 44} erg s{sup -1}) Type II events of both short and long durations, as well as luminous Type I events from compact stars that may have experienced significant mass loss. Accretion power may unbind the remaining infalling material, causing a sudden decrease in the brightness of some long duration Type II events. This scenario may be relevant for explaining some of the recently discovered classes of peculiar and rare supernovae.

  15. Modelling asteroid brightness variations. II - The interpretability of light curves and phase curves

    NASA Technical Reports Server (NTRS)

    Karttunen, H.; Bowell, E.

    1989-01-01

    Light curves and phase curves have been computed for various asteroid models using the Lumme-Bowell (1981) scattering law. The effects of the scattering parameters on light curves were found to be almost negligible for homogeneous surfaces. The effects on phase curves were more distinct, but changing any of the scattering parameters affects the phase curves in a very similar way, making it impossible to find a unique set of parameter values corresponding to a given phase curve. Light curve amplitudes, on the other hand, depend very strongly on body shape. At least in the case of a triaxial ellipsoid it is possible to determine the axial ratios. Some observed irregularities of light curves can also be modelled easily, but the uniqueness of such models is far from obvious.

  16. Do the Kepler AGN light curves need reprocessing?

    NASA Astrophysics Data System (ADS)

    Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.; Williams, Joshua; Carini, Michael T.

    2015-10-01

    We gauge the impact of spacecraft-induced effects on the inferred variability properties of the light curve of the Seyfert 1 AGN Zw 229-15 observed by Kepler. We compare the light curve of Zw 229-15 obtained from the Kepler MAST data base with a reprocessed light curve constructed from raw pixel data. We use the first-order structure function, SF(δt), to fit both light curves to the damped power-law PSD (power spectral density) of Kasliwal et al. On short time-scales, we find a steeper log PSD slope (γ = 2.90 to within 10 per cent) for the reprocessed light curve as compared to the light curve found on MAST (γ = 2.65 to within 10 per cent) - both inconsistent with a damped random walk (DRW) which requires γ = 2. The log PSD slope inferred for the reprocessed light curve is consistent with previous results that study the same reprocessed light curve. The turnover time-scale is almost identical for both light curves (27.1 and 27.5 d for the reprocessed and MAST data base light curves). Based on the obvious visual difference between the two versions of the light curve and on the PSD model fits, we conclude that there remain significant levels of spacecraft-induced effects in the standard pipeline reduction of the Kepler data. Reprocessing the light curves will change the model inferenced from the data but is unlikely to change the overall scientific conclusions reached by Kasliwal et al. - not all AGN light curves are consistent with the DRW.

  17. Modelling high-energy pulsar light curves from first principles

    NASA Astrophysics Data System (ADS)

    Cerutti, Benoît; Philippov, Alexander A.; Spitkovsky, Anatoly

    2016-04-01

    Current models of gamma-ray light curves in pulsars suffer from large uncertainties on the precise location of particle acceleration and radiation. Here, we present an attempt to alleviate these difficulties by solving for the electromagnetic structure of the oblique magnetosphere, particle acceleration, and the emission of radiation self-consistently, using 3D spherical particle-in-cell simulations. We find that the low-energy radiation is synchro-curvature radiation from the polar-cap regions within the light cylinder. In contrast, the high-energy emission is synchrotron radiation that originates exclusively from the Y-point and the equatorial current sheet where relativistic magnetic reconnection accelerates particles. In most cases, synthetic high-energy light curves contain two peaks that form when the current sheet sweeps across the observer's line of sight. We find clear evidence of caustics in the emission pattern from the current sheet. High-obliquity solutions can present up to two additional secondary peaks from energetic particles in the wind region accelerated by the reconnection-induced flow near the current sheet. The high-energy radiative efficiency depends sensitively on the viewing angle, and decreases with increasing pulsar inclination. The high-energy emission is concentrated in the equatorial regions where most of the pulsar spin-down is released and dissipated. These results have important implications for the interpretation of gamma-ray pulsar data.

  18. Light shaping along 3D curves and particle manipulation

    NASA Astrophysics Data System (ADS)

    Rodrigo, José A.; Alieva, Tatiana

    2015-03-01

    We present a non-iterative holographic technique for efficient and versatile laser beam shaping along arbitrary 3D curves. Light beams with intensity shaped for several 3D curves: Tilted ring, Viviani's curve, Archimedean spiral, and trefoil-knotted curve have been experimentally generated and applied for optical trapping of micrometer-sized dielectric particles. The high intensity gradients and independent phase control prescribed along the curve make this kind of laser trap attractive for multiple particle manipulation and allow for forward and backward motion to the light source. Indeed, different configurations of tractor beam traps are experimentally demonstrated. This technique can also be applied for laser micro-machining.

  19. Light curve demography via Bayesian functional data analysis

    NASA Astrophysics Data System (ADS)

    Loredo, Thomas; Budavari, Tamas; Hendry, Martin A.; Kowal, Daniel; Ruppert, David

    2015-08-01

    Synoptic time-domain surveys provide astronomers, not simply more data, but a different kind of data: large ensembles of multivariate, irregularly and asynchronously sampled light curves. We describe a statistical framework for light curve demography—optimal accumulation and extraction of information, not only along individual light curves as conventional methods do, but also across large ensembles of related light curves. We build the framework using tools from functional data analysis (FDA), a rapidly growing area of statistics that addresses inference from datasets that sample ensembles of related functions. Our Bayesian FDA framework builds hierarchical models that describe light curve ensembles using multiple levels of randomness: upper levels describe the source population, and lower levels describe the observation process, including measurement errors and selection effects. Schematically, a particular object's light curve is modeled as the sum of a parameterized template component (modeling population-averaged behavior) and a peculiar component (modeling variability across the population), subsequently subjected to an observation model. A functional shrinkage adjustment to individual light curves emerges—an adaptive, functional generalization of the kind of adjustments made for Eddington or Malmquist bias in single-epoch photometric surveys. We are applying the framework to a variety of problems in synoptic time-domain survey astronomy, including optimal detection of weak sources in multi-epoch data, and improved estimation of Cepheid variable star luminosities from detailed demographic modeling of ensembles of Cepheid light curves.

  20. Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

    NASA Technical Reports Server (NTRS)

    Harding, A. K.; Kalapotharakos, C.; Kazanas, D.; Contopoulos, I.

    2012-01-01

    The Fermi Large Area Telescope has provided an unprecedented database for pulsar emission studies that includes gamma-ray light curves for over 100 pulsars. Modeling these light curves can reveal and constrain the geometry of the particle accelerator, as well as the pulsar magnetic field structure. We have constructed 3D magnetosphere models with finite conductivity, that bridge the extreme vacuum and force-free solutions used in previous light curves modeling. We are investigating the shapes of pulsar gamma-ray light curves using these dissipative solutions with two different approaches: (l) assuming geometric emission patterns of the slot gap and outer gap, and (2) using the parallel electric field provided by the resistive models to compute the trajectories and . emission of the radiating particles. The light curves using geometric emission patterns show a systematic increase in gamma-ray peak phase with increasing conductivity, introducing a new diagnostic of these solutions. The light curves using the model electric fields are very sensitive to the conductivity but do not resemble the observed Fermi light curves, suggesting that some screening of the parallel electric field, by pair cascades not included in the models, is necessary

  1. Cepheid light curve demography via Bayesian functional data analysis

    NASA Astrophysics Data System (ADS)

    Loredo, Thomas J.; Hendry, Martin; Kowal, Daniel; Ruppert, David

    2016-01-01

    Synoptic time-domain surveys provide astronomers, not simply more data, but a different kind of data: large ensembles of multivariate, irregularly and asynchronously sampled light curves. We describe a statistical framework for light curve demography—optimal accumulation and extraction of information, not only along individual light curves as conventional methods do, but also across large ensembles of related light curves. We build the framework using tools from functional data analysis (FDA), a rapidly growing area of statistics that addresses inference from datasets that sample ensembles of related functions. Our Bayesian FDA framework builds hierarchical models that describe light curve ensembles using multiple levels of randomness: upper levels describe the source population, and lower levels describe the observation process, including measurement errors and selection effects. Roughly speaking, a particular object's light curve is modeled as the sum of a parameterized template component (modeling population-averaged behavior) and a peculiar component (modeling variability across the population), subsequently subjected to an observation model. A functional shrinkage adjustment to individual light curves emerges—an adaptive, functional generalization of the kind of adjustments made for Eddington or Malmquist bias in single-epoch photometric surveys. We describe ongoing work applying the framework to improved estimation of Cepheid variable star luminosities via FDA-based refinement and generalization of the Cepheid period-luminosity relation.

  2. Asteroid Shape and Spin Axis Modeling Via Light Curve Inversion

    NASA Astrophysics Data System (ADS)

    Friz, Paul; Gokhale, V.

    2013-01-01

    We present light curves and shape and spin axis models for the five asteroids: 291 Alice, 281 Lucretia, 321 Florentina, 714 Ulula, and 3169 Ostro. These models were obtained using data taken from the Truman Observatory, the Asteroid Photometric Catalogue, and the Minor Planet Center. Knowledge of individual asteroids shapes and spin axes is vital to understanding the solar system. However, currently only 213 out of the 500,000 asteroids with known orbits have been modeled. By taking many light curves of asteroids over several apparitions it is possible to determine their shapes and spin axes by a process known as light curve inversion.

  3. Using Kepler Light Curves for Astronomy Education and Public Outreach

    NASA Astrophysics Data System (ADS)

    Cash, Jennifer; Rivers, S.; Eleby, J.; Gould, A.; Komatsu, T.

    2014-01-01

    We will present our efforts related to Education and Public Outreach activities using Kepler Light Curves. We are currently developing interactive web based activities to introduce the public to the general topic of Stellar Variability and Intrinsic Variable Stars in particular using the high quality light curves of over a dozen Kepler targets. Along with the public website, we are exploring areas to develop teacher guides to use Kepler Light Curves in the middle and high school classrooms. These efforts are supported through a NASA EPSCoR grant "South Carolina Joint Venture Program" via a subaward to SC State University.

  4. Bolometric and UV light curves of core-collapse supernovae

    SciTech Connect

    Pritchard, T. A.; Roming, P. W. A.; Brown, Peter J.; Bayless, Amanda J.; Frey, Lucille H.

    2014-06-01

    The Swift UV-Optical Telescope (UVOT) has been observing core-collapse supernovae (CCSNe) of all subtypes in the UV and optical since 2005. Here we present 50 CCSNe observed with the Swift UVOT, analyzing their UV properties and behavior. Where we have multiple UV detections in all three UV filters (λ {sub c} = 1928-2600 Å), we generate early time bolometric light curves, analyze the properties of these light curves and the UV contribution to them, and derive empirical corrections for the UV-flux contribution to optical-IR based bolometric light curves.

  5. QUEST1 VARIABILITY SURVEY. III. LIGHT CURVE CATALOG UPDATE

    SciTech Connect

    Rengstorf, A. W.; Thompson, D. L.; Mufson, S. L.; Honeycutt, R. K.; Adams, B.; Baltay, C.; Gebhard, M.; Andrews, P.; Coppi, P.; Emmet, W.; Vivas, A. K.; Abad, C.; Bongiovanni, A.; Briceno, C.; Bruzual, G.; Prugna, F. Della; Hernandez, J.; Bailyn, C.; Ferrin, I.; Fuenmayor, F.

    2009-03-15

    This paper reports an update to the QUEST1 (QUasar Equatorial Survey Team, Phase 1) Variability Survey (QVS) light curve catalog, which links QVS instrumental magnitude light curves to Sloan Digital Sky Survey (SDSS) objects and photometry. In the time since the original QVS catalog release, the overlap between publicly available SDSS data and QVS data has increased by 8% in sky coverage and 16,728 in number of matched objects. The astrometric matching and the treatment of SDSS masks have been refined for the updated catalog. We report on these improvements and present multiple bandpass light curves, global variability information, and matched SDSS photometry for 214,941 QUEST1 objects.

  6. New Developments in Eclipsing Binary Light Curve Modeling

    NASA Astrophysics Data System (ADS)

    Milone, E. F.; Stagg, C. R.

    1994-03-01

    The light curve modeling of binary stars has continued to evolve since its founding by Henry Norris Russell (see Russell and Merrill 1952 and citations therein) nearly a century ago, accelerated in the 1950s by Kopal's introduction of Roche geometry into models and by the development of synthetic light curve computer code in the 1970's. Improved physics and the use of more kinds of observational input are providing another round of important advances that promise to enlarge our knowledge of both binary stars and ensembles containing them. Here we discuss the newer horizons of light curve modeling and the steps being taken toward them.

  7. New Light Curves and Orbital Solution for AM Leonis

    NASA Astrophysics Data System (ADS)

    Hiller, Mary E.; Osborn, Wayne; Terrell, Dirk

    2004-04-01

    New UBVRI photometry has been obtained for the W UMa eclipsing system AM Leonis. The data have been used to derive nine times of minimum and to construct light curves. The minimum timings show that the system recently had a significant period increase. Modeling of the light curves shows AM Leo to be an overcontact system with a mass ratio of 2.51. Both Rucinski & Duerbeck's absolute magnitude calibration for W UMa stars applied to our photometry and the radial velocity curve combined with our derived parameters indicate a distance near 125 pc, larger than the 77 pc from the Hipparcos parallax.

  8. Interpretation of OAO-2 ultraviolet light curves of beta Doradus

    NASA Technical Reports Server (NTRS)

    Hutchinson, J. L.; Lillie, C. F.; Hill, S. J.

    1975-01-01

    Middle-ultraviolet light curves of beta Doradus, obtained by OAO-2, are presented along with other evidence indicating that the small additional bumps observed on the rising branches of these curves have their origin in shock-wave phenomena in the upper atmosphere of this classical Cepheid. A simple piston-driven spherical hydrodynamic model of the atmosphere is developed to explain the bumps, and the calculations are compared with observations. The model is found to be consistent with the shapes of the light curves as well as with measurements of the H-alpha radial velocities.

  9. Closed Paths of Light Trapped in a Closed Fermat Curve

    ERIC Educational Resources Information Center

    Dana-Picard, Thierry; Naiman, Aaron

    2002-01-01

    Geometric constructions have previously been shown that can be interpreted as rays of light trapped either in polygons or in conics, by successive reflections. The same question, trapping light in closed Fermat curves, is addressed here. Numerical methods are used to study the behaviour of the reflection points of a triangle when the degree of the…

  10. The hidden X-ray breaks in afterglow light curves

    SciTech Connect

    Curran, P. A.; Wijers, R. A. M. J.; Horst, A. J. van der; Starling, R. L. C.

    2008-05-22

    Gamma-Ray Burst (GRB) afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX, or pre-Swift era. Specifically, relatively few breaks, consistent with jet breaks, are observed in the X-ray light curves of these bursts. If these breaks are truly missing, it has serious consequences for the interpretation of GRB jet collimation and energy requirements, and the use of GRBs as standard candles.Here we address the issue of X-ray breaks which are possibly 'hidden' and hence the light curves are misinterpreted as being single power-laws. We show how a number of precedents, including GRB 990510 and GRB 060206, exist for such hidden breaks and how, even with the well sampled light curves of the Swift era, these breaks may be left misidentified. We do so by synthesising X-ray light curves and finding general trends via Monte Carlo analysis. Furthermore, in light of these simulations, we discuss how to best identify achromatic breaks in afterglow light curves via multi-wavelength analysis.

  11. PERIOD VARIATION AND ASYMMETRY LIGHT CURVES OF XY URSAE MAJORIS

    SciTech Connect

    Yuan Jinzhao

    2010-05-15

    New CCD photometric observations of the chromospherically active binary XY Ursae Majoris (XY UMa) were obtained every year since 2006. The light curves obtained in the late Spring of 2006 show obvious variations on a short timescale, while the light curves obtained in 2008 December do not. But both sets of light curves are markedly asymmetric, and were analyzed using the 2003 version of the Wilson-Devinney code with spot model. New absolute physical parameters are obtained. It is found that the total spotted area on the more massive component covers 7% of the photospheric surface in 2008 December. Fitting all available light minimum times including the newly obtained ones with a sinusoidal ephemeris and a four-part linear ephemeris reveals that the orbital period undergoes quasi-periodic oscillation rather than sinusoidal variations. Between the two mechanisms of magnetic activity and a third body around the eclipsing pair, the former one is more plausible.

  12. X-ray afterglow light curves: toward a standard candle?

    NASA Astrophysics Data System (ADS)

    Gendre, B.; Galli, A.; Boër, M.

    2008-05-01

    We investigate the clustering of afterglow light curves observed at X-ray and optical wavelengths. We construct a sample of 34 bursts with known distance and X-ray afterglow. We correct the light curves for cosmological effects and compare the observed X-ray fluxes one day after the burst. We check for correlations between the observed flux and the burst spectral and temporal properties. We confirm the previous result of Boër and Gendre (2000) that X-ray afterglow light curves cluster in luminosity, even when we consider the SWIFT data. We observe this clustering only for the afterglow light curves; the inclusion of prompt-related data broaden the distribution. The same clustering is observed for the optical light curves; GRB sources can be divided in three classes, namely optical and X-ray bright afterglows, optical and X-ray dim ones, and optically bright-X-ray dim ones. We argue that this clustering is related to the fireball total energy, the external medium density, the fraction of fireball energy going in relativistic electrons and magnetic fields. These parameters can be either fixed to a standard value, or correlated.

  13. The Chaotic Light Curves of Accreting Black Holes

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    2007-01-01

    We present model light curves for accreting Black Hole Candidates (BHC) based on a recently developed model of these sources. According to this model, the observed light curves and aperiodic variability of BHC are due to a series of soft photon injections at random (Poisson) intervals and the stochastic nature of the Comptonization process in converting these soft photons to the observed high energy radiation. The additional assumption of our model is that the Comptonization process takes place in an extended but non-uniform hot plasma corona surrounding the compact object. We compute the corresponding Power Spectral Densities (PSD), autocorrelation functions, time skewness of the light curves and time lags between the light curves of the sources at different photon energies and compare our results to observation. Our model reproduces the observed light curves well, in that it provides good fits to their overall morphology (as manifest by the autocorrelation and time skewness) and also to their PSDs and time lags, by producing most of the variability power at time scales 2 a few seconds, while at the same time allowing for shots of a few msec in duration, in accordance with observation. We suggest that refinement of this type of model along with spectral and phase lag information can be used to probe the structure of this class of high energy sources.

  14. Modeling magnetization curves in magnetic thin films with striped patterns

    NASA Astrophysics Data System (ADS)

    Di Pietro Martínez, M.; Milano, J.; Eddrief, M.; Marangolo, M.; Bustingorry, S.

    2016-04-01

    In this work, we study magnetic thin films presenting magnetic stripe patterns. A fingerprint of such domains is a linear behavior of the in-plane magnetization curves below a given saturation field. We present free energy models for the in-plane magnetization curves which permit us to extract key geometrical information about the stripe patterns, such as the maximum canted angle of the magnetization and the domain wall width. As an example, we discuss in this work magnetization curves for Fe1-x Ga x magnetic films which present a stripe pattern with a period of 160 nm and we found a typical maximum canted angle of {{85}{^\\circ}} and a domain wall width around 30 nm.

  15. Spatial Reasoning Training Through Light Curves Of Model Asteroids

    NASA Astrophysics Data System (ADS)

    Ziffer, Julie; Nakroshis, Paul A.; Rudnick, Benjamin T.; Brautigam, Maxwell J.; Nelson, Tyler W.

    2015-11-01

    Recent research has demonstrated that spatial reasoning skills, long known to be crucial to math and science success, are teachable. Even short stints of training can improve spatial reasoning skills among students who lack them (Sorby et al., 2006). Teaching spatial reasoning is particularly valuable to women and minorities who, through societal pressure, often doubt their spatial reasoning skill (Hill et al., 2010). We have designed a hands on asteroid rotation lab that provides practice in spatial reasoning tasks while building the student’s understanding of photometry. For our tool, we mount a model asteroid, with any shape of our choosing, on a slowly rotating motor shaft, whose speed is controlled by the experimenter. To mimic an asteroid light curve, we place the model asteroid in a dark box, shine a movable light source upon our asteroid, and record the light reflected onto a moveable camera. Students may then observe changes in the light curve that result from varying a) the speed of rotation, b) the model asteroid’s orientation with respect to the motor axis, c) the model asteroid’s shape or albedo, and d) the phase angle. After practicing with our tool, students are asked to pair new objects to their corresponding light curves. To correctly pair objects to their light curves, students must imagine how light scattering off of a three dimensional rotating object is imaged on a ccd sensor plane, and then reduced to a series of points on a light curve plot. Through the use of our model asteroid, the student develops confidence in spatial reasoning skills.

  16. Surface Imaging of HIP 106231 via Light Curve Inversion

    NASA Astrophysics Data System (ADS)

    Roettenbacher, Rachael; Harmon, Robert

    2006-10-01

    The star HIP 106231 (LO Pegasi) was observed with the intention of mapping its starspots. Starspots, similar to sunspots on the Sun, are dark areas on the surface of a star caused by intense magnetic fields. CCD images of HIP 106231 and the surrounding star field were obtained using an 8-inch Meade Schmidt-Cassegrain Telescope in conjunction with a Santa Barbara Instruments Group ST-8E CCD Camera and CFW8 filter wheel. Aperture photometry was used to create light curves (i.e. plots of brightness vs. time) for the B, V, R and I photometric filters. The light curves were analyzed via Light Curve Inversion, which is a technique that produces an image of the starspots based on the variations in the star's brightness they produce as they rotate into and out of view of Earth. We present a map which indicates the presence of a mid-latitude spot or projection from a polar spot.

  17. Vaporization of comet nuclei - Light curves and life times

    NASA Technical Reports Server (NTRS)

    Cowan, J. J.; Ahearn, M. F.

    1979-01-01

    The effects of vaporization from the nucleus of a comet are examined and it is shown that a latitude dependence of vaporization can explain the asymmetries in cometary light curves. An attempt is made to explain the observed variation in molecular production rates with heliocentric distance when employing CO2 and clathrate hydrate ice as cometary nuclei substances. The energy balance equation and the vapor pressure equations of water and CO2 are used in calculating the vaporization from a surface. Calculations were carried out from both dry-ice and water-ice nuclei, using a variety of different effective visual albedos, but primarily for a thermal infrared of 0 (emission). Attention is given to cometary lifetimes and light curves and it was determined that the asymmetry in light curves occurs (occasionally) as a 'seasonal' effect due to a variation in the angle between the comet's rotation axis and the sun-comet line.

  18. CONSTRAINING PULSAR MAGNETOSPHERE GEOMETRY WITH {gamma}-RAY LIGHT CURVES

    SciTech Connect

    Romani, Roger W.; Watters, Kyle P. E-mail: kwatters@stanford.ed

    2010-05-01

    We demonstrate a method for quantitatively comparing {gamma}-ray pulsar light curves with magnetosphere beaming models. With the Fermi LAT providing many pulsar discoveries and high-quality pulsar light curves for the brighter objects, such a comparison allows greatly improved constraints on the emission zone geometry and the magnetospheric physics. Here we apply the method to Fermi LAT light curves of a set of bright pulsars known since EGRET or before. We test three approximate models for the magnetosphere structure and two popular schemes for the location of the emission zone, the two pole caustic model and the outer gap (OG) model. We find that OG models and relatively physical B fields approximating force-free dipole magnetospheres are preferred at high statistical significance. An application to the full LAT pulsar sample will allow us to follow the emission zone's evolution with pulsar spindown.

  19. Light synthesis program for binary stars. II. Light curve and color curve effects in a contact system

    SciTech Connect

    Linnell, A.P.

    1986-01-01

    VW Cephei's observed light and color curves are presently noted to agree with theoretical curves for a Rucinski (1978) hot secondary model, with a single spot, added to the underlying hot secondary model, furnishing a reasonably accurate representation of UBVRI photometric data. In this model, the implied baroclinic photosphere is consistent with the Webbink (1977) scenario for mass circulation and energy transport in W-type W UMa systems. Current data, however, cannot unambiguously discriminate between the two acceptable models. 58 references.

  20. Type II Supernovae: Model Light Curves and Standard Candle Relationships

    NASA Astrophysics Data System (ADS)

    Kasen, Daniel; Woosley, S. E.

    2009-10-01

    A survey of Type II supernovae explosion models has been carried out to determine how their light curves and spectra vary with their mass, metallicity, and explosion energy. The presupernova models are taken from a recent survey of massive stellar evolution at solar metallicity supplemented by new calculations at subsolar metallicity. Explosions are simulated by the motion of a piston near the edge of the iron core and the resulting light curves and spectra are calculated using full multi-wavelength radiation transport. Formulae are developed that describe approximately how the model observables (light curve luminosity and duration) scale with the progenitor mass, explosion energy, and radioactive nucleosynthesis. Comparison with observational data shows that the explosion energy of typical supernovae (as measured by kinetic energy at infinity) varies by nearly an order of magnitude—from 0.5 to 4.0 × 1051 ergs, with a typical value of ~0.9 × 1051 ergs. Despite the large variation, the models exhibit a tight relationship between luminosity and expansion velocity, similar to that previously employed empirically to make SNe IIP standardized candles. This relation is explained by the simple behavior of hydrogen recombination in the supernova envelope, but we find a sensitivity to progenitor metallicity and mass that could lead to systematic errors. Additional correlations between light curve luminosity, duration, and color might enable the use of SNe IIP to obtain distances accurate to ~20% using only photometric data.

  1. TYPE II SUPERNOVAE: MODEL LIGHT CURVES AND STANDARD CANDLE RELATIONSHIPS

    SciTech Connect

    Kasen, Daniel; Woosley, S. E.

    2009-10-01

    A survey of Type II supernovae explosion models has been carried out to determine how their light curves and spectra vary with their mass, metallicity, and explosion energy. The presupernova models are taken from a recent survey of massive stellar evolution at solar metallicity supplemented by new calculations at subsolar metallicity. Explosions are simulated by the motion of a piston near the edge of the iron core and the resulting light curves and spectra are calculated using full multi-wavelength radiation transport. Formulae are developed that describe approximately how the model observables (light curve luminosity and duration) scale with the progenitor mass, explosion energy, and radioactive nucleosynthesis. Comparison with observational data shows that the explosion energy of typical supernovae (as measured by kinetic energy at infinity) varies by nearly an order of magnitude-from 0.5 to 4.0 x 10{sup 51} ergs, with a typical value of approx0.9 x 10{sup 51} ergs. Despite the large variation, the models exhibit a tight relationship between luminosity and expansion velocity, similar to that previously employed empirically to make SNe IIP standardized candles. This relation is explained by the simple behavior of hydrogen recombination in the supernova envelope, but we find a sensitivity to progenitor metallicity and mass that could lead to systematic errors. Additional correlations between light curve luminosity, duration, and color might enable the use of SNe IIP to obtain distances accurate to approx20% using only photometric data.

  2. The astrophysical torus. 2: Light curves of SS 433

    NASA Astrophysics Data System (ADS)

    Sanbuichi, Kiyotaka; Fukue, Jun

    1993-10-01

    Using the mass function obtained by D'Odorico et al. (1991), we recalculate the theoretical light curves of SS 433 in the primary eclipse and confront them with observations. We assume that in SS 433 there exists a geometrically thick torus around a compact object, and that the primary eclipse is an eclipse of the torus by a companion of an early-type star. The main parameters are the shape of the tori, the size of the tori, and the binary mass ratio. We obtain light curves for several combinations of parameters. The light curves for sufficiently thick tori are deep at the mid-eclipse and preferable, while those for geometrically thin tori are shallow. The duration of eclipse for a large torus is long and beneficial, while that for a small torus is short. Finally, Delta m at mid-eclipse for a thick torus around a neutron star becomes approximately 0.6 and suitable, whereas for thick tori around a black hole it is approximately 0.3. Hence, under the new mass function, geometrically thick and wide tori around a neutron star can well reproduce the observed light curves of SS 433.

  3. X-Ray Afterglow Light Curves: Toward A Standard Candle?

    NASA Astrophysics Data System (ADS)

    Gendre, B.; Galli, A.; Boër, M.

    2008-08-01

    We investigate the clustering of afterglow light curves observed at X-ray and optical wavelengths. We have constructed a sample of 61 bursts with known distance and X-ray afterglow. This sample includes bursts observed by BeppoSAX, XMM-Newton, Chandra, and Swift. We correct the light curves for cosmological effects and compare the observed X-ray fluxes 1 day after the burst. We check for correlations between the observed flux and the burst spectral and temporal properties. We confirm the previous result of Boër & Gendre that X-ray afterglow light curves cluster in luminosity, even when we consider the last Swift data. We observe this clustering only for the afterglow light curves; the inclusion of prompt-related data broadens the distribution. A similar clustering is observed for the optical light curves; gamma-ray burst (GRB) sources can be divided into three classes, namely, optically and X-ray bright afterglows, optically and X-ray dim ones, and optically bright but X-ray dim ones. We argue that this clustering is related to the fireball total energy, the external medium density, and the fraction of fireball energy going into relativistic electrons and magnetic fields. These parameters can be either fixed to a standard value or correlated. We finally propose a method for the estimation of the GRB source redshift based on the observed X-ray flux 1 day after the burst and optical properties. Using this method, we compute a redshift of 1.4 +/- 0.2 for GRB 980519 and of 1.9 +/- 0.3 for GRB 040827. We tested this method on three recently detected Swift GRBs with known redshift, and found it in good agreement with the reported distance from optical spectroscopy.

  4. UNSUPERVISED TRANSIENT LIGHT CURVE ANALYSIS VIA HIERARCHICAL BAYESIAN INFERENCE

    SciTech Connect

    Sanders, N. E.; Soderberg, A. M.; Betancourt, M.

    2015-02-10

    Historically, light curve studies of supernovae (SNe) and other transient classes have focused on individual objects with copious and high signal-to-noise observations. In the nascent era of wide field transient searches, objects with detailed observations are decreasing as a fraction of the overall known SN population, and this strategy sacrifices the majority of the information contained in the data about the underlying population of transients. A population level modeling approach, simultaneously fitting all available observations of objects in a transient sub-class of interest, fully mines the data to infer the properties of the population and avoids certain systematic biases. We present a novel hierarchical Bayesian statistical model for population level modeling of transient light curves, and discuss its implementation using an efficient Hamiltonian Monte Carlo technique. As a test case, we apply this model to the Type IIP SN sample from the Pan-STARRS1 Medium Deep Survey, consisting of 18,837 photometric observations of 76 SNe, corresponding to a joint posterior distribution with 9176 parameters under our model. Our hierarchical model fits provide improved constraints on light curve parameters relevant to the physical properties of their progenitor stars relative to modeling individual light curves alone. Moreover, we directly evaluate the probability for occurrence rates of unseen light curve characteristics from the model hyperparameters, addressing observational biases in survey methodology. We view this modeling framework as an unsupervised machine learning technique with the ability to maximize scientific returns from data to be collected by future wide field transient searches like LSST.

  5. Theoretical light curves for deflagration models of type Ia supernova

    NASA Astrophysics Data System (ADS)

    Blinnikov, S. I.; Röpke, F. K.; Sorokina, E. I.; Gieseler, M.; Reinecke, M.; Travaglio, C.; Hillebrandt, W.; Stritzinger, M.

    2006-07-01

    Aims.We present synthetic bolometric and broad-band UBVRI light curves of SNe Ia for four selected 3D deflagration models of thermonuclear supernovae. Methods: .The light curves are computed with the 1D hydro code stella, which models (multi-group time-dependent) non-equilibrium radiative transfer inside SN ejecta. Angle-averaged results from 3D hydrodynamical explosion simulations with the composition determined in a nucleosynthetic postprocessing step served as the input to the radiative transfer model. Results: .The predicted model {UBV} light curves do agree reasonably well with the observed ones for SNe Ia in the range of low to normal luminosities, although the underlying hydrodynamical explosion models produced only a modest amount of radioactive {}56Ni(i.e. 0.24-0.42 M⊙) and relatively low kinetic energy in the explosion (less than 0.7 × 1051 erg). The evolution of predicted B and V fluxes in the model with a {}56Nimass of 0.42 M⊙ follows the observed decline rate after the maximum very well, although the behavior of fluxes in other filters deviates somewhat from observations, and the bolometric decline rate is a bit slow. The material velocity at the photospheric level is on the order of 104 km s-1 for all models. Using our models, we check the validity of Arnett's rule, relating the peak luminosity to the power of the deposited radioactive heating, and we also check the accuracy of the procedure for extracting the {}56Nimass from the observed light curves. Conclusions: .We find that the comparison between theoretical light curves and observations provides a useful tool to validate SN Ia models. The steps necessary for improving the agreement between theory and observations are set out.

  6. Unsupervised Transient Light Curve Analysis via Hierarchical Bayesian Inference

    NASA Astrophysics Data System (ADS)

    Sanders, N. E.; Betancourt, M.; Soderberg, A. M.

    2015-02-01

    Historically, light curve studies of supernovae (SNe) and other transient classes have focused on individual objects with copious and high signal-to-noise observations. In the nascent era of wide field transient searches, objects with detailed observations are decreasing as a fraction of the overall known SN population, and this strategy sacrifices the majority of the information contained in the data about the underlying population of transients. A population level modeling approach, simultaneously fitting all available observations of objects in a transient sub-class of interest, fully mines the data to infer the properties of the population and avoids certain systematic biases. We present a novel hierarchical Bayesian statistical model for population level modeling of transient light curves, and discuss its implementation using an efficient Hamiltonian Monte Carlo technique. As a test case, we apply this model to the Type IIP SN sample from the Pan-STARRS1 Medium Deep Survey, consisting of 18,837 photometric observations of 76 SNe, corresponding to a joint posterior distribution with 9176 parameters under our model. Our hierarchical model fits provide improved constraints on light curve parameters relevant to the physical properties of their progenitor stars relative to modeling individual light curves alone. Moreover, we directly evaluate the probability for occurrence rates of unseen light curve characteristics from the model hyperparameters, addressing observational biases in survey methodology. We view this modeling framework as an unsupervised machine learning technique with the ability to maximize scientific returns from data to be collected by future wide field transient searches like LSST.

  7. The rising light curves of Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Firth, R. E.; Sullivan, M.; Gal-Yam, A.; Howell, D. A.; Maguire, K.; Nugent, P.; Piro, A. L.; Baltay, C.; Feindt, U.; Hadjiyksta, E.; McKinnon, R.; Ofek, E.; Rabinowitz, D.; Walker, E. S.

    2015-02-01

    We present an analysis of the early, rising light curves of 18 Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory and the La Silla-QUEST variability survey. We fit these early data flux using a simple power law (f(t) = α × tn) to determine the time of first light (t0), and hence the rise time (trise) from first light to peak luminosity, and the exponent of the power-law rise (n). We find a mean uncorrected rise time of 18.98 ± 0.54 d, with individual supernova (SN) rise times ranging from 15.98 to 24.7 d. The exponent n shows significant departures from the simple `fireball model' of n = 2 (or f(t) ∝ t2) usually assumed in the literature. With a mean value of n = 2.44 ± 0.13, our data also show significant diversity from event to event. This deviation has implications for the distribution of 56Ni throughout the SN ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The range of n found also confirms that the 56Ni distribution is not standard throughout the population of SNe Ia, in agreement with earlier work measuring such abundances through spectral modelling. We also show that the duration of the very early light curve, before the luminosity has reached half of its maximal value, does not correlate with the light-curve shape or stretch used to standardize SNe Ia in cosmological applications. This has implications for the cosmological fitting of SN Ia light curves.

  8. Inferring asymmetric limb cloudiness on exoplanets from transit light curves

    NASA Astrophysics Data System (ADS)

    von Paris, P.; Gratier, P.; Bordé, P.; Leconte, J.; Selsis, F.

    2016-05-01

    Context. Clouds have been shown to be present in many exoplanetary atmospheres. Cloud formation modeling predicts considerable inhomogeneities of cloud cover, consistent with optical phase curve observations. However, optical phase curves cannot resolve some existing degeneracies between cloud location and cloud optical properties. Aims: We present a conceptually simple technique for detecting inhomogeneous cloud cover on exoplanets. Such an inhomogeneous cloud cover produces an asymmetric primary transit of the planet in front of the host star. Asymmetric transits produce characteristic residuals that are different from standard symmetric models. Furthermore, bisector spans can be used to determine asymmetries in the transit light curve. Methods: We apply a model of asymmetric transits to the light curves of HAT-P-7b, Kepler-7b, and HD 209458b and search for possible cloud signatures. The nearly uninterrupted Kepler photometry is particularly well suited for this method since it allows for a very high time resolution. Results: We do not find any statistically sound cloud signature in the data of the considered planets. For HAT-P-7b, a tentative detection of an asymmetric cloud cover is found, consistent with analysis of the optical phase curve. Based on Bayesian probability arguments, a symmetric model with an offset in the transit ephemeris is still the most viable model. This work demonstrates that for suitable targets, namely low-gravity planets around bright stars, the method can be used to constrain cloud cover characteristics and is thus a helpful additional tool for the study of exoplanetary atmospheres.

  9. Fractal analysis of light curves for the microquasar GX 339-4

    NASA Astrophysics Data System (ADS)

    Prosvetov, A. V.; Grebenev, S. A.

    2014-11-01

    Results of a fractal analysis of the X-ray light curves from accreting black holes in low-mass binary systems are presented for the object GX 339-4 as an example. The fractal dimension of the light curves is shown to be strongly dependent on the presence of quasi-periodic oscillations (QPOs) in the observations. A correlation between the fractal dimension of the light curves and the frequency of the QPO peak has been revealed. A method supplementary to a Fourier analysis that allows the pattern of accretion disk emission as a function of time scales to be investigated is proposed. The results of this analysis can be explained if the accretion disk is separated by the QPO region into two zones with different emission parameters.

  10. Using comet light-curve asymmetries to predict comet returns

    NASA Astrophysics Data System (ADS)

    Festou, M.; Rickman, H.; Kamel, L.

    1990-05-01

    The gravitational attractions of the sun and planets do not account completely for the orbital motions of short-period comets. To clarify the roles of the radial and transverse components of the nongravitational force on such comets, observational data on gas production rates from the comets are used here as a diagnostic of the force. The shapes of the production curves, based mostly on visual light curves, correlate very well with the nongravitational delays or advances of a number of comets. This correlation is used here to predict a substantial advance of the recent perihelion passage of comet P/Brorsen-Metcalf, as verified by observations.

  11. X-ray afterglow light curves : toward standard candle ?

    NASA Astrophysics Data System (ADS)

    Gendre, B.; Galli, A.; Boër, M.

    2007-07-01

    We investigate the clustering of afterglow light curves observed in X-ray and in optical before the launch of SWIFT in light of SWIFT observations. We have constructed a sample of 34 bursts with known distance and X-ray afterglow. This sample includes bursts observed by BeppoSAX, XMM-Newton, Chandra, and SWIFT. We correct the light curves for cosmological effects and compare the observed X-ray fluxes at 1 day after the burst. We check if there is any correlation between the observed flux and the burst spectral and temporal properties. We find that X-ray afterglow light curves cluster in luminosity, even in the SWIFT era. We show that this clustering is due only to the afterglow, and that the inclusion of prompt-related data broaden the distribution and hide the clustering. The same clustering is observed in optical, and we found three sub-division between optical and X-ray bright afterglows, dim ones, and optically bright -X-ray dim ones. We argue that the observed optical and X-ray clustering are related to the fireball total energy, the external medium density, the fraction of fireball energy going in relativistic electrons and magnetic fields. These parameters are either all fixed to a standard value, or all linked together.

  12. SDO/AIA Light Curves and Implications for Coronal Heating: Model Predictions

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.; Viall, Nicholeen M.

    2010-01-01

    It seems largely agreed that many coronal loops---those observed at a temperature of about 1 MK---are bundles of unresolved strands that are heated by storms of impulsive nanoflares. The nature of coronal heating in hotter loops and in the very important but largely ignored diffuse component of active regions is much less clear. Is it also impulsive or is it quasi steady? The spectacular new data from the Atmospheric Imaging Assembly (AIA) telescopes on the Solar Dynamics Observatory (SDO) offer an excellent opportunity to address this question. We analyze the light curves of coronal loops and the diffuse corona in 6 different AIA channels and compare them with the predicted light curves from theoretical models. Light curves in the different AIA channels reach their peak intensities with predictable orderings as a function the nanoflare storm properties. We show that while some sets of light curves exhibit clear evidence of cooling after nanoflare storms, other cases are less straightforward to interpret. Complications arise because of line-of-sight integration through many different structures, the broadband nature of the AIA channels, and because physical properties can change substantially depending on the magnitude of the energy release. Nevertheless, the light curves exhibit predictable and understandable patterns. This presentation emphasizes the modeling aspects of our study. A companion presentation emphasizes the observations.

  13. Imaging Starspots on LO Pegasi via Light-curve Inversion

    NASA Astrophysics Data System (ADS)

    Harmon, Robert O.; Deskins, R.; Vutisalchavakul, N.

    2007-12-01

    We present maps of the star LO Pegasi obtained via Light-curve Inversion, a computational technique which produces an image of a star's surface features based on variations in the star's observed brightness as dark starspots rotate into and out of view from Earth. LO Pegasi is a rapidly rotating (P=10.17 hr) K8V young solar analog. We inverted BVRI light curves obtained from CCD images acquired on July 7-9 and July 22-23, 2007 at Perkins Observatory in Delaware, OH. Using multiple filters significantly improves the latitude resolution of our maps. Our inversions revealed the presence of a large mid-latitude spot or spotted region on the map from July 7-9, which appears to have evolved into a more complex two-spot configuration by July 22-23. The authors wish to acknowledge the support of the NSF REU Program and the Ohio Wesleyan University Summer Science Research Program.

  14. Multi-wavelength analysis of Ellerman Bomb Light Curves

    NASA Astrophysics Data System (ADS)

    Herlender, M.; Berlicki, A.

    We present the results of a multi-wavelength photometric analysis of Ellerman Bomb (EB) observations obtained from the Dutch Open Telescope. In our data we have found 6 EBs located in the super-penumbra of the main spot in the active region NOAA 10781. We present light curves of EB observed in the Hα line centre and wing +0.7 Å, in the Ca II H line centre and wing~+2.35 Å, in the G-band and in the TRACE 1600 Å filter. We have shown that EBs were visible in the G-band and moreover, there was a good correlation between the light curves in the G-band and in the Hα line wings. We also found quasi-periodic oscillations of EBs brightness in the G-band, CaII H line and TRACE 1600 Å filter.

  15. Enhancements of Bayesian Blocks; Application to Large Light Curve Databases

    NASA Technical Reports Server (NTRS)

    Scargle, Jeff

    2015-01-01

    Bayesian Blocks are optimal piecewise linear representations (step function fits) of light-curves. The simple algorithm implementing this idea, using dynamic programming, has been extended to include more data modes and fitness metrics, multivariate analysis, and data on the circle (Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations, Scargle, Norris, Jackson and Chiang 2013, ApJ, 764, 167), as well as new results on background subtraction and refinement of the procedure for precise timing of transient events in sparse data. Example demonstrations will include exploratory analysis of the Kepler light curve archive in a search for "star-tickling" signals from extraterrestrial civilizations. (The Cepheid Galactic Internet, Learned, Kudritzki, Pakvasa1, and Zee, 2008, arXiv: 0809.0339; Walkowicz et al., in progress).

  16. Describing Blazhko light curves with almost periodic functions

    NASA Astrophysics Data System (ADS)

    Benko, J. M.; Szabo, R.

    2016-05-01

    Recent results of photometric space missions such as CoRoT and Kepler showed that the cycle-to-cycle variations of the Blazhko modulation is very frequent. These variations have either multiperiodic or irregular (chaotic/stochastic) nature. We present a mathematical framework in which all of these variations can be handled. We applied the theory of band-limited almost periodic functions to the modulated RR Lyrae light curves. It yields several interesting results: e.g. the harmonics in the Fourier representation of these functions are not exact multiplets of the base frequency or the modulation function depends on the harmonics. Such phenomena are reported for observed RR Lyrae stars as well showing that the almost periodic functions are promising in the mathematical description of the Blazhko RR Lyrae light curves.

  17. THE LOS ALAMOS SUPERNOVA LIGHT-CURVE PROJECT: COMPUTATIONAL METHODS

    SciTech Connect

    Frey, Lucille H.; Even, Wesley; Hungerford, Aimee L.; Whalen, Daniel J.; Fryer, Chris L.; Fontes, Christopher J.; Colgan, James

    2013-02-15

    We have entered the era of explosive transient astronomy, in which current and upcoming real-time surveys such as the Large Synoptic Survey Telescope, the Palomar Transient Factory, and the Panoramic Survey Telescope and Rapid Response System will detect supernovae in unprecedented numbers. Future telescopes such as the James Webb Space Telescope may discover supernovae from the earliest stars in the universe and reveal their masses. The observational signatures of these astrophysical transients are the key to unveiling their central engines, the environments in which they occur, and to what precision they will pinpoint cosmic acceleration and the nature of dark energy. We present a new method for modeling supernova light curves and spectra with the radiation hydrodynamics code RAGE coupled with detailed monochromatic opacities in the SPECTRUM code. We include a suite of tests that demonstrate how the improved physics and opacities are indispensable to modeling shock breakout and light curves when radiation and matter are tightly coupled.

  18. The first light curve analysis of eclipsing binary NR Cam

    NASA Astrophysics Data System (ADS)

    Tavakkoli, F.; Hasanzadeh, A.; Poro, A.

    2015-05-01

    New observations of the eclipsing binary system NR Cam were carried out using a CCD in B, V, and R filters and new times of light minimum and new ephemeris were obtained. The B, V, and R light curves were analyzed using both the Binary Maker 3.0 and PHOEBE 0.31 programs to determine some geometrical and physical parameters of the system. These results show that NR Cam is an overcontact binary and that both components are Main Sequence stars. The O'Connell effect on NR Cam was studied and some variations in spot parameters were obtained over the different years.

  19. CALCULATING TIME LAGS FROM UNEVENLY SAMPLED LIGHT CURVES

    SciTech Connect

    Zoghbi, A.; Reynolds, C.; Cackett, E. M.

    2013-11-01

    Timing techniques are powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency- and energy-dependent time lags as tools for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved due to the evenly sampled light curves obtained using XMM-Newton. Continuously sampled data are, however, not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al., we discuss and use a maximum likelihood method to obtain frequency-dependent lags that takes into account light curve gaps. Instead of calculating the lag directly, the method estimates the most likely lag values at a particular frequency given two observed light curves. We use Monte Carlo simulations to assess the method's applicability and use it to obtain lag-energy spectra from Suzaku data for two objects, NGC 4151 and MCG-5-23-16, that had previously shown signatures of iron K reverberation. The lags obtained are consistent with those calculated using standard methods using XMM-Newton data.

  20. A Degeneracy in DRW Modelling of AGN Light Curves

    NASA Astrophysics Data System (ADS)

    Kozłowski, Szymon

    2016-04-01

    Individual light curves of active galactic nuclei (AGNs) are nowadays successfully modelled with the damped random walk (DRW) stochastic process, characterized by the power exponential covariance matrix of the signal, with the power β = 1. By Monte Carlo simulation means, we generate mock AGN light curves described by non-DRW stochastic processes (0.5 ≤ β ≤ 1.5 and β ≠ 1) and show they can be successfully and well-modelled as a single DRW process, obtaining comparable goodness of fits. A good DRW fit, in fact, may not mean that DRW is the true underlying process leading to variability and it cannot be used as a proof for it. When comparing the input (non-DRW) and measured (DRW) process parameters, the recovered time scale (amplitude) increases (decreases) with the increasing input β. In practice, this means that the recovered DRW parameters may lead to biased (or even non-existing) correlations of the variability and physical parameters of AGNs if the true AGN variability is caused by non-DRW stochastic processes. The proper way of identifying the processes leading to variability are model-independent structure functions and/or power spectral densities and then using such information on the covariance matrix of the signal in light curve modelling.

  1. PAIR INSTABILITY SUPERNOVAE: LIGHT CURVES, SPECTRA, AND SHOCK BREAKOUT

    SciTech Connect

    Kasen, Daniel; Woosley, S. E.; Heger, Alexander

    2011-06-20

    For the initial mass range (140 M{sub sun} < M < 260 M{sub sun}) stars die in a thermonuclear runaway triggered by the pair-production instability. The supernovae they make can be remarkably energetic (up to {approx}10{sup 53} erg) and synthesize considerable amounts of radioactive isotopes. Here we model the evolution, explosion, and observational signatures of representative pair instability supernovae (PI SNe) spanning a range of initial masses and envelope structures. The predicted light curves last for hundreds of days and range in luminosity from very dim to extremely bright (L {approx} 10{sup 44} erg s{sup -1}). The most massive events are bright enough to be seen at high redshift, but the extended light curve duration ({approx}1 yr)-prolonged by cosmological time-dilation-may make it difficult to detect them as transients. A more promising approach may be to search for the brief and luminous outbreak occurring when the explosion shock wave first reaches the stellar surface. Using a multi-wavelength radiation-hydrodynamics code we calculate that, in the rest frame, the shock breakout transients of PI SNe reach luminosities of 10{sup 45}-10{sup 46} erg s{sup -1}, peak at wavelengths {approx}30-170 A, and last for several hours. We discuss how observations of the light curves, spectra, and breakout emission can be used to constrain the mass, radius, and metallicity of the progenitor.

  2. A degeneracy in DRW modelling of AGN light curves

    NASA Astrophysics Data System (ADS)

    Kozłowski, Szymon

    2016-07-01

    Individual light curves of active galactic nuclei (AGNs) are nowadays successfully modelled with the damped random walk (DRW) stochastic process, characterized by the power exponential covariance matrix of the signal, with the power β = 1. By Monte Carlo simulation means, we generate mock AGN light curves described by non-DRW stochastic processes (0.5 ≤ β ≤ 1.5 and β ≠ 1) and show they can be successfully and well modelled as a single DRW process, obtaining comparable goodness of fits. A good DRW fit, in fact, may not mean that DRW is the true underlying process leading to variability and it cannot be used as a proof for it. When comparing the input (non-DRW) and measured (DRW) process parameters, the recovered time-scale (amplitude) increases (decreases) with the increasing input β. In practice, this means that the recovered DRW parameters may lead to biased (or even non-existing) correlations of the variability and physical parameters of AGNs if the true AGN variability is caused by non-DRW stochastic processes. The proper way of identifying the processes leading to variability are model-independent structure functions and/or power spectral densities and then using such information on the covariance matrix of the signal in light-curve modelling.

  3. New Horizons approach photometry of Pluto and Charon: light curves and Solar phase curves

    NASA Astrophysics Data System (ADS)

    Zangari, A. M.; Buie, M. W.; Buratti, B. J.; Verbiscer, A.; Howett, C.; Weaver, H. A., Jr.; Olkin, C.; Ennico Smith, K.; Young, L. A.; Stern, S. A.

    2015-12-01

    While the most captivating images of Pluto and Charon were shot by NASA's New Horizons probe on July 14, 2015, the spacecraft also imaged Pluto with its LOng Range Reconnaissance Imager ("LORRI") during its Annual Checkouts and Approach Phases, with campaigns in July 2013, July 2014, January 2015, March 2015, April 2015, May 2015 and June 2015. All but the first campaign provided full coverage of Pluto's 6.4 day rotation. Even though many of these images were taken when surface features on Pluto and Charon were unresolved, these data provide a unique opportunity to study Pluto over a timescale of several months. Earth-based data from an entire apparition must be combined to create a single light curve, as Pluto is never otherwise continuously available for observing due to daylight, weather and scheduling. From the spacecraft, Pluto's sub-observer latitude remained constant to within 0.05 degrees of 43.15 degrees, comparable to a week's worth of change as seen from Earth near opposition. During the July 2013 to June 2015 period, Pluto's solar phase curve increased from 11 degrees to 15 degrees, a small range, but large compared to Earth's 2 degree limit. The slope of the solar phase curve hints at properties such as surface roughness. Using PSF photometry that takes into account the ever-increasing sizes of Pluto and Charon as seen from New Horizons, as well as surface features discovered at closest approach, we present rotational light curves and solar phase curves of Pluto and Charon. We will connect these observations to previous measurements of the system from Earth.

  4. Neutral versus charged defect patterns in curved crystals.

    PubMed

    Azadi, Amir; Grason, Gregory M

    2016-07-01

    Characterizing the complex spectrum of topological defects in ground states of curved crystals is a long-standing problem with wide implications, from the mathematical Thomson problem to diverse physical realizations, including fullerenes and particle-coated droplets. While the excess number of "topologically charged" fivefold disclinations in a closed, spherical crystal is fixed, here we study the elementary transition from defect-free, flat crystals to curved crystals possessing an excess of "charged" disclinations in their bulk. Specifically, we consider the impact of topologically neutral patterns of defects-in the form of multidislocation chains or "scars" stable for small lattice spacing-on the transition from neutral to charged ground-state patterns of a crystalline cap bound to a spherical surface. Based on the asymptotic theory of caps in continuum limit of vanishing lattice spacing, we derive the morphological phase diagram of ground-state defect patterns, spanned by surface coverage of the sphere and forces at the cap edge. For the singular limit of zero edge forces, we find that scars reduce (by half) the threshold surface coverage for excess disclinations. Even more significant, scars flatten the geometric dependence of excess disinclination number on Gaussian curvature, leading to a transition between stable "charged" and "neutral" patterns that is, instead, critically sensitive to the compressive vs tensile nature of boundary forces on the cap. PMID:27575209

  5. Finding Every Stellar Flare in the Kepler Light Curves

    NASA Astrophysics Data System (ADS)

    Davenport, James R. A.

    2016-01-01

    Data from the Kepler and K2 missions continue to challenge our understanding of stellar activity, from complex morphologies of flares on low-mass stars, to rates of "superflares" on stars like the Sun. I will present results from the first uniform search for stellar flares in every Kepler light curve. This is the largest sample of white-light stellar flares ever assembled. Our analysis includes long- and short-cadence data from over 200,000 stars, and will shed light on the possibility of using flares as a stellar age indicator. I will also describe the exciting prospects that K2, TESS, and LSST hold for studying stellar flares in a Galactic context.

  6. Light curves from supernova shock breakout through an extended wind

    SciTech Connect

    Ginzburg, Sivan; Balberg, Shmuel

    2014-01-01

    Recent observations suggest that some supernovae may be the result of an explosion into an optically thick circumstellar material, the product of pre-explosion mass loss (wind) by the progenitor star. This scenario has been studied previously both analytically and numerically. However, many previous studies base their analysis on the diffusion approximation for radiation transfer, which is inappropriate in the optically thin outer layers of the wind. Here we study the deviations from diffusion and calculate light curves more accurately using a Monte Carlo approach to photon transfer. We distinguish between 'compact' winds, for which the diffusion approximation is appropriate, and 'extended' winds, which require a more delicate treatment of the radiation. We show that this effect is more significant than that of the light-travel time difference to a distant observer, which has a secondary influence on the light curves of extended-wind systems. We also comment on the applicability of the widely used flux-limited diffusion approximation in this context: we find that it generally does not reproduce the Monte Carlo results. The flux-limited diffusion approximation leads to results that are not only quantitatively but also qualitatively wrong in the extended-wind regime.

  7. Observations of fuors. I. Light curve of V 1057 Cyg

    SciTech Connect

    Ibragimov, M.A.; Shevchenko, V.S.

    1988-01-01

    The photographic magnitudes m/sub pg/, m/sub pv/, m/sub pr/ of the fuor V 1057 Cyg obtained during the period July 1968-August 1970 and photoelectric UBVRI' observations during the period July 1078-December 1985 are given. At the time of the rise and the light maximum of V 1057 Cyg, 26 estimates were obtained of m/sub pg/, 20 of m/sub pv/, and three of m/sub pr/. The color index upper limit V - I < 3.5 was obtained in the pre-outburst epoch. Analysis of the B, V, R light curves obtained from 300 observation nights reveals a periodic component in the small-scale light curve with a period of about 12 days and an amplitude of about 0.1 V. There has been a further slowing down in the rate of decrease of the brightness: from 1982 through 1986 the brightness of V 1057 Cyg did not decrease by more than O.2 V, whereas during the preceding four years the decrease in the brightness was ..delta..V > 0.4.

  8. Light-Curve Survey of Jupiter Trojan Asteroids

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Melita, M.; Ortiz, J. L.; Licandro, J.; Williams, I. P.; Jones, D.

    2008-09-01

    Trojan asteroids are an interesting population of minor bodies due to their dynamical characteristics, their physical properties and that they are relatively isolated located at the snow-line The main hypotheses about the origin of the Jupiter Trojans assumed that they formed either during the final stages of the planetary formation (Marzari & Scholl 1998), or during the epoch of planetary migration (Morbidelli et al. 2005), in any case more than 3.8 Gy. ago. The dynamical configuration kept the Trojans isolated from the asteroid Main Belt throughout the history of the Solar System. In spite of eventual interactions with other populations of minor bodies like the Hildas, the Jupiter family comets, and the Centaurs, their collisional evolution has been dictated mostly by the intrapopulation collisions (Marzari et al. 1996, 1997). Therefore, the Jupiter Trojans may be considered primordial bodies, whose dynamical and physical properties can provide important clues about the environment of planetary formation. The available sample of Jupiter Trojans light-curves is small and mainly restricted to the largest objects. According to the MPC-website (updated last in March 2006), the present sample of rotation periods and light-curve-amplitudes of the Jupiter Trojan asteroids is composed by 25 objects with some information about their periods and by 10 of them with only an amplitude estimation. A survey of contact binary Trojan asteroids has been done by Mann et al. 2007, where they have recorded more than 100 amplitudes from sparse-sampled light-curves and very-wellresolved rotational periods. More than 2000 Trojan asteroids have been discovered up to date, so, there is an urgent need to enlarge the sample of intrinsic rotation periods and accurate light-curve amplitudes and to extend it to smaller sizes. Results and Discusions We requested 26 nights of observation in the second semester of 2007, to begin with the survey. They were scheduled for the following instruments

  9. Marginalizing Instrument Systematics in HST WFC3 Transit Light Curves

    NASA Astrophysics Data System (ADS)

    Wakeford, H. R.; Sing, D. K.; Evans, T.; Deming, D.; Mandell, A.

    2016-03-01

    Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7 μm probe primarily the H2O absorption band at 1.4 μm, and have provided low-resolution transmission spectra for a wide range of exoplanets. We present the application of marginalization based on Gibson to analyze exoplanet transit light curves obtained from HST WFC3 to better determine important transit parameters such as Rp/R*, which are important for accurate detections of H2O. We approximate the evidence, often referred to as the marginal likelihood, for a grid of systematic models using the Akaike Information Criterion. We then calculate the evidence-based weight assigned to each systematic model and use the information from all tested models to calculate the final marginalized transit parameters for both the band-integrated and spectroscopic light curves to construct the transmission spectrum. We find that a majority of the highest weight models contain a correction for a linear trend in time as well as corrections related to HST orbital phase. We additionally test the dependence on the shift in spectral wavelength position over the course of the observations and find that spectroscopic wavelength shifts {δ }λ (λ ) best describe the associated systematic in the spectroscopic light curves for most targets while fast scan rate observations of bright targets require an additional level of processing to produce a robust transmission spectrum. The use of marginalization allows for transparent interpretation and understanding of the instrument and the impact of each systematic evaluated statistically for each data set, expanding the ability to make true and comprehensive comparisons between exoplanet atmospheres.

  10. Transit light curves with finite integration time: Fisher information analysis

    SciTech Connect

    Price, Ellen M.; Rogers, Leslie A.

    2014-10-10

    Kepler has revolutionized the study of transiting planets with its unprecedented photometric precision on more than 150,000 target stars. Most of the transiting planet candidates detected by Kepler have been observed as long-cadence targets with 30 minute integration times, and the upcoming Transiting Exoplanet Survey Satellite will record full frame images with a similar integration time. Integrations of 30 minutes affect the transit shape, particularly for small planets and in cases of low signal to noise. Using the Fisher information matrix technique, we derive analytic approximations for the variances and covariances on the transit parameters obtained from fitting light curve photometry collected with a finite integration time. We find that binning the light curve can significantly increase the uncertainties and covariances on the inferred parameters when comparing scenarios with constant total signal to noise (constant total integration time in the absence of read noise). Uncertainties on the transit ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4 for Jupiter-size planets around Sun-like stars for integration times of 30 minutes compared to instantaneously sampled light curves. Similarly, uncertainties on the mid-transit time for Earth and Jupiter-size planets increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are largely unaffected by finite integration times. While correlations among the transit depth, ingress duration, and transit duration all increase in magnitude with longer integration times, the mid-transit time remains uncorrelated with the other parameters. We provide code in Python and Mathematica for predicting the variances and covariances at www.its.caltech.edu/∼eprice.

  11. Classification of CoRoT Exoplanet Light Curves

    NASA Astrophysics Data System (ADS)

    Sarro, L. M.; Debosscher, J.; Aerts, C.

    2006-11-01

    We describe the methodology developed for the classification of the exoplanet light curves to be assembled by the CoRoT space mission. A supervised classification method will be used to deliver the N3 data products to the CoRoT Additional Programme community. Unsupervised classification will also be performed, but at a later stage of the mission. In the current paper, we provide the class definitions and attributes under consideration for the fast supervised classification. These definitions and attributes will be improved after each long run of CoRoT.

  12. Light curve solutions of the ultrashort-period Kepler binaries

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Dimitrov, D.

    2015-02-01

    We carried out light curve solutions of the ultrashort-period binaries with MS components observed by $Kepler$. All six targets turned out almost in thermal contact with contact or slightly overcontact configurations. Two of them, KID 4921906 and KID 6309193, are not eclipsing but reveal ellipsoidal and spot variability. One of the components of KID 8108785 exhibits inherent, quasi-sinusoidal, small-amplitude variability. KID 12055255 turned out a very rare case of ultrashort-period overcontact binary consisting of two M dwarfs. Our modeling indicated that the variability of KID 9532219 is due to eclipses but not to $\\delta$ Sct pulsations as it was previously supposed.

  13. A new approach to the analysis of Mira light curves

    NASA Technical Reports Server (NTRS)

    Mennessier, M. O.; Barthes, D.; Mattei, J. A.

    1990-01-01

    Two different but complementary methods for predicting Mira luminosities are presented. One method is derived from a Fourier analysis, it requires performing deconvolution, and its results are not certain due to the inherent instability of deconvolution problems. The other method is a learning method utilizing artificial intelligence techniques where a light curve is presented as an ordered sequence of pseudocycles, and rules are learned by linking the characteristics of several consecutive pseudocycles to one characteristic of the future cycle. It is observed that agreement between these methods is obtainable when it is possible to eliminate similar false frequencies from the preliminary power spectrum and to improve the degree of confidence in the rules.

  14. Variability in GRB light curves: Introducing Orthogonal Matching Pursuit

    NASA Astrophysics Data System (ADS)

    Dereli, Husne; Bégué, Damien; Ryde, Felix

    2016-07-01

    Constraining the variability of GRBs is important as it is one of the few keys to estimate many unknown parameters, such as the emission radius, the Lorentz factor, the size of the progenitor. In this work, we introduced the Orthogonal Matching Pursuit (OMP) method to study GRB light curves and to compute the minimum time variability of GRBs. Commonly used in medical sciences, this method reconstructs a signal by choosing among predefined functional shapes. We will discuss the implementation of the code, and compare its performances with those of other dedicated methods (Haar wavelet analysis, peak finding algorithm and step wise filter correlation).

  15. The Interesting Light Curve and Pulsation Frequencies of KIC 9204718

    NASA Astrophysics Data System (ADS)

    Turner, G.; Holaday, J.

    2013-06-01

    In previous work by Uytterhoeven et al. (2011) the Kepler object KIC 9204718 (HD 176843) was identified as a binary system with a d Scuti-type component. Both long- and short-cadence data were obtained from the MAST archive and analyzed. In this paper we show the results of period analysis on one quarter of short-cadence data in which were obtained two pulsation periods, the dominant of which has a period of 0.026479 day and the secondary of 0.029068 day, respectively. We also present the interesting light curve of the object over several quarters of long-cadence data sets.

  16. Hilbert-Curve Fractal Antenna With Radiation- Pattern Diversity

    NASA Technical Reports Server (NTRS)

    Nessel, James A.; Miranda, Felix A.; Zaman, Afroz

    2007-01-01

    A printed, folded, Hilbert-curve fractal microwave antenna has been designed and built to offer advantages of compactness and low mass, relative to other antennas designed for the same operating frequencies. The primary feature of the antenna is that it offers the advantage of radiation-pattern diversity without need for electrical or mechanical switching: it can radiate simultaneously in an end-fire pattern at a frequency of 2.3 GHz (which is in the S-band) and in a broadside pattern at a frequency of 16.8 GHz (which is in the Ku-band). This radiation-pattern diversity could be utilized, for example, in applications in which there were requirements for both S-band ground-to-ground communications and Ku-band ground-to-aircraft or ground-to-spacecraft communications. The lack of switching mechanisms or circuitry makes this antenna more reliable, easier, and less expensive to fabricate than it otherwise would be.

  17. Broadband turbulent spectra in gamma-ray burst light curves

    SciTech Connect

    Van Putten, Maurice H. P. M.; Guidorzi, Cristiano; Frontera, Filippo

    2014-05-10

    Broadband power density spectra offer a window to understanding turbulent behavior in the emission mechanism and, at the highest frequencies, in the putative inner engines powering long gamma-ray bursts (GRBs). We describe a chirp search method alongside Fourier analysis for signal detection in the Poisson noise-dominated, 2 kHz sampled, BeppoSAX light curves. An efficient numerical implementation is described in O(Nnlog n) operations, where N is the number of chirp templates and n is the length of the light-curve time series, suited for embarrassingly parallel processing. For the detection of individual chirps over a 1 s duration, the method is one order of magnitude more sensitive in signal-to-noise ratio than Fourier analysis. The Fourier-chirp spectra of GRB 010408 and GRB 970816 show a continuation of the spectral slope with up to 1 kHz of turbulence identified in low-frequency Fourier analysis. The same continuation is observed in an average spectrum of 42 bright, long GRBs. An outlook on a similar analysis of upcoming gravitational wave data is included.

  18. SIMULATED PERFORMANCE OF TIMESCALE METRICS FOR APERIODIC LIGHT CURVES

    SciTech Connect

    Findeisen, Krzysztof; Hillenbrand, Lynne; Cody, Ann Marie

    2015-01-10

    Aperiodic variability is a characteristic feature of young stars, massive stars, and active galactic nuclei. With the recent proliferation of time-domain surveys, it is increasingly essential to develop methods to quantify and analyze aperiodic variability. We develop three timescale metrics that have been little used in astronomy—Δm-Δt plots, peak-finding, and Gaussian process regression—and present simulations comparing their effectiveness across a range of aperiodic light curve shapes, characteristic timescales, observing cadences, and signal to noise ratios. We find that Gaussian process regression is easily confused by noise and by irregular sampling, even when the model being fit reflects the process underlying the light curve, but that Δm-Δt plots and peak-finding can coarsely characterize timescales across a broad region of parameter space. We make public the software we used for our simulations, both in the spirit of open research and to allow others to carry out analogous simulations for their own observing programs.

  19. A Review of Correlated Noise in Exoplanet Light Curves

    NASA Astrophysics Data System (ADS)

    Cubillos, Patricio; Harrington, J.; Blecic, J.; Hardy, R. A.; Hardin, M.

    2013-10-01

    A number of the occultation light curves of exoplanets exhibit time-correlated residuals (a.k.a. correlated or red noise) in their model fits. The correlated noise might arise from inaccurate models or unaccounted astrophysical or telescope systematics. A correct assessment of the correlated noise is important to determine true signal-to-noise ratios of a planet's physical parameters. Yet, there are no in-depth statistical studies in the literature for some of the techniques currently used (RMS-vs-bin size plot, prayer beads, and wavelet-based modeling). We subjected these correlated-noise assessment techniques to basic tests on synthetic data sets to characterize their features and limitations. Initial results indicate, for example, that, sometimes the RMS-vs-bin size plots present artifacts when the bin size is similar to the observation duration. Further, the prayer beads doesn't correctly increase the uncertainties to compensate for the lack of accuracy if there is correlated noise. We have applied these techniques to several Spitzer secondary-eclipse hot-Jupiter light curves and discuss their implications. This work was supported in part by NASA planetary atmospheres grant NNX13AF38G and Astrophysics Data Analysis Program NNX12AI69G.

  20. The light curve of a transient X-ray source

    NASA Technical Reports Server (NTRS)

    Kaluzienski, L. J.; Holt, S. S.; Boldt, E. A.; Serlemitsos, P. J.; Eadie, G.; Pounds, K. A.; Ricketts, M. J.; Watson, M.

    1975-01-01

    The Ariel-5 satellite has monitored the X-ray light curve of A1524-62 almost continuously from 40 days prior to maximum light until its disappearance below the effective experimental sensitivity. The source exhibited maximum light on Dec. 4, 1974, at a level of 0.9 the apparent magnitude of the Crab Nebula in the energy band 3-6 keV. Although similar to previously reported transient sources with a decay time constant of about 2 months, the source exhibited an extended, variable preflare on-state of about 1 month at a level of greater than 0.1 maximum light. The four bright (greater than 0.2 of the Crab Nebula) transient sources observed during the first half-year of Ariel-5 operation are indicative of a galactic disk distribution, a luminosity at maximum in excess of 10 to the 37-th power ergs/sec, a frequency of occurrence which may be as high as 100/yr, and a median decay time which is less than 1 month.

  1. Testing the recovery of stellar rotation signals from Kepler light curves using a blind hare-and-hounds exercise

    NASA Astrophysics Data System (ADS)

    Aigrain, S.; Llama, J.; Ceillier, T.; Chagas, M. L. das; Davenport, J. R. A.; García, R. A.; Hay, K. L.; Lanza, A. F.; McQuillan, A.; Mazeh, T.; de Medeiros, J. R.; Nielsen, M. B.; Reinhold, T.

    2015-07-01

    We present the results of a blind exercise to test the recoverability of stellar rotation and differential rotation in Kepler light curves. The simulated light curves lasted 1000 d and included activity cycles, Sun-like butterfly patterns, differential rotation and spot evolution. The range of rotation periods, activity levels and spot lifetime were chosen to be representative of the Kepler data of solar-like stars. Of the 1000 simulated light curves, 770 were injected into actual quiescent Kepler light curves to simulate Kepler noise. The test also included five 1000-d segments of the Sun's total irradiance variations at different points in the Sun's activity cycle. Five teams took part in the blind exercise, plus two teams who participated after the content of the light curves had been released. The methods used included Lomb-Scargle periodograms and variants thereof, autocorrelation function and wavelet-based analyses, plus spot modelling to search for differential rotation. The results show that the `overall' period is well recovered for stars exhibiting low and moderate activity levels. Most teams reported values within 10 per cent of the true value in 70 per cent of the cases. There was, however, little correlation between the reported and simulated values of the differential rotation shear, suggesting that differential rotation studies based on full-disc light curves alone need to be treated with caution, at least for solar-type stars. The simulated light curves and associated parameters are available online for the community to test their own methods.

  2. VizieR Online Data Catalog: V346 Cen multiwavelength light curves (Mayer+, 2016)

    NASA Astrophysics Data System (ADS)

    Mayer, P.; Harmanec, P.; Wolf, M.; Nemravova, J.; Prsa, A.; Fremat, Y.; Zejda, M.; Liska, J.; Jurysek, J.; Honkova, K.; Masek, M.

    2016-06-01

    We present photographic light curves from O'Connell (1939, Publications of the Riverview College Observatory, 2, 5), uvby light curves from Gimenez et al. (1986A&AS...66...45G), BVR light curves from 0.6 m reflector with a CCD camera, Mt. John, New Zealand, green light curve from Sonnar 4/135mm telephoto lens with a CCD ATIK16IC camera, Sutherland, South Africa and BVRI light curves from 0.3m Meade Schmidt-Cassegrain reflector with a CCD camera. (5 data files).

  3. OBSERVATIONS OF DOPPLER BOOSTING IN KEPLER LIGHT CURVES

    SciTech Connect

    Van Kerkwijk, Marten H.; Breton, Rene P.; Justham, Stephen; Rappaport, Saul A.; Podsiadlowski, Philipp; Han, Zhanwen

    2010-05-20

    Among the initial results from Kepler were two striking light curves, for KOI 74 and KOI 81, in which the relative depths of the primary and secondary eclipses showed that the more compact, less luminous object was hotter than its stellar host. That result became particularly intriguing because a substellar mass had been derived for the secondary in KOI 74, which would make the high temperature challenging to explain; in KOI 81, the mass range for the companion was also reported to be consistent with a substellar object. We re-analyze the Kepler data and demonstrate that both companions are likely to be white dwarfs. We also find that the photometric data for KOI 74 show a modulation in brightness as the more luminous star orbits, due to Doppler boosting. The magnitude of the effect is sufficiently large that we can use it to infer a radial velocity amplitude accurate to 1 km s{sup -1}. As far as we are aware, this is the first time a radial-velocity curve has been measured photometrically. Combining our velocity amplitude with the inclination and primary mass derived from the eclipses and primary spectral type, we infer a secondary mass of 0.22 {+-} 0.03 M{sub sun}. We use our estimates to consider the likely evolutionary paths and mass-transfer episodes of these binary systems.

  4. Video meteor light curve analysis of Orionids and Geminids and developing a method for obtaining the absolute light curves of shower meteors from the single station data

    NASA Astrophysics Data System (ADS)

    Grašić, L.; Milanović, N.; Pavlović, D.

    2016-01-01

    We developed a method for obtaining the absolute light curves of the shower meteors from single station video data. We found that even though the height of a meteor atmospheric trajectory obtained by using this method may have a large error, the absolute light curve shape is preserved. We used our method to calculate the F parameters of the Orionid and Geminid light curves. The light curves were obtained from the single station video data by the instrument with a limiting sensitivity of 3.5m. We found that for our sample of the light curves the zenith distance of meteor radiant does not affect the F parameter for either of the two showers. The value of F parameter of the Orionids obtained in this paper matches the values obtained by other authors, whilst for the Geminids it is significantly different.

  5. Improve angular dependence of emission intensity in top-emitting organic light-emitting devices by using curved surfaces as substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Yifan; Yang, Tong; Ou, Xiali; Gao, Qiang

    2016-03-01

    We have demonstrated an effective way to suppress the viewing angle dependence of the emission intensity of top-emitting organic light-emitting devices (TOLEDs) by fabricating devices on curved surfaces. From this approach, curved light emission surface has been obtained and TOLEDs with curved surface exhibit a relatively dispersed light emission pattern. As a result, the variation of emission intensity with viewing angles can be relieved. In addition, we can almost observe the same luminance and efficiency in OLEDs with and without curved surface light emission.

  6. Analysis of selected Kepler Mission planetary light curves

    NASA Astrophysics Data System (ADS)

    Rhodes, M. D.; Budding, E.

    2014-06-01

    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 http://exoplanetarchive.ipac.caltech.edu, 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, 2012), 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.

  7. GAMMA-RAY LIGHT CURVES FROM PULSAR MAGNETOSPHERES WITH FINITE CONDUCTIVITY

    SciTech Connect

    Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes

    2012-07-20

    We investigate the shapes of {gamma}-ray pulsar light curves using three-dimensional pulsar magnetosphere models of finite conductivity. These models, covering the entire spectrum of solutions between vacuum and force-free magnetospheres, for the first time afford mapping the GeV emission of more realistic, dissipative pulsar magnetospheres. To this end we generate model light curves following two different approaches: (1) We employ the emission patterns of the slot and outer gap models in the field geometries of magnetospheres with different conductivity {sigma}. (2) We define realistic trajectories of radiating particles in magnetospheres of different {sigma} and compute their Lorentz factor under the influence of magnetospheric electric fields and curvature radiation-reaction; with these at hand we then calculate the emitted radiation intensity. The light curves resulting from these prescriptions are quite sensitive to the value of {sigma}, especially in the second approach. While still not self-consistent, these results are a step forward in understanding the physics of pulsar {gamma}-radiation.

  8. Predicting Fundamental Stellar Parameters From Photometric Light Curves

    NASA Astrophysics Data System (ADS)

    Miller, Adam; Richards, J.; Bloom, J. S.; a larger Team

    2014-01-01

    We present a new machine-learning-based framework for the prediction of the fundamental stellar parameters, Teff, log g, and [Fe/H], based on the photometric light curves of variable stellar sources. The method was developed following a systematic spectroscopic survey of stellar variability. Variable sources were selected from repeated Sloan Digital Sky Survey (SDSS) observations of Stripe 82, and spectroscopic observations were obtained with Hectospec on the 6.5-m Multi-Mirror Telescope. In sum, spectra were obtained for ~9000 stellar variables (including ~3000 from the SDSS archive), for which we measured Teff, log g, and [Fe/H] using the Segue Stellar Parameters Pipeline (SSPP). Examining the full sample of ~67k variables in Stripe 82, we show that the vast majority of photometric variables are consistent with main-sequence stars, even after restricting the search to high galactic latitudes. From the spectroscopic sample we confirm that most of these stellar variables are G and K dwarfs, though there is a bias in the output of the SSPP that prevents the identification of M type variables. We are unable to identify the dominant source of variability for these stars, but eclipsing systems and/or star spots are the most likely explanation. We develop a machine-learning model that can determine Teff, log g, and [Fe/H] without obtaining a spectrum. Instead, the random-forest-regression model uses SDSS color information and light-curve features to infer stellar properties. We detail how the feature set is pruned and the model is optimized to produce final predictions of Teff, log g, and [Fe/H] with a typical scatter of 165 K, 0.42 dex, and 0.33 dex, respectively. We further show that for the subset of variables with at least 50 observations in the g band the typical scatter reduces to 75 K, 0.19 dex, and 0.16 dex, respectively. We consider these results an important step on the path to the efficient and optimal extraction of information from future time

  9. Predicting Fundamental Stellar Parameters from Photometric Light Curves

    NASA Astrophysics Data System (ADS)

    Miller, A.

    We present a new machine learning based framework for the prediction of the fun- damental stellar parameters, Teff, logg, and [Fe/H], based on the photometric light curves of variable stellar sources. The method was developed following a systematic spectroscopic survey of stellar variability. Variable sources were selected from re- peated Sloan Digital Sky Survey (SDSS) observations of Stripe 82, and spectroscopic observations were obtained with Hectospec on the 6.5-m Multi-Mirror Telescope. In sum, spectra were obtained for ˜9,000 stellar variables (including ˜3,000 from the SDSS archive), for which we measured Teff, log g, and [Fe/H] using the Segue Stellar Parameters Pipeline (SSPP). Examining the full sample of ˜67,000 variables in Stripe 82, we show that the vast majority of photometric variables are consistent with main-sequence stars, even after restricting the search to high galactic latitudes. From the spectroscopic sample we confirm that most of these stellar variables are G and K dwarfs, though there is a bias in the output of the SSPP that prevents the identification of M type variables. We are unable to identify the dominant source of variability for these stars, but eclipsing systems and/or star spots are the most likely explanation. We develop a machine learning model that can determine Teff , log g, and [Fe/H] without obtaining a spectrum. Instead, the random forest regression model uses SDSS color information and light curve features to infer stellar properties. We detail how the feature set is pruned and the model is optimized to produce final predictions of Teff, log g, and [Fe/H] with a typical scatter of 165 K, 0.42 dex, and 0.33 dex, respectively. We further show that for the subset of variables with at least 50 observations in the g band the typical scatter reduces to 75 K, 0.19 dex, and 0.16 dex, respectively. We consider these results an important step on the path to the efficient and optimal extraction of information from future time

  10. Supervised Detection of Anomalous Light Curves in Massive Astronomical Catalogs

    NASA Astrophysics Data System (ADS)

    Nun, Isadora; Pichara, Karim; Protopapas, Pavlos; Kim, Dae-Won

    2014-09-01

    The development of synoptic sky surveys has led to a massive amount of data for which resources needed for analysis are beyond human capabilities. In order to process this information and to extract all possible knowledge, machine learning techniques become necessary. Here we present a new methodology to automatically discover unknown variable objects in large astronomical catalogs. With the aim of taking full advantage of all information we have about known objects, our method is based on a supervised algorithm. In particular, we train a random forest classifier using known variability classes of objects and obtain votes for each of the objects in the training set. We then model this voting distribution with a Bayesian network and obtain the joint voting distribution among the training objects. Consequently, an unknown object is considered as an outlier insofar it has a low joint probability. By leaving out one of the classes on the training set, we perform a validity test and show that when the random forest classifier attempts to classify unknown light curves (the class left out), it votes with an unusual distribution among the classes. This rare voting is detected by the Bayesian network and expressed as a low joint probability. Our method is suitable for exploring massive data sets given that the training process is performed offline. We tested our algorithm on 20 million light curves from the MACHO catalog and generated a list of anomalous candidates. After analysis, we divided the candidates into two main classes of outliers: artifacts and intrinsic outliers. Artifacts were principally due to air mass variation, seasonal variation, bad calibration, or instrumental errors and were consequently removed from our outlier list and added to the training set. After retraining, we selected about 4000 objects, which we passed to a post-analysis stage by performing a cross-match with all publicly available catalogs. Within these candidates we identified certain known

  11. Supervised detection of anomalous light curves in massive astronomical catalogs

    SciTech Connect

    Nun, Isadora; Pichara, Karim; Protopapas, Pavlos; Kim, Dae-Won

    2014-09-20

    The development of synoptic sky surveys has led to a massive amount of data for which resources needed for analysis are beyond human capabilities. In order to process this information and to extract all possible knowledge, machine learning techniques become necessary. Here we present a new methodology to automatically discover unknown variable objects in large astronomical catalogs. With the aim of taking full advantage of all information we have about known objects, our method is based on a supervised algorithm. In particular, we train a random forest classifier using known variability classes of objects and obtain votes for each of the objects in the training set. We then model this voting distribution with a Bayesian network and obtain the joint voting distribution among the training objects. Consequently, an unknown object is considered as an outlier insofar it has a low joint probability. By leaving out one of the classes on the training set, we perform a validity test and show that when the random forest classifier attempts to classify unknown light curves (the class left out), it votes with an unusual distribution among the classes. This rare voting is detected by the Bayesian network and expressed as a low joint probability. Our method is suitable for exploring massive data sets given that the training process is performed offline. We tested our algorithm on 20 million light curves from the MACHO catalog and generated a list of anomalous candidates. After analysis, we divided the candidates into two main classes of outliers: artifacts and intrinsic outliers. Artifacts were principally due to air mass variation, seasonal variation, bad calibration, or instrumental errors and were consequently removed from our outlier list and added to the training set. After retraining, we selected about 4000 objects, which we passed to a post-analysis stage by performing a cross-match with all publicly available catalogs. Within these candidates we identified certain known

  12. Low mass SN Ia and the late light curve

    SciTech Connect

    Colgate, S.A.; Fryer, C.L.; Hand, K.P.

    1995-12-31

    The late bolometric light curves of type Ia supernovae, when measured accurately over several years, show an exponential decay with a 56d half-life over a drop in luminosity of 8 magnitudes (10 half-lives). The late-time light curve is thought to be governed by the decay of Co{sup 56}, whose 77d half-life must then be modified to account for the observed decay time. Two mechanisms, both relying upon the positron fraction of the Co{sup 56} decay, have been proposed to explain this modification. One explanation requires a large amount of emission at infra-red wavelengths where it would not be detected. The other explanation has proposed a progressive transparency or leakage of the high energy positrons (Colgate, Petschek and Kriese, 1980). For the positrons to leak out of the expanding nebula at the required rate necessary to produce the modified 56d exponential, the mass of the ejecta from a one foe (10{sup 51} erg in kinetic energy) explosion must be small, M{sub ejec} = 0.4M{sub {circle_dot}} with M{sub ejec} {proportional_to} KE{sup 0.5}. Thus, in this leakage explanation, any reasonable estimate of the total energy of the explosion requires that the ejected mass be very much less than the Chandrasekhar mass of 1.4M{sub {circle_dot}}. This is very difficult to explain with the ``canonical`` Chandrasekhar-mass thermonuclear explosion that disintegrates the original white dwarf star. This result leads us to pursue alternate mechanisms of type Ia supernovae. These mechanisms include sub-Chandrasekhar thermonuclear explosions and the accretion induced collapse of Chandrasekhar mass white dwarfs. We will summarize the advantages and disadvantages of both mechanisms with considerable detail spent on our new accretion induced collapse simulations. These mechanisms lead to lower Ni{sup 56} production and hence result in type Ia supernovae with luminosities decreased down to {approximately} 50% that predicted by the ``standard`` model.

  13. Bioconvective patterns, synchrony, and survival. [in light-limited growth model of motile algae culture

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1990-01-01

    With and without bioconvective pattern formation, a theoretical model predicts growth in light-limited cultures of motile algae. At the critical density for pattern formation, the resulting doubly exponential population curves show an inflection. Such growth corresponds quantitatively to experiments in mechanically unstirred cultures. This attaches survival value to synchronized pattern formation.

  14. Disk irradiation and light curves of x ray novae

    NASA Technical Reports Server (NTRS)

    Kim, S.-W.; Wheeler, J. C.; Mineshige, S.

    1994-01-01

    We study the disk instability and the effect of irradiation on outbursts in the black hole X-ray nova system. In both the optical and soft X-rays, the light curves of several X-ray novae, A0620-00, GH 2000+25, Nova Muscae 1991 (GS 1124-68), and GRO J0422+32, show a main peak, a phase of exponential decline, a secondary maximum or reflare, and a final bump in the late decay followed by a rapid decline. Basic disk thermal limit cycle instabilities can account for the rapid rise and overall decline, but not the reflare and final bump. The rise time of the reflare, about 10 days, is too short to represent a viscous time, so this event is unlikely to be due to increased mass flow from the companion star. We explore the possibility that irradiation by X-rays produced in the inner disk can produce these secondary effects by enhancing the mass flow rate within the disk. Two plausible mechanisms of irradiation of the disk are considered: direct irradiation from the inner hot disk and reflected radiation from a corona or other structure above the disk. Both of these processes will be time dependent in the context of the disk instability model and result in more complex time-dependent behavior of the disk structure. We test both disk instability and mass transfer burst models for the secondary flares in the presence of irradiation.

  15. Imaging Starspots on II Pegasi via Light-curve Inversion

    NASA Astrophysics Data System (ADS)

    Vutisalchavakul, Nalin; Deskins, Ryan; Harmon, Robert

    2007-10-01

    Starspots on the star II Pegasi were mapped via the method of Light-curve Inversion, which infers the appearance of the dark spots based on the brightness variations they produce as the star rotates. Our data were obtained with the 0.4-meter Vanderbilt/Tennessee State University Automated Photometric Telescope from September 1995 to January 1996 and from November 1988 to September 1992 (Henry, et al. 1995, ApJSS, 97, 513). For the first data set our results suggest that II Peg has opposite differential rotation to that of the Sun, with higher latitude spots having shorter rotation periods. We analyzed the second data set in an attempt to confirm this, but found that no definite conclusion could be drawn, though differential rotation is clearly present. The difficulty arises in part because the data were obtained through only two photometric filters (B and V), which limits the resolution in latitude. Future observations of the star through a larger set of filters might resolve this ambiguity.

  16. THE TRANSIT LIGHT CURVE OF AN EXOZODIACAL DUST CLOUD

    SciTech Connect

    Stark, Christopher C.

    2011-10-15

    Planets embedded within debris disks gravitationally perturb nearby dust and can create clumpy, azimuthally asymmetric circumstellar ring structures that rotate in lock with the planet. The Earth creates one such structure in the solar zodiacal dust cloud. In an edge-on system, the dust 'clumps' periodically pass in front of the star as the planet orbits, occulting and forward-scattering starlight. In this paper, we predict the shape and magnitude of the corresponding transit signal. To do so, we model the dust distributions of collisional, steady-state exozodiacal clouds perturbed by planetary companions. We examine disks with dusty ring structures formed by the planet's resonant trapping of in-spiraling dust for a range of planet masses and semi-major axes, dust properties, and disk masses. We synthesize edge-on images of these models and calculate the transit signatures of the resonant ring structures. The transit light curves created by dusty resonant ring structures typically exhibit two broad transit minima that lead and trail the planetary transit. We find that Jupiter-mass planets embedded within disks hundreds of times denser than our zodiacal cloud can create resonant ring structures with transit depths up to {approx}10{sup -4}, possibly detectable with Kepler. Resonant rings produced by planets more or less massive than Jupiter produce smaller transit depths. Observations of these transit signals may provide upper limits on the degree of asymmetry in exozodiacal clouds.

  17. Rotating Type Ia SN progenitors: explosion and light curves

    SciTech Connect

    Dominguez, I.; Piersanti, L.; Gagliardi, S.; Straniero, O.; Tornambe, A.; Bravo, E.

    2005-10-21

    High redshift SNe Ia have been recently used to calibrate the cosmological distance scale and to infer the existence of the dark energy. The reliability of such a method depends on the effective knowledge of the absolute brightness of this class of supernovae. This would require a complete understanding of the physics of SNeIa.Starting from an accreting rotating white dwarf, the only progenitor that we found to be able to grow till the Chandrasekhar mass and undergo a thermonuclear explosion, we simulate the explosion, deriving the nucleosynthesis and the light curve. We explore the final outcome in the framework of a 1D delayed detonation model, where the characteristic density for which the transition from deflagration to detonation takes place is a free parameter.Although preliminary, our results imply that rotating white dwarfs produce a range of explosive conditions, characterized by different ignition densities and total masses. Maximum luminosities of successfully explosive models differ up to 0.11 mag. In a few cases, the formation of a small highly neutronised remnant is found.

  18. Light-Induced Surface Patterning of Silica.

    PubMed

    Kang, Hong Suk; Lee, Seungwoo; Choi, Jaeho; Lee, Hongkyung; Park, Jung-Ki; Kim, Hee-Tak

    2015-10-27

    Manipulating the size and shape of silica precursor patterns using simple far-field light irradiation and transforming such reconfigured structures into inorganic silica patterns by pyrolytic conversion are demonstrated. The key concept of our work is the use of an azobenzene incorporated silica precursor (herein, we refer to this material as azo-silane composite) as ink in a micromolding process. The moving direction of azo-silane composite is parallel to light polarization direction; in addition, the amount of azo-silane composite movement can be precisely determined by controlling light irradiation time. By exploiting this peculiar phenomenon, azo-silane composite patterns produced using the micromolding technique are arbitrarily manipulated to obtain various structural features including high-resolution size or sophisticated shape. The photoreconfigured patterns formed with azo-silane composites are then converted into pure silica patterns through pyrolytic conversion. The pyrolytic converted silica patterns are uniformly formed over a large area, ensuring crack-free formation and providing high structural fidelity. Therefore, this optical manipulation technique, in conjunction with the pyrolytic conversion process, opens a promising route to the design of silica patterns with finely tuned structural features in terms of size and shape. This platform for designing silica structures has significant value in various nanotechnology fields including micro/nanofluidic channel for lab-on-a-chip devices, transparent superhydrophobic surfaces, and optoelectronic devices. PMID:26389813

  19. Transient structure in the high-energy X-ray light curve of NP 0532

    NASA Technical Reports Server (NTRS)

    Ryckman, S. G.; Ricker, G. R.; Scheepmaker, A.; Ballintine, J. E.; Doty, J. P.; Downey, P. M.; Lewin, W. H. G.

    1977-01-01

    The paper reports the observation of pulsed fractions in the primary and secondary peaks, as well as in the interpulse region, of the high-energy X-ray light curve of NP 0532. A statistical analysis of light-curve data is performed, and a similar analysis is carried out using simulated data. It is concluded that a previously reported third peak in the light curve was transient in nature.

  20. The Regulus occultation light curve and the real atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Veverka, J.; Wasserman, L.

    1974-01-01

    An inversion of the light curve observed during the July 7, 1959, occultation of Regulus by Venus leads to the conclusion that the light curve cannot be reconciled with models of the Venus atmosphere based on spacecraft observations. The event occurred in daylight and, under the subsequently difficult observation conditions, it seems likely that the Regulus occultation light curve is marred by a systematic errors in spite of the competence of the observers involved.

  1. RADIOACTIVELY POWERED RISING LIGHT CURVES OF TYPE Ia SUPERNOVAE

    SciTech Connect

    Piro, Anthony L.

    2012-11-10

    The rising luminosity of the recent, nearby supernova 2011fe shows a quadratic dependence with time during the first Almost-Equal-To 0.5-4 days. In addition, studies of the composite light curves formed from stacking together many Type Ia supernovae (SNe Ia) have found similar power-law indices for the rise, but may also show some dispersion that may indicate diversity. I explore what range of power-law rises are possible due to the presence of radioactive material near the surface of the exploding white dwarf (WD). I summarize what constraints such a model places on the structure of the progenitor and the distribution and velocity of ejecta. My main conclusion is that for the inferred explosion time for SN 2011fe, its rise requires an increasing mass fraction X {sub 56} Almost-Equal-To (4-6) Multiplication-Sign 10{sup -2} of {sup 56}Ni distributed between a depth of Almost-Equal-To 10{sup -2} and 0.3 M {sub Sun} below the WD's surface. Radioactive elements this shallow are not found in simulations of a single C/O detonation. Scenarios that may produce this material include helium-shell burning during a double-detonation ignition, a gravitationally confined detonation, and a subset of deflagration to detonation transition models. In general, the power-law rise can differ from quadratic depending on the details of the velocity, density, and radioactive deposition gradients in a given event. Therefore, comparisons of this work with observed bolometric rises of SNe Ia would place strong constraints on the properties of the shallow outer layers, providing important clues for identifying the elusive progenitors of SNe Ia.

  2. Radioactively Powered Rising Light Curves of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Piro, Anthony L.

    2012-11-01

    The rising luminosity of the recent, nearby supernova 2011fe shows a quadratic dependence with time during the first ≈0.5-4 days. In addition, studies of the composite light curves formed from stacking together many Type Ia supernovae (SNe Ia) have found similar power-law indices for the rise, but may also show some dispersion that may indicate diversity. I explore what range of power-law rises are possible due to the presence of radioactive material near the surface of the exploding white dwarf (WD). I summarize what constraints such a model places on the structure of the progenitor and the distribution and velocity of ejecta. My main conclusion is that for the inferred explosion time for SN 2011fe, its rise requires an increasing mass fraction X 56 ≈ (4-6) × 10-2 of 56Ni distributed between a depth of ≈10-2 and 0.3 M ⊙ below the WD's surface. Radioactive elements this shallow are not found in simulations of a single C/O detonation. Scenarios that may produce this material include helium-shell burning during a double-detonation ignition, a gravitationally confined detonation, and a subset of deflagration to detonation transition models. In general, the power-law rise can differ from quadratic depending on the details of the velocity, density, and radioactive deposition gradients in a given event. Therefore, comparisons of this work with observed bolometric rises of SNe Ia would place strong constraints on the properties of the shallow outer layers, providing important clues for identifying the elusive progenitors of SNe Ia.

  3. Properties of GRB light curves from magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Beniamini, Paz; Granot, Jonathan

    2016-07-01

    The energy dissipation mechanism within gamma-ray burst (GRB) outflows, driving their extremely luminous prompt γ-ray emission is still uncertain. The leading candidates are internal shocks and magnetic reconnection. While the emission from internal shocks has been extensively studied, that from reconnection still has few quantitative predictions. We study the expected prompt-GRB emission from magnetic reconnection and compare its temporal and spectral properties to observations. The main difference from internal shocks is that for reconnection one expects relativistic bulk motions with Lorentz factors Γ'≳ a few in the jet's bulk frame. We consider such motions of the emitting material in two antiparallel directions (e.g. of the reconnecting magnetic-field lines) within an ultrarelativistic (with Γ ≫ 1) thin spherical reconnection layer. The emission's relativistic beaming in the jet's frame greatly affects the light curves. For emission at radii R0 < R < R0 + ΔR (with Γ = const), the observed pulse width is ΔT ˜ (R0/2cΓ2) max (1/Γ', ΔR/R0), i.e. up to ˜Γ' times shorter than for isotropic emission in the jet's frame. We consider two possible magnetic reconnection modes: a quasi-steady state with continuous plasma flow into and out of the reconnection layer, and sporadic reconnection in relativistic turbulence that produces relativistic plasmoids. Both of these modes can account for many observed prompt-GRB properties: variability, pulse asymmetry, the very rapid declines at their end and pulse evolutions that are either hard to soft (for Γ' ≲ 2) or intensity tracking (for Γ' > 2). However, the relativistic turbulence mode is more likely to be relevant for the prompt sub-MeV emission and can naturally account also for the peak luminosity - peak frequency correlation.

  4. Variability in the light curve of tidal disruption events†

    NASA Astrophysics Data System (ADS)

    Lu, Zu-Jia; Lin, Da-Bin; Xie, Ling-Hua; Liang, En-Wei

    The X-ray light curve of Sw~J1644+57 indicates this event would be due to a tidal disruption. The lightcurve shows large amplitude fluctuation. As proposed by Lyubarskii (1997), the aperiodic variability observed in the Galactic X-ray binaries and active galactic nuclei is likely from the fluctuation of the viscous parameter in their disks. We explain the significant fluctuation of the late X-ray lightcurve (t>106 seconds) of Sw J1644+57 with this model. We assume the stochastic variations in the viscous parameter featuring as α(R,t) = α0 [1+β(R,t)], where the time-scale for varying β(R,t) is set as ten times of the dynamic time-scale for disk at the radius R (Janiuk & Misra 2012). Based on the simulation results of Lodato et al. (2009), we describe the fallback behavior of the tidal disruption as Ṁ fb ~ {[(t - t b )/t fb ]κ n + [(t - t b )/t fb ]5n/3}-1/n for t > t b and Ṁ fb=0 for other situations, where κ=10.0, n=0.5, t fb=103τ, and t b =102τ in which τ=2π(R f 3/GM BH)1/2 and R f =5r g is the pericentre distance. Figure 1 compare the power-density spectra (PDS) derived from the observed and our simulated lightcurves. It is found the our simulations are well consistent with the observations.

  5. Light curves of the latest FUor: Indication of a close binary

    NASA Astrophysics Data System (ADS)

    Hackstein, M.; Haas, M.; Kóspál, Á.; Hambsch, F.-J.; Chini, R.; Ábrahám, P.; Moór, A.; Pozo Nuñez, F.; Ramolla, M.; Westhues, Ch.; Kaderhandt, L.; Fein, Ch.; Barr Domínguez, A.; Hodapp, K.-W.

    2015-10-01

    We monitored the recent FUor 2MASS J06593158-0405277 (V960 Mon) since November 2009 at various observatories and multiple wavelengths. After the outburst by nearly 2.9 mag in r around September 2014 the brightness gently fades until April 2015 by nearly 1 mag in U and 0.5 mag in z. Thereafter the brightness at λ> 5000 Å was constant until June 2015 while the shortest wavelengths (U,B) indicate a new rise, similar to that seen for the FUor V2493 Cyg (HBC722). Our near-infrared (NIR) monitoring between December 2014 and April 2015 shows a smaller outburst amplitude (~2 mag) and a smaller (0.2-0.3 mag) post-outburst brightness decline. Optical and NIR color-magnitude diagrams indicate that the brightness decline is caused by growing extinction. The post-outburst light curves are modulated by an oscillating color-neutral pattern with a period of about 17 days and an amplitude declining from ~0.08 mag in October 2014 to ~0.04 mag in May 2015. The properties of the oscillating pattern lead us to suggest the presence of a close binary with eccentric orbit. The light curve Table is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/L12

  6. Application of Geodetic VLBI Data to Obtaining Long-Term Light Curves for Astrophysics

    NASA Technical Reports Server (NTRS)

    Kijima, Masachika

    2010-01-01

    The long-term light curve is important to research on binary black holes and disk instability in AGNs. The light curves have been drawn mainly using single dish data provided by the University of Michigan Radio Observatory and the Metsahovi Radio Observatory. Hence, thus far, we have to research on limited sources. I attempt to draw light curves using VLBI data for those sources that have not been monitored by any observatories with single dish. I developed software, analyzed all geodetic VLBI data available at the IVS Data Centers, and drew the light curves at 8 GHz. In this report, I show the tentative results for two AGNs. I compared two light curves of 4C39.25, which were drawn based on single dish data and on VLBI data. I confirmed that the two light curves were consistent. Furthermore, I succeeded in drawing the light curve of 0454-234 with VLBI data, which has not been monitored by any observatory with single dish. In this report, I suggest that the geodetic VLBI archive data is useful to obtain the long-term light curves at radio bands for astrophysics.

  7. appaloosa: Python-based flare finding code for Kepler light curves

    NASA Astrophysics Data System (ADS)

    Davenport, James R. A.

    2016-08-01

    The appaloosa suite automates flare-finding in every Kepler light curves. It builds quiescent light curve models that include long- and short-cadence data through iterative de-trending and includes completeness estimates via artificial flare injection and recovery tests.

  8. Generalized Fermat's principle and action for light rays in a curved spacetime

    NASA Astrophysics Data System (ADS)

    Frolov, Valeri P.

    2013-09-01

    We start with formulation of the generalized Fermat’s principle for light propagation in a curved spacetime. We apply Pontryagin’s minimum principle of the optimal control theory and obtain an effective Hamiltonian for null geodesics in a curved spacetime. We explicitly demonstrate that dynamical equations for this Hamiltonian correctly reproduce null geodesic equations. Other forms of the action for light rays in a curved spacetime are also discussed.

  9. An online repository of Swift/XRT light curves of γ-ray bursts

    NASA Astrophysics Data System (ADS)

    Evans, P. A.; Beardmore, A. P.; Page, K. L.; Tyler, L. G.; Osborne, J. P.; Goad, M. R.; O'Brien, P. T.; Vetere, L.; Racusin, J.; Morris, D.; Burrows, D. N.; Capalbi, M.; Perri, M.; Gehrels, N.; Romano, P.

    2007-07-01

    Context: Swift data are revolutionising our understanding of Gamma Ray Bursts. Since bursts fade rapidly, it is desirable to create and disseminate accurate light curves rapidly. Aims: To provide the community with an online repository of X-ray light curves obtained with Swift. The light curves should be of the quality expected of published data, but automatically created and updated so as to be self-consistent and rapidly available. Methods: We have produced a suite of programs which automatically generates Swift/XRT light curves of GRBs. Effects of the damage to the CCD, automatic readout-mode switching and pile-up are appropriately handled, and the data are binned with variable bin durations, as necessary for a fading source. Results: The light curve repository website (http://www.swift.ac.uk/xrt_curves) contains light curves, hardness ratios and deep images for every GRB which Swift's XRT has observed. When new GRBs are detected, light curves are created and updated within minutes of the data arriving at the UK Swift Science Data Centre.

  10. Light-curve solutions for S Cancri and TT Hydrae with rapid rotation

    NASA Technical Reports Server (NTRS)

    Van Hamme, W.; Wilson, R. E.

    1993-01-01

    Physical model light- and velocity-curve solutions for S Cancri and TT Hydrae are obtained, and analyses with incorporation of asynchronous rotation are carried out. A photometric rotation rate for the primary star of TT Hya is determined, and excellent agreement with results from spectral line profiles is found. Both separate light- and velocity-curve solutions and simultaneous light-velocity solutions are listed. The photometric rotation for S Cnc from existing light curves is indeterminate, but is compatible with line profile measures. Evidence for third light from the light curves of S Cnc is found. An explanation for the apparent conflict between the rotational states and mass-transfer activities of the two binaries is suggested.

  11. 3D shape shearography with integrated structured light projection for strain inspection of curved objects

    NASA Astrophysics Data System (ADS)

    Anisimov, Andrei G.; Groves, Roger M.

    2015-05-01

    Shearography (speckle pattern shearing interferometry) is a non-destructive testing technique that provides full-field surface strain characterization. Although real-life objects especially in aerospace, transport or cultural heritage are not flat (e.g. aircraft leading edges or sculptures), their inspection with shearography is of interest for both hidden defect detection and material characterization. Accurate strain measuring of a highly curved or free form surface needs to be performed by combining inline object shape measuring and processing of shearography data in 3D. Previous research has not provided a general solution. This research is devoted to the practical questions of 3D shape shearography system development for surface strain characterization of curved objects. The complete procedure of calibration and data processing of a 3D shape shearography system with integrated structured light projector is presented. This includes an estimation of the actual shear distance and a sensitivity matrix correction within the system field of view. For the experimental part a 3D shape shearography system prototype was developed. It employs three spatially-distributed shearing cameras, with Michelson interferometers acting as the shearing devices, one illumination laser source and a structured light projector. The developed system performance was evaluated with a previously reported cylinder specimen (length 400 mm, external diameter 190 mmm) loaded by internal pressure. Further steps for the 3D shape shearography prototype and the technique development are also proposed.

  12. Neptune's Dynamic Atmosphere from Kepler K2 Observations: Implications for Brown Dwarf Light Curve Analyses

    NASA Astrophysics Data System (ADS)

    Simon, Amy A.; Rowe, Jason F.; Gaulme, Patrick; Hammel, Heidi B.; Casewell, Sarah L.; Fortney, Jonathan J.; Gizis, John E.; Lissauer, Jack J.; Morales-Juberias, Raul; Orton, Glenn S.; Wong, Michael H.; Marley, Mark S.

    2016-02-01

    Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired nine months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune's zonal wind profile, and confirms observed cloud feature variability. Although Neptune's clouds vary in location and intensity on short and long timescales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extrasolar planet variability measurements. In particular we suggest that the balance between large, relatively stable, atmospheric features and smaller, more transient, clouds controls the character of substellar atmospheric variability. Atmospheres dominated by a few large spots may show inherently greater light curve stability than those which exhibit a greater number of smaller features.

  13. 'Self-absorbed' GeV light curves of gamma-ray burst afterglows

    SciTech Connect

    Panaitescu, A.; Vestrand, W. T.; Woźniak, P.

    2014-06-10

    We investigate the effect that the absorption of high-energy (above 100 MeV) photons produced in gamma-ray burst afterglow shocks has on the light curves and spectra of Fermi Large Area Telescope (LAT) afterglows. Afterglows produced by the interaction of a relativistic outflow with a wind-like medium peak when the blast wave deceleration sets in, and the afterglow spectrum could be hardening before that peak, as the optical thickness to pair formation is decreasing. In contrast, in afterglows produced in the interaction with a homogeneous medium, the optical thickness to pair formation should increase and yield a light curve peak when it reaches unity, followed by a fast light curve decay, accompanied by spectral softening. If energy is injected in the blast wave, then the accelerated increase of the optical thickness yields a convex afterglow light curve. Other features, such as a double-peak light curve or a broad hump, can arise from the evolution of the optical thickness to photon-photon absorption. Fast decays and convex light curves are seen in a few LAT afterglows, but the expected spectral softening is rarely seen in (and difficult to measure with) LAT observations. Furthermore, for the effects of photon-photon attenuation to shape the high-energy afterglow light curve without attenuating it too much, the ejecta initial Lorentz factor must be in a relatively narrow range (50-200), which reduces the chance of observing those effects.

  14. Determination of the Light Curve of the Artificial Satellite by its Rotation Path as Preparation to the Inverse Problem Solution

    NASA Astrophysics Data System (ADS)

    Pavlenko, Daniil

    Developing the algorithm of estimation of the rotational parameters of the artificial satellite by its light curve, we face the necessity to compute test light curves for various initially given types of rotation and specific features of lighting of the satellite. In the present study the algorithm of creation of such light curves with the simulation method and the obtained result are described.

  15. TYPE Ia SUPERNOVA LIGHT-CURVE INFERENCE: HIERARCHICAL BAYESIAN ANALYSIS IN THE NEAR-INFRARED

    SciTech Connect

    Mandel, Kaisey S.; Friedman, Andrew S.; Kirshner, Robert P.; Wood-Vasey, W. Michael

    2009-10-10

    We present a comprehensive statistical analysis of the properties of Type Ia supernova (SN Ia) light curves in the near-infrared using recent data from Peters Automated InfraRed Imaging TELescope and the literature. We construct a hierarchical Bayesian framework, incorporating several uncertainties including photometric error, peculiar velocities, dust extinction, and intrinsic variations, for principled and coherent statistical inference. SN Ia light-curve inferences are drawn from the global posterior probability of parameters describing both individual supernovae and the population conditioned on the entire SN Ia NIR data set. The logical structure of the hierarchical model is represented by a directed acyclic graph. Fully Bayesian analysis of the model and data is enabled by an efficient Markov Chain Monte Carlo algorithm exploiting the conditional probabilistic structure using Gibbs sampling. We apply this framework to the JHK{sub s} SN Ia light-curve data. A new light-curve model captures the observed J-band light-curve shape variations. The marginal intrinsic variances in peak absolute magnitudes are sigma(M{sub J}) = 0.17 +- 0.03, sigma(M{sub H}) = 0.11 +- 0.03, and sigma(M{sub Ks}) = 0.19 +- 0.04. We describe the first quantitative evidence for correlations between the NIR absolute magnitudes and J-band light-curve shapes, and demonstrate their utility for distance estimation. The average residual in the Hubble diagram for the training set SNe at cz > 2000kms{sup -1} is 0.10 mag. The new application of bootstrap cross-validation to SN Ia light-curve inference tests the sensitivity of the statistical model fit to the finite sample and estimates the prediction error at 0.15 mag. These results demonstrate that SN Ia NIR light curves are as effective as corrected optical light curves, and, because they are less vulnerable to dust absorption, they have great potential as precise and accurate cosmological distance indicators.

  16. Comparison of 1998 and 1999 Leonid Light Curve Morphology and Meteoroid Structure

    NASA Technical Reports Server (NTRS)

    Murray, Ian S.; Beech, Martin; Taylor, Michael J.; Jenniskens, Peter; Hawkes, Robert L.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Photometric low-light level video observations of 1999 Leonid storm meteors have been obtained from airborne platforms during the Leonid multi-instrument aircraft campaign (Leonid MAC). The 1999 Leonid light curves tend to be skewed towards the end point of the trajectory, while the 1998 Leonid light curves were not. The variation in the light curves from 1998 and 1999 can be explained as an overall reduction in the mass distribution index, alpha from approximately 1.95 in 1998 to approximately 1.75 in 1999. We have interpreted this behavior as being either indicative of a gradual loss of the "glue" that keeps the grains together, or the fact that the meteoroids sampled in 1998 had a different morphological structure to those sampled in 1999. The early fragmentation of a dustball meteoroid results in a light curve that peaks sooner than that predicted by classical single body ablation theory.

  17. Analysis of the variations in the light curve of U Pegasi and starspot activity

    NASA Astrophysics Data System (ADS)

    Zhai, Di-Sheng; Zhang, Xiao-Yu

    1989-03-01

    Nine two-color light curves observed between 1950 and 1983 of the W UMa type contact binary U Peg were analyzed. The distortions in the light curves during 1958-1970 can be successfully simulated with starspot activity. Using an improved W-D program containing differential correction of spot parameters, the spot parameters, longitude, latitude, temperature and radius, and their time variations are obtained. The photometric solutions at the various epochs also show that there may be other factors causing light curve distortion, including variation in the temperature difference between the two components, instability of the common shell and some other physical factors unaccounted for by present physical models.

  18. A light-curve distortion-wave analysis of eight RS Canum Venaticorum systems

    NASA Astrophysics Data System (ADS)

    Caton, D. B.

    1986-01-01

    A program of differential U,B,V photometry of 14 RS CVn systems carried out at Rosemary Hill Observatory in 1978 - 1981 is described, and an analysis of the light curves for the characteristic distortion wave for eight of the systems is presented. The V light curves of the systems are shown. Significant waves were observed in RS CVn, RZ Eri, and RW UMa. No significant waves were found in UX Com, GK Hya, AR Lac, LX Per, or TY Pyx. Unusual light curve distortions were observed in UX Com and AR Lac.

  19. A method used for finding the period of the light curve

    NASA Astrophysics Data System (ADS)

    Tao, Jun; Qian, Bochen; Liang, Zhaogang; Pan, Hongjian

    Usually Jurkevich method has been used to find periods of light curves and to test the periods by means of the values of their V2m. However, no firm rule exists for assessing the significance of a minimum in the V2m plot. A reasonable method used to evaluate periodicity is to fit trial periods to the historic light curves and then to get their amplitudes. We use this method to the historical light curve of OJ 287 and find that its main period is 11.9 years, which is in good agreement with the results obtained by other authors.

  20. Active Curved Polymers Form Vortex Patterns on Membranes

    NASA Astrophysics Data System (ADS)

    Denk, Jonas; Huber, Lorenz; Reithmann, Emanuel; Frey, Erwin

    2016-04-01

    Recent in vitro experiments with FtsZ polymers show self-organization into different dynamic patterns, including structures reminiscent of the bacterial Z ring. We model FtsZ polymers as active particles moving along chiral, circular paths by Brownian dynamics simulations and a Boltzmann approach. Our two conceptually different methods point to a generic phase behavior. At intermediate particle densities, we find self-organization into vortex structures including closed rings. Moreover, we show that the dynamics at the onset of pattern formation is described by a generalized complex Ginzburg-Landau equation.

  1. Active Curved Polymers Form Vortex Patterns on Membranes.

    PubMed

    Denk, Jonas; Huber, Lorenz; Reithmann, Emanuel; Frey, Erwin

    2016-04-29

    Recent in vitro experiments with FtsZ polymers show self-organization into different dynamic patterns, including structures reminiscent of the bacterial Z ring. We model FtsZ polymers as active particles moving along chiral, circular paths by Brownian dynamics simulations and a Boltzmann approach. Our two conceptually different methods point to a generic phase behavior. At intermediate particle densities, we find self-organization into vortex structures including closed rings. Moreover, we show that the dynamics at the onset of pattern formation is described by a generalized complex Ginzburg-Landau equation. PMID:27176542

  2. A Numerical Method for Calculating Stellar Occultation Light Curves from an Arbitrary Atmospheric Model

    NASA Technical Reports Server (NTRS)

    Chamberlain, D. M.; Elliot, J. L.

    1997-01-01

    We present a method for speeding up numerical calculations of a light curve for a stellar occultation by a planetary atmosphere with an arbitrary atmospheric model that has spherical symmetry. This improved speed makes least-squares fitting for model parameters practical. Our method takes as input several sets of values for the first two radial derivatives of the refractivity at different values of model parameters, and interpolates to obtain the light curve at intermediate values of one or more model parameters. It was developed for small occulting bodies such as Pluto and Triton, but is applicable to planets of all sizes. We also present the results of a series of tests showing that our method calculates light curves that are correct to an accuracy of 10(exp -4) of the unocculted stellar flux. The test benchmarks are (i) an atmosphere with a l/r dependence of temperature, which yields an analytic solution for the light curve, (ii) an atmosphere that produces an exponential refraction angle, and (iii) a small-planet isothermal model. With our method, least-squares fits to noiseless data also converge to values of parameters with fractional errors of no more than 10(exp -4), with the largest errors occurring in small planets. These errors are well below the precision of the best stellar occultation data available. Fits to noisy data had formal errors consistent with the level of synthetic noise added to the light curve. We conclude: (i) one should interpolate refractivity derivatives and then form light curves from the interpolated values, rather than interpolating the light curves themselves; (ii) for the most accuracy, one must specify the atmospheric model for radii many scale heights above half light; and (iii) for atmospheres with smoothly varying refractivity with altitude, light curves can be sampled as coarsely as two points per scale height.

  3. Multicolor Light Curve Simulations of Population III Core-Collapse Supernovae: From Shock Breakout to 56Co Decay

    NASA Astrophysics Data System (ADS)

    Tolstov, Alexey; Nomoto, Ken’ichi; Tominaga, Nozomu; Ishigaki, Miho N.; Blinnikov, Sergey; Suzuki, Tomoharu

    2016-04-01

    The properties of the first generation of stars and their supernova (SN) explosions remain unknown due to the lack of actual observations. Recently, many transient surveys have been conducted and the feasibility of detecting supernovae (SNe) of Pop III stars is growing. In this paper, we study the multicolor light curves for a number of metal-free core-collapse SN models (25–100 {M}ȯ ) to determine the indicators for the detection and identification of first generation SNe. We use mixing-fallback supernova explosion models that explain the observed abundance patterns of metal-poor stars. Numerical calculations of the multicolor light curves are performed using the multigroup radiation hydrodynamic code stella. The calculated light curves of metal-free SNe are compared with non-zero-metallicity models and several observed SNe. We have found that the shock breakout characteristics, the evolution of the photosphere’s velocity, the luminosity, and the duration and color evolution of the plateau, that is, all of the SN phases from shock breakout to 56Co decay, are helpful for estimating the parameters of the SN progenitor: the mass, the radius, the explosion energy, and the metallicity. We conclude that the multicolor light curves could potentially be used to identify first-generation SNe in current (Subaru/HSC) and future transient surveys (LSST, James Webb Space Telescope). They are also suitable for identifying low-metallicity SNe in the nearby universe (PTF, Pan-STARRS, Gaia).

  4. Gamma-ray burst prompt emission light curves and power density spectra in the ICMART model

    SciTech Connect

    Zhang, Bo; Zhang, Bing E-mail: zhang@physics.unlv.edu

    2014-02-20

    In this paper, we simulate the prompt emission light curves of gamma-ray bursts (GRBs) within the framework of the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. This model applies to GRBs with a moderately high magnetization parameter σ in the emission region. We show that this model can produce highly variable light curves with both fast and slow components. The rapid variability is caused by many locally Doppler-boosted mini-emitters due to turbulent magnetic reconnection in a moderately high σ flow. The runaway growth and subsequent depletion of these mini-emitters as a function of time define a broad slow component for each ICMART event. A GRB light curve is usually composed of multiple ICMART events that are fundamentally driven by the erratic GRB central engine activity. Allowing variations of the model parameters, one is able to reproduce a variety of light curves and the power density spectra as observed.

  5. Light curve morphology analysis of contact binaries observed with the Kepler satellite

    NASA Astrophysics Data System (ADS)

    Debski, Bartłomiej; Zoła, Stanisław

    2014-09-01

    Light-curve morphology analysis of contact binaries provides model-independent insight into the short-term evolution of the system activity. Light-curve morphology applied to the Kepler data of contact binaries reveals directly the migration spot connection to the light curve's intrinsic rapid changes. Since the flat-bottom secondary minima cannot be studied in the way Tran et al. (2013) or Conroy et al. (2014) did, we measure the actual light-curve minimum, instead of the presumed mid-eclipse time. This, combined with the study of the minimum depth, allowed us to uncover the direction of the spot migration for particular binaries. At the same time, the O'Connell effect evolution and the maxima separation confronted with modeling based on the Wilson-Devinney code agree with polar dark spots. The combined results of this new approach offer constraints on the star spots size, temperature and latitude at high precision.

  6. A two-component model for fitting light curves of core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Nagy, A. P.; Vinkó, J.

    2016-05-01

    We present an improved version of a light curve model that is able to estimate the physical properties of different types of core-collapse supernovae that have double-peaked light curves and do so in a quick and efficient way. The model is based on a two-component configuration consisting of a dense inner region and an extended low-mass envelope. Using this configuration, we estimate the initial parameters of the progenitor by fitting the shape of the quasi-bolometric light curves of 10 SNe, including Type IIP and IIb events, with model light curves. In each case we compare the fitting results with available hydrodynamic calculations and also match the derived expansion velocities with the observed ones. Furthermore, we compare our calculations with hydrodynamic models derived by the SNEC code and examine the uncertainties of the estimated physical parameters caused by the assumption of constant opacity and the inaccurate knowledge of the moment of explosion.

  7. Infrared supernova light curves and asymmetric stellar mass loss

    NASA Technical Reports Server (NTRS)

    Emmering, Robert T.; Chevalier, Roger A.

    1988-01-01

    Infrared dust emission echos from Type II supernovae are a natural consequence of the heating of circumstellar dust by the supernova light. Red supergiants, the likely progenitors of most Type II supernovae, are known in some cases to have asymmetric circumstellar envelopes. It is noted that an asymmetric dust distribution can have a substantial effect on the evolution of an infrared echo and results are presented for an ellipsoidal dust distribution. The angle between the symmetry axis and the line of sight is unknown in any particular case so that detailed observations of a number of supernovae will be necessary to test for asymmetries. Asymmetries may also be observable in the radio structure of supernovae and in a possible scattered-light echo.

  8. Reconstruct light curves from unevenly sampled variability data with artificial neural networks

    NASA Astrophysics Data System (ADS)

    Wang, Qi-Jie; Cao, Xinwu

    2014-07-01

    Light curves are usually constructed from discrete observational data by interpolation. In most cases, the observation data is temporally uneven, and therefore the light curve is usually derived by the interpolation of the binned data with the spline function, which is intended for reducing the "high sample noise" (i.e., the variability in the timescales comparable with the bin width). Such a practice of course reduces the time resolution of the light curve. It is known that function approximation is one of the most important applications of the artificial neural networks (ANN). In this work, for the first time we tentatively use the ANN to construct light curves from unevenly sampled variability data. To demonstrate the advantages of ANN for signal reconstruction over commonly used cubic spline function scheme, two sets of simulated periodic functions are used with random noises of varying magnitudes, one single frequency based and one multiple (two) frequency based. These signal reconstruction tests show that the ANN is clearly superior to the cubic spline scheme. As a case study, we use the uneven long-term multi-band monitoring data of BL lacertae to derive the light curves with ANN. It is found that the light curves derived with ANN have higher time resolution than those with the cubic spline function adopted in previous works. We recommend using ANN for the signal reconstruction in astrophysical data analysis as well as that of in other fields.

  9. VizieR Online Data Catalog: DD Mon BV light curves (Qian+ 1997)

    NASA Astrophysics Data System (ADS)

    Qian, S.; Liu, Q.; Yang, Y.; Gu, S.; Huang, Z.

    1997-04-01

    New BV light curves of the short-period eclipsing binary system DD Mon have been obtained. Light-curve variability is seen in both B and V bands as compared with the light curves obtained in 1986 by Yamasaki et al. (1990AJ.....99.1218Y). The light curves are analyzed by using Wilson-Devinney's synthetic light-curve program, and the present photometric solution reveals that DD Mon is a near-contact binary with the secondary component filling the Roche lobe. Combined with Yamasaki et al.'s (1990AJ.....99.1218Y) spectroscopic results, absolute quantities of DD Mon are derived: mass of the primary M1=1.05+/-0.08M⊙, mass of the secondary M2=0.47+/-0.04M⊙, radius of the primary R1=1.36+/-0.04R⊙, radius of the secondary R2=1.03+/-0.03R⊙. These results show that the components of DD Mon have evolved away from the ZAMS and through a mass-transfer process to the present semi-detached state. The variation in shape of the light curve may be caused by the evolution of the system and the activity of dark spots. (2 data files).

  10. Accretion disc time lag distributions: applying CREAM to simulated AGN light curves

    NASA Astrophysics Data System (ADS)

    Starkey, D. A.; Horne, Keith; Villforth, C.

    2016-02-01

    Active galactic nuclei (AGN) vary in their brightness across all wavelengths. Moreover, longer wavelength ultraviolet-optical continuum light curves appear to be delayed with respect to shorter wavelength light curves. A simple way to model these delays is by assuming thermal reprocessing of a variable point source (a lamp post) by a blackbody accretion disc. We introduce a new method, CREAM (Continuum REprocessed AGN Markov Chain Monte Carlo), that models continuum variations using this lamp post model. The disc light curves lag the lamp post emission with a time delay distribution sensitive to the disc temperature-radius profile and inclination. We test CREAM's ability to recover both inclination and product of black hole mass and accretion rate {Mdot{M}}, and show that the code is also able to infer the shape of the driving light curve. CREAM is applied to synthetic light curves expected from 1000 s exposures of a 17th magnitude AGN with a 2-m telescope in Sloan g and i bands with Signal-to-Noise Ratio (SNR) of 500-900 depending on the filter and lunar phase. We also test CREAM on poorer quality g and i light curves with SNR = 100. We find in the high-SNR case that CREAM can recover the accretion disc inclination to within an uncertainty of 5° and an {Mdot{M}} to within 0.04 dex.

  11. Optical design and optimization of planar curved LED end-lit light bar.

    PubMed

    Yu, Jyh-Cheng; Chen, Zhi-Yao; Kao, Bang-De

    2014-10-10

    This study investigates the optical design of planar curved LED end-lit light bars using v cuts as light-diverting structures. The application of LEDs in automotive lighting has become popular, especially in signal lamps and daytime running lamps. Most designs adopt a direct back light using arrays of LEDs with diffusive coupling optics, which often causes problems such as low uniformity, glaring, and excessive LEDs. Edge-lit LED light guides in automotive applications share a similar principle with the light-guide plates in back-light models of LCD but with much more complicated geometry. However, related literature on the optical design of nonrectangular light-guide plates is very limited. This study addresses the design of planar curved LED end-lit light bars and the optimization scheme for illuminance uniformity. V cuts are used as the optical coupling features, and the lead angles of the v cuts are varied to achieve optimum axial luminous intensity. This study presents a solution to reduce the illuminance difference between the inner and the outer portions of curved light bars by introducing gradual taper v cuts across the curved section. A line graph with preselected anchor points is proposed to define the size distribution of evenly spaced v cuts along the light bar. A fuzzy optimization scheme is then applied to iterate the anchor size to achieve illuminance uniformity. The designs of a planar curve light bar with a rectangular cross section and a light-guide ring with a circular cross section are presented to illustrate the design scheme. PMID:25322433

  12. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    NASA Astrophysics Data System (ADS)

    Dyudina, Ulyana; Zhang, Xi; Li, Liming; Kopparla, Pushkar; Ingersoll, Andrew P.; Dones, Luke; Verbiscer, Anne; Yung, Yuk L.

    2016-05-01

    Reflected light curves observed for exoplanets indicate that a few of them host bright clouds. We estimate how the light curve and total stellar heating of a planet depends on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet’s phase. These observations cover broadbands at 0.59–0.72 and 0.39–0.5 μm, and narrowbands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24–0.28 μm. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter and Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of ˜1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating. Division of Geological and Planetary Sciences, 150-21 California Institute of Technology, Pasadena, CA 91125 USA.

  13. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    NASA Astrophysics Data System (ADS)

    Dyudina, Ulyana; Zhang, Xi; Li, Liming; Kopparla, Pushkar; Ingersoll, Andrew P.; Dones, Luke; Verbiscer, Anne; Yung, Yuk L.

    2016-05-01

    Reflected light curves observed for exoplanets indicate that a few of them host bright clouds. We estimate how the light curve and total stellar heating of a planet depends on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet’s phase. These observations cover broadbands at 0.59–0.72 and 0.39–0.5 μm, and narrowbands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24–0.28 μm. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter and Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of ∼1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating. Division of Geological and Planetary Sciences, 150-21 California Institute of Technology, Pasadena, CA 91125 USA.

  14. CSI 2264: Characterizing Young Stars in NGC 2264 with Stochastically Varying Light Curves

    NASA Astrophysics Data System (ADS)

    Stauffer, John; Cody, Ann Marie; Rebull, Luisa; Hillenbrand, Lynne A.; Turner, Neal J.; Carpenter, John; Carey, Sean; Terebey, Susan; Morales-Calderón, María; Alencar, Silvia H. P.; McGinnis, Pauline; Sousa, Alana; Bouvier, Jerome; Venuti, Laura; Hartmann, Lee; Calvet, Nuria; Micela, Giusi; Flaccomio, Ettore; Song, Inseok; Gutermuth, Rob; Barrado, David; Vrba, Frederick J.; Covey, Kevin; Herbst, William; Gillen, Edward; Medeiros Guimarães, Marcelo; Bouy, Herve; Favata, Fabio

    2016-03-01

    We provide CoRoT and Spitzer light curves and other supporting data for 17 classical T Tauri stars in NGC 2264 whose CoRoT light curves exemplify the “stochastic” light curve class as defined in 2014 by Cody et al. The most probable physical mechanism to explain the optical variability within this light curve class is time-dependent mass accretion onto the stellar photosphere, producing transient hot spots. Where we have appropriate spectral data, we show that the veiling variability in these stars is consistent in both amplitude and timescale with the optical light curve morphology. The veiling variability is also well-correlated with the strength of the He i 6678 Å emission line, predicted by models to arise in accretion shocks on or near the stellar photosphere. Stars with accretion burst light curve morphology also have variable mass accretion. The stochastic and accretion burst light curves can both be explained by a simple model of randomly occurring flux bursts, with the stochastic light curve class having a higher frequency of lower amplitude events. Members of the stochastic light curve class have only moderate mass accretion rates. Their Hα profiles usually have blueshifted absorption features, probably originating in a disk wind. The lack of periodic signatures in the light curves suggests that little of the variability is due to long-lived hot spots rotating into or out of our line of sight; instead, the primary driver of the observed photometric variability is likely to be instabilities in the inner disk that lead to variable mass accretion. Based on data from the Spitzer and CoRoT missions, as well as the Canada-France-Hawaii Telescope (CFHT) MegaCam CCD, and the European Southern Observatory Very Large Telescope, Paranal Chile, under program 088.C-0239. The CoRoT space mission was developed and is operated by the French space agency CNES, with particpiation of ESA’s RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain

  15. Studying wave optics in the light curves of exoplanet microlensing

    NASA Astrophysics Data System (ADS)

    Mehrabi, Ahmad; Rahvar, Sohrab

    2013-05-01

    We study the wave optics features of gravitational microlensing by a binary lens composed of a planet and a parent star. In this system, the source star near the caustic line produces a pair of images in which they can play the role of secondary sources for the observer. This optical system is similar to the Young double-slit experiment. The coherent wavefronts from a source on the lens plane can form a diffraction pattern on the observer plane. This diffraction pattern has two modes from the close- and wide-pair images. From the observational point of view, we study the possibility of detecting this effect through the Square Kilometre Array (SKA) project in the resonance and high-magnification channels of binary lensing. While the red giant sources do not seem to satisfy the spatial coherency condition, during the caustic crossing a small part of a source traversing the caustic line can produce coherent pair images. Observations of wave optics effects at longer wavelengths accompanied by optical observations of a microlensing event provide extra information on the parameter space of the planet. These observations can provide a new basis for the study of exoplanets.

  16. Imprints of the quasar structure in time-delay light curves: Microlensing-aided reverberation mapping

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Tewes, M.

    2014-11-01

    The advent of large area photometric surveys has raised a great deal of interest in the possibility of using broadband photometric data, instead of spectra, to measure the size of the broad line region of active galactic nuclei. We describe here a new method that uses time-delay lensed quasars where one or several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. We show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single-band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, we show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images that is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques that use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.

  17. WTF- and A- Stars: Spectroscopic Analysis of Kepler Light Curves

    NASA Astrophysics Data System (ADS)

    Grae Short, Miona; Soderblom, David R.

    2016-01-01

    Analysis of Kepler data in 2012 found that in a sample of about 2000 A- and F- stars, 1% of them seemed to exhibit white light flares. However, such stars are not thought to have the convective envelopes needed to produce the magnetic dynamos that yield flares. We use the same Kepler data but examine the flaring stars more comprehensively by analyzing the pixel data in order to predict whether this flare-like behavior may be caused by smaller, less luminous M dwarfs exhibiting genuine flares in the line of sight of the A- and F-stars. The implications of finding verifiable flare activity in a subset of these stars would be enough to incite further investigation of the physical processes that allow this to take place. Yet, if that were not the case, this project would further be able to demonstrate the steps necessary to correct for false-positives in finding flares in A- and F- stars.

  18. Periodicity in some light curves of the solar analogue V352 Canis Majoris

    NASA Astrophysics Data System (ADS)

    Kajatkari, P.; Jetsu, L.; Cole, E.; Hackman, T.; Henry, G. W.; Joutsiniemi, S.-L.; Lehtinen, J.; Mäkelä, V.; Porceddu, S.; Ryynänen, K.; Solea, V.

    2015-05-01

    Aims: We applied the Continuous Period Search (CPS) method to 14 yr of V-band photometry of the active G6.5 solar analog V352 CMa. Our aim was to show that CPS can successfully model the presence or absence of periodicity in low-amplitude light curves. Methods: CPS computes values for the mean brightness, photometric period, amplitude and minimum of selected datasets. We also applied the Power Spectrum Method (PSM) to these datasets and compared the performance of this frequently applied method to that of CPS. Results: We found an apparent 11.7 ± 0.5 yr cycle in the mean brightness. The mean of the individual photometric rotation periods is 7.24 ± 0.22 days. The lower limit for the differential rotation coefficient is |k| > 0.12, assuming that period changes in V352 CMa follow the solar pattern. The Kuiper method detected stable, active longitudes rotating with a period of 7.157 ± 0.002 days, from the epochs of light minimum, but these structures vanished after the year 2009. CPS performed better than the traditional PSM, because the latter assumes a sinusoidal model for the data even when this was not correct. The analysed photometry and numerical results of the analysis are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A84

  19. Time Curves: Folding Time to Visualize Patterns of Temporal Evolution in Data.

    PubMed

    Bach, Benjamin; Shi, Conglei; Heulot, Nicolas; Madhyastha, Tara; Grabowski, Tom; Dragicevic, Pierre

    2016-01-01

    We introduce time curves as a general approach for visualizing patterns of evolution in temporal data. Examples of such patterns include slow and regular progressions, large sudden changes, and reversals to previous states. These patterns can be of interest in a range of domains, such as collaborative document editing, dynamic network analysis, and video analysis. Time curves employ the metaphor of folding a timeline visualization into itself so as to bring similar time points close to each other. This metaphor can be applied to any dataset where a similarity metric between temporal snapshots can be defined, thus it is largely datatype-agnostic. We illustrate how time curves can visually reveal informative patterns in a range of different datasets. PMID:26529718

  20. Are the variability properties of the Kepler AGN light curves consistent with a damped random walk?

    NASA Astrophysics Data System (ADS)

    Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.

    2015-08-01

    We test the consistency of active galactic nuclei (AGN) optical flux variability with the damped random walk (DRW) model. Our sample consists of 20 multiquarter Kepler AGN light curves including both Type 1 and 2 Seyferts, radio-loud and -quiet AGN, quasars, and blazars. Kepler observations of AGN light curves offer a unique insight into the variability properties of AGN light curves because of the very rapid (11.6-28.6 min) and highly uniform rest-frame sampling combined with a photometric precision of 1 part in 105 over a period of 3.5 yr. We categorize the light curves of all 20 objects based on visual similarities and find that the light curves fall into five broad categories. We measure the first-order structure function of these light curves and model the observed light curve with a general broken power-law power spectral density (PSD) characterized by a short-time-scale power-law index γ and turnover time-scale τ. We find that less than half the objects are consistent with a DRW and observe variability on short time-scales (˜2 h). The turnover time-scale τ ranges from ˜10-135 d. Interesting structure function features include pronounced dips on rest-frame time-scales ranging from 10-100 d and varying slopes on different time-scales. The range of observed short-time-scale PSD slopes and the presence of dip and varying slope features suggests that the DRW model may not be appropriate for all AGN. We conclude that AGN variability is a complex phenomenon that requires a more sophisticated statistical treatment.

  1. The 100,000-Magnitude Light Curve For the Eruption of Recurrent Nova T Pyx

    NASA Astrophysics Data System (ADS)

    Schaefer, Bradley E.

    2012-01-01

    The recurrent nova T Pyx erupted on 14 April 2011, its sixth known eruption. As part of an intensive campaign organized by the AAVSO, T Pyx now has 100,000 points in its eruption light curve. The coverage for T Pyx exceeds by far the second place (36,776 magnitudes for U Sco in 2010) and the third place ( 3000 magnitudes for RS Oph in 2006) nova light curves. (1) T Pyx underwent a mysterious pre-eruption rise 11 days before the start of the fast rising thermonuclear explosion, brightening to 1.1 mag above the quiescent level, then returning towards quiescence before the start of the eruption. (2) T Pyx is the first-ever nova that has been followed from the start of the fast rise, and in this case with fast times series and multicolor photometry. For the first 2.0 days, the light curve is well fit by a uniformly expanding shell model, only to then suffer a slight decline in brightness. (3) The pre-eruption orbital period was measured just 40 days prior to the eruption to be 0.07622916+-0.00000008 days. (4) The eruption light curve up to 120 days after the start of the eruption was virtually identical with the light curves from all prior eruptions. But starting at day 125, the light curve has continued declining slowly, rather than the sudden sharp drop by two magnitudes as was seen in the 1967 light curve. (5) The surprisingly short interval between the 1967 and 2011 eruptions is now no longer surprising with the realization that the accretion rate is proportional to the blue flux, so the drop in the average accretion rate from 1944-1967 (22 years) to 1967-2011 (44.33 year) by a factor of two implies an eruption date of 1967+2X22 = 2011. Supported by the National Science Foundation (AST-1109420).

  2. Full Bayesian hierarchical light curve modeling of core-collapse supernova populations

    NASA Astrophysics Data System (ADS)

    Sanders, Nathan; Betancourt, Michael; Soderberg, Alicia Margarita

    2016-06-01

    While wide field surveys have yielded remarkable quantities of photometry of transient objects, including supernovae, light curves reconstructed from this data suffer from several characteristic problems. Because most transients are discovered near the detection limit, signal to noise is generally poor; because coverage is limited to the observing season, light curves are often incomplete; and because temporal sampling can be uneven across filters, these problems can be exacerbated at any one wavelength. While the prevailing approach of modeling individual light curves independently is successful at recovering inferences for the objects with the highest quality observations, it typically neglects a substantial portion of the data and can introduce systematic biases. Joint modeling of the light curves of transient populations enables direct inference on population-level characteristics as well as superior measurements for individual objects. We present a new hierarchical Bayesian model for supernova light curves, where information inferred from observations of every individual light curve in a sample is partially pooled across objects to constrain population-level hyperparameters. Using an efficient Hamiltonian Monte Carlo sampling technique, the model posterior can be explored to enable marginalization over weakly-identified hyperparameters through full Bayesian inference. We demonstrate our technique on the Pan-STARRS1 (PS1) Type IIP supernova light curve sample published by Sanders et al. (2015), consisting of nearly 20,000 individual photometric observations of more than 70 supernovae in five photometric filters. We discuss the Stan probabilistic programming language used to implement the model, computational challenges, and prospects for future work including generalization to multiple supernova types. We also discuss scientific results from the PS1 dataset including a new relation between the peak magnitude and decline rate of SNe IIP, a new perspective on the

  3. THE DISCOVERY OF ELLIPSOIDAL VARIATIONS IN THE KEPLER LIGHT CURVE OF HAT-P-7

    SciTech Connect

    Welsh, William F.; Orosz, Jerome A.; Seager, Sara; Fortney, Jonathan J.; Jenkins, Jon; Rowe, Jason F.; Koch, David; Borucki, William J.

    2010-04-20

    We present an analysis of the early Kepler observations of the previously discovered transiting planet HAT-P-7b. The light curve shows the transit of the star, the occultation of the planet, and the orbit phase-dependent light from the planet. In addition, phase-dependent light from the star is present, known as 'ellipsoidal variations'. The very nearby planet (only four stellar radii away) gravitationally distorts the star and results in a flux modulation twice per orbit. The ellipsoidal variations can confuse interpretation of the planetary phase curve if not self-consistently included in the modeling. We fit the light curve using the Roche potential approximation and derive improved planet and orbit parameters.

  4. Gamma-ray pulsar light curves as probes of magnetospheric structure

    NASA Astrophysics Data System (ADS)

    Harding, A. K.

    2016-06-01

    > The large number of -ray pulsars discovered by the Fermi Gamma-Ray Space Telescope since its launch in 2008 dwarfs the handful that were previously known. The variety of observed light curves makes possible a tomography of both the ensemble-averaged field structure and the high-energy emission regions of a pulsar magnetosphere. Fitting the -ray pulsar light curves with model magnetospheres and emission models has revealed that most of the high-energy emission, and the particles acceleration, takes place near or beyond the light cylinder, near the current sheet. As pulsar magnetosphere models become more sophisticated, it is possible to probe magnetic field structure and emission that are self-consistently determined. Light curve modelling will continue to be a powerful tool for constraining the pulsar magnetosphere physics.

  5. Atlas of Light Curves and Photometric Monitoring of The Non-Resolved Space Objects

    NASA Astrophysics Data System (ADS)

    Koshkin, N.; Shakun, L.; Korobeinikova, E.; Strakhova, S.; Melikiants, S.; Dragomiretsky, V.; Ryabov, A.

    2013-09-01

    Photometric monitoring is a tool for remote diagnostics of the satellite rotation around its center of mass. This information is important in many cases. For example, in case of abnormal mode of the satellite functioning. And also to take into account the orientation of non-spherical body (eg, space debris) in the numerical integration of its motion when it is expected to close approach with the another spacecraft. This paper presents the results of long-term (since 1980) photometric monitoring of both operational satellites, and large bodies of space debris in low-Earth orbit (LEO). The light curves of the non-resolved cosmic objects (CO), which are recorded prior to 2004, were obtained using electrophotometer (PMT with multialkaline cathode) in the visible wavelength range without using a filter. The light curves, which are recorded after 2004, were obtained using a TV CCD-camera also without the use of filters. For tracking low-orbit satellites was used telescope KT-50 on alt-azimuth mounting, which allows one to tracking the objects moving at a high angular velocity. The diameter of main mirror is 0.5 m, focal length is 3 m. For any ?O is given his international (COSPAR) number and NORAD catalog number, and provides information about its form and initial orbital elements. The brightness of satellite presented in magnitudes. He reduced with considering the atmosphere's light extinction and is related to a distance of 1000 km. For each passage and light curve is pointed the date and UTC. The light curves of stabilized CO have only small light variations and they show the dependence from the phase angle. Rotating CO have periodic light curves. The type (kind) and the periods of the light curves change with the time.

  6. A novel method for designing dichroic color filter transmittance curves for lighting applications

    NASA Astrophysics Data System (ADS)

    Qi, Rui; Shum, Frank

    2014-09-01

    This paper focuses on designing dichroic filters for changing the color of light-emitting diode (LED) lamps. Dichroic filters are composed of multiple dielectric layers on a substrate. By applying a dichroic filter, some of the LED's spectral energy is reflected and some is transmitted, which changes the lamp's color. Conventional methods to obtain spectral transmittance curves have shortcomings. The design criteria for the transmittance curves are incompatible with the metrics used in lighting applications, such as correlated color temperature (CCT) and color rendering index (CRI). Thus, the color rendering performance and the optical transmission of a lighting system are not optimized. This observation leads to the development of a proposed method for designing dichroic filter transmittance curves to provide accurate color shift, high CRI, and sufficient optical transmission. The method initially uses the transmittance curve of an existing color filter that provides a roughly close color shift for the LED lamp to calculate the transmittance curve that causes an accurate color shift by polynomial approximation. Based on the approximated curve, a preliminary transmittance curve without the effect of the LED lamp's secondary optics is derived and verified in thin-film design and optical design software tools. Further, the derived preliminary transmittance curve is optimized by applying an algorithm to loop through a large amount of representative curves fluctuating near the preliminary curve. The resulting dichroic filter provides an accurate color shift (ΔCCT = -800±50K, Duv = ±0.003), high CRI (Ra and R9 <= 95), and sufficient luminous flux transmission (<= 70%).

  7. Timescale stretch parameterization of Type Ia supernova B-band light curves

    SciTech Connect

    Goldhaber, G.; Groom, D.E.; Kim, A.; Aldering, G.; Astier, P.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fruchter, A.S.; Goobar, A.; Hook, I.; Irwin, M.; Kim, M.; Knop, R.A.; Lidman, C.; McMahon, R.; Nugent, P.E.; Pain, R.; Panagia, N.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente, P.; Schaefer, B.; Walton, N.A.; York, T.

    2001-04-01

    R-band intensity measurements along the light curve of Type Ia supernovae discovered by the Cosmology Project (SCP) are fitted in brightness to templates allowing a free parameter the time-axis width factor w identically equal to s times (1+z). The data points are then individually aligned in the time-axis, normalized and K-corrected back to the rest frame, after which the nearly 1300 normalized intensity measurements are found to lie on a well-determined common rest-frame B-band curve which we call the ''composite curve.'' The same procedure is applied to 18 low-redshift Calan/Tololo SNe with Z < 0.11; these nearly 300 B-band photometry points are found to lie on the composite curve equally well. The SCP search technique produces several measurements before maximum light for each supernova. We demonstrate that the linear stretch factor, s, which parameterizes the light-curve timescale appears independent of z, and applies equally well to the declining and rising parts of the light curve. In fact, the B band template that best fits this composite curve fits the individual supernova photometry data when stretched by a factor s with chi 2/DoF {approx} 1, thus as well as any parameterization can, given the current data sets. The measurement of the data of explosion, however, is model dependent and not tightly constrained by the current data. We also demonstrate the 1 + z light-cure time-axis broadening expected from cosmological expansion. This argues strongly against alternative explanations, such as tired light, for the redshift of distant objects.

  8. Light Curve Solutions of Eclipsing Binaries in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Rawls, Meredith L.; Rao, M. S.

    2012-01-01

    We present model light curves for nine eclipsing binary stars in the Large Magellanic Cloud (LMC). These systems are detached binaries with nearly circular orbits, and were pseudorandomly selected from three of 21 LMC regions in the Optical Gravitational Lensing Experiment II (OGLE-II) survey. We make use of light curves, orbital periods, and binary classification as reported in Wyrzykowski et al. (2003). We present light curve solutions created with the software PHysics Of Eclipsing BinariEs (PHOEBE, Prsa & Zwitter 2005). Each solution has the best-fit mass ratio q, system inclination i, component temperatures T1 and T2, and modified Kopal potentials Ω1 and Ω2. PHOEBE employs a Nelder & Mead's Simplex fitting method that adjusts all the input parameters to find the best fit to the light curve. Many of the light curves have significant scatter, which can lead to multiple degenerate best-fit solutions, and we discuss what can be done in the future to refine our results, derive global stellar parameters, and place these nine systems in a larger context. We acknowledge the support of the International Research Experience for Students (IRES) program, which is sponsored by the NSF and administered by NSO/GONG.

  9. A Fourier Optics Method for Calculating Stellar Occultation Light Curves by Objects with Thin Atmospheres

    NASA Astrophysics Data System (ADS)

    Young, E. F.

    2012-08-01

    A stellar occultation occurs when a solar system object passes in front of a distant star. The light curves resulting from stellar occultations can reveal many aspects of the obscuring object. For airless bodies, the diffraction light curve specifies the object's size, distance and, if several chords are observed, shape. Occultation light curves are especially sensitive to the presence of atmospheres; the refraction light curve is a function of the atmosphere's density, pressure, and temperature profiles. The goal of this paper is to develop a practical algorithm to model the simultaneous effects of diffraction and refraction for objects in which both phenomena are observable. The algorithm we present is flexible: it can be used to calculate light curves by objects with arbitrary shapes and arbitrary atmospheres (including the presence of opacity sources such as hazes), provided that the atmosphere can be represented by a thin screen with a phase delay and an opacity defined at each location in the screen. Because the algorithm is limited at present to thin atmospheres (in which rays from a star are bent but undergo virtually no translation as they pass through an atmosphere), the gas giants, Earth, Mars, and Venus are not treated. Examples of stellar occultations are presented for round or irregularly shaped objects having thin atmospheres of various column densities.

  10. Variation of the period and light curves of the solar-type contact binary EQ Tauri

    NASA Astrophysics Data System (ADS)

    Yuan, Jinzhao; Qian, Shengbang

    2007-10-01

    We present two new sets of complete light curves of EQ Tauri (EQ Tau) observed in 2000 October and 2004 December. These were analysed, together with the light curves obtained by Yang & Liu in 2001 December, with the 2003 version of the Wilson-Devinney code. In the three observing seasons, the light curves show a noticeable variation in the time-scale of years. The more massive component of EQ Tau is a solar-type star (G2) with a very deep convective envelope, which rotates about 80 times as fast as the Sun. Therefore, the change can be explained by dark-spot activity on the common convective envelope. The assumed unperturbed part of the light curve and the radial velocities published by Rucinski et al. were used to determine the basic parameters of the system, which were kept fixed for spot modelling in the three sets of light curves. The results reveal that the total spotted area on the more massive component covers 18, 3 and 20 per cent of the photospheric surface in the three observing seasons, respectively. Polar spots and high-latitude spots are found. The analysis of the orbital period has demonstrated that it undergoes cyclical oscillation, which is due to either a tertiary component or periodic magnetic activity in the more massive component.

  11. Kepler Eclipsing Binary Stars. III. Classification of Kepler Eclipsing Binary Light Curves with Locally Linear Embedding

    NASA Astrophysics Data System (ADS)

    Matijevič, Gal; Prša, Andrej; Orosz, Jerome A.; Welsh, William F.; Bloemen, Steven; Barclay, Thomas

    2012-05-01

    We present an automated classification of 2165 Kepler eclipsing binary (EB) light curves that accompanied the second Kepler data release. The light curves are classified using locally linear embedding, a general nonlinear dimensionality reduction tool, into morphology types (detached, semi-detached, overcontact, ellipsoidal). The method, related to a more widely used principal component analysis, produces a lower-dimensional representation of the input data while preserving local geometry and, consequently, the similarity between neighboring data points. We use this property to reduce the dimensionality in a series of steps to a one-dimensional manifold and classify light curves with a single parameter that is a measure of "detachedness" of the system. This fully automated classification correlates well with the manual determination of morphology from the data release, and also efficiently highlights any misclassified objects. Once a lower-dimensional projection space is defined, the classification of additional light curves runs in a negligible time and the method can therefore be used as a fully automated classifier in pipeline structures. The classifier forms a tier of the Kepler EB pipeline that pre-processes light curves for the artificial intelligence based parameter estimator.

  12. A FOURIER OPTICS METHOD FOR CALCULATING STELLAR OCCULTATION LIGHT CURVES BY OBJECTS WITH THIN ATMOSPHERES

    SciTech Connect

    Young, E. F.

    2012-08-15

    A stellar occultation occurs when a solar system object passes in front of a distant star. The light curves resulting from stellar occultations can reveal many aspects of the obscuring object. For airless bodies, the diffraction light curve specifies the object's size, distance and, if several chords are observed, shape. Occultation light curves are especially sensitive to the presence of atmospheres; the refraction light curve is a function of the atmosphere's density, pressure, and temperature profiles. The goal of this paper is to develop a practical algorithm to model the simultaneous effects of diffraction and refraction for objects in which both phenomena are observable. The algorithm we present is flexible: it can be used to calculate light curves by objects with arbitrary shapes and arbitrary atmospheres (including the presence of opacity sources such as hazes), provided that the atmosphere can be represented by a thin screen with a phase delay and an opacity defined at each location in the screen. Because the algorithm is limited at present to thin atmospheres (in which rays from a star are bent but undergo virtually no translation as they pass through an atmosphere), the gas giants, Earth, Mars, and Venus are not treated. Examples of stellar occultations are presented for round or irregularly shaped objects having thin atmospheres of various column densities.

  13. KEPLER ECLIPSING BINARY STARS. III. CLASSIFICATION OF KEPLER ECLIPSING BINARY LIGHT CURVES WITH LOCALLY LINEAR EMBEDDING

    SciTech Connect

    Matijevic, Gal; Prsa, Andrej; Orosz, Jerome A.; Welsh, William F.; Bloemen, Steven; Barclay, Thomas E-mail: andrej.prsa@villanova.edu

    2012-05-15

    We present an automated classification of 2165 Kepler eclipsing binary (EB) light curves that accompanied the second Kepler data release. The light curves are classified using locally linear embedding, a general nonlinear dimensionality reduction tool, into morphology types (detached, semi-detached, overcontact, ellipsoidal). The method, related to a more widely used principal component analysis, produces a lower-dimensional representation of the input data while preserving local geometry and, consequently, the similarity between neighboring data points. We use this property to reduce the dimensionality in a series of steps to a one-dimensional manifold and classify light curves with a single parameter that is a measure of 'detachedness' of the system. This fully automated classification correlates well with the manual determination of morphology from the data release, and also efficiently highlights any misclassified objects. Once a lower-dimensional projection space is defined, the classification of additional light curves runs in a negligible time and the method can therefore be used as a fully automated classifier in pipeline structures. The classifier forms a tier of the Kepler EB pipeline that pre-processes light curves for the artificial intelligence based parameter estimator.

  14. Comparison of BRDF-Predicted and Observed Light Curves of GEO Satellites

    NASA Astrophysics Data System (ADS)

    Ceniceros, A.; Dao, P.; Gaylor, D.; Rast, R.; Anderson, J.; Pinon, E., III

    Although the amount of light received by sensors on the ground from Resident Space Objects (RSOs) in geostationary orbit (GEO) is small, information can still be extracted in the form of light curves (temporal brightness or apparent magnitude). Previous research has shown promising results in determining RSO characteristics such as shape, size, reflectivity, and attitude by processing simulated light curve data with various estimation algorithms. These simulated light curves have been produced using one of several existing analytic Bidirectional Reflectance Distribution Function (BRDF) models. These BRDF models have generally come from researchers in computer graphics and machine vision and have not been shown to be realistic for telescope observations of RSOs in GEO. While BRDFs have been used for SSA analysis and characterization, there is a lack of research on the validation of BRDFs with regards to real data. In this paper, we compared telescope data provided by the Air Force Research Laboratory (AFRL) with predicted light curves from the Ashikhmin-Premoze BRDF and two additional popular illumination models, Ashikhmin-Shirley and Cook-Torrance. We computed predicted light curves based on two line mean elements (TLEs), shape model, attitude profile, observing ground station location, observation time and BRDF. The predicted light curves were then compared with AFRL telescope data. The selected BRDFS provided accurate apparent magnitude trends and behavior, but uncertainties due to lack of attitude information and deficiencies in our satellite model prevented us from obtaining a better match to the real data. The current findings present a foundation for ample future research.

  15. On the reduction of occultation light curves. [stellar occultations by planets

    NASA Technical Reports Server (NTRS)

    Wasserman, L.; Veverka, J.

    1973-01-01

    The two basic methods of reducing occultation light curves - curve fitting and inversion - are reviewed and compared. It is shown that the curve fitting methods have severe problems of nonuniqueness. In addition, in the case of occultation curves dominated by spikes, it is not clear that such solutions are meaningful. The inversion method does not suffer from these drawbacks. Methods of deriving temperature profiles from refractivity profiles are then examined. It is shown that, although the temperature profiles are sensitive to small errors in the refractivity profile, accurate temperatures can be obtained, particularly at the deeper levels of the atmosphere. The ambiguities that arise when the occultation curve straddles the turbopause are briefly discussed.

  16. Nova Light Curves From The Solar Mass Ejection Imager (SMEI) - II. The extended catalog

    NASA Astrophysics Data System (ADS)

    Hounsell, R.; Darnley, M. J.; Bode, M. F.; Harman, D. J.; Surina, F.; Starrfield, S.; Holdsworth, D. L.; Bewsher, D.; Hick, P. P.; Jackson, B. V.; Buffington, A.; Clover, J. M.; Shafter, A. W.

    2016-04-01

    We present the results from observing nine Galactic novae in eruption with the Solar Mass Ejection Imager (SMEI) between 2004 and 2009. While many of these novae reached peak magnitudes that were either at or approaching the detection limits of SMEI, we were still able to produce light curves that in many cases contained more data at and around the initial rise, peak, and decline than those found in other variable star catalogs. For each nova, we obtained a peak time, maximum magnitude, and for several an estimate of the decline time ({t}{{2}}). Interestingly, although of lower quality than those found in Hounsell et al., two of the light curves may indicate the presence of a pre-maximum halt. In addition, the high cadence of the SMEI instrument has allowed the detection of low-amplitude variations in at least one of the nova light curves.

  17. Multi-filter Light Curves of 29 Very Short Period Candidate Contact Binaries.

    NASA Astrophysics Data System (ADS)

    Koen, C.; Koen, T.; Gray, R. O.

    2016-06-01

    Light curves of 26 probable contact binary stars are made available, from a list of candidates with the shortest periods known. This is supplemented by sets of light curves of three previously studied systems. Photometry was obtained in the Johnson UBV, Cousins RI system. All stars but one were observed in four wavebands, either UBV RC or {BV}{({RI})}C, depending on brightness. Tentative spectral classifications are given for 23 of the stars. Effective temperatures are derived from infrared and optical photometric indices, and from spectral types. These are generally in good agreement. The multicolor photometry, spectral typing, and estimated effective temperatures can be used to model these systems in detail. A preliminary study, based on Fourier coefficients of the light curves, suggests that all the systems are indeed eclipsing stars, with all but a handful probably in contact configurations.

  18. Stellar Surface Image of LO Pegasi via Light-curve Inversion

    NASA Astrophysics Data System (ADS)

    Harmon, Robert O.; Moore, C.; Decker, R.

    2009-01-01

    We present images of dark starspots on the surface of the K8 main-sequence star LO Pegasi. CCD images of the star and surrounding field were acquired through B, V, R and I filters at Perkins Observatory in June and July, 2008. The images were dark-subtracted and flat-fielded and then aperture photometry was performed to yield light curves through each of the four filters. These light curves were then simultaneously inverted via an algorithm devised by one of us (Harmon) so as to yield images of the spots based on the rotational modulation they produced in the light curves. The use of multiple filters significantly improves the latitude resolution of the reconstructions. Comparison of our results with results from 2006 and 2007 shows that the spot structure was more complex in 2008 than in the prior years. This research was funded by the NSF REU Program and the Ohio Wesleyan University Summer Science Research Program.

  19. An efficient method to compute microlensed light curves for point sources

    NASA Technical Reports Server (NTRS)

    Witt, Hans J.

    1993-01-01

    We present a method to compute microlensed light curves for point sources. This method has the general advantage that all microimages contributing to the light curve are found. While a source moves along a straight line, all micro images are located either on the primary image track or on the secondary image tracks (loops). The primary image track extends from - infinity to + infinity and is made of many sequents which are continuously connected. All the secondary image tracks (loops) begin and end on the lensing point masses. The method can be applied to any microlensing situation with point masses in the deflector plane, even for the overcritical case and surface densities close to the critical. Furthermore, we present general rules to evaluate the light curve for a straight track arbitrary placed in the caustic network of a sample of many point masses.

  20. ROTATIONAL PROPERTIES OF JUPITER TROJANS. I. LIGHT CURVES OF 80 OBJECTS

    SciTech Connect

    Mottola, Stefano; Erikson, Anders; Gonano-Beurer, Maria; Carsenty, Uri; Hahn, Gerhard; Di Martino, Mario; Carbognani, Albino; Schober, Hans-Josef; Lahulla, Felix; Delbo, Marco; Lagerkvist, Claes-Ingvar

    2011-05-15

    We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150 km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers.

  1. A PHYSICALLY BASED METHOD FOR SCALING CEPHEID LIGHT CURVES FOR FUTURE DISTANCE DETERMINATIONS

    SciTech Connect

    Freedman, Wendy L.; Madore, Barry F. E-mail: barry@obs.carnegiescience.ed

    2010-08-10

    We present a technique for decomposing Cepheid light curves into their fundamental constituent parts, that is, their radius and temperature variations. We demonstrate that any given pair of optical luminosity and color curves can be used to predict the shape, amplitude, and phase of a Cepheid's light variation at any other wavelength. With such predictions in hand, a single new observation at any given new wavelength can be used to normalize the properties of the predicted light curve, and in specific, derive a precise value of the time-averaged mean. We suggest that this method will be of great advantage in efficiently observing and precisely obtaining the mean properties of known Cepheids scheduled to be observed at new wavelengths, specifically in the mid-infrared where James Webb Space Telescope will be operating.

  2. The Kepler Light Curve of V344 LYR: Constraining the Thermal-Viscous Limit Cycle Instability

    NASA Technical Reports Server (NTRS)

    Cannizzo, J. K.; Still, M. D.; Howell, S. B.; Wood, M. A.; Smale, A. P.

    2010-01-01

    We present time dependent modeling based on the accretion disk limit cycle model for a 90 d light curve of the short period SU UMa-type dwarf nova V344 Lyr taken by Kepler. The unprecedented precision and cadence (1 minute) far surpass that generally available for long term light curves. The data encompass a super outburst, preceded by three normal (i.e., short) outbursts and followed by two normal outbursts. The main decay of the super outburst is nearly perfectly exponential, decaying at a rate approx.12 d/mag, while the much more rapid decays of the normal outbursts exhibit a faster-than-exponential shape. We show that the standard limit cycle model can account for the light curve, without the need for either the thermal-tidal instability or enhanced mass transfer.

  3. Rotational Properties of Jupiter Trojans. I. Light Curves of 80 Objects

    NASA Astrophysics Data System (ADS)

    Mottola, Stefano; Di Martino, Mario; Erikson, Anders; Gonano-Beurer, Maria; Carbognani, Albino; Carsenty, Uri; Hahn, Gerhard; Schober, Hans-Josef; Lahulla, Felix; Delbò, Marco; Lagerkvist, Claes-Ingvar

    2011-05-01

    We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150 km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers.

  4. Changing Amplitudes: Detecting RR Lyrae Light Curve Shape Variations in the Galactic Disk and Inner Halo

    NASA Astrophysics Data System (ADS)

    De Lee, Nathan M.; Kinemuchi, K.; Pepper, J.; Rodriguez, J. E.

    2014-01-01

    In this poster we will discuss our ongoing program to use extant light curves from the Kilodegree Extremely Little Telescope (KELT) survey to find and characterize RR Lyrae (RRL) stars in the disk and inner halo of the Milky Way. RRL stars are of particular interest because they are standard candles and can be used to map out structure in the galaxy. The periods and shape of RRL light curves also contain information about their Oosterhoff type, which can probe galactic formation history, and metallicity respectively. Although there have been several large photometric surveys for RR Lyrae in the nearby galaxy (OGLE, NSVS, ASAS, and MACHO to name a few), they have each been limited in either sky coverage or number of epochs. The KELT survey represents a new generation of surveys that has many epochs over a large portion of the sky. KELT samples 60% of the sky in both northern and southern hemispheres, and has a long-time-baseline of 4-8 years with a very high cadence rate of less than 20 minutes. This translates into 4,000 to 9,000 epochs per light curve with completeness out to 3 kpc from the Sun. Recent results from both Kepler and ground based surveys results suggest that as many as 50% of RR Lyrae stars show long-term modulation of their light curve shapes (Blazhko effect). These stars combined with RRL stars that pulsate in more than one mode give a sample of objects that the KELT survey is uniquely suited to explore. This poster concentrates on a pilot project to examine RRL stars in a limited number of KELT fields. In particular, we focus on, detecting RR Lyrae, developing a light curve shape-metallicity relationship in the KELT band-pass, and some initial characterization of RRL with either amplitude-modulated or period-modulated light curves.

  5. Rapidly rotating lenses: repeating features in the light curves of short-period binary microlenses

    NASA Astrophysics Data System (ADS)

    Penny, Matthew T.; Kerins, Eamonn; Mao, Shude

    2011-11-01

    Microlensing is most sensitive to binary lenses with relatively large orbital separations, and as such, typical binary microlensing events show little or no orbital motion during the event. However, despite the strength of binary microlensing features falling off rapidly as the lens separation decreases, we show that it is possible to detect repeating features in the light curve of binary microlenses that complete several orbits during the microlensing event. We investigate the light-curve features of such rapidly rotating lens (RRL) events. We derive analytical limits on the range of parameters where these effects are detectable, and confirm these numerically. Using a population synthesis Galactic model, we estimate the RRL event rate for a ground-based and a space-based microlensing survey to be 0.32fb and 7.8fb events per year, respectively, assuming year-round monitoring, where fb is the binary fraction. We detail how RRL event parameters can be quickly estimated from their light curves, and suggest a method to model RRL events using timing measurements of light-curve features. Modelling RRL light curves will yield the lens orbital period and possibly measurements of all orbital elements, including the inclination and eccentricity. Measurement of the period from the light curve allows a mass-distance relation to be defined, which when combined with a measurement of microlens parallax or finite-source effects can yield a mass measurement to a twofold degeneracy. With sub-per cent accuracy photometry, it is possible to detect planetary companions, but the likelihood of this is very small.

  6. Observable fractions of core-collapse supernova light curves brightened by binary companions

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.; Liu, Zheng-Wei; Izzard, Robert G.

    2015-07-01

    Many core-collapse supernova progenitors are presumed to be in binary systems. If a star explodes in a binary system, the early supernova light curve can be brightened by the collision of the supernova ejecta with the companion star. The early brightening can be observed when the observer is in the direction of the hole created by the collision. Based on a population synthesis model, we estimate the fractions of core-collapse supernovae in which the light-curve brightening by the collision can be observed. We find that 0.19 per cent of core-collapse supernova light curves can be observed with the collisional brightening. Type Ibc supernova light curves are more likely to be brightened by the collision (0.53 per cent) because of the high fraction of the progenitors being in binary systems and their proximity to the companion stars. Type II and IIb supernova light curves are less affected (˜10-3 and ˜10-2 per cent, respectively). Although the early, slow light-curve declines of some Type IIb and Ibc supernovae are argued to be caused by the collision with the companion star (e.g. SN 2008D), the small expected fraction, as well as the unrealistically small separation required, disfavour the argument. The future transient survey by the Large Synoptic Survey Telescope is expected to detect ˜10 Type Ibc supernovae with the early collisional brightening per year, and they will be able to provide information on supernova progenitors in binary systems.

  7. Light Curve Simulation Using Spacecraft CAD Models and Empirical Material Spectral BRDFS

    NASA Astrophysics Data System (ADS)

    Willison, A.; Bedard, D.

    This paper presents a Matlab-based light curve simulation software package that uses computer-aided design (CAD) models of spacecraft and the spectral bidirectional reflectance distribution function (sBRDF) of their homogenous surface materials. It represents the overall optical reflectance of objects as a sBRDF, a spectrometric quantity, obtainable during an optical ground truth experiment. The broadband bidirectional reflectance distribution function (BRDF), the basis of a broadband light curve, is produced by integrating the sBRDF over the optical wavelength range. Colour-filtered BRDFs, the basis of colour-filtered light curves, are produced by first multiplying the sBRDF by colour filters, and integrating the products. The software package's validity is established through comparison of simulated reflectance spectra and broadband light curves with those measured of the CanX-1 Engineering Model (EM) nanosatellite, collected during an optical ground truth experiment. It is currently being extended to simulate light curves of spacecraft in Earth orbit, using spacecraft Two-Line-Element (TLE) sets, yaw/pitch/roll angles, and observer coordinates. Measured light curves of the NEOSSat spacecraft will be used to validate simulated quantities. The sBRDF was chosen to represent material reflectance as it is spectrometric and a function of illumination and observation geometry. Homogeneous material sBRDFs were obtained using a goniospectrometer for a range of illumination and observation geometries, collected in a controlled environment. The materials analyzed include aluminum alloy, two types of triple-junction photovoltaic (TJPV) cell, white paint, and multi-layer insulation (MLI). Interpolation and extrapolation methods were used to determine the sBRDF for all possible illumination and observation geometries not measured in the laboratory, resulting in empirical look-up tables. These look-up tables are referenced when calculating the overall sBRDF of objects, where

  8. An 8 h characteristic time-scale in submillimetre light curves of Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Kelly, Brandon; Bower, Geoffrey C.; Marrone, Daniel P.; Stone, Jordan; Plambeck, Richard

    2014-08-01

    We compile and analyse long-term (≈10 yr) submillimetre (submm - 1.3, 0.87, 0.43 mm) wavelength light curves of the Galactic Centre black hole, Sagittarius A*. The 0.87 and 0.43 mm data are taken from the literature, while the majority of the 1.3 mm light curve is from previously unpublished SMA and CARMA data. We show that on minute to a few hour time-scales, the variability is consistent with a red noise process with a 230 GHz power-spectrum slope of β =2.3^{+0.8}_{-0.6} at 95 per cent confidence. The light curve is decorrelated (white noise) on long (month to year) times. We measure a transition time between red and white noise of τ = 8_{-4}^{+3} h at 230 GHz at 95 per cent confidence, with consistent results at 345 and 690 GHz. This corresponds to ≈10 orbital times or ≈1 inflow (viscous) time at R = 3Rs, a typical radius producing the 230 GHz emission as measured by very long baseline interferometry and found in theoretical accretion flow and jet models. This time-scale is shorter (longer) than those measured by some analyses of radio (near-infrared) light curves. It is roughly consistent with the analogous time-scale inferred in studies of quasar optical light curves after accounting for the difference in emission radius. We find evidence that the submm variability persists at least down to the innermost stable circular orbit, if not the event horizon. These results can be compared quantitatively with similar analyses at different wavebands to test for connections between the variability mechanisms, and with light curves from theoretical models of accreting black holes.

  9. Light Curves and Spectra from a Thermonuclear Explosion of a White Dwarf Merger

    NASA Astrophysics Data System (ADS)

    van Rossum, Daniel R.; Kashyap, Rahul; Fisher, Robert; Wollaeger, Ryan T.; García-Berro, Enrique; Aznar-Siguán, Gabriela; Ji, Suoqing; Lorén-Aguilar, Pablo

    2016-08-01

    Double-degenerate (DD) mergers of carbon–oxygen white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). However, many outstanding questions surround DD mergers, including the characteristics of their light curves and spectra. We have recently identified a spiral instability in the post-merger phase of DD mergers and demonstrated that this instability self-consistently leads to detonation in some cases. We call this the spiral merger SN Ia model. Here, we utilize the SuperNu radiative transfer software to calculate three-dimensional synthetic light curves and spectra of the spiral merger simulation with a system mass of 2.1 {M}ȯ from Kashyap et al. Because of their large system masses, both violent and spiral merger light curves are slowly declining. The spiral merger resembles very slowly declining SNe Ia, including SN 2001ay, and provides a more natural explanation for its observed properties than other SN Ia explosion models. Previous synthetic light curves and spectra of violent DD mergers demonstrate a strong dependence on viewing angle, which is in conflict with observations. Here, we demonstrate that the light curves and spectra of the spiral merger are less sensitive to the viewing angle than violent mergers, in closer agreement with observation. We find that the spatial distribution of 56Ni and IMEs follows a characteristic hourglass shape. We discuss the implications of the asymmetric distribution of 56Ni for the early-time gamma-ray observations of 56Ni from SN 2014J. We suggest that DD mergers that agree with the light curves and spectra of normal SNe Ia will likely require a lower system mass.

  10. Periodicity analysis of the radio light curve of the Seyfert galaxy III Zw 2

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Xie, G. Z.; Dai, H.; Chen, L. E.; Yi, T. F.; Tang, Y. K.; Bao, Y. Y.; Lü, L. Z.; Na, W. W.; Ren, J. Y.

    2010-02-01

    We have analyzed the radio light curves of the Seyfert galaxy III Zw 2 at 22 and 37 GHz taken from the database of Metsähovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity, with very complicated non-sinusoidal variations. Period of Pobs = 5.14 ± 0.19 yr was consistently identified by three methods: the Jurkevich method, the power spectrum intensity estimation method and the discrete correlation function method. The variability period of about 5.14 yr in III Zw 2 is caused most likely by the helical motion of the jet.

  11. Reconstruction of the Structure of Accretion Disks in Dwarf Novae from the Multi-Band Light Curves of Early Superhumps

    NASA Astrophysics Data System (ADS)

    Uemura, Makoto; Kato, Taichi; Ohshima, Tomohito; Maehara, Hiroyuki

    2012-10-01

    We propose a new method to reconstruct the structure of accretion disks in dwarf novae using multi-band light curves of early superhumps. Our model assumes that early superhumps are caused by the rotation effect of non-axisymmetrically flaring disks. We have developed a Bayesian model for this reconstruction, in which a smoother disk-structure tends to have a higher prior probability. We analyzed simultaneous optical and near-infrared photometric data of early superhumps of the dwarf nova, V455 And using this technique. The reconstructed disk has two flaring parts in the outermost region of the disk. These parts are responsible for the primary and secondary maxima of the light curves. The height-to-radius ratio is h/r 0.20-0.25 in the outermost region. In addition to the outermost flaring structures, flaring arm-like patterns can be seen in an inner region of the reconstructed disk. The overall profile of the reconstructed disk is reminiscent of the disk structure that is deformed by the tidal effect. However, an inner arm-like pattern, which is responsible for the secondary minimum in the light curve, cannot be reproduced only by the tidal effect. It implies the presence of another mechanism that deforms the disk structure. Alternatively, the temperature distribution of the disk could be non-axisymmetric. We demonstrate that the disk structure with weaker arm-like patterns is optimal in the model including the irradiation effect. However, the strongly irradiated disk gives quite blue colors, which may conflict with the observation. Our results suggest that the amplitude of early superhumps depends mainly on the height of the outermost flaring regions of the disk. We predict that early superhumps can be detected with an amplitude of > 0.02 mag in about 90% of WZ Sge stars.

  12. Using Light Curves to Characterize Size and Shape of Pseudo-Debris

    NASA Technical Reports Server (NTRS)

    Rodriquez, Heather M.; Abercromby, Kira J.; Jarvis, Kandy S.; Barker, Edwin

    2006-01-01

    Photometric measurements were collected for a new study aimed at estimating orbital debris sizes based on object brightness. To obtain a size from optical measurements the current practice is to assume an albedo and use a normalized magnitude to calculate optical size. However, assuming a single albedo value may not be valid for all objects or orbit types; material type and orientation can mask an object s true optical cross section. This experiment used a CCD camera to record data, a 300 W Xenon, Ozone Free collimated light source to simulate solar illumination, and a robotic arm with five degrees of freedom to move the piece of simulated debris through various orientations. The pseudo-debris pieces used in this experiment originate from the European Space Operations Centre s ESOC2 ground test explosion of a mock satellite. A uniformly illuminated white ping-pong ball was used as a zero-magnitude reference. Each debris piece was then moved through specific orientations and rotations to generate a light curve. This paper discusses the results of five different object-based light curves as measured through an x-rotation. Intensity measurements, from which each light curve was generated, were recorded in five degree increments from zero to 180 degrees. Comparing light curves of different shaped and sized pieces against their characteristic length establishes the start of a database from which an optical size estimation model will be derived in the future.

  13. Bolometric light curves and explosion parameters of 38 stripped-envelope core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Lyman, J. D.; Bersier, D.; James, P. A.; Mazzali, P. A.; Eldridge, J. J.; Fraser, M.; Pian, E.

    2016-03-01

    Literature data are collated for 38 stripped-envelope core-collapse supernovae (SE SNe; i.e. SNe IIb, Ib, Ic and Ic-BL) that have good light-curve coverage in more than one optical band. Using bolometric corrections derived in previous work, the bolometric light curve of each SN is recovered and template bolometric light curves provided. Peak light distributions and decay rates are investigated; SNe subtypes are not cleanly distinguished in this parameter space, although some grouping of types does occur and there is a suggestion of a Phillips-like relation for most SNe Ic-BL. The bolometric light curves are modelled with a simple analytical prescription and compared to results from more detailed modelling. Distributions of the explosion parameters show the extreme nature of SNe Ic-BL in terms of their 56Ni mass and the kinetic energy, however ejected masses are similar to other subtypes. SNe Ib and Ic have very similar distributions of explosion parameters, indicating a similarity in progenitors. SNe IIb are the most homogeneous subtype and have the lowest average values for 56Ni mass, ejected mass, and kinetic energy. Ejecta masses for each subtype and SE SNe as a whole are inconsistent with those expected from very massive stars. The majority of the ejecta mass distribution is well described by more moderately massive progenitors in binaries, indicating these are the dominant progenitor channel for SE SNe.

  14. Using Light Curves to Characterize Size and Shape of Pseudo-Debris

    NASA Astrophysics Data System (ADS)

    Rodriguez, H.; Abercromby, K.; Jarvis, K.; Barker, E.

    Photometric measurements were collected for a new study aimed at estimating orbital debris sizes based on object brightness. To obtain a size from optical measurements the current practice is to assume an albedo and use a normalized magnitude to calculate optical size. However, assuming a single albedo value may not be valid for all objects or orbit types and material type and orientation can mask an object's true optical cross section. This experiment used a CCD camera to record data, a 300 W Xenon Ozone Free collimated light source to simulate solar illumination, and a robotic arm with five degrees of freedom to move the piece of simulated debris through various orientations. The pseudo-debris pieces used in this experiment originate from the European Space Operations Centre's ESOC2 ground test explosion of a mock satellite. A uniformly illuminated white ping-pong ball was used as a zero-magnitude reference. Each debris piece was then moved through specific orientations and rotations to generate a light curve. This paper discusses the results of five different object-based light curves as measured through an x-rotation. Intensity measurements, from which each light curve was generated, were recorded in five degree increments from zero to 360 degrees. Comparing light curves of different shaped and sized pieces against their characteristic length establishes the start of a database from which an optical size estimation model will be derived in the future.

  15. Gamma-Ray Pulsar Light Curves in Offset Polar Cap Geometry

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; DeCesar, Megan; Miller, M. Coleman

    2011-01-01

    Recent studies have shown that gamma-ray pulsar light curves are very sensitive to the geometry of the pulsar magnetic field. Pulsar magnetic field geometries, such as the retarded vacuum dipole and force-free magnetospheres, used to model high-energy light curves have distorted polar caps that are offset from the magnetic axis in the direction opposite to rotation. Since this effect is due to the sweepback of field lines near the light cylinder, offset polar caps are a generic property of pulsar magnetospheres and their effects should be included in gamma-ray pulsar light curve modeling. In slot gap models (having two-pole caustic geometry), the offset polar caps cause a strong azimuthal asymmetry of the particle acceleration around the magnetic axis. We have studied the effect of the offset polar caps in both retarded vacuum dipole and force-free geometry on the model high-energy pulse profile. We find that. corn pared to the profile:-; derived from :-;ymmetric caps, the flux in the pulse peaks, which are caustics formed along the trailing magnetic field lines. increases significantly relative to the off-peak emission. formed along leading field lines. The enhanced contrast produces greatly improved slot gap model fits to Fermi pulsar light curves like Vela, which show very little off-peak emIssIon.

  16. PERTURBATIONS OF SNe Ia LIGHT CURVES, COLORS, AND SPECTRAL FEATURES BY CIRCUMSTELLAR DUST

    SciTech Connect

    Amanullah, Rahman; Goobar, Ariel

    2011-07-01

    It has been suggested that multiple scattering on circumstellar dust could explain the non-standard reddening observed in the line of sight to Type Ia supernovae. In this work, we use Monte Carlo simulations to examine how the scattered light would affect the shape of optical light curves and spectral features. We find that the effects on the light curve widths, apparent time evolution of color excess, and blending of spectral features originating at different photospheric velocities should allow for tests of the circumstellar dust hypothesis on a case by case basis. Our simulations also show that for circumstellar shells with radii r = 10{sup 16}-10{sup 19} cm, the light curve modifications are well described by the empirical {Delta}m{sub 15} parameter and intrinsic color variations of order {sigma}{sub BV} = 0.05-0.1 arise naturally. For large shell radii an excess light curve tail is expected in B-band, as observed in, e.g., SN2006X.

  17. THE EFFECT OF A TIME-VARYING ACCRETION DISK SIZE ON QUASAR MICROLENSING LIGHT CURVES

    SciTech Connect

    Blackburne, Jeffrey A.; Kochanek, Christopher S. E-mail: ckochanek@astronomy.ohio-state.ed

    2010-08-01

    Microlensing perturbations to the magnification of gravitationally lensed quasar images are dependent on the angular size of the quasar. If quasar variability at visible wavelengths is caused by a change in the area of the accretion disk, it will affect the microlensing magnification. We derive the expected signal, assuming that the luminosity scales with some power of the disk area, and estimate its amplitude using simulations. We discuss the prospects for detecting the effect in real-world data and for using it to estimate the logarithmic slope of the luminosity's dependence on disk area. Such an estimate would provide a direct test of the standard thin accretion disk model. We tried fitting six seasons of the light curves of the lensed quasar HE 0435-1223 including this effect as a modification to the Kochanek et al. approach to estimating time delays. We find a dramatic improvement in the goodness of fit and relatively plausible parameters, but a robust estimate will require a full numerical calculation in order to correctly model the strong correlations between the structure of the microlensing magnification patterns and the magnitude of the effect. We also comment briefly on the effect of this phenomenon for the stability of time-delay estimates.

  18. LATE-TIME LIGHT CURVES OF TYPE II SUPERNOVAE: PHYSICAL PROPERTIES OF SUPERNOVAE AND THEIR ENVIRONMENT

    SciTech Connect

    Otsuka, Masaaki; Meixner, Margaret; Panagia, Nino; Fabbri, Joanna; Barlow, Michael J.; Wesson, Roger; Clayton, Geoffrey C.; Andrews, Jennifer E.; Gallagher, Joseph S.; Sugerman, Ben E. K.; Ercolano, Barbara; Welch, Douglas E-mail: otsuka@asiaa.sinica.edu.tw

    2012-01-01

    We present BVRIJHK-band photometry of six core-collapse supernovae, SNe 1999bw, 2002hh, 2003gd, 2004et, 2005cs, and 2006bc, measured at late epochs (>2 yr) based on the Hubble Space Telescope (HST), and the Gemini North, and WIYN telescopes. We also show the JHK light curves of supernova impostor SN 2008S up to day 575 because it was serendipitously in our SN 2002hh field of view. Of our 43 HST observations in total, 36 observations are successful in detecting the light from the SNe alone and measuring magnitudes of all the targets. HST observations show a resolved scattered light echo around SN 2003gd at day 1520 and around SN 2002hh at day 1717. Our Gemini and WIYN observations detected SNe 2002hh and 2004et as well. Combining our data with previously published data, we show VRIJHK-band light curves and estimate decline magnitude rates at each band in four different phases. Our prior work on these light curves and other data indicate that dust is forming in our targets from days {approx}300 to 400, supporting SN dust formation theory. In this paper we focus on other physical properties derived from late-time light curves. We estimate {sup 56}Ni masses for our targets (0.5-14 Multiplication-Sign 10{sup -2} M{sub Sun }) from the bolometric light curve of each of days {approx}150-300 using SN 1987A as a standard (7.5 Multiplication-Sign 10{sup -2} M{sub Sun }). The flattening or sometimes increasing fluxes in the late-time light curves of SNe 2002hh, 2003gd, 2004et, and 2006bc indicate the presence of light echoes. We estimate the circumstellar hydrogen density of the material causing the light echo and find that SN 2002hh is surrounded by relatively dense materials (n(H) >400 cm{sup -3}) and SNe 2003gd and 2004et have densities more typical of the interstellar medium ({approx}1 cm{sup -3}). We analyze the sample as a whole in the context of physical properties derived in prior work. The {sup 56}Ni mass appears well correlated with progenitor mass with a slope of 0

  19. The Varying Light Curve and Timings of the Ultrashort-period Contact Binary KIC 9532219

    NASA Astrophysics Data System (ADS)

    Lee, Jae Woo; Hong, Kyeongsoo; Koo, Jae-Rim; Park, Jang-Ho

    2016-03-01

    KIC 9532219 is a W UMa-type eclipsing binary with an orbital period of 0.1981549 days that is below the short-period limit (˜0.22 days) of the period distribution for contact binaries. The Kepler light curve of the system exhibits striking changes in both eclipse depths and light maxima. Applying third-body and spot effects, the light-curve synthesis indicates that the eclipsing pair is currently in a marginal contact stage with a mass ratio of q = 1.20, an orbital inclination of i = 66.°0, a temperature difference of T1-T2 = 172 K, and a third light of l3 = 75.9%. To understand the light variations with time, we divided up the light curve into 312 segments and analyzed them separately. The results reveal that variation of eclipse depth is primarily caused by changing amounts of contamination due to the nearby star KIC 9532228 between the Kepler Quarters and that the variable O’Connell effect originates from the starspot activity on the less massive primary component. Based on our light-curve timings, a period study of KIC 9532219 indicates that the orbital period has varied as a combination of a downward parabola and a light-travel-time (LTT) effect due to a third body, which has a period of 1196 days and a minimum mass of 0.0892 M⊙ in an orbit of eccentricity 0.150. The parabolic variation could be a small part of a second LTT orbit due to a fourth component in a wider orbit, instead of either mass transfer or angular momentum loss.

  20. Characterizing the V-band Light-curves of Hydrogen-rich Type II Supernovae

    NASA Astrophysics Data System (ADS)

    Anderson, Joseph P.; González-Gaitán, Santiago; Hamuy, Mario; Gutiérrez, Claudia P.; Stritzinger, Maximilian D.; Olivares E., Felipe; Phillips, Mark M.; Schulze, Steve; Antezana, Roberto; Bolt, Luis; Campillay, Abdo; Castellón, Sergio; Contreras, Carlos; de Jaeger, Thomas; Folatelli, Gastón; Förster, Francisco; Freedman, Wendy L.; González, Luis; Hsiao, Eric; Krzemiński, Wojtek; Krisciunas, Kevin; Maza, José; McCarthy, Patrick; Morrell, Nidia I.; Persson, Sven E.; Roth, Miguel; Salgado, Francisco; Suntzeff, Nicholas B.; Thomas-Osip, Joanna

    2014-05-01

    We present an analysis of the diversity of V-band light-curves of hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several magnitude measurements are defined, together with decline rates at different epochs, and time durations of different phases. It is found that magnitudes measured at maximum light correlate more strongly with decline rates than those measured at other epochs: brighter supernovae at maximum generally have faster declining light-curves at all epochs. We find a relation between the decline rate during the "plateau" phase and peak magnitudes, which has a dispersion of 0.56 mag, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the "plateau" stage, through to the brightest events which decline much faster. A large range in optically thick phase durations is observed, implying a range in progenitor envelope masses at the epoch of explosion. During the radioactive tails, we find many supernovae with faster declining light-curves than expected from full trapping of radioactive emission, implying low mass ejecta. It is suggested that the main driver of light-curve diversity is the extent of hydrogen envelopes retained before explosion. Finally, a new classification scheme is introduced where hydrogen-rich events are typed as simply "SN II" with an "s 2" value giving the decline rate during the "plateau" phase, indicating its morphological type. Based on observations obtained with the du-Pont and Swope telescopes at LCO, and the Steward Observatory's CTIO60, SO90 and CTIO36 telescopes.

  1. Characterizing the V-band light-curves of hydrogen-rich type II supernovae

    SciTech Connect

    Anderson, Joseph P.; González-Gaitán, Santiago; Hamuy, Mario; Gutiérrez, Claudia P.; Antezana, Roberto; De Jaeger, Thomas; Förster, Francisco; González, Luis; Stritzinger, Maximilian D.; Contreras, Carlos; Olivares E, Felipe; Phillips, Mark M.; Campillay, Abdo; Castellón, Sergio; Hsiao, Eric; Schulze, Steve; Bolt, Luis; Folatelli, Gastón; Freedman, Wendy L.; Krzemiński, Wojtek; and others

    2014-05-01

    We present an analysis of the diversity of V-band light-curves of hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several magnitude measurements are defined, together with decline rates at different epochs, and time durations of different phases. It is found that magnitudes measured at maximum light correlate more strongly with decline rates than those measured at other epochs: brighter supernovae at maximum generally have faster declining light-curves at all epochs. We find a relation between the decline rate during the 'plateau' phase and peak magnitudes, which has a dispersion of 0.56 mag, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the 'plateau' stage, through to the brightest events which decline much faster. A large range in optically thick phase durations is observed, implying a range in progenitor envelope masses at the epoch of explosion. During the radioactive tails, we find many supernovae with faster declining light-curves than expected from full trapping of radioactive emission, implying low mass ejecta. It is suggested that the main driver of light-curve diversity is the extent of hydrogen envelopes retained before explosion. Finally, a new classification scheme is introduced where hydrogen-rich events are typed as simply 'SN II' with an 's {sub 2}' value giving the decline rate during the 'plateau' phase, indicating its morphological type.

  2. Shock Breakout and Early Light Curves of Type II-P Supernovae Observed with Kepler

    NASA Astrophysics Data System (ADS)

    Garnavich, Peter M.; Tucker, Bradley E.; Rest, Armin; Shaya, Edward J.; Olling, Robert; Kasen, Daniel; Villar, Victoria; KEGS

    2016-01-01

    We discovered two transient events in the Kepler field with light curves that strongly suggest they are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate the rise time to maximum for KSN2011a and KSN2011d as 10.5±0.4 and 13.3±0.4 rest-frame days respectively. We find the progenitor radius of KSN2011a (280±20 R⊙) to be significantly smaller than that for KSN2011d (490±20 R⊙) but both have similar explosion energies of 2.0±0.3 ×1051 erg.The rising light curve of KSN2011d is an excellent match to that predicted by simple models of exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the RSG. A mass loss rate of 10-4 M⊙ yr-1 from the RSG can explain the fast rise without impacting the optical flux at maximum light or the shape of the post-maximum light curve.No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar interaction suspected in the fast rising light curve. The early light curve of KSN2011d does show excess emission consistent with model predictions of a shock breakout. This is the first optical detection of a shock breakout from a type II-P supernova.

  3. Shock Breakout and Early Light Curves of Type II-P Supernovae Observed with Kepler

    NASA Astrophysics Data System (ADS)

    Garnavich, P. M.; Tucker, B. E.; Rest, A.; Shaya, E. J.; Olling, R. P.; Kasen, D.; Villar, A.

    2016-03-01

    We discovered two transient events in the Kepler field with light curves that strongly suggest they are type II-P supernovae (SNe II-P). Using the fast cadence of the Kepler observations we precisely estimate the rise time to maximum for KSN2011a and KSN2011d as 10.5 ± 0.4 and 13.3 ± 0.4 rest-frame days, respectively. Based on fits to idealized analytic models, we find the progenitor radius of KSN2011a (280 ± 20 R⊙) to be significantly smaller than that for KSN2011d (490 ± 20 R⊙), but both have similar explosion energies of 2.0 ± 0.3 × 1051 erg. The rising light curve of KSN2011d is an excellent match to that predicted by simple models of exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models predict, possibly due to the supernova shock wave moving into pre-existing wind or mass-loss from the RSG. A mass-loss rate of 10-4M⊙ yr-1 from the RSG can explain the fast rise without impacting the optical flux at maximum light or the shape of the post-maximum light curve. No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar interaction suspected in the fast rising light curve. The early light curve of KSN2011d does show excess emission consistent with model predictions of a shock breakout. This is the first optical detection of a shock breakout from a SNe II-P.

  4. Ultraviolet light curves of beta Lyrae: Comparison of OAO A-2, IUE, and Voyager Observations

    NASA Technical Reports Server (NTRS)

    Kondo, Yoji; Mccluskey, George E.; Silvis, Jeffery M. S.; Polidan, Ronald S.; Mccluskey, Carolina P. S.; Eaton, Joel A.

    1994-01-01

    The six-band ultraviolet light curves of beta Lyrae obtained with the Orbiting Astronomical Observatory (OAO) A-2 in 1970 exhibited a very unusual behavior. The secondary minimum deepened at shorter wavelength, indicating that one was not observing light variations caused primarily by the eclipses of two stars having a roughly Planckian energy distribution. It was then suggested that the light variations were caused by a viewing angle effect of an optically thick, ellipsoidal circumbinary gas cloud. Since 1978 beta Lyrae has been observed with the International Ultraviolet Explorer (IUE) satellite. We have constructed ultraviolet light curves from the IUE archival data for comparison with the OAO A-2 results. We find that they are in substantial agreement with each other. The Voyager ultraviolet spectrometer was also used to observe this binary during a period covered by IUE observations. The Voyager results agree with those of the two other satellite observatories at wavelengths longer than about 1350 A. However, in the wavelength region shorter than the Lyman-alpha line at 1216 A, the light curves at 1085 and 965 A show virtually no light variation except an apparent flaring near phase 0.7, which is also in evidence at longer wavelengths. We suggest that the optically thick circumbinary gas cloud, which envelops the two stars completely, assumes a roughly spherical shape when observed at these shorter wavelengths.

  5. The problem of the W-type light curve of W Ursae Majoris

    NASA Astrophysics Data System (ADS)

    Linnell, Albert P.

    1987-05-01

    Proposals to explain the W-type light curves of W UMa are discussed, and observational data are found to be inconsistent with an explanation of the curves in terms of starspots preferentially located on the primary component. The Rucinski (1983) hot-secondary model produces a reasonably close fit to most of the previously published UBVRI data, consistent with the existence of an enthalpy gradient between components of W UMa and the photosphere, though it fails to fit the ANS data of Eaton et al. (1980) in the FUV. The observed transition to a marginally A-type light curve at 2200 A can be explained by a UV excess on the primary component.

  6. A SIGNATURE OF CHEMICAL SEPARATION IN THE COOLING LIGHT CURVES OF TRANSIENTLY ACCRETING NEUTRON STARS

    SciTech Connect

    Medin, Zach; Cumming, Andrew E-mail: cumming@physics.mcgill.ca

    2014-03-01

    We show that convection driven by chemical separation can significantly affect the cooling light curves of accreting neutron stars after they go into quiescence. We calculate the thermal relaxation of the neutron star ocean and crust including the thermal and compositional fluxes due to convection. After the inward propagating cooling wave reaches the base of the neutron star ocean, the ocean begins to freeze, driving chemical separation. The resulting convection transports heat inward, giving much faster cooling of the surface layers than found assuming the ocean cools passively. The light curves including convection show a rapid drop in temperature weeks after outburst. Identifying this signature in observed cooling curves would constrain the temperature and composition of the ocean as well as offer a real time probe of the freezing of a classical multicomponent plasma.

  7. Exploring the Potential Diversity of Early Type Ia Supernova Light Curves

    NASA Astrophysics Data System (ADS)

    Piro, Anthony L.; Morozova, Viktoriya S.

    2016-07-01

    During the first several days after explosion, Type Ia supernova light curves probe the outer layers of the exploding star, and therefore provide important clues for identifying their progenitors. We investigate how both the shallow 56Ni distribution and the presence of circumstellar material shape these early light curves. This is performed using a series of numerical experiments with parameterized properties for systematic exploration. Although not all of the considered models may be realized in nature (and indeed there are arguments why some of them should not occur), the spirit of this work is to provide a broader exploration of the diversity of possibilities. We find that shallower 56Ni leads to steeper, bluer light curves. Differences in the shape of the rise can introduce errors in estimating the explosion time, and thus impact efforts to infer upper limits on the progenitor or companion radius from a lack of observed shock cooling emission. Circumstellar material can lead to significant luminosity during the first few days, but its presence can be difficult to identify depending on the degree of nickel mixing. In some cases, the hot emission of circumstellar material may even lead to a signature similar to an interaction with a companion, and thus in the future additional diagnostics should be gathered for properly assessing early light curves.

  8. THE KEPLER LIGHT CURVE OF V344 Lyrae: CONSTRAINING THE THERMAL-VISCOUS LIMIT CYCLE INSTABILITY

    SciTech Connect

    Cannizzo, J. K.; Howell, S. B.; Wood, M. A.; Smale, A. P. E-mail: Martin.D.Still@nasa.go

    2010-12-20

    We present time-dependent modeling based on the accretion disk limit cycle model for a 270 d light curve of the short-period SU UMa-type dwarf nova V344 Lyr taken by Kepler. The unprecedented precision and cadence (1 minute) far surpass that generally available for long-term light curves. The data encompass two superoutbursts and 17 normal (i.e., short) outbursts. The main decay of the superoutbursts is nearly perfectly exponential, decaying at a rate {approx}12 d mag{sup -1}, while the much more rapid decays of the normal outbursts exhibit a faster-than-exponential shape. Our modeling using the basic accretion disk limit cycle can produce the main features of the V344 Lyr light curve, including the peak outburst brightness. Nevertheless, there are obvious deficiencies in our model light curves. (1) The rise times we calculate, both for the normal and superoutbursts, are too fast. (2) The superoutbursts are too short. (3) The shoulders on the rise to superoutburst have more structure than the shoulders in the observed superoutbursts and are too slow, comprising about a third to half of the total viscous plateau, rather than the {approx}10% observed. However, one of the {alpha}{sub cold} {r_reversible} {alpha}{sub hot} interpolation schemes we investigate (one that is physically motivated) does yield longer superoutbursts with suitably short, less structured shoulders.

  9. Comparing the Light Curves of Simulated Type Ia Supernovae with Observations Using Data-driven Models

    NASA Astrophysics Data System (ADS)

    Diemer, Benedikt; Kessler, Richard; Graziani, Carlo; Jordan, George C., IV; Lamb, Donald Q.; Long, Min; van Rossum, Daniel R.

    2013-08-01

    We propose a robust, quantitative method to compare the synthetic light curves of a Type Ia supernova (SN Ia) explosion model with a large set of observed SNe Ia, and derive a figure of merit for the explosion model's agreement with observations. The synthetic light curves are fit with the data-driven model SALT2 which returns values for stretch, color, and magnitude at peak brightness, as well as a goodness-of-fit parameter. Each fit is performed multiple times with different choices of filter bands and epoch range in order to quantify the systematic uncertainty on the fitted parameters. We use a parametric population model for the distribution of observed SN Ia parameters from large surveys, and extend it to represent red, dim, and bright outliers found in a low-redshift SN Ia data set. We discuss the potential uncertainties of this population model and find it to be reliable given the current uncertainties on cosmological parameters. Using our population model, we assign each set of fitted parameters a likelihood of being observed in nature, and a figure of merit based on this likelihood. We define a second figure of merit based on the quality of the light curve fit, and combine the two measures into an overall figure of merit for each explosion model. We compute figures of merit for a variety of one-, two-, and three-dimensional explosion models and show that our evaluation method allows meaningful inferences across a wide range of light curve quality and fitted parameters.

  10. Fractal Property in the Light Curve of BL Lac Object S5 0716 + 714

    NASA Astrophysics Data System (ADS)

    Ou, J. W.; Zheng, Y. G.

    2014-09-01

    In this paper, we compile the historical R-band data of S5 0716 + 714 from literature and obtain its fractal dimension by using a fractal method and then simulate the data with the Weierstrass-Mandelbrot (W-M) function. It is considered that the light curve has a fractal property.

  11. Photometric light curves for ten rapidly rotating stars in Alpha Persei, the Pleiades, and the field

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Schild, Rudolph E.; Stauffer, John R.; Jones, Burton F.

    1993-01-01

    We present the results from a photometric monitoring program of ten rapidly rotating stars observed during 1991 using the FLWO 48-in. telescope. Brightness variations for an additional six cluster stars observed with the Lick 40-in. telescope are also given. The periods and light curves for seven Alpha Persei members, two Pleiades members, and one naked T Tauri field star are reported.

  12. Stella Surface Imaging of LO Pegasi via Light-Curve Inversion

    NASA Astrophysics Data System (ADS)

    Miller, Jessie; Richard, Andrea; Harmon, Robert

    2009-10-01

    The purpose of this research was to map the starspots on LO Pegasi (HIP 106231), a K8 main-sequence star, in order to create an image of the star's photosphere. CCD images of LO Pegasi were taken during May, June, and July 2009 through B, V, R, and I photometric filters using a 0.2-m Meade Instruments LX200 Schmidt-Cassegrain telescope and Santa Barbara Instruments Group ST-8XE CCD camera at Perkins Observatory. Differential aperture photometry was performed on the images so as to create light curves in the form of plots of intensity vs. rotational phase. The lightcurves were processed via the Light-Curve Inversion (LI) algorithm. This algorithm creates a reconstructed image of the star's surface showing the locations of starspots. The locations of the spots visible on the 2009 are at lower latitudes than those deduced from the 2008 light curves. In addition, overall dimming observed of LO Pegasi since 2008 implies that there is a spot on the visible pole. Since a polar spot does not modulate the rotational light curve, it is not reproduced in our images.

  13. Variable Stars in the 3.6 Year DIRBE Near-Infrared Light Curve Archive

    NASA Astrophysics Data System (ADS)

    Kraemer, Kathleen E.; Price, S. D.; Smith, B. J.; Kuchar, T. A.; Mizuno, D. R.; Webb, J.

    2011-05-01

    The 3.6 year light curve archive created by Price et al. (2010) from the cryo+post-cryo Diffuse Infrared Background Experiment (DIRBE) mission contains a wealth of variable star information at 1.25, 2.2, 3.5, and 4.9 microns. Of the 2700 objects in the archive, over 500 show strong variability and another 75 show potential variability. We have combined visible observations obtained during the DIRBE extended mission with the infrared archive to investigate wavelength-dependent phase lags between the visible and the near-IR maxima, extending the study of Smith et al. (2006) to those stars with periods longer than the 300 day cryo mission. Of those 518 stars exhibiting strong near-infrared variability, 200 have visible light curves in the American Association of Variable Star Observers database during the DIRBE mission. Because viewing geometry for both the visible observers and DIRBE mission limited the opportunities for observing the stars, the light curves were inspected to determine if the peaks were defined well enough to determine phase lags among the five wavebands. For those objects that have sufficient data, we investigate a number of methods to best estimate the peaks and thus find the phase lags, if any. We have also examined the differences in phase dependence on variable type, e.g. Miras, SRa's, SRb's, and carbon stars. The DIRBE light curve data are available to the community through the Vizier service at the Centre de Donnees Astronomique de Strasbourg.

  14. Extending ROSAT Light Curves of Ecliptic Pole AGN Formation and Galaxy Evolution

    NASA Technical Reports Server (NTRS)

    Malkan, Matthew A.

    1997-01-01

    In collaboration with UCLA graduate student Fred Baganoff, Professor Malkan has obtained the longest continuous light curves ever available for a large sample (# = 60) of active galactic nuclei. This was accomplished by using the ROSATAII-Sky Survey, which covered the ecliptic pole regions once every 9O-minute orbit. Using this Astrophysics Data Processing grant from NASA, we extended these light curves by combining the RASS data with pointed observations over the next several years of operation of the ROSAT PSPC. This lengthens the baselines of about half of the light curves from a few months up to a few years. The proportion of AGN showing variability increases substantially with this improvement. In fact most AGN in this representative sample are now shown to be significantly variable in the X-rays. We are also able to say something about the amplitudes of variability on timescales from days to years, with more detail than previously has been possible. We have also identified some dependence of the X-ray variability properties on a) the luminosity of the AGN; and b) The presence of a "Blazar" nucleus. By extending the ROSAT light curves, we are also able to learn more about the correlation of X-ray and optical emission on longer time-scales. It appears to be very weak, at best.

  15. Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

    NASA Technical Reports Server (NTRS)

    Nousek, J. A.; Kouveliotou, C.; Grupe, D.; Page, K.; Granot, J.; Ramirez-Ruiz, E.; Patel, S. K.; Burrows, D. N.; Mangano, V.; Barthelmy, S.

    2005-01-01

    We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments. These power law segments are separated by two corresponding break times. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadx activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission: from photons that are radiated at large angles relative to our line of sight. The first break in the light curve takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve. This energy injection increases the energy of the afterglow shock by at least a factor of f greater than or approx. equal to 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.

  16. ULTRAVIOLET LIGHT CURVES OF SUPERNOVAE WITH THE SWIFT ULTRAVIOLET/OPTICAL TELESCOPE

    SciTech Connect

    Brown, Peter J.; Roming, Peter W. A.; Nousek, John; Vanden Berk, Daniel; Holland, Stephen T.; Immler, Stefan; Gehrels, Neil; Panagia, Nino; Still, Martin

    2009-05-15

    We present ultraviolet (UV) observations of supernovae (SNe) obtained with the UltraViolet/Optical Telescope (UVOT) on board the Swift spacecraft. This is the largest sample of UV light curves from any single instrument and covers all major SN types and most subtypes. The UV light curves of SNe Ia are fairly homogenous, while SNe Ib/c and IIP show more variety in their light-curve shapes. The UV-optical colors clearly differentiate SNe Ia and IIP, particularly at early times. The color evolution of SNe IIP, however, makes their colors similar to SNe Ia at about 20 days after explosion. SNe Ib/c are shown to have varied UV-optical colors. The use of UV colors to help type SNe will be important for high-redshift SNe discovered in optical observations. These data can be added to ground-based optical and near infrared data to create bolometric light curves of individual objects and as checks on generic bolometric corrections used in the absence of UV data. This sample can also be compared with rest-frame UV observations of high-redshift SNe observed at optical wavelengths.

  17. Exploring the Variable Sky with LINEAR. III. Classification of Periodic Light Curves

    NASA Astrophysics Data System (ADS)

    Palaversa, Lovro; Ivezić, Željko; Eyer, Laurent; Ruždjak, Domagoj; Sudar, Davor; Galin, Mario; Kroflin, Andrea; Mesarić, Martina; Munk, Petra; Vrbanec, Dijana; Božić, Hrvoje; Loebman, Sarah; Sesar, Branimir; Rimoldini, Lorenzo; Hunt-Walker, Nicholas; VanderPlas, Jacob; Westman, David; Stuart, J. Scott; Becker, Andrew C.; Srdoč, Gregor; Wozniak, Przemyslaw; Oluseyi, Hakeem

    2013-10-01

    We describe the construction of a highly reliable sample of ~7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg2 of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is several magnitudes fainter than most other wide-angle surveys; the photometric errors range from ~0.03 mag at r = 15 to ~0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about 25 million objects, we selected ~200,000 most probable candidate variables with r < 17 and visually confirmed and classified ~7000 periodic variables using phased light curves. The reliability and uniformity of visual classification across eight human classifiers was calibrated and tested using a catalog of variable stars from the SDSS Stripe 82 region and verified using an unsupervised machine learning approach. The resulting sample of periodic LINEAR variables is dominated by 3900 RR Lyrae stars and 2700 eclipsing binary stars of all subtypes and includes small fractions of relatively rare populations such as asymptotic giant branch stars and SX Phoenicis stars. We discuss the distribution of these mostly uncataloged variables in various diagrams constructed with optical-to-infrared SDSS, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer photometry, and with LINEAR light-curve features. We find that the combination of light-curve features and colors enables classification schemes much more powerful than when colors or light curves are each used separately. An interesting side result is a robust and precise quantitative description of a strong correlation between the light-curve period and color/spectral type for close and contact eclipsing binary stars (β Lyrae and W UMa): as the color-based spectral type varies from K4 to F5, the median period

  18. EXPLORING THE VARIABLE SKY WITH LINEAR. III. CLASSIFICATION OF PERIODIC LIGHT CURVES

    SciTech Connect

    Palaversa, Lovro; Eyer, Laurent; Rimoldini, Lorenzo; Ivezić, Željko; Loebman, Sarah; Hunt-Walker, Nicholas; VanderPlas, Jacob; Westman, David; Becker, Andrew C.; Ruždjak, Domagoj; Sudar, Davor; Božić, Hrvoje; Galin, Mario; Kroflin, Andrea; Mesarić, Martina; Munk, Petra; Vrbanec, Dijana; Sesar, Branimir; Stuart, J. Scott; Srdoč, Gregor; and others

    2013-10-01

    We describe the construction of a highly reliable sample of ∼7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg{sup 2} of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is several magnitudes fainter than most other wide-angle surveys; the photometric errors range from ∼0.03 mag at r = 15 to ∼0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about 25 million objects, we selected ∼200,000 most probable candidate variables with r < 17 and visually confirmed and classified ∼7000 periodic variables using phased light curves. The reliability and uniformity of visual classification across eight human classifiers was calibrated and tested using a catalog of variable stars from the SDSS Stripe 82 region and verified using an unsupervised machine learning approach. The resulting sample of periodic LINEAR variables is dominated by 3900 RR Lyrae stars and 2700 eclipsing binary stars of all subtypes and includes small fractions of relatively rare populations such as asymptotic giant branch stars and SX Phoenicis stars. We discuss the distribution of these mostly uncataloged variables in various diagrams constructed with optical-to-infrared SDSS, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer photometry, and with LINEAR light-curve features. We find that the combination of light-curve features and colors enables classification schemes much more powerful than when colors or light curves are each used separately. An interesting side result is a robust and precise quantitative description of a strong correlation between the light-curve period and color/spectral type for close and contact eclipsing binary stars (β Lyrae and W UMa): as the color-based spectral type varies from K4 to F5, the

  19. EXQUISITE NOVA LIGHT CURVES FROM THE SOLAR MASS EJECTION IMAGER (SMEI)

    SciTech Connect

    Hounsell, R.; Bode, M. F.; Darnley, M. J.; Mawson, N. R.; Steele, I. A.; Hick, P. P.; Buffington, A.; Jackson, B. V.; Clover, J. M.; Shafter, A. W.; Evans, A.; Eyres, S. P. S.; O'Brien, T. J.

    2010-11-20

    We present light curves of three classical novae (CNe; KT Eridani, V598 Puppis, V1280 Scorpii) and one recurrent nova (RS Ophiuchi) derived from data obtained by the Solar Mass Ejection Imager (SMEI) on board the Coriolis satellite. SMEI provides near complete skymap coverage with precision visible-light photometry at 102 minute cadence. The light curves derived from these skymaps offer unprecedented temporal resolution around, and especially before, maximum light, a phase of the eruption normally not covered by ground-based observations. They allow us to explore fundamental parameters of individual objects including the epoch of the initial explosion, the reality and duration of any pre-maximum halt (found in all three fast novae in our sample), the presence of secondary maxima, speed of decline of the initial light curve, plus precise timing of the onset of dust formation (in V1280 Sco) leading to estimation of the bolometric luminosity, white dwarf mass, and object distance. For KT Eri, Liverpool Telescope SkyCamT data confirm important features of the SMEI light curve and overall our results add weight to the proposed similarities of this object to recurrent rather than to CNe. In RS Oph, comparison with hard X-ray data from the 2006 outburst implies that the onset of the outburst coincides with extensive high-velocity mass loss. It is also noted that two of the four novae we have detected (V598 Pup and KT Eri) were only discovered by ground-based observers weeks or months after maximum light, yet these novae reached peak magnitudes of 3.46 and 5.42, respectively. This emphasizes the fact that many bright novae per year are still overlooked, particularly those of the very fast speed class. Coupled with its ability to observe novae in detail even when relatively close to the Sun in the sky, we estimate that as many as five novae per year may be detectable by SMEI.

  20. THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

    SciTech Connect

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  1. Physical Characteristics of Faint Meteors by Light Curve and High-resolution Observations

    NASA Astrophysics Data System (ADS)

    Subasinghe, Dilini; Campbell-Brown, Margaret D.; Stokan, Edward

    2014-11-01

    The physical structure of a meteoroid may be inferred from optical observations, particularly the light curve, of a meteor. For example: a classically shaped (late peaked) light curve is seen as evidence of a solid single body, whereas a symmetric light curve may indicate a dustball structure. High-resolution optical observations show how the meteoroid fragments: continuously, leaving a long wake, or discretely, leaving several distinct pieces. Calculating the orbit of the meteoroid using two station data then allows the object to be associated with asteroidal or cometary parent bodies. Optical observations thus provide simultaneous information on meteoroid structure, fragmentation mode, and origin.CAMO (the Canadian Automated Meteor Observatory) has been continuously collecting faint (masses < 10-4 kg) two station optical meteors with image-intensified narrow field (with a resolution of up to 3 meters per pixel) and wide field (26 by 19 degrees) cameras since 2010. The narrow field, telescopic cameras allow the meteor fragmentation to be studied using a pair of mirrors to track the meteor. The wide-field cameras provide the light curve and trajectory solution.We present preliminary results from classifying light curves and high-resolution optical observations for 3000 faint meteors recorded since 2010. We find that most meteors (both asteroidal and cometary) show long trails, while meteors with short trails are the second most common morphology. It is expected that meteoroids that experience negligible fragmentation have the shortest trails, so our results imply that the majority of small meteoroids fragment during ablation. A surprising observation is that almost equal fractions of asteroidal and cometary meteors fragment (showing long trails), implying a similar structure for both types of meteoroids.

  2. Devil in the Details: Investigating Astrophysical Phenomena with Kepler Light Curves

    NASA Astrophysics Data System (ADS)

    Jenkins, Jon Michael; SOC, Kepler; SO, Kepler; Kepler Science Team

    2011-05-01

    The light curves produced by the Kepler photometer are unprecedented in their photometric precision, completeness, and contiguity. Moreover, although Kepler was designed to detect 100 ppm changes in brightness corresponding to transits of Earth-size planets crossing Sun-size stars, the Kepler light curves preserve intrinsic intensity variations across a large dynamic range, including those of RR Lyrae stars, which can increase their brightness by more than a factor of two over a few hours. The large dynamic range and phenomenal photometric precision of Kepler promises to revolutionize the study of intrinsic stellar variability and a wide variety of variable stars on timescales from minutes to several years. In this paper, we describe the science pipeline processing that produces the uncorrected and the systematic error-corrected light curves, and give examples of residual instrumental artifacts that can be found in the data, such as those caused by thermal changes due to the position of the spacecraft with relation to the sun or heaters cycling on and off on various spacecraft components (which can change the shape of the telescope and alter its focus), as well as examples of processing artifacts that can occur. We also describe algorithms in development that promise to improve our ability to identify and remove instrumental signatures and further reduce the incidence of processing artifacts in the archival light curves, thereby increasing the usability of the corrected light curves for astrophysical investigations. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by the NASA Science Mission Directorate.

  3. Superluminous Supernovae Powered by Magnetars: Late-time Light Curves and Hard Emission Leakage

    NASA Astrophysics Data System (ADS)

    Wang, S. Q.; Wang, L. J.; Dai, Z. G.; Wu, X. F.

    2015-01-01

    Recently, research performed by two groups has revealed that the magnetar spin-down energy injection model with full energy trapping can explain the early-time light curves of SN 2010gx, SN 2013dg, LSQ12dlf, SSS120810, and CSS121015 but fails to fit the late-time light curves of these superluminous supernovae (SLSNe). These results imply that the original magnetar-powered model is challenged in explaining these SLSNe. Our paper aims to simultaneously explain both the early- and late-time data/upper limits by considering the leakage of hard emissions. We incorporate quantitatively the leakage effect into the original magnetar-powered model and derive a new semianalytical equation. Comparing the light curves reproduced by our revised magnetar-powered model with the observed data and/or upper limits of these five SLSNe, we found that the late-time light curves reproduced by our semianalytical equation are in good agreement with the late-time observed data and/or upper limits of SN 2010gx, CSS121015, SN 2013dg, and LSQ12dlf and the late-time excess of SSS120810, indicating that the magnetar-powered model might be responsible for these SLSNe and that the gamma-ray and X-ray leakages are unavoidable when the hard photons were down-Comptonized to softer photons. To determine the details of the leakage effect and unveil the nature of SLSNe, more high-quality bolometric light curves and spectra of SLSNe are required.

  4. A LIGHT CURVE ANALYSIS OF CLASSICAL NOVAE: FREE-FREE EMISSION VERSUS PHOTOSPHERIC EMISSION

    SciTech Connect

    Hachisu, Izumi; Kato, Mariko E-mail: mariko@educ.cc.keio.ac.jp

    2015-01-10

    We analyzed light curves of seven relatively slower novae, PW Vul, V705 Cas, GQ Mus, RR Pic, V5558 Sgr, HR Del, and V723 Cas, based on an optically thick wind theory of nova outbursts. For fast novae, free-free emission dominates the spectrum in optical bands rather than photospheric emission, and nova optical light curves follow the universal decline law. Faster novae blow stronger winds with larger mass-loss rates. Because the brightness of free-free emission depends directly on the wind mass-loss rate, faster novae show brighter optical maxima. In slower novae, however, we must take into account photospheric emission because of their lower wind mass-loss rates. We calculated three model light curves of free-free emission, photospheric emission, and their sum for various white dwarf (WD) masses with various chemical compositions of their envelopes and fitted reasonably with observational data of optical, near-IR (NIR), and UV bands. From light curve fittings of the seven novae, we estimated their absolute magnitudes, distances, and WD masses. In PW Vul and V705 Cas, free-free emission still dominates the spectrum in the optical and NIR bands. In the very slow novae, RR Pic, V5558 Sgr, HR Del, and V723 Cas, photospheric emission dominates the spectrum rather than free-free emission, which makes a deviation from the universal decline law. We have confirmed that the absolute brightnesses of our model light curves are consistent with the distance moduli of four classical novae with known distances (GK Per, V603 Aql, RR Pic, and DQ Her). We also discussed the reason why the very slow novae are about ∼1 mag brighter than the proposed maximum magnitude versus rate of decline relation.

  5. The Information Content in Analytic Spot Models of Broadband Precision Light Curves

    NASA Astrophysics Data System (ADS)

    Walkowicz, Lucianne M.; Basri, Gibor; Valenti, Jeff A.

    2013-04-01

    We present the results of numerical experiments to assess degeneracies in light curve models of starspots. Using synthetic light curves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler light curves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsin i or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the light curve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

  6. Search for light curve modulations among Kepler candidates. Three very low-mass transiting companions

    NASA Astrophysics Data System (ADS)

    Lillo-Box, J.; Ribas, A.; Barrado, D.; Merín, B.; Bouy, H.

    2016-07-01

    Context. Light curve modulations in the sample of Kepler planet candidates allows the disentangling of the nature of the transiting object by photometrically measuring its mass. This is possible by detecting the effects of the gravitational pull of the companion (ellipsoidal modulations) and in some cases, the photometric imprints of the Doppler effect when observing in a broad band (Doppler beaming). Aims: We aim to photometrically unveil the nature of some transiting objects showing clear light curve modulations in the phase-folded Kepler light curve. Methods: We selected a subsample among the large crop of Kepler objects of interest (KOIs) based on their chances to show detectable light curve modulations, i.e., close (a< 12 R⋆) and large (in terms of radius, according to their transit signal) candidates. We modeled their phase-folded light curves with consistent equations for the three effects, namely, reflection, ellipsoidal and beaming (known as REB modulations). Results: We provide detailed general equations for the fit of the REB modulations for the case of eccentric orbits. These equations are accurate to the photometric precisions achievable by current and forthcoming instruments and space missions. By using this mathematical apparatus, we find three close-in very low-mass companions (two of them in the brown dwarf mass domain) orbiting main-sequence stars (KOI-554, KOI-1074, and KOI-3728), and reject the planetary nature of the transiting objects (thus classifying them as false positives). In contrast, the detection of the REB modulations and transit/eclipse signal allows the measurement of their mass and radius that can provide important constraints for modeling their interiors since just a few cases of low-mass eclipsing binaries are known. Additionally, these new systems can help to constrain the similarities in the formation process of the more massive and close-in planets (hot Jupiters), brown dwarfs, and very low-mass companions.

  7. Four color light curves and period changes investigation of the contact binary BX Peg

    NASA Astrophysics Data System (ADS)

    Li, Kai; Hu, Shaoming; Guo, Difu; Jiang, Yunguo; Gao, Dongyang; Chen, Xu

    2015-11-01

    We presented BVRcIc light curves of BX Peg obtained by the Weihai Observatory 1.0-m telescope of Shandong University. The W-D code was used to analyze the four color light curves, it is shown that BX Peg is a W-subtype shallow contact binary with a fill-out factor of f = 14.6 % . The asymmetric light curves were explained by a dark spot on the less massive hot component. A total of 328 times of minimum light were used to study the orbital period variation of BX Peg. We found that the orbital period of BX Peg was continuous decrease with a rate of dp / dt = - 2.07 ×10-7 d yr-1 superimposed on a cyclic oscillation with a period of 57.8 yr. The secular period decrease should be caused by the angular momentum loss via magnetic stellar wind. The cyclic modulation is very likely to be produced by the light travel time effect due to a tertiary companion.

  8. VizieR Online Data Catalog: Light curves of type Ia supernovae in SNLS (Guy+, 2010)

    NASA Astrophysics Data System (ADS)

    Guy, J.; Sullivan, M.; Conley, A.; Regnault, N.; Astier, P.; Balland, C.; Basa, S.; Carlberg, R. G.; Fouchez, D.; Hardin, D.; Hook, I. M.; Howell, D. A.; Pain, R.; Palanque-Delabrouille, N.; Perrett, K. M.; Pritchet, C. J.; Rich, J.; Ruhlmann-Kleider, V.; Balam, D.; Baumont, S.; Ellis, R. S.; Fabbro, S.; Fakhouri, H. K.; Fourmanoit, N.; Gonzalez-Gaitan, S.; Graham, M. L.; Hsiao, E.; Kronborg, T.; Lidman, C.; Mourao, A. M.; Perlmutter, S.; Ripoche, P.; Suzuki, N.; Walker, E. S.

    2010-07-01

    The following files contain the Type Ia supernovae light curves of the Supernova Legacy Survey 3-year sample and the parameters needed to estimate luminosity distances: the apparent rest-frame B-band magnitude at maximum light, a shape parameter (stretch factor or X1) and a colour that approximately corresponds to the rest-frame B-V colour (plus a constant offset) at maximum light in B-band. Those parameters were obtained with two light curve fitters: SALT2 (Guy et al., 2007A&A...466...11G) and SiFTO (Conley et al., 2008ApJ...681..482C). The light curves are in the magnitude system defined in Regnault et al. (2009, Cat. J/A+A/506/999). Fluxes and uncertainties are given for a fiducial zero point of 30, a magnitude is mag=-2.5log10(Flux)+30. An additional table that is not in the paper gives the approximate coordinates of SNe images in MegaCam focal plane. They are needed to estimate the filter transmission function. This data can also be downloaded at the University of Toronto's Research Repository https://tspace.library.utoronto.ca/handle/1807/24512 (3 data files).

  9. Collimated Light Source Using Patterned Organic Light-Emitting Diodes and Microlens

    NASA Astrophysics Data System (ADS)

    Sukekazu Aratani,; Masaya Adachi,; Masao Shimizu,; Tatsuya Sugita,; Toshinari Shibasaki,; Katsusuke Shimazaki,

    2010-04-01

    We developed for the first time a collimated organic light-emitting diode (OLED) light source using a patterned OLED and a microlens. The structure of the collimated OLED light source was designed by conventional ray-tracking simulation. We demonstrated that the collimated OLED light source enhanced the luminance of a liquid crystal display (LCD) with a low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. The collimated OLED light source with the patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.

  10. Infrared light curves of the contact binary 44 i Bootis and evidence for a new period change

    NASA Astrophysics Data System (ADS)

    Lunel, M.; Bergeat, J.; Garnier, R.

    1985-07-01

    The results of a new observing campaign, conducted in April 1980 and equipped with the steady curves of March 1978 are presented and discussed. Seven infrared light curves of the contact binary 44 i Bootis, including five complete curves secured on a single night during one week, are reported. When the ephemeris of Duerbeck (1975) is used, sine terms are detected in the light curves. Evidence of a period jump (+13 x 10 to the -7th day), presumably in 1978-1979, or a slow period change of 6.7 x 10 to the -10th originating in 1976 is shown by an O-C diagram of observations. A new ephemeris is proposed, and when used, the light curves of April 1980 are found to be identical with the reference curves of March 1978 and devoid of any asymmetry. The statements of Hopp and Witzigmann (1982) on a possible correlation of period changes with activity in light curves are considered.

  11. B and V light curves of the very short-period binary VZ Piscium

    SciTech Connect

    Samec, R.G. )

    1989-07-01

    The very short-period W Ursae Majoris system VZ Psc was observed on two consecutive nights with the facilities at Lowell Observatory. The observations covering the eclipse portions of the light curves yielded four epochs of minimum light and an improved ephemeris. A period study covering nearly 27,000 cycles revealed that the period has remained rather constant with no discernible long-term variation. The light curves, defined by 321 observations with the B filter and 317 with the V filter, display shallow eclipse depths and are highly asymmetric with maxima occurring at phases 0.29 and 0.72. The maximum following primary eclipse is somewhat fainter and redder than the maximum following secondary eclipse. 16 refs.

  12. VizieR Online Data Catalog: BVIc light curves of 57 Cepheids (Berdnikov+,

    NASA Astrophysics Data System (ADS)

    Berdnikov, L. N.; Kniazev, A. Yu.; Sefako, R.; Kravtsov, V. V.; Zhujko, S. V.

    2014-04-01

    In 2008-2013, we obtained 11333 CCD BV Ic frames for 57 Cepheids from the General Catalogue of Variable Stars. We performed our observations with the 76-cm telescope of the South AfricanAstronomicalObservatory (SAAO, South Africa) and the 40-cm telescope of the Cerro Armazones Astronomical Observatory of the Universidad Catolica del Norte (OCA, Chile) using the SBIG ST-10XME CCD camera. The tables of observations, the plots of light curves, and the current light elements are presented. Comparison of our light curves with those constructed from photoelectric observations shows that the differences between their mean magnitudes exceed 0.05mag in 20% of the cases. This suggests the necessity of performing CCD observations for all Cepheids. (2 data files).

  13. Convexity of the Photosynthetic Light-Response Curve in Relation to Intensity and Direction of Light during Growth.

    PubMed Central

    Ogren, E.

    1993-01-01

    Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyxa sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient through the leaf was not fully matched by a corresponding gradient in photosynthetic capacity. The degree to which the leaf gradients were matched was quantified by measuring photosynthesis at both leaf surfaces using modulated fluorescence. Two principal growth conditions were identified as those causing mismatch of leaf gradients and lowering of the convexity relative to cells. The first was growth under low light, where leaves did not develop any noteworthy gradient in photosynthetic capacity. This led to decreased convexity, particularly in old leaves with high chlorophyll content and, hence, steep light gradients. Second and less conspicuous was growth under high light conditions when light was given bilaterally rather than unilaterally, which yielded leaves of high photosynthetic capacity at both surfaces. Two situations were also identified that caused the convexity to decrease at the chloroplast level: (a) increased light during growth, for both leaves and cells, and (b) increased CO2 concentration during measurement of high-light-grown leaves. These changes of the intrinsic convexity were interpreted to indicate that the convexity declines with increased capacity of ribulose-1,5-bisphosphate carboxylase/oxygenase relative to the capacity of electron transport. PMID:12231754

  14. Backlight units based on light extraction from a curved optical fiber

    NASA Astrophysics Data System (ADS)

    Fujieda, Ichiro; Arizono, Kazuma; Nishida, Kazuki; Takigawa, Naoki

    2014-06-01

    A backlight unit is constructed by laying out a plastic optical fiber (POF) in a curved trench fabricated in a light-guide plate. First, the light leaks out of the POF at curved sections and enters the plate. Next, the light is extracted from the plate by some microstructures fabricated on the surfaces of the plate. Coupled to a laser diode, its optical power can be efficiently and uniformly delivered over a large area via the POF. In this experiment, we fabricated a 10 cm×10 cm×3 mm prototype unit with off-the-shelf components. It becomes see-through when the space around the POF is filled with index-matching oil. One can build an arbitrary-shaped planar light source by tiling multiple cells and connecting them by a POF. The light inside the POF is depleted as it propagates downstream. This can be compensated by decreasing the radii of curvature. Microstructures on the light-guide plate can distort the passage of ambient light. For a see-through unit, we can distribute them sparsely and/or use absorbers. A see-through backlight unit is a relatively unexplored device, and it might pave the way for new applications.

  15. The pattern of secondary root formation in curving roots of Arabidopsis thaliana (L.) Heynh

    NASA Technical Reports Server (NTRS)

    Fortin, M. C.; Pierce, F. J.; Poff, K. L.

    1989-01-01

    A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thaliana. The number of secondary roots increased on the convex side and decreased on the concave side of any curved main root axes in comparison with straight roots used as the control. The same phenomenon was observed with the curved main roots of plants grown on a clinostat and of mutant plants exhibiting random root orientation. The data suggest that the pattern of lateral root formation is associated with curvature but is independent of the environmental stimuli used to induce curvature.

  16. Near-infrared light curves of Type Ia supernovae: studying properties of the second maximum

    NASA Astrophysics Data System (ADS)

    Dhawan, S.; Leibundgut, B.; Spyromilio, J.; Maguire, K.

    2015-04-01

    Type Ia supernovae (SNe Ia) have been proposed to be much better distance indicators at near-infrared (NIR) compared to optical wavelengths - the effect of dust extinction is expected to be lower and it has been shown that SNe Ia behave more like `standard candles' at NIR wavelengths. To better understand the physical processes behind this increased uniformity, we have studied the Y, J and H-filter light curves of 91 SNe Ia from the literature. We show that the phases and luminosities of the first maximum in the NIR light curves are extremely uniform for our sample. The phase of the second maximum, the late-phase NIR luminosity and the optical light-curve shape are found to be strongly correlated, in particular more luminous SNe Ia reach the second maximum in the NIR filters at a later phase compared to fainter objects. We also find a strong correlation between the phase of the second maximum and the epoch at which the SN enters the Lira law phase in its optical colour curve (epochs ˜ 15 to 30 d after B-band maximum). The decline rate after the second maximum is very uniform in all NIR filters. We suggest that these observational parameters are linked to the nickel and iron mass in the explosion, providing evidence that the amount of nickel synthesized in the explosion is the dominating factor shaping the optical and NIR appearance of SNe Ia.

  17. Phase shifts and nonellipsoidal light curves: Challenges from mass determinations in x-ray binary stars

    NASA Astrophysics Data System (ADS)

    Cantrell, Andrew Glenn

    We consider two types of anomalous observations which have arisen from efforts to measure dynamical masses of X-ray binary stars: (1) Radial velocity curves which seemingly show the primary and the secondary out of antiphase in most systems, and (2) The observation of double-waved light curves which deviate significantly from the ellipsoidal modulations expected for a Roche lobe filling star. We consider both problems with the joint goals of understanding the physical origins of the anomalous observations, and using this understanding to allow robust dynamical determinations of mass in X-ray binary systems. In our analysis of phase-shifted radial velocity curves, we discuss a comprehensive sample of X-ray binaries with published phase-shifted radial velocity curves. We show that the most commonly adopted explanation for phase shifts is contradicted by many observations, and consider instead a generalized form of a model proposed by Smak in 1970. We show that this model is well supported by a range of observations, including some systems which had previously been considered anomalous. We lay the groundwork for the derivation of mass ratios based on our explanation for phase shifts, and we discuss the work necessary to produce more detailed physical models of the phase shift. In our analysis of non-ellipsoidal light curves, we focus on the very well-studied system A0620-00. We present new VIH SMARTS photometry spanning 1999-2007, and supplement this with a comprehensive collection of archival data obtained since 1981. We show that A0620-00 undergoes optical state changes within X-ray quiescence and argue that not all quiescent data should be used for determinations of the inclination. We identify twelve light curves which may reliably be used for determining the inclination. We show that the accretion disk contributes significantly to all twelve curves and is the dominant source of nonellipsoidal variations. We derive the disk fraction for each of the twelve curves

  18. Visible and Near-infrared Light Curves of SN 2009nr

    NASA Astrophysics Data System (ADS)

    Heath, Jonathan; Bryngelson, Ginger

    2014-03-01

    This study explores the behavior of SN 2009nr, an apparently normal type Ia supernova (SN Ia). A plot of this object's brightness over time is known as a light curve. Because of the uniformity of their light curves, SNe Ia are valuable markers for determining the expansion of the universe and other cosmological parameters. Understanding the properties of these supernovae is vital in order to build our confidence in their use as standard candles. A small, but increasing number of SN Ia late-time observations have been made in the near-infrared (NIR). Most exhibit a flattening of the NIR power even as the visible light declines at a steady rate. It is still unclear as to why they exhibit this behavior and how typical this is. In order to characterize the late behavior of SNe Ia, images of SN 2009nr were analyzed using the Image Reduction and Analysis Facility (IRAF). NIR (J, H, K) images were taken with the 4m Mayall Telescope at Kitt Peak National-Observatory using the FLAMINGOS IR Imaging Spectrometer while visible (B, V, R, I) images used the Mosaic 1 imager. The supernova's apparent magnitude for each night of observation (by filter) was found by using reference stars. We present preliminary light curves of SN 2009nr and a comparison to another SN observed at similar epochs.

  19. Light Curve Analysis of the Short Period Solar-Type Binary, EK Comae Berenices

    NASA Astrophysics Data System (ADS)

    Samec, Ronald G.; Gray, Jamison D.; Carrigan, Brian

    1995-05-01

    The thirteenth mag variable, EK Comae Berenices, was discovered by Kinman (1966) in a study of the fields near the North Galactic Pole. He identified it as a W UMa variable. This binary was brought to our attention by the AAVSO observer,Borovicka, who conducted a thorough visual investigation. Subsequently, we obtained complete B,V photoelectric light curves of the system phased from observations taken 11, 12 and 14 February and 9, 12 May, 1994 at Lowell Observatory, Flagstaff, Arizona. The 0.78-m National Undergraduate Research Observatory reflector was used with a thermoelectrically cooled PMT. Five epochs of minimicrons light were determined from observations made during two secondary and three primary eclipses. The bisection-of-chords technique was utilized in their determination. Improved linear and quadratic ephemerides were calculated from all available epochs of minima. The quadratic term of the second ephemeris is marginally significant and negative. Because of its small magnitude and doubtful significance, we cannot regard it as proof that the orbital evolution of EK Com is now dominated by magnetic breaking. The B, V simultaneous light curve solution yields an extreme mass ratio of 3.3 and a fill-out of 10%. We also modeled a 12 degree super-luminous region on the cooler component, simultaneously adjusting its parameters in the WD differential corrections procedure along with the other light curve parameters.

  20. Gamma-Ray Pulsar Light Curves in Vacuum and Force-Free Geometry

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; DeCesar, Megan E.; Miller, M. Coleman; Kalapotharakos, Constantinos; Contopoulos, Ioannis

    2011-01-01

    Recent studies have shown that gamma-ray pulsar light curves are very sensitive to the geometry of the pulsar magnetic field. Pulsar magnetic field geometries, such as the retarded vacuum dipole and force-free magnetospheres have distorted polar caps that are offset from the magnetic axis in the direction opposite to rotation. Since this effect is due to the sweepback of field lines near the light cylinder, offset polar caps are a generic property of pulsar magnetospheres and their effects should be included in gamma-ray pulsar light curve modeling. In slot gap models (having two-pole caustic geometry), the offset polar caps cause a strong azimuthal asymmetry of the particle acceleration around the magnetic axis. We have studied the effect of the offset polar caps in both retarded vacuum dipole and force-free geometry on the model high-energy pulse profiles. We find that, compared to the profiles derived from symmetric caps, the flux in the pulse peaks, which are caustics formed along the trailing magnetic field lines, increases significantly relative to the off-peak emission, formed along leading field lines. The enhanced contrast produces improved slot gap model fits to Fermi pulsar light curves like Vela, with vacuum dipole fits being more favorable.

  1. Photometric Monitoring of Non-resolved Space Debris and Databases of Optical Light Curves

    NASA Astrophysics Data System (ADS)

    Schildknecht, Thomas; Koshkin, Nikolay; Korobeinikova, Elen; Melikiants, Seda; Shakun, Leonid; Strakhova, Svetlana; Linder, Esther; Silha, Jiri; Hager, Monika

    The population of space debris increased drastically during the last years. Collisions involving massive objects may produce large number of fragments leading to significantly growth of the space debris population. An effective remediation measure in order to stabilize the population in LEO, is therefore the removal of large, massive space debris. To remove these objects, not only precise orbits, but also more detailed information about their attitude states will be required. One important property of an object targeted for removal is its spin period and spin axis orientation. If we observe a rotating object, the observer sees different surface areas of the object which leads to changes in the measured intensity. Rotating objects will produce periodic brightness variations with frequencies which are related to the spin periods. Photometric monitoring is the real tool for remote diagnostics of the satellite rotation around its center of mass. This information is also useful, for example, in case of contingency. Moreover, it is also important to take into account the orientation of non-spherical body (e.g. space debris) in the numerical integration of its motion when a close approach with the another spacecraft is predicted. We introduce the two databases of light curves: the AIUB data base, which contains about a thousand light curves of LEO, MEO and high-altitude debris objects (including a few functional objects) obtained over more than seven years, and the data base of the Astronomical Observatory of Odessa University (Ukraine), which contains the results of more than 10 years of photometric monitoring of functioning satellites and large space debris objects in low Earth orbit. AIUB used its 1m ZIMLAT telescope for all light curves. For tracking low-orbit satellites, the Astronomical Observatory of Odessa used the KT-50 telescope, which has an alt-azimuth mount and allows tracking objects moving at a high angular velocity. The diameter of the KT-50 main mirror is

  2. New Precision CCD Light Curves, Analyses, and Absolute Parameters for the Overcontact Binaries V842 Her and DZ Psc

    NASA Astrophysics Data System (ADS)

    Bradstreet, D. H.; Hargis, J. R.; Sanders, S. J.

    2004-12-01

    New V & Rc light curves and the derived absolute parameters are presented for the overcontact systems DZ Psc and V842 Her. These systems were selected for photometric study because the existing radial velocity solutions (Rucinski et al. 1999, 2003) necessitate precision light curves to complete the description of the absolute geometric and orbital parameters. Data were obtained using the 41-cm telescope at the Eastern University Observatory equipped with an SBIG ST-10XME CCD. DZ Psc (NSV 223; P=0.36613 d) is a low mass ratio, high fillout W-type contact binary with two previously published light curves. We confirm the total nature of the secondary eclipse and find clear evidence of spot activity. The light curve is asymmetric between primary and secondary eclipse, with the level of secondary eclipse exhibiting a definite negative slope. We also find the light curve has changed between the 2003 and 2004 observing seasons; the depth of secondary eclipse has increased by nearly 0.04 mag in R. We will present a new light and radial velocity curve solution using Binary Maker 3 (Bradstreet & Steelman 2002) and Wilson-Devinney and compare this to the solution by Niarchos & Gazeas (2004). A period study, using newly derived and previously existing times of minimum light, will also be presented. V842 Her (P=0.41903 d) is a W-type contact binary with two previously published light curves. The light curve exhibits a total primary eclipse and slight asymmetries in the maxima due to the presence of spots. A light curve solution has been previously published but no solutions exist that incorporate the mass ratio information from the recent radial velocity data. We present a new light and radial velocity solution using our higher precision V & Rc light curves as well as a period study.

  3. Microphase separation patterns in diblock copolymers on curved surfaces using a nonlocal Cahn-Hilliard equation.

    PubMed

    Jeong, Darae; Kim, Junseok

    2015-11-01

    We investigate microphase separation patterns on curved surfaces in three-dimensional space by numerically solving a nonlocal Cahn-Hilliard equation for diblock copolymers. In our model, a curved surface is implicitly represented as the zero level set of a signed distance function. We employ a discrete narrow band grid that neighbors the curved surface. Using the closest point method, we apply a pseudo-Neumann boundary at the boundary of the computational domain. The boundary treatment allows us to replace the Laplace-Beltrami operator by the standard Laplacian operator. In particular, we can apply standard finite difference schemes in order to approximate the nonlocal Cahn-Hilliard equation in the discrete narrow band domain. We employ a type of unconditionally stable scheme, which was introduced by Eyre, and use the Jacobi iterative to solve the resulting implicit discrete system of equations. In addition, we use the minimum number of grid points for the discrete narrow band domain. Therefore, the algorithm is simple and fast. Numerous computational experiments are provided to study microphase separation patterns for diblock copolymers on curved surfaces in three-dimensional space. PMID:26577816

  4. A Simple yet Accurate Method for Students to Determine Asteroid Rotation Periods from Fragmented Light Curve Data

    ERIC Educational Resources Information Center

    Beare, R. A.

    2008-01-01

    Professional astronomers use specialized software not normally available to students to determine the rotation periods of asteroids from fragmented light curve data. This paper describes a simple yet accurate method based on Microsoft Excel[R] that enables students to find periods in asteroid light curve and other discontinuous time series data of…

  5. Extrasolar Storms: Pressure-dependent Changes in Light-curve Phase in Brown Dwarfs from Simultaneous HST and Spitzer Observations

    NASA Astrophysics Data System (ADS)

    Yang, Hao; Apai, Dániel; Marley, Mark S.; Karalidi, Theodora; Flateau, Davin; Showman, Adam P.; Metchev, Stanimir; Buenzli, Esther; Radigan, Jacqueline; Artigau, Étienne; Lowrance, Patrick J.; Burgasser, Adam J.

    2016-07-01

    We present Spitzer/Infrared Array Camera Ch1 and Ch2 monitoring of six brown dwarfs during eight different epochs over the course of 20 months. For four brown dwarfs, we also obtained simulataneous Hubble Space Telescope (HST)/WFC3 G141 grism spectra during two epochs and derived light curves in five narrowband filters. Probing different pressure levels in the atmospheres, the multiwavelength light curves of our six targets all exhibit variations, and the shape of the light curves evolves over the timescale of a rotation period, ranging from 1.4 to 13 hr. We compare the shapes of the light curves and estimate the phase shifts between the light curves observed at different wavelengths by comparing the phase of the primary Fourier components. We use state-of-the-art atmosphere models to determine the flux contribution of different pressure layers to the observed flux in each filter. We find that the light curves that probe higher pressures are similar and in phase, but are offset and often different from the light curves that probe lower pressures. The phase differences between the two groups of light curves suggest that the modulations seen at lower and higher pressures may be introduced by different cloud layers.

  6. THE KEPLER LIGHT CURVE OF THE UNIQUE DA WHITE DWARF BOKS 53856

    SciTech Connect

    Holberg, J. B.; Howell, Steve B. E-mail: howell@noao.edu

    2011-08-15

    The faint (g = 16.9) hot white dwarf BOKS 53856 was observed by the Kepler Mission in short cadence mode during mid-2009. Analysis of these observations reveals a highly stable modulation with a period of 6.1375 hr and a 2.46% half-amplitude. The folded light curve has an unusual shape that is difficult to explain in terms of a binary system containing an unseen companion more luminous than an L0 brown dwarf. Optical spectra of BOKS 53856 show a T{sub eff} = 34,000 K, log g = 8.0 DA white dwarf. There are few, if any, known white dwarfs in this temperature range exhibiting photometric variations similar to those we describe. A magnetic spin-modulated white dwarf model can in principle explain the light curve, an interpretation supported by spectral observations of the H{alpha} line showing evidence of Zeeman splitting.

  7. Type Ia supernovae: Pulsating delayed detonation models, IR light curves, and the formation of molecules

    NASA Technical Reports Server (NTRS)

    Hoflich, Peter; Khokhlov, A.; Wheeler, C.

    1995-01-01

    We computed optical and infrared light curves of the pulsating class of delayed detonation models for Type Ia supernovae (SNe Ia). It is demonstrated that observations of the IR light curves can be used to identify subluminous SNe Ia by testing whether secondary maxima occur in the IR. Our pulsating delayed detonation models are in agreement with current observations both for subluminous and normal bright SN Ia, namely SN1991bg, SN1992bo, and SN1992bc. Observations of molecular bands provide a test to distinguish whether strongly subluminous supernovae are a consequence of the pulsating mechanism occurring in a high-mass white dwarf (WD) or, alternatively, are formed by the helium detonation in a low-mass WD as was suggested by Woosley. In the latter case, no carbon is left after the explosion of low-mass WDs whereas a log of C/O-rich material is present in pulsating delayed detonation models.

  8. REVISITING THE LIGHT CURVES OF GAMMA-RAY BURSTS IN THE RELATIVISTIC TURBULENCE MODEL

    SciTech Connect

    Lin, Da-Bin; Gu, Wei-Min; Hou, Shu-Jin; Liu, Tong; Sun, Mou-Yuan; Lu, Ju-Fu E-mail: lujf@xmu.edu.cn

    2013-10-10

    Rapid temporal variability has been widely observed in the light curves of gamma-ray bursts (GRBs). One possible mechanism for such variability is related to the relativistic eddies in the jet. In this paper, we include the contribution of the inter-eddy medium together with the eddies to the gamma-ray emission. We show that the gamma-ray emission can either lead or lag behind the observed synchrotron emission, where the latter originates in the inter-eddy medium and provides most of the seed photons for producing gamma-ray emission through inverse Compton scattering. As a consequence, we argue that the lead/lag found in non-stationary short-lived light curves may not reveal the intrinsic lead/lag of different emission components. In addition, our results may explain the lead of gamma-ray emission with respect to optical emission observed in GRB 080319B.

  9. Rapidly evolving light curves of Low Mass X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Muhli, P.; Hakala, P. J.; Hjalmarsdotter, L.; Hannikainen, D. C.; Schultz, J.

    2004-07-01

    A few Galactic Low Mass X-Ray Binaries (LMXBs) have shown drastically evolving X-ray and/or optical orbital light curves. In two short-period LMXBs, MS 1603+2600 (= UW CrB, P[orb] = 111 min) and 4U 1916-053 (see e.g. Homer et al. 2001), the variations in the light curve morphology seem to be repeating in a periodic manner. We present first results of a photometric monitoring campaign of MS 1603+2600, showing evidence of a 5-day superorbital period in this yet unclassified source. The observations also unraveled optical flares, reminiscent of type I bursts, suggesting a neutron star primary.

  10. A model to simulate synthetic light curves of solar-like stars

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Messina, S.; Pagano, I.; Rodonò, M.

    2006-01-01

    A model to synthesize stellar variability induced by solar-like magnetic activity is presented. It is based on the model introduced by Lanza et al. (2003) and Lanza, Rodonò& Pagano (2004) to fit the time variations of the solar bolometric and spectral irradiances. The model parameters are scaled in the case of solar-like stars in order to provide light curve amplitudes comparable with those observed for active stars with rotation periods ≤ 10 days. Simultaneous light curves in different optical passbands can be synthesized with the model in order to test, e.g., the methods that were recently proposed to detect planetary transit signatures in multiband photometric observations by space-borne telescopes.

  11. Radial Velocity and Light Curves Analysis of the Contact Binary V839 Ophiuchi

    NASA Astrophysics Data System (ADS)

    Pazhouhesh, R.; Edalati, M. T.

    2003-09-01

    Complete UBV light curves of the W Ursae Majoris binary V839 Oph obtained in the year 2000 are presented. The available spectroscopic data of V839 Oph is new and we used the first radial velocity data of this system obtained by Rucinski and Lu (1999) for analysis. The radial velocity and light curves analysis was made with the latest version of Wilson programme (1998) and the geometric and physical elements of the system are derived. By searching the simultaneous solutions of the system we have determined the masses and radii of the components: 1.61Msolar and 1.49402Rsolar for the primary component; 0.50Msolar and 0.90147Rsolar for the secondary component. We estimated effective temperatures of 6650+/-18 (K) for the primary and 6554+/-15 (K) for the secondary component.

  12. Radial Velocity and Light Curve Analysis of the Eclipsing Binary Nn Vir

    NASA Astrophysics Data System (ADS)

    Pazhouhesh, R.; Melendo, E. G.

    2005-04-01

    The eclipsing binary NN Vir is a short period system showing an EW-type light curve. Photometric observations of NN Vir were done by Gomez Ferrellad and Garcia Melendo (1997) at Esteve Duran Observatory. The first spectroscopic observations of this system were obtained by Rucinski and Lu (1999). The radial velocity and light curves analysis was made with the latest version of the Wilson program (1998), and the geometric and physical elements of the system are derived. From the simultaneous solutions of the system, we determined the masses and radii of the components: 1.89 M ⊙ and 1.65 R ⊙ for the primary component; 0.93 M ⊙ and 1.23 R ⊙ for the secondary component. We estimated effective temperatures of 7030 K for the primary and 6977 K for the secondary component.

  13. 3D Modeling of Spectra and Light Curves of Hot Jupiters with PHOENIX; a First Approach

    NASA Astrophysics Data System (ADS)

    Jiménez-Torres, J. J.

    2016-04-01

    A detailed global circulation model was used to feed the PHOENIX code and calculate 3D spectra and light curves of hot Jupiters. Cloud free and dusty radiative fluxes for the planet HD179949b were modeled to show differences between them. The PHOENIX simulations can explain the broad features of the observed 8 μm light curves, including the fact that the planet-star flux ratio peaks before the secondary eclipse. The PHOENIX reflection spectrum matches the Spitzer secondary-eclipse depth at 3.6 μm and underpredicts eclipse depths at 4.5, 5.8 and 8.0 μm. These discrepancies result from the chemical composition and suggest the incorporation of different metallicities in future studies.

  14. Study of a light curve of Beta Persei at 3428 A

    NASA Technical Reports Server (NTRS)

    Chen, K.-Y.; Merrill, J. E.; Richardson, W. W.

    1977-01-01

    Photometric light-curve data obtained during Copernicus satellite observations of Beta Persei in the Balmer continuum at 3428 A are analyzed and reduced. A small but significant fluctuation with a period of very nearly 0.069167 day in the photometric counts is tentatively attributed to a small perturbation in spacecraft attitude introduced each time the satellite passes from daylight into darkness. The light curve is intensity-rectified, phase-rectified, and solved on the assumption that the limb darkening follows the linear cosine law. The resulting distributions of luminosity among the three components of Beta Persei are plotted, and it is shown that the effective temperature of Algol B may be higher than 5000 K.

  15. BINARY CANDIDATES IN THE JOVIAN TROJAN AND HILDA POPULATIONS FROM NEOWISE LIGHT CURVES

    SciTech Connect

    Sonnett, S.; Mainzer, A.; Masiero, J.; Bauer, J.; Grav, T.

    2015-02-01

    Determining the binary fraction for a population of asteroids, particularly as a function of separation between the two components, helps describe the dynamical environment at the time the binaries formed, which in turn offers constraints on the dynamical evolution of the solar system. We searched the NEOWISE archival data set for close and contact binary Trojans and Hildas via their diagnostically large light curve amplitudes. We present 48 out of 554 Hilda and 34 out of 953 Trojan binary candidates in need of follow-up to confirm their large light curve amplitudes and subsequently constrain the binary orbit and component sizes. From these candidates, we calculate a preliminary estimate of the binary fraction without confirmation or debiasing of 14%-23% for Trojans larger than ∼12 km and 30%-51% for Hildas larger than ∼4 km. Once the binary candidates have been confirmed, it should be possible to infer the underlying, debiased binary fraction through estimation of survey biases.

  16. A Periodicity Analysis of the Light Curve of 3C 454.3

    NASA Astrophysics Data System (ADS)

    Li, Huai-Zhen; Xie, Guang-Zhong; Zhou, Shu-Bai; Liu, Hong-Tao; Cha, Guang-Wei; Ma, Li; Mao, Li-Sheng

    2006-08-01

    We analyzed the radio light curves of 3C 454.3 at frequencies 22 and 37 GHz taken from the database of Metsähovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity with very complicated non-sinusoidal variations. Two possible periods, a very weak one of 1.57+/-0.12 yr and a very strong one of 6.15+/-0.50 yr were consistently identified by two methods, the Jurkevich method and power spectrum estimation. The period of 6.15+/-0.50 yr is consistent with results previously reported by Ciaramella et al. and Webb et al. Applying the binary black hole model to the central structure we found black hole masses of 1.53×109Modot and 1.86×108Modot, and predicted that the next radio outburst is to take place in 2006 March and April.

  17. VizieR Online Data Catalog: Praesepe members light curves (Kovacs+, 2014)

    NASA Astrophysics Data System (ADS)

    Kovacs, G.; Hartman, J. D.; Bakos, G. A.; Quinn, S. N.; Penev, K.; Latham, D. W.; Bhatti, W.; Csubry, Z.; de Val-Borro, M.

    2014-07-01

    Light curves used in the time series analysis of Praesepe are presented. There are 381 light curves on instrumental Sloan r' magnitude scale with the zero points determined by the 2MASS magnitudes according to Eq. (1) of the paper. We present two types of magnitudes: a) external parameter decorrelated (EPD) and b), the ones obtained after the application of a trend filtering algorithm (TFA) on the EPD time series. These two methods are briefly described in the paper and in detail in the references therein. Here we just note that both methods are intended to filter out systematics due to environmental effects (instrumental, weather, etc.). For TFA filtering we used 600 templates and did not apply signal reconstruction. (5 data files).

  18. The 3.5 micron light curves of long period variable stars. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Strecker, D. W.

    1973-01-01

    Infrared observations at an effective wavelength of 3.5 microns of a selected group of long period variable (LPV) stars are presented. Mira type and semiregular stars of M, S, and C spectral classifications were monitored throughout the full cycle of variability. Although the variable infrared radiation does not exactly repeat in intensity or time, the regularity is sufficient to produce mean 3.5 micron light curves. The 3.5 micron maximum radiation lags the visual maximum by about one-seventh of a cycle, while the minimum 3.5 micron intensity occurs nearly one-half cycle after infrared maximum. In some stars, there are inflections or humps on the ascending portion of the 3.5 micron light curve which may also be seen in the visual variations.

  19. VizieR Online Data Catalog: HL Aur light curves and minima (Zhang+ 1997)

    NASA Astrophysics Data System (ADS)

    Zhang, R. X.; Fang, M. J.; Zhai, D. S.

    1996-11-01

    Photoelectric observations of HL Aur were carried out with the 60cm reflector of Beijing Astronomical Observatory in 1990 and 1994, and the first photoelectric BV light curves were obtained along with a newly derived ephemeris. The period of the system appears to be constant over the past 65-years. Using the Wilson-Devinney program a photometric analysis of the B and V light curves is performed. It is evident that HL Aur is a near-contact binary with a mass ratio of q=m2/m1=0.722+/-0.011. The primary component of the system is essentially in contact with its Roche lobe, while the secondary is detached but nearly in contact with its lobe. It is found that the components of the system are slightly evolved and located near the terminal-age main sequence. The binary is consistent with the general evolutionary picture for near-contact systems. (3 data files).

  20. BEER analysis of Kepler and CoRoT light curves. III. Spectroscopic confirmation of seventy new beaming binaries discovered in CoRoT light curves

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Faigler, S.; Mazeh, T.

    2015-08-01

    Context. The BEER algorithm searches stellar light curves for the BEaming, Ellipsoidal, and Reflection photometric modulations that are caused by a short-period companion. These three effects are typically of very low amplitude and can mainly be detected in light curves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. Aims: Applying the algorithm to wide-field photometric surveys such as CoRoT and Kepler offers an opportunity to better understand the statistical properties of short-period binaries. It also widens the window for detecting intrinsically rare systems, such as short-period brown-dwarf and massive-planetary companions to main-sequence stars. Methods: Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87 mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiber-allocations with dedicated softwares, we acquired six spectra for 231 candidates and seven spectra for another 50 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842 Å, yielded a radial-velocity precision of ~1 km s-1. Spectra containing lines of more than one star were analyzed with the two-dimensional correlation algorithm TODCOR. Results: The measured radial velocities confirmed the binarity of seventy of the BEER candidates - 45 single-line binaries, 18 double-line binaries, and 7 diluted binaries. We show that red giants introduce a major source of false candidates and demonstrate a way to improve BEER's performance in extracting higher fidelity samples from future searches of CoRoT light curves. The periods of the confirmed binaries span a range of 0.3-10 days and show a rise in the number of binaries per ΔlogP toward longer periods. The estimated mass ratios of the double-line binaries and the mass ratios assigned to the single

  1. The light curve of a transient X-ray source. [the aeriel satellites

    NASA Technical Reports Server (NTRS)

    Kaluzienski, L. J.; Holt, S. S.; Boldt, E. A.; Serlemitsos, P. J.; Eadie, G.; Pounds, K. A.; Ricketts, M. J.; Watson, M.

    1975-01-01

    The Ariel-V satellite monitored the X-ray light curve of A1524-62 almost continuously from 40 days prior to maximum light until its disappearance below the effective experimental sensitivity. The source exhibited maximum light on approximately 4 December 1974, at a level of 0.9 the apparent magnitude of the Crab Nebula in the energy band 3-6 keV. Although similar to previously reported transient sources with a decay time constant of approximately 2 months, the source exhibited an extended, variable pre-flare on-state of about 1 month at a level of greater than approximately 0.1 maximum light. The four bright (greater than 0.2 of the Crab Nebula) transient sources observed during the first half-year of Ariel-V operation are indicative of a galactic disk distribution, and a luminosity at maximum in excess of 10 to the 37th power ergs/sec.

  2. New Light Curves and Period Studies of V502 OPH W UMA System

    NASA Astrophysics Data System (ADS)

    Awadalla, Nabil S.

    NEW LIGHT CURVES AND PERIOD STUDIES OF V502 OPH W UMa SYSTEM N.S.Awadalla National Research Institute of Astronomy and Geophysics( NRIAG ) Helwan Cairo EGYPT New BVR photoelectric observations of the W UMa eclipsing binary system V502 Oph have been presented and analyzed. The geometric and physical elements of the system have been obtained and compared to the previous results. The classification of the system concerning the sub-type of the W UMa binary has been studied as well as its evolution stage. Its period variation in a view of the light time effect has been examin

  3. EVOLUTION OF X-RAY SPECTRA AND LIGHT CURVES OF V1494 AQUILAE

    SciTech Connect

    Rohrbach, J. G.; Ness, J.-U.; Starrfield, S. E-mail: Jan-Uwe.Ness@asu.edu E-mail: juness@sciops.esa.int

    2009-06-15

    We present six Chandra X-ray spectra and light curves obtained for the nova V1494 Aql (1999 No. 2) in outburst. The first three observations were taken with the Advanced CCD Imaging Spectrometer (ACIS-I) on days 134, 187, and 248 after outburst. The count rates were 1.00, 0.69, and 0.53 counts s{sup -1}, respectively. We found no significant periodicity in the ACIS light curves. The X-ray spectra show continuum emission and lines originating from N and O. We found acceptable spectral fits using isothermal APEC models with significantly increased elemental abundances of O and N for all observations. On day 248 after outburst a bright soft component appeared in addition to the fading emission lines. The Chandra observations on days 300, 304, and 727 were carried out with the High Resolution Camera/Low Energy Transmission Grating Spectrometer (LETGS). The spectra consist of continuum emission plus strong emission lines of O and N, implying a high abundance of these elements. On day 300, a flare occurred and periodic oscillations were detected in the light curves taken on days 300 and 304. This flare must have originated deep in the outflowing material since it was variable on short timescales. The spectra extracted immediately before and after the flare are remarkably similar, implying that the flare was an extremely isolated event. Our attempts to fit blackbody, cloudy, or APEC models to the LETGS spectra failed, owing to the difficulty in disentangling continuum and emission-line components. The spectrum extracted during the flare shows a significant increase in the strengths of many of the lines and the appearance of several previously undetected lines. In addition, some of the lines seen before and after the flare are not present during the flare. On day 727 only the count rate from the zeroth order could be derived, and the source was too faint for the extraction of a light curve or spectrum.

  4. VizieR Online Data Catalog: Multi-band light curve of WASP-36 (Mancini+, 2016)

    NASA Astrophysics Data System (ADS)

    Mancini, L.; Kemmer, J.; Southworth, J.; Bott, K.; Molliere, P.; Ciceri, S.; Chen, G.; Henning, T.

    2016-05-01

    17 light curves of five transits of the extrasolar planetary system WASP-36, observed between 2012 and 2015, are presented. Four of the transits were observed simultaneously in the SDSS griz passbands using the seven-beam GROND imager on the MPG 2.2-m telescope. A fifth was observed in Cousins R with the CAHA 1.23-m telescope. (2 data files).

  5. Ensemble Learning Method for Outlier Detection and its Application to Astronomical Light Curves

    NASA Astrophysics Data System (ADS)

    Nun, Isadora; Protopapas, Pavlos; Sim, Brandon; Chen, Wesley

    2016-09-01

    Outlier detection is necessary for automated data analysis, with specific applications spanning almost every domain from financial markets to epidemiology to fraud detection. We introduce a novel mixture of the experts outlier detection model, which uses a dynamically trained, weighted network of five distinct outlier detection methods. After dimensionality reduction, individual outlier detection methods score each data point for “outlierness” in this new feature space. Our model then uses dynamically trained parameters to weigh the scores of each method, allowing for a finalized outlier score. We find that the mixture of experts model performs, on average, better than any single expert model in identifying both artificially and manually picked outliers. This mixture model is applied to a data set of astronomical light curves, after dimensionality reduction via time series feature extraction. Our model was tested using three fields from the MACHO catalog and generated a list of anomalous candidates. We confirm that the outliers detected using this method belong to rare classes, like Novae, He-burning, and red giant stars; other outlier light curves identified have no available information associated with them. To elucidate their nature, we created a website containing the light-curve data and information about these objects. Users can attempt to classify the light curves, give conjectures about their identities, and sign up for follow up messages about the progress made on identifying these objects. This user submitted data can be used further train of our mixture of experts model. Our code is publicly available to all who are interested.

  6. LFN, QPO and fractal dimension of X-ray light curves from black hole binaries

    NASA Astrophysics Data System (ADS)

    Prosvetov, Art; Grebenev, Sergey

    The origin of the low frequency noise (LFN) and quasi-periodic oscillations (QPO) observed in X-ray flux of Galactic black hole binaries is still not recognized in spite of multiple studies and attempts to model this phenomenon. There are known correlations between the QPO frequency, X-ray power density, X-ray flux and spectral state of the system, but there is no model that can do these dependences understandable. For the low frequency (~1 Hz) QPO we still have no even an idea capable to explain their production and don't know even what part of an accretion disc is responsible for them. Here we attempted to measure the fractal dimension of X-ray light curves of several black hole X-ray binaries and to study its correlation with the frequency of quasi periodic oscillations observed in their X-ray light-curves. The fractal dimension is a measure of the space-filling capacity of the light curves' profile. To measure the fractal dimension we used R/S method, which is fast enough and has good reputation in financial analytic and materials sciences. We found that if no QPO were observed in X-ray flux from the particular source, the fractal dimension is equal to the unique value which is independent on the source, its luminosity or its spectral state. On the other hand if QPO were detected in the flux, the fractal dimension deviated from its usual value. Also, we found a clear correlation between the QPO frequency and the fractal dimension of the emission. The relationship between these two parameters is solid but nonlinear. We believe that the analysis of X-ray light curves of black hole binaries using the fractal dimension has a good scientific potential and may provide an addition information on the geometry of accretion flow and fundamental physical parameters of the system.

  7. Connection between the rapidly varying and smooth components in the light curves of Seyfert galaxies

    SciTech Connect

    Gagen-Torn, V.A.

    1987-11-01

    It is shown that for some Seyfert galaxies whose light curves contain a fast (burst) component and a smooth component (components I and II) the amplitude of the flux variation of component I is proportional to the flux of component II. Since components I and II are also identical in their color characteristics, it is very probable that the variability is due to a single smoothly varying and fluctuating source.

  8. VizieR Online Data Catalog: V960 Mon light curves (Hackstein+, 2015)

    NASA Astrophysics Data System (ADS)

    Hackstein, M.; Haas, M.; Kospal, A.; Hambsch, F.-J.; Chini, R.; Abraham, P.; Moor, A.; Pozo Nunez, F.; Ramolla, M.; Westhues, C.; Kaderhandt, L.; Fein, C.; Barr Dominguez, A.; Hodapp, K.-W.

    2015-10-01

    Photometric light curves for V960Mon (2MASS J06593158-0405277) from different telescopes at multiple wavelengths between September 2009 to June 2015. This comprises optical observations from Universitaetssternwarte Bochum (USB) in Chile as part of the Bochum Galatic Disk Survey (GDS, 2015AN....336..590H), Konkoly Observatory in Hungary, and the Remote Observatory Atacama Desert (ROAD) in Chile, as well as near-infrared data from USB. (1 data file).

  9. VizieR Online Data Catalog: Ji light curves of WTS-2 (Birkby+, 2014)

    NASA Astrophysics Data System (ADS)

    Birkby, J. L.; Cappetta, M.; Cruz, P.; Koppenhoefer, J.; Ivanyuk, O.; Mustill, A. J.; Hodgkin, S. T.; Pinfield, D. J.; Sipocz, B.; Kovacs, G.; Saglia, R.; Pavlenko, Y.; Barrado, D.; Bayo, A.; Campbell, D.; Catalan, S.; Fossati, L.; Galvez-Ortiz, M.-C.; Kenworthy, M.; Lillo-Box, J.; Martin, E. L.; Mislis, D.; de Mooij, E. J. W.; Nefs, S. V.; Snellen, I. A. G.; Stoev, H.; Zendejas, J.; Del Burgo, C.; Barnes, J.; Goulding, N.; Haswell, C. A.; Kuznetsov, M.; Lodieu, N.; Murgas, F.; Palle, E.; Solano, E.; Steele, P.; Tata, R.

    2015-07-01

    The infrared light curves of the WTS were generated from time series photometry taken with the WFCAM imager mounted at the prime focus of UKIRT. In order to confirm the transit of WTS-2 b and to help constrain the transit model, on 2010 July 18 we obtained further time series photometry in the Sloan i band using the Wide Field Camera (WFC) on the 2.5m Isaac Newton Telescope (INT) at Roque de Los Muchachos, La Palma. (2 data files).

  10. X-Rays from the Explosion Site: Fifteen Years of Light Curves of SN 1993J

    NASA Technical Reports Server (NTRS)

    Chandra, Poonam; Dwarkadas, Vikram V.; Ray, Alak; Immler, Stefan; Pooley, David

    2009-01-01

    We present a comprehensive analysis of the X-ray light curves of SN 1993J in a nearby galaxy M81. This is the only supernova other than SN 1987A, which is so extensively followed in the X-ray bands. Here we report on SN 1993J observations with the Chandra in the year 2005 and 2008, and Swift observations in 2005, 2006 and 2008. We combined these observations with all available archival data of SN 1993J, which includes ROSAT, ASCA, Chandra, and XMM-Newton, observations from 1993 April to 2006 August. In this paper we report the X-ray light curves of SN 1993J, extending up to fifteen years, in the soft (0.3-2.4 keV), hard (2-8 keV) and combined (0.3-8 keV) bands. The hard and soft-band fluxes decline at different rates initially, but after about 5 years they both undergo a t(sup -1) decline. The soft X-rays, which are initially low, start dominating after a few hundred days. We interpret that most of the emission below 8 keV is coming from the reverse shock which is radiative initially for around first 1000-2000 days and then turn into adiabatic shock. Our hydrodynamic simulation also confirms the reverse shock origin of the observed light curves. We also compare the Ha line luminosity of SN 1993J with its X-ray light curve and note that the Ha line luminosity has a fairly high fraction of the X-ray emission, indicating presence of clumps in the emitting plasma.

  11. Synthetic Spectra and Light Curves of Interacting Binaries and Exoplanets with Circumstellar Material: SHELLSPEC

    NASA Astrophysics Data System (ADS)

    Budaj, Ján

    2012-04-01

    Program SHELLSPEC is designed to calculate light-curves, spectra and images of interacting binaries and extrasolar planets immersed in a moving circumstellar environment which is optically thin. It solves simple radiative transfer along the line of sight in moving media. The assumptions include LTE and optional known state quantities and velocity fields in 3D. Optional (non)transparent objects such as a spot, disc, stream, jet, shell or stars may be defined (embedded) in 3D and their composite synthetic spectrum calculated. The Roche model can be used as a boundary condition for the radiative transfer. Recently, a new model of the reflection effect, dust and Mie scattering were incorporated into the code. ɛ Aurigae is one of the most mysterious objects on the sky. Prior modeling of its light-curve assumed a dark, inclined, disk of dust with a central hole to explain the light-curve with a sharp mid-eclipse brightening. Our model consists of two geometrically thick flared disks: an internal optically thick disk and an external optically thin disk which absorbs and scatters radiation. Shallow mid-eclipse brightening may result from eclipses by nearly edge-on flared (dusty or gaseous) disks. Mid-eclipse brightening may also be due to strong forward scattering and optical properties of the dust which can have an important effect on the light-curves. There are many similarities between interacting binary stars and transiting extrasolar planets. The reflection effect which is briefly reviewed is one of them. The exact Roche shape and temperature distributions over the surface of all currently known transiting extrasolar planets have been determined. In some cases (HAT-P-32b, WASP-12b, WASP-19b), departures from the spherical shape can reach 7-15%.

  12. CfA3: 185 TYPE Ia SUPERNOVA LIGHT CURVES FROM THE CfA

    SciTech Connect

    Hicken, Malcolm; Challis, Peter; Kirshner, Robert P.; Bakos, Gaspar; Berlind, Perry; Brown, Warren R.; Caldwell, Nelson; Calkins, Mike; Cho, Richard; Contreras, Maria; Jha, Saurabh; Matheson, Tom; Modjaz, Maryam; Rest, Armin; Michael Wood-Vasey, W.; Barton, Elizabeth J.; Bragg, Ann; Briceno, Cesar; Ciupik, Larry; Dendy, Kristi-Concannon E-mail: kirshner@cfa.harvard.edu

    2009-07-20

    We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains the largest number of homogeneously observed and reduced nearby SNe Ia (z {approx}< 0.08) published to date. It more than doubles the nearby sample, bringing SN Ia cosmology to the point where systematic uncertainties dominate. Our natural system photometry has a precision of {approx}<0.02 mag in BVRIr'i' and {approx}<0.04 mag in U for points brighter than 17.5 mag. We also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system BVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars, where available for the same SN, reveal agreement at the level of a few hundredths mag in most cases. We find that 1991bg-like SNe Ia are sufficiently distinct from other SNe Ia in their color and light-curve-shape/luminosity relation that they should be treated separately in light-curve/distance fitter training samples. The CfA3 sample will contribute to the development of better light-curve/distance fitters, particularly in the few dozen cases where near-infrared photometry has been obtained and, together, can help disentangle host-galaxy reddening from intrinsic supernova color, reducing the systematic uncertainty in SN Ia distances due to dust.

  13. Light Curve Periodic Variability of Cyg X-1 using Jurkevich Method

    NASA Astrophysics Data System (ADS)

    Dong, Ai-Jun; Tang, Yan-Ke; Gai, Ning

    2014-09-01

    The Jurkevich method is a useful method to explore periodicity in the unevenly sampled observational data. In this work, we adopted the method to the light curve of Cyg X-1 from 1996 to 2012, and found that there is an interesting period of 370 days, which appears in both low/hard and high/soft states. That period may be correlated with black hole physics and accretion disk geometry.

  14. Modeling of Gamma-ray Pulsar Light Curves Using the Force-free Magnetic Field

    NASA Astrophysics Data System (ADS)

    Bai, Xue-Ning; Spitkovsky, Anatoly

    2010-06-01

    Gamma-ray emission from pulsars has long been modeled using a vacuum dipole field. This approximation ignores changes in the field structure caused by the magnetospheric plasma and strong plasma currents. We present the first results of gamma-ray pulsar light-curve modeling using the more realistic field taken from three-dimensional force-free (FF) magnetospheric simulations. Having the geometry of the field, we apply several prescriptions for the location of the emission zone, comparing the light curves to observations. We find that when the emission region is chosen according to the conventional slot-gap (or two-pole caustic) prescription, the model fails to produce double-peak pulse profiles, mainly because the size of the polar cap in the FF magnetosphere is larger than the vacuum field polar cap. This suppresses caustic formation in the inner magnetosphere. The conventional outer-gap model is capable of producing only one peak under general conditions because a large fraction of open field lines does not cross the null charge surface. We propose a novel "separatrix layer" model, where the high-energy emission originates from a thin layer on the open field lines just inside of the separatrix that bounds the open flux tube. The emission from this layer generates two strong caustics on the sky map due to the effect we term "Sky Map Stagnation" (SMS). It is related to the fact that the FF field asymptotically approaches the field of a rotating split monopole, and the photons emitted on such field lines in the outer magnetosphere arrive to the observer in phase. The double-peak light curve is a natural consequence of SMS. We show that most features of the currently available gamma-ray pulsar light curves can be reasonably well reproduced and explained with the separatrix layer model using the FF field. Association of the emission region with the current sheet will guide more detailed future studies of the magnetospheric acceleration physics.

  15. Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

    SciTech Connect

    Nousek, J.A.; Kouveliotou, C.; Grupe, D.; Page, K.; Granot, J.; Ramirez-Ruiz, E.; Patel, S.K.; Burrows, D.N.; Mangano, V.; Barthelmy, S.; Beardmore, A.P.; Campana, S.; Capalbi, M.; Chincarini, G.; Cusumano, G.; Falcone, A.D.; Gehrels, N.; Giommi, P.; Goad, M.; Godet, O.; Hurkett, C.; /Penn State U., Astron. Astrophys. /NASA, Marshall /Leicester U. /KIPAC, Menlo Park /Princeton, Inst. Advanced Study /NASA, Marshall /IASF, Palermo /Brera Observ. /Frascati /Milan Bicocca U. /NASA, Goddard

    2005-08-17

    We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments: (1) an initial very steep decay ({infinity} t{sup -a} with 3 {approx}< a{sub 1} {approx}< 5) , followed by (2) a very shallow decay (0.2 {approx}< a{sub 2} {approx}< 0.8), and finally (3) a somewhat steeper decay (1 {approx}< a{sub 3} {approx}< 1.5). These power law segments are separated by two corresponding break times, 300 s {approx}< t{sub break,1} {approx}< 500 s and 10{sup 3} s {approx}< t{sub break,2} {approx}< 10{sup 4} s. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadic activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission, from photons that are radiated at large angles relative to our line of sight. The first break in the light curve (t{sub break,1}) takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay (a{sub 2}) likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve (t{sub break,2}). This energy injection increases the energy of the afterglow shock by at least a factor of f {approx}> 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.

  16. Presenting new exoplanet candidates for the CoRoT chromatic light curves

    NASA Astrophysics Data System (ADS)

    Boufleur, Rodrigo; Emilio, Marcelo; Andrade, Laerte; Janot-Pacheco, Eduardo; De La Reza, Ramiro

    2015-08-01

    One of the most promising topics of modern Astronomy is the discovery and characterization of extrasolar planets due to its importance for the comprehension of planetary formation and evolution. Missions like MOST (Microvariability and Oscillations of Stars Telescope) (Walker et al., 2003) and especially the satellites dedicated to the search for exoplanets CoRoT (Convection, Rotation and planetary Transits) (Baglin et al., 1998) and Kepler (Borucki et al., 2003) produced a great amount of data and together account for hundreds of new discoveries. An important source of error in the search for planets with light curves obtained from space observatories are the displacements occuring in the data due to external causes. This artificial charge generation phenomenon associated with the data is mainly caused by the impact of high energy particles onto the CCD (Pinheiro da Silva et al. 2008), although other sources of error, not as well known also need to be taken into account. So, an effective analysis of the light curves depends a lot on the mechanisms employed to deal with these phenomena. To perform our research, we developed and applied a different method to fix the light curves, the CDAM (Corot Detrend Algorithm Modified), inspired by the work of Mislis et al. (2012). The paradigms were obtained using the BLS method (Kovács et al., 2002). After a semiautomatic pre-analysis associated with a visual inspection of the planetary transits signatures, we obtained dozens of exoplanet candidates in very good agreement with the literature and also new unpublished cases. We present the study results and characterization of the new cases for the chromatic channel public light curves of the CoRoT satellite.

  17. Correlation of circumstellar SiO maser spot distribution with the stellar light curve

    NASA Astrophysics Data System (ADS)

    Oyadomari, M.; Imai, H.; Nagayama, T.; Oyama, T.; Matsumoto, N.; Nakashima, J.; Cho, S.-H.

    2016-07-01

    We have investigated the distributions of silicon monoxide (SiO) v = 2 and v = 3 J = 1 → 0 masers around long-period variables (LPVs) in VLBI observations using the VLBI Exploration of Radio Astrometry (VERA) combined with the Nobeyama 45 m telescope. We find some examples of correlation of a maser spot distribution with the stellar light curve, which may provide a clue to elucidating the pumping mechanism of circumstellar SiO masers.

  18. WHAT CAN WE LEARN FROM THE RISING LIGHT CURVES OF RADIOACTIVELY POWERED SUPERNOVAE?

    SciTech Connect

    Piro, Anthony L.

    2013-05-20

    The light curve of the explosion of a star with a radius {approx}< 10-100 R{sub Sun} is powered mostly by radioactive decay. Observationally, such events are dominated by hydrogen-deficient progenitors and classified as Type I supernovae (SNe I), i.e., white dwarf thermonuclear explosions (Type Ia), and core collapses of hydrogen-stripped massive stars (Type Ib/c). Current transient surveys are finding SNe I in increasing numbers and at earlier times, allowing their early emission to be studied in unprecedented detail. Motivated by these developments, we summarize the physics that produces their rising light curves and discuss ways in which observations can be utilized to study these exploding stars. The early radioactive-powered light curves probe the shallowest deposits of {sup 56}Ni. If the amount of {sup 56}Ni mixing in the outermost layers of the star can be deduced, then it places important constraints on the progenitor and properties of the explosive burning. In practice, we find that it is difficult to determine the level of mixing because it is hard to disentangle whether the explosion occurred recently and one is seeing radioactive heating near the surface or whether the explosion began in the past and the radioactive heating is deeper in the ejecta. In the latter case, there is a ''dark phase'' between the moment of explosion and the first observed light emitted once the shallowest layers of {sup 56}Ni are exposed. Because of this, simply extrapolating a light curve from radioactive heating back in time is not a reliable method for estimating the explosion time. The best solution is to directly identify the moment of explosion, either through observing shock breakout (in X-ray/UV) or the cooling of the shock-heated surface (in UV/optical), so that the depth being probed by the rising light curve is known. However, since this is typically not available, we identify and discuss a number of other diagnostics that are helpful for deciphering how recently an

  19. Distribution of Micronuclei in Human Fibroblasts across the Bragg Curve of Light and Heavy Ions

    NASA Technical Reports Server (NTRS)

    Hada, M.; Lacy, S.; Gridley, D. S.; Rusek, A.; Cucinotta, F. A.; Wu, H.

    2007-01-01

    The space environment consists of energetic particles of varying mass and energy, and understanding the :biological Bragg curve" is essential in optimizing shielding effectiveness against space radiation induced biological impacts. The "biological Bragg curve" is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. Previously, we studied the induction of micronuclei (MN) across the Bragg curve of energetic Fe and Si ions, and observed no increased yield of MN at the location of the Bragg peak. However, the ratio of mono- to bi-nucleated cells, which indicates inhibition of cell progression, was found higher at the Bragg peak location in comparison to the plateau region of the Bragg curve. Here, we report the induction of MN in normal human fibroblast cells across the Bragg curve of incident protons generated at Loma Linda University. Similar to Si and Fe ions, the ratio of mono- to bi-nucleated cells showed a clear spike as the protons reached the Bragg peak. Unlike the two heavy ions, however, the MN yield also increased at the Bragg peak location. These results confirm the hypothesis that severely damaged cells at the Bragg peak of heavy, but not light ions are more likely to go through reproductive death and not be evaluated for micronuclei.

  20. The search for single exoplanet transits in the Kepler light curves

    NASA Astrophysics Data System (ADS)

    Foreman-Mackey, Daniel; Hogg, David W.; Schölkopf, Bernhard

    2015-08-01

    The planet discoveries made using data from the Kepler mission have revolutionized the field of exoplanet statistics. Thousands of planets have been discovered with orbital periods ranging from hours to two years. Some of the most dynamically interesting planets (Jupiter analogs, for example) only show a single transit in the four-year baseline of the Kepler mission and, as a result, they have not yet been found. Upcoming transit surveys like K2, TESS, and PLATO all have shorter contiguous observation baselines. It is therefore crucial to develop robust techniques for the discovery of single transit events. We present a search procedure designed to find single transits using a supervised classification model. To search for a transit signal in a given month-long light curve from Kepler, we train a random forest classifier on tens of thousands of simulated transit signals injected into the light curve of the same star at other times. Using a different set of simulations, we tune the model to maximize the precision of the recovered signals---minimizing the false alarm rate. With this model, we classify each section of the test light curve into two categories: transit and no transit. We demonstrate that this model is robust to systematic false positives and present an automated catalog of convincing single transit candidates.

  1. Orbital Period Variation and Morphological Light Curve Studies for the W UMa Binary BB Pegasi

    NASA Astrophysics Data System (ADS)

    Hanna, Magdy A.; Awadalla, Nabil S.

    2011-06-01

    The photometric light curves of the W-type W UMa eclipsing contact binary system BB Pegasi have been found to be extremely asymmetric over all the observed 63 years in all wavelengths UBVR. The light curves have been characterized by occultation primary minima. So, the morphology of these light curves has been studied in view of these different asymmetric degrees. The system shows a distinct O'Connell effect as well as depth variation. A 22.96 years cycle, of dark spots group, has been determined for the system combined with about the same cycling for the depth variations (22.78 yr). Also, an analysis of the measurements of mid-eclipse times of BB Peg has been presented. The analysis indicates a period decrease of 5.62× 10-8 d/yr, which can be interpreted in terms of mass transfer of rate -4.38 × 10-8 M_⊙/yr, from the more to the less massive component. The O-C diagram shows a damping sine wave covering two different cycles of 17.0 yr and 12.87 yr with amplitudes equal to 0.0071 and 0.0013 day, respectively. These unequal durations show a non periodicity which may be explained as a result of magnetic activity cycling variations due to star spots. The obtained characteristics are consistent when applying Applegate's (1992) mechanism.

  2. IMAGING STARSPOT EVOLUTION ON KEPLER TARGET KIC 5110407 USING LIGHT-CURVE INVERSION

    SciTech Connect

    Roettenbacher, Rachael M.; Monnier, John D.; Harmon, Robert O.; Barclay, Thomas; Still, Martin

    2013-04-10

    The Kepler target KIC 5110407, a K-type star, shows strong quasi-periodic light curve fluctuations likely arising from the formation and decay of spots on the stellar surface rotating with a period of 3.4693 days. Using an established light-curve inversion algorithm, we study the evolution of the surface features based on Kepler space telescope light curves over a period of two years (with a gap of .25 years). At virtually all epochs, we detect at least one large spot group on the surface causing a 1%-10% flux modulation in the Kepler passband. By identifying and tracking spot groups over a range of inferred latitudes, we measured the surface differential rotation to be much smaller than that found for the Sun. We also searched for a correlation between the 17 stellar flares that occurred during our observations and the orientation of the dominant surface spot at the time of each flare. No statistically significant correlation was found except perhaps for the very brightest flares, suggesting that most flares are associated with regions devoid of spots or spots too small to be clearly discerned using our reconstruction technique. While we may see hints of long-term changes in the spot characteristics and flare statistics within our current data set, a longer baseline of observation will be needed to detect the existence of a magnetic cycle in KIC 5110407.

  3. ON THE LACK OF TIME DILATION SIGNATURES IN GAMMA-RAY BURST LIGHT CURVES

    SciTech Connect

    Kocevski, Daniel

    2013-03-10

    We examine the effects of time dilation on the temporal profiles of gamma-ray burst (GRB) pulses. By using prescriptions for the shape and evolution of prompt gamma-ray spectra, we can generate a simulated population of single-pulsed GRBs at a variety of redshifts and observe how their light curves would appear to a gamma-ray detector here on Earth. We find that the observer frame duration of individual pulses does not increase with redshift as 1 + z, which one would expect from cosmological expansion. This time dilation is masked by an opposite and often stronger effect: with increasing redshift and decreasing signal-to-noise ratio only the brightest portion of the light curve can be detected. The results of our simulation are consistent with the fact that the simple time dilation of GRB light curves has not materialized in either the Swift or Fermi detected GRBs with known redshift. We show that the measured durations and associated E{sub iso} estimates for GRBs detected near the instrument's detection threshold should be considered lower limits to the true values. Furthermore, we conclude that attempts at distinguishing between long and short GRBs, at even moderate redshifts, cannot be done based on a burst's temporal properties alone.

  4. THE LICK AGN MONITORING PROJECT: PHOTOMETRIC LIGHT CURVES AND OPTICAL VARIABILITY CHARACTERISTICS

    SciTech Connect

    Walsh, Jonelle L.; Bentz, Misty C.; Barth, Aaron J.; Minezaki, Takeo; Sakata, Yu; Yoshii, Yuzuru; Baliber, Nairn; Bennert, Vardha Nicola; Street, Rachel A.; Treu, Tommaso; Li Weidong; Filippenko, Alexei V.; Stern, Daniel; Brown, Timothy M.; Canalizo, Gabriela; Gates, Elinor L.; Greene, Jenny E.; Malkan, Matthew A.; Woo, Jong-Hak

    2009-11-01

    The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies selected to have black holes with masses roughly in the range 10{sup 6}-10{sup 7} M {sub sun}, as well as the well-studied active galactic nucleus (AGN) NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broadband B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76 m Katzman Automatic Imaging Telescope, the 2 m Multicolor Active Galactic Nuclei Monitoring telescope, the Palomar 60 inch (1.5 m) telescope, and the 0.80 m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the photometric measurements, and present the AGN continuum light curves. We measure various variability characteristics of each of the light curves. We do not detect any evidence for a time lag between the B- and V-band variations, and we do not find significant color variations for the AGNs in our sample.

  5. Current methods for analyzing light curves of solar-like stars

    NASA Astrophysics Data System (ADS)

    Ballot, J.

    2010-12-01

    CoRoT has allowed a quantitative leap for the solar-like-star seismology thanks to 5-month-long uninterrupted timeseries of high-precision photometric data. Kepler is also starting to deliver similar data. Now, several F and G main-sequence stars have been analyzed. The techniques developed to interpret light curves directly inherit from the experience got on the Sun with helioseismology. I describe in this review the methods currently used to analyze these light curves. First, these data provide an accurate determination of the stellar rotation rate. This is possible thanks to the magnetic activity of stars. The power spectra of light curves put also constraints on the stellar granulation, which can be directly compared to 3-D stellar atmosphere models; this shows still unexplained discrepancies. I then detailed a standard method for extracting p-mode characteristics (frequency, amplitude and lifetime). CoRoT has revealed unexpected short life times for F stars. Last, I also discuss errors and biases of mode frequencies, especially the ones due to the simplified description of the rotation generally used.

  6. AN INVESTIGATION OF THE RELATIONSHIP BETWEEN SHAPE AND ROTATION TO EXPLAIN THE LIGHT CURVE OF NEREID

    SciTech Connect

    Hesselbrock, Andrew J.; Alexander, S. G.; Harp, Thomas W.; Abel, N. P.

    2013-06-15

    The observed photometric variability of Nereid over both short and long time scales has been known for some time and has remained a mystery. Schaefer et al. have documented some twenty years worth of observations that reveal that Nereid's light curve shows both short period intranight variations and long term active and inactive episodes. In this work, we report on a set of computational simulations of both the orbital and rotational motion of Nereid in an effort to understand Nereid's behavior. We model Nereid as an ellipsoid that is subject to torques from other bodies, and we calculate both its orbital and rotational motion. In addition, we only consider the case where Nereid is uniformly reflecting with no albedo variations on its surface. Thus, any brightness variations are caused solely by Nereid's changing orientation. We find for reasonable geometries, orientation, and spin rates that we can reproduce some of the features, but not all, of the observed light curve for Nereid. In particular, we show how active and inactive episodes can arise; however, our calculated light curve differs from observations in other aspects.

  7. Light curve modeling of the short-period W UMa star GSC 02049-01164

    NASA Astrophysics Data System (ADS)

    Fox-Machado, Lester; Echevarria, Juan; Gonzalez-Buitrago, Diego; Michel, Raul

    2015-08-01

    The preliminary results of an analysis of the time-series photometric data of the binary star GSC 02049-01164 (ROTSE1 J164341.65+251748.1) are presented.GSC 02049-01164 was observed for eight consecutive nights from 2013, May 31 to June 07 UT with the 0.84m telescope of the San Pedro Martir Observatory in Mexico. The data were acquired through a Johnson V filter. The propierties of the GSC 02040-01164 light curve are consistent with a short period contact binary of W UMa type. The light curve is characterized by a small difference between the two out-of-eclipse maxima by about 0.035 mag and a flat bottom at the secondary minimum due to a total eclipse. Moreover, the primary and secondary eclipses accur almost at 0.5 phase interval suggesting a circular orbit. The period of the binary is 0.3256 d. In an effort to gain a better understanding of the binary system and determine its physical properties we have analyzed the light curve with the software PHOEBE V.0 0.31a. We have found that GSC 02049-01164 binary system has a mass ratio of ~ 0.42, an inclination of ~ 85 degrees, a semi-major axis of ~ 2.23 Rsun. The degree of overcontact of the stellar components is about 13 %.

  8. A historical light curve of ON 231 and its periodic analysis

    NASA Astrophysics Data System (ADS)

    Liu, F. K.; Xie, G. Z.; Bai, J. M.

    1995-03-01

    All data in the B band for BL Lac object ON 231 have been compiled into a light curve from twenty-six publications, dating back to 1982; 560 values are available. The light curve shows that ON 231 is very active and exhibits very complicated non-sinusoidal variations. The light curve probably consists of three kinds of behaviors. The first may be non-periodic or with a period at least longer than the duration of historical observations. In this case, the source seems to maintain two states of intensities, changing in mean behavior from a bright level with mean B magnitude 15.45 to a faint level with about 16.45 mag between 1969 and 1972. After detailed Jurkevich V2m test analysis, we found that the second is periodic, with a period of 13.6 +/- 1.3 years (or 26.6 +/- 0.8 years) with outburst structure of one magnitude with total width of about 6 years. The third one is sporadic, superposing on the previous two behaviors. The periods of 0.981 +/- 0.005 years (or 2.02, 3.01, ... years) and of a few days are not significant and may be spurious.

  9. The bolometric light curves and physical parameters of stripped-envelope supernovae

    NASA Astrophysics Data System (ADS)

    Prentice, S. J.; Mazzali, P. A.; Pian, E.; Gal-Yam, A.; Kulkarni, S. R.; Rubin, A.; Corsi, A.; Fremling, C.; Sollerman, J.; Yaron, O.; Arcavi, I.; Zheng, W.; Kasliwal, M. M.; Filippenko, A. V.; Cenko, S. B.; Cao, Y.; Nugent, P. E.

    2016-05-01

    The optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (SNe) are constructed using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak luminosity Lp, enabling the construction of a luminosity function. Subsequently, the mass of 56Ni synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNe Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median Lp, in erg s-1, of log(Lp) = 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median MNi = 0.34, 0.16, 0.14, and 0.11 M⊙, respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from Lp/2 to Lp more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.

  10. Testing Microvariability in Quasar Differential Light Curves Using Several Field Stars

    NASA Astrophysics Data System (ADS)

    de Diego, José A.; Polednikova, Jana; Bongiovanni, Angel; Pérez García, Ana M.; De Leo, Mario A.; Verdugo, Tomás; Cepa, Jordi

    2015-08-01

    Microvariability consists of small timescale variations of low amplitude in the photometric light curves of quasars and represents an important tool to investigate their inner core. Detection of quasar microvariations is challenging because of their non-periodicity, as well as the need for high monitoring frequency and a high signal-to-noise ratio. Statistical tests developed for the analysis of quasar differential light curves usually show either low power or low reliability, or both. In this paper we compare two statistical procedures to perform tests on several stars with enhanced power and high reliability. We perform light curve simulations of variable quasars and non-variable stars and analyze them with statistical procedures developed from the F-test and the analysis of variance. The results show a large improvement in the power of both statistical probes and a larger reliability when several stars are included in the analysis. The results from the simulations agree with those obtained from observations of real quasars. The high power and high reliability of the tests discussed in this paper improve the results that can be obtained from short and long timescale variability studies. These techniques are not limited to quasar variability; on the contrary, they can be easily implemented for other sources, such as variable stars. Their applications to future research and to the analysis of large-field photometric monitoring archives could reveal new variable sources.

  11. A light curve and its analysis of Type Ia SN 1604

    NASA Astrophysics Data System (ADS)

    Lee, Eun Hee; Lee, Dae-Young; Mihn, Byeong-Hee

    2015-08-01

    SN 1604, known as Kepler’s supernova, was first detected by European observers, but a full light curve including its peak brightness and initial decline part can only be completed by extra data from Korean royal astronomers of four centuries ago. Nowadays, it is considered one of the Type Ia galactic supernovae, which show the empirical correlation between decline rate and peak luminosity - so called Phillips relation or width-luminosity (W-L) relation. Here, we reconstruct a new light curve based on both the Korean and European records of SN 1604. Using this light curve and W-L relation, we present an observed rise time and decline rates after peak, and derive its absolute peak magnitude and distance. In this study, observed rise time (≈ 19±1 days) shows a good agreement with typical mean time of Type Ia SNe, while the initial decline rates such as Δm15(V) and Δm20(V) represent steeper and faster values than the extra-galactic SNe Ia. Moreover, its absolute peak magnitude and distance derived from the W-L relation show much fainter and nearer values, respectively than the estimated results by different methods

  12. Three Fundamental Periods in an 87 Year Light Curve of the Symbiotic Star MWC 560

    NASA Astrophysics Data System (ADS)

    Leibowitz, Elia M.; Formiggini, Liliana

    2015-08-01

    We construct a visual light curve of the symbiotic star MWC covering the last 87 years of its history. The data were assembled from the literature and from the AAVSO data bank. Most of the periodic components of the system brightness variation can be accounted for by the operation of three basic clocks of the periods P1 = 19,000 days, P2 = 1943 days, and P3 = 722 days. These periods can plausibly, and consistently with the observations, be attributed to three physical mechanisms in the system: the working of a solar-like magnetic dynamo cycle in the outer layers of the giant star of the system, the binary orbit cycle, and the sidereal rotation cycle of the giant star. MWC 560 is the seventh symbiotic star with historical light curves that reveal similar basic characteristics of the systems. The light curves of all these stars are well interpreted on the basis of the current understanding of the physical processes that are the major sources of the optical luminosity of these symbiotic systems.

  13. Analysis of the early spectra and light curve of SN 1987A

    NASA Technical Reports Server (NTRS)

    Hauschildt, Peter H.; Ensman, Lisa M.

    1994-01-01

    Numerical modeling of supernova spectra, light curves, and hydrodynamics requires physical inputs, numerical techniques, approximations, and assumptions which must be thoroughly understood in order to study the details of supernova explosions. Here, we discuss some of these in the context of the early evolution of supernova 1987A. Gray radiation-hydrodynamics is used to calculate the bolometric light curve and the hydrodynamic evolution of the supernova. Synthetic spectra are then obtained for the resulting density and velocity structure. The spectrum calculations are performed using a special-relativistic treatment of the radiative transfer equation in the comoving frame, line blanketing by about 10(exp 5) spectral lines, and departures from local thermodynamic equilibrium (LTE) for H I, He I, Mg II, and Ca II. We find that we are able to simultaneously fit the early light curve and spectra reasonably well, using a progenitor model from Arnett (1991a), without fine-tuning the free parameters. Temperature structures and radiative equilibrium, non-LTE effects, homologous expansion, and mean opacities are discussed.

  14. X-ray Light Curves and Accretion Disk Structure of EX Hydrae

    SciTech Connect

    Hoogerwerf, R; Brickhouse, N S; Mauche, C W

    2005-04-12

    We present X-ray light curves for the cataclysmic variable EX Hydrae obtained with the Chandra High Energy Transmission Grating Spectrometer and the Extreme Ultraviolet Explorer Deep Survey photometer. We confirm earlier results on the shape and amplitude of the binary light curve and discuss a new feature: the phase of the minimum in the binary light curve, associated with absorption by the bulge on the accretion disk, increases with wavelength. We discuss several scenarios that could account for this trend and conclude that, most likely, the ionization state of the bulge gas is not constant, but rather decreases with binary phase. We also conclude that photoionization of the bulge by radiation originating from the white dwarf is not the main source of ionization, but that it is heated by shocks originating from the interaction between the in-flowing material from the companion and the accretion disk. The findings in this paper provide a strong test for accretion disk models in close binary systems.

  15. An Investigation of How a Meteor Light Curve is Modified by Meteor Shape and Atmospheric Density Perturbations

    NASA Technical Reports Server (NTRS)

    Stokan, E.; Campbell-Brown, M. D.

    2011-01-01

    This is a preliminary investigation of how perturbations to meteoroid shape or atmospheric density affect a meteor light curve. A simple equation of motion and ablation are simultaneously solved numerically to give emitted light intensity as a function of height. It is found that changing the meteoroid shape, by changing the relationship between the cross-section area and the mass, changes the curvature and symmetry of the light curve, while making a periodic oscillation in atmospheric density gives a small periodic oscillation in the light curve.

  16. Smooth Light Curves from a Bumpy Ride: Relativistic Blast Wave Encounters a Density Jump

    SciTech Connect

    Nakar, Ehud; Granot, Jonathan; /KIPAC, Menlo Park

    2006-06-06

    Some gamma-ray burst (GRB) afterglow light curves show significant variability, which often includes episodes of rebrightening. Such temporal variability had been attributed in several cases to large fluctuations in the external density, or density ''bumps''. Here we carefully examine the effect of a sharp increase in the external density on the afterglow light curve by considering, for the first time, a full treatment of both the hydrodynamic evolution and the radiation in this scenario. To this end we develop a semi-analytic model for the light curve and carry out several elaborate numerical simulations using a one dimensional hydrodynamic code together with a synchrotron radiation code. Two spherically symmetric cases are explored in detail--a density jump in a uniform external medium, and a wind termination shock. The effect of density clumps is also constrained. Contrary to previous works, we find that even a very sharp (modeled as a step function) and large (by a factor of a >> 1) increase in the external density does not produce sharp features in the light curve, and cannot account for significant temporal variability in GRB afterglows. For a wind termination shock, the light curve smoothly transitions between the asymptotic power laws over about one decade in time, and there is no rebrightening in the optical or X-rays that could serve as a clear observational signature. For a sharp jump in a uniform density profile we find that the maximal deviation {Delta}{alpha}{sub max} of the temporal decay index {alpha} from its asymptotic value (at early and late times), is bounded (e.g, {Delta}{alpha}{sub max} < 0.4 for {alpha} = 10); {Delta}{alpha}{sub max} slowly increases with {alpha}, converging to {Delta}{alpha}{sub max} {approx} 1 at very large {alpha} values. Therefore, no optical rebrightening is expected in this case as well. In the X-rays, while the asymptotic flux is unaffected by the density jump, the fluctuations in {alpha} are found to be comparable to

  17. GAMMA-RAY LIGHT CURVES AND VARIABILITY OF BRIGHT FERMI-DETECTED BLAZARS

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Antolini, E.; Bonamente, E.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Bastieri, D.; Brigida, M.; Bruel, P. E-mail: stefano.ciprini@pg.infn.i E-mail: stefan@astro.su.s E-mail: stefan@astro.su.s E-mail: sarac@slac.stanford.ed

    2010-10-10

    This paper presents light curves as well as the first systematic characterization of variability of the 106 objects in the high-confidence Fermi Large Area Telescope Bright AGN Sample (LBAS). Weekly light curves of this sample, obtained during the first 11 months of the Fermi survey (2008 August 4-2009 July 4), are tested for variability and their properties are quantified through autocorrelation function and structure function analysis. For the brightest sources, 3 or 4 day binned light curves are extracted in order to determine power density spectra (PDSs) and to fit the temporal structure of major flares. More than 50% of the sources are found to be variable with high significance, where high states do not exceed 1/4 of the total observation range. Variation amplitudes are larger for flat spectrum radio quasars and low/intermediate synchrotron frequency peaked BL Lac objects. Autocorrelation timescales derived from weekly light curves vary from four to a dozen of weeks. Variable sources of the sample have weekly and 3-4 day bin light curves that can be described by 1/f {sup {alpha}} PDS, and show two kinds of gamma-ray variability: (1) rather constant baseline with sporadic flaring activity characterized by flatter PDS slopes resembling flickering and red noise with occasional intermittence and (2)-measured for a few blazars showing strong activity-complex and structured temporal profiles characterized by long-term memory and steeper PDS slopes, reflecting a random walk underlying mechanism. The average slope of the PDS of the brightest 22 FSRQs and of the 6 brightest BL Lacs is 1.5 and 1.7, respectively. The study of temporal profiles of well-resolved flares observed in the 10 brightest LBAS sources shows that they generally have symmetric profiles and that their total duration vary between 10 and 100 days. Results presented here can assist in source class recognition for unidentified sources and can serve as reference for more detailed analysis of the

  18. Supernova 1987A: neutrino-driven explosions in three dimensions and light curves

    NASA Astrophysics Data System (ADS)

    Utrobin, V. P.; Wongwathanarat, A.; Janka, H.-Th.; Müller, E.

    2015-09-01

    Context. The well-observed and well-studied type IIP Supernova 1987A (SN 1987A), produced by the explosion of a blue supergiant in the Large Magellanic Cloud, is a touchstone for the evolution of massive stars, the simulation of neutrino-driven explosions, and the modeling of light curves and spectra. Aims: In the framework of the neutrino-driven explosion mechanism, we study the dependence of explosion properties on the structure of different blue supergiant progenitors and compare the corresponding light curves with observations of SN 1987A. Methods: Three-dimensional (3D) simulations of neutrino-driven explosions are performed with the explicit, finite-volume, Eulerian, multifluid hydrodynamics code Prometheus, using of four available presupernova models as initial data. At a stage of almost homologous expansion, the hydrodynamical and composition variables of the 3D models are mapped to a spherically symmetric configuration, and the simulations are continued with the implicit, Lagrangian radiation-hydrodynamics code Crab to follow the blast-wave evolution into the SN outburst. Results: All of our 3D neutrino-driven explosion models, with explosion energies compatible with SN 1987A, produce 56Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail. Two of our models (based on the same progenitor) yield maximum velocities of around 3000 km s-1 for the bulk of ejected 56Ni, consistent with observational data. In all of our models inward mixing of hydrogen during the 3D evolution leads to minimum velocities of hydrogen-rich matter below 100 km s-1, which is in good agreement with spectral observations. However, the explosion of only one of the considered progenitors reproduces the shape of the broad light curve maximum of SN 1987A fairly well. Conclusions: The considered presupernova models, 3D explosion simulations, and light-curve calculations can explain the basic observational features of SN 1987A, except for those

  19. Period and light-curve fluctuations of the Kepler Cepheid V1154 Cygni

    NASA Astrophysics Data System (ADS)

    Derekas, A.; Szabó, Gy. M.; Berdnikov, L.; Szabó, R.; Smolec, R.; Kiss, L. L.; Szabados, L.; Chadid, M.; Evans, N. R.; Kinemuchi, K.; Nemec, J. M.; Seader, S. E.; Smith, J. C.; Tenenbaum, P.

    2012-09-01

    We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V1154 Cyg; V = 9.1 mag, P ≈ 4.9 d) based on almost 600 d of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O - C values, the cycle lengths show a scatter of 0.015-0.02 d over 120 cycles covered by the observations. A very slight correlation between the individual Fourier parameters and the O - C values was found, suggesting that the O - C variations might be due to the instability of the light-curve shape. Random-fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated light curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the light-time effect.

  20. OO Aquilae: a solar-type contact binary with intrinsic light curve changes

    NASA Astrophysics Data System (ADS)

    Li, Hua-Li; Wei, Jian-Yan; Yang, Yuan-Gui; Dai, Hai-Feng

    2016-01-01

    New multi-color photometry of the solar-type contact binary OO Aql was obtained in 2012 and 2013, using the 60 cm telescope at Xinglong Station of the National Astronomical Observatories, Chinese Academy of Sciences. From two sets of light curves LC1 and LC2, photometric models were performed by using the 2003 version of the Wilson-Devinney code. The overcontact factor of the binary system was determined to be f = 37.0(±0.5)%. The intrinsic variability of this binary occurs in light maxima and minima, which could result from a possible third component and magnetic activity of the late type components. Based on all available light minimum times, the orbital period may change in a complicated mode, i.e., sudden period jumps or continuous period variations. The period of OO Aql may possibly undergo a secular period decrease with a rate of dP/dt = -3.63(±0.30) × 10-8 d yr-1, superimposed by two possible cyclic variations in the O - C curve. The long-term period decrease may be interpreted as conserved mass transfer from the more massive component to the less massive one. The 21.5-yr oscillation may be attributed to cyclic magnetic activity, and the 69.3-yr one may result from the light-time effect of an unseen tertiary body.

  1. Achromatic optical correlator for white light pattern recognition

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Liu, Hua-Kuang; Chen, Ming; Cai, Luzhong

    1987-01-01

    An achromatic optical correlator using spatially multiplexed achromatic matched spatial filters (MSFs) for white light optical pattern recognition is presented. The MSF array is synthesizd using a monochromatic laser and its achromaticity is achieved by adjusting the scale and spatial carrier frequency of each MSF to accommodate the wavelength variations in white light correlation detections. Systems analysis and several experimental results showing the correlation peak intensity using white-light illumination are presented.

  2. Fraunhofer Diffraction Patterns from Apertures Illuminated with Nonparallel Light.

    ERIC Educational Resources Information Center

    Klingsporn, Paul E.

    1979-01-01

    Discusses several aspects of Fraunhofer diffraction patterns from apertures illuminated by diverging light. Develops a generalization to apertures of arbitrary shape which shows that the sizes of the pattern are related by a simple scale factor. Uses the Abbe theory of image formation by diffraction to discuss the intensity of illumination of the…

  3. Searching for transits in the WTS with the difference imaging light curves

    NASA Astrophysics Data System (ADS)

    Zendejas Dominguez, Jesus

    2013-12-01

    The search for exo-planets is currently one of the most exiting and active topics in astronomy. Small and rocky planets are particularly the subject of intense research, since if they are suitably located from their host star, they may be warm and potentially habitable worlds. On the other hand, the discovery of giant planets in short-period orbits provides important constraints on models that describe planet formation and orbital migration theories. Several projects are dedicated to discover and characterize planets outside of our solar system. Among them, the Wide-Field Camera Transit Survey (WTS) is a pioneer program aimed to search for extra-solar planets, that stands out for its particular aims and methodology. The WTS has been in operation since August 2007 with observations from the United Kingdom Infrared Telescope, and represents the first survey that searches for transiting planets in the near-infrared wavelengths; hence the WTS is designed to discover planets around M-dwarfs. The survey was originally assigned about 200 nights, observing four fields that were selected seasonally (RA = 03, 07, 17 and 19h) during a year. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. For the most complete field (19h-1145 epochs) in the survey, we produce an alternative set of light curves by using the method of difference imaging, which is a photometric technique that has shown important advantages when used in crowded fields. A quantitative comparison between the photometric precision achieved with both methods is carried out in this work. We remove systematic effects using the sysrem algorithm, scale the error bars on the light curves, and perform a comparison of the corrected light curves. The results show that the aperture photometry light curves provide slightly better precision for objects with J < 16. However, difference photometry light curves present a significant improvement for

  4. CCD Photometric Observations and Light Curve Synthesis of the Near-Contact Binary XZ Canis Minoris

    NASA Astrophysics Data System (ADS)

    Kim, Chun-Hwey; Park, Jang-Ho; Lee, Jae Woo; Jeong, Jang-Hae

    2009-06-01

    Through the photometric observations of the near-contact binary, XZ CMi, new BV light curves were secured and seven times of minimum light were determined. An intensive period study with all published timings, including ours, confirms that the period of XZ CMi has varied in a cyclic period variation superposed on a secular period decrease over last 70 years. Assuming the cyclic change of period to occur by a light-time effect due to a third-body, the light-time orbit with a semi-amplitude of 0.0056d, a period of 29y and an eccentricity of 0.71 was calculated. The observed secular period decrease of -5.26× 10^{-11} d/P was interpreted as a result of simultaneous occurrence of both a period decrease of -8.20 × 10^{-11} d/P by angular momentum loss (AML) due to a magnetic braking stellar wind and a period increase of 2.94 × 10^{-11} d/P by a mass transfer from the less massive secondary to the primary components in the system. In this line the decreasi! ng rate of period due to AML is about 3 times larger than the increasing one by a mass transfer in their absolute values. The latter implies a mass transfer of dot M_{s}= 3.21 × 10^{-8} M_⊙ y^{-1} from the less massive secondary to the primary. The BV light curves with the latest Wilson-Devinney binary code were analyzed for two separate models of 8200K and 7000K as the photospheric temperature of the primary component. Both models confirm that XZ CMi is truly a near-contact binary with a less massive secondary completely filling Roche lobe and a primary inside the inner Roche lobe and there is a third-light corresponding to about 15-17% of the total system light. However, the third-light source can not be the same as the third-body suggested from the period study. At the present, however, we can not determine which one between two models is better fitted to the observations because of a negligible difference of sum (O-C)^2 between them. The diversity of mass ratios, with which previous investigators were in

  5. Spectral optimization simulation of white light based on the photopic eye-sensitivity curve

    NASA Astrophysics Data System (ADS)

    Dai, Qi; Hao, Luoxi; Lin, Yi; Cui, Zhe

    2016-02-01

    Spectral optimization simulation of white light is studied to boost maximum attainable luminous efficacy of radiation at high color-rendering index (CRI) and various color temperatures. The photopic eye-sensitivity curve V(λ) is utilized as the dominant portion of white light spectra. Emission spectra of a blue InGaN light-emitting diode (LED) and a red AlInGaP LED are added to the spectrum of V(λ) to match white color coordinates. It is demonstrated that at the condition of color temperature from 2500 K to 6500 K and CRI above 90, such white sources can achieve spectral efficacy of 330-390 lm/W, which is higher than the previously reported theoretical maximum values. We show that this eye-sensitivity-based approach also has advantages on component energy conversion efficiency compared with previously reported optimization solutions.

  6. Light curve solutions and out-of-eclipse variabilities of six eccentric Kepler binaries

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Vasileva, D.; Dimitrov, D.

    2016-04-01

    As a result from light curve solutions of six eccentric Kepler binaries we determined their orbital elements and stellar parameters. We established linear dependence of their eccentricities on the orbital periods. Besides eclipses all targets reveal out-of-eclipse light variabilities modulated on different time scales. KIC 11409698, KIC 5284133 and KIC 8316503, the targets with the biggest eccentricities in our sample, exhibit tidally induced light brightening (hump) around the periastron phase. Just they reveal considerable reflection effect due to the big temperature difference of their components (above 2200 K). The detected humps confirmed the theoretical dependence of the hump amplitude on the eccentricity and mass ratio. KIC 12557713 and KIC 7691527 show photospheric activity caused by two diametrically opposite cool spots on the lateral sides of their primary components (flip-flop effect). We found flares in the Kepler data of KIC 7691527 that is another appearance of the activity of this target.

  7. Kinematics of illumination patterns and light echoes from flashes.

    PubMed

    Zhong, Qi

    2016-09-01

    Flash-induced light echoes-the observation of light reflected from a burst-have been observed in astronomical settings for more than a century and have been observed in the laboratory recently. Because of the flight time of light, perceived light echoes are different from real light illumination patterns on a scattering plane, neglecting interreflections and non-opaque scattering effects. The shape and motion of real illumination patterns are studied from a spherical flash. Then, ellipsoids of constant time delay for a specifically chosen coordinate system are applied. Generally, perceived light echoes are elliptical annular rings and the center of a light echo will not start at the flash, which leads to light echoes moving angularly toward the flash instead of away from it, a phenomenon actually recorded by other groups. The brightness of perceived light echoes was studied, and maximum brightness occurred close to the flash's projective point on the scattering plane. Two specific examples are given and a magnification effect between perceived echoes and real illumination patterns is proposed. PMID:27607505

  8. Modeling Type IIn Supernovae: Understanding How Shock Development Effects Light Curves Properties

    NASA Astrophysics Data System (ADS)

    De La Rosa, Janie

    2016-06-01

    Type IIn supernovae are produced when massive stars experience dramatic mass loss phases caused by opacity edges or violent explosions. Violent mass ejections occur quite often just prior to the collapse of the star. If the final episode happens just before collapse, the outward ejecta is sufficiently dense to alter the supernova light-curve, both by absorbing the initial supernova light and producing emission when the supernova shock hits the ejecta. Initially, the ejecta is driven by shock progating through the interior of the star, and eventually expands through the circumstellar medium, forming a cold dense shell. As the shock wave approaches the shell, there is an increase in UV and optical radiation at the location of the shock breakout. We have developed a suite of simple semi-analytical models in order to understand the relationship between our observations and the properties of the expanding SN ejecta. When we compare Type IIn observations to a set of modeled SNe, we begin to see the influence of initial explosion conditions on early UV light curve properties such as peak luminosities and decay rate.The fast rise and decay corresponds to the models representing a photosphere moving through the envelope, while the modeled light curves with a slower rise and decay rate are powered by 56Ni decay. However, in both of these cases, models that matched the luminosity were unable to match the low radii from the blackbody models. The effect of shock heating as the supernova material blasts through the circumstellar material can drastically alter the temperature and position of the photosphere. The new set of models redefine the initial modeling conditions to incorporate an outer shell-like structure, and include late-time shock heating from shocks produced as the supernova ejecta travels through the inhomogeneous circumstellar medium.

  9. ellc: A fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets

    NASA Astrophysics Data System (ADS)

    Maxted, P. F. L.

    2016-06-01

    Context. Very high quality light curves are now available for thousands of detached eclipsing binary stars and transiting exoplanet systems as a result of surveys for transiting exoplanets and other large-scale photometric surveys. Aims: I have developed a binary star model (ellc) that can be used to analyse the light curves of detached eclipsing binary stars and transiting exoplanet systems that is fast and accurate, and that can include the effects of star spots, Doppler boosting and light-travel time within binaries with eccentric orbits. Methods: The model represents the stars as triaxial ellipsoids. The apparent flux from the binary is calculated using Gauss-Legendre integration over the ellipses that are the projection of these ellipsoids on the sky. The model can also be used to calculate the flux-weighted radial velocity of the stars during an eclipse (Rossiter-McLaghlin effect). The main features of the model have been tested by comparison to observed data and other light curve models. Results: The model is found to be accurate enough to analyse the very high quality photometry that is now available from space-spaced instruments, flexible enough to model a wide range of eclipsing binary stars and extrasolar planetary systems, and fast enough to enable the use of modern Monte Carlo methods for data analysis and model testing. The software package is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A111

  10. ANALYTIC MODELS FOR ALBEDOS, PHASE CURVES, AND POLARIZATION OF REFLECTED LIGHT FROM EXOPLANETS

    SciTech Connect

    Madhusudhan, Nikku; Burrows, Adam E-mail: burrows@astro.princeton.edu

    2012-03-01

    New observational facilities are becoming increasingly capable of observing reflected light from transiting and directly imaged extrasolar planets. In this study, we provide an analytic framework to interpret observed phase curves, geometric albedos, and polarization of giant planet atmospheres. We compute the observables for non-conservative Rayleigh scattering in homogeneous semi-infinite atmospheres using both scalar and vector formalisms. In addition, we compute phase curves and albedos for Lambertian, isotropic, and anisotropic scattering phase functions. We provide analytic expressions for geometric albedos and spherical albedos as a function of the scattering albedo for Rayleigh scattering in semi-infinite atmospheres. Given an observed geometric albedo our prescriptions can be used to estimate the underlying scattering albedo of the atmosphere, which in turn is indicative of the scattering and absorptive properties of the atmosphere. We also study the dependence of polarization in Rayleigh scattering atmospheres on the orbital parameters of the planet-star system, particularly on the orbital inclination. We show how the orbital inclination of non-transiting exoplanets can be constrained from their observed polarization parameters. We consolidate the formalism, solution techniques, and results from analytic models available in the literature, often scattered in various sources, and present a systematic procedure to compute albedos, phase curves, and polarization of reflected light.

  11. Constraining the Physical Properties of Meteor Stream Particles by Light Curve Shapes Using the Virtual Meteor Observatory

    NASA Technical Reports Server (NTRS)

    Koschny, D.; Gritsevich, M.; Barentsen, G.

    2011-01-01

    Different authors have produced models for the physical properties of meteoroids based on the shape of a meteor's light curve, typically from short observing campaigns. We here analyze the height profiles and light curves of approx.200 double-station meteors from the Leonids and Perseids using data from the Virtual Meteor Observatory, to demonstrate that with this web-based meteor database it is possible to analyze very large datasets from different authors in a consistent way. We compute the average heights for begin point, maximum luminosity, and end heights for Perseids and Leonids. We also compute the skew of the light curve, usually called the F-parameter. The results compare well with other author's data. We display the average light curve in a novel way to assess the light curve shape in addition to using the F-parameter. While the Perseids show a peaked light curve, the average Leonid light curve has a more flat peak. This indicates that the particle distribution of Leonid meteors can be described by a Gaussian distribution; the Perseids can be described with a power law. The skew for Leonids is smaller than for Perseids, indicating that the Leonids are more fragile than the Perseids.

  12. Estimation of fatigue strain-life curves for austenitic stainless steels in light water reactor environments.

    SciTech Connect

    Chopra, O. K.; Smith, J. L.

    1998-02-12

    The ASME Boiler and Pressure Vessel Code design fatigue curves for structural materials do not explicitly address the effects of reactor coolant environments on fatigue life. Recent test data indicate a significant decrease in fatigue lives of austenitic stainless steels (SSs) in light water reactor (LWR) environments. Unlike those of carbon and low-alloy steels, environmental effects on fatigue lives of SSs are more pronounced in low-dissolved-oxygen (low-DO) water than in high-DO water, This paper summarizes available fatigue strain vs. life data on the effects of various material and loading variables such as steel type, DO level, strain range, and strain rate on the fatigue lives of wrought and cast austenitic SSs. Statistical models for estimating the fatigue lives of these steels in LWR environments have been updated with a larger data base. The significance of the effect of environment on the current Code design curve has been evaluated.

  13. Obtaining the curve “Phase shift vs gray level” of a spatial light modulator Holoeye LC2012

    NASA Astrophysics Data System (ADS)

    Villalobos-Mendoza, B.; Granados-Agustín, F. S.; Aguirre-Aguirre, D.; Cornejo-Rodríguez, A.

    2015-04-01

    In this work, the process to obtain the curve “Graylevel vs phase shift” of a transmissive spatial light modulator (SLM) HoloeyeLC2012 is described. This work arises from the need that exists for having a new optical surface testing method at INAOE's Optical Workshop. The SLM was placed in one arm of a Twyman-Green interferometer. The fringe shifts in the interference patterns were produced by displaying the different gray levels in the SLM. The gray level images displayed in the SLM were divided in two equal parts, the upper part was varying the different gray levels from 0 to 255 and the lower part stayed fixed with a gray level of 0 as reference. We show the different phase shifts and the experimental interferograms. From this analysis it was found out that a noticeable phase shift can be obtained from the 50 to the 190 gray levels.

  14. Perception of light source distance from shading patterns.

    PubMed

    Schütt, Heiko H; Baier, Franziska; Fleming, Roland W

    2016-01-01

    Varying the distance of a light source from an object alters both the intensity and spatial distribution of surface shading patterns. We tested whether observers can use such cues to infer light source distance. Participants viewed stereoscopic renderings of rough objects with diffuse and glossy surfaces, which were illuminated by a point source at a range of distances. In one task, they adjusted the position of a small probe dot in three dimensions to report the apparent location of the light in the scene. In a second task, they adjusted the shading on one object (by moving an invisible light source) until it appeared to be illuminated from the same distance as another object. Participants' responses increased linearly with the true light source distance, suggesting that they have clear intuitions about how light source distance affects shading patterns for a variety of different surfaces. However, there were also systematic errors: Subjects overestimated light source distance in the probe adjustment task, and in both experiments, roughness and glossiness affected responses. We find the pattern of results is predicted surprisingly well by a simplistic model based only on the area of the image that exceeds a certain intensity threshold. Thus, although subjects can report light source distance, they may rely on simple--sometimes erroneous--heuristics to do so. PMID:26868887

  15. Preliminary NIR Late Light Curve of the Type Ia Supernova SN2009nr

    NASA Astrophysics Data System (ADS)

    Heath, Jonathan; Bryngelson, G.

    2013-01-01

    Type Ia supernovae (SNe Ia) are important in determining the expansion of the universe based on the uniformity of their light curves. It is essential to understand the behavior of these supernovae in order to strengthen our confidence in their use as standard candles. A small, but increasing number of SNe Ia have been observed later than the 200 day epoch in the near-infrared (NIR). Most of these exhibit a flattening of the NIR power, even as the visible light declines at a steady rate. It is unclear as to exactly what causes this behavior, and how typical it is. In order to characterize the late behavior of SNe Ia, images of the supernova SN2009nr were analyzed using the Image Reduction and Analysis Facility (IRAF). These images were taken with the 4m Mayall Telescope at Kitt Peak National-Observatory using the FLAMINGOS IR Imaging Spectrometer. The supernova’s magnitude was normalized with respect to the magnitudes of known stars so that traits related to the supernova may be compared to others. We present preliminary NIR (J, H, K) light curves of the observed supernova and compare them to other SNe Ia observed at these epochs.

  16. Apsidal Motion and a Light Curve Solution for 13 LMC Eccentric Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Zasche, P.; Wolf, M.; Vraštil, J.; Pilarčík, L.

    2015-12-01

    New CCD observations for 13 eccentric eclipsing binaries from the Large Magellanic Cloud were carried out using the Danish 1.54 m telescope located at the La Silla Observatory in Chile. These systems were observed for their times of minimum and 56 new minima were obtained. These are needed for accurate determination of the apsidal motion. Besides that, in total 436 times of minimum were derived from the photometric databases OGLE and MACHO. The O - C diagrams of minimum timings for these B-type binaries were analyzed and the parameters of the apsidal motion were computed. The light curves of these systems were fitted using the program PHOEBE, giving the light curve parameters. We derived for the first time relatively short periods of the apsidal motion ranging from 21 to 107 years. The system OGLE-LMC-ECL-07902 was also analyzed using the spectra and radial velocities, resulting in masses of 6.8 and 4.4 M⊙ for the eclipsing components. For one system (OGLE-LMC-ECL-20112), the third-body hypothesis was also used to describe the residuals after subtraction of the apsidal motion, resulting in a period of about 22 years. For several systems an additional third light was also detected, which makes these systems suspect for triplicity. Based on data collected with the Danish 1.54 m telescope at the ESO La Silla Observatory.

  17. Light Curve Solutions of Ten Eccentric Kepler Binaries, Three of them with Tidally Induced Humps

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Vasileva, D.

    2015-06-01

    We carried out light curve solutions of ten detached eclipsing eccentric binaries observed by Kepler. The formal errors of the derived parameters from the light curve solutions are below 1%. Our results give indications that the components of the eccentric binaries (especially those with mass ratios below 0.5) do not follow precisely the empirical relations between the stellar parameters derived from the study of circular-orbit binaries. We found the following peculiarities of the targets: (a) the components of KIC 9474969 have almost the same temperatures while their radii and masses differ by a factor around 2.5; (b) KIC 6949550 reveals semi-regular light variations with an amplitude of 0.004 and a period around 7 d which are modulated by long-term variations; (c) KIC 6220470, KIC 11071207, and KIC 9474969 exhibit tidally induced `hump' around the periastron. These are the targets with the biggest relative radii of our sample. We derived the dependence of the hump amplitude on the relative stellar radii, eccentricity, and mass ratio of eccentric binary consisting of MS stars.

  18. Multidimensional radiative transfer calculations of the light curves and spectra of Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Kasen, D.; Thomas, R. C.; Röpke, F.; Woosley, S. E.

    2008-07-01

    The explosion of a white dwarf star in a Type Ia supernova (SN Ia) explosion leads to the burning and ejection of stellar material at a few percent of the speed of light. The spectacle we observe in the months that follow is from the leaking of radiation from this glowing mass of radioactive debris. The modeling of SN Ia light curves and spectra represents a complex problem in time-dependent radiative transfer. Here we discuss numerical methods, in particular Monte Carlo methods, for calculating 3D multi-wavelength radiative transport on massively parallel machines. Our approach involves a newly developed domain decomposition technique in which the memory load is distributed over multiple processors and photon packets are communicated from node to node. We present results for 2-dimensional models that explore white dwarf explosions over a range of explosion paradigms and ignition conditions. These models give insight into how variations in the initial conditions of the explosion affect the light curve we finally observe. We conclude with an outlook (and some initial results) for large scale 3D radiation transport calculations of SNe Ia in an era of petascale computing.

  19. Newly Discovered AGN and their Multi-year Light Curves from Kepler

    NASA Astrophysics Data System (ADS)

    Shaya, Edward J.; Olling, R.; Mushotzky, R.

    2014-01-01

    Variability seen at the center of a galaxy is an easy and reliable way to identify AGN. The Kepler space mission provides the ability to find galaxies with very low amplitude variability over a wide range in time delays. We report on a 2 year project to monitor ~400 galaxies with Kepler and our reduction software to stabilize long term photometric trends. We will present light curves for several of our newly discovered AGN with variability measured from the 30 minute to ~2 year timescales. The optical variability that Kepler explores is probably related to accretion disk instabilities, variation in accretion rate or changes in the accretion disk's structure. We developed, in a white paper, a future Kepler project to monitor of order 10,000 galaxies. Statistical analysis of light curves from hundreds of AGN would reveal the physical character of gas, dust or stars falling into AGN or eclipsing the light source and allow better models to be developed of the inner accretion disks/tori. In addition, this project should also find a large number of supernovae and other exotic transient events such as stellar tidal disruption and eta Carinae or P-Cygni type outbursts.

  20. A Simple Model for the Light Curve Generated by a Shoemaker-Levy 9 Impact

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Mordecai-Mark, Mac Low

    1995-01-01

    The impact of a typical Shoemaker-Levy 9 fragment produced three light peaks as seen from Earth. The first peak is related to the entry of the fragment into the Jovian atmosphere. The second peak occurs when the exploding fireball rises above Jupiter's limb into direct view from Earth. The third peak, much the brightest, occurs when the ejecta plume falls back on the atmosphere. By contrast, Galileo, which had a direct view of the impacts, saw two peaks, one at entry, and one at plumefall. Here we present a simple, highly idealized model of a ballistic plume, which we then use to fit the observed light curve of the R impact as recorded at Mauna Kea and Mount Palomar. From the light curve we find that the nominal R fragment had diameter 450-500 m and mass approx. 2-3 x 10(exp 13) g. The uncertainty in the mass is probably about a factor of 3, with a smaller event more likely than a larger one.

  1. Multiperiodicity, modulations and flip-flops in variable star light curves. I. Carrier fit method

    NASA Astrophysics Data System (ADS)

    Pelt, J.; Olspert, N.; Mantere, M. J.; Tuominen, I.

    2011-11-01

    Context. The light curves of variable stars are commonly described using simple trigonometric models, that make use of the assumption that the model parameters are constant in time. This assumption, however, is often violated, and consequently, time series models with components that vary slowly in time are of great interest. Aims: In this paper we introduce a class of data analysis and visualization methods which can be applied in many different contexts of variable star research, for example spotted stars, variables showing the Blazhko effect, and the spin-down of rapid rotators. The methods proposed are of explorative type, and can be of significant aid when performing a more thorough data analysis and interpretation with a more conventional method. Methods: Our methods are based on a straightforward decomposition of the input time series into a fast "clocking" periodicity and smooth modulating curves. The fast frequency, referred to as the carrier frequency, can be obtained from earlier observations (for instance in the case of photometric data the period can be obtained from independently measured radial velocities), postulated using some simple physical principles (Keplerian rotation laws in accretion disks), or estimated from the data as a certain mean frequency. The smooth modulating curves are described by trigonometric polynomials or splines. The data approximation procedures are based on standard computational packages implementing simple or constrained least-squares fit -type algorithms. Results: Using both artificially generated data sets and observed data, we demonstrate the utility of the proposed methods. Our interest is mainly focused on cases where multiperiodicity, trends or abrupt changes take place in the variable star light curves. Conclusions: The presented examples show that the proposed methods significantly enrich the traditional toolbox for variable star researchers. Applications of the methods to solve problems of astrophysical interest

  2. What powers the 3000-day light curve of SN 2006gy?

    NASA Astrophysics Data System (ADS)

    Fox, Ori D.; Smith, Nathan; Ammons, S. Mark; Andrews, Jennifer; Bostroem, K. Azalee; Cenko, S. Bradley; Clayton, Geoffrey C.; Dwek, Eli; Filippenko, Alexei V.; Gallagher, Joseph S.; Kelly, Patrick L.; Mauerhan, Jon C.; Miller, Adam A.; Van Dyk, Schuyler D.

    2015-12-01

    SN 2006gy was the most luminous supernova (SN) ever observed at the time of its discovery and the first of the newly defined class of superluminous supernovae (SLSNe). The extraordinary energetics of SN 2006gy and all SLSNe (>1051 erg) require either atypically large explosion energies (e.g. pair-instability explosion) or the efficient conversion of kinetic into radiative energy (e.g. shock interaction). The mass-loss characteristics can therefore offer important clues regarding the progenitor system. For the case of SN 2006gy, both a scattered and thermal light echo from circumstellar material (CSM) have been reported at later epochs (day ˜800), ruling out the likelihood of a pair-instability event and leading to constraints on the characteristics of the CSM. Owing to the proximity of the SN to the bright host-galaxy nucleus, continued monitoring of the light echo has not been trivial, requiring the high resolution offered by the Hubble Space Telescope (HST) or ground-based adaptive optics (AO). Here, we report detections of SN 2006gy using HST and Keck AO at ˜3000 d post-explosion and consider the emission mechanism for the very late-time light curve. While the optical light curve and optical spectral energy distribution are consistent with a continued scattered-light echo, a thermal echo is insufficient to power the K'-band emission by day 3000. Instead, we present evidence for late-time infrared emission from dust that is radiatively heated by CSM interaction within an extremely dense dust shell, and we consider the implications on the CSM characteristics and progenitor system.

  3. A phase response curve to single bright light pulses in human subjects

    NASA Technical Reports Server (NTRS)

    Khalsa, Sat Bir S.; Jewett, Megan E.; Cajochen, Christian; Czeisler, Charles A.

    2003-01-01

    The circadian pacemaker is differentially sensitive to the resetting effects of retinal light exposure, depending upon the circadian phase at which the light exposure occurs. Previously reported human phase response curves (PRCs) to single bright light exposures have employed small sample sizes, and were often based on relatively imprecise estimates of circadian phase and phase resetting. In the present study, 21 healthy, entrained subjects underwent pre- and post-stimulus constant routines (CRs) in dim light (approximately 2-7 lx) with maintained wakefulness in a semi-recumbent posture. The 6.7 h bright light exposure stimulus consisted of alternating 6 min fixed gaze (approximately 10 000 lx) and free gaze (approximately 5000-9000 lx) exposures. Light exposures were scheduled across the circadian cycle in different subjects so as to derive a PRC. Plasma melatonin was used to determine the phase of the onset, offset, and midpoint of the melatonin profiles during the CRs. Phase shifts were calculated as the difference in phase between the pre- and post-stimulus CRs. The resultant PRC of the midpoint of the melatonin rhythm revealed a characteristic type 1 PRC with a significant peak-to-trough amplitude of 5.02 h. Phase delays occurred when the light stimulus was centred prior to the critical phase at the core body temperature minimum, phase advances occurred when the light stimulus was centred after the critical phase, and no phase shift occurred at the critical phase. During the subjective day, no prolonged 'dead zone' of photic insensitivity was apparent. Phase shifts derived using the melatonin onsets showed larger magnitudes than those derived from the melatonin offsets. These data provide a comprehensive characterization of the human PRC under highly controlled laboratory conditions.

  4. An analysis of the massless planet approximation in transit light curve models

    NASA Astrophysics Data System (ADS)

    Millholland, Sarah; Ruch, Gerry

    2015-08-01

    Many extrasolar planet transit light curve models use the approximation of a massless planet. They approximate the planet as orbiting elliptically with the host star at the orbit’s focus instead of depicting the planet and star as both orbiting around a common center of mass. This approximation should generally be very good because the transit is a small fraction of the full-phase curve and the planet to stellar mass ratio is typically very small. However, to fully examine the legitimacy of this approximation, it is useful to perform a robust, all-parameter space-encompassing statistical comparison between the massless planet model and the more accurate model.Towards this goal, we establish two questions: (1) In what parameter domain is the approximation invalid? (2) If characterizing an exoplanetary system in this domain, what is the error of the parameter estimates when using the simplified model? We first address question (1). Given each parameter vector in a finite space, we can generate the simplified and more complete model curves. Associated with these model curves is a measure of the deviation between them, such as the root mean square (RMS). We use Gibbs sampling to generate a sample that is distributed according to the RMS surface. The high-density regions in the sample correspond to a large deviation between the models. To determine the domains of these high-density areas, we first employ the Ordering Points to Identify the Clustering Structure (OPTICS) algorithm. We then characterize the subclusters by performing the Patient Rule Induction Method (PRIM) on the transformed Principal Component spaces of each cluster. This process yields descriptors of the parameter domains with large discrepancies between the models.To consider question (2), we start by generating synthetic transit curve observations in the domains specified by the above analysis. We then derive the best-fit parameters of these synthetic light curves according to each model and examine

  5. Probing Millisecond Pulsar Emission Geometry Using Light Curves From the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Venter, Christo; Harding, Alice; Guillemot, L.

    2009-01-01

    An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from 3D emission modeling, including the Special Relativistic effects of aberration and time-of-flight delays and also rotational sweepback of 13-field lines, in the geometric context of polar cap (PC), slot gap (SG), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly-rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by SG and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production -- even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We also find exclusive differentiation of the current gamma-ray MSP population into two MSP sub-classes: light curve shapes and lags across wavebands impose either pair-starved PC (PSPC) or SG / OG-type geometries. In the first case, the radio pulse has a small lag with respect to the single gamma-ray pulse, while the (first) gamma-ray peak usually trails the radio by a large phase offset in the latter case. Finally, we find that the flux correction factor as a function of magnetic inclination and observer angles is typically of order unity for all models. Our calculation of light curves and flux correction factor f(_, _, P) for the case of MSPs is therefore complementary to the "ATLAS paper" of Watters et al. for younger pulsars.

  6. Stellar Granulation as the Source of High-frequency Flicker in Kepler Light Curves

    NASA Astrophysics Data System (ADS)

    Cranmer, Steven R.; Bastien, Fabienne A.; Stassun, Keivan G.; Saar, Steven H.

    2014-02-01

    A large fraction of cool, low-mass stars exhibit brightness fluctuations that arise from a combination of convective granulation, acoustic oscillations, magnetic activity, and stellar rotation. Much of the short-timescale variability takes the form of stochastic noise, whose presence may limit the progress of extrasolar planet detection and characterization. In order to lay the groundwork for extracting useful information from these quasi-random signals, we focus on the origin of the granulation-driven component of the variability. We apply existing theoretical scaling relations to predict the star-integrated variability amplitudes for 508 stars with photometric light curves measured by the Kepler mission. We also derive an empirical correction factor that aims to account for the suppression of convection in F-dwarf stars with magnetic activity and shallow convection zones. So that we can make predictions of specific observational quantities, we performed Monte Carlo simulations of granulation light curves using a Lorentzian power spectrum. These simulations allowed us to reproduce the so-called flicker floor (i.e., a lower bound in the relationship between the full light-curve range and power in short-timescale fluctuations) that was found in the Kepler data. The Monte Carlo model also enabled us to convert the modeled fluctuation variance into a flicker amplitude directly comparable with observations. When the magnetic suppression factor described above is applied, the model reproduces the observed correlation between stellar surface gravity and flicker amplitude. Observationally validated models like these provide new and complementary evidence for a possible impact of magnetic activity on the properties of near-surface convection.

  7. A Global Model of The Light Curves and Expansion Velocities of Type II-plateau Supernovae

    NASA Astrophysics Data System (ADS)

    Pejcha, Ondřej; Prieto, Jose L.

    2015-02-01

    We present a new self-consistent and versatile method that derives photospheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photometric measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ~230 velocity and ~6800 mag measurements distributed over 21 photometric passbands spanning wavelengths from 0.19 to 2.2 μm. The light-curve differences among the Type II-Plateau supernovae are well modeled by assuming different rates of photospheric radius expansion, which we explain as different density profiles of the ejecta, and we argue that steeper density profiles result in flatter plateaus, if everything else remains unchanged. The steep luminosity decline of Type II-Linear supernovae is due to fast evolution of the photospheric temperature, which we verify with a successful fit of SN 1980K. Eliminating the need for theoretical supernova atmosphere models, we obtain self-consistent relative distances, reddenings, and nickel masses fully accounting for all internal model uncertainties and covariances. We use our global fit to estimate the time evolution of any missing band tailored specifically for each supernova, and we construct spectral energy distributions and bolometric light curves. We produce bolometric corrections for all filter combinations in our sample. We compare our model to the theoretical dilution factors and find good agreement for the B and V filters. Our results differ from the theory when the I, J, H, or K bands are included. We investigate the reddening law toward our supernovae and find reasonable agreement with standard \\mathscr{R}_V˜ 3.1 reddening law in UBVRI bands. Results for other bands are inconclusive. We make our fitting code publicly available.

  8. Evidence for rapid variability in the optical light curve of the Type Ia SN 2014J⋆

    NASA Astrophysics Data System (ADS)

    Bonanos, A. Z.; Boumis, P.

    2016-01-01

    We present results of high-cadence monitoring of the optical light curve of the nearby, Type Ia SN 2014J in M 82, using the 2.3 m Aristarchos telescope. B and V-band photometry on days 15-18 after tmax(B) was obtained with a cadence of 2 min per band, revealing evidence for rapid variability at the 0.02-0.05 mag level on timescales of 15-60 min on all four nights. The decline slope was measured as steeper in the B-band than in the V-band, and to steadily decrease in both bands from 0.15 mag day-1 (night 1) to 0.04 mag day-1 (night 4) in V, and from 0.19 mag day-1 (night 1) to 0.06 mag day-1 (night 4) in B, corresponding to the onset of the secondary maximum. We propose that rapid variability could be due to one or a combination of the following scenarios: the clumpiness of the ejecta, their interaction with circumstellar material, the asymmetry of the explosion, or the mechanism causing the secondary maximum in the near-infrared light curve. We encourage the community to undertake high-cadence monitoring of future, nearby and bright supernovae to investigate the intraday behaviour of their light curves. Based on observations made with the 2.3 m Aristarchos telescope, Helmos Observatory, Greece, which is operated by the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Greece.Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A19

  9. The 2010 Eruption of the Recurrent Nova U Scorpii: The Multi-wavelength Light Curve

    NASA Astrophysics Data System (ADS)

    Pagnotta, Ashley; Schaefer, Bradley E.; Clem, James L.; Landolt, Arlo U.; Handler, Gerald; Page, Kim L.; Osborne, Julian P.; Schlegel, Eric M.; Hoffman, Douglas I.; Kiyota, Seiichiro; Maehara, Hiroyuki

    2015-09-01

    The recurrent nova U Scorpii most recently erupted in 2010. Our collaboration observed the eruption in bands ranging from the Swift XRT and UVOT w2 (193 nm) to K-band (2200 nm), with a few serendipitous observations stretching down to WISE W2 (4600 nm). Considering the time and wavelength coverage, this is the most comprehensively observed nova eruption to date. We present here the resulting multi-wavelength light curve covering the two months of the eruption as well as a few months into quiescence. For the first time, a U Sco eruption has been followed all the way back to quiescence, leading to the discovery of new features in the light curve, including a second, as-yet-unexplained, plateau in the optical and near-infrared. Using this light curve we show that U Sco nearly fits the broken power law decline predicted by Hachisu & Kato, with decline indices of -1.71 ± 0.02 and -3.36 ± 0.14. With our unprecedented multi-wavelength coverage, we construct daily spectral energy distributions and then calculate the total radiated energy of the eruption, {E}{rad}={6.99}-0.57+0.83× {10}44 {erg}. From that, we estimate the total amount of mass ejected by the eruption to be {m}{ej}={2.10}-0.17+0.24× {10}-6{M}⊙ . We compare this to the total amount of mass accreted by U Sco before the eruption, to determine whether the white dwarf undergoes a net mass loss or gain, but find that the values for the amount of mass accreted are not precise enough to make a useful comparison.

  10. Constraints on shallow {sup 56}Ni from the early light curves of type Ia supernovae

    SciTech Connect

    Piro, Anthony L.

    2014-03-20

    Ongoing transient surveys are presenting an unprecedented account of the rising light curves of Type Ia supernovae (SNe Ia). This early emission probes the shallowest layers of the exploding white dwarf (WD), which can provide constraints on the progenitor star and the properties of the explosive burning. We use semianalytic models of radioactively powered rising light curves to analyze these observations. As we have summarized in previous work, the main limiting factor in determining the surface distribution of {sup 56}Ni is the lack of an unambiguously identified time of explosion, as would be provided by detection of shock breakout or shock-heated cooling. Without this the SN may in principle exhibit a 'dark phase' for a few hours to days, where the only emission is from shock-heated cooling that is too dim to be detected. We show that by assuming a theoretically motivated time-dependent velocity evolution, the explosion time can be better constrained, albeit with potential systematic uncertainties. This technique is used to infer the surface {sup 56}Ni distributions of three recent SNe Ia that were caught especially early in their rise. In all three we find fairly similar {sup 56}Ni distributions. Observations of SN 2011fe and SN 2012cg probe shallower depths than SN 2009ig, and in these two cases {sup 56}Ni is present merely ∼10{sup –2} M {sub ☉} from the WDs' surfaces. The uncertainty in this result is up to an order of magnitude given the difficulty of precisely constraining the explosion time. We also use our conclusions about the explosion times to reassess radius constraints for the progenitor of SN 2011fe, as well as discuss the roughly t {sup 2} power law that is inferred for many observed rising light curves.

  11. Magnetar-driven Shock Breakout and Double-peaked Supernova Light Curves

    NASA Astrophysics Data System (ADS)

    Kasen, Daniel; Metzger, Brian D.; Bildsten, Lars

    2016-04-01

    The light curves of some luminous supernovae are suspected to be powered by the spindown energy of a rapidly rotating magnetar. Here we describe a possible signature of the central engine: a burst of shock breakout emission occurring several days after the supernova explosion. The energy input from the magnetar inflates a high-pressure bubble that drives a shock through the pre-exploded supernova ejecta. If the magnetar is powerful enough, that shock will near the ejecta surface and become radiative. At the time of shock breakout, the ejecta will have expanded to a large radius (∼ {10}14 cm) so that the radiation released is at optical/ultraviolet wavelengths ({T}{{eff}} ≈ 20,000 K) and lasts for several days. The luminosity and timescale of this magnetar-driven shock breakout are similar to the first peak observed recently in the double-peaked light curve of SN-LSQ14BDQ. However, for a large region of model parameter space, the breakout emission is predicted to be dimmer than the diffusive luminosity from direct magnetar heating. A distinct double-peaked light curve may therefore only be conspicuous if thermal heating from the magnetar is suppressed at early times. We describe how such a delay in heating may naturally result from inefficient dissipation and thermalization of the pulsar wind magnetic energy. Without such suppression, the breakout may only be noticeable as a small bump or kink in the early luminosity or color evolution, or as a small but abrupt rise in the photospheric velocity. A similar breakout signature may accompany other central engines in supernovae, such as a black hole accreting fallback material.

  12. Stellar granulation as the source of high-frequency flicker in Kepler light curves

    SciTech Connect

    Cranmer, Steven R.; Saar, Steven H.; Bastien, Fabienne A.; Stassun, Keivan G.

    2014-02-01

    A large fraction of cool, low-mass stars exhibit brightness fluctuations that arise from a combination of convective granulation, acoustic oscillations, magnetic activity, and stellar rotation. Much of the short-timescale variability takes the form of stochastic noise, whose presence may limit the progress of extrasolar planet detection and characterization. In order to lay the groundwork for extracting useful information from these quasi-random signals, we focus on the origin of the granulation-driven component of the variability. We apply existing theoretical scaling relations to predict the star-integrated variability amplitudes for 508 stars with photometric light curves measured by the Kepler mission. We also derive an empirical correction factor that aims to account for the suppression of convection in F-dwarf stars with magnetic activity and shallow convection zones. So that we can make predictions of specific observational quantities, we performed Monte Carlo simulations of granulation light curves using a Lorentzian power spectrum. These simulations allowed us to reproduce the so-called flicker floor (i.e., a lower bound in the relationship between the full light-curve range and power in short-timescale fluctuations) that was found in the Kepler data. The Monte Carlo model also enabled us to convert the modeled fluctuation variance into a flicker amplitude directly comparable with observations. When the magnetic suppression factor described above is applied, the model reproduces the observed correlation between stellar surface gravity and flicker amplitude. Observationally validated models like these provide new and complementary evidence for a possible impact of magnetic activity on the properties of near-surface convection.

  13. A GLOBAL MODEL OF THE LIGHT CURVES AND EXPANSION VELOCITIES OF TYPE II-PLATEAU SUPERNOVAE

    SciTech Connect

    Pejcha, Ondřej; Prieto, Jose L.

    2015-02-01

    We present a new self-consistent and versatile method that derives photospheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photometric measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ∼230 velocity and ∼6800 mag measurements distributed over 21 photometric passbands spanning wavelengths from 0.19 to 2.2 μm. The light-curve differences among the Type II-Plateau supernovae are well modeled by assuming different rates of photospheric radius expansion, which we explain as different density profiles of the ejecta, and we argue that steeper density profiles result in flatter plateaus, if everything else remains unchanged. The steep luminosity decline of Type II-Linear supernovae is due to fast evolution of the photospheric temperature, which we verify with a successful fit of SN 1980K. Eliminating the need for theoretical supernova atmosphere models, we obtain self-consistent relative distances, reddenings, and nickel masses fully accounting for all internal model uncertainties and covariances. We use our global fit to estimate the time evolution of any missing band tailored specifically for each supernova, and we construct spectral energy distributions and bolometric light curves. We produce bolometric corrections for all filter combinations in our sample. We compare our model to the theoretical dilution factors and find good agreement for the B and V filters. Our results differ from the theory when the I, J, H, or K bands are included. We investigate the reddening law toward our supernovae and find reasonable agreement with standard R{sub V}∼3.1 reddening law in UBVRI bands. Results for other bands are inconclusive. We make our fitting code publicly available.

  14. The light curve of SN 1987A revisited: constraining production masses of radioactive nuclides

    SciTech Connect

    Seitenzahl, Ivo R.; Timmes, F. X.; Magkotsios, Georgios

    2014-09-01

    We revisit the evidence for the contribution of the long-lived radioactive nuclides {sup 44}Ti, {sup 55}Fe, {sup 56}Co, {sup 57}Co, and {sup 60}Co to the UVOIR light curve of SN 1987A. We show that the V-band luminosity constitutes a roughly constant fraction of the bolometric luminosity between 900 and 1900 days, and we obtain an approximate bolometric light curve out to 4334 days by scaling the late time V-band data by a constant factor where no bolometric light curve data is available. Considering the five most relevant decay chains starting at {sup 44}Ti, {sup 55}Co, {sup 56}Ni, {sup 57}Ni, and {sup 60}Co, we perform a least squares fit to the constructed composite bolometric light curve. For the nickel isotopes, we obtain best fit values of M({sup 56}Ni) = (7.1 ± 0.3) × 10{sup –2} M {sub ☉} and M({sup 57}Ni) = (4.1 ± 1.8) × 10{sup –3} M {sub ☉}. Our best fit {sup 44}Ti mass is M({sup 44}Ti) = (0.55 ± 0.17) × 10{sup –4} M {sub ☉}, which is in disagreement with the much higher (3.1 ± 0.8) × 10{sup –4} M {sub ☉} recently derived from INTEGRAL observations. The associated uncertainties far exceed the best fit values for {sup 55}Co and {sup 60}Co and, as a result, we only give upper limits on the production masses of M({sup 55}Co) < 7.2 × 10{sup –3} M {sub ☉} and M({sup 60}Co) < 1.7 × 10{sup –4} M {sub ☉}. Furthermore, we find that the leptonic channels in the decay of {sup 57}Co (internal conversion and Auger electrons) are a significant contribution and constitute up to 15.5% of the total luminosity. Consideration of the kinetic energy of these electrons is essential in lowering our best fit nickel isotope production ratio to [{sup 57}Ni/{sup 56}Ni] = 2.5 ± 1.1, which is still somewhat high but is in agreement with gamma-ray observations and model predictions.

  15. UBV Photometry, Times of Minimum, and Light Curve Solutions for the Algol system, RU Eri

    NASA Astrophysics Data System (ADS)

    Shope, S.; Sowell, J.; Williamon, R.

    1999-12-01

    RU Eri is an Algol system with partial eclipses and a period of 15 hours. The components appear to be slightly evolved F and K stars. UBV photometry has been acquired over six seasons with the 36-inch telescope at the DeKalb County (GA) School System's Fernbank Science Center. Times of minimum have been determined per filter and season, and a literature search has provided additional values for examining the possibility of period changes. Preliminary light curve solutions using all of our data have been derived with the Wilson-Devinney binary star code.

  16. Multi-band optical light-curve behavior of core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Kumar, Brijesh

    2014-01-01

    We present survey results obtained from the UBVRI optical photometric follow-up of 19 bright core-collapse SNe during 2002-2012 using 1-m class optical telescopes operated by the Aryabhatta Research Institute of Observational Science (acronym ARIES), Nainital India. This homogeneous set of data have been used to study behavior of optical light/color curve, and to gain insight into objet-to-object peculiarity. We derive integrated luminosities for types IIP, Ibc and luminous SNe. Two peculiar type IIP events having photometric properties similar to normal IIP and spectroscopic properties similar to sub-lumnious IIP have been identified.

  17. Soft X-Ray Transient Light Curves as Standard Candles: Exponential Versus Linear Decays

    NASA Astrophysics Data System (ADS)

    Shahbaz, T.; Charles, P. A.; King, A. R.

    1998-01-01

    A recent paper by King & Ritter (KR) proposed that the light curves of Soft X-ray Transients (SXTs) are dominated by the effect of irradiation of the accretion disc by the central X-rays. This prevents the onset of the cooling wave which would otherwise return the disc to the quiescent state, and so prolongs the outbursts beyond those in dwarf nova discs. KR show that the decay of the resulting X-ray light curve should be exponential or linear depending on whether or not the observed peak X-ray luminosity is sufficient to ionize the outer edge of the accretion disc. Here we examine the observed X-ray decays, and show that they are exponential or linear according as the peak luminosity is greater or smaller than the critical value defined by KR, strongly suggesting that the light curves are indeed irradiation-dominated. We show further that the occurrence of an exponential or linear decay tends to favour the same type of decay in subsequent outbursts, so that systems usually show only one or the other type. We use the equations of KR and the observed X-ray light curve to determine the size Rh of the hot disc at the peak of the outburst. For exponential decays, Rh is found to be comparable to the circularization radius, as expected since the disc consists entirely of material transferred from the secondary since the previous outburst. Further, Rh is directly proportional to the time at which one sees the secondary maximum (ts), as expected if ts is the viscous timescale of the irradiated disc. This implies that the orders of magnitude of the viscosity parameter alpha and disc aspect ratio H/R are such that alpha(H/R) approx. 0.01. Observation of a secondary maximum calibrates the peak luminosity and gives the distance (Dkpc) to the source as Dkpc = 4.3 x 3-5ts3/2eta1/2f1/2Fp-1/2ptaud-1/2, where Fp is the peak flux, taud is the epsilon-folding time of the decay in days, eta is the radiation efficiency parameter and f is the ratio of the disc mass at the start of the

  18. Soft X-ray transient light curves as standard candles: exponential versus linear decays

    NASA Astrophysics Data System (ADS)

    Shahbaz, T.; Charles, P. A.; King, A. R.

    1998-12-01

    A recent paper by King & Ritter proposed that the light curves of soft X-ray transients (SXTs) are dominated by the effect of irradiation of the accretion disc by the central X-rays. This prevents the onset of the cooling wave which would otherwise return the disc to the quiescent state, and so prolongs the outbursts beyond those in dwarf nova discs. KR show that the decay of the resulting X-ray light curve should be exponential or linear depending on whether or not the observed peak X-ray luminosity is sufficient to ionize the outer edge of the accretion disc. Here we examine the observed X-ray decays, and show that they are exponential or linear according to whether the peak luminosity is greater or smaller than the critical value defined by KR, strongly suggesting that the light curves are indeed irradiation dominated. We show further that the occurrence of an exponential or linear decay tends to favour the same type of decay in subsequent outbursts, so that systems usually show only one or the other type. We use the equations of KR and the observed X-ray light curve to determine the size R_h of the hot disc at the peak of the outburst. For exponential decays, R_h is found to be comparable to the circularization radius, as expected, since the disc consists entirely of material transferred from the secondary since the previous outburst. Further, R_h is directly proportional to the time at which one sees the secondary maximum (t_s), as expected, if t_s is the viscous time-scale of the irradiated disc. This implies that the orders of magnitude of the viscosity parameter alpha and disc aspect ratio H/R are such that alpha(H/R)~0.01. Observation of a secondary maximum calibrates the peak luminosity and gives the distance (D_kpc) to the source as D_kpc=4.3x10^-5t^3/2_sepsilon^1/2f^1/2F^-1/2_ptau^-1/2_d where F_p is the peak flux, tau_d is the e-folding time of the decay in days, epsilon is the radiation efficiency parameter and f is the ratio of the disc mass at the

  19. Discriminating solar and antisolar differential rotation in high-precision light curves

    NASA Astrophysics Data System (ADS)

    Reinhold, Timo; Arlt, Rainer

    2015-04-01

    Context. Surface differential rotation (DR) is one major ingredient of the magnetic field generation process in the Sun and likely in other stars. The term solar-like differential rotation describes the observation that solar equatorial regions rotate faster than polar ones. The opposite effect of polar regions rotating faster than equatorial ones (termed as antisolar DR) has only been observed in a few stars, although there is evidence from theoretical dynamo models. Aims: We present a new method of detecting the sign of DR (i.e., solar-like or antisolar DR) by analyzing long-term high-precision light curves with the Lomb-Scargle periodogram. Methods: We compute the Lomb-Scargle periodogram and identify a set of significant periods Pk, which we associate with active regions located at different latitudes on the stellar surface. If detectable, the first harmonics (P_k') of these periods were identified to compute their peak-height-ratios rk:= h(P'k)/h(Pk) . Spots rotating at lower latitudes generate less sine-shaped light curves, which requires additional power in the harmonics, and results in larger ratios rk. Comparing different ratios rk and the associated periods Pk yields information about the spot latitudes, and reveals the sign of DR. Results: We tested our method on different sets of synthetic light curves all exhibiting solar-like DR. The number of cases where our method detects antisolar DR is the false-positive rate of our method. Depending on the set of light curves, the noise level, the required minimum peak separation, and the presence or absence of spot evolution, our method fails to detect the correct sign in at most 20%. We applied our method to 50 Kepler G stars and found 21-34 stars with solar-like DR and 5-10 stars with antisolar DR, depending on the minimum peak separation. Conclusions: The method is able to determine the sign of DR in a statistical way with a low false-positive rate. Applying our method to real data might suggest that - within

  20. VizieR Online Data Catalog: Lick AGN monitoring 2011: light curves (Barth+, 2015)

    NASA Astrophysics Data System (ADS)

    Barth, A. J.; Bennert, V. N.; Canalizo, G.; Filippenko, A. V.; Gates, E. L.; Greene, J. E.; Li, W.; Malkan, M. A.; Pancoast, A.; Sand, D. J.; Stern, D.; Treu, T.; Woo, J.-H.; Assef, R. J.; Bae, H.-J.; Brewer, B. J.; Cenko, S. B.; Clubb, K. I.; Cooper, M. C.; Diamond-Stanic, A. M.; Hiner, K. D.; Honig, S. F.; Hsiao, E.; Kandrashoff, M. T.; Lazarova, M. S.; Nierenberg, A. M.; Rex, J.; Silverman, J. M.; Tollerud, E. J.; Walsh, J. L.

    2015-05-01

    This project was allocated 69 nights at the Lick 3m Shane telescope, distributed between 2011 March 27 and June 13. Observations were conducted using the Kast double spectrograph (3440-5515Å on the blue side and 5410-8200Å on the red side). In order to extend our light curves for two AGNs, we also requested additional observations from other observers using the Kast spectrograph: Mrk 50 from 2011 January through March, and Zw 229-015 in June and July. For Zw 229-015, three additional observations were taken 20-23 days after the end of our main campaign. See section 3. (2 data files).

  1. ellc: Light curve model for eclipsing binary stars and transiting exoplanets

    NASA Astrophysics Data System (ADS)

    Maxted, P. F. L.

    2016-03-01

    ellc analyzes the light curves of detached eclipsing binary stars and transiting exoplanet systems. The model represents stars as triaxial ellipsoids, and the apparent flux from the binary is calculated using Gauss-Legendre integration over the ellipses that are the projection of these ellipsoids on the sky. The code can also calculate the fluxweighted radial velocity of the stars during an eclipse (Rossiter-McLaghlin effect). ellc can model a wide range of eclipsing binary stars and extrasolar planetary systems, and can enable the use of modern Monte Carlo methods for data analysis and model testing.

  2. VizieR Online Data Catalog: VI light curves of SMC type II Cepheids (Soszynski+, 2010)

    NASA Astrophysics Data System (ADS)

    Soszynski, I.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Ulaczyk, K.; Poleski, R.

    2010-11-01

    The eighth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains type II Cepheids in the Small Magellanic Cloud (SMC). The sample consists of 43 objects, including 17 BL Her, 17 W Vir and 9 RV Tau stars (first examples ever found in the SMC). Seven stars have been classified as peculiar W Vir stars - a recently identified subclass of type II Cepheids. These stars have distinctive light curves, are brighter and bluer than the ordinary W Vir variables. We confirm that a large fraction of the peculiar W Vir stars are members of binary systems. (3 data files).

  3. Expected Performance of the CoRoT Planet Search from Light Curve Beauty Contests

    NASA Astrophysics Data System (ADS)

    Moutou, C.; Aigrain, S.; Almenara, J.; Alonso, R.; Auvergne, M.; Barge, P.; Blouin, D.; Borde, P.; Cabrera, J.; Carone, L.; Cautain, R.; Deeg, H.; Erikson, A.; Fressin, F.; Guis, V.; Leger, A.; Guterman, P.; Irwin, M.; Kabath, P.; Lanza, A.; Maceroni, C.; Mazeh, T.; Ollivier, M.; Pont, F.; Paetzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Schneider, J.; Tamuz, O.; Voss, H.; Zucker, S.

    2007-07-01

    The CoRoT space mission, scheduled for launch in December 2006, has two primary science goals: asteroseismology and the detection of planetary transits, the latter being the subject of this contribution. Given its expected photometric performance and its 150 day observing window, CoRoT will detect planets with periods up to 75 days and radii down to 2 Earth radii. To prepare for the data analysis and evaluate the detection limits of the mission, a number of blind exercises to detect planets in simulated light curves have been carried out within the CoRoT exoplanet community, and their results to date are summarized here.

  4. Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves

    SciTech Connect

    Hicken, Malcolm; Wood-Vasey, W.Michael; Blondin, Stephane; Challis, Peter; Jha, Saurabh; Kelly, Patrick L.; Rest, Armin; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2012-04-06

    We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013{sub -0.068}{sup +0.066} (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (R{sub V} = 3.1), and MLCS2k2 (R{sub V} = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < {Delta} < 1.2. MLCS2k2 with R{sub V} = 3.1 overestimates host-galaxy extinction while R{sub V} {approx} 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2{sigma}, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.

  5. IMPROVED DARK ENERGY CONSTRAINTS FROM {approx}100 NEW CfA SUPERNOVA TYPE Ia LIGHT CURVES

    SciTech Connect

    Hicken, Malcolm; Challis, Peter; Kirshner, Robert P.; Wood-Vasey, W. Michael; Blondin, Stephane; Jha, Saurabh; Kelly, Patrick L.; Rest, Armin E-mail: kirshner@cfa.harvard.edu

    2009-08-01

    We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013{sup +0.066} {sub -0.068} (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (R{sub V} = 3.1), and MLCS2k2 (R{sub V} = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < {delta} < 1.2. MLCS2k2 with R{sub V} = 3.1 overestimates host-galaxy extinction while R{sub V} {approx} 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2{sigma}, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.

  6. Infrared light curves of Shoemaker-Levy 9 impacts H, Q1 and S

    NASA Astrophysics Data System (ADS)

    Shykula, J. T.; Kilkenny, D.; Whittet, D. C. B.; Laney, C. D.

    1995-02-01

    The plumes associated with Comet Shoemaker-Levy 9 fragments H, Q1 and S impacting Jupiter have been observed in the infrared at 2.2 mum. Measurements were carried out in the standard K passband with a time resolution of 5 s. The results are plotted against time to provide a light curve for each of the impacts. A time evolution of the plume for each event is thus illustrated, yielding accurate information about the rise and fall of the plume, in addition to the timing of the peak. Our observations appear to support an explosive model for cometary ablation deep in the Jovian atmosphere.

  7. Effect of repeated insertions of curved sequences in DNA plasmids: a light-scattering study

    NASA Astrophysics Data System (ADS)

    Beretta, Stefano; Chirico, Giuseppe; Baldini, Giancarlo; Kapp, U.; Badaracco, G.

    1993-06-01

    The effect of the insertion of different amounts (from 0 to 6) of the curved sequence AluI in pUC18m plasmid (2686 base pairs, bp) is studied by dynamic light scattering. This sequence is a highly repeated 113 base pairs long sequence from Artemia Franciscana shrimp. A 30% compaction of the plasmids containing 2 and 6 adjacent AluI sequences compared to pUC8 plasmid (2717 bp) is observed. Furthermore the behavior of the translational diffusion coefficient Dt versus the number of adjacent AluI insertion is not monotonic.

  8. VizieR Online Data Catalog: Light curves of WASP-67 transit events (Mancini+, 2014)

    NASA Astrophysics Data System (ADS)

    Mancini, L.; Southworth, J.; Ciceri, S.; Calchi Novati, S.; Dominik, M.; Henning, T.; Jorgensen, U. G.; Korhonen, H.; Nikolov, N.; Alsubai, K. A.; Bozza, V.; Bramich, D. M.; D'Ago, G.; Figuera Jaimes, R.; Galianni, P.; Gu, S.-H.; Harpose, K.; Hinse, T.; Hundertmark, M.; Juncher, D.; Kains, N.; Popovas, A.; Rabus, M.; Rahvar, S.; Skottfelt, J.; Snodgrass, C.; Street, R.; Surdej, J.; Tsapras, Y.; Vilela, C.; Wang, X.-B.; Wertz, O.

    2014-07-01

    5 light curves of two transits of the extrasolar planetary system WASP-67, observed on 2012 June 4 and 2013 June 22, are presented. Four of the datasets were obtained using the MPG 2.2-m telescope, GROND camera and filters similar to Sloan g', r', i', z', at the ESO Observatory in La Silla (Chile). Another data set was obtained using the 1.54-m Danish telescope, DFOSC camera and Bessel-R filter at the ESO Observatory in La Silla (Chile). (5 data files).

  9. VizieR Online Data Catalog: Light curves of WASP-80 transit events (Mancini+, 2014)

    NASA Astrophysics Data System (ADS)

    Mancini, L.; Southworth, J.; Ciceri, S.; Dominik, M.; Henning, T.; Jorgensen, U. G.; Lanza, A. F.; Rabus, M.; Snodgrass, C.; Vilela, C.; Alsubai, K. A.; Bozza, V.; Bramich, D. M.; Calchi Novati, S.; D'Ago, G.; Figuera Jaimes, R.; Galianni, P.; Gu, S.-H.; Harpose, K.; Hinse, T.; Hundertmark, M.; Juncher, D.; Kains, N.; Korhonen, H.; Popovas, A.; Rahvar, S.; Skottfelt, J.; Street, R.; Surdej, J.; Tsapras, Y.; Wang, X.-B.; Wertz, O.

    2014-01-01

    8 light curves of one transit of the extrasolar planetary system WASP-80, observed on 2013 June 16, are presented. Seven of the datasets were obtained using the MPG/ESO 2.2-m telescope, GROND camera and filters similar to Sloan g', r', i', z', and J, H, K at the ESO Observatory in La Silla (Chile). Another data set was obtained using the 1.54-m Danish telescope, DFOSC camera and Bessel-i filter at La Silla (Chile). (8 data files).

  10. The First Systematic Study of Type Ibc Supernova Multi-band Light Curves

    NASA Astrophysics Data System (ADS)

    Drout, Maria R.; Soderberg, Alicia M.; Gal-Yam, Avishay; Cenko, S. Bradley; Fox, Derek B.; Leonard, Douglas C.; Sand, David J.; Moon, Dae-Sik; Arcavi, Iair; Green, Yoav

    2011-11-01

    We present detailed optical photometry for 25 Type Ibc supernovae (SNe Ibc) within d ≈ 150 Mpc obtained with the robotic Palomar 60 inch telescope in 2004-2007. This study represents the first uniform, systematic, and statistical sample of multi-band SNe Ibc light curves available to date. We correct the light curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V - R) color of extinction-corrected SNe Ibc at Δt ≈ 10 days after V-band maximum is tightly distributed, lang(V - R) V10rang = 0.26 ± 0.06 mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, langE(B - V)rang ≈ 0.4 mag. A comparison of the extinction-corrected light curves for helium-rich (Type Ib) and helium-poor (Type Ic) SNe reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of langMR rang = -17.9 ± 0.9 mag and langMR rang = -18.3 ± 0.6 mag for SNe Ib and Ic, respectively. Focusing on the broad-lined (BL) SNe Ic, we find that they are more luminous than the normal SNe Ibc sample, langMR rang = -19.0 ± 1.1 mag, with a probability of only 1.6% that they are drawn from the same population of explosions. By comparing the peak absolute magnitudes of SNe Ic-BL with those inferred for local engine-driven explosions (GRB-SN 1998bw, XRF-SN 2006aj, and SN 2009bb) we find a 25% probability that relativistic SNe are drawn from the overall SNe Ic-BL population. Finally, we fit analytic models to the light curves to derive typical 56Ni masses of M Ni ≈ 0.2 and 0.5 M ⊙ for SNe Ibc and SNe Ic-BL, respectively. With reasonable assumptions for the photospheric velocities, we further extract kinetic energy and ejecta mass values of M ej ≈ 2 M ⊙ and EK ≈ 1051 erg for SNe Ibc, while for SNe Ic-BL we find higher values, M ej ≈ 5 M ⊙ and EK ≈ 1052 erg. We discuss the implications for the progenitors of

  11. A study of the light curve periodic behavior of quasar 3C 345.

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong; Xie, Guangzhong; Bai, Jinming

    All the data for the B band of the quasar 3C 345, presented in twenty-one publications and dating back to 1896, have been compiled to be a light curve. Altogether 1642 values are available. Using Jurkevich's method, the authors have found a period of 10.1±0.8 years (or 21.8±1.5 years) for the outbursts in 3C 345. Based on this period, one can predict that the next outburst should be at its maximum around January 2002.

  12. Optical Monitoring of Markarian 335 from 1994 to 2001 and Its Historical Light Curve

    NASA Astrophysics Data System (ADS)

    Tao, Jun; Qian, Bochen; Fan, Junhui

    2004-07-01

    Photometric CCD observations (V, R, and I) of Seyfert 1 galaxy Markarian 335 (Mrk 335) were carried out from 1994 to 2001. During this monitoring period, the source was generally quiescent, but possible microvariation was found for 1999 November 20. If a hot spot on the accretion disk was responsible for this microvariation, then there is probably a supermassive black hole of around 3×107 Msolar at the center of the source. The historical light curve from 1974 to 2000 was also compiled, and a possible period of 6.3 yr was found using the Jurkevich method.

  13. The Automatic Light Curves Generated by Danish 1.54m Telescope

    NASA Astrophysics Data System (ADS)

    Skoda, Petr

    2015-12-01

    We present the Ondřejov Southern Photometry Survey, being conducted at the Danish 1.54m telescope in remote observing mode by several groups of Czech stellar astronomers. The automatic astrometry and photometry pipelines run on every CCD frame combined with sophisticated parallelized cross-matching and clustering algorithms result in an on-the-fly generation of light curves of every single object in the field. To allow powerful querying and visualization of current database of more than half billion of measurements, the technology of Virtual Observatory is used, combining IVOA protocols and powerful visualization tools as Aladin, TOPCAT and SPLAT-VO.

  14. Recurrence plot analysis of nonstationary data: The understanding of curved patterns

    NASA Astrophysics Data System (ADS)

    Facchini, A.; Kantz, H.; Tiezzi, E.

    2005-08-01

    Recurrence plots of the calls of the Nomascus concolor (Western black crested gibbon) and Hylobates lar (White-handed gibbon) show characteristic circular, curved, and hyperbolic patterns superimposed to the main temporal scale of the signal. It is shown that these patterns are related to particular nonstationarities in the signal. Some of them can be reproduced by artificial signals like frequency modulated sinusoids and sinusoids with time divergent frequency. These modulations are too faint to be resolved by conventional time-frequency analysis with similar precision. Therefore, recurrence plots act as a magnifying glass for the detection of multiple temporal scales in slightly modulated signals. The detected phenomena in these acoustic signals can be explained in the biomechanical context by taking in account the role of the muscles controlling the vocal folds.

  15. VizieR Online Data Catalog: Light curves for the eclipsing binary V1094 Tau (Maxted+, 2015)

    NASA Astrophysics Data System (ADS)

    Maxted, P. F. L.; Hutcheon, R. J.; Torres, G.; Lacy, C. H. S.; Southworth, J.; Smalley, B.; Pavlovski, K.; Marschall, L. A.; Clausen, J. V.

    2015-04-01

    Photometric light curves of the detached eclipsing binary V1094 Tau in the Stroemgren u-,v-,b- and y-bands, and in the Johnson V-band. The curves in the Stroemgren bands were obtained with the Stroemgren Automatic Telescope (SAT) at ESO, La Silla. The curves in the V-band were obtained with the NFO telescope in New Mexico and with the URSA telescope at the University of Arkansas. (6 data files).

  16. VizieR Online Data Catalog: An SX Phoenicis Variable light curve (Kim+, 2007)

    NASA Astrophysics Data System (ADS)

    Kim, C.; Jeon, J.-B.; Kim, S.-L.; Yushchenko, A. V.

    2009-05-01

    We present investigation of V=17mag star, which appears to be SX Phe type variable. Observations at 1.8 and 1.0 meter telescopes of Boyhunsan and Mount Lemon observatories permit us to improve the light elements and to investigate the power spectrum. We applied a Fourier decomposition to the data in order to determine the component frequencies of the synthetic light curve, and five components including a pair of closely separated components of f1=24.6539 and f2=24.8173 c/d were identified. We proposed that one of these two components corresponds to a non-radial oscillation mode. Other observed frequencies are the combinations of the first two. Metallicity of the star was estimated to be [Fe/H]<-2. We also found that one of the faint variable stars, No. 14, in the field is RRc type pulsator. (2 data files).

  17. Design a light pattern of multiple concentric circles for LED fishing lamps using Fourier series and an energy mapping method.

    PubMed

    Shen, S C; Li, J S; Huang, M C

    2014-06-01

    Fourier series and an energy mapping method were used in this study to design a lens that produces a light pattern of multiple concentric circles (LPMCC) for a light-emitting diode (LED) fishing lamp. Fourier series were used to represent the light intensity distribution curve (LIDC) of the LPMCC light pattern. Energy mapping involves performing angular energy mapping based on the LIDCs of an LED light source and LPMCC to design a freeform lens. Type I and Type II LPMCC lenses were designed according to the phototaxis behavior of fish to create a LPMCC light pattern of interleaving light-dark zones that attracts fish shoals to stay in an area for a long period. The experimental results indicated that, in comparing the LIDCs of the Type I and II lenses with the respective simulation values, the normalized cross-correlation (NCC) value reached 96%. According to a 24-hour observation of the phototaxis of Poecilia reticulata to evaluate the effectiveness of the proposed light pattern to attract fish, when a fish shoal was habituated to a light source that emitted constant illumination light, it gradually moved away from the intense light zone and hovered around the junction of the light and dark zones. In the future, the design used in this study can be applied to LED fishing lamps to replace traditional fishing lamps. PMID:24921540

  18. A UNIFORM SEARCH FOR SECONDARY ECLIPSES OF HOT JUPITERS IN KEPLER Q2 LIGHT CURVES

    SciTech Connect

    Coughlin, J. L.; Lopez-Morales, M.

    2012-02-15

    In this paper, we present the results of searching the Kepler Q2 public data set for the secondary eclipses of 76 hot Jupiter planet candidates from the list of 1235 candidates published by Borucki et al. This search has been performed by modeling both the Kepler pre-search data conditioned light curves and new light curves produced via our own photometric pipeline. We derive new stellar and planetary parameters for each system, while calculating robust errors for both. We find 16 systems with 1{sigma}-2{sigma}, 14 systems with 2{sigma}-3{sigma}, and 6 systems with >3{sigma} confidence level secondary eclipse detections in at least one light curve produced via the Kepler pre-search data conditioned light curve or our own pipeline; however, results can vary depending on the light curve modeled and whether eccentricity is allowed to vary or not. We estimate false alarm probabilities of 31%, 10%, and 6% for the 1{sigma}-2{sigma}, 2{sigma}-3{sigma}, and >3{sigma} confidence intervals, respectively. Comparing each secondary eclipse result to theoretical expectations, we find that the majority of detected planet candidates emit more light than expected owing to thermal blackbody emission in the optical Kepler bandpass, and present a trend of increasing excess emission with decreasing maximum effective planetary temperature. These results agree with previously published optical secondary eclipse data for other hot Jupiters. We explore modeling biases, significant planetary albedos, non-local thermodynamic equilibrium or other thermal emission, significant internal energy generation, and misidentification of brown dwarfs, low-mass stars, or stellar blends as possible causes of both the excess emission and its correlation with expected planetary temperature. Although we find that no single cause is able to explain all of the planet candidates, significant planetary albedos, with a general trend of increasing planetary albedos with decreasing atmospheric temperatures, are

  19. Structuring Light by Concentric-Ring Patterned Magnetic Metamaterial Cavities.

    PubMed

    Zeng, Jinwei; Gao, Jie; Luk, Ting S; Litchinitser, Natalia M; Yang, Xiaodong

    2015-08-12

    Ultracompact and tunable beam converters pose a significant potential for modern optical technologies ranging from classical and quantum communication to optical manipulation. Here we design and demonstrate concentric-ring patterned structures of magnetic metamaterial cavities capable of tailoring both polarization and phase of light by converting circularly polarized light into a vector beam with an orbital angular momentum. We experimentally illustrate the realization of both radially and azimuthally polarized vortex beams using such concentric-ring patterned magnetic metamaterials. These results contribute to the advanced complex light manipulation with optical metamaterials, making it one step closer to realizing the simultaneous control of polarization and orbital angular momentum of light on a chip. PMID:26121268

  20. VizieR Online Data Catalog: Fourier analysis of HD 49330 CoRoT light curve (Huat+, 2009)

    NASA Astrophysics Data System (ADS)

    Huat, A.-L.; Hubert, A.-M.; Baudin, F.; Floquet, M.; Neiner, C.; Fremat, Y.; Gutierrez-Soto, J.; Andrade, L.; de Batz, B.; Diago, P. D.; Emilio, M.; Espinosa, F. Lara; Fabregat, J.; Janot-Pacheco, E.; Leroy, B.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.; Catala, C.; Michel, E.; Samadi, R.

    2009-09-01

    This work analyses the high precision photometric light curve obtained for the CoRoT target HD49330 (B0.5 IVe) which was observed during 136.886 days with a sample of 32s. During the CoRoT run the star underwent an outburst often observed in hot Be star. The CoRoT light curve was analysed using Fourier methods and non-linear least square fitting. (5 data files).

  1. Light curve and fan-shaped coma of comet P/Tempel 2 in 1988-1989

    NASA Technical Reports Server (NTRS)

    Akisawa, Hiroki; Tsumura, Mitsunori; Nakamura, Akimasa; Watanabe, Jun-Ichi

    1992-01-01

    Visual and Photographic Monitoring observations of comet P/Tempel 2 were carried out by a Japanese amateur group 'Hoshi-no-Hiroba' in 1988-1989. We analyzed the light curve and the time variation of the fan-shaped coma. The light curve was asymmetric to the perihelion passage. The fan angle in September-October was wider than that in December. The direction of the fan generally coincided with Sekanina's prediction (1988).

  2. KIC 4552982: outbursts and pulsations in the longest-ever pseudo-continuous light curve of a ZZ Ceti

    NASA Astrophysics Data System (ADS)

    Bell, K. J.; Hermes, J. J.; Bischoff-Kim, A.; Moorhead, S.; Castanheira, B. G.; Montgomery, M. H.; Winget, D. E.

    2015-09-01

    KIC 4552982 was the first ZZ Ceti (hydrogen-atmosphere pulsating white dwarf) identified to lie in the Kepler field, resulting in the longest pseudo-continuous light curve ever obtained for this type of variable star. In addition to the pulsations, this light curve exhibits stochastic episodes of brightness enhancement unlike any previously studied white dwarf phenomenon. We briefly highlight the basic outburst and pulsation properties in these proceedings.

  3. VizieR Online Data Catalog: GTC transit light curves of CoRoT-29b (Palle+, 2016)

    NASA Astrophysics Data System (ADS)

    Palle, E.; Chen, G.; Alonso, R.; Nowak, G.; Deeg, H.; Cabrera, J.; Murgas, F.; Parviainen, H.; Nortmann, L.; Hoyer, S.; Prieto-Arranz, J.; Nespral, D.; Cabrera Lavers, A.; Iro, N.

    2016-04-01

    2 transit light curves of the hot Jupiter CoRoT-29b obtained on the nights of 2014/7/31 and 2015/7/8 using the OSIRIS instrument at the 10.4-m GTC telescope. The light curves have been integrated over the bandpass of 515-915nm, where the wavelength range of 755-765 nm has been excluded due to presence of strong telluric O2 absorption. (2 data files).

  4. The effect of background galaxy contamination on the absolute magnitude and light curve speed class of type Ia supernovae

    NASA Technical Reports Server (NTRS)

    Boisseau, John R.; Wheeler, J. Craig

    1991-01-01

    Observational data are presented in support of the hypothesis that background galaxy contamination is present in the photometric data of Ia supernovae and that this effect can account for the observed dispersion in the light curve speeds of most of Ia supernovae. The implication is that the observed dispersion in beta is artificial and that most of Ia supernovae have nearly homogeneous light curves. The result supports the notion that Ia supernovae are good standard candles.

  5. DISCOVERY OF A TIGHT CORRELATION FOR GAMMA-RAY BURST AFTERGLOWS WITH 'CANONICAL' LIGHT CURVES

    SciTech Connect

    Dainotti, Maria Giovanna; Ostrowski, Michal; Willingale, Richard; Capozziello, Salvatore; Cardone, Vincenzo Fabrizio E-mail: mio@oa.uj.edu.p E-mail: capozziello@na.infn.i

    2010-10-20

    Gamma-ray bursts (GRBs) observed up to redshifts z>8 are fascinating objects to study due to their still unexplained relativistic outburst mechanisms and their possible use to test cosmological models. Our analysis of 77 GRB afterglows with known redshifts revealed a physical subsample of long GRBs with the canonical plateau breaking to power-law light curves with a significant luminosity L*{sub X}-break time T*{sub a} correlation in the GRB rest frame. This subsample forms approximately the upper envelope of the studied distribution. We have also found a similar relation for a small sample of GRB afterglows that belong to the intermediate class between the short and the long ones. It proves that within the full sample of afterglows there exist physical subclasses revealed here by tight correlations of their afterglow properties. The afterglows with regular ('canonical') light curves obey not only the mentioned tight physical scaling, but-for a given T*{sub a}-the more regular progenitor explosions lead to preferentially brighter afterglows.

  6. Type IIP supernova progenitor properties from Pan-STARRS1 light curves

    NASA Astrophysics Data System (ADS)

    Sanders, Nathan; Soderberg, A. M.; Pan-STARRS1 CfA Supernova Group

    2014-01-01

    We discuss a comprehensive and uniform analysis of the light curves of more than 100 spectroscopically-confirmed Type II supernovae discovered by the Pan-STARRS1 (PS1) survey. Our sample is drawn from more than 4 years of multi-band optical/NIR (grizy) imaging from the PS1 Medium-Deep Survey (MDS). We have developed and applied a Bayesian methodology for modeling the supernova light curves. This framework robustly models available data and produces constraints on the full, multiwavelength evolution of each object in the sample, even when observations are sparse or coverage is limited. We focus on the most common class of massive star explosion, Type IIP supernovae, with a typical redshift of z = 0.1 in our sample. Utilizing the deep imaging, high cadence (1-2 day), and long survey duration of the PS1 MDS, we test for variation in the rise time behavior, plateau duration, and temperature evolution of the supernovae. We discuss inferences on the distribution of progenitor star and explosion properties (mass, radius, and energy) permitted by these measurements, and their implications for our understanding of the death processes of massive stars in the local universe.

  7. A Light Curve Probe of Stellar Surface Convection and Measure of Stellar Surface Gravity

    NASA Astrophysics Data System (ADS)

    Bastien, Fabienne A.; Stassun, Keivan; Basri, Gibor S.; Pepper, Joshua

    2016-01-01

    We recently found that high quality light curves, such as those obtained by NASA's Kepler, K2, and the soon-to-be-launched TESS missions, may be used to measure stellar surface gravity via granulation-driven light curve "flicker." Here, we describe our updated and extended the relation, which is now calibrated against a more robust set of asteroseismically derived surface gravities and which we apply to over 28,000 Kepler stars. We discuss how we treat phenomena, such as exoplanet transits and shot noise, that adversely affect the measurement of flicker, and we explore the limitations of the technique. We suggest that flicker may be used to probe convection in stars with surface gravities as low as 1.5, and we show that, in concert with asteroseismically measured surface gravities, it might be used to examine differences in the convective properties of red giant, red clump, and secondary clump stars. Finally, we highlight further applications of flicker, such as astrodensity profiling or its use in studying other types of stars with convective outer layers.

  8. Optical Light Curves of RS Oph (2006) and Hydrogen Burning Turnoff

    NASA Astrophysics Data System (ADS)

    Hachisu, I.; Kato, M.; Kiyota, S.; Kubotera, K.; Maehara, H.; Nakajima, K.; Ishii, Y.; Kamada, M.; Mizoguchi, S.; Nishiyama, S.; Sumitomo, N.; Tanaka, K.; Yamanaka, M.; Sadakane, K.

    2008-12-01

    We report coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ˜ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop in the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady hydrogen shell-burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 ± 0.01 {M}_⊙, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the hydrogen burning turnoff. Observational data of y magnitudes are provided in astro-ph/ arXiv:0807.1240, together with other multi-wavelength light curve data.

  9. POST-FLARE ULTRAVIOLET LIGHT CURVES EXPLAINED WITH THERMAL INSTABILITY OF LOOP PLASMA

    SciTech Connect

    Reale, F.; Landi, E.; Orlando, S.

    2012-02-10

    In the present work, we study the C8 flare that occurred on 2000 September 26 at 19:49 UT and observed by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation spectrometer from the beginning of the impulsive phase to well beyond the disappearance in the X-rays. The emission first decayed progressively through equilibrium states until the plasma reached 2-3 MK. Then, a series of cooler lines, i.e., Ca X, Ca VII, Ne VI, O IV, and Si III (formed in the temperature range log T = 4.3-6.3 under equilibrium conditions), are emitted at the same time and all evolve in a similar way. Here, we show that the simultaneous emission of lines with such a different formation temperature is due to thermal instability occurring in the flaring plasma as soon as it has cooled below {approx}2 MK. We can qualitatively reproduce the relative start time of the light curves of each line in the correct order with a simple (and standard) model of a single flaring loop. The agreement with the observed light curves is greatly improved, and a slower evolution of the line emission is predicted, if we assume that the model loop consists of an ensemble of subloops or strands heated at slightly different times. Our analysis can be useful for flare observations with the Solar Dynamics Observatory/Extreme ultraviolet Variability Experiment.

  10. Hydrodynamics associated to the X-ray light curve of A0620-00

    NASA Astrophysics Data System (ADS)

    Coronado, Y.; Mendoza, S.

    2015-12-01

    From 1975 to 1976, an outburst was detected in the light curve of the X-ray transient A0620-00 using the Ariel V and SAS-3 experiments. In this article we model the outburst with the hydrodynamical model proposed by Mendoza et al. (Mon. Not. R. Astron. Soc. 395:1403, 2009). The physical model is constructed assuming basic mass and momentum conservation laws associated to the motion of the shock waves developed inside the expanding relativistic jet of the source. These internal shock waves are produced as a result of periodic variations of the injected mass and velocity of the flow at the base of the jet. The observations of this X-ray light curve present two clear bumps. The first one is modelled assuming periodic variations of the injected velocity at the base of the jet, while the second one can either be modelled by further velocity oscillations, or by a periodic variation of the mass injection rate at the base of the jet at a latter time. This latter model is statistically more significant for the observed data, than the former. The fitting of the data fixes different parameters of the model, such as the mean mass injection rate at the base of the jet and the oscillation frequency of the flow as measured on the rest frame of the central source.

  11. CLASSICAL NOVAE IN ANDROMEDA: LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY AND GALEX

    SciTech Connect

    Cao Yi; Lou Yuqing; Kasliwal, Mansi M.; Neill, James D.; Kulkarni, S. R.; Quimby, Robert M.; Ben-Ami, Sagi; Bloom, Joshua S.; Cenko, S. Bradley; Nugent, Peter E.; Law, Nicholas M.; Ofek, Eran O.; Poznanski, Dovi

    2012-06-20

    We present optical light curves of 29 novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic and rapid cadences in PTF monitoring of M31, from one day to ten minutes, provide excellent temporal coverage of nova light curves, enabling us to record the photometric evolution of M31 novae in unprecedented detail. We also detect eight of these novae in the near-ultraviolet (UV) band with the Galaxy Evolution Explorer (GALEX) satellite. Novae M31N 2009-10b and M31N 2010-11a show prominent UV emission peaking a few days prior to their optical maxima, possibly implying aspherical outbursts. Additionally, our blueshifted spectrum of the recent outburst of PT And (M31N 2010-12a) indicates that it is a recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously assumed. Finally, we systematically searched for novae in all confirmed globular clusters (GCs) of M31 and found only M31N 2010-10f associated with Bol 126. The specific nova rate in the M31 GC system is thus about one per year, which is not enhanced relative to the rate outside the GC system.

  12. Seeing double: the frequency and detectability of double-peaked superluminous supernova light curves

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Smartt, S. J.

    2016-03-01

    The discovery of double-peaked light curves in some superluminous supernovae (SLSNe) offers an important new clue to their origins. We examine the published photometry of all Type Ic SLSNe, finding 14 objects with constraining data or limits around the time of explosion. Of these, eight (including the already identified SN 2006oz and LSQ14bdq) show plausible flux excess at the earliest epochs, which deviate by 2-9σ from polynomial fits to the rising light curves. Simple scaling of the LSQ14bdq data show that they are all consistent with a similar double-peaked structure. PS1-10pm provides multicolour UV data indicating a temperature of Tbb = 25000 ± 5000 K during the early `bump' phase. We find that a double-peak cannot be excluded in any of the other six objects, and that this behaviour may be ubiquitous. The homogeneity of the observed bumps is unexpected for interaction-powered models. Engine-powered models can explain the observations if all progenitors have extended radii or the central engine drives shock breakout emission several days after the supernova explosion.

  13. The spectra and light curves of two gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Knight, F. K.; Matteson, J. L.; Peterson, L. E.

    1981-01-01

    Observations made by the Hard X-ray and Low Energy Gamma-Ray Experiment on board HEAO-1 of the spectra and light curves of two gamma-ray bursts for which localized arrival directions will become available are presented. The burst of October 20, 1977 is found to exhibit a fluence of 0.000031 + or - 0.000005 erg/sq cm over the energy range 0.135-2.05 MeV and a duration of 38.7 sec, while that of November 10, 1977 is found to have a fluence of 0.000021 + or - 0.000008 erg/sq cm between 0.125 and 3 MeV over 2.8 sec. The light curves of both bursts exhibit time fluctuations down to the limiting time resolution of the detectors. The spectrum of the October burst can be fit by a power law of index -1.93 + or -0.16, which is harder than any other gamma-burst spectrum yet reported. The spectrum of the second burst is softer (index -2.4 + or - 0.7), and is consistent with the upper index in the double power law fit to the burst of April 27, 1972.

  14. THE TRANSIT LIGHT CURVE PROJECT. XIII. SIXTEEN TRANSITS OF THE SUPER-EARTH GJ 1214b

    SciTech Connect

    Carter, Joshua A.; Winn, Joshua N.; Holman, Matthew J.; Fabrycky, Daniel; Berta, Zachory K.; Burke, Christopher J.; Nutzman, Philip

    2011-04-01

    We present optical photometry of 16 transits of the super-Earth GJ 1214b, allowing us to refine the system parameters and search for additional planets via transit timing. Starspot-crossing events are detected in two light curves, and the star is found to be variable by a few percent. Hence, in our analysis, special attention is given to systematic errors that result from starspots. The planet-to-star radius ratio is 0.11610 {+-} 0.00048, subject to a possible upward bias by a few percent due to the unknown spot coverage. Even assuming this bias to be negligible, the mean density of the planet can be either 3.03 {+-} 0.50 g cm{sup -3} or 1.89 {+-} 0.33 g cm{sup -3}, depending on whether the stellar radius is estimated from evolutionary models, or from an empirical mass-luminosity relation combined with the light curve parameters. One possible resolution is that the orbit is eccentric (e {approx} 0.14), which would favor the higher density, and hence a much thinner atmosphere for the planet. The transit times were found to be periodic within about 15 s, ruling out the existence of any other super-Earths with periods within a factor of two of the known planet.

  15. The 1991-2012 light curve of the old nova HR Lyrae

    SciTech Connect

    Honeycutt, R. K.; Shears, J.; Kafka, S.; Robertson, J. W.; Henden, A. A. E-mail: bunburyobservatory@hotmail.com E-mail: Jeff.Robertson@atu.edu

    2014-05-01

    The 22 yr light curve of HR Lyr, acquired with a typical cadence of 2-6 days, is examined for periodic and quasi-periodic variations. No persistent periodicities are revealed. Rather, the light curve variations often take the form of nearly linear rises and falls having typical e-folding times of about 100 days. Occasional ∼0.6 mag outbursts are also seen, with properties similar to those of small outbursts found in some nova-like cataclysmic variables. When the photometry is formed into yearly averages, a decline of 0.012 ± 0.005 mag yr{sup –1} is apparent, consistent with the fading of irradiation-induced M-dot following the nova. The equivalent width of Hα is tabulated at three epochs over the interval 1986-2008 in order to compare with a recent result for DK Lac in which Hα was found to be fading 50 yr after the nova. However, our results for such a fading in HR Lyr are inconclusive.

  16. Period and light-curve study of the contact eclipsing binary V523 Cas

    NASA Astrophysics Data System (ADS)

    Mohammadi, Mahya; Abedi, Abbas; Riazi, Nematollah

    2016-04-01

    CCD photometry of the eclipsing W Uma binary system V523 Cas in U, B, V and RC filters was carried out during eight nights in 2012. The physical and geometrical parameters of this system are obtained. A possible pulsation period of one of the components is obtained by analyzing the residuals of the ephemeris light curve. Our observations contain 16 times of minimum light. We combined these with all available published times of minimum. By fitting a quadratic curve to the O-C values, a new ephemeris of the system is calculated. By attributing the period change to mass transfer, we find a mass transfer rate of 4 ×10-12 M⊙/yr. Also, Period (80.58 yr) and the minimum mass (0.3 M⊙) of a possible third body is estimated. In addition, the possible existence of a fourth body with a mass of order 0.15 M⊙ is discussed. These third and fourth bodies could be low-mass main-sequence stars (red dwarfs).

  17. Cosmological Parameter Uncertainties from SALT-II Type Ia Supernova Light Curve Models

    SciTech Connect

    Mosher, J.; Guy, J.; Kessler, R.; Astier, P.; Marriner, J.; Betoule, M.; Sako, M.; El-Hage, P.; Biswas, R.; Pain, R.; Kuhlmann, S.; Regnault, N.; Frieman, J. A.; Schneider, D. P.

    2014-08-29

    We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ~120 low-redshift (z < 0.1) SNe Ia, ~255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ~290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w (input) – w (recovered)) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty, the average bias on w is –0.014 ± 0.007.

  18. Cosmological parameter uncertainties from SALT-II type Ia supernova light curve models

    SciTech Connect

    Mosher, J.; Sako, M.; Guy, J.; Astier, P.; Betoule, M.; El-Hage, P.; Pain, R.; Regnault, N.; Marriner, J.; Biswas, R.; Kuhlmann, S.; Schneider, D. P.

    2014-09-20

    We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ∼120 low-redshift (z < 0.1) SNe Ia, ∼255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ∼290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w {sub input} – w {sub recovered}) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty; the average bias on w is –0.014 ± 0.007.

  19. Extracting Periodic Transit Signals from Noisy Light Curves using Fourier Series

    NASA Astrophysics Data System (ADS)

    Samsing, Johan

    2015-07-01

    We present a simple and powerful method for extracting transit signals associated with a known transiting planet from noisy light curves. Assuming the orbital period of the planet is known and the signal is periodic, we illustrate that systematic noise can be removed in Fourier space at all frequencies by only using data within a fixed time frame with a width equal to an integer number of orbital periods. This results in a reconstruction of the full transit signal, which on average is unbiased despite no prior knowledge of either the noise or the transit signal itself being used in the analysis. The method therefore has clear advantages over standard phase folding, which normally requires external input such as nearby stars or noise models for removing systematic components. In addition, we can extract the full orbital transit signal (360°) simultaneously, and Kepler-like data can be analyzed in just a few seconds. We illustrate the performance of our method by applying it to a dataset composed of light curves from Kepler with a fake injected signal emulating a planet with rings. For extracting periodic transit signals, our presented method is in general the optimal and least biased estimator and could therefore lead the way toward the first detections of, e.g., planet rings and exo-trojan asteroids.

  20. A search for periodicity in the light curves of selected blazars

    NASA Astrophysics Data System (ADS)

    Kudryavtseva, N. A.; Pyatunina, T. B.

    2006-01-01

    We present an analysis of multifrequency light curves of the sources 2223-052 (3C 446), 2230+114 (CTA 102), and 2251+158 (3C 454.3), which had shown evidence of quasiperiodic activity. The analysis made use of data from the University of Michigan Radio Astronomy Observatory (USA) at 4.8, 8, and 14.5 GHz, as well as the Metsahovi Radio Astronomy Observatory (Finland) at 22 and 37 GHz. Application of two different methods (the discrete autocorrelation function and the method of Jurkevich) both revealed evidence for periodicity in the flux variations of these sources at essentially all frequencies. The periods derived for at least two of the sources—2223-052 and 2251+158—are in good agreement with the time interval between the appearance of successive VLBI components. The derived periods for 2251+158 (P = 12.4 yr and 2223-052 (P = 5.8 yr) coincide with the periods found earlier by other authors based on optical light curves.

  1. Spitzer Light Curves of Dusty AGB Stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin; Meixner, Margaret; Riebel, David; Vijh, Uma; Hora, Joe; Boyer, Martha; Cook, Kem; Groenewegen, Martin; Whitelock, Patricia; Ita, Yoshifusa; Feast, Michael; Kemper, Ciska; Marengo, Massimo; Otsuka, Masaaki; Srinivasan, Sundar

    2014-12-01

    Asymptotic giant branch (AGB) variable stars are, together with supernovae, the main sources of enrichment of the interstellar medium (ISM) in processed material, particularly carbon, nitrogen and heavy s-process elements. The dustiest, extreme AGB stars contribute the largest enrichment per star. We propose to measure the first light curves for 32 of the dustiest AGB variable stars in the Small Magellanic Cloud (SMC) using the warm Spitzer mission's IRAC 3.6 and 4.5 micron imaging for monthly imaging measurements. We know most are variable based on dual-epoch observations from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) surveys of the SMC and ground-based near-infrared observations, but we have not observed these dusty SMC stars at the mid-infrared wavelengths available to Spitzer. Only Spitzer will be able to measure the light curve of this key phase of the AGB: the dustiest and indeed final stage of the AGB. Without this information, our developing picture of AGB evolution is decidedly incomplete. The observations we propose will test the validity of AGB evolution models, and, thus, their predictions of the return of mass and nucleosynthetic products to the ISM. A value-added component to this study is that we will obtain variability information on other AGB stars that lie within the fields of view of our observations. This proposal continues the studies we have begun with our Cycle 9 program (pid 90219) and our Cycle 10 program (pid 10154).

  2. Characterization of a Novel Melt Curve by Use of the Roche LightCycler HSV 1/2 Analyte-Specific Reagent Real-Time PCR Assay: Frequencies of This Novel (Low) Melt Curve and Commonly Encountered (Intermediate) Melt Curves

    PubMed Central

    Almradi, Amro; Espy, Mark J.; Prada, Anne E.; Gibson, John P.; Pritt, Bobbi S.

    2014-01-01

    We characterize a novel probe binding-site polymorphism detectable solely by melt curve analysis using the Roche LightCycler HSV 1/2 analyte-specific reagent real-time PCR assay. The frequencies of this novel (47°C) and previously described intermediate (60 to 62°C) melt curves were 0.016% and 4.9%, respectively. PMID:24352998

  3. Power-density spectrum of non-stationary short-lived light curves

    NASA Astrophysics Data System (ADS)

    Guidorzi, Cristiano

    2011-08-01

    The power-density spectrum of a light curve is often calculated as the average of a number of spectra derived on individual time intervals the light curve is divided into. This procedure implicitly assumes that each time interval is a different sample function of the same stochastic ergodic process. While this assumption can be applied to many astrophysical sources, there remains a class of transient, highly non-stationary and short-lived events, such as gamma-ray bursts, for which this approach is often inadequate. The power spectrum statistics of a constant signal affected by statistical (Poisson) noise are known to be a χ22 in the Leahy normalization. However, this is no more the case when a non-stationary signal is also present. As a consequence, the uncertainties on the power spectrum cannot be calculated on the basis of the χ22 properties, as assumed by tools such as XRONOS POWSPEC. We generalize the result in the case of a non-stationary signal affected by uncorrelated white noise and show that the new distribution is a non-central χ22(λ), whose non-central value λ is the power spectrum of the deterministic function describing the non-stationary signal. Finally, we test these results in the case of synthetic curves of gamma-ray bursts. We end up with a new formula for calculating the power spectrum uncertainties. This is crucial in the case of non-stationary short-lived processes affected by uncorrelated statistical noise, for which ensemble averaging does not make any physical sense.

  4. Physical characteristics of faint meteors by light curve and high-resolution observations, and the implications for parent bodies

    NASA Astrophysics Data System (ADS)

    Subasinghe, Dilini; Campbell-Brown, Margaret D.; Stokan, Edward

    2016-04-01

    Optical observations of faint meteors (10-7 < mass < 10-4 kg) were collected by the Canadian Automated Meteor Observatory between 2010 April and 2014 May. These high-resolution (metre scale) observations were combined with two-station light-curve observations and the meteoroid orbit to classify meteors and attempt to answer questions related to meteoroid fragmentation, strength, and light-curve shape. The F parameter was used to classify the meteor light-curve shape; the observed morphology was used to classify the fragmentation mode; and the Tisserand parameter described the origin of the meteoroid. We find that most meteor light curves are symmetric (mean F parameter 0.49), show long distinct trails (continuous fragmentation), and are cometary in origin. Meteors that show no obvious fragmentation (presumably single body objects) show mostly symmetric light curves, surprisingly, and this indicates that light-curve shape is not an indication of fragility or fragmentation behaviour. Approximately 90 per cent of meteors observed with high-resolution video cameras show some form of fragmentation. Our results also show, unexpectedly, that meteors which show negligible fragmentation are more often on high-inclination orbits (i > 60°) than low-inclination ones. We also find that dynamically asteroidal meteors fragment as often as dynamically cometary meteors, which may suggest mixing in the early Solar system, or contamination between the dynamic groups.

  5. STEPWISE FILTER CORRELATION METHOD AND EVIDENCE OF SUPERPOSED VARIABILITY COMPONENTS IN GAMMA-RAY BURST PROMPT EMISSION LIGHT CURVES

    SciTech Connect

    Gao He; Zhang Binbin; Zhang Bing E-mail: zhang@physics.univ.edu

    2012-04-01

    Gamma-ray bursts (GRBs) have variable light curves. Although most models attribute the observed variability to one physical origin (e.g., central engine activity, clumpy circumburst medium, or relativistic turbulence), some models invoke two physically distinct variability components. We develop a method, namely, the stepwise filter correlation method, to decompose the variability components in a GRB light curve. Based on a low-pass filter technique, we progressively filter the high-frequency signals from the light curve, and then perform a correlation analysis between each adjunct pair of filtered light curves. Our simulations suggest that if a mock light curve contains a 'slow' variability component superposed on a rapidly varying time sequence, the correlation coefficient as a function of the filter frequency would display a prominent 'dip' feature around the frequency of the slow component. Through simulations, we demonstrate that this method can identify significant clustering structures of a light curve in the frequency domain, and we prove that it can catch superposed signals that are otherwise not easy to retrieve based on other methods (e.g., the power density spectrum analysis method). We apply this method to 266 Burst and Transient Source Experiment bright GRBs. We find that the majority of the bursts have clear evidence of such a superposition effect. We perform a statistical analysis of the identified variability components and discuss the implications for GRB physics.

  6. Photometric analysis of the contact binary star V829 Hercules using light curves on three consecutive years

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Özkardeş, B.

    2006-12-01

    New BVR light curves and photometric analysis of the contact binary star arxiv:V829 Her are presented. The light curves were obtained at the ÇOMU Observatory in the consecutive years 2003, 2004 and 2005. Firstly, the variation of the orbital period of the system was studied. The sinusoidal and secular changes were found and examined in terms of two plausible mechanisms, namely (i) the conservative mass transfer between the components of the system and (ii) the light-time effect due to an unseen component in the system. The instrumental magnitudes of all observed stars in this study were converted into standard magnitudes. We also study nature of asymmetries and the intrinsic variability in the light curves of the system. Light variations are summarized: (a) changes of light levels of both maxima and (b) changes of the depths of both primary and secondary eclipses. These peculiar asymmetries were interpreted in terms of dark spot(s) on the surface of the large and more massive component star. The present BVR light curves and radial velocity curves obtained by Lu, W., Rucinski, S. M., 1999. AJ 118, 515 were analysed by means of the latest version of the Wilson-Devinney program, simultaneously. Thus, the absolute parameters of the system were also derived.

  7. VARIABILITY IN PROTO-PLANETARY NEBULAE. I. LIGHT CURVE STUDIES OF 12 CARBON-RICH OBJECTS

    SciTech Connect

    Hrivnak, Bruce J.; Lu Wenxian; Maupin, Richard E.; Spitzbart, Bradley D. E-mail: wen.lu@valpo.ed E-mail: bspitzbart@cfa.harvard.ed

    2010-02-01

    We have carried out long-term (14 years) V and R photometric monitoring of 12 carbon-rich proto-planetary nebulae. The light and color curves display variability in all of them. The light curves are complex and suggest multiple periods, changing periods, and/or changing amplitudes, which are attributed to pulsation. A dominant period has been determined for each and found to be in the range of approx150 days for the coolest (G8) to 35-40 days for the warmest (F3). A clear, linear inverse relationship has been found in the sample between the pulsation period and the effective temperature and also an inverse relationship between the amplitude of light variation and the effective temperature. These are consistent with the expectation for a pulsating post-asymptotic giant branch (post-AGB) star evolving toward higher temperature at constant luminosity. The published spectral energy distributions and mid-infrared images show these objects to have cool (200 K), detached dust shells and published models imply that intensive mass loss ended 400-2000 years ago. The detection of periods as long as 150 days in these requires a revision in the published post-AGB evolution models that couple the pulsation period to the mass loss rate and that assume that intensive mass loss ended when the pulsation period had decreased to 100 days. This revision will have the effect of extending the timescale for the early phases of post-AGB evolution. It appears that real time evolution in the pulsation periods of individual objects may be detectable on the timescale of two or three decades.

  8. UBVRI Light Curves of the Seyfert Galaxy NGC 7469 During 1990-1998: Microvariability

    NASA Astrophysics Data System (ADS)

    Merkulova, N. I.

    2000-02-01

    Observations of the nuclear region of the Seyfert galaxy NGC 7469 obtained at Crimean Astrophysical Observatory with the 1.25 m telescope are presented. During 64 nights on nine observational runs between 1990 September 24 and 1998 October 22 in each spectral band of the Johnson UBVRI system, about 1500 measurements have been performed simultaneously through the round aperture 20" in diameter using differential photometry techniques. The estimated accuracy of each measurement is about 0.01 mag. During the observing period 1990-1996 the mean luminosity of the nucleus was almost constant; only overlapping brightness fluctuations were observed. The mean luminosity level has been raised in 1996 October. The peak amplitude (maximum flux/minimum flux) Fmax/Fmin=2.09 on the light curves was observed in the U band, while the minimum amplitude Fmax/Fmin=1.32 was in the I band for the entire observation period. Using structure function (SF) analysis, the following conclusions have been made: (1) Long-term variability is caused by the same processes in the optical, because the slope b of the SF is approximately equal for all wave bands, except for the I band the slope is appreciably distinguished from the others. This would be an indication of the presence of an independent IR energy source in NGC 7469. (2) Considering the same time interval (from 6 minutes to 2 hr) for intranight variability on SFs at different wave bands, one can conclude that flicker noise causes variations observed on the light curve at the UV region (U and B bands), while at the near-IR region the light curve is formed by mixed shot noise and flicker noise-the greater the wavelength, the more the contribution of shot noise processes. (3) On intranight light curves of the NGC 7469 there exist rapid flares with durations ~25 minutes at U band, ~55 minutes at B, V bands, and ~2 hr at R, I bands-a typical timescale of intranight variability increasing with the increasing wavelength. In order to examine the

  9. Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

    SciTech Connect

    Li, Ben; He, Feng; Ouyang, Jiting; Duan, Xiaoxi

    2015-12-15

    Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

  10. Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

    NASA Astrophysics Data System (ADS)

    Li, Ben; He, Feng; Duan, Xiaoxi; Ouyang, Jiting

    2015-12-01

    Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

  11. The optical light curve of the low-mass X-ray binary GX 9 + 9

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.

    1990-01-01

    The detection of a small modulation in the light curve of the GX 9 + 9 optical counterpart at the same period as determined from the X-ray data is reported. The optical variability is roughly sinusoidal in shape with a period of 4.198 + or - 0.0094 hours and an average peak-to-peak amplitude in the B of 0.19 mag with comparable amplitudes in the V and R bandpasses, and has superposed flickering with a typical amplitude of six percent. The mass of the companion star is deduced to be 0.4 solar mass, which corresponds to an early M-type star. The bulk of the optical light arises in the accretion disk, while the variability arises from orbital modulation of the light reprocessed off the companion star and a bright spot. It is suggested that the X-ray modulation might be due to the asymmetries of X-rays reflected off the bright spot.

  12. THE MULTI-COLOR LIGHT CURVES OF THE W UMa TYPE CONTACT BINARY EP ANDROMEDAE

    SciTech Connect

    Liao, W.-P.; Qian, S.-B.; Li, K.; He, J.-J.; Zhao, E.-G.; Zhou, X.

    2013-10-01

    New multi-color CCD photometric light curves of the eclipsing binary EP And were obtained over six nights in 2006, 2011, and 2012. Using the Wilson-Devinney code, we computed the photometric elements of this system. It was discovered that EP And is a W-type W UMa contact binary system with a mass ratio of q = 2.685 and a degree of contact factor f = 24.9%, rather than an A-type system. Combining 28 newly determined times of minimum light derived from 1999 to 2012 with others collected from the literature, a long-term increase (dP/dt = +5.22 Multiplication-Sign 10{sup -8} days yr{sup -1}) with a sinusoidal variation (A = 0.0109 days; T = 40.89 yr) in the orbital period was found. The orbital period secular increases may be interpreted as conservative mass transfer from the less massive component to the more massive one, and cyclic variations of the orbital period may be caused by the light-travel time effect through the presence of a third body. The evolutionary status and the age of the system are also discussed.

  13. GLOBAL MAPPING OF EARTH-LIKE EXOPLANETS FROM SCATTERED LIGHT CURVES

    SciTech Connect

    Kawahara, Hajime; Fujii, Yuka

    2010-09-10

    Scattered lights from terrestrial exoplanets provide valuable information about their planetary surface. Applying the surface reconstruction method proposed by Fujii et al. to both diurnal and annual variations of scattered light, we develop a reconstruction method of land distribution with both longitudinal and latitudinal resolutions. We find that one can recover a global map of an idealized Earth-like planet on the following assumptions: (1) cloudlessness, (2) a face-on circular orbit, (3) known surface types and their reflectance spectra, (4) lack of atmospheric absorption, (5) known rotation rate, (6) a static map, and (7) the absence of a moon. Using the dependence of light curves on planetary obliquity, we also show that the obliquity can be measured by adopting the {chi}{sup 2} minimization or the extended information criterion. We demonstrate the feasibility of our methodology by applying it to a multi-band photometry of a cloudless model Earth with future space missions such as the occulting ozone observatory (O3). We conclude that future space missions can estimate both the surface distribution and the obliquity at least for cloudless Earth-like planets within 5 pc.

  14. Light curves and absolute magnitudes of four recent fast LMC novae

    NASA Astrophysics Data System (ADS)

    Hearnshaw, J. B.; Livingston, C. M.; Gilmore, A. C.; Kilmartin, P. M.

    2004-05-01

    The light curves of four recent fast LMC novae (Nova LMC 1988a, 1992, 1995, 2000) have been analysed to obtain the parameter t2, the time for a two magnitude decline below maximum light. Using the calibration of Della Valle & Livio (1995), values of MV at maximum are obtained. The weighted mean distance modulus to the LMC based on these novae is 18.89 ± 0.16. This differs significantly drom the distance modulus adpoted by Della Valle & Livio of 18.50, but only differs at the 1σ-level from Feast's (1999) value of 18.70 ± 0.10. The evidence based on these novae suggests that either: (i) DMLMC = 18.50 is too close for the LMC; or (ii) some novae in the LMC, including these four, are significantly underluminous at maximum light compared with those in M31, by about 0.4 mag. This could be a metallicity effect, given that more metal-rich M31 novae were predominantly used by Della Valle & Livio to obtain their calibration.

  15. Prefabricated light-polymerizing plastic pattern for partial denture framework.

    PubMed

    Takaichi, Atsushi; Wakabayashi, Noriyuki; Igarashi, Yoshimasa

    2011-10-01

    Our aim is to report an application of a prefabricated light-polymerizing plastic pattern to construction of removable partial denture framework without the use of a refractory cast. A plastic pattern for the lingual bar was adapted on the master cast of a mandibular Kennedy class I partially edentulous patient. The pattern was polymerized in a light chamber. Cobalt-chromium wires were employed to minimize the potential distortion of the plastic framework. The framework was carefully removed from the master cast and invested with phosphate-bonded investment for the subsequent casting procedures. A retentive clasp was constructed using 19-gauge wrought wire and was welded to the framework by means of laser welding machine. An excellent fit of the framework in the patient's mouth was observed in the try-in and the insertion of the denture. The result suggests that this method minimizes laboratory cost and time for partial denture construction. PMID:22346178

  16. Prefabricated light-polymerizing plastic pattern for partial denture framework

    PubMed Central

    Takaichi, Atsushi; Wakabayashi, Noriyuki; Igarashi, Yoshimasa

    2011-01-01

    Our aim is to report an application of a prefabricated light-polymerizing plastic pattern to construction of removable partial denture framework without the use of a refractory cast. A plastic pattern for the lingual bar was adapted on the master cast of a mandibular Kennedy class I partially edentulous patient. The pattern was polymerized in a light chamber. Cobalt–chromium wires were employed to minimize the potential distortion of the plastic framework. The framework was carefully removed from the master cast and invested with phosphate-bonded investment for the subsequent casting procedures. A retentive clasp was constructed using 19-gauge wrought wire and was welded to the framework by means of laser welding machine. An excellent fit of the framework in the patient's mouth was observed in the try-in and the insertion of the denture. The result suggests that this method minimizes laboratory cost and time for partial denture construction. PMID:22346178

  17. Lightness identification of patterned three-dimensional, real objects

    PubMed Central

    Robilotto, Rocco; Zaidi, Qasim

    2010-01-01

    Conventional studies of lightness constancy have almost exclusively used flat plain stimuli and have shown that lightness matches across illuminants cannot be explained by physical matches of reflectance or luminance. The perceptual qualities that underlie lightness judgments still remain largely unknown. Real objects are often 3-D and patterned, giving additional cues for identification. We examine the perceptual strategies that underlie material identification of real objects. Stimuli were randomly crumpled papers printed with achromatic patterns with precisely calibrated mean reflectance and reflectance contrast, placed in backgrounds under varying levels of illumination. Observers were asked to identify objects based on physical reflectance differences. Reflectance identification functions were simulated by simple models that perform object identification based on dissimilarities in perceived brightness (luminance dissimilarity modified by light adaptation) or perceived contrast (contrast dissimilarity modified by mean luminance). The reflectance identification results were also recreated in two control experiments, using identical stimuli conditions, where choices were based explicitly on dissimilarities in perceived brightness or contrast. Rather than a reverse optics model of lightness perception where observers first estimate illuminant intensity and then extract relative lightness by discounting the illuminant, this study supports the use of simple percepts such as brightness and contrast. PMID:16489856

  18. Patterns and properties of polarized light in air and water

    PubMed Central

    Cronin, Thomas W.; Marshall, Justin

    2011-01-01

    Natural sources of light are at best weakly polarized, but polarization of light is common in natural scenes in the atmosphere, on the surface of the Earth, and underwater. We review the current state of knowledge concerning how polarization and polarization patterns are formed in nature, emphasizing linearly polarized light. Scattering of sunlight or moonlight in the sky often forms a strongly polarized, stable and predictable pattern used by many animals for orientation and navigation throughout the day, at twilight, and on moonlit nights. By contrast, polarization of light in water, while visible in most directions of view, is generally much weaker. In air, the surfaces of natural objects often reflect partially polarized light, but such reflections are rarer underwater, and multiple-path scattering degrades such polarization within metres. Because polarization in both air and water is produced by scattering, visibility through such media can be enhanced using straightforward polarization-based methods of image recovery, and some living visual systems may use similar methods to improve vision in haze or underwater. Although circularly polarized light is rare in nature, it is produced by the surfaces of some animals, where it may be used in specialized systems of communication. PMID:21282165

  19. The EB factory project. I. A fast, neural-net-based, general purpose light curve classifier optimized for eclipsing binaries

    SciTech Connect

    Paegert, Martin; Stassun, Keivan G.; Burger, Dan M.

    2014-08-01

    We describe a new neural-net-based light curve classifier and provide it with documentation as a ready-to-use tool for the community. While optimized for identification and classification of eclipsing binary stars, the classifier is general purpose, and has been developed for speed in the context of upcoming massive surveys such as the Large Synoptic Survey Telescope. A challenge for classifiers in the context of neural-net training and massive data sets is to minimize the number of parameters required to describe each light curve. We show that a simple and fast geometric representation that encodes the overall light curve shape, together with a chi-square parameter to capture higher-order morphology information results in efficient yet robust light curve classification, especially for eclipsing binaries. Testing the classifier on the ASAS light curve database, we achieve a retrieval rate of 98% and a false-positive rate of 2% for eclipsing binaries. We achieve similarly high retrieval rates for most other periodic variable-star classes, including RR Lyrae, Mira, and delta Scuti. However, the classifier currently has difficulty discriminating between different sub-classes of eclipsing binaries, and suffers a relatively low (∼60%) retrieval rate for multi-mode delta Cepheid stars. We find that it is imperative to train the classifier's neural network with exemplars that include the full range of light curve quality to which the classifier will be expected to perform; the classifier performs well on noisy light curves only when trained with noisy exemplars. The classifier source code, ancillary programs, a trained neural net, and a guide for use, are provided.

  20. The EB Factory Project. I. A Fast, Neural-net-based, General Purpose Light Curve Classifier Optimized for Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Paegert, Martin; Stassun, Keivan G.; Burger, Dan M.

    2014-08-01

    We describe a new neural-net-based light curve classifier and provide it with documentation as a ready-to-use tool for the community. While optimized for identification and classification of eclipsing binary stars, the classifier is general purpose, and has been developed for speed in the context of upcoming massive surveys such as the Large Synoptic Survey Telescope. A challenge for classifiers in the context of neural-net training and massive data sets is to minimize the number of parameters required to describe each light curve. We show that a simple and fast geometric representation that encodes the overall light curve shape, together with a chi-square parameter to capture higher-order morphology information results in efficient yet robust light curve classification, especially for eclipsing binaries. Testing the classifier on the ASAS light curve database, we achieve a retrieval rate of 98% and a false-positive rate of 2% for eclipsing binaries. We achieve similarly high retrieval rates for most other periodic variable-star classes, including RR Lyrae, Mira, and delta Scuti. However, the classifier currently has difficulty discriminating between different sub-classes of eclipsing binaries, and suffers a relatively low (~60%) retrieval rate for multi-mode delta Cepheid stars. We find that it is imperative to train the classifier's neural network with exemplars that include the full range of light curve quality to which the classifier will be expected to perform; the classifier performs well on noisy light curves only when trained with noisy exemplars. The classifier source code, ancillary programs, a trained neural net, and a guide for use, are provided.

  1. Toward realistic dynamics of rotating orbital debris and implications for light curve

    NASA Astrophysics Data System (ADS)

    Ojakangas, G.; Hill, N.

    2011-09-01

    Optical observations of rotating space debris near GEO contain important information on size, shape, composition, and rotational states, but these aspects are difficult to extract due to data limitations and the high number of degrees of freedom in the modeling process. For tri-axial rigid debris objects created by satellite fragmentations, the most likely initial rotation states have large components of angular velocity directed along the intermediate axis of inertia, leading to large reorientations of the body on the timescale of the rotation period. This lends some support to the simplest possible interpretation of light curves -- that they represent sets of random orientations of the objects of study, although such rotation states do not typically sample orientation space uniformly even over a large number of rotations. Furthermore, effects of solar radiation can cause significant modification of rotation states within timescales of hours, for cm-sized objects of irregular shape. In order to examine the rotational dynamics under solar influence, a set of seven firstorder coupled equations of motion were assembled in state form: three are Euler equations describing the rates of change of the components of angular velocity in the body frame, and four describe the rates of change of the components of the unit quaternion. Quaternions are four-dimensional extensions of complex numbers that form a seamless, singularity-free representation of body orientation on S3. The Euler equations contain explicit terms describing torque from solar radiation. Numerical integrations reveal widely varying rotation states, such that in general, light curves for small objects of irregular shape can be expected to radically change character between different observation epochs. Because the axis of maximum rotational inertia tends to be roughly coincident with the normal to the largest projected cross-sectional area, internal friction or magnetic damping, if significant, may lead to

  2. Light-Curve Modelling Constraints on the Obliquities and Aspect Angles of the Young Fermi Pulsars

    NASA Technical Reports Server (NTRS)

    Pierbattista, M.; Harding, A. K.; Grenier, I. A.; Johnson, T. J.; Caraveo, P. A.; Kerr, M.; Gonthier, P. L.

    2015-01-01

    In more than four years of observation the Large Area Telescope on board the Fermi satellite has identified pulsed gamma-ray emission from more than 80 young or middle-aged pulsars, in most cases providing light curves with high statistics. Fitting the observed profiles with geometrical models can provide estimates of the magnetic obliquity alpha and of the line of sight angle zeta, yielding estimates of the radiation beaming factor and radiated luminosity. Using different gamma-ray emission geometries (Polar Cap, Slot Gap, Outer Gap, One Pole Caustic) and core plus cone geometries for the radio emission, we fit gamma-ray light curves for 76 young or middle-aged pulsars and we jointly fit their gamma-ray plus radio light curves when possible. We find that a joint radio plus gamma-ray fit strategy is important to obtain (alpha, zeta) estimates that can explain simultaneously detectable radio and gamma-ray emission: when the radio emission is available, the inclusion of the radio light curve in the fit leads to important changes in the (alpha, gamma) solutions. The most pronounced changes are observed for Outer Gap and One Pole Caustic models for which the gamma-ray only fit leads to underestimated alpha or zeta when the solution is found to the left or to the right of the main alpha-zeta plane diagonal respectively. The intermediate-to-high altitude magnetosphere models, Slot Gap, Outer Gap, and One pole Caustic, are favored in explaining the observations. We find no apparent evolution of a on a time scale of 106 years. For all emission geometries our derived gamma-ray beaming factors are generally less than one and do not significantly evolve with the spin-down power. A more pronounced beaming factor vs. spin-down power correlation is observed for Slot Gap model and radio-quiet pulsars and for the Outer Gap model and radio-loud pulsars. The beaming factor distributions exhibit a large dispersion that is less pronounced for the Slot Gap case and that decreases from

  3. UBV Photometry, Times of Minimum, and Light Curve Solutions for the Algol system, YY Cet

    NASA Astrophysics Data System (ADS)

    Ponce, V.; Williamon, R.; Sowell, J.

    1999-12-01

    YY Cet is an Algol system with partial eclipses and a period of 19 hours. The components appear to be slightly evolved A/F and G/K stars. UBV photometry has been acquired over four seasons with the 36-inch telescope at the DeKalb County (GA) School System's Fernbank Science Center. Times of minimum have been determined per filter and season, and a literature search has provided additional values for examining the possibility of period changes. Preliminary light curve solutions using all of our data have been derived with the Wilson-Devinney binary star code. V. Ponce wishes to acknowledge support from the NSF's Research Experiences for Undergraduates (REU) program administered through the Georgia Institute of Technology.

  4. CHANDRA OBSERVATIONS OF SN 1987A: THE SOFT X-RAY LIGHT CURVE REVISITED

    SciTech Connect

    Helder, E. A.; Broos, P. S.; Burrows, D. N.; Dewey, D.; Dwek, E.; McCray, R.; Park, S.; Racusin, J. L.; Zhekov, S. A.

    2013-02-10

    We report on the present stage of SN 1987A as observed by the Chandra X-Ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by {approx}6 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2} per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.

  5. Observations and Light Curve Solutions of Four Ultrashort-Period Binaries

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Popov, V.; Vasileva, D.; Petrov, N.

    2016-03-01

    The paper presents light curve solutions of our observations of four new ultrashort-period eclipsing binaries with MS components. Two of them have periods almost at the upper limit (0.22 days) of the ultrashort-period binaries, while the periods of around 0.18 days of CSS J171508.5+350658 and CSS J214633.8+120016 are amongst the shortest known orbital periods. CSS J171410.0+445850, CSS J214633.8+120016 and CSS J224326.0+154532 are overcontact binaries with fillout factors around 0.25 while CSS J171508.5+350658 is a semidetached system. The two targets with shortest periods consist of M dwarfs.

  6. Spectral analysis of stellar light curves by means of neural networks

    NASA Astrophysics Data System (ADS)

    Tagliaferri, R.; Ciaramella, A.; Milano, L.; Barone, F.; Longo, G.

    1999-06-01

    Periodicity analysis of unevenly collected data is a relevant issue in several scientific fields. In astrophysics, for example, we have to find the fundamental period of light or radial velocity curves which are unevenly sampled observations of stars. Classical spectral analysis methods are unsatisfactory to solve the problem. In this paper we present a neural network based estimator system which performs well the frequency extraction in unevenly sampled signals. It uses an unsupervised Hebbian nonlinear neural algorithm to extract, from the interpolated signal, the principal components which, in turn, are used by the MUSIC frequency estimator algorithm to extract the frequencies. The neural network is tolerant to noise and works well also with few points in the sequence. We benchmark the system on synthetic and real signals with the Periodogram and with the Cramer-Rao lower bound. This work was been partially supported by IIASS, by MURST 40\\% and by the Italian Space Agency.

  7. Late Light Curves of SN 2002cx-like Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Lair, Jessica C.; Kilgore, E. E.; Milne, P.; Bryngelson, G. L.; Leising, M. D.

    2013-01-01

    The use of Type Ia Supernovae (SNe Ia) in cosmological studies as “standard candle” distance indicators lead to the need for a better understanding of these objects. SN 2002cx was a very peculiar SNe Ia that did not fit into any of the known subclasses of SNe Ia and needs to be further understood. We present late-time optical photometry of three more recently discovered objects that have been determined to be SN 2002cx-like Type Ia supernovae: SN 2005hk, SN 2008A, and SN 2008ae. The light curves of these objects show late-time decline rates that are slower than what is seen in normal SNe Ia in the V,R, and I bands, but faster in the B-band.

  8. Starspot Modulation of BVRI Light Curves of LO Pegasi from 2012 June-October

    NASA Astrophysics Data System (ADS)

    Harmon, Robert O.; Avril, R.; Rossi De La Fuente, E.; Brechtel, C. E.

    2013-01-01

    We present BVRI light curves acquired at Perkins Observatory in 2012 June-October of the K8V star LO Pegasi, a young solar analog known to exhibit magnetic activity on its surface in the form of large starspots. We find that the amplitudes of the brightness variations have diminished significantly in comparison to data acquired from 2006-2011, and that the overall brightness is comparable to the brightness minima in the prior years. We speculate that these changes are due to the growth of a polar spot, coupled with a reduction in the relative sizes of projections of the polar spot into lower-latitude regions and/or a reduction in the area covered by independent spots at lower latitudes. This work was funded by the National Science Foundation Research Experiences for Undergraduates Program Award #1003992 and Ohio Wesleyan University.

  9. Resurrecting Bobrovnikoff to produce crowd-sourced cometary light curves using DSLR photometry

    NASA Astrophysics Data System (ADS)

    White, S.

    2014-04-01

    One of the aims of cometary observation is putting together the light curve. As well as recording the measurements of magnitude made by observers over a period of time, it feeds the anticipation of professionals and amateurs alike in answering the question "How bright will it be?". This developmental paper acknowledges the accepted wide variety of historic magnitude estimation methods and notes that the stringent rules of modern CCD photometry render it inaccessible to many amateur observers. The paper proposes a method which uses quantity, rather than quality, of individual observations to eliminate inaccuracy. It draws on principles of crowd sourcing already used with great success at the interface between professional and amateur astronomers

  10. Light-curve modelling constraints on the obliquities and aspect angles of the young Fermi pulsars

    NASA Astrophysics Data System (ADS)

    Pierbattista, M.; Harding, A. K.; Grenier, I. A.; Johnson, T. J.; Caraveo, P. A.; Kerr, M.; Gonthier, P. L.

    2015-03-01

    In more than four years of observation the Large Area Telescope on board the Fermi satellite has identified pulsed γ-ray emission from more than 80 young or middle-aged pulsars, in most cases providing light curves with high statistics. Fitting the observed profiles with geometrical models can provide estimates of the magnetic obliquity α and of the line of sight angle ζ, yielding estimates of the radiation beaming factor and radiated luminosity. Using different γ-ray emission geometries (Polar Cap, Slot Gap, Outer Gap, One Pole Caustic) and core plus cone geometries for the radio emission, we fit γ-ray light curves for 76 young or middle-aged pulsars and we jointly fit their γ-ray plus radio light curves when possible. We find that a joint radio plus γ-ray fit strategy is important to obtain (α,ζ) estimates that can explain simultaneously detectable radio and γ-ray emission: when the radio emission is available, the inclusion of the radio light curve in the fit leads to important changes in the (α,ζ) solutions. The most pronounced changes are observed for Outer Gap and One Pole Caustic models for which the γ-ray only fit leads to underestimated α or ζ when the solution is found to the left or to the right of the main α-ζ plane diagonal respectively. The intermediate-to-high altitude magnetosphere models, Slot Gap, Outer Gap, and One pole Caustic, are favoured in explaining the observations. We find no apparent evolution of α on a time scale of 106 years. For all emission geometries our derived γ-ray beaming factors are generally less than one and do not significantly evolve with the spin-down power. A more pronounced beaming factor vs. spin-down power correlation is observed for Slot Gap model and radio-quiet pulsars and for the Outer Gap model and radio-loud pulsars. The beaming factor distributions exhibit a large dispersion that is less pronounced for the Slot Gap case and that decreases from radio-quiet to radio-loud solutions. For all

  11. A universal approach to the calculation of the transit light curves

    NASA Astrophysics Data System (ADS)

    Abubekerov, M. K.; Gostev, N. Yu.

    2013-07-01

    We have developed a universal approach to compute accurately the brightness of eclipsing binary systems during the transit of a planet in front of the stellar disc. This approach is uniform for all values of the system parameters and applicable to most limb-darkening laws used in astrophysics. In the cases of the linear and quadratic limb-darkening laws, we obtained analytical expressions for the light curve and its derivatives in terms of elementary functions, elliptic integrals and a piecewise-defined function of one variable. In the cases of the logarithmic and square-root laws of limb darkening, the flux and its derivatives were expressed in terms of integrals which can be efficiently computed using the Gaussian quadrature formula, taking into account singularities of the integrand.

  12. Light curve solutions of the eclipsing Kepler binaries KIC 8088354 and KIC 3241619

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, Diana; Atanasova, Teodora

    2016-01-01

    We carried out light curve solutions of two detached eclipsing binaries with circular orbits observed by Kepler: KIC 8088354 and KIC 3241619. We established that: (i) The eclipses of KIC 8088354 are partial while KIC 3241619 undergoes total eclipse; (ii) the components of both targets are of spectral types G-K; (iii) the radii of the components of the objects differ by 20-30 %; (iv) the relative luminosities of their secondaries are considerably smaller than those of the primaries. The global parameters of KIC 8088354 and KIC 3241619 (temperatures, luminosities, radii and masses of the components) were found to obey satisfactorily the empirical relations of MS stars. We analyzed the additional short-term and long-term variability of the targets superposed on the eclipses.

  13. Correlation Analysis of Optical and Radio Light Curves for a Large Sample of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Smith, A. G.; Aller, H. D.; Aller, M. F.

    1995-08-01

    The Rosemary Hill Observatory has accumulated internally consistent light curves extending over as much as 26 years for a large sample of active galactic nuclei. Forty-six of these optical records have been compared with similar radio records from the University of Michigan Radio Astronomy Observatory and the Algonquin Radio Observatory. For 18 objects, pairs of records were sufficiently long and unconfused to allow reliable application of the Discrete Correlation Function analysis; this group included 8 BL Lacertids, 8 quasars, and 2 Seyfert galaxies. Nine of the 18 sources showed positive radio-optical correlations, with the radio events lagging the optical by intervals ranging from 0 to 14 months. Consistent with the relativistic beaming model of the BL Lacertids, the group displaying correlations was dominated by this type of object.

  14. Observations and Light Curve Solutions of Four Ultrashort-Period Binaries

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Popov, V.; Vasileva, D.; Petrov, N.

    2016-06-01

    The paper presents light curve solutions of our observations of four new ultrashort-period eclipsing binaries with MS components. Two of them have periods almost at the upper limit (0.22 days) of the ultrashort-period binaries, while the periods of around 0.18 days of CSS J171508.5+350658 and CSS J214633.8+120016 are amongst the shortest known orbital periods. CSS J171410.0+445850, CSS J214633.8+120016 and CSS J224326.0+154532 are overcontact binaries with fillout factors around 0.25 while CSS J171508.5+350658 is a semidetached system. The two targets with shortest periods consist of M dwarfs.

  15. 100-year DASCH Light Curves of Kepler Planet-Candidate Host Stars

    NASA Astrophysics Data System (ADS)

    Tang, Sumin; Sasselov, Dimitar; Grindlay, Jonathan; Los, Edward; Servillat, Mathieu

    2013-07-01

    We present 100 year light curves of Kepler planet-candidate host stars from the Digital Access to a Sky Century at Harvard (DASCH) project. 261 out of 997 host stars have at least 10 good measurements on DASCH scans of the Harvard plates. 109 of them have at least 100 good measurements, including 70% (73 out of 104) of all host stars with g <= 13 mag, and 44% (100 out of 228) of all host stars with g <= 14 mag. Our typical photometric uncertainty is ~0.1-0.15 mag. No variation is found at 3σ level for these host stars, including 21 confirmed or candidate hot Jupiter systems which might be expected to show enhanced flares from magnetic interactions between dwarf primaries and their close and relatively massive planet companions.

  16. THE FIRST SYSTEMATIC STUDY OF TYPE Ibc SUPERNOVA MULTI-BAND LIGHT CURVES

    SciTech Connect

    Drout, Maria R.; Soderberg, Alicia M.; Gal-Yam, Avishay; Arcavi, Iair; Green, Yoav; Cenko, S. Bradley; Fox, Derek B.; Leonard, Douglas C.; Sand, David J.; Moon, Dae-Sik

    2011-11-10

    We present detailed optical photometry for 25 Type Ibc supernovae (SNe Ibc) within d Almost-Equal-To 150 Mpc obtained with the robotic Palomar 60 inch telescope in 2004-2007. This study represents the first uniform, systematic, and statistical sample of multi-band SNe Ibc light curves available to date. We correct the light curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V - R) color of extinction-corrected SNe Ibc at {Delta}t Almost-Equal-To 10 days after V-band maximum is tightly distributed, ((V - R){sub V10}) = 0.26 {+-} 0.06 mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, (E(B - V)) Almost-Equal-To 0.4 mag. A comparison of the extinction-corrected light curves for helium-rich (Type Ib) and helium-poor (Type Ic) SNe reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of (M{sub R}) = -17.9 {+-} 0.9 mag and (M{sub R}) = -18.3 {+-} 0.6 mag for SNe Ib and Ic, respectively. Focusing on the broad-lined (BL) SNe Ic, we find that they are more luminous than the normal SNe Ibc sample, (M{sub R}) = -19.0 {+-} 1.1 mag, with a probability of only 1.6% that they are drawn from the same population of explosions. By comparing the peak absolute magnitudes of SNe Ic-BL with those inferred for local engine-driven explosions (GRB-SN 1998bw, XRF-SN 2006aj, and SN 2009bb) we find a 25% probability that relativistic SNe are drawn from the overall SNe Ic-BL population. Finally, we fit analytic models to the light curves to derive typical {sup 56}Ni masses of M{sub Ni} Almost-Equal-To 0.2 and 0.5 M{sub Sun} for SNe Ibc and SNe Ic-BL, respectively. With reasonable assumptions for the photospheric velocities, we further extract kinetic energy and ejecta mass values of M{sub ej} Almost-Equal-To 2 M{sub Sun} and E{sub K} Almost-Equal-To 10{sup 51} erg for SNe Ibc, while for SNe Ic

  17. Optical monitoring of the Seyfert galaxy NGC 4151 and possible periodicities in its historical light curve

    NASA Astrophysics Data System (ADS)

    Guo, Di-Fu; Hu, Shao-Ming; Tao, Jun; Yin, Hong-Xing; Chen, Xu; Pan, Hong-Jian

    2014-08-01

    We report B, V and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0 m telescope at Weihai Observatory of Shandong University and the 1.56 m telescope at Shanghai Astronomical Observatory from 2005 December to 2013 February. Combining all available data from literature, we have constructed a historical light curve from 1910 to 2013 to study the periodicity of the source using three different methods (the Jurkevich method, the Lomb-Scargle periodogram method and the Discrete Correlation Function method). We find possible periods of P1 = 4 ± 0.1, P2 = 7.5 ± 0.3 and P3 = 15.9 ± 0.3 yr.

  18. AN Lyn: a multiperiodic Delta Scuti star showing atypical light curves

    NASA Astrophysics Data System (ADS)

    Rodriguez, E.; Gonzalez-Bedolla, S. F.; Rolland, A.; Costa, V.; Lopez-Gonzalez, M. J.; Lopez de Coca, P.

    1997-07-01

    We have collected simultaneous uvby photometry of the Delta Sct star AN Lyn during the years 1995 and 1996 at the observatories of San Pedro Mertir, Mexico and Sierra Nevada, Spain. Firstly, analysis of frequencies of our 1995's data set was carried out using the Discrete Fourier Transform method, as described in Lopez de Coca et al. (1984), to the filter v. The periodograms showed a principal peak at v1 ~ 10.1756 c/d, very close to that frequency which corresponds to the period P ~0.0982739 d derived from earlier works. After prewhitening for v1 we found a second peak at 20.3525 c/d that corresponds to 2*v1. When these two frequencies are subtracted from the light curves, the periodograms show some peaks that reveal that additional frequencies are remaining in the spectra at very low amplitude as compared with the amplitude of the main peak (less than 5%).

  19. Chandra Observations of SN 1987A: The Soft X-Ray Light Curve Revisited

    NASA Technical Reports Server (NTRS)

    Helder, E. A.; Broos, P. S.; Dewey, D.; Dwek, E.; McCray, R.; Park, S.; Racusin, J. L.; Zhekov, S. A.; Burrows, D. N.

    2013-01-01

    We report on the present stage of SN 1987A as observed by the Chandra X-Ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by approximately 6 x 10(exp-13) erg s(exp-1)cm(exp-2) per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.

  20. Finite source sizes and the information content of macho-type lens search light curves

    NASA Technical Reports Server (NTRS)

    Nemiroff, Robert J.; Wickramasinghe, W. A. D. T.

    1994-01-01

    If the dark halo matter is primarily composed of Massive Compact Halo Objects (MACHOs) toward the lower end of the possible detection range (less than 10(exp -3) solar mass) a fraction of the lens detection events should involve the lens crossing directly in front of the disk of the background star. Previously, Nemiroff has shown that each crossing would create an inflection point in the light curve of the MACHO event. Such inflection points would allow a measure of the time it took for the lens to cross the stellar disk. Given an independent estimate of the stellar radius by other methods, one could then obtain a more accurate estimate of the velocity of the lens. This velocity could then, in turn, be used to obtain a more accurate estimate of the mass range for the MACHO or disk star doing the lensing.

  1. HZ Her/Her X-1: Study of the light curve dips

    NASA Astrophysics Data System (ADS)

    Igna, Ciprian Dacian

    The HZ Her/Her X-1 X-ray binary exhibits rapid and variable X-ray absorption features. These were noticed soon after the discovery of its periodic flux variations, such as X-ray pulsations and eclipses, and were named light curve dips by Giacconi et al. 1973. Their properties were analyzed, debated and documented ever since. The largest existing set of detailed observations of Her X-1 are contained in the data archive of NASA's Rossi X-ray Timing Explorer (RXTE)/Proportional Counter Array (PCA). From this entire light curve, several hundred new light curve dips were documented, based on X-ray Softness Ratio (SR), making this thesis the most extensive study of HZ Her/Her X-1's dips to date. The dips were classified into 12 different categories in order to study their statistical distribution, intensity, duration, symmetry and SR evolution. Some dips properties depend on Her X-1's 35-day X-ray cycle, which is caused by the precessing disk around the neutron star. The 35-day phase of dips was determined using Turn-On (TO) times calculated from the February 1996 - December 2009 RXTE/All Sky Monitor (ASM) light curve. 147 TOs were found by cross-correlation with X-ray cycle templates, and the 22 Burst and Transient Source Experiment TOs were confirmed. Thus this study also has the longest time period yet for the analysis of the 35-day X-ray cycle. The set of 147 TOs does not correlate with 0.2 or 0.7 orbital phases, disproving the reports over the past 30 years. The ASM-based 35-day cycle lengths range from 33.2 to 36.7 days, with an average of 34.7 +/- 0.2 days. The observed timing of dips is illustrated in the 35-day phase vs. orbital phase plot, and compared to models. The current large set of dips gives much better detail than that of Crosa & Boynton 1980. A model for dips is developed here, which takes dips to be caused by blockage of the line of sight to the neutron star by the site of the accretion stream - disk collision. An extensive investigation of the model

  2. Light Curve Analysis for W UMa-Type Eclipsing Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Henderson, Scott; Peach, N.; Olsen, T.

    2006-12-01

    We report results from summer 2006 in an ongoing study of eclipsing binary stars. Our investigations have focused on the measurement and interpretation of light curves for W UMa-type systems 44i Boötis and VW Cephei. These contact binaries have component stars of spectral type G, and revolve with periods of 6.43 and 6.67 hours. Dome automation and scripting capabilities introduced this summer have significantly reduced experimental uncertainties in our data. In support of previous findings we continue to observe an increase in the orbital period of 44i Boo at a rate of 10.4 µs/epoch or 14.2 ms/yr. Residuals computed after incorporating the increasing period suggest an underlying sinusoidal oscillation with a 61.5 year period and amplitude of 648 seconds. AAPT Member Thomas Olsen is sponsoring the lead presenter, SPS Member Scott Henderson, and the co-presenter, SPS Member Nick Peach.

  3. Type II Supernova Energetics and Comparison of Light Curves to Shock-cooling Models

    NASA Astrophysics Data System (ADS)

    Rubin, Adam; Gal-Yam, Avishay; De Cia, Annalisa; Horesh, Assaf; Khazov, Danny; Ofek, Eran O.; Kulkarni, S. R.; Arcavi, Iair; Manulis, Ilan; Yaron, Ofer; Vreeswijk, Paul; Kasliwal, Mansi M.; Ben-Ami, Sagi; Perley, Daniel A.; Cao, Yi; Cenko, S. Bradley; Rebbapragada, Umaa D.; Woźniak, P. R.; Filippenko, Alexei V.; Clubb, K. I.; Nugent, Peter E.; Pan, Y.-C.; Badenes, C.; Howell, D. Andrew; Valenti, Stefano; Sand, David; Sollerman, J.; Johansson, Joel; Leonard, Douglas C.; Horst, J. Chuck; Armen, Stephen F.; Fedrow, Joseph M.; Quimby, Robert M.; Mazzali, Paulo; Pian, Elena; Sternberg, Assaf; Matheson, Thomas; Sullivan, M.; Maguire, K.; Lazarevic, Sanja

    2016-03-01

    During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of 57 R-band SN II light curves that are well-monitored during their rise, with \\gt 5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 1-3 days. We show that the energy per unit mass (E/M) can be deduced to roughly a factor of five by comparing early-time optical data to the 2011 model of Rabinak & Waxman, while the progenitor radius cannot be determined based on R-band data alone. We find that SN II explosion energies span a range of E/M = (0.2-20) × 1051 erg/(10 {M}⊙ ), and have a mean energy per unit mass of < E/M> =0.85× {10}51 erg/(10 {M}⊙ ), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, E/M is positively correlated with the amount of 56Ni produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate ({{Δ }}{m}15), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.

  4. Indications of Technology in Planetary Transit Light Curves due to Dark-side Illumination

    NASA Astrophysics Data System (ADS)

    Sallmen, S.; Korpela, E. J.

    2014-03-01

    In this project, we analyze potential effects on transit light curves induced by an extraterrestrial civilization's use of orbiting mirrors to illuminate the dark side of a tidally locked planet. Previous efforts to detect civilizations based on side effects of planetary-scale engineering have focused on structures affecting the host star output. For example, searches have been performed for IR signatures of Dyson spheres, giant structures that trap most or all of the visible emissions of a star, and radiate only waste heat (Carrigan 2009). However, many civilizations are likely to be less advanced in their engineering efforts, yet still capable of sending small spacecraft into orbit. Since M dwarfs are the most common type of star in the solar neighborhood, it seems plausible that many of the nearby habitable planets orbit M stars, despite the small habitable zone around such stars. Planets orbiting inside the habitable zone of these dim, low-mass stars will be tidally locked. Logically, civilizations evolving on such planets might be inspired to illuminate their planet's dark side by placing a fleet of small thin mirrors into planetary orbit. To provide significant illumination, these mirrors would have a collective surface area of the order of the disk area of the planet. Based on this assumption, we explore the impact on transit light curves of such a collection of orbiting mirrors. We incorporate the effects of limb darkening and model the mirror fleet's effects for Earth-like (M = 0.5 to 3 MEarth) planets whose orbits will be tidally locked within the habitable zone of their host star.

  5. CfA4: LIGHT CURVES FOR 94 TYPE Ia SUPERNOVAE

    SciTech Connect

    Hicken, Malcolm; Challis, Peter; Kirshner, Robert P.; Bakos, Gaspar; Berlind, Perry; Brown, Warren R.; Caldwell, Nelson; Calkins, Mike; Falco, Emilio; Fernandez, Jose; Friedman, Andrew S.; Groner, Ted; Hartman, Joel; Rest, Armin; Cramer, Claire E.; Wood-Vasey, W. Michael; Currie, Thayne; De Kleer, Kathy; Esquerdo, Gil; Everett, Mark; and others

    2012-06-01

    We present multi-band optical photometry of 94 spectroscopically confirmed Type Ia supernovae (SNe Ia) in the redshift range 0.0055-0.073, obtained between 2006 and 2011. There are a total of 5522 light-curve points. We show that our natural-system SN photometry has a precision of {approx}< 0.03 mag in BVr'i', {approx}< 0.06 mag in u', and {approx}< 0.07 mag in U for points brighter than 17.5 mag and estimate that it has a systematic uncertainty of 0.014, 0.010, 0.012, 0.014, 0.046, and 0.073 mag in BVr'i'u'U, respectively. Comparisons of our standard-system photometry with published SN Ia light curves and comparison stars reveal mean agreement across samples in the range of {approx}0.00-0.03 mag. We discuss the recent measurements of our telescope-plus-detector throughput by direct monochromatic illumination by Cramer et al. This technique measures the whole optical path through the telescope, auxiliary optics, filters, and detector under the same conditions used to make SN measurements. Extremely well characterized natural-system passbands (both in wavelength and over time) are crucial for the next generation of SN Ia photometry to reach the 0.01 mag accuracy level. The current sample of low-z SNe Ia is now sufficiently large to remove most of the statistical sampling error from the dark-energy error budget. But pursuing the dark-energy systematic errors by determining highly accurate detector passbands, combining optical and near-infrared (NIR) photometry and spectra, using the nearby sample to illuminate the population properties of SNe Ia, and measuring the local departures from the Hubble flow will benefit from larger, carefully measured nearby samples.

  6. Reverberation mapping the dusty torus in Active Galactic Nuclei using Spitzer and optical light curves

    NASA Astrophysics Data System (ADS)

    Robinson, Andrew

    Dusty molecular tori play a central role in unification models for active galactic nuclei (AGN) and are also the dominant source of their mid-IR emission. Our limited knowledge of the size and structure of AGN tori and how these properties vary with luminosity hinders our ability to understand the observed spectral energy distribution and hence AGN demographics. Ultimately this inhibits our ability to understand the obscured AGN population and the cosmic evolution of super-massive black holes. Although the torus is, in general, inaccessible to direct imaging, its properties can be studied by analyzing the time response of the dust emission from the torus with respect to variations in the AGN continuum luminosity; a technique known as reverberation mapping. With this goal, we have completed a 2.5-year monitoring campaign on 12 broad-line AGN, using the Spitzer Space Telescope supported by ground-based optical observations, to measure the temporal response of thetorus 3.5 and 4.6μm mid-IR dust emission to variations in the AGN UV/optical continuum. The data obtained from the first 1.5 years in Spitzer Cycle 8 have been analysed. The aim of this project is to complete the time series analysis of the complete 2.5 year light curves, and to model these light curves in order extract structural and physical information contained in data, such as the size of the torus, its radial depth, opening angle, inclination and dust composition. This project will help to maximize the scientific returns on a significant investment of Spitzer Space Telescope time and supports the NASA strategic goal to "explore the origin and evolution of the galaxies, stars and planets that make up our universe".

  7. TYPE Ia SUPERNOVA LIGHT CURVE INFERENCE: HIERARCHICAL MODELS IN THE OPTICAL AND NEAR-INFRARED

    SciTech Connect

    Mandel, Kaisey S.; Narayan, Gautham; Kirshner, Robert P.

    2011-04-20

    We have constructed a comprehensive statistical model for Type Ia supernova (SN Ia) light curves spanning optical through near-infrared (NIR) data. A hierarchical framework coherently models multiple random and uncertain effects, including intrinsic supernova (SN) light curve covariances, dust extinction and reddening, and distances. An improved BAYESN Markov Chain Monte Carlo code computes probabilistic inferences for the hierarchical model by sampling the global probability density of parameters describing individual SNe and the population. We have applied this hierarchical model to optical and NIR data of 127 SNe Ia from PAIRITEL, CfA3, Carnegie Supernova Project, and the literature. We find an apparent population correlation between the host galaxy extinction A{sub V} and the ratio of total-to-selective dust absorption R{sub V} . For SNe with low dust extinction, A{sub V} {approx}< 0.4, we find R{sub V} {approx} 2.5-2.9, while at high extinctions, A{sub V} {approx}> 1, low values of R{sub V} < 2 are favored. The NIR luminosities are excellent standard candles and are less sensitive to dust extinction. They exhibit low correlation with optical peak luminosities, and thus provide independent information on distances. The combination of NIR and optical data constrains the dust extinction and improves the predictive precision of individual SN Ia distances by about 60%. Using cross-validation, we estimate an rms distance modulus prediction error of 0.11 mag for SNe with optical and NIR data versus 0.15 mag for SNe with optical data alone. Continued study of SNe Ia in the NIR is important for improving their utility as precise and accurate cosmological distance indicators.

  8. The long-term light curve of the cataclysmic variable V794 Aquilae

    SciTech Connect

    Honeycutt, R. K.; Kafka, S.; Robertson, J. W. E-mail: skafka@aip.org

    2014-01-01

    The 1990-2012 light curve of the nova-like (NL) cataclysmic variable V794 Aql is studied in order to characterize and better understand the transitions to and from the faint state, and the variations within the bright state. Investigations of earlier portions of this data had concluded that the transitions to the low state were much slower than the rapid recovery, giving a sawtoothed appearance to the light curve. This behavior differs from that of most other VY Scl stars, which led to an interpretation of the large amplitude sawtooths as being due to an accretion disk (AD) instability. However, more recent photometry strongly suggests that the bright state itself has transitions of 1-1.5 mag, and that earlier studies had intermixed these bright state variations with the transitions to the low state. These newly recognized variations within the bright state sometimes appear as small outbursts (OBs) with typical amplitudes of 0.5-1.5 mag and spacings of ∼15-50 days. The rise times of the OBs are 2-3 times faster than the decline times. We argue that the V794 Aql bright state variations are due to AD behavior similar to that seen in dwarf novae, but with varying degrees of stability. Similar regular small OBs have also been reported in other NL CVs, which we compare with V794 Aql. The true deep low states in V794 Aql appear to be normal, having transition speeds and shapes very similar to the transitions in other VY Scl stars.

  9. Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2

    SciTech Connect

    Jha, Saurabh; Riess, Adam G.; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-01-05

    We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band light curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz {ge} 2500 km s{sup -1}), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with H{sub 0}d{sub SN} {ge} 7400 km s{sup -1} yield an expansion rate that is 6.5 {+-} 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R{sub V} {approx_equal} 2.7, but optical colors alone provide weak constraints on R{sub V}.

  10. Ground-based Light Curves Two Pluto Days Before the New Horizons Passage

    NASA Astrophysics Data System (ADS)

    Bosh, A. S.; Pasachoff, J. M.; Babcock, B. A.; Durst, R. F.; Seeger, C. H.; Levine, S. E.; Abe, F.; Suzuki, D.; Nagakane, M.; Sickafoose, A. A.; Person, M. J.; Zuluaga, C.; Kosiarek, M. R.

    2015-12-01

    We observed the occultation of a 12th magnitude star, one of the two brightest occultation stars ever in our dozen years of continual monitoring of Pluto's atmosphere through such studies, on 29 June 2015 UTC. At Canterbury University's Mt. John University Observatory on the south island of New Zealand, in clear sky, we used our POETS frame-transfer CCD at 10 Hz with GPS timing on the 1-m McLellan telescope as well as an infrared camera on an 0.6-m telescope and three-color photometry at a slower cadence on a second 0.6-m telescope. The light curves show a central flash, indicating that we were close to the center of the occultation path, and allowing us to explore Pluto's atmosphere lower than usual. The light curves show that Pluto's atmosphere remained robust. Observations from 0.5- and 0.4-m telescopes at the Auckland Observatory gave the first half of the occultation before clouds came in. We coordinated our observations with aircraft observations with NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) and its High Speed Imaging Photometer for Occultations (HIPO). Our ground-based and airborne stellar-occultation effort came only just over two weeks of Earth days and two Pluto days (based on Pluto's rotational period) before the flyby of NASA's New Horizons spacecraft, meaning that the mission's exquisite snapshot of Pluto's atmosphere can be placed in the context of our series of ground-based occultation observations carried out on a regular basis since 2002 following a first Pluto occultation observed in 1988 from aloft. Our observations were supported by NASA Planetary Astronomy grants NNX12AJ29G to Williams College, NNX15AJ82G to Lowell Observatory, and NNX10AB27G to MIT, and by the National Research Foundation of South Africa. We thank Alan Gilmore, Pam Kilmartin, Robert Lucas, Paul Tristam, and Carolle Varughese for assistance at Mt. John.

  11. Modeling Indications of Technology in Planetary Transit Light Curves-Dark-side Illumination

    NASA Astrophysics Data System (ADS)

    Korpela, Eric J.; Sallmen, Shauna M.; Leystra Greene, Diana

    2015-08-01

    We analyze potential effects of an extraterrestrial civilization’s use of orbiting mirrors to illuminate the dark side of a synchronously rotating planet on planetary transit light curves. Previous efforts to detect civilizations based on side effects of planetary-scale engineering have focused on structures affecting the host star output (e.g., Dyson spheres). However, younger civilizations are likely to be less advanced in their engineering efforts, yet still capable of sending small spacecraft into orbit. Since M dwarfs are the most common type of star in the solar neighborhood, it seems plausible that many of the nearest habitable planets orbit dim, low-mass M stars, and will be in synchronous rotation. Logically, a civilization evolving on such a planet may be inspired to illuminate their planet’s dark side by placing a single large mirror at the L2 Lagrangian point, or launching a fleet of small thin mirrors into planetary orbit. We briefly examine the requirements and engineering challenges of such a collection of orbiting mirrors, then explore their impact on transit light curves. We incorporate stellar limb darkening and model a simplistic mirror fleet’s effects for transits of Earth-like (R = 0.5 to 2 {R}{Earth}) planets which would be synchronously rotating for orbits within the habitable zone of their host star. Although such an installation is undetectable in Kepler data, the James Webb Space Telescope will provide the sensitivity necessary to detect a fleet of mirrors orbiting Earth-like habitable planets around nearby stars.

  12. Discrimination of airborne material particles from light scattering (TAOS) patterns

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni F.; Pan, Yong-Le; Videen, Gorden; Aptowicz, Kevin B.; Chang, Richard K.

    2013-05-01

    Two-dimensional angle-resolved optical scattering (TAOS) is an experimental method which collects the intensity pattern of monochromatic light scattered by a single, micron-sized airborne particle. In general, the interpretation of these patterns and the retrieval of the particle refractive index, shape or size alone, are difficult problems. The solution proposed herewith relies on a learning machine (LM): rather than identifying airborne particles from their scattering patterns, TAOS patterns themselves are classified. The LM consists of two interacting modules: a feature extraction module and a linear classifier. Feature extraction relies on spectrum enhancement, which includes the discrete cosine Fourier transform and non-linear operations. Linear classification relies on multivariate statistical analysis. Interaction enables supervised training of the LM. The application described in this article aims at discriminating the TAOS patterns of single bacterial spores (Bacillus subtilis) from patterns of atmospheric aerosol and diesel soot particles. The latter are known to interfere with the detection of bacterial spores. Classification has been applied to a data set with more than 3000 TAOS patterns from various materials. Some classification experiments are described, where the size of training sets has been varied as well as many other parameters which control the classifier. By assuming all training and recognition patterns to come from the respective reference materials only, the most satisfactory classification result corresponds to ≍ 20% false negatives from Bacillus subtilis particles and <= 11% false positives from environmental and diesel particles.

  13. Study on Noncontact Pulmonary Function Test Using Pattern Light Projection

    NASA Astrophysics Data System (ADS)

    Aoki, Hirooki; Koshiji, Kohji

    The pulmonary function test by spirometer is generally conducted. The test subjects, especially children, women and older people, feel uncomfortable as the mouthpiece and nasal plug must be attached to the face of them. We have studied the nonrestraint pulmonary function test using the dot matrix pattern projection in order to decrease the burden to the examinee. In our proposed system, the pattern light projector illuminates the thorax with the dot matrix pattern light. And the CCD camera takes a series of images of the dot matrix pattern. The three dimensional shape of the thorax surface can be calculated by the distribution of light dots. And the respiratory waveform is calculated by the time-series change of the three dimensional shape. The respiratory waveform of our system was similar to one of spirometer. Therefore, we clarified that our proposed system can equivalently measure the respiration with spirometer. And we compared the volume change of the three dimensional shape calculated by our system with the expired tidal volume measured by the expiration gas analyzer. And we examined the relationship between the expired tidal volume and the volume change of the thorax surface.

  14. The Rise and Fall of Type Ia Supernova Light Curves in the SDSS-II Supernova Survey

    SciTech Connect

    Hayden, Brian T.; Garnavich, Peter M.; Kessler, Richard; Frieman, Joshua A.; Jha, Saurabh W.; Bassett, Bruce; Cinabro, David; Dilday, Benjamin; Kasen, Daniel; Marriner, John; Nichol, Robert C.; /Portsmouth U., ICG /Baltimore, Space Telescope Sci. /Johns Hopkins U.

    2010-01-01

    We analyze the rise and fall times of Type Ia supernova (SN Ia) light curves discovered by the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. From a set of 391 light curves k-corrected to the rest-frame B and V bands, we find a smaller dispersion in the rising portion of the light curve compared to the decline. This is in qualitative agreement with computer models which predict that variations in radioactive nickel yield have less impact on the rise than on the spread of the decline rates. The differences we find in the rise and fall properties suggest that a single 'stretch' correction to the light curve phase does not properly model the range of SN Ia light curve shapes. We select a subset of 105 light curves well observed in both rise and fall portions of the light curves and develop a '2-stretch' fit algorithm which estimates the rise and fall times independently. We find the average time from explosion to B-band peak brightness is 17.38 {+-} 0.17 days, but with a spread of rise times which range from 13 days to 23 days. Our average rise time is shorter than the 19.5 days found in previous studies; this reflects both the different light curve template used and the application of the 2-stretch algorithm. The SDSS-II supernova set and the local SNe Ia with well-observed early light curves show no significant differences in their average rise-time properties. We find that slow-declining events tend to have fast rise times, but that the distribution of rise minus fall time is broad and single peaked. This distribution is in contrast to the bimodality in this parameter that was first suggested by Strovink (2007) from an analysis of a small set of local SNe Ia. We divide the SDSS-II sample in half based on the rise minus fall value, t{sub r} - t{sub f} {approx}< 2 days and t{sub r} - t{sub f} > 2 days, to search for differences in their host galaxy properties and Hubble residuals; we find no difference in host galaxy properties or Hubble residuals in our

  15. INTERPRETATION OF STRONG SHORT-TERM CENTRAL PERTURBATIONS IN THE LIGHT CURVES OF MODERATE-MAGNIFICATION MICROLENSING EVENTS

    SciTech Connect

    Han, C.; Hwang, K.-H.; Kim, D.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Soszynski, I.; Ulaczyk, K.; Abe, F.; Fukui, A.; Furusawa, K.; Itow, Y.; Monard, L. A. B.; McCormick, J.; Szewczyk, O.; Wyrzykowski, L.; Bond, I. A.; Botzler, C. S.; Hearnshaw, J. B.

    2009-11-10

    To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.

  16. A Multiyear Light Curve of Scorpius X-1 Based on Compton Gamma Ray Observatory BATSE Spectroscopy Detector Observations

    NASA Astrophysics Data System (ADS)

    McNamara, B. J.; Harrison, T. E.; Mason, P. A.; Templeton, M.; Heikkila, C. W.; Buckley, T.; Galvan, E.; Silva, A.; Harmon, B. A.

    1998-06-01

    A multiyear light curve of the low mass X-ray binary, Scorpius X-1, is constructed based on the Compton Gamma Ray Observatory Burst and Transient Source Experiment (BATSE) Spectroscopy Detector (SD) data in the nominal energy range of 10-20 keV. A detailed discussion is given of the reduction process of the BATSE/SD data. Corrections to the SD measurements are made for off-axis pointings, spectral and bandpass changes, and differences in the eight SD sensitivities. The resulting 4.4 yr Sco X-1 SD light curve is characterized in terms of the timescales over which various types of emission changes occur. This light curve is then compared with Sco X-1 light curves obtained by Ariel 5, the BATSE Large Area Detectors (LADs), and the RXTE all-sky monitor (ASM). Coincident temporal coverage by the BATSE/SD and RXTE/ASM allows a direct comparison of the behavior of Sco X-1 over a range of high energies to be made. These ASM light curves are then used to discuss model constraints on the Sco X-1 system.

  17. Interpretation of Strong Short-Term Central Perturbations in the Light Curves of Moderate-Magnification Microlensing Events

    NASA Astrophysics Data System (ADS)

    Han, C.; Hwang, K.-H.; Kim, D.; Udalski, A.; Abe, F.; Monard, L. A. B.; McCormick, J.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.; Wyrzykowski, Ł.; Ulaczyk, K.; OGLE Collaboration; Bond, I. A.; Botzler, C. S.; Fukui, A.; Furusawa, K.; Hearnshaw, J. B.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Korpela, A.; Lin, W.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Ohnishi, K.; Tokumura, T.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Sako, T.; Skuljan, L.; Sullivan, D. S.; Sumi, T.; Sweatman, W. L.; Tristram, P. J.; Yock, P. C. M.; MOA Collaboration; Allen, W.; Christie, G. W.; De Poy, D. L.; Dong, S.; Gaudi, B. S.; Gould, A.; Lee, C.-U.; Natusch, T.; Park, B.-G.; Pogge, R. W.; μFUN Collaboration; Albrow, M. D.; Allan, A.; Batista, V.; Beaulieu, J. P.; Bennett, D. P.; Brillant, S.; Bode, M.; Bramich, D. M.; Burgdorf, M.; Caldwell, J. A. R.; Calitz, H.; Cassan, A.; Corrales, E.; Dieters, S.; Prester, D. D.; Dominik, M.; Donatowicz, J.; Fouque, P.; Greenhill, J.; Hill, K.; Hoffman, M.; Horne, K.; Jørgensen, U. G.; Kains, N.; Kubas, D.; Marquette, J. B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Snodgrass, C.; Steele, I.; Street, R.; Tsapras, Y.; Wambsganss, J.; Williams, A.; Zub, M.; PLANET/RoboNet Collaboration

    2009-11-01

    To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.

  18. A Multi-Year Light Curve of Scorpius X-1 Based on CGRO BATSE Spectroscopy Detector Observations

    NASA Technical Reports Server (NTRS)

    McNamara, B. J.; Harrison, T. E.; Mason, P. A.; Templeton, M.; Heikkila, C. W.; Buckley, T.; Galvan, E.; Silva, A.; Harmon, B. A.

    1998-01-01

    A multi-year light curve of the low mass X-ray binary, Scorpius X-1, is constructed based on the Compton Gamma-ray Observatory (CGRO) Burst and Transient Source Experiment (BATSE) Spectroscopy Detector (SD) data in the nominal energy range of 10-20 keV. A detailed discussion is given of the reduction process of the BATSE/SD data. Corrections to the SD measurements are made for off-axis pointings, spectral and bandpass changes, and differences in the eight SD sensitivities. The resulting 4.4 year Sco X-1 SD light curve is characterized in terms of the time scales over which various types of emission changes occur. This light curve is then compared with Sco X-1 light curves obtained by Axiel 5, the BATSE Large Area Detectors (LADs), and the RXTE all-sky monitor (ASM). Coincident temporal coverage by the BATSE/SD and RXTE/ASM allows a direct comparison of the behavior of Sco X-1 over a range of high energies to be made. These ASM light curves are then used to discuss model constraints on the Sco X-1 system.

  19. PERIOD CHANGES AND FOUR-COLOR LIGHT CURVES OF THE ACTIVE OVERCONTACT BINARY V396 MONOCEROTIS

    SciTech Connect

    Liu, L.; Qian, S.-B.; Liao, W.-P.; He, J.-J.; Zhu, L.-Y.; Li, L.-J.; Zhao, E.-G. E-mail: LiuL@ynao.ac.cn

    2011-02-15

    This paper analyzes the first obtained four-color light curves of V396 Mon using the 2003 version of the W-D code. It is confirmed that V396 Mon is a shallow W-type contact binary system with a mass ratio q = 2.554({+-}0.004) and a degree of contact factor f = 18.9%({+-}1.2%). A period investigation based on all available data shows that the period of the system includes a long-term decrease (dP/dt = -8.57 x 10{sup -8} days yr{sup -1}) and an oscillation (A{sub 3} = 0.0160 day, T{sub 3} = 42.4 yr). They are caused by angular momentum loss and light-time effect, respectively. The suspect third body is possibly a small M-type star (about 0.31 solar mass). Though some observations indicate that this system has strong magnetic activity, by our analysis we found that the Applegate mechanism cannot explain the periodic changes. This binary is an especially important system according to Qian's statistics of contact binaries as its mass ratio lies near the proposed pivot point about which the physical structure of contact binaries supposedly oscillates.

  20. Characterizing mid-ultraviolet to optical light curves of nearby type IIn supernovae

    DOE PAGESBeta

    de la Rosa, Janie; Roming, Pete; Pritchard, Tyler; Fryer, Chris

    2016-03-21

    Here, we present early mid-ultraviolet and optical observations of Type IIn supernovae (SNe IIn) observed from 2007 to 2013. Our results focus on the properties of UV light curves: peak absolute magnitudes, temporal decay, and color evolution. During early times, this sample demonstrates that UV light decays faster than optical, and each event transitions from a predominantly UV-bright phase to an optically bright phase. In order to understand early UV behavior, we generate and analyze the sample's blackbody luminosity, temperature, and radius as the SN ejecta expand and cool. Since most of our observations were detected post maximum luminosity, wemore » introduce a method for estimating the date of peak magnitude. When our observations are compared based on filter, we find that even though these SNe IIn vary in peak magnitudes, there are similarities in UV decay rates. We use a simple semi-analytical SN model in order to understand the effects of the explosion environment on our UV observations. Understanding the UV characteristics of nearby SNe IIn during an early phase can provide valuable information about the environment surrounding these explosions, leading us to evaluating the diversity of observational properties in this subclass.« less

  1. Characterizing Mid-ultraviolet to Optical Light Curves of Nearby Type IIn Supernovae

    NASA Astrophysics Data System (ADS)

    de la Rosa, Janie; Roming, Pete; Pritchard, Tyler; Fryer, Chris

    2016-03-01

    We present early mid-ultraviolet and optical observations of Type IIn supernovae (SNe IIn) observed from 2007 to 2013. Our results focus on the properties of UV light curves: peak absolute magnitudes, temporal decay, and color evolution. During early times, this sample demonstrates that UV light decays faster than optical, and each event transitions from a predominantly UV-bright phase to an optically bright phase. In order to understand early UV behavior, we generate and analyze the sample's blackbody luminosity, temperature, and radius as the SN ejecta expand and cool. Since most of our observations were detected post maximum luminosity, we introduce a method for estimating the date of peak magnitude. When our observations are compared based on filter, we find that even though these SNe IIn vary in peak magnitudes, there are similarities in UV decay rates. We use a simple semi-analytical SN model in order to understand the effects of the explosion environment on our UV observations. Understanding the UV characteristics of nearby SNe IIn during an early phase can provide valuable information about the environment surrounding these explosions, leading us to evaluating the diversity of observational properties in this subclass.

  2. Characterizing quasar ionization echoes - towards long-term AGN light curves

    NASA Astrophysics Data System (ADS)

    Schirmer, Mischa; Davies, Rebecca; Keel, William; Turner, James; Nagao, Tohru; Fu, Hai; Levenson, Nancy; Diaz, Ruben

    2014-08-01

    Green Bean galaxies (GBs) are rare type-2 quasars featuring ultra-luminous emission line regions extending over 20-40 kpc. Due to different light travel times from the AGN into the ionized gas, the latter retains a memory of the AGN's X-ray luminosity over the past several 10,000 years. Evidence from X-ray, optical and mid-IR data shows that the nuclear energy output in GBs must have dropped recently by several orders of magnitude. We are witnessing the final stages in the lives of the most luminous type-2 quasars. The ionization echoes allow us to study SMBH growth, massive outflows, and the co-evolution of the host galaxies from a new perspective. Using GMOS-N/S, we want to complete our imaging survey of all 17 known GBs, obtain a shallow IFU survey, and study one particularly exciting galaxy in greater depth. For the latter, we want to demonstrate that individual AGN light curves, extending over several 10,000 years, can be reconstructed from GBs. Hence this study is complementary to classical monitoring and reverberation mapping.

  3. Patterning of nanostructured thin films by structured light illumination

    SciTech Connect

    Haro-Poniatowski, E.; Fort, E.; Lacharme, J.P.; Ricolleau, C.

    2005-10-03

    Light-induced reshaping of silver nanostructured films near the percolation threshold are investigated using a KrF excimer laser emitting at 248 nm. Depending on the laser intensity and the number of pulses, striking effects are observed for which the irregular particles melt and transform into spherical shaped particles. We show that the laser-induced modifications can be spatially designed by irradiating through masks and gratings taking advantage of their respective diffractive properties. This permits an easy and well controlled way to produce a variety of submicron patterning. The induced patterns accurately coincide with the intensity variations of the illumination field.

  4. Homogeneous studies of transiting extrasolar planets - IV. Thirty systems with space-based light curves

    NASA Astrophysics Data System (ADS)

    Southworth, John

    2011-11-01

    I calculate the physical properties of 32 transiting extrasolar planet and brown-dwarf systems from existing photometric observations and measured spectroscopic parameters. The systems studied include 15 observed by the CoRoT satellite, 10 by Kepler and five by the Deep Impact spacecraft. Inclusion of the objects studied in previous papers leads to a sample of 58 transiting systems with homogeneously measured properties. The Kepler data include observations from Quarter 2, and my analyses of several of the systems are the first to be based on short-cadence data from this satellite. The light curves are modelled using the JKTEBOP code, with attention paid to the treatment of limb darkening, contaminating light, orbital eccentricity, correlated noise and numerical integration over long exposure times. The physical properties are derived from the light-curve parameters, spectroscopic characteristics of the host star and constraints from five sets of theoretical stellar model predictions. An alternative approach using a calibration from eclipsing binary star systems is explored and found to give comparable results whilst imposing a much smaller computational burden. My results are in good agreement with published properties for most of the transiting systems, but discrepancies are identified for CoRoT-5, CoRoT-8, CoRoT-13, Kepler-5 and Kepler-7. Many of the error bars quoted in the literature are underestimated. Refined orbital ephemerides are given for CoRoT-8 and for the Kepler planets. Asteroseismic constraints on the density of the host stars are in good agreement with the photometric equivalents for HD 17156 and TrES-2, but not for HAT-P-7 and HAT-P-11. Complete error budgets are generated for each transiting system, allowing identification of the observations best-suited to improve measurements of their physical properties. Whilst most systems would benefit from further photometry and spectroscopy, HD 17156, HD 80606, HAT-P-7 and TrES-2 are now extremely well

  5. Light-curve analysis of KIC 12557548b: an extrasolar planet with a comet-like tail

    NASA Astrophysics Data System (ADS)

    Budaj, J.

    2013-09-01

    Context. An object with a very peculiar light curve was recently discovered using Kepler data. When this object was discovered, it was suggested that this object may be a transiting disintegrating extrasolar planet with a comet-like dusty tail. Aims: We aim to verify this model by modelling the light curve and put constraints on the geometry of the dust region and various dust properties. Methods: We modified the code SHELLSPEC, which is designed for modelling interacting binary stars to calculate the light curves of such planets. Mie absorption and scattering on spherical dust grains with realistic dust opacities, phase functions, and a finite radius of the source of the scattered light are taken into account Results: The light curve is reanalysed using long- and short-cadence Kepler observations from the first 14 quarters. The orbital period of the planet was improved. We prove that the peculiar light curve agrees with the idea of a planet with a comet-like tail. The light curve has a prominent pre-transit brightening and a less prominent post-transit brightening. Both are caused by the forward scattering and are a strong function of the particle size. This feature enabled us to estimate a typical particle size (radius) in the dust tail of about 0.1-1 micron. However, there is an indication that the particle size changes (decreases) along the tail. The dust density in the tail is a steep decreasing function of the distance from the planet, which indicates a significant tail destruction caused by the star-planet interaction. Several possible combinations of other dust properties are tabulated. We reveal interesting periodic long-term evolution of the tail on a time scale of about 1.3 years and also argue that the "planet" does not show a uniform behaviour, but may have at least two constituents. This exoplanet's tail evolution may find an analogy in the comet tail disconnection events caused by the magnetic/coronal activity of the Sun while the light curve with

  6. A BAYESIAN APPROACH TO THE ANALYSIS OF TIME SYMMETRY IN LIGHT CURVES: RECONSIDERING SCORPIUS X-1 OCCULTATIONS

    SciTech Connect

    Blocker, Alexander W.; Protopapas, Pavlos; Alcock, Charles R.

    2009-08-20

    We present a new approach to the analysis of time symmetry in light curves, such as those in the X-ray at the center of the Scorpius X-1 occultation debate. Our method uses a new parameterization for such events (the bilogistic event profile) and provides a clear, physically relevant characterization of each event's key features. We also demonstrate a Markov chain Monte Carlo algorithm to carry out this analysis, including a novel independence chain configuration for the estimation of each event's location in the light curve. These tools are applied to the Scorpius X-1 light curves presented in Chang et al., providing additional evidence based on the time series that the events detected thus far are most likely not occultations by trans-Neptunian objects.

  7. Remarkable modification of light curves for shadowing effects on irregular surfaces - The case of the asteroid 37 Fides

    NASA Technical Reports Server (NTRS)

    Zappala, V.; Di Martino, M.; Scaltriti, F.; Burchi, R.; Milano, L.; Young, J. W.; Wahlgren, G.; Pavlovski, K.

    1983-01-01

    Photometric observations of the asteroid 37 Fides carried out at four observatories are reported. The data were taken at phase angles ranging from approximately 2-23 deg. A composite of the light curves obtained revealed that, considering a period of 7.33 hr, the full cycle light curve exhibits one maximum and one minimum. An increase in brightness was observed following a primary minimum, a factor that indicated the cyclical appearance and disappearance of a large topographical feature. It is concluded that the 7.33 hr period is the rotational speed of the asteroid, in contrast with a previously held 14.66 hr rotational period. The method is concluded useful for identifying rotational periods of asteroids when only partial light curve data from different sources is available, and when the projections can be checked observationally.

  8. LONG-TERM TRANSIT TIMING MONITORING AND REFINED LIGHT CURVE PARAMETERS OF HAT-P-13b

    SciTech Connect

    Fulton, Benjamin J.; Shporer, Avi; Winn, Joshua N.; Holman, Matthew J.; Pal, Andras; Zachary Gazak, J.

    2011-09-15

    We present 10 new transit light curves of the transiting hot Jupiter HAT-P-13b, obtained during two observational seasons by three different telescopes. When combined with 12 previously published light curves, we have a sample consisting of 22 transit light curves, spanning 1041 days across four observational seasons. We use this sample to examine the recently observed large-amplitude transit timing variations (TTVs) by Pal et al. and give refined system parameters. We find that the transit times are consistent with a linear ephemeris, with the exception of a single transit time, from UT 2009 November 5, for which the measured mid-transit time significantly deviates from our linear ephemeris. The nature of this deviation is not clear, and the rest of the data do not show any significant TTVs.

  9. Synthetic light-curve analysis of the very short period binaries TY Bootis, AD Cancri, and V523 Cassiopeiae

    SciTech Connect

    Samec, R.G.; Van Hamme, W.; Bookmyer, B.B. Clemson Univ., SC South Carolina Univ., Conway Florida International Univ., Miami )

    1989-12-01

    New photometric observations of TY Boo, AD Cnc, and V523 Cas are subjected to synthetic light-curve analyses using the Wilson-Devinney code. Solutions for each of the systems, and the several competing theories of contact binary structure are discussed in light of the results. Both AD Cnc and V523 Cas are modeled with subluminous regions, and the resulting starspot parameters are reported. A simultaneous solution of the B, V light curves and the radial-velocity curves of V523 Cas is presented. Spectroscopic and photometric mass ratios were found to be discordant for both TY Boo and V523 Cas. However, recent spectroscopic work by Groissman seems to remove the discordancy for TY Boo. Absolute parameters are derived for V523 Cas. 43 refs.

  10. Synthetic light-curve analysis of the very short period binaries TY Bootis, AD Cancri, and V523 Cassiopeiae

    NASA Astrophysics Data System (ADS)

    Samec, Ronald G.; van Hamme, Walter; Bookmyer, Beverly B.

    1989-12-01

    New photometric observations of TY Boo, AD Cnc, and V523 Cas are subjected to synthetic light-curve analyses using the Wilson-Devinney code. Solutions for each of the systems, and the several competing theories of contact binary structure are discussed in light of the results. Both AD Cnc and V523 Cas are modeled with subluminous regions, and the resulting starspot parameters are reported. A simultaneous solution of the B, V light curves and the radial-velocity curves of V523 Cas is presented. Spectroscopic and photometric mass ratios were found to be discordant for both TY Boo and V523 Cas. However, recent spectroscopic work by Groissman seems to remove the discordancy for TY Boo. Absolute parameters are derived for V523 Cas.

  11. Toward Characterization of the Type IIP Supernova Progenitor Population: A Statistical Sample of Light Curves from Pan-STARRS1

    NASA Astrophysics Data System (ADS)

    Sanders, N. E.; Soderberg, A. M.; Gezari, S.; Betancourt, M.; Chornock, R.; Berger, E.; Foley, R. J.; Challis, P.; Drout, M.; Kirshner, R. P.; Lunnan, R.; Marion, G. H.; Margutti, R.; McKinnon, R.; Milisavljevic, D.; Narayan, G.; Rest, A.; Kankare, E.; Mattila, S.; Smartt, S. J.; Huber, M. E.; Burgett, W. S.; Draper, P. W.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Wainscoat, R. J.; Waters, C.

    2015-02-01

    In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4 yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as "Type IIL" SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of <~ 0.2 mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.

  12. Surface Patterning of Ceramic Phosphor Plate for Light Extraction

    NASA Astrophysics Data System (ADS)

    Mao, An

    Light-Emitting Diodes (LEDs) are expected to replace traditional lighting sources in the near future due to their energy-efficiency, optical design flexibility and good reliability over traditional lighting sources. III-V nitride blue LEDs with powdered phosphors have been used commercially to get white emission. However, due to scattering losses, thermal issues as well as the surface reactivity with common encapsulants, LEDs fabricated with powdered phosphors have limitations in achieving high luminous efficacy, high chromatic stability and good color-rendering properties. Solid, non-scattering phosphors could avoid many of these limitations, but issues of light extraction and coupling of excitation radiation to the phosphor require development to insure efficient operation. Photonic crystal structures fabricated into or on non-scattering phosphors can be used to address these challenges. In this thesis, a lift-off process with bilayer resist system is developed to create nanopatterns. A photonic crystal structure is fabricated by low cost molecular transfer lithography (MxL) with bi-layer resist system on non-scattering phosphor plate used for white emission to increase the extraction efficiency. In Chapter 1, some basic background concepts which appear frequently in this thesis are introduced. These concepts include the Stokes shift and backscattering phenomenon for powder phosphors as well as non-scattering phosphors. In Chapter 2, a non-scattering single crystal phosphor with a patterned surface is proposed to replace the powdered phosphors used for color converted LEDs. A non-scattering phosphor YAG:Ce ceramic phosphor plate (CPP) patterned with TiO2 photonic crystal structure is selected for convenience to demonstrate the concept. The physical origin of light extraction of the proposed structure is discussed. The simulation principles and results are discussed in this chapter to find the optimized photonic crystal structure for light extraction. In Chapter 3

  13. The Historical Record of η Carinae I. The Visual Light Curve, 1595-2000

    NASA Astrophysics Data System (ADS)

    Frew, David J.

    2004-12-01

    Eta Carinae is one of the most massive luminous blue variable stars (LBVs) in the Milky Way. Here a new historic light curve is presented which supersedes earlier works, and is based almost completely on a critically-assessed compilation of primary sources. Only observations made relative to unambiguously identified comparison stars are used and, unlike earlier efforts, the data are reduced homogenously to the V scale. The light curve is extended through to the present using a database of photoelectric and CCD measures compiled elsewhere, and totals about 1500 points, including about 500 before 1950. A primary motivation for this work is to provide a definitive light curve for eta Car over the maximum time-line possible, to be used as a resource for further investigation.The observation by Keyser leads to an inferred magnitude of mV = 3.5 ± 0.5 in 1595-96, while new magnitude estimates for 1677, 1687, and 1752 are mV = 3.3 ± 0.3, mV = 3.4 ±0.4, and mV = 2.3 ± 0.3 respectively. Contrary to accepted wisdom, there is only weak observational evidence to show that eta Car was varying markedly prior to the Great Eruption beginning in the 1830s, though this is not ruled out. A slow rise from mV approx. 3.5 at the start of the 17th century to mV approx. 2.3 around 1750, with a further slow brightening to around 1830, is also a tenable hypothesis. There is, however, no evidence for a long-duration eruption having occurred between 1500 and1800. The well-known Great Eruption commenced in 1837 and lasted until at least 1856. The brightness declined rapidly between 1858 and 1868, before a small brightening or plateau occurred in 1869-71; there is some evidence for a change in the spectrum in Feb 1871. The Lesser Eruption occurred in 1887-95, the onset of which was within two months of a predicted spectroscopic event, suggesting a causal link. A preliminary look at the photographic magnitudes suggests a marked change in colour index during the Lesser Eruption. Another

  14. VizieR Online Data Catalog: BAT6 sample optical and X-ray light curves (Melandri+, 2014)

    NASA Astrophysics Data System (ADS)

    Melandri, A.; Covino, S.; Rogantini, D.; Salvaterra, R.; Sbarufatti, B.; Bernardini, M. G.; Campana, S.; D'Avanzo, P.; D'Elia, V.; Fugazza, D.; Ghirlanda, G.; Ghisellini, G.; Nava, L.; Vergani, S. D.; Tagliaferri, G.

    2014-03-01

    We followed the classification scheme described in Margutti et al. (2013, Cat. J/MNRAS/428/729/) that divided the light curves in four main classes: class 0 for events decaying with simple power-law; class Ia (Ib) for a smooth broken power-law that goes from a shallower (steeper) to a steeper (shallower) decay; class IIa or IIb for events that display steep-shallow-steep (canonical) or shallow-steep-shallow decays respectively; and finally, class III for those events that show a late-time break in their light curves. (6 data files).

  15. Unlocking the secrets of supernovae through their light curves, spectra & polarization

    NASA Astrophysics Data System (ADS)

    Hillier, D. John; Dessart, Luc; Li, Chendong

    2013-06-01

    Utilizing the radiative transfer code CMFGEN, we have undertaken time-dependent radiative transfer calculations that compute the light curve and spectra for Type Ia, Ib, Ic, and II supernovae (SNe) through the photospheric and nebular phases. The non-LTE calculations allow for a multitude of atomic processes (bound-bound, bound-free, free-free, collisional, charge exchange, and Penning ionization) and for non-thermal excitation and ionization from non-thermal electrons created by the degradation in energy of high-energy (˜1 MeV) gamma-rays. The proper inclusion of all these processes requires a vast amount of atomic data. Not all the atomic data is available, and the quality of the available atomic data varies considerably. We have confirmed the results of Utrobin and Chugai (2005) that time dependent terms must be included in the statistical equilibrium equations in order to model the Hα evolution of SN 1987A, shown that time dependent terms influence other spectral features, and shown that these conclusions also apply to the modeling of Type II SNe in general. The inclusion of non-thermal processes has allowed us to model Hα and He I emission in Type II SNe into the nebular phase, and to model the He I emission in Type Ib and Ic SNe. Our calculations show that the He deficiency in Ic SNe is unlikely to be real - instead, the absence of He I on SNe Ic spectra is more likely related to inefficient excitation of He Iions. Simply by varying the amount of mixing we are able to create spectra of Type Ib and Ic SNe using the SAME progenitor model. Based on a new grid of SNe Ib/c models, we confirm previous findings that the typically fast-rising narrow-peak fast-declining SNe Ib/c light curves imply ejecta masses ≲5M, favoring intermediate-mass massive stars in interacting binaries. We are successfully applying CMFGEN to model Type Ia SNe, and are currently exploring the role of mixing and non-thermal processes in these SNe. We highlight the differences between the

  16. MODELING THE LIGHT CURVE OF THE TRANSIENT SCP06F6

    SciTech Connect

    Chatzopoulos, Emmanouil; Wheeler, J. Craig; Vinko, J. E-mail: wheel@astro.as.utexas.ed

    2009-10-20

    We consider simple models based on core collapse or pair-formation supernovae (SNe) to account for the light curve of the transient SCP06F6. A radioactive decay diffusion model provides estimates of the mass of the required radioactive nickel and the ejecta as functions of the unknown redshift. An opacity change such as by dust formation or a recombination front may account for the rapid decline from maximum. Within this class of model, the redshift must be less than z approx 1 or the nickel mass would exceed the total mass of the ejecta; the radiated energy would exceed the kinetic energy, and kinematic and photometric estimates of the radius would disagree. We particularly investigate two specific redshifts: z = 0.143, for which Gaensicke et al. have proposed that the unidentified broad absorption features in the spectrum of SCP06F6 are C{sub 2} Swan bands, and z = 0.57 based on a crude agreement with the Ca H and K and UV iron-peak absorption features that are characteristic of SNe of various types. For the lower redshift, we obtain a nickel mass of 0.3 M {sub sun} and an ejected envelope mass of approx 38 M {sub sun}, while for the latter case we find 4.8 M {sub sun} and 20 M {sub sun}, respectively, for fiducial parameters. The kinetic energy of the ejecta, while dependent on uncertain parameters, is generally large, approx10{sup 52} erg, throughout this range of redshift. The ejected masses and kinetic energies are smaller for a more tightly constrained model invoking envelope recombination. We also discuss the possibilities of circumstellar matter (CSM) shell diffusion and shock interaction models. In general, optically thick CSM diffusion models can fit the data with the underlying energy coming from an energetic buried SN. Models in which the CSM is of lower density so that the shock energy is both rapidly thermalized and radiated tend not to be self-consistent. We suggest that a model of SCP06F6 worth further exploration is one in which the redshift is

  17. Investigation of the energy dependence of the orbital light curve in LS 5039

    NASA Astrophysics Data System (ADS)

    Chang, Z.; Zhang, S.; Ji, L.; Chen, Y. P.; Kretschmar, P.; Kuulkers, E.; Collmar, W.; Liu, C. Z.

    2016-08-01

    LS 5039 is so far the best studied γ-ray binary system at multi-wavelength energies. A time resolved study of its spectral energy distribution (SED) shows that above 1 keV its power output is changing along its binary orbit as well as being a function of energy. To disentangle the energy dependence of the power output as a function of orbital phase, we investigated in detail the orbital light curves as derived with different telescopes at different energy bands. We analysed the data from all existing INTEGRAL/IBIS/ISGRI observations of the source and generated the most up-to-date orbital light curves at hard X-ray energies. In the γ-ray band, we carried out orbital phase-resolved analysis of Fermi-LAT data between 30 MeV and 10 GeV in 5 different energy bands. We found that, at ≲100 MeV and ≳1 TeV the peak of the γ-ray emission is near orbital phase 0.7, while between ˜100 MeV and ˜1 GeV it moves close to orbital phase 1.0 in an orbital anti-clockwise manner. This result suggests that the transition region in the SED at soft γ-rays (below a hundred MeV) is related to the orbital phase interval of 0.5-1.0 but not to the one of 0.0-0.5, when the compact object is "behind" its companion. Another interesting result is that between 3 and 20 GeV no orbital modulation is found, although Fermi-LAT significantly (˜18σ) detects LS 5039. This is consistent with the fact that at these energies, the contributions to the overall emission from the inferior conjunction phase region (INFC, orbital phase 0.45 to 0.9) and from the superior conjunction phase region (SUPC, orbital phase 0.9 to 0.45) are equal in strength. At TeV energies the power output is again dominant in the INFC region and the flux peak occurs at phase ˜0.7.

  18. A Theoretical Light-Curve Model for the 1999 Outburst of U Scorpii

    NASA Astrophysics Data System (ADS)

    Hachisu, Izumi; Kato, Mariko; Kato, Taichi; Matsumoto, Katsura

    2000-01-01

    A theoretical light curve for the 1999 outburst of U Scorpii is presented in order to obtain various physical parameters of the recurrent nova. Our U Sco model consists of a very massive white dwarf (WD) with an accretion disk and a lobe-filling, slightly evolved, main-sequence star (MS). The model includes a reflection effect by the companion and the accretion disk together with a shadowing effect on the companion by the accretion disk. The early visual light curve (with a linear phase of t~1-15 days after maximum) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit (MWD=1.37+/-0.01 Msolar), in which optically thick winds blowing from the WD play a key role in determining the nova duration. The ensuing plateau phase (t~15-30 days) is also reproduced by the combination of a slightly irradiated MS and a fully irradiated flaring-up disk with a radius ~1.4 times the Roche lobe size. The cooling phase (t~30-40 days) is consistent with a low-hydrogen content of X~0.05 of the envelope for the 1.37 Msolar WD. The best-fit parameters are the WD mass of MWD~1.37 Msolar, the companion mass of MMS~1.5 Msolar (0.8-2.0 Msolar is acceptable), the inclination angle of the orbit (i~80deg), and the flaring-up edge, the vertical height of which is ~0.30 times the accretion disk radius. The duration of the strong wind phase (t~0-17 days) is very consistent with the BeppoSAX supersoft X-ray detection at t~19-20 days because supersoft X-rays are self-absorbed by the massive wind. The envelope mass at the peak is estimated to be ~3×10-6 Msolar, which is indicates an average mass accretion rate of ~2.5×10-7 Msolar yr-1 during the quiescent phase between 1987 and 1999. These quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.

  19. Assessment of the Large Meteoroid Characteristics from the Light Curves Obtained by Satellite and Groundbased Networks

    NASA Astrophysics Data System (ADS)

    Nemtchinov, I. V.; Spalding, R. E.; Jacobs, C.; Tagliaferri, E.; Artem'eva, N. A.; Golub, A. P.; Kosarev, I. B.; Popova, O. P.; Svettsov, V. V.; Shuvalov, V. V.

    1995-09-01

    A relatively small number of satellites at high altitude orbits (20,000 km or higher) provide coverage of most of the Earth's surface. It is possible to have essentially continuous, day and night, all weather coverage over the entire surface of the Earth [1]. Space based infrared sensors have detected over 200 bright flashes in the atmosphere since 1972. Average number of flashes per year is 30. In addition optical sensors have detected 16 light curves in the visible (mainly during the last year). These bright flashes have been caused by explosive disintegration of large meteoroids in the atmosphere. Information from IR sensors and light curves have been analyzed. This analysis give important information on the energy - frequency distribution of the impacting meteoroids, their sizes, strengths and even composition. For an example, preatmospheric kinetic energies of meteoroids which caused 15 April 1988, 1 October 1990, 4 October 1991 and 1 February 1994 events are 8-9, 5-8, 1-2, and 40 kt TNT respectively. Three of them were stones or chondrites and deposited their energy at the altitudes of 30 to 45 km. Last one was probably an iron (initial velocity 24 km/sec, angle of trajectory inclination 45 degrees [2]) and penetrated to the altitude of about 20 km (strength of about 100 Mdyn/cm^2). Radiation-hydrodynamic 1D, 2D and even 3D numerical simulations [3,4] of the meteoroid flight in the atmosphere for various sizes, velocities, heights of flights have been conducted and used in the analysis. They were based on the detailed tables of spectral opacities for hot air and ablated material for various wavelengths, temperatures, densities, and composition (iron, stone, chondrite and cometary material). Radiation heat transfer, ablation, fragmentation, and dispersion of fragments have been taken into account. Detailed spectra of the emitted radiation has been obtained. Data from satellite network has been compared with the data from ground based photographic networks and

  20. Weathering Patterns of Ignitable Liquids with the Advanced Distillation Curve Method

    PubMed Central

    Bruno, Thomas J; Allen, Samuel

    2013-01-01

    One can take advantage of the striking similarity of ignitable liquid vaporization (or weathering) patterns and the separation observed during distillation to predict the composition of residual compounds in fire debris. This is done with the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. Analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin layer chromatography, FTIR, Karl Fischer coulombic titrimetry, refractometry, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. We have applied this method on product streams such as finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oils streams (used automotive and transformer oils). In this paper, we present results on a variety of ignitable liquids that are not commodity fuels, chosen from the Ignitable Liquids Reference Collection (ILRC). These measurements are assembled into a preliminary database. From this selection, we discuss the significance and forensic application of the temperature data grid and the composition explicit data channel of the ADC. PMID:26401423

  1. Weathering Patterns of Ignitable Liquids with the Advanced Distillation Curve Method.

    PubMed

    Bruno, Thomas J; Allen, Samuel

    2013-01-01

    One can take advantage of the striking similarity of ignitable liquid vaporization (or weathering) patterns and the separation observed during distillation to predict the composition of residual compounds in fire debris. This is done with the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. Analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin layer chromatography, FTIR, Karl Fischer coulombic titrimetry, refractometry, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. We have applied this method on product streams such as finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oils streams (used automotive and transformer oils). In this paper, we present results on a variety of ignitable liquids that are not commodity fuels, chosen from the Ignitable Liquids Reference Collection (ILRC). These measurements are assembled into a preliminary database. From this selection, we discuss the significance and forensic application of the temperature data grid and the composition explicit data channel of the ADC. PMID:26401423

  2. VizieR Online Data Catalog: Occultation lights curves (Herald+ 2016)

    NASA Astrophysics Data System (ADS)

    Herald, Dave; Murrumbateman; Breit, Derek; Dunham, David; Frappa, Eric; Gault, Dave; George, Tony; Hayamizu, Tsutomu; Loader, Brian; Manek, Jan; Miyashita, Kazuhisa; Pavlov, Hristo; Preston, Steve; Soma, Mitsuru; Talbot, John; Timerson, Brad

    Lunar occultation light curves have been recorded since the mid-20th century using high-speed photomultipliers. Running at high cadence for high angular resolution, such recordings were usually made on large telescopes and limited to the brighter stars - and were not large in number. While a small number of video recordings of lunar and asteroidal occultations were made from about 1980, they became common from about the year 2000, when inexpensive low-light security cameras became available. As of 2016, almost all lunar and asteroidal occultation observations are recorded using video, with the video recording being measured using software packages such as Limovie [http://astro-limovie.info/limovie/limovie_en.html], and Tangra [http://www.hristopavlov.net/Tangra3/]. As a result, light curves are now routinely generated for almost all lunar and asteroidal occultation observations, especially those coordinated through the International Occultation Timing Association and related organisations around the world. This is resulting in large numbers of occultation light curves being obtained each year - albeit with some limitations on time resolution and signal-to-noise ratios. As of 2016, video recordings are mainly made using one or other of the two international video standards - NTSC, or PAL. Both NTSC and PAL use an interlaced video scan, whereby each frame of the video is comprised of two interlaced, time-sequential, fields. The frame rate of an NTSC system is 29.97 frames/sec (59.94 fields/sec), while that for PAL is 25 frames/sec ( 50 fields/sec). Consistent with broadcast television standards, the majority of video cameras used for recording occultations use 8-bit CCD's. However some video recordings are made using progressive scan, 12 to 16-bit digital video systems. For lunar occultations, the temporal resolution is governed by a combination of the frame (or field) rate of the video recording, and the rate of motion of the moon. The typical topocentric motion of

  3. VizieR Online Data Catalog: Occultation lights curves (Herald+ 2016)

    NASA Astrophysics Data System (ADS)

    Herald, Dave; Breit, Derek; Dunham, David; Frappa, Eric; Gault, Dave; George, Tony; Hayamizu, Tsutomu; Loader, Brian; Manek, Jan; Miyashita, Kazuhisa; Pavlov, Hristo; Preston, Steve; Soma, Mitsuru; Talbot, John; Timerson, Brad

    Lunar occultation light curves have been recorded since the mid-20th century using high-speed photomultipliers. Running at high cadence for high angular resolution, such recordings were usually made on large telescopes and limited to the brighter stars - and were not large in number. While a small number of video recordings of lunar and asteroidal occultations were made from about 1980, they became common from about the year 2000, when inexpensive low-light security cameras became available. As of 2016, almost all lunar and asteroidal occultation observations are recorded using video, with the video recording being measured using software packages such as Limovie [http://astro-limovie.info/limovie/limovie_en.html], and Tangra [http://www.hristopavlov.net/Tangra3/]. As a result, light curves are now routinely generated for almost all lunar and asteroidal occultation observations, especially those coordinated through the International Occultation Timing Association and related organisations around the world. This is resulting in large numbers of occultation light curves being obtained each year - albeit with some limitations on time resolution and signal-to-noise ratios. As of 2016, video recordings are mainly made using one or other of the two international video standards - NTSC, or PAL. Both NTSC and PAL use an interlaced video scan, whereby each frame of the video is comprised of two interlaced, time-sequential, fields. The frame rate of an NTSC system is 29.97 frames/sec (59.94 fields/sec), while that for PAL is 25 frames/sec ( 50 fields/sec). Consistent with broadcast television standards, the majority of video cameras used for recording occultations use 8-bit CCD's. However some video recordings are made using progressive scan, 12 to 16-bit digital video systems. For lunar occultations, the temporal resolution is governed by a combination of the frame (or field) rate of the video recording, and the rate of motion of the moon. The typical topocentric motion of

  4. VizieR Online Data Catalog: V light curve of SDSS J080434.20+510349.2 (Zharikov+, 2008)

    NASA Astrophysics Data System (ADS)

    Zharikov, S. V.; Tovmassian, G. H.; Neustroev, V. V.; Michel, R.; Zurita, C.; Echevarria, J.; Bikmaev, I. F.; Pavlenko, E. P.; Jeon, Y.-B.; Valyavin, G. G.; Aviles, A.

    2008-05-01

    We observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 to study the origin of long-term variability found in its light curve. Multi-longitude, time-resolved, photometric observations were acquired to analyze this uncommon behavior, which has been found in two newly discovered CVs. This study of SDSS J080434.20+510349.2 concerns primarily the understanding of the nature of the observed, double-humped, light curve and its relation to a cyclic brightening that occurs during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, about 0.4mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07mag and a periodicity of 42.48min, which is half of the orbital period of the system. We observed in addition two "mini-outbursts" of the system of up to 0.6mag, which have a duration of about 4days each. The "mini-outburst" has a symmetric profile and is repeated in approximately every 32days. Subsequent monitoring of the system shows a cyclical behavior of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2. (2 data files).

  5. Fringe Pattern of the PEP-II Synchrotron-Light Interferometers

    SciTech Connect

    Fisher, Alan; /SLAC

    2005-09-19

    Synchrotron-light interferometry is used to measure the vertical beam sizes in the high-energy and low-energy rings (HER and LER) of the PEP-II B Factory at SLAC. Light from a point in a dipole magnet is diffracted by two slits and then imaged onto a CCD camera. A curve fitting algorithm matches the measured interference fringes to a calculated pattern that includes the effect on the modulation depth of the fringes due to both the small but nonzero source size and the narrow bandpass of the optical filter. These formulas are derived here. Next, an additional focusing term from the primary mirror in the vacuum chamber is considered. The mirror needs extensive cooling due to the intense fan of synchrotron x-rays and is likely to have a slight stress-induced curvature, which must be considered to determine the true source size.

  6. Optical Transients Powered by Magnetars: Dynamics, Light Curves, and Transition to the Nebular Phase

    NASA Astrophysics Data System (ADS)

    Wang, Ling-Jun; Wang, S. Q.; Dai, Z. G.; Xu, Dong; Han, Yan-Hui; Wu, X. F.; Wei, Jian-Yan

    2016-04-01

    Millisecond magnetars can be formed via several channels: core collapse of massive stars, accretion-induced collapse of white dwarfs (WDs), double WD mergers, double neutron star (NS) mergers, and WD-NS mergers. Because the mass of ejecta from these channels could be quite different, their light curves are also expected to be diverse. We evaluate the dynamic evolution of optical transients powered by millisecond magnetars. We find that the magnetar with a short spin-down timescale converts its rotational energy mostly into the kinetic energy of the transient, while the energy of a magnetar with a long spin-down timescale goes into radiation of the transient. This leads us to speculate that hypernovae could be powered by magnetars with short spin-down timescales. At late times the optical transients will gradually evolve into a nebular phase because of the photospheric recession. We treat the photosphere and nebula separately because their radiation mechanisms are different. In some cases the ejecta could be light enough that the magnetar can accelerate it to a relativistic speed. It is well known that the peak luminosity of a supernova (SN) occurs when the luminosity is equal to the instantaneous energy input rate, as shown by Arnett. We show that photospheric recession and relativistic motion can modify this law. The photospheric recession always leads to a delay of the peak time {t}{pk} relative to the time {t}× at which the SN luminosity equals the instantaneous energy input rate. Relativistic motion, however, may change this result significantly.

  7. Characterizing high-energy light curves of Fermi/LatGRBs - Oral Presentation

    SciTech Connect

    Gillette, Jarred

    2015-08-23

    A systematic analysis of the light curves of Gamma-Ray Burst (GRBs) with redshift and detected at high-energy (> 100 MeV) by Fermi/LAT has never been done before our work, because there were only a handful of detections. Now we have 20 of those, which we can use to characterize the GRBs in their rest frame. We compared a characteristic decay times Tc of GRBs with redshifts using the new "Pass8" data, and used a Crystal Ball function to parametrize GRB characteristics. An unexpected anti-correlation between Tc and the peak flux was observed. This means that brighter peaked GRBs have shorter durations. There is also no correlation between Tc and the decay index, which is one of the competing hypothesis on the origin of the high-energy emission. We did not observe any bimodality, which is seen in GRBs at lower energies.

  8. AN X-RAY AND OPTICAL LIGHT CURVE MODEL OF THE ECLIPSING SYMBIOTIC BINARY SMC3

    SciTech Connect

    Kato, Mariko; Hachisu, Izumi; Mikolajewska, Joanna

    2013-01-20

    Some binary evolution scenarios for Type Ia supernovae (SNe Ia) include long-period binaries that evolve to symbiotic supersoft X-ray sources in their late stage of evolution. However, symbiotic stars with steady hydrogen burning on the white dwarf's (WD) surface are very rare, and the X-ray characteristics are not well known. SMC3 is one such rare example and a key object for understanding the evolution of symbiotic stars to SNe Ia. SMC3 is an eclipsing symbiotic binary, consisting of a massive WD and red giant (RG), with an orbital period of 4.5 years in the Small Magellanic Cloud. The long-term V light curve variations are reproduced as orbital variations in the irradiated RG, whose atmosphere fills its Roche lobe, thus supporting the idea that the RG supplies matter to the WD at rates high enough to maintain steady hydrogen burning on the WD. We also present an eclipse model in which an X-ray-emitting region around the WD is almost totally occulted by the RG swelling over the Roche lobe on the trailing side, although it is always partly obscured by a long spiral tail of neutral hydrogen surrounding the binary in the orbital plane.

  9. Pluto and Charon Color Light Curves from New Horizons on Approach

    NASA Astrophysics Data System (ADS)

    Ennico, Kimberly; Howett, C. J. A.; Olkin, C. B.; Reuter, D. C.; Buratti, B. J.; Buie, M. W.; Grundy, W. M.; Parker, A. H.; Zangari, A. M.; Binzel, R. P.; Cook, J. C.; Cruikshank, D. P.; Dalle Ore, C. M.; Earle, A. M.; Jennings, D. E.; Linscott, I. R.; Parker, J. Wm.; Protopapa, S.; Singer, K. N.; Spencer, J. R.; Stern, S. A.; Tsang, C. C. C.; Verbiscer, A. J.; Weaver, H. A.; Young, L. A.

    2015-11-01

    On approach to the Pluto system, New Horizons’ Ralph Instrument’s Multicolor Visible Imaging Camera (MVIC) observed Pluto and Charon, spatially separated, between April 9 and June 23, 2015. In this period, Pluto and Charon were observed to transition from unresolved objects to resolved and their integrated disk intensities were measured in four MVIC filters: blue (400-550 nm), red (540-700 nm), near-infrared (780-975 nm), and methane (860-910 nm). The measurement suite sampled the bodies over all longitudes. We will present the color rotational light curves for Pluto and Charon and compare them to previous (Buie, M. et al. 2010 AJ 139, 1117; Buratti, B.J. et al 2015 ApJ 804, L6) and concurrent ground-based BVR monitoring. We will also compare these data to color images of the encounter hemisphere taken during New Horizons’ July 14, 2015 Pluto and Charon flyby, as this data set provides a unique bridge between Pluto & Charon as viewed as astronomical targets versus the complex worlds that early data from New Horizons has revealed them to be. This work was supported by NASA’s New Horizons project.

  10. The nature of very faint X-ray binaries: hints from light curves

    NASA Astrophysics Data System (ADS)

    Heinke, C. O.; Bahramian, A.; Degenaar, N.; Wijnands, R.

    2015-03-01

    Very faint X-ray binaries (VFXBs), defined as having peak luminosities LX of 1034-1036 erg s-1, have been uncovered in significant numbers, but remain poorly understood. We analyse three published outburst light curves of two transient VFXBs using the exponential and linear decay formalism of King & Ritter. The decay time-scales and brink luminosities suggest orbital periods of order 1 h. We review various estimates of VFXB properties, and compare these with suggested explanations of the nature of VFXBs. We suggest that: (1) VFXB outbursts showing linear decays might be explained as partial drainings of the disc of `normal' X-ray transients, and many VFXB outbursts may belong to this category; (2) VFXB outbursts showing exponential decays are best explained by old, short-period systems involving mass transfer from a low-mass white dwarf or brown dwarf; (3) persistent (or quasi-persistent) VFXBs, which maintain an LX of 1034-1035 erg s-1 for years, may be explained by magnetospheric choking of the accretion flow in a propeller effect, permitting a small portion of the flow to accrete on to the neutron star's surface. We thus predict that (quasi-) persistent VFXBs may also be transitional millisecond pulsars, turning on as millisecond radio pulsars when their LX drops below 1032 erg s-1.

  11. Characterizing high-energy light curves of Fermi/Lat GRBs

    SciTech Connect

    Gillette, Jarred

    2015-08-21

    A systematic analysis of the light curves of Gamma-Ray Burst (GRBs) with redshift and detected at high-energy (> 100 MeV) by Fermi/LAT has never been done before our work, because there were only a handful of detections. Now we have 20 of those, which we can use to characterize the GRBs in their rest frame. We compared a characteristic decay times Tc of GRBs with redshifts using the new “Pass 8” data, and used a Crystal Ball function to parametrize GRB characteristics. An unexpected anti-correlation between Tc and the peak flux was observed. This means that brighter peaked GRBs have shorter durations. There is also no correlation between the Tc and the decay index, which makes the anti-correlation with brightness more clear. This results appears to be consistent with the External Shock model, which is one of the competing hypothesis on the origin of the high-energy emission. We did not observe any bimodality, which is seen in GRBs at lower energies.

  12. IRTF/SPeX Observations of the Unusual Kepler Light Curve System KIC8462852

    NASA Astrophysics Data System (ADS)

    Lisse, C. M.; Sitko, M. L.; Marengo, M.

    2015-12-01

    We have utilized the NASA/IRTF 3 m SpeX instrument’s high-resolution spectral mode to observe and characterize the near-infrared flux emanating from the unusual Kepler light curve system KIC 8462852. By comparing the resulting 0.8–4.2 μm spectrum to a mesh of model photospheric spectra, the 6 emission line analyses of the Rayner et al. catalog, and the 25 system collections of debris disks we have observed to date using SpeX under the Near InfraRed Debris disk Survey, we have been able to additionally characterize the system. Within the errors of our measurements, this star looks like a normal solar abundance main-sequence F1V to F3V dwarf star without any obvious traces of significant circumstellar dust or gas. Using Connelley & Greene’s emission measures, we also see no evidence of significant ongoing accretion onto the star nor any stellar outflow away from it. Our results are inconsistent with large amounts of static close-in obscuring material or the unusual behavior of a YSO system, but are consistent with the favored episodic giant comet models of a Gyr old stellar system favored by Boyajian et al. We speculate that KIC 8462852, like the ∼1.4 Gyr old F2V system η Corvi, is undergoing a late heavy bombardment, but is only in its very early stages.

  13. Early-time polarized optical light curve of GRB 131030A

    NASA Astrophysics Data System (ADS)

    King, O. G.; Blinov, D.; Giannios, D.; Papadakis, I.; Angelakis, E.; Baloković, M.; Fuhrmann, L.; Hovatta, T.; Khodade, P.; Kiehlmann, S.; Kylafis, N.; Kus, A.; Myserlis, I.; Modi, D.; Panopoulou, G.; Papamastorakis, I.; Pavlidou, V.; Pazderska, B.; Pazderski, E.; Pearson, T. J.; Rajarshi, C.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Zensus, J. A.

    2014-11-01

    We report the polarized optical light curve of a gamma-ray burst afterglow obtained using the RoboPol instrument. Observations began 655 s after the initial burst of gamma-rays from GRB 131030A, and continued uninterrupted for 2 h. The afterglow displayed a low, constant fractional linear polarization of p = (2.1 ± 1.6) per cent throughout, which is similar to the interstellar polarization measured on nearby stars. The optical brightness decay is consistent with a forward-shock propagating in a medium of constant density, and the low polarization fraction indicates a disordered magnetic field in the shock front. This supports the idea that the magnetic field is amplified by plasma instabilities on the shock front. These plasma instabilities produce strong magnetic fields with random directions on scales much smaller than the total observable region of the shock, and the resulting randomly-oriented polarization vectors sum to produce a low net polarization over the total observable region of the shock.

  14. CfAIR2: Near-infrared Light Curves of 94 Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Friedman, Andrew S.; Wood-Vasey, W. M.; Marion, G. H.; Challis, Peter; Mandel, Kaisey S.; Bloom, Joshua S.; Modjaz, Maryam; Narayan, Gautham; Hicken, Malcolm; Foley, Ryan J.; Klein, Christopher R.; Starr, Dan L.; Morgan, Adam; Rest, Armin; Blake, Cullen H.; Miller, Adam A.; Falco, Emilio E.; Wyatt, William F.; Mink, Jessica; Skrutskie, Michael F.; Kirshner, Robert P.

    2015-09-01

    CfAIR2 is a large, homogeneously reduced set of near-infrared (NIR) light curves (LCs) for Type Ia supernovae (SNe Ia) obtained with the 1.3 m Peters Automated InfraRed Imaging TELescope. This data set includes 4637 measurements of 94 SNe Ia and 4 additional SNe Iax observed from 2005 to 2011 at the Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona. CfAIR2 includes {{JHK}}s photometric measurements for 88 normal and 6 spectroscopically peculiar SN Ia in the nearby universe, with a median redshift of z ˜ 0.021 for the normal SN Ia. CfAIR2 data span the range from -13 days to +127 days from B-band maximum. More than half of the LCs begin before the time of maximum, and the coverage typically contains ˜13-18 epochs of observation, depending on the filter. We present extensive tests that verify the fidelity of the CfAIR2 data pipeline, including comparison to the excellent data of the Carnegie Supernova Project. CfAIR2 contributes to a firm local anchor for SN cosmology studies in the NIR. Because SN Ia are more nearly standard candles in the NIR and are less vulnerable to the vexing problems of extinction by dust, CfAIR2 will help the SN cosmology community develop more precise and accurate extragalactic distance probes to improve our knowledge of cosmological parameters, including dark energy and its potential time variation.

  15. Temporal Deconvolution Study of Long and Short Gamma-Ray Burst Light Curves

    NASA Astrophysics Data System (ADS)

    Bhat, P. N.; Briggs, Michael S.; Connaughton, Valerie; Kouveliotou, Chryssa; van der Horst, Alexander J.; Paciesas, William; Meegan, Charles A.; Bissaldi, Elisabetta; Burgess, Michael; Chaplin, Vandiver; Diehl, Roland; Fishman, Gerald; Fitzpatrick, Gerard; Foley, Suzanne; Gibby, Melissa; Giles, Misty M.; Goldstein, Adam; Greiner, Jochen; Gruber, David; Guiriec, Sylvain; von Kienlin, Andreas; Kippen, Marc; McBreen, Sheila; Preece, Robert; Rau, Arne; Tierney, Dave; Wilson-Hodge, Colleen

    2012-01-01

    The light curves of gamma-ray bursts (GRBs) are believed to result from internal shocks reflecting the activity of the GRB central engine. Their temporal deconvolution can reveal potential differences in the properties of the central engines in the two populations of GRBs which are believed to originate from the deaths of massive stars (long) and from mergers of compact objects (short). We present here the results of the temporal analysis of 42 GRBs detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope. We deconvolved the profiles into pulses, which we fit with lognormal functions. The distributions of the pulse shape parameters and intervals between neighboring pulses are distinct for both burst types and also fit with lognormal functions. We have studied the evolution of these parameters in different energy bands and found that they differ between long and short bursts. We discuss the implications of the differences in the temporal properties of long and short bursts within the framework of the internal shock model for GRB prompt emission.

  16. Historical light curve and the 2016 outburst of the symbiotic star StHalpha 169

    NASA Astrophysics Data System (ADS)

    Munari, Ulisse; Graziani, Mauro; Jurdana-Sepic, Rajka

    2016-07-01

    Accurate BVRI optical photometry of StHa 169 has been collected during the period 2005-2016. It reveals two outbursts, in 2009 and 2016, both peaking at B=13.6. The mean brightness in quiescence was B=15.29. In response to the 2016 outburst, the integrated absolute flux of the emission lines increased by a factor of 7 for Balmer, 9 for HeI lines, and 4.5 for HeII 4686, the Balmer continuum turned into strong emission, and [NeV] 3526 and OVI Raman 6825 Ang emissions disappeared. We have reconstructed the 1897-1951 B-band light curve of StHa 169 from Harvard historical plates. On top of a slow decline from a large outburst, ending in 1916, several brightenings are visible. Two fast-evolving outbursts, separated by 510 days, occurred in 1934 and 1935, peaking at B=13.7. The brightness in quiescence was the same as we measured in 2005-2016.

  17. Spectrashift Exoplanet Transit Search Project: 40,000 Light Curves and Counting

    NASA Astrophysics Data System (ADS)

    Kaye, Thomas G.; Healy, David

    2009-05-01

    Spectrashift has recently branched out from its radial velocity work detecting exoplanets, and has now fully implemented an exoplanet transit search program. Junk Bond Observatory's 0.8 meter fully automated RC telescope has been engaged in this effort full-time since October of 2008. To date the search has examined more than 40,000 light curves. The Spectrashift strategy is to look at fewer but fainter stars putting this search into the magnitude range the majority of professional searches can not penetrate. Custom software was developed for the reduction pipeline to handle the volume of data. The software implements artificial intelligence algorithms to sort out the most likely candidates for human inspection at the end of the pipeline. To date the project has come up with several "triple hits" where a transit-like event has happened on three occasions. The Spectrashift team's ultimate goal is to include a network of non-professional telescopes around the world for 24 hour coverage of star fields. It is believed this is the first serious non-professional transit search effort.

  18. M DWARFS IN SLOAN DIGITAL SKY SURVEY STRIPE 82: PHOTOMETRIC LIGHT CURVES AND FLARE RATE ANALYSIS

    SciTech Connect

    Kowalski, Adam F.; Hawley, Suzanne L.; Hilton, Eric J.; Becker, Andrew C.; Sesar, Branimir; West, Andrew A.; Bochanski, John J.

    2009-08-15

    We present a flare rate analysis of 50,130 M dwarf light curves in Sloan Digital Sky Survey Stripe 82. We identified 271 flares using a customized variability index to search {approx}2.5 million photometric observations for flux increases in the u and g bands. Every image of a flaring observation was examined by eye and with a point-spread function-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of H{alpha} in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify eight as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type m dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with {delta}u {>=} 0.7 mag on stars with u < 22 is 1.3 flares hr{sup -1} deg{sup -2} but can vary significantly with the line of sight.

  19. M Dwarfs in Sloan Digital Sky Survey Stripe 82: Photometric Light Curves and Flare Rate Analysis

    NASA Astrophysics Data System (ADS)

    Kowalski, Adam F.; Hawley, Suzanne L.; Hilton, Eric J.; Becker, Andrew C.; West, Andrew A.; Bochanski, John J.; Sesar, Branimir

    2009-08-01

    We present a flare rate analysis of 50,130 M dwarf light curves in Sloan Digital Sky Survey Stripe 82. We identified 271 flares using a customized variability index to search ~2.5 million photometric observations for flux increases in the u and g bands. Every image of a flaring observation was examined by eye and with a point-spread function-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of Hα in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify eight as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type m dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with Δu >= 0.7 mag on stars with u < 22 is 1.3 flares hr-1 deg-2 but can vary significantly with the line of sight. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.

  20. The BVRI Light Curves And Period Analysis Of The Beta Lyrae System XX Leonis

    NASA Astrophysics Data System (ADS)

    Zasche, P.; Wolf, M.; Svoboda, P.

    2007-08-01

    The contact eclipsing binary system XX Leonis (P = 0.97 days, sp A8) has been analysed using the PHOEBE programme, based on the Wilson Devinney code. The BVRI light curves were obtained during spring 2006 using the 20-cm telescope and ST-7 CCD detector. The effective temperature of the primary component determined from the photometric analysis is T=(7889±61)K, the inclination of the orbit is i=(89.98±2.45)deg and the photometric mass ratio q=(0.41±0.01). Also the third body hypothesis was suggested, based on the period analysis using 57 minimum times and resulting the period of the third body p3= (52.96±0.01)yr, amplitude A=(0.057±0.029)d and eccentricity e=(0.79±0.08) which gives the minimum mass m3,min=(3.6±0.8)M_sun.

  1. IRTF/SPeX Observations of the Unusual Kepler Light Curve System KIC8462852

    NASA Astrophysics Data System (ADS)

    Lisse, C. M.; Sitko, M. L.; Marengo, M.

    2015-12-01

    We have utilized the NASA/IRTF 3 m SpeX instrument's high-resolution spectral mode to observe and characterize the near-infrared flux emanating from the unusual Kepler light curve system KIC 8462852. By comparing the resulting 0.8-4.2 μm spectrum to a mesh of model photospheric spectra, the 6 emission line analyses of the Rayner et al. catalog, and the 25 system collections of debris disks we have observed to date using SpeX under the Near InfraRed Debris disk Survey, we have been able to additionally characterize the system. Within the errors of our measurements, this star looks like a normal solar abundance main-sequence F1V to F3V dwarf star without any obvious traces of significant circumstellar dust or gas. Using Connelley & Greene's emission measures, we also see no evidence of significant ongoing accretion onto the star nor any stellar outflow away from it. Our results are inconsistent with large amounts of static close-in obscuring material or the unusual behavior of a YSO system, but are consistent with the favored episodic giant comet models of a Gyr old stellar system favored by Boyajian et al. We speculate that KIC 8462852, like the ˜1.4 Gyr old F2V system η Corvi, is undergoing a late heavy bombardment, but is only in its very early stages.

  2. The XMM-Newton/EPIC X-Ray Light Curve Analysis of WR 6

    NASA Astrophysics Data System (ADS)

    Ignace, R.; Gayley, K. G.; Hamann, W.-R.; Huenemoerder, D. P.; Oskinova, L. M.; Pollock, A. M. T.; McFall, M.

    2013-09-01

    We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 day period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for event clustering in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays are generated in a stationary shock structure. In this context we favor a corotating interaction region (CIR) and present a phenomenological model for X-rays from a CIR structure. We show that a CIR has the potential to account simultaneously for the X-ray variability and constraints provided by the spectral analysis. Ultimately, the viability of the CIR model will require both intermittent long-term X-ray monitoring of WR 6 and better physical models of CIR X-ray production at large radii in stellar winds. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

  3. THE XMM-NEWTON/EPIC X-RAY LIGHT CURVE ANALYSIS OF WR 6

    SciTech Connect

    Ignace, R.; Gayley, K. G.; Hamann, W.-R.; Oskinova, L. M.; Huenemoerder, D. P.; Pollock, A. M. T.; McFall, M.

    2013-09-20

    We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 day period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for event clustering in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays are generated in a stationary shock structure. In this context we favor a corotating interaction region (CIR) and present a phenomenological model for X-rays from a CIR structure. We show that a CIR has the potential to account simultaneously for the X-ray variability and constraints provided by the spectral analysis. Ultimately, the viability of the CIR model will require both intermittent long-term X-ray monitoring of WR 6 and better physical models of CIR X-ray production at large radii in stellar winds.

  4. SUPER-CHANDRASEKHAR-MASS LIGHT CURVE MODELS FOR THE HIGHLY LUMINOUS TYPE Ia SUPERNOVA 2009dc

    SciTech Connect

    Kamiya, Yasuomi; Tanaka, Masaomi; Nomoto, Ken'ichi; Blinnikov, Sergei I.; Sorokina, Elena I.; Suzuki, Tomoharu

    2012-09-10

    Several highly luminous Type Ia supernovae (SNe Ia) have been discovered. Their high luminosities are difficult to explain with the thermonuclear explosions of Chandrasekhar-mass white dwarfs (WDs). In the present study, we estimate the progenitor mass of SN 2009dc, one of the extremely luminous SNe Ia, using the hydrodynamical models as follows. Explosion models of super-Chandrasekhar-mass (super-Ch-mass) WDs are constructed, and multi-color light curves (LCs) are calculated. The comparison between our calculations and the observations of SN 2009dc suggests that the exploding WD has a super-Ch mass of 2.2-2.4 M{sub Sun }, producing 1.2-1.4 M{sub Sun} of {sup 56}Ni, if the extinction by its host galaxy is negligible. If the extinction is significant, the exploding WD is as massive as {approx}2.8 M{sub Sun }, and {approx}1.8 M{sub Sun} of {sup 56}Ni is necessary to account for the observations. Whether the host-galaxy extinction is significant or not, the progenitor WD must have a thick carbon-oxygen layer in the outermost zone (20%-30% of the WD mass), which explains the observed low expansion velocity of the ejecta and the presence of carbon. Our estimate of the mass of the progenitor WD, especially for the extinction-corrected case, is challenging to the current scenarios of SNe Ia. Implications for the progenitor scenarios are also discussed.

  5. A uniform analysis of HD 209458b Spitzer/IRAC light curves with Gaussian process models

    NASA Astrophysics Data System (ADS)

    Evans, Thomas M.; Aigrain, Suzanne; Gibson, Neale; Barstow, Joanna K.; Amundsen, David S.; Tremblin, Pascal; Mourier, Pierre

    2015-07-01

    We present an analysis of Spitzer/Infrared Array Camera primary transit and secondary eclipse light curves measured for HD 209458b, using Gaussian process models to marginalize over the intrapixel sensitivity variations in the 3.6 and 4.5 μm channels and the ramp effect in the 5.8 and 8.0 μm channels. The main advantage of this approach is that we can account for a broad range of degeneracies between the planet signal and systematics without actually having to specify a deterministic functional form for the latter. Our results do not confirm a previous claim of water absorption in transmission. Instead, our results are more consistent with a featureless transmission spectrum, possibly due to a cloud deck obscuring molecular absorption bands. For the emission data, our values are not consistent with the thermal inversion in the dayside atmosphere that was originally inferred from these data. Instead, we agree with another re-analysis of these same data, which concluded a non-inverted atmosphere provides a better fit. We find that a solar-abundance clear-atmosphere model without a thermal inversion underpredicts the measured emission in the 4.5 μm channel, which may suggest the atmosphere is depleted in carbon monoxide. An acceptable fit to the emission data can be achieved by assuming that the planet radiates as an isothermal blackbody with a temperature of 1484 ± 18 K.

  6. Historic Light Curve and Long-Term Optical Variation of BL Lacertae 2200+420

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Xie, G. Z.; Pecontal, E.; Pecontal, A.; Copin, Y.

    1998-11-01

    In this paper, historical optical (UBVRI) data and newly observed data from the Yunnan Observatory of China (over ~100 yr) are presented for BL Lacertae. Large variations of ΔU = 5.12 mag, ΔB = 5.31 mag, ΔV = 4.73 mag, ΔR = 2.59 mag, and ΔI = 2.54 mag, and color indices of U-B = -0.11 +/- 0.20, B-V = 1.0 +/- 0.11, V-R = 0.73 +/- 0.19, V-I = 1.42 +/- 0.25, R-I = 0.82 +/- 0.11, and B-I = 2.44 +/- 0.29 have been obtained from the literature. The Jurkevich method is used to investigate the existence of periods in the B-band light curve, and a long-term period of 14 yr is found. The 0.6 and 0.88 yr periods reported by Webb et al. are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectrum flattens when the source brightens.

  7. TEMPORAL DECONVOLUTION STUDY OF LONG AND SHORT GAMMA-RAY BURST LIGHT CURVES

    SciTech Connect

    Bhat, P. N.; Briggs, Michael S.; Connaughton, Valerie; Paciesas, William; Burgess, Michael; Chaplin, Vandiver; Goldstein, Adam; Guiriec, Sylvain; Kouveliotou, Chryssa; Fishman, Gerald; Bissaldi, Elisabetta; Diehl, Roland; Foley, Suzanne; Greiner, Jochen; Gruber, David; Fitzpatrick, Gerard; Gibby, Melissa; Giles, Misty M.; and others

    2012-01-10

    The light curves of gamma-ray bursts (GRBs) are believed to result from internal shocks reflecting the activity of the GRB central engine. Their temporal deconvolution can reveal potential differences in the properties of the central engines in the two populations of GRBs which are believed to originate from the deaths of massive stars (long) and from mergers of compact objects (short). We present here the results of the temporal analysis of 42 GRBs detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope. We deconvolved the profiles into pulses, which we fit with lognormal functions. The distributions of the pulse shape parameters and intervals between neighboring pulses are distinct for both burst types and also fit with lognormal functions. We have studied the evolution of these parameters in different energy bands and found that they differ between long and short bursts. We discuss the implications of the differences in the temporal properties of long and short bursts within the framework of the internal shock model for GRB prompt emission.

  8. The Importance of 56Ni in Shaping the Light Curves of Type II Supernovae

    NASA Astrophysics Data System (ADS)

    Nakar, Ehud; Poznanski, Dovi; Katz, Boaz

    2016-06-01

    What intrinsic properties shape the light curves of SNe II? To address this question we derive observational measures that are robust (i.e., insensitive to detailed radiative transfer) and constrain the contribution from 56Ni as well as a combination of the envelope mass, progenitor radius, and explosion energy. By applying our methods to a sample of SNe II from the literature, we find that a 56Ni contribution is often significant. In our sample, its contribution to the time-weighted integrated luminosity during the photospheric phase ranges between 8% and 72% with a typical value of 30%. We find that the 56Ni relative contribution is anti-correlated with the luminosity decline rate. When added to other clues, this in turn suggests that the flat plateaus often observed in SNe II are not a generic feature of the cooling envelope emission, and that without 56Ni many of the SNe that are classified as II-P would have shown a decline rate that is steeper by up to 1 mag/100 days. Nevertheless, we find that the cooling envelope emission, and not 56Ni contribution, is the main driver behind the observed range of decline rates. Furthermore, contrary to previous suggestions, our findings indicate that fast decline rates are not driven by lower envelope masses. We therefore suggest that the difference in observed decline rates is mainly a result of different density profiles of the progenitors.

  9. A New Relationship Between Soft X-Rays and EUV Flare Light Curves

    NASA Astrophysics Data System (ADS)

    Thiemann, Edward

    2016-05-01

    Solar flares are the result of magnetic reconnection in the solar corona which converts magnetic energy into kinetic energy resulting in the rapid heating of solar plasma. As this plasma cools, it emits radiation at different EUV wavelengths when the dropping temperature passes a line’s temperature of formation. This results in a delay in the emissions from cooler EUV lines relative to hotter EUV lines. Therefore, characterizing how this hot plasma cools is important for understanding how the corresponding geo-effective extreme ultraviolet (EUV) irradiance evolves in time. I present a simple new framework in which to study flare cooling by using a Lumped Element Thermal Model (LETM). LETM is frequently used in science and engineering to simplify a complex multi-dimensional thermal system by reducing it to a 0-D thermal circuit. For example, a structure that conducts heat out of a system is simplified with a resistive element and a structure that allows a system to store heat is simplified with a capacitive element. A major advantage of LETM is that the specific geometry of a system can be ignored, allowing for an intuitive analysis of the major thermal processes. I show that LETM is able to accurately reproduce the temporal evolution of cooler flare emission lines based on hotter emission line evolution. In particular, it can be used to predict the evolution of EUV flare light curves using the NOAA X-Ray Sensor (XRS).

  10. The changing X-ray light curves of the intermediate polar FO Aquarii

    NASA Astrophysics Data System (ADS)

    Beardmore, A. P.; Mukai, K.; Norton, A. J.; Osborne, J. P.; Hellier, C.

    1998-06-01

    Comparison of five X-ray observations of the intermediate polar FO Aqr reveals that the morphology of the X-ray light curve changes considerably with time. In particular, power spectra of the 1988 Ginga and 1993 ASCA data reveal strong sideband and orbital variations, whereas the 1990 Ginga observation does not. This suggests that the amount of stream-fed accretion varies with epoch, and the system was accreting predominantly from a disc in 1990. In contrast to other intermediate polars, the X-ray spin-pulse profiles show significant variations between observations, ranging from relatively sinusoidal to sawtooth-shaped at medium energies. During the 1988 and 1990 observations a notch is visible at spin phase zero, due to the presence of an interpulse at phase 0.85, which is absent during the other observations. At lower energies a narrow pulse of emission is seen at spin phase 0.2. We interpret the pulse profile from the 1990 Ginga observation using a model for accretion from a disc on to a dipolar magnetic field, the axis of which is offset from the white dwarf centre by ~0.15 white dwarf radii. In order to account for the later occurrence of the hardness-ratio maximum in 1988 and 1993, we suggest that the accretion-rate profile changes so that accretion is favoured along the field lines which trail the magnetic pole. This also accounts for the disappearance of the interpulse and notch in 1993.

  11. VizieR Online Data Catalog: UBVRIz light curves of 51 Type II supernovae (Galbany+, 2016)

    NASA Astrophysics Data System (ADS)

    Galbany, L.; Hamuy, M.; Phillips, M. M.; Suntzeff, N. B.; Maza, J.; de Jaeger, T.; Moraga, T.; Gonzalez-Gaitan, S.; Krisciunas, K.; Morrell, N. I.; Thomas-Osip, J.; Krzeminski, W.; Gonzalez, L.; Antezana, R.; Wishnjewski, M.; McCarthy, P.; Anderson, J. P.; Gutierrez, C. P.; Stritzinger, M.; Folatelli, G.; Anguita, C.; Galaz, G.; Green, E. M.; Impey, C.; Kim, Y.-C.; Kirhakos, S.; Malkan, M. A.; Mulchaey, J. S.; Phillips, A. C.; Pizzella, A.; Prosser, C. F.; Schmidt, B. P.; Schommer, R. A.; Sherry, W.; Strolger, L.-G.; Wells, L. A.; Williger, G. M.

    2016-08-01

    This paper presents a sample of multi-band, visual-wavelength light curves of 51 type II supernovae (SNe II) observed from 1986 to 2003 in the course of four different surveys: the Cerro Tololo Supernova Survey, the Calan Tololo Supernova Program (C&T), the Supernova Optical and Infrared Survey (SOIRS), and the Carnegie Type II Supernovae Survey (CATS). Near-infrared photometry and optical spectroscopy of this set of SNe II will be published in two companion papers. A list of the SNe II used in this study is presented in Table1. The first object in our list is SN 1986L and it is the only SN observed with photoelectric techniques (by M.M.P and S.K., using the Cerro Tololo Inter-American Observatory (CTIO) 0.9m equipped with a photometer and B and V filters). The remaining SNe were observed using a variety of telescopes equipped with CCD detectors and UBV(RI)KCz filters (see Table5). The magnitudes for the photometric sequences of the 51 SNe II are listed in Table4. In every case, these sequences were derived from observations of Landolt standards (see Appendix D in Hamuy et al. 2001ApJ...558..615H for the definition of the z band and Stritzinger et al. 2002AJ....124.2100S for the description of the z-band standards). Table5 lists the resulting UBVRIz magnitudes for the 51 SNe. (3 data files).

  12. Photometric analysis of the contact binary star V842 Hercules on the basis of seasonal light curves

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Özkardeş, B.

    2009-04-01

    We present new BVR light curves and photometric analysis of the contact binary star V842 Her. The light curves were obtained at the ÇOMU Observatory in the consecutive years 2003, 2004, 2005, and also 2007. We studied the variation of the orbital period of the system. The O- C diagram shows a quasi-sinusoidal form superimposed on a parabola. The parabolic variation, which indicates the secular increase of the orbital period of the system, was interpreted in terms of the combined effect of mass transfer between the components of the system and mass loss by a stellar wind from the system. The sinusoidal form of the orbital period variation was considered as an apparent change and interpreted in term of the light-time effect due to an unseen component in the system. We have also studied the nature of asymmetries and the intrinsic variability in the light curves of the system. The differences between light levels of both maxima (i.e. O'Connell effect) and minima are changing with time. These peculiar asymmetries were explained by a dark spot on the surface of the large and more massive component star. The present BVR light curves and radial velocity curves obtained by [Rucinski, S.M., Lu, W., 1999. AJ 118, 2451] were analysed by means of the Wilson-Devinney method supplemented with a Monte Carlo type algorithm. Absolute parameters of the system were also derived. They are m1 = 0.38 m⊙, m2 = 1.45 m⊙, R1 = 0.81 R⊙, R2 = 1.47 R⊙, M = 5m.08 and M = 4m.06.

  13. Self-Esteem Trajectories among Ethnic Minority Adolescents: A Growth Curve Analysis of the Patterns and Predictors of Change

    ERIC Educational Resources Information Center

    Greene, Melissa L.; Way, Niobe

    2005-01-01

    The current study presents a growth curve analysis of self-esteem among Black, Latino, and Asian American high school students. A series of hierarchical linear models were used to examine patterns and predictors of change in self-esteem over time. Results revealed an average increase in self-esteem with age. Although boys and girls experienced…

  14. High-precision 2MASS JHK{sub s} light curves and other data for RR Lyrae star SDSS J015450 + 001501: Strong constraints for nonlinear pulsation models

    SciTech Connect

    Szabó, Róbert; Ivezić, Željko; Kiss, László L.; Kolláth, Zoltán; Jones, Lynne; Becker, Andrew C.; Davenport, James R. A.; Sesar, Branimir; Cutri, Roc M.

    2014-01-01

    We present and discuss an extensive data set for the non-Blazhko ab-type RR Lyrae star SDSS J015450+001501, including optical Sloan Digital Sky Survey ugriz light curves and spectroscopic data, LINEAR and Catalina Sky Survey unfiltered optical light curves, and infrared Two Micron All Sky Survey (2MASS) JHK{sub s} and Wide-field Infrared Survey Explorer W1 and W2 light curves. Most notable is that light curves obtained by 2MASS include close to 9000 photometric measures collected over 3.3 yr and provide an exceedingly precise view of near-infrared variability. These data demonstrate that static atmosphere models are insufficient to explain multiband photometric light-curve behavior and present strong constraints for nonlinear pulsation models for RR Lyrae stars. It is a challenge to modelers to produce theoretical light curves that can explain data presented here, which we make publicly available.

  15. The light curve shapes as a key to resolving the origin of long secondary periods in red giant stars

    SciTech Connect

    Soszyński, I.; Udalski, A. E-mail: udalski@astrouw.edu.pl

    2014-06-10

    We present a study of Optical Gravitational Lensing Experiment light curves of red giant stars exhibiting long secondary periods (LSPs)—an enigmatic phenomenon commonly observed in stars on the upper red giant branch and asymptotic giant branch. We show that the light curves of LSP stars are essentially identical to those of the spotted variables with one dark spot on their photospheres. Such behavior can be explained by the presence of a dusty cloud orbiting the red giant together with a low-mass companion in a close, circular orbit. We argue that the binary scenario is in agreement with most of the observational properties of LSP variables, including non-sinusoidal shapes of their radial velocity curves.

  16. Dynamics and Afterglow Light Curves of Gamma-Ray Burst Blast Waves Encountering a Density Bump or Void

    NASA Astrophysics Data System (ADS)

    Uhm, Z. Lucas; Zhang, Bing

    2014-07-01

    We investigate the dynamics and afterglow light curves of gamma-ray burst blast waves that encounter various density structures (such as bumps, voids, or steps) in the surrounding ambient medium. We present and explain the characteristic response features that each type of density structure in the medium leaves on the forward shock (FS) and reverse shock (RS) dynamics for blast waves with either a long-lived or short-lived RS. We show that when the ambient medium density drops, the blast waves exhibit in some cases a period of an actual acceleration (even during their deceleration stage) due to adiabatic cooling of blast waves. Comparing numerical examples that have different shapes of bumps or voids, we propose a number of consistency tests that must be satisfied by correct modeling of blast waves. Our model results successfully pass these tests. Employing a Lagrangian description of blast waves, we perform a sophisticated calculation of afterglow emission. We show that as a response to density structures in the ambient medium, the RS light curves produce more significant variations than the FS light curves. Some observed features (such as rebrightenings, dips, or slow wiggles) can be more easily explained within the RS model. We also discuss the origin of these different features imprinted on the FS and RS light curves.

  17. Light curve analysis for eclipsing systems with exoplanets. The systems Kepler-5b, Kepler-6b, and Kepler-7b

    NASA Astrophysics Data System (ADS)

    Gostev, N. Yu.

    2011-07-01

    High-accuracy light curves for the binaries with exoplanets Kepler-5b, Kepler-6b, and Kepler-7b have been analyzed. The radii of the stars and the planets and the orbital inclinations of the binaries are derived. Reliable estimates of the linear and quadratic limb-darkening coefficients and their confidence intervals (uncertainties) are presented.