Aspherical Supernovae: Effects on Early Light Curves

NASA Astrophysics Data System (ADS)

Afsariardchi, Niloufar; Matzner, Christopher D.

2018-04-01

Early light from core-collapse supernovae, now detectable in high-cadence surveys, holds clues to a star and its environment just before it explodes. However, effects that alter the early light have not been fully explored. We highlight the possibility of nonradial flows at the time of shock breakout. These develop in sufficiently nonspherical explosions if the progenitor is not too diffuse. When they do develop, nonradial flows limit ejecta speeds and cause ejecta–ejecta collisions. We explore these phenomena and their observational implications using global, axisymmetric, nonrelativistic FLASH simulations of simplified polytropic progenitors, which we scale to representative stars. We develop a method to track photon production within the ejecta, enabling us to estimate band-dependent light curves from adiabatic simulations. Immediate breakout emission becomes hidden as an oblique flow develops. Nonspherical effects lead the shock-heated ejecta to release a more constant luminosity at a higher, evolving color temperature at early times, effectively mixing breakout light with the early light curve. Collisions between nonradial ejecta thermalize a small fraction of the explosion energy; we will address emission from these collisions in a subsequent paper.

A GLOBAL MODEL OF THE LIGHT CURVES AND EXPANSION VELOCITIES OF TYPE II-PLATEAU SUPERNOVAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pejcha, Ondřej; Prieto, Jose L., E-mail: pejcha@astro.princeton.edu

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 resultmore » 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.« less

Light Curves and Spectra from a Unimodal Core-collapse Supernova

DOE PAGES

Wollaeger, Ryan T.; Hungerford, Aimee L.; Fryer, Chris L.; ...

2017-08-23

To assess the effectiveness of optical emission as a probe of spatial asymmetry in core-collapse supernovae (CCSNe), we apply in this paper the radiative transfer software SuperNu to a unimodal CCSN model. The SNSPH radiation hydrodynamics software was used to simulate an asymmetric explosion of a 16more » $${M}_{\\odot }$$ zero-age main-sequence binary star. The ejecta has 3.36 $${M}_{\\odot }$$ with 0.024 $${M}_{\\odot }$$ of radioactive 56Ni, with unipolar asymmetry along the z-axis. For 96 discrete angular views, we find a ratio between maximum and minimum peak total luminosities of ~1.36. The brightest light curves emerge from views orthogonal to the z-axis. Multigroup spectra from UV to IR are obtained. We find a shift in wavelength with viewing angle in a near-IR Ca ii emission feature, consistent with Ca being mostly in the unimode. We compare emission from the gray gamma-ray transfer in SuperNu and from the detailed gamma-ray transfer code Maverick. Relative to the optical light curves, the brightness of the gamma-ray emission is more monotonic with respect to viewing angle. UBVRI broadband light curves are also calculated. Parallel with the unimode, the U and B bands have excess luminosity at $$\\gtrsim 10$$ days post-explosion, due to 56Ni on the unimode. Finally, we compare our CCSN model with SN 2002ap, which is thought to have a similar ejecta morphology.« less

Light Curves and Spectra from a Unimodal Core-collapse Supernova

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wollaeger, Ryan T.; Hungerford, Aimee L.; Fryer, Chris L.

To assess the effectiveness of optical emission as a probe of spatial asymmetry in core-collapse supernovae (CCSNe), we apply in this paper the radiative transfer software SuperNu to a unimodal CCSN model. The SNSPH radiation hydrodynamics software was used to simulate an asymmetric explosion of a 16more » $${M}_{\\odot }$$ zero-age main-sequence binary star. The ejecta has 3.36 $${M}_{\\odot }$$ with 0.024 $${M}_{\\odot }$$ of radioactive 56Ni, with unipolar asymmetry along the z-axis. For 96 discrete angular views, we find a ratio between maximum and minimum peak total luminosities of ~1.36. The brightest light curves emerge from views orthogonal to the z-axis. Multigroup spectra from UV to IR are obtained. We find a shift in wavelength with viewing angle in a near-IR Ca ii emission feature, consistent with Ca being mostly in the unimode. We compare emission from the gray gamma-ray transfer in SuperNu and from the detailed gamma-ray transfer code Maverick. Relative to the optical light curves, the brightness of the gamma-ray emission is more monotonic with respect to viewing angle. UBVRI broadband light curves are also calculated. Parallel with the unimode, the U and B bands have excess luminosity at $$\\gtrsim 10$$ days post-explosion, due to 56Ni on the unimode. Finally, we compare our CCSN model with SN 2002ap, which is thought to have a similar ejecta morphology.« less

Pre-nebular Light Curves of SNe I

DOE PAGES

Arnett, W. David; Fryer, Christopher; Matheson, Thomas

2017-08-29

We compare analytic predictions of supernova light curves with recent high-quality data from SN2011fe (Ia), KSN2011b (Ia), and the Palomar Transient Factory and the La Silla-QUEST variability survey (LSQ) (Ia). Because of the steady, fast cadence of observations, KSN2011b provides unique new information on SNe Ia: the smoothness of the light curve, which is consistent with significant large-scale mixing during the explosion, possibly due to 3D effects (e.g., Rayleigh–Taylor instabilities), and provides support for a slowly varying leakage (mean opacity). For a more complex light curve (SN2008D, SN Ib), we separate the luminosity due to multiple causes and indicate themore » possibility of a radioactive plume. The early rise in luminosity is shown to be affected by the opacity (leakage rate) for thermal and non-thermal radiation. A general derivation of Arnett's rule again shows that it depends upon all processes heating the plasma, not just radioactive ones, so that SNe Ia will differ from SNe Ibc if the latter have multiple heating processes.« less

Pre-nebular Light Curves of SNe I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnett, W. David; Fryer, Christopher; Matheson, Thomas

We compare analytic predictions of supernova light curves with recent high-quality data from SN2011fe (Ia), KSN2011b (Ia), and the Palomar Transient Factory and the La Silla-QUEST variability survey (LSQ) (Ia). Because of the steady, fast cadence of observations, KSN2011b provides unique new information on SNe Ia: the smoothness of the light curve, which is consistent with significant large-scale mixing during the explosion, possibly due to 3D effects (e.g., Rayleigh–Taylor instabilities), and provides support for a slowly varying leakage (mean opacity). For a more complex light curve (SN2008D, SN Ib), we separate the luminosity due to multiple causes and indicate themore » possibility of a radioactive plume. The early rise in luminosity is shown to be affected by the opacity (leakage rate) for thermal and non-thermal radiation. A general derivation of Arnett’s rule again shows that it depends upon all processes heating the plasma, not just radioactive ones, so that SNe Ia will differ from SNe Ibc if the latter have multiple heating processes.« less

Pre-nebular Light Curves of SNe I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnett, W. David; Fryer, Christopher; Matheson, Thomas

We compare analytic predictions of supernova light curves with recent high-quality data from SN2011fe (Ia), KSN2011b (Ia), and the Palomar Transient Factory and the La Silla-QUEST variability survey (LSQ) (Ia). Because of the steady, fast cadence of observations, KSN2011b provides unique new information on SNe Ia: the smoothness of the light curve, which is consistent with significant large-scale mixing during the explosion, possibly due to 3D effects (e.g., Rayleigh–Taylor instabilities), and provides support for a slowly varying leakage (mean opacity). For a more complex light curve (SN2008D, SN Ib), we separate the luminosity due to multiple causes and indicate themore » possibility of a radioactive plume. The early rise in luminosity is shown to be affected by the opacity (leakage rate) for thermal and non-thermal radiation. A general derivation of Arnett's rule again shows that it depends upon all processes heating the plasma, not just radioactive ones, so that SNe Ia will differ from SNe Ibc if the latter have multiple heating processes.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hachisu, Izumi; Kato, Mariko, E-mail: hachisu@ea.c.u-tokyo.ac.jp, 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 theirmore » 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.« less

Light curve variations of the eclipsing binary V367 Cygni

NASA Astrophysics Data System (ADS)

Akan, M. C.

1987-07-01

The long-period eclipsing binary star V367 Cygni has been observed photoelectrically in two colours, B and V, in 1984, 1985, and 1986. These new light curves of the system have been discussed and compared for the light-variability with the earlier ones presented by Heiser (1962). Using some of the previously published photoelectric light curves and the present ones, several primary minima times have been derived to calculate the light elements. Any attempt to obtain a photometric solution of the binary is complicated by the peculiar nature of the light curve caused by the presence of the circumstellar matter in the system. Despite this difficulty, however, some approaches are being carried out to solve the light curves which are briefly discussed.

New Binary Systems With Asymmetric Light Curves

NASA Astrophysics Data System (ADS)

Virnina, Natalia A.

2010-12-01

We present the results of investigation of the light curves of 27 newly discovered binary systems. Among the examined curves, there were 10 curves with statistically significant asymmetry of maximums, according the 3σ criterion for the difference between the maximal brightness. Half of these 10 curves have a higher first maximum, another half the second one. Two of these 10 curves, USNO-B1.0 1629-0064825 = VSX J052807.9+725606 and USNO-B1.0 1586-0116785, show the largest difference between magnitudes in maxima. The star VSX J052807.9+725606 also shows the secondary minimum, which is shifted from the phase φ = 0.5. The shape of the curve argues that the physical processes of this star could be close to that of well known short periodic binary system V361 Lyr, which has a spot on the surface of one star of the system. Another star, USNO-B1.0 1586-0116785, probably has a cold spot, or several spots, in the photosphere of one of the components.

Late-time Flattening of Type Ia Supernova Light Curves: Constraints from SN 2014J in M82

NASA Astrophysics Data System (ADS)

Yang, Yi; Wang, Lifan; Baade, Dietrich; Brown, Peter. J.; Cikota, Aleksandar; Cracraft, Misty; Höflich, Peter A.; Maund, Justyn R.; Patat, Ferdinando; Sparks, William B.; Spyromilio, Jason; Stevance, Heloise F.; Wang, Xiaofeng; Wheeler, J. Craig

2018-01-01

The very nearby Type Ia supernova 2014J in M82 offers a rare opportunity to study the physics of thermonuclear supernovae at extremely late phases (≳800 days). Using the Hubble Space Telescope, we obtained 6 epochs of high-precision photometry for SN 2014J from 277 days to 1181 days past the B-band maximum light. The reprocessing of electrons and X-rays emitted by the radioactive decay chain {}57{Co}\\to {}57{Fe} is needed to explain the significant flattening of both the F606W-band and the pseudo-bolometric light curves. The flattening confirms previous predictions that the late-time evolution of type Ia supernova luminosities requires additional energy input from the decay of 57Co. By assuming the F606W-band luminosity scales with the bolometric luminosity at ∼500 days after the B-band maximum light, a mass ratio {}57{Ni}{/}56{Ni}∼ {0.065}-0.004+0.005 is required. This mass ratio is roughly ∼3 times the solar ratio and favors a progenitor white dwarf with a mass near the Chandrasekhar limit. A similar fit using the constructed pseudo-bolometric luminosity gives a mass ratio {}57{Ni}{/}56{Ni}∼ {0.066}-0.008+0.009. Astrometric tests based on the multi-epoch HST ACS/WFC images reveal no significant circumstellar light echoes in between 0.3 and 100 pc from the supernova.

Periodicity Analysis of X-ray Light Curves of SS 433

NASA Astrophysics Data System (ADS)

Wang, Jun-yi; Lu, Xiang-long; Zhao, Qiu-wen; Dong, Dian-qiao; Lao, Bao-qiang; Lu, Yang; Wei, Yan-heng; Wu, Xiao-cong; An, Tao

2017-01-01

SS 433 is sofar the unique X-ray binary that has the simultaneously detected orbital period, super-orbital period, and nutation period, as well as a bidirectional spiral jet. The study on its X-ray light variability is helpful for understanding the dynamic process of the system, and the correlations between the different wavebands. In this paper, two time-series analysis techniques, i.e., the Lomb-Scargle periodogram and weighted wavelet Z-transform, are employed to search for the periods in the Swift/BAT (Burst Alert Telescope) (15-50 keV) and RXTE/ASM (Rose X-ray Timing Explorer/All Sky Monitor) (1.5-3, 3- 4, and 5-12 keV) light curves of SS 433, and the Monte Carlo simulation is performed for the obtained periodical components. For the 15-50 keV energy band, five significant periodical components are detected, which are P1(∼6.29 d), P2 (∼6.54 d), P3 (∼13.08 d), P4 (∼81.50 d), and P5 (∼162.30 d). For the 3-5 and 5-12 keV energy bands, the periodical components P3 (∼13 d) and P5 (∼162 d) are detected in both energy bands. However, for the 1.5-3 keV energy band, no significant periodic signal is detected. P5 is the strongest periodic signal in the power spectrum for all the energy bands of 3-5, 5-12, and 15-50 keV, and it is consistent with the previous result obtained from the study of optical light curves. Furthermore, in combination with the radio spiral jet of SS 433, it is suggested that the X-ray and optical variability of P5 (∼162 d) is probably related to the precession of its relativistic jet. The high correlation between the X-ray and optical light curves may also imply that the X-ray and optical radiations are of the same physical origin. P3 shows a good agreement with the orbital period (∼13.07 d) obtained by the previous study, and P2 and P4 are respectively the high-frequency harmonics of P3 and P5. P1 is detected only in the power spectrum of the 15-50 keV energy band, and it is consistent with the nutation period of the system. As

Multi-band Emission Light Curves of Jupiter: Insights on Brown Dwarfs and Directly Imaged Exoplanets

NASA Astrophysics Data System (ADS)

Zhang, Xi; Ge, Huazhi; Orton, Glenn S.; Fletcher, Leigh N.; Sinclair, James; Fernandes, Joshua; Momary, Thomas W.; Kasaba, Yasumasa; Sato, Takao M.; Fujiyoshi, Takuya

2016-10-01

Many brown dwarfs exhibit significant infrared flux variability (e.g., Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750, 105), ranging from several to twenty percent of the brightness. Current hypotheses include temperature variations, cloud holes and patchiness, and cloud height and thickness variations (e.g., Apai et al. 2013, ApJ, 768, 121; Robinson and Marley 2014, ApJ, 785, 158; Zhang and Showman 2014, ApJ, 788, L6). Some brown dwarfs show phase shifts in the light curves among different wavelengths (e.g., Buenzli et al. 2012, ApJ, 760, L31; Yang et al. 2016, arXiv:1605.02708), indicating vertical variations of the cloud distribution. The current observational technique can barely detect the brightness changes on the surfaces of nearby brown dwarfs (Crossfield et al. 2014, Nature, 505, 654) let alone resolve detailed weather patterns that cause the flux variability. The infrared emission maps of Jupiter might shed light on this problem. Using COMICS at Subaru Telescope, VISIR at Very Large Telescope (VLT) and NASA's Infrared Telescope Facility (IRTF), we obtained infrared images of Jupiter over several nights at multiple wavelengths that are sensitive to several pressure levels from the stratosphere to the deep troposphere below the ammonia clouds. The rotational maps and emission light curves are constructed. The individual pixel brightness varies up to a hundred percent level and the variation of the full-disk brightness is around several percent. Both the shape and amplitude of the light curves are significantly distinct at different wavelengths. Variation of light curves at different epochs and phase shift among different wavelengths are observed. We will present principle component analysis to identify dominant emission features such as stable vortices, cloud holes and eddies in the belts and zones and strong emissions in the aurora region. A radiative transfer model is used to simulate those features to get a more quantitative

A SEMI-ANALYTICAL MODEL OF VISIBLE-WAVELENGTH PHASE CURVES OF EXOPLANETS AND APPLICATIONS TO KEPLER- 7 B AND KEPLER- 10 B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Renyu; Demory, Brice-Olivier; Seager, Sara

2015-03-20

Kepler has detected numerous exoplanet transits by measuring stellar light in a single visible-wavelength band. In addition to detection, the precise photometry provides phase curves of exoplanets, which can be used to study the dynamic processes on these planets. However, the interpretation of these observations can be complicated by the fact that visible-wavelength phase curves can represent both thermal emission and scattering from the planets. Here we present a semi-analytical model framework that can be applied to study Kepler and future visible-wavelength phase curve observations of exoplanets. The model efficiently computes reflection and thermal emission components for both rocky andmore » gaseous planets, considering both homogeneous and inhomogeneous surfaces or atmospheres. We analyze the phase curves of the gaseous planet Kepler- 7 b and the rocky planet Kepler- 10 b using the model. In general, we find that a hot exoplanet’s visible-wavelength phase curve having a significant phase offset can usually be explained by two classes of solutions: one class requires a thermal hot spot shifted to one side of the substellar point, and the other class requires reflective clouds concentrated on the same side of the substellar point. Particularly for Kepler- 7 b, reflective clouds located on the west side of the substellar point can best explain its phase curve. The reflectivity of the clear part of the atmosphere should be less than 7% and that of the cloudy part should be greater than 80%, and the cloud boundary should be located at 11° ± 3° to the west of the substellar point. We suggest single-band photometry surveys could yield valuable information on exoplanet atmospheres and surfaces.« less

VizieR Online Data Catalog: GTC transit light curves of HAT-P-32b (Nortmann+, 2016)

NASA Astrophysics Data System (ADS)

Nortmann, L.; Palle, E.; Murgas, F.; Dreizler, S.; Iro, N.; Cabrera-Lavers, A.

2016-05-01

We provide two transit light curves of the hot Jupiter HAT-P-32b obtained on the nights of 2012/09/15 and 2012/09/30 using the OSIRIS instrument at the 10.4-m GTC telescope. The data was obtained by using OSIRIS in broad slit spectroscopy mode and covering the wavelength region between 518nm-918nm. For the night of 2012/09/30 we further provide twenty narrowband light curves which were created by summing the flux over 20-nm-wide channels instead over the whole wavelength region. We provide several auxiliary parameters of the observations which we have used to correct the data from correlated noise. These auxiliary parameters are the position drift of the stars on the CCD detector in spatial and dispersion direction, air mass and seeing (FWHM). (23 data files).

Late-time Light Curves of Type II Supernovae: Physical Properties of Supernovae and Their Environment

NASA Astrophysics Data System (ADS)

Otsuka, Masaaki; Meixner, Margaret; Panagia, Nino; Fabbri, Joanna; Barlow, Michael J.; Clayton, Geoffrey C.; Gallagher, Joseph S.; Sugerman, Ben E. K.; Wesson, Roger; Andrews, Jennifer E.; Ercolano, Barbara; Welch, Douglas

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 ~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 56Ni masses for our targets (0.5-14 × 10-2 M ⊙) from the bolometric light curve of each of days ~150-300 using SN 1987A as a standard (7.5 × 10-2 M ⊙). 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-3) and SNe 2003gd and 2004et have densities more typical of the interstellar medium (~1 cm-3). We analyze the sample as a whole in the context of physical properties derived in prior work. The 56Ni mass appears well correlated with progenitor mass with a slope of 0.31 × 10-2, supporting the previous work by Maeda et al., who focus on more massive Type II SNe. The

Analytic reflected light curves for exoplanets

NASA Astrophysics Data System (ADS)

Haggard, Hal M.; Cowan, Nicolas B.

2018-07-01

The disc-integrated reflected brightness of an exoplanet changes as a function of time due to orbital and rotational motions coupled with an inhomogeneous albedo map. We have previously derived analytic reflected light curves for spherical harmonic albedo maps in the special case of a synchronously rotating planet on an edge-on orbit (Cowan, Fuentes & Haggard). In this paper, we present analytic reflected light curves for the general case of a planet on an inclined orbit, with arbitrary spin period and non-zero obliquity. We do so for two different albedo basis maps: bright points (δ-maps), and spherical harmonics (Y_ l^m-maps). In particular, we use Wigner D-matrices to express an harmonic light curve for an arbitrary viewing geometry as a non-linear combination of harmonic light curves for the simpler edge-on, synchronously rotating geometry. These solutions will enable future exploration of the degeneracies and information content of reflected light curves, as well as fast calculation of light curves for mapping exoplanets based on time-resolved photometry. To these ends, we make available Exoplanet Analytic Reflected Lightcurves, a simple open-source code that allows rapid computation of reflected light curves.

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.

The Carnegie Supernova Project I. Analysis of stripped-envelope supernova light curves

NASA Astrophysics Data System (ADS)

Taddia, F.; Stritzinger, M. D.; Bersten, M.; Baron, E.; Burns, C.; Contreras, C.; Holmbo, S.; Hsiao, E. Y.; Morrell, N.; Phillips, M. M.; Sollerman, J.; Suntzeff, N. B.

2018-02-01

Stripped-envelope (SE) supernovae (SNe) include H-poor (Type IIb), H-free (Type Ib), and He-free (Type Ic) events thought to be associated with the deaths of massive stars. The exact nature of their progenitors is a matter of debate with several lines of evidence pointing towards intermediate mass (Minit< 20 M⊙) stars in binary systems, while in other cases they may be linked to single massive Wolf-Rayet stars. Here we present the analysis of the light curves of 34 SE SNe published by the Carnegie Supernova Project (CSP-I) that are unparalleled in terms of photometric accuracy and wavelength range. Light-curve parameters are estimated through the fits of an analytical function and trends are searched for among the resulting fit parameters. Detailed inspection of the dataset suggests a tentative correlation between the peak absolute B-band magnitude and Δm15(B), while the post maximum light curves reveals a correlation between the late-time linear slope and Δm15. Making use of the full set of optical and near-IR photometry, combined with robust host-galaxy extinction corrections, comprehensive bolometric light curves are constructed and compared to both analytic and hydrodynamical models. This analysis finds consistent results among the two different modeling techniques and from the hydrodynamical models we obtained ejecta masses of 1.1-6.2M⊙, 56Ni masses of 0.03-0.35M⊙, and explosion energies (excluding two SNe Ic-BL) of 0.25-3.0 × 1051 erg. Our analysis indicates that adopting κ = 0.07 cm2 g-1 as the mean opacity serves to be a suitable assumption when comparing Arnett-model results to those obtained from hydrodynamical calculations. We also find that adopting He I and O I line velocities to infer the expansion velocity in He-rich and He-poor SNe, respectively, provides ejecta masses relatively similar to those obtained by using the Fe II line velocities, although the use of Fe II as a diagnostic does imply higher explosion energies. The inferred range

The Peculiar Light Curve of J1415+1320: A Case Study in Extreme Scattering Events

NASA Astrophysics Data System (ADS)

Vedantham, H. K.; Readhead, A. C. S.; Hovatta, T.; Koopmans, L. V. E.; Pearson, T. J.; Blandford, R. D.; Gurwell, M. A.; Lähteenmäki, A.; Max-Moerbeck, W.; Pavlidou, V.; Ravi, V.; Reeves, R. A.; Richards, J. L.; Tornikoski, M.; Zensus, J. A.

2017-08-01

The radio light curve of J1415+1320 (PKS 1413+135) shows time-symmetric and recurring U-shaped features across the centimeter-wave and millimeter-wave bands. The symmetry of these features points to lensing by an intervening object as the cause. U-shaped events in radio light curves in the centimeter-wave band have previously been attributed to Extreme scattering events (ESE). ESEs are thought to be the result of lensing by compact plasma structures in the Galactic interstellar medium, but the precise nature of these plasma structures remains unknown. Since the strength of a plasma lens evolves with wavelength λ as {λ }2, the presence of correlated variations at over a wide wavelength range casts doubt on the canonical ESE interpretation for J1415+1320. In this paper, we critically examine the evidence for plasma lensing in J1415+1320. We compute limits on the lensing strength and the associated free-free opacity of the putative plasma lenses. We compare the observed and model ESE light curves, and also derive a lower limit on the lens distance based on the effects of parallax due to the Earth’s orbit around the Sun. We conclude that plasma lensing is not a viable interpretation for J1415+1320's light curves and that symmetric U-shaped features in the radio light curves of extragalactic sources do not present prima facie evidence for ESEs. The methodology presented here is generic enough to be applicable to any plasma-lensing candidate.

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.

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.

REFLECTED LIGHT CURVES, SPHERICAL AND BOND ALBEDOS OF JUPITER- AND SATURN-LIKE EXOPLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyudina, Ulyana; Kopparla, Pushkar; Ingersoll, Andrew P.

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 μ m, and narrowbands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24–0.28 μ m. We simulate the images of the planets with a ray-tracingmore » 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.« less

Characterization of Type Ia Supernova Light Curves Using Principal Component Analysis of Sparse Functional Data

NASA Astrophysics Data System (ADS)

He, Shiyuan; Wang, Lifan; Huang, Jianhua Z.

2018-04-01

With growing data from ongoing and future supernova surveys, it is possible to empirically quantify the shapes of SNIa light curves in more detail, and to quantitatively relate the shape parameters with the intrinsic properties of SNIa. Building such relationships is critical in controlling systematic errors associated with supernova cosmology. Based on a collection of well-observed SNIa samples accumulated in the past years, we construct an empirical SNIa light curve model using a statistical method called the functional principal component analysis (FPCA) for sparse and irregularly sampled functional data. Using this method, the entire light curve of an SNIa is represented by a linear combination of principal component functions, and the SNIa is represented by a few numbers called “principal component scores.” These scores are used to establish relations between light curve shapes and physical quantities such as intrinsic color, interstellar dust reddening, spectral line strength, and spectral classes. These relations allow for descriptions of some critical physical quantities based purely on light curve shape parameters. Our study shows that some important spectral feature information is being encoded in the broad band light curves; for instance, we find that the light curve shapes are correlated with the velocity and velocity gradient of the Si II λ6355 line. This is important for supernova surveys (e.g., LSST and WFIRST). Moreover, the FPCA light curve model is used to construct the entire light curve shape, which in turn is used in a functional linear form to adjust intrinsic luminosity when fitting distance models.

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.

Estimation of error on the cross-correlation, phase and time lag between evenly sampled light curves

NASA Astrophysics Data System (ADS)

Misra, R.; Bora, A.; Dewangan, G.

2018-04-01

Temporal analysis of radiation from Astrophysical sources like Active Galactic Nuclei, X-ray Binaries and Gamma-ray bursts provides information on the geometry and sizes of the emitting regions. Establishing that two light-curves in different energy bands are correlated, and measuring the phase and time-lag between them is an important and frequently used temporal diagnostic. Generally the estimates are done by dividing the light-curves into large number of adjacent intervals to find the variance or by using numerically expensive simulations. In this work we have presented alternative expressions for estimate of the errors on the cross-correlation, phase and time-lag between two shorter light-curves when they cannot be divided into segments. Thus the estimates presented here allow for analysis of light-curves with relatively small number of points, as well as to obtain information on the longest time-scales available. The expressions have been tested using 200 light curves simulated from both white and 1 / f stochastic processes with measurement errors. We also present an application to the XMM-Newton light-curves of the Active Galactic Nucleus, Akn 564. The example shows that the estimates presented here allow for analysis of light-curves with relatively small (∼ 1000) number of points.

BEER ANALYSIS OF KEPLER AND CoRoT LIGHT CURVES. I. DISCOVERY OF KEPLER-76b: A HOT JUPITER WITH EVIDENCE FOR SUPERROTATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

We present the first case in which the BEER algorithm identified a hot Jupiter in the Kepler light curve, and its reality was confirmed by orbital solutions based on follow-up spectroscopy. The companion Kepler-76b was identified by the BEER algorithm, which detected the BEaming (sometimes called Doppler boosting) effect together with the Ellipsoidal and Reflection/emission modulations (BEER), at an orbital period of 1.54 days, suggesting a planetary companion orbiting the 13.3 mag F star. Further investigation revealed that this star appeared in the Kepler eclipsing binary catalog with estimated primary and secondary eclipse depths of 5 Multiplication-Sign 10{sup -3} andmore » 1 Multiplication-Sign 10{sup -4}, respectively. Spectroscopic radial velocity follow-up observations with Tillinghast Reflector Echelle Spectrograph and SOPHIE confirmed Kepler-76b as a transiting 2.0 {+-} 0.26 M{sub Jup} hot Jupiter. The mass of a transiting planet can be estimated from either the beaming or the ellipsoidal amplitude. The ellipsoidal-based mass estimate of Kepler-76b is consistent with the spectroscopically measured mass while the beaming-based estimate is significantly inflated. We explain this apparent discrepancy as evidence for the superrotation phenomenon, which involves eastward displacement of the hottest atmospheric spot of a tidally locked planet by an equatorial superrotating jet stream. This phenomenon was previously observed only for HD 189733b in the infrared. We show that a phase shift of 10. Degree-Sign 3 {+-} 2. Degree-Sign 0 of the planet reflection/emission modulation, due to superrotation, explains the apparently inflated beaming modulation, resolving the ellipsoidal/beaming amplitude discrepancy. Kepler-76b is one of very few confirmed planets in the Kepler light curves that show BEER modulations and the first to show superrotation evidence in the Kepler band. Its discovery illustrates for the first time the ability of the BEER algorithm to detect

Automated Blazar Light Curves Using Machine Learning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Spencer James

2017-07-27

This presentation describes a problem and methodology pertaining to automated blazar light curves. Namely, optical variability patterns for blazars require the construction of light curves and in order to generate the light curves, data must be filtered before processing to ensure quality.

More Unusual Light Curves from Kepler

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-03-01

Twenty-three new objects have been added to the growing collection of stars observed to have unusual dips in their light curves. A recent study examines these stars and the potential causes of their strange behavior.An Influx of DataThe primary Kepler mission provided light curves for over 100,000 stars, and its continuation K2 is observing another 20,000 stars every three months. As we enter an era where these enormous photometric data sets become commonplace Gaia will obtain photometry for millions of stars, and LSST billions its crucial that we understand the different categories of variability observed in these stars.The authors find three different types of light curves among their 23 unusual stars. Scallop-shell curves (top) show many undulations; persistent flux-dip class curves (middle) have discrete triangularly shaped flux dips; transient, narrow dip class curves (bottom) have only one dip that is variable in depth. The authors speculate a common cause for the scallop-shell and persistent flux-dip stars, and a different cause for the transient flux-dip stars. [Stauffer et al. 2017]After filtering out the stars with planets, those in binary systems, those with circumstellar disks, and those with starspots, a number of oddities remain: a menagerie of stars with periodic variability that cant be accounted for in these categories. Some of these stars are now famous (for instance, Boyajians star); some are lesser known. But by continuing to build up this sample of stars with unusual light curves, we have a better chance of understanding the sources of variability.Building the MenagerieTo this end, a team of scientists led by John Stauffer (Spitzer Science Center at Caltech) has recently hunted for more additions to this sample in the K2 data set. In particular, they searched through the light curves from stars in the Oph and Upper Scorpius star-forming region a data set that makes up the largest collection of high-quality light curves for low-mass, pre

Absolute Distances to Nearby Type Ia Supernovae via Light Curve Fitting Methods

NASA Astrophysics Data System (ADS)

Vinkó, J.; Ordasi, A.; Szalai, T.; Sárneczky, K.; Bányai, E.; Bíró, I. B.; Borkovits, T.; Hegedüs, T.; Hodosán, G.; Kelemen, J.; Klagyivik, P.; Kriskovics, L.; Kun, E.; Marion, G. H.; Marschalkó, G.; Molnár, L.; Nagy, A. P.; Pál, A.; Silverman, J. M.; Szakáts, R.; Szegedi-Elek, E.; Székely, P.; Szing, A.; Vida, K.; Wheeler, J. C.

2018-06-01

We present a comparative study of absolute distances to a sample of very nearby, bright Type Ia supernovae (SNe) derived from high cadence, high signal-to-noise, multi-band photometric data. Our sample consists of four SNe: 2012cg, 2012ht, 2013dy and 2014J. We present new homogeneous, high-cadence photometric data in Johnson–Cousins BVRI and Sloan g‧r‧i‧z‧ bands taken from two sites (Piszkesteto and Baja, Hungary), and the light curves are analyzed with publicly available light curve fitters (MLCS2k2, SNooPy2 and SALT2.4). When comparing the best-fit parameters provided by the different codes, it is found that the distance moduli of moderately reddened SNe Ia agree within ≲0.2 mag, and the agreement is even better (≲0.1 mag) for the highest signal-to-noise BVRI data. For the highly reddened SN 2014J the dispersion of the inferred distance moduli is slightly higher. These SN-based distances are in good agreement with the Cepheid distances to their host galaxies. We conclude that the current state-of-the-art light curve fitters for Type Ia SNe can provide consistent absolute distance moduli having less than ∼0.1–0.2 mag uncertainty for nearby SNe. Still, there is room for future improvements to reach the desired ∼0.05 mag accuracy in the absolute distance modulus.

Marginalizing Instrument Systematics in HST WFC3 Transit Light Curves

NASA Technical Reports Server (NTRS)

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

2016-01-01

Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7 microns probe primarily the H2O absorption band at 1.4 microns, 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 "ramp" probability (R (sub p)) divided by "ramp" total (R (sub asterisk)), 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 delta (sub lambda) times lambda) 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.

Light Curves of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

NASA Astrophysics Data System (ADS)

De Cia, Annalisa; Gal-Yam, A.; Rubin, A.; Leloudas, G.; Vreeswijk, P.; Perley, D. A.; Quimby, R.; Yan, Lin; Sullivan, M.; Flörs, A.; Sollerman, J.; Bersier, D.; Cenko, S. B.; Gal-Yam, M.; Maguire, K.; Ofek, E. O.; Prentice, S.; Schulze, S.; Spyromilio, J.; Valenti, S.; Arcavi, I.; Corsi, A.; Howell, D. A.; Mazzali, P.; Kasliwal, M. M.; Taddia, F.; Yaron, O.

2018-06-01

We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2 mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span ‑22 ≲ M g ≲ ‑20 mag, and these peaks are not powered by radioactive 56Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the 56Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 M ⊙ of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of 56Co, up to ∼400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.

Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6–5856: Constraints on the orbital geometry and relativistic flow

DOE PAGES

An, Hongjun; Romani, Roger W.

2017-04-04

We present broadband spectral energy distributions and light curves of the gamma-ray binary 1FGL J1018.6–5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a simple one-zone model is inadequate to explainmore » the IBS emission, but that beamed Synchrotron-self Compton radiation from adiabatically accelerated plasma in the shocked pulsar wind can reproduce the complex multiband light curves, including the variable X-ray spike coincident with the gamma-ray maximum. Furthermore, the model requires an inclination of ~50° and an orbital eccentricity of ~0.35, consistent with the limited constraints from existing optical observations. This picture motivates searches for pulsations from the energetic young pulsar powering the wind shock.« less

Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6–5856: Constraints on the orbital geometry and relativistic flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Hongjun; Romani, Roger W.

We present broadband spectral energy distributions and light curves of the gamma-ray binary 1FGL J1018.6–5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a simple one-zone model is inadequate to explainmore » the IBS emission, but that beamed Synchrotron-self Compton radiation from adiabatically accelerated plasma in the shocked pulsar wind can reproduce the complex multiband light curves, including the variable X-ray spike coincident with the gamma-ray maximum. Furthermore, the model requires an inclination of ~50° and an orbital eccentricity of ~0.35, consistent with the limited constraints from existing optical observations. This picture motivates searches for pulsations from the energetic young pulsar powering the wind shock.« less

Light-curve analysis of KOI 2700b: the second extrasolar planet with a comet-like tail

NASA Astrophysics Data System (ADS)

Garai, Z.

2018-03-01

Context. The Kepler object KOI 2700b (KIC 8639908b) was discovered recently as the second exoplanet with a comet-like tail. It exhibits a distinctly asymmetric transit profile, likely indicative of the emission of dusty effluents and reminiscent of KIC 12557548b, the first exoplanet with a comet-like tail. Aim. The scientific goal of this work is to verify the disintegrating-planet scenario of KOI 2700b by modeling its light curve and to put constraints on various tail and planet properties, as was done in the case of KIC 12557548b. Methods: We obtained the phase-folded and binned transit light curve of KOI 2700b, which we subsequently iteratively modeled using the radiative-transfer code SHELLSPEC. We modeled the comet-like tail as part of a ring around the parent star and we also included the solid body of the planet in the model. During the modeling we applied selected species and dust particle sizes. Results: We confirmed the disintegrating-planet scenario of KOI 2700b. Furthermore, via modeling, we derived some interesting features of KOI 2700b and its comet-like tail. It turns out that the orbital plane of the planet and its tail are not edge-on, but the orbital inclination angle is from the interval [85.1, 88.6] deg. In comparison with KIC 12557548b, KOI 2700b exhibits a relatively low dust density decreasing in its tail. We also derived the dust density at the beginning of the ring and the highest optical depth through the tail in front of the star, based on a tail-model with a cross-section of 0.05 × 0.05 R⊙ at the beginning and 0.09 × 0.09 R⊙ at its end. Our results show that the dimension of the planet is Rp/Rs ≤ 0.014 (Rp ≤ 0.871 R⊕, or ≤5551 km). We also estimated the mass-loss rate from KOI 2700b, and we obtained Ṁ values from the interval [5.05 × 107, 4.41 × 1015] g s-1. On the other hand, we could not draw any satisfactory conclusions about the typical grain size in the dust tail.

Transit Timing Variation analysis with Kepler light curves of KOI 227 and Kepler 93b

NASA Astrophysics Data System (ADS)

Dulz, Shannon; Reed, Mike

2017-01-01

By searching for transit signals in approximately 150,000 stars, NASA’s Kepler Space telescope found thousands of exoplanets over its primary mission from 2009 to 2013 (Tenenbaum et al. 2014, ApJS, 211, 6). Yet, a detailed follow-up examination of Kepler light curves may contribute more evidence on system dynamics and planetary atmospheres of these objects. Kepler’s continuous observing of these systems over the mission duration produced light curves of sufficient duration to allow for the search for transit timing variations. Transit timing variations over the course of many orbits may indicate a precessing orbit or the existence of a non-transiting third body such as another exoplanet. Flux contributions of the planet just prior to secondary eclipse may provide a measurement of bond albedo from the day-side of the transiting planet. Any asymmetries of the transit shape may indicate thermal asymmetries which can measure upper atmosphere motion of the planet. These two factors can constrain atmospheric models of close orbiting exoplanets. We first establish our procedure with the well-documented TTV system, KOI 227 (Nesvorny et al. 2014, ApJ, 790, 31). Using the test case of KOI 227, we analyze Kepler-93b for TTVs and day-side flux contributions. Kepler-93b is likely a rocky planet with R = 1.50 ± 0.03 Earth Radii and M = 2.59 ± 2.0 Earth Masses (Marcy et al. 2014, ApJS, 210, 20). This research is funded by a NASA EPSCoR grant.

The mass of the black hole in 1A 0620-00, revisiting the ellipsoidal light curve modelling

NASA Astrophysics Data System (ADS)

van Grunsven, Theo F. J.; Jonker, Peter G.; Verbunt, Frank W. M.; Robinson, Edward L.

2017-12-01

The mass distribution of stellar-mass black holes can provide important clues to supernova modelling, but observationally it is still ill constrained. Therefore, it is of importance to make black hole mass measurements as accurate as possible. The X-ray transient 1A 0620-00 is well studied, with a published black hole mass of 6.61 ± 0.25 M⊙, based on an orbital inclination i of 51.0° ± 0.9°. This was obtained by Cantrell et al. (2010) as an average of independent fits to V-, I- and H-band light curves. In this work, we perform an independent check on the value of i by re-analysing existing YALO/SMARTS V-, I- and H-band photometry, using different modelling software and fitting strategy. Performing a fit to the three light curves simultaneously, we obtain a value for i of 54.1° ± 1.1°, resulting in a black hole mass of 5.86 ± 0.24 M⊙. Applying the same model to the light curves individually, we obtain 58.2° ± 1.9°, 53.6° ± 1.6° and 50.5° ± 2.2° for V-, I- and H-band, respectively, where the differences in best-fitting i are caused by the contribution of the residual accretion disc light in the three different bands. We conclude that the mass determination of this black hole may still be subject to systematic effects exceeding the statistical uncertainty. Obtaining more accurate masses would be greatly helped by continuous phase-resolved spectroscopic observations simultaneous with photometry.

LCC: Light Curves Classifier

NASA Astrophysics Data System (ADS)

Vo, Martin

2017-08-01

Light Curves Classifier uses data mining and machine learning to obtain and classify desired objects. This task can be accomplished by attributes of light curves or any time series, including shapes, histograms, or variograms, or by other available information about the inspected objects, such as color indices, temperatures, and abundances. After specifying features which describe the objects to be searched, the software trains on a given training sample, and can then be used for unsupervised clustering for visualizing the natural separation of the sample. The package can be also used for automatic tuning parameters of used methods (for example, number of hidden neurons or binning ratio). Trained classifiers can be used for filtering outputs from astronomical databases or data stored locally. The Light Curve Classifier can also be used for simple downloading of light curves and all available information of queried stars. It natively can connect to OgleII, OgleIII, ASAS, CoRoT, Kepler, Catalina and MACHO, and new connectors or descriptors can be implemented. In addition to direct usage of the package and command line UI, the program can be used through a web interface. Users can create jobs for ”training” methods on given objects, querying databases and filtering outputs by trained filters. Preimplemented descriptors, classifier and connectors can be picked by simple clicks and their parameters can be tuned by giving ranges of these values. All combinations are then calculated and the best one is used for creating the filter. Natural separation of the data can be visualized by unsupervised clustering.

VizieR Online Data Catalog: K2-141 b radial velocity and light curve (Barragan+, 2018)

NASA Astrophysics Data System (ADS)

Barragan, O.; Gandolfi, D.; Dai, F.; Livingston, J.; Persson, C. M.; Hirano, T.; Narita, N.; Csizmadia, Sz.; Winn, J. N.; Nespral, D.; Prieto-Arranz, J.; Smith, A. M. S.; Nowak, G.; Albrecht, S.; Antoniciello, G.; Bo Justesen, A.; Cabrera, J.; Cochran, W. D.; Deeg, H..; Eigmuller, P.; Endl, M.; Erikson, A.; Fridlund, M.; Fukui, A.; Grziwa, S.; Guenther, E.; Hatzes, A. P.; Hidalgo, D.; Johnson, M. C.; Korth, J.; Palle, E.; Patzold, M.; Rauer, H.; Tanaka, Y.; van Eylen, V.

2018-01-01

Light curve and radial velocities for K2-141 (EPIC 246393474). Light curve comes from campaing 12 of the extended Kepler mission, K2. Radial velocity data was obtained with HARPS at th3 3.6m telescope, ESO. FIES data comes from observations at the Nordic Optical Telescope (NOT). (3 data files).

Flare Characteristics from X-ray Light Curves

NASA Astrophysics Data System (ADS)

Gryciuk, M.; Siarkowski, M.; Sylwester, J.; Gburek, S.; Podgorski, P.; Kepa, A.; Sylwester, B.; Mrozek, T.

2017-06-01

A new methodology is given to determine basic parameters of flares from their X-ray light curves. Algorithms are developed from the analysis of small X-ray flares occurring during the deep solar minimum of 2009, between Solar Cycles 23 and 24, observed by the Polish Solar Photometer in X-rays (SphinX) on the Complex Orbital Observations Near-Earth of Activity of the Sun-Photon (CORONAS- Photon) spacecraft. One is a semi-automatic flare detection procedure that gives start, peak, and end times for single ("elementary") flare events under the assumption that the light curve is a simple convolution of a Gaussian and exponential decay functions. More complex flares with multiple peaks can generally be described by a sum of such elementary flares. Flare time profiles in the two energy ranges of SphinX (1.16 - 1.51 keV, 1.51 - 15 keV) are used to derive temperature and emission measure as a function of time during each flare. The result is a comprehensive catalogue - the SphinX Flare Catalogue - which contains 1600 flares or flare-like events and is made available for general use. The methods described here can be applied to observations made by Geosynchronous Operational Environmental Satellites (GOES), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and other broad-band spectrometers.

Light Curve and SED Modeling of the Gamma-Ray Binary 1FGL J1018.6–5856: Constraints on the Orbital Geometry and Relativistic Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Hongjun; Romani, Roger W., E-mail: hjan@chungbuk.ac.kr

We present broadband spectral energy distributions and light curves of the gamma-ray binary 1FGL J1018.6−5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a simple one-zone model is inadequate to explainmore » the IBS emission, but that beamed Synchrotron-self Compton radiation from adiabatically accelerated plasma in the shocked pulsar wind can reproduce the complex multiband light curves, including the variable X-ray spike coincident with the gamma-ray maximum. The model requires an inclination of ∼50° and an orbital eccentricity of ∼0.35, consistent with the limited constraints from existing optical observations. This picture motivates searches for pulsations from the energetic young pulsar powering the wind shock.« less

Infrared rotational light curves on Jupiter induced by wave activities and cloud patterns andimplications on brown dwarfs

NASA Astrophysics Data System (ADS)

Ge, Huazhi; Zhang, Xi; Fletcher, Leigh; Orton, Glenn S.; Sinclair, James Andrew; Fernandes,, Joshua; Momary, Thomas W.; Warren, Ari; Kasaba, Yasumasa; Sato, Takao M.; Fujiyoshi, Takuya

2017-10-01

Many brown dwarfs exhibit infrared rotational light curves with amplitude varying from a fewpercent to twenty percent (Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750,105). Recently, it was claimed that weather patterns, especially planetary-scale waves in thebelts and cloud spots, are responsible for the light curves and their evolutions on brown dwarfs(Apai et al. 2017, Science, 357, 683). Here we present a clear relationship between the direct IRemission maps and light curves of Jupiter at multiple wavelengths, which might be similar withthat on cold brown dwarfs. Based on infrared disk maps from Subaru/COMICS and VLT/VISIR,we constructed full maps of Jupiter and rotational light curves at different wavelengths in thethermal infrared. We discovered a strong relationship between the light curves and weatherpatterns on Jupiter. The light curves also exhibit strong multi-bands phase shifts and temporalvariations, similar to that detected on brown dwarfs. Together with the spectra fromTEXES/IRTF, our observations further provide detailed information of the spatial variations oftemperature, ammonia clouds and aerosols in the troposphere of Jupiter (Fletcher et al. 2016,Icarus, 2016 128) and their influences on the shapes of the light curves. We conclude that waveactivities in Jupiter’s belts (Fletcher et al. 2017, GRL, 44, 7140), cloud holes, and long-livedvortices such as the Great Red Spot and ovals control the shapes of IR light curves and multi-wavelength phase shifts on Jupiter. Our finding supports the hypothesis that observed lightcurves on brown dwarfs are induced by planetary-scale waves and cloud spots.

Periodicity Analysis of X-ray Light Curves of SS 433

NASA Astrophysics Data System (ADS)

Wang, J. Y.; Lu, X. L.; Zhao, Q. W.; Dong, D. Q.; Lao, B. Q.; Lu, Y.; Wei, Y. H.; Wu, X. C.; An, T.

2016-03-01

SS 433 is the only X-ray binary to date that was detected to have a pair of well-collimated jets, and its orbital period, super orbital period, and nutation period were all detected at the same time. The study on the periodic X-ray variabilities is helpful for understanding its dynamic process of the central engine and the correlation with other bands. In the present paper, two time series analysis techniques, Lomb-Scargle periodogram and weighted wavelet Z-transform, are employed to search for the periodicities from the Swift/BAT (Burst Alert Telescope)(15--50 keV) and RXTE/ASM (Rossi X-Ray Timing Explorer/All-Sky Monitor)(1.5--3, 3--5 and 5--12 keV) light curves of SS 433, and the Monte Carlo simulation is performed. For the 15--50 keV energy band, five significant periodic signals are detected, which are P_1(˜6.29 d), P_2 (˜6.54 d), P_3 (˜13.08 d), P_4 (˜81.50 d), and P_5 (˜162.30 d). For the 3--5 and 5--12 keV energy bands, periodic signals P_3 (˜13 d) and P_5 (˜162 d) are detected in both energy bands. However, for the 1.5--3 keV energy band, no significant periodic signal is detected. P_5 has the strongest periodic signal in the power spectrum for all the energy bands of 3--5, 5--12, and 15--50 keV, and it is consistent with that obtained by previous study in optical band. Further, due to the existence of relativistic radio jets, the X-ray and optical band variability of P_5 (˜162 d) is probably related to the precession of the relativistic jets. High coherence between X-ray and optical light curves may also imply that the X-ray and optical emissions are of the same physical origin. P_3 shows a good agreement with the orbital period (˜13.07 d) first obtained by previous study, and P_2 and P_4 are the high frequency harmonic components of P_3 and P_5, respectively. P_1 is detected from the power spectrum of 15--50 keV energy band only, and it is consistent with the systematic nutation period. As the power of energy band decreases (from hard X-ray to

A Light-curve Analysis of Gamma-Ray Nova V959 Mon: Distance and White Dwarf Mass

NASA Astrophysics Data System (ADS)

Hachisu, Izumi; Kato, Mariko

2018-05-01

V959 Mon is a nova detected in gamma-rays. It was discovered optically about 50 days after the gamma-ray detection owing to its proximity to the Sun. The nova’s speed class is unknown because of the lack of the earlier half of its optical light curve and a short supersoft X-ray phase due to eclipse by the disk rim. Using the universal decline law and time-stretching method, we analyzed the data on V959 Mon and obtained nova parameters. We estimated the distance modulus in the V band to be (m ‑ M) V = 13.15 ± 0.3 for the reddening of E(B ‑ V) = 0.38 ± 0.01 by directly comparing it with novae of a similar type—LV Vul, V1668 Cyg, IV Cep, and V1065 Cen. The distance to V959 Mon is 2.5 ± 0.5 kpc. If we assume that the early phase of the light curve of V959 Mon is the same as that of time-stretched light curves of LV Vul, our model fitting of the light curve suggests that the white dwarf (WD) mass is 0.9–1.15 M ⊙, which is consistent with a neon nova identification. At the time of gamma-ray detection the photosphere of the nova envelope extends to 5–8 R ⊙ (about two or three times the binary separation) and the wind mass-loss rate is (3{--}4)× {10}-5 {M}ȯ yr‑1. The period of hard X-ray emission is consistent with the time of appearance of the companion star from the nova envelope. The short supersoft X-ray turnoff time is consistent with the epoch when the WD photosphere shrank to behind the rising disk rim, which occurred 500 days before nuclear burning turned off.

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.

Supernovae with two peaks in the optical light curve and the signature of progenitors with low-mass extended envelopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakar, Ehud; Piro, Anthony L.

2014-06-20

Early observations of supernova light curves are powerful tools for shedding light on the pre-explosion structures of their progenitors and their mass-loss histories just prior to explosion. Some core-collapse supernovae that are detected during the first days after the explosion prominently show two peaks in the optical bands, including the R and I bands, where the first peak appears to be powered by the cooling of shocked surface material and the second peak is clearly powered by radioactive decay. Such light curves have been explored in detail theoretically for SN 1993J and 2011dh, where it was found that they maymore » be explained by progenitors with extended, low-mass envelopes. Here, we generalize these results. We first explore whether any double-peaked light curve of this type can be generated by a progenitor with a 'standard' density profile, such as a red supergiant or a Wolf-Rayet star. We show that a standard progenitor (1) cannot produce a double-peaked light curve in the R and I bands and (2) cannot exhibit a fast drop in the bolometric luminosity as is seen after the first peak. We then explore the signature of a progenitor with a compact core surrounded by extended, low-mass material. This may be a hydrostatic low-mass envelope or material ejected just prior to the explosion. We show that it naturally produces both of these features. We use this result to provide simple formulae to estimate (1) the mass of the extended material from the time of the first peak, (2) the extended material radius from the luminosity of the first peak, and (3) an upper limit on the core radius from the luminosity minimum between the two peaks.« less

The Palomar Transient Factory and RR Lyrae: The Metallicity–Light Curve Relation Based on ab-type RR Lyrae in the Kepler Field

NASA Astrophysics Data System (ADS)

Ngeow, Chow-Choong; Yu, Po-Chieh; Bellm, Eric; Yang, Ting-Chang; Chang, Chan-Kao; Miller, Adam; Laher, Russ; Surace, Jason; Ip, Wing-Huen

2016-12-01

The wide-field synoptic sky surveys, known as the Palomar Transient Factory (PTF) and the intermediate Palomar Transient Factory (iPTF), will accumulate a large number of known and new RR Lyrae. These RR Lyrae are good tracers to study the substructure of the Galactic halo if their distance, metallicity, and galactocentric velocity can be measured. Candidates of halo RR Lyrae can be identified from their distance and metallicity before requesting spectroscopic observations for confirmation. This is because both quantities can be obtained via their photometric light curves, because the absolute V-band magnitude for RR Lyrae is correlated with metallicity, and the metallicity can be estimated using a metallicity–light curve relation. To fully utilize the PTF and iPTF light-curve data in related future work, it is necessary to derive the metallicity–light curve relation in the native PTF/iPTF R-band photometric system. In this work, we derived such a relation using the known ab-type RR Lyrae located in the Kepler field, and it is found to be {[{Fe}/{{H}}]}PTF}=-4.089{--}7.346P+1.280{φ }31 (where P is pulsational period and {φ }31 is one of the Fourier parameters describing the shape of the light curve), with a dispersion of 0.118 dex. We tested our metallicity–light curve relation with new spectroscopic observations of a few RR Lyrae in the Kepler field, as well as several data sets available in the literature. Our tests demonstrated that the derived metallicity–light curve relation could be used to estimate metallicities for the majority of the RR Lyrae, which are in agreement with the published values.

Spotted star light curve numerical modeling technique and its application to HII 1883 surface imaging

NASA Astrophysics Data System (ADS)

Kolbin, A. I.; Shimansky, V. V.

2014-04-01

We developed a code for imaging the surfaces of spotted stars by a set of circular spots with a uniform temperature distribution. The flux from the spotted surface is computed by partitioning the spots into elementary areas. The code takes into account the passing of spots behind the visible stellar limb, limb darkening, and overlapping of spots. Modeling of light curves includes the use of recent results of the theory of stellar atmospheres needed to take into account the temperature dependence of flux intensity and limb darkening coefficients. The search for spot parameters is based on the analysis of several light curves obtained in different photometric bands. We test our technique by applying it to HII 1883.

Silicon micromachined broad band light source

NASA Technical Reports Server (NTRS)

George, Thomas (Inventor); Jones, Eric (Inventor); Tuma, Margaret L. (Inventor); Eastwood, Michael (Inventor); Hansler, Richard (Inventor)

2004-01-01

A micro electromechanical system (MEMS) broad band incandescent light source includes three layers: a top transmission window layer; a middle filament mount layer; and a bottom reflector layer. A tungsten filament with a spiral geometry is positioned over a hole in the middle layer. A portion of the broad band light from the heated filament is reflective off the bottom layer. Light from the filament and the reflected light of the filament are transmitted through the transmission window. The light source may operate at temperatures of 2500 K or above. The light source may be incorporated into an on board calibrator (OBC) for a spectrometer.

Analysis of photometric light curves solution for massive contact OB binary stars. LY Aurigae, BH Centauri, SV Centauri

NASA Astrophysics Data System (ADS)

Avvakumova, E. A.

2010-01-01

We searched for signs of the presence of circumstellar gaseous matter in photometric data for massive contact early-type binaries by analyzing residual curves (the dependence of the difference between the observed and theoretical brightness variations on the orbital-period phase) for three such stars. The residual curves make it possible to estimate the influence of gas in the common envelope on the observed light curves for different phase intervals and to qualitatively describe the character of the distortion of the light from the system’s components. Changes of the residual curves from filter to filter indicate varying conditions in the circumstellar matter. Changes of the residual curves from one observation epoch to another indicate varying conditions in the circumstellar matter. We compared the residual curves obtained for different photometric bands and epochs via a correlation analysis. The distortion of light from the components of LY Aurigae in the ultraviolet differs from that in the visual. The distortion of light from the components of SV Centauri is appreciable, but not selective, and does not vary in time, while the distortion of light from BH Centauri possesses a strong selective component. A comparison of the radii computed for the components of BH Centauri and SV Centauri shows that the gas distribution near these binaries varies in time.

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.

Polyp detection rates using magnification with narrow band imaging and white light.

PubMed

Gilani, Nooman; Stipho, Sally; Panetta, James D; Petre, Sorin; Young, Michele A; Ramirez, Francisco C

2015-05-16

To compare the yield of adenomas between narrow band imaging and white light when using high definition/magnification. This prospective, non-randomized comparative study was performed at the endoscopy unit of veteran affairs medical center in Phoenix, Arizona. Consecutive patients undergoing first average risk colorectal cancer screening colonoscopy were selected. Two experienced gastroenterologists performed all the procedures that were blinded to each other's findings. Demographic details were recorded. Data are presented as mean ± SEM. Proportional data were compared using the χ(2) test and means were compared using the Student's t test. Tandem colonoscopy was performed in a sequential and segmental fashion using one of 3 strategies: white light followed by narrow band imaging [Group A: white light (WL) → narrow band imaging (NBI)]; narrow band imaging followed by white light (Group B: NBI → WL) and, white light followed by white light (Group C: WL → WL). Detection rate of missed polyps and adenomas were evaluated in all three groups. Three hundred patients were studied (100 in each Group). Although the total time for the colonoscopy was similar in the 3 groups (23.8 ± 0.7, 22.2 ± 0.5 and 24.1 ± 0.7 min for Groups A, B and C, respectively), it reached statistical significance between Groups B and C (P < 0.05). The cecal intubation time in Groups B and C was longer than for Group A (6.5 ± 0.4 min and 6.5 ± 0.4 min vs 4.9 ± 0.3 min; P < 0.05). The withdrawal time for Groups A and C was longer than Group B (18.9 ± 0.7 min and 17.6 ± 0.6 min vs 15.7 ± 0.4 min; P < 0.05). Overall miss rate for polyps and adenomas detected in three groups during the second look was 18% and 17%, respectively (P = NS). Detection rate for polyps and adenomas after first look with white light was similar irrespective of the light used during the second look (WL → WL: 13.7% for polyps, 12.6% for adenomas; WL → NBI: 14.2% for polyps, 11.3% for adenomas). Miss rate of

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.

Exoplanet Atmospheres: From Light-Curve Analyses to Radiative-Transfer Modeling

NASA Astrophysics Data System (ADS)

Cubillos, Patricio; Harrington, Joseph; Blecic, Jasmina; Rojo, Patricio; Stemm, Madison; Lust, Nathaniel B.; Foster, Andrew S.; Loredo, Thomas J.

2015-01-01

Multi-wavelength transit and secondary-eclipse light-curve observations are some of the most powerful techniques to probe the thermo-chemical properties of exoplanets. Although the small planet-to-star constrast ratios demand a meticulous data analysis, and the limited available spectral bands can further restrain constraints, a Bayesian approach can robustly reveal what constraints can we set, given the data.We review the main aspects considered during the analysis of Spitzer time-series data by our group with an aplication to WASP-8b and TrES-1. We discuss the applicability and limitations of the most commonly used correlated-noise estimators. We describe our open-source Bayesian Atmospheric Radiative Transfer (BART) code. BART calculates the planetary emission or transmission spectrum by solving a 1D line-by-line radiative-transfer equation. The generated spectra are integrated over determined bandpasses for comparison to the data. Coupled to our Multi-core Markov-chain Monte Carlo (MC3) statistical package, BART constrains the temperature profile and chemical abundances in the planet's atmosphere. We apply the BART retrieval code to the HD 209458b data set to estimate the planet's temperature profile and molecular abundances.This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. JB holds a NASA Earth and Space Science Fellowship.

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

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.

lcps: Light curve pre-selection

NASA Astrophysics Data System (ADS)

Schlecker, Martin

2018-05-01

lcps searches for transit-like features (i.e., dips) in photometric data. Its main purpose is to restrict large sets of light curves to a number of files that show interesting behavior, such as drops in flux. While lcps is adaptable to any format of time series, its I/O module is designed specifically for photometry of the Kepler spacecraft. It extracts the pre-conditioned PDCSAP data from light curves files created by the standard Kepler pipeline. It can also handle csv-formatted ascii files. lcps uses a sliding window technique to compare a section of flux time series with its surroundings. A dip is detected if the flux within the window is lower than a threshold fraction of the surrounding fluxes.

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

NASA Astrophysics Data System (ADS)

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.; Piro, Anthony L.; Shappee, B. J.; Stritzinger, Maximilian D.; Baltay, C.; Brown, Peter J.; Conseil, Emmanuel; Klotz, Alain; Nugent, Peter E.; Turpin, Damien; Parker, Stu; Rabinowitz, D.; Hsiao, Eric Y.; Morrell, Nidia; Campillay, Abdo; Castellón, Sergio; Corco, Carlos; González, Consuelo; Krisciunas, Kevin; Serón, Jacqueline; Tucker, Brad E.; Walker, E. S.; Baron, E.; Cain, C.; Childress, Michael J.; Folatelli, Gastón; Freedman, Wendy L.; Hamuy, Mario; Hoeflich, P.; Persson, S. E.; Scalzo, Richard; Schmidt, Brian; Suntzeff, Nicholas B.

2018-05-01

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from ‑12 to +140 days with respect to the epoch of B-band maximum ({t}{B\\max }). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ∼2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred <22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ > 1800 Å) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca II and Si II absorption features, and a nearly constant photospheric velocity of the Si II λ6355 line at ∼12,000 {km} {{{s}}}-1 that began ∼5 days before {t}{B\\max }. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements. This paper includes data gathered with the 6.5 m Magellan Baade Telescope, located at Las Campanas Observatory, Chile.

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

DOE PAGES

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.; ...

2018-05-18

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (more » $${t}_{{B}_{\\max }}$$). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ~2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56 Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred < 22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ >1800) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ~12,000 km s -1 that began ~5 days before $${t}_{{B}_{\\max }}$$. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.« less

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (more » $${t}_{{B}_{\\max }}$$). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ~2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56 Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred < 22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ >1800) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ~12,000 km s -1 that began ~5 days before $${t}_{{B}_{\\max }}$$. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.« less

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.

The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0

NASA Astrophysics Data System (ADS)

Kochanek, C. S.; Shappee, B. J.; Stanek, K. Z.; Holoien, T. W.-S.; Thompson, Todd A.; Prieto, J. L.; Dong, Subo; Shields, J. V.; Will, D.; Britt, C.; Perzanowski, D.; Pojmański, G.

2017-10-01

The All-Sky Automated Survey for Supernovae (ASAS-SN) is working toward imaging the entire visible sky every night to a depth of V˜ 17 mag. The present data covers the sky and spans ˜2-5 years with ˜100-400 epochs of observation. The data should contain some ˜1 million variable sources, and the ultimate goal is to have a database of these observations publicly accessible. We describe here a first step, a simple but unprecedented web interface https://asas-sn.osu.edu/ that provides an up to date aperture photometry light curve for any user-selected sky coordinate. The V band photometry is obtained using a two-pixel (16.″0) radius aperture and is calibrated against the APASS catalog. Because the light curves are produced in real time, this web tool is relatively slow and can only be used for small samples of objects. However, it also imposes no selection bias on the part of the ASAS-SN team, allowing the user to obtain a light curve for any point on the celestial sphere. We present the tool, describe its capabilities, limitations, and known issues, and provide a few illustrative examples.

The light curve of SN 1987A revisited: constraining production masses of radioactive nuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seitenzahl, Ivo R.; Timmes, F. X.; Magkotsios, Georgios, E-mail: ivo.seitenzahl@anu.edu.au

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, andmore » {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.« less

Multi-band, multi-epoch observations of the transiting warm Jupiter WASP-80b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukui, Akihiko; Kuroda, Daisuke; Kawashima, Yui

WASP-80b is a warm Jupiter transiting a bright late-K/early-M dwarf, providing a good opportunity to extend the atmospheric study of hot Jupiters toward the lower temperature regime. We report multi-band, multi-epoch transit observations of WASP-80b by using three ground-based telescopes covering from optical (g', R{sub c}, and I{sub c} bands) to near-infrared (NIR; J, H, and K{sub s} bands) wavelengths. We observe 5 primary transits, each in 3 or 4 different bands simultaneously, obtaining 17 independent transit light curves. Combining them with results from previous works, we find that the observed transmission spectrum is largely consistent with both a solarmore » abundance and thick cloud atmospheric models at a 1.7σ discrepancy level. On the other hand, we find a marginal spectral rise in the optical region compared to the NIR region at the 2.9σ level, which possibly indicates the existence of haze in the atmosphere. We simulate theoretical transmission spectra for a solar abundance but hazy atmosphere, finding that a model with equilibrium temperature of 600 K can explain the observed data well, having a discrepancy level of 1.0σ. We also search for transit timing variations, but find no timing excess larger than 50 s from a linear ephemeris. In addition, we conduct 43 day long photometric monitoring of the host star in the optical bands, finding no significant variation in the stellar brightness. Combined with the fact that no spot-crossing event is observed in the five transits, our results confirm previous findings that the host star appears quiet for spot activities, despite the indications of strong chromospheric activities.« less

Testing Cataclysmic Variable Evolution Models with Light Curves of >10,000 Magnitudes Over >100 years and Fully-Corrected to Johnson B & V

NASA Astrophysics Data System (ADS)

Schaefer, Bradley E.

2014-06-01

A combination of magnitudes from the Harvard and Sonneberg plates stacks and the AAVSO data base can create very well-sampled light curves with >10,000 magnitudes and covering all of 1890-2014 for roughly a hundred cataclysmic variables (CVs; novae, novalikes, and dwarf novae). Care must be taken to get all these magnitudes into a modern magnitude system. For the archival plates, these are all close to the B magnitude system so that color terms are small, hence, with the use of modern B magnitudes for the comparison stars, these magnitudes can all be placed onto the Johnson B system. For the archival visual observations, the original comparison sequences can always be found, and the magnitudes for the CV and comparisons must be converted from visual to V, so that the reported magnitudes can be fully corrected to Johnson V. The uncertainties from the plates and the visual magnitudes can always be beaten down by daily or yearly averaging to typical real total error bars of ±0.03 mag, and these are always much smaller than the sampling error arising from flickering and greatly smaller than the range of variations. These very-well-sampled >100 year Johnson B & V light curves can be used to test long term evolution models for CVs. With colleagues, I have made light curves for old novae (GK Per from 1890-2014 with 47,000 mags, V603 Aql from 1898-2014 using 22,722 mags, Q Cyg from 1876-2014 with 6400 mags, T CrB from 1855-2014 using 104,000 mags), Z Cam stars (Z Cam from 1923-2014 with 90,000 mags), and dwarf novae (SS Cyg from 1896-2014 with 403,800 mags). The relative accretion rate is given by both the average flux and by the inverse of the average peak-to-peak time for the dwarf novae. By this means, I have measured the changes in the accretion rate for many CVs and how they change on a yearly basis for a century and longer. These observations are directly compared to various CV evolution models. A complex set of agreements and disagreements is found.

EVEREST: Pixel Level Decorrelation of K2 Light Curves

NASA Astrophysics Data System (ADS)

Luger, Rodrigo; Agol, Eric; Kruse, Ethan; Barnes, Rory; Becker, Andrew; Foreman-Mackey, Daniel; Deming, Drake

2016-10-01

We present EPIC Variability Extraction and Removal for Exoplanet Science Targets (EVEREST), an open-source pipeline for removing instrumental noise from K2 light curves. EVEREST employs a variant of pixel level decorrelation to remove systematics introduced by the spacecraft’s pointing error and a Gaussian process to capture astrophysical variability. We apply EVEREST to all K2 targets in campaigns 0-7, yielding light curves with precision comparable to that of the original Kepler mission for stars brighter than {K}p≈ 13, and within a factor of two of the Kepler precision for fainter targets. We perform cross-validation and transit injection and recovery tests to validate the pipeline, and compare our light curves to the other de-trended light curves available for download at the MAST High Level Science Products archive. We find that EVEREST achieves the highest average precision of any of these pipelines for unsaturated K2 stars. The improved precision of these light curves will aid in exoplanet detection and characterization, investigations of stellar variability, asteroseismology, and other photometric studies. The EVEREST pipeline can also easily be applied to future surveys, such as the TESS mission, to correct for instrumental systematics and enable the detection of low signal-to-noise transiting exoplanets. The EVEREST light curves and the source code used to generate them are freely available online.

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.

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.

Type II Supernova Energetics and Comparison of Light Curves to Shock-Cooling Models

NASA Technical Reports Server (NTRS)

Rubin, Adam; Gal-Yam, Avishay; Cia, Annalisa De; Horesh, Assaf; Khazov, Danny; Ofek, Eran O.; Kulkarni, S. R.; Arcavi, Iair; Manulis, Ilan; Cenko, S. Bradley

2016-01-01

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 greater than 5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 13 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 EM = (0.2-20) x 10(exp 51) erg/(10 M stellar mass), and have a mean energy per unit mass of E/ M = 0.85 x 10(exp 51) erg(10 stellar mass), 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 Ni-56 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 (Delta m(sub15), 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.

FBEYE: Analyzing Kepler light curves and validating flares

NASA Astrophysics Data System (ADS)

Johnson, Emily; Davenport, James R. A.; Hawley, Suzanne L.

2017-12-01

FBEYE, the "Flares By-Eye" detection suite, is written in IDL and analyzes Kepler light curves and validates flares. It works on any 3-column light curve that contains time, flux, and error. The success of flare identification is highly dependent on the smoothing routine, which may not be suitable for all sources.

High-Resolution Synchrotron Infrared Spectroscopy of Thiophosgene: the νb{1}, νb{5}, 2νb{4}, and νb{2} + 2νb{6} bands

NASA Astrophysics Data System (ADS)

McKellar, Bob; Billinghurst, Brant E.

2015-06-01

Thiophosgene (Cl_2CS) is a favorite model system for studies of photophysics, vibrational dynamics, and intersystem interactions. But at high resolution its infrared spectrum is very congested due to hot bands and multiple isotopic species. Previously, we reported the first high resolution IR study of this molecule, analyzing the νb{2} (504 wn) and νb{4} (471 wn) fundamental bands. Here we continue, with analysis of the νb{1} (1139 wn) and νb{5} (820 wn) fundamentals for the two most abundant isotopologues, 35Cl2CS and 35Cl37ClCS, based on spectra with a resolution of about 0.001 wn obtained at the Canadian Light Source far-infrared beamline using synchrotron radiation and a Bruker IFS125 Fourier transform spectrometer. The νb{2} + νb{4} (942 wn) and νb{2} + 2νb{6} (1104 wn) bands are also studied here. But so far the νb{2} + νb{6} combination band (795 wn) resists analysis, as do the weak νb{3} (292.9 wn) and νb{6} (≈300? wn) fundamentals. A.R.W. McKellar, B.E.Billinghurst, J. Mol. Spectrosc. 260, 66 (2010).

Polyp detection rates using magnification with narrow band imaging and white light

PubMed Central

Gilani, Nooman; Stipho, Sally; Panetta, James D; Petre, Sorin; Young, Michele A; Ramirez, Francisco C

2015-01-01

AIM: To compare the yield of adenomas between narrow band imaging and white light when using high definition/magnification. METHODS: This prospective, non-randomized comparative study was performed at the endoscopy unit of veteran affairs medical center in Phoenix, Arizona. Consecutive patients undergoing first average risk colorectal cancer screening colonoscopy were selected. Two experienced gastroenterologists performed all the procedures that were blinded to each other’s findings. Demographic details were recorded. Data are presented as mean ± SEM. Proportional data were compared using the χ2 test and means were compared using the Student’s t test. Tandem colonoscopy was performed in a sequential and segmental fashion using one of 3 strategies: white light followed by narrow band imaging [Group A: white light (WL) → narrow band imaging (NBI)]; narrow band imaging followed by white light (Group B: NBI → WL) and, white light followed by white light (Group C: WL → WL). Detection rate of missed polyps and adenomas were evaluated in all three groups. RESULTS: Three hundred patients were studied (100 in each Group). Although the total time for the colonoscopy was similar in the 3 groups (23.8 ± 0.7, 22.2 ± 0.5 and 24.1 ± 0.7 min for Groups A, B and C, respectively), it reached statistical significance between Groups B and C (P < 0.05). The cecal intubation time in Groups B and C was longer than for Group A (6.5 ± 0.4 min and 6.5 ± 0.4 min vs 4.9 ± 0.3 min; P < 0.05). The withdrawal time for Groups A and C was longer than Group B (18.9 ± 0.7 min and 17.6 ± 0.6 min vs 15.7 ± 0.4 min; P < 0.05). Overall miss rate for polyps and adenomas detected in three groups during the second look was 18% and 17%, respectively (P = NS). Detection rate for polyps and adenomas after first look with white light was similar irrespective of the light used during the second look (WL → WL: 13.7% for polyps, 12.6% for adenomas; WL → NBI: 14.2% for polyps, 11.3% for

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.

Multi-frequency properties of synthetic blazar radio light curves within the shock-in-jet scenario

NASA Astrophysics Data System (ADS)

Fromm, C. M.; Fuhrmann, L.; Perucho, M.

2015-08-01

Context. Blazars are among the most powerful extragalactic objects as a sub-class of active galactic nuclei. They launch relativistic jets and their emitted radiation shows strong variability across the entire electro-magnetic spectrum. The mechanisms producing the variability are still controversial, and different models have been proposed to explain the observed variations in multi-frequency blazar light curves. Aims: We investigate the capabilities of the classical shock-in-jet model to explain and reconstruct the observed evolution of flares in the turnover frequency - turnover flux density (νm-Sm) plane and their frequency dependent light curve parameters. With a detailed parameter space study, we provide the framework for future, detailed comparisons of observed flare signatures with the shock-in-jet scenario. Methods: Based on the shock model, we compute synthetic single-dish light curves at different radio frequencies (2.6 to 345 GHz) and for different physical conditions in a conical jet (e.g. magnetic field geometry and Doppler factor). From those we extract the slopes of the different energy loss stages within the (νm-Sm) plane and deduce the frequency dependence of different light curve parameters, such as flare amplitude, time scale, and cross-band delays. Results: The evolution of the Doppler factor along the jet has the strongest influence on the evolution of the flare and on the frequency dependent light curve parameters. The synchrotron stage can be hidden in the Compton or in the adiabatic stage, depending mainly on the evolution of the Doppler factor, which makes it difficult to detect its signature in observations. In addition, we show that the time lags between different frequencies can be used as an efficient tool to better constrain the physical properties of these objects. Appendix A is available in electronic form at http://www.aanda.org

Type II Supernova Light Curves and Spectra from the CfA

NASA Astrophysics Data System (ADS)

Hicken, Malcolm; Friedman, Andrew S.; Blondin, Stephane; Challis, Peter; Berlind, Perry; Calkins, Mike; Esquerdo, Gil; Matheson, Thomas; Modjaz, Maryam; Rest, Armin; Kirshner, Robert P.

2017-11-01

We present multiband photometry of 60 spectroscopically confirmed supernovae (SNe): 39 SNe II/IIP, 19 IIn, 1 IIb, and 1 that was originally classified as a IIn but later as a Ibn. Of these, 46 have only optical photometry, 6 have only near-infrared (NIR) photometry, and 8 have both optical and NIR. The median redshift of the sample is 0.016. We also present 195 optical spectra for 48 of the 60 SN. There are 26 optical and 2 NIR light curves of SNe II/IIP with redshifts z> 0.01, some of which may give rise to useful distances for cosmological applications. All photometry was obtained between 2000 and 2011 at the Fred Lawrence Whipple Observatory (FLWO), via the 1.2 m and 1.3 m PAIRITEL telescopes for the optical and NIR, respectively. Each SN was observed in a subset of the u\\prime {UBVRIr}\\prime I\\prime {{JHK}}s bands. There are a total of 2932 optical and 816 NIR light curve points. Optical spectra were obtained using the FLWO 1.5 m Tillinghast telescope with the FAST spectrograph and the MMT Telescope with the Blue Channel Spectrograph. Our photometry is in reasonable agreement with select samples from the literature: two-thirds of our star sequences have average V offsets within ±0.02 mag and roughly three-quarters of our light curves have average differences within ±0.04 mag. The data from this work and the literature will provide insight into SN II explosions, help with developing methods for photometric SN classification, and contribute to their use as cosmological distance indicators.

An Empirical Fitting Method for Type Ia Supernova Light Curves: A Case Study of SN 2011fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, WeiKang; Filippenko, Alexei V., E-mail: zwk@astro.berkeley.edu

We present a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe Ia). We find that a variant broken-power-law function provides a good fit, with the simple assumption that the optical emission is approximately the blackbody emission of the expanding fireball. This function is mathematically analytic and is derived directly from the photospheric velocity evolution. When deriving the function, we assume that both the blackbody temperature and photospheric velocity are constant, but the final function is able to accommodate these changes during the fitting procedure. Applying it to the case study of SN 2011fe givesmore » a surprisingly good fit that can describe the light curves from the first-light time to a few weeks after peak brightness, as well as over a large range of fluxes (∼5 mag, and even ∼7 mag in the g band). Since SNe Ia share similar light-curve shapes, this fitting method has the potential to fit most other SNe Ia and characterize their properties in large statistical samples such as those already gathered and in the near future as new facilities become available.« less

Exploring Algorithms for Stellar Light Curves With TESS

NASA Astrophysics Data System (ADS)

Buzasi, Derek

2018-01-01

The Kepler and K2 missions have produced tens of thousands of stellar light curves, which have been used to measure rotation periods, characterize photometric activity levels, and explore phenomena such as differential rotation. The quasi-periodic nature of rotational light curves, combined with the potential presence of additional periodicities not due to rotation, complicates the analysis of these time series and makes characterization of uncertainties difficult. A variety of algorithms have been used for the extraction of rotational signals, including autocorrelation functions, discrete Fourier transforms, Lomb-Scargle periodograms, wavelet transforms, and the Hilbert-Huang transform. In addition, in the case of K2 a number of different pipelines have been used to produce initial detrended light curves from the raw image frames.In the near future, TESS photometry, particularly that deriving from the full-frame images, will dramatically further expand the number of such light curves, but details of the pipeline to be used to produce photometry from the FFIs remain under development. K2 data offers us an opportunity to explore the utility of different reduction and analysis tool combinations applied to these astrophysically important tasks. In this work, we apply a wide range of algorithms to light curves produced by a number of popular K2 pipeline products to better understand the advantages and limitations of each approach and provide guidance for the most reliable and most efficient analysis of TESS stellar data.

Modeling of a Robust Confidence Band for the Power Curve of a Wind Turbine.

PubMed

Hernandez, Wilmar; Méndez, Alfredo; Maldonado-Correa, Jorge L; Balleteros, Francisco

2016-12-07

Having an accurate model of the power curve of a wind turbine allows us to better monitor its operation and planning of storage capacity. Since wind speed and direction is of a highly stochastic nature, the forecasting of the power generated by the wind turbine is of the same nature as well. In this paper, a method for obtaining a robust confidence band containing the power curve of a wind turbine under test conditions is presented. Here, the confidence band is bound by two curves which are estimated using parametric statistical inference techniques. However, the observations that are used for carrying out the statistical analysis are obtained by using the binning method, and in each bin, the outliers are eliminated by using a censorship process based on robust statistical techniques. Then, the observations that are not outliers are divided into observation sets. Finally, both the power curve of the wind turbine and the two curves that define the robust confidence band are estimated using each of the previously mentioned observation sets.

Modeling of a Robust Confidence Band for the Power Curve of a Wind Turbine

PubMed Central

Hernandez, Wilmar; Méndez, Alfredo; Maldonado-Correa, Jorge L.; Balleteros, Francisco

2016-01-01

Having an accurate model of the power curve of a wind turbine allows us to better monitor its operation and planning of storage capacity. Since wind speed and direction is of a highly stochastic nature, the forecasting of the power generated by the wind turbine is of the same nature as well. In this paper, a method for obtaining a robust confidence band containing the power curve of a wind turbine under test conditions is presented. Here, the confidence band is bound by two curves which are estimated using parametric statistical inference techniques. However, the observations that are used for carrying out the statistical analysis are obtained by using the binning method, and in each bin, the outliers are eliminated by using a censorship process based on robust statistical techniques. Then, the observations that are not outliers are divided into observation sets. Finally, both the power curve of the wind turbine and the two curves that define the robust confidence band are estimated using each of the previously mentioned observation sets. PMID:27941604

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

DOE PAGES

Fox, Ori D.; Smith, Nathan; Ammons, S. Mark; ...

2015-10-27

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 (>10 51 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 outmore » 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). Furthermore, 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.« less

The X-Ray Light Curve of the Very Luminous Supernova SN 1978K in NGC 1313

NASA Astrophysics Data System (ADS)

Schlegel, Eric M.; Petre, R.; Colbert, E. J. M.

1996-01-01

We present the 0.5-2.0 keV light curve of the X-ray luminous supernova SN 1978K in NGC 1313, based on six ROSAT observations spanning 1990 July to t994 July. SN 1978K is one of a few supernovae or supernova remnants that are very luminous (˜1039-1040 ergs s-1) in the X-ray, optical, and radio bands, and the first, at a supernova age of 10-20 yr, for which sufficient data exist to create an X-ray light curve. The X-ray flux is approximately constant over the 4 yr sampled by our observations, which were obtained 12-16 yr after the initial explosion. Three models exist to explain the large X-ray luminosity: pulsar input, a reverse shock running back into the expanding debris of the supernova, and the outgoing shock crushing of cloudlets in the debris field. Based upon calculations of Chevalier & Fransson, a pulsar cannot provide sufficient energy to produce the soft X-ray luminosity. Based upon the models and the light curve to date, it is not possible to discern the evolutionary phase of the supernova.

FIRST PRECISION LIGHT CURVE ANALYSIS OF THE NEGLECTED EXTREME MASS RATIO SOLAR-TYPE BINARY HR BOOTIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samec, Ronald G.; Benkendorf, Barry; Dignan, James B.

2015-04-15

HR Bootis is a neglected binary that is found to be a solar-type (G2V) extreme mass ratio binary (EMRB). It was discovered by Hanley and Shapley in 1940. Surprisingly, little has been published in the intervening years. In 1999 it was characterized by a 0.31587 day orbital period. Since that time it has been observed by various observers who have determined ∼20 timings of minimum light over the past ∼15,000 orbits. Our observations in 2012 represent the first precision curves in the BVR{sub c}I{sub c} Johnson–Cousins wavelength bands. The light curves have rather low amplitudes, averaging some 0.5 magnitudes, yetmore » they exhibit total eclipses, which is typical of the rare group of solar-type EMRBs. An improved linear ephemeris was computed along with a quadratic ephemeris showing a decaying orbit, which indicates magnetic breaking may be occurring. The light curve solution reveals that HR Boo is a contact system with a somewhat low 21% Roche-lobe fill-out but a mass ratio of q = 4.09 (0.2444), which defines it as an EMRB. Two spots, both hot, were allowed to iterate to fit the light curve asymmetries. Their radii are 32° and 16°. Both are high-latitude polar spots indicative of strong magnetic activity. The shallow contact yet nearly equal component temperatures makes it an unusual addition to this group.« less

SNaX: A Database of Supernova X-Ray Light Curves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, Mathias; Dwarkadas, Vikram V., E-mail: Mathias_Ross@msn.com, E-mail: vikram@oddjob.uchicago.edu

We present the Supernova X-ray Database (SNaX), a compilation of the X-ray data from young supernovae (SNe). The database includes the X-ray fluxes and luminosities of young SNe, from days to years after outburst. The original goal and intent of this study was to present a database of Type IIn SNe (SNe IIn), which we have accomplished. Our ongoing goal is to expand the database to include all SNe for which published data are available. The database interface allows one to search for SNe using various criteria, plot all or selected data points, and download both the data and themore » plot. The plotting facility allows for significant customization. There is also a facility for the user to submit data that can be directly incorporated into the database. We include an option to fit the decay of any given SN light curve with a power-law. The database includes a conversion of most data points to a common 0.3–8 keV band so that SN light curves may be directly compared with each other. A mailing list has been set up to disseminate information about the database. We outline the structure and function of the database, describe its various features, and outline the plans for future expansion.« less

Light curve of the optical counterpart of 2A0311-227

NASA Technical Reports Server (NTRS)

Williams, G.; Hiltner, W. A.

1980-01-01

Visual and blue light curves are presented for the optical counterpart of the X-ray source 2A0311-227. This system, which is the newest member of the AM Herculis class of binaries, has an orbital period of 81 minutes which also modulates the visual light curve. A Fourier analysis of the data has revealed the presence of a 6-minute oscillation, at least in the visual light curve. Whether or not it is also present in the blue light curve is unclear.

The bumpy light curve of Type IIn supernova iPTF13z over 3 years

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyholm, A.; Sollerman, J.; Taddia, F.

A core-collapse (CC) supernova (SN) of Type IIn is dominated by the interaction of SN ejecta with the circumstellar medium (CSM). Some SNe IIn (e.g. SN 2006jd) have episodes of re-brightening ("bumps") in their light curves. We present iPTF13z, a Type IIn SN discovered on 2013 February 1 by the intermediate Palomar Transient Factory (iPTF). This SN showed at least five bumps in its declining light curve between 130 and 750 days after discovery. We analyse this peculiar behaviour and try to infer the properties of the CSM, of the SN explosion, and the nature of the progenitor star. Wemore » obtained multi-band optical photometry for over 1000 days after discovery with the P48 and P60 telescopes at Palomar Observatory. We obtained low-resolution optical spectra during the same period. We did an archival search for progenitor outbursts. We analyse the photometry and the spectra, and compare iPTF13z to other SNe IIn. In particular we derive absolute magnitudes, colours, a pseudo-bolometric light curve, and the velocities of the different components of the spectral lines. A simple analytical model is used to estimate the properties of the CSM. iPTF13z had a light curve peaking at M r ≤ 18.3 mag. The five bumps during its decline phase had amplitudes ranging from 0.4 to 0.9 mag and durations between 20 and 120 days. The most prominent bumps appeared in all the different optical bands, when covered. The spectra of this SN showed typical SN IIn characteristics, with emission lines of Hα (with broad component FWHM ~ 10 3 - 10 4 km s -1 and narrow component FWHM ~ 10 2 km s -1 ) and He i, but also with Fe ii, Ca ii, Na i D and Hβ P Cygni profiles (with velocities of ~ 10 3 km s -1). A pre-explosion outburst was identified lasting ≳ 50 days, with M r ≤ 15 mag around 210 days before discovery. Large, variable progenitor mass-loss rates (≳ 0.01M ⊙ yr -1) and CSM densities (10 -16 g cm -3) are derived. The SN was hosted by a metal-poor dwarf galaxy at redshift z

Type II supernova energetics and comparison of light curves to shock-cooling models

DOE PAGES

Rubin, Adam; Gal-Yam, Avishay; De Cia, Annalisa; ...

2016-03-16

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, withmore » $$\\gt 5$$ 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) × 10 51 erg/(10 $${M}_{\\odot }$$), and have a mean energy per unit mass of $$\\langle E/M\\rangle =0.85\\times {10}^{51}$$ erg/(10 $${M}_{\\odot }$$), 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 ($${\\rm{\\Delta }}{m}_{15}$$), 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. Lastly, this limits the possible power sources for such events.« less

Band structures of TiO2 doped with N, C and B*

PubMed Central

Xu, Tian-Hua; Song, Chen-Lu; Liu, Yong; Han, Gao-Rong

2006-01-01

This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that the three 2p bands of impurity atom are located above the valence-band maximum and below the Ti 3d bands, and that along with the decreasing of impurity atomic number, the fluctuations become more intensive. We cannot observe obvious band-gap narrowing in our result. Therefore, the cause of absorption in visible light might be the isolated impurity atom 2p states in band-gap rather than the band-gap narrowing. PMID:16532532

The effects of low-intensity narrow-band blue-light treatment compared to bright white-light treatment in seasonal affective disorder.

PubMed

Meesters, Ybe; Duijzer, Wianne B; Hommes, Vanja

2018-05-01

Ever since a new photoreceptor was discovered with a highest sensitivity to 470-490 nm blue light, it has been speculated that blue light has some advantages in the treatment of Seasonal Affective Disorder (SAD) over more traditional treatments. In this study we compared the effects of exposure to narrow-band blue light (BLUE) to those of broad-wavelength white light (BLT) in the treatment of SAD. In a 15-day design, 45 patients suffering from SAD completed 30-min sessions of light treatment on 5 consecutive days. 21 subjects received white-light treatment (BLT, broad-wavelength without UV, 10 000 lx, irradiance 31.7 W/m 2 ), 24 subjects received narrow-band blue light (BLUE, 100 lx, irradiance 1.0 W/m 2 ). All participants completed weekly questionnaires concerning mood and energy levels, and were also assessed by means of the SIGH-SAD, which is the primary outcome measure. On day 15, SIGH-SAD ratings were significantly lower than on day 1 (BLT 73.2%, effect size 3.37; BLUE 67%, effect size 2.63), which outcomes were not statistically significant different between both conditions. Small sample size. Light treatment is an effective treatment for SAD. The use of narrow-band blue light is equally effective as a treatment using bright white-light. Copyright © 2018 Elsevier B.V. All rights reserved.

SN 2015as: a low-luminosity Type IIb supernova without an early light-curve peak

NASA Astrophysics Data System (ADS)

Gangopadhyay, Anjasha; Misra, Kuntal; Pastorello, A.; Sahu, D. K.; Tomasella, L.; Tartaglia, L.; Singh, Mridweeka; Dastidar, Raya; Srivastav, S.; Ochner, P.; Brown, Peter J.; Anupama, G. C.; Benetti, S.; Cappellaro, E.; Kumar, Brajesh; Kumar, Brijesh; Pandey, S. B.

2018-05-01

We present results of the photometric (from 3 to 509 d post-explosion) and spectroscopic (up to 230 d post-explosion) monitoring campaign of the He-rich Type IIb supernova (SN) 2015as. The (B - V) colour evolution of SN 2015as closely resemble those of SN 2008ax, suggesting that SN 2015as belongs to the SN IIb subgroup that does not show the early, short-duration photometric peak. The light curve of SN 2015as reaches the B-band maximum about 22 d after the explosion, at an absolute magnitude of -16.82 ± 0.18 mag. At ˜75 d after the explosion, its spectrum transitions from that of a SN II to a SN Ib. P Cygni features due to He I lines appear at around 30 d after explosion, indicating that the progenitor of SN 2015as was partially stripped. For SN 2015as, we estimate a 56Ni mass of ˜0.08 M⊙ and ejecta mass of 1.1-2.2 M⊙, which are similar to the values inferred for SN 2008ax. The quasi-bolometric analytical light-curve modelling suggests that the progenitor of SN 2015as has a modest mass (˜0.1 M⊙), a nearly compact (˜0.05 × 1013 cm) H envelope on top of a dense, compact (˜2 × 1011 cm) and a more massive (˜1.2 M⊙) He core. The analysis of the nebular phase spectra indicates that ˜0.44 M⊙ of O is ejected in the explosion. The intensity ratio of the [Ca II]/[O I] nebular lines favours either a main-sequence progenitor mass of ˜15 M⊙ or a Wolf-Rayet star of 20 M⊙.

GERLUMPH Data Release 2: 2.5 Billion Simulated Microlensing Light Curves

NASA Astrophysics Data System (ADS)

Vernardos, G.; Fluke, C. J.; Bate, N. F.; Croton, D.; Vohl, D.

2015-04-01

In the upcoming synoptic all-sky survey era of astronomy, thousands of new multiply imaged quasars are expected to be discovered and monitored regularly. Light curves from the images of gravitationally lensed quasars are further affected by superimposed variability due to microlensing. In order to disentangle the microlensing from the intrinsic variability of the light curves, the time delays between the multiple images have to be accurately measured. The resulting microlensing light curves can then be analyzed to reveal information about the background source, such as the size of the quasar accretion disk. In this paper we present the most extensive and coherent collection of simulated microlensing light curves; we have generated \\gt 2.5 billion light curves using the GERLUMPH high resolution microlensing magnification maps. Our simulations can be used to train algorithms to measure lensed quasar time delays, plan future monitoring campaigns, and study light curve properties throughout parameter space. Our data are openly available to the community and are complemented by online eResearch tools, located at http://gerlumph.swin.edu.au.

TOWARD CHARACTERIZATION OF THE TYPE IIP SUPERNOVA PROGENITOR POPULATION: A STATISTICAL SAMPLE OF LIGHT CURVES FROM Pan-STARRS1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanders, N. E.; Soderberg, A. M.; Chornock, R.

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 significantmore » 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.« less

VizieR Online Data Catalog: SN 2007on and SN 2011iv light curves (Gall+, 2018)

NASA Astrophysics Data System (ADS)

Gall, C.; Stritzinger, M. D.; Ashall, C.; Baron, E.; Burns, C. R.; Hoeflich, P.; Hsiao, E. Y.; Mazzali, P. A.; Phillips, M. M.; Filippenko, A. V.; Anderson, J. P.; Benetti, S.; Brown, P. J.; Campillay, A.; Challis, P.; Contreras, C.; Elias de La Rosa, N.; Folatelli, G.; Foley, R. J.; Fraser, M.; Holmbo, S.; Marion, G. H.; Morrell, N.; Pan, Y.-C.; Pignata, G.; Suntzeff, N. B.; Taddia, F.; Torres Robledo, S.; Valenti, S.

2017-11-01

Detailed optical and NIR light curves of SN 2007on obtained by the first phase of the Carnegie Supernova Project (CSP-I, 2004-2009; Hamuy et al., 2006PASP..118....2H) were published by Stritzinger et al. (2011, Cat. J/AJ/142/156).UV uvw2-, uvm2-, and uvw1-band imaging of both SN 2007on and SN 2011iv were obtained with Swift (+ UVOT). Photome- try of SN 2007on and SN 2011iv was computed following the method described in detail by Brown et al. (2014Ap&SS.354...89B), who use the calibration published by Breeveld et al. (2011, AIPCS, 1358, 373). The Swift UVOT images and photometry are also available as part of the Swift Optical Ultraviolet Supernova Archive (SOUSA; Brown et al. 2014Ap&SS.354...89B). Optical ugriBV-band imaging of SN 2007on and SN 2011iv was obtained with the Henrietta Swope 1.0m telescope (+ SITe3 direct CCD camera) located at the Las Campanas Observatory (LCO). The NIR YJH-band imaging of SN 2007on was obtained with the Swope (+ RetroCam) and the Irenee du Pont 2.5m (+ WIRC: Wide Field Infrared Camera) telescopes (Stritzinger et al., Cat. J/AJ/142/156), while in the case of SN 2011iv all NIR YJH-band imaging was taken with RetroCam attached to the Irenee du Pont telescope. The optical local sequence is calibrated relative to Landolt (1992AJ....104..372L) (BV) and Smith et al. (2002AJ....123.2121S) (ugri) standard-star fields observed over multiple photometric nights. The NIR J-band and H-band local sequences were calibrated relative to the Persson et al. (1998AJ....116.2475P) standard stars, while the Y- band local sequence was calibrated relative to standard Y-band magnitudes computed using a combination of stellar atmosphere models (Castelli & Kurucz, 2003, IAUSymp, 210, A20) with the J-Ks colours of the Persson et al. standard-star catalogue (Hamuy et al., 2006PASP..118....2H). (5 data files).

CSI 2264: Characterizing Young Stars In NGC 2264 With Short-Duration Periodic Flux Dips in Their Light Curves

DTIC Science & Technology

2015-04-01

curve (it was not observed by CoRoT in 2008). We have subsequently obtained optical and IR spectra of it from SOAR (see Appendix) that indicate a spectral...CoRoT light curve. We also obtained a SOAR optical spectrum of Mon-1131. Based on measures of the depths of the TiO bands in that spectrum, we...scales in Table 4, one from Table 6 of Pecaut & Mamajek (2013; PM13), and one from Cohen & Kuhi ( 1979 ; CK79). For many of the stars, the calculation

Oscillatory patterns in the light curves of five long-term monitored type 1 active galactic nuclei

NASA Astrophysics Data System (ADS)

Kovačević, Andjelka B.; Pérez-Hernández, Ernesto; Popović, Luka Č.; Shapovalova, Alla I.; Kollatschny, Wolfram; Ilić, Dragana

2018-04-01

New combined data of five well-known type 1 active galactic nuclei (AGNs) are probed with a novel hybrid method in a search for oscillatory behaviour. Additional analysis of artificial light curves obtained from the coupled oscillatory models gives confirmation for detected periods that could have a physical background. We find periodic variations in the long-term light curves of 3C 390.3, NGC 4151 and NGC 5548, and E1821 + 643, with correlation coefficients larger than 0.6. We show that the oscillatory patterns of two binary black hole candidates, NGC 5548 and E1821 + 643, correspond to qualitatively different dynamical regimes of chaos and stability, respectively. We demonstrate that the absence of oscillatory patterns in Arp 102B could be the result of a weak coupling between oscillatory mechanisms. This is the first good evidence that 3C 390.3 and Arp 102B, categorized as double-peaked Balmer line objects, have qualitative different dynamics. Our analysis shows a novelty in the oscillatory dynamical patterns of the light curves of these type 1 AGNs.

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

NASA Astrophysics Data System (ADS)

Juvan, Ines G.; Lendl, M.; Cubillos, P. E.; Fossati, L.; Tregloan-Reed, J.; Lammer, H.; Guenther, E. W.; Hanslmeier, A.

2018-02-01

Several studies have shown that stellar activity features, such as occulted and non-occulted starspots, can affect the measurement of transit parameters biasing studies of transit timing variations and transmission spectra. We present PyTranSpot, which we designed to model multiband transit light curves showing starspot anomalies, inferring both transit and spot parameters. The code follows a pixellation approach to model the star with its corresponding limb darkening, spots, and transiting planet on a two dimensional Cartesian coordinate grid. We combine PyTranSpot with a Markov chain Monte Carlo framework to study and derive exoplanet transmission spectra, which provides statistically robust values for the physical properties and uncertainties of a transiting star-planet system. We validate PyTranSpot's performance by analyzing eleven synthetic light curves of four different star-planet systems and 20 transit light curves of the well-studied WASP-41b system. We also investigate the impact of starspots on transit parameters and derive wavelength dependent transit depth values for WASP-41b covering a range of 6200-9200 Å, indicating a flat transmission spectrum.

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.

ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waszczak, Adam; Chang, Chan-Kao; Cheng, Yu-Chi

We fit 54,296 sparsely sampled asteroid light curves in the Palomar Transient Factory survey to a combined rotation plus phase-function model. Each light curve consists of 20 or more observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find that the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude, and other light-curve attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining ∼53,000 fitted periods. By this method we findmore » that 9033 of our light curves (of ∼8300 unique asteroids) have “reliable” periods. Subsequent consideration of asteroids with multiple light-curve fits indicates a 4% contamination in these “reliable” periods. For 3902 light curves with sufficient phase-angle coverage and either a reliable fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than ∼2 g cm{sup −3}, while C types have a lower limit of between 1 and 2 g cm{sup −3}. These results are in agreement with previous density estimates. For 5–20 km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types’ differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes (and apparent-magnitude residuals) to those of the Minor Planet Center’s nominal (G = 0.15, rotation-neglecting) model; our phase-function plus Fourier-series fitting reduces asteroid photometric

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).

A doubly curved reflector X-band antenna with integrated IFF array

NASA Astrophysics Data System (ADS)

Alia, F.; Barbati, S.

Primary radar antennas and Identification Friend or Foe (IFF) antennas must rotate with the same speed and synchronism, so that the target echo and IFF transponder mark will appear to the operator at the same time and at the same angular direction. A doubly-curved reflector antenna with a six-element microstrip array integrated in the reflector surface is presented to meet this requirement. The main antenna operates at X-band for low angle search radar, while the secondary antenna operates at L-band for IFF functions. The new configuration minimizes masking of the X-band radiated energy as a result of the IFF L-band elements. In fact, the only effect of the microstrip array on the X-band radiation pattern is the presence of several sidelobes in the + or - 90 deg angular region. The proposed new solution is compared to three other L-band/X-band integrated antenna configurations, and is found to be more advantageous with respect to masking, mechanical aspects, and production costs.

The bumpy light curve of Type IIn supernova iPTF13z over 3 years

NASA Astrophysics Data System (ADS)

Nyholm, A.; Sollerman, J.; Taddia, F.; Fremling, C.; Moriya, T. J.; Ofek, E. O.; Gal-Yam, A.; De Cia, A.; Roy, R.; Kasliwal, M. M.; Cao, Y.; Nugent, P. E.; Masci, F. J.

2017-08-01

A core-collapse (CC) supernova (SN) of Type IIn is dominated by the interaction of SN ejecta with the circumstellar medium (CSM). Some SNe IIn (e.g. SN 2006jd) have episodes of re-brightening ("bumps") in their light curves. We present iPTF13z, a Type IIn SN discovered on 2013 February 1 by the intermediate Palomar Transient Factory (iPTF). This SN showed at least five bumps in its declining light curve between 130 and 750 days after discovery. We analyse this peculiar behaviour and try to infer the properties of the CSM, of the SN explosion, and the nature of the progenitor star. We obtained multi-band optical photometry for over 1000 days after discovery with the P48 and P60 telescopes at Palomar Observatory. We obtained low-resolution optical spectra during the same period. We did an archival search for progenitor outbursts. We analyse the photometry and the spectra, and compare iPTF13z to other SNe IIn. In particular we derive absolute magnitudes, colours, a pseudo-bolometric light curve, and the velocities of the different components of the spectral lines. A simple analytical model is used to estimate the properties of the CSM. iPTF13z had a light curve peaking at Mr ≲ - 18.3 mag. The five bumps during its decline phase had amplitudes ranging from 0.4 to 0.9 mag and durations between 20 and 120 days. The most prominent bumps appeared in all the different optical bands, when covered. The spectra of this SN showed typical SN IIn characteristics, with emission lines of Hα (with broad component FWHM 103 - 104 km s-1 and narrow component FWHM 102 km s-1) and He I, but also with Fe II, Ca II, Na I D and Hβ P Cygni profiles (with velocities of 103km s-1). A pre-explosion outburst was identified lasting ≳ 50 days, with Mr ≈ - 15 mag around 210 days before discovery. Large, variable progenitor mass-loss rates (≳0.01M⊙ yr-1) and CSM densities (≳10-16 g cm-3) are derived. The SN was hosted by a metal-poor dwarf galaxy at redshift z = 0.0328. We suggest that

Multi-filter Transit Observations of HAT-P-3b and TrES-3b with Multiple Northern Hemisphere Telescopes

NASA Astrophysics Data System (ADS)

Ricci, D.; Sada, P. V.; Navarro-Meza, S.; López-Valdivia, R.; Michel, R.; Fox Machado, L.; Ramón-Fox, F. G.; Ayala-Loera, C.; Brown Sevilla, S.; Reyes-Ruiz, M.; La Camera, A.; Righi, C.; Cabona, L.; Tosi, S.; Truant, N.; Peterson, S. W.; Prieto-Arranz, J.; Velasco, S.; Pallé, E.; Deeg, H.

2017-06-01

We present a photometric follow-up of transiting exoplanets HAT-P-3b and TrES-3b, observed by using several optical and near-infrared filters, with four small-class telescopes (D = 36-152 cm) in the Northern Hemisphere. Two of the facilities present their first scientific results. New 10 HAT-P-3b light curves and new 26 TrES-3b light curves are reduced and combined by filter to improve the quality of the photometry. Combined light curves fitting is carried out independently by using two different analysis packages, allowing the corroboration of the orbital and physical parameters in the literature. Results find no differences in the relative radius with the observing filter. In particular, we report for HAT-P-3b a first estimation of the planet-to-star radius {R}p/{R}* ={0.1112}-0.0026+0.0025 in the B band which is coherent with values found in the VRIz‧JH filters. Concerning TrES-3b, we derive a value for the orbital period of P = 1.3061862 ± 0.0000001 days which shows no linear variations over nine years of photometric observations.

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.

Modelling gamma-ray light curves of phase-aligned millisecond pulsars

NASA Astrophysics Data System (ADS)

Chang, Shan; Zhang, Li; Li, Xiang; Jiang, Zejun

2018-04-01

Three gamma-ray millisecond pulsars (MSPs), PSR J1939+2134, PSR J1959+2048, and PSR J0034-0534, have been confirmed to have a common feature of phase-aligned in radio and gamma-ray bands. With a geometric (two-pole caustic) model and a physical outer gap model (revised 3D outer gap model) in a three dimensional (3D) retarded magnetic dipole with a perturbation magnetic field, the observed features of these MSPs are studied. In order to obtained the best-fitting model parameters, the Markov chain Monte Carlo technique is used and reasonable GeV band light curves for three MSPs are given. Our calculations indicate that MSPs emit high energy photons with smaller inclination angles (α ≈ 10°-50°), larger view angles (ζ ≈ 65°-100°), and smaller perturbation factor (ɛ ≈ -0.15-0.1). Note that the factor ɛ, describing the strength of the perturbed magnetic field, is all less than zero in these two models, so the magnetic field caused by current-induced play a leading role in the pulsed location of MSPs.

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.

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.

The Kepler Light Curves of AGN: A Detailed Analysis

DOE PAGES

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.; ...

2018-04-25

Here, we present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistentmore » with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.« less

The Kepler Light Curves of AGN: A Detailed Analysis

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.; Malkan, Matt; Howell, Steve B.; Gelino, Dawn M.

2018-04-01

We present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistent with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.

The Kepler Light Curves of AGN: A Detailed Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.

Here, we present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistentmore » with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.« less

UNSUPERVISED TRANSIENT LIGHT CURVE ANALYSIS VIA HIERARCHICAL BAYESIAN INFERENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanders, N. E.; Soderberg, A. M.; Betancourt, M., E-mail: nsanders@cfa.harvard.edu

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. Wemore » 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.« less

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.

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).

Delayed detonation models for normal and subluminous type Ia sueprnovae: Absolute brightness, light curves, and molecule formation

NASA Technical Reports Server (NTRS)

Hoflich, P.; Khokhlov, A. M.; Wheeler, J. C.

1995-01-01

We compute optical and infrared light curves of the pulsating class of delayed detonation models for Type Ia supernovae (SN Ia's) using an elaborate treatment of the Local Thermodynamic Equilbrium (LTE) radiation transport, equation of state and ionization balance, expansion opacity including the cooling by CO, Co(+), and SiO, and a Monte Carlo gamma-ray deposition scheme. The models have an amount of Ni-56 in the range from approximately or equal to 0.1 solar mass up to 0.7 solar mass depending on the density at which the transition from a deflagration to a detonation occurs. Models with a large nickel production give light curves comparable to those of typical Type Ia supernovae. Subluminous supernovae can be explained by models with a low nickel production. Multiband light curves are presented in comparison with the normally bright event SN 1992bc and the subluminous events Sn 1991bg and SN 1992bo to establish the principle that the delayed detonation paradigm in Chandrasekhar mass models may give a common explosion mechanism accounting for both normal and subluminous SN Ia's. Secondary IR-maxima are formed in the models of normal SN Ia's as a photospheric effect if the photospheric radius continues to increase well after maximum light. Secondary maxima appear later and stronger in models with moderate expansion velocities and with radioactive material closer to the surface. Model light curves for subluminous SN Ia's tend to show only one 'late' IR-maximum. In some delayed detonation models shell-like envelopes form, which consist of unburned carbon and oxygen. The formation of molecules in these envelopes is addressed. If the model retains a C/O-envelope and is subluminous, strong vibration bands of CO may appear, typically several weeks past maximum light. CO should be very weak or absent in normal Sn Ia's.

CSI 2264: CHARACTERIZING YOUNG STARS IN NGC 2264 WITH STOCHASTICALLY VARYING LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stauffer, John; Rebull, Luisa; Carey, Sean

2016-03-15

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 strengthmore » 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.« less

Rectification of light refraction in curved waveguide arrays.

PubMed

Longhi, Stefano

2009-02-15

An "optical ratchet" for discretized light in photonic lattices, which enables observing rectification of light refraction at any input beam conditions, is theoretically presented, and a possible experimental implementation based on periodically curved zigzag waveguide arrays is proposed.

A self-sacrifice template route to iodine modified BiOIO3: band gap engineering and highly boosted visible-light active photoreactivity.

PubMed

Feng, Jingwen; Huang, Hongwei; Yu, Shixin; Dong, Fan; Zhang, Yihe

2016-03-21

The development of high-performance visible-light photocatalysts with a tunable band gap has great significance for enabling wide-band-gap (WBG) semiconductors visible-light sensitive activity and precisely tailoring their optical properties and photocatalytic performance. In this work we demonstrate the continuously adjustable band gap and visible-light photocatalysis activation of WBG BiOIO3via iodine surface modification. The iodine modified BiOIO3 was developed through a facile in situ reduction route by applying BiOIO3 as the self-sacrifice template and glucose as the reducing agent. By manipulating the glucose concentration, the band gap of the as-prepared modified BiOIO3 could be orderly narrowed by generation of the impurity or defect energy level close to the conduction band, thus endowing it with a visible light activity. The photocatalytic assessments uncovered that, in contrast to pristine BiOIO3, the modified BiOIO3 presents significantly boosted photocatalytic properties for the degradation of both liquid and gaseous contaminants, including Rhodamine B (RhB), methyl orange (MO), and ppb-level NO under visible light. Additionally, the band structure evolution as well as photocatalysis mechanism triggered by the iodine surface modification is investigated in detail. This study not only provides a novel iodine surface-modified BiOIO3 for environmental application, but also provides a facile and general way to develop highly efficient visible-light photocatalysts.

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.

Gamma-Ray Pulsar Light Curves as Probes of Magnetospheric Structure

NASA Technical Reports Server (NTRS)

Harding, A. K.

2016-01-01

The large number of gamma-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 gamma-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 modeling will continue to be a powerful tool for constraining the pulsar magnetosphere physics.

QUEST1 Variability Survey. III. Light Curve Catalog Update

NASA Astrophysics Data System (ADS)

Rengstorf, A. W.; Thompson, D. L.; Mufson, S. L.; Andrews, P.; Honeycutt, R. K.; Vivas, A. K.; Abad, C.; Adams, B.; Bailyn, C.; Baltay, C.; Bongiovanni, A.; Briceño, C.; Bruzual, G.; Coppi, P.; Della Prugna, F.; Emmet, W.; Ferrín, I.; Fuenmayor, F.; Gebhard, M.; Hernández, J.; Magris, G.; Musser, J.; Naranjo, O.; Oemler, A.; Rosenzweig, P.; Sabbey, C. N.; Sánchez, Ge.; Sánchez, Gu.; Schaefer, B.; Schenner, H.; Sinnott, J.; Snyder, J. A.; Sofia, S.; Stock, J.; van Altena, W.

2009-03-01

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. Based on observations obtained at the Llano del Hato National Astronomical Observatory, operated by the Centro de Investigaciones de Astronomía for the Ministerio de Ciencia y Tecnologia of Venezuela.

LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE WITH SUBSTANTIAL MASS LOSS USING THE NEW OPEN-SOURCE SUPERNOVA EXPLOSION CODE (SNEC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morozova, Viktoriya; Renzo, Mathieu; Ott, Christian D.

We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different broad bands assuming blackbody emission. As a first application of SNEC, we consider the explosions of a grid of 15 M{sub ⊙} (at zero-age main sequence, ZAMS) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. Themore » resulting light curves exhibit plateaus with durations of ∼20–100 days if ≳1.5–2 M{sub ⊙} of hydrogen-rich material is left and no plateau if less hydrogen-rich material is left. If these shorter plateau lengths are not seen for SNe IIP in nature, it suggests that, at least for ZAMS masses ≲20 M{sub ⊙}, hydrogen mass loss occurs as an all or nothing process. This perhaps points to the important role binary interactions play in generating the observed mass-stripped supernovae (i.e., Type Ib/c events). These light curves are also unlike what is typically seen for SNe IIL, arguing that simply varying the amount of mass loss cannot explain these events. The most stripped models begin to show double-peaked light curves similar to what is often seen for SNe IIb, confirming previous work that these supernovae can come from progenitors that have a small amount of hydrogen and a radius of ∼500 R{sub ⊙}.« less

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.

AEOLUS: A MARKOV CHAIN MONTE CARLO CODE FOR MAPPING ULTRACOOL ATMOSPHERES. AN APPLICATION ON JUPITER AND BROWN DWARF HST LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karalidi, Theodora; Apai, Dániel; Schneider, Glenn

Deducing the cloud cover and its temporal evolution from the observed planetary spectra and phase curves can give us major insight into the atmospheric dynamics. In this paper, we present Aeolus, a Markov chain Monte Carlo code that maps the structure of brown dwarf and other ultracool atmospheres. We validated Aeolus on a set of unique Jupiter Hubble Space Telescope (HST) light curves. Aeolus accurately retrieves the properties of the major features of the Jovian atmosphere, such as the Great Red Spot and a major 5 μm hot spot. Aeolus is the first mapping code validated on actual observations of amore » giant planet over a full rotational period. For this study, we applied Aeolus to J- and H-band HST light curves of 2MASS J21392676+0220226 and 2MASS J0136565+093347. Aeolus retrieves three spots at the top of the atmosphere (per observational wavelength) of these two brown dwarfs, with a surface coverage of 21% ± 3% and 20.3% ± 1.5%, respectively. The Jupiter HST light curves will be publicly available via ADS/VIZIR.« less

Enhancing the visibility of injuries with narrow-banded beams of light within the visible light spectrum.

PubMed

Limmen, Roxane M; Ceelen, Manon; Reijnders, Udo J L; Joris Stomp, S; de Keijzer, Koos C; Das, Kees

2013-03-01

The use of narrow-banded visible light sources in improving the visibility of injuries has been hardly investigated, and studies examining the extent of this improvement are lacking. In this study, narrow-banded beams of light within the visible light spectrum were used to explore their ability in improving the visibility of external injuries. The beams of light were induced by four crime-lites(®) providing narrow-banded beams of light between 400 and 550 nm. The visibility of the injuries was assessed through specific long-pass filters supplied with the set of crime-lites(®) . Forty-three percent of the examined injuries improved in visibility by using the narrow-banded visible light. In addition, injuries were visualized that were not visible or just barely visible to the naked eye. The improvements in visibility were particularly marked with the use of crime-lites(®) "violet" and "blue" covering the spectrum between 400-430 and 430-470 nm. The simple noninvasive method showed a great potential contribution in injury examination. © 2012 American Academy of Forensic Sciences.

The ALMA Band 9 receiver. Design, construction, characterization, and first light

NASA Astrophysics Data System (ADS)

Baryshev, A. M.; Hesper, R.; Mena, F. P.; Klapwijk, T. M.; van Kempen, T. A.; Hogerheijde, M. R.; Jackson, B. D.; Adema, J.; Gerlofsma, G. J.; Bekema, M. E.; Barkhof, J.; de Haan-Stijkel, L. H. R.; van den Bemt, M.; Koops, A.; Keizer, K.; Pieters, C.; Koops van het Jagt, J.; Schaeffer, H. H. A.; Zijlstra, T.; Kroug, M.; Lodewijk, C. F. J.; Wielinga, K.; Boland, W.; de Graauw, M. W. M.; van Dishoeck, E. F.; Jager, H.; Wild, W.

2015-05-01

Aims: We describe the design, construction, and characterization of the Band 9 heterodyne receivers (600-720 GHz) for the Atacama Large Millimeter/submillimeter Array (ALMA). First-light Band 9 data, obtained during ALMA commissioning and science verification phases, are presented as well. Methods: The ALMA Band 9 receiver units (so-called "cartridges"), which are installed in the telescope's front end, have been designed to detect and down-convert two orthogonal linear polarization components of the light collected by the ALMA antennas. The light entering the front end is refocused with a compact arrangement of mirrors, which is fully contained within the cartridge. The arrangement contains a grid to separate the polarizations and two beam splitters to combine each resulting beam with a local oscillator signal. The combined beams are fed into independent double-sideband mixers, each with a corrugated feedhorn coupling the radiation by way of a waveguide with backshort cavity into an impedance-tuned superconductor-insulator-superconductor (SIS) junction that performs the heterodyne down-conversion. Finally, the generated intermediate frequency (IF) signals are amplified by cryogenic and room-temperature HEMT amplifiers and exported to the telescope's IF back end for further processing and, finally, correlation. Results: The receivers have been constructed and tested in the laboratory and they show an excellent performance, complying with ALMA requirements. Performance statistics on all 73 Band 9 receivers are reported. Importantly, two different tunnel-barrier technologies (necessitating different tuning circuits) for the SIS junctions have been used, namely conventional AlOx barriers and the more recent high-current-density AlN barriers. On-sky characterization and tests of the performance of the Band 9 cartridges are presented using commissioning data. Continuum and line images of the low-mass protobinary IRAS 16293-2422 are presented which were obtained as part

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.

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.

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.

The light curve of CV Serpentis, the sometimes-eclipsing Wolf-Rayet star

NASA Technical Reports Server (NTRS)

Schild, R.; Liller, W.

1975-01-01

New photoelectric observations of the B-magnitude of CV Ser made in 1973 and 1974 show no clear evidence of an eclipse, but they establish night-to-night variability of several percent, a systematic brightness change of 0.035 mag during a portion of the single orbit observed in 1973, and irregular flaring in 1974. We made iris photometer measurements of Harvard patrol plates taken between 1905 June and 1953 July, and find no evidence of a very deep eclipse such as observed by Hjellming and Hiltner. We present several new light curves and discuss then in the light of the recent results of Cowley et al.

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

Spectral Filtering Criteria for U-Band Test Light for In-Service Line Monitoring in Optical Fiber Networks

NASA Astrophysics Data System (ADS)

Honda, Nazuki; Izumita, Hisashi; Nakamura, Minoru

2006-06-01

In the fiber-to-the-home era, thousands of optical fibers will have to be accommodated in the central offices of optical access networks. To reduce maintenance costs and improve the service reliability of optical fiber networks, the authors must develop an optical fiber line testing system with a function for in-service line monitoring that uses a test light with a wavelength different from the communication light wavelength. To monitor an in-service line in an optical network, the effective rejection ratio of the test light must be taken into account. This ratio depends on the spectrum of the test light from the optical time-domain reflectometer and the rejection band of the filter in front of the optical network unit. The dependence of the effective rejection ratio as a function of the sideband suppression ratio (SBSR) and of the ratio of the rejection band to the bandwidth of the sideband noise d/D is clarified. When d/D =0.1 and the target effective rejection ratio of the filter is -40 dB, the SBSR and the filter loss of the termination cable must be -70 and -43 dB, respectively, or the SBSR must be -80 dB. When d/D < 0.5 and the target effective rejection ratio of the filter is -40 dB, the SBSR is also required to be -80 dB. In-service line monitoring for a 10-Gb/s transmission using a 1650-nm test light with an SBSR of -80 dB is also demonstrated.

On Light-Like Extremal Surfaces in Curved Spacetimes

NASA Astrophysics Data System (ADS)

Huang, Shou-Jun; He, Chun-Lei

2014-01-01

In this paper, we are concerned with light-like extremal surfaces in curved spacetimes. It is interesting to find that under a diffeomorphic transformation of variables, the light-like extremal surfaces can be described by a system of nonlinear geodesic equations. Particularly, we investigate the light-like extremal surfaces in Schwarzschild spacetime in detail and some new special solutions are derived systematically with aim to compare with the known results and to illustrate the method.

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

Light curves for bump Cepheids computed with a dynamically zoned pulsation code

NASA Technical Reports Server (NTRS)

Adams, T. F.; Castor, J. I.; Davis, C. G.

1980-01-01

The dynamically zoned pulsation code developed by Castor, Davis, and Davison was used to recalculate the Goddard model and to calculate three other Cepheid models with the same period (9.8 days). This family of models shows how the bumps and other features of the light and velocity curves change as the mass is varied at constant period. The use of a code that is capable of producing reliable light curves demonstrates that the light and velocity curves for 9.8 day Cepheid models with standard homogeneous compositions do not show bumps like those that are observed unless the mass is significantly lower than the 'evolutionary mass.' The light and velocity curves for the Goddard model presented here are similar to those computed independently by Fischel, Sparks, and Karp. They should be useful as standards for future investigators.

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.

A B-C-N hybrid porous sheet: an efficient metal-free visible-light absorption material.

PubMed

Lu, Ruifeng; Li, Feng; Salafranca, Juan; Kan, Erjun; Xiao, Chuanyun; Deng, Kaiming

2014-03-07

The polyphenylene network, known as porous graphene, is one of the most important and widely studied two-dimensional materials. As a potential candidate for photocatalysis and photovoltaic energy generation, its application has been limited by the low photocatalytic activity in the visible-light region. State-of-the-art hybrid density functional theory investigations are presented to show that an analogous B-C-N porous sheet outperforms the pristine polyphenylene network with significantly enhanced visible-light absorption. Compared with porous graphene, the calculated energy gap of the B-C-N hybrid crystal shrinks to 2.7 eV and the optical absorption peak remarkably shifts to the visible light region. The redox potentials of water splitting are well positioned in the middle of the band gap. Hybridizations among B_p, N_p and C_p orbitals are responsible for these findings. Valence and conduction band calculations indicate that the electrons and holes can be effectively separated, reducing charge recombination and improving the photoconversion efficiency. Moreover, the band gap and optical properties of the B-C-N hybrid porous sheet can be further finely engineered by external strain.

Broad-band spectrophotometry of the hot Jupiter HAT-P-12b from the near-UV to the near-IR

NASA Astrophysics Data System (ADS)

Mallonn, M.; Nascimbeni, V.; Weingrill, J.; von Essen, C.; Strassmeier, K. G.; Piotto, G.; Pagano, I.; Scandariato, G.; Csizmadia, Sz.; Herrero, E.; Sada, P. V.; Dhillon, V. S.; Marsh, T. R.; Künstler, A.; Bernt, I.; Granzer, T.

2015-11-01

Context. The detection of trends or gradients in the transmission spectrum of extrasolar planets is possible with observations at very low spectral resolution. Transit measurements of sufficient accuracy using selected broad-band filters allow for an initial characterization of the atmosphere of the planet. Aims: We want to investigate the atmosphere of the hot Jupiter HAT-P-12b for an increased absorption at the very blue wavelength regions caused by scattering. Furthermore, we aim for a refinement of the transit parameters and the orbital ephemeris. Methods: We obtained time series photometry of 20 transit events and analyzed them homogeneously, along with eight light curves obtained from the literature. In total, the light curves span a range from 0.35 to 1.25 microns. During two observing seasons over four months each, we monitored the host star to constrain the potential influence of starspots on the derived transit parameters. Results: We rule out the presence of a Rayleigh slope extending over the entire optical wavelength range, a flat spectrum is favored for HAT-P-12b with respect to a cloud-free atmosphere model spectrum. A potential cause of such gray absorption is the presence of a cloud layer at the probed latitudes. Furthermore, in this work we refine the transit parameters, the ephemeris and perform a TTV analysis in which we found no indication for an unseen companion. The host star showed a mild non-periodic variability of up to 1%. However, no stellar rotation period could be detected to high confidence.

Topologically trivial and nontrivial edge bands in graphene induced by irradiation

NASA Astrophysics Data System (ADS)

Yang, Mou; Cai, Zhi-Jun; Wang, Rui-Qiang; Bai, Yan-Kui

2016-08-01

We proposed a minimal model to describe the Floquet band structure of two-dimensional materials with light-induced resonant inter-band transition. We applied it to graphene to study the band features caused by the light irradiation. Linearly polarized light induces pseudo gaps (gaps are functions of wavevector), and circularly polarized light causes real gaps on the quasi-energy spectrum. If the polarization of light is linear and along the longitudinal direction of zigzag ribbons, flat edge bands appear in the pseudo gaps, and if it is in the lateral direction of armchair ribbons, curved edge bands can be found. For the circularly polarized cases, edge bands arise and intersect in the gaps of both types of ribbons. The edge bands induced by the circularly polarized light are helical and those by linearly polarized light are topologically trivial ones. The Chern number of the Floquet band, which reflects the number of pairs of helical edge bands in graphene ribbons, can be reduced into the winding number at resonance.

Intensive Monitoring Survey of Nearby Galaxies (IMSNG): Catching Early Light Curves of Supernovae

NASA Astrophysics Data System (ADS)

Im, Myungshin; IMSNG Team

2018-01-01

SNe light curves have been used to study the expansion history of the universe, and a lot of efforts have gone into understanding the overall shape of the radioactively powered light curve. However, we still have little direct observational evidence for the theorized SN progenitor systems. Recent studies suggest that the light curve of a supernova shortly after its explosion (< 1 day) contains valuable information about its progenitor system and can be used to set a limit on the progenitor size, R*. In order to catch the early light curve of SNe explosion and understand SNe progenitors, we are performing a ~8hr interval monitoring survey of nearby galaxies (d < 50 Mpc) with 1-m class telescopes around the world. Through this survey, we expect to catch the very early precursor emission as faint as R=21 mag (~0.1 Rsun for the progenitor). This poster outlines this project, and present a few scientific highlights, such as the early light curve of SN 2015F in NGC 2442.

The Effect of an Offset Polar Cap Dipolar Magnetic Field on the Modeling of the Vela Pulsar's Gamma-Ray Light Curves

NASA Technical Reports Server (NTRS)

Barnard, M.; Venter, C.; Harding, A. K.

2016-01-01

We performed geometric pulsar light curve modeling using static, retarded vacuum, and offset polar cap (PC) dipole B-fields (the latter is characterized by a parameter epsilon), in conjunction with standard two-pole caustic (TPC) and outer gap (OG) emission geometries. The offset-PC dipole B-field mimics deviations from the static dipole (which corresponds to epsilon equals 0). In addition to constant-emissivity geometric models, we also considered a slot gap (SG) E-field associated with the offset-PC dipole B-field and found that its inclusion leads to qualitatively different light curves. Solving the particle transport equation shows that the particle energy only becomes large enough to yield significant curvature radiation at large altitudes above the stellar surface, given this relatively low E-field. Therefore, particles do not always attain the radiation-reaction limit. Our overall optimal light curve fit is for the retarded vacuum dipole field and OG model, at an inclination angle alpha equals 78 plus or minus 1 degree and observer angle zeta equals 69 plus 2 degrees or minus 1 degree. For this B-field, the TPC model is statistically disfavored compared to the OG model. For the static dipole field, neither model is significantly preferred. We found that smaller values of epsilon are favored for the offset-PC dipole field when assuming constant emissivity, and larger epsilon values favored for variable emissivity, but not significantly so. When multiplying the SG E-field by a factor of 100, we found improved light curve fits, with alpha and zeta being closer to best fits from independent studies, as well as curvature radiation reaction at lower altitudes.

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.

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.

Energy transfer and colour tunability in UV light induced Tm3+/Tb3+/Eu3+: ZnB glasses generating white light emission.

PubMed

Naresh, V; Gupta, Kiran; Parthasaradhi Reddy, C; Ham, Byoung S

2017-03-15

A promising energy transfer (Tm 3+ →Tb 3+ →Eu 3+ ) approach is brought forward to generate white light emission under ultraviolet (UV) light excitation for solid state lightening. Tm 3+ /Tb 3+ /Eu 3+ ions are combinedly doped in zinc borate glass system in view of understanding energy transfer process resulting in white light emission. Zinc borate (host) glass displayed optical and luminescence properties due to formation of Zn(II) x -[O(-II)] y centres in the ZnB glass matrix. At 360nm (UV) excitation, triply doped Tm 3+ /Tb 3+ /Eu 3+ : ZnB glasses simultaneously shown their characteristic emission bands in blue (454nm: 1 D 2 → 3 F 4 ), green (547nm: 5 D 4 → 7 F 5 ) and red (616nm: 5 D 0 → 7 F 2 ) regions. In triple ions doped glasses, energy transfer dynamics is discussed in terms of Forster-Dexter theory, excitation & emission profiles, lifetime curves and from partial energy level diagram of three ions. The role of Tb 3+ in ET from Tm 3+ →Eu 3+ was discussed using branch model. From emission decay analysis, energy transfer probability (P) and efficiency (η) were evaluated. Colour tunability from blue to white on varying (Tb 3+ , Eu 3+ ) content is demonstrated from Commission Internationale de L'Eclairage (CIE) chromaticity coordinates. Based on chromaticity coordinates, other colour related parameters like correlated colour temperature (CCT) and colour purity are also computed for the studied glass samples. An appropriate blending of such combination of rare earth ions could show better suitability as potential candidates in achieving multi-colour and warm/cold white light emission for white LEDs application in the field of solid state lightening. Copyright © 2016 Elsevier B.V. All rights reserved.

New Light Curves and Analysis of the Overcontact Binaries PP Lac and DK Sge

NASA Astrophysics Data System (ADS)

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

2004-12-01

As a by-product of the ongoing work with the Catalog and AtLas of Eclipsing Binaries database (CALEB; Bradstreet et al. 2004), several hundred eclipsing binary systems have been identified that have either unpublished or poor quality light curves. We present new V & Rc light curves for the overcontact systems PP Lac and DK Sge, both chosen because their deep eclipses (peak-to-peak amplitudes of nearly 0.7 mag) help constrain the light curve modelling. Data were obtained using the 41-cm telescope at the Eastern University Observatory equipped with an SBIG ST-10XME CCD. PP Lac (P= 0.40116 d) is a W-type contact binary with only one previously published light curve (Dumont & Maraziti 1990), but the data are sparse and almost non-existent at primary eclipse. Modelling of these data gave varying results; the published mass ratios differ by nearly 0.3. Our data confirms the noted differing eclipse depths but we find the primary eclipse to be total. We present a new light curve solution using Binary Maker 3 (Bradstreet & Steelman 2002) and Wilson-Devinney, finding the mass ratio to be well-constrained by the duration of total eclipse. A period study will be presented using previously existing and newly derived times of minimum light. DK Sge (P=0.62182 d) appears to be an A-type contact binary with no published light curve. The eclipses are partial, with the primary eclipse being deeper by about 0.08 mag. The maxima show evidence of a slight asymmetry, although the light curve appears to be repeatable over the 1 month of observations. We present the first light curve solution using Binary Maker 3 and Wilson-Devinney, but have limited mass ratio constraints due to the absence of radial velocity data. A period study will be presented using previously existing and newly derived times of minimum light.

Revisiting the Phase Curves of WASP-43b: Confronting Re-analyzed Spitzer Data with Cloudy Atmospheres

NASA Astrophysics Data System (ADS)

Mendonça, João M.; Malik, Matej; Demory, Brice-Olivier; Heng, Kevin

2018-04-01

Recently acquired Hubble and Spitzer phase curves of the short-period hot Jupiter WASP-43b make it an ideal target for confronting theory with data. On the observational front, we re-analyze the 3.6 and 4.5 μm Spitzer phase curves and demonstrate that our improved analysis better removes residual red noise due to intra-pixel sensitivity, which leads to greater fluxes emanating from the nightside of WASP-43b, thus reducing the tension between theory and data. On the theoretical front, we construct cloud-free and cloudy atmospheres of WASP-43b using our Global Circulation Model (GCM), THOR, which solves the non-hydrostatic Euler equations (compared to GCMs that typically solve the hydrostatic primitive equations). The cloud-free atmosphere produces a reasonable fit to the dayside emission spectrum. The multi-phase emission spectra constrain the cloud deck to be confined to the nightside and have a finite cloud-top pressure. The multi-wavelength phase curves are naturally consistent with our cloudy atmospheres, except for the 4.5 μm phase curve, which requires the presence of enhanced carbon dioxide in the atmosphere of WASP-43b. Multi-phase emission spectra at higher spectral resolution, as may be obtained using the James Webb Space Telescope, and a reflected-light phase curve at visible wavelengths would further constrain the properties of clouds in WASP-43b.

Using Machine Learning To Predict Which Light Curves Will Yield Stellar Rotation Periods

NASA Astrophysics Data System (ADS)

Agüeros, Marcel; Teachey, Alexander

2018-01-01

Using time-domain photometry to reliably measure a solar-type star's rotation period requires that its light curve have a number of favorable characteristics. The probability of recovering a period will be a non-linear function of these light curve features, which are either astrophysical in nature or set by the observations. We employ standard machine learning algorithms (artificial neural networks and random forests) to predict whether a given light curve will produce a robust rotation period measurement from its Lomb-Scargle periodogram. The algorithms are trained and validated using salient statistics extracted from both simulated light curves and their corresponding periodograms, and we apply these classifiers to the most recent Intermediate Palomar Transient Factory (iPTF) data release. With this pipeline, we anticipate measuring rotation periods for a significant fraction of the ∼4x108 stars in the iPTF footprint.

PLUTO AND CHARON WITH THE HUBBLE SPACE TELESCOPE. I. MONITORING GLOBAL CHANGE AND IMPROVED SURFACE PROPERTIES FROM LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buie, Marc W.; Young, Eliot F.; Young, Leslie A.

We present new light-curve measurements of Pluto and Charon taken with the Advanced Camera for Surveys High-resolution Camera on the Hubble Space Telescope. The observations were collected from 2002 June to 2003 June at 12 distinct sub-Earth longitudes over a range of solar phase angle 0.{sup 0}36-1.{sup 0}74-a larger range than previously measured. The new measurements of Pluto show that the light-curve amplitude has decreased since the mutual event season in the late 1980s. We also show that the average brightness has increased in the F555W (Johnson V equivalent) passband while the brightness has decreased in the F435W (Johnson Bmore » equivalent) passband. These data thus indicate a substantial reddening of the reflected light from Pluto. We find a weighted mean (B - V) = 0.9540 {+-} 0.0010 that is considerably higher than the long-standing value of (B - V) = 0.868 {+-} 0.003 most recently measured in 1992-1993. This change in color cannot be explained by the evolving viewing geometry and provides the strongest evidence to date for temporal changes on the surface of Pluto that are expected to be linked to volatile transport processes. We also report on the discovery of a new rotational modulation of Pluto's hemispherical color that ranges from 0.92 to 0.98 with the least red color at the longitude of maximum light and most red at minimum light. The phase coefficient of Pluto is nearly the same as measured in 1992-1993 with a value of {beta} {sub B} = 0.0392 {+-} 0.0064 and {beta} {sub V} = 0.0355 {+-} 0.0045 mag deg{sup -1} for the F435W and F555W data, respectively. The Pluto phase curve is still very close to linear but a small but significant nonlinearity is seen in the data. In contrast, the light curve of Charon is essentially the same as in 1992/1993, albeit with much less noise. We confirm that Charon's Pluto-facing hemisphere is 8% brighter than the hemisphere facing away from Pluto. The color of Charon is independent of longitude and has a mean

NEPTUNE'S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES.

PubMed

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.

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

Extended source effect on microlensing light curves by an Ellis wormhole

NASA Astrophysics Data System (ADS)

Tsukamoto, Naoki; Gong, Yungui

2018-04-01

We can survey an Ellis wormhole which is the simplest Morris-Thorne wormhole in our Galaxy with microlensing. The light curve of a point source microlensed by the Ellis wormhole shows approximately 4% demagnification while the total magnification of images lensed by a Schwarzschild lens is always larger than unity. We investigate an extended source effect on the light curves microlensed by the Ellis wormhole. We show that the depth of the gutter of the light curves of an extended source is smaller than the one of a point source since the magnified part of the extended source cancels the demagnified part out. We can, however, distinguish between the light curves of the extended source microlensed by the Ellis wormhole and the ones by the Schwarzschild lens in their shapes even if the size of the source is a few times larger than the size of an Einstein ring on a source plane. If the relative velocity of a star with the radius of 1 06 km at 8 kpc in the bulge of our Galaxy against an observer-lens system is smaller than 10 km /s on a source plane, we can detect microlensing of the star lensed by the Ellis wormhole with the throat radius of 1 km at 4 kpc.

Supernova Light Curves and Spectra from Two Different Codes: Supernu and Phoenix

NASA Astrophysics Data System (ADS)

Van Rossum, Daniel R; Wollaeger, Ryan T

2014-08-01

The observed similarities between light curve shapes from Type Ia supernovae, and in particular the correlation of light curve shape and brightness, have been actively studied for more than two decades. In recent years, hydronamic simulations of white dwarf explosions have advanced greatly, and multiple mechanisms that could potentially produce Type Ia supernovae have been explored in detail. The question which of the proposed mechanisms is (or are) possibly realized in nature remains challenging to answer, but detailed synthetic light curves and spectra from explosion simulations are very helpful and important guidelines towards answering this question.We present results from a newly developed radiation transport code, Supernu. Supernu solves the supernova radiation transfer problem uses a novel technique based on a hybrid between Implicit Monte Carlo and Discrete Diffusion Monte Carlo. This technique enhances the efficiency with respect to traditional implicit monte carlo codes and thus lends itself perfectly for multi-dimensional simulations. We show direct comparisons of light curves and spectra from Type Ia simulations with Supernu versus the legacy Phoenix code.

ELECTROMAGNETIC EMISSION FROM LONG-LIVED BINARY NEUTRON STAR MERGER REMNANTS. II. LIGHT CURVES AND SPECTRA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siegel, Daniel M.; Ciolfi, Riccardo, E-mail: daniel.siegel@aei.mpg.de, E-mail: riccardo.ciolfi@unitn.it

2016-03-01

Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in amore » companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ∼10{sup 7} s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ∼10{sup 2}–10{sup 4} s after the BNS merger with luminosities of L{sub X} ∼ 10{sup 46}–10{sup 48} erg s{sup −1}. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.« less

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.

The effect of an offset polar cap dipolar magnetic field on the modeling of the Vela pulsar’s γ-ray light curves

PubMed Central

Barnard, M.; Venter, C.; Harding, A. K.

2018-01-01

We performed geometric pulsar light curve modeling using static, retarded vacuum, and offset polar cap (PC) dipole B-fields (the latter is characterized by a parameter ε), in conjunction with standard two-pole caustic (TPC) and outer gap (OG) emission geometries. The offset-PC dipole B-field mimics deviations from the static dipole (which corresponds to ε = 0). In addition to constant-emissivity geometric models, we also considered a slot gap (SG) E-field associated with the offset-PC dipole B-field and found that its inclusion leads to qualitatively different light curves. Solving the particle transport equation shows that the particle energy only becomes large enough to yield significant curvature radiation at large altitudes above the stellar surface, given this relatively low E-field. Therefore, particles do not always attain the radiation-reaction limit. Our overall optimal light curve fit is for the retarded vacuum dipole field and OG model, at an inclination angle α=78−1+1° and observer angle ζ=69−1+2°. For this B-field, the TPC model is statistically disfavored compared to the OG model. For the static dipole field, neither model is significantly preferred. We found that smaller values of ε are favored for the offset-PC dipole field when assuming constant emissivity, and larger ε values favored for variable emissivity, but not significantly so. When multiplying the SG E-field by a factor of 100, we found improved light curve fits, with α and ζ being closer to best fits from independent studies, as well as curvature radiation reaction at lower altitudes. PMID:29681648

New quasar survey with WIRO: The light curves of quasars over ~15 year timescales

NASA Astrophysics Data System (ADS)

Griffith, Emily; Bassett, Neil; Deam, Sophie; Dixon, Don; Harvey, William; Lee, Daniel; Lyke, Bradley; Haze Nunez, Evan; Parziale, Ryan; Witherspoon, Catherine; Myers, Adam D.; Findlay, Joseph; Kobulnicky, Henry A.; Dale, Daniel A.

2017-01-01

Quasars, a type of active galactic nuclei (AGN), are known to vary in brightness on 10 day to 7 year timescales. While it has been proposed that this variability is caused by instability in the accretion disk, Poisson processes, or microlensing, the exact cause remains mysterious. Understanding the physical mechanisms that drive quasar variability will require imaging of quasars over a wide range of timescales. In particular, the observations required to constrain longer timescales can be difficult to conduct. This summer ~1000 quasars in Stripe 82 were observed in ugriz wavelength bands using WIRO, the University of Wyoming’s 2.3-meter telescope. Using these images, earlier data from the Sloan Digital Sky Survey's observations of Stripe 82, as well as various data reduction methods, the quasars’ magnitude can be studied on our extended 3 day to 15 year timescale. Here, we present the light curves of ~1000 quasars in ugriz bands as observed over the last 15 years. Thiswork is supported by the National Science Foundation under REU grant AST 1560461.

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.

The DOHA algorithm: a new recipe for cotrending large-scale transiting exoplanet survey light curves

NASA Astrophysics Data System (ADS)

Mislis, D.; Pyrzas, S.; Alsubai, K. A.; Tsvetanov, Z. I.; Vilchez, N. P. E.

2017-03-01

We present DOHA, a new algorithm for cotrending photometric light curves obtained by transiting exoplanet surveys. The algorithm employs a novel approach to the traditional 'differential photometry' technique, by selecting the most suitable comparison star for each target light curve, using a two-step correlation search. Extensive tests on real data reveal that DOHA corrects both intra-night variations and long-term systematics affecting the data. Statistical studies conducted on a sample of ∼9500 light curves from the Qatar Exoplanet Survey reveal that DOHA-corrected light curves show an rms improvement of a factor of ∼2, compared to the raw light curves. In addition, we show that the transit detection probability in our sample can increase considerably, even up to a factor of 7, after applying DOHA.

Analysis of new high-precision transit light curves of WASP-10 b: starspot occultations, small planetary radius, and high metallicity

NASA Astrophysics Data System (ADS)

Maciejewski, G.; Raetz, St.; Nettelmann, N.; Seeliger, M.; Adam, C.; Nowak, G.; Neuhäuser, R.

2011-11-01

Context. The WASP-10 planetary system is intriguing because different values of radius have been reported for its transiting exoplanet. The host star exhibits activity in terms of photometric variability, which is caused by the rotational modulation of the spots. Moreover, a periodic modulation has been discovered in transit timing of WASP-10 b, which could be a sign of an additional body perturbing the orbital motion of the transiting planet. Aims: We attempt to refine the physical parameters of the system, in particular the planetary radius, which is crucial for studying the internal structure of the transiting planet. We also determine new mid-transit times to confirm or refute observed anomalies in transit timing. Methods: We acquired high-precision light curves for four transits of WASP-10 b in 2010. Assuming various limb-darkening laws, we generated best-fit models and redetermined parameters of the system. The prayer-bead method and Monte Carlo simulations were used to derive error estimates. Results: Three transit light curves exhibit signatures of the occultations of dark spots by the planet during its passage across the stellar disk. The influence of stellar activity on transit depth is taken into account while determining system parameters. The radius of WASP-10 b is found to be no greater than 1.03+0.07-0.03 Jupiter radii, a value significantly smaller than most previous studies indicate. We calculate interior structure models of the planet, assuming a two-layer structure with one homogeneous envelope atop a rock core. The high value of the WASP-10 b's mean density allows one to consider the planet's internal structure including 270 to 450 Earth masses of heavy elements. Our new mid-transit times confirm that transit timing cannot be explained by a constant period if all literature data points are considered. They are consistent with the ephemeris assuming a periodic variation of transit timing. We show that possible starspot features affecting the

Bumpy light curves of interacting supernovae

NASA Astrophysics Data System (ADS)

Nyholm, Anders

2017-04-01

A supernova (SN) is the explosive destruction of a star. Via a luminous outpouring of radiation, the SN can rival the brightness of its SN host galaxy for months or years. In the past decade, astronomical surveys regularly observing the sky to deep limiting magnitudes have revealed that core collapse SNe (the demises of massive stars) are sometimes preceded by eruptive episodes by the progenitor stars during the years before the eventual SN explosion. Such SNe tend to show strong signatures of interaction between the SN ejecta and the circumstellar medium (CSM) deposited by the star before the SN explosion, likely by mass-loss episodes like the ones we have started to observe regularly. The complex CSM resolved around certain giant stars in our own galaxy and the eruptions of giant stars like Eta Carinae in the 19th century can be seen in this context. As the SN ejecta of an interacting SN sweep up the CSM of the progenitor, radiation from this process offers observers opportunity to scan the late mass loss history of the progenitor. In this thesis, interacting SNe and eruptive mass loss of their progenitors is discussed. The SN iPTF13z (discovered by the intermediate Palomar Transient Factory, iPTF) is presented. This transient was followed with optical photometry and spectroscopy during 1000 days and displayed a light curve with several conspicuous re-brigthenings ("bumps"), likely arising from SN ejecta interacting with denser regions in the CSM. Around 200 days before discovery, in archival data we found a clear precursor outburst lasting ∼50 days. A well-observed (but not necessarily well understood) event like SN 2009ip, which showed both precursor outbursts and a light curve bump, makes an interesting comparison object. The embedding of the (possible) SN in a CSM makes it hard to tell if a destructive SN explosion actually happened. In this respect, iPTF13z is compared to e.g. SN 2009ip but also to long-lived interacting SNe like SN 1988Z. Some suggestions

Light Curve and Orbital Period Analysis of VX Lac

NASA Astrophysics Data System (ADS)

Yılmaz, M.; Nelson, R. H.; Şenavcı, H. V.; İzci, D.; Özavcı, İ.; Gümüş, D.

2017-04-01

In this study, we performed simultaneously light curve and radial velocity, and also period analyses of the eclipsing binary system VX Lac. Four color (BVRI) light curves of the system were analysed using the W-D code. The results imply that VX Lac is a classic Algol-type binary with a mass ratio of q=0.27, of which the less massive secondary component fills its Roche lobe. The orbital period behaviour of the system was analysed by assuming the light time effect (LITE) from a third body. The O-C analysis yielded a mass transfer rate of dM/dt=1.86×10-8M⊙yr-1 and the minimal mass of the third body to be M3=0.31M⊙. The residuals from mass transfer and the third body were also analysed because another cyclic variation is seen in O-C diagram. This periodic variation was examined under the hypotheses of stellar magnetic activity and fourth body.

Calculating Galactic Distances Through Supernova Light Curve Analysis (Abstract)

NASA Astrophysics Data System (ADS)

Glanzer, J.

2018-06-01

(Abstract only) The purpose of this project is to experimentally determine the distance to the galaxy M101 by using data that were taken on the type Ia supernova SN 2011fe at the Paul P. Feder Observatory. Type Ia supernovae are useful for determining distances in astronomy because they all have roughly the same luminosity at the peak of their outburst. Comparing the apparent magnitude to the absolute magnitude allows a measurement of the distance. The absolute magnitude is estimated in two ways: using an empirical relationship from the literature between the rate of decline and the absolute magnitude, and using sncosmo, a PYTHON package used for supernova light curve analysis that fits model light curves to the photometric data.

Zooxanthellae harvested by ciliates associated with brown band syndrome of corals remain photosynthetically competent.

PubMed

Ulstrup, Karin E; Kühl, Michael; Bourne, David G

2007-03-01

Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae.

Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent▿

PubMed Central

Ulstrup, Karin E.; Kühl, Michael; Bourne, David G.

2007-01-01

Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

Light curves and spectra from a thermonuclear explosion of a white dwarf merger

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Rossum, Daniel R.; Kashyap, Rahul; Fisher, Robert

Double-degenerate (DD) mergers of carbon–oxygen white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). But, 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. 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 2.1more » $${M}_{\\odot }$$ 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. Finally, 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.« less

Light curves and spectra from a thermonuclear explosion of a white dwarf merger

DOE PAGES

van Rossum, Daniel R.; Kashyap, Rahul; Fisher, Robert; ...

2016-08-15

Double-degenerate (DD) mergers of carbon–oxygen white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). But, 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. 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 2.1more » $${M}_{\\odot }$$ 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. Finally, 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.« less

Discovery of Rotational Modulations in the Planetary-mass Companion 2M1207b: Intermediate Rotation Period and Heterogeneous Clouds in a Low Gravity Atmosphere

NASA Astrophysics Data System (ADS)

Zhou, Yifan; Apai, Dániel; Schneider, Glenn H.; Marley, Mark S.; Showman, Adam P.

2016-02-01

Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves directly probe the rotational periods of ultra-cool objects. We present here, for the first time, time-resolved high-precision photometric measurements of a planetary-mass companion, 2M1207b. We observed the binary system with Hubble Space Telescope/Wide Field Camera 3 in two bands and with two spacecraft roll angles. Using point-spread function-based photometry, we reach a nearly photon-noise limited accuracy for both the primary and the secondary. While the primary is consistent with a flat light curve, the secondary shows modulations that are clearly detected in the combined light curve as well as in different subsets of the data. The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters, respectively. By fitting sine waves to the light curves, we find a consistent period of {10.7}-0.6+1.2 hr and similar phases in both bands. The J- and H-band amplitude ratio of 2M1207b is very similar to a field brown dwarf that has identical spectral type but different J-H color. Importantly, our study also measures, for the first time, the rotation period for a directly imaged extra-solar planetary-mass companion.

New limb-darkening coefficients for modeling binary star light curves

NASA Technical Reports Server (NTRS)

Van Hamme, W.

1993-01-01

We present monochromatic, passband-specific, and bolometric limb-darkening coefficients for a linear as well as nonlinear logarithmic and square root limb-darkening laws. These coefficients, including the bolometric ones, are needed when modeling binary star light curves with the latest version of the Wilson-Devinney light curve progam. We base our calculations on the most recent ATLAS stellar atmosphere models for solar chemical composition stars with a wide range of effective temperatures and surface gravitites. We examine how well various limb-darkening approximations represent the variation of the emerging specific intensity across a stellar surface as computed according to the model. For binary star light curve modeling purposes, we propose the use of a logarithmic or a square root law. We design our tables in such a manner that the relative quality of either law with respect to another can be easily compared. Since the computation of bolometric limb-darkening coefficients first requires monochromatic coefficients, we also offer tables of these coefficients (at 1221 wavelength values between 9.09 nm and 160 micrometer) and tables of passband-specific coefficients for commonly used photometric filters.

Light Curve and Analysis of the Eclipsing Binary BF Centauri

NASA Astrophysics Data System (ADS)

Morris, M. A.; Wolf, G. W.

2003-12-01

The eclipsing binary star BF Centauri was observed photometrically by GWW in the uvby filter system from Mt. John Observatory in New Zealand during 1982, 1989 and 1998. It was also observed spectroscopically at 10 A/mm by W. A. Lawson in 1993 at Mt. Stromlo in Australia to obtain a radial velocity solution. The combined light curves and spectroscopic results have been analyzed using the 1998 version of Robert Wilson's WD light-curve programs. A consistent model for the system will be presented. This analysis was done as a part of a senior research project by MAM, who would like to acknowledge financial support from the Missouri Space Grant Consortium.

CONFIRMATION OF HOT JUPITER KEPLER-41b VIA PHASE CURVE ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quintana, Elisa V.; Rowe, Jason F.; Caldwell, Douglas A.

We present high precision photometry of Kepler-41, a giant planet in a 1.86 day orbit around a G6V star that was recently confirmed through radial velocity measurements. We have developed a new method to confirm giant planets solely from the photometric light curve, and we apply this method herein to Kepler-41 to establish the validity of this technique. We generate a full phase photometric model by including the primary and secondary transits, ellipsoidal variations, Doppler beaming, and reflected/emitted light from the planet. Third light contamination scenarios that can mimic a planetary transit signal are simulated by injecting a full rangemore » of dilution values into the model, and we re-fit each diluted light curve model to the light curve. The resulting constraints on the maximum occultation depth and stellar density combined with stellar evolution models rules out stellar blends and provides a measurement of the planet's mass, size, and temperature. We expect about two dozen Kepler giant planets can be confirmed via this method.« less

VizieR Online Data Catalog: GRB Swift X-ray light curves analysis (Margutti+, 2013)

NASA Astrophysics Data System (ADS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, L.; Burrows, D. N.; Capalbi, M.; Evans, P. A.; Gehrels, N.; Kennea, J.; Mangano, V.; Moretti, A.; Nousek, J.; Osborne, J. P.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Sbarufatti, B.; Stafford, S.; Stamatikos, M.

2013-11-01

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of 'memory' of the prompt γ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt γ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the γ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX,iso{prop.to}E1.00+/-0.06γ,iso/E0.60+/-0.10pk. (3 data files).

APSIDAL MOTION AND A LIGHT CURVE SOLUTION FOR 13 LMC ECCENTRIC ECLIPSING BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zasche, P.; Wolf, M.; Vraštil, J.

2015-12-15

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 thesemore » 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{sub ⊙} 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.« less

Exquisite Nova Light Curves from the Solar Mass Ejection Imager (SMEI)

NASA Astrophysics Data System (ADS)

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

2010-11-01

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.

Identification of the feature that causes the I-band secondary maximum of a Type Ia supernova

NASA Astrophysics Data System (ADS)

Jack, D.; Baron, E.; Hauschildt, P. H.

2015-06-01

We obtained a time series of spectra covering the secondary maximum in the I band of the bright Type Ia supernova 2014J in M82 with the TIGRE telescope. Comparing the observations with theoretical models calculated with the time dependent extension of the PHOENIX code, we identify the feature that causes the secondary maximum in the I-band light curve. Fe II 3d6(3D)4s-3d6(5D)4p and similar high-excitation transitions produce a blended feature at ˜7500 Å, which causes the rise of the light curve towards the secondary maximum. The series of observed spectra of SN 2014J and archival data of SN 2011fe confirm this conclusion. We further studied the plateau phase of the R-band light curve of SN 2014J and searched for features which contribute to the flux. The theoretical models do not clearly indicate a new feature that may cause the R-band plateau phase. However, Co II features in the range of 6500-7000 Å and the Fe II feature of the I band are clearly seen in the theoretical spectra, but do not appear to provide all of the flux necessary for the R-band plateau.

Gamma-Ray Light Curves And Variability Of Bright Fermi -Detected Blazars

DOE PAGES

Abdo, A. A.

2010-09-22

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% ofmore » 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 α 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

NEPTUNE’S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES

PubMed Central

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.

2017-01-01

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. PMID:28127087

Design of compact surface optical coupler based on vertically curved silicon waveguide for high-numerical-aperture single-mode optical fiber

NASA Astrophysics Data System (ADS)

Atsumi, Yuki; Yoshida, Tomoya; Omoda, Emiko; Sakakibara, Youichi

2017-09-01

A surface optical coupler based on a vertically curved Si waveguide was designed for coupling with high-numerical aperture single-mode optical fibers with a mode-field diameter of 5 µm. This coupler has a quite small device size, with a height of approximately 12 µm, achieved by introducing an effective spot-size converter configured with the combination of an extremely short Si exponential-inverse taper and a dome-structured SiO2 lens formed on the coupler top. The designed coupler shows high-efficiency optical coupling, with a loss of 0.8 dB for TE polarized light, as well as broad-band coupling with a 0.5-dB-loss band of 420 nm.

More Rapidly Rotating PMS M Dwarfs with Light Curves Suggestive of Orbiting Clouds of Material

NASA Astrophysics Data System (ADS)

Stauffer, John; Rebull, Luisa; David, Trevor J.; Jardine, Moira; Collier Cameron, Andrew; Cody, Ann Marie; Hillenbrand, Lynne A.; Barrado, David; van Eyken, Julian; Melis, Carl; Briceno, Cesar

2018-02-01

In a previous paper, using data from K2 Campaign 2, we identified 11 very low mass members of the ρ Oph and Upper Scorpius star-forming region as having periodic photometric variability and phased light curves showing multiple scallops or undulations. All of the stars with the “scallop-shell” light curve morphology are mid-to-late M dwarfs without evidence of active accretion and with photometric periods generally <1 day. Their phased light curves have too much structure to be attributed to non-axisymmetrically distributed photospheric spots and rotational modulation. We have now identified an additional eight probable members of the same star-forming region plus three stars in the Taurus star-forming region with this same light curve morphology and sharing the same period and spectral type range as the previous group. We describe the light curves of these new stars in detail and present their general physical characteristics. We also examine the properties of the overall set of stars in order to identify common features that might help elucidate the causes of their photometric variability.

Rotation curves of galaxies and the stellar mass-to-light ratio

NASA Astrophysics Data System (ADS)

Haghi, Hosein; Khodadadi, Aziz; Ghari, Amir; Zonoozi, Akram Hasani; Kroupa, Pavel

2018-03-01

Mass models of a sample of 171 low- and high-surface brightness galaxies are presented in the context of the cold dark matter (CDM) theory using the NFW dark matter halo density distribution to extract a new concentration-viral mass relation (c - Mvir). The rotation curves (RCs) are calculated from the total baryonic matter based on the 3.6 μm-band surface photometry, the observed distribution of neutral hydrogen, and the dark halo, in which the three adjustable parameters are the stellar mass-to-light ratio, halo concentration and virial mass. Although accounting for a NFW dark halo profile can explain rotation curve observations, the implied c - Mvir relation from RC analysis strongly disagrees with that resulting from different cosmological simulations. Also, the M/L -color correlation of the studied galaxies is inconsistent with that expected from stellar population synthesis models with different stellar initial mass functions. Moreover, we show that the best-fitting stellar M/L - ratios of 51 galaxies (30% of our sample) have unphysically negative values in the framework of the ΛCDM theory. This can be interpreted as a serious crisis for this theory. This suggests either that the commonly used NFW halo profile, which is a natural result of ΛCDM cosmological structure formation, is not an appropriate profile for the dark halos of galaxies, or, new dark matter physics or alternative gravity models are needed to explain the rotational velocities of disk galaxies.

Energy transfer and colour tunability in UV light induced Tm3 +/Tb3 +/Eu3 +: ZnB glasses generating white light emission

NASA Astrophysics Data System (ADS)

Naresh, V.; Gupta, Kiran; Parthasaradhi Reddy, C.; Ham, Byoung S.

2017-03-01

A promising energy transfer (Tm3 + → Tb3 + → Eu3 +) approach is brought forward to generate white light emission under ultraviolet (UV) light excitation for solid state lightening. Tm3 +/Tb3 +/Eu3 + ions are combinedly doped in zinc borate glass system in view of understanding energy transfer process resulting in white light emission. Zinc borate (host) glass displayed optical and luminescence properties due to formation of Zn(II)x-[O(- II)]y centres in the ZnB glass matrix. At 360 nm (UV) excitation, triply doped Tm3 +/Tb3 +/Eu3 +: ZnB glasses simultaneously shown their characteristic emission bands in blue (454 nm: 1D2 → 3F4), green (547 nm: 5D4 → 7F5) and red (616 nm: 5D0 → 7F2) regions. In triple ions doped glasses, energy transfer dynamics is discussed in terms of Forster-Dexter theory, excitation & emission profiles, lifetime curves and from partial energy level diagram of three ions. The role of Tb3 + in ET from Tm3 + → Eu3 + was discussed using branch model. From emission decay analysis, energy transfer probability (P) and efficiency (η) were evaluated. Colour tunability from blue to white on varying (Tb3 +, Eu3 +) content is demonstrated from Commission Internationale de L'Eclairage (CIE) chromaticity coordinates. Based on chromaticity coordinates, other colour related parameters like correlated colour temperature (CCT) and colour purity are also computed for the studied glass samples. An appropriate blending of such combination of rare earth ions could show better suitability as potential candidates in achieving multi-colour and warm/cold white light emission for white LEDs application in the field of solid state lightening.

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.

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…

Some characteristics of heavy and light bands of Rickettsia prowazekii on Renografin gradients.

PubMed Central

Hanson, B A; Wisseman, C L; Waddell, A; Silverman, D J

1981-01-01

Suspensions of partially purified Rickettsia prowazekii yielded two bands of organisms when centrifuged to equilibrium in Renografin density gradients. Rickettsiae from the lower, heavy band were defective in their infective and metabolic activities, as compared to organisms from the light band. The greater density in Renografin of heavy-banding organisms was due to their lack of permeability barrier to it, as evidenced by the absence of plasmolysis in hypertonic Renografin. In contrast, light-banding rickettsiae were able to exclude Renografin, since they were plasmolyzed in it. The proportion of heavy-banding organisms in a rickettsial suspension was influenced by the growth phase they were in when harvested from infected yolk sacs, as well as by the conditions and media to which they subsequently were exposed. We have concluded that these defective forms arise from the degeneration of light-banding rickettsiae. This separation of two functional classes of rickettsiae in Renografin density gradients has been exploited (i) to increase the uniformity of the suspensions by removing many noninfectious particles and (ii) to determine rapidly the integrity of certain properties of the cytoplasmic membrane of organisms exposed to a variety of conditions. Images PMID:6796519

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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,more » 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.« less

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.

Broad self-trapped and slow light bands based on negative refraction and interference of magnetic coupled modes.

PubMed

Fang, Yun-Tuan; Ni, Zhi-Yao; Zhu, Na; Zhou, Jun

2016-01-13

We propose a new mechanism to achieve light localization and slow light. Through the study on the coupling of two magnetic surface modes, we find a special convex band that takes on a negative refraction effect. The negative refraction results in an energy flow concellation effect from two degenerated modes on the convex band. The energy flow concellation effect leads to forming of the self-trapped and slow light bands. In the self-trapped band light is localized around the source without reflection wall in the waveguide direction, whereas in the slow light band, light becomes the standing-waves and moving standing-waves at the center and the two sides of the waveguide, respectively.

Origin of the Two Bands in the B800 Ring and Their Involvement in the Energy Transfer Network of Allochromatium vinosum.

PubMed

Schröter, Marco; Alcocer, Marcelo J P; Cogdell, Richard J; Kühn, Oliver; Zigmantas, Donatas

2018-03-15

Bacterial photosynthesis features robust and adaptable energy-harvesting processes in which light-harvesting proteins play a crucial role. The peripheral light-harvesting complex of the purple bacterium Allochromatium vinosum is particularly distinct, featuring a double peak structure in its B800 absorption band. Two hypotheses-not necessarily mutually exclusive-concerning the origin of this splitting have been proposed; either two distinct B800 bacteriochlorophyll site energies are involved, or an excitonic dimerization of bacteriochlorophylls within the B800 ring takes place. Through the use of two-dimensional electronic spectroscopy, we present unambiguous evidence that excitonic interaction shapes the split band. We further identify and characterize all of the energy transfer pathways within this complex by using a global kinetic fitting procedure. Our approach demonstrates how the combination of two-dimensional spectral resolution and self-consistent fitting allows for extraction of information on light-harvesting processes, which would otherwise be inaccessible due to signal congestion.

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.

EXTRASOLAR STORMS: PRESSURE-DEPENDENT CHANGES IN LIGHT-CURVE PHASE IN BROWN DWARFS FROM SIMULTANEOUS HST AND SPITZER OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hao; Apai, Dániel; Karalidi, Theodora

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 andmore » 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.« less

Photometric light curves for seven rapidly-rotating K dwarfs in the Pleiades and Alpha Persei clusters

NASA Technical Reports Server (NTRS)

Stauffer, John R.; Schild, Rudolph A.; Baliunas, Sallie L.; Africano, John L.

1987-01-01

Light curves and period estimates were obtained for several Pleiades and Alpha Persei cluster K dwarfs which were identified as rapid rotators in earlier spectroscopic studies. A few of the stars have previously-published light curves, making it possible to study the long-term variability of the light-curve shapes. The general cause of the photometric variability observed for these stars is an asymmetric distribution of photospheric inhomogeneities (starspots). The presence of these inhomogeneities combined with the rotation of the star lead to the light curves observed. The photometric periods derived are thus identified with the rotation period of the star, making it possible to estimate equatorial rotational velocities for these K dwarfs. These data are of particular importance because the clusters are sufficiently young that stars of this mass should have just arrived on the main sequence. These data could be used to estimate the temperatures and sizes of the spot groups necessary to produce the observed light curves for these stars.

A direct method to solve optimal knots of B-spline curves: An application for non-uniform B-spline curves fitting.

PubMed

Dung, Van Than; Tjahjowidodo, Tegoeh

2017-01-01

B-spline functions are widely used in many industrial applications such as computer graphic representations, computer aided design, computer aided manufacturing, computer numerical control, etc. Recently, there exist some demands, e.g. in reverse engineering (RE) area, to employ B-spline curves for non-trivial cases that include curves with discontinuous points, cusps or turning points from the sampled data. The most challenging task in these cases is in the identification of the number of knots and their respective locations in non-uniform space in the most efficient computational cost. This paper presents a new strategy for fitting any forms of curve by B-spline functions via local algorithm. A new two-step method for fast knot calculation is proposed. In the first step, the data is split using a bisecting method with predetermined allowable error to obtain coarse knots. Secondly, the knots are optimized, for both locations and continuity levels, by employing a non-linear least squares technique. The B-spline function is, therefore, obtained by solving the ordinary least squares problem. The performance of the proposed method is validated by using various numerical experimental data, with and without simulated noise, which were generated by a B-spline function and deterministic parametric functions. This paper also discusses the benchmarking of the proposed method to the existing methods in literature. The proposed method is shown to be able to reconstruct B-spline functions from sampled data within acceptable tolerance. It is also shown that, the proposed method can be applied for fitting any types of curves ranging from smooth ones to discontinuous ones. In addition, the method does not require excessive computational cost, which allows it to be used in automatic reverse engineering applications.

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).

Orbital Light Curves of UU Aquarii in Stunted Outburst

NASA Astrophysics Data System (ADS)

Robertson, J. W.; Honeycutt, R. K.; Henden, A. A.; Campbell, R. T.

2018-02-01

Stunted outbursts are ∼0.ͫ6 eruptions, typically lasting 5–10 days, which are found in some novalike cataclysmic variables, including UU Aqr. The mechanism responsible for stunted outbursts is uncertain but is likely related to an accretion disk instability or to variations in the mass transfer rate. A campaign to monitor the eclipse light curves in UU Aqr has been conducted in order to detect any light curve distortions due to the appearance of a hot spot on the disk at the location of the impact point of the accretion stream. If stunted outbursts are due to a temporary mass transfer enhancement, then predictable deformations of the orbital light curve are expected to occur during such outbursts. This study used 156 eclipses on 135 nights during the years 2000–2012. During this interval, random samples found the system to be in stunted outbursts 4%–5% of the time, yielding ∼7 eclipses obtained during some stage of stunted outburst. About half of the eclipses obtained during stunted outbursts showed clear evidence for hot spot enhancement, providing strong evidence that the stunted outbursts in UU Aqr are associated with mass transfer variations. The other half of the eclipses during stunted outburst showed little or no evidence for hot spot enhancement. Furthermore, there were no systematic changes in the hot spot signature as stunted outbursts progressed. Therefore, we have tentatively attributed the changes in hot spot visibility during stunted outburst to random blobby accretion, which likely further modulates the strength of the accretion stream on orbital timescales.

The massive binary CPD - 41° 7742. II. Optical light curve and X-ray observations

NASA Astrophysics Data System (ADS)

Sana, H.; Antokhina, E.; Royer, P.; Manfroid, J.; Gosset, E.; Rauw, G.; Vreux, J.-M.

2005-10-01

In the first paper of this series, we presented a detailed high-resolution spectroscopic study of CPD - 41° 7742, deriving for the first time an orbital solution for both components of the system. In this second paper, we focus on the analysis of the optical light curve and on recent XMM-Newton X-ray observations. In the optical, the system presents two eclipses, yielding an inclination i˜77°. Combining the constraints from the photometry with the results of our previous work, we derive the absolute parameters of the system. We confirm that the two components of CPD - 41° 7742 are main sequence stars (O9 V + B1-1.5 V) with masses (M_1˜18 M⊙ and M_2˜10 M⊙) and respective radii (R_1˜7.5 R⊙ and R_2˜5.4 R⊙) close to the typical values expected for such stars. We also report an unprecedented set of X-ray observations that almost uniformly cover the 2.44-day orbital cycle. The X-ray emission from CPD - 41° 7742 is well described by a two-temperature thermal plasma model with energies close to 0.6 and 1.0 keV, thus slightly harder than typical early-type emission. The X-ray light curve shows clear signs of variability. The emission level is higher when the primary is in front of the secondary. During the high emission state, the system shows a drop of its X-ray emission that almost exactly matches the optical eclipse. We interpret the main features of the X-ray light curve as the signature of a wind-photosphere interaction, in which the overwhelming primary O9 star wind crashes into the secondary surface. Alternatively the light curve could result from a wind-wind interaction zone located near the secondary star surface. As a support to our interpretation, we provide a phenomenological geometric model that qualitatively reproduces the observed modulations of the X-ray emission.

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.

Type IIP supernova light curves affected by the acceleration of red supergiant winds

NASA Astrophysics Data System (ADS)

Moriya, Takashi J.; Förster, Francisco; Yoon, Sung-Chul; Gräfener, Götz; Blinnikov, Sergei I.

2018-05-01

We introduce the first synthetic light-curve model set of Type IIP supernovae exploded within circumstellar media in which the acceleration of the red supergiant winds is taken into account. Because wind acceleration makes the wind velocities near the progenitors low, the density of the immediate vicinity of the red supergiant supernova progenitors can be higher than that extrapolated by using a constant terminal wind velocity. Therefore, even if the mass-loss rate of the progenitor is relatively low, it can have a dense circumstellar medium at the immediate stellar vicinity and the early light curves of Type IIP supernovae are significantly affected by it. We adopt a simple β velocity law to formulate the wind acceleration. We provide bolometric and multicolour light curves of Type IIP supernovae exploding within such accelerated winds from the combinations of three progenitors, 12-16 M⊙; five β, 1-5; seven mass-loss rates, 10-5-10-2 M⊙ yr-1; and four explosion energies, (0.5-2) × 1051 erg. All the light-curve models are available at https://goo.gl/o5phYb. When the circumstellar density is sufficiently high, our models do not show a classical shock breakout as a consequence of the interaction with the dense and optically thick circumstellar media. Instead, they show a delayed `wind breakout', substantially affecting early light curves of Type IIP supernovae. We find that the mass-loss rates of the progenitors need to be 10-3-10-2 M⊙ yr-1 to explain typical rise times of 5-10 d in Type IIP supernovae assuming a dense circumstellar radius of 1015 cm.

Generation of three wide frequency bands within a single white-light cavity

NASA Astrophysics Data System (ADS)

Othman, Anas; Yevick, David; Al-Amri, M.

2018-04-01

We theoretically investigate the double-Λ scheme inside a Fabry-Pérot cavity employing a weak probe beam and two strong driving fields together with an incoherent pumping mechanism. By generating analytical expressions for the susceptibility and applying the white-light cavity conditions, we devise a procedure that reaches the white-light condition at a smaller gas density than the values typically cited in similar previous studies. Further, when the intensities of the two driving fields are equal, a single giant white band is obtained, while for unequal driving fields three white bands can be present in the cavity. Two additional techniques are then advanced for generating three white bands and a method is described for displacing the center frequency of the bands. Finally, some potential applications are suggested.

Multi-band transmission color filters for multi-color white LEDs based visible light communication

NASA Astrophysics Data System (ADS)

Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

2017-11-01

Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

REVISITING EVIDENCE OF CHAOS IN X-RAY LIGHT CURVES: THE CASE OF GRS 1915+105

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mannattil, Manu; Gupta, Himanshu; Chakraborty, Sagar, E-mail: mmanu@iitk.ac.in, E-mail: hiugupta@iitk.ac.in, E-mail: sagarc@iitk.ac.in

2016-12-20

Nonlinear time series analysis has been widely used to search for signatures of low-dimensional chaos in light curves emanating from astrophysical bodies. A particularly popular example is the microquasar GRS 1915+105, whose irregular but systematic X-ray variability has been well studied using data acquired by the Rossi X-ray Timing Explorer . With a view to building simpler models of X-ray variability, attempts have been made to classify the light curves of GRS 1915+105 as chaotic or stochastic. Contrary to some of the earlier suggestions, after careful analysis, we find no evidence for chaos or determinism in any of the GRS 1915+105 classes. Themore » dearth of long and stationary data sets representing all the different variability classes of GRS 1915+105 makes it a poor candidate for analysis using nonlinear time series techniques. We conclude that either very exhaustive data analysis with sufficiently long and stationary light curves should be performed, keeping all the pitfalls of nonlinear time series analysis in mind, or alternative schemes of classifying the light curves should be adopted. The generic limitations of the techniques that we point out in the context of GRS 1915+105 affect all similar investigations of light curves from other astrophysical sources.« less

Kepler-91b: a planet at the end of its life. Planet and giant host star properties via light-curve variations

NASA Astrophysics Data System (ADS)

Lillo-Box, J.; Barrado, D.; Moya, A.; Montesinos, B.; Montalbán, J.; Bayo, A.; Barbieri, M.; Régulo, C.; Mancini, L.; Bouy, H.; Henning, T.

2014-02-01

the stellar atmosphere at the pericentre. We also detected three small dims in the phase-folded light curve. The combination of two of them agrees with the theoretical characteristics expected for secondary eclipse. Conclusions: Kepler-91b could be the previous stage of the planet engulfment, which has recently been detected for BD+48 740. Our estimations show that Kepler-91b will be swallowed by its host star in less than 55 Myr. Among the confirmed planets around giant stars, this is the closest to its host star. At pericentre, the star subtends an angle of 48°, covering around 10% of the sky as seen from the planet. The planetary atmosphere seems to be inflated probably due to the high stellar irradiation. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut fur Astronomie (Heidelberg) and the Instituto de Astrofísica de Andalucía (IAA-CSIC, Granada).Appendix A is available in electronic form at http://www.aanda.org

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

A Semiautomatic Pipeline for Be Star Light Curves

NASA Astrophysics Data System (ADS)

Rímulo, L. R.; Carciofi, A. C.; Rivinius, T.; Okazaki, A.

2016-11-01

Observational and theoretical studies from the last decade have shown that the Viscous Decretion Disk (VDD) scenario, in which turbulent viscosity is the physical mechanism responsible for the transport of material and angular momentum ejected from the star to the outer regions of the disk, is the only viable model for explaining the circumstellar disks of Be stars. In the α-disk approach applied to the VDD, the dimensionless parameter α is a measure of the turbulent viscosity. Recently, combining the time-dependent evolution of a VDD α-disk with non-LTE radiative transfer calculations, the first measurement of the α parameter was made, for the disk dissipation of the Be star ω CMa. It was found that α≍ 1 for that Be disk. The main motivation of this present work is the statistical determination of the α parameter. For this purpose, we present a pipeline that will allow the semiautomatic determination of the α parameter of several dozens of light curves of Be stars available from photometric surveys, In this contribution, we describe the pipeline, outlining the main staps required for the semiautomatic analysis of light curves

Gamma-Ray Burst Prompt Emission Light Curves and Power Density Spectra in the ICMART Model

NASA Astrophysics Data System (ADS)

Zhang, Bo; Zhang, Bing

2014-02-01

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.

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).

Observations and light curve solutions of a selection of shallow-contact W UMa binaries

NASA Astrophysics Data System (ADS)

Kjurkchieva, Diana P.; Popov, Velimir A.; Vasileva, Doroteya L.; Petrov, Nikola I.

2018-07-01

Photometric observations in Sloan g‧ and i‧ bands of the W UMa binaries V0951 Per, CSS J062803.2+571604, CSS J222157.2+275308, CSS J075135.6+382028, V0338 Dra, NSVS 2256852, NSVS 4666412, V1355 Tau, NSVS 4808227, NSVS 4726498, CSS J075350.1+264830 and HL Lyn are presented. The light curve solutions revealed that these binaries have overcontact configurations with small fillout factors (within 0.1-0.2). Seven of them undergo total eclipses and their photometric mass ratios should be accepted with confidence. The temperature differences of the components of CSS J062803.2+571604 and NSVS 2256852 exceed 1100 K which is unusual for overcontact binaries. We suspect that NSVS 2256852 is a probable candidate for merger due to its small mass ratio of q = 0.16 and to the registered decreasing of the orbital period.

THE WISE LIGHT CURVES OF POLARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, Thomas E.; Campbell, Ryan K., E-mail: tharriso@nmsu.edu, E-mail: Ryan.Campbell@humboldt.edu

2015-08-15

We have extracted the WISE (Wide-field Infrared Survey Explorer) single-exposure data for a sample of 72 polars, which are highly magnetic cataclysmic variables (CVs). We combine these data with both published and unpublished optical and infrared data to explore the origins of the large amplitude variations seen in these systems. In nearly every case, we find evidence for cyclotron emission in the WISE bandpasses. We find that the derived magnetic field strengths for some polars are either too high, or cyclotron emission from lower field components, located spatially coincident to the main accreting poles, must be occurring. We have alsomore » estimated field strengths for a number of polars where no such values exist. In addition, contrary to expectations, we find that emission from the fundamental cyclotron harmonic (n = 1) appears to be nearly always present when the magnetic field is of the appropriate strength that it falls within a WISE bandpass. We find that the light curves for RBS 490, an ultrashort-period (46 minutes) CV, suggest that it is a polar. Modeling its spectrum indicates that its donor star is much hotter than expected. Nearly all of the detected polars show 11.5 μm (“W3 band”) excesses. The general lack of variability seen in the W3 bandpass light curves for higher-field polars demonstrates that these excesses are probably not due to cyclotron emission. There is circumstantial evidence that these excesses can be attributed to bremsstrahlung emission from their accretion streams. Reduction of the Spitzer 24 μm image of V1500 Cyg shows that it appears to be located at the center of a small nebula.« less

Decoding of the light changes in eclipsing Wolf-Rayet binaries. I. A non-classical approach to the solution of light curves

NASA Astrophysics Data System (ADS)

Perrier, C.; Breysacher, J.; Rauw, G.

2009-09-01

Aims: We present a technique to determine the orbital and physical parameters of eclipsing eccentric Wolf-Rayet + O-star binaries, where one eclipse is produced by the absorption of the O-star light by the stellar wind of the W-R star. Methods: Our method is based on the use of the empirical moments of the light curve that are integral transforms evaluated from the observed light curves. The optical depth along the line of sight and the limb darkening of the W-R star are modelled by simple mathematical functions, and we derive analytical expressions for the moments of the light curve as a function of the orbital parameters and the key parameters of the transparency and limb-darkening functions. These analytical expressions are then inverted in order to derive the values of the orbital inclination, the stellar radii, the fractional luminosities, and the parameters of the wind transparency and limb-darkening laws. Results: The method is applied to the SMC W-R eclipsing binary HD 5980, a remarkable object that underwent an LBV-like event in August 1994. The analysis refers to the pre-outburst observational data. A synthetic light curve based on the elements derived for the system allows a quality assessment of the results obtained.

X-ray light curves of active galactic nuclei are phase incoherent

NASA Technical Reports Server (NTRS)

Krolik, Julian; Done, Chris; Madejski, Grzegorz

1993-01-01

We compute the Fourier phase spectra for the light curves of five low-luminosity active galactic nuclei observed by EXOSAT. There is no statistically significant phase coherence in any of them. This statement is equivalent, subject to a technical caveat, to a demonstration that their fluctuation statistics are Gaussian. Models in which the X-ray output is controlled wholly by a unitary process undergoing a nonlinear limit cycle are therefore ruled out, while models with either a large number of randomly excited independent oscillation modes or nonlinearly interacting spatially dependent oscillations are favored. We also demonstrate how the degree of phase coherence in light curve fluctuations influences the application of causality bounds on internal length scales.

VizieR Online Data Catalog: Light curves of WASP-52 (Mancini+, 2017)

NASA Astrophysics Data System (ADS)

Mancini, L.; Southworth, J.; Raia, G.; Tregloan-Reed, J.; Molliere, P.; Bozza, V.; Bretton, M.; Bruni, I.; Ciceri, S.; D'Ago, G.; Dominik, M.; Hinse, T. C.; Hundertmark, M.; Jorgensen, U. G.; Korhonen, H.; Rabus, M.; Rahvar, S.; Starkey, D.; Calchi Novati, S.; Figuera Jaimes, R.; Henning, T.; Juncher, D.; Haugbolle, T.; Kains, N.; Popovas, A.; Schmidt, R. W.; Skottfelt, J.; Snodgrass, C.; Surdej, J.; Wertz, O.

2018-03-01

Light curves of transit events of the extrasolar planet WASP-52b. One of the datasets was obtained using the Cassini 1.52m Telescope (Gunn r) at the Astronomical Observatory of Bologna in Loiano (Italy). Three of the datasets were obtained using the Zeiss 1.23m telescope (Cousins R and Cousins I) at the German-Spanish Astronomical Centre at Calar Alto (Spain). Four of the datasets were obtained using the MPG 2.2m telescope (Sloan g, Sloan r, Sloan i, Sloan z) at the ESO Observatory in La Silla (Chile). Four of the datasets were obtained using the 1.54m Danish Telescope at the ESO Observatory in La Silla (Chile). (2 data files).

Candidate Binary Trojan and Hilda Asteroids from Rotational Light Curves

NASA Astrophysics Data System (ADS)

Sonnett, Sarah M.; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph R.; Bauer, James M.; Kramer, Emily A.

2017-10-01

Jovian Trojans (hereafter, Trojans) are asteroids in stable orbits at Jupiter's L4 and L5 Lagrange points, and Hilda asteroids are inwards of the Trojans in 3:2 mean-motion resonance with Jupiter. Due to their special dynamical properties, observationally constraining the formation location and dynamical histories of Trojans and HIldas offers key input for giant planet migration models. A fundamental parameter in assessing formation location is the bulk density - with low-density objects associated with an ice-rich formation environment in the outer solar system and high-density objects typically linked to the warmer inner solar system. Bulk density can only be directly measured during a close fly-by or by determining the mutual orbits of binary asteroid systems. With the aim of determining densities for a statistically significant sample of Trojans and Hildas, we are undertaking an observational campaign to confirm and characterize candidate binary asteroids published in Sonnett et al. (2015). These objects were flagged as binary candidates because their large NEOWISE brightness variations imply shapes so elongated that they are not likely explained by a singular equilibrium rubble pile and instead may be two elongated, gravitationally bound asteroids. We are obtaining densely sampled rotational light curves of these possible binaries to search for light curve features diagnostic of binarity and to determine the orbital properties of any confirmed binary systems by modeling the light curve. We compare the We present an update on this follow-up campaign and comment on future steps.

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.

THE VARYING LIGHT CURVE AND TIMINGS OF THE ULTRASHORT-PERIOD CONTACT BINARY KIC 9532219

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jae Woo; Hong, Kyeongsoo; Koo, Jae-Rim

2016-03-20

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 T{sub 1}–T{sub 2} = 172 K, and a third light of l{sub 3} = 75.9%.more » 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{sub ⊙} 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.« less

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.

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.

VizieR Online Data Catalog: 5 exoplanet light and RV curves (Mancini+, 2018)

NASA Astrophysics Data System (ADS)

Mancini, L.; Esposito, M.; Covino, E.; Southworth, J.; Biazzo, K.; Bruni, I.; Ciceri, S.; Evans, D.; Lanza, A. F.; Poretti, E.; Sarkis, P.; Smith, A. M. S.; Brogi, M.; Affer, L.; Benatti, S.; Bignamini, A.; Boccato, C.; Bonomo, A. S.; Borsa, F.; Carleo, I.; Claudi, R.; Cosentino, R.; Damasso, M.; Desidera, S.; Giacobbe, P.; Gonzalez-Alvarez, E.; Gratton, R.; Harutyunyan, A.; Leto, G.; Maggio, A.; Malavolta, L.; Maldonado, J.; Martinez-Fiorenzano, A.; Masiero, S.; Micela, G.; Molinari, E.; Nascimbeni, V.; Pagano, I.; Pedani, M.; Piotto, G.; Rainer, M.; Scandariato, G.; Smareglia, R.; Sozzetti, A.; Andreuzzi, G.; Henning, T.

2018-02-01

Radial velocity measurements of HAT-P-3, HAT-P-12, HAT-P-22, WASP-39, and WASP-60 obtained with HARPS-N at the 3.5m TNG telescope. Light curves of transit events of the extrasolar planet HAT-P-3b, HAT-P-12b and WASP-60b. Two of the datasets were obtained using the Cassini 1.52m Telescope (Gunn r and Gunn i) at the Astronomical Observatory of Bologna in Loiano (Italy). Ten of the datasets were obtained using the Zeiss 1.23m telescope (Cousins R and Cousins I) at the German-Spanish Astronomical Centre at Calar Alto (Spain). Four of the datasets were obtained using the 2.2m telescope (Stromgren u, Gunn g, Gunn r, Johnson I) at the German-Spanish Astronomical Centre at Calar Alto (Spain). One of the datasets was obtained using the 2.5m Isaac Newton Telescope (INT) in La Palma (Spain). (4 data files).

Split-face comparison between single-band and dual-band pulsed light technology for treatment of photodamage.

PubMed

Varughese, Neal; Keller, Lauren; Goldberg, David J

2016-08-01

Intense pulsed light (IPL) has a well-recognized role in the treatment of photodamaged skin. To assess the safety and efficacy of a novel single-band IPL handpiece versus dual-band IPL handpiece in the treatment of photodamage. This was a prospective, single-center split-face study with 20 enrolled participants. Three treatments, 21 days apart, were administered to the subjects and follow-up was performed for 20 weeks. The left side of the face was treated with the single-band handpiece. The right side of the face was treated with the dual-band handpiece. Blinded investigators assessed the subjects' skin texture, pigmented components of photodamage, and presence of telangiectasia both before and after treatment, utilizing a five-point scale. Pigmented components of photodamage, skin texture, and presence of telangiectasias on the left and right side of the face were improved at the end of treatment. At 20-week follow-up, the side treated with single-band handpiece showed improvement in telangiectasia and pigmentation that was statistically superior to the contralateral side treated with the dual-band handpiece. Both devices equally improved textural changes. No adverse effects were noted with either device. Both single-band and dual-band IPL technology are safe and effective in the treatment of photodamaged facial skin. IPL treatment with a single-band handpiece yielded results comparable or superior to dual-band technology.

Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

PubMed Central

2012-01-01

Background Plant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED) technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses. Results We have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD). The average photosynthetic PFD (PPFD) in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%), which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD) of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm) grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength), the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg) and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1) was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1. Conclusions The plant lighting system, with a computer with a graphical user interface

Broadband turbulent spectra in gamma-ray burst light curves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Putten, Maurice H. P. M.; Guidorzi, Cristiano; Frontera, Filippo, E-mail: mvp@sejong.ac.kr

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 onemore » 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.« less

Increased visible-light photocatalytic activity of TiO2 via band gap manipulation

NASA Astrophysics Data System (ADS)

Pennington, Ashley Marie

Hydrogen gas is a clean burning fuel that has potential applications in stationary and mobile power generation and energy storage, but is commercially produced from non-renewable fossil natural gas. Using renewable biomass as the hydrocarbon feed instead could provide sustainable and carbon-neutral hydrogen. We focus on photocatalytic oxidation and reforming of methanol over modified titanium dioxide (TiO2) nanoparticles to produce hydrogen gas. Methanol is used as a model for biomass sugars. By using a photocatalyst, we aim to circumvent the high energy cost of carrying out endothermic reactions at commercial scale. TiO2 is a semiconductor metal oxide of particular interest in photocatalysis due to its photoactivity under ultraviolet illumination and its stability under catalytic reaction conditions. However, TiO2 primarily absorbs ultraviolet light, with little absorption of visible light. While an effective band gap for absorbance of photons from visible light is 1.7 eV, TiO2 polymorphs rutile and anatase, have band gaps of 3.03 eV and 3.20 eV respectively, which indicate ultraviolet light. As most of incident solar radiation is visible light, we hypothesize that decreasing the band gap of TiO2 will increase the efficiency of TiO2 as a visible-light active photocatalyst. We propose to modify the band gap of TiO2 by manipulating the catalyst structure and composition via metal nanoparticle deposition and heteroatom doping in order to more efficiently utilize solar radiation. Of the metal-modified Degussa P25 TiO2 samples (P25), the copper and nickel modified samples, 1%Cu/P25 and 1%Ni/P25 yielded the lowest band gap of 3.05 eV each. A difference of 0.22 eV from the unmodified P25. Under visible light illumination 1%Ni/P25 and 1%Pt/P25 had the highest conversion of methanol of 9.9% and 9.6%, respectively.

Light Curves of Lucy Targets: Leucus and Polymele

NASA Astrophysics Data System (ADS)

Buie, Marc W.; Zangari, Amanda M.; Marchi, Simone; Levison, Harold F.; Mottola, Stefano

2018-06-01

We present new observations from 2016 of two Jupiter Trojan asteroids that are targets for the Lucy Discovery mission. The extremely long rotation period of (11351) Leucus is confirmed and refined to a secure value of 445.732 ± 0.021 hr with photometric parameters of H r = 11.046 ± 0.003 and G r = 0.58 ± 0.02 in the SDSS r‧ filter. This leads to a geometric albedo of p V = 4.7%. The amplitude of the light curve was measured to be 0.61 mag, unchanged from the value of one-fourth of a revolution earlier, suggesting a low obliquity. The first light-curve observations for (15094) Polymele are also presented. This object is revealed to have a much shorter rotation period of 5.8607 ± 0.0005 hr with a very low amplitude of 0.09 mag. Its photometric parameters are H r = 11.691 ± 0.002 and G r = 0.22 ± 0.02. These values lead to a refined geometric albedo of p V = 7.3%. This object is either nearly spherical or was being viewed nearly pole-on in 2016. Further observations are required to fully determine the spin pole orientation and convex-hull shapes.

Machine Learning Techniques for Stellar Light Curve Classification

NASA Astrophysics Data System (ADS)

Hinners, Trisha A.; Tat, Kevin; Thorp, Rachel

2018-07-01

We apply machine learning techniques in an attempt to predict and classify stellar properties from noisy and sparse time-series data. We preprocessed over 94 GB of Kepler light curves from the Mikulski Archive for Space Telescopes (MAST) to classify according to 10 distinct physical properties using both representation learning and feature engineering approaches. Studies using machine learning in the field have been primarily done on simulated data, making our study one of the first to use real light-curve data for machine learning approaches. We tuned our data using previous work with simulated data as a template and achieved mixed results between the two approaches. Representation learning using a long short-term memory recurrent neural network produced no successful predictions, but our work with feature engineering was successful for both classification and regression. In particular, we were able to achieve values for stellar density, stellar radius, and effective temperature with low error (∼2%–4%) and good accuracy (∼75%) for classifying the number of transits for a given star. The results show promise for improvement for both approaches upon using larger data sets with a larger minority class. This work has the potential to provide a foundation for future tools and techniques to aid in the analysis of astrophysical data.

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.

Hierarchical Models for Type Ia Supernova Light Curves in the Optical and Near Infrared

NASA Astrophysics Data System (ADS)

Mandel, Kaisey; Narayan, G.; Kirshner, R. P.

2011-01-01

I have constructed a comprehensive statistical model for Type Ia supernova optical and near infrared light curves. Since the near infrared light curves are excellent standard candles and are less sensitive to dust extinction and reddening, the combination of near infrared and optical data better constrains the host galaxy extinction and improves the precision of distance predictions to SN Ia. A hierarchical probabilistic model coherently accounts for multiple random and uncertain effects, including photometric error, intrinsic supernova light curve variations and correlations across phase and wavelength, dust extinction and reddening, peculiar velocity dispersion and distances. An improved BayeSN MCMC code is implemented for computing probabilistic inferences for individual supernovae and the SN Ia and host galaxy dust populations. I use this hierarchical model to analyze nearby Type Ia supernovae with optical and near infared data from the PAIRITEL, CfA3, and CSP samples and the literature. Using cross-validation to test the robustness of the model predictions, I find that the rms Hubble diagram scatter of predicted distance moduli is 0.11 mag for SN with optical and near infrared data versus 0.15 mag for SN with only optical data. Accounting for the dispersion expected from random peculiar velocities, the rms intrinsic prediction error is 0.08-0.10 mag for SN with both optical and near infrared light curves. I discuss results for the inferred intrinsic correlation structures of the optical-NIR SN Ia light curves and the host galaxy dust distribution captured by the hierarchical model. The continued observation and analysis of Type Ia SN in the optical and near infrared is important for improving their utility as precise and accurate cosmological distance indicators.

Fourier Decomposition of RR Lyrae light curves and the SX Phe population in the central region of NGC 3201

NASA Astrophysics Data System (ADS)

Arellano Ferro, A.; Ahumada, J. A.; Calderón, J. H.; Kains, N.

2014-10-01

CCD time-series observations of the central region of the globular cluster NGC 3201 were obtained with the aim of performing the Fourier decomposition of the light curves of the RR Lyrae stars present in that field. This procedure gave the mean values, for the metallicity, of [Fe/H] [ZW] = - 1.483±0.006 (statistical) ±0.090 (systematic), and for the distance, 5.000±0.001 kpc (statistical) ±0.220 (systematic). The values found from two RRc stars are consistent with those derived previously. The differential reddening of the cluster was investigated and individual reddenings for the RR Lyrae stars were estimated from their V - I curves. We found an average value of E(B - V) = 0.23±0.02. An investigation of the light curves of stars in the blue straggler region led to the discovery of three new SX Phe stars. The period-luminosity relation of the SX Phe stars was used for an independent determination of the distance to the cluster and of the individual reddenings. We found a distance of 5.0 kpc.

Accurate photometric light curves of the lensed components of Q2237+0305 derived with an optimal image subtraction technique: Evidence for microlensing in image A

NASA Astrophysics Data System (ADS)

Moreau, O.; Libbrecht, C.; Lee, D.-W.; Surdej, J.

2005-06-01

Using an optimal image subtraction technique, we have derived the V and R light curves of the four lensed QSO components of Q2237+0305 from the monitoring CCD frames obtained by the GLITP collaboration with the 2.6 m NOT telescope in 1999/2000 (Alcalde et al. 2002). We give here a detailed account of the data reduction and analysis and of the error estimates. In agreement with Woźniak et al. (2000a,b), the good derived photometric accuracy of the GLITP data allows to discuss the possible interpretation of the light curve of component A as due to a microlensing event taking place in the deflecting galaxy. This interpretation is strengthened by the colour dependence of the early rise of the light curve of component A, as it probably corresponds to a caustics crossing by the QSO source.

Atlas of the Light Curves and Phase Plane Portraits of Selected Long-Period Variables

NASA Astrophysics Data System (ADS)

Kudashkina, L. S.; Andronov, I. L.

2017-12-01

For a group of the Mira-type stars, semi-regular variables and some RV Tau - type stars the limit cycles were computed and plotted using the phase plane diagrams. As generalized coordinates x and x', we have used φ - the brightness of the star and its phase derivative. We have used mean phase light curves using observations of various authors from the databases of AAVSO, AFOEV, VSOLJ, ASAS and approximated using a trigonometric polynomial of statistically optimal degree. For a simple sine-like light curve, the limit cycle is a simple ellipse. In a case of more complicated light curve, in which harmonics are statistically significant, the limit cycle has deviations from the ellipse. In an addition to a classical analysis, we use the error estimates of the smoothing function and its derivative to constrain an "error corridor" in the phase plane.

A Kepler study of starspot lifetimes with respect to light-curve amplitude and spectral type

NASA Astrophysics Data System (ADS)

Giles, Helen A. C.; Collier Cameron, Andrew; Haywood, Raphaëlle D.

2017-12-01

Wide-field high-precision photometric surveys such as Kepler have produced reams of data suitable for investigating stellar magnetic activity of cooler stars. Starspot activity produces quasi-sinusoidal light curves whose phase and amplitude vary as active regions grow and decay over time. Here we investigate, first, whether there is a correlation between the size of starspots - assumed to be related to the amplitude of the sinusoid - and their decay time-scale and, secondly, whether any such correlation depends on the stellar effective temperature. To determine this, we computed the auto-correlation functions of the light curves of samples of stars from Kepler and fitted them with apodised periodic functions. The light-curve amplitudes, representing spot size, were measured from the root-mean-squared scatter of the normalized light curves. We used a Monte Carlo Markov Chain to measure the periods and decay time-scales of the light curves. The results show a correlation between the decay time of starspots and their inferred size. The decay time also depends strongly on the temperature of the star. Cooler stars have spots that last much longer, in particular for stars with longer rotational periods. This is consistent with current theories of diffusive mechanisms causing starspot decay. We also find that the Sun is not unusually quiet for its spectral type - stars with solar-type rotation periods and temperatures tend to have (comparatively) smaller starspots than stars with mid-G or later spectral types.

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

DOE PAGES

Prentice, S. J.; Mazzali, P. A.; Pian, E.; ...

2016-02-08

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 L p , enabling the construction of a luminosity function. Subsequently, the mass of 56 Ni 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 (SNemore » Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median L p , in erg s -1 , of log(L p) = 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 M Ni = 0.34, 0.16, 0.14, and 0.11 M ⊙ , respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from L p /2 to L p more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.« less

What can we Learn from the Rising Light Curves of Radioactively Powered Supernovae?

NASA Astrophysics Data System (ADS)

Piro, Anthony L.; Nakar, Ehud

2013-05-01

The light curve of the explosion of a star with a radius <~ 10-100 R ⊙ 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 56Ni. If the amount of 56Ni 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 56Ni 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 explosion occurred. As an

Discrete Electronic Bands in Semiconductors and Insulators: Potential High-Light-Yield Scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Hongliang; Du, Mao-Hua

Bulk semiconductors and insulators typically have continuous valence and conduction bands. In this paper, we show that valence and conduction bands of a multinary semiconductor or insulator can be split to narrow discrete bands separated by large energy gaps. This unique electronic structure is demonstrated by first-principles calculations in several quaternary elpasolite compounds, i.e., Cs 2NaInBr 6, Cs 2NaBiCl 6, and Tl 2NaBiCl 6. The narrow discrete band structure in these quaternary elpasolites is due to the large electronegativity difference among cations and the large nearest-neighbor distances in cation sublattices. We further use Cs 2NaInBr 6 as an example tomore » show that the narrow bands can stabilize self-trapped and dopant-bound excitons (in which both the electron and the hole are strongly localized in static positions on adjacent sites) and promote strong exciton emission at room temperature. The discrete band structure should further suppress thermalization of hot carriers and may lead to enhanced impact ionization, which is usually considered inefficient in bulk semiconductors and insulators. Finally, these characteristics can enable efficient room-temperature light emission in low-gap scintillators and may overcome the light-yield bottleneck in current scintillator research.« less

Discrete Electronic Bands in Semiconductors and Insulators: Potential High-Light-Yield Scintillators

DOE PAGES

Shi, Hongliang; Du, Mao-Hua

2015-05-12

Bulk semiconductors and insulators typically have continuous valence and conduction bands. In this paper, we show that valence and conduction bands of a multinary semiconductor or insulator can be split to narrow discrete bands separated by large energy gaps. This unique electronic structure is demonstrated by first-principles calculations in several quaternary elpasolite compounds, i.e., Cs 2NaInBr 6, Cs 2NaBiCl 6, and Tl 2NaBiCl 6. The narrow discrete band structure in these quaternary elpasolites is due to the large electronegativity difference among cations and the large nearest-neighbor distances in cation sublattices. We further use Cs 2NaInBr 6 as an example tomore » show that the narrow bands can stabilize self-trapped and dopant-bound excitons (in which both the electron and the hole are strongly localized in static positions on adjacent sites) and promote strong exciton emission at room temperature. The discrete band structure should further suppress thermalization of hot carriers and may lead to enhanced impact ionization, which is usually considered inefficient in bulk semiconductors and insulators. Finally, these characteristics can enable efficient room-temperature light emission in low-gap scintillators and may overcome the light-yield bottleneck in current scintillator research.« less

Focusing of light through turbid media by curve fitting optimization

NASA Astrophysics Data System (ADS)

Gong, Changmei; Wu, Tengfei; Liu, Jietao; Li, Huijuan; Shao, Xiaopeng; Zhang, Jianqi

2016-12-01

The construction of wavefront phase plays a critical role in focusing light through turbid media. We introduce the curve fitting algorithm (CFA) into the feedback control procedure for wavefront optimization. Unlike the existing continuous sequential algorithm (CSA), the CFA locates the optimal phase by fitting a curve to the measured signals. Simulation results show that, similar to the genetic algorithm (GA), the proposed CFA technique is far less susceptible to the experimental noise than the CSA. Furthermore, only three measurements of feedback signals are enough for CFA to fit the optimal phase while obtaining a higher focal intensity than the CSA and the GA, dramatically shortening the optimization time by a factor of 3 compared with the CSA and the GA. The proposed CFA approach can be applied to enhance the focus intensity and boost the focusing speed in the fields of biological imaging, particle trapping, laser therapy, and so on, and might help to focus light through dynamic turbid media.

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXVIII - Ultraviolet light curves for Alpha Lupi and BW Vulpeculae

NASA Technical Reports Server (NTRS)

Lesh, J. R.

1978-01-01

Photometric data from the Wisconsin Experiment Package on OAO-2 have been used to construct light curves at three ultraviolet wavelengths for Alpha Lup and at seven wavelengths for BW Vul. Both stars are well-known variables of the Beta Cephei (Beta Canis Majoris) type. The light curves for Alpha Lup are in good agreement with the radial-velocity period. A temperature variation of 400-500 K is derived. The BW Vul light curves confirm recent ephemerides based on a secularly varying period and show a stillstand near light maximum at some wavelengths. Both stars exhibit increasing light amplitude at the shortest ultraviolet wavelengths. There is little evidence for cycle-to-cycle variations on a time scale of the order of 1 day.

Photonic band edge assisted spontaneous emission enhancement from all Er3+ 1-D photonic band gap structure

NASA Astrophysics Data System (ADS)

Chiasera, A.; Meroni, C.; Varas, S.; Valligatla, S.; Scotognella, F.; Boucher, Y. G.; Lukowiak, A.; Zur, L.; Righini, G. C.; Ferrari, M.

2018-06-01

All Er3+ doped dielectric 1-D Photonic Band Gap Structure was fabricated by rf-sputtering technique. The structure was constituted by of twenty pairs of SiO2/TiO2 alternated layers doped with Er3+ ions. The scanning electron microscopy was used to check the morphology of the structure. Transmission measurements put in evidence the stop band in the range 1500 nm-1950 nm. The photoluminescence measurements were obtained by optically exciting the sample and detecting the emitted light in the 1.5 μm region at different detection angles. Luminescence spectra and luminescence decay curves put in evidence that the presence of the stop band modify the emission features of the Er3+ ions.

New methods for deriving cometary secular light curves: C/1995 O1 (Hale-Bopp) revisited

NASA Astrophysics Data System (ADS)

Womack, Maria; Lastra, Nathan; Harrington, Olga; Curtis, Anthony; Wierzchos, Kacper; Ruffini, Nicholas; Charles, Mentzer; Rabson, David; Cox, Timothy; Rivera, Isabel; Micciche, Anthony

2017-10-01

We present an algorithm for reducing scatter and increasing precision in a comet light curve. As a demonstration, we processed apparent magnitudes of comet Hale-Bopp from 16 highly experienced observers (archived with the International Comet Quarterly), correcting for distance from Earth and phase angle. Different observers tend to agree on the difference in magnitudes of an object at different distances, but the magnitude reported by observer is shifted relative to that of another for an object at a fixed distance. We estimated the shifts using a self-consistent statistical approach, leading to a sharper light curve and improving the precision of the measured slopes. The final secular lightcurve for comet Hale-Bopp ranges from -7 au (pre-perihelion) to +8 au (post-perihelion) and is the best secular light curve produced to date for this “great” comet. We discuss Hale-Bopp’s lightcurve evolution and possibly related physical implications, and potential usefulness of this light curve for comparisons with other future bright comets. We also assess the appropriateness of using secular lightcurves to characterize dust production rates in Hale-Bopp and other dust-rich comets. M.W. acknowledges support from NSF grant AST-1615917.

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.

The Los Alamos Supernova Light Curve Project: Current Projects and Future Directions

NASA Astrophysics Data System (ADS)

Wiggins, Brandon Kerry; Los Alamos Supernovae Research Group

2015-01-01

The Los Alamos Supernova Light Curve Project models supernovae in the ancient and modern universe to determine the luminosities of observability of certain supernovae events and to explore the physics of supernovae in the local universe. The project utilizes RAGE, Los Alamos' radiation hydrodynamics code to evolve the explosions of progenitors prepared in well-established stellar evolution codes. RAGE allows us to capture events such as shock breakout and collisions of ejecta with shells of material which cannot be modeled well in other codes. RAGE's dumps are then ported to LANL's SPECTRUM code which uses LANL's OPLIB opacities database to calculate light curves and spectra. In this paper, we summarize our recent work in modeling supernovae.

Variable classification in the LSST era: exploring a model for quasi-periodic light curves

NASA Astrophysics Data System (ADS)

Zinn, J. C.; Kochanek, C. S.; Kozłowski, S.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Mróz, P.; Pawlak, M.

2017-06-01

The Large Synoptic Survey Telescope (LSST) is expected to yield ˜107 light curves over the course of its mission, which will require a concerted effort in automated classification. Stochastic processes provide one means of quantitatively describing variability with the potential advantage over simple light-curve statistics that the parameters may be physically meaningful. Here, we survey a large sample of periodic, quasi-periodic and stochastic Optical Gravitational Lensing Experiment-III variables using the damped random walk (DRW; CARMA(1,0)) and quasi-periodic oscillation (QPO; CARMA(2,1)) stochastic process models. The QPO model is described by an amplitude, a period and a coherence time-scale, while the DRW has only an amplitude and a time-scale. We find that the periodic and quasi-periodic stellar variables are generally better described by a QPO than a DRW, while quasars are better described by the DRW model. There are ambiguities in interpreting the QPO coherence time due to non-sinusoidal light-curve shapes, signal-to-noise ratio, error mischaracterizations and cadence. Higher order implementations of the QPO model that better capture light-curve shapes are necessary for the coherence time to have its implied physical meaning. Independent of physical meaning, the extra parameter of the QPO model successfully distinguishes most of the classes of periodic and quasi-periodic variables we consider.

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.

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.

Neutral and ionized polycyclic aromatic hydrocarbons, diffuse interstellar bands and the ultraviolet extinction curve

NASA Technical Reports Server (NTRS)

Salama, Farid; Allamandola, Louis John

1993-01-01

Neutral naphthalene C10H8, phenanthrene C14H10 and pyrene C16H10 absorb strongly in the ultraviolet region and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these polycyclic aromatic hydrocarbons (PAHs) absorb in the visible C10H8(+) has 13 discrete absorption bands which fall between 6800 and 4500 A. The strongest band at 6741 A falls close to the weak 6742 A diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8(+) is responsible for some of the DIBs can be tested by searching for new DIBs at 6520 and 6151 A, other strong naphthalene cation band positions. If C10H8(+) is indeed responsible for the 6742 A feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10(+) is dominated by a strong band at 4435 A in an Ar matrix and 4395 A in Ne, wavelengths which fall very close to the strongest DIB at 4430 A. If C16H10(+) or a closely related pyrene-like ion, is indeed responsible for the 4430 A feature, it accounts for 0.2% of the cosmic carbon. An intense, very broad UV-to-visible continuum is reported which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR radiation.

An action spectrum for UV-B radiation and the rat lens.

PubMed

Merriam, J C; Löfgren, S; Michael, R; Söderberg, P; Dillon, J; Zheng, L; Ayala, M

2000-08-01

To determine an action spectrum for UV-B radiation and the rat lens and to show the effect of the atmosphere and the cornea on the action spectrum. One eye of young female rats was exposed to 5-nm bandwidths of UV-B radiation (290, 295, 300, 305, 310, and 315 nm). Light scattering of exposed and nonexposed lenses was measured 1 week after irradiation. A quadratic polynomial was fit to the dose-response curve for each wave band. The dose at each wave band that produced a level of light scattering greater than 95% of the nonexposed lenses was defined as the maximum acceptable dose (MAD). Transmittance of the rat cornea was measured with a fiberoptic spectrophotometer. The times to be exposed to the MAD in Stockholm (59.3 degrees N) and La Palma (28 degrees N) were compared. Significant light scattering was detected after UV-B at 295, 300, 305, 310, and 315 nm. The lens was most sensitive to UV-B at 300 nm. Correcting for corneal transmittance showed that the rat lens is at least as sensitive to UV radiation at 295 nm as at 300 nm. The times to be exposed to the MAD at each wave band were greater in Stockholm than in La Palma, and in both locations the theoretical time to be exposed to the MAD was least at 305 nm. After correcting for corneal transmittance, the biological sensitivity of the rat lens to UV-B is at least as great at 295 nm as at 300 nm. After correcting for transmittance by the atmosphere, UV-B at 305 nm is the most likely wave band to injure the rat lens in both Stockholm and La Palma.

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.

Statistical evaluation of the influence of the uncertainty budget on B-spline curve approximation

NASA Astrophysics Data System (ADS)

Zhao, Xin; Alkhatib, Hamza; Kargoll, Boris; Neumann, Ingo

2017-12-01

In the field of engineering geodesy, terrestrial laser scanning (TLS) has become a popular method for detecting deformations. This paper analyzes the influence of the uncertainty budget on free-form curves modeled by B-splines. Usually, free-form estimation is based on scanning points assumed to have equal accuracies, which is not realistic. Previous findings demonstrate that the residuals still contain random and systematic uncertainties caused by instrumental, object-related and atmospheric influences. In order to guarantee the quality of derived estimates, it is essential to be aware of all uncertainties and their impact on the estimation. In this paper, a more detailed uncertainty budget is considered, in the context of the "Guide to the Expression of Uncertainty in Measurement" (GUM), which leads to a refined, heteroskedastic variance covariance matrix (VCM) of TLS measurements. Furthermore, the control points of B-spline curves approximating a measured bridge are estimated. Comparisons are made between the estimated B-spline curves using on the one hand a homoskedastic VCM and on the other hand the refined VCM. To assess the statistical significance of the differences displayed by the estimates for the two stochastic models, a nested model misspecification test and a non-nested model selection test are described and applied. The test decisions indicate that the homoskedastic VCM should be replaced by a heteroskedastic VCM in the direction of the suggested VCM. However, the tests also indicate that the considered VCM is still inadequate in light of the given data set and should therefore be improved.

Broad-band absorbers for reduction of parasitic light: two alternative solutions

NASA Astrophysics Data System (ADS)

Giovannini, Hughes; Lemarquis, F.; Akhouayri, H.; Cathelinaud, Michel; Torchio, Philippe; Amra, C.; Cousin, Bernard; Laubier, D.; Otrio, Georges

2018-04-01

This paper, "Broad-band absorbers for reduction of parasitic light: two alternative solutions," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

3.6 AND 4.5 {mu}m PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knutson, Heather A.; Lewis, Nikole; Showman, Adam P.

2012-07-20

We present new, full-orbit observations of the infrared phase variations of the canonical hot Jupiter HD 189733b obtained in the 3.6 and 4.5 {mu}m bands using the Spitzer Space Telescope. When combined with previous phase curve observations at 8.0 and 24 {mu}m, these data allow us to characterize the exoplanet's emission spectrum as a function of planetary longitude and to search for local variations in its vertical thermal profile and atmospheric composition. We utilize an improved method for removing the effects of intrapixel sensitivity variations and robustly extracting phase curve signals from these data, and we calculate our best-fit parametersmore » and uncertainties using a wavelet-based Markov Chain Monte Carlo analysis that accounts for the presence of time-correlated noise in our data. We measure a phase curve amplitude of 0.1242% {+-} 0.0061% in the 3.6 {mu}m band and 0.0982% {+-} 0.0089% in the 4.5 {mu}m band, corresponding to brightness temperature contrasts of 503 {+-} 21 K and 264 {+-} 24 K, respectively. We find that the times of minimum and maximum flux occur several hours earlier than predicted for an atmosphere in radiative equilibrium, consistent with the eastward advection of gas by an equatorial super-rotating jet. The locations of the flux minima in our new data differ from our previous observations at 8 {mu}m, and we present new evidence indicating that the flux minimum observed in the 8 {mu}m is likely caused by an overshooting effect in the 8 {mu}m array. We obtain improved estimates for HD 189733b's dayside planet-star flux ratio of 0.1466% {+-} 0.0040% in the 3.6 {mu}m band and 0.1787% {+-} 0.0038% in the 4.5 {mu}m band, corresponding to brightness temperatures of 1328 {+-} 11 K and 1192 {+-} 9 K, respectively; these are the most accurate secondary eclipse depths obtained to date for an extrasolar planet. We compare our new dayside and nightside spectra for HD 189733b to the predictions of one-dimensional radiative transfer models

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.

VizieR Online Data Catalog: BV(RI)c light curves of DD Indi (Samec+, 2016)

NASA Astrophysics Data System (ADS)

Samec, R. G.; Norris, C. L.; van Hamme, W.; Faulkner, D. R.; Hill, R. L.

2017-01-01

Our photometry was taken with the Southeastern Association for Research in Astronomy (SARA South) Telescope at Cerro Tololo InterAmerican Observatory (CTIO) in remote mode. The 24 inch F/11 Boller and Chivens reflector was used on five nights, 2013 June 21, July 30, August 01 and 29, and September 01 with the ARC Camera cooled to -110°C. Sample nightly B, V, and B-V color light curves are given for 2013 July 30, August 29, and September 01 using standard BVRcIc Johnson-Cousins filters in Figures 2(a), (b), and (c) in the paper. The precision of a single observation was excellent, 4, 7, 5, and 6mmag in Ic, Rc, V, and B, respectively. The observations included, 313 in B, and 310 in V, 301 in Rc and 261 in Ic. Exposure times varied from 40 to 60s in B, 16 to 25s in V, and 20s in R and I. Our complete set of observations is given in Table1. (1 data file).

Nonclassical-light generation in a photonic-band-gap nonlinear planar waveguide

NASA Astrophysics Data System (ADS)

Peřina, Jan, Jr.; Sibilia, Concita; Tricca, Daniela; Bertolotti, Mario

2004-10-01

The optical parametric process occurring in a photonic-band-gap planar waveguide is studied from the point of view of nonclassical-light generation. The nonlinearly interacting optical fields are described by the generalized superposition of coherent signals and noise using the method of operator linear corrections to a classical strong solution. Scattered backward-propagating fields are taken into account. Squeezed light as well as light with sub-Poissonian statistics can be obtained in two-mode fields under the specified conditions.

Human Adolescent Phase Response Curves to Bright White Light.

PubMed

Crowley, Stephanie J; Eastman, Charmane I

2017-08-01

Older adolescents are particularly vulnerable to circadian misalignment and sleep restriction, primarily due to early school start times. Light can shift the circadian system and could help attenuate circadian misalignment; however, a phase response curve (PRC) to determine the optimal time for receiving light and avoiding light is not available for adolescents. We constructed light PRCs for late pubertal to postpubertal adolescents aged 14 to 17 years. Participants completed 2 counterbalanced 5-day laboratory sessions after 8 or 9 days of scheduled sleep at home. Each session included phase assessments to measure the dim light melatonin onset (DLMO) before and after 3 days of free-running through an ultradian light-dark (wake-sleep) cycle (2 h dim [~20 lux] light, 2 h dark). In one session, intermittent bright white light (~5000 lux; four 20-min exposures) was alternated with 10 min of dim room light once per day for 3 consecutive days. The time of light varied among participants to cover the 24-h day. For each individual, the phase shift to bright light was corrected for the free-run derived from the other laboratory session with no bright light. One PRC showed phase shifts in response to light start time relative to the DLMO and another relative to home sleep. Phase delay shifts occurred around the hours corresponding to home bedtime. Phase advances occurred during the hours surrounding wake time and later in the afternoon. The transition from delays to advances occurred at the midpoint of home sleep. The adolescent PRCs presented here provide a valuable tool to time bright light in adolescents.

K2 and Herschel/PACS light curve of the Centaur 2060 Chiron

NASA Astrophysics Data System (ADS)

Marton, G.; Kiss, C.; Müller, T. G.; Lellouch, E.; Pál, A.; Molnár, L.

2017-09-01

Recently 2060 Chiron was identified to harbor a ring system (Ortiz et al. 2015) similar to the other Centaur 10199 Chariklo (Braga-Ribas et al. 2014). We observed 2060 Chiron in the visible range in Campaign 12 of the Kepler/K2 mission, that lasted from Dec 15 2016 to March 4 2017. We obtained the thermal light curve with the PACS photometer camera of the Herschel Space Observatory as a "Must Do Observation", taken at 70 and 160 μm on 25 December, 2012. The presence of the ring affects the rotational light curve both in the visible range and in the thermal infrared. With our new observations we can disentangle the contribution of the main body and the ring material.

Robust indirect band gap and anisotropy of optical absorption in B-doped phosphorene.

PubMed

Wu, Zhi-Feng; Gao, Peng-Fei; Guo, Lei; Kang, Jun; Fang, Dang-Qi; Zhang, Yang; Xia, Ming-Gang; Zhang, Sheng-Li; Wen, Yu-Hua

2017-12-06

A traditional doping technique plays an important role in the band structure engineering of two-dimensional nanostructures. Since electron interaction is changed by doping, the optical and electrochemical properties could also be significantly tuned. In this study, density functional theory calculations have been employed to explore the structural stability, and electronic and optical properties of B-doped phosphorene. The results show that all B-doped phosphorenes are stable with a relatively low binding energy. Of particular interest is that these B-doped systems exhibit an indirect band gap, which is distinct from the direct one of pure phosphorene. Despite the different concentrations and configurations of B dopants, such indirect band gaps are robust. The screened hybrid density functional HSE06 predicts that the band gap of B-doped phosphorene is slightly smaller than that of pure phosphorene. Spatial charge distributions at the valence band maximum (VBM) and the conduction band minimum (CBM) are analyzed to understand the features of an indirect band gap. By comparison with pure phosphorene, B-doped phosphorenes exhibit strong anisotropy and intensity of optical absorption. Moreover, B dopants could enhance the stability of Li adsorption on phosphorene with less sacrifice of the Li diffusion rate. Our results suggest that B-doping is an effective way of tuning the band gap, enhancing the intensity of optical absorption and improving the performances of Li adsorption, which could promote potential applications in novel optical devices and lithium-ion batteries.

Uninterrupted optical light curves of main-belt asteroids from the K2 mission

NASA Astrophysics Data System (ADS)

Szabó, R.; Pál, A.; Sárneczky, K.; Szabó, Gy. M.; Molnár, L.; Kiss, L. L.; Hanyecz, O.; Plachy, E.; Kiss, Cs.

2016-11-01

Context. Because the second reaction wheel failed, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 mission, the telescope is staring at the plane of the Ecliptic. Thousands of solar system bodies therefore cross the K2 fields and usually cause additional noise in the highly accurate photometric data. Aims: We here follow the principle that some person's noise is another person's signal and investigate the possibility of deriving continuous asteroid light curves. This is the first such endeavor. In general, we are interested in the photometric precision that the K2 mission can deliver on moving solar system bodies. In particular, we investigate space photometric optical light curves of main-belt asteroids. Methods: We studied the K2 superstamps that cover the fields of M35, and Neptune together with Nereid, which were observed in the long-cadence mode (29.4 min sampling). Asteroid light curves were generated by applying elongated apertures. We used the Lomb-Scargle method to determine periodicities that are due to rotation. Results: We derived K2 light curves of 924 main-belt asteroids in the M35 field and 96 in the path of Neptune and Nereid. The light curves are quasi-continuous and several days long. K2 observations are sensitive to longer rotational periods than typical ground-based surveys. Rotational periods are derived for 26 main-belt asteroids for the first time. The asteroid sample is dominated by faint objects (>20 mag). Owing to the faintness of the asteroids and the high density of stars in the M35 field, only 4.0% of the asteroids with at least 12 data points show clear periodicities or trends that signal a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach 60% to successfully recover rotational periods. Full Tables 1-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130

Multi-band transit observations of the TrES-2b exoplanet

NASA Astrophysics Data System (ADS)

Mislis, D.; Schröter, S.; Schmitt, J. H. M. M.; Cordes, O.; Reif, K.

2010-02-01

We present a new data set of transit observations of the TrES-2b exoplanet taken in spring 2009, using the 1.2 m Oskar-Lühning telescope (OLT) of Hamburg Observatory and the 2.2 m telescope at Calar Alto Observatory using BUSCA (Bonn University Simultaneous CAmera). Both the new OLT data, taken with the same instrumental setup as our data taken in 2008, as well as the simultaneously recorded multicolor BUSCA data confirm the low inclination values reported previously, and in fact suggest that the TrES-2b exoplanet has already passed the first inclination threshold (imin,1 = 83.417°) and is not eclipsing the full stellar surface any longer. Using the multi-band BUSCA data we demonstrate that the multicolor light curves can be consistently fitted with a given set of limb darkening coefficients without the need to adjust these coefficients, and further, we can demonstrate that wavelength dependent stellar radius changes must be small as expected from theory. Our new observations provide further evidence for a change of the orbit inclination of the transiting extrasolar planet TrES-2b reported previously. We examine in detail possible causes for this inclination change and argue that the observed change should be interpreted as nodal regression. While the assumption of an oblate host star requires an unreasonably large second harmonic coefficient, the existence of a third body in the form of an additional planet would provide a very natural explanation for the observed secular orbit change. Given the lack of clearly observed short-term variations of transit timing and our observed secular nodal regression rate, we predict a period between approximately 50 and 100 days for a putative perturbing planet of Jovian mass. Such an object should be detectable with present-day radial velocity (RV) techniques, but would escape detection through transit timing variations. Photometric transit data are only available in electronic form at the CDS via anonymous ftp to cdsarc

Study on Variability and Spectral Properties of Blazar 3C 273 with Long-term Multi-band Optical Monitoring from 2006 to 2015

NASA Astrophysics Data System (ADS)

Zeng, Wei; Zhao, Qing-Jiang; Dai, Ben-Zhong; Jiang, Ze-Jun; Geng, Xiong-Fei; Yang, Shen-Bang; Liu, Zhen; Wang, Dong-Dong; Feng, Zhang-Jing; Zhang, Li

2018-02-01

We present long-term optical multi-band photometric monitoring of blazar 3C 273, from 2006 May 19 to 2015 March 31 with high temporal resolution in the BVRI bands. The source is in a steady state and showed very small variability, with the values of the fractional variability amplitude of {F}{var}=0.457+/- 0.014 % , 0.391+/- 0.012 % , 0.264+/- 0.043 % and 0.460+/- 0.014 % in B, V, R and I, respectively. The intra-night point-to-point fractional variability (F pp ) in each band is below 1.0%, and the F pp variation amplitude increase from the B-band to the I-band. We find a variability with the timescale of 5.8 ± 2.9 minutes in the I-band on 2009 March 11. This fast variability requires the comoving magnetic field strength in the jet above 18 G with a Doppler factor {δ }D∼ 10. Using the discrete correlation function (DCF), the B- and I-band light curves are examined for correlation on whole campaign. Low significance (∼99.73 percent confidence) correlations with the I-band lags the B-band variations are observed. The spectral behaviors in the different variability episodes are studied. “Bluer-when-brighter” spectral behavior is presented for the whole campaign, while there is an opposite tendency when {{{F}}}V> 30.2 {mJy}. The weak of the correlation between B- and I-band and the spectrum analysis indicate that the optical radiation consists of two variable components.

Light-curve and spectral properties of ultra-stripped core-collapse supernovae

NASA Astrophysics Data System (ADS)

Moriya, Takashi J.

2017-11-01

We discuss light-curve and spectral properties of ultra-stripped core-collapse supernovae. Ultra-stripped supernovae are supernovae with ejecta masses of only ~0.1M ⊙ whose progenitors lose their envelopes due to binary interactions with their compact companion stars. We follow the evolution of an ultra-stripped supernova progenitor until core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultra-stripped supernovae based on the nucleosynthesis results. We show that ultra-stripped supernovae synthesize ~0.01M ⊙ of the radioactive 56Ni, and their typical peak luminosity is around 1042 erg s-1 or -16 mag. Their typical rise time is 5 - 10 days. By comparing synthesized and observed spectra, we find that SN 2005ek and some of so-called calcium-rich gap transients like PTF10iuv may be related to ultra-stripped supernovae.

Day-Scale Variability of 3C 279 and Searches for Correlations in Gamma-Ray, X-Ray and Optical Bands

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Villata, M.; Balonek, T. J.; Bertsch, D. L.; Bock, H.; Boettcher, M.; Carini, M. T.; Collmar, W.; DeFrancesco, G.; Ferrera, E. C.;

1998 UBV Light Curves of Eclipsing Binary AI Draconis and Absolute Parameters

NASA Astrophysics Data System (ADS)

Jassur, D. M. Z.; Khaledian, M. S.; Kermani, M. H.

New UBV photometry of Algol-Type eclipsing binary star AI Dra and the absolute physical parameters of this system have been presented. The light curve analysis carried out by the method of differential corrections indicates that both components are inside their Roche-Lobes. From combining the photometric solution with spectroscopic data obtained from velocity curve analysis, it has been found that the system consist of a main sequence primary and an evolved (subgiant) secondary.

High-precision multiwavelength eclipse photometry of the ultra-hot gas giant exoplanet WASP-103 b

NASA Astrophysics Data System (ADS)

Delrez, L.; Madhusudhan, N.; Lendl, M.; Gillon, M.; Anderson, D. R.; Neveu-VanMalle, M.; Bouchy, F.; Burdanov, A.; Collier-Cameron, A.; Demory, B.-O.; Hellier, C.; Jehin, E.; Magain, P.; Maxted, P. F. L.; Queloz, D.; Smalley, B.; Triaud, A. H. M. J.

2018-02-01

We present 16 occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103b, in addition to five new radial velocity measurements. We combine these observations with archival data and perform a global analysis of the resulting extensive data set, accounting for the contamination from a nearby star. We detect the thermal emission of the planet in both the z΄ and KS bands, the measured occultation depths being 699±110 ppm (6.4σ) and 3567_{-350}^{+400} ppm (10.2σ), respectively. We use these two measurements, together with recently published HST/WFC3 data, to derive joint constraints on the properties of WASP-103b's dayside atmosphere. On one hand, we find that the z΄ band and WFC3 data are best fit by an isothermal atmosphere at 2900 K or an atmosphere with a low H2O abundance. On the other hand, we find an unexpected excess in the KS band measured flux compared to these models, which requires confirmation with additional observations before any interpretation can be given. From our global data analysis, we also derive a broad-band optical transmission spectrum that shows a minimum around 700 nm and increasing values towards both shorter and longer wavelengths. This is in agreement with a previous study based on a large fraction of the archival transit light curves used in our analysis. The unusual profile of this transmission spectrum is poorly matched by theoretical spectra and is not confirmed by more recent observations at higher spectral resolution. Additional data, in both emission and transmission, are required to better constrain the atmospheric properties of WASP-103b.

Mysterious eclipses in the light curve of KIC8462852: a possible explanation

NASA Astrophysics Data System (ADS)

Neslušan, L.; Budaj, J.

2017-04-01

Context. Apart from thousands of "regular" exoplanet candidates, Kepler satellite has discovered a small number of stars exhibiting peculiar eclipse-like events. They are most probably caused by disintegrating bodies transiting in front of the star. However, the nature of the bodies and obscuration events, such as those observed in KIC 8462852, remain mysterious. A swarm of comets or artificial alien mega-structures have been proposed as an explanation for the latter object. Aims: We explore the possibility that such eclipses are caused by the dust clouds associated with massive parent bodies orbiting the host star. Methods: We assumed a massive object and a simple model of the dust cloud surrounding the object. Then, we used the numerical integration to simulate the evolution of the cloud, its parent body, and resulting light-curves as they orbit and transit the star. Results: We found that it is possible to reproduce the basic features in the light-curve of KIC 8462852 with only four objects enshrouded in dust clouds. The fact that they are all on similar orbits and that such models require only a handful of free parameters provides additional support for this hypothesis. Conclusions: This model provides an alternative to the comet scenario. With such physical models at hand, at present, there is no need to invoke alien mega-structures for an explanation of these light-curves.

Investigation of Structure in the Light Curves of a Sample of Newly Discovered Long Period Variable Stars

NASA Astrophysics Data System (ADS)

Craine, E. R.; Culver, R. B.; Eykholt, R.; Flurchick, K. M.; Kraus, A. L.; Tucker, R. A.; Walker, D. K.

2015-09-01

Long period variable stars exhibit hump structures, and possibly flares, in their light curves. While the existence of humps is not controversial, the presence of flaring activity is less clear. Mining of a sky survey database of new variable star discoveries (the first MOTESS-GNAT Variable Star Catalog (MG1-VSC)) has led to identification of 47 such stars for which there are sufficient data to explore the presence of anomalous light curve features. We find a number of hump structures, and see one possible flare, suggesting that they are rare events. We present light curves and measured parameters for these stars, and a population statistical analysis.

The Prompt-afterglow Connection in Gamma-ray Bursts: a Comprehensive Statistical Analysis of Swift X-ray Light-curves

NASA Technical Reports Server (NTRS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, Lorella; Burrows, D. N.; Capalbi, M.; Evans, P. A.;

The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift X-ray light curves

NASA Astrophysics Data System (ADS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, L.; Burrows, D. N.; Capalbi, M.; Evans, P. A.; Gehrels, N.; Kennea, J.; Mangano, V.; Moretti, A.; Nousek, J.; Osborne, J. P.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Sbarufatti, B.; Stafford, S.; Stamatikos, M.

2013-01-01

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30 keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of `memory' of the prompt γ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt γ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the γ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX, iso∝E1.00 ± 0.06γ, iso/E0.60 ± 0.10pk.

The effect of lunarlike satellites on the orbital infrared light curves of Earth-analog planets.

PubMed

Moskovitz, Nicholas A; Gaidos, Eric; Williams, Darren M

2009-04-01

We have investigated the influence of lunarlike satellites on the infrared orbital light curves of Earth-analog extrasolar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet and determine its orbit. We used an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites are assumed to lack an atmosphere, have a low thermal inertia like that of the Moon, and span a range of plausible radii. The planets are assumed to have thermal and orbital properties that mimic those of Earth, while their obliquities and orbital longitudes of inferior conjunction remain free parameters. Even if the gross thermal properties of the planet can be independently constrained (e.g., via spectroscopy or visible-wavelength detection of specular glint from a surface ocean), only the largest (approximately Mars-sized) lunarlike satellites can be detected by light curve data from a TPF-like instrument (i.e., one that achieves a photometric signal-to-noise ratio of 10 to 20 at infrared wavelengths). Nondetection of a lunarlike satellite can obfuscate the interpretation of a given system's infrared light curve so that it may resemble a single planet with high obliquity, different orbital longitude of vernal equinox relative to inferior conjunction, and in some cases drastically different thermal characteristics. If the thermal properties of the planet are not independently established, then the presence of a lunarlike satellite cannot be inferred from infrared data, which would thus demonstrate that photometric light curves alone can only be used for preliminary study, and the addition of spectroscopic data will be necessary.

Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

NASA Astrophysics Data System (ADS)

Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

2016-08-01

We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min-1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

Neurofilament light chain and oligoclonal bands are prognostic biomarkers in radiologically isolated syndrome.

PubMed

Matute-Blanch, Clara; Villar, Luisa M; Álvarez-Cermeño, José C; Rejdak, Konrad; Evdoshenko, Evgeniy; Makshakov, Gleb; Nazarov, Vladimir; Lapin, Sergey; Midaglia, Luciana; Vidal-Jordana, Angela; Drulovic, Jelena; García-Merino, Antonio; Sánchez-López, Antonio J; Havrdova, Eva; Saiz, Albert; Llufriu, Sara; Alvarez-Lafuente, Roberto; Schroeder, Ina; Zettl, Uwe K; Galimberti, Daniela; Ramió-Torrentà, Lluís; Robles, René; Quintana, Ester; Hegen, Harald; Deisenhammer, Florian; Río, Jordi; Tintoré, Mar; Sánchez, Alex; Montalban, Xavier; Comabella, Manuel

2018-04-01

The prognostic role of cerebrospinal fluid molecular biomarkers determined in early pathogenic stages of multiple sclerosis has yet to be defined. In the present study, we aimed to investigate the prognostic value of chitinase 3 like 1 (CHI3L1), neurofilament light chain, and oligoclonal bands for conversion to clinically isolated syndrome and to multiple sclerosis in 75 patients with radiologically isolated syndrome. Cerebrospinal fluid levels of CHI3L1 and neurofilament light chain were measured by enzyme-linked immunosorbent assay. Uni- and multivariable Cox regression models including as covariates age at diagnosis of radiologically isolated syndrome, number of brain lesions, sex and treatment were used to investigate associations between cerebrospinal fluid CHI3L1 and neurofilament light chain levels and time to conversion to clinically isolated syndrome and multiple sclerosis. Neurofilament light chain levels and oligoclonal bands were independent risk factors for the development of clinically isolated syndrome (hazard ratio = 1.02, P = 0.019, and hazard ratio = 14.7, P = 0.012, respectively) and multiple sclerosis (hazard ratio = 1.03, P = 0.003, and hazard ratio = 8.9, P = 0.046, respectively). The best cut-off to classify cerebrospinal fluid neurofilament light chain levels into high and low was 619 ng/l, and high neurofilament light chain levels were associated with a trend to shorter time to clinically isolated syndrome (P = 0.079) and significant shorter time to multiple sclerosis (P = 0.017). Similarly, patients with radiologically isolated syndrome presenting positive oligoclonal bands converted faster to clinically isolated syndrome and multiple sclerosis (P = 0.005 and P = 0.008, respectively). The effects of high neurofilament light chain levels shortening time to clinically isolated syndrome and multiple sclerosis were more pronounced in radiologically isolated syndrome patients with ≥37 years compared to younger patients. Cerebrospinal fluid

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…

Cross-linked g-C3 N4 /rGO nanocomposites with tunable band structure and enhanced visible light photocatalytic activity.

PubMed

Li, Yibing; Zhang, Haimin; Liu, Porun; Wang, Dan; Li, Ying; Zhao, Huijun

2013-10-11

Cross-linked rather than non-covalently bonded graphitic carbon nitride (g-C3 N4 )/reduced graphene oxide (rGO) nanocomposites with tunable band structures have been successfully fabricated by thermal treatment of a mixture of cyanamide and graphene oxide with different weight ratios. The experimental results indicate that compared to pure g-C3 N4 , the fabricated CN/rGO nanocomposites show narrowed bandgaps with an increased in the rGO ratio. Furthermore, the band structure of the CN/rGO nanocomposites can be readily tuned by simply controlling the weight ratio of the rGO. It is found that an appropriate rGO ratio in nanocomposite leads to a noticeable positively shifted valence band edge potential, meaning an increased oxidation power. The tunable band structure of the CN/rGO nanocomposites can be ascribed to the formation of C-O-C covalent bonding between the rGO and g-C3 N4 layers, which is experimentally confirmed by Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) data. The resulting nanocomposites are evaluated as photocatalysts by photocatalytic degradation of rhodamine B (RhB) and 4-nitrophenol under visible light irradiation (λ > 400 nm). The results demonstrate that the photocatalytic activities of the CN/rGO nanocomposites are strongly influenced by rGO ratio. With a rGO ratio of 2.5%, the CN/rGO-2.5% nanocomposite exhibits the highest photocatalytic efficiency, which is almost 3.0 and 2.7 times that of pure g-C3 N4 toward photocatalytic degradation of RhB and 4-nitrophenol, respectively. This improved photocatalytic activity could be attributed to the improved visible light utilization, oxidation power, and electron transport property, due to the significantly narrowed bandgap, positively shifted valence band-edge potential, and enhanced electronic conductivity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chlorophyll b degradation by chlorophyll b reductase under high-light conditions.

PubMed

Sato, Rei; Ito, Hisashi; Tanaka, Ayumi

2015-12-01

The light-harvesting chlorophyll a/b binding protein complex of photosystem II (LHCII) is the main antenna complex of photosystem II (PSII). Plants change their LHCII content depending on the light environment. Under high-light conditions, the content of LHCII should decrease because over-excitation damages the photosystem. Chlorophyll b is indispensable for accumulating LHCII, and chlorophyll b degradation induces LHCII degradation. Chlorophyll b degradation is initiated by chlorophyll b reductase (CBR). In land plants, NON-YELLOW COLORING 1 (NYC1) and NYC1-Like (NOL) are isozymes of CBR. We analyzed these mutants to determine their functions under high-light conditions. During high-light treatment, the chlorophyll a/b ratio was stable in the wild-type (WT) and nol plants, and the LHCII content decreased in WT plants. The chlorophyll a/b ratio decreased in the nyc1 and nyc1/nol plants, and a substantial degree of LHCII was retained in nyc1/nol plants after the high-light treatment. These results demonstrate that NYC1 degrades the chlorophyll b on LHCII under high-light conditions, thus decreasing the LHCII content. After the high-light treatment, the maximum quantum efficiency of the PSII photochemistry was lower in nyc1 and nyc1/nol plants than in WT and nol plants. A larger light-harvesting system would damage PSII in nyc1 and nyc1/nol plants. The fluorescence spectroscopy of the leaves indicated that photosystem I was also damaged by the excess LHCII in nyc1/nol plants. These observations suggest that chlorophyll b degradation by NYC1 is the initial reaction for the optimization of the light-harvesting capacity under high-light conditions.

Squeezed light at 1550 nm with a quantum noise reduction of 12.3 dB.

PubMed

Mehmet, Moritz; Ast, Stefan; Eberle, Tobias; Steinlechner, Sebastian; Vahlbruch, Henning; Schnabel, Roman

2011-12-05

Continuous-wave squeezed states of light at the wavelength of 1550 nm have recently been demonstrated, but so far the obtained factors of noise suppression still lag behind today's best squeezing values demonstrated at 1064 nm. Here we report on the realization of a half-monolithic nonlinear resonator based on periodically-poled potassium titanyl phosphate which enabled the direct detection of up to 12.3 dB of squeezing at 5 MHz. Squeezing was observed down to a frequency of 2 kHz which is well within the detection band of gravitational wave interferometers. Our results suggest that a long-term stable 1550 nm squeezed light source can be realized with strong squeezing covering the entire detection band of a 3rd generation gravitational-wave detector such as the Einstein Telescope.

B(M1) values in the band-crossing of shears bands in 197Pb

NASA Astrophysics Data System (ADS)

Krücken, R.; Cooper, J. R.; Beausang, C. W.; Novak, J. R.; Dewald, A.; Klug, T.; Kemper, G.; von Brentano, P.; Carpenter, M.; Wiedenhöver, I.

We present details of the band crossing mechanism of shears bands using the example of 197Pb. Absolute reduced matrix elements B(M1) were determined by means of a RDM lifetime measurement in one of the shears bands in 197Pb. The experiment was performed using the New Yale Plunger Device (NYPD) in conjunction with the Gammasphere array. Band mixing calculations on the basis of the semi-classical model of the shears mechanism are used to describe the transition matrix elements B(M1) and energies throughout the band-crossing regions. Good agreement with the data was obtained and the detailed composition of the states in the shears band are discussed.

Reliable inference of light curve parameters in the presence of systematics

NASA Astrophysics Data System (ADS)

Gibson, Neale P.

2016-10-01

Time-series photometry and spectroscopy of transiting exoplanets allow us to study their atmospheres. Unfortunately, the required precision to extract atmospheric information surpasses the design specifications of most general purpose instrumentation. This results in instrumental systematics in the light curves that are typically larger than the target precision. Systematics must therefore be modelled, leaving the inference of light-curve parameters conditioned on the subjective choice of systematics models and model-selection criteria. Here, I briefly review the use of systematics models commonly used for transmission and emission spectroscopy, including model selection, marginalisation over models, and stochastic processes. These form a hierarchy of models with increasing degree of objectivity. I argue that marginalisation over many systematics models is a minimal requirement for robust inference. Stochastic models provide even more flexibility and objectivity, and therefore produce the most reliable results. However, no systematics models are perfect, and the best strategy is to compare multiple methods and repeat observations where possible.

The EB factory project. I. A fast, neural-net-based, general purpose light curve classifier optimized for eclipsing binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 withmore » 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.« less

Light polarization management via reflection from arrays of sub-wavelength metallic twisted bands

NASA Astrophysics Data System (ADS)

Nawrot, M.; Haberko, J.; Zinkiewicz, Ł.; Wasylczyk, P.

2017-12-01

With constant progress of nano- and microfabrication technologies, photolithography in particular, a number of sub-wavelength metallic structures have been demonstrated that can be used to manipulate light polarization. Numerical simulations of light propagation hint that helical twisted bands can have interesting polarization properties. We use three-dimensional two-photon photolithography (direct laser writing) to fabricate a few-micrometer-thick arrays of twisted bands and coat them uniformly with metal. We demonstrate that circular polarization can be generated from linear polarization upon reflection from such structures over a broad range of frequencies in the mid infrared.

A new supernova light curve modeling program

NASA Astrophysics Data System (ADS)

Jäger, Zoltán; Nagy, Andrea P.; Biro, Barna I.; Vinkó, József

2017-12-01

Supernovae are extremely energetic explosions that highlight the violent deaths of various types of stars. Studying such cosmic explosions may be important because of several reasons. Supernovae play a key role in cosmic nucleosynthesis processes, and they are also the anchors of methods of measuring extragalactic distances. Several exotic physical processes take place in the expanding ejecta produced by the explosion. We have developed a fast and simple semi-analytical code to model the the light curve of core collapse supernovae. This allows the determination of their most important basic physical parameters, like the the radius of the progenitor star, the mass of the ejected envelope, the mass of the radioactive nickel synthesized during the explosion, among others.

The effects of low-intensity narrow-band blue-light treatment compared to bright white-light treatment in sub-syndromal seasonal affective disorder.

PubMed

Meesters, Ybe; Winthorst, Wim H; Duijzer, Wianne B; Hommes, Vanja

2016-02-18

The discovery of a novel photoreceptor in the retinal ganglion cells with a highest sensitivity of 470-490 nm blue light has led to research on the effects of short-wavelength light in humans. Several studies have explored the efficacy of monochromatic blue or blue-enriched light in the treatment of SAD. In this study, a comparison has been made between the effects of broad-wavelength light without ultraviolet (UV) wavelengths compared to narrow-band blue light in the treatment of sub-syndromal seasonal affective disorder (Sub-SAD). In a 15-day design, 48 participants suffering from Sub-SAD completed 20-minute sessions of light treatment on five consecutive days. 22 participants were given bright white-light treatment (BLT, broad-wavelength light without UV 10 000 lux, irradiance 31.7 Watt/m(2)) and 26 participants received narrow-band blue light (BLUE, 100 lux, irradiance 1.0 Watt/m(2)). All participants completed daily and weekly questionnaires concerning mood, activation, sleep quality, sleepiness and energy. Also, mood and energy levels were assessed by means of the SIGH-SAD, the primary outcome measure. On day 15, SIGH-SAD ratings were significantly lower than on day 1 (BLT 54.8 %, effect size 1.7 and BLUE 50.7 %, effect size 1.9). No statistically significant differences were found on the main outcome measures. Light treatment is an effective treatment for Sub-SAD. The use of narrow-band blue-light treatment is equally effective as bright white-light treatment. This study was registered in the Dutch Trial Register (Nederlands Trial Register TC =  4342 ) (20-12-2013).

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocevski, Daniel; Petrosian, Vahe

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 decreasingmore » 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.« less

VizieR Online Data Catalog: BV(RI)c light curves of NSVS 5066754 (Samec+, 2016)

NASA Astrophysics Data System (ADS)

Samec, R. G.; Nyaude, R.; Caton, D. B.; Faulkner, D. R.

2017-01-01

Our BVRcIc light curves were taken with the Dark 0.81m reflector at Philips Gap, North Carolina, on 17-20 inclusive, 2014 May with a thermoelectrically cooled (-40°C) 2K*2K Apogee Alta U44 CCD using standard Johnson-Cousins BVRcIc filters (320 observations with an exposure time of 60s in B, 333 observations with an exposure time of 24s in V, 338 observations with an exposure time of 20s in Rc, and 258 observations with an exposure time of 20s in Ic). Our complete set of observations is given in Table2. (1 data file).

SN 2009ip: CONSTRAINING THE LATEST EXPLOSION PROPERTIES BY ITS LATE-PHASE LIGHT CURVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moriya, Takashi J., E-mail: moriyatk@astro.uni-bonn.de

We constrain the explosion and circumstellar properties at the 2012b event of SN 2009ip based on its recently reported late-phase bolometric light curve. The explosion energy and ejected mass at the 2012b event are estimated as 0.01 M{sub ⊙} and 2 × 10{sup 49} erg, respectively. The circumstellar medium is assumed to have two components: an inner shell and an outer wind. The inner shell, which is likely created at the 2012a event, has a mass of 0.2 M{sub ⊙}. The outer wind is created by the wind mass loss before the 2012a mass ejection, and the progenitor is estimatedmore » to have had a mass-loss rate of about 0.1 M{sub ⊙} yr{sup −1} with a wind velocity of 550 km s{sup −1} before the 2012a event. The estimated explosion energy and ejected mass indicate that the 2012b event is not caused by a regular SN.« less

On Correlated-noise Analyses Applied to Exoplanet Light Curves

NASA Astrophysics Data System (ADS)

Cubillos, Patricio; Harrington, Joseph; Loredo, Thomas J.; Lust, Nate B.; Blecic, Jasmina; Stemm, Madison

2017-01-01

Time-correlated noise is a significant source of uncertainty when modeling exoplanet light-curve data. A correct assessment of correlated noise is fundamental to determine the true statistical significance of our findings. Here, we review three of the most widely used correlated-noise estimators in the exoplanet field, the time-averaging, residual-permutation, and wavelet-likelihood methods. We argue that the residual-permutation method is unsound in estimating the uncertainty of parameter estimates. We thus recommend to refrain from this method altogether. We characterize the behavior of the time averaging’s rms-versus-bin-size curves at bin sizes similar to the total observation duration, which may lead to underestimated uncertainties. For the wavelet-likelihood method, we note errors in the published equations and provide a list of corrections. We further assess the performance of these techniques by injecting and retrieving eclipse signals into synthetic and real Spitzer light curves, analyzing the results in terms of the relative-accuracy and coverage-fraction statistics. Both the time-averaging and wavelet-likelihood methods significantly improve the estimate of the eclipse depth over a white-noise analysis (a Markov-chain Monte Carlo exploration assuming uncorrelated noise). However, the corrections are not perfect when retrieving the eclipse depth from Spitzer data sets, these methods covered the true (injected) depth within the 68% credible region in only ˜45%-65% of the trials. Lastly, we present our open-source model-fitting tool, Multi-Core Markov-Chain Monte Carlo (MC3). This package uses Bayesian statistics to estimate the best-fitting values and the credible regions for the parameters for a (user-provided) model. MC3 is a Python/C code, available at https://github.com/pcubillos/MCcubed.

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.

The cataclysmic variable AE Aquarii: orbital variability in V band

NASA Astrophysics Data System (ADS)

Zamanov, R.; Latev, G.

2017-07-01

We present 62.7 hours observations of the cataclysmic variable AE Aqr in Johnson V band. These are non-published archive electro-photometric data obtained during the time period 1993 to 1999. We construct the orbital variability in V band and obtain a Fourier fit to the double-wave quiescent light curve. The strongest flares in our data set are in phase interval 0.6 - 0.8. The data can be downloaded from http://www.astro.bas.bg/~rz/DATA/AEAqr.elphot.dat.

Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample

NASA Astrophysics Data System (ADS)

Sesar, Branimir; Hernitschek, Nina; Mitrović, Sandra; Ivezić, Željko; Rix, Hans-Walter; Cohen, Judith G.; Bernard, Edouard J.; Grebel, Eva K.; Martin, Nicolas F.; Schlafly, Edward F.; Burgett, William S.; Draper, Peter W.; Flewelling, Heather; Kaiser, Nick; Kudritzki, Rolf P.; Magnier, Eugene A.; Metcalfe, Nigel; Tonry, John L.; Waters, Christopher

2017-05-01

RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) 3π survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves (≲ 12 epochs in each of five bands, taken over a 4.5 year period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2 s in > 80 % of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date. The PS1 sample of ˜45,000 RRab stars is pure (90%) and complete (80% at 80 kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period-luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.

Multiple color light curves and period changes investigation of the contact binary HV Aqr

NASA Astrophysics Data System (ADS)

Li, K.; Qian, S.-B.

2013-07-01

New V, R and I light curves of the short period binary system, HV Aqr, are presented. Photometric solutions were derived using the Wilson-Devinney code. Our new determined light curves do not show O'Connell effect. The nearly symmetry and complete eclipses of the light curves of HV Aqr enable us to determine high-precision photometric parameters of the binary system. The new solutions suggest that HV Aqr is a low mass ratio (q=0.1455) deep contact binary with a contact degree of f=55.9%. Based on all available times of light minimum, we analyzed the long-term period changes of HV Aqr. A secular decrease rate of dP/dt=8.84(±0.18)×10-8 days yr-1 was determined. The continuous period decrease can be explained by the mass transfer from the primary component to the secondary and angular momentum loss via magnetic stellar wind. A conservative mass transfer rate of dM1/dt=1.81×10-8M⊙ yr-1 and angular momentum loss rate at dJ/dt=5.96×1045 g cm2 s-1 yr-1 were derived. As the orbital period decreases, the contact degree of HV Aqr will become deeper and finally it will evolve into a single rapid-rotation star.

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.

Light Curves of the Type II-P Supernova SN 2017eaw: The First 200 Days

NASA Astrophysics Data System (ADS)

Tsvetkov, D. Yu.; Shugarov, S. Yu.; Volkov, I. M.; Pavlyuk, N. N.; Vozyakova, O. V.; Shatsky, N. I.; Nikiforova, A. A.; Troitsky, I. S.; Troitskaya, Yu. V.; Baklanov, P. V.

2018-05-01

We present the results of our UBVRI photometry for the type II-P supernova SN 2017eaw in NGC6946 obtained fromMay 14 to December 7, 2017, at several telescopes, including the 2.5-m telescope at the CaucasusHigh-Altitude Observatory of the SAIMSU. The dates andmagnitudes atmaximumlight and the light-curve parameters have been determined. The color evolution, extinction, and peak luminosity of SN 2017eaw are discussed. The results of our preliminary radiation-gasdynamic simulations of its light curves with the STELLA code describe satisfactorily the UBVRI observational data.

Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B

NASA Technical Reports Server (NTRS)

Zhou, Yifan; Apai, Daniel; Metchev, Stanimir; Lew, Ben W. P.; Schneider, Glenn; Marley, Mark S.; Karalidi, Theodora; Manjavacas, Elena; Bedin, Luigi R.; Cowan, Nicolas B.;

The Astrophysics of Visible-light Orbital Phase Curves in the Space Age

NASA Astrophysics Data System (ADS)

Shporer, Avi

2017-07-01

The field of visible-light continuous time series photometry is now at its golden age, manifested by the continuum of past (CoRoT, Kepler), present (K2), and future (TESS, PLATO) space-based surveys delivering high precision data with a long baseline for a large number of stars. The availability of the high-quality data has enabled astrophysical studies not possible before, including, for example, detailed asteroseismic investigations and the study of the exoplanet census including small planets. This has also allowed to study the minute photometric variability following the orbital motion in stellar binaries and star-planet systems which is the subject of this review. We focus on systems with a main sequence primary and a low-mass secondary, from a small star to a massive planet. The orbital modulations are induced by a combination of gravitational and atmospheric processes, including the beaming effect, tidal ellipsoidal distortion, reflected light, and thermal emission. Therefore, the phase curve shape contains information about the companion’s mass and atmospheric characteristics, making phase curves a useful astrophysical tool. For example, phase curves can be used to detect and measure the mass of short-period low-mass companions orbiting hot fast-rotating stars out of reach of other detection methods. Another interesting application of phase curves is using the orbital phase modulations to look for non-transiting systems, which comprise the majority of stellar binary and star-planet systems. We discuss the science done with phase curves, the first results obtained so far, and the current difficulties and open questions related to this young and evolving subfield.

VizieR Online Data Catalog: R-band light curves of type II supernovae (Rubin+, 2016)

NASA Astrophysics Data System (ADS)

Rubin, A.; Gal-Yam, A.; De Cia, A.; Horesh, A.; Khazov, D.; Ofek, E. O.; Kulkarni, S. R.; Arcavi, I.; Manulis, I.; Yaron, O.; Vreeswijk, P.; Kasliwal, M. M.; Ben-Ami, S.; Perley, D. A.; Cao, Y.; Cenko, S. B.; Rebbapragada, U. D.; Wozniak, P. R.; Filippenko, A. V.; Clubb, K. I.; Nugent, P. E.; Pan, Y.-C.; Badenes, C.; Howell, D. A.; Valenti, S.; Sand, D.; Sollerman, J.; Johansson, J.; Leonard, D. C.; Horst, J. C.; Armen, S. F.; Fedrow, J. M.; Quimby, R. M.; Mazzali, P.; Pian, E.; Sternberg, A.; Matheson, T.; Sullivan, M.; Maguire, K.; Lazarevic, S.

2016-05-01

Our sample consists of 57 SNe from the PTF (Law et al. 2009PASP..121.1395L; Rau et al. 2009PASP..121.1334R) and the intermediate Palomar Transient Factory (iPTF; Kulkarni 2013ATel.4807....1K) surveys. Data were routinely collected by the Palomar 48-inch survey telescope in the Mould R-band. Follow-up observations were conducted mainly with the robotic 60-inch telescope using an SDSS r-band filter, with additional telescopes providing supplementary photometry and spectroscopy (see Gal-Yam et al. 2011, J/ApJ/736/159). The full list of SNe, their coordinates, and classification spectra are presented in Table 1. Most of the spectra were obtained with the Double Spectrograph on the 5m Hale telescope at Palomar Observatory, the Kast spectrograph on the Shane 3m telescope at Lick Observatory, the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m telescope, and the DEep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II 10m telescope. (2 data files).

Slow-light, band-edge waveguides for tunable time delays.

PubMed

Povinelli, M; Johnson, Steven; Joannopoulos, J

2005-09-05

We propose the use of slow-light, band-edge waveguides for compact, integrated, tunable optical time delays. We show that slow group velocities at the photonic band edge give rise to large changes in time delay for small changes in refractive index, thereby shrinking device size. Figures of merit are introduced to quantify the sensitivity, as well as the accompanying signal degradation due to dispersion. It is shown that exact calculations of the figures of merit for a realistic, three-dimensional grating structure are well predicted by a simple quadratic-band model, simplifying device design. We present adiabatic taper designs that attain <0.1% reflection in short lengths of 10 to 20 times the grating period. We show further that cascading two gratings compensates for signal dispersion and gives rise to a constant tunable time delay across bandwidths greater than 100GHz. Given typical loss values for silicon-on-insulator waveguides, we estimate that gratings can be designed to exhibit tunable delays in the picosecond range using current fabrication technology.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holberg, J. B.; Howell, Steve B., E-mail: holberg@argus.lpl.arizona.edu, 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 thismore » 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.« less

The 1991-2012 light curve of the old nova HR Lyrae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Honeycutt, R. K.; Shears, J.; Kafka, S.

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 themore » 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.« less

THREE FUNDAMENTAL PERIODS IN AN 87 YEAR LIGHT CURVE OF THE SYMBIOTIC STAR MWC 560

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leibowitz, Elia M.; Formiggini, Liliana, E-mail: elia@astro.tau.ac.il

2015-08-15

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 ofmore » 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.« less

Against the Wind: Radio Light Curves of Type IA Supernovae Interacting with Low-Density Circumstellar Shells

DOE PAGES

Harris, Chelsea E.; Nugent, Peter E.; Kasen, Daniel N.

2016-05-26

For decades a wide variety of observations spanning the radio through optical and on to the X-ray have attempted to uncover signs of type Ia supernovae (SNe Ia) interacting with a circumstellar medium (CSM). The goal of these studies is to constrain the nature of the hypothesized SN Ia mass-donor companion. A continuous CSM is typically assumed when interpreting observations of interaction. However, while such models have been successfully applied to core-collapse SNe, the assumption of continuity may not be accurate for SNe Ia, because shells of CSM could be formed by pre-supernova eruptions (novae). In this work, we modelmore » the interaction of SNe with a spherical, low-density, finite-extent CSM and create a suite of synthetic radio synchrotron light curves. We find that CSM shells produce sharply peaked light curves. We also identify a fiducial set of models that obey a common evolution and can be used to generate radio light curves for an interaction with an arbitrary shell. The relations obeyed by the fiducial models can be used to deduce CSM properties from radio observations; we demonstrate this by applying them to the nondetections of SN 2011fe and SN 2014J. Finally, we explore a multiple shell CSM configuration and describe its more complicated dynamics and the resultant radio light curves.« less

AGAINST THE WIND: RADIO LIGHT CURVES OF TYPE IA SUPERNOVAE INTERACTING WITH LOW-DENSITY CIRCUMSTELLAR SHELLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Chelsea E.; Nugent, Peter E.; Kasen, Daniel N., E-mail: chelseaharris@berkeley.edu

2016-06-01

For decades a wide variety of observations spanning the radio through optical and on to the X-ray have attempted to uncover signs of type Ia supernovae (SNe Ia) interacting with a circumstellar medium (CSM). The goal of these studies is to constrain the nature of the hypothesized SN Ia mass-donor companion. A continuous CSM is typically assumed when interpreting observations of interaction. However, while such models have been successfully applied to core-collapse SNe, the assumption of continuity may not be accurate for SNe Ia, because shells of CSM could be formed by pre-supernova eruptions (novae). In this work, we modelmore » the interaction of SNe with a spherical, low-density, finite-extent CSM and create a suite of synthetic radio synchrotron light curves. We find that CSM shells produce sharply peaked light curves. We also identify a fiducial set of models that obey a common evolution and can be used to generate radio light curves for an interaction with an arbitrary shell. The relations obeyed by the fiducial models can be used to deduce CSM properties from radio observations; we demonstrate this by applying them to the nondetections of SN 2011fe and SN 2014J. Finally, we explore a multiple shell CSM configuration and describe its more complicated dynamics and the resultant radio light curves.« less

High-Resolution Spectroscopy of the νb{16} Band of 1,3,5-TRIOXANE

NASA Astrophysics Data System (ADS)

Gibson, Bradley M.; Koeppen, Nicole; McCall, Benjamin J.

2014-06-01

1,3,5-trioxane, often used as a solid fuel or source of formaldehyde, is a symmetric top of the C3v group. Although the microwave and low-resolution vibrational spectra have been studied extensively, only the νb{17} band near 1072 wn has been observed with rotational resolution. Here, we will present our studies of trioxane vapor from 1140-1220 wn, covering the νb{16} band at a resolution of approximately 30 MHz. Solid trioxane was heated, and the resulting vapor was entrained in a continuous supersonic expansion of argon. Continuous-wave cavity ringdown spectroscopy was then performed using a frequency-stabilized external cavity quantum cascade laser (EC-QCL) as the light source. In addition to providing new ro-vibrational transition frequencies of trioxane, the present work serves to validate our newly-developed EC-QCL spectrometer and will be used to evaluate the cooling performance of the sheath-flow supercritical fluid expansion source currently under development. Oka, T., Tsuchiya, K., Iwata, S., and Morino, Y. Microwave Spectrum of s-Trioxane. Bull. Chem. Soc. Jpn. 37 (1964), 4-7. Stair, A.T. Jr. and Nielsen, J. Rud. Vibrational Spectra of sym-Trioxane. J. Chem. Phys. 27 (1957), 402-407. Henninot, J-F., Bolvin, H., Demaison, J., and Lemoine, B. The Infrared Spectrum of Trioxane in a Supersonic Slit Jet. J. Mol. Spect. 152 (1992), 62-68. Gibson, B.M., Stewart, J.T., and McCall, B.J., contribution TJ14, presented at the 68th International Symposium on Molecular Spectroscopy, Columbus, OH, USA, 2013.

A Multi-year Search for Transits of Proxima Centauri. I. Light Curves Corresponding to Published Ephemerides

NASA Astrophysics Data System (ADS)

Blank, David L.; Feliz, Dax; Collins, Karen A.; White, Graeme L.; Stassun, Keivan G.; Curtis, Ivan A.; Hart, Rhodes; Kielkopf, John F.; Nelson, Peter; Relles, Howard; Stockdale, Christopher; Jayawardene, Bandupriya; Pennypacker, Carlton R.; Shankland, Paul; Reichart, Daniel E.; Haislip, Joshua B.; Kouprianov, Vladimir V.

2018-06-01

Proxima Centauri has become the subject of intense study since the radial-velocity (RV) discovery by Anglada-Escudé et al. of a planet orbiting this nearby M dwarf every ∼11.2 days. If Proxima Centauri b transits its host star, independent confirmation of its existence is possible, and its mass and radius can be measured in units of the stellar host mass and radius. To date, there have been three independent claims of possible transit-like event detections in light curve observations obtained by the MOST satellite (in 2014–15), the Bright Star Survey Telescope telescope in Antarctica (in 2016), and the Las Campanas Observatory (in 2016). The claimed possible detections are tentative, due in part to the variability intrinsic to the host star, and in the case of the ground-based observations, also due to the limited duration of the light curve observations. Here, we present preliminary results from an extensive photometric monitoring campaign of Proxima Centauri, using telescopes around the globe and spanning from 2006 to 2017, comprising a total of 329 observations. Considering our data that coincide directly and/or phased with the previously published tentative transit detections, we are unable to independently verify those claims. We do, however, verify the previously reported ubiquitous and complex variability of the host star. We discuss possible interpretations of the data in light of the previous claims, and we discuss future analyses of these data that could more definitively verify or refute the presence of transits associated with the RV-discovered planet.

Tunable slow light in graphene-based hyperbolic metamaterial waveguide operating in SCLU telecom bands.

PubMed

Tyszka-Zawadzka, Anna; Janaszek, Bartosz; Szczepański, Paweł

2017-04-03

The tunability of slow light in graphene-based hyperbolic metamaterial waveguide operating in SCLU telecom bands is investigated. For the first time it has been shown that proper design of a GHMM structure forming waveguide layer and the geometry of the waveguide itself allows stopped light to be obtained in an almost freely selected range of wavelengths within SCLU bands. In particular, the possibility of controlling light propagation in GHMM waveguides by external biasing has been presented. The change of external electric field enables the stop light of the selected wavelength as well as the control of a number of modes, which can be stopped, cut off or supported. Proposed GHMM waveguides could offer great opportunities in the field of integrated photonics that are compatible with CMOS technology, especially since such structures can be utilized as photonic memory cells, tunable optical buffers, delays, optical modulators etc.

Lorenz curve of a light beam: evaluating beam quality from a majorization perspective.

PubMed

Porras, Miguel A; Gonzalo, Isabel; Ahmir Malik, M

2017-08-01

We introduce a novel approach for the characterization of the quality of a laser beam that is not based on particular criteria for beam width definition. The Lorenz curve of a light beam is a sophisticated version of the so-called power-in-the-bucket curve, formed by the partial sums of discretized joint intensity distribution in the near and far fields, sorted in decreasing order. According to majorization theory, a higher Lorenz curve implies that all measures of spreading in phase space, and, in particular, all Rényi (and Shannon) entropy-based measures of the beam width products in near and far fields, are unanimously smaller, providing a strong assessment of a better beam quality. Two beams whose Lorenz curves intersect can be considered of relatively better or lower quality only according to specific criteria, which can be inferred from the plot of the respective Lorenz curves.

High Throughput Light Absorber Discovery, Part 2: Establishing Structure-Band Gap Energy Relationships.

PubMed

Suram, Santosh K; Newhouse, Paul F; Zhou, Lan; Van Campen, Douglas G; Mehta, Apurva; Gregoire, John M

2016-11-14

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4 V 1.5 Fe 0.5 O 10.5 as a light absorber with direct band gap near 2.7 eV. The strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platform for identifying new optical materials.

Rotation curves of galaxies and the stellar mass-to-light ratio

NASA Astrophysics Data System (ADS)

Haghi, Hosein; Khodadadi, Aziz; Ghari, Amir; Zonoozi, Akram Hasani; Kroupa, Pavel

2018-07-01

Mass models of a sample of 171 low- and high-surface brightness galaxies are presented in the context of the cold dark matter (CDM) theory using the NFW dark matter halo density distribution to extract a new concentration-viral mass relation (c-Mvir). The rotation curves (RCs) are calculated from the total baryonic matter based on the 3.6 μm-band surface photometry, the observed distribution of neutral hydrogen, and the dark halo, in which the three adjustable parameters are the stellar mass-to-light ratio, halo concentration, and virial mass. Although accounting for a NFW dark halo profile can explain RC observations, the implied c-Mvir relation from RC analysis strongly disagrees with that resulting from different cosmological simulations. Also, the M/L-colour correlation of the studied galaxies is inconsistent with that expected from stellar population synthesis models with different stellar initial mass functions. Moreover, we show that the best-fitting stellar M/L ratios of 51 galaxies (30 per cent of our sample) have unphysically negative values in the framework of the ΛCDM theory. This can be interpreted as a serious crisis for this theory. This suggests either that the commonly used NFW halo profile, which is a natural result of ΛCDM cosmological structure formation, is not an appropriate profile for the dark haloes of galaxies, or, new dark matter physics or alternative gravity models are needed to explain the rotational velocities of disc galaxies.

Type Ia Supernova Light Curve Inference: Hierarchical Models for Nearby SN Ia in the Optical and Near Infrared

NASA Astrophysics Data System (ADS)

Mandel, Kaisey; Kirshner, R. P.; Narayan, G.; Wood-Vasey, W. M.; Friedman, A. S.; Hicken, M.

2010-01-01

I have constructed a comprehensive statistical model for Type Ia supernova light curves spanning optical through near infrared data simultaneously. The near infrared light curves are found to be excellent standard candles (sigma(MH) = 0.11 +/- 0.03 mag) that are less vulnerable to systematic error from dust extinction, a major confounding factor for cosmological studies. A hierarchical statistical framework incorporates coherently multiple sources of randomness and uncertainty, including photometric error, intrinsic supernova light curve variations and correlations, dust extinction and reddening, peculiar velocity dispersion and distances, for probabilistic inference with Type Ia SN light curves. Inferences are drawn from the full probability density over individual supernovae and the SN Ia and dust populations, conditioned on a dataset of SN Ia light curves and redshifts. To compute probabilistic inferences with hierarchical models, I have developed BayeSN, a Markov Chain Monte Carlo algorithm based on Gibbs sampling. This code explores and samples the global probability density of parameters describing individual supernovae and the population. I have applied this hierarchical model to optical and near infrared data of over 100 nearby Type Ia SN from PAIRITEL, the CfA3 sample, and the literature. Using this statistical model, I find that SN with optical and NIR data have a smaller residual scatter in the Hubble diagram than SN with only optical data. The continued study of Type Ia SN in the near infrared will be important for improving their utility as precise and accurate cosmological distance indicators.

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

A New Light Curve and Analysis of the Long Period Eclipsing Binary BF Draconis

NASA Astrophysics Data System (ADS)

Wolf, G. W.; Craig, L. E.; Caffey, J. F.

1999-01-01

The star BF Draconis was found to be an eclipsing binary by Strohmeier, Knigge and Ott (1962) and originally thought to be an Algol-type system with a period of 5.6 days. A spectrographic study by Imbert (1985) showed that the period was actually double this value and that the system consisted of two well-separated, almost-equal F-type stars in elliptical orbit. Diethelm, Wolf and Agerer (1993) later published a preliminary light curve of this system showing minima of unequal depth and width with a displaced secondary, confirming the elliptical orbit but disagreeing with Imbert on the specific orbital parameters. As a part of our long-term program of obtaining improved light curves of double-lined spectroscopic and eclipsing binaries, we have observed BF Draconis for the past four years using the 0.4 meter telescope at the Baker Observatory of Southwest Missouri State University. Complete light curves in the Cousins BVRI passbands have been obtained with our Photometrics CCD system, and a new model and orbital parameters for the binary have been determined using the Wilson-Devinney program. This research has been supported by NSF Grants AST-9315061 and AST-9605822 and NASA Grant NGT5-40060.

AstroImageJ: Image Processing and Photometric Extraction for Ultra-precise Astronomical Light Curves

NASA Astrophysics Data System (ADS)

Collins, Karen A.; Kielkopf, John F.; Stassun, Keivan G.; Hessman, Frederic V.

2017-02-01

ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other scientific fields. Here we present AstroImageJ (AIJ), which provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction. Although AIJ maintains the general purpose image processing capabilities of ImageJ, AIJ is streamlined for time-series differential photometry, light curve detrending and fitting, and light curve plotting, especially for applications requiring ultra-precise light curves (e.g., exoplanet transits). AIJ reads and writes standard Flexible Image Transport System (FITS) files, as well as other common image formats, provides FITS header viewing and editing, and is World Coordinate System aware, including an automated interface to the astrometry.net web portal for plate solving images. AIJ provides research grade image calibration and analysis tools with a GUI driven approach, and easily installed cross-platform compatibility. It enables new users, even at the level of undergraduate student, high school student, or amateur astronomer, to quickly start processing, modeling, and plotting astronomical image data with one tightly integrated software package.

Know the Planet, Know the Star: Precise Stellar Densities from Kepler Transit Light Curves

NASA Astrophysics Data System (ADS)

Sandford, Emily; Kipping, David

2017-12-01

The properties of a transiting planet’s host star are written in its transit light curve. The light curve can reveal the stellar density ({ρ }* ) and the limb-darkening profile in addition to the characteristics of the planet and its orbit. For planets with strong prior constraints on orbital eccentricity, we may measure these stellar properties directly from the light curve; this method promises to aid greatly in the characterization of transiting planet host stars targeted by the upcoming NASA Transiting Exoplanet Survey Satellite mission and any long-period, singly transiting planets discovered in the same systems. Using Bayesian inference, we fit a transit model, including a nonlinear limb-darkening law, to 66 Kepler transiting planet hosts to measure their stellar properties. We present posterior distributions of ρ *, limb-darkening coefficients, and other system parameters for these stars. We measure densities to within 5% for the majority of our target stars, with the dominant precision-limiting factor being the signal-to-noise ratio of the transits. Of our measured stellar densities, 95% are in 3σ or better agreement with previously published literature values. We make posterior distributions for all of our target Kepler objects of interest available online at 10.5281/zenodo.1028515.

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

VizieR Online Data Catalog: BV(RI)c light curves of FF Vul (Samec+, 2016)

NASA Astrophysics Data System (ADS)

Samec, R. G.; Nyaude, R.; Caton, D.; van Hamme, W.

2017-02-01

The present BVRcIc light curves were taken by DC, the Dark Sky Observatory 0.81m reflector at Phillips Gap, North Carolina. These were taken on 2015 September 12, 13, 14 and 15, and October 15, with a thermoelectrically cooled (-40°C) 2*2K Apogee Alta camera. Additional observations were obtained remotely with the SARA north 0.91m reflector at KPNO on 2015 September 20 and October 11, with the ARC 2*2K camera cooled to -110°C. Individual observations were taken at both sites with standard Johnson-Cousins filters, and included 444 field images in B, 451 in V, 443 in Rc, and 445 in Ic. The standard error was ~7mmag in each of B, V, Rc and Ic. Nightly images were calibrated with 25 bias frames, five flat frames in each filter, and ten 300s dark frames. The exposure times were 40-50s in B, 25-30s in V, 15-25s in Rc and Ic. Our observations are listed in Table1. (1 data file).

CSI 2264: Characterizing Accretion-burst Dominated Light Curves for Young Stars in NGC 2264

NASA Astrophysics Data System (ADS)

Stauffer, John; Cody, Ann Marie; Baglin, Annie; Alencar, Silvia; Rebull, Luisa; Hillenbrand, Lynne A.; Venuti, Laura; Turner, Neal J.; Carpenter, John; Plavchan, Peter; Findeisen, Krzysztof; Carey, Sean; Terebey, Susan; Morales-Calderón, María; Bouvier, Jerome; Micela, Giusi; Flaccomio, Ettore; Song, Inseok; Gutermuth, Rob; Hartmann, Lee; Calvet, Nuria; Whitney, Barbara; Barrado, David; Vrba, Frederick J.; Covey, Kevin; Herbst, William; Furesz, Gabor; Aigrain, Suzanne; Favata, Fabio

2014-04-01

Based on more than four weeks of continuous high-cadence photometric monitoring of several hundred members of the young cluster NGC 2264 with two space telescopes, NASA's Spitzer and the CNES CoRoT (Convection, Rotation, and planetary Transits), we provide high-quality, multi-wavelength light curves for young stellar objects whose optical variability is dominated by short-duration flux bursts, which we infer are due to enhanced mass accretion rates. These light curves show many brief—several hours to one day—brightenings at optical and near-infrared wavelengths with amplitudes generally in the range of 5%-50% of the quiescent value. Typically, a dozen or more of these bursts occur in a 30 day period. We demonstrate that stars exhibiting this type of variability have large ultraviolet (UV) excesses and dominate the portion of the u - g versus g - r color-color diagram with the largest UV excesses. These stars also have large Hα equivalent widths, and either centrally peaked, lumpy Hα emission profiles or profiles with blueshifted absorption dips associated with disk or stellar winds. Light curves of this type have been predicted for stars whose accretion is dominated by Rayleigh-Taylor instabilities at the boundary between their magnetosphere and inner circumstellar disk, or where magneto-rotational instabilities modulate the accretion rate from the inner disk. Among the stars with the largest UV excesses or largest Hα equivalent widths, light curves with this type of variability greatly outnumber light curves with relatively smooth sinusoidal variations associated with long-lived hot spots. We provide quantitative statistics for the average duration and strength of the accretion bursts and for the fraction of the accretion luminosity associated with these bursts. 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

Photometric Type Ia supernova surveys in narrow-band filters

NASA Astrophysics Data System (ADS)

Xavier, Henrique S.; Abramo, L. Raul; Sako, Masao; Benítez, Narciso; Calvão, Maurício O.; Ederoclite, Alessandro; Marín-Franch, Antonio; Molino, Alberto; Reis, Ribamar R. R.; Siffert, Beatriz B.; Sodré, Laerte.

2014-11-01

We study the characteristics of a narrow-band Type Ia supernova (SN) survey through simulations based on the upcoming Javalambre Physics of the accelerating Universe Astrophysical Survey. This unique survey has the capabilities of obtaining distances, redshifts and the SN type from a single experiment thereby circumventing the challenges faced by the resource-intensive spectroscopic follow-up observations. We analyse the flux measurements signal-to-noise ratio and bias, the SN typing performance, the ability to recover light-curve parameters given by the SALT2 model, the photometric redshift precision from Type Ia SN light curves and the effects of systematic errors on the data. We show that such a survey is not only feasible but may yield large Type Ia SN samples (up to 250 SNe at z < 0.5 per month of search) with low core-collapse contamination (˜1.5 per cent), good precision on the SALT2 parameters (average σ _{m_B}=0.063, σ _{x_1}=0.47 and σc = 0.040) and on the distance modulus (average σμ = 0.16, assuming an intrinsic scatter σint = 0.14), with identified systematic uncertainties σsys ≲ 0.10σstat. Moreover, the filters are narrow enough to detect most spectral features and obtain excellent photometric redshift precision of σz = 0.005, apart from ˜2 per cent of outliers. We also present a few strategies for optimizing the survey's outcome. Together with the detailed host galaxy information, narrow-band surveys can be very valuable for the study of SN rates, spectral feature relations, intrinsic colour variations and correlations between SN and host galaxy properties, all of which are important information for SN cosmological applications.

[Application of melting curve to analyze genotype of Duffy blood group antigen Fy-a/b].

PubMed

Chen, Xue; Zhou, Chang-Hua; Hong, Ying; Gong, Tian-Xiang

2012-12-01

This study was aimed to establish the real-time multiple-PCR with melting curve analysis for Duffy blood group Fy-a/b genotyping. According to the sequence of mRNA coding for β-actin and Fy-a/b, the primers of β-actin and Fy-a/b were synthesized. The real-time multiple-PCR with melting curve analysis for Fy-a/b genotyping was established. The Fy-a/b genotyping of 198 blood donors in Chinese Chengdu area has been investigated by melting curve analysis and PCR-SSP. The results showed that the results of Fy-a/b genotype by melting curve analysis were consistent with PCR-SSP. In all of 198 donors in Chinese Chengdu, 178 were Fy(a) (+) (89.9%), 19 were Fy(a) (+) Fy(b) (+) (9.6%), and 1 was Fy(b) (+) (0.5%). The gene frequency of Fy(a) was 0.947, while that of Fy(b) was 0.053. It is concluded that the genotyping method of Duffy blood group with melting curve analysis is established, which can be used as a high-throughput screening tool for Duffy blood group genotyping; and the Fy(a) genotype is the major of Duffy blood group of donors in Chinese Chengdu area.

An Unusual Strong Visible-Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen-Occupied Oxygen Vacancies.

PubMed

Yang, Yongqiang; Yin, Li-Chang; Gong, Yue; Niu, Ping; Wang, Jian-Qiang; Gu, Lin; Chen, Xingqiu; Liu, Gang; Wang, Lianzhou; Cheng, Hui-Ming

2018-02-01

Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO 2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO 2 , an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO 2 by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid Light-curve Changes and Probable Flip-flop Activity of the W UMa-type Binary V410 Aur

NASA Astrophysics Data System (ADS)

Luo, Xia; Wang, Kun; Zhang, Xiaobin; Deng, Licai; Luo, Yangping; Luo, Changqing

2017-09-01

New photometric observations of a W UMa system, V410 Aur, were carried out over 10 nights from 2014 December 19 to 2015 February 8, from which four sets of light curves were obtained. The light curves show many unusual behavioral features, including changing occultation depths, transit minima, and asymmetric maxima. The four sets of light curves have been separately analyzed with the Wilson-Devinney method. The results suggest a totally eclipsing contact configuration for the system. Over a surprisingly short time span of only 52 days, the dominant spot distortion phase jumped twice between phases 0.0 and 0.5. The light-curve variations can be interpreted by the presence of two cool spots on the massive component. Based on our analysis, it is further suggested that the peculiar behavioral patterns are probably caused by the presence of two permanent, active large spots separated in longitude by about 180°, whose locations remain almost unchanged throughout. Our study demonstrates that the system has been undergoing typical flip-flop activity. We therefore conclude that V410 Aur is a W UMa-type system exhibiting flip-flop activity.

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

DOE PAGES

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan; ...

2016-09-23

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

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.

Transit light curves with finite integration time: Fisher information analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 curvemore » 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.« less

ON THE APPARENT ORBITAL INCLINATION CHANGE OF THE EXTRASOLAR TRANSITING PLANET TrES-2b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scuderi, Louis J.; Dittmann, Jason A.; Males, Jared R.

2010-05-01

On 2009 June 15 UT the transit of TrES-2b was detected using the University of Arizona's 1.55 m Kuiper Telescope with 2.0-2.5 millimag rms accuracy in the I band. We find a central transit time of T{sub c} = 2454997.76286 {+-} 0.00035 HJD, an orbital period of P = 2.4706127 {+-} 0.0000009 days, and an inclination angle of i = 83.{sup 0}92 {+-} 0{sup 0}.05, which is consistent with our re-fit of the original I-band light curve of O'Donovan et al. where we find i = 83.{sup 0}84 {+-} 0{sup 0}.05. We calculate an insignificant inclination change of {Delta}i =more » -0.{sup 0}08 {+-} 0{sup 0}.07 over the last three years, and as such, our observations rule out, at the {approx}11{sigma} level, the apparent change of orbital inclination to i{sub predicted} = 83.{sup 0}35 {+-} 0{sup 0}.1 as predicted by Mislis and Schmitt and Mislis et al. for our epoch. Moreover, our analysis of a recently published Kepler Space Telescope light curve for TrES-2b finds an inclination of i = 83.{sup 0}91 {+-} 0.{sup 0}03 for a similar epoch. These Kepler results definitively rule out change in i as a function of time. Indeed, we detect no significant changes in any of the orbital parameters of TrES-2b.« less

Photometric evolution of seven recent novae and the double-component characterizing the light curve of those emitting in gamma rays

NASA Astrophysics Data System (ADS)

Munari, U.; Hambsch, F.-J.; Frigo, A.

2017-08-01

The BVI light curves of seven recent novae (I.e. V1534 Sco, V1535 Sco, V2949 Oph, V3661 Oph, MASTER OT J010603.18-744715.8, TCP J1734475-240942 and ASASSN-16ma) have been extensively mapped with daily robotic observations from Atacama (Chile): five belong to the Galactic bulge, one to the Small Magellanic Cloud and another is a Galactic disc object. The two programme novae detected in γ-rays by Fermi-LAT (I.e. TCP J1734475-240942 and ASASSN-16ma) are bulge objects with unevolved companions. They distinguish themselves by showing a double-component optical light curve. The first component to develop is the fireball from freely expanding, ballistic-launched ejecta, with a time of passage through maximum that is strongly dependent on wavelength (˜1 d delay between the B and I bands). The second component, emerging simultaneously with the nova detection in γ-rays, evolves at a slower pace, its optical brightness being proportional to the γ-ray flux, and its passage through maximum not dependent on wavelength. The fact that γ-rays are detected at a flux level that differs by four times from novae at the distance of the bulge seems to suggest that γ-ray emission is not a widespread property of normal novae. We discuss the advantages offered by high-quality photometric observations collected with only one telescope (as opposed to data provided by a number of different instruments). We also observe the effects of the wavelength dependence of fireball expansion, the recombination in the flashed wind of a giant companion, the subtle presence of hiccups and plateaus, and the super-soft X-ray emission and its switch-off. Four programme novae (V2949 Oph, V3661 Oph, TCP J18102829-2729590 and ASASSN-16ma) have normal dwarf companions: V1534 Sco contains an M3 III giant, V1535 Sco a K-type giant and MASTER OT J010603.18-744715.8 a subgiant. We also comment briefly on the maximum absolute magnitude relation with decline time (MMRD).

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.

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.

Dynamics and afterglow light curves of gamma-ray burst blast waves encountering a density bump or void

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uhm, Z. Lucas; Zhang, Bing, E-mail: uhm@pku.edu.cn, E-mail: zhang@physics.unlv.edu

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 blastmore » 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.« less

Common Envelope Light Curves. I. Grid-code Module Calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galaviz, Pablo; Marco, Orsola De; Staff, Jan E.

The common envelope (CE) binary interaction occurs when a star transfers mass onto a companion that cannot fully accrete it. The interaction can lead to a merger of the two objects or to a close binary. The CE interaction is the gateway of all evolved compact binaries, all stellar mergers, and likely many of the stellar transients witnessed to date. CE simulations are needed to understand this interaction and to interpret stars and binaries thought to be the byproduct of this stage. At this time, simulations are unable to reproduce the few observational data available and several ideas have been putmore » forward to address their shortcomings. The need for more definitive simulation validation is pressing and is already being fulfilled by observations from time-domain surveys. In this article, we present an initial method and its implementation for post-processing grid-based CE simulations to produce the light curve so as to compare simulations with upcoming observations. Here we implemented a zeroth order method to calculate the light emitted from CE hydrodynamic simulations carried out with the 3D hydrodynamic code Enzo used in unigrid mode. The code implements an approach for the computation of luminosity in both optically thick and optically thin regimes and is tested using the first 135 days of the CE simulation of Passy et al., where a 0.8  M {sub ⊙} red giant branch star interacts with a 0.6  M {sub ⊙} companion. This code is used to highlight two large obstacles that need to be overcome before realistic light curves can be calculated. We explain the nature of these problems and the attempted solutions and approximations in full detail to enable the next step to be identified and implemented. We also discuss our simulation in relation to recent data of transients identified as CE interactions.« less

Light-Induced Type-II Band Inversion and Quantum Anomalous Hall State in Monolayer FeSe

NASA Astrophysics Data System (ADS)

Wang, Z. F.; Liu, Zhao; Yang, Jinlong; Liu, Feng

2018-04-01

Coupling a quantum anomalous Hall (QAH) state with a superconducting state offers an attractive approach to detect the signature alluding to a topological superconducting state [Q. L. He et al., Science 357, 294 (2017), 10.1126/science.aag2792], but its explanation could be clouded by disorder effects in magnetic doped QAH materials. On the other hand, an antiferromagnetic (AFM) quantum spin Hall (QSH) state is identified in the well-known high-temperature 2D superconductor of monolayer FeSe [Z. F. Wang et al., Nat. Mater. 15, 968 (2016), 10.1038/nmat4686]. Here, we report a light-induced type-II band inversion (BI) and a QSH-to-QAH phase transition in the monolayer FeSe. Depending on the handedness of light, a spin-tunable QAH state with a high Chern number of ±2 is realized. In contrast to the conventional type-I BI resulting from intrinsic spin-orbital coupling (SOC), which inverts the band an odd number of times and respects time reversal symmetry, the type-II BI results from a light-induced handedness-dependent effective SOC, which inverts the band an even number of times and does not respect time reversal symmetry. The interplay between these two SOC terms makes the spin-up and -down bands of an AFM QSH state respond oppositely to a circularly polarized light, leading to the type-II BI and an exotic topological phase transition. Our finding affords an exciting opportunity to detect Majorana fermions in one single material without magnetic doping.

Crash testing difference-smoothing algorithm on a large sample of simulated light curves from TDC1

NASA Astrophysics Data System (ADS)

Rathna Kumar, S.

2017-09-01

In this work, we propose refinements to the difference-smoothing algorithm for the measurement of time delay from the light curves of the images of a gravitationally lensed quasar. The refinements mainly consist of a more pragmatic approach to choose the smoothing time-scale free parameter, generation of more realistic synthetic light curves for the estimation of time delay uncertainty and using a plot of normalized χ2 computed over a wide range of trial time delay values to assess the reliability of a measured time delay and also for identifying instances of catastrophic failure. We rigorously tested the difference-smoothing algorithm on a large sample of more than thousand pairs of simulated light curves having known true time delays between them from the two most difficult 'rungs' - rung3 and rung4 - of the first edition of Strong Lens Time Delay Challenge (TDC1) and found an inherent tendency of the algorithm to measure the magnitude of time delay to be higher than the true value of time delay. However, we find that this systematic bias is eliminated by applying a correction to each measured time delay according to the magnitude and sign of the systematic error inferred by applying the time delay estimator on synthetic light curves simulating the measured time delay. Following these refinements, the TDC performance metrics for the difference-smoothing algorithm are found to be competitive with those of the best performing submissions of TDC1 for both the tested 'rungs'. The MATLAB codes used in this work and the detailed results are made publicly available.

Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hicken, Malcolm; /Harvard-Smithsonian Ctr. Astrophys. /Harvard U.; Wood-Vasey, W.Michael

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.more » 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.« less

Ground-based K-band detection of thermal emission from the exoplanet TrES-3b

NASA Astrophysics Data System (ADS)

de Mooij, E. J. W.; Snellen, I. A. G.

2009-01-01

Context: Secondary eclipse measurements of transiting extrasolar planets with the Spitzer Space Telescope have yielded several direct detections of thermal exoplanet light. Since Spitzer operates at wavelengths longward of 3.6 μm, arguably one of the most interesting parts of the planet spectrum (from 1 to 3 μm) is inaccessible with this satellite. This region is at the peak of the planet's spectral energy distribution and is also the regime where molecular absorption bands can significantly influence the measured emission. Aims: So far, 2.2 μm K-band secondary eclipse measurements, which are possible from the ground, have not yet lead to secure detections. The aim of this paper is to measure the secondary eclipse of the very hot Jupiter TrES-3b in K-band, and in addition to observe its transit, to obtain an accurate planet radius in the near infrared. Methods: We have used the william herschell telescope (WHT) to observe the secondary eclipse, and the united kingdom infrared telescope (UKIRT) to observe the transit of TrES-3b. Both observations involved significant defocusing of the telescope, aimed to produce high-cadence time series of several thousand frames at high efficiency, with the starlight spread out over many pixels. Results: We detect the secondary eclipse of TrES-3b with a depth of -0.241 ± 0.043% (~6σ). This corresponds to a day-side brightness temperature of TB(2.2 μm) = 2040 ± 185 K, which is consistent with current models of the physical properties of this planet's upper atmosphere. The centre of the eclipse seems slightly offset from phase φ=0.5 by Δφ = -0.0042 ± 0.0027, which could indicate that the orbit of TrES-3b is non-circular. Analysis of the transit data shows that TrES-3b has a near-infrared radius of 1.338 ± 0.016 R_Jup, showing no significant deviation from optical measurements.

Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis.

PubMed

Drout, M R; Piro, A L; Shappee, B J; Kilpatrick, C D; Simon, J D; Contreras, C; Coulter, D A; Foley, R J; Siebert, M R; Morrell, N; Boutsia, K; Di Mille, F; Holoien, T W-S; Kasen, D; Kollmeier, J A; Madore, B F; Monson, A J; Murguia-Berthier, A; Pan, Y-C; Prochaska, J X; Ramirez-Ruiz, E; Rest, A; Adams, C; Alatalo, K; Bañados, E; Baughman, J; Beers, T C; Bernstein, R A; Bitsakis, T; Campillay, A; Hansen, T T; Higgs, C R; Ji, A P; Maravelias, G; Marshall, J L; Bidin, C Moni; Prieto, J L; Rasmussen, K C; Rojas-Bravo, C; Strom, A L; Ulloa, N; Vargas-González, J; Wan, Z; Whitten, D D

2017-12-22

On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days postmerger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in rapid neutron capture (r-process) nucleosynthesis in the universe. Copyright © 2017, American Association for the Advancement of Science.

Period Estimation for Sparsely-sampled Quasi-periodic Light Curves Applied to Miras

NASA Astrophysics Data System (ADS)

He, Shiyuan; Yuan, Wenlong; Huang, Jianhua Z.; Long, James; Macri, Lucas M.

2016-12-01

We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequency parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period-luminosity relations.

Conjugation of fiber-coupled wide-band light sources and acousto-optical spectral elements

NASA Astrophysics Data System (ADS)

Machikhin, Alexander; Batshev, Vladislav; Polschikova, Olga; Khokhlov, Demid; Pozhar, Vitold; Gorevoy, Alexey

2017-12-01

Endoscopic instrumentation is widely used for diagnostics and surgery. The imaging systems, which provide the hyperspectral information of the tissues accessible by endoscopes, are particularly interesting and promising for in vivo photoluminescence diagnostics and therapy of tumour and inflammatory diseases. To add the spectral imaging feature to standard video endoscopes, we propose to implement acousto-optical (AO) filtration of wide-band illumination of incandescent-lamp-based light sources. To collect maximum light and direct it to the fiber-optic light guide inside the endoscopic probe, we have developed and tested the optical system for coupling the light source, the acousto-optical tunable filter (AOTF) and the light guide. The system is compact and compatible with the standard endoscopic components.

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.

Quadratic band touching points and flat bands in two-dimensional topological Floquet systems

NASA Astrophysics Data System (ADS)

Du, Liang; Zhou, Xiaoting; Fiete, Gregory A.

2017-01-01

In this paper we theoretically study, using Floquet-Bloch theory, the influence of circularly and linearly polarized light on two-dimensional band structures with Dirac and quadratic band touching points, and flat bands, taking the nearest neighbor hopping model on the kagome lattice as an example. We find circularly polarized light can invert the ordering of this three-band model, while leaving the flat band dispersionless. We find a small gap is also opened at the quadratic band touching point by two-photon and higher order processes. By contrast, linearly polarized light splits the quadratic band touching point (into two Dirac points) by an amount that depends only on the amplitude and polarization direction of the light, independent of the frequency, and generally renders dispersion to the flat band. The splitting is perpendicular to the direction of the polarization of the light. We derive an effective low-energy theory that captures these key results. Finally, we compute the frequency dependence of the optical conductivity for this three-band model and analyze the various interband contributions of the Floquet modes. Our results suggest strategies for optically controlling band structure and interaction strength in real systems.

Modeling Phase-Aligned Gamma-Ray and Radio Millisecond Pulsar Light Curves

NASA Technical Reports Server (NTRS)

Venter, C.; Johnson, T.; Harding, A.

2012-01-01

Since the discovery of the first eight gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope, this population has been steadily expanding. Four of the more recent detections, PSR J00340534, PSR J1939+2134 (B1937+21; the first MSP ever discovered), PSR J1959+2048 (B1957+20; the first discovery of a black widow system), and PSR J2214+3000, exhibit a phenomenon not present in the original discoveries: nearly phase-aligned radio and gamma-ray light curves (LCs). To account for the phase alignment, we explore models where both the radio and gamma-ray emission originate either in the outer magnetosphere near the light cylinder or near the polar caps. Using a Markov Chain Monte Carlo technique to search for best-fit model parameters, we obtain reasonable LC fits for the first three of these MSPs in the context of altitude-limited outer gap (alOG) and two-pole caustic (alTPC) geometries (for both gamma-ray and radio emission). These models differ from the standard outer gap (OG)/two-pole caustic (TPC) models in two respects: the radio emission originates in caustics at relatively high altitudes compared to the usual conal radio beams, and we allow both the minimum and maximum altitudes of the gamma-ray and radio emission regions to vary within a limited range (excluding the minimum gamma-ray altitude of the alTPC model, which is kept constant at the stellar radius, and that of the alOG model, which is set to the position-dependent null charge surface altitude). Alternatively, phase-aligned solutions also exist for emission originating near the stellar surface in a slot gap scenario (low-altitude slot gap (laSG) models). We find that the alTPC models provide slightly better LC fits than the alOG models, and both of these give better fits than the laSG models (for the limited range of parameters considered in the case of the laSG models). Thus, our fits imply that the phase-aligned LCs are likely of caustic origin, produced in the outer magnetosphere, and

Exoplanet Transit Spectroscopy Using WFC3: WASP-12 b, WASP-17 b, and WASP-19 b

NASA Technical Reports Server (NTRS)

Mandell, Avram Max; Haynes, Korey N.; Sinukoff, Evan; Madhusudhan, Nikku; Burrows, Adam; Deming, Drake

2013-01-01

We report an analysis of transit spectroscopy of the extrasolar planets WASP-12 b, WASP-17 b, and WASP-19 b using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). We analyze the data for a single transit for each planet using a strategy similar, in certain aspects, to the techniques used by Berta et al., but we extend their methodology to allow us to correct for channel- or wavelength-dependent instrumental effects by utilizing the band-integrated time series and measurements of the drift of the spectrum on the detector over time. We achieve almost photon-limited results for individual spectral bins, but the uncertainties in the transit depth for the band-integrated data are exacerbated by the uneven sampling of the light curve imposed by the orbital phasing of HST's observations. Our final transit spectra for all three objects are consistent with the presence of a broad absorption feature at 1.4 nano meter most likely due to water. However, the amplitude of the absorption is less than that expected based on previous observations with Spitzer, possibly due to hazes absorbing in the NIR or non-solar compositions. The degeneracy of models with different compositions and temperature structures combined with the low amplitude of any features in the data preclude our ability to place unambiguous constraints on the atmospheric composition without additional observations with WFC3 to improve the signal-to-noise ratio and/or a comprehensive multi-wavelength analysis.

The extraneous eclipses on binary light curves: KIC 5255552, KIC 10091110, and KIC 11495766

NASA Astrophysics Data System (ADS)

Zhang, J.; Qian, S. B.; Wang, S. M.; Sun, L. L.; Wu, Y.; Jiang, L. Q.

2018-03-01

Aims: We aim to find more eclipsing multiple systems and obtain their parameters, thus increasing our understanding of multiple systems. Methods: The extraneous eclipses on the Kepler binary light curves indicating extraneous bodies were searched. The binary light curves were analyzed using the binary model, and the extraneous eclipses were studied on their periodicity and shape changes. Results: Three binaries with extraneous eclipses on the binary light curves were found and studied based on the Kepler observations. The object KIC 5255552 is an eclipsing triple system with a fast changing inner binary and an outer companion uncovered by three groups of extraneous eclipses of 862.1(±0.1) d period. The KIC 10091110 is suggested to be a double eclipsing binary system with several possible extraordinary coincidences: the two binaries share similar extremely small mass ratios (0.060(13) and 0.0564(18)), similar mean primary densities (0.3264(42) ρ⊙ and 0.3019(28) ρ⊙), and, most notably, the ratio of the two binaries' periods is very close to integer 2 (8.5303353/4.2185174 = 2.022). The KIC 11495766 is a probable triple system with a 120.73 d period binary and (at least) one non-eclipse companion. Furthermore, very close to it in the celestial sphere, there is a blended background stellar binary of 8.3404432 d period. A first list of 25 eclipsing multiple candidates is presented, with the hope that it will be beneficial for study of eclipsing multiples.

On the mean profiles of radio pulsars - II. Reconstruction of complex pulsar light curves and other new propagation effects

NASA Astrophysics Data System (ADS)

Hakobyan, H. L.; Beskin, V. S.; Philippov, A. A.

2017-08-01

Our previous paper outlined the general aspects of the theory of radio light curve and polarization formation for pulsars. We predicted the one-to-one correspondence between the tilt of the linear polarization position angle of the the circular polarization. However, some of the radio pulsars indicate a clear deviation from that correlation. In this paper, we apply the theory of the radio wave propagation in the pulsar magnetosphere for the analysis of individual effects leading to these deviations. We show that within our theory the circular polarization of a given mode can switch its sign, without the need to introduce a new radiation mode or other effects. Moreover, we show that the generation of different emission modes on different altitudes can explain pulsars, that presumably have the X-O-X light-curve pattern, different from what we predict. General properties of radio emission within our propagation theory are also discussed. In particular, we calculate the intensity patterns for different radiation altitudes and present light curves for different observer viewing angles. In this context we also study the light curves and polarization profiles for pulsars with interpulses. Further, we explain the characteristic width of the position angle curves by introducing the concept of a wide emitting region. Another important feature of radio polarization profiles is the shift of the position angle from the centre, which in some cases demonstrates a weak dependence on the observation frequency. Here we demonstrate that propagation effects do not necessarily imply a significant frequency-dependent change of the position angle curve.

MOST light-curve analysis of the γ Doradus pulsator HR 8799, showing resonances and amplitude variations

NASA Astrophysics Data System (ADS)

Sódor, Á.; Chené, A.-N.; De Cat, P.; Bognár, Zs.; Wright, D. J.; Marois, C.; Walker, G. A. H.; Matthews, J. M.; Kallinger, T.; Rowe, J. F.; Kuschnig, R.; Guenther, D. B.; Moffat, A. F. J.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.

2014-08-01

Context. The central star of the HR 8799 system is a γ Doradus-type pulsator. The system harbours four planetary-mass companions detected by direct imaging, and is a good solar system analogue. The masses of the companions are not accurately known because the estimation depends greatly on the age of the system, which is also not known with sufficient accuracy. Asteroseismic studies of the star might help to better constrain the age of HR 8799. We organized an extensive photometric and multi-site spectroscopic observing campaign to study the pulsations of the central star. Aims: The aim of the present study is to investigate the pulsation properties of HR 8799 in detail via the ultra-precise 47 d nearly continuous photometry obtained with the Microvariability and Oscillations in STars (MOST) space telescope, and to find as many independent pulsation modes as possible, which is the prerequisite for an asteroseismic age determination. Methods: We carried out Fourier analysis of the wide-band photometric time series. Results: We find that resonance and sudden amplitude changes characterize the pulsation of HR 8799. The dominant frequency is always at f1 = 1.978 d-1.Many multiples of one-ninth of the dominant frequency appear in the Fourier spectrum of the MOST data: n/9 f1, where n = {1,2,3,4,5,6,7,8,9,10,13,14,17,18}. Our analysis also reveals that many of these peaks show strong amplitude decrease and phase variations even on the 47 d time scale. The dependencies between the pulsation frequencies of HR 8799 make the planned subsequent asteroseismic analysis rather difficult. We point out some resemblance between the light curve of HR 8799 and the modulated pulsation light curves of Blazhko RR Lyrae stars. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.

Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations

NASA Astrophysics Data System (ADS)

Hoeflich, P.; Hsiao, E. Y.; Ashall, C.; Burns, C. R.; Diamond, T. R.; Phillips, M. M.; Sand, D.; Stritzinger, M. D.; Suntzeff, N.; Contreras, C.; Krisciunas, K.; Morrell, N.; Wang, L.

2017-09-01

We study the optical light curve (LC) relations of Type Ia supernovae (SNe Ia) for their use in cosmology using high-quality photometry published by the Carnegie Supernova Project (CSP-I). We revisit the classical luminosity decline rate (Δm 15) relation and the Lira relation, as well as investigate the time evolution of the (B - V) color and B(B - V), which serves as the basis of the color-stretch relation and Color-MAgnitude Intercept Calibrations (CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (DDT) producing normal-bright and subluminous SNe Ia. Empirical LC relations can be understood as having the same physical underpinnings, I.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some three to four weeks past maximum, the photosphere recedes to 56Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density ρ c of the WD because at higher densities, more electron-capture elements are produced at the expense of 56Ni production. This results in a Δm 15 spread of 0.1 mag in normal-bright and 0.7 mag in subluminous SNe Ia and ≈0.2 mag in the Lira relation. We show why color-magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on Δm 15 with little dispersion in both the CSP-I sample and our DDT models. This allows intrinsic SN Ia variations to be separated from the interstellar reddening characterized by E(B - V) and R B . Invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario.

Ukrainian Database and Atlas of Light Curves of Artificial Space Objects

NASA Astrophysics Data System (ADS)

Koshkin, N.; Savanevich, V.; Pohorelov, A.; Shakun, L.; Zhukov, V.; Korobeynikova, E.; Strakhova, S.; Moskalenko, S.; Kashuba, V.; Krasnoshchokov, A.

This paper describes the Ukrainian database of long-term photometric observations of resident space objects (RSO). For the purpose of using this database for the outer space monitoring and space situational awareness (SSA) the open internet resource has been developed. The paper shows examples of using the Atlas of light curves of RSO's for analyzing the state of rotation around the center of mass of several active and non-functioning satellites in orbit.

Broadband tunable electromagnetically induced transparency analogue metamaterials based on graphene in terahertz band

NASA Astrophysics Data System (ADS)

Wang, Yue; Leng, Yanbing; Wang, Li; Dong, Lianhe; Liu, Shunrui; Wang, Jun; Sun, Yanjun

2018-06-01

Most of the actively controlled electromagnetically induced transparency analogue (EIT-like) metamaterials were implemented with narrowband modulations. In this paper, a broadband tunable EIT-like metamaterial based on graphene in the terahertz band is presented. It consists of a cut wire as the bright resonator and two couples of H-shaped resonators in mirror symmetry as the dark resonators. A broadband tunable property of transmission amplitude is realized by changing the Fermi level of graphene. Furthermore, the geometries of the metamaterial structure are optimized to achieve the ideal curve through the simulation. Such EIT-like metamaterials proposed here are promising candidates for designing active wide-band slow-light devices, wide-band terahertz active filters, and wide-band terahertz modulators.

Stellar granulation as the source of high-frequency flicker in Kepler light curves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cranmer, Steven R.; Saar, Steven H.; Bastien, Fabienne A.

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 alsomore » 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.« less

Light intensity of curved laryngoscope blades in Philadelphia emergency departments.

PubMed

Levitan, Richard M; Kelly, John J; Kinkle, William C; Fasano, Charles

2007-09-01

Laryngoscopy and tracheal intubation requires laryngeal exposure and illumination. The objective of this study is to assess variation in laryngoscope lights across different emergency departments (EDs). A convenience sample of 3 Mac #4 blade and handle pairs in each of 17 Philadelphia area EDs was tested with a digital light meter to derive the median lux at the distal tip. For each blade tested, we characterized blade design (American, English, or German) and light type (fiber-illuminated versus conventional bulb-on-blade) and measured light-to-tip distance. A total of 50 blades and handle pairs were tested (one ED had only 2 Mac #4 blades). American designs were the most common (38/50), followed by English (6/50) and German (3/50) designs. Three blades had hybrid design features and acrylic light-conducting fibers. Median luminance varied from 11 lux to 5,627 lux. The glass fiber-illuminated blades (n=13) produced greater luminance (median 1,205 lux; interquartile range [IQR] 726 to 2,176 lux) than bulb-on-blade designs (median 689 lux; IQR 290 to 906 lux). German fiber-illuminated blades produced the highest luminance (median 1,937 lux; IQR 1,453 to 3,782 lux). English bulb-on-blade designs produced more luminance (median 915 lux; IQR 745 to 1270 lux) than American (median 689 lux; IQR 269 to 807 lux). German and English blades had shorter light-to-tip distances (median 51 mm and 47 mm, respectively) than American blades (65 mm). Curved laryngoscope blades in different EDs have marked variation in light intensity. The contribution of luminance to laryngoscopy performance warrants investigation.

Analysis of HD 73045 light curve data

NASA Astrophysics Data System (ADS)

Das, Mrinal Kanti; Bhatraju, Naveen Kumar; Joshi, Santosh

2018-04-01

In this work we analyzed the Kepler light curve data of HD 73045. The raw data has been smoothened using standard filters. The power spectrum has been obtained by using a fast Fourier transform routine. It shows the presence of more than one period. In order to take care of any non-stationary behavior, we carried out a wavelet analysis to obtain the wavelet power spectrum. In addition, to identify the scale invariant structure, the data has been analyzed using a multifractal detrended fluctuation analysis. Further to characterize the diversity of embedded patterns in the HD 73045 flux time series, we computed various entropy-based complexity measures e.g. sample entropy, spectral entropy and permutation entropy. The presence of periodic structure in the time series was further analyzed using the visibility network and horizontal visibility network model of the time series. The degree distributions in the two network models confirm such structures.

Dual-band and polarization-insensitive terahertz absorber based on fractal Koch curves

NASA Astrophysics Data System (ADS)

Ma, Yan-Bing; Zhang, Huai-Wu; Li, Yuan-Xun; Wang, Yi-Cheng; Lai, Wei-En; Li, Jie

2014-05-01

We report the design, fabrication, and characterization of a dual-band and polarization-insensitive metamaterial absorber (MA), which consists of periodically arranged fractal Koch curves acting as the top resonator array and a metallic ground plane separated by a dielectric spacer. Compared with conventional MAs, a more compact size and multi-frequency operation are achieved by using fractal geometry as the unit cell of the MA. Both the effective medium theory and the multi-reflection interference theory are employed to investigate the underlying physical mechanism of the proposed terahertz MA, and results indicate that the latter theory is not suitable for explaining the absorption mechanism in our investigated structure. Two absorption peaks are observed at 0.226 THz and 0.622 THz with absorptivities of 91.3% and 95.6% respectively and good agreements between the full-wave simulation and experimental results are achieved.

Quadratic band touching points and flat bands in two-dimensional topological Floquet systems

NASA Astrophysics Data System (ADS)

Du, Liang; Zhou, Xiaoting; Fiete, Gregory; The CenterComplex Quantum Systems Team

In this work we theoretically study, using Floquet-Bloch theory, the influence of circularly and linearly polarized light on two-dimensional band structures with Dirac and quadratic band touching points, and flat bands, taking the nearest neighbor hopping model on the kagome lattice as an example. We find circularly polarized light can invert the ordering of this three band model, while leaving the flat-band dispersionless. We find a small gap is also opened at the quadratic band touching point by 2-photon and higher order processes. By contrast, linearly polarized light splits the quadratic band touching point (into two Dirac points) by an amount that depends only on the amplitude and polarization direction of the light, independent of the frequency, and generally renders dispersion to the flat band. The splitting is perpendicular to the direction of the polarization of the light. We derive an effective low-energy theory that captures these key results. Finally, we compute the frequency dependence of the optical conductivity for this 3-band model and analyze the various interband contributions of the Floquet modes. Our results suggest strategies for optically controlling band structure and interaction strength in real systems. We gratefully acknowledge funding from ARO Grant W911NF-14-1-0579 and NSF DMR-1507621.

Positional glow curve simulation for thermoluminescent detector (TLD) system design

NASA Astrophysics Data System (ADS)

Branch, C. J.; Kearfott, K. J.

1999-02-01

Multi- and thin element dosimeters, variable heating rate schemes, and glow-curve analysis have been employed to improve environmental and personnel dosimetry using thermoluminescent detectors (TLDs). Detailed analysis of the effects of errors and optimization of techniques would be highly desirable. However, an understanding of the relationship between TL light production, light attenuation, and precise heating schemes is made difficult because of experimental challenges involved in measuring positional TL light production and temperature variations as a function of time. This work reports the development of a general-purpose computer code, thermoluminescent detector simulator, TLD-SIM, to simulate the heating of any TLD type using a variety of conventional and experimental heating methods including pulsed focused or unfocused lasers with Gaussian or uniform cross sections, planchet, hot gas, hot finger, optical, infrared, or electrical heating. TLD-SIM has been used to study the impact on the TL light production of varying the input parameters which include: detector composition, heat capacity, heat conductivity, physical size, and density; trapped electron density, the frequency factor of oscillation of electrons in the traps, and trap-conduction band potential energy difference; heating scheme source terms and heat transfer boundary conditions; and TL light scatter and attenuation coefficients. Temperature profiles and glow curves as a function of position time, as well as the corresponding temporally and/or spatially integrated glow values, may be plotted while varying any of the input parameters. Examples illustrating TLD system functions, including glow curve variability, will be presented. The flexible capabilities of TLD-SIM promises to enable improved TLD system design.

PERIOD ESTIMATION FOR SPARSELY SAMPLED QUASI-PERIODIC LIGHT CURVES APPLIED TO MIRAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Shiyuan; Huang, Jianhua Z.; Long, James

2016-12-01

We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequencymore » parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period–luminosity relations.« less

3.6 and 4.5 μm Phase Curves of the Highly Irradiated Eccentric Hot Jupiter WASP-14b

NASA Astrophysics Data System (ADS)

Wong, Ian; Knutson, Heather A.; Lewis, Nikole K.; Kataria, Tiffany; Burrows, Adam; Fortney, Jonathan J.; Schwartz, Joel; Agol, Eric; Cowan, Nicolas B.; Deming, Drake; Désert, Jean-Michel; Fulton, Benjamin J.; Howard, Andrew W.; Langton, Jonathan; Laughlin, Gregory; Showman, Adam P.; Todorov, Kamen

2015-10-01

We present full-orbit phase curve observations of the eccentric (e ∼ 0.08) transiting hot Jupiter WASP-14b obtained in the 3.6 and 4.5 μm bands using the Spitzer Space Telescope. We use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise. Our measured secondary eclipse depths of 0.1882% ± 0.0048% and 0.2247% ± 0.0086% at 3.6 and 4.5 μm, respectively, are both consistent with a blackbody temperature of 2402 ± 35 K. We place a 2σ upper limit on the nightside flux at 3.6 μm and find it to be 9% ± 1% of the dayside flux, corresponding to a brightness temperature of 1079 K. At 4.5 μm, the minimum planet flux is 30% ± 5% of the maximum flux, corresponding to a brightness temperature of 1380 ± 65 K. We compare our measured phase curves to the predictions of one-dimensional radiative transfer and three-dimensional general circulation models. We find that WASP-14b’s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion. These same models tend to overpredict the nightside emission at 3.6 μm, while underpredicting the nightside emission at 4.5 μm. We propose that this discrepancy might be explained by an enhanced global C/O ratio. In addition, we find that the phase curves of WASP-14b (7.8 MJup) are consistent with a much lower albedo than those of other Jovian mass planets with thermal phase curve measurements, suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes.

3.6 AND 4.5 μm PHASE CURVES OF THE HIGHLY IRRADIATED ECCENTRIC HOT JUPITER WASP-14b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Ian; Knutson, Heather A.; Lewis, Nikole K.

We present full-orbit phase curve observations of the eccentric (e ∼ 0.08) transiting hot Jupiter WASP-14b obtained in the 3.6 and 4.5 μm bands using the Spitzer Space Telescope. We use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise. Our measured secondary eclipse depths of 0.1882% ± 0.0048% and 0.2247% ± 0.0086% at 3.6 and 4.5 μm, respectively, are both consistent with a blackbody temperature of 2402 ± 35 K. We place a 2σ upper limit on the nightside flux at 3.6 μm and find it to be 9% ±more » 1% of the dayside flux, corresponding to a brightness temperature of 1079 K. At 4.5 μm, the minimum planet flux is 30% ± 5% of the maximum flux, corresponding to a brightness temperature of 1380 ± 65 K. We compare our measured phase curves to the predictions of one-dimensional radiative transfer and three-dimensional general circulation models. We find that WASP-14b’s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion. These same models tend to overpredict the nightside emission at 3.6 μm, while underpredicting the nightside emission at 4.5 μm. We propose that this discrepancy might be explained by an enhanced global C/O ratio. In addition, we find that the phase curves of WASP-14b (7.8 M{sub Jup}) are consistent with a much lower albedo than those of other Jovian mass planets with thermal phase curve measurements, suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes.« less

Interpreting the human phase response curve to multiple bright-light exposures.

PubMed

Strogatz, S H

1990-01-01

Czeisler and his colleagues have recently reported that bright light can induce strong (Type O) resetting of the human circadian pacemaker. This surprising result shows that the human clock is more responsive to light than has been previously thought. The interpretation of their results is subtle, however, because of an unconventional aspect of their experimental protocol: They measured the phase shift after three cycles of the bright-light stimulus, rather than after the usual single pulse. A natural question is whether the apparent Type O response could reflect the summation of three weaker Type 1 responses to each of the daily light pulses. In this paper I show mathematically that repeated Type 1 resetting cannot account for the observed Type O response. This finding corroborates the strong resetting reported by Czeisler et al., and supports their claim that bright light induces strong resetting by crushing the amplitude of the circadian pacemaker. Furthermore, the results indicate that back-to-back light pulses can have a cooperative effect different from that obtained by simple iteration of a phase response curve (PRC). In this sense the resetting response of humans is similar to that of Drosophila, Kalanchoe, and Culex, and is more complex than that predicted by conventional PRC theory. To describe the way in which light resets the human circadian pacemaker, one needs a theory that includes amplitude resetting, as pioneered by Winfree and developed for humans by Kronauer.

IMPROVED DARK ENERGY CONSTRAINTS FROM {approx}100 NEW CfA SUPERNOVA TYPE Ia LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hicken, Malcolm; Challis, Peter; Kirshner, Robert P.

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 largestmore » 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.« less

Low light adaptation: energy transfer processes in different types of light harvesting complexes from Rhodopseudomonas palustris.

PubMed

Moulisová, Vladimíra; Luer, Larry; Hoseinkhani, Sajjad; Brotosudarmo, Tatas H P; Collins, Aaron M; Lanzani, Guglielmo; Blankenship, Robert E; Cogdell, Richard J

2009-12-02

Energy transfer processes in photosynthetic light harvesting 2 (LH2) complexes isolated from purple bacterium Rhodopseudomonas palustris grown at different light intensities were studied by ground state and transient absorption spectroscopy. The decomposition of ground state absorption spectra shows contributions from B800 and B850 bacteriochlorophyll (BChl) a rings, the latter component splitting into a low energy and a high energy band in samples grown under low light (LL) conditions. A spectral analysis reveals strong inhomogeneity of the B850 excitons in the LL samples that is well reproduced by an exponential-type distribution. Transient spectra show a bleach of both the low energy and high energy bands, together with the respective blue-shifted exciton-to-biexciton transitions. The different spectral evolutions were analyzed by a global fitting procedure. Energy transfer from B800 to B850 occurs in a mono-exponential process and the rate of this process is only slightly reduced in LL compared to high light samples. In LL samples, spectral relaxation of the B850 exciton follows strongly nonexponential kinetics that can be described by a reduction of the bleach of the high energy excitonic component and a red-shift of the low energetic one. We explain these spectral changes by picosecond exciton relaxation caused by a small coupling parameter of the excitonic splitting of the BChl a molecules to the surrounding bath. The splitting of exciton energy into two excitonic bands in LL complex is most probably caused by heterogenous composition of LH2 apoproteins that gives some of the BChls in the B850 ring B820-like site energies, and causes a disorder in LH2 structure.

Aberration correction considering curved sample surface shape for non-contact two-photon excitation microscopy with spatial light modulator.

PubMed

Matsumoto, Naoya; Konno, Alu; Inoue, Takashi; Okazaki, Shigetoshi

2018-06-18