Photometric Study of the Solar Type Pre-Contact Binary, V2421 Cygni

NASA Astrophysics Data System (ADS)

Hill, Robert L.; Shebs, T.; Samec, R. G.; Kring, J.; Van Hamme, W. V.; Faulkner, D. R.

2013-06-01

We present the first precision BVRI light curves, and synthetic light curve solutions and a period study for the 14th magnitude (V) pre-contact W UMa Binary, V2421 Cygni. Observations were taken with the NURO 0.81-m Lowell reflector on 30 September, 1 and 2 October. Our light curves were premodeled with Binary Maker 3.0, and solved with the Wilson-Devinney program. The observations included 140 B, 149 V, 139 R and 135 I individual and calibrated observations. These were taken with the Lowell CRYOTIGER cooled (-100k) 2KX2K NASACAM. Three mean times of minimum light were determined, including HJDMin I = 2455469.82375±0.00037, and 2455471.72232±0.0012 and HJDMin II = 2455470.77149±0.0012. Eight eclipse timings were taken from the the literature for our calculation of its first precision ephemeris: JD Tmin I = 2455469.8238± 0.0047 + 0.6331290 ± 0.0000015 d*E The light curve has the appearance of an Algol (EA) type, however it is made up of dwarf solar type components in a detached mode with a period of only 0.6331 days. The light curve solution gives a mass ratio of ~0.5, an inclination of 86° and amplitudes of 1.3, 1.1, 0.98, and 0.87 in B,V,R and I, respectively. Flare-like disruptions occur in the light curves following the primary and secondary eclipses. The fill-outs are 83% and 98% for star one (hotter more massive component) and star two, respectively. The model includes two hot spots, possibly, stream spots (one a direct hit and the second, a splash spot). Further observations are needed to determine its orbital evolution. We thank USC, Lancaster for their support of our membership in NURO for the past 8 years, the American Astronomical Society for its support through its small research program and Arizona Space grant for the partial support for our student’s travel.

Contact Binaries on Their Way Towards Merging

NASA Astrophysics Data System (ADS)

Gazeas, K.

2015-07-01

Contact binaries are the most frequently observed type of eclipsing star system. They are small, cool, low-mass binaries belonging to a relatively old stellar population. They follow certain empirical relationships that closely connect a number of physical parameters with each other, largely because of constraints coming from the Roche geometry. As a result, contact binaries provide an excellent test of stellar evolution, specifically for stellar merger scenarios. Observing campaigns by many authors have led to the cataloging of thousands of contact binaries and enabled statistical studies of many of their properties. A large number of contact binaries have been found to exhibit extraordinary behavior, requiring follow-up observations to study their peculiarities in detail. For example, a doubly-eclipsing quadruple system consisting of a contact binary and a detached binary is a highly constrained system offering an excellent laboratory to test evolutionary theories for binaries. A new observing project was initiated at the University of Athens in 2012 in order to investigate the possible lower limit for the orbital period of binary systems before coalescence, prior to merging.

Photometric investigation of the totally eclipsing contact binary V12 in the intermediate-age open cluster NGC 7789

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

Qian, S.-B.; Wang, J.-J.; Liu, L.

2015-02-01

NGC 7789 is an intermediate-age open cluster with an age similar to the mean age of contact binary stars. V12 is a bright W UMa-type binary star with an orbital period of 0.3917 days. The first complete light curves of V12 in the V, R, and I bands are presented and analyzed with the Wilson–Devinney (W-D) method. The results show that V12 is an intermediate-contact binary (f=43.0(±2.2)%) with a mass ratio of 3.848, and it is a W-type contact binary where the less massive component is slightly hotter than the more massive one. The asymmetry of the light curves ismore » explained by the presence of a dark spot on the more massive component. The derived orbital inclination (i=83{sub .}{sup ∘}6) indicates that it is a totally eclipsing binary, which suggests that the determined parameters are reliable. The orbital period may show a long-term increase at a rate of P-dot =+2.48(±0.17)×10{sup −6} days yr{sup −1} that reveals a rapid mass transfer from the less massive component to the more massive one. However, more observations are needed to confirm this conclusion. The presence of an intermediate-contact binary in an intermediate-age open cluster may suggest that some contact binaries have a very short pre-contact timescale. The presence of a third body and/or stellar collision may help to shorten the pre-contact evolution.« less

SuperWASP J015100.23-100524.2: A SPOTTED SHALLOW-CONTACT BINARY BELOW THE PERIOD LIMIT

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

Qian, S. B.; Zhang, B.; He, J. J.

2015-10-15

SuperWASP J015100.23-100524.2 (hereafter J015100) is an eclipsing binary with an orbital period of 0.d2145 that is below the short-period limit of contact binary stars. Complete light curves of J015100 in B, V, R, and I bands are presented and are analyzed with the Wilson–Devinney method. It has been discovered that J015100 is a shallow-contact binary (f = 14.6(±2.7)%) with a mass ratio of 3.128. It is a W-type contact binary where the less massive component is about 130 K hotter than the more massive one. The asymmetries of light curves are explained as one dark spot on the more massivemore » component. The detection of J015100 as a contact binary below the period limit suggests that contact binaries below this limit are not rapidly destroyed. This shallow-contact system may be formed from a detached short-period binary similar to DV Psc (Sp. = K4/K5; P = 0.d30855) via orbital shrinkage due to angular momentum loss through magnetic stellar wind.« less

Continued Kinematic and Photometric Investigations of Hierarchical Solar-type Multiple Star Systems

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

Roberts, Lewis C. Jr.; Marinan, Anne D.; Tokovinin, Andrei

2017-03-01

We observed 15 of the solar-type binaries within 67 pc of the Sun previously observed by the Robo-AO system in the visible, with the PHARO near-infrared camera and the PALM-3000 adaptive optics system on the 5 m Hale telescope. The physical status of the binaries is confirmed through common proper motion and detection of orbital motion. In the process, we detected a new candidate companion to HIP 95309. We also resolved the primary of HIP 110626 into a close binary, making that system a triple. These detections increase the completeness of the multiplicity survey of the solar-type stars within 67more » pc of the Sun. Combining our observations of HIP 103455 with archival astrometric measurements and RV measurements, we are able to compute the first orbit of HIP 103455, showing that the binary has a 68 year period. We place the components on a color–magnitude diagram and discuss each multiple system individually.« less

Nitride Conversion: A Novel Approach to c-Si Solar Cell Metallization

NASA Astrophysics Data System (ADS)

Hook, David Henry

Metallization of commercial-grade c-Si solar cells is currently accomplished by screen-printing fine lines of a Ag/PbO-glass paste amalgam (Ag-frit) onto the insulating SiNx antireflective coating (ARC) that lies atop the shallow n-type emitter layer of the cell. Upon annealing, the glass etches SiNx and permits the crystallization of Ag near the electrically-active emitter interface, thus contacting the cell. While entirely functional, the contact interface produced by Ag-frit metallization is non-ideal, and Ag metal itself is expensive; its use adds to overall solar cell costs. The following work explores the use of Ti-containing alloys as metallization media for c-Si solar cells. There is a -176 kJ [mol N]--1 free energy change associated with the conversion of Si3N4 to TiN. By combining Ti with a low-melting point metal, this reaction can take place at temperatures as low as 750°C in the bulk. Combinations of Ti with Cu, Sn, Ag, and Pb ternary and binary systems are investigated. On unmetallized, c-Si textured solar cells it is shown that 900 nm of stoichiometric Ti6Sn 5 is capable of converting the SiNx ARC to TiN and Ti5Si3, both of which are conducting materials with electrically low-barriers to contact with n-type Si. Alongside electron microscopy, specific contact resistivity (rho c) measurements are used to determine the interfacial quality of TiN/Ti5Si3 contacts to n-Si. Circular transmission line model (CTLM) measurements are utilized for the characterization of reacted Ag0.05Cu0.69Ti0.26, Sn0.35 Ag0.27Ti0.38, and Ti6Sn5 contacts. rhoc values as low as 26 muOcm 2 are measured for reacted Ti6Sn5-SiN x on conventional c-Si solar cells. This value is approximately 2-3 orders of magnitude lower than rhoc of contacts produced by traditional Ag-frit metallization. Viable 1x1 cm, Ti6Sn5-metallized solar cells on 5x5 cm substrates were fabricated through a collaboration with the Georgia Institute of Technology (GA Tech). Front-side metallization was performed at NCSU; cells were then shipped to GA Tech for rear-side metallization, Ag-plating to increase the metal thickness, and cell isolation. This collaboration produced a 16.9% efficient, Ti6Sn5-metallized cell compared to a 17.4% efficient Ag frit-metallized control cell that had experienced an identical temperature profile. It was found that the annealing profiles associated with conversion-metallization promote H2 desorption from the SiN x ARC and thus negatively affect cell passivation. Strategies exist for decreasing the heat experienced by conversion-metallized cells, doing so would increase the overall efficiency and improve other relevant metrics. Solar industry analysis indicates that c-Si cells will increase in efficiency by switching to high sheet-resistance p-type emitters; there will be a marked need for a contact mechanism with a near-ideal, low barrier-height interfaces to these next-generation layers. SiN x ARC conversion to TiN/Ti5Si3 represents an economical means of achieving low rhoc contact to both n and p-type Si when compared to metallization by Ag frit.

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34 +0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-06-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34+0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

Photometric Study of The Solar Type, Total Eclipsing Binary, TYC 2853-18-1

NASA Astrophysics Data System (ADS)

Samec, Ronald G.; Figg, E. R.; Faulkner, D.; Van Hamme, W.

2009-12-01

We present an analysis of the Solar-Type eclipsing binary, TYC 2853-18-1 (Persei), based on observations taken at the National Undergraduate Research Observatory (NURO) and the Southeastern Association for Research in Astronomy (SARA) in the Fall, 2007 and Spring, 2008. Light curves, a period study and a synthetic light curve solution are presented for this variable which was recently discovered by TYCHO as an eclipsing binary (2006, IBVS 5700). Our CCD observations of TYC 2853-18-1 [GSC 2853 0018, RA(2000) = 02h 47m 07.996s, DEC(2000) = +41° 22’ 32.80"] were taken on 20,27 December, 2007 at Lowell Observatory with the 0.81-m reflector with NURO time and 25 November, 3 December, 2007 and 19 February, 2008 via remote observing from Kitt Peak with SARA. NURO observations were take with the thermoelectrically cooled (<-100C) 2KX2K CCD NASACAM. Standard BVRcIc Johnson-Cousins filters were used. Our light curve solution was calculated with the 2004 Wilson code. Mean times of eclipse include, HJDMinI = 2454516.6131(±0.0005), 2454440.52974(±0.00008), 2454438.7605 (±0.0001), 2454462.6464 (±0.0003), HJDMinII = 2454455.71985 (±0.00060), 255462.7943 (±0.0002). These, including the epoch by ROTSE (2006, IBVS 5699) and the epoch calculated by the Wilson code, yielded the following ephemeris: HJD Hel Min I =2451370.8753(±.0.0010)d + 0.2949039 (±0.0000001)E Our unspotted Wilson code solution reveals TYC 2853-18-1 to be a W-type W UMa contact binary with unequal eclipse depths (amplitudes are 0.72 and 0.61 mags in V). It has shallow contact (8% fill-out) and a brief, but total eclipse. Its curves dictate a mass ratio of 2.62±0.01, a component temperature difference of only 73±5 ° K and an inclination of 82.0±0.2°. Spot activity is indicated by night to night variations. We wish to thank the NURO and SARA for their allocation of observing time, as well as NASA and the AAS for their support in paying for travel and publication expenses.

A photometric analysis of the neglected EW-type binary V336 TrA

NASA Astrophysics Data System (ADS)

Kriwattanawong, W.; Sarotsakulchai, T.; Maungkorn, S.; Reichart, D. E.; Haislip, J. B.; Kouprianov, V. V.; LaCluyze, A. P.; Moore, J. P.

2018-05-01

This study presents an analysis of photometric light curves and absolute parameters for the EW-type binary V336 TrA. VRI imaging observations were taken in 2013 by using the robotic telescopes PROMPT 4 and PROMPT 5 at Cerro Tololo Inter-American Observatory (CTIO), Chile. The observed light curves were fitted by using the Wilson-Devinney method. The results showed that V336 TrA is a W-type contact binary with a mass ratio of q = 1.396. The binary is a weak contact system with a fill-out factor of f = 15.69%. The system contains components with masses of 0.653 M⊙ and 0.912 M⊙ for the hotter and the cooler, respectively. The location of the secondary (less massive) component on the log M - log L diagram was found to be near the TAMS. The component has evolved to be oversize and overluminous. The orbital angular momentum of the binary was found to be log Jo = 51.61 cgs, less than all detached systems for same mass. The system has undergone angular momentum and/or mass loss, during the binary evolution from the detached to contact system.

The Impact of Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Dupuy, Trent; Mann, Andrew; Huber, Daniel

2018-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion. We now update these results with multi-epoch imaging to reject non-comoving background stars and securely identify even the least massive stellar companions, as well as tracing out the orbital motion of stellar companions. These results are beginning to reveal not just the fraction of binaries that do not host planets, but also potential explanations for planet survival even in some very close, dynamically active binary systems.

Research on the Orbital Period of Massive Binaries

NASA Astrophysics Data System (ADS)

Zhao, E.; Qain, S.

2011-12-01

Massive binary is the kind of binary, whose spectral type is earlier than B5. Research on massive binary plays an important role in the mass and angular momentum transfer or loss between the components, and the evolution of binary. Some massive binaries are observed and analyzed, including O-type binary LY Aur, B-type contact binary RZ Pyx and B-type semi-detached binary AI Cru. It is found that all of their periods have a long-term increasing, which indicates that the system is undergoing a Case A slow mass transfer stage on the nuclear time-scale of the secondary. Moreover, analysis show a cyclic change of orbital period, which can be explained by the light-travel effect time of the third body.

Shapes and binary fractions of Jovian Trojans and Hildas through NEOWISE

NASA Astrophysics Data System (ADS)

Sonnett, S.; Mainzer, A.; Grav, T.; Bauer, J.; Masiero, J.; Stevenson, R.; Nugent, C.

2014-07-01

Jovian Trojans (hereafter, Trojans) and Hildas are indicative of planetary migration patterns since their capture and physical state must be explained by dynamical evolution models. Early models of minimal planetary migration necessitate that Trojans were dynamically captured from the giant planet region (e.g., Marzari & Scholl 1998). The Nice model instead suggests that Trojans were injected from the outer solar system during a period of significant giant planet migration (e.g., Morbidelli et al. 2005). A more recent version of the Nice model suggests that asymmetric scatterings and collisions would have taken place, producing dissimilar L4 and L5 clouds (Nesvorny et al. 2013). Each of these formation scenarios predicts a different origin and/or collisional evolution for Trojans, which can be inferred from rotation properties. Namely, the physical shape as a function of size helps determine the degree of collisional processing (Farinella et al. 1992). Also, the binary fraction as a function of separation between the two components can be used to determine the dominant binary formation mechanism and thus helps characterize the dynamical environment (e.g., Kern & Elliot 2006). Rotational variation usually corresponds to elongated shapes, but high amplitudes (> 0.9 magnitudes; Sheppard & Jewitt 2004) can only be explained by close or contact binaries. Therefore, rotational lightcurves can be used to infer both shape and the presence of a close companion. Motivated by the need for more observational constraints on solar system formation models and a poor understanding of the rotation properties and binary fraction of Trojans and Hildas, we are studying their rotational lightcurve amplitudes using infrared photometry from NEOWISE (Mainzer et al. 2011; Grav et al. 2011) in order to determine debiased rotational lightcurve amplitude distributions for various Trojan subpopulations and for Trojans compared to Hildas. Preliminary amplitude distributions show a large fraction of potential close or contact binaries (having Δ m > 0.9). These distributions can be used to constrain the collisional and dynamical history of solar system formation models.

Front contact solar cell with formed emitter

DOEpatents

Cousins, Peter John

2014-11-04

A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

Front contact solar cell with formed emitter

DOEpatents

Cousins, Peter John [Menlo Park, CA

2012-07-17

A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

Method of fabricating a back-contact solar cell and device thereof

DOEpatents

Li, Bo; Smith, David; Cousins, Peter

2014-07-29

Methods of fabricating back-contact solar cells and devices thereof are described. A method of fabricating a back-contact solar cell includes forming an N-type dopant source layer and a P-type dopant source layer above a material layer disposed above a substrate. The N-type dopant source layer is spaced apart from the P-type dopant source layer. The N-type dopant source layer and the P-type dopant source layer are heated. Subsequently, a trench is formed in the material layer, between the N-type and P-type dopant source layers.

Method of fabricating a back-contact solar cell and device thereof

DOEpatents

Li, Bo; Smith, David; Cousins, Peter

2016-08-02

Methods of fabricating back-contact solar cells and devices thereof are described. A method of fabricating a back-contact solar cell includes forming an N-type dopant source layer and a P-type dopant source layer above a material layer disposed above a substrate. The N-type dopant source layer is spaced apart from the P-type dopant source layer. The N-type dopant source layer and the P-type dopant source layer are heated. Subsequently, a trench is formed in the material layer, between the N-type and P-type dopant source layers.

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

Tokovinin, Andrei, E-mail: atokovinin@ctio.noao.edu

Seven spectroscopic orbits in nearby solar-type multiple stars are presented. The primary of the chromospherically active star HIP 9642 is a 4.8 day double-lined pair; the outer 420 year visual orbit is updated, but remains poorly constrained. HIP 12780 is a quadruple system consisting of the resolved 6.7 year pair FIN 379 Aa,Ab, for which the combined orbit, masses, and orbital parallax are determined here, and the single-lined binary Ba,Bb with a period of 27.8 days. HIP 28790 is a young quintuple system composed of two close binaries, Aa,Ab and Ba,Bb, with periods of 221 and 13 days, respectively, and a singlemore » distant component C. Its subsystem Ba,Bb is peculiar, having a spectroscopic mass ratio of 0.89 but a magnitude difference of ∼2.2 mag. HIP 64478 also contains five stars: the A-component is a 29 year visual pair with a previously known 4 day twin subsystem, while the B-component is a contact binary with a period of 5.8 hr, seen nearly pole-on.« less

Reduced Carrier Recombination in PbS - CuInS2 Quantum Dot Solar Cells

PubMed Central

Sun, Zhenhua; Sitbon, Gary; Pons, Thomas; Bakulin, Artem A.; Chen, Zhuoying

2015-01-01

Energy loss due to carrier recombination is among the major factors limiting the performance of TiO2/PbS colloidal quantum dot (QD) heterojunction solar cells. In this work, enhanced photocurrent is achieved by incorporating another type of hole-transporting QDs, Zn-doped CuInS2 (Zn-CIS) QDs into the PbS QD matrix. Binary QD solar cells exhibit a reduced charge recombination associated with the spatial charge separation between these two types of QDs. A ~30% increase in short-circuit current density and a ~20% increase in power conversion efficiency are observed in binary QD solar cells compared to cells built from PbS QDs only. In agreement with the charge transfer process identified through ultrafast pump/probe spectroscopy between these two QD components, transient photovoltage characteristics of single-component and binary QDs solar cells reveal longer carrier recombination time constants associated with the incorporation of Zn-CIS QDs. This work presents a straightforward, solution-processed method based on the incorporation of another QDs in the PbS QD matrix to control the carrier dynamics in colloidal QD materials and enhance solar cell performance. PMID:26024021

Photometric Study of the near-contact short period Algol system, AK Canis Minoris

NASA Astrophysics Data System (ADS)

Samec, Ronald G.; McDermith, Richard J.; Gray, Jamison D.; Carrigan, Brian

1995-05-01

As a part of our departments new undergraduate research program, we are surveying the eccentric eclipsing binary (EEB) candidates of Hegedus (1988). AK CMi is listed as a system with a displaced secondary. The observations were taken 10 to 15 February 1994, inclusive, at Lowell Obsevatory, Flagstaff, Arizona. A thermoelectrically cooled EMI 6256S ( S-13 cathode) PMT was used in conjunction with the 0.78 m National Undergraduate Research Observatory reflector. Two precision epochs of minimicrons light were determined from the observations made during primary and secondary eclipses. They are: Min I = 2449396.7032(5) and Min II = 2449395.8546(3). Targeting the last twenty-three years of data, we calculated improved linear and quadratic ephemerides. The quadratic term, -1.0(2)E-10, suggests that AK CMi is undergoing a continuous period decrease. This may be due to magnetic braking arising from the fast rotating solar-type secondary component. There is little evidence from the present light curves that AK CMi has a eccentric orbit. Assymetries near secondary minima possibly induced by an intermittent gas stream may be responsible for the classification of AK CMi as an EEB. The light curve solution reveals that AK CMi is a short period Algol with an A spectral-type primary component and an early K-type secondary. We calculated mass ratio of 0.5 and a secondary component fillout of 90% showing that AK CMi is a near contact binary.

A new mechanism of long-term period variations for W UMa-type contact binaries

NASA Astrophysics Data System (ADS)

Liu, L.; Qian, S.-B.; Xiong, X.

2018-03-01

W UMa-type contact binaries belong to close binary systems whose components exactly overflow their Roche lobes and share a common convective envelope (CCE). In the last twenty years, the long-term variations of their orbital periods have been thought to depend on several mechanisms. Now, we suggest a new mechanism: CCE-dominated mechanism. The CCE-dominated mechanism is found based on our numerical result, especially at high mass ratios, that the orbital periods (P) of contact binaries change very much with their fill-out factors (f). Because f is taken as a measurement of the thickness of CCE, the physical cause for the variation of P is a mass transfer between CCE and components. Further, an f-dominated simplification model for this mechanism is introduced. According to it, P may change in a long-term oscillation way with a similar time scale of the thermal modulation, meanwhile q is decreasing slowly till the two components merge. It could be also applied to explain the presence of extremely short period, high mass ratio and deep contact binaries. Moreover, the CCE-dominated mechanism should always work due to mass transfer and mass loss both occurring via CCE. Therefor, the effect of CCE on the variations of orbital periods may have been underestimated before.

Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems

NASA Astrophysics Data System (ADS)

Jacobson, Seth A.; Scheeres, Daniel J.

2011-07-01

We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high- e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, "rubble pile" asteroid geophysics, and gravitational interactions. The YORP effect torques a "rubble pile" asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thus creating a chaotic ternary system. The initially chaotic binary can be stabilized to create a synchronous binary by components of the fissioned secondary asteroid impacting the primary asteroid, solar gravitational perturbations, and mutual body tides. These results emphasize the importance of the initial component size distribution and configuration within the parent asteroid. NEAs may go through multiple binary cycles and many YORP-induced rotational fissions during their approximately 10 Myr lifetime in the inner Solar System. Rotational fission and the ensuing dynamics are responsible for all NEA systems including the most commonly observed synchronous binaries.

Fabrication of back-contacted silicon solar cells using thermomigration to create conductive vias

DOEpatents

Gee, James M; Schmit, Russell R.

2007-01-30

Methods of manufacturing back-contacted silicon solar cells fabricated using a gradient-driven solute transport process, such as thermomigration or electromigration, to create n-type conductive vias connecting the n-type emitter layer on the front side to n-type ohmic contacts located on the back side.

Front contact solar cell with formed electrically conducting layers on the front side and backside

DOEpatents

Cousins, Peter John

2012-06-26

A bipolar solar cell includes a backside junction formed by a silicon substrate and a first doped layer of a first dopant type on the backside of the solar cell. A second doped layer of a second dopant type makes an electrical connection to the substrate from the front side of the solar cell. A first metal contact of a first electrical polarity electrically connects to the first doped layer on the backside of the solar cell, and a second metal contact of a second electrical polarity electrically connects to the second doped layer on the front side of the solar cell. An external electrical circuit may be electrically connected to the first and second metal contacts to be powered by the solar cell.

Chromium Trioxide Hole-Selective Heterocontacts for Silicon Solar Cells.

PubMed

Lin, Wenjie; Wu, Weiliang; Liu, Zongtao; Qiu, Kaifu; Cai, Lun; Yao, Zhirong; Ai, Bin; Liang, Zongcun; Shen, Hui

2018-04-25

A high recombination rate and high thermal budget for aluminum (Al) back surface field are found in the industrial p-type silicon solar cells. Direct metallization on lightly doped p-type silicon, however, exhibits a large Schottky barrier for the holes on the silicon surface because of Fermi-level pinning effect. As a result, low-temperature-deposited, dopant-free chromium trioxide (CrO x , x < 3) with high stability and high performance is first applied in a p-type silicon solar cell as a hole-selective contact at the rear surface. By using 4 nm CrO x between the p-type silicon and Ag, we achieve a reduction of the contact resistivity for the contact of Ag directly on p-type silicon. For further improvement, we utilize a CrO x (2 nm)/Ag (30 nm)/CrO x (2 nm) multilayer film on the contact between Ag and p-type crystalline silicon (c-Si) to achieve a lower contact resistance (40 mΩ·cm 2 ). The low-resistivity Ohmic contact is attributed to the high work function of the uniform CrO x film and the depinning of the Fermi level of the SiO x layer at the silicon interface. Implementing the advanced hole-selective contacts with CrO x /Ag/CrO x on the p-type silicon solar cell results in a power conversion efficiency of 20.3%, which is 0.1% higher than that of the cell utilizing 4 nm CrO x . Compared with the commercialized p-type solar cell, the novel CrO x -based hole-selective transport material opens up a new possibility for c-Si solar cells using high-efficiency, low-temperature, and dopant-free deposition techniques.

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

Tokovinin, Andrei, E-mail: atokovinin@ctio.noao.edu

To improve the statistics of hierarchical multiplicity, secondary components of wide nearby binaries with solar-type primaries were surveyed at the SOAR telescope for evaluating the frequency of subsystems. Images of 17 faint secondaries were obtained with the SOAR Adaptive Module that improved the seeing; one new 0.''2 binary was detected. For all targets, photometry in the g', i', z' bands is given. Another 46 secondaries were observed by speckle interferometry, resolving 7 close subsystems. Adding literature data, the binarity of 95 secondary components is evaluated. We found that the detection-corrected frequency of secondary subsystems with periods in the well-surveyed rangemore » from 10{sup 3} to 10{sup 5} days is 0.21 ± 0.06—same as the normal frequency of such binaries among solar-type stars, 0.18. This indicates that wide binaries are unlikely to be produced by dynamical evolution of N-body systems, but are rather formed by fragmentation.« less

Photovoltaic solar cell

DOEpatents

Nielson, Gregory N; Cruz-Campa, Jose Luis; Okandan, Murat; Resnick, Paul J

2014-05-20

A photovoltaic solar cell for generating electricity from sunlight is disclosed. The photovoltaic solar cell comprises a plurality of spaced-apart point contact junctions formed in a semiconductor body to receive the sunlight and generate the electricity therefrom, the plurality of spaced-apart point contact junctions having a first plurality of regions having a first doping type and a second plurality of regions having a second doping type. In addition, the photovoltaic solar cell comprises a first electrical contact electrically connected to each of the first plurality of regions and a second electrical contact electrically connected to each of the second plurality of regions, as well as a passivation layer covering major surfaces and sidewalls of the photovoltaic solar cell.

Photovoltaic solar cell

DOEpatents

Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J

2013-11-26

A photovoltaic solar cell for generating electricity from sunlight is disclosed. The photovoltaic solar cell comprises a plurality of spaced-apart point contact junctions formed in a semiconductor body to receive the sunlight and generate the electicity therefrom, the plurality of spaced-apart point contact junctions having a first plurality of regions having a first doping type and a second plurality of regions having a second doping type. In addition, the photovoltaic solar cell comprises a first electrical contact electrically connected to each of the first plurality of regions and a second electrical contact electrically connected to each of the second plurality of regions, as well as a passivation layer covering major surfaces and sidewalls of the photovoltaic solar cell.

From wide to close binaries?

NASA Astrophysics Data System (ADS)

Eggleton, Peter P.

The mechanisms by which the periods of wide binaries (mass 8 solar mass or less and period 10-3000 d) are lengthened or shortened are discussed, synthesizing the results of recent theoretical investigations. A system of nomenclature involving seven evolutionary states, three geometrical states, and 10 types of orbital-period evolution is developed and applied; classifications of 71 binaries are presented in a table along with the basic observational parameters. Evolutionary processes in wide binaries (single-star-type winds, magnetic braking with tidal friction, and companion-reinforced attrition), late case B systems, low-mass X-ray binaries, and triple systems are examined in detail, and possible evolutionary paths are shown in diagrams.

BVR{sub c}I{sub c} observations and analyses on V2421 Cygni, a precontact W UMa binary

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

Samec, R. G.; Shebs, Travis S.; Faulkner, D. R.

2014-01-01

We present the first precision BVRI light curves, synthetic light curve solutions, and a period study for the high amplitude solar type binary, V2421 Cygni. The light curves have the appearance of an Algol (EA) type; however, it is made up of dwarf solar type components in a detached mode with a period of only 0.6331 days with an amplitude of about a full magnitude, i.e., it is a precontact W UMa binary. Flare-like disruptions occur in the light curves following the primary and secondary eclipses possibly due to the line-of-sight track of a gas stream. An associated stream spotmore » and splash spot cause bright equatorial spots on the stellar surface of the primary star. The more massive star is the gainer, making this system a classic, albeit dwarf, Algol.« less

Large area tunnel oxide passivated rear contact n -type Si solar cells with 21.2% efficiency: Large area tunnel oxide passivated rear contact n -type Si solar cells

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

Tao, Yuguo; Upadhyaya, Vijaykumar; Chen, Chia-Wei

This paper reports on the implementation of carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n+ polysilicon layer provides excellent rear contact passivation with implied open-circuit voltage iVoc of 714mV and saturation current density J0b of 10.3 fA/cm2 for the back surface field region. The durability of this passivation scheme is also investigated for a back-end high temperature process. In combination with an ion-implanted Al2O3-passivated boron emitter and screen-printed front metal grids,more » this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm2 commercial grade n-type Czochralski wafers.« less

Investigations into the thermal non-equilibrium of W UMa-type contact binaries

NASA Astrophysics Data System (ADS)

Xiong, Xiao; Liu, Liang; Qian, Sheng-Bang

2018-05-01

Traditionally, some physical details (e.g., magnetic braking, energy transfer, angular momentum loss, etc.) have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio (M 2/M 1) of a contact system, the weaker the deviation from thermal equilibrium. On this basis, a variation trend of fill-out factor (f) changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase.

The CHARA Array Resolves the 1.1 Day Period Spectroscopic Binary HD 146361, the Shortest Period System Resolved To-Date

NASA Astrophysics Data System (ADS)

Raghavan, Deepak; McAlister, H. A.

2007-12-01

We present a visual orbit for the spectroscopic binary, HD 146361, derived from observations at the CHARA Array's long baseline interferometer. The 26 calibrated visibility measurements obtained during May - July 2007 allow us to determine a full orbital solution and component masses for this known spectroscopic binary. The HD 146361 pair has a circular orbit of nearly equal-mass components with a good quality double-lined spectroscopic orbit (Dave Latham, private communication). We have adopted the well-constrained spectroscopic orbital elements and fit the angular semi-major axis, inclination, and longitude of nodes to the binary visibility curve equations. Using these elements and the Hipparcos parallax of 46.11 ± 0.98 mas, we obtain component masses of 1.046 ± 0.084 Msol and 1.000 ± 0.080 Msol. We have planned further observations of this system to reduce the mass uncertainties and may present an updated result at the meeting. This is the shortest period spectroscopic binary resolved as of yet with an interferometer. This work is being done in the context of Raghavan's thesis project, which is a survey of solar-type stars in the solar neighborhood. By completing this survey, we hope to build a comprehensive view of the environments around solar-type stars and improve our understanding of their habitats by analyzing their companions of all types - stars, brown dwarfs, and planets. We have chosen an unbiased, volume-limited sample of 455 primary stars as representatives of the solar-type stars in our Galaxy. Our effort is a modern update to the seminal work of Duquennoy & Mayor (1991) and will contribute to the broader subjects of stellar evolution and planetary system formation, evolution, and stability. Research at the CHARA Array is supported by the College of Arts and Sciences at Georgia State University and by the National Science Foundation through NSF Grant AST 0606958.

Three close binaries in different evolutionary stages in the old open cluster NGC 188

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

Zhu, L. Y.; Qian, S. B.; Liu, L.

2014-02-01

NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q = 0.15, while ES Cep has a relatively high-mass ratio, q = 0.69,more » indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.« less

DIRECT N-BODY MODELING OF THE OLD OPEN CLUSTER NGC 188: A DETAILED COMPARISON OF THEORETICAL AND OBSERVED BINARY STAR AND BLUE STRAGGLER POPULATIONS

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

Geller, Aaron M.; Hurley, Jarrod R.; Mathieu, Robert D., E-mail: a-geller@northwestern.edu, E-mail: mathieu@astro.wisc.edu, E-mail: jhurley@astro.swin.edu.au

2013-01-01

Following on from a recently completed radial-velocity survey of the old (7 Gyr) open cluster NGC 188 in which we studied in detail the solar-type hard binaries and blue stragglers of the cluster, here we investigate the dynamical evolution of NGC 188 through a sophisticated N-body model. Importantly, we employ the observed binary properties of the young (180 Myr) open cluster M35, where possible, to guide our choices for parameters of the initial binary population. We apply pre-main-sequence tidal circularization and a substantial increase to the main-sequence tidal circularization rate, both of which are necessary to match the observed tidalmore » circularization periods in the literature, including that of NGC 188. At 7 Gyr the main-sequence solar-type hard-binary population in the model matches that of NGC 188 in both binary frequency and distributions of orbital parameters. This agreement between the model and observations is in a large part due to the similarities between the NGC 188 and M35 solar-type binaries. Indeed, among the 7 Gyr main-sequence binaries in the model, only those with P {approx}> 1000 days begin to show potentially observable evidence for modifications by dynamical encounters, even after 7 Gyr of evolution within the star cluster. This emphasizes the importance of defining accurate initial conditions for star cluster models, which we propose is best accomplished through comparisons with observations of young open clusters like M35. Furthermore, this finding suggests that observations of the present-day binaries in even old open clusters can provide valuable information on their primordial binary populations. However, despite the model's success at matching the observed solar-type main-sequence population, the model underproduces blue stragglers and produces an overabundance of long-period circular main-sequence-white-dwarf binaries as compared with the true cluster. We explore several potential solutions to the paucity of blue stragglers and conclude that the model dramatically underproduces blue stragglers through mass-transfer processes. We suggest that common-envelope evolution may have been incorrectly imposed on the progenitors of the spurious long-period circular main-sequence-white-dwarf binaries, which perhaps instead should have gone through stable mass transfer to create blue stragglers, thereby bringing both the number and binary frequency of the blue straggler population in the model into agreement with the true blue stragglers in NGC 188. Thus, improvements in the physics of mass transfer and common-envelope evolution employed in the model may in fact solve both discrepancies with the observations. This project highlights the unique accessibility of open clusters to both comprehensive observational surveys and full-scale N-body simulations, both of which have only recently matured sufficiently to enable such a project, and underscores the importance of open clusters to the study of star cluster dynamics.« less

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2013-07-23

Methods of forming contacts for back-contact solar cells are described. In one embodiment, a method includes forming a thin dielectric layer on a substrate, forming a polysilicon layer on the thin dielectric layer, forming and patterning a solid-state p-type dopant source on the polysilicon layer, forming an n-type dopant source layer over exposed regions of the polysilicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions.

The Algol-like binary TT Hydrae - The stars, circumstellar matter, and superionized plasma

NASA Technical Reports Server (NTRS)

Plavec, Mirek J.

1988-01-01

This paper reports on superionized UV emission lines discovered in TT Hydrae (HD 97528), a semidetached eclipsing binary system in the Southern-Hemisphere sky. The list of emission lines observed is typical for interacting nondegenerate binaries of the Algol type, but with system-specific relative-intensity characteristics. The primary component of the system is a B9.5 V main-sequence star with effective temperature of 9800 K. Its mass equals 2.25 solar masses; the radius is 1.9 solar radii; and surface gravity log g equals 4.23. The secondary star has a mass of 0.41 solar mass and fills its critical Roche lobe. Evidence obtained on mass interaction supports the conclusion that HD 97528 is a normal semidetached system.

WW Geminorum: An Early B-type Eclipsing Binary Evolving into the Contact Phase

NASA Astrophysics Data System (ADS)

Yang, Y.-G.; Yang, Y.; Dai, H.-F.; Yin, X.-G.

2014-11-01

WW Gem is a B-type eclipsing binary with a period of 1.2378 days. The CCD photometry of this binary was performed in 2013 December using the 85 cm telescope at the Xinglong Stations of the National Astronomical Observatories of China. Using the updated W-D program, the photometric model was deduced from the VRI light curves. The results imply that WW Gem is a near-contact eclipsing binary whose primary component almost fills its Roche lobe. The photometric mass ratio is q ph = 0.48(± 0.05). All collected times of minimum light, including two new ones, were used for the period studies. The orbital period changes of WW Gem could be described by an upward parabola, possibly overlaid by a light-time orbit with a period of P mod = 7.41(± 0.04) yr and a semi-amplitude of A = 0.0079 days(± 0.0005 days), respectively. This kind of cyclic oscillation may be attributed to the light-travel time effect via the third body. The long-term period increases at a rate of dP/dt = +3.47(±0.04) × 10-8 day yr-1, which may be explained by the conserved mass transfer from the less massive component to the more massive one. With mass transfer, the massive binary WW Gem may be evolving into a contact binary.

LY Aurigua: A mass-transferring O-type contact binary with a tertiary stellar companion

NASA Astrophysics Data System (ADS)

Zhao, Ergang; Qian, Shengbang; Li, Linjia; He, Jiajia; Liu, Liang; Wang, Jingjing; Zhang, Jia

2014-01-01

LY Aur is a contact massive close binary with a period of a little more than four days. The first O-C analysis of this early-type binary presented in this paper suggests that the period of the system is increasing continuously at a rate of dP/dt=+7.2×10-7 days/year, while a cyclic oscillation with the period of 12.5 years is obvious. The long-term increasing can be explained by mass transfer from the less massive companion to the more one on the nuclear time-scale of less massive body, which suggests that the contact configuration will be broken and this binary will evolve into a semi-detached system. The periodic oscillation may be the consequence of the light-travel time effect of the third body, whose mass is no less than 3.4 M⊙. It is expected that the third body may play an important role for the origin and evolution of the system by removing angular momentum from the central system, making the eclipsing pairs to have a low angular momentum, while initially it may have had a longer orbital period, with larger angular momentum. The original system may have evolved into the present contact configuration via a case A mass transfer.

Numerical Simulations of Close and Contact Binary Systems Having Bipolytropic Equation of State

NASA Astrophysics Data System (ADS)

Kadam, Kundan; Clayton, Geoffrey C.; Motl, Patrick M.; Marcello, Dominic; Frank, Juhan

2017-01-01

I present the results of the numerical simulations of the mass transfer in close and contact binary systems with both stars having a bipolytropic (composite polytropic) equation of state. The initial binary systems are obtained by a modifying Hachisu’s self-consistent field technique. Both the stars have fully resolved cores with a molecular weight jump at the core-envelope interface. The initial properties of these simulations are chosen such that they satisfy the mass-radius relation, composition and period of a late W-type contact binary system. The simulations are carried out using two different Eulerian hydrocodes, Flow-ER with a fixed cylindrical grid, and Octo-tiger with an AMR capable cartesian grid. The detailed comparison of the simulations suggests an agreement between the results obtained from the two codes at different resolutions. The set of simulations can be treated as a benchmark, enabling us to reliably simulate mass transfer and merger scenarios of binary systems involving bipolytropic components.

The Search for Bright Variable Stars in Open Cluster NGC 6819.

NASA Astrophysics Data System (ADS)

Talamantes, Antonio; Sandquist, E. L.

2009-01-01

During this research period data was taken for seven nights at the 1m telescope at Mt. Laguna Observatory for the open cluster NGC 6819. For four of the nights data was taken using a V-band filter. For the three nights remaining nights the data was taken using an R-band filter. Photometry was done using the ISIS image subtraction package. Six new variable stars were located using these techniques. These variable types include a pulsating variable, five detached eclipsing binaries. Of the detached eclipsing binaries, three are near the cluster turnoff and two in the blue straggler region(and one of these has total eclipses). Nine previously known variables(six contact binaries, two detached eclipsing binaries and one near-contact binary) were also studied.

BVRI Photometric Study of the Short Period, Solar Type, Semi-Detached Binary, NSVS 10083189

NASA Astrophysics Data System (ADS)

Samec, Ronald G.; Caton, Daniel B.; Olsen, Amber; Faulkner, Danny R.; Hill, Robert L.

2017-06-01

Precision BVRcIc light curves of NSVS 5066754 were taken on 11 nights in February through April 2015 at Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University and on 1 night on the SARA 1-m reflector at Kitt Peak National Observatory in remote mode. It is an ~ F8V eclipsing binary with a period of 0.4542238 (2) d.Seven times of minimum light were calculated, for 5 primary and 2 secondary eclipses from our present observations:HJD I = 2457067.75453±0.0003, 2457088.64907±0.0001, 2457089.55708±0.0001, 2457098.64163±0.0004, 24557113.63117±0.0002HJD II = 2457066.61874±0.0008, 2457067.52329±0.0017.In addition, seven observations at minima were introduced as low weighted times of minimum light taken from archived NSVS Data.The following decreasing quadratic ephemeris was determined from all available times of minimum light in this study covering some 15 years:JD Hel MinI = 2457089.55665±0.00054d + 0.4542179±0. 0000006 X E -0.00000000049±0.00000000005 × E2We note that this result has a strong level of confidence. This again gives evidence that the components are coming into contact possibly due to magnetic braking as indicated by dark spot activity on the binary.We initially modeled the B,V,R,I curves simultaneously with the Wilson-Devinney program in a shallow contact configuration (mode 3) as indicated by our Binary Maker 3 fits. This led to a near but non-contact configuration. Next, the general Mode 2 was used to give clues regarding the configuration. During this investigation, the primary component came into contact while the secondary star remained detached. Next, a solution was determined in a semidetached, mode 4 state (larger component filling its critical lobe and the secondary under filing. This may indicate that NSVS 10083189 is coming into contact for the first time. The mode and the period change corroborate.Our semi-detached, near contact solution, gave a mass ratio of 0.58, with component temperatures of 6250 and 4573 K. A 15° radius cool spot with a t-factor of 0.85 was determined on the primary star. The fill-out of the secondary star was 99%. Further details will be given in our poster paper.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2015-10-20

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2014-07-15

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

First Photometric Investigation of the Neglected EW-type Binary System V502 Her

NASA Astrophysics Data System (ADS)

Zhao, Ergang; Qian, Shengbang; Liao, Wenping; He, Jiajia; Shi, Xiangdong; Zhang, Jia

2018-04-01

V502 Her is a neglected EW-type binary, which has been known for more than 60 years. The first multi-color CCD photometric light curve and spectroscopic observations of contact binary V502 Her was obtained. Based on the LAMOST data, its spectrum can be found to be F5. Together with solutions of light curves by using the Wilson-Devinney code, it infers that V502 Her is an A-type W UMa contact binary system with the mass ratio of q = 0.313 and the filling factor of f = 38.1%. According to all minimum times from the literature and our observations, the orbital period was analyzed and a long-term increase with a periodic change (P 3 = 26.8 years) was computed. The orbital period increase may be caused by the mass transfer from a less-massive component to the more massive one, which indicates that V502 Her is in the thermal relaxation oscillation (TRO) controller stage, while the light-travel time effect (LTTE) through the presence of a cool third body may lead to the periodic variation.

Low mass companions to nearby stars: Spectral classification and its relation to the stellar/substellar break

NASA Technical Reports Server (NTRS)

Kirkpatrick, J. Davy; Mccarthy, Donald W., Jr.

1994-01-01

The relationship between mass and spectral class for main-sequence stars has never been obtained for dwarfs cooler than M6; currently, the true nature of objects classified as M7, M8, M9, or later (be they stellar or substellar) is not known. In this paper, spectral types for the components in five low mass binary systems are estimated based on previously published infrared speckle measurements, red/infrared photometry, and parallax data, together with newly acquired high signal-to-noise composite spectra of the systems and revised magnitude difference relations for M dwarfs. For two of these binaries, the secondary has a smaller mass (less than 0.09 solar mass) than any object having a dynamically measured mass and a known spectral type, thus extending the spectral class/mass relation to lower masses than has previously been possible. Data from the higher mass components (0.09 solar mass less than M less than 0.40 solar mass) are consistent with earlier results; the two lowest mass objects -- though having mass errors which could place them on either side of the M dwarf/brown dwarf dividing line (Mass is about 0.08 solar mass) -- are found to have spectral types no cooler than M6.5 V. An extrapolation of the updated spectral class/mass relation to the hydrogen-burning limit suggests that objects of type M7 and later may be substellar. Direct confirmation of this awaits the discovery of a close, very late-type binary for which dynamical masses can be measured.

New Results on Contact Binary Stars

NASA Astrophysics Data System (ADS)

He, J.; Qian, S.; Zhu, L.; Liu, L.; Liao, W.

2014-08-01

Contact binary star is a kind of close binary with the strongest interaction binary system. Their formations and evolutions are unsolved problems in astrophysics. Since 2000, our groups have observed and studied more than half a hundred of contact binaries. In this report, I will summarize our new results of some contact binary stars (e.g. UZ CMi, GSC 03526-01995, FU Dra, GSC 0763-0572, V524 Mon, MR Com, etc.). They are as follow: (1) We discovered that V524 Mon and MR Com are shallow-contact binaries with their period decreasing; (2) GSC 03526-01995 is middle-contact binary without a period increasing or decreasing continuously; (3) UZ CMi, GSC 0763-0572 and FU Dra are middle-contact binaries with the period increasing continuously; (4) UZ CMi, GSC 03526-01995, FU Dra and V524 Mon show period oscillation which may imply the presence of additional components in these contact binaries.

The Solar-Type Hard-Binary Frequency and Distributions of Orbital Parameters in the Open Cluster M37

NASA Astrophysics Data System (ADS)

Geller, Aaron M.; Meibom, Soren; Barnes, Sydney A.; Mathieu, Robert D.

2014-02-01

Binary stars, and particularly the short-period ``hard'' binaries, govern the dynamical evolution of star clusters and determine the formation rates and mechanisms for exotic stars like blue stragglers and X-ray sources. Understanding the near-primordial hard-binary population of star clusters is of primary importance for dynamical models of star clusters, which have the potential to greatly advance our understanding of star cluster evolution. Yet the binary frequencies and distributions of binary orbital parameters (period, eccentricity, etc.) for young coeval stellar populations are poorly known, due to a lack of necessary observations. The young (~540 Myr) open cluster M37 hosts a rich binary population that can be used to empirically define these initial conditions. Importantly, this cluster has been the target of a comprehensive WIYN/Hydra radial-velocity (RV) survey, from which we have already identified a nearly complete sample of 329 solar-type (1.5 <=M [M_⊙] <=1.0) members in M37. Of these stars, 82 show significant RV variability, indicative of a binary companion. We propose to build upon these data with a multi-epoch RV survey using WIYN/Hydra to derive kinematic orbital solutions for these 82 binaries in M37. This project was granted time in 2013B and scheduled for later this year. We anticipate that about half of the detected binaries in M37 will acquire enough RV measurements (>=10) in 2013B to begin searching for orbital solutions. With this proposal and perhaps one additional semester we should achieve >=10 RV measurements for the remaining binaries.

The first photometric investigation and orbital period variation analysis of the W UMa type binary IK Bootis

NASA Astrophysics Data System (ADS)

Kriwattanawong, Wichean; Sanguansak, Nuanwan; Maungkorn, Sakdawoot

2017-08-01

With new CCD observations of the W UMa type binary IK Boo, we present the first investigation of photometric parameters and orbital period change. The BVRc light curve fit shows that IK Boo is a W-type contact system with a mass ratio of q = 1.146 and a shallow contact with a fill-out factor of f = 2.22%. The orbital period decrease was found to be a rate of -3.28 × 10-7 d yr-1, corresponding to a mass transfer from the more massive to the less massive component with a rate of -2.83 × 10-6 M⊙ yr-1. The inner and outer critical Roche lobes will contract and cause the contact degree to increase. Therefore, IK Boo may evolve into a deeper contact system. Furthermore, a possible cyclic variation was found with a period of 9.74 yr, which could be explained by the light-travel time effect due to the existence of a third companion in the system.

WW Geminorum: An early B-type eclipsing binary evolving into the contact phase

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

Yang, Y.-G.; Dai, H.-F.; Yin, X.-G.

2014-11-01

WW Gem is a B-type eclipsing binary with a period of 1.2378 days. The CCD photometry of this binary was performed in 2013 December using the 85 cm telescope at the Xinglong Stations of the National Astronomical Observatories of China. Using the updated W-D program, the photometric model was deduced from the VRI light curves. The results imply that WW Gem is a near-contact eclipsing binary whose primary component almost fills its Roche lobe. The photometric mass ratio is q {sub ph} = 0.48(± 0.05). All collected times of minimum light, including two new ones, were used for the periodmore » studies. The orbital period changes of WW Gem could be described by an upward parabola, possibly overlaid by a light-time orbit with a period of P {sub mod} = 7.41(± 0.04) yr and a semi-amplitude of A = 0.0079 days(± 0.0005 days), respectively. This kind of cyclic oscillation may be attributed to the light-travel time effect via the third body. The long-term period increases at a rate of dP/dt = +3.47(±0.04) × 10{sup –8} day yr{sup –1}, which may be explained by the conserved mass transfer from the less massive component to the more massive one. With mass transfer, the massive binary WW Gem may be evolving into a contact binary.« less

WIYN OPEN CLUSTER STUDY. XLVIII. THE HARD-BINARY POPULATION OF NGC 188

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

Geller, Aaron M.; Mathieu, Robert D., E-mail: a-geller@northwestern.edu, E-mail: mathieu@astro.wisc.edu

2012-08-15

We present an in-depth study of the hard-binary population of the old (7 Gyr) open cluster NGC 188. Utilizing 85 spectroscopic binary orbits out of a complete sample of 129 detected binary members, we study the cluster binary frequency and the distributions of binary orbital elements among the main-sequence (MS), giant, and blue straggler (BS) populations. The results are derived from our ongoing radial velocity survey of the cluster, which spans in magnitude from the brightest stars in the cluster to V = 16.5 (about 1.1-0.9 M{sub Sun} ), and extends to a projected radius of 17 pc ({approx}13 coremore » radii). Our detectable binaries have periods ranging from a few days to of order 10{sup 4} days, and thus are hard binaries that dynamically power the cluster. The MS solar-type hard binaries in NGC 188 are nearly indistinguishable from similar binaries in the Galactic field. We observe a global solar-type MS hard-binary frequency in NGC 188 of 23% {+-} 2%, which when corrected for incompleteness results in a frequency of 29% {+-} 3% for binaries with periods less than 10{sup 4} days. For MS hard binaries in the cluster, we observe a log-period distribution that rises toward our detection limit, a roughly Gaussian eccentricity distribution centered on e = 0.35 (for binaries with periods longer than the circularization period), and a secondary-mass distribution that rises toward lower-mass companions. Importantly, the NGC 188 BS binaries show significantly different characteristics than the solar-type MS binaries in NGC 188. We observe a BS hard-binary frequency of 76% {+-} 19%, three times that of the MS. The excess of this binary frequency over the normal MS binary frequency is valid at the >99% confidence level. Furthermore, the BS binary eccentricity-log-period distribution is distinct from that of the MS at the 99% confidence level, with the majority of the BS binaries having periods of order 1000 days and lower eccentricities. The secondary-mass distribution for these long-period BS binaries is narrow and peaked with a mean value of about 0.5 M{sub Sun }. Predictions for mass-transfer products are most closely consistent with the binary properties of these NGC 188 BSs, which comprise two-thirds of the BS population. Additionally, we compare the NGC 188 binaries to those evolved within the sophisticated Hurley et al. (2005) N-body open cluster simulation. The MS hard-binary population predicted by the simulation is significantly different from the MS hard-binary population observed in NGC 188, in frequency and distributions of period and eccentricity. Many of these differences result from the adopted initial binary population, while others reflect on the physics used in the simulation (e.g., tidal circularization). Additional simulations with initial conditions that are better motivated by observations are necessary to properly investigate the dynamical evolution of a rich binary population in open clusters like NGC 188.« less

First Precision Photometric Observations and Analyses of The Totally Eclipsing, Solar Type Binary, V573 Pegasi

NASA Astrophysics Data System (ADS)

Samec, Ronald G.; Caton, Daniel B.; Faulkner, Danny R.

2018-06-01

CCD, VRI light curves of V573 Peg were taken in 26,27 September and 2, 4 and 6 October, 2017 at the Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University by D. Caton. V573 Peg was discovered by the SAVS survey which classified it as a V= 0.51 amplitude, EW variable. They included a rough spectrum identifying the binary was about a type G, although the period would indicate it is an F-type contact binary. Five times of minimum light were calculated, two primary eclipses and three secondary, from our present observations:HJD I = 2458023.6420±0.0012, 2458028.6522±0.0021,HJD II = 2458022.5991±0.0011, 2458023.8510±0.0010 and 2458028.8608±0.0005,The following linear and quadratic ephemerides were determined from all available times of minimum light.JD Hel MinI = 2456876.49437±0.00078d + 0.41745021±0. 00000017 × E, -JD Hel MinI = 2456876.49580±0.00023d + 0. 417448601±0.000000083× E - 0.000000000274±0.000000000012 X E2A 14-year period study (24 times of minimum light) revealed that the orbital period decreasing with a high level of confidence, possibly due to magnetic braking. The mass ratio is found to be somewhat extreme, M2/M1=0.2629±0.0006.Its Roche Lobe fill-out is 25%. The solution had no need of spots. The temperature difference of the components is about ~130 K, with the secondary as the hotter star, so it is a W-type W UMa Binary. The inclination is 80.4±0.1° . The secondary eclipse shows a time of constant light with an eclipse duration of 24 minutes. More details of our results will be given at the meeting.

Absolute and geometric parameters of contact binary GW Cnc

NASA Astrophysics Data System (ADS)

Gürol, B.; Gökay, G.; Saral, G.; Gürsoytrak, S. H.; Cerit, S.; Terzioğlu, Z.

2016-07-01

We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system GW Cnc. We analyzed the photometric data obtained in 2010 and 2011 at Ankara University Observatory (AUO) and the spectroscopic data obtained in 2010 at TUBITAK National Observatory (TUG) by using the Wilson-Devinney (2013 revision) code to obtain the absolute and geometrical parameters. We derived masses and radii of the eclipsing system to be M1 = 0.257M⊙ , M2 = 0.971M⊙ , R1 = 0.526R⊙ and R2 = 0.961R⊙ with an orbital inclination i(∘) = 83.38 ± 0.25 and we determined the GW Cnc system to be a W-type W UMa over-contact binary with a mass ratio of q = 3.773 ± 0.007 .

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars

NASA Astrophysics Data System (ADS)

Moe, Maxwell; Di Stefano, Rosanne

2017-06-01

We compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, common proper motion, etc. Each observational technique is sensitive to companions across a narrow parameter space of orbital periods P and mass ratios q = {M}{comp}/M 1. After combining the samples from the various surveys and correcting for their respective selection effects, we find that the properties of companions to O-type and B-type main-sequence (MS) stars differ among three regimes. First, at short orbital periods P ≲ 20 days (separations a ≲ 0.4 au), the binaries have small eccentricities e ≲ 0.4, favor modest mass ratios < q> ≈ 0.5, and exhibit a small excess of twins q > 0.95. Second, the companion frequency peaks at intermediate periods log P (days) ≈ 3.5 (a ≈ 10 au), where the binaries have mass ratios weighted toward small values q ≈ 0.2-0.3 and follow a Maxwellian “thermal” eccentricity distribution. Finally, companions with long orbital periods log P (days) ≈ 5.5-7.5 (a ≈ 200-5000 au) are outer tertiary components in hierarchical triples and have a mass ratio distribution across q ≈ 0.1-1.0 that is nearly consistent with random pairings drawn from the initial mass function. We discuss these companion distributions and properties in the context of binary-star formation and evolution. We also reanalyze the binary statistics of solar-type MS primaries, taking into account that 30% ± 10% of single-lined spectroscopic binaries likely contain white dwarf companions instead of low-mass stellar secondaries. The mean frequency of stellar companions with q > 0.1 and log P (days) < 8.0 per primary increases from 0.50 ± 0.04 for solar-type MS primaries to 2.1 ± 0.3 for O-type MS primaries. We fit joint probability density functions f({M}1,q,P,e)\

Encapsulant Characterization and Doped Passivated Contacts for Use in a Luminescent Solar Concentrator

NASA Astrophysics Data System (ADS)

Fogel, Derek

We report progress towards encapsulant characterization and the fabrication of passivated interdigitated back contact silicon solar cells using spin-on dopants for use in a luminescent solar concentrator. For the luminescent solar concentrator to be successful, the encapsulants used to assemble the final device must not contribute to optical losses and the tandem cell must exhibit excellent passivation and low contact resistivity values. The index of refraction of polydimethylsiloxane (PDMS) is calculated to be 1.405-1.415 for 600-800 nm and 1.475-1.505 is calculated for ethylene vinyl acetate (EVA). The absorption coefficient is calculated to be less than 0.1 cm-1 for PDMS and less than 0.5 cm-1 for EVA at wavelengths less than 1000 nm. Polysilicon / SiOx passivated contact symmetric structures grown using plasma-enhanced chemical vapor deposition (PECVD) and low pressure chemical vapor deposition (LPCVD) and subsequently doped using P, B, and Ga spin-on dopants are fabricated, and their passivation and contact properties are analyzed. The n-type, P-doped passivated contact gives an implied open circuit voltage (iVOC) of 708 mV in PECVD and 727 mV in LPCVD. The p-type, B-doped passivated contact gives an iVOC of 667 mV in PECVD and 689 mV in LPCVD. The p-type, Ga-doped passivated contact, which has not been previously reported, gives an iVOC of 731 mV in PECVD and 714 mV in LPCVD. For the n-type, P-doped contact a low metal to polysilicon contact resistivity of 23.8 mO-cm2 was measured for Al on PECVD and 15.8 mO-cm2 was measured for Al on LPCVD. For the p-type, B-doped contact a low metal to polysilicon contact resistivity of 0.3 mO-cm2 was measured for Al on LPCVD. These results are encouraging for the processing of passivated interdigitated back contact solar cells, and present a route towards high-efficiency Si PV at low cost.

Physical Parameters of Components in Close Binary Systems: IV

NASA Astrophysics Data System (ADS)

Gazeas, K. D.; Baran, A.; Niarchos, P.; Zola, S.; Kreiner, J. M.; Ogloza, W.; Rucinski, S. M.; Zakrzewski, B.; Siwak, M.; Pigulski, A.; Drozdz, M.

2005-03-01

The paper presents new geometric, photometric and absolute parameters, derived from combined spectroscopic and photometric solutions, for ten contact binary systems. The analysis shows that three systems (EF Boo, GM Dra and SW Lac) are of W-type with shallow to moderate contact. Seven systems (V417 Aql, AH Aur, YY CrB, UX Eri, DZ Psc, GR Vir and NN Vir) are of A-type in a deep contact configuration. For six systems (V417 Aql, YY CrB, GM Dra, UX Eri, SW Lac and GR Vir) a spot model is introduced to explain the O'Connell effect in their light curves. The photometric and geometric elements of the systems are combined with the spectroscopic data taken at David Dunlap Observatory to yield the absolute parameters of the components.

UBV Photometry of Selected Eclipsing Binaries in the Magellanic Clouds.

NASA Astrophysics Data System (ADS)

Davidge, Timothy John

1987-12-01

UBV photoelectric observations of five eclipsing binaries in the Magellanic Clouds are presented and discussed in detail. The systems studied are HV162O and HV1669 in the Small Magellanic Cloud and HV2241, HV2765, and HV5943 in the Large Magellanic Cloud. Classification spectra indicate that the components of these systems are of spectral type late O or early B. The systems are located in moderately crowded areas. Therefore, CCD observations were used to construct models of the star fields around the variables. These were used to correct the photoelectric measurements for contamination. Light curve solutions were found with the Wilson -Devinney program. A two dimensional search of parameter space involving the mass ratio and the surface potential of the secondary component was employed. This procedure was tested by numerical simulation and was found to predict the light curve elements, including the mass ratios, within their estimated uncertainties. It appears likely that none of the systems are in contact, a surprising result considering the high frequency of early type contact binaries in the solar neighborhood. The light curve solutions were then used to compute the absolute dimensions of the components. Only one system, HV2241, has a radial velocity curve, allowing its absolute dimensions to be well established. Less accurate absolute dimensions were calculated for the remaining systems using photometric information. The components were then placed on H-R diagrams and compared with theoretical models of stellar evolution. The positions of the components on these diagrams appear to support the existence of convective core overshooting. The evolutionary status of the systems was also discussed. The system with the most accurately determined absolute dimensions, HV2241, appears to have undergone, or is nearing the end of, Case A mass transfer. Two other systems, HV1620 and HV1669, may also be involved in mass transfer. Finally, the use of eclipsing binaries as distance indicators was investigated. The distance modulus of the LMC was computed in two ways. One approach used the absolute dimensions found with the radial velocity data while the other employed the method of photometric parallaxes. The latter technique was also used to calculate the distance modulus of the SMC.

SARA South Observations and Analysis of the Solar Type, Totally Eclipsing, Over Contact Binary, PY Aquarii

NASA Astrophysics Data System (ADS)

Chamberlain, Heather; Samec, Ronald G.; Caton, Daniel Bruce; Van Hamme, Walter

2018-01-01

PY Aqr (GSC 05191-00853) is a solar Type (T ~ 5750K) eclipsing binary. It was observed in July to October, 2017 at Cerro Tololo in remote mode with the 0.6-m SARA South reflector. Two times of minimum light were calculated from our present observations, a primary and a secondary eclipse:HJD Min I = 2457951.7762±0.0006 HJD Min II = 2458019.5295±00.0003. Both weighted as 1.0.In addition, four timings were determined from online data given in IBVS 5600 and five observations at minima were determined from archived All Sky Automated Survey Data:HJD Min I = 2452908.3165, 2452912.33612 HJD Min II = 2452877.5621, 2452913.34465. All weighted as 0.5.ASAS Observations at minima: 2452094.688, 2453478.882, 2453266.576, 2452093.685 and 54729.600. Each weighted as 0.10The following linear and quadratic ephemerides were determined from all available times of minimum light:JD Hel Min I=2452951.7443±0.0008d + 0.402093441±0.000000099 X E {1} JD Hel Min I=2452951.7439±0.0007d + 0.4020912±0.0000007 X E +0.00000000018 ± 0.00000000006 X E2 {2}A BVRI Bessell filtered simultaneous Wilson-Devinney Program (W-D) solution reveals that the system has a mass ratio of ~0.34 and a component temperature difference of only ~40 K. One low luminosity (Tfact ~ 0.94, ~66 degree radius) large cool region of spots was iterated on the primary component in the WD Synthetic Light Curve computations. It appears in the Southern Hemisphere (colatitude 155 degrees). The Roche Lobe fill-out of the binary is ~17%. The inclination is ~86 degrees. An eclipse duration of ~10 minutes was determined for the primary eclipse and the light curve solution. Additional and more detailed information is given in this report.

Period Study and Analyses of 2017 Observations of the Totally Eclipsing, Solar Type Binary, MT Camelopardalis

NASA Astrophysics Data System (ADS)

Faulkner, Danny R.; Samec, Ronald G.; Caton, Daniel B.

2018-06-01

We report here on a period study and the analysis of BVRcIc light curves (taken in 2017) of MT Cam (GSC03737-01085), which is a solar type (T ~ 5500K) eclipsing binary. D. Caton observed MT Cam on 05, 14, 15, 16, and 17, December 2017 with the 0.81-m reflector at Dark Sky Observatory. Six times of minimum light were calculated from four primary eclipses and two secondary eclipses:HJD I = 24 58092.4937±0.0002, 2458102.74600±0.0021, 2458104.5769±0.0002, 2458104.9434±0.0029HJD II = 2458103.6610±0.0001, 2458104.7607±0.0020,Six times of minimum light were also calculated from data taken by Terrell, Gross, and Cooney, in their 2016 and 2004 observations (reported in IBVS #6166; TGC, hereafter). In addition, six more times of minimum light were taken from the literature. From all 18 times of minimum light, we determined the following light elements:JD Hel Min I=2458102.7460(4) + 0.36613937(5) EWe found the orbital period was constant over the 14 years spanning all observations. We note that TGC found a slightly increasing period. However, our results were obtained from a period study rather than comparison of observations from only two epochs by the Wilson-Devinney (W-D) Program. A BVRcIc Johnson-Cousins filtered simultaneous W-D Program solution gives a mass ratio (0.3385±0.0014) very nearly the same as TGC’s (0.347±0.003), and a component temperature difference of only ~40 K. As with TGC, no spot was needed in the modeling. Our modeling (beginning with Binary Maker 3.0 fits) was done without prior knowledge of TGC’s. This shows the agreement achieved when independent analyses are done with the W-D code. The present observations were taken 1.8 years later than the last curves by TGC, so some variation is expected.The Roche Lobe fill-out of the binary is ~13% and the inclination is ~83.5 degrees. The system is a shallow contact W-type W UMa Binary, albeit, the amplitudes of the primary and secondary eclipse are very nearly identical. An eclipse duration of ~21 minutes was determined for the secondary eclipse and the light curve solution. Additional and more detailed information is given in the poster paper.

Rotational Synchronization May Enhance Habitability for Circumbinary Planets: Kepler Binary Case Studies

NASA Astrophysics Data System (ADS)

Mason, Paul A.; Zuluaga, Jorge I.; Clark, Joni M.; Cuartas-Restrepo, Pablo A.

2013-09-01

We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.

Are Binary Separations related to their System Mass?

NASA Astrophysics Data System (ADS)

Sterzik, M. F.; Durisen, R. H.

2004-08-01

We compile most recent multiplicity fractions and binary separation distributions for different primary masses, including very low-mass and brown dwarf primaries, and compare them with dynamical decay models of small-N clusters. The model predictions are based on detailed numerical calculations of the internal cluster dynamics, as well as on Monte-Carlo methods. Both observations and models reflect the same trends: (1) The multiplicity fraction is an increasing function of the primary mass. (2) The mean binary separations are increasing with the system mass in the sense that very low-mass binaries have average separations around ≈ 4AU, while the binary separation distribution for solar-type primaries peaks at ≈ 40AU. M-type binary systems apparently preferentially populate intermediate separations. Similar specific energy at the time of cluster formation for all cluster masses can possibly explain this trend.

The first eclipsing binary catalogue from the MOA-II data base

NASA Astrophysics Data System (ADS)

Li, M. C. A.; Rattenbury, N. J.; Bond, I. A.; Sumi, T.; Bennett, D. P.; Koshimoto, N.; Abe, F.; Asakura, Y.; Barry, R.; Bhattacharya, A.; Donachie, M.; Evans, P.; Freeman, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Saito, To.; Sharan, A.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Yonehara, A.

2017-09-01

We present the first catalogue of eclipsing binaries in two MOA (Microlensing Observations in Astrophysics) fields towards the Galactic bulge, in which over 8000 candidates, mostly contact and semidetached binaries of periods <1 d, were identified. In this paper, the light curves of a small number of interesting candidates, including eccentric binaries, binaries with noteworthy phase modulations and eclipsing RS Canum Venaticorum type stars, are shown as examples. In addition, we identified three triple object candidates by detecting the light-travel-time effect in their eclipse time variation curves.

A ROSAT Survey of Contact Binary Stars

NASA Astrophysics Data System (ADS)

Geske, M. T.; Gettel, S. J.; McKay, T. A.

2006-01-01

Contact binary stars are common variable stars that are all believed to emit relatively large fluxes of X-rays. In this work we combine a large new sample of contact binary stars derived from the ROTSE-I telescope with X-ray data from the ROSAT All Sky Survey (RASS) to estimate the X-ray volume emissivity of contact binary stars in the Galaxy. We obtained X-ray fluxes for 140 contact binaries from the RASS, as well as two additional stars observed by the XMM-Newton observatory. From these data we confirm the emission of X-rays from all contact binary systems, with typical luminosities of approximately 1.0×1030 ergs s-1. Combining calculated luminosities with an estimated contact binary space density, we find that contact binaries do not have strong enough X-ray emission to account for a significant portion of the Galactic X-ray background.

DEBRIS DISKS AROUND SOLAR-TYPE STARS: OBSERVATIONS OF THE PLEIADES WITH THE SPITZER SPACE TELESCOPE

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

Sierchio, J. M.; Rieke, G. H.; Su, K. Y. L.

2010-04-01

We present Spitzer MIPS observations at 24 {mu}m of 37 solar-type stars in the Pleiades and combine them with previous observations to obtain a sample of 71 stars. We report that 23 stars, or 32% +- 6.8%, have excesses at 24 {mu}m at least 10% above their photospheric emission. We compare our results with studies of debris disks in other open clusters and with a study of A stars to show that debris disks around solar-type stars at 115 Myr occur at nearly the same rate as around A-type stars. We analyze the effects of binarity and X-ray activity onmore » the excess flux. Stars with warm excesses tend not to be in equal-mass binary systems, possibly due to clearing of planetesimals by binary companions in similar orbits. We find that the apparent anti-correlations in the incidence of excess and both the rate of stellar rotation and also the level of activity as judged by X-ray emission are statistically weak.« less

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

Yang, Y.-G.; Dai, H.-F.; Zhang, X.-B.

We present new photometry for the eclipsing binary V1241 Tau, which was obtained on six nights between 2011 December and 2012 January using the 85 cm telescope at the Xinglong station of the National Astronomical Observatories of China. By using the updated Wilson-Devinney code, photometric models with third lights were deduced from two sets of light curves. The result implies that V1241 Tau is an Algol-type near-contact binary (NCB), whose mass ratio and filling-out of the primary are q = 0.545 ({+-} 0.003) and f{sub 1} = 82.4% ({+-} 0.2%), respectively. Based on all available times of minimum light spanningmore » over 80 yr, the O - C curve of V1241 Tau appears to show a quasi-sinusoidal oscillation, i.e., a light-time orbit. The modulated period and amplitude are P{sub mod} = 47.4 ({+-} 1.7) yr and A = 0.0087 ({+-} 0.0005) days, respectively. This kind of period variation may be more likely attributed to the light-time effect via a presence of an unseen third body. From an analysis of 23 Algol-type NCBs with EB-type light curves, we determine that the fill-out for the primary f{sub 1} will increase as the orbital period P decreases. With angular momentum loss, the orbit of the binary will shrink, which causes f{sub 1} to increase. The primary component finally fills its Roche lobe, and the binary evolves into contact configuration. Therefore, this kind of Algol-type NCB with EB-type light curves, such as V1241 Tau, may be a progenitor of the A-type W UMa binary.« less

Prospective Genotyping of Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Isolates by Use of a Novel, Highly Discriminatory Binary Typing System

PubMed Central

Zhou, Fei; Sintchenko, Vitali; Gilbert, Gwendolyn L.

2012-01-01

In settings of high methicillin-resistant Staphylococcus aureus (MRSA) prevalence, detection of nosocomial transmission events can be difficult without strain typing. Prospective typing of all MRSA isolates could potentially identify transmission in a timely fashion, making infection control responses to outbreaks more effective. We describe the development and evaluation of a novel 19-target binary typing system for MRSA using the multiplex-PCR/reverse line blot hybridization platform. Pulse-field gel electrophoresis (PFGE), spa typing, and phage-derived open reading frame (PDORF) typing were performed for comparison. The system was utilized to identify transmission events in three general surgical wards over a 12-month period. Initial MRSA isolates from 273 patients were differentiated into 55 unique binary types. One or more potential contacts colonized with the same MRSA strain were identified in 69 of 87 cases (79%) in which definite or possible nosocomial MRSA acquisition had occurred. The discriminatory power of the typing system was similar to that of PFGE (Simpson's index of diversity [D] = 0.994, versus 0.987) and higher than that of spa typing (D = 0.926). Strain typing reduced the total number of potential MRSA-colonized source contacts from 859 to 212 and revealed temporal clustering of transmission events. Prospective MRSA typing using this novel binary typing method can rapidly identify nosocomial transmission events, even in high-prevalence settings, which allows timely infection control interventions. The system is rapid, inexpensive, discriminatory, and suitable for routine, high-throughput use in the hospital microbiology laboratory. PMID:22895043

The Tarantula Massive Binary Monitoring. I. Observational campaign and OB-type spectroscopic binaries

NASA Astrophysics Data System (ADS)

Almeida, L. A.; Sana, H.; Taylor, W.; Barbá, R.; Bonanos, A. Z.; Crowther, P.; Damineli, A.; de Koter, A.; de Mink, S. E.; Evans, C. J.; Gieles, M.; Grin, N. J.; Hénault-Brunet, V.; Langer, N.; Lennon, D.; Lockwood, S.; Maíz Apellániz, J.; Moffat, A. F. J.; Neijssel, C.; Norman, C.; Ramírez-Agudelo, O. H.; Richardson, N. D.; Schootemeijer, A.; Shenar, T.; Soszyński, I.; Tramper, F.; Vink, J. S.

2017-02-01

Context. Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus's core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2-O7) tend to have shorter orbital periods than later spectral types (O9.2-O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe's peak of star formation at redshifts z 1 to 2 which are estimated to have Z 0.5 Z⊙. The log of observations and RV measurements for all targets are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A84

What we learn from eclipsing binaries in the ultraviolet

NASA Technical Reports Server (NTRS)

Guinan, Edward F.

1990-01-01

Recent results on stars and stellar physics from IUE (International Ultraviolet Explorer) observations of eclipsing binaries are discussed. Several case studies are presented, including V 444 Cyg, Aur stars, V 471 Tau and AR Lac. Topics include stellar winds and mass loss, stellar atmospheres, stellar dynamos, and surface activity. Studies of binary star dynamics and evolution are discussed. The progress made with IUE in understanding the complex dynamical and evolutionary processes taking place in W UMa-type binaries and Algol systems is highlighted. The initial results of intensive studies of the W UMa star VW Cep and three representative Algol-type binaries (in different stages of evolution) focused on gas flows and accretion, are included. The future prospects of eclipsing binary research are explored. Remaining problems are surveyed and the next challenges are presented. The roles that eclipsing binaries could play in studies of stellar evolution, cluster dynamics, galactic structure, mass luminosity relations for extra galactic systems, cosmology, and even possible detection of extra solar system planets using eclipsing binaries are discussed.

Concentrating Solar Power Projects - ISCC Kuraymat | Concentrating Solar

Science.gov Websites

: 20.0 MW Gross: 20.0 MW Status: Operational Start Year: 2011 Do you have more information, corrections . Contact(s): Bothayna Rashed Company: NREA Start Production: June 2011 Project Type: Commercial

Optical Flares and a Long-lived Dark Spot on a Cool Shallow Contact Binary

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Wang, J.-J.; Zhu, L.-Y.; Snoonthornthum, B.; Wang, L.-Z.; Zhao, E. G.; Zhou, X.; Liao, W.-P.; Liu, N.-P.

2014-05-01

W UMa-type stars are contact systems where both cool components fill the critical Roche lobes and share a common convective envelope. Long and unbroken time-series photometry is expected to play an important role in their origin and activity. The newly discovered short-period W UMa-type star, CSTAR 038663, was monitored continuously by Chinese Small Telescope ARray (CSTAR) in Antarctica during the winters of 2008 and 2010. There were 15 optical flares recorded in the i band during the winter of 2010. This was the first time such flares were detected from a W UMa-type star. By analyzing the nearly unbroken photometric data from 2008, it is discovered that CSTAR 038663 is a W-type shallow contact binary system (f = 10.6(± 2.9)%) with a high mass ratio of q = 1.12(± 0.01), where the less massive component is slightly hotter than the more massive one. The asymmetric light curves are explained by the presence of a dark spot on the more massive component. Its temperature is about 800 K lower than the stellar photosphere and it covers 2.1% of the total photospheric surface. The lifetime of the dark spot is longer than 116 days. Using 725 eclipse times, we found that the observed-calculated (O-C) curve may show a cyclic variation that is explained by the presence of a close-in third body. Both the shallow contact configuration and the extremely high mass ratio suggest that CSTAR 038663 is presently evolving into a contact system with little mass transfer. The formation and evolution is driven by the loss of angular momentum via magnetic braking, and the close-in companion star is expected to play an important role, removing angular momentum from the central eclipsing binary.

SEARCHING FOR BINARY Y DWARFS WITH THE GEMINI MULTI-CONJUGATE ADAPTIVE OPTICS SYSTEM (GeMS)

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

Opitz, Daniela; Tinney, C. G.; Faherty, Jacqueline K.

The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs alsomore » hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System. We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than ∼0.5–1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e., 10{sup 42} erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.« less

Vincenzo LaSalvia | NREL

Science.gov Websites

;Utilization of Tabula Rasa to stabilize bulk lifetimes in n-Cz silicon for high-performance solar cell /SiOx/pc-Si passivated contacts to n-type Si solar cells." Presented at the 40th IEEE Photovoltaic , and P. Stradins. "Heterojunction rear passivated contact for high efficiency n-Cz Si solar cells

Solar cell with a gallium nitride electrode

DOEpatents

Pankove, Jacques I.

1979-01-01

A solar cell which comprises a body of silicon having a P-N junction therein with a transparent conducting N-type gallium nitride layer as an ohmic contact on the N-type side of the semiconductor exposed to solar radiation.

ROTATIONAL SYNCHRONIZATION MAY ENHANCE HABITABILITY FOR CIRCUMBINARY PLANETS: KEPLER BINARY CASE STUDIES

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

Mason, Paul A.; Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A.

2013-09-10

We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in somemore » cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.« less

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

PubMed Central

Mostafa, Ahmad; Medraj, Mamoun

2017-01-01

Fabrication of solar and electronic silicon wafers involves direct contact between solid, liquid and gas phases at near equilibrium conditions. Understanding of the phase diagrams and thermochemical properties of the Si-dopant binary systems is essential for providing processing conditions and for understanding the phase formation and transformation. In this work, ten Si-based binary phase diagrams, including Si with group IIIA elements (Al, B, Ga, In and Tl) and with group VA elements (As, Bi, N, P and Sb), have been reviewed. Each of these systems has been critically discussed on both aspects of phase diagram and thermodynamic properties. The available experimental data and thermodynamic parameters in the literature have been summarized and assessed thoroughly to provide consistent understanding of each system. Some systems were re-calculated to obtain a combination of the best evaluated phase diagram and a set of optimized thermodynamic parameters. As doping levels of solar and electronic silicon are of high technological importance, diffusion data has been presented to serve as a useful reference on the properties, behavior and quantities of metal impurities in silicon. This paper is meant to bridge the theoretical understanding of phase diagrams with the research and development of solar-grade silicon production, relying on the available information in the literature and our own analysis. PMID:28773034

The OGLE Collection of Variable Stars. Over 450 000 Eclipsing and Ellipsoidal Binary Systems Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

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

2016-12-01

We present a collection of 450 598 eclipsing and ellipsoidal binary systems detected in the OGLE fields toward the Galactic bulge. The collection consists of binary systems of all types: detached, semi-detached, and contact eclipsing binaries, RS CVn stars, cataclysmic variables, HW Vir binaries, double periodic variables, and even planetary transits. For all stars we provide the I- and V-band time-series photometry obtained during the OGLE-II, OGLE-III, and OGLE-IV surveys. We discuss methods used to identify binary systems in the OGLE data and present several objects of particular interest.

A Photometric Study of the Eclipsing Binary Star PY Boötis

NASA Astrophysics Data System (ADS)

Michaels, E. J.

2016-12-01

Presented here are the first precision multi-band CCD photometry of the eclipsing binary star PY Boötis. Best-fit stellar models were determined by analyzing the light curves with the Wilson-Devinney program. Asymmetries in the light curves were interpreted as resulting from magnetic activity which required spots to be included in the model. The resulting model is consistent with a W-type contact eclipsing binary having total eclipses.

VizieR Online Data Catalog: First analysis of the binary IK Boo (Kriwattanawong+, 2017)

NASA Astrophysics Data System (ADS)

Kriwattanawong, W.; Sanguansak, N.; Maungkorn, S.

2017-03-01

With new CCD observations of the W UMa type binary IK Boo, we present the first investigation of photometric parameters and orbital period change. The BVRc light curve fit shows that IK Boo is a W-type contact system with a mass ratio of q=1.146 and a shallow contact with a fill-out factor of f=2.22%. The orbital period decrease is found at a rate of -3.28x10-7d/yr, corresponding to a mass transfer from the more massive to the less massive component with a rate of -2.83x10-6M_ȯ/yr. The inner and outer critical Roche lobes will contract and cause the contact degree to increase. Therefore, IK Boo may evolve into a deeper contact system. Furthermore, a possible cyclic variation is found to have a period of 9.74yr, that could be explained by the light-travel time effect, due to the existence of a third companion in the system. (2 data files).

SAGE III/ISS L2 Solar Event Species Profiles (Native) V5 (g3bsspb)

Atmospheric Science Data Center

2017-12-21

SAGE III/ISS L2 Solar Event Species Profiles (Native) V5 (g3bsspb)   Project ... present Temporal Resolution:  1 file per event File Format:  BINARY Tools:  Earthdata ... Radiation Longwave Radiation Shortwave Radiation Event Tag Event Type Obs Beta Angle Order Data:  ...

The Nature and Evolutionary History of GRO J1744-28

NASA Technical Reports Server (NTRS)

Rappaport, S.

1997-01-01

GRO J1744-28 is the first known X-ray source to display bursts, periodic pulsations, and quasi-periodic oscillations. This source may thus provide crucial clues that will lead to an understanding of the differences in the nature of the X-ray variability from various accreting neutron stars. The orbital period is 11.8 days, and the measured mass function of 1.31 x 10(exp -4) solar mass is one of the smallest among all known binaries. If we assume that the donor star is a low-mass giant transferring matter through the inner Lagrange point, then we can show that its mass is lower than approximately 0.7 solar mass and probably closer to 0.25 solar mass. Higher mass, but unevolved, donor stars are shown to be implausible. We also demonstrate that the current He core mass of the donor star lies in the range of 0.20-0.25 solar mass. Thus, this system is most likely in the final stages of losing its hydrogen-rich envelope, with only a small amount of mass remaining in the envelope. If this picture is correct, then GRO J1744-28 may well represent the closest observational link that we have between the low-mass X-ray binaries and recycled binary pulsars in wide orbits. We have carried out a series of binary evolution calculations and explored, both systematically and via a novel Monte Carlo approach, the range of initial system parameters and input physics that can lead to the binary parameters of the present-day GRO J1744-28 system. The input parameters include both the initial total mass and the core mass of the donor star, the neutron-star mass, the strength of the magnetic braking, the mass-capture fraction, and the specifics of the core mass/radius relation for giants. Through these evolution calculations, we compute probability distributions for the current binary system parameters (i.e., the total mass, core mass, radius, luminosity, and K-band magnitude of the donor star, the neutron star mass, the orbital inclination angle, and the semimajor axis of the binary). Our calculations yield the following values for the GRO J1744-28 system parameters (with 95% confidence limits in parentheses): donor star mass: 0.24 solar mass (0.2-0.7 solar mass); He core mass of the donor star: 0.22 solar mass (0.20-0.25 solar mass); neutron-star mass: 1.7 solar mass (1.39-1.96 solar mass); orbital inclination angle: 18deg (7deg-22deg); semi- major axis: 64 lt-s (60-67 lt-s); radius of the donor star: 6.2 solar radius(6-9 solar radius); luminosity of donor star: 23 solar luminosity (15-49 solar luminosity), and long-term mass transfer rate at the current epoch: 5 x 10(exp -10)solar mass/yr (2 x 10(exp -10) to 5 x 10(exp -9)solar mass/yr). We deduce that the magnetic field of the underlying neutron star lies in the range of approximately 1.8 x 10(exp 11)G to approximately 7 x 10(exp 11)G, with a most probable value of 2.7 x 10(exp 11)G. This is evidently sufficiently strong to funnel the accretion flow onto the magnetic polar caps and suppress the thermonuclear flashes that would otherwise give rise to the type 1 X-ray bursts observed in most X-ray bursters. We present a simple paradigm for magnetic accreting neutron stars where X-ray pulsars, GRO J1744-28, the Rapid Burster, and the type 1 X-ray bursters may form a continuum of possible behaviors among accreting neutron stars, with the strength of the neutron-star magnetic field serving as a crucial parameter that determines the mode of X-ray variability from a given object.

Primordial main equence binary stars in the globular cluster M71

NASA Technical Reports Server (NTRS)

Yan, Lin; Mateo, Mario

1994-01-01

We report the identification of five short-period variables near the center of the metal-rich globular cluster M71. Our observations consist of multiepoch VI charge coupled device (CCD) images centered on the cluster and covering a 6.3 min x 6.3 min field. Four of these variables are contact eclipsing binaries with periods between 0.35 and 0.41 days; one is a detached or semidetached eclipsing binary with a period of 0.56 days. Two of the variables were first identified as possible eclipsing binaries in an earlier survey by Hodder et al. (1992). We have used a variety of arguments to conclude that all five binary stars are probable members of M71, a result that is consistent with the low number (0.15) of short-period field binaries expected along this line of sight. Based on a simple model of how contact binaries evolve from initially detached binaries, we have determined a lower limit of 1.3% on the frequency of primordial binaries in M71 with initial orbital periods in the range 2.5 - 5 days. This implies that the overall primordial binary frequency, f, is 22(sup +26)(sub -12)% assuming df/d log P = const ( the 'flat' distribution), or f = 57(sup +15)(sub -8)% for df/d log P = 0.032 log P + const as observed for G-dwarf binaries in the solar neighborhood (the 'sloped' distribution). Both estimates of f correspond to binaries with initial periods shorter than 800 yr since any longer-period binaries would have been disrupted over the lifetime of the cluster. Our short-period binary frequency is in excellent agreement with the observed frequency of red-giant binaries observed in globulars if we adopt the flat distribution. For the sloped distribution, our results significantly overestimate the number of red-giant binaries. All of the short-period M71 binaries lie within 1 mag of the luminosity of the cluster turnoff in the color-magnitude diagram despite the fact we should have easily detected similar eclipsing binaries 2 - 2.5 mag fainter than this. We discuss the implications of this on our estimates of the binary frequency in M71 and on the formation of blue stragglers.

Influence of the transition region between p- and n-type polycrystalline silicon passivating contacts on the performance of interdigitated back contact silicon solar cells

NASA Astrophysics Data System (ADS)

Reichel, Christian; Müller, Ralph; Feldmann, Frank; Richter, Armin; Hermle, Martin; Glunz, Stefan W.

2017-11-01

Passivating contacts based on thin tunneling oxides (SiOx) and n- and p-type semi-crystalline or polycrystalline silicon (poly-Si) enable high passivation quality and low contact resistivity, but the integration of these p+/n emitter and n+/n back surface field junctions into interdigitated back contact silicon solar cells poses a challenge due to high recombination at the transition region from p-type to n-type poly-Si. Here, the transition region was created in different configurations—(a) p+ and n+ poly-Si regions are in direct contact with each other ("pn-junction"), using a local overcompensation (counterdoping) as a self-aligning process, (b) undoped (intrinsic) poly-Si remains between the p+ and n+ poly-Si regions ("pin-junction"), and (c) etched trenches separate the p+ and n+ poly-Si regions ("trench")—in order to investigate the recombination characteristics and the reverse breakdown behavior of these solar cells. Illumination- and injection-dependent quasi-steady state photoluminescence (suns-PL) and open-circuit voltage (suns-Voc) measurements revealed that non-ideal recombination in the space charge regions with high local ideality factors as well as recombination in shunted regions strongly limited the performance of solar cells without a trench. In contrast, solar cells with a trench allowed for open-circuit voltage (Voc) of 720 mV, fill factor of 79.6%, short-circuit current (Jsc) of 41.3 mA/cm2, and a conversion efficiencies (η) of 23.7%, showing that a lowly conducting and highly passivating intermediate layer between the p+ and n+ poly-Si regions is mandatory. Independent of the configuration, no hysteresis was observed upon multiple stresses in reverse direction, indicating a controlled and homogeneously distributed breakdown, but with different breakdown characteristics.

A PHOTOMETRIC STUDY OF FOUR RECENTLY DISCOVERED CONTACT BINARIES: 1SWASP J064501.21+342154.9, 1SWASP J155822.10-025604.8, 1SWASP J212808.86+151622.0, AND UCAC4 436-062932

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

Djurašević, G.; Latković, O.; Cséki, A.

We present new, high-quality multicolor observations of four recently discovered contact binaries, 1SWASP J064501.21+342154.9, 1SWASP J155822.10-025604.8, 1SWASP J212808.86+151622.0, and UCAC4 436-062932, and analyze their light curves to determine orbital and physical parameters using the modeling program of G. Djurašević. In the absence of spectroscopic observations, the effective temperatures of the brighter components are estimated from the color indices, and the mass ratios are determined with the q -search method. The analysis shows that all four systems are W UMa type binaries in shallow contact configurations, consisting of late-type main-sequence primaries and evolved secondaries with active surface regions (dark or bright spots) resultingmore » from magnetic activity or ongoing transfer of thermal energy between the components. We compare the derived orbital and stellar parameters for these four variables with a large sample of previously analyzed W UMa stars and find that our results fit it well.« less

Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells

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

Yang, Guangtao; Ingenito, Andrea; Hameren, Nienke van

2016-01-18

Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySimore » was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (R{sub sh n-type} = 95 Ω/□ and R{sub sh p-type} = 120 Ω/□). An efficiency of 19.2% (V{sub oc} = 673 mV, J{sub sc} = 38.0 mA/cm{sup 2}, FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a V{sub OC} of 696 mV was also measured.« less

Tunnel oxide passivated contacts formed by ion implantation for applications in silicon solar cells

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

Reichel, Christian, E-mail: christian.reichel@ise.fraunhofer.de; National Renewable Energy Laboratory; Feldmann, Frank

Passivated contacts (poly-Si/SiO{sub x}/c-Si) doped by shallow ion implantation are an appealing technology for high efficiency silicon solar cells, especially for interdigitated back contact (IBC) solar cells where a masked ion implantation facilitates their fabrication. This paper presents a study on tunnel oxide passivated contacts formed by low-energy ion implantation into amorphous silicon (a-Si) layers and examines the influence of the ion species (P, B, or BF{sub 2}), the ion implantation dose (5 × 10{sup 14 }cm{sup −2} to 1 × 10{sup 16 }cm{sup −2}), and the subsequent high-temperature anneal (800 °C or 900 °C) on the passivation quality and junction characteristics using double-sided contacted silicon solar cells.more » Excellent passivation quality is achieved for n-type passivated contacts by P implantations into either intrinsic (undoped) or in-situ B-doped a-Si layers with implied open-circuit voltages (iV{sub oc}) of 725 and 720 mV, respectively. For p-type passivated contacts, BF{sub 2} implantations into intrinsic a-Si yield well passivated contacts and allow for iV{sub oc} of 690 mV, whereas implanted B gives poor passivation with iV{sub oc} of only 640 mV. While solar cells featuring in-situ B-doped selective hole contacts and selective electron contacts with P implanted into intrinsic a-Si layers achieved V{sub oc} of 690 mV and fill factor (FF) of 79.1%, selective hole contacts realized by BF{sub 2} implantation into intrinsic a-Si suffer from drastically reduced FF which is caused by a non-Ohmic Schottky contact. Finally, implanting P into in-situ B-doped a-Si layers for the purpose of overcompensation (counterdoping) allowed for solar cells with V{sub oc} of 680 mV and FF of 80.4%, providing a simplified and promising fabrication process for IBC solar cells featuring passivated contacts.« less

MM Herculis - An eclipsing binary of the RS CVn

NASA Technical Reports Server (NTRS)

Sowell, J. R.; Hall, D. S.; Henry, G. W.; Burke, E. W., Jr.; Milone, E. F.

1983-01-01

V, B and U differential photoelectric photometry has been obtained for the RS Canum Venaticorum-class eclipsing binary star MM Her, with the light outside the eclipse being Fourier-analyzed to study wave migration and amplitude. These, together with the mean light level of the system, have been monitored from 1976 through 1980. Observations within the eclipse have revealed eclipses to be partial, rather than total as previously thought. The geometric elements of the presently rectified light curve are forced on the pre-1980 light curves and found to be compatible. With these elements, and previously obtained double line radial velocity curves, new absolute dimensions of 1.18 solar masses and 1.58 solar radii are calculated for the hotter star and 1.27 solar masses and 2.83 solar radii for the cooler star. The plotting of color indices on the color-color curve indicates G2V and K2IV spectral types.

Vulcan Identification of Eclipsing Binaries in the Kepler Field of View

NASA Astrophysics Data System (ADS)

Mjaseth, Kimberly; Batalha, N.; Borucki, W.; Caldwell, D.; Latham, D.; Martin, K. R.; Rabbette, M.; Witteborn, F.

2007-05-01

We report the discovery of 236 new eclipsing binary stars located in and around the field of view of the Kepler Mission. The binaries were identified from photometric light curves from the Vulcan exoplanet transit survey. The Vulcan camera is comprised of a modest aperture (10cm) f/2.8 Canon lens focusing a 7° x 7° field of view onto a 4096 x 4096 Kodak CCD. The system yields an hour-to-hour relative precision of 0.003 on 12th magnitude stars and saturates at 9th magnitude. The binaries have magnitudes in the range of 9.5 < V < 13.5 and periods ranging from 0.5 to 13 days. The milli-magnitude photometric precision allows detection of transits as shallow as 1%. The catalog contains a total of 273 eclipsing binary stars, including detached systems (high and low mass ratio), contact binaries, and triple systems. We present the derived orbital/transit properties, light curves, and stellar properties for selected targets. In addition, we summarize the results of radial velocity follow-up work. Support for this work came from NASA's Discovery Program and NASA's Origins of the Solar System Program.

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

NASA Astrophysics Data System (ADS)

Kjurkchieva, Diana Petrova; Popov, Velimir Angelov; Lyubenova Vasileva, Doroteya; Petrov, Nikola Ivanov

2018-04-01

Photometric observations in Sloan g‧ and i‧ bands of W UMa binaries NSVS 4340949, T-Dra0–00959, GSC 03950–00707, NSVS 4665041, NSVS 4803568, MM Peg, MM Com and NSVS 4751449 are presented. The light curve solutions revealed that the components of each target are of G and K spectral types. The binaries of the sample have middle-contact configurations whose fillout factors are within the range 0.2–0.4. The only exception is NSVS 4751449 which is in deeper contact (fillout factor of 0.55). It precisely obeys the relation between mass ratio and fillout factor for deep, low mass ratio overcontact binaries. One of the eclipses of almost all targets (except MM Peg) is an occultation and their photometric mass ratios and solutions could be accepted with confidence. We found that the target components have almost equal temperatures but differ considerably in size and mass. The components of the partially-eclipsed MM Peg have close parameters. Our solutions reveal that NSVS 4340949, T-Dra0–00959, NSVS 4803568 and MM Com are of W subtype while GSC 03950–00707, NSVS 4665041, MM Peg and NSVS 4751449 are of A subtype. This subclassification is well-determined for all totally-eclipsed binaries. The targets confirm the trends in which W-subtype systems have smaller periods and lower temperatures than A subtype binaries.

FIRST PHOTOMETRIC INVESTIGATION OF THE NEWLY DISCOVERED W UMa-TYPE BINARY STAR MR Com

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

Qian, S.-B.; Liu, N.-P.; Liao, W.-P.

By analyzing multi-color light curves of the newly discovered W UMa-type binary, MR Com, we discovered that it is a shallow-contact binary with a degree of contact factor of f = 10.0% {+-} 2.1%. Photometric solutions reveal that MR Com is a W-type system with a mass ratio of q = 3.9 where the less massive component is about 90 K hotter than the more massive one. By investigating all of the available times of minimum light, we found that the general trend of the Observed-Calculated (O - C) curve shows a downward parabolic variation while it undergoes a cyclicmore » variation with a small amplitude of 0.0031 days and a period of 10.1 yr. The downward parabolic change corresponds to a long-term decrease in the orbital period at a rate of P-dot = -5.3 x 10{sup -7} days yr{sup -1} that may be caused by a combination of a mass transfer and an angular momentum loss (AML) via magnetic braking. Among the 16 shallow-contact systems with a decreasing orbital period, MR Com has the lowest mass ratio (e.g., 1/q = 0.26). The shallow-contact configuration, the low-mass ratio, and the long-term period decrease all suggest that systems similar to MR Com are on the AML-controlled stage of the evolutionary scheme proposed by Qian. They will oscillate around a critical mass ratio and evolve into a deep contact with a higher mass ratio. The small-amplitude cyclic change in the O - C curve was analyzed for the light-travel time effect via the presence of an extremely cool stellar companion.« less

SAGE III/ISS L1B Solar Event Transmission Data (Native) V5 (g3btb)

Atmospheric Science Data Center

2017-12-21

SAGE III/ISS L1B Solar Event Transmission Data (Native) V5 (g3btb)   Project Title:  ... present Temporal Resolution:  1 file per event File Format:  BINARY Tools:  Earthdata ... Radiation Longwave Radiation Shortwave Radiation Event Tag Event Type Obs Beta Angle Order Data:  ...

DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

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

Eggl, Siegfried; Pilat-Lohinger, Elke; Haghighipour, Nader, E-mail: siegfried.eggl@univie.ac.at

2013-02-20

Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the {alpha} Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery ofmore » {alpha} Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the {alpha} Centauri system.« less

Review of status developments of high-efficiency crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Yao, Yao; Xiao, Shaoqing; Gu, Xiaofeng

2018-03-01

In order to further improve cell efficiency and reduce cost in achieving grid parity, a large number of PV manufacturing companies, universities and research institutes have been devoted to a variety of low-cost and high-efficiency crystalline Si solar cells. In this article, the cell structures, characteristics and efficiency progresses of several types of high-efficiency crystalline Si solar cells that have been in small scale production or are promising in mass production are presented, including passivated emitter rear cell, tunnel oxide passivated contact solar cell, interdigitated back contact cell, heterojunction with intrinsic thin-layer cell, and heterojunction solar cells with interdigitated back contacts. Both the industrialization status and future development trend of high-efficiency crystalline silicon solar cells are also pinpointed.

Electron-selective contacts via ultra-thin organic interface dipoles for silicon organic heterojunction solar cells

NASA Astrophysics Data System (ADS)

Reichel, Christian; Würfel, Uli; Winkler, Kristina; Schleiermacher, Hans-Frieder; Kohlstädt, Markus; Unmüssig, Moritz; Messmer, Christoph A.; Hermle, Martin; Glunz, Stefan W.

2018-01-01

In the last years, novel materials for the formation of electron-selective contacts on n-type crystalline silicon (c-Si) heterojunction solar cells were explored as an interfacial layer between the metal electrode and the c-Si wafer. Besides inorganic materials like transition metal oxides or alkali metal fluorides, also interfacial layers based on organic molecules with a permanent dipole moment are promising candidates to improve the contact properties. Here, the dipole effect plays an essential role in the modification of the interface and effective work function of the contact. The amino acids L-histidine, L-tryptophan, L-phenylalanine, glycine, and sarcosine, the nucleobase adenine, and the heterocycle 4-hydroxypyridine were investigated as dipole materials for an electron-selective contact on the back of p- and n-type c-Si with a metal electrode based on aluminum (Al). Furthermore, the effect of an added fluorosurfactant on the resulting contact properties was examined. The performance of n-type c-Si solar cells with a boron diffusion on the front was significantly increased when L-histidine and/or the fluorosurfactant was applied as a full-area back surface field. This improvement was attributed to the modification of the interface and the effective work function of the contact by the dipole material which was corroborated by numerical device simulations. For these solar cells, conversion efficiencies of 17.5% were obtained with open-circuit voltages (Voc) of 625 mV and fill factors of 76.3%, showing the potential of organic interface dipoles for silicon organic heterojunction solar cells due to their simple formation by solution processing and their low thermal budget requirements.

Long-term orbital period behaviour of low mass ratio contact binaries GR Vir and FP Boo

NASA Astrophysics Data System (ADS)

Ćetinkaya, Halil; Soydugan, Faruk

2017-02-01

In this study, we investigated orbital period variations of two low mass ratio contact binaries GR Vir and FP Boo based on published minima times. From the O-C analysis, it was found that FP Boo indicates orbital period decrease while the period of GR Vir is increasing. Mass transfer process was used to explain increase and decrease in the orbital periods. In the O-C diagrams of both systems periodic variations also exist. Cyclic changes can be explained as being the result of a light-travel time effect via a third component around the eclipsing binaries. In order to interpret of cyclic orbital period changes for GR Vir, which has late-type components, possible magnetic activity cycles of the components have been also considered.

Back wall solar cell

NASA Technical Reports Server (NTRS)

Brandhorst, H. W., Jr. (Inventor)

1978-01-01

A solar cell is disclosed which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, a metallic Schottky diode layer may be used, in which case no additional back contact is needed. A contact such as a gridded contact, previous to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Imaging Survey of Subsystems in Secondary Components to Nearby Southern Dwarfs

NASA Astrophysics Data System (ADS)

Tokovinin, Andrei

2014-10-01

To improve the statistics of hierarchical multiplicity, secondary components of wide nearby binaries with solar-type primaries were surveyed at the SOAR telescope for evaluating the frequency of subsystems. Images of 17 faint secondaries were obtained with the SOAR Adaptive Module that improved the seeing; one new 0.''2 binary was detected. For all targets, photometry in the g', i', z' bands is given. Another 46 secondaries were observed by speckle interferometry, resolving 7 close subsystems. Adding literature data, the binarity of 95 secondary components is evaluated. We found that the detection-corrected frequency of secondary subsystems with periods in the well-surveyed range from 103 to 105 days is 0.21 ± 0.06—same as the normal frequency of such binaries among solar-type stars, 0.18. This indicates that wide binaries are unlikely to be produced by dynamical evolution of N-body systems, but are rather formed by fragmentation. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory, the University of North Carolina at Chapel Hill, and Michigan State University.

Nonlinear Tides in Close Binary Systems

NASA Astrophysics Data System (ADS)

Weinberg, Nevin N.; Arras, Phil; Quataert, Eliot; Burkart, Josh

2012-06-01

We study the excitation and damping of tides in close binary systems, accounting for the leading-order nonlinear corrections to linear tidal theory. These nonlinear corrections include two distinct physical effects: three-mode nonlinear interactions, i.e., the redistribution of energy among stellar modes of oscillation, and nonlinear excitation of stellar normal modes by the time-varying gravitational potential of the companion. This paper, the first in a series, presents the formalism for studying nonlinear tides and studies the nonlinear stability of the linear tidal flow. Although the formalism we present is applicable to binaries containing stars, planets, and/or compact objects, we focus on non-rotating solar-type stars with stellar or planetary companions. Our primary results include the following: (1) The linear tidal solution almost universally used in studies of binary evolution is unstable over much of the parameter space in which it is employed. More specifically, resonantly excited internal gravity waves in solar-type stars are nonlinearly unstable to parametric resonance for companion masses M' >~ 10-100 M ⊕ at orbital periods P ≈ 1-10 days. The nearly static "equilibrium" tidal distortion is, however, stable to parametric resonance except for solar binaries with P <~ 2-5 days. (2) For companion masses larger than a few Jupiter masses, the dynamical tide causes short length scale waves to grow so rapidly that they must be treated as traveling waves, rather than standing waves. (3) We show that the global three-wave treatment of parametric instability typically used in the astrophysics literature does not yield the fastest-growing daughter modes or instability threshold in many cases. We find a form of parametric instability in which a single parent wave excites a very large number of daughter waves (N ≈ 103[P/10 days] for a solar-type star) and drives them as a single coherent unit with growth rates that are a factor of ≈N faster than the standard three-wave parametric instability. These are local instabilities viewed through the lens of global analysis; the coherent global growth rate follows local rates in the regions where the shear is strongest. In solar-type stars, the dynamical tide is unstable to this collective version of the parametric instability for even sub-Jupiter companion masses with P <~ a month. (4) Independent of the parametric instability, the dynamical and equilibrium tides excite a wide range of stellar p-modes and g-modes by nonlinear inhomogeneous forcing; this coupling appears particularly efficient at draining energy out of the dynamical tide and may be more important than either wave breaking or parametric resonance at determining the nonlinear dissipation of the dynamical tide.

Chemical Composition of RR Lyn - an Eclipsing Binary System with Am and λ Boo Type Components

NASA Astrophysics Data System (ADS)

Jeong, Yeuncheol; Yushchenko, Alexander V.; Doikov, Dmytry N.; Gopka, Vira F.; Yushchenko, Volodymyr O.

2017-06-01

High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5-1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.

Fabrication of multijunction high voltage concentrator solar cells by integrated circuit technology

NASA Technical Reports Server (NTRS)

Valco, G. J.; Kapoor, V. J.; Evans, J. C., Jr.; Chai, A.-T.

1981-01-01

Standard integrated circuit technology has been developed for the design and fabrication of planar multijunction (PMJ) solar cell chips. Each 1 cm x 1 cm solar chip consisted of six n(+)/p, back contacted, internally series interconnected unit cells. These high open circuit voltage solar cells were fabricated on 2 ohm-cm, p-type 75 microns thick, silicon substrates. A five photomask level process employing contact photolithography was used to pattern for boron diffusions, phorphorus diffusions, and contact metallization. Fabricated devices demonstrated an open circuit voltage of 3.6 volts and a short circuit current of 90 mA at 80 AMl suns. An equivalent circuit model of the planar multi-junction solar cell was developed.

Calculation of Gallium-metal-Arsenic phase diagrams

NASA Technical Reports Server (NTRS)

Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

1991-01-01

Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

Chromospherically active stars. IV - HD 178450 = V478 Lyr: An early-type BY Draconis type binary

NASA Technical Reports Server (NTRS)

Fekel, Francis C.

1988-01-01

It is shown that the variable star HD 178450 = V478 Lyr is a chromospherically active G8 V single-lined spectroscopic binary with a period of 2.130514 days. This star is characterized by strong UV emission features and a filled-in H-alpha absorption line which is variable in strength. Classified as an early-type BY Draconis system, it is similar to the BY Dra star HD 175742 = V775 Her. The unseen secondary of HD 178450 has a mass of about 0.3 solar masses and is believed to be an M2-M3 dwarf.

A New Photometric Investigation of the W UMa-Type Binary BI CVn

NASA Astrophysics Data System (ADS)

Qian, S.-B.; He, J.-J.; Liu, L.; Zhu, L.-Y.; Liao, W. P.

2008-12-01

New photometric observations and their investigation of the W UMa-type binary, BI CVn, are presented. The variations of the orbital period were analyzed based on 12 new determined times of light minimum together with the others compiled from the literature. It is discovered that the period of BI CVn shows a long-term period decrease at a rate of \\dot{P}=-1.51(± 0.12)× {10^{-7}} days year-1 while it undergoes a cyclic variation with a period of 27.0 years and an amplitude of 0fd0151. Photometric solutions determined with the Wilson-Devinney method suggest that BI CVn is a contact binary with a degree of contact of 18.0(±1.7)%. The asymmetry of the light curves was interpreted by the presence of dark spots on both components, and absolute parameters were determined by combining the photometric elements with the spectroscopic solutions given by Lu. The observed period decrease can be plausibly explained by a combination of the mass transfer from the primary to the secondary and angular momentum loss via magnetic braking. The cyclic period oscillation suggests that BI CVn is a triple system containing a tertiary component with a mass no less than 0.58 M sun in a 27.0 year orbit. As in the cases of the other contact binaries (e.g., AH Cnc, AP Leo, AD Cnc, and UX Eri), it is possible that this tertiary companion played an important role for the formation and evolution of the contact system by removing angular momentum from the central system via Kozai oscillation or a combination of Kozai cycle and tidal friction, which causes the eclipsing pair to have a short initial orbital period (e.g., P < 5d). In that case, can the initially detached system evolve into the present contact configuration via a combination of magnetic torques from stellar winds and a case A mass transfer?

Concentrating Solar Power Projects - Extresol-2 | Concentrating Solar Power

Science.gov Websites

Sesmero (Badajoz) Owner(s): ACS/Cobra Group (100%) Technology: Parabolic trough Turbine Capacity: Net : 158,000 MWh/yr (Expected/Planned) Contact(s): Manuel Cortes; Ana Salazar Company: ACS/Cobra Group Break Project Type: Commercial Participants Developer(s): ACS/Cobra Group Owner(s) (%): ACS/Cobra Group (100

Concentrating Solar Power Projects - Extresol-3 | Concentrating Solar Power

Science.gov Websites

Sesmero (Badajoz) Owner(s): ACS/Cobra Group (100%) Technology: Parabolic trough Turbine Capacity: Net : 158,000 MWh/yr (Expected/Planned) Contact(s): Manuel Cortes; Ana Salazar Company: ACS/Cobra Group Break years Project Type: Commercial Participants Developer(s): ACS/Cobra Group Owner(s) (%): ACS/Cobra Group

The O-type eclipsing contact binary LY Aurigae - member of a quadruple system

NASA Astrophysics Data System (ADS)

Mayer, Pavel; Drechsel, Horst; Harmanec, Petr; Yang, Stephenson; Šlechta, Miroslav

2013-11-01

The eclipsing binary LY Aur (O9 II + O9 III) belongs to the rare class of early-type contact systems. We obtained 23 new spectra at the Ondřejov and Dominion Astrophysical Observatories, which were analysed with four older Calar Alto and one ELODIE archive spectra. A new result of this study is that the visual companion of LY Aur - the spectral lines of which are clearly seen in our spectra - is also an SB1 binary having an orbital period of 20.46d, an eccentric orbit, and a radial velocity semi-amplitude of 33 km s-1. The Hα line blend contains an emission component, which shows dependence on the orbital phase of the eclipsing system, with the strongest emission around the secondary eclipse. Revised elements of the eclipsing binary and the orbital solution of the companion binary are determined from our set of spectra and new light-curve solutions of the eclipsing pair. The mass of the primary of 25.5 M⊙ agrees well with its spectral type, whereas the secondary mass of 14 M⊙ is smaller than expected. From an O-C analysis of the minimum times of LY Aur that span more than 40 years, we found that the orbital period is decreasing, indicating the presence of interaction processes. The system is likely in a phase of non-conservative mass exchange. Based on spectral observations collected at the German-Spanish Observatory, Calar Alto, Spain; Dominion Astrophysical Observatory, Canada; Ondřejov Observatory, Czech Republic, and an archival Haute Provence Observatory ELODIE spectrum.

Stellar and Circumstellar Properties of Low-Mass, Young, Subarcsecond Binaries

NASA Astrophysics Data System (ADS)

Bruhns, Sara; Prato, L. A.

2014-01-01

We present a study of the stellar and circumstellar characteristics of close (< 1''), young (< 2 to 3 Myr), low-mass (<1 solar mass) binary stars in the Taurus star forming region. Low-resolution (R ~ 2000) spectra were taken in the K-band using adaptive optics to separate the observations for each component and identify the individual spectral types, extinction, and K-band excess. Combining these data with stellar luminosities allows us to estimate the stellar masses and ages. We also measured equivalent widths of the hydrogen Brackett gamma line in order to estimate the strength of gas accretion. We obtained spectra for six binary systems with separations from 1'' down to 0.3''. In the CZ Tau binary we found that the fainter secondary star spectrum appears to be of earlier spectral type than the primary; we speculate on the origin of this inversion.

Photometric studies for two contact binaries: V532 Monocerotis and GU Orionis

NASA Astrophysics Data System (ADS)

Yang, Yuangui; Dai, Haifeng; Yuan, Huiyu; Zhang, Xiliang; Zhang, Liyun

2017-08-01

We present photometry and spectroscopy data for V532 Mon and GU Ori, observed in 2011 and 2016. From the spectral observations, the spectral types are determined to be F5V for V532 Mon and G0V for GU Ori. With the 2015-version Wilson-Devinney program, the photometric solutions are simultaneously deduced from VR light curves (LCs). The intrinsic variability for V532 Mon is found by comparing LCs in 2004 and 2011, while the asymmetric LCs for GU Ori are modeled by a cool spot on the more massive component. The results imply that the two stars are A-type contact binaries. The mass ratios and fill-out factors are, respectively, q = 0.190(±0.006) and f = 43.7(±0.9)% for V532 Mon and q = 0.455(±0.020) and f = 26.9(±1.3)% for GU Ori. From the (O - C) curves, it is found that their orbital periods may be undergoing long-term variations. The rates of period change are dP/dt = -1.72(±0.05) × 10-7 d yr-1 for V532 Mon and dP/dt = +1.45(±0.01) × 10-7 d yr-1 for GU Ori. V532 Mon with a decreasing period will evolve into a deep-contact binary, while GU Ori with an increasing period may evolve into a broken-contact case.

TOWARD PRECISE AGES FOR SINGLE STARS IN THE FIELD. GYROCHRONOLOGY CONSTRAINTS AT SEVERAL Gyr USING WIDE BINARIES. I. AGES FOR INITIAL SAMPLE

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

Chaname, Julio; Ramirez, Ivan

2012-02-10

We present a program designed to obtain age-rotation measurements of solar-type dwarfs to be used in the calibration of gyrochronology relations at ages of several Gyr. This is a region of parameter space crucial for the large-scale study of the Milky Way, and where the only constraint available today is that provided by the Sun. Our program takes advantage of a set of wide binaries selected so that one component is an evolved star and the other is a main-sequence star of FGK type. In this way, we obtain the age of the system from the evolved star, while themore » rotational properties of the main-sequence component provide the information relevant for gyrochronology regarding the spin-down of solar-type stars. By mining currently available catalogs of wide binaries, we assemble a sample of 37 pairs well positioned for our purposes: 19 with turnoff or subgiant primaries and 18 with white dwarf components. Using high-resolution optical spectroscopy, we measure precise stellar parameters for a subset of 15 of the pairs with turnoff/subgiant components and use these to derive isochronal ages for the corresponding systems. Ages for 16 of the 18 pairs with white dwarf components are taken from the literature. The ages of this initial sample of 31 wide binaries range from 1 to 9 Gyr, with precisions better than {approx}20% for almost half of these systems. When combined with measurements of the rotation period of their main-sequence components, these wide binary systems would potentially provide a similar number of points useful for the calibration of gyrochronology relations at very old ages.« less

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

Tokovinin, Andrei; Horch, Elliott P., E-mail: atokovinin@ctio.noao.edu, E-mail: horche2@southernct.edu

Statistical characterization of secondary subsystems in binaries helps to distinguish between various scenarios of multiple-star formation. The Differential Speckle Survey Instrument was used at the Gemini-N telescope for several hours in 2015 July to probe the binarity of 25 secondary components in nearby solar-type binaries. Six new subsystems were resolved, with meaningful detection limits for the remaining targets. The large incidence of secondary subsystems agrees with other similar studies. The newly resolved subsystem HIP 115417 Ba,Bb causes deviations in the observed motion of the outer binary from which an astrometric orbit of Ba,Bb with a period of 117 years ismore » deduced.« less

Self-aligned Ni-P ohmic contact scheme for silicon solar cells by electroless deposition

NASA Astrophysics Data System (ADS)

Lee, Eun Kyung; Lim, Dong Chan; Lee, Kyu Hwan; Lim, Jae-Hong

2012-08-01

We report a Ni-P metallization scheme for low resistance ohmic contacts to n-type Si for silicon solar cells. As-deposited Ni-P contacts to n-type Si showed a specific contact resistance of 6.42 × 10-4 Ω·cm2. The specific contact resistance decreased with increasing thermal annealing temperature. When the Ni-P contact was annealed at 600°C for 30 min in ambient air, the specific contact resistance was greatly decreased, to 6.37 × 10-5Ω·cm2. The improved ohmic property was attributed to the decrease in the work function due to the formation of Ni-silicides from Ni in-diffusion during the thermal annealing process. Effects of the annealing process on the electrical and crystal properties of the contacts were investigated by means of various resistivity measurements (circular transmission line method (c-TLM), 4-point probe), glancing angle x-ray diffraction (GAXRD), and x-ray photoelectron spectroscopy (XPS).

C60 as an Efficient n-Type Compact Layer in Perovskite Solar Cells.

PubMed

Wojciechowski, Konrad; Leijtens, Tomas; Siprova, Svetlana; Schlueter, Christoph; Hörantner, Maximilian T; Wang, Jacob Tse-Wei; Li, Chang-Zhi; Jen, Alex K-Y; Lee, Tien-Lin; Snaith, Henry J

2015-06-18

Organic-inorganic halide perovskite solar cells have rapidly evolved over the last 3 years. There are still a number of issues and open questions related to the perovskite material, such as the phenomenon of anomalous hysteresis in current-voltage characteristics and long-term stability of the devices. In this work, we focus on the electron selective contact in the perovskite solar cells and physical processes occurring at that heterojunction. We developed efficient devices by replacing the commonly employed TiO2 compact layer with fullerene C60 in a regular n-i-p architecture. Detailed spectroscopic characterization allows us to present further insight into the nature of photocurrent hysteresis and charge extraction limitations arising at the n-type contact in a standard device. Furthermore, we show preliminary stability data of perovskite solar cells under working conditions, suggesting that an n-type organic charge collection layer can increase the long-term performance.

Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

PubMed

Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

2016-02-10

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

Contrasting performance of donor-acceptor copolymer pairs in ternary blend solar cells and two-acceptor copolymers in binary blend solar cells.

PubMed

Khlyabich, Petr P; Rudenko, Andrey E; Burkhart, Beate; Thompson, Barry C

2015-02-04

Here two contrasting approaches to polymer-fullerene solar cells are compared. In the first approach, two distinct semi-random donor-acceptor copolymers are blended with phenyl-C61-butyric acid methyl ester (PC61BM) to form ternary blend solar cells. The two poly(3-hexylthiophene)-based polymers contain either the acceptor thienopyrroledione (TPD) or diketopyrrolopyrrole (DPP). In the second approach, semi-random donor-acceptor copolymers containing both TPD and DPP acceptors in the same polymer backbone, termed two-acceptor polymers, are blended with PC61BM to give binary blend solar cells. The two approaches result in bulk heterojunction solar cells that have the same molecular active-layer components but differ in the manner in which these molecular components are mixed, either by physical mixing (ternary blend) or chemical "mixing" in the two-acceptor (binary blend) case. Optical properties and photon-to-electron conversion efficiencies of the binary and ternary blends were found to have similar features and were described as a linear combination of the individual components. At the same time, significant differences were observed in the open-circuit voltage (Voc) behaviors of binary and ternary blend solar cells. While in case of two-acceptor polymers, the Voc was found to be in the range of 0.495-0.552 V, ternary blend solar cells showed behavior inherent to organic alloy formation, displaying an intermediate, composition-dependent and tunable Voc in the range from 0.582 to 0.684 V, significantly exceeding the values achieved in the two-acceptor containing binary blend solar cells. Despite the differences between the physical and chemical mixing approaches, both pathways provided solar cells with similar power conversion efficiencies, highlighting the advantages of both pathways toward highly efficient organic solar cells.

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.

The Plutino Population: An Abundance of Contact Binaries

NASA Astrophysics Data System (ADS)

Thirouin, Audrey; Sheppard, Scott S.

2018-06-01

We observed 12 Plutinos over two separated years with the 4.3 m Lowell’s Discovery Channel Telescope. Here, we present the first light-curve data for those objects. Three of them (2014 JL80, 2014 JO80, and 2014 JQ80) display a large light-curve amplitude explainable by a single elongated object, but they are most likely caused by a contact binary system due to their light-curve morphology. These potential contact binaries have rotational periods from 6.3 to 34.9 hr and peak-to-peak light-curve variability between 0.6 and 0.8 mag. We present partial light curves, allowing us to constrain the light-curve amplitude and the rotational period of another nine Plutinos. By merging our data with the literature, we estimate that up to ∼40% of the Plutinos could be contact binaries. Interestingly, we found that all of the suspected contact binaries in the 3:2 resonance are small with absolute magnitude H > 6 mag. Based on our sample and the literature, up to ∼50% of the small Plutinos are potential contact binaries.

Binary-corrected velocity dispersions from single- and multi-epoch radial velocities: massive stars in R136 as a test case

NASA Astrophysics Data System (ADS)

Cottaar, M.; Hénault-Brunet, V.

2014-02-01

Orbital motions from binary stars can broaden the observed line-of-sight velocity distribution of a stellar system and artificially inflate the measured line-of-sight velocity dispersion, which can in turn lead to erroneous conclusions about the dynamical state of the system. Recently, a maximum-likelihood procedure was proposed to recover the intrinsic velocity dispersion of a resolved star cluster from a single epoch of radial velocity data of individual stars, which was achieved by simultaneously fitting the intrinsic velocity distribution of the single stars and the centers of mass of the binaries along with the velocity shifts caused by binary orbital motions. Assuming well-characterized binary properties, this procedure can accurately reproduce intrinsic velocity dispersions below 1 km s-1 for solar-type stars. Here we investigate the systematic offsets induced when the binary properties are uncertain and we show that two epochs of radial velocity data with an appropriate baseline can help to mitigate these systematic effects. We first test the method described above using Monte Carlo simulations, taking into account the large uncertainties in the binary properties of OB stars. We then apply it to radial velocity data in the young massive cluster R136 for which the intrinsic velocity dispersion of O-type stars is known from an intensive multi-epoch approach. For typical velocity dispersions of young massive clusters (≳4 km s-1) and with a single epoch of data, we demonstrate that the method can just about distinguish between a cluster in virial equilibrium and an unbound cluster. This is due to the higher spectroscopic binary fraction and more loosely constrained distributions of orbital parameters of OB stars compared to solar-type stars. By extending the maximum-likelihood method to multi-epoch data, we show that the accuracy on the fitted velocity dispersion can be improved by only a few percent by using only two epochs of radial velocities. This procedure offers a promising method of accurately measuring the intrinsic stellar velocity dispersion in other systems for which the binary properties are poorly constrained, for example, young clusters and associations whose luminosity is dominated by OB stars. Appendix A is available in electronic form at http://www.aanda.org

Trench process and structure for backside contact solar cells with polysilicon doped regions

DOEpatents

De Ceuster, Denis; Cousins, Peter John; Smith, David D

2014-03-18

A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

Trench process and structure for backside contact solar cells with polysilicon doped regions

DOEpatents

De Ceuster, Denis; Cousins, Peter John; Smith, David D

2013-05-28

A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

Trench process and structure for backside contact solar cells with polysilicon doped regions

DOEpatents

De Ceuster, Denis; Cousins, Peter John; Smith, David D.

2010-12-14

A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

Rotational modulation of hydrogen Lyman alpha flux from 44ii Bootis

NASA Technical Reports Server (NTRS)

Vilhu, O.; Neff, J. E.; Rahunen, T.

1988-01-01

Observations with IUE that cover the entire 6.4 hr orbital cycle of the late-type contact binary 44i Bootis are presented. Intrinsic stellar hydrogen Lyman alpha emission flux was determined from low-resolution IUE spectra, compensating for geocoronal emission and for interstellar absorption. The variation of the stellar Lyman alpha emission flux correlates well with the variation of the C II and C IV emission fluxes, and shows orbital modulation in phase with the visual light curve. The ratio of Lyman alpha to CII flux (15 to 20) is similar to that observed in solar active regions. Hydrogen Lyman alpha emission is thus one of the most important cooling channels in the outer atmosphere of 44i Boo. A high-resolution spectrum of the Lyman alpha line was obtained between orbital phases 0.0 and 0.6. The integrated flux in the observed high-resolution Lyman alpha profile is consistent with the fluxes determined using low-resolution spectra, and the composite profile indicates that both components of this binary have equally active chromospheres and transition regions. The uncertainty in the interstellar hydrogen column density cannot mimic the observed variation in the integrated Lyman alpha flux, because the stellar line is very much broader than the interstellar absorption.

Rotational modulation of hydrogen Lyman alpha flux from 44i Bootis

NASA Technical Reports Server (NTRS)

Vilhu, O.; Neff, J. E.; Rahunen, T.

1989-01-01

Observations with IUE that cover the entire 6.4 hr orbital cycle of the late-type contact binary 44i Bootis are presented. Intrinsic stellar hydrogen Lyman alpha emission flux was determined from low-resolution IUE spectra, compensating for geocoronal emission and for interstellar absorption. The variation of the stellar Lyman alpha emission flux correlates well with the variation of the CII and CIV emission fluxes, and shows orbital modulation in phase with the visual light curve. The ratio of Lyman alpha to CII flux (15 to 20) is similar to that observed in solar active regions. Hydrogen Lyman alpha emission is thus one of the most important cooling channels in the outer atmosphere of 44i Boo. A high-resolution spectrum of the Lyman alpha line was obtained between orbital phases 0.0 and 0.6. The integrated flux in the observed high-resolution Lyman alpha profile is consistent with the fluxes determined using low-resolution spectra, and the composite profile indicates that both components of this binary have equally active chromospheres and transition regions. The uncertainty in the interstellar hydrogen column density cannot mimic the observed variation in the integrated Lyman alpha flux, because the stellar line is very much broader than the interstellar absorption.

Ge nanopillar solar cells epitaxially grown by metalorganic chemical vapor deposition

PubMed Central

Kim, Youngjo; Lam, Nguyen Dinh; Kim, Kangho; Park, Won-Kyu; Lee, Jaejin

2017-01-01

Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning. High quality n-ohmic contact is realized by protecting the top contact area during the nanopillar patterning. The short circuit current density and the power conversion efficiency of the Ge nanopillar solar cell are demonstrated to be improved up to 18 and 30%, respectively, compared to those of the Ge solar cell with a planar surface. PMID:28209964

Orbital period variations of two W UMa-type binaries: UY UMa and EF Boo

NASA Astrophysics Data System (ADS)

Yu, Yun-Xia; Zhang, Xu-Dong; Hu, Ke; Xiang, Fu-Yuan

2017-08-01

The orbital period variations of two W UMa-type contact binaries, UY UMa and EF Boo, are analyzed by using all available times of light minimum. It is detected that the general trends of their (O - C) curves show an upward parabolic variation, which reveals their continuous period increases at the rates of dP / dt = 2.545 ×10-7 days yr-1 and dP / dt = 2.623 ×10-7 days yr-1 , respectively. Meanwhile, UY UMa also shows a cyclic period variation with a small amplitude of A = 0.0026 days superposed on the long-term increase. Due to their contact configurations, the secular period increases are interpreted as a result of mass transfer from the less massive component to the more massive one. The cyclic period variation of UY UMa may be interpreted in terms of either the magnetic activity or the light time effect.

WZ Cygni: A Marginal Contact Binary in a Triple System?

NASA Astrophysics Data System (ADS)

Lee, Jae Woo; Kim, Seung-Lee; Lee, Chung-Uk; Kim, Ho-Il; Park, Jang-Ho; Hinse, Tobias Cornelius

2011-07-01

We present new multiband CCD photometry for WZ Cyg made on 22 nights in two observing seasons of 2007 and 2008. Our light-curve synthesis indicates that the system is in poor thermal contact with a fill-out factor of 4.8% and a temperature difference of 1447 K. Including our 40 timing measurements, a total of 371 times of minimum light spanning more than 112 yr were used for a period study. Detailed analysis of the O-C diagram showed that the orbital period has varied by a combination of an upward parabola and a sinusoid. The upward parabola means continuous period increase and indicates that some stellar masses are thermally transferred to the more massive primary star at a rate of about 5.80 × 10-8 M sun yr-1. The sinusoidal variation with a period of 47.9 yr and a semi-amplitude of 0.008 days can most likely be interpreted as the light-travel-time effect due to the existence of a low-mass M-type tertiary companion with a projected mass of M 3sin i 3 = 0.26 M sun. We examined the evolutionary status of WZ Cyg from the absolute dimensions of the eclipsing pair. It belongs to the marginal contact binary systems before the broken contact phase, consisting of a massive primary star with spectral type F4 and a secondary star with type K1.

Metal electrode for amorphous silicon solar cells

DOEpatents

Williams, Richard

1983-01-01

An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

Tidal Synchronization and Differential Rotation of Kepler Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Lurie, John C.; Vyhmeister, Karl; Hawley, Suzanne L.; Adilia, Jamel; Chen, Andrea; Davenport, James R. A.; Jurić, Mario; Puig-Holzman, Michael; Weisenburger, Kolby L.

2017-12-01

Few observational constraints exist for the tidal synchronization rate of late-type stars, despite its fundamental role in binary evolution. We visually inspected the light curves of 2278 eclipsing binaries (EBs) from the Kepler Eclipsing Binary Catalog to identify those with starspot modulations, as well as other types of out-of-eclipse variability. We report rotation periods for 816 EBs with starspot modulations, and find that 79% of EBs with orbital periods of less than 10 days are synchronized. However, a population of short-period EBs exists, with rotation periods typically 13% slower than synchronous, which we attribute to the differential rotation of high-latitude starspots. At 10 days, there is a transition from predominantly circular, synchronized EBs to predominantly eccentric, pseudosynchronized EBs. This transition period is in good agreement with the predicted and observed circularization period for Milky Way field binaries. At orbital periods greater than about 30 days, the amount of tidal synchronization decreases. We also report 12 previously unidentified candidate δ Scuti and γ Doradus pulsators, as well as a candidate RS CVn system with an evolved primary that exhibits starspot occultations. For short-period contact binaries, we observe a period-color relation and compare it to previous studies. As a whole, these results represent the largest homogeneous study of tidal synchronization of late-type stars.

CCD photometric analysis of the W UMa-type binary V376 Andromeda

NASA Astrophysics Data System (ADS)

Çiçek, C.

2011-01-01

This study presents the absolute parameters of the contact binary system V376 And. CCD photometric observations were made at the Çanakkale Onsekiz Mart University Observatory in 2004. The instrumental magnitudes of all observed stars were converted into standard magnitudes. New BV light curves of the system were analysed using the Wilson-Devinney method supplemented with a Monte Carlo type algorithm. Since there are large asymmetries between maxima (i.e., O'Connell effect) in these light curves, two different models (one with a cool spot and one with a hot spot) were applied to the photometric data. The best fit, which was obtained with a large hot spot on the secondary component, gives V376 And as an A sub-type contact binary in poor thermal contact and a small value of the filling factor ( f ≈ 0.07). Combining the solutions of our light curves and Rucinski et al. (2001)'s radial velocity curves, the following absolute parameters of the components were determined: M1 = 2.44 ± 0.04 M ⊙, M2 = 0.74 ± 0.03 M ⊙, R1 = 2.60 ± 0.03 R ⊙, R2 = 1.51 ± 0.02 R ⊙, L1 = 40 ± 4 L ⊙ and L2 = 5 ± 1 L ⊙. We also discuss the evolution of the system, which appears to have an age of 1.6 Gyr. The distance to V376 And was calculated as 230 ± 20 pc from this analysis, taking into account interstellar extinction.

Close encounters of the third-body kind. [intruding bodies in binary star systems

NASA Technical Reports Server (NTRS)

Davies, M. B.; Benz, W.; Hills, J. G.

1994-01-01

We simulated encounters involving binaries of two eccentricities: e = 0 (i.e., circular binaries) and e = 0.5. In both cases the binary contained a point mass of 1.4 solar masses (i.e., a neutron star) and a 0.8 solar masses main-sequence star modeled as a polytrope. The semimajor axes of both binaries were set to 60 solar radii (0.28 AU). We considered intruders of three masses: 1.4 solar masses (a neutron star), 0.8 solar masses (a main-sequence star or a higher mass white dwarf), and 0.64 solar masses (a more typical mass white dwarf). Our strategy was to perform a large number (40,000) of encounters using a three-body code, then to rerun a small number of cases with a three-dimensional smoothed particle hydrodynamics (SPH) code to determine the importance of hydrodynamical effects. Using the results of the three-body runs, we computed the exchange across sections, sigma(sub ex). From the results of the SPH runs, we computed the cross sections for clean exchange, denoted by sigma(sub cx); the formation of a triple system, denoted by sigma(sub trp); and the formation of a merged binary with an object formed from the merger of two of the stars left in orbit around the third star, denoted by sigma(sub mb). For encounters between either binary and a 1.4 solar masses neutron star, sigma(sub cx) approx. 0.7 sigma(sub ex) and sigma(sub mb) + sigma(sub trp) approx. 0.3 sigma(sub ex). For encounters between either binary and the 0.8 solar masses main-sequence star, sigma(sub cx) approx. 0.50 sigma(sub ex) and sigma(sub mb) + sigma(sub trp) approx. 1.0 sigma(sub ex). If the main sequence star is replaced by a main-sequence star of the same mass, we have sigma(sub cx) approx. 0.5 sigma(sub ex) and sigma(sub mb) + sigma(sub trp) approx. 1.6 sigma(sub ex). Although the exchange cross section is a sensitive function of intruder mass, we see that the cross section to produce merged binaries is roughly independent of intruder mass. The merged binaries produced have semi-major axes much larger than either those of the original binaries or those of binaries produced in clean exchanges. Coupled with their lower kick velocities, received from the encounters, their larger size will enhance their cross section, shortening the waiting time to a subsequent encounter with another single star.

Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities

NASA Astrophysics Data System (ADS)

Haase, Felix; Kiefer, Fabian; Schäfer, Sören; Kruse, Christian; Krügener, Jan; Brendel, Rolf; Peibst, Robby

2017-08-01

We demonstrate an independently confirmed 25.0%-efficient interdigitated back contact silicon solar cell with passivating polycrystalline silicon (poly-Si) on oxide (POLO) contacts that enable a high open circuit voltage of 723 mV. We use n-type POLO contacts with a measured saturation current density of J 0n = 4 fA cm-2 and p-type POLO contacts with J 0p = 10 fA cm-2. The textured front side and the gaps between the POLO contacts on the rear are passivated by aluminum oxide (AlO x ) with J 0AlO x = 6 fA cm-2 as measured after deposition. We analyze the recombination characteristics of our solar cells at different process steps using spatially resolved injection-dependent carrier lifetimes measured by infrared lifetime mapping. The implied pseudo-efficiency of the unmasked cell, i.e., cell and perimeter region are illuminated during measurement, is 26.2% before contact opening, 26.0% after contact opening and 25.7% for the finished cell. This reduction is due to an increase in the saturation current density of the AlO x passivation during chemical etching of the contact openings and of the rear side metallization. The difference between the implied pseudo-efficiency and the actual efficiency of 25.0% as determined by designated-area light current-voltage (I-V) measurements is due to series resistance and diffusion of excess carriers into the non-illuminated perimeter region.

A VLT/NACO survey for triple and quadruple systems among visual pre-main sequence binaries

NASA Astrophysics Data System (ADS)

Correia, S.; Zinnecker, H.; Ratzka, Th.; Sterzik, M. F.

2006-12-01

Aims.This paper describes a systematic search for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries. Methods: .We conducted an Adaptive Optics survey of a sample of 58 PMS wide binaries from various star-forming regions, which include 52 T Tauri systems with mostly K- and M-type primaries, with the NIR instrument NACO at the VLT. Results: .Of these 52 systems, 7 are found to be triple (2 new) and 7 quadruple (1 new). The new close companions are most likely physically bound based on their probability of chance projection and, for some of them, on their position on a color-color diagram. The corresponding degree of multiplicity among wide binaries (number of triples and quadruples divided by the number of systems) is 26.9 ± 7.2% in the projected separation range ~0.07 arcsec -12'', with the largest contribution from the Taurus-Auriga cloud. We also found that this degree of multiplicity is twice in Taurus compared to Ophiuchus and Chamaeleon for which the same number of sources are present in our sample. Considering a restricted sample composed of systems at distance 140-190 pc, the degree of multiplicity is 26.8 ± 8.1%, in the separation range 10/14 AU-1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed frequency agrees with results from previous multiplicity surveys within the uncertainties, although a significant overabundance of quadruple systems compared to triple systems is apparent. Tentatively including the spectroscopic pairs in our restricted sample and comparing the multiplicity fractions to those measured for solar-type main-sequence stars in the solar neighborhood leads to the conclusion that both the ratio of triples to binaries and the ratio of quadruples to triples seems to be in excess among young stars. Most of the current numerical simulations of multiple star formation, and especially smoothed particles hydrodynamics simulations, over-predict the fraction of high-order multiplicity when compared to our results. The circumstellar properties around the individual components of our high-order multiple systems tend to favor mixed systems (i.e. systems including components of wTTS and cTTS type), which is in general agreement with previous studies of disks in binaries, with the exception of Taurus, where we find a preponderance of similar type of components among the multiples studied.

Spectroscopic observations of the detached binary PG 1413 + 015

NASA Technical Reports Server (NTRS)

Fulbright, Michael S.; Liebert, James; Bergeron, P.; Green, Richard

1993-01-01

We present improved estimates of the stellar parameters of the eclipsing, precataclysmic binary system PG 1413 + 015 (GH Vir), which has an orbital period of only 8h16m. Model atmosphere fits a Balmer line profiles yield T(eff) = 48,800 +/- 1200 K and log g = 7.70 +/- 0.11 for the DAO white dwarf primary star, from which a mass of 0.51 +/- 0.04 solar mass is inferred using evolutionary models. An ultraviolet spectrum obtained with the IUE Observatory has a slope consistent with this temperature and the assumption of no interstellar extinction. A red CCD spectrum of the secondary star during the 12-minute total eclipse indicates a spectral type of M3 V-M5 V. Reanalysis of the eclipse light curve leads to an inferred radius of 0.15 solar radius and a mass of 0.10 solar mass for the secondary, the latter being marginally consistent with the spectral type. Reprocessing on the facing side of the secondary produces phase-dependent Balmer line emission and detectable variations in the continuum from 6500-9000 A. The observed levels of reprocessing are consistent with expectations based on the above stellar parameters.

A Photometric Study of the Eclipsing Binary NSV 1000

NASA Astrophysics Data System (ADS)

Richards, T. J.; Bembrick, C. S.

2018-06-01

Abstract NSV 1000 is an unstudied eclipsing binary in Hydrus. Our photometric research in the period 2014-2016 shows it is a W UMa system with a period of 0.336 579 6(3) d, consistent with the catalogued period. Model fitting to our B, V, and Ic light curves shows the two stars are barely in contact. The parameters derived from the fit satisfy the broadly defined characteristics of a W-type W UMa system.

Observations and Analysis of the F-type Near-Contact Binary, NSVS 1054 1123

NASA Astrophysics Data System (ADS)

Caton, Daniel Bruce; Samec, Ronald G.; Faulkner, Danny R.

2018-01-01

NSVS 1054 1123 is a F2±2 type (T~ 6750K) eclipsing binary. It was observed in April and May, 2015 at the Appalachian State University’s Dark Sky Observatory in North Carolina with the 32-inch telescope. Six times of minimum light were determined from our present observations, which include two primary eclipses and four secondary eclipses:HJD Min I = 2457113.9330 ±0. 0.0002, 24 57147.8761 ±0.0001,HJD Min II = 2457117.80391 ±0.0006, 2457136.8600 ±0. 0007, 2457148.77040 ±0.0004, 2457151.7468 ±0.0002In addition, six observations at minima were introduced as low weighted times of minimum light taken from archived NSVS Data.The following quadratic ephemerides was determined from all available times of minimum light:JD Hel Min I=2457147.87646±0.00049d + 0 .5954966±0.0000065 X E -0.0000000017± 0.0000000007 X E2A period decrease may indicate that the binary is undergoing magnetic braking and is approaching its contact configuration. A BVRcIc simultaneous (preliminary) Wilson-Devinney Program (W-D) solution indicates that the system has a mass ratio of 0.5828±0.0004, and a component temperature difference of 2350 K. The large DT in the components verify that the binary is not in contact. A Binary Maker fitted hot spot altered slightly but was not eliminated in the WD Synthetic Light Curve Computations. It remains on the larger component at the equator on the correct (following) side for a stream spot directed from the secondary component (as dictated by the Coriolis effect). This could indicate that the components are near filling their respective Roche Lobes. The fill-out of our model is -0.036 for the primary component and -0.048 for the secondary component. The inclination is ~79 degrees, not enough for the system to undergo a total eclipse.Additional and more detailed information is given in this report.

BVRI Photometric Study of the High Mass Ratio, Detached, Pre-contact W UMa Binary GQ Cancri

NASA Astrophysics Data System (ADS)

Samec, R. G.; Olson, A.; Caton, D.; Faulkner, D. R.

2017-12-01

CCD BVRcIc light curves of GQ Cancri were observed in April 2013 using the SARA North 0.9-meter Telescope at Kitt Peak National Observatory in Arizona in remote mode. It is a high-amplitude (V 0.9 magnitude) K0±V type eclipsing binary (T1 5250 K) with a photometrically-determined mass ratio of M2 / M1 = 0.80. Its spectral color type classifies it as a pre-contact W UMa Binary (PCWB). The Wilson-Devinney Mode 2 solutions show that the system has a detached binary configuration with fill-outs of 94% and 98% for the primary and secondary component, respectively. As expected, the light curve is asymmetric due to spot activity. Three times of minimum light were calculated, for two primary eclipses and one secondary eclipse, from our present observations. In total, some 26 times of minimum light covering nearly 20 years of observation were used to determine linear and quadratic ephemerides. It is noted that the light curve solution remained in a detached state for every iteration of the computer runs. The components are very similar with a computed temperature difference of only 4 K, and the flux of the primary component accounts for 53±55% of the system's light in B, V, Rc, and Ic. A 12-degree radius high latitude white spot (faculae) was iterated on the primary component.

The close binary frequency of Wolf-Rayet stars as a function of metallicity in M31 and M33

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

Neugent, Kathryn F.; Massey, Philip, E-mail: kneugent@lowell.edu, E-mail: phil.massey@lowell.edu

Massive star evolutionary models generally predict the correct ratio of WC-type and WN-type Wolf-Rayet stars at low metallicities, but underestimate the ratio at higher (solar and above) metallicities. One possible explanation for this failure is perhaps single-star models are not sufficient and Roche-lobe overflow in close binaries is necessary to produce the 'extra' WC stars at higher metallicities. However, this would require the frequency of close massive binaries to be metallicity dependent. Here we test this hypothesis by searching for close Wolf-Rayet binaries in the high metallicity environments of M31 and the center of M33 as well as in themore » lower metallicity environments of the middle and outer regions of M33. After identifying ∼100 Wolf-Rayet binaries based on radial velocity variations, we conclude that the close binary frequency of Wolf-Rayets is not metallicity dependent and thus other factors must be responsible for the overabundance of WC stars at high metallicities. However, our initial identifications and observations of these close binaries have already been put to good use as we are currently observing additional epochs for eventual orbit and mass determinations.« less

A contact binary asteroid evolutionary cycle driven by BYORP & the classical Laplace plane

NASA Astrophysics Data System (ADS)

Rieger, Samantha; Scheeres, Daniel J.

2017-10-01

Several contact binaries have been observed to have high obliquities distributed around 90°. With this information, we explore the possibility of these high obliquities being a key characteristic that causes an evolutionary cycle of contact binary formation and separation.The contact binary cycle begins with a single asteroid that is spinning up due to the YORP effect. For the binary cycle we assume YORP will drive the obliquity to 90°. Eventually, the asteroid will reach a critical spin frequency that will cause the asteroid to fission into a binary. We assume that the mass-ratio, q, of the system is greater than 0.2. With a high q, the secondary will not escape/impact the primary but will evolve through tides into a stable circular double-synchronous orbit. The binary being synchronous will cause the forces from BYORP to have secular effects on the system. For this cycle, BYORP will need to expand the secondary away from the primary.As the system expands, we have found that the secondary will follow the classical Laplace plane. Therefore, the secondary’s orbit will increase in inclination with respect to the equator as the secondary’s orbit expands. The Laplace plane is a stable orbit to perturbations from J2 & Sun tides except for an instability region that exists for primaries with obliquities above 68.875° & a secondary orbital radius of 13.5-19.5 primary radii. Once BYORP expands the secondary into this instability region, the eccentricity of the secondary’s orbit will increase until the orbit intersects with the primary & causes an impact. This impact will create a contact binary with a new obliquity that will randomly range from 23°-150°. The cycle will begin again with YORP driving the contact binary to an obliquity of 90°.Our contribution will discuss the proposed contact binary cycle in more detail, including the mechanics of the system that drives the events given above. We will include investigations into how losing synchronous lock will disrupt the eccentricity growth in the Laplace plane instability region. We will also discuss the time scales of each event to help predict which part of the cycle we will most likely to be observing when discovering new contact binaries & binary systems.

A survey of stellar families: Multiplicity of solar-type stars

NASA Astrophysics Data System (ADS)

Raghavan, Deepak

I present the results of a comprehensive assessment of companions to 454 solar- type stars within 25 pc. New observational aspects of this work include surveys for (1) very close companions with long-baseline interferometry at the Center for High Angular Resolution Astronomy (CHARA) Array, (2) close companions with speckle interferometry, and (3) wide proper motion companions identified by blinking multi-epoch archival images. I have also obtained and included unpublished results from extensive radial velocity monitoring programs. The many sources utilized enable a thorough evaluation of stellar and brown dwarf companions. The results presented here include eight new companion discoveries, four of which are wide common proper motion pairs discovered by blinking archival images, and four more are from the spectroscopic data. The overall observed fractions of single, double, triple, and higher order systems are 57%±3%, 33%±2%, 8%±1%, and 3%±1%, respectively, counting all stellar and brown dwarf companions. The incompleteness analysis indicates that only a few undiscovered companions remain in this well-studied sample, showing that a majority of the solar-type stars are single. Bluer, more massive stars are more likely to have companions than redder, less massive ones. I confirm earlier expectations that more active stars are more likely to have companions. A preliminary, but important indication is that brown dwarfs, like planets, prefer stars with higher metallicity, tentatively suggesting that brown dwarfs may form like planets when they are companions to stars. The period distribution is unimodal and roughly Gaussian with peak and median values of about 300 years. The period-eccentricity relation shows a roughly flat distribution beyond the circularization limit of about 12 days. The mass- ratio distribution shows a clear discontinuity near a value of one, indicating a preference for twins, which are not confined to short orbital periods, suggesting that stars form by multiple formation mechanisms. The ratio of planet hosts among single, binary, and multiple systems are statistically indistinguishable, suggesting that planets are as likely to form around single stars as they are around components of binary or multiple systems at sufficiently wide separations. INDEX WORDS: Stellar multiplicity, Binary stars, Solar-type stars, Solar neighborhood, Exoplanet systems, Brown dwarfs, Survey, Long baseline interferometry, Radial velocity

Preparation of p-type NiO films by reactive sputtering and their application to CdTe solar cells

NASA Astrophysics Data System (ADS)

Ishikawa, Ryousuke; Furuya, Yasuaki; Araki, Ryouichi; Nomoto, Takahiro; Ogawa, Yohei; Hosono, Aikyo; Okamoto, Tamotsu; Tsuboi, Nozomu

2016-02-01

Transparent p-type NiO films were prepared by reactive sputtering using the facing-target system under Ar-diluted O2 gas at Tsub of 30 and 200 °C. The increasing intensity of dominant X-ray diffraction (XRD) peaks indicates improvements in the crystallinity of NiO films upon Cu doping. In spite of the crystallographic and optical changes after Cu-doping, the electrical properties of Cu-doped NiO films were slightly improved. Upon Ag-doping at 30 °C under low O2 concentration, on the other hand, the intensity of the dominant (111) XRD peaks was suppressed and p-type conductivity increased from ˜10-3 to ˜10-1 S cm-1. Finally, our Ag-doped NiO films were applied as the back contact of CdTe solar cells. CdTe solar cells with a glass/ITO/CdS/CdTe/NiO structure exhibited an efficiency of 6.4%, suggesting the high potential of using p-type NiO for the back-contact film in thin-film solar cells.

Three-body affairs in the outer solar system

NASA Astrophysics Data System (ADS)

Funato, Yoko; Makino, Junichiro; Hut, Piet; Kokubo, Eiichiro; Kinoshita, Daisuke

Recent observations have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper Belt. The TNO binaries are strikingly different from asteroid binaries in four respects: their frequency is an order of magnitude larger, the mass ratio of their components is closer to unity, and their orbits are wider and highly eccentric. Two explanations have been proposed for their formation, one assuming large numbers of massive bodies, and one assuming large numbers of light bodies. We argue that both assumptions are unwarranted, and we show how TNO binaries can be produced from a modest number of intermediate-mass bodies of the type predicted by the gravitational instability theory for the formation of planetesimals. We start with a TNO binary population similar to the asteroid binary population, but subsequently modified by three-body exchange reactions, a process that is far more efficient in the Kuiper belt, because of the much smaller tidal perturbations by the Sun. Our mechanism can naturally account for all four characteristics that distinguish TNO binaries from main-belt asteroid binaries.

Applications of novel effects derived from Si ingot growth inside Si melt without contact with crucible wall using noncontact crucible method to high-efficiency solar cells

NASA Astrophysics Data System (ADS)

Nakajima, Kazuo; Ono, Satoshi; Kaneko, Yuzuru; Murai, Ryota; Shirasawa, Katsuhiko; Fukuda, Tetsuo; Takato, Hidetaka; Jensen, Mallory A.; Youssef, Amanda; Looney, Erin E.; Buonassisi, Tonio; Martel, Benoit; Dubois, Sèbastien; Jouini, Anis

2017-06-01

The noncontact crucible (NOC) method was proposed for obtaining Si single bulk crystals with a large diameter and volume using a cast furnace and solar cells with high conversion efficiency and yield. This method has several novel characteristics that originate from its key feature that ingots can be grown inside a Si melt without contact with a crucible wall. Si ingots for solar cells were grown by utilizing the merits resulting from these characteristics. Single ingots with high quality were grown by the NOC method after furnace cleaning, and the minority carrier lifetime was measured to investigate reduction of the number of impurities. A p-type ingot with a convex growth interface in the growth direction was also grown after furnace cleaning. For p-type solar cells prepared using wafers cut from the ingot, the highest and average conversion efficiencies were 19.14% and 19.0%, respectively, which were obtained using the same solar cell structure and process as those employed to obtain a conversion efficiency of 19.1% for a p-type Czochralski (CZ) wafer. Using the cast furnace, solar cells with a conversion efficiency and yield as high as those of CZ solar cells were obtained by the NOC method.

THE ORIGIN OF ENHANCED ACTIVITY IN THE SUNS OF M67

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

Reiners, A.; Giampapa, M. S., E-mail: Ansgar.Reiners@phys.uni-goettingen.d, E-mail: giampapa@noao.ed

2009-12-10

We report the results of the analysis of high-resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sin iapprox< 2-3 km s{sup -1}) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of evenmore » solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of v sin i = 4 +- 0.5 km s{sup -1}, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency.« less

Reverse Algols

NASA Technical Reports Server (NTRS)

Leung, K. C.

1989-01-01

Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.

Robo-AO Discovery and Basic Characterization of Wide Multiple Star Systems in the Pleiades, Praesepe, and NGC 2264 Clusters

NASA Astrophysics Data System (ADS)

Hillenbrand, Lynne A.; Zhang, Celia; Riddle, Reed L.; Baranec, Christoph; Ziegler, Carl; Law, Nicholas M.; Stauffer, John

2018-02-01

We identify and roughly characterize 66 candidate binary star systems in the Pleiades, Praesepe, and NGC 2264 star clusters, based on robotic adaptive optics imaging data obtained using Robo-AO at the Palomar 60″ telescope. Only ∼10% of our imaged pairs were previously known. We detect companions at red optical wavelengths, with physical separations ranging from a few tens to a few thousands of au. A three-sigma contrast curve generated for each final image provides upper limits to the brightness ratios for any undetected putative companions. The observations are sensitive to companions with a maximum contrast of ∼6m at larger separations. At smaller separations, the mean (best) raw contrast at 2″ is 3.ͫ8 (6m), at 1″ is 3.ͫ0 (4.ͫ5), and at 0.″5 is 1.ͫ9 (3m). Point-spread function subtraction can recover nearly the full contrast in the closer separations. For detected candidate binary pairs, we report separations, position angles, and relative magnitudes. Theoretical isochrones appropriate to the Pleiades and Praesepe clusters are then used to determine the corresponding binary mass ratios, which range from 0.2 to 0.9 in q={m}2/{m}1. For our sample of roughly solar-mass (FGK type) stars in NGC 2264 and sub-solar-mass (K and early M-type) primaries in the Pleiades and Praesepe, the overall binary frequency is measured at ∼15.5% ± 2%. However, this value should be considered a lower limit to the true binary fraction within the specified separation and mass ratio ranges in these clusters, given that complex and uncertain corrections for sensitivity and completeness have not been applied.

Contact integrity testing of stress-tested silicon terrestrial solar cells

NASA Technical Reports Server (NTRS)

Prince, J. L.; Lathrop, J. W.; Witter, G. W.

1980-01-01

A test procedure was developed and applied to terrestrial silicon solar cells in order to determine the effect of accelerated environmental and time-temperature aging on metal contact integrity. Quantities of cells of four different manufacturers were given the contact integrity test after being subjected to accelerated stress tests that included forward bias-temperature, thermal cycle and thermal shock, power cycle, and bias-temperature humidity tests at two temperature-humidity levels. Significant effects due to certain stress tests were found for some cell types. It is concluded that cells fabricated using plated nickel/solder metallization showed significantly more serious contact integrity degradation than silver-metallized cells.

What and whence 1I/`Oumuamua: a contact binary from the debris of a young planetary system?

NASA Astrophysics Data System (ADS)

Gaidos, E.

2018-07-01

The first confirmed interstellar interloper in our Solar system, 1I/`Oumuamua, is likely to be a minor body ejected from another star, but its brief flyby and faintness made it difficult to study. Two remarkable properties are its large (up to 2.5 mag) rotational variability and its motion relative to the Sun before encounter. The former suggests an extremely elongated shape (aspect ratio ≥ 10) and the latter an origin from the protoplanetary disc of a young star in a nearby association. Against expectations, it is also not comet-like. 1I/`Oumuamua's variability can also be explained if it is a contact binary composed of near-equilibrium ellipsoidal components and heterogeneous surfaces, i.e. brighter, dust-mantled inner-facing hemispheres and darker, dust-free outer-facing poles. Such shapes are a plausible outcome of radiation, tides, and collisions in systems where planets are clearing planetesimal discs. The probability that 1I/`Oumuamua has the same motion as a young (≲100 Myr) stellar association by coincidence is <1 per cent. If it is young, its detection versus more numerous, older counterparts could be explained as a selection effect due to darkening of surfaces by Galactic cosmic rays and loss of dust. 1I/`Oumuamua's apparent lack of ices can be explained if ejected rocky planetesimals are characteristically smaller and thus far more numerous than their icy counterparts: the Solar system may currently host several such objects captured by the combined gravity of Jupiter and the Sun.

What and Whence 1I/`Oumuamua: A Contact Binary from the Debris of a Young Planetary System?

NASA Astrophysics Data System (ADS)

Gaidos, E.

2018-04-01

The first confirmed interstellar interloper in our Solar System, 1I/`Oumuamua, is likely to be a minor body ejected from another star, but its brief flyby and faintness made it difficult to study. Two remarkable properties are its large (up to 2.5 mag) rotational variability and its motion relative to the Sun before encounter. The former suggests an extremely elongated shape (aspect ratio ≥10) and the latter an origin from the protoplanetary disk of a young star in a nearby association. Against expectations, it is also not comet-like. 1I/`Oumuamua's variability can also be explained if it is a contact binary composed of near-equilibrium ellipsoidal components and heterogeneous surfaces, i.e. brighter, dust-mantled inner-facing hemispheres and darker, dust-free outer-facing poles. Such shapes are a plausible outcome of radiation, tides and collisions in systems where planets are clearing planetesimal disks. The probability that 1I/'Oumuamua has the same motion as a young (≲ 100 Myr) stellar association by coincidence is <1%. If it is young, its detection vs. more numerous, older counterparts could be explained as a selection effect due to darkening of surfaces by Galactic cosmic rays and loss of dust. 1I/`Oumuamua's apparent lack of ices can be explained if ejected rocky planetesimals are characteristically smaller and thus far more numerous than their icy counterparts: the Solar System may currently host several such objects captured by the combined gravity of Jupiter and the Sun.

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.

Development of technologies for welding interconnects to fifty-micron thick silicon solar cells

NASA Technical Reports Server (NTRS)

Patterson, R. E.

1982-01-01

A program was conducted to develop technologies for welding interconnects to 50 microns thick, 2 by 2 cm solar cells. The cells were characterized with respect to electrical performance, cell thickness, silver contact thickness, contact waviness, bowing, and fracture strength. Weld schedules were independently developed for each of the three cell types and were coincidentally identical. Thermal shock tests (100 cycles from 100 C to -180 C) were performed on 16 cell coupons for each cell type without any weld joint failures or electrical degradation. Three 48 cell modules (one for each cell type) were assembled with 50 microns thick cells, frosted fused silica covers, silver clad Invar interconnectors, and Kapton substrates.

Welding interconnects to 50-micron silicon solar cells

NASA Technical Reports Server (NTRS)

Patterson, R. E.; Mesch, H. G.

1983-01-01

A program was conducted to develop technologies for welding interconnects to 50-micron thick, 2 by 2 cm solar cells obtained from three suppliers. The cells were characterized with respect to electrical performance, cell thickness, silver contact thickness, contact waviness, bowing, and fracture strength. Weld schedules were independently developed for each of the three cell types and were coincidentally identical. Thermal shock tests (100 cycles from 100 deg to -180 deg C) were performed on 16-cell coupons for each cell type without any weld joint failures or electrical degradation. Three 48-cell modules (one for each cell type) were assembled with 50-micron thick cells, frosted fused silica covers, silver clad Invar interconnectors, and Kapton substrates.

A search for spectroscopic binaries among the runaway O type stars

NASA Technical Reports Server (NTRS)

Stone, R. C.

1982-01-01

Numerous radial velocity measurements of medium dispersion were made for the 10 brighter stars given in Stone's list of very probable O type runaways. All plates were measured with the KPNO PDS microdensitometer, and a new iterative reductional analysis was used to derive plate velocities, which are estimated to be 1.6 times more accurate internally than those found by using the traditional method. Of thse stars, psi Per, alpha Cam, HD 188209, and 26 Cep are identified as probable velocity variables, while 9 Sge, lambda Cep, and HD 218915 are classed as possible variables. If the source of this variability is Keplerian rather than atmospheric, which cannot be established unequivocally from the observations of this paper, psi Per could be a spectroscopic binary with a black hole companion, and at least 1.2 solar mass. The detection of runaway binary systems from radial velocity measurements is discussed.

Detection of the Simplest Sugar, Glycolaldehyde, in a Solar-type Protostar with ALMA

NASA Astrophysics Data System (ADS)

Jørgensen, Jes K.; Favre, Cécile; Bisschop, Suzanne E.; Bourke, Tyler L.; van Dishoeck, Ewine F.; Schmalzl, Markus

2012-09-01

Glycolaldehyde (HCOCH2OH) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. In this Letter we present the first detection of 13 transitions of glycolaldehyde around a solar-type young star, through Atacama Large Millimeter Array (ALMA) observations of the Class 0 protostellar binary IRAS 16293-2422 at 220 GHz (6 transitions) and 690 GHz (7 transitions). The glycolaldehyde lines have their origin in warm (200-300 K) gas close to the individual components of the binary. Glycolaldehyde co-exists with its isomer, methyl formate (HCOOCH3), which is a factor 10-15 more abundant toward the two sources. The data also show a tentative detection of ethylene glycol, the reduced alcohol of glycolaldehyde. In the 690 GHz data, the seven transitions predicted to have the highest optical depths based on modeling of the 220 GHz lines all show redshifted absorption profiles toward one of the components in the binary (IRAS 16293B) indicative of infall and emission at the systemic velocity offset from this by about 0farcs2 (25 AU). We discuss the constraints on the chemical formation of glycolaldehyde and other organic species—in particular, in the context of laboratory experiments of photochemistry of methanol-containing ices. The relative abundances appear to be consistent with UV photochemistry of a CH3OH-CO mixed ice that has undergone mild heating. The order of magnitude increase in line density in these early ALMA data illustrates its huge potential to reveal the full chemical complexity associated with the formation of solar system analogs.

Multifrequency observations of symbiotic stars

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.

1988-01-01

The discovery of symbiotic stars is described, and the results of multifrequency observations made during the past two decades are presented. Observational data identify symbiotic stars as long-period binary systems that can be divided into two basic physical classes: detached symbiotics containing a red giant (or a Mira variable), and semidetached symbiotics containing a lobe-filling red giant and a solar-type main sequence star. Three components are typically observed: (1) the cool giant component with an effective temperature of 2500-4000 K, which can be divided by the IR spectral classification into normal M giants (S-types) and heavily reddened Mira variables (D-types); (2) the hot companion displaying a bright blue continuum at UV wavelengths, which is sometimes also an X-ray source; and (3) a gaseous nebula enveloping the binary.

A Catalog of 1022 Bright Contact Binary Stars

NASA Astrophysics Data System (ADS)

Gettel, S. J.; Geske, M. T.; McKay, T. A.

2006-01-01

In this work we describe a large new sample of contact binary stars extracted in a uniform manner from sky patrol data taken by the ROTSE-I telescope. Extensive ROTSE-I light-curve data are combined with J-, H-, and K-band near-infrared data taken from the Two Micron All Sky Survey to add color information. Contact binary candidates are selected using the observed period-color relation. Candidates are confirmed by visual examination of the light curves. To enhance the utility of this catalog, we derive a new J-H period-color-luminosity relation and use this to estimate distances for the entire catalog. From these distance estimates we derive an estimated contact binary space density of (1.7+/-0.6)×10-5 pc-3.

The Cluster AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster M22

NASA Astrophysics Data System (ADS)

Rozyczka, M.; Thompson, I. B.; Pych, W.; Narloch, W.; Poleski, R.; Schwarzenberg-Czerny, A.

2017-09-01

The field of the globular cluster M22 (NGC 6656) was monitored between 2000 and 2008 in a search for variable stars. BV light curves were obtained for 359 periodic, likely periodic, and long-term variables, 238 of which are new detections. 39 newly detected variables, and 63 previously known ones are members or likely members of the cluster, including 20 SX Phe, 10 RRab and 16 RRc type pulsators, one BL Her type pulsator, 21 contact binaries, and 9 detached or semi-detached eclipsing binaries. The most interesting among the identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a β Lyr type binary on the blue horizontal branch, V129 - a blue/yellow straggler with a W UMa-like light curve, located halfway between the extreme horizontal branch and red giant branch, and V134 - an extreme horizontal branch object with P=2.33 d and a nearly sinusoidal light curve. All four of them are proper motion members of the cluster. Among nonmembers, a P=2.83 d detached eclipsing binary hosting a δ Sct type pulsator was found, and a peculiar P=0.93 d binary with ellipsoidal modulation and narrow minimum in the middle of one of the descending shoulders of the sinusoid. We also collected substantial new data for previously known variables. In particular we revise the statistics of the occurrence of the Blazhko effect in RR Lyr type variables of M22.

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces

PubMed Central

Litzov, Ivan; Brabec, Christoph J.

2013-01-01

Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeOx) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n-type- and p-type-like MeOx interface materials consisting of binary compounds AxBy. Their performance for applications as electron transport/extraction layers (ETL/EEL) and as hole transport/extraction layers (HTL/HEL) in inverted BHJ solar cells will be reviewed and discussed. PMID:28788423

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces.

PubMed

Litzov, Ivan; Brabec, Christoph J

2013-12-10

Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeO x ) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n -type- and p -type-like MeO x interface materials consisting of binary compounds A x B y . Their performance for applications as electron transport/extraction layers (ETL/EEL) and as hole transport/extraction layers (HTL/HEL) in inverted BHJ solar cells will be reviewed and discussed.

Spectral irradiance curve calculations for any type of solar eclipse

NASA Technical Reports Server (NTRS)

Deepak, A.; Merrill, J. E.

1974-01-01

A simple procedure is described for calculating the eclipse function (EF), alpha, and hence the spectral irradiance curve (SIC), (1-alpha), for any type of solar eclipse: namely, the occultation (partial/total) eclipse and the transit (partial/annular) eclipse. The SIC (or the EF) gives the variation of the amount (or the loss) of solar radiation of a given wavelength reaching a distant observer for various positions of the moon across the sun. The scheme is based on the theory of light curves of eclipsing binaries, the results of which are tabulated in Merrill's Tables, and is valid for all wavelengths for which the solar limb-darkening obeys the cosine law: J = sub c (1 - X + X cost gamma). As an example of computing the SIC for an occultation eclipse which may be total, the calculations for the March 7, 1970, eclipse are described in detail.

Can binary stars test solar models?

NASA Technical Reports Server (NTRS)

Popper, D. M.; Ulrich, R. K.

1986-01-01

The position in the H-R diagram of the approximately solar-mass component of the Hyades eclipsing binary, HD 27130, is compared with the predictions of stellar structure theory. The stellar models are calibrated by matching a model with the solar heavy element composition and age to the solar radius and luminosity. The comparison to the Hyades binary then is a test of the prediction that the initial solar luminosity was only about 0.7 times the present solar luminosity. The agreement is satisfactory, lending a measure of confidence to the solar model employed, provided that the initial helium abundance of the Hyades stars is not greater than that of the sun and is not less by more than about 0.03 in Y. Unless the model is grossly incorrect, the inference of Stromgren, Olsen, and Gustafsson (1982) from the 'Hyades anomaly' in intermediate-band photometry that Y(Hyades) is less than Y(solar) by 0.1 or 0.15 is rejected by the observed properties of HD 27130.

p-type Mesoscopic nickel oxide/organometallic perovskite heterojunction solar cells.

PubMed

Wang, Kuo-Chin; Jeng, Jun-Yuan; Shen, Po-Shen; Chang, Yu-Cheng; Diau, Eric Wei-Guang; Tsai, Cheng-Hung; Chao, Tzu-Yang; Hsu, Hsu-Cheng; Lin, Pei-Ying; Chen, Peter; Guo, Tzung-Fang; Wen, Ten-Chin

2014-04-23

In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics.

p-type Mesoscopic Nickel Oxide/Organometallic Perovskite Heterojunction Solar Cells

PubMed Central

Wang, Kuo-Chin; Jeng, Jun-Yuan; Shen, Po-Shen; Chang, Yu-Cheng; Diau, Eric Wei-Guang; Tsai, Cheng-Hung; Chao, Tzu-Yang; Hsu, Hsu-Cheng; Lin, Pei-Ying; Chen, Peter; Guo, Tzung-Fang; Wen, Ten-Chin

2014-01-01

In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics. PMID:24755642

What Makes Red Giants Tick? Linking Tidal Forces, Activity, and Solar-Like Oscillations via Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Rawls, Meredith L.; Gaulme, Patrick; McKeever, Jean; Jackiewicz, Jason

2016-01-01

Thanks to advances in asteroseismology, red giants have become astrophysical laboratories for studying stellar evolution and probing the Milky Way. However, not all red giants show solar-like oscillations. It has been proposed that stronger tidal interactions from short-period binaries and increased magnetic activity on spotty giants are linked to absent or damped solar-like oscillations, yet each star tells a nuanced story. In this work, we characterize a subset of red giants in eclipsing binaries observed by Kepler. The binaries exhibit a range of orbital periods, solar-like oscillation behavior, and stellar activity. We use orbital solutions together with a suite of modeling tools to combine photometry and spectroscopy in a detailed analysis of tidal synchronization timescales, star spot activity, and stellar evolution histories. These red giants offer an unprecedented opportunity to test stellar physics and are important benchmarks for ensemble asteroseismology.

Photometric Monitoring of Short-Period Contact Binaries

NASA Astrophysics Data System (ADS)

Vanko, M.

2001-12-01

The first photoelectric B,V light curves of the contact binary FU Dra, as well as new B,V light curves of the contact binaries AH Aur, UV Lyn and YY CrB, obtained at the Stará Lesná and Skalnaté Pleso Observatories, are presented. New photometric elements of AH Aur, FU Dra and UV Lyn computed from these light curves were combined with published spectroscopic elements to derive the absolute parameters of the systems.

Photometric study and orbital period analysis of the W UMa type contact binary VZ Psc

NASA Astrophysics Data System (ADS)

Ma, S.; Li, K.; Li, Q.-C.; Gao, H.-Y.

2018-02-01

VZ Psc is a W-type contact binary system with a short period of 0.26125897 days. B, V, Rc and Ic light curves of the eclipsing binary system were obtained by using the 1.0 m reflecting telescope at Weihai Observatory of Shandong University. By collecting 136 times of minimum light, we studied the orbital period change of VZ Psc. A sinusoidal variation was discovered in the O - C diagram, and the amplitude of 0.d0023 and the period of 17.7 year were obtained. This can be caused by Applegate mechanism or light-time effect. Both the mechanisms are suited according to our investigation, but we prefer the latter that the light-time effect due to the presence of a third body results in the cyclic variation. By using the W-D program, we analyzed the four color light curves. Because of the asymmetric light curves and the possible third body, we used the spot mode of W-D program with and without L3. We found that a hot spot on the primary component with the third light leads to the best result. A very high filling factor of 94.4% ± 2.8% and orbit inclination of 53.2° were obtained.

Preliminary elements of the low mass ratio and moderate fill-out factor VSX J045718.3+405643 (GSC 02898-02901)

NASA Astrophysics Data System (ADS)

Acerbi, F.; Martignoni, M.; Barani, C.

2018-05-01

We present the results of our investigation of the geometrical parameters of the W UMa-type binary system VSX J045718.3+405643 (short name VSX J0457) based on new CCD B, V and Ic light curves. Our observations were carried out during six nights in November and December 2016 using the 0.25 m telescope of the Stazione Astronomica Betelgeuse in Magnago, Northern Italy. Six new times of minima and light elements have been determined and the observed light curves were analysed using the Wilson-Devinney code. The output model reveals that the system is a contact binary of A-Subtype of the W Ursae Majoris systems with a mass ratio of q ∼ 0.26 and a degree of contact factor f ∼ 32%. The primary component is hotter than the secondary by 95 K, this suggests us that the system is under thermal contact. The high orbital inclination (i = 82°.2) implies that VSX J0457 is a total eclipsing binary system and the photometric parameters here obtained are quite reliable. The absolute physical parameters of the two components in VSX J0457 are estimated. Based on these estimated parameters the evolutionary state of the system components is investigated and discussed. Combining our photometric solution with the 3-D correlation obtained for contact binaries by Gazeas (2009) we derive the masses and radii of the components of this eclipsing system as M1 = 1.44M⊙, M2 = 0.38M⊙, R1 = 1.55R⊙ and R2 = 0.87R⊙. The distance to VSX J0457 was calculated as 147 pc from this analysis, taking into account interstellar extinction.

Photometric study of two eclipsing binary stars: Light curve analysis and system parameters for GU CMa and SWASP J011732.10+525204.9

NASA Astrophysics Data System (ADS)

Shokry, A.; Saad, S. M.; Hamdy, M. A.; Beheary, M. M.; Abolazm, M. S.; Gadallah, K. A.; El-Depsey, M. H.; Al-Gazzar, M. S.

2018-02-01

A new photometric study of two eclipsing binary systems (GU CMa and SWASP J011732.10+525204.9) is presented. The accepted solutions of analyzing the light curves revealed that GU CMa is a semi-detached system consisting of two early spectral type components, (B2 and B2.5) while SWASP J011732.10+525204.9 is a contact binary with two late type components (K2 and M1). The primary component of each system is the massive one. The geometric configuration indicates that SWASP J011732.10+525204.9 passes through a very critical phase in which each component exactly fills its limited lobe with zero fill out ratio. New times of minimum and the absolute physical parameters for each system are determined. The evolution status for each system has been investigated.

New visual companions of solar-type stars within 25 pc

NASA Astrophysics Data System (ADS)

Chini, R.; Fuhrmann, K.; Barr, A.; Pozo, F.; Westhues, C.; Hodapp, K.

2014-01-01

We report the discovery of faint common-proper-motion companions to the nearby southern solar-type stars HD 43162, HD 67199, HD 114837, HD 114853, HD 129502, HD 165185, HD 197214 and HD 212330 from near-infrared imaging and astrometry. We also confirm the previously identified tertiary components around HD 165401 and HD 188088. Since the majority of these stars were already known as binaries, they ascend now to higher level systems. A particularly interesting case is the G6.5 V BY Dra-type variable HD 43162, which harbours two common-proper-motion companions at distances of 410 and 2740 au. Our limited study shows that the inventory of common-proper-motion companions around nearby bright stars is still not completely known.

A NEW CLASS OF NASCENT ECLIPSING BINARIES WITH EXTREME MASS RATIOS

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

Moe, Maxwell; Stefano, Rosanne Di, E-mail: mmoe@cfa.harvard.edu

2015-03-10

Early B-type main-sequence (MS) stars (M {sub 1} ≈ 5-16 M {sub ☉}) with closely orbiting low-mass stellar companions (q = M {sub 2}/M {sub 1} < 0.25) can evolve to produce Type Ia supernovae, low-mass X-ray binaries, and millisecond pulsars. However, the formation mechanism and intrinsic frequency of such close extreme mass-ratio binaries have been debated, especially considering none have hitherto been detected. Utilizing observations of the Large Magellanic Cloud galaxy conducted by the Optical Gravitational Lensing Experiment, we have discovered a new class of eclipsing binaries in which a luminous B-type MS star irradiates a closely orbiting low-massmore » pre-MS companion that has not yet fully formed. The primordial pre-MS companions have large radii and discernibly reflect much of the light they intercept from the B-type MS primaries (ΔI {sub refl} ≈ 0.02-0.14 mag). For the 18 definitive MS + pre-MS eclipsing binaries in our sample with good model fits to the observed light-curves, we measure short orbital periods P = 3.0-8.5 days, young ages τ ≈ 0.6-8 Myr, and small secondary masses M {sub 2} ≈ 0.8-2.4 M {sub ☉} (q ≈ 0.07-0.36). The majority of these nascent eclipsing binaries are still associated with stellar nurseries, e.g., the system with the deepest eclipse ΔI {sub 1} = 2.8 mag and youngest age τ = 0.6 ± 0.4 Myr is embedded in the bright H II region 30 Doradus. After correcting for selection effects, we find that (2.0 ± 0.6)% of B-type MS stars have companions with short orbital periods P = 3.0-8.5 days and extreme mass ratios q ≈ 0.06-0.25. This is ≈10 times greater than that observed for solar-type MS primaries. We discuss how these new eclipsing binaries provide invaluable insights, diagnostics, and challenges for the formation and evolution of stars, binaries, and H II regions.« less

The first gravitational-wave source from the isolated evolution of two stars in the 40-100 solar mass range.

PubMed

Belczynski, Krzysztof; Holz, Daniel E; Bulik, Tomasz; O'Shaughnessy, Richard

2016-06-23

The merger of two massive (about 30 solar masses) black holes has been detected in gravitational waves. This discovery validates recent predictions that massive binary black holes would constitute the first detection. Previous calculations, however, have not sampled the relevant binary-black-hole progenitors--massive, low-metallicity binary stars--with sufficient accuracy nor included sufficiently realistic physics to enable robust predictions to better than several orders of magnitude. Here we report high-precision numerical simulations of the formation of binary black holes via the evolution of isolated binary stars, providing a framework within which to interpret the first gravitational-wave source, GW150914, and to predict the properties of subsequent binary-black-hole gravitational-wave events. Our models imply that these events form in an environment in which the metallicity is less than ten per cent of solar metallicity, and involve stars with initial masses of 40-100 solar masses that interact through mass transfer and a common-envelope phase. These progenitor stars probably formed either about 2 billion years or, with a smaller probability, 11 billion years after the Big Bang. Most binary black holes form without supernova explosions, and their spins are nearly unchanged since birth, but do not have to be parallel. The classical field formation of binary black holes we propose, with low natal kicks (the velocity of the black hole at birth) and restricted common-envelope evolution, produces approximately 40 times more binary-black-holes mergers than do dynamical formation channels involving globular clusters; our predicted detection rate of these mergers is comparable to that from homogeneous evolution channels. Our calculations predict detections of about 1,000 black-hole mergers per year with total masses of 20-80 solar masses once second-generation ground-based gravitational-wave observatories reach full sensitivity.

The first gravitational-wave source from the isolated evolution of two stars in the 40-100 solar mass range

NASA Astrophysics Data System (ADS)

Belczynski, Krzysztof; Holz, Daniel E.; Bulik, Tomasz; O'Shaughnessy, Richard

2016-06-01

The merger of two massive (about 30 solar masses) black holes has been detected in gravitational waves. This discovery validates recent predictions that massive binary black holes would constitute the first detection. Previous calculations, however, have not sampled the relevant binary-black-hole progenitors—massive, low-metallicity binary stars—with sufficient accuracy nor included sufficiently realistic physics to enable robust predictions to better than several orders of magnitude. Here we report high-precision numerical simulations of the formation of binary black holes via the evolution of isolated binary stars, providing a framework within which to interpret the first gravitational-wave source, GW150914, and to predict the properties of subsequent binary-black-hole gravitational-wave events. Our models imply that these events form in an environment in which the metallicity is less than ten per cent of solar metallicity, and involve stars with initial masses of 40-100 solar masses that interact through mass transfer and a common-envelope phase. These progenitor stars probably formed either about 2 billion years or, with a smaller probability, 11 billion years after the Big Bang. Most binary black holes form without supernova explosions, and their spins are nearly unchanged since birth, but do not have to be parallel. The classical field formation of binary black holes we propose, with low natal kicks (the velocity of the black hole at birth) and restricted common-envelope evolution, produces approximately 40 times more binary-black-holes mergers than do dynamical formation channels involving globular clusters; our predicted detection rate of these mergers is comparable to that from homogeneous evolution channels. Our calculations predict detections of about 1,000 black-hole mergers per year with total masses of 20-80 solar masses once second-generation ground-based gravitational-wave observatories reach full sensitivity.

1SWASP J200503.05-343726.5: A high mass ratio eclipsing binary near the period limit

NASA Astrophysics Data System (ADS)

Bin, Zhang; Shengbang, Qian; Zejda, Miloslav; Liying, Zhu; Nianping, Liu

2017-07-01

First CCD photometric light curves of the eclipsing binary system 1SWASP J200503.05-343726.5 are presented. Our complete light curves in V, R and I bands using the Bessell filter show an out-of-eclipsing distortion, which means that the components of the system may be active. The preliminary photometric solutions with a cool star-spot are derived by using the 2013 version of the Wilson-Devinney (W-D) code. The photometric solutions suggest that 1SWASP J200503.05-343726.5 is a shallow-contact eclipsing binary(f = 9.0 %) with a mass ratio of q = 1.0705 , which is very high for late-type binary systems near the period limit. The primary component is about 230 K hotter than the secondary component. Based on our new CCD eclipse times, the orbital period change was analyzed. According to O - C diagram, the orbital period of the 1SWASP J200503.05-343726.5 shows an increase at a rate of P˙ = + 5.43 ×10-8 days year-1. The period increase may be caused by mass transfer from the less massive component to the more massive one. This shallow-contact system may be formed from a detached short-period binary via orbital shrinkage because of dynamical interactions with a third component or by magnetic braking.

The enigmatic star EZ Pegasi - A mystery solved?

NASA Technical Reports Server (NTRS)

Howell, S. B.; Bopp, B. W.

1985-01-01

EZ Peg, a ninth-magnitude G star that has been classified by various authors as an irregular variable, a U Gem system, and a contact binary, is shown to have all the spectroscopic and photometric characteristics of an active-chromosphere RS CVn binary. It is suggested that the reported outburst of 1943, when the spectrum appeared to be that of a B star, never occurred. The strong Ca II H and K reversals, viewed with low spectral resolution, caused the photospheric Ca II absorption to appear abnormally weak, mimicking a much earlier spectral type.

Type-inversion as a working mechanism of high voltage MAPbBr3(Cl)-based halide perovskite solar cells.

PubMed

Kedem, Nir; Kulbak, Michael; Brenner, Thomas M; Hodes, Gary; Cahen, David

2017-02-22

Using several metals with different work functions as solar cell back contact we identify majority carrier type inversion in methylammonium lead bromide (MAPbBr3, without intentional doping) as the basis for the formation of a p-n junction. MAPbBr 3 films deposited on TiO 2 are slightly n-type, whereas in a full device they are strongly p-type. The charge transfer between the metal electrode and the halide perovskite (HaP) film is shown to determine the dominant charge carrier type of the HaP and, thus, also of the final cells. Usage of Pt, Au and Pb as metal electrodes shows the effects of metal work function on minority carrier diffusion length and majority carrier concentration in the HaP, as well as on built-in voltage, band bending, and open circuit voltage (V OC ) within a solar cell. V OC > 1.5 V is demonstrated. The higher the metal WF, the higher the carrier concentration induced in the HaP, as indicated by a narrower space charge region and a smaller minority carrier diffusion length. From the analysis of bias-dependent electron beam-induced currents, the HaP carrier concentrations are estimated to be ∼ 1 × 10 17 cm -3 with Au and 2-3 × 10 18 cm -3 with Pt. A model in which type-inversion stretches across the entire film width implies formation of the p-n junction away from the interface, near the back-contact metal electrode. This work highlights the importance of the contact metal on device performance in that contact engineering can also serve to control the carrier concentration in HaP.

Evolution of Optical Binary Fraction in Sparse Stellar Systems

NASA Astrophysics Data System (ADS)

Li, Zhongmu; Mao, Caiyan

2018-05-01

This work studies the evolution of the fraction of optical binary stars (OBF; not including components such as neutron stars and black holes), which is caused by stellar evolution, and the contributions of various binaries to OBF via the stellar population synthesis technique. It is shown that OBF decreases from 1 to about 0.81 for stellar populations with the Salpeter initial mass function (IMF), and to about 0.85 for the case of the Kroupa IMF, on a timescale of 15 Gyr. This result depends on metallicity, slightly. The contributions of binaries varying with mass ratio, orbital period, separation, spectral types of primary and secondary, contact degree, and pair type to OBF are calculated for stellar populations with different ages and metallicities. The contribution of different kinds of binaries to OBF depends on age and metallicity. The results can be used for estimating the global OBF of star clusters or galaxies from the fraction of a kind of binary. It is also helpful for estimating the primordial and future binary fractions of sparse stellar systems from the present observations. Our results are suitable for studying field stars, open clusters, and the outer part of globular clusters, because the OBF of such objects is affected by dynamical processes, relatively slightly, but they can also be used for giving some limits for other populations.

The moderately interacting Algol-type eclipsing binary RY Geminorum

NASA Technical Reports Server (NTRS)

Plavec, Mirek J.; Dobias, Jan J.

1987-01-01

Ultraviolet spectra of the Algol-type semidetached system RY Geminorum, whose components can be described as A0 V and K0 IV, have been matched to the ultraviolet spectrum by Kurucz (1979) model atmospheres, and a best fit is found for T(eff) = 9150 K. Comparison with standard star spectra requires that this value be raised to 9400 K. The color excess of the system is determined to be no more than E(B-V) = 0.03 mag; the distance to the system is about 360 pc. The masses are approximately 2.36 and 0.38 solar masses, and the radii are 2.5 and 5.8 solar radii, respectively. The separation of the two centers is 26 solar radii. Evidence for a circumstellar line absorption is found in optical and ultraviolet spectrograms, and evidence is found in IUE spectra taken in partial eclipse for circumstellar emission lines of the type detected previously in the WS Serpentis stars and in several semidetected systems of the Algol type.

Multiplicity of the Galactic Senior Citizens: A high-resolution search for cool subdwarf companions

NASA Astrophysics Data System (ADS)

Ziegler, Carl; Law, Nicholas M.

2015-01-01

Cool subdwarfs, with spectral types late K and M, are the oldest members of the low-mass stellar population. Mostly present in the galactic halo, subdwarfs are characterized by their low metallicity and high proper-motions. Understanding their binary fraction could give key insights into the star formation process early in the Milky Way's history. However, because of their low luminosity and relative rarity in the solar neighborhood, binary surveys of cool subdwarfs have suffered from small sample sizes and large incompleteness gaps. It appears, however, that the binary fraction of red subdwarfs is much lower than for their main-sequence cousins. Using the highly efficient Robo-AO system, we present the largest high-resolution survey of subdwarfs yet. We find from 349 target cool subdwarfs, 39 are in multiple systems, 13 newly discovered, for a binary fraction of 11 ± 1.8%.

Is supernova 1987A a stripped asymptotic-branch giant in a binary system?

NASA Technical Reports Server (NTRS)

Joss, P. C.; Podsiadlowski, PH.; Hsu, J. J. L.; Rappaport, S.

1988-01-01

It is proposed that the progenitor of supernova 1987A was a previously undetected red star in orbit about a blue supergiant. The progenitor was the remnant of an asymptotic-branch giant that had lost most of its hydrogen-rich envelope to its blue companion by type C mass transfer. A detailed evolutionary model strongly supports the feasibility of this proposition. It is found that the original mass of the supernova precursor was 10-15 solar (unless a large fraction of the mass was ejected from the binary sytem), and its final mass, just before the supernova event, was 3-6 solar. The system remained bound, with a new orbital period of 3-10 yr and an eccentricity of 0.1-0.4. This picture can provide plausible qualitative explanations for several anomalies in the observational properties of this supernova.

The double-lined spectroscopic binary Iota Pegasi

NASA Technical Reports Server (NTRS)

Fekel, F. C.; Tomkin, J.

1983-01-01

Reticon observations of the spectroscopic binary Iota Peg at 6430 A show the secondary star's weak, but well defined lines. Determinations have accordingly been made of the secondary velocity curve as well as that of the primary, together with the orbits and the minimum masses of the two components. The 1.31 + or - 0.02 and 0.81 + or - 0.01 solar mass minimum masses are sufficiently close to the expected actual masses to suggest eclipses, despite the relatively long, 10.2-day period. The spectral type of the secondary is estimated to be G8 V.

Preparation and application of nanoglued binary titania-silica aerogel.

PubMed

Luo, Liang; Cooper, Adrienne T; Fan, Maohong

2009-01-15

Nanoglued binary titania (TiO2)-silica (SiO2) aerogel, as a novel type of photocatalyst, has been synthesized on glass substrates. Using an about-to-gel SiO2 sol as nanoglue, anatase TiO2 aerogel was immobilized into a three-dimensional mesoporous network of the SiO2. Factorial designs were employed to optimize both TiO2 aerogel and binary TiO2-SiO2 aerogel synthesis. Characterization of the as-prepared TiO2 and binary samples by surface area, porosity, and surface chemical composition showed that the photocatalysts were high-surface-area nanoporous materials, with a Ti4+ valency. The binary aerogel exhibited high photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light; the reaction followed the pseudo first-order Langmuir-Hinshelwood (L-H) kinetic model. Fluorescence spectroscopy revealed that the hydroxyl (*OH) radical was formed during the illumination of the binary TiO2-SiO2 aerogel in a solution of probe molecules, which corroborates the probable mechanism of hydroxyl radical oxidation of contaminants in photocatalytic reactions.

Solar cell with back side contacts

DOEpatents

Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J; Wanlass, Mark Woodbury; Clews, Peggy J

2013-12-24

A III-V solar cell is described herein that includes all back side contacts. Additionally, the positive and negative electrical contacts contact compoud semiconductor layers of the solar cell other than the absorbing layer of the solar cell. That is, the positive and negative electrical contacts contact passivating layers of the solar cell.

Physical properties and catalog of EW-type eclipsing binaries observed by LAMOST

NASA Astrophysics Data System (ADS)

Qian, Sheng-Bang; He, Jia-Jia; Zhang, Jia; Zhu, Li-Ying; Shi, Xiang-Dong; Zhao, Er-Gang; Zhou, Xiao

2017-08-01

EW-type eclipsing binaries (hereafter called EWs) are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common envelope. Numerous EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index (VSX) by 2017 March 13. 7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were identified. Stellar atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic observations. In the paper, those EWs are cataloged and their properties are analyzed. The distributions of orbital period (P), effective temperature (T), gravitational acceleration (log(g)), metallicity ([Fe/H]) and radial velocity (RV) are presented for these observed EW-type systems. It is shown that about 80.6% of sample stars have metallicity below zero, indicating that EW-type systems are old stellar populations. This is in agreement with the conclusion that EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion years. The unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the systems. The correlations between orbital period and effective temperature, gravitational acceleration and metallicity are presented and their scatters are mainly caused by (i) the presence of third bodies and (ii) sometimes wrongly determined periods. It is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital periods. It is found that extremely short-period EWs may be older than their long-period cousins because they have lower metallicities. This reveals that they have a longer timescale of pre-contact evolution and their formation and evolution aremainly driven by angular momentum loss via magnetic braking.

Spectroscopic binaries in the Solar Twin Planet Search program: from substellar-mass to M dwarf companions

NASA Astrophysics Data System (ADS)

dos Santos, Leonardo A.; Meléndez, Jorge; Bedell, Megan; Bean, Jacob L.; Spina, Lorenzo; Alves-Brito, Alan; Dreizler, Stefan; Ramírez, Iván; Asplund, Martin

2017-12-01

Previous studies on the rotation of Sun-like stars revealed that the rotational rates of young stars converge towards a well-defined evolution that follows a power-law decay. It seems, however, that some binary stars do not obey this relation, often by displaying enhanced rotational rates and activity. In the Solar Twin Planet Search program, we observed several solar twin binaries, and found a multiplicity fraction of 42 per cent ± 6 per cent in the whole sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and HIP 103983) clearly exhibit the aforementioned anomalies. We investigated the configuration of the binaries in the program, and discovered new companions for HIP 6407, HIP 54582, HIP 62039 and HIP 30037, of which the latter is orbited by a 0.06 M⊙ brown dwarf in a 1 m long orbit. We report the orbital parameters of the systems with well-sampled orbits and, in addition, the lower limits of parameters for the companions that only display a curvature in their radial velocities. For the linear trend binaries, we report an estimate of the masses of their companions when their observed separation is available, and a minimum mass otherwise. We conclude that solar twin binaries with low-mass stellar companions at moderate orbital periods do not display signs of a distinct rotational evolution when compared to single stars. We confirm that the three peculiar stars are double-lined binaries, and that their companions are polluting their spectra, which explains the observed anomalies.

The simulation of CZTS solar cell for performance improvement

NASA Astrophysics Data System (ADS)

Kumar, Atul; Thakur, Ajay D.

2018-05-01

A Copper-Zinc-Tin-Sulphide (CZTS) based solar cell of Mo/CZTS/CdS/ZnO is simulated using SCAPS. Quantum efficiency and IV curve of the simulated output of CZTS solar cell is mapped with highest efficiency reported in literature for CZTS solar cell. A modification in back contact thus shottky barrier, spike type band alignment at the CZTS-n type layer junction and higher electron mobility (owing to alkali doping in CZT)S are implement in simulation of CZTS solar cell. An improvement in the solar cell efficiency compared to the standard cell configuration of Mo/CZTS/CdS/ZnO is found. CZTS is plagued with low Voc and low FF which can be increased by optimization as suggested in paper.

Near-Earth Asteroid 2005 CR37: Radar Images and Photometry of a Candidate Contact Binary

NASA Technical Reports Server (NTRS)

Benner, Lance A. M.; Nolan, Michael C.; Ostro, Steven J.; Giorgini, Jon D.; Pray, Donald P.; Harris, Alan W.; Magri, Christopher; Margot, Jean-Luc

2006-01-01

Arecibo (2380 MHz, 13 cm) radar observations of 2005 CR37 provide detailed images of a candidate contact binary: a 1.8-km-long, extremely bifurcated object. Although the asteroid's two lobes are round, there are regions of modest topographic relief, such as an elevated, 200-m-wide facet, that suggest that the lobes are geologically more complex than either coherent fragments or homogeneous rubble piles. Since January 1999, about 9% of NEAs larger than approx.200 m imaged by radar can be described as candidate contact binaries.

A ROTSE-I/ROSAT Survey of X-ray Emission from Contact Binary Stars

NASA Astrophysics Data System (ADS)

Geske, M.; McKay, T.

2005-05-01

Using public data from the ROSAT All Sky Survey (RASS) and the ROTSE-I Sky Patrols, the incidence of strong x-ray emissions from contact binary systems was examined. The RASS data was matched to an expanded catalog of contact binary systems from the ROTSE-I data, using a 35 arc second radius. X-ray luminosities for matching objects were then determined. This information was then used to evaluate the total x-ray emissions from all such objects, in order to determine their contribution to the galactic x-ray background.

Thin film photovoltaic device

DOEpatents

Catalano, Anthony W.; Bhushan, Manjul

1982-01-01

A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids.

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

Samec, R. G.; Melton, R. A.; Figg, E. R.

GSC 3355 0394 has an EB-type light curve, which is dominated by hot and cool spot activities. It displays night-to-night variations in light-curve shapes. The period study yields six new times of minimum light and the first precision ephemeris, HJD T{sub min}I = 2, 454, 408.9547 {+-} 0.0017 + 0.4621603 {+-} 0.0000008d*E. VR{sub c}I{sub c} standard magnitudes are presented. BVRI Wilson synthetic light-curve solutions are calculated for both a Mode 4 (V1010 Oph-type, semidetached, more massive component filling its Roche lobe) configuration and a Mode 3, contact configuration (fill-out 100% or critical contact). The critical contact is the lowest residualmore » solution. Four major spot regions are needed to model this binary, at least one is evidently a stream spot.« less

Reliability analysis of InGaN/GaN multi-quantum-well solar cells under thermal stress

NASA Astrophysics Data System (ADS)

Huang, Xuanqi; Fu, Houqiang; Chen, Hong; Lu, Zhijian; Baranowski, Izak; Montes, Jossue; Yang, Tsung-Han; Gunning, Brendan P.; Koleske, Dan; Zhao, Yuji

2017-12-01

We investigate the thermal stability of InGaN solar cells under thermal stress at elevated temperatures from 400 °C to 500 °C. High Resolution X-Ray Diffraction analysis reveals that material quality of InGaN/GaN did not degrade after thermal stress. The external quantum efficiency characteristics of solar cells were well-maintained at all temperatures, which demonstrates the thermal robustness of InGaN materials. Analysis of current density-voltage (J-V) curves shows that the degradation of conversion efficiency of solar cells is mainly caused by the decrease in open-circuit voltage (Voc), while short-circuit current (Jsc) and fill factor remain almost constant. The decrease in Voc after thermal stress is attributed to the compromised metal contacts. Transmission line method results further confirmed that p-type contacts became Schottky-like after thermal stress. The Arrhenius model was employed to estimate the failure lifetime of InGaN solar cells at different temperatures. These results suggest that while InGaN solar cells have high thermal stability, the degradation in the metal contact could be the major limiting factor for these devices under high temperature operation.

The COBAIN (COntact Binary Atmospheres with INterpolation) Code for Radiative Transfer

NASA Astrophysics Data System (ADS)

Kochoska, Angela; Prša, Andrej; Horvat, Martin

2018-01-01

Standard binary star modeling codes make use of pre-existing solutions of the radiative transfer equation in stellar atmospheres. The various model atmospheres available today are consistently computed for single stars, under different assumptions - plane-parallel or spherical atmosphere approximation, local thermodynamical equilibrium (LTE) or non-LTE (NLTE), etc. However, they are nonetheless being applied to contact binary atmospheres by populating the surface corresponding to each component separately and neglecting any mixing that would typically occur at the contact boundary. In addition, single stellar atmosphere models do not take into account irradiance from a companion star, which can pose a serious problem when modeling close binaries. 1D atmosphere models are also solved under the assumption of an atmosphere in hydrodynamical equilibrium, which is not necessarily the case for contact atmospheres, as the potentially different densities and temperatures can give rise to flows that play a key role in the heat and radiation transfer.To resolve the issue of erroneous modeling of contact binary atmospheres using single star atmosphere tables, we have developed a generalized radiative transfer code for computation of the normal emergent intensity of a stellar surface, given its geometry and internal structure. The code uses a regular mesh of equipotential surfaces in a discrete set of spherical coordinates, which are then used to interpolate the values of the structural quantites (density, temperature, opacity) in any given point inside the mesh. The radiaitive transfer equation is numerically integrated in a set of directions spanning the unit sphere around each point and iterated until the intensity values for all directions and all mesh points converge within a given tolerance. We have found that this approach, albeit computationally expensive, is the only one that can reproduce the intensity distribution of the non-symmetric contact binary atmosphere and can be used with any existing or new model of the structure of contact binaries. We present results on several test objects and future prospects of the implementation in state-of-the-art binary star modeling software.

Silver-free solar cell interconnection by laser spot welding of thin aluminum layers: analysis of process limits for ns- and μs-lasers

NASA Astrophysics Data System (ADS)

Schulte-Huxel, H.; Blankemeyer, S.; Kajari-Schröder, S.; Brendel, R.

2014-03-01

We investigate a laser welding process for contacting aluminum metallized crystalline silicon solar cells to a 10-μm-thick aluminum layers on a glass substrate. The reduction of the solar cell metallization thickness is analyzed with respect to laser induced damage using SiNx passivated silicon wafers. Additionally, we measure the mechanical stress of the laser welds by perpendicular tear-off as well as the electrical contact resistance. We apply two types of laser processes; one uses one to eight 20-ns-laser pulses at 355 nm with fluences between 12 and 40 J/cm2 and the other single 1.2-μs-laser pulses at 1064 nm with 33 to 73 J/cm2. Ns laser pulses can contact down to 1-μm-thick aluminum layers on silicon without inducing laser damage to the silicon and lead to sufficient strong mechanical contact. In case of μs laser pulses the limiting thickness is 2 μm.

Optical–Mid-infrared Period–Luminosity Relations for W UMa-type Contact Binaries Based on Gaia DR 1: 8% Distance Accuracy

NASA Astrophysics Data System (ADS)

Chen, Xiaodian; Deng, Licai; de Grijs, Richard; Wang, Shu; Feng, Yuting

2018-06-01

W Ursa Majoris (W UMa)-type contact binary systems (CBs) are useful statistical distance indicators because of their large numbers. Here, we establish (orbital) period–luminosity relations (PLRs) in 12 optical to mid-infrared bands (GBVRIJHK s W1W2W3W4) based on 183 nearby W UMa-type CBs with accurate Tycho–Gaia parallaxes. The 1σ dispersion of the PLRs decreases from optical to near- and mid-infrared wavelengths. The minimum scatter, 0.16 mag, implies that W UMa-type CBs can be used to recover distances to 7% precision. Applying our newly determined PLRs to 19 open clusters containing W UMa-type CBs demonstrates that the PLR and open cluster CB distance scales are mutually consistent to within 1%. Adopting our PLRs as secondary distance indicators, we compiled a catalog of 55,603 CB candidates, of which 80% have distance estimates based on a combination of optical, near-infrared, and mid-infrared photometry. Using Fourier decomposition, 27,318 high-probability W UMa-type CBs were selected. The resulting 8% distance accuracy implies that our sample encompasses the largest number of objects with accurate distances within a local volume with a radius of 3 kpc available to date. The distribution of W UMa-type CBs in the Galaxy suggests that in different environments, the CB luminosity function may be different: larger numbers of brighter (longer-period) W UMa-type CBs are found in younger environments.

A homogeneous sample of binary galaxies: Basic observational properties

NASA Technical Reports Server (NTRS)

Karachentsev, I. D.

1990-01-01

A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies.

MESA models for the evolutionary status of the epsilon Aurigae disk-eclipsed binary system

NASA Astrophysics Data System (ADS)

Stencel, Robert E.; Gibson, Justus

2018-06-01

The brightest member of the class of disk-eclipsed binary stars is the Algol-like long-period binary, epsilon Aurigae (HD 31964, F0Iap + disk, http://adsabs.harvard.edu/abs/2016SPIE.9907E..17S ). Using MESA (Modules for Experiments in Stellar Astrophysics, version 9575), we have made an evaluation of its evolutionary state. We sought to satisfy several observational constraints, including: (1) requiring evolutionary tracks to pass close to the current temperature and luminosity of the primary star; (2) obtaining a period near the observed value of 27.1 years; (3) matching a mass function of 3.0; (4) concurrent Roche lobe overflow and mass transfer; (5) an isotopic ratio 12C / 13C = 5 and, (6) matching the interferometrically determined angular diameter. A MESA model starting with binary masses of 9.85 + 4.5 solar masses, with a 100 day initial period, produces a 1.2 + 10.6 solar masses result having a 547 day period, plus a single digit 12C / 13C ratio. These values were reached near an age of 20 Myr, when the donor star comes close to the observed luminosity and temperature for epsilon Aurigae A, as a post-RGB/pre-AGB star. Contemporaneously, the accretor then appears as an upper main sequence, early B-type star. This benchmark model can provide a basis for further exploration of this interacting binary, and other long period binary stars. This report has been submitted to MNRAS, along with a parallel investigation of mass transfer stream and disk sub-structure. The authors are grateful to the estate of William Herschel Womble for the support of astronomy at the University of Denver.

Circumbinary habitability niches

NASA Astrophysics Data System (ADS)

Mason, Paul A.; Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A.; Clark, Joni M.

2015-07-01

Binaries could provide the best niches for life in the Galaxy. Although counterintuitive, this assertion follows directly from stellar tidal interaction theory and the evolution of lower mass stars. There is strong evidence that chromospheric activity of rapidly rotating young stars may be high enough to cause mass loss from atmospheres of potentially habitable planets. The removal of atmospheric water is most critical. Tidal breaking in binaries could help reduce magnetic dynamo action and thereby chromospheric activity in favour of life. We call this the Binary Habitability Mechanism (BHM) that we suggest allows for water retention at levels comparable to or better than the Earth. We discuss novel advantages that life may exploit, in these cases, and suggest that life may even thrive on some circumbinary planets. We find that while many binaries do not benefit from BHM, high-quality niches do exist for various combinations of stars between 0.55 and 1.0 solar masses. For a given pair of stellar masses, BHM operates only for certain combinations of period and eccentricity. Binaries having a solar-type primary seem to be quite well-suited niches having wide and distant habitable zones with plentiful water and sufficient light for photosynthetic life. We speculate that, as a direct result of BHM, conditions may be suitable for life on several planets and possibly even moons of giant planets orbiting some binaries. Lower mass combinations, while more restrictive in parameter space, provide niches lasting many billions of years and are rich suppliers of photosynthetic photons. We provide a publicly available web-site (http://bit.ly/BHM-calculator or http://bit.ly/BHM-calculator-mirror), which calculates the BHM effects presented in this paper.

Multilayer-Grown Ultrathin Nanostructured GaAs Solar Cells as a Cost-Competitive Materials Platform for III-V Photovoltaics.

PubMed

Gai, Boju; Sun, Yukun; Lim, Haneol; Chen, Huandong; Faucher, Joseph; Lee, Minjoo L; Yoon, Jongseung

2017-01-24

Large-scale deployment of GaAs solar cells in terrestrial photovoltaics demands significant cost reduction for preparing device-quality epitaxial materials. Although multilayer epitaxial growth in conjunction with printing-based materials assemblies has been proposed as a promising route to achieve this goal, their practical implementation remains challenging owing to the degradation of materials properties and resulting nonuniform device performance between solar cells grown in different sequences. Here we report an alternative approach to circumvent these limitations and enable multilayer-grown GaAs solar cells with uniform photovoltaic performance. Ultrathin single-junction GaAs solar cells having a 300-nm-thick absorber (i.e., emitter and base) are epitaxially grown in triple-stack releasable multilayer assemblies by molecular beam epitaxy using beryllium as a p-type impurity. Microscale (∼500 × 500 μm 2 ) GaAs solar cells fabricated from respective device layers exhibit excellent uniformity (<3% relative) of photovoltaic performance and contact properties owing to the suppressed diffusion of p-type dopant as well as substantially reduced time of epitaxial growth associated with ultrathin device configuration. Bifacial photon management employing hexagonally periodic TiO 2 nanoposts and a vertical p-type metal contact serving as a metallic back-surface reflector together with specialized epitaxial design to minimize parasitic optical losses for efficient light trapping synergistically enable significantly enhanced photovoltaic performance of such ultrathin absorbers, where ∼17.2% solar-to-electric power conversion efficiency under simulated AM1.5G illumination is demonstrated from 420-nm-thick single-junction GaAs solar cells grown in triple-stack epitaxial assemblies.

DEEP, LOW-MASS RATIO OVERCONTACT BINARY SYSTEMS. XII. CK BOOTIS WITH POSSIBLE CYCLIC MAGNETIC ACTIVITY AND ADDITIONAL COMPANION

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

Yang, Y.-G.; Qian, S.-B.; Soonthornthum, B., E-mail: yygcn@163.com, E-mail: qsb@ynao.ac.cn

2012-05-15

We present precision CCD photometry, a period study, and a two-color simultaneous Wilson code solution of the short-period contact binary CK Bootis. The asymmetric light curves were modeled by a dark spot on the primary component. The result identifies that CK Boo is an A-type W UMa binary with a high fillout of f = 71.7({+-} 4.4)%. From the O - C curve, it is found that the orbital period changes in a complicated mode, i.e., a long-term increase with two sinusoidal variations. One cyclic oscillation with a period of 10.67({+-} 0.20) yr may result from magnetic activity cycles, whichmore » are identified by the variability of Max. I - Max. II. Another sinusoidal variation (i.e., A = 0.0131 days({+-} 0.0009 days) and P{sub 3} = 24.16({+-} 0.64) yr) may be attributed to the light-time effect due to a third body. This kind of additional companion can extract angular momentum from the central binary system. The orbital period secularly increases at a rate of dP/dt = +9.79 ({+-}0.80) Multiplication-Sign 10{sup -8} days yr{sup -1}, which may be interpreted by conservative mass transfer from the secondary to the primary. This kind of deep, low-mass ratio overcontact binaries may evolve into a rapid-rotating single star, only if the contact configuration do not break down at J{sub spin} > (1/3)J{sub orb}.« less

PHOTOMETRIC STUDY OF THE VERY SHORT PERIOD SHALLOW CONTACT BINARY DD COMAE BERENICES

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

Zhu, L.; Qian, S.-B.; Mikulasek, Z.

2010-07-15

The first photometric solutions of the very short period (VSP) close binary DD Comae Berenices (P = 0fd26920811) based on our new complete (IR){sub C} light curves are derived by the 2003 version Wilson-Van Hamme code. They show that the system belongs to shallow contact W-type W UMa systems with a degree of overcontact of 8.7%. The observed light curve distortions are explained by employing the spots model due to the late-type nature of both components. We have collected all available photometric data about the system with emphasis on the individual observational data, which we treated simultaneously using our ownmore » method based on the usage of computed model light curves as templates. We recalculated published times of light minimum and added new ones of our own to construct an O - C diagram that spans over 70 years. Using a least squares method orthogonal quadratic model function, we found that the orbital period of DD Com is continuously increasing with P-dot =0.00401(22) s yr{sup -1}. The period increase may be caused by the mass transfer from the less-massive component to the more-massive one. With the period increase, the binary is evolving from the present shallow contact phase to the broken stage predicted by the thermal relaxation oscillation (TRO) theory. Compared with other VSP systems, DD Com is a rare system that lies on the expanding phase of the TRO cycle. Until now, only four such systems including DD Com are found in this stage. Thus, this target is another good observational proof of the TRO theory in a very short period region.« less

Close Binary Star Speckle Interferometry on the McMath-Pierce 0.8-Meter Solar Telescope

NASA Astrophysics Data System (ADS)

Wiley, Edward; Harshaw, Richard; Jones, Gregory; Branston, Detrick; Boyce, Patrick; Rowe, David; Ridgely, John; Estrada, Reed; Genet, Russell

2015-09-01

Observations were made in April 2014 to assess the utility of the 0.8-meter solar telescope at the McMath-Pierce Solar Observatory at Kitt Peak National Observatory for performing speckle interferometry observations of close binary stars. Several configurations using science cameras, acquisition cameras, eyepieces, and flip mirrors were evaluated. Speckle images were obtained and recommendations for further improvement of the acquisition system are presented.

VizieR Online Data Catalog: Photometric analysis of contact binaries (Lapasset+ 1996)

NASA Astrophysics Data System (ADS)

Lapasset, E.; Gomez, M.; Farinas, R.

1996-09-01

We present BV light-curve synthetic analyses of three short-period contact (W UMa) binaries: HY Pavonis (P=~0.35days), AW Virginis (P=~0.35days), and BP Velorum (P=~0.26days). Different possible configurations for wide range of the mass ratio were explored in each case making use of the Wilson-Devinney code. The photometric parameters of the systems were determined from the synthetic light-curve solutions that best fit the observations. AW Vir has two components of very similar temperatures and therefore the subtype (A or W) remains undetermined. HY Pav and BP Vel are best modeled by W-type configurations and the asymmetries in the light curves are reproduced by introducing cool spots on the more massive secondary components. Although BP Vel lies in the region of the open cluster Cr 173, its distance modulus, in principle, rules it out as a cluster member. (6 data files).

A theoretical study of heterojunction and graded band gap type solar cells

NASA Technical Reports Server (NTRS)

Sutherland, J. E.; Hauser, J. R.

1977-01-01

A computer program was designed for the analysis of variable composition solar cells and applied to several proposed solar cell structures using appropriate semiconductor materials. The program simulates solar cells made of a ternary alloy of two binary semiconductors with an arbitrary composition profile, and an abrupt or Gaussian doping profile of polarity n-on-p or p-on-n with arbitrary doping levels. Once the device structure is specified, the program numerically solves a complete set of differential equations and calculates electrostatic potential, quasi-Fermi levels, carrier concentrations and current densities, total current density and efficiency as functions of terminal voltage and position within the cell. These results are then recorded by computer in tabulated or plotted form for interpretation by the user.

Spectroscopic observations of V443 Herculis - A symbiotic binary with a low mass white dwarf

NASA Technical Reports Server (NTRS)

Dobrzycka, Danuta; Kenyon, Scott J.; Mikolajewska, Joanna

1993-01-01

We present an analysis of new and existing photometric and spectroscopic observations of the symbiotic binary V443 Herculis. This binary system consists of a normal M5 giant and a hot compact star. These two objects have comparable luminosities: about 1500 solar for the M5 giant and about 1000 solar for the compact star. We identify three nebular regions in this binary: a small, highly ionized volume surrounding the hot component, a modestly ionized shell close to the red giant photosphere, and a less dense region of intermediate ionization encompassing both binary components. The system parameters for V443 Her suggest the hot component currently declines from a symbiotic nova eruption.

OBSERVATIONS OF HIERARCHICAL SOLAR-TYPE MULTIPLE STAR SYSTEMS

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

Roberts, Lewis C. Jr.; Tokovinin, Andrei; Mason, Brian D.

2015-10-15

Twenty multiple stellar systems with solar-type primaries were observed at high angular resolution using the PALM-3000 adaptive optics system at the 5 m Hale telescope. The goal was to complement the knowledge of hierarchical multiplicity in the solar neighborhood by confirming recent discoveries by the visible Robo-AO system with new near-infrared observations with PALM-3000. The physical status of most, but not all, of the new pairs is confirmed by photometry in the Ks band and new positional measurements. In addition, we resolved for the first time five close sub-systems: the known astrometric binary in HIP 17129AB, companions to the primariesmore » of HIP 33555, and HIP 118213, and the companions to the secondaries in HIP 25300 and HIP 101430. We place the components on a color–magnitude diagram and discuss each multiple system individually.« less

The binary companion of the classical Cepheid AW Per

NASA Technical Reports Server (NTRS)

Evans, Nancy Remage

1989-01-01

An analysis of IUE spectra of the companion of AW Per shows it to be an extreme BpSi/HeW star with a spectral type of B7 V to B8 V. The flux of the composite spectrum from 1200 A through V is found to be well matched by F7 Ib and B8 V standard stars with Delta M(V) = 3.1 mag. The results suggest that the mass of the Cepheid must be greater than 4.7 solar masses. The flux distribution of the star and the mass limits from the orbit are consistent with a companion that is itself a binary.

A new strategy to engineer polymer bulk heterojunction solar cells with thick active layers via self-assembly of the tertiary columnar phase

DOE PAGES

Li, Hongfei; Yang, Zhenhua; Pan, Cheng; ...

2017-07-14

Here, we report that the addition of a non-photoactive tertiary polymer phase in the binary bulk heterojunction (BHJ) polymer solar cell leads to a self-assembled columnar nanostructure, enhancing the charge mobilities and photovoltaic efficiency with surprisingly increased optimal active blend thicknesses over 300 nm, 3–4 times larger than that of the binary counterpart. Using the prototypical poly(3-hexylthiophene) (P3HT):fullerene blend as a model BHJ system, we discover that the inert poly(methyl methacrylate) (PMMA) added in the binary BHJ blend self-assembles into vertical columns, which not only template the phase segregation of electron acceptor fullerenes but also induce the out-of-plane rotation ofmore » the edge-on-orientated crystalline P3HT phase. Using complementary interrogation methods including neutron reflectivity, X-ray scattering, atomic force microscopy, transmission electron microscopy, and molecular dynamics simulations, we show that the enhanced charge transport originates from the more randomized molecular stacking of the P3HT phase and the spontaneous segregation of fullerenes at the P3HT/PMMA interface, driven by the high surface tension between the two polymeric components. The results demonstrate a potential method for increasing the thicknesses of high-performance polymer BHJ solar cells with improved photovoltaic efficiency, alleviating the burden of stringently controlling the ultrathin blend thickness during the roll-to-roll-type large-area manufacturing environment.« less

An examination of astrophysical habitats for targeted SETI

NASA Technical Reports Server (NTRS)

Doyle, Laurance R.; Mckay, Christopher P.; Reynolds, Ray T.; Whitmire, Daniel P.; Matese, John J.

1991-01-01

Planetary atmospheric radiative transfer models have recently given valuable insights into the definition of the solar system's ecoshell. In addition, however, results have indicated that constraints on solar evolution also need to be addressed, with even minor solar variations, (mass loss, for example), having important consequences from an exobiological standpoint. Following the definition of the solar system's ecoshell evolution, the ecoshells around different stellar spectral types can then be modeled. In this study the astrophysical constraints on the definition of ecoshells and possible exobiological habitats includes: (1) the investigation of the evolution of the solar system's ecoshell under different initial solar/stellar model conditions as indicated by both solar abundance considerations as well as planetary evidence; (2) an outline of considerations necessary to define the ecoshells around the most abundant spectral-type stars, the K and M stars looking at the effects on exobiological habitats of planetary rotational tidal locking effects, and stellar flare/chromospheric-activity cycles, among other effects; (3) a preliminary examination of the factors defining the expected ecoshells around binary stars determining the of regular stellar eclipses, and the expected shortening of the semi-major axis. These results can then be applied to the targeted microwave search for extraterrestrial intelligent signals by constraining the ecoshell space in the solar neighborhood.

Dynamic mass exchange in doubly degenerate binaries. I - 0.9 and 1.2 solar mass stars

NASA Technical Reports Server (NTRS)

Benz, W.; Cameron, A. G. W.; Press, W. H.; Bowers, R. L.

1990-01-01

The dynamic mass exchange process in doubly degenerate binaries was investigated using a three-dimensional numerical simulation of the evolution of a doubly degenerate binary system in which the primary is a 1.2-solar-mass white dwarf and the Roche lobe filling secondary is a 0.9-solar-mass dwarf. The results show that, in a little more than two orbital periods, the secondary is completely destroyed and transformed into a thick disk orbiting about the primary. Since only a very small fraction of the mass (0.0063 solar mass) escapes the system, the evolution of the binary results in the formation of a massive object. This object is composed of three parts, the initial white dwarf primary, a very hot pressure-supported spherical envelope, and a rotationally supported outer disk. The evolution of the system can be understood in terms of a simple analytical model where it is shown that the angular momentum carried by the mass during the transfer and stored in the disk determines the evolution of the system.

Spectroscopic orbits of nearby solar-type dwarfs - II.

NASA Astrophysics Data System (ADS)

Gorynya, N. A.; Tokovinin, A.

2018-03-01

Several nearby solar-type dwarfs with variable radial velocity were monitored to find their spectroscopic orbits. First orbital elements of 15 binaries (HIP 12144, 17895, 27970, 32329, 38636, 39072, 40479, 43004, 73700, 79234, 84696, 92140, 88656, 104514, and 112222) are determined. The previously known orbits of HIP 5276, 21443, 28678, and 41214 are confirmed and updated. The orbital periods range from 2 d to 4 yr. There are eight hierarchical systems with additional distant companions among those 19 stars. The outer visual orbit of the triple system HIP 17895 is updated and the masses of all its components are estimated. We provide radial velocities of another 16 Hipparcos stars without orbital solutions, some of those with long periods or false claims of variability.

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

Tokovinin, Andrei, E-mail: atokovinin@ctio.noao.edu

Radial velocity (RV) monitoring of solar-type visual binaries has been conducted at the CTIO/SMARTS 1.5 m telescope to study short-period systems. The data reduction is described, and mean and individual RVs of 163 observed objects are given. New spectroscopic binaries are discovered or suspected in 17 objects, and for some of them the orbital periods could be determined. Subsystems are efficiently detected even in a single observation by double lines and/or by the RV difference between the components of visual binaries. The potential of this detection technique is quantified by simulation and used for statistical assessment of 96 wide binariesmore » within 67 pc. It is found that 43 binaries contain at least one subsystem, and the occurrence of subsystems is equally probable in either primary or secondary components. The frequency of subsystems and their periods matches the simple prescription proposed by the author. The remaining 53 simple wide binaries with a median projected separation of 1300 AU have an RV difference distribution between their components that is not compatible with the thermal eccentricity distribution f (e) = 2e but rather matches the uniform eccentricity distribution.« less

Poly-crystalline silicon-oxide films as carrier-selective passivating contacts for c-Si solar cells

NASA Astrophysics Data System (ADS)

Yang, Guangtao; Guo, Peiqing; Procel, Paul; Weeber, Arthur; Isabella, Olindo; Zeman, Miro

2018-05-01

The poly-Si carrier-selective passivating contacts (CSPCs) parasitically absorb a substantial amount of light, especially in the form of free carrier absorption. To minimize these losses, we developed CSPCs based on oxygen-alloyed poly-Si (poly-SiOx) and deployed them in c-Si solar cells. Transmission electron microscopy analysis indicates the presence of nanometer-scale silicon crystals within such poly-SiOx layers. By varying the O content during material deposition, we can manipulate the crystallinity of the poly-SiOx material and its absorption coefficient. Also, depending on the O content, the bandgap of the poly-SiOx material can be widened, making it transparent for longer wavelength light. Thus, we optimized the O alloying, doping, annealing, and hydrogenation conditions. As a result, an extremely high passivation quality for both n-type poly-SiOx (J0 = 3.0 fA/cm2 and iVoc = 740 mV) and p-type poly-SiOx (J0 = 17.0 fA/cm2 and iVoc = 700 mV) is obtained. A fill factor of 83.5% is measured in front/back-contacted solar cells with both polarities made up of poly-SiOx. This indicates that the carrier transport through the junction between poly-SiOx and c-Si is sufficiently efficient. To demonstrate the merit of poly-SiOx layers' high transparency at long wavelengths, they are deployed at the back side of interdigitated back-contacted (IBC) solar cells. A preliminary cell efficiency of 19.7% is obtained with much room for further improvement. Compared to an IBC solar cell with poly-Si CSPCs, a higher internal quantum efficiency at long wavelengths is observed for the IBC solar cell with poly-SiOx CSPCs, thus demonstrating the potential of poly-SiOx in enabling higher JSC.

Thin film photovoltaic device

DOEpatents

Catalano, A.W.; Bhushan, M.

1982-08-03

A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids. 5 figs.

THE FIRST PHOTOMETRIC INVESTIGATION OF THE NEGLECTED W-UMa-TYPE BINARY STAR UZ CMi

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

Qian, S.-B.; Li, K.; Liao, W.-P.

2013-04-15

UZ CMi was a W-UMa-type binary star found more than 80 years ago. However, it has been neglected in photometric investigations. Here, the first complete light curves in the B, V, R, and I bands are presented and analyzed using the Wilson and Devinney method. It is discovered that UZ CMi is a contact binary (f = 38.4({+-} 2.3)%) with a mass ratio of 0.45. The derived orbital inclination (i = 87 Degree-Sign ) indicates that it is a total eclipsing binary, which suggests that the determined parameters are reliable. By using 17 new eclipse times together with those collectedmore » from the literature, we found that the general trend of the observed-calculated (O - C) curve shows an upward parabolic variation that corresponds to a long-term increase in the orbital period at a rate of P-dot = +4.1 x 10{sup -8} days yr{sup -1}. The continuous increase may be caused by a mass transfer from the less massive component to the more massive one. This suggests that UZ CMi is in the thermal relaxation oscillation controlled stage of the evolutionary scheme proposed by Qian. UZ CMi will oscillate around a critical mass ratio and the contact configuration cannot be broken. After the upward parabolic change was removed, the (O - C){sub 2} curve of the photoelectric and charge-coupled device data revealed a cyclic variation with a small amplitude of 0.0026 days and a period of 21.1 yr. The cyclic change was analyzed for the light-travel time effect via the presence of an extremely cool stellar companion.« less

Large area low-cost space solar cell development

NASA Technical Reports Server (NTRS)

Baraona, C. R.; Cioni, J. L.

1982-01-01

A development program to produce large-area (5.9 x 5.9 cm) space quality silicon solar cells with a cost goal of 30 $/watt is descibed. Five cell types under investigation include wraparound dielectric, mechanical wraparound and conventional contact configurations with combinations of 2 or 10 ohm-cm resistivity, back surface reflectors and/or fields, and diffused or ion implanted junctions. A single step process to cut cell and cover-glass simultaneously is being developed. A description of cell developments by Applied Solar Energy Corp., Spectrolab and Spire is included. Results are given for cell and array tests, performed by Lockheed, TRW and NASA. Future large solar arrays that might use cells of this type are discussed.

Astrophysical Implications of the Binary Black-hole Merger GW150914

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; van den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; and; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2016-02-01

The discovery of the gravitational-wave (GW) source GW150914 with the Advanced LIGO detectors provides the first observational evidence for the existence of binary black hole (BH) systems that inspiral and merge within the age of the universe. Such BH mergers have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively “heavy” BHs (≳ 25 {M}⊙ ) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with a metallicity lower than about 1/2 of the solar value. The rate of binary-BH (BBH) mergers inferred from the observation of GW150914 is consistent with the higher end of rate predictions (≳ 1 Gpc-3 yr-1) from both types of formation models. The low measured redshift (z≃ 0.1) of GW150914 and the low inferred metallicity of the stellar progenitor imply either BBH formation in a low-mass galaxy in the local universe and a prompt merger, or formation at high redshift with a time delay between formation and merger of several Gyr. This discovery motivates further studies of binary-BH formation astrophysics. It also has implications for future detections and studies by Advanced LIGO and Advanced Virgo, and GW detectors in space.

Astrophysical Implications of the Binary Black Hole Merger GW150914

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.;

On the structure of contact binaries. I - The contact discontinuity

NASA Technical Reports Server (NTRS)

Shu, F. H.; Lubow, S. H.; Anderson, L.

1976-01-01

The problem of the interior structure of contact binaries is reviewed, and a simple resolution of the difficulties which plague the theory is suggested. It is proposed that contact binaries contain a contact discontinuity between the lower surface of the common envelope and the Roche lobe of the cooler star. This discontinuity is maintained against thermal diffusion by fluid flow, and the transition layer is thin to the extent that the dynamical time scale is short in comparison with the thermal time scale. The idealization that the transition layer has infinitesimal thickness allows a simple formulation of the structure equations which are closed by appropriate jump conditions across the discontinuity. The further imposition of the standard boundary conditions suffices to define a unique model for the system once the chemical composition, the masses of the two stars, and the orbital separation are specified.

High-efficiency silicon heterojunction solar cells: Status and perspectives

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

De Wolf, S.; Geissbuehler, J.; Loper, P.

Silicon heterojunction technology (HJT) uses silicon thin-film deposition techniques to fabricate photovoltaic devices from mono-crystalline silicon wafers (c-Si). This enables energy-conversion efficiencies above 21 %, also at industrial-production level. In this presentation we review the present status of this technology and point out recent trends. We first discuss how the properties of thin hydrogenated amorphous silicon (a-Si:H) films can be exploited to fabricate passivating contacts, which is the key to high- efficiency HJT solar cells. Such contacts enable very high operating voltages, approaching the theoretical limits, and yield small temperature coefficients. With this approach, an increasing number of groups aremore » reporting devices with conversion efficiencies well over 20 % on both-sides contacted n-type cells, Panasonic leading the field with 24.7 %. Exciting results have also been obtained on p-type wafers. Despite these high voltages, important efficiency gains can still be made in fill factor and optical design. This requires improved understanding of carrier transport across device interfaces and reduced parasitic absorption in HJT solar cells. For the latter, several strategies can be followed: Short-wavelength losses can be reduced by replacing the front a-Si:H films with wider-bandgap window layers, such as silicon alloys or even metal oxides. Long- wavelength losses are mitigated by introducing new high-mobility TCO’s such as hydrogenated indium oxide, and also by designing new rear reflectors. Optical shadow losses caused by the front metallization grid are significantly reduced by replacing printed silver electrodes with fine-line plated copper contacts, leading also to possible cost advantages. The ultimate approach to minimize optical losses is the implementation of back-contacted architectures, which are completely devoid of grid shadow losses and parasitic absorption in the front layers can be minimized irrespective of electrical transport requirements. The validity of this approach was convincingly demonstrated by Panasonic, Japan in 2014, reporting on an interdigitated back-contacted HJT cell with an efficiency of 25.6%, setting the new single-junction c-Si record. Finally, given the virtually perfect surface passivation and excellent red response of HJT solar cells, we anticipate these devices will also become the preferred bottom cell in ultra-high efficiency c-Si-based tandem devices, exploiting better the solar spectrum. Such tandem cells have the potential to overcome the fundamental single-junction limit of silicon solar cells (29.4%). Combining HJT cells with perovskite solar cells as top cell appears to be particularly appealing.« less

Silicon heterojunction solar cell with passivated hole selective MoOx contact

NASA Astrophysics Data System (ADS)

Battaglia, Corsin; de Nicolás, Silvia Martín; De Wolf, Stefaan; Yin, Xingtian; Zheng, Maxwell; Ballif, Christophe; Javey, Ali

2014-03-01

We explore substoichiometric molybdenum trioxide (MoOx, x < 3) as a dopant-free, hole-selective contact for silicon solar cells. Using an intrinsic hydrogenated amorphous silicon passivation layer between the oxide and the silicon absorber, we demonstrate a high open-circuit voltage of 711 mV and power conversion efficiency of 18.8%. Due to the wide band gap of MoOx, we observe a substantial gain in photocurrent of 1.9 mA/cm2 in the ultraviolet and visible part of the solar spectrum, when compared to a p-type amorphous silicon emitter of a traditional silicon heterojunction cell. Our results emphasize the strong potential for oxides as carrier selective heterojunction partners to inorganic semiconductors.

Period variation studies of six contact binaries in M4

NASA Astrophysics Data System (ADS)

Rukmini, Jagirdar; Shanti Priya, Devarapalli

2018-04-01

We present the first period study of six contact binaries in the closest globular cluster M4 the data collected from June 1995‑June 2009 and Oct 2012‑Sept 2013. New times of minima are determined for all the six variables and eclipse timing (O-C) diagrams along with the quadratic fit are presented. For all the variables, the study of (O-C) variations reveals changes in the periods. In addition, the fundamental parameters for four of the contact binaries obtained using the Wilson-Devinney code (v2003) are presented. Planned observations of these binaries using the 3.6-m Devasthal Optical Telescope (DOT) and the 4-m International Liquid Mirror Telescope (ILMT) operated by the Aryabhatta Research Institute of Observational Sciences (ARIES; Nainital) can throw light on their evolutionary status from long term period variation studies.

Investigation into the effects of surface stripping ZnO nanosheets.

PubMed

Barnett, Chris J; Jackson, Georgina; Jones, Daniel R; Lewis, Aled R; Welsby, Kathryn; Evans, Jon E; McGettrick, James D; Watson, Trystan; Maffeis, Thierry G G; Dunstan, Peter R; Barron, Andrew R; Cobley, Richard J

2018-04-20

ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

Investigation into the effects of surface stripping ZnO nanosheets

NASA Astrophysics Data System (ADS)

Barnett, Chris J.; Jackson, Georgina; Jones, Daniel R.; Lewis, Aled R.; Welsby, Kathryn; Evans, Jon E.; McGettrick, James D.; Watson, Trystan; Maffeis, Thierry G. G.; Dunstan, Peter R.; Barron, Andrew R.; Cobley, Richard J.

2018-04-01

ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

The formation mechanism of 4179 Toutatis' elongated bilobed structure in a close Earth encounter scenario

NASA Astrophysics Data System (ADS)

Hu, Shoucun; Ji, Jianghui; Richardson, Derek C.; Zhao, Yuhui; Zhang, Yun

2018-07-01

The optical images of near-Earth asteroid 4179 Toutatis acquired by Chang'e-2 spacecraft show that Toutatis has an elongated contact binary configuration, with the contact point located along the long axis. We speculate that such configuration may have resulted from a low-speed impact between two components. In this work, we performed a series of numerical simulations and compared the results with the optical images, to examine the mechanism and better understand the formation of Toutatis. Herein, we propose a scenario that an assumed separated binary precursor could undergo a close encounter with Earth, leading to an impact between the primary and secondary, and the elongation is caused by Earth's tide. The precursor is assumed to be a doubly synchronous binary with a semimajor axis of 4Rp (radius of primary) and the two components are represented as spherical cohesionless self-gravitating granular aggregates. The mutual orbits are simulated in a Monte Carlo routine to provide appropriate parameters for our N-body simulations of impact and tidal distortion. We employ the PKDGRAV package with a soft-sphere discrete element method to explore the entire scenarios. The results show that contact binary configurations are natural outcomes under this scenario, whereas the shape of the primary is almost not affected by the impact of the secondary. However, our simulations further provide an elongated contact binary configuration best matching to the shape of Toutatis at an approaching distance rp = 1.4-1.5 Re (Earth radius), indicative of a likely formation scenario for configurations of Toutatis-like elongated contact binaries.

The formation mechanism of 4179 Toutatis' elongated bi-lobed structure in a close Earth encounter scenario

NASA Astrophysics Data System (ADS)

Hu, Shoucun; Ji, Jianghui; Richardson, Derek C.; Zhao, Yuhui; Zhang, Yun

2018-04-01

The optical images of near-Earth asteroid 4179 Toutatis acquired by Chang'e-2 spacecraft show that Toutatis has an elongated contact binary configuration, with the contact point located along the long axis. We speculate that such configuration may have resulted from a low-speed impact between two components. In this work, we performed a series of numerical simulations and compared the results with the optical images, to examine the mechanism and better understand the formation of Toutatis. Herein we propose an scenario that an assumed separated binary precursor could undergo a close encounter with Earth, leading to an impact between the primary and secondary, and the elongation is caused by Earth's tide. The precursor is assumed to be a doubly synchronous binary with a semi-major axis of 4 Rp (radius of primary) and the two components are represented as spherical cohesionless self-gravitating granular aggregates. The mutual orbits are simulated in a Monte Carlo routine to provide appropriate parameters for our N-body simulations of impact and tidal distortion. We employ the pkdgrav package with a soft-sphere discrete element method (SSDEM) to explore the entire scenarios. The results show that contact binary configurations are natural outcomes under this scenario, whereas the shape of the primary is almost not affected by the impact of the secondary. However, our simulations further provide an elongated contact binary configuration best-matching to the shape of Toutatis at an approaching distance rp = 1.4 ˜ 1.5 Re (Earth radius), indicative of a likely formation scenario for configurations of Toutatis-like elongated contact binaries.

An X-Ray Survey of the Open Cluster NGC 6475 (M7) with ROSAT

NASA Technical Reports Server (NTRS)

Prosser, Charles F.; Stauffer, John R.; Caillault, J.-P.; Balachandran, Suchitra; Stern, Robert A.; Randich, Sofia

1995-01-01

A ROSAT x-ray survey, with complimentary optical photometry, of the open cluster NGC 6475 has enabled the detection of approx. 50 late-F to K0 and approx. 70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low. galactic latitude, 220 Myr old cluster. The x-ray observations reported here have a typical limiting sensitivity of L(sub x) approx. equal to 10(exp 29) erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the x-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the x rays. The ratio between x-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of x-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in x-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of x-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.

Investigation of welded interconnection of large area wraparound contacted silicon solar cells

NASA Technical Reports Server (NTRS)

Lott, D. R.

1984-01-01

An investigation was conducted to evaluate the welding and temperature cycle testing of large area 5.9 x 5.9 wraparound silicon solar cells utilizing printed circuit substrates with SSC-155 interconnect copper metals and the LMSC Infrared Controlled weld station. An initial group of 5 welded modules containing Phase 2 developmental 5.9 x 5.9 cm cells were subjected to cyclical temperatures of + or 80 C at a rate of 120 cycles per day. Anomalies were noted in the adhesion of the cell contact metallization; therefore, 5 additional modules were fabricated and tested using available Phase I cells with demonstrated contact integrity. Cycling of the later module type through 12,000 cycles indicated the viability of this type of lightweight flexible array concept. This project demonstrated acceptable use of an alternate interconnect copper in combination with large area wraparound cells and emphasized the necessity to implement weld pull as opposed to solder pull procedures at the cell vendors for cells that will be interconnected by welding.

Time-series photometric spot modeling. 2: Fifteen years of photometry of the bright RS CVn binary HR 7275

NASA Technical Reports Server (NTRS)

Strassmeier, K. G.; Hall, D. S.; Henry, G. W.

1994-01-01

We present a time-dependent spot modeling analysis of 15 consecutive years of V-band photometry of the long-period (P(sub orb) = 28.6 days) RS CVn binary HR 7275. This baseline in time is one of the longest, uninterrupted intervals a spotted star has been observed. The spot modeling analysis yields a total of 20 different spots throughout the time span of our observations. The distribution of the observed spot migration rates is consistent with solar-type differential rotation and suggests a lower limit of the differential-rotation coefficient of 0.022 +/-0.004. The observed, maximum lifetime of a single spot (or spot group) is 4.5 years, the minimum lifetime is approximately one year, but an average spot lives for 2.2 years. If we assume that the mechanical shear by differential rotation sets the upper limit to the spot lifetime, the observed maximum lifetime in turn sets an upper limit to the differential-rotation coefficient, namely 0.04 +/- 0.01. This would be differential rotation just 5 to 8 times less than the solar value and one of the strongest among active binaries. We found no conclusive evidence for the existence of a periodic phenomenon that could be attributed to a stellar magnetic cycle.

The RECONS Hunt for Intriguing Binaries in the Solar Neighborhood

NASA Astrophysics Data System (ADS)

Bean, J. L.; Henry, T. J.; Jao, W. C.; Subasavage, J. P.

2001-12-01

As part of an effort to characterize the Sun's neighbors, photometric research was carried out on two samples of low-mass stars known or suspected to lie within 25 parsecs of the Sun. Quality filtered optical photometric data (UBVRI) from published research were merged with recently released infrared data (JHK) from the Two Micron All Sky Survey (2MASS) to create comprehensive long baseline V-I or V-K colors for more than 1400 stars. These were then combined with parallaxes from the NStars Database to create color-absolute magnitude diagrams. The results of this research include increasing the breadth of the NStars Database by adding photometric data for over 1400 stars, and identifying intriguing multiple systems (close spectroscopic binaries, BY Dra types, RS CVn systems) as well as white dwarfs and evolved stars in the solar neighborhood. More than two dozen objects have been identified as probable new multiple systems from their positions above the main sequence. Additional investigations for these intriguing systems are planned, including observations made with the GSU CHARA Array to resolve very close binary systems. This research is a continuation of the work done by RECONS (Research Consortium on Nearby Stars) based at Georgia Sate U., Johns Hopkins U., and U. Virginia, and NASA's Nearby Stars Project (NStars).

New precision orbits of bright double-lined spectroscopic binaries. IX. HD 54371, HR 2692, and 16 ursa majoris

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

Fekel, Francis C.; Williamson, Michael H.; Muterspaugh, Matthew W.

2015-02-01

With extensive sets of new radial velocities we have determined orbital elements for three previously known spectroscopic binaries, HD 54371, HR 2692, and 16 UMa. All three systems have had the lines of their secondaries detected for the first time. The orbital periods range from 16.24 to 113.23 days, and the three binaries have modestly or moderately eccentric orbits. The secondary to primary mass ratios range from 0.50 to 0.64. The orbital dimensions (a{sub 1} sin i and a{sub 2} sin i) and minimum masses (m{sub 1} sin{sup 3} i and m{sub 2} sin{sup 3} i) of the binary componentsmore » all have accuracies of ⩽1%. With our spectroscopic results and the Hipparcos data, we also have determined astrometric orbits for two of the three systems, HR 2692 and 16 UMa. The primaries of HD 54371 and 16 UMa are solar-type stars, and their secondaries are likely K or M dwarfs. The primary of HR 2692 is a late-type subgiant and its secondary is a G or K dwarf. The primaries of both HR 2692 and 16 UMa may be pseudosynchronously rotating, while that of HD 54371 is rotating faster than its pseudosynchronous velocity.« less

Lightcurve Analysis of L5 Trojan Asteroids at the Center for Solar System Studies 2017 September to December

NASA Astrophysics Data System (ADS)

Stephens, Robert D.; Warner, Brian D.

2018-04-01

Lightcurves for four Jovian Trojan asteroids were obtained at the Center for Solar System Studies (CS3) from 2017 September to December. From observations in 2016 June, 2759 Idomeneus was found to be another candidate for the special case of very wide binaries. This would be the fifth confirmed Jovian Trojan binary asteroid.

Road to Grid Parity through Deployment of Low-Cost 21.5% N-Type Si Solar Cells

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

Velundur, Vijay

This project seeks to develop and deploy differentiated 21.5% efficient n-type Si solar cells while reaching the SunShot module cost goal of ≤ $0.50/W. This objective hinges on development of enabling low cost technologies that simplify the manufacturing process and reduce overall processing costs. These comprise of (1) Boron emitter formation and passivation; (2) Simplified processing process for emitter and BSF layers; and (3) Advanced metallization for the front and back contacts.

The generation and morphology of single-crystal silicon carbide wear particles under adhesive conditions

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1981-01-01

Sliding friction experiments were performed in vacuum at room temperature on a plane-type SiC surface in contact with iron-based binary alloys. Multiangular and spherical wear particles were found to form as a result of multipass sliding. The multiangular particles were produced by primary and secondary cracking of the 0001, 10(-)10, and 11(-)20 plane-type cleavage planes under the Hertzian stress field or local inelastic deformation zone. When alloy surfaces are in contact with silicon carbide under a load of 0.2 N, the alloy around the contact area is subjected to stresses that are close to the elastic limit in the elastic deformation region and/or exceed it. It was also found that spherical wear particles may be produced by two mechanisms: a penny-shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and the attrition and fatigue of wear particles.

ROSAT x ray survey observations of active chromospheric binary systems and other selected sources

NASA Technical Reports Server (NTRS)

Ramsey, Lawrence W.

1993-01-01

The connection between processes that produce optical chromospheric activity indicators and those that produce x-rays in RS CVn binary systems by taking advantage of the ROSAT All-Sky Survey (RASS) results and our unique ground-based data set was investigated. In RS CVn systems, excess emission in the Ca 2 resonance (K & H) and infrared triplet (IRT) lines and in the Balmer lines of hydrogen is generally cited as evidence for chromospheric activity, which is usually modeled as scaled up solar-type activity. X-ray emission in RS CVn systems is believed to arise from coronal loop structures. Results from spectra data obtained from RASS observations are discussed and presented.

A solution for the binary system V1373 Orionis

NASA Astrophysics Data System (ADS)

Hauck, Norbert

2016-02-01

Binary system V1373 Ori (HD 36107) has been investigated in the photometric passbands VIc and by spectroscopy (radial velocities). Modelling of the data delivered a single and consistent solution for a detached configuration consisting of a large K-type giant primary component having a radius of 39.40 ± 0.43 Rsun and a mass of 1.132 ± 0.043 Msun, and an invisible dwarf secondary component having a mass of 0.661 ± 0.025 Msun. The red giant fits into a stellar model for a moderately sub-solar metallicity of Z = 0.008. [English and German online-version available under www.bav-astro.eu/rb/rb2016-2/4.html].

Origin of Photovoltage Enhancement via Interfacial Modification with Silver Nanoparticles Embedded in an a-SiC:H p-Type Layer in a-Si:H Solar Cells.

PubMed

Li, Tiantian; Zhang, Qixing; Ni, Jian; Huang, Qian; Zhang, Dekun; Li, Baozhang; Wei, Changchun; Yan, Baojie; Zhao, Ying; Zhang, Xiaodan

2017-03-29

We used silver nanoparticles (Ag-NPs) embedded in the p-type semiconductor layer of hydrogenated amorphous silicon (a-Si:H) solar cells in the Schottky barrier contact design to modify the interface between aluminum-doped ZnO (ZnO:Al, AZO) and p-type hydrogenated amorphous silicon carbide (p-a-SiC:H) without plasmonic absorption. The high work function of the Ag-NPs provided a good channel for the transport of photogenerated holes. A p-type nanocrystalline SiC:H layer was used to compensate for the real surface defects and voids on the surface of Ag-NPs to reduce recombination at the AZO/p-type layer interface, which then enhanced the photovoltage of single-junction a-Si:H solar cells to values as high as 1.01 V. The Ag-NPs were around 10 nm in diameter and thermally stable in the p-type a-SiC:H film at the solar-cell process temperature. We will also show that a wide range of photovoltages between 1.01 and 2.89 V could be obtained with single-, double-, and triple-junction solar cells based on the single-junction a-Si:H solar cells with tunable high photovoltage. These solar cells are suitable photocathodes for solar water-splitting applications.

Spectroscopic observations of the symbiotic binary RW Hydrae

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Fernandez-Castro, Telmo

1987-01-01

Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear shell source which is replenished by the wind of the red giant at a rate of about 10 to the -8th solar mass/yr. Results indicate that the binary is surrounded by an H II region (of radius of about 10 AU) which gives rise to the observed emission lines and radio emission. The He(2+) and O(2+) regions are found to be confined to the immediate vicinity of the hot component.

Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars

NASA Technical Reports Server (NTRS)

Maggio, A.; Vaiana, G. S.; Haisch, B. M.; Stern, R. A.; Bookbinder, J.

1990-01-01

Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emissions more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary.

Multi-stage flash degaser

DOEpatents

Rapier, P.M.

1980-06-26

A multi-stage flash degaser is incorporated in an energy conversion system having a direct-contact, binary-fluid heat exchanger to remove essentially all of the noncondensable gases from geothermal brine ahead of the direct-contact binary-fluid heat exchanger in order that the heat exchanger and a turbine and condenser of the system can operate at optimal efficiency.

Transparent electrodes in silicon heterojunction solar cells: Influence on contact passivation

DOE PAGES

Tomasi, Andrea; Sahli, Florent; Seif, Johannes Peter; ...

2015-10-26

Charge carrier collection in silicon heterojunction solar cells occurs via intrinsic/doped hydrogenated amorphous silicon layer stacks deposited on the crystalline silicon wafer surfaces. Usually, both the electron and hole collecting stacks are externally capped by an n-type transparent conductive oxide, which is primarily needed for carrier extraction. Earlier, it has been demonstrated that the mere presence of such oxides can affect the carrier recombination in the crystalline silicon absorber. Here, we present a detailed investigation of the impact of this phenomenon on both the electron and hole collecting sides, including its consequences for the operating voltages of silicon heterojunction solarmore » cells. As a result, we define guiding principles for improved passivating contact design for high-efficiency silicon solar cells.« less

Transparent electrodes in silicon heterojunction solar cells: Influence on contact passivation

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

Tomasi, Andrea; Sahli, Florent; Seif, Johannes Peter

Charge carrier collection in silicon heterojunction solar cells occurs via intrinsic/doped hydrogenated amorphous silicon layer stacks deposited on the crystalline silicon wafer surfaces. Usually, both the electron and hole collecting stacks are externally capped by an n-type transparent conductive oxide, which is primarily needed for carrier extraction. Earlier, it has been demonstrated that the mere presence of such oxides can affect the carrier recombination in the crystalline silicon absorber. Here, we present a detailed investigation of the impact of this phenomenon on both the electron and hole collecting sides, including its consequences for the operating voltages of silicon heterojunction solarmore » cells. As a result, we define guiding principles for improved passivating contact design for high-efficiency silicon solar cells.« less

Silicon heterojunction solar cell with passivated hole selective MoO{sub x} contact

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

Battaglia, Corsin; Yin, Xingtian; Zheng, Maxwell

2014-03-17

We explore substoichiometric molybdenum trioxide (MoO{sub x}, x < 3) as a dopant-free, hole-selective contact for silicon solar cells. Using an intrinsic hydrogenated amorphous silicon passivation layer between the oxide and the silicon absorber, we demonstrate a high open-circuit voltage of 711 mV and power conversion efficiency of 18.8%. Due to the wide band gap of MoO{sub x}, we observe a substantial gain in photocurrent of 1.9 mA/cm{sup 2} in the ultraviolet and visible part of the solar spectrum, when compared to a p-type amorphous silicon emitter of a traditional silicon heterojunction cell. Our results emphasize the strong potential for oxides as carrier selectivemore » heterojunction partners to inorganic semiconductors.« less

A CAUTIONARY TALE: MARVELS BROWN DWARF CANDIDATE REVEALS ITSELF TO BE A VERY LONG PERIOD, HIGHLY ECCENTRIC SPECTROSCOPIC STELLAR BINARY

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

Mack, Claude E. III; Stassun, Keivan G.; De Lee, Nathan

2013-05-15

We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R {approx}< 30, 000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin i {approx} 50 M{sub Jup}) to a solar-type primary. At least three properties of this system allow it to masquerade as a singlemore » star with a very-low-mass companion: its large eccentricity (e {approx} 0.8), its relatively long period (P {approx} 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight ({omega} {approx} 189 Degree-Sign ). As a result of these properties, for {approx}95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e {approx} 0.3). Only during the {approx}5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of {approx}15 km s{sup -1} reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.« less

Evaluation of transition metal oxide as carrier-selective contacts for silicon heterojunction solar cells

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

Ding, L.; Boccard, Matthieu; Holman, Zachary

2015-04-06

"Reducing light absorption in the non-active solar cell layers, while enabling the extraction of the photogenerated minority carriers at quasi-Fermi levels are two key factors to improve current generation and voltage, and therefore efficiency of silicon heterojunction solar devices. To address these two critical aspects, transition metal oxide materials have been proposed as alternative to the n- and p-type amorphous silicon used as electron and hole selective contacts, respectively. Indeed, transition metal oxides such as molybdenum oxide, titanium oxide, nickel oxide or tungsten oxide combine a wide band gap typically over 3 eV with a band structure and theoretical bandmore » alignment with silicon that results in high transparency to the solar spectrum and in selectivity for the transport of only one carrier type. Improving carrier extraction or injection using transition metal oxide has been a topic of investigation in the field of organic solar cells and organic LEDs; from these pioneering works a lot of knowledge has been gained on materials properties, ways to control these during synthesis and deposition, and their impact on device performance. Recently, the transfer of some of this knowledge to silicon solar cells and the successful application of some metal oxide to contact heterojunction devices have gained much attention. In this contribution, we investigate the suitability of various transition metal oxide films (molybdenum oxide, titanium oxide, and tungsten oxide) deposited either by thermal evaporation or sputtering as transparent hole or electron selective transport layer for silicon solar cells. In addition to systematically characterize their optical and structural properties, we use photoemission spectroscopy to relate compound stoichiometry to band structure and characterize band alignment to silicon. The direct silicon/metal oxide interface is further analyzed by quasi-steady state photoconductance decay method to assess the quality of surface passivation. In complement, we construct full device structures incorporating in some cases surface passivation schemes, with measured initial conversion efficiency over 15% and evaluate the carrier transport properties using temperature-dependent current-voltage and capacitance-voltage measurements. With this detailed characterization study, we aim at providing the framework to assess the potential of a material as a carrier selective contact and the understanding of how each of the aforementioned parameters on the metal oxide films influence the full solar cell operating performances.« less

Study of binary asteroids with three space missions

NASA Astrophysics Data System (ADS)

Kovalenko, Irina; Doressoundiram, Alain; Hestroffer, Daniel

Binary and multiple asteroids are common in the Solar system and encountered in various places going from Near-Earth region, to the main-belt, Trojans and Centaurs, and beyond Neptune. Their study can provide insight on the Solar System formation and its subsequent dynamical evolution. Binaries are also objects of high interest because they provide fundamental physical parameters such as mass and density, and hence clues on the early Solar System, or other processes that are affecting asteroid over time. We will present our current project on analysis of such systems based on three space missions. The first one is the Herschel space observatory (ESA), the largest infrared telescope ever launched. Thirty Centaurs and trans-Neptunian binaries were observed by Herschel and the measurement allowed to define size, albedo and thermal properties [1]. The second one is the satellite Gaia (ESA). This mission is designed to chart a three-dimensional map of the Galaxy. Gaia will provide positional measurements of Solar System Objects - including asteroid binaries - with unprecedented accuracy [2]. And the third one is the proposed mission AIDA, which would study the effects of crashing a spacecraft into an asteroid [3]. The objectives are to demonstrate the ability to modify the trajectory of an asteroid, to precisely measure its trajectory change, and to characterize its physical properties. The target of this mission is a binary system: (65803) Didymos. This encompasses orbital characterisations for both astrometric and resolved binaries, as well as unbound orbit, study of astrometric binaries, derivation of densities, and general statistical analysis of physical and orbital properties of trans-Neptunian and other asteroid binaries. Acknowledgements : work supported by Labex ESEP (ANR N° 2011-LABX-030) [1] Müller T., Lellouch E., Stansberry J. et al. 2009. TNOs are Cool: A Survey of the Transneptunian Region. EM&P 105, 209-219. [2] Mignard F., Cellino A., Muinonen K. et al. 2007. The Gaia Mission: Expected Applications to Asteroid Science. EM&P 1001, 97-125. [3] Galvez A., Carnelli I. et al. 2013. AIDA: The Asteroid Impact & Deflection Assessment Mission. EPSC 2013 - 1043.

Terrestrial Planet Formation Around Close Binary Stars

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Quintana, Elisa V.

2003-01-01

Most stars reside in multiple star systems; however, virtually all models of planetary growth have assumed an isolated single star. Numerical simulations of the collapse of molecular cloud cores to form binary stars suggest that disks will form within such systems. Observations indirectly suggest disk material around one or both components within young binary star systems. If planets form at the right places within such circumstellar disks, they can remain in stable orbits within the binary star systems for eons. We are simulating the late stages of growth of terrestrial planets around close binary stars, using a new, ultrafast, symplectic integrator that we have developed for this purpose. The sum of the masses of the two stars is one solar mass, and the initial disk of planetary embryos is the same as that used for simulating the late stages of terrestrial planet growth within our Solar System and in the Alpha Centauri wide binary star system. Giant planets &are included in the simulations, as they are in most simulations of the late stages of terrestrial planet accumulation in our Solar System. When the stars travel on a circular orbit with semimajor axis of up to 0.1 AU about their mutual center of mass, the planetary embryos grow into a system of terrestrial planets that is statistically identical to those formed about single stars, but a larger semimajor axis and/or a significantly eccentric binary orbit can lead to significantly more dynamically hot terrestrial planet systems.

Search for Gravitational Waves from Compact Binary Coalescence in LIGO and Virgo Data from S5 and VSR1

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.;

Hybrid emitter all back contact solar cell

DOEpatents

Loscutoff, Paul; Rim, Seung

2016-04-12

An all back contact solar cell has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. The other emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The solar cell includes contact holes that allow metal contacts to connect to corresponding emitters.

Photometric Analyses of the Short-Period Contact Binaries HY Pavonis, AW Virginis, and BP Velorum

NASA Astrophysics Data System (ADS)

Lapasset, Emilio; Gomez, Mercedes; Farinas, Raul

1996-04-01

We present BV light curve synthetic analyses of three short period contact (W UMa) binaries: HY Pavonis (P ~0.35 days), AW Virginis (P ~0.35 days), and BP Velorum (P ~0.26 days). Different possible configurations for a wide range of the mass ratio were explored in each case making use of the Wilson-Divinney code. The photometric parameters of the systems were determined from the synthetic light curve solutions that best fit the observations. AW Vir has two components of very similar temperatures and therefore the subtype (A or W) remains undetermined. HY Pav and BP Vel are best modeled by W-type configurations and the asymmetries in the light curves are reproduced by introducing cool spots on the more massive secondary components. Even when BP Vel lies in the region of the open cluster Cr 173, its distance modulus, in principle, rules it out as a cluster member. (SECTION: Stars)

The interaction between giant gaseous protoplanets and the primitive solar nebula

NASA Technical Reports Server (NTRS)

Cameron, A. G. W.

1979-01-01

The manner in which a giant gaseous protoplanet becomes embedded in the primitive solar nebula determines surface boundary conditions which must be used in studying the evolution of such objects. On the one hand, if the system resembles a contact binary system, then the envelope of the protoplanet should approach the entropy of the surrounding nebula. On the other hand angular momentum transfer by resonance and tidal effects between the nebula and the protoplanet may cause the nebula to exhibit a zone of avoidance near the protoplanet, thus inhibiting exchange of material. This problem has been studied with a computer program developed by D. N. C. Lin which simulates disk hydrodynamics by particle motions with dissipation. These studies suggest that for expected values of the protoplanet/protosun mass ratios, significant inhibition of mass exchange is likely, so that it is a reasonable next step to undertake protoplanet evolution studies with the imposition of minimum protoplanet surface temperatures.

EXTRASOLAR BINARY PLANETS. II. DETECTABILITY BY TRANSIT OBSERVATIONS

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

Lewis, K. M.; Ida, S.; Ochiai, H.

2015-05-20

We discuss the detectability of gravitationally bound pairs of gas-giant planets (which we call “binary planets”) in extrasolar planetary systems that are formed through orbital instability followed by planet–planet dynamical tides during their close encounters, based on the results of N-body simulations by Ochiai et al. (Paper I). Paper I showed that the formation probability of a binary is as much as ∼10% for three giant planet systems that undergo orbital instability, and after post-capture long-term tidal evolution, the typical binary separation is three to five times the sum of the physical radii of the planets. The binary planets aremore » stable during the main-sequence lifetime of solar-type stars, if the stellarcentric semimajor axis of the binary is larger than 0.3 AU. We show that detecting modulations of transit light curves is the most promising observational method to detect binary planets. Since the likely binary separations are comparable to the stellar diameter, the shape of the transit light curve is different from transit to transit, depending on the phase of the binary’s orbit. The transit durations and depth for binary planet transits are generally longer and deeper than those for the single planet case. We point out that binary planets could exist among the known inflated gas-giant planets or objects classified as false positive detections at orbital radii ≳0.3 AU, propose a binary planet explanation for the CoRoT candidate SRc01 E2 1066, and show that binary planets are likely to be present in, and could be detected using, Kepler-quality data.« less

On the nature of the symbiotic binary AX Persei

NASA Technical Reports Server (NTRS)

Mikolajewska, Joanna; Kenyon, Scott J.

1992-01-01

Photometric and spectroscopic observations of the symbiotic binary AX Persei are presented. This system contains a red giant that fills its tidal lobe and transfers material into an accretion disk surrounding a low-mass main-sequence star. The stellar masses - 1 solar mass for the red giant and about 0.4 solar mass for the companion - suggest AX Per is poised to enter a common envelope phase of evolution. The disk luminosity increases from L(disk) about 100 solar luminosity in quiescence to L(disk) about 5700 solar luminosity in outburst for a distance of d = 2.5 kpc. Except for visual maximum, high ionization permitted emission lines - such as He II - imply an EUV luminosity comparable to the disk luminosity. High-energy photons emitted by a hot boundary layer between the disk and central star ionize a surrounding nebula to produce this permitted line emission. High ionization forbidden lines form in an extended, shock-excited region well out of the binary's orbital plane and may be associated with mass loss from the disk.

The effects of close binaries on the magnetic activity of M dwarfs as probed using close white dwarf companions

NASA Astrophysics Data System (ADS)

Morgan, D. P.

2017-01-01

I present a study of close white dwarf (WD) and M dwarf (dM) binary systems (WD+dM) to examine the effects that close companions have on magnetic field generation in dMs. Using the Sloan Digital Sky Survey (SDSS) Data Release 8 spectroscopic database, I constructed a sample of 1756 WD+dM high-quality pairs. I show that early-type dMs (M4), where stars become fully convective, the activity fraction and activity lifetimes of WD+dM binary systems become more comparable to those of the field dMs. The implications of having a close binary companion may include: increased stellar rotation through disk disruption, tidal effects, and/or angular momentum exchange. Thus, the similarity in activity between late-type field dMs and late-type dMs with close companions is likely due to the mechanism generating magnetic fields being less sensitive to the effects caused by a close companion; namely, increased stellar rotation. Using a subset of 181 close WD+dM pairs, matched to the time-domain SDSS Stripe 82 catalog, I show that enhanced magnetic activity extends to the flaring behavior of dMs in close binaries. Specifically, early spectral type dMs (M0-M4), in close WD+dM pairs, are two orders of magnitude more likely to flare than field dMs, whereas late-type dMs (M4-M6) in close WD+dM pairs flare as frequently or less than the late-type field dM sample. To test whether the presence of a close companion leads to star-star interactions, I searched for correlations between the WD occultations and flares from the dM member in KOI-256, an eclipsing WD+dM system. I find no correlations between the flaring activity of the dM and the WD occultations, indicating the there are no obvious signs of star-star interactions at work. In addition, the dM member of KOI-256 flares more than any other dM observed by Kepler and shows evidence for solar-like magnetic activity cycles, a feature not seen in many dMs to date.

Designing a Template Bank to Observe Compact Binary Coalescences in Advanced Ligo's Second Observing Run

NASA Technical Reports Server (NTRS)

Dal Canton, Tito; Harry, Ian W.

2017-01-01

We describe the methodology and novel techniques used to construct a set of waveforms, or template bank, applicable to searches for compact binary coalescences in Advanced LIGO's second observing run. This template bank is suitable for observing systems composed of two neutron stars, two black holes, or a neutron star and a black hole. The Post-Newtonian formulation is used to model waveforms with total mass less than 4 Solar Mass and the most recent effective-one-body model, calibrated to numerical relativity to include the merger and ringdown, is used for total masses greater than 4 Solar Mass. The effects of spin precession, matter, orbital eccentricity and radiation modes beyond the quadrupole are neglected. In contrast to the template bank used to search for compact binary mergers in Advanced LIGO's first observing run, here we are including binary-black-hole systems with total mass up to several hundreds of solar masses, thereby improving the ability to observe such systems. We introduce a technique to vary the starting frequency of waveform filters so that our bank can simultaneously contain binary-neutron-star and high-mass binary-black hole waveforms. We also introduce a lower-bound on the filter waveform length, to exclude very short-duration, high-mass templates whose sensitivity is strongly reduced by the characteristics and performance of the interferometers.

Period change of a contact binary system RW Comae Berenices

NASA Astrophysics Data System (ADS)

Maithong, Wiraporn; Phao-ai, Parinda

2017-08-01

In this work, we studied about the period change of a contact binary system RW Comae Berenices. The binary system was observed on March 9th, 2016 by the 105 mm diameter of a refraction telescope with the DSLR digital camera at the Regional Observatory for the Public Nakhon Ratchasima, Thailand. The photometry used the IRIS program. The period change was analyzed by used the O-C diagram. The result shows that the period of the RW Comae Berenices is increasing with 1.89×10-3 seconds/year.

Far-infrared data for symbiotic stars. II - The IRAS survey observations

NASA Technical Reports Server (NTRS)

Kenyon, S. J.; Fernandez-Castro, T.; Stencel, R. E.

1988-01-01

IRAS survey data for all known symbiotic binaries are reported. S type systems have 25 micron excesses much larger than those of single red giant stars, suggesting that these objects lose mass more rapidly than do normal giants. D type objects have far-IR colors similar to those of Mira variables, implying mass-loss rate of about 10 to the -6th solar masses/yr. The near-IR extinctions of the D types indicate that their Mira components are enshrouded in optically thick dust shells, while their hot companions lie outside the shells. If this interpretation of the data is correct, then the very red near-IR colors of D type symbiotic stars are caused by extreme amounts of dust absorption rather than dust emission. The small group of D prime objects possesses far-IR colors resembling those of compact planetary nebulae or extreme OH/IR stars. It is speculated that these binaries are not symbiotic stars at all, but contain a hot compact star and an exasymptotic branch giant which is in the process of ejecting a planetary nebula shell.

Multi-color light curves and orbital period research of eclipsing binary V1073 Cyg

NASA Astrophysics Data System (ADS)

Tian, Xiao-Man; Zhu, Li-Ying; Qian, Sheng-Bang; Li, Lin-Jia; Jiang, Lin-Qiao

2018-02-01

New multi-color BV RcIc photometric observations are presented for the W UMa type eclipsing binary V1073 Cyg. The multi-color light curve analysis with the Wilson-Devinney procedure yielded the absolute parameters of this system, showing that V1073 Cyg is a shallow contact binary system with a fill-out factor f = 0.124(±0.011). We collected all available times of light minima spanning 119 yr, including CCD data to construct the O ‑ C curve, and performed detailed O ‑ C analysis. The O ‑ C diagram shows that the period change is complex. A long-term continuous decrease and a cyclic variation exist. The period is decreasing at a rate of Ṗ = ‑1.04(±0.18) × 10‑10 d cycle‑1 and, with the period decrease, V1073 Cyg will evolve to the deep contact stage. The cyclic variation with a period of P 3 = 82.7(±3.6) yr and an amplitude of A = 0.028(±0.002)d may be explained by magnetic activity of one or both components or the light travel time effect caused by a distant third companion with M 3(i‧ = 90°) = 0.511 M⊙.

Picosecond energy transfer and multiexciton transfer outpaces Auger recombination in binary CdSe nanoplatelet solids.

PubMed

Rowland, Clare E; Fedin, Igor; Zhang, Hui; Gray, Stephen K; Govorov, Alexander O; Talapin, Dmitri V; Schaller, Richard D

2015-05-01

Fluorescence resonance energy transfer (FRET) enables photosynthetic light harvesting, wavelength downconversion in light-emitting diodes (LEDs), and optical biosensing schemes. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells, non-contact chromophore pumping from a proximal LED, and markedly reduced gain thresholds. However, the fastest reported FRET time constants involving spherical quantum dots (0.12-1 ns; refs 7-9) do not outpace biexciton Auger recombination (0.01-0.1 ns; ref. 10), which impedes multiexciton-driven applications including electrically pumped lasers and carrier-multiplication-enhanced photovoltaics. Few-monolayer-thick semiconductor nanoplatelets (NPLs) with tens-of-nanometre lateral dimensions exhibit intense optical transitions and hundreds-of-picosecond Auger recombination, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that interplate FRET (∼6-23 ps, presumably for co-facial arrangements) can occur 15-50 times faster than Auger recombination and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies.

Picosecond energy transfer and multiexciton transfer outpaces Auger recombination in binary CdSe nanoplatelet solids

NASA Astrophysics Data System (ADS)

Rowland, Clare E.; Fedin, Igor; Zhang, Hui; Gray, Stephen K.; Govorov, Alexander O.; Talapin, Dmitri V.; Schaller, Richard D.

2015-05-01

Fluorescence resonance energy transfer (FRET) enables photosynthetic light harvesting, wavelength downconversion in light-emitting diodes (LEDs), and optical biosensing schemes. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells, non-contact chromophore pumping from a proximal LED, and markedly reduced gain thresholds. However, the fastest reported FRET time constants involving spherical quantum dots (0.12-1 ns; refs , , ) do not outpace biexciton Auger recombination (0.01-0.1 ns; ref. ), which impedes multiexciton-driven applications including electrically pumped lasers and carrier-multiplication-enhanced photovoltaics. Few-monolayer-thick semiconductor nanoplatelets (NPLs) with tens-of-nanometre lateral dimensions exhibit intense optical transitions and hundreds-of-picosecond Auger recombination, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that interplate FRET (˜6-23 ps, presumably for co-facial arrangements) can occur 15-50 times faster than Auger recombination and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies.

Physical Properties and Evolutionary States of EA-type Eclipsing Binaries Observed by LAMOST

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Zhang, J.; He, J.-J.; Zhu, L.-Y.; Zhao, E.-G.; Shi, X.-D.; Zhou, X.; Han, Z.-T.

2018-03-01

About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4< P< 1 days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.

High-efficiency silicon heterojunction solar cells: Status and perspectives

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

De Wolf, S.

Silicon heterojunction technology (HJT) uses silicon thin-film deposition techniques to fabricate photovoltaic devices from mono-crystalline silicon wafers (c-Si). This enables energy-conversion efficiencies above 21 %, also at industrial-production level. In this presentation we review the present status of this technology and point out recent trends. We first discuss how the properties of thin hydrogenated amorphous silicon (a-Si:H) films can be exploited to fabricate passivating contacts, which is the key to high- efficiency HJT solar cells. Such contacts enable very high operating voltages, approaching the theoretical limits, and yield small temperature coefficients. With this approach, an increasing number of groups aremore » reporting devices with conversion efficiencies well over 20 % on n-type wafers, Panasonic leading the field with 24.7 %. Exciting results have also been obtained on p-type wafers. Despite these high voltages, important efficiency gains can still be made in fill factor and optical design. This requires improved understanding of carrier transport across device interfaces and reduced parasitic absorption in HJT solar cells. For the latter, several strategies can be followed: Short- wavelength losses can be reduced by replacing the front a-Si:H films with wider-bandgap window layers, such as silicon alloys or even metal oxides. Long-wavelength losses are mitigated by introducing new high-mobility TCO’s such as hydrogenated indium oxide, and also by designing new rear reflectors. Optical shadow losses caused by the front metalisation grid are significantly reduced by replacing printed silver electrodes with fine-line plated copper contacts, leading also to possible cost advantages. The ultimate approach to minimize optical losses is the implementation of back-contacted architectures, which are completely devoid of grid shadow losses and parasitic absorption in the front layers can be minimized irrespective of electrical transport requirements. The validity of this approach was convincingly demonstrated by Panasonic, Japan in 2014, reporting on an interdigitated back-contacted HJT cell with an efficiency of 25.6%, setting the new single-junction c-Si record. Finally, given the virtually perfect surface passivation and excellent red response of HJT solar cells, we anticipate these devices will also become the preferred bottom cell in ultra-high efficiency c-Si-based tandem devices, exploiting better the solar spectrum. Such tandem cells have the potential to overcome the fundamental single-junction limit of silicon solar cells (29.4%). Combining HJT cells with perovskite solar cells as top cell appears to be particularly appealing.« less

Perovskite Solar Cells with Large-Area CVD-Graphene for Tandem Solar Cells.

PubMed

Lang, Felix; Gluba, Marc A; Albrecht, Steve; Rappich, Jörg; Korte, Lars; Rech, Bernd; Nickel, Norbert H

2015-07-16

Perovskite solar cells with transparent contacts may be used to compensate for thermalization losses of silicon solar cells in tandem devices. This offers a way to outreach stagnating efficiencies. However, perovskite top cells in tandem structures require contact layers with high electrical conductivity and optimal transparency. We address this challenge by implementing large-area graphene grown by chemical vapor deposition as a highly transparent electrode in perovskite solar cells, leading to identical charge collection efficiencies. Electrical performance of solar cells with a graphene-based contact reached those of solar cells with standard gold contacts. The optical transmission by far exceeds that of reference devices and amounts to 64.3% below the perovskite band gap. Finally, we demonstrate a four-terminal tandem device combining a high band gap graphene-contacted perovskite top solar cell (Eg = 1.6 eV) with an amorphous/crystalline silicon bottom solar cell (Eg = 1.12 eV).

An Eccentric Binary Millisecond Pulsar in the Galactic Plane

NASA Technical Reports Server (NTRS)

Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri;

Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires.

PubMed

Levtchenko, Alexandra; Le Gall, Sylvain; Lachaume, Raphaël; Michallon, Jérôme; Collin, Stéphane; Alvarez, José; Djebbour, Zakaria; Kleider, Jean-Paul

2018-06-22

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell's performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V bi ) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively. Consequently, the solar cell's performance is degraded if either the doping concentration of the c-Si core, or/and the work function of the back contact is too low. By inserting a thin (p) a-Si:H layer between both core/absorber and back contact/absorber, the performance of the solar cell can be improved by partly fixing the V bi at both interfaces due to strong electrostatic screening effect. Depositing such a buffer layer playing the role of an electrostatic screen for charge carriers is a suggested way of enhancing the performance of solar cells based on radial p-i-n or n-i-p nanowire array.

Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires

NASA Astrophysics Data System (ADS)

Levtchenko, Alexandra; Le Gall, Sylvain; Lachaume, Raphaël; Michallon, Jérôme; Collin, Stéphane; Alvarez, José; Djebbour, Zakaria; Kleider, Jean-Paul

2018-06-01

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell’s performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V bi) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively. Consequently, the solar cell’s performance is degraded if either the doping concentration of the c-Si core, or/and the work function of the back contact is too low. By inserting a thin (p) a-Si:H layer between both core/absorber and back contact/absorber, the performance of the solar cell can be improved by partly fixing the V bi at both interfaces due to strong electrostatic screening effect. Depositing such a buffer layer playing the role of an electrostatic screen for charge carriers is a suggested way of enhancing the performance of solar cells based on radial p-i-n or n-i-p nanowire array.

Searching for Solar System Wide Binaries with Pan-STARRS-1

NASA Astrophysics Data System (ADS)

Holman, Matthew J.; Protopapas, P.; Tholen, D. J.

2007-10-01

Roughly 60% of the observing time of the Pan-STARRS-1 (PS1) telescope will be dedicated to a "3pi steradian" survey with an observing cadence that is designed for the detection of near-Earth asteroids and slow-moving solar system bodies. Over this course of its 3.5 year cience mission, this unprecedented survey will discover nearly every asteroid, Trojan, Centaur, long-period comet, short-period comet, and trans-neptunian object (TNO) brighter than magnitude R=23. This census will be used to address a large number of questions regarding the physical and dynamical properties of the various small body populations of the solar system. Roughly 1-2% of TNOs are wide binaries with companions at separations greater than 1 arcsec and brightness differences less than 2 magnitudes (Kern & Elliot 2006; Noll et al 2007). These can be readily detected by PS1; we will carry out such a search with PS1 data. To do so, we will modify the Pan-STARRS Moving Object Processing System (MOPS) such that it will associate the components of resolved or marginally resolved binaries, link such pairs of detections obtained at different epochs, and the estimate the relative orbit of the binary. We will also determine the efficiency with which such binaries are detected as a function of the binary's relative orbit and the relative magnitudes of the components. Based on an estimated 7000 TNOs that PS1 will discover, we anticipate finding 70-140 wide binaries. The PS1 data, 60 epochs over three years, is naturally suited to determining the orbits of these objects. Our search will accurately determine the binary fraction for a variety of subclasses of TNOs.

High-Resolution Spectroscopy of some very Active Southern Stars

NASA Technical Reports Server (NTRS)

Soderblom, David R.; King, Jeremy R.; Henry, Todd J.

1998-01-01

We have obtained high-resolution echelle spectra of 18 solar-type stars that an earlier survey showed to have very high levels of Ca II H and K emission. Most of these stars belong to close binary systems, but five remain as probable single stars or well-separated binaries that are younger than the Pleiades on the basis of their lithium abundances and H.alpha emission. Three of these probable single stars also lie more than 1 mag above the main sequence in a color-magnitude diagram, and appear to have ages of 10 to 15 Myr. Two of them, HD 202917 and HD 222259, also appear to have a kinematic association with the pre-main-sequence multiple system HD 98800.

Structural and spectral studies of sunspots. [umbral core modelling

NASA Technical Reports Server (NTRS)

Wyller, A. A.

1974-01-01

Observations of umbral cores, both by multicolor photometry and by narrow band photometry in the vicinity of the sodium D lines, are described, and evidence is given which supports the validity of many umbral models, each of which describes different aspects of the observed umbral cores. Theoretical studies carried on at the observatory include the following: (1) Zeeman profiles of the sodium D sub 2 line and other lines; (2) turbulent heat conduction, sound waves, and the missing flux in sunspots; (3) chromospheric heating above spots by Alfven waves; (4) magnetic convection in the sun and solar neutrinos; (5) models of starspots on flare stars; (5) starspots on the primaries of contact binary systems; and (6) implications of starspots on red dwarfs.

Astrophysics to z approx. 10 with Gravitational Waves

NASA Technical Reports Server (NTRS)

Stebbins, Robin; Hughes, Scott; Lang, Ryan

2007-01-01

The most useful characterization of a gravitational wave detector's performance is the accuracy with which astrophysical parameters of potential gravitational wave sources can be estimated. One of the most important source types for the Laser Interferometer Space Antenna (LISA) is inspiraling binaries of black holes. LISA can measure mass and spin to better than 1% for a wide range of masses, even out to high redshifts. The most difficult parameter to estimate accurately is almost always luminosity distance. Nonetheless, LISA can measure luminosity distance of intermediate-mass black hole binary systems (total mass approx.10(exp 4) solar mass) out to z approx.10 with distance accuracies approaching 25% in many cases. With this performance, LISA will be able to follow the merger history of black holes from the earliest mergers of proto-galaxies to the present. LISA's performance as a function of mass from 1 to 10(exp 7) solar mass and of redshift out to z approx. 30 will be described. The re-formulation of LISA's science requirements based on an instrument sensitivity model and parameter estimation will be described.

Multi-stage flash degaser

DOEpatents

Rapier, Pascal M.

1982-01-01

A multi-stage flash degaser (18) is incorporated in an energy conversion system (10) having a direct-contact, binary-fluid heat exchanger to remove essentially all of the noncondensable gases from geothermal brine ahead of the direct-contact binary-fluid heat exchanger (22) in order that the heat exchanger (22) and a turbine (48) and condenser (32) of the system (10) can operate at optimal efficiency.

On orbital period changes of two low-mass-ratio and deep-contact binaries: FN Cam and KN Per

NASA Astrophysics Data System (ADS)

Hu, Ke; Jiang, Zhen-Hua; Yu, Yun-Xia; Xiang, Fu-Yuan

2018-07-01

The orbital period changes of two low-mass-ratio and deep-contact binaries, FN Cam and KN Per, are investigated by using all available times of light minimum taken from the databases and literature. It is found that the orbital periods of FN Cam and KN Per show secular increase at a rate of P˙ = 4.38 ×10-7 days year-1 and P˙ = 4.18 ×10-7 days year-1 , respectively. The secular period increase suggests that FN Cam and KN Per are undergoing continuous mass transfer from the less massive secondary component to the more massive primary one. A statistical analysis of 53 low-mass-ratio and deep-contact binaries indicates that all of them should contain at least a continuous period change (secular increase/decrease or cyclic oscillation). Moreover, the rates of the secular period variations can be at a common level of P˙ ∼10-7 days year-1. In addition, the cyclic period oscillation has been detected for only 43% of sample stars, which indicates that it should be not popular for all low-mass-ratio and deep-contact binaries.

First photometric study of ultrashort-period contact binary 1SWASP J140533.33+114639.1

NASA Astrophysics Data System (ADS)

Zhang, Bin; Qian, Sheng-Bang; Michel, Ri; Soonthornthum, Boonrucksar; Zhu, Li-Ying

2018-03-01

In this paper, CCD photometric light curves for the short-period eclipsing binary 1SWASP J140533.33+114639.1 (hereafter J1405) in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devinney (W-D) code. It is discovered that J1405 is a W-subtype shallow contact binary with a contact degree of f = 7.9 ± 0.5% and a mass ratio of q = 1.55 ± 0.02. In order to explain the asymmetric light curves of the system, a cool starspot on the more massive component is employed. This shallow contact eclipsing binary may have been formed from a short-period detached system through orbital shrinkage due to angular momentum loss. Based on the (O – C) method, the variation of orbital period is studied using all the available times of minimum light. The (O – C) diagram reveals that the period is increasing continuously at a rate of dP/dt = +2.09 × 10‑7, d yr‑1, which can be explained by mass transfer from the less massive component to the more massive one.

Absolute and geometric parameters of contact binary BO Arietis

NASA Astrophysics Data System (ADS)

Gürol, B.; Gürsoytrak, S. H.; Bradstreet, D. H.

2015-08-01

We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system BO Ari from analyzed CCD (BVRI) light curves and radial velocity data. The photometric data were obtained in 2009 and 2010 at Ankara University Observatory (AUO) and the spectroscopic observations were made in 2007 and 2010 at TUBITAK National Observatory (TUG). These light and radial velocity observations were analyzed simultaneously by using the Wilson-Devinney (2013 revision) code to obtain absolute and geometrical parameters. The system was determined to be an A-type W UMa system. Combining our photometric solution with the spectroscopic data we derived masses and radii of the eclipsing system to be M1 = 0.995M⊙,M2 = 0.189M⊙,R1 = 1.090R⊙ and R2 = 0.515R⊙ . Finally, we discuss the evolutionary status of the system.

Absolute and geometric parameters of contact binary V1918 Cyg

NASA Astrophysics Data System (ADS)

Gürol, B.

2016-08-01

We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system V1918 Cyg from analyzed CCD (BVR) light curves and radial velocity data. We used the photometric data published by Yang et al. (2013) and spectroscopic data obtained in 2012 at TUBITAK National Observatory (TUG). The light and radial velocity observations were analyzed simultaneously by using the Wilson-Devinney (2015 revision) code to obtain absolute and geometrical parameters of the system. It is confirmed that the system is an A-type W UMa as indicated by Yang et al. (2013). Combining our spectroscopic data with the photometric solution we derived masses and radii of the eclipsing system as M1 = 1.302M⊙ , M2 = 0.362M⊙ , R1 = 1.362R⊙ and R2 = 0.762R⊙ . Finally, we discuss the evolutionary status of the system.

Pyramid solar micro-grid

NASA Astrophysics Data System (ADS)

Huang, Bin-Juine; Hsu, Po-Chien; Wang, Yi-Hung; Tang, Tzu-Chiao; Wang, Jia-Wei; Dong, Xin-Hong; Hsu, Hsin-Yi; Li, Kang; Lee, Kung-Yen

2018-03-01

A novel pyramid solar micro-grid is proposed in the present study. All the members within the micro-grid can mutually share excess solar PV power each other through a binary-connection hierarchy. The test results of a 2+2 pyramid solar micro-grid consisting of 4 individual solar PV systems for self-consumption are reported.

Back-junction back-contact n-type silicon solar cell with diffused boron emitter locally blocked by implanted phosphorus

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

Müller, Ralph, E-mail: ralph.mueller@ise.fraunhofer.de; Schrof, Julian; Reichel, Christian

2014-09-08

The highest energy conversion efficiencies in the field of silicon-based photovoltaics have been achieved with back-junction back-contact (BJBC) silicon solar cells by several companies and research groups. One of the most complex parts of this cell structure is the fabrication of the locally doped p- and n-type regions, both on the back side of the solar cell. In this work, we introduce a process sequence based on a synergistic use of ion implantation and furnace diffusion. This sequence enables the formation of all doped regions for a BJBC silicon solar cell in only three processing steps. We observed that implantedmore » phosphorus can block the diffusion of boron atoms into the silicon substrate by nearly three orders of magnitude. Thus, locally implanted phosphorus can be used as an in-situ mask for a subsequent boron diffusion which simultaneously anneals the implanted phosphorus and forms the boron emitter. BJBC silicon solar cells produced with such an easy-to-fabricate process achieved conversion efficiencies of up to 21.7%. An open-circuit voltage of 674 mV and a fill factor of 80.6% prove that there is no significant recombination at the sharp transition between the highly doped emitter and the highly doped back surface field at the device level.« less

AN M DWARF COMPANION TO AN F-TYPE STAR IN A YOUNG MAIN-SEQUENCE BINARY

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

Eigmüller, Ph.; Csizmadia, Sz.; Erikson, A.

2016-03-15

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung–Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 ± 0.073) M{sub ⊙}more » and a radius of (1.474 ± 0.040) R{sub ⊙}. The companion is an M dwarf with a mass of (0.188 ± 0.014) M{sub ⊙} and a radius of (0.234 ± 0.009) R{sub ⊙}. The orbital period is (1.35121 ± 0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin–orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass–radius relation of both components are in agreement with this finding.« less

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

Li, Hongfei; Yang, Zhenhua; Pan, Cheng

Here, we report that the addition of a non-photoactive tertiary polymer phase in the binary bulk heterojunction (BHJ) polymer solar cell leads to a self-assembled columnar nanostructure, enhancing the charge mobilities and photovoltaic efficiency with surprisingly increased optimal active blend thicknesses over 300 nm, 3–4 times larger than that of the binary counterpart. Using the prototypical poly(3-hexylthiophene) (P3HT):fullerene blend as a model BHJ system, we discover that the inert poly(methyl methacrylate) (PMMA) added in the binary BHJ blend self-assembles into vertical columns, which not only template the phase segregation of electron acceptor fullerenes but also induce the out-of-plane rotation ofmore » the edge-on-orientated crystalline P3HT phase. Using complementary interrogation methods including neutron reflectivity, X-ray scattering, atomic force microscopy, transmission electron microscopy, and molecular dynamics simulations, we show that the enhanced charge transport originates from the more randomized molecular stacking of the P3HT phase and the spontaneous segregation of fullerenes at the P3HT/PMMA interface, driven by the high surface tension between the two polymeric components. The results demonstrate a potential method for increasing the thicknesses of high-performance polymer BHJ solar cells with improved photovoltaic efficiency, alleviating the burden of stringently controlling the ultrathin blend thickness during the roll-to-roll-type large-area manufacturing environment.« less

Back contact buffer layer for thin-film solar cells

DOEpatents

Compaan, Alvin D.; Plotnikov, Victor V.

2014-09-09

A photovoltaic cell structure is disclosed that includes a buffer/passivation layer at a CdTe/Back contact interface. The buffer/passivation layer is formed from the same material that forms the n-type semiconductor active layer. In one embodiment, the buffer layer and the n-type semiconductor active layer are formed from cadmium sulfide (CdS). A method of forming a photovoltaic cell includes the step of forming the semiconductor active layers and the buffer/passivation layer within the same deposition chamber and using the same material source.

Performance and Metastability of CdTe Solar Cells with a Te Back-Contact Buffer Layer

NASA Astrophysics Data System (ADS)

Moore, Andrew

Thin-film CdTe photovoltaics are quickly maturing into a viable clean-energy solution through demonstration of competitive costs and performance stability with existing energy sources. Over the last half decade, CdTe solar technology has achieved major gains in performance; however, there are still aspects that can be improved to progress toward their theoretical maximum efficiency. Perhaps equally valuable as high photovoltaic efficiency and a low levelized cost of energy, is device reliability. Understanding the root causes for changes in performance is essential for accomplishing long-term stability. One area for potential performance enhancement is the back contact of the CdTe device. This research incorporated a thin-film Te-buffer layer into the contact structure, between the CdTe and contact metal. The device performance and characteristics of many different back contact configurations were rigorously studied. CdTe solar cells fabricated with the Te-buffer contact showed short-circuit current densities and open-circuit voltages that were on par with the traditional back-contacts used at CSU. However, the Te-buffer contact typically produced 2% larger fill-factors on average, leading to greater conversation efficiency. Furthermore, using the Te buffer allowed for incorporation of 50% less Cu, which is used for p-type doping but is also known to decrease lifetime and stability. This resulted in an additional 3% fill-factor gain with no change in other parameters compared to the standard-Cu treated device. In order to better understand the physical mechanisms of the Te-buffer contact, electrical and material properties of the Te layer were extracted and used to construct a simple energy band diagram. The Te layer was found to be highly p-type (>1018 cm-3) and possess a positive valence-band offset of 0.35-0.40 eV with CdTe. An existing simulation model incorporating the Te-layer properties was implemented and validated by comparing simulated results of CdTe device performance to experimental values. The Te layer improves performance is attributed to a reduction in the downward energy band bending between the CdTe and typical contact metals. The stability, or rather the metastability, of CdTe solar cells was also studied with a focus on the Te back contact. A metastable device has a series of quasi-stable local energy-minimuma which the device may transition among. This work primarily focused on changes, both beneficial and detrimental, caused by diffusion and drift of atoms in the CdTe lattice. As atoms moved and/or became ionized their defect states were shifted, which resulted in changes in the CdTe doping and recombination. Changes in performance for devices in equilibrium and under stress conditions were analyzed by electrical and material characterization. Mobile impurities and mechanisms responsible for the changes were identified--primarily the migration of interstitial Cu and Cl. The stability of CdTe solar cells with different back contacts were compared. It was found that any contact that included the Te layer was almost always more stable than the traditional contact used at CSU, most likely because of less sensitivity to the impurity profiles in the CdTe. Moreover, the Te contact configuration that introduced the least amount of Cu into the CdTe was discovered to be the most stable, both in storage and under stress conditions.

Investigation of back surface fields effect on bifacial solar cells

NASA Astrophysics Data System (ADS)

Sepeai, Suhaila; Sulaiman, M. Y.; Sopian, Kamaruzzaman; Zaidi, Saleem H.

2012-11-01

A bifacial solar cell, in contrast with a conventional monofacial solar cell, produces photo-generated current from both front and back sides. Bifacial solar cell is an attractive candidate for enhancing photovoltaic (PV) market competitiveness as well as supporting the current efforts to increase efficiency and lower material costs. This paper reports on the fabrication of bifacial solar cells using phosphorus-oxytrichloride (POCl3) emitter formation on p-type, nanotextured silicon (Si) wafer. Backside surface field was formed through Al-diffusion using conventional screen-printing process. Bifacial solar cells with a structure of n+pp+ with and without back surface field (BSF) were fabricated in which silicon nitride (SiN) anti reflection and passivation films were coated on both sides, followed by screen printing of Argentum (Ag) and Argentum/Aluminum (Ag/Al) on front and back contacts, respectively. Bifacial solar cells without BSF exhibited open circuit voltage (VOC) of 535 mV for front and 480 mV for back surface. With Al-alloyed BSF bifacial solar cells, the VOC improved to 580 mV for the front surface and 560 mV for the back surface. Simulation of bifacial solar cells using PC1D and AFORS software demonstrated good agreement with experimental results. Simulations showed that best bifacial solar cells are achieved through a combination of high lifetime wafer, low recombination back surface field, reduced contact resistance, and superior surface passivation.

Nature of type 1 Supernovae

NASA Technical Reports Server (NTRS)

Shklovskiy, I. S.

1980-01-01

The nature of type 1 supernovae (SN 1) is discussed through a comparison of observational evidence and theoretical perspectives relating to both type 1 and 2 supernovae. In particular two hypotheses relating to SN 1 phenomenon are examined: the first proposing that SN 1 are components of binary systems in which, at a comparatively late stage of evolution, overflow of the mass occurs; the second considers pre-SN 1 to be recently evolved stars with a mass greater than 1.4 solar mass (white dwarfs). In addition, an explanation of the reduced frequency of flares of SN 1 in spiral galaxies as related to that in elliptical galaxies is presented.

Individual Dynamical Masses of Ultracool Dwarfs

NASA Astrophysics Data System (ADS)

Dupuy, Trent J.; Liu, Michael C.

2017-08-01

We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis of resolved imaging from Keck Observatory and Hubble Space Telescope and unresolved astrometry from CFHT/WIRCam yields parallactic distances for all systems, robust orbit determinations for 23 systems, and photocenter orbits for 19 systems. As a result, we measure 38 precise individual masses spanning 30-115 {M}{Jup}. We determine a model-independent substellar boundary that is ≈70 {M}{Jup} in mass (≈L4 in spectral type), and we validate Baraffe et al. evolutionary model predictions for the lithium-depletion boundary (60 {M}{Jup} at field ages). Assuming each binary is coeval, we test models of the substellar mass-luminosity relation and find that in the L/T transition, only the Saumon & Marley “hybrid” models accounting for cloud clearing match our data. We derive a precise, mass-calibrated spectral type-effective temperature relation covering 1100-2800 K. Our masses enable a novel direct determination of the age distribution of field brown dwarfs spanning L4-T5 and 30-70 {M}{Jup}. We determine a median age of 1.3 Gyr, and our population synthesis modeling indicates our sample is consistent with a constant star formation history modulated by dynamical heating in the Galactic disk. We discover two triple-brown-dwarf systems, the first with directly measured masses and eccentricities. We examine the eccentricity distribution, carefully considering biases and completeness, and find that low-eccentricity orbits are significantly more common among ultracool binaries than solar-type binaries, possibly indicating the early influence of long-lived dissipative gas disks. Overall, this work represents a major advance in the empirical view of very low-mass stars and brown dwarfs.

Anchoring Technology for In Situ Exploration of Small Bodie

NASA Technical Reports Server (NTRS)

Steltzner, A.; Nasif, A.

2000-01-01

Comets, asteroids and other small bodies found in the solar system do not possess enough gravity to ensure spacecraft contact forces sufficient to allow many types of in situ science, such as core or surface sampling.

Extrasolar binary planets. I. Formation by tidal capture during planet-planet scattering

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

Ochiai, H.; Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp

2014-08-01

We have investigated (1) the formation of gravitationally bounded pairs of gas-giant planets (which we call 'binary planets') from capturing each other through planet-planet dynamical tide during their close encounters and (2) the subsequent long-term orbital evolution due to planet-planet and planet-star quasi-static tides. For the initial evolution in phase 1, we carried out N-body simulations of the systems consisting of three Jupiter-mass planets taking into account the dynamical tide. The formation rate of the binary planets is as much as 10% of the systems that undergo orbital crossing, and this fraction is almost independent of the initial stellarcentric semimajormore » axes of the planets, while ejection and merging rates sensitively depend on the semimajor axes. As a result of circularization by the planet-planet dynamical tide, typical binary separations are a few times the sum of the physical radii of the planets. After the orbital circularization, the evolution of the binary system is governed by long-term quasi-static tide. We analytically calculated the quasi-static tidal evolution in phase 2. The binary planets first enter the spin-orbit synchronous state by the planet-planet tide. The planet-star tide removes angular momentum of the binary motion, eventually resulting in a collision between the planets. However, we found that the binary planets survive the tidal decay for the main-sequence lifetime of solar-type stars (∼10 Gyr), if the binary planets are beyond ∼0.3 AU from the central stars. These results suggest that the binary planets can be detected by transit observations at ≳ 0.3 AU.« less

A Survey of Ca II H and K Chromospheric Emission in Southern Solar-Type Stars

NASA Astrophysics Data System (ADS)

Henry, Todd J.; Soderblom, David R.; Donahue, Robert A.; Baliunas, Sallie L.

1996-01-01

More than 800 southern stars within 50 pc have been observed for chromospheric emission in the cores of the Ca II H and K lines. Most of the sample targets were chosen to be G dwarfs on the basis of colors and spectral types. The bimodal distribution in stellar activity first noted in a sample of northern stars by Vaughan and Preston in 1980 is confirmed, and the percentage of active stars, about 30%, is remarkably consistent between the northern and southern surveys. This is especially compelling given that we have used an entirely different instrumental setup and stellar sample than used in the previous study. Comparisons to the Sun, a relatively inactive star, show that most nearby solar-type stars have a similar activity level, and presumably a similar age. We identify two additional subsamples of stars -- a very active group, and a very inactive group. The very active group may be made up of young stars near the Sun, accounting for only a few percent of the sample, and appears to be less than ~0.1 Gyr old. Included in this high-activity tail of the distribution, however, is a subset of very close binaries of the RS CVn or W UMa types. The remaining members of this population may be undetected close binaries or very young single stars. The very inactive group of stars, contributting ~5%--10% to the total sample, may be those caught in a Maunder Minimum type phase. If the observations of the survey stars are considered to be a sequence of snapshots of the Sun during its life, we might expect that the Sun will spend about 10% of the remainder of its main sequence life in a Maunder Minimum phase.

Dynamical fate of wide binaries in the solar neighborhood

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

Weinberg, M.D.; Shapiro, S.L.; Wasserman, I.

1987-01-01

An analytical model is presented for the evolution of wide binaries in the Galaxy. The study is pertinent to the postulated solar companion, Nemesis, which may disturb the Oort cloud and cause catastrophic comet showers to strike the earth every 26 Myr. Distant gravitational encounters are modeled by Fokker-Planck coefficients for advection and diffusion of the orbital binding energy. It is shown that encounters with passing stars cause a diffusive evolution of the binding energy and semimajor axis. Encounters with subclumps in giant molecular clouds disrupt orbits to a degree dependent on the cumulative number of stellar encounters. The timemore » scales of the vents and the limitations of scaling laws used are discussed. Results are provided from calculations of galactic distribution of wide binaries and the evolution of wide binary orbits. 38 references.« less

An Isotope Study of Hydrogenation of poly-Si/SiOx Passivated Contacts for Si Solar Cells: Preprint

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

Schnabel, Manuel; Nemeth, William; van de Loo, Bas, W.H.

2017-06-26

For many years, the record Si solar cell efficiency stood at 25.0%. Only recently have several companies and institutes managed to produce more efficient cells, using passivated contacts of made doped poly-Si or a-Si:H and a passivating intrinsic interlayer in all cases. Common to these designs is the need to passivate the layer stack with hydrogen. In this contribution, we perform a systematic study of passivated contact passivation by hydrogen, using poly-Si/SiOx passivated contacts on n-Cz-Si, and ALD Al2O3 followed by a forming gas anneal (FGA) as the hydrogen source. We study p-type and n-type passivated contacts with implied Vocmore » exceeding 690 and 720 mV, respectively, and perform either the ALD step or the FGA with deuterium instead of hydrogen in order to separate the two processes via SIMS. By examining the deuterium concentration at the SiOx in both types of samples, we demonstrate that the FGA supplies negligible hydrogen species to the SiOx, regardless of whether the FGA is hydrogenated or deuterated. Instead, it supplies the thermal energy needed for hydrogen species in the Al2O3 to diffuse there. Furthermore, the concentration of hydrogen species at the SiOx can saturate while implied Voc continues to increase, showing that the energy from the FGA is also required for hydrogen species already at the SiOx to find recombination-active defects to passivate.« less

Study of neglected (near-)contact binaries using small telescopes

NASA Astrophysics Data System (ADS)

Zejda, Miloslav; Zhang, Jia; Qian, Shengbang; Zhu, Liying; Mikulášek, Zdeněk

2016-07-01

We present the first results of our new program aimed at relatively bright neglected (near-)contact binaries. The targets can be observed using small telescopes from several to several tens of centimeters in diameter. Light ephemeris determined by phenomenological modeling and physical parameters of the system obtained by Wilson-Devinney method are given for the first stars V373 Dra, OQ UMa from our program.

Solar photocatalytic degradation of mono azo methyl orange and diazo reactive green 19 in single and binary dye solutions: adsorbability vs photodegradation rate.

PubMed

Ong, Soon-An; Min, Ohm-Mar; Ho, Li-Ngee; Wong, Yee-Shian

2013-05-01

The objective of this study was to examine the effects of adsorbability and number of sulfonate group on solar photocatalytic degradation of mono azo methyl orange (MO) and diazo Reactive Green 19 (RG19) in single and binary dye solutions. The adsorption capacity of MO and RG19 onto the TiO₂ was 16.9 and 26.8 mg/g, respectively, in single dye solution, and reduced to 5.0 and 23.1 mg/g, respectively, in the binary dye solution. The data obtained for photocatalytic degradation of MO and RG19 in single and binary dye solution were well fitted with the Langmuir-Hinshelwood kinetic model. The pseudo-first-order rate constants of diazo RG19 were significant higher than the mono azo MO either in single or binary dye solutions. The higher number of sulfonate group in RG19 contributed to better adsorption capacity onto the surface of TiO₂ than MO indicating greater photocatalytic degradation rate.

A lightweight solar array study

NASA Technical Reports Server (NTRS)

Josephs, R. H.

1977-01-01

A sample module was assembled to model a portion of a flexible extendable solar array, a type that promises to become the next generation of solar array design. The resulting study of this module is intended to provide technical support to the array designer for lightweight component selection, specifications, and tests. Selected from available lightweight components were 127-micron-thick wrap-around contacted solar cells, 34- micron-thick sputtered glass covers, and as a substrate a 13-micron-thick polyimide film clad with a copper printed circuit. Each component displayed weaknesses. The thin solar cells had excessive breakage losses. Sputtered glass cover adhesion was poor, and the covered cell was weaker than the cell uncovered. Thermal stresses caused some cell delamination from the model solar array substrate.

Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films

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

Zhang, Xinyu, E-mail: xinyu.zhang@anu.edu.au; Wan, Yimao; Bullock, James

2016-08-01

This work explores the application of transparent nitrogen doped copper oxide (CuO{sub x}:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuO{sub x}:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuO{sub x}:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contactmore » resistivity of ∼10 mΩ cm{sup 2} has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.« less

Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

The friction and wear of metals and binary alloys in contact with an abrasive grit of single-crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various metals and iron-base binary alloys (alloying elements Ti, Cr, Mn, Ni, Rh and W) in contact with single crystal silicon carbide riders. Results indicate that the friction force in the plowing of metal and the groove height (corresponding to the wear volume of the groove) decrease linearly as the shear strength of the bulk metal increases. The coefficient of friction and groove height generally decrease, and the contact pressure increases with an increase in solute content of binary alloys. There appears to be very good correlation of the solute to iron atomic ratio with the decreasing rate of change of coefficient of friction, the decreasing rate of change of groove height and the increasing rate of change of contact pressure with increasing solute content. These rates of change increase as the solute to iron atomic radius ratio increases or decreases from unity.

Impact of dopant concentrations on emitter formation with spin on dopant source in n-type crystalline silicon solar cells

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

Singha, Bandana; Solanki, Chetan Singh

Use of a suitable dopant source for emitter formation is an essential requirement in n-type crystalline silicon solar cells. Boron spin on dopant source, used as alternative to mostly used BBr{sub 3} liquid source, can yield an emitter with less diffusion induced defects under controlled conditions. Different concentrations of commercially available spin on dopant source is used and optimized in this work for sheet resistance values of the emitter ranging from 30 Ω/□ to 70 Ω/□ with emitter doping concentrations suitable for ohmic contacts. The dopant concentrations diluted with different ratios improves the carrier lifetime and thus improves the emittermore » performance. Hence use of suitable dopant source is essential in forming emitters in n-type crystalline silicon solar cells.« less

Ejection of rocky and icy material from binary star systems: implications for the origin and composition of 1I/`Oumuamua

NASA Astrophysics Data System (ADS)

Jackson, Alan P.; Tamayo, Daniel; Hammond, Noah; Ali-Dib, Mohamad; Rein, Hanno

2018-06-01

In single-star systems like our own Solar system, comets dominate the mass budget of bodies ejected into interstellar space, since they form further away and are less tightly bound. However, 1I/`Oumuamua, the first interstellar object detected, appears asteroidal in its spectra and lack of detectable activity. We argue that the galactic budget of interstellar objects like 1I/`Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single-star systems or widely separated binaries. We further show that in circumbinary systems, rocky bodies should be ejected in comparable numbers to icy ones. This suggests that a substantial fraction of interstellar objects discovered in future should display an active coma. We find that the rocky population, of which 1I/`Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries.

A solar-type star polluted by calcium-rich supernova ejecta inside the supernova remnant RCW 86

NASA Astrophysics Data System (ADS)

Gvaramadze, Vasilii V.; Langer, Norbert; Fossati, Luca; Bock, Douglas C.-J.; Castro, Norberto; Georgiev, Iskren Y.; Greiner, Jochen; Johnston, Simon; Rau, Arne; Tauris, Thomas M.

2017-06-01

When a massive star in a binary system explodes as a supernova, its companion star may be polluted with heavy elements from the supernova ejecta. Such pollution has been detected in a handful of post-supernova binaries 1 , but none of them is associated with a supernova remnant. We report the discovery of a binary G star strongly polluted with calcium and other elements at the position of the candidate neutron star [GV2003] N within the young galactic supernova remnant RCW 86. Our discovery suggests that the progenitor of the supernova that produced RCW 86 could have been a moving star, which exploded near the edge of its wind bubble and lost most of its initial mass because of common-envelope evolution shortly before core collapse, and that the supernova explosion might belong to the class of calcium-rich supernovae — faint and fast transients 2,3 , the origin of which is strongly debated 4-6 .

Multiplicity of Massive Stars

NASA Astrophysics Data System (ADS)

Zinnecker, Hans

We review the multiplicity of massive stars by compiling the abstracts of the most relevant papers in the field. We start by discussing the massive stars in the Orion Trapezium Cluster and in other Galactic young clusters and OB associations, and end with the R136 cluster in the LMC. The multiplicity of field O-stars and runaway OB stars is also reviewed. The results of both visual and spectroscopic surveys are presented, as well as data for eclipsing systems. Among the latter, we find the most massive known binary system WR20a, with two ~,80M_⊙ components in a 3 day orbit. Some 80% of the wide visual binaries in stellar associations are in fact hierarchical triple systems, where typically the more massive of the binary components is itself a spectroscopic or even eclipsing binary pair. The multiplicity (number of companions) of massive star primaries is significantly higher than for low-mass solar-type primaries or for young low-mass T Tauri stars. There is also a striking preponderance of very close nearly equal mass binary systems (the origin of which has recently been explained in an accretion scenario). Finally, we offer a new idea as to the origin of massive Trapezium systems, frequently found in the centers of dense young clusters.

Kepler eclipsing binary stars. IV. Precise eclipse times for close binaries and identification of candidate three-body systems

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

Conroy, Kyle E.; Stassun, Keivan G.; Prša, Andrej

2014-02-01

We present a catalog of precise eclipse times and analysis of third-body signals among 1279 close binaries in the latest Kepler Eclipsing Binary Catalog. For these short-period binaries, Kepler's 30 minute exposure time causes significant smearing of light curves. In addition, common astrophysical phenomena such as chromospheric activity, as well as imperfections in the light curve detrending process, can create systematic artifacts that may produce fictitious signals in the eclipse timings. We present a method to measure precise eclipse times in the presence of distorted light curves, such as in contact and near-contact binaries which exhibit continuously changing light levelsmore » in and out of eclipse. We identify 236 systems for which we find a timing variation signal compatible with the presence of a third body. These are modeled for the light travel time effect and the basic properties of the third body are derived. This study complements J. A. Orosz et al. (in preparation), which focuses on eclipse timing variations of longer period binaries with flat out-of-eclipse regions. Together, these two papers provide comprehensive eclipse timings for all binaries in the Kepler Eclipsing Binary Catalog, as an ongoing resource freely accessible online to the community.« less

Constraints on the Progenitor System of SN 2016gkg from a Comprehensive Statistical Analysis

NASA Astrophysics Data System (ADS)

Sravan, Niharika; Marchant, Pablo; Kalogera, Vassiliki; Margutti, Raffaella

2018-01-01

Type IIb supernovae (SNe) present a unique opportunity for understanding the progenitors of stripped-envelope SNe because the stellar progenitor of several SNe IIb have been identified in pre-explosion images. In this paper, we use Bayesian inference and a large grid of non-rotating solar-metallicity single and binary stellar models to derive the associated probability distributions of single and binary progenitors of the SN IIb 2016gkg using existing observational constraints. We find that potential binary star progenitors have smaller pre-SN hydrogen-envelope and helium-core masses than potential single-star progenitors typically by 0.1 M ⊙ and 2 M ⊙, respectively. We find that, a binary companion, if present, is a main-sequence or red-giant star. Apart from this, we do not find strong constraints on the nature of the companion star. We demonstrate that the range of progenitor helium-core mass inferred from observations could help improve constraints on the progenitor. We find that the probability that the progenitor of SN 2016gkg was a binary is 22% when we use constraints only on the progenitor luminosity and effective temperature. Imposing the range of pre-SN progenitor hydrogen-envelope mass and radius inferred from SN light curves, the probability that the progenitor is a binary increases to 44%. However, there is no clear preference for a binary progenitor. This is in contrast to binaries being the currently favored formation channel for SNe IIb. Our analysis demonstrates the importance of statistical inference methods to constrain progenitor channels.

Long-orbital-period Prepolars Containing Early K-type Donor Stars. Bottleneck Accretion Mechanism in Action

NASA Astrophysics Data System (ADS)

Tovmassian, G.; González–Buitrago, D.; Zharikov, S.; Reichart, D. E.; Haislip, J. B.; Ivarsen, K. M.; LaCluyze, A. P.; Moore, J. P.; Miroshnichenko, A. S.

2016-03-01

We studied two objects identified as cataclysmic variables (CVs) with periods exceeding the natural boundary for Roche-lobe-filling zero-age main sequence (ZAMS) secondary stars. We present observational results for V1082 Sgr with a 20.82 hr orbital period, an object that shows a low luminosity state when its flux is totally dominated by a chromospherically active K star with no signs of ongoing accretion. Frequent accretion shutoffs, together with characteristics of emission lines in a high state, indicate that this binary system is probably detached, and the accretion of matter on the magnetic white dwarf takes place through stellar wind from the active donor star via coupled magnetic fields. Its observational characteristics are surprisingly similar to V479 And, a 14.5 hr binary system. They both have early K-type stars as donor stars. We argue that, similar to the shorter-period prepolars containing M dwarfs, these are detached binaries with strong magnetic components. Their magnetic fields are coupled, allowing enhanced stellar wind from the K star to be captured and channeled through the bottleneck connecting the two stars onto the white dwarf’s magnetic pole, mimicking a magnetic CV. Hence, they become interactive binaries before they reach contact. This will help to explain an unexpected lack of systems possessing white dwarfs with strong magnetic fields among detached white+red dwarf systems.

ABSOLUTE PROPERTIES OF THE HIGHLY ECCENTRIC, SOLAR-TYPE ECLIPSING BINARY HD 74057

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

Sowell, James R.; Henry, Gregory W.; Fekel, Francis C., E-mail: jim.sowell@physics.gatech.edu, E-mail: gregory.w.henry@gmail.com, E-mail: fekel@evans.tsuniv.edu

2012-01-15

We have obtained Stroemgren b and y differential photometric observations of the solar-type eclipsing binary HD 74057 plus follow-up high-resolution, red wavelength spectroscopic observations. The system has an orbital period of 31.2198 days, a high eccentricity of 0.47, and is seen almost exactly edge on with an inclination of 89.{sup 0}8. The two main-sequence G0 stars are nearly identical in all physical characteristics. We used the Wilson-Devinney program to obtain a simultaneous solution of our photometric and spectroscopic observations. The resulting masses of the components are M{sub 1} = 1.138 {+-} 0.003 M{sub Sun} and M{sub 2} = 1.131 {+-}more » 0.003 M{sub Sun }, and the radii are R{sub 1} = 1.064 {+-} 0.002 R{sub Sun} and R{sub 2} = 1.049 {+-} 0.002 R{sub Sun }. The effective temperatures are 5900 K (fixed) and 5843 K, and the iron abundance, [Fe/H], is estimated to be +0.07. A comparison with evolutionary tracks suggests that the system may be even more metal rich. The components rotate with periods of 8.4 days, significantly faster than the predicted pseudosynchronous period of 12.7 days. We see evidence that one or both components have cool spots. Both stars are close to the zero-age main sequence and are about 1.0 Gyr old.« less

Long term evolution of surface features on the unusual close binary V361 Lyr

NASA Astrophysics Data System (ADS)

Lister, T. A.

2009-02-01

V361 Lyr has been recognized as an unusual, possibly unique, pre-contact binary which is though to be evolving from a detached binary system into a W UMa contact binary system due to Angular Momentum Loss (AML) and mass transfer. The mass transfer and resulting hot spot on the secondary star allow the physics of accretion to be studied without the normal difficulties of disks and winds that are present in T Tauri stars. I present light curves obtained over a 10 year period as part of long term monitoring program obtained with a variety of telescopes, collect all available times of minima from the literature along with those determined from the light curves and determine the rate of period change.

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David D.; Cousins, Peter John

2015-07-21

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David; Cousins, Peter

2012-12-04

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David D.; Cousins, Peter John

2014-07-22

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

Method of manufacturing a hybrid emitter all back contact solar cell

DOEpatents

Loscutoff, Paul; Rim, Seung

2017-02-07

A method of manufacturing an all back contact solar cell which has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. A second emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The method further includes forming contact holes that allow metal contacts to connect to corresponding emitters.

Concentrating Solar Power Projects - ACME Solar Tower | Concentrating Solar

Science.gov Websites

: 2.5 MW Gross: 2.5 MW Status: Operational Start Year: 2011 Do you have more information, corrections Contact(s): SolarPACES Start Production: April 2011 Participants Developer(s): ACME Group ; eSolar Owner(s

HIP 13962 - The Possible Former Member of Binary System with Supernova

NASA Astrophysics Data System (ADS)

Yushchenko, V.; Yushchenko, A.; Gopka, V.; Shavrina, A.; Kovtyukh, V.; Hong, K. S.; Mkrtichian, D.; Thano, N. A.

2016-12-01

The runaway supergiant star HIP 13962 (spectral type G0Ia) was recently pointed as a possible former binary companion of young pulsar PSR J0826+2637. The spectra of HIP 13962 were obtained in Haute-Provence observatory (France), in Bohuynsan observatory (Korea), and also in NARIT (Thailand) with 1.9, 1.8, and 2.4 meter telescopes respectively. The spectra were obtained in 1995, 2003, 2005, 2014, and 2015. Significant variations of the spectrum are detected. The cores of strong lines show complicated structure, the brightness of the star is variable. The cycles of photometric variations have been changed. We analyzed the spectral observations and present the preliminary chemical composition for elements from iron to lead. The abundance pattern can not be fitted by solar system r- & s-process abundance distribution.

A faint type of supernova from a white dwarf with a helium-rich companion.

PubMed

Perets, H B; Gal-Yam, A; Mazzali, P A; Arnett, D; Kagan, D; Filippenko, A V; Li, W; Arcavi, I; Cenko, S B; Fox, D B; Leonard, D C; Moon, D-S; Sand, D J; Soderberg, A M; Anderson, J P; James, P A; Foley, R J; Ganeshalingam, M; Ofek, E O; Bildsten, L; Nelemans, G; Shen, K J; Weinberg, N N; Metzger, B D; Piro, A L; Quataert, E; Kiewe, M; Poznanski, D

2010-05-20

Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The 'old' environment near the supernova location, and the very low derived ejected mass ( approximately 0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive (44)Ti.

Protoplanetary Disk Masses from Stars to Brown Dwarfs

NASA Astrophysics Data System (ADS)

Mohanty, Subhanjoy; Greaves, Jane; Mortlock, Daniel; Pascucci, Ilaria; Scholz, Aleks; Thompson, Mark; Apai, Daniel; Lodato, Giuseppe; Looper, Dagny

2013-08-01

We present SCUBA-2 850 μm observations of seven very low mass stars (VLMS) and brown dwarfs (BDs). Three are in Taurus and four in the TW Hydrae Association (TWA), and all are classical T Tauri (cTT) analogs. We detect two of the three Taurus disks (one only marginally), but none of the TWA ones. For standard grains in cTT disks, our 3σ limits correspond to a dust mass of 1.2 M ⊕ in Taurus and a mere 0.2 M ⊕ in the TWA (3-10× deeper than previous work). We combine our data with other submillimeter/millimeter (sub-mm/mm) surveys of Taurus, ρ Oph, and the TWA to investigate the trends in disk mass and grain growth during the cTT phase. Assuming a gas-to-dust mass ratio of 100:1 and fiducial surface density and temperature profiles guided by current data, we find the following. (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is ~100 AU for intermediate-mass stars, solar types, and VLMS, and ~20 AU for BDs. (2) While the upper envelope of apparent disk masses increases with M * from BDs to VLMS to solar-type stars, no such increase is observed from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate stellar masses. (3) Many of the disks around Taurus and ρ Oph intermediate-mass and solar-type stars evince an opacity index of β ~ 0-1, indicating significant grain growth. Of the only four VLMS/BDs in these regions with multi-wavelength measurements, three are consistent with considerable grain growth, though optically thick disks are not ruled out. (4) For the TWA VLMS (TWA 30A and B), combining our 850 μm fluxes with the known accretion rates and ages suggests substantial grain growth by 10 Myr, comparable to that in the previously studied TWA cTTs Hen 3-600A and TW Hya. The degree of grain growth in the TWA BDs (2M1207A and SSPM1102) remains largely unknown. (5) A Bayesian analysis shows that the apparent disk-to-stellar mass ratio has a roughly constant mean of log10[M disk/M *] ≈ -2.4 all the way from intermediate-mass stars to VLMS/BDs, supporting previous qualitative suggestions that the ratio is ~1% throughout the stellar/BD domain. (6) Similar analysis shows that the disk mass in close solar-type Taurus binaries (sep <100 AU) is significantly lower than in singles (by a factor of 10), while that in wide solar-type Taurus binaries (>=100 AU) is closer to that in singles (lower by a factor of three). (7) We discuss the implications of these results for planet formation around VLMS/BDs, and for the observed dependence of accretion rate on stellar mass.

Observations of hot stars and eclipsing binaries with FRESIP

NASA Technical Reports Server (NTRS)

Gies, Douglas R.

1994-01-01

The FRESIP project offers an unprecedented opportunity to study pulsations in hot stars (which vary on time scales of a day) over a several year period. The photometric data will determine what frequencies are present, how or if the amplitudes change with time, and whether there is a connection between pulsation and mass loss episodes. It would initiate a new field of asteroseismology studies of hot star interiors. A search should be made for selected hot stars for inclusion in the list of project targets. Many of the primary solar mass targets will be eclipsing binaries, and I present estimates of their frequency and typical light curves. The photometric data combined with follow up spectroscopy and interferometric observations will provide fundamental data on these stars. The data will provide definitive information on the mass ratio distribution of solar-mass binaries (including the incidence of brown dwarf companions) and on the incidence of planets in binary systems.

Corrosion inhibitors for solar heating and cooling systems

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Deramus, G. E., Jr.

1977-01-01

Problems dealing with corrosion and corrosion protection of solar heating and cooling systems are discussed. A test program was conducted to find suitable and effective corrosion inhibitors for systems employing either water or antifreeze solutions for heat transfer and storage. Aluminum-mild-steel-copper-stainless steel assemblies in electrical contact were used to simulate a multimetallic system which is the type most likely to be employed. Several inhibitors show promise for this application.

Dumb-bell-shaped equilibrium figures for fiducial contact-binary asteroids and EKBOs

NASA Astrophysics Data System (ADS)

Descamps, Pascal

2015-01-01

In this work, we investigate the equilibrium figures of a dumb-bell-shaped sequence with which we are still not well acquainted. Studies have shown that these elongated and nonconvex figures may realistically replace the classic “Roche binary approximation” for modeling putative peanut-shaped or contact binary asteroids. The best-fit dumb-bell shapes, combined with the known rotational period of the objects, provide estimates of the bulk density of these objects. This new class of mathematical figures has been successfully tested on the observed light curves of three noteworthy small bodies: main-belt Asteroid 216 Kleopatra, Trojan Asteroid 624 Hektor and Edgeworth-Kuiper-belt object 2001 QG298. Using the direct observations of Kleopatra and Hektor obtained with high spatial resolution techniques and fitting the size of the dumb-bell-shaped solutions, we derived new physical characteristics in terms of equivalent radius, 62.5 ± 5 km and 92 ± 5 km, respectively, and bulk density, 4.4 ± 0.4 g cm-3 and 2.43 ± 0.35 g cm-3, respectively. In particular, the growing inadequacy of the radar shape model for interpreting any type of observations of Kleopatra (light curves, AO images, stellar occultations) in a satisfactory manner suggests that Kleopatra is more likely to be a dumb-bell-shaped object than a “dog-bone.”

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.

Cool stars, stellar systems, and the sun; Proceedings of the 7th Cambridge Workshop, Tucson, AZ, Oct. 9-12, 1991

NASA Technical Reports Server (NTRS)

Giampapa, Mark S. (Editor); Bookbinder, Jay A. (Editor)

1992-01-01

Consideration is given to HST observations of late-type stars, molecular absorption in the UV spectrum of Alpha Ori, EUV emission from late-type stars, Rosat observations of the Pleiades cluster, a deep ROSAT observation of the Hyades cluster, optical spectroscopy detected by EXOSAT, stellar photospheric convection, a structure of the solar X-ray corona, magnetic surface images of the BY Dra Star HD 82558, a Zebra interpretatin of BY Dra stars, optical flares on II Peg, a low-resolution spectroscopic survey of post-T tauri candidates, millimeter and sub-millimeter emission from flare stars, and activity in tidally interacting binaries. Attention is also given to modeling stellar angular momentum evolution, extended 60-micron emission from nearby Mira variables, the PANDORA atmosphere program, the global properties of active regions, oscillations in a stratified atmosphere, lithium abundances in northern RS CVn binaries, a new catalog of cool dwarf stars, the Far UV Spectrograph Explorer, and development of reflecting coronagraphs.

Detecting a Hot Companion to the Progenitor of the Type Ic Supernova 1994I in M51

NASA Astrophysics Data System (ADS)

Van Dyk, Schuyler

2013-10-01

Core-collapse supernovae {SNe} are the endpoints of the lives of massive stars {with initial mass > 8 solar masses}. We are reasonably confident that the progenitor stars for most hydrogen-rich Type II SNe are red supergiants, based in part on direct identifications with HST. However, the progenitors of the stripped-envelope He-rich Type Ib and He-poor Type Ic SNe have yet to be directly identified. These SNe are thought to arise from either single, high-mass stars in the Wolf-Rayet phase or, alternatively, from lower-mass stars in interacting binary systems. Both models can account for the required extensive envelope stripping. Until a progenitor is identified for these SN types, our best hope of testing these progenitor models is to detect the companion star to the progenitor, if the binary model holds. This star is predicted to be a hot supergiant. Therefore, it is best detected in the ultraviolet. The only SN which is sufficiently nearby and experienced low enough reddening to be a viable target for this detection is the SN Ic 1994I in M51. Furthermore, the SN was imaged by HST when it was still bright, so we can pinpoint its location. We therefore propose, as part of the UV Initiative in Cycle 21, to image the site in F275W and F336W to levels deep enough to significantly detect a putative progenitor companion, if it exists. The proposed observations will provide an important test of the binary progenitor hypothesis.

Highly efficient single-junction GaAs thin-film solar cell on flexible substrate.

PubMed

Moon, Sunghyun; Kim, Kangho; Kim, Youngjo; Heo, Junseok; Lee, Jaejin

2016-07-20

There has been much interest in developing a thin-film solar cell because it is lightweight and flexible. The GaAs thin-film solar cell is a top contender in the thin-film solar cell market in that it has a high power conversion efficiency (PCE) compared to that of other thin-film solar cells. There are two common structures for the GaAs solar cell: n (emitter)-on-p (base) and p-on-n. The former performs better due to its high collection efficiency because the electron diffusion length of the p-type base region is much longer than the hole diffusion length of the n-type base region. However, it has been limited to fabricate highly efficient n-on-p single-junction GaAs thin film solar cell on a flexible substrate due to technical obstacles. We investigated a simple and fast epitaxial lift-off (ELO) method that uses a stress originating from a Cr/Au bilayer on a 125-μm-thick flexible substrate. A metal combination of AuBe/Pt/Au is employed as a new p-type ohmic contact with which an n-on-p single-junction GaAs thin-film solar cell on flexible substrate was successfully fabricated. The PCE of the fabricated single-junction GaAs thin-film solar cells reached 22.08% under air mass 1.5 global illumination.

Carrier Selective, Passivated Contacts for High Efficiency Silicon Solar Cells based on Transparent Conducting Oxides

DOE PAGES

Young, David L.; Nemeth, William; Grover, Sachit; ...

2014-01-01

We describe the design, fabrication and results of passivated contacts to n-type silicon utilizing thin SiO 2 and transparent conducting oxide layers. High temperature silicon dioxide is grown on both surfaces of an n-type wafer to a thickness <50 Å, followed by deposition of tin-doped indium oxide (ITO) and a patterned metal contacting layer. As deposited, the thin-film stack has a very high J0, contact, and a non-ohmic, high contact resistance. However, after a forming gas anneal, the passivation quality and the contact resistivity improve significantly. The contacts are characterized by measuring the recombination parameter of the contact (J0, contact)more » and the specific contact resistivity (ρ contact) using a TLM pattern. The best ITO/SiO 2 passivated contact in this study has J 0,contact = 92.5 fA/cm 2 and ρ contact = 11.5 mOhm-cm 2. These values are placed in context with other passivating contacts using an analysis that determines the ultimate efficiency and the optimal area fraction for contacts for a given set of (J0, contact, ρ contact) values. The ITO/SiO 2 contacts are found to have a higher J0, contact, but a similar ρ contact compared to the best reported passivated contacts.« less

LUT Reveals a New Mass-transferring Semi-detached Binary

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Zhou, X.; Zhu, L.-Y.; Zejda, M.; Soonthornthum, B.; Zhao, E.-G.; Zhang, J.; Zhang, B.; Liao, W.-P.

2015-12-01

GQ Dra is a short-period eclipsing binary in a double stellar system that was discovered by Hipparcos. Complete light curves in the UV band were obtained with the Lunar-based Ultraviolet Telescope in 2014 November and December. Photometric solutions are determined using the W-D (Wilson and Devinney) method. It is discovered that GQ Dra is a classical Algol-type semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available times of minimum light suggests that the orbital period is increasing continuously at a rate of \\dot{P}=+3.48(+/- 0.23)× {10}-7 days yr-1. This could be explained by mass transfer from the secondary to the primary, which is in agreement with the semi-detached configuration with a lobe-filling secondary. By assuming a conservation of mass and angular momentum, the mass transfer rate is estimated as \\dot{m}=9.57(+/- 0.63)× {10}-8 {M}⊙ {{yr}}-1. All of these results reveal that GQ Dra is a mass-transferring semi-detached binary in a double system that was formed from an initially detached binary star. After the massive primary evolves to fill the critical Roche lobe, the mass transfer will be reversed and the binary will evolve into a contact configuration with two sub-giant or giant component stars.

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

NASA Astrophysics Data System (ADS)

Tomasi, Andrea; Paviet-Salomon, Bertrand; Jeangros, Quentin; Haschke, Jan; Christmann, Gabriel; Barraud, Loris; Descoeudres, Antoine; Seif, Johannes Peter; Nicolay, Sylvain; Despeisse, Matthieu; de Wolf, Stefaan; Ballif, Christophe

2017-04-01

For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%.

A new photometric study of the triple star system EF Draconis

NASA Astrophysics Data System (ADS)

Yang, Yuan-Gui

2012-04-01

We present new charge-coupled device (CCD) photometry for the triple star EF Draconis, obtained in 2009 and 2011. Using the updated Wilson-Devinney program, the photometric solutions were deduced from two sets of light curves. The results indicate that EF Dra is an A-type W UMa binary with a contact degree of f = 46.7%(±0.6%) and a third light of l3 ≃ 1.5%. Through analyzing the O — C curve, it is found that the orbital period shows a long-time increase with a light-time orbit. The period, semi-amplitude and eccentricity of the third body are Pmod = 17.20(±0.18) yr, A = 0.0039d(±0.0002d) and e = 0.49(±0.02) respectively. This kind of tertiary companion may extract angular momentum from the central system. The orbital period of EF Dra secularly increases at a rate of dP/dt = +3.72(±0.07) × 10-7 d yr-1, which may be interpreted by mass transfer from the less massive to the more massive component. As period increases, the separation between components may increase, which will cause the contact degree to decrease. With mass transferring, the spin angular momentum will increase, while the orbital angular momentum will decrease. Only if the contact configuration would merge at could this kind of deep-contact binary with period increasing, such as EF Dra, evolve into a rapidly-rotating single star.

Formation of Kuiper-belt binaries through multiple chaotic scattering encounters with low-mass intruders

NASA Astrophysics Data System (ADS)

Astakhov, Sergey A.; Lee, Ernestine A.; Farrelly, David

2005-06-01

The discovery that many trans-Neptunian objects exist in pairs, or binaries, is proving invaluable for shedding light on the formation, evolution and structure of the outer Solar system. Based on recent systematic searches it has been estimated that up to 10 per cent of Kuiper-belt objects might be binaries. However, all examples discovered to date are unusual, as compared with near-Earth and main-belt asteroid binaries, for their mass ratios of the order of unity and their large, eccentric orbits. In this article we propose a common dynamical origin for these compositional and orbital properties based on four-body simulations in the Hill approximation. Our calculations suggest that binaries are produced through the following chain of events. Initially, long-lived quasi-bound binaries form by two bodies getting entangled in thin layers of dynamical chaos produced by solar tides within the Hill sphere. Next, energy transfer through gravitational scattering with a low-mass intruder nudges the binary into a nearby non-chaotic, stable zone of phase space. Finally, the binary hardens (loses energy) through a series of relatively gentle gravitational scattering encounters with further intruders. This produces binary orbits that are well fitted by Kepler ellipses. Dynamically, the overall process is strongly favoured if the original quasi-bound binary contains comparable masses. We propose a simplified model of chaotic scattering to explain these results. Our findings suggest that the observed preference for roughly equal-mass ratio binaries is probably a real effect; that is, it is not primarily due to an observational bias for widely separated, comparably bright objects. Nevertheless, we predict that a sizeable population of very unequal-mass Kuiper-belt binaries is probably awaiting discovery.

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

NASA Solar Array Demonstrates Commercial Potential

NASA Technical Reports Server (NTRS)

Creech, Gray

2006-01-01

A state-of-the-art solar-panel array demonstration site at NASA's Dryden Flight Research Center provides a unique opportunity for studying the latest in high-efficiency solar photovoltaic cells. This five-kilowatt solar-array site (see Figure 1) is a technology-transfer and commercialization success for NASA. Among the solar cells at this site are cells of a type that was developed in Dryden Flight Research Center s Environmental Research Aircraft and Sensor Technology (ERAST) program for use in NASA s Helios solar-powered airplane. This cell type, now denoted as A-300, has since been transferred to SunPower Corporation of Sunnyvale, California, enabling mass production of the cells for the commercial market. High efficiency separates these advanced cells from typical previously commercially available solar cells: Whereas typical previously commercially available cells are 12 to 15 percent efficient at converting sunlight to electricity, these advanced cells exhibit efficiencies approaching 23 percent. The increase in efficiency is due largely to the routing of electrical connections behind the cells (see Figure 2). This approach to increasing efficiency originated as a solution to the problem of maximizing the degree of utilization of the limited space available atop the wing of the Helios airplane. In retrospect, the solar cells in use at this site could be used on Helios, but the best cells otherwise commercially available could not be so used, because of their lower efficiencies. Historically, solar cells have been fabricated by use of methods that are common in the semiconductor industry. One of these methods includes the use of photolithography to define the rear electrical-contact features - diffusions, contact openings, and fingers. SunPower uses these methods to produce the advanced cells. To reduce fabrication costs, SunPower continues to explore new methods to define the rear electrical-contact features. The equipment at the demonstration site includes two fixed-angle solar arrays and one single-axis Sun-tracking array. One of the fixed arrays contains typical less-efficient commercial solar cells and is being used as a baseline for comparison of the other fixed array, which contains the advanced cells. The Sun-tracking array tilts to follow the Sun, using an advanced, real-time tracking device rather than customary pre-programmed mechanisms. Part of the purpose served by the demonstration is to enable determination of any potential advantage of a tracking array over a fixed array. The arrays are monitored remotely on a computer that displays pertinent information regarding the functioning of the arrays.

Fabricating solar cells with silicon nanoparticles

DOEpatents

Loscutoff, Paul; Molesa, Steve; Kim, Taeseok

2014-09-02

A laser contact process is employed to form contact holes to emitters of a solar cell. Doped silicon nanoparticles are formed over a substrate of the solar cell. The surface of individual or clusters of silicon nanoparticles is coated with a nanoparticle passivation film. Contact holes to emitters of the solar cell are formed by impinging a laser beam on the passivated silicon nanoparticles. For example, the laser contact process may be a laser ablation process. In that case, the emitters may be formed by diffusing dopants from the silicon nanoparticles prior to forming the contact holes to the emitters. As another example, the laser contact process may be a laser melting process whereby portions of the silicon nanoparticles are melted to form the emitters and contact holes to the emitters.

A spectrum synthesis program for binary stars

NASA Technical Reports Server (NTRS)

Linnell, Albert P.; Hubeny, Ivan

1994-01-01

A new program produces synthetic spectra of binary stars at arbitrary values of orbital longitude, including longitudes of partial or complete eclipse. The stellar components may be distorted, either tidally or rotationally, or both. Either or both components may be rotating nonsynchronously. We illustrate the program performance with two cases: EE Peg, an eclipsing binary with small distortion, and SX Aur, an eclipsing binary that is close to contact.

The First Precision CCD Observations of the Near Contact Binary, UY Muscae

NASA Astrophysics Data System (ADS)

McKenzie, R.; Stoddard, M. L.; Samec, R. G.; Faulkner, D. R.

2003-05-01

As a part of our study of solar type stars with gas streams we observed UY Muscae [Star "y" (Oosterhoff, BAIN #148, 1928) GSC 8987 392, α (2000) = 12h 30m 47s , δ (2000) = -66° 01' 52.8"]. The observations were taken at CTIO in Chili with the 0.9-m reflector on 18, 19, 20, 23 May 2001, by RGS and DRF. The CFIM T2K CCD camera with standard UBVRcIc filters in quad mode were used. More than 200 observations were taken in each pass band. The stars (GSC 8987 1279 α (2000) = 12h30m43.7s, δ (2000) = -65°59 '45") and (GSC 8987 1884, α (2000) = 12h30m45.7s, δ (2000) = -66°01 '5") were used as comparison and check stars, respectively. Two mean epochs of minimum light were determined from primary and secondary eclipses, HJD = 2452047.6239(0.0017) and 2452049.5918(0.0005) . Standard errors are given in parentheses. We calculated the following ephemeris from our data: HJD Tmin I = 2452047.6240(0.0003) + 0.562273(0.000151)d*E . A UBVRI synthetic light curve solution was calculated using the Wilson Code. It indicates the primary (more massive) component is under-filling its Roche lobe [fill-out = 94.4(0.001) critical lobe. This is similar to an Algol system. The final parameters include a mass ratio, m2/m1 = 0.551(0.001) , and a temperature difference T1-T2 = 1280(3)K. Two spots were modeled: a stream spot with a temperature factor of 1.060(0.002) very near the L1 point of the primary component and a solar type dark spot of radius 25.2(0.3)° with a T factor of 0.970( 0.001). Large night to night variations in the light curve lead us to believe that the components are saturated with magnetic activity. It is possible that the system was previously in contact and is undergoing TRO oscillations. Our model indicates that the components are currently separating. Further results of this study will be presented. We wish to thank CTIO for their allocation of observing time, and a small research grant from the American Astronomical Society which supported this run.

Simultaneous multiple wavelength upconversion in a core-shell nanoparticle for enhanced near infrared light harvesting in a dye-sensitized solar cell.

PubMed

Yuan, Chunze; Chen, Guanying; Li, Lin; Damasco, Jossana A; Ning, Zhijun; Xing, Hui; Zhang, Tianmu; Sun, Licheng; Zeng, Hao; Cartwright, Alexander N; Prasad, Paras N; Ågren, Hans

2014-10-22

The efficiency of most photovoltaic devices is severely limited by near-infrared (NIR) transmission losses. To alleviate this limitation, a new type of colloidal upconversion nanoparticles (UCNPs), hexagonal core-shell-structured β-NaYbF4:Er(3+)(2%)/NaYF4:Nd(3+)(30%), is developed and explored in this work as an NIR energy relay material for dye-sensitized solar cells (DSSCs). These UCNPs are able to harvest light energy in multiple NIR regions, and subsequently convert the absorbed energy into visible light where the DSSCs strongly absorb. The NIR-insensitive DSSCs show compelling photocurrent increases through binary upconversion under NIR light illumination either at 785 or 980 nm, substantiating efficient energy relay by these UCNPs. The overall conversion efficiency of the DSSCs was improved with the introduction of UCNPs under simulated AM 1.5 solar irradiation.

Optimization of GaAs Nanowire Pin Junction Array Solar Cells by Using AlGaAs/GaAs Heterojunctions

NASA Astrophysics Data System (ADS)

Wu, Yao; Yan, Xin; Wei, Wei; Zhang, Jinnan; Zhang, Xia; Ren, Xiaomin

2018-04-01

We optimized the performance of GaAs nanowire pin junction array solar cells by introducing AlGaAs/GaAs heterejunctions. AlGaAs is used for the p type top segment for axial junctions and the p type outer shell for radial junctions. The AlGaAs not only serves as passivation layers for GaAs nanowires but also confines the optical generation in the active regions, reducing the recombination loss in heavily doped regions and the minority carrier recombination at the top contact. The results show that the conversion efficiency of GaAs nanowires can be greatly enhanced by using AlGaAs for the p segment instead of GaAs. A maximum efficiency enhancement of 8.42% has been achieved in this study. And for axial nanowire, by using AlGaAs for the top p segment, a relatively long top segment can be employed without degenerating device performance, which could facilitate the fabrication and contacting of nanowire array solar cells. While for radial nanowires, AlGaAs/GaAs nanowires show better tolerance to p-shell thickness and surface condition.

Optimization of GaAs Nanowire Pin Junction Array Solar Cells by Using AlGaAs/GaAs Heterojunctions.

PubMed

Wu, Yao; Yan, Xin; Wei, Wei; Zhang, Jinnan; Zhang, Xia; Ren, Xiaomin

2018-04-25

We optimized the performance of GaAs nanowire pin junction array solar cells by introducing AlGaAs/GaAs heterejunctions. AlGaAs is used for the p type top segment for axial junctions and the p type outer shell for radial junctions. The AlGaAs not only serves as passivation layers for GaAs nanowires but also confines the optical generation in the active regions, reducing the recombination loss in heavily doped regions and the minority carrier recombination at the top contact. The results show that the conversion efficiency of GaAs nanowires can be greatly enhanced by using AlGaAs for the p segment instead of GaAs. A maximum efficiency enhancement of 8.42% has been achieved in this study. And for axial nanowire, by using AlGaAs for the top p segment, a relatively long top segment can be employed without degenerating device performance, which could facilitate the fabrication and contacting of nanowire array solar cells. While for radial nanowires, AlGaAs/GaAs nanowires show better tolerance to p-shell thickness and surface condition.

A New Catalog of Contact Binary Stars from ROTSE-I Sky Patrols

NASA Astrophysics Data System (ADS)

Gettel, S. J.; McKay, T. A.; Geske, M. T.

2005-05-01

Over 65,000 variable stars have been detected in the data from the ROTSE-I Sky Patrols. Using period-color and light curve selection techniques, about 5000 objects have been identified as contact binaries. This selection is tested for completeness against EW objects in the GCVS. By utilizing infrared color data from 2MASS, we fit a period-color-luminosity relation to these stars and estimate their distances.

Period changes of two contact binaries: DF Hya and WZ And

NASA Astrophysics Data System (ADS)

Bulut, A.; Bulut, I.

2018-02-01

Orbital period variations of two contact binaries DF Hya and WZ And are analyzed with the least-squares method by using all available minima times. It is shown that the period variations of these systems are due mainly to the Light-Time Effect (LITE) due originates from gravitational influence of a third body. New LITE elements such as, orbital periods and minimum masses of possibility third bodies are given.

Concentrating Solar Power Projects - Copiapó | Concentrating Solar Power |

Science.gov Websites

MW Status: Under development Start Year: 2019 Do you have more information, corrections, or comments Generation: 1,800,000 MWh/yr (Expected) Contact(s): Webmaster Solar Company: Solar Reserve Start Production

DISCOVERY OF A RED GIANT WITH SOLAR-LIKE OSCILLATIONS IN AN ECLIPSING BINARY SYSTEM FROM KEPLER SPACE-BASED PHOTOMETRY

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

Hekker, S.; Debosscher, J.; De Ridder, J.

2010-04-20

Oscillating stars in binary systems are among the most interesting stellar laboratories, as these can provide information on the stellar parameters and stellar internal structures. Here we present a red giant with solar-like oscillations in an eclipsing binary observed with the NASA Kepler satellite. We compute stellar parameters of the red giant from spectra and the asteroseismic mass and radius from the oscillations. Although only one eclipse has been observed so far, we can already determine that the secondary is a main-sequence F star in an eccentric orbit with a semi-major axis larger than 0.5 AU and orbital period longermore » than 75 days.« less

19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact

PubMed Central

2015-01-01

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (∼10 nm) of amorphous TiO2 deposited at 120 °C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm2 and a high power conversion efficiency of 19.2%. PMID:25679010

Investigation of Proposed Process Sequence for the Array Automated Assembly Task, Phase 2. [low cost silicon solar array fabrication

NASA Technical Reports Server (NTRS)

Mardesich, N.; Garcia, A.; Bunyan, S.; Pepe, A.

1979-01-01

The technological readiness of the proposed process sequence was reviewed. Process steps evaluated include: (1) plasma etching to establish a standard surface; (2) forming junctions by diffusion from an N-type polymeric spray-on source; (3) forming a p+ back contact by firing a screen printed aluminum paste; (4) forming screen printed front contacts after cleaning the back aluminum and removing the diffusion oxide; (5) cleaning the junction by a laser scribe operation; (6) forming an antireflection coating by baking a polymeric spray-on film; (7) ultrasonically tin padding the cells; and (8) assembling cell strings into solar circuits using ethylene vinyl acetate as an encapsulant and laminating medium.

19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact.

PubMed

Yin, Xingtian; Battaglia, Corsin; Lin, Yongjing; Chen, Kevin; Hettick, Mark; Zheng, Maxwell; Chen, Cheng-Ying; Kiriya, Daisuke; Javey, Ali

2014-12-17

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (∼10 nm) of amorphous TiO 2 deposited at 120 °C by atomic layer deposition as the transparent electron-selective contact. The TiO 2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm 2 and a high power conversion efficiency of 19.2%.

X-ray binary formation in low-metallicity blue compact dwarf galaxies

NASA Astrophysics Data System (ADS)

Brorby, M.; Kaaret, P.; Prestwich, A.

2014-07-01

X-rays from binaries in small, metal-deficient galaxies may have contributed significantly to the heating and reionization of the early Universe. We investigate this claim by studying blue compact dwarfs (BCDs) as local analogues to these early galaxies. We constrain the relation of the X-ray luminosity function (XLF) to the star formation rate (SFR) using a Bayesian approach applied to a sample of 25 BCDs. The functional form of the XLF is fixed to that found for near-solar metallicity galaxies and is used to find the probability distribution of the normalization that relates X-ray luminosity to SFR. Our results suggest that the XLF normalization for low-metallicity BCDs (12+log(O/H) < 7.7) is not consistent with the XLF normalization for galaxies with near-solar metallicities, at a confidence level 1-5 × 10- 6. The XLF normalization for the BCDs is found to be 14.5± 4.8 ({M}_{⊙}^{-1} yr), a factor of 9.7 ± 3.2 higher than for near-solar metallicity galaxies. Simultaneous determination of the XLF normalization and power-law index result in estimates of q = 21.2^{+12.2}_{-8.8} ({M}_{⊙}^{-1} yr) and α = 1.89^{+0.41}_{-0.30}, respectively. Our results suggest a significant enhancement in the population of high-mass X-ray binaries in BCDs compared to the near-solar metallicity galaxies. This suggests that X-ray binaries could have been a significant source of heating in the early Universe.

Physical Structure of Four Symbiotic Binaries

NASA Technical Reports Server (NTRS)

Kenyon, Scott J. (Principal Investigator)

1997-01-01

Disk accretion powers many astronomical objects, including pre-main sequence stars, interacting binary systems, and active galactic nuclei. Unfortunately, models developed to explain the behavior of disks and their surroundings - boundary layers, jets, and winds - lack much predictive power, because the physical mechanism driving disk evolution - the viscosity - is not understood. Observations of many types of accreting systems are needed to constrain the basic physics of disks and provide input for improved models. Symbiotic stars are an attractive laboratory for studying physical phenomena associated with disk accretion. These long period binaries (P(sub orb) approx. 2-3 yr) contain an evolved red giant star, a hot companion, and an ionized nebula. The secondary star usually is a white dwarf accreting material from the wind of its red giant companion. A good example of this type of symbiotic is BF Cygni: our analysis shows that disk accretion powers the nuclear burning shell of the hot white dwarf and also manages to eject material perpendicular to the orbital plane (Mikolajewska, Kenyon, and Mikolajewski 1989). The hot components in other symbiotic binaries appear powered by tidal overflow from a very evolved red giant companion. We recently completed a study of CI Cygni and demonstrated that the accreting secondary is a solar-type main sequence star, rather than a white dwarf (Kenyon et aL 1991). This project continued our study of symbiotic binary systems. Our general plan was to combine archival ultraviolet and optical spectrophotometry with high quality optical radial velocity observations to determine the variation of line and continuum sources as functions of orbital phase. We were very successful in generating orbital solutions and phasing UV+optical spectra for five systems: AG Dra, V443 Her, RW Hya, AG Peg, and AX Per. Summaries of our main results for these systems appear below. A second goal of our project was to consider general models for the outbursts of symbiotic stars, with an emphasis on understanding the differences between disk-driven and nuclear-powered eruptions.

A Be-type star with a black-hole companion.

PubMed

Casares, J; Negueruela, I; Ribó, M; Ribas, I; Paredes, J M; Herrero, A; Simón-Díaz, S

2014-01-16

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the approximately 80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (ref. 5; also known as HD 215227), although that conclusion was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of MWC 656. This, together with an improved radial velocity curve of the Be star through fitting sharp Fe II profiles from the equatorial disk, and a refined Be classification (to that of a B1.5-B2 III star), indicates that a black hole of 3.8 to 6.9 solar masses orbits MWC 656, the candidate counterpart of the γ-ray source AGL J2241+4454 (refs 5, 6). The black hole is X-ray quiescent and fed by a radiatively inefficient accretion flow giving a luminosity less than 1.6 × 10(-7) times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect in conventional X-ray surveys.

Process and structures for fabrication of solar cells with laser ablation steps to form contact holes

DOEpatents

Harley, Gabriel; Smith, David D; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

2013-11-19

Contact holes of solar cells are formed by laser ablation to accomodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thickness.

Evolution of the symbiotic binary system AG Dranconis

NASA Technical Reports Server (NTRS)

Mikolajewska, Joanna; Kenyon, Scott J; Mikolajewski, Maciej; Garcia, Michael R.; Polidan, Ronald S.

1995-01-01

We present an analysis of new and archival photometric and spectroscopic observations of the symbiotic star AG Draconis. This binary has undergone several 1 - 3 mag optical and ultraviolet eruptions during the past 15 years. Our combination of optical and ultraviolet spectroscopic data allow a more complete analysis of this system than in previous papers. AG Dra is composed of a K-type bright giant M(sub g) approximately 1.5 solar mass) and a hot, compact star M(sub h approximatelly 0.4 - 0.6 solar mass) embedded in a dense, low metallicity nebula. The hot component undergoes occasional thermonuclear runaways that produce 2 - 3 mag optical/ultraviolet eruptions. During these eruptions, the hot component develops a low velocity wind that quenches x-ray emission from the underlying hot white dwarf. The photoionized nebula changes its volume by a factor of 5 throughout an eruptin cycle. The K bright giant occults low ionization emission lines during superior conjunctions at all outburst phases but does not occult high ionization lines in outburst (and perhaps quiescence). This geometry and the component masses suggest a system inclination of i approximately 30 deg - 45 deg.

Performance Enhancement of Polymer Solar Cells by Using Two Polymer Donors with Complementary Absorption Spectra.

PubMed

Lu, Heng; Zhang, Xuejuan; Li, Cuihong; Wei, Hedi; Liu, Qian; Li, Weiwei; Bo, Zhishan

2015-07-01

Performance enhancement of polymer solar cells (PSCs) is achieved by expanding the absorption of the active layer of devices. To better match the spectrum of solar radiation, two polymers with different band gaps are used as the donor material to fabricate ternary polymer cells. Ternary blend PSCs exhibit an enhanced short-circuit current density and open-circuit voltage in comparison with the corresponding HD-PDFC-DTBT (HD)- and DT-PDPPTPT (DPP)-based binary polymer solar cells, respectively. Ternary PSCs show a power conversion efficiency (PCE) of 6.71%, surpassing the corresponding binary PSCs. This work demonstrates that the fabrication of ternary PSCs by using two polymers with complementary absorption is an effective way to improve the device performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical Bath Deposition of p-Type Transparent, Highly Conducting (CuS)x:(ZnS)1-x Nanocomposite Thin Films and Fabrication of Si Heterojunction Solar Cells.

PubMed

Xu, Xiaojie; Bullock, James; Schelhas, Laura T; Stutz, Elias Z; Fonseca, Jose J; Hettick, Mark; Pool, Vanessa L; Tai, Kong Fai; Toney, Michael F; Fang, Xiaosheng; Javey, Ali; Wong, Lydia Helena; Ager, Joel W

2016-03-09

P-type transparent conducting films of nanocrystalline (CuS)x:(ZnS)1-x were synthesized by facile and low-cost chemical bath deposition. Wide angle X-ray scattering (WAXS) and high resolution transmission electron microscopy (HRTEM) were used to evaluate the nanocomposite structure, which consists of sub-5 nm crystallites of sphalerite ZnS and covellite CuS. Film transparency can be controlled by tuning the size of the nanocrystallites, which is achieved by adjusting the concentration of the complexing agent during growth; optimal films have optical transmission above 70% in the visible range of the spectrum. The hole conductivity increases with the fraction of the covellite phase and can be as high as 1000 S cm(-1), which is higher than most reported p-type transparent materials and approaches that of n-type transparent materials such as indium tin oxide (ITO) and aluminum doped zinc oxide (AZO) synthesized at a similar temperature. Heterojunction p-(CuS)x:(ZnS)1-x/n-Si solar cells were fabricated with the nanocomposite film serving as a hole-selective contact. Under 1 sun illumination, an open circuit voltage of 535 mV was observed. This value compares favorably to other emerging heterojunction Si solar cells which use a low temperature process to fabricate the contact, such as single-walled carbon nanotube/Si (370-530 mV) and graphene/Si (360-552 mV).

The first orbital parameters and period variation of the short-period eclipsing binary AQ Boo

NASA Astrophysics Data System (ADS)

Wang, Shuai; Zhang, Liyun; Pi, Qingfeng; Han, Xianming L.; Zhang, Xiliang; Lu, Hongpeng; Wang, Daimei; Li, TongAn

2016-10-01

We obtained the first VRI CCD light curves of the short-period contact eclipsing binary AQ Boo, which was observed on March 22 and April 19 in 2014 at Xinglong station of National Astronomical Observatories, and on January 20, 21 and February 28 in 2015 at Kunming station of Yunnan Observatories of Chinese Academy of Sciences, China. Using our six newly obtained minima and the minima that other authors obtained previously, we revised the ephemeris of AQ Boo. By fitting the O-C (observed minus calculated) values of the minima, the orbital period of AQ Boo shows a decreasing tendency P˙ = - 1.47(0.17) ×10-7 days/year. We interpret the phenomenon by mass transfer from the secondary (more massive) component to the primary (less massive) one. By using the updated Wilson & Devinney program, we also derived the photometric orbital parameters of AQ Boo for the first time. We conclude that AQ Boo is a near contact binary with a low contact factor of 14.43%, and will become an over-contact system as the mass transfer continues.

PRS J0045-7319: A massive SMC binary

NASA Astrophysics Data System (ADS)

Bell, J. F.

1994-04-01

The existence of X-ray binary systems shows that neutron stars are found in orbit around massive stars. Before these systems enter the mass accretion phase, one would expect the neutron star might be detectable as a radio pulsar. The discovery of PSR B1259-63 by Johnston et al. (1992, Astrophys. J. Lett, 387, L37), which is in orbit around the Be star SS2883, provided the first evidence for such systems. PSR J0045-7319 was discovered in a systematic search of the Magellanic Clouds for radio pulsars by McConnell et al. (1991, Mon. Not. R. Astron. Soc., 249, 645). Its dispersion measure of 105 pc/cu cm assures its association with the Small Magellanic Cloud making it the only known pulsar in the SMC. The discovery of regular Doppler shifts of the pulse period of PSR J0045-7319 implies that the pulsar is in a highly eccentric 51-day binary orbit, making it the most luminous binary pulsar known (Kaspi et al., 1993, submitted to Astrophys. J.). The observed Keplerian orbital parameters show that the companion mass is greater the 4 solar mass. Optical observations of the field reveal a 16th magnitude, 11 solar mass, B1 main-sequence star, which we conclude is the pulsar's companion. The timing observations imply that this pulsar has not been spun up by accretion from the companion. This suggests that, like the PSR B1259-63 binary system, the PSR J0045-7319 system is a progenitor of an X-ray binary system. At periastron the pulsar approaches to within six stellar radii of the companion.

The electrical losses induced by silver paste in n-type silicon solar cells

NASA Astrophysics Data System (ADS)

Aoyama, Takayuki; Aoki, Mari; Sumita, Isao; Yoshino, Yasushi; Ohshita, Yoshio; Ogura, Atsushi

2017-10-01

Aluminum-added silver paste (Ag/Al paste) has been used for p+ emitter of n-type solar cells. The electrical losses due to shunting and recombination caused by the paste in the cells have been reported to originate from huge metallic spikes due to the aluminum. However, whether the aluminum actually induces the losses has not been clarified yet. In this study, the “floating contact method” is applied to aluminum-free silver (Al-free Ag) paste to investigate the effects of aluminum extraction from the Ag/Al paste and to understand how the aluminum principally induces the losses for the p+ emitter. Furthermore, the interfacial morphology between the Al-free Ag paste and p-type silicon is investigated. The Ag paste itself creates tiny crystallites for the p+ emitter, resulting in shunting and recombination. The result indicates that the aluminum addition to Ag paste is not the main reason for the electrical losses in the n-type solar cells.

A Mechanical Switch Using Spectral Microshifts

NASA Astrophysics Data System (ADS)

Mitchell, Gordon L.; Saaski, Elric W.; Hartl, James C.

1989-02-01

Among the simplest fiber optic sensors, are those which operate in a binary fashion; they were the first sensor types to be developed. Early experiments with fiber bundles and shutters produced demonstrations of, for example, displacement sensors. Typical applications range from position sensing for aircraft landing gear to counting objects on a production line. Because they frequently replace electrical snap action switches, binary sensors are generally called optical switches. Optical switch applications account for a much larger market than the more complex analog measurements discussed in the balance of this volume. This paper presents an optical switch concept that uses a single fiber and is tolerant of back reflections. The sensor element is a low finesse Fabry-Perot pressure sensor which replaces the electrical contact in a conventional snap action switch.

Friction and wear of iron-base binary alloys in sliding contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Multipass sliding friction experiments were conducted with various iron base binary alloys in contact with a single crystal silicon carbide surface in vacuum. Results indicate that the atomic size and concentration of alloy elements play important roles in controlling the transfer and friction properties of iron base binary alloys. Alloys having high solute concentration produce more transfer than do alloys having low solute concentration. The coefficient of friction during multipass sliding generally increases with an increase in the concentration of alloying element. The change of friction with succeeding passes after the initial pass also increases as the solute to iron, atomic radius ratio increases or decreases from unity.

Method for fabricating solar cells having integrated collector grids

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr. (Inventor)

1979-01-01

A heterojunction or Schottky barrier photovoltaic device comprising a conductive base metal layer compatible with and coating predominately the exposed surface of the p-type substrate of the device such that a back surface field region is formed at the interface between the device and the base metal layer, a transparent, conductive mixed metal oxide layer in integral contact with the n-type layer of the heterojunction or Schottky barrier device having a metal alloy grid network of the same metal elements of the oxide constituents of the mixed metal oxide layer embedded in the mixed metal oxide layer, an insulating layer which prevents electrical contact between the conductive metal base layer and the transparent, conductive metal oxide layer, and a metal contact means covering the insulating layer and in intimate contact with the metal grid network embedded in the transparent, conductive oxide layer for conducting electrons generated by the photovoltaic process from the device.

The Very Short Period M Dwarf Binary SDSS J001641-000925

NASA Astrophysics Data System (ADS)

Davenport, James R. A.; Becker, Andrew C.; West, Andrew A.; Bochanski, John J.; Hawley, Suzanne L.; Holtzman, Jon; Gunning, Heather C.; Hilton, Eric J.; Munshi, Ferah A.; Albright, Meagan

2013-02-01

We present follow-up observations and analysis of the recently discovered short period low-mass eclipsing binary, SDSS J001641-000925. With an orbital period of 0.19856 days, this system has one of the shortest known periods for an M dwarf binary system. Medium-resolution spectroscopy and multi-band photometry for the system are presented. Markov Chain Monte Carlo modeling of the light curves and radial velocities yields estimated masses for the stars of M 1 = 0.54 ± 0.07 M ⊙ and M 2 = 0.34 ± 0.04 M ⊙, and radii of R 1 = 0.68 ± 0.03 R ⊙ and R 2 = 0.58 ± 0.03 R ⊙, respectively. This solution places both components above the critical Roche overfill limit, providing strong evidence that SDSS J001641-000925 is the first verified M-dwarf contact binary system. Within the follow-up spectroscopy we find signatures of non-solid body rotation velocities, which we interpret as evidence for mass transfer or loss within the system. In addition, our photometry samples the system over nine years, and we find strong evidence for period decay at the rate of \\dot{P}\\sim 8 s yr-1. Both of these signatures raise the intriguing possibility that the system is in over-contact, and actively losing angular momentum, likely through mass loss. This places SDSS J001641-000925 as not just the first M-dwarf over-contact binary, but one of the few systems of any spectral type known to be actively undergoing coalescence. Further study of SDSS J001641-000925 is ongoing to verify the nature of the system, which may prove to be a unique astrophysical laboratory. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Support for the design and construction of the Magellan Echellette Spectrograph was received from the Observatories of the Carnegie Institution of Washington, the School of Science of the Massachusetts Institute of Technology, and the National Science Foundation in the form of a collaborative Major Research Instrument grant to Carnegie and MIT (AST0215989).

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.

Unravelling the Composition Dependent Anomalies of Pair Hydrophobicity in Water-Ethanol Binary Mixtures.

PubMed

Halder, Ritaban; Jana, Biman

2018-06-05

Aqueous binary mixtures have received immense attention in recent years because of their extensive application in several biological and industrial processes. Water-ethanol binary mixture serves as a unique system because it exhibits composition dependent alteration of dynamic and thermodynamic properties. Our present work demonstrates how different compositions of water-ethanol binary mixtures affect the pair hydrophobicity of different hydrophobes. Pair hydrophobicity is measured by the depth of the first minimum (contact minima) of potential of mean force (PMF) profile between two hydrophobes. The pair hydrophobicity is found to be increased with addition of ethanol to water up to mole fraction of 0.10 and decreased with further addition of ethanol. This observation is shown to be true for three different pairs of hydrophobes. Decomposition of PMF into enthalpic and entropic contribution indicates a switch from entropic to enthalpic stabilization of the contact minimum upon addition of ethanol to water. The gain in mixing enthalpy of the binary solvent system upon association of two hydrophobes is found to be the determining factor for the stabilization of contact minimum. Several static/dynamics quantities (average composition fluctuations, diffusion coefficients, fluctuations in total dipole moment, propensity of ethyl-ethyl association, etc) of the ethanol-water binary mixture also show irregularities around xEtOH =0.10-0.15. We have also discovered that the hydrogen bonding pattern of ethanol rather than water reveals a change in trend near the similar composition range. As the anomalous behaviour of the physical/dynamical properties along with the pair hydrophobicity in aqueous binary mixture of amphiphilic solutes is common phenomena, our results may provide a general viewpoint on these aspects.

A 3D dynamical model of the colliding winds in binary systems

NASA Astrophysics Data System (ADS)

Parkin, E. R.; Pittard, J. M.

2008-08-01

We present a three-dimensional (3D) dynamical model of the orbital-induced curvature of the wind-wind collision region in binary star systems. Momentum balance equations are used to determine the position and shape of the contact discontinuity between the stars, while further downstream the gas is assumed to behave ballistically. An Archimedean spiral structure is formed by the motion of the stars, with clear resemblance to high-resolution images of the so-called `pinwheel nebulae'. A key advantage of this approach over grid or smoothed particle hydrodynamic models is its significantly reduced computational cost, while it also allows the study of the structure obtained in an eccentric orbit. The model is relevant to symbiotic systems and γ-ray binaries, as well as systems with O-type and Wolf-Rayet stars. As an example application, we simulate the X-ray emission from hypothetical O+O and WR+O star binaries, and describe a method of ray tracing through the 3D spiral structure to account for absorption by the circumstellar material in the system. Such calculations may be easily adapted to study observations at wavelengths ranging from the radio to γ-ray.

Observations and Light Curve Solutions of Ultrashort-Period Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Kjurkchieva, Diana P.; Dimitrov, Dinko P.; Ibryamov, Sunay I.; Vasileva, Doroteya L.

2018-02-01

Photometric observations in V and I bands and low-dispersion spectra of 10 ultrashort-period binaries (NSVS 2175434, NSVS 2607629, NSVS 5038135, NSVS 8040227, NSVS 9747584, NSVS 4876238, ASAS 071829-0336.7, SWASP 074658.62+224448.5, NSVS 2729229, NSVS 10632802) are presented. One of them, NSVS 2729229, is newly discovered target. The results from modelling and analysis of our observations revealed that (i) eight targets have overcontact configurations with considerable fill-out factor (up to 0.5), while NSVS 4876238 and ASAS 0718-03 have almost contact configurations; (ii) NSVS 4876238 is rare ultrashort-period binary of detached type; (iii) all stellar components are late dwarfs; (iv) the temperature difference of the components of each target does not exceed 400 K; (v) NSVS 2175434 and SWASP 074658.62 + 224448.5 exhibit total eclipses and their parameters could be assumed as well determined; (v) NSVS 2729229 shows emission in the Hα line. Masses, radii, and luminosities of the stellar components were estimated by the empirical relation `period, orbital axis' for short- and ultrashort-period binaries. We found linear relations mass-luminosity and mass-radius for the stellar components of our targets.

Solar cells having integral collector grids

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr. (Inventor)

1978-01-01

A heterojunction or Schottky barrier photovoltaic device is described, comprising a conductive base metal layer. A back surface field region was formed at the interface between the device and the base metal layer, a transparent, conductive mixed metal oxide layer in integral contact with the n-type layer of the heterojunction or Schottky barrier device. A metal alloy grid network was included. An insulating layer prevented electrical contact between the conductive metal base layer and the transparent, conductive metal oxide layer.

Solar Cels With Reduced Contact Areas

NASA Technical Reports Server (NTRS)

Daud, T.; Crotty, G. T.; Kachare, A. H.; Lewis, J. T.

1987-01-01

Efficiency of silicon solar cells increased about 20 percent using smaller metal-contact area on silicon at front and back of each cell. Reduction in contact area reduces surface recombination velocity under contact and thus reduces reverse saturation current and increases opencircuit voltage..

A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions.

PubMed

Geller, Aaron M; Mathieu, Robert D

2011-10-19

In open star clusters, where all members formed at about the same time, blue straggler stars are typically observed to be brighter and bluer than hydrogen-burning main-sequence stars, and therefore should already have evolved into giant stars and stellar remnants. Correlations between blue straggler frequency and cluster binary star fraction, core mass and radial position suggest that mass transfer or mergers in binary stars dominates the production of blue stragglers in open clusters. Analytic models, detailed observations and sophisticated N-body simulations, however, argue in favour of stellar collisions. Here we report that the blue stragglers in long-period binaries in the old (7 × 10(9)-year) open cluster NGC 188 have companions with masses of about half a solar mass, with a surprisingly narrow mass distribution. This conclusively rules out a collisional origin, as the collision hypothesis predicts a companion mass distribution with significantly higher masses. Mergers in hierarchical triple stars are marginally permitted by the data, but the observations do not favour this hypothesis. The data are highly consistent with a mass transfer origin for the long-period blue straggler binaries in NGC 188, in which the companions would be white dwarfs of about half a solar mass.

Properties of the Binary Black Hole Merger GW150914

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Camp, J. B.

2016-01-01

On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a gravitational-wave transient (GW150914); we characterize the properties of the source and its parameters. The data around the time of the event were analyzed coherently across the LIGO network using a suite of accurate waveform models that describe gravitational waves from a compact binary system in general relativity. GW150914 was produced by a nearly equal mass binary black hole of masses 36(+5/-4) solar mass and 29(+4/-4) solar mass; for each parameter we report the median value and the range of the 90% credible interval. The dimensionless spin magnitude of the more massive black hole is bound to be less than 0.7 (at 90% probability). The luminosity distance to the source is 410(+160/-180) Mpc, corresponding to a redshift 0.09(+0.03/-0.04) assuming standard cosmology. The source location is constrained to an annulus section of 610 sq deg, primarily in the southern hemisphere. The binary merges into a black hole of mass 62(+4/-4) solar mass and spin 0.67(+0.05/-0.07). This black hole is significantly more massive than any other inferred from electromagnetic observations in the stellar-mass regime.

Observational Δν-ρ¯ Relation for δ Sct Stars using Eclipsing Binaries and Space Photometry

NASA Astrophysics Data System (ADS)

García Hernández, A.; Martín-Ruiz, S.; Monteiro, Mário J. P. F. G.; Suárez, J. C.; Reese, D. R.; Pascual-Granado, J.; Garrido, R.

2015-10-01

Delta Scuti (δ Sct) stars are intermediate-mass pulsators, whose intrinsic oscillations have been studied for decades. However, modeling their pulsations remains a real theoretical challenge, thereby even hampering the precise determination of global stellar parameters. In this work, we used space photometry observations of eclipsing binaries with a δ Sct component to obtain reliable physical parameters and oscillation frequencies. Using that information, we derived an observational scaling relation between the stellar mean density and a frequency pattern in the oscillation spectrum. This pattern is analogous to the solar-like large separation but in the low order regime. We also show that this relation is independent of the rotation rate. These findings open the possibility of accurately characterizing this type of pulsator and validate the frequency pattern as a new observable for δ Sct stars.

Dynamics of groups around interacting double ellipticals: Measuring dark matter haloes

NASA Technical Reports Server (NTRS)

Quintana, H.

1990-01-01

Binary galaxies, as binary stars, are important to measure masses, as suggested by Page (1952). Because three orbit parameters are measurable for galaxies at one instant of time, severe uncertainties remain in the orbit and mass determinations. These uncertainties can partly be overcome by statistical studies of selected samples and/or n-body simulations. Close double galaxies (and isolated galaxies) could also be useful to estimate dynamical masses if we can find test particles around them. Interacting elliptical pairs or dumb-bell galaxies are found with a large range, between 0-1200 km s(exp -1), of relative radial velocities. Standard 2-body orbit calculations, highly uncertain due to projection factors, suggest for the largest velocity differences very large galaxy masses, if the systems are bound and stationary. However, recent n-body simulations model these binaries as galaxies captured from hyperbolic orbits, requiring masses of order a few times 10(exp 11) solar maximum (Borne et al. 1988), but producing systems that are short lived. A different picture appears when we study observationally the dynamical mass of interacting double ellipticals using faint satellite galaxies. These satellites contribute little luminosity and, presumably, little mass to the system. The authors present results of two such groups, basically forming systems of test particles, around the dumb-bells NGC 4782/3 and IC 5049. They also briefly discuss the satellite group around the central dumb-bell in the cluster Sersic 40/6. Apparently, they detect large quantities of dark matter in the vicinity of these dumb-bell galaxies, because the system masses of approx. 4.5 times 10(exp 13) solar mass and 8 times 10(exp 13) solar mass for NGC 4782/3 and IC 5049, respectively, are quite high. Likewise, the mass of the Sersic 40/6 inner core is 7 times 10(exp 13) solar mass. The possibility that a common massive dark matter halo increases the merging times of these types of galaxies is suggested. Here, the authors assume H sub o = 100 km s (exp -1) Mpc(exp -1).

Searching for Rapid Orbital Decay of WASP-18b

NASA Astrophysics Data System (ADS)

Wilkins, Ashlee N.; Delrez, Laetitia; Barker, Adrian J.; Deming, Drake; Hamilton, Douglas; Gillon, Michael; Jehin, Emmanuel

2017-02-01

The WASP-18 system, with its massive and extremely close-in planet, WASP-18b (M p = 10.3M J , a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q‧, the modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q‧ being larger than was inferred from solar-type stars and find that Q‧ ≥ 1 × 106, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.

Searching for Rapid Orbital Decay of WASP-18b

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

Wilkins, Ashlee N.; Deming, Drake; Hamilton, Douglas

2017-02-20

The WASP-18 system, with its massive and extremely close-in planet, WASP-18b ( M{sub p} = 10.3 M{sub J}, a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q ′, the modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled publishedmore » transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer ) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope ) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q ′ being larger than was inferred from solar-type stars and find that Q ′ ≥ 1 × 10{sup 6}, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.« less

Thermal phase diagram of acetamide-benzoic acid and benzoic acid-phthalimide binary systems for solar thermal applications

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

Kumar, Rohitash, E-mail: dootrohit1976@gmail.com; Department of Physics & Center for Solar Energy, Indian Institute of Technology Jodhpur, Rajasthan, India 342011, +91-291-2449045; Kumar, Ravindra

2016-05-06

Thermal properties of Acetamide (AM) – Benzoic acid (BA) and Benzoic acid (BA) – Phthalimide (PM) binary eutectic systems are theoretically calculated using thermodynamic principles. We found that the binary systems of AM-BA at 67.6 : 32.4 molar ratio, BA-PM at 89.7 : 10.3 molar ratio form eutectic mixtures with melting temperatures ~ 54.5 °C and 114.3 °C respectively. Calculated latent heat of fusion for these eutectic mixtures are 191 kJ/kg and 146.5 kJ/kg respectively. These melting temperatures and heat of fusions of these eutectic mixtures make them suitable for thermal energy storage applications in solar water heating and solarmore » cooking systems.« less

Systematic description of the effect of particle shape on the strength properties of granular media

NASA Astrophysics Data System (ADS)

Azéma, Emilien; Estrada, Nicolas; Preechawuttipong, Itthichai; Delenne, Jean-Yves; Radjai, Farhang

2017-06-01

In this paper, we explore numerically the effect of particle shape on the mechanical behavior of sheared granular packings. In the framework of the Contact Dynamic (CD)Method, we model angular shape as irregular polyhedral particles, non-convex shape as regular aggregates of four overlapping spheres, elongated shape as rounded cap rectangles and platy shape as square-plates. Binary granular mixture consisting of disks and elongated particles are also considered. For each above situations, the number of face of polyhedral particles, the overlap of spheres, the aspect ratio of elongated and platy particles, are systematically varied from spheres to very angular, non-convex, elongated and platy shapes. The level of homogeneity of binary mixture varies from homogenous packing to fully segregated packings. Our numerical results suggest that the effects of shape parameters are nonlinear and counterintuitive. We show that the shear strength increases as shape deviate from spherical shape. But, for angular shapes it first increases up to a maximum value and then saturates to a constant value as the particles become more angular. For mixture of two shapes, the strength increases with respect of the increase of the proportion of elongated particles, but surprisingly it is independent with the level of homogeneity of the mixture. A detailed analysis of the contact network topology, evidence that various contact types contribute differently to stress transmission at the micro-scale.

Intraspecific Signals Inducing Aggregation in Periplaneta americana (Insecta: Dictyoptera).

PubMed

Imen, Saïd; Christian, Malosse; Virginie, Durier; Colette, Rivault

2015-06-01

Chemical communication is necessary to induce aggregation and to maintain the cohesion of aggregates in Periplaneta americana (L.) cockroaches. We aimed to identify the chemical message inducing aggregation in this species. Two types of bioassays were used-binary choice tests in Petri dishes and tests in Y-olfactometer. Papers conditioned by direct contact of conspecifics induce aggregation when proposed in binary choice tests and were attractive in a Y-olfactometer. The identification of the molecules present on these conditioned papers indicated that dichloromethane extracts contained mainly cuticular hydrocarbons whereas methanol extracts contained more volatile molecules. Only a mixture of extracts in both solvents induced aggregation. High concentrations of cuticular hydrocarbons are necessary to induce aggregation when presented alone. When presented with volatile molecules present in methanol extracts, low concentrations of cuticular hydrocarbons are sufficient to induce aggregation if they are presented in contact. Among volatile molecules collected on filter paper, a mixture of three compounds-hexadecanoic acid, pentadecanoic acid, and pentaethylene glycol-induced aggregation. Our results provide evidence that aggregation processes in P. americana relies on a dual mechanism: attraction over long distances by three volatile molecules and maintenance on site by contact with cuticular hydrocarbons. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The MUCHFUSS photometric campaign

NASA Astrophysics Data System (ADS)

Schaffenroth, V.; Geier, S.; Heber, U.; Gerber, R.; Schneider, D.; Ziegerer, E.; Cordes, O.

2018-06-01

Hot subdwarfs (sdO/Bs) are the helium-burning cores of red giants, which have lost almost all of their hydrogen envelope. This mass loss is often triggered by common envelope interactions with close stellar or even substellar companions. Cool companions like late-type stars or brown dwarfs are detectable via characteristic light-curve variations like reflection effects and often also eclipses. To search for such objects, we obtained multi-band light curves of 26 close sdO/B binary candidates from the MUCHFUSS project with the BUSCA instrument. We discovered a new eclipsing reflection effect system (P = 0.168938 d) with a low-mass M dwarf companion (0.116 M⊙). Three more reflection effect binaries found in the course of the campaign have already been published; two of them are eclipsing systems, and in one system only showing the reflection effect but no eclipses, the sdB primary is found to be pulsating. Amongst the targets without reflection effect a new long-period sdB pulsator was discovered and irregular light variations were found in two sdO stars. The found light variations allowed us to constrain the fraction of reflection effect binaries and the substellar companion fraction around sdB stars. The minimum fraction of reflection effect systems amongst the close sdB binaries might be greater than 15% and the fraction of close substellar companions in sdB binaries may be as high as 8.0%. This would result in a close substellar companion fraction to sdB stars of about 3%. This fraction is much higher than the fraction of brown dwarfs around possible progenitor systems, which are solar-type stars with substellar companions around 1 AU, as well as close binary white dwarfs with brown dwarf companions. This might suggest that common envelope interactions with substellar objects are preferentially followed by a hot subdwarf phase.

Thin insulating tunneling contacts for efficient and water-resistant perovskite solar cells

DOE PAGES

Wang, Qi; Dong, Qingfeng; Li, Tao; ...

2016-05-17

Here, we demonstrated that inserting a tunneling layer between perovskite and electron transport layer could significantly increase device performance by suppressing carrier recombination at the cathode contact. The tunneling layer can also serve as an encapsulation layer to prevent perovskite film from damage caused by water or moisture. This method is simple because it does not need lattice matching between the buffer layer and perovskite. The low temperature solution process makes it compatible with many types of perovskite materials, and may be applied for anode contact as well. The freedom to choose any insulating layer for contact enables more devicemore » designs and manufacturing.« less

SAGE III L2 Solar Event Species Profiles (Binary)

Atmospheric Science Data Center

2016-06-14

... Search and Order:  Earthdata Search   FTP Access:  Data Pool V3  |  Data Pool V4 Parameters:  Aerosol ... Data Additional Info:  Data Format: Big Endian/IEEE Binary; Avg Size in MB: 0.044 SCAR-B Block:  ...

Episodic accretion in binary protostars emerging from self-gravitating solar mass cores

NASA Astrophysics Data System (ADS)

Riaz, R.; Vanaverbeke, S.; Schleicher, D. R. G.

2018-06-01

Observations show a large spread in the luminosities of young protostars, which are frequently explained in the context of episodic accretion. We tested this scenario with numerical simulations that follow the collapse of a solar mass molecular cloud using the GRADSPH code, thereby varying the strength of the initial perturbations and temperature of the cores. A specific emphasis of this paper is to investigate the role of binaries and multiple systems in the context of episodic accretion and to compare their evolution to the evolution in isolated fragments. Our models form a variety of low-mass protostellar objects including single, binary, and triple systems in which binaries are more active in exhibiting episodic accretion than isolated protostars. We also find a general decreasing trend in the average mass accretion rate over time, suggesting that the majority of the protostellar mass is accreted within the first 105 years. This result can potentially help to explain the surprisingly low average luminosities in the majority of the protostellar population.

Dynamical Mass Segregation Versus Disruption of Binary Stars in Dense Stellar Systems

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, C.; Deng, L.

2013-01-01

Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses due to gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr-old Large Magellanic Cloud cluster NGC 1818 is characterized by an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 solar masses) with increasing distance from the cluster center. This offers unprecedented support of the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems (with relatively low binding energies compared to the kinetic energy of their stellar members) in star clusters, which we could unravel by virtue of the cluster's unique combination of youth and high stellar density.

Revealing Companions to Nearby Stars with Astrometric Acceleration

DTIC Science & Technology

2012-07-01

objects, such as stellar -mass black holes or failed supernova (Gould & Salim 2002). Table 4 includes a sample of some of the most interesting dis...knowledge of binary and multiple star statistics is needed for the study of star formation, for stellar population synthesis, for predicting the...frequency of supernovae, blue stragglers, X-ray binaries, etc. The statistical properties of binaries strongly depend on stellar mass. Only for nearby solar

Concentrating Solar Power Projects - Solaben 6 | Concentrating Solar Power

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: Operational Start Year: 2013 Do you have more information, corrections, or comments? Background Technology MWh/yr (Estimated) Contact(s): Allison Lenthall Company: Abengoa Solar Start Production: August 2013

Concentrating Solar Power Projects - Solaben 1 | Concentrating Solar Power

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: Operational Start Year: 2013 Do you have more information, corrections, or comments? Background Technology MWh/yr (Estimated) Contact(s): Allison Lenthall Company: Abengoa Solar Start Production: August 2013

Shapes, rotation, and pole solutions of the selected Hilda and Trojan asteroids

NASA Astrophysics Data System (ADS)

Gritsevich, Maria; Sonnett, Sarah; Torppa, Johanna; Mainzer, Amy; Muinonen, Karri; Penttilä, Antti; Grav, Thomas; Masiero, Joseph; Bauer, James; Kramer, Emily

2017-04-01

Binary asteroid systems contain key information about the dynamical and chemical environments in which they formed. For example, determining the formation environments of Trojan and Hilda asteroids (in 1:1 and 3:2 mean-motion resonance with Jupiter, respectively) will provide critical constraints on how small bodies and the planets that drive their migration must have moved throughout Solar System history, see e.g. [1-3]. Therefore, identifying and characterizing binary asteroids within the Trojan and Hilda populations could offer a powerful means of discerning between Solar System evolution models. Dozens of possibly close or contact binary Trojans and Hildas were identified within the data obtained by NEOWISE [4]. Densely sampled light curves of these candidate binaries have been obtained in order to resolve rotational light curve features that are indicative of binarity (e.g., [5-7]). We present analysis of the shapes, rotation, and pole solutions of some of the follow-up targets observed with optical ground-based telescopes. For modelling the asteroid photometric properties, we use parameters describing the shape, surface light scattering properties and spin state of the asteroid. Scattering properties of the asteroid surface are modeled using a two parameter H-G12 magnitude system. Determination of the initial best-fit parameters is carried out by first using a triaxial ellipsoid shape model, and scanning over the period values and spin axis orientations, while fitting the other parameters, after which all parameters were fitted, taking the initial values for spin properties from the spin scanning. In addition to the best-fit parameters, we also provide the distribution of the possible solution, which should cover the inaccuracies of the solution, caused by the observing errors and model. The distribution of solutions is generated by Markov-Chain Monte Carlo sampling the spin and shape model parameters, using both an ellipsoid shape model and a convex model, Gaussian curvature of which is defined as a spherical harmonics series [8]. References: [1] Marzari F. and Scholl H. (1998), A&A, 339, 278. [2] Morbidelli A. et al. (2005), Nature, 435, 462. [3] Nesvorny D. et al. (2013), ApJ, 768, 45. [4] Sonnett S. et al. (2015), ApJ, 799, 191. [5] Behrend R. et al. (2006), A&A, 446, 1177. [6] Lacerda P. and Jewitt D. C. (2007), AJ, 133, 1393. [7] Oey J. (2016), MPB, 43, 45. [8] Muinonen et al., ACM 2017.

Multigrid contact detection method

NASA Astrophysics Data System (ADS)

He, Kejing; Dong, Shoubin; Zhou, Zhaoyao

2007-03-01

Contact detection is a general problem of many physical simulations. This work presents a O(N) multigrid method for general contact detection problems (MGCD). The multigrid idea is integrated with contact detection problems. Both the time complexity and memory consumption of the MGCD are O(N) . Unlike other methods, whose efficiencies are influenced strongly by the object size distribution, the performance of MGCD is insensitive to the object size distribution. We compare the MGCD with the no binary search (NBS) method and the multilevel boxing method in three dimensions for both time complexity and memory consumption. For objects with similar size, the MGCD is as good as the NBS method, both of which outperform the multilevel boxing method regarding memory consumption. For objects with diverse size, the MGCD outperform both the NBS method and the multilevel boxing method. We use the MGCD to solve the contact detection problem for a granular simulation system based on the discrete element method. From this granular simulation, we get the density property of monosize packing and binary packing with size ratio equal to 10. The packing density for monosize particles is 0.636. For binary packing with size ratio equal to 10, when the number of small particles is 300 times as the number of big particles, the maximal packing density 0.824 is achieved.

Interdigitated Back-Surface-Contact Solar Cell Modeling Using Silvaco Atlas

DTIC Science & Technology

2015-06-01

11 2. Solar Spectrum ...................................................................................13 3. PV Cell Efficiency...Figure 10. Spectrum of solar radiance, from [12]. 14 3. PV Cell Efficiency There are many factors that affect the efficiency of a solar cell. Metal...BACK-SURFACE-CONTACT SOLAR CELL MODELING USING SILVACO ATLAS by Shawn E. Green June 2015 Thesis Advisor: Sherif Michael Second Reader

A Search for Black Holes and Neutron Stars in the Kepler Field

NASA Astrophysics Data System (ADS)

Orosz, Jerome; Short, Donald; Welsh, William; Windmiller, Gur; Dabney, David

2018-01-01

Black holes and neutron stars represent the final evolutionary stages of the most massive stars. In addition to their use as probes into the evolution of massive stars, black holes and neutron stars are ideal laboratories to test General Relativity in the strong field limit. The number of neutron stars and black holes in the Milky Way is not precisely known, but there are an estimated one billion neutron stars in the galaxy based on the observed numbers of radio pulsars. The number of black holes is about 100 million, based on the behavior of the Initial Mass Function at high stellar masses.All of the known steller-mass black holes (and a fair number of neutron stars) are in ``X-ray binaries'' that were discovered because of their luminous X-ray emission. The requirement to be in an X-ray-emitting binary places a strong observational bias on the discovery of stellar-mass black holes. Thus the 21 known black hole binaries represent only the very uppermost tip of the population iceberg.We have conducted an optical survey using Kepler data designed to uncover black holes and neutron stars in both ``quiescent'' X-ray binaries and ``pre-contact'' X-ray binaries. We discuss how the search was conducted, including how potentially interesting light curves were classified and the how variability types were identified. Although we did not find any convincing candidate neutron star or black hole systems, we did find a few noteworthy binary systems, including two binaries that contain low-mass stars with unusually low albedos.

A periodicity of approximately 1 hour in X-ray emission from the active galaxy RE J1034+396.

PubMed

Gierliński, Marek; Middleton, Matthew; Ward, Martin; Done, Chris

2008-09-18

Active galactic nuclei and quasars are thought to be scaled-up versions of Galactic black hole binaries, powered by accretion onto supermassive black holes with masses of 10(6)-10(9) M[symbol: see text], as opposed to the approximately 10 M [symbol: see text] in binaries (here M [symbol: see text] is the solar mass). One example of the similarities between these two types of systems is the characteristic rapid X-ray variability seen from the accretion flow. The power spectrum of this variability in black hole binaries consists of a broad noise with multiple quasi-periodic oscillations superimposed on it. Although the broad noise component has been observed in many active galactic nuclei, there have hitherto been no significant detections of quasi-periodic oscillations. Here we report the discovery of an approximately 1-hour X-ray periodicity in a bright active galaxy, RE J1034+396. The signal is highly statistically significant (at the 5.6 sigma level) and very coherent, with quality factor Q > 16. The X-ray modulation arises from the direct vicinity of the black hole.

19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO 2 Contact

DOE PAGES

Yin, Xingtian; Battaglia, Corsin; Lin, Yongjing; ...

2014-09-25

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (~10 nm) of amorphous TiO 2 deposited at 120°C by atomic layer deposition as the transparent electron-selective contact. The TiO 2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. Lastly, a hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm 2 and a high power conversion efficiency ofmore » 19.2%.« less

Laser processing of solar cells with anti-reflective coating

DOEpatents

Harley, Gabriel; Smith, David D.; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

2016-02-16

Contact holes of solar cells are formed by laser ablation to accommodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thicknesses.

Chromospherically active stars. VI - HD 136901 = UV CrB: A massive ellipsoidal K giant single-lined spectroscopic binary

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Kirkpatrick, J. Davy; Yang, Xinxing; Strassmeier, Klaus G.

1989-01-01

The variable star HD 136901 = UV CrB is a chromospherically active K2 III single-lined spectroscopic binary with an orbital period of 18.665 days. It has modest-strength Ca H and K emission and UV features, while H-alpha is a strong absorption feature containing little or no emission. The inclination of the system is 53 + or - 12 deg. The v sin i of the primary is 42 + or - 2 km/s, resulting in a minimum radius of 15.5 + or - 0.8 solar. When compared with the Roche lobe radius, this results in a mass ratio of 2.90 or larger. Additional constraints indicate that the secondary has a mass between 0.85 and 1.25 solar. Thus, the mass of the primary is at least 2.5 solar and probably is in the range 2.5-4 solar.

Absolute Parameters and Physical Nature of the Low-amplitude Contact Binary HI Draconis

NASA Astrophysics Data System (ADS)

Papageorgiou, A.; Christopoulou, P.-E.

2015-05-01

We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VRcIc CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f = 24 ± 4(%) and temperature difference between the components of 330 K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: Mh = 1.72 ± 0.08 {{M}⊙ } and Mc = 0.43 ± 0.02 {{M}⊙ }, Rh = 1.98 ± 0.03 {{R}⊙ } and Rc = 1.08 ± 0.02 {{R}⊙ }, and Lh = 9.6 ± 0.1 {{L}⊙ } and Lc = 2.4 ± 0.1 {{L}⊙ }. Based on these results the initial masses of the progenitors (1.11 ± 0.03 {{M}⊙ } and 2.25 ± 0.07 {{M}⊙ }, respectively) and a rough estimate of the age of the system of 2.4 Gyr are discussed.

Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries

NASA Astrophysics Data System (ADS)

Murphy, Simon J.; Moe, Maxwell; Kurtz, Donald W.; Bedding, Timothy R.; Shibahashi, Hiromoto; Boffin, Henri M. J.

2018-03-01

The orbital parameters of binaries at intermediate periods (102-103 d) are difficult to measure with conventional methods and are very incomplete. We have undertaken a new survey, applying our pulsation timing method to Kepler light curves of 2224 main-sequence A/F stars and found 341 non-eclipsing binaries. We calculate the orbital parameters for 317 PB1 systems (single-pulsator binaries) and 24 PB2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. The method reaches down to small mass ratios q ≈ 0.02 and yields a highly homogeneous sample. We parametrize the mass-ratio distribution using both inversion and Markov-Chain Monte Carlo forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q ≈ 0.2. While solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6σ) population of extreme-mass-ratio companions (q < 0.1) to our intermediate-mass primaries. Across periods of 100-1500 d and at q > 0.1, we measure the binary fraction of current A/F primaries to be 15.4 per cent ± 1.4 per cent, though we find that a large fraction of the companions (21 per cent ± 6 per cent) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9 per cent ± 2.1 per cent over the same parameter space. Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5 per cent for primaries M1 < 0.8 M⊙, but then increases linearly with log M1, demonstrating that natal discs around more massive protostars M1 ≳ 1 M⊙ become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution.

Concentrating Solar Power Projects - Orellana | Concentrating Solar Power |

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: Operational Start Year: 2012 Do you have more information, corrections, or comments? Background Technology (Estimated) Contact(s): SolarPACES Start Production: August 2012 Cost (approx): 240,000,000 Euro PPA/Tariff

Concentrating Solar Power Projects - Solacor 2 | Concentrating Solar Power

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Status: Operational Start Year: 2012 Do you have more information, corrections, or comments? Background : 100,000 MWh/yr (Estimated) Contact(s): Allison Lenthall Company: Abengoa Solar Start Production: March 9

Concentrating Solar Power Projects - Aurora Solar Energy Project |

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development Start Year: 2020 Do you have more information, corrections, or comments? Background Technology : 495,000 MWh/yr (Expected) Contact(s): Webmaster Solar Key References: Fact sheet Break Ground: 2018 Start

Concentrating Solar Power Projects - Solaben 2 | Concentrating Solar Power

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Concentrating Solar Power Projects - Solacor 1 | Concentrating Solar Power

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Concentrating Solar Power Projects - Dhursar | Concentrating Solar Power |

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: 125.0 MW Status: Operational Start Year: 2014 Do you have more information, corrections, or comments Electricity Generation: 280,000 MWh/yr (Expected) Contact(s): Webmaster Solar Start Production: November 11

Concentrating Solar Power Projects - Solaben 3 | Concentrating Solar Power

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Concentrating Solar Power Projects - Arenales | Concentrating Solar Power |

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MW Status: Operational Start Year: 2013 Do you have more information, corrections, or comments Electricity Generation: 166,000 MWh/yr (Estimated) Contact(s): SolarPACES Break Ground: November 2011 Start

The PyCBC search for binary black hole coalescences in Advanced LIGO's first observing run

NASA Astrophysics Data System (ADS)

Willis, Joshua; LIGO Scientific Collaboration

2017-01-01

Advanced LIGO's first observing run saw the first detections of binary black hole coalescences. We describe the PyCBC matched filter analysis, and the results of that search for binary systems with total mass up to 100 solar masses. This is a matched filter search for general-relativistic signals from binary black hole systems. Two signals, GW150914 and GW151226, were identified with very high significance, and a third possible signal, LVT151012, was found, though at much lower significance. Supported by NSF award PHY-1506254.

Chaotic Zones around Rotating Small Bodies

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

Lages, José; Shevchenko, Ivan I.; Shepelyansky, Dima L., E-mail: jose.lages@utinam.cnrs.fr

Small bodies of the solar system, like asteroids, trans-Neptunian objects, cometary nuclei, and planetary satellites, with diameters smaller than 1000 km usually have irregular shapes, often resembling dumb-bells or contact binaries. The spinning of such a gravitating dumb-bell creates around it a zone of chaotic orbits. We determine its extent analytically and numerically. We find that the chaotic zone swells significantly if the rotation rate is decreased; in particular, the zone swells more than twice if the rotation rate is decreased 10 times with respect to the “centrifugal breakup” threshold. We illustrate the properties of the chaotic orbital zones in examples ofmore » the global orbital dynamics about asteroid 243 Ida (which has a moon, Dactyl, orbiting near the edge of the chaotic zone) and asteroid 25143 Itokawa.« less

Concentrating Solar Power Projects - La Florida | Concentrating Solar Power

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| NREL Florida This page provides information on La Florida, a concentrating solar power (CSP : March 20, 2017 Project Overview Project Name: La Florida Country: Spain Location: Badajoz (Badajoz Solar Resource: La Florida Weather Station Electricity Generation: 175,000 MWh/yr (Estimated) Contact(s

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

NASA Astrophysics Data System (ADS)

Jiang, Dengkai; Chen, Xuefei; Li, Lifang; Han, Zhanwen

2017-11-01

Two blue-straggler sequences discovered in globular cluster M30 provide a strong constraint on the formation mechanisms of blue stragglers. We study the formation of blue-straggler binaries through binary evolution, and find that binary evolution can contribute to the blue stragglers in both of the sequences. Whether a blue-straggler is located in the blue sequence or red sequence depends on the contribution of the mass donor to the total luminosity of the binary, which is generally observed as a single star in globular clusters. The blue stragglers in the blue sequence have a cool white dwarf companion, while the majority (˜60%) of the objects in the red sequence are binaries that are still experiencing mass transfer. However, there are also some objects for which the donors have just finished the mass transfer (the stripped-core stars, ˜10%) or the blue stragglers (the accretors) have evolved away from the blue sequence (˜30%). Meanwhile, W UMa contact binaries found in both sequences may be explained by various mass ratios, that is, W UMa contact binaries in the red sequence have two components with comparable masses (e.g., mass ratio q ˜ 0.3-1.0), while those in the blue sequence have low mass ratios (e.g., q< 0.3). However, the fraction of the blue sequence in M30 cannot be reproduced by binary population synthesis if we assumed the initial parameters of a binary sample to be the same as those of the field. This possibly indicates that dynamical effects on binary systems are very important in globular clusters.

Materials, device, and interface engineering to improve polymer-based solar cells

NASA Astrophysics Data System (ADS)

Hau, Steven Kin

The continued depletion of fossil fuel resources has lead to the rise in energy production costs which has lead to the search for an economically viable alternative energy source. One alternative of particular interest is solar energy. A promising alternative to inorganic materials is organic semiconductor polymer solar cells due to their advantages of being cheaper, light weight, flexible and made into large areas by roll-to-roll processing. In this dissertation, an integrated approach is taken to improve the overall performance of polymer-based solar cells by the development of new polymer materials, device architectures, and interface engineering of the contacts between layers. First, a new class of metallated conjugated polymers is explored as potential solar cell materials. Systematic modifications to the molecular units on the main chain of amorphous metallated Pt-polymers show a correlation that improving charge carrier mobility also improves solar cell performance leading to mobilities as high as 1 x 10-2 cm2/V·s and efficiencies as high as 4.1%. Second, an inverted device architecture using a more air stable electrode (Ag) is demonstrated to improve the ambient stability of unencapsulated P3HT:PCBM devices showing over 80% efficiency retention after 40 days of exposure. To further demonstrate the potential for roll-to-roll processing of polymer solar cells, solution processed Ag-nanoparticles were used to replace the vacuum deposited Ag anode electrode for inverted solar cells showing efficiencies as high as 3%. In addition, solution processed polymer based electrodes were demonstrated as a replacement to the expensive and brittle indium tin oxide showing efficiencies of 3% on flexible substrate solar cells. Third, interface engineering of the n-type (high temperature sol-gel processed TiO2 or ZnO, low temperature processed ZnO nanoparticles) electron selective metal oxide contacts in inverted solar cells with self-assembled monolayers (SAM) show improved device performance. Modifying the n-type layer in inverted cells with C60-SAMs containing different anchoring groups leads to an improvement in photocurrent density and fill factor leading to efficiencies as high as 4.9%.

Laser process and corresponding structures for fabrication of solar cells with shunt prevention dielectric

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

Harley, Gabriel; Smith, David D.; Dennis, Tim

Contact holes of solar cells are formed by laser ablation to accommodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thicknesses.

A collision model for grain-resolving simulations of flows over dense, mobile, polydisperse granular sediment beds

DOE PAGES

Biegert, Edward; Vowinckel, Bernhard; Meiburg, Eckart

2017-03-21

We present a collision model for phase-resolved Direct Numerical Simulations of sediment transport that couple the fluid and particles by the Immersed Boundary Method. Typically, a contact model for these types of simulations comprises a lubrication force for particles in close proximity to another solid object, a normal contact force to prevent particles from overlapping, and a tangential contact force to account for friction. Our model extends the work of previous authors to improve upon the time integration scheme to obtain consistent results for particle-wall collisions. Furthermore, we account for polydisperse spherical particles and introduce new criteria to account formore » enduring contact, which occurs in many sediment transport situations. This is done without using arbitrary values for physically-defined parameters and by maintaining the full momentum balance of a particle in enduring contact. Lastly, we validate our model against several test cases for binary particle-wall collisions as well as the collective motion of a sediment bed sheared by a viscous flow, yielding satisfactory agreement with experimental data by various authors.« less

A collision model for grain-resolving simulations of flows over dense, mobile, polydisperse granular sediment beds

NASA Astrophysics Data System (ADS)

Biegert, Edward; Vowinckel, Bernhard; Meiburg, Eckart

2017-07-01

We present a collision model for phase-resolved Direct Numerical Simulations of sediment transport that couple the fluid and particles by the Immersed Boundary Method. Typically, a contact model for these types of simulations comprises a lubrication force for particles in close proximity to another solid object, a normal contact force to prevent particles from overlapping, and a tangential contact force to account for friction. Our model extends the work of previous authors to improve upon the time integration scheme to obtain consistent results for particle-wall collisions. Furthermore, we account for polydisperse spherical particles and introduce new criteria to account for enduring contact, which occurs in many sediment transport situations. This is done without using arbitrary values for physically-defined parameters and by maintaining the full momentum balance of a particle in enduring contact. We validate our model against several test cases for binary particle-wall collisions as well as the collective motion of a sediment bed sheared by a viscous flow, yielding satisfactory agreement with experimental data by various authors.

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, James L.

1996-01-01

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/.mu.c-Si) solar cells which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell.

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, J.L.

1996-07-23

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/{micro}c-Si) solar cells are disclosed which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell. 4 figs.

A SURVEY OF THE HIGH ORDER MULTIPLICITY OF NEARBY SOLAR-TYPE BINARY STARS WITH Robo-AO

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

Riddle, Reed L.; Bui, Khanh; Dekany, Richard G.

2015-01-20

We conducted a survey of nearby binary systems composed of main sequence stars of spectral types F and G in order to improve our understanding of the hierarchical nature of multiple star systems. Using Robo-AO, the first robotic adaptive optics instrument, we collected high angular resolution images with deep and well-defined detection limits in the Sloan Digital Sky Survey i' band. A total of 695 components belonging to 595 systems were observed. We prioritized observations of faint secondary components with separations over 10'' to quantify the still poorly constrained frequency of their subsystems. Of the 214 secondaries observed, 39 containmore » such subsystems; 19 of those were discovered with Robo-AO. The selection-corrected frequency of secondary subsystems with periods from 10{sup 3.5} to 10{sup 5} days is 0.12 ± 0.03, the same as the frequency of such companions to the primary. Half of the secondary pairs belong to quadruple systems where the primary is also a close pair, showing that the presence of subsystems in both components of the outer binary is correlated. The relatively large abundance of 2+2 quadruple systems is a new finding, and will require more exploration of the formation mechanism of multiple star systems. We also targeted close binaries with periods less than 100 yr, searching for their distant tertiary components, and discovered 17 certain and 2 potential new triples. In a subsample of 241 close binaries, 71 have additional outer companions. The overall frequency of tertiary components is not enhanced, compared to all (non-binary) targets, but in the range of outer periods from 10{sup 6} to 10{sup 7.5} days (separations on the order of 500 AU), the frequency of tertiary components is 0.16 ± 0.03, exceeding the frequency of similar systems among all targets (0.09) by almost a factor of two. Measurements of binary stars with Robo-AO allowed us to compute first orbits for 9 pairs and to improve orbits of another 11 pairs.« less

The evolution of massive stars including mass loss - Presupernova models and explosion

NASA Technical Reports Server (NTRS)

Woosley, S. E.; Langer, Norbert; Weaver, Thomas A.

1993-01-01

The evolution of massive stars of 35, 40, 60, and 85 solar masses is followed through all stages of nuclear burning to the point of Fe core collapse. Critical nuclear reaction and mass-loss rates are varied. Efficient mass loss during the Wolf-Rayet (WR) stage is likely to lead to final masses as small as 4 solar masses. For a reasonable parameterization of the mass loss, there may be convergence of all WR stars, both single and in binaries, to a narrow band of small final masses. Our representative model, a 4.25 solar-mass WR presupernova derived from a 60 solar mass star, is followed through a simulated explosion, and its explosive nucleosynthesis and light curve are determined. Its properties are similar to those observed in Type Ib supernovae. The effects of the initial mass and mass loss on the presupernova structure of small mass WR models is also explored. Important properties of the presupernova star and its explosion can only be obtained by following the complete evolution starting on the main sequence.

Photometric Study of Two Totally Eclipsing Contact Binaries: V789 Her and V1007 Cas

NASA Astrophysics Data System (ADS)

Li, K.; Xia, Q.-Q.; Hu, S.-M.; Guo, D.-F.; Chen, X.

2018-07-01

Two sets of V and R c light curves of V789 Her and one complete set of BVR c I c light curves of V1007 Cas were observed and presented. By analyzing all these light curves together with the Sloan g‧i‧ light curves observed by Kjurkchieva et al., we determined that both systems are W-subtype contact binaries and that V789 Her is a medium contact system, while V1007 Cas is a shallow contact system. Because the two binaries show totally eclipsing primary minima, the photometric results are reliable. In addition, the light curves of the two systems are asymmetric, requiring a dark spot on the primary or the secondary component in the modeling. By compiling all available times of minimum light including literatures, SuperWASP archive and ours, we analyzed the orbital period variations. We derived that the O ‑ C diagram of V789 Her displays a periodic oscillation whose period and amplitude are 29.2 years and 0.0179 days and the period of V1007 Cas exhibits a continuous decrease at dP/dt = ‑1.78(±0.09) × 10‑7 days yr‑1. The cyclic period modulation of V789 Her is probably attributed to the light travel time effect via a tertiary companion with very small mass. The continuous period decrease of V1007 Cas may result from the mass transfer between the two components. However, we cannot rule out the possibility of angular momentum loss because V1007 Cas shows strong magnetic activity. By analyzing the evolutionary status of the components of the two systems, we determined that they exhibit typical characteristics of other W-subtype contact binaries.

Constraining f(R) gravity in solar system, cosmology and binary pulsar systems

NASA Astrophysics Data System (ADS)

Liu, Tan; Zhang, Xing; Zhao, Wen

2018-02-01

The f (R) gravity can be cast into the form of a scalar-tensor theory, and scalar degree of freedom can be suppressed in high-density regions by the chameleon mechanism. In this article, for the general f (R) gravity, using a scalar-tensor representation with the chameleon mechanism, we calculate the parametrized post-Newtonian parameters γ and β, the effective gravitational constant Geff, and the effective cosmological constant Λeff. In addition, for the general f (R) gravity, we also calculate the rate of orbital period decay of the binary system due to gravitational radiation. Then we apply these results to specific f (R) models (Hu-Sawicki model, Tsujikawa model and Starobinsky model) and derive the constraints on the model parameters by combining the observations in solar system, cosmological scales and the binary systems.

Optimization of Controllable Factors in the Aluminum Silicon Eutectic Paste and Rear Silicon Nitride Mono-Passivation Layer of PERC Solar Cells

NASA Astrophysics Data System (ADS)

Park, Sungeun; Park, Hyomin; Kim, Dongseop; Yang, JungYup; Lee, Dongho; Kim, Young-Su; Kim, Hyun-Jong; Suh, Dongchul; Min, Byoung Koun; Kim, Kyung Nam; Park, Se Jin; Kim, Donghwan; Lee, Hae-Seok; Nam, Junggyu; Kang, Yoonmook

2018-05-01

Passivated emitter and rear contact (PERC) is a promising technology owing to high efficiency can be achieved with p-type wafer and their easily applicable to existing lines. In case of using p-type mono wafer, 0.5-1% efficiency increase is expected with PERC technologies compared to existing Al BSF solar cells, while for multi-wafer solar cells it is 0.5-0.8%. We addressed the optimization of PERC solar cells using the Al paste. The paste was prepared from the aluminum-silicon alloy with eutectic composition to avoid the formation of voids that degrade the open-circuit voltage. The glass frit of the paste was changed to improve adhesion. Scanning electron microscopy revealed voids and local back surface field between the aluminum electrode and silicon base. We confirmed the conditions on the SiNx passivation layer for achieving higher efficiency and better adhesion for long-term stability. The cell characteristics were compared across cells containing different pastes. PERC solar cells with the Al/Si eutectic paste exhibited the efficiency of 19.6%.

The variety of MHD shock waves interactions in the solar wind flow

NASA Technical Reports Server (NTRS)

Grib, S. A.

1995-01-01

Different types of nonlinear shock wave interactions in some regions of the solar wind flow are considered. It is shown, that the solar flare or nonflare CME fast shock wave may disappear as the result of the collision with the rotational discontinuity. By the way the appearance of the slow shock waves as the consequence of the collision with other directional discontinuity namely tangential is indicated. Thus the nonlinear oblique and normal MHD shock waves interactions with different solar wind discontinuities (tangential, rotational, contact, shock and plasmoidal) both in the free flow and close to the gradient regions like the terrestrial magnetopause and the heliopause are described. The change of the plasma pressure across the solar wind fast shock waves is also evaluated. The sketch of the classification of the MHD discontinuities interactions, connected with the solar wind evolution is given.

Internal quantum efficiency mapping analysis for a >20%-efficiency n-type bifacial solar cell with front-side emitter formed by BBr3 thermal diffusion

NASA Astrophysics Data System (ADS)

Simayi, Shalamujiang; Mochizuki, Toshimitsu; Kida, Yasuhiro; Shirasawa, Katsuhiko; Takato, Hidetaka

2017-10-01

This paper presents a large-area (239-cm2) high-efficiency n-type bifacial solar cell that is processed using tube-furnace thermal diffusion employing liquid sources BBr3 for the front-side boron emitter and POCl3 for the rear-side phosphorus back surface field (BSF). The SiN x /Al2O3 stack was applied to the front-side boron emitter as a passivation layer. Both the front and rear-side electrodes are obtained using screen-printed contacts with H-patterns. The resulting highest-efficiency solar cell has front- and rear-side efficiencies of 20.3 and 18.7%, respectively, while the corresponding bifaciality is up to 92%. Finally, the passivation quality of the SiN x /Al2O3 stack on the front-side boron emitter and rear-side phosphorus BSF is investigated and visualized by measuring the internal quantum efficiency mapping of the bifacial solar cell.

A strategy for tissue self-organization that is robust to cellular heterogeneity and plasticity.

PubMed

Cerchiari, Alec E; Garbe, James C; Jee, Noel Y; Todhunter, Michael E; Broaders, Kyle E; Peehl, Donna M; Desai, Tejal A; LaBarge, Mark A; Thomson, Matthew; Gartner, Zev J

2015-02-17

Developing tissues contain motile populations of cells that can self-organize into spatially ordered tissues based on differences in their interfacial surface energies. However, it is unclear how self-organization by this mechanism remains robust when interfacial energies become heterogeneous in either time or space. The ducts and acini of the human mammary gland are prototypical heterogeneous and dynamic tissues comprising two concentrically arranged cell types. To investigate the consequences of cellular heterogeneity and plasticity on cell positioning in the mammary gland, we reconstituted its self-organization from aggregates of primary cells in vitro. We find that self-organization is dominated by the interfacial energy of the tissue-ECM boundary, rather than by differential homo- and heterotypic energies of cell-cell interaction. Surprisingly, interactions with the tissue-ECM boundary are binary, in that only one cell type interacts appreciably with the boundary. Using mathematical modeling and cell-type-specific knockdown of key regulators of cell-cell cohesion, we show that this strategy of self-organization is robust to severe perturbations affecting cell-cell contact formation. We also find that this mechanism of self-organization is conserved in the human prostate. Therefore, a binary interfacial interaction with the tissue boundary provides a flexible and generalizable strategy for forming and maintaining the structure of two-component tissues that exhibit abundant heterogeneity and plasticity. Our model also predicts that mutations affecting binary cell-ECM interactions are catastrophic and could contribute to loss of tissue architecture in diseases such as breast cancer.

Multi-Material Front Contact for 19% Thin Film Solar Cells.

PubMed

van Deelen, Joop; Tezsevin, Yasemin; Barink, Marco

2016-02-06

The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,Ga)Se₂ (CIGS), CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO) sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat.

The origin of ultra-compact binaries

NASA Technical Reports Server (NTRS)

Hachisu, Izumi; Miyaji, Shigeki; Saio, Hideyuki

1987-01-01

The origin of ultra-compact binaries composed of a neutron star and a low-mass (about 0.06 solar mass) white dwarf is considered. Taking account of the systemic losses of mass and angular momentum, it was found that a serious difficulty exists in the scenarios which involve tidal captures of a normal star (a main sequence star or a red giant) by a neutron star. This difficulty can be avoided if a red giant star is captured by a massive white dwarf (M is approx. greater than 1.2 solar masses), which becomes a neutron star through the accretion induced collapse.

Concentrating Solar Power Projects - Megha Solar Plant | Concentrating

Science.gov Websites

: Parabolic trough Turbine Capacity: Net: 50.0 MW Gross: 50.0 MW Status: Operational Start Year: 2014 Do you /Planned) Contact(s): Webmaster Solar Break Ground: December 2011 Start Production: November 13, 2014 Cost

Merging Black Hole Binaries in Galactic Nuclei: Implications for Advanced-LIGO Detections

NASA Astrophysics Data System (ADS)

Antonini, Fabio; Rasio, Frederic A.

2016-11-01

Motivated by the recent detection of gravitational waves from the black hole binary merger GW150914, we study the dynamical evolution of (stellar-mass) black holes in galactic nuclei, where massive star clusters reside. With masses of ˜ {10}7 {M}⊙ and sizes of only a few parsecs, nuclear star clusters (NSCs) are the densest stellar systems observed in the local universe and represent a robust environment where black hole binaries can dynamically form, harden, and merge. We show that due to their large escape speeds, NSCs can retain a large fraction of their merger remnants. Successive mergers can then lead to significant growth and produce black hole mergers of several tens of solar masses similar to GW150914 and up to a few hundreds of solar masses, without the need to invoke extremely low metallicity environments. We use a semi-analytical approach to describe the dynamics of black holes in massive star clusters. Our models give a black hole binary merger rate of ≈ 1.5 {{Gpc}}-3 {{yr}}-1 from NSCs, implying up to a few tens of possible detections per year with Advanced LIGO. Moreover, we find a local merger rate of ˜ 1 {{Gpc}}-3 {{yr}}-1 for high mass black hole binaries similar to GW150914; a merger rate comparable to or higher than that of similar binaries assembled dynamically in globular clusters (GCs). Finally, we show that if all black holes receive high natal kicks, ≳ 50 {km} {{{s}}}-1, then NSCs will dominate the local merger rate of binary black holes compared to either GCs or isolated binary evolution.

Inversion layer solar cell fabrication and evaluation. [etching on silicon films

NASA Technical Reports Server (NTRS)

Call, R. L.

1974-01-01

Inversion layer solar cells were fabricated by etching through the diffused layer on p-type silicon wafers in a comb-like contact pattern. The charge separation comes from an induced p-n junction at the surface. The inverted surface is caused by a layer of transparent material applied to the surface that either contains free positive ions or that creates donor states at the interface. Cells are increased from 3 ma I sub sc to 100 ma by application of sodium silicate. The action is unstable, however, and decays. Non-mesa contaminated oxide cells were fabricated with short circuit currents of over 100 ma measured in the sun. Cells of this type have demonstrated stability.

A Binary Nature of the Marginal CP Star Sigma Sculptoris

NASA Astrophysics Data System (ADS)

Janík, Jan; Krtička, Jiří; Mikulášek, Zdeněk; Zverko, Juraj; Pintado, Olga; Paunzen, Ernst; Prvák, Milan; Skalický, Jan; Zejda, Miloslav; Adam, Christian

2018-05-01

The A2 V star σ Scl was suspected of being a low-amplitude rotating variable of the Ap-type star by several authors. Aiming to decide whether the star is a variable chemically peculiar (CP) star, we searched for the photometric and spectroscopic variability, and determined chemical abundances of σ Scl. The possible variability was tested using several types of periodograms applied to the photometry from Long-Term Photometry of Variables project (LTPV) and Hipparcos. Sixty spectrograms of high signal-to-noise (S/N) were obtained and used for chemical analysis of the stellar atmosphere and for looking for spectral variability that is symptomatic for the CP stars. We did not find any signs of the light variability or prominent chemical peculiarity, that is specific for the CP stars. The only exception is the abundance of scandium, which is significantly lower than the solar one and yttrium and barium, which are strongly overabundant. As a by-product of the analysis, and with the addition of 29 further spectra, we found that σ Scl is a single-lined spectroscopic binary with orbital period of 46.877(8) d. We argue that σ Scl is not an Ap star, but rather a marginal Am star in SB1 system. The spectral energy distribution of the binary reveals infrared excess due to circumstellar material.

Eclipsing Binaries From the CSTAR Project at Dome A, Antarctica

NASA Astrophysics Data System (ADS)

Yang, Ming; Zhang, Hui; Wang, Songhu; Zhou, Ji-Lin; Zhou, Xu; Wang, Lingzhi; Wang, Lifan; Wittenmyer, R. A.; Liu, Hui-Gen; Meng, Zeyang; Ashley, M. C. B.; Storey, J. W. V.; Bayliss, D.; Tinney, Chris; Wang, Ying; Wu, Donghong; Liang, Ensi; Yu, Zhouyi; Fan, Zhou; Feng, Long-Long; Gong, Xuefei; Lawrence, J. S.; Liu, Qiang; Luong-Van, D. M.; Ma, Jun; Wu, Zhenyu; Yan, Jun; Yang, Huigen; Yang, Ji; Yuan, Xiangyan; Zhang, Tianmeng; Zhu, Zhenxi; Zou, Hu

2015-04-01

The Chinese Small Telescope ARray (CSTAR) has observed an area around the Celestial South Pole at Dome A since 2008. About 20,000 light curves in the i band were obtained during the observation season lasting from 2008 March to July. The photometric precision achieves about 4 mmag at i = 7.5 and 20 mmag at i = 12 within a 30 s exposure time. These light curves are analyzed using Lomb-Scargle, Phase Dispersion Minimization, and Box Least Squares methods to search for periodic signals. False positives may appear as a variable signature caused by contaminating stars and the observation mode of CSTAR. Therefore, the period and position of each variable candidate are checked to eliminate false positives. Eclipsing binaries are removed by visual inspection, frequency spectrum analysis, and a locally linear embedding technique. We identify 53 eclipsing binaries in the field of view of CSTAR, containing 24 detached binaries, 8 semi-detached binaries, 18 contact binaries, and 3 ellipsoidal variables. To derive the parameters of these binaries, we use the Eclipsing Binaries via Artificial Intelligence method. The primary and secondary eclipse timing variations (ETVs) for semi-detached and contact systems are analyzed. Correlated primary and secondary ETVs confirmed by false alarm tests may indicate an unseen perturbing companion. Through ETV analysis, we identify two triple systems (CSTAR J084612.64-883342.9 and CSTAR J220502.55-895206.7). The orbital parameters of the third body in CSTAR J220502.55-895206.7 are derived using a simple dynamical model.

Calculation of optical parameters for covalent binary alloys used in optical memories/solar cells: a modified approach

NASA Astrophysics Data System (ADS)

Bhatnagar, Promod K.; Gupta, Poonam; Singh, Laxman

2001-06-01

Chalcogenide based alloys find applications in a number of devices like optical memories, IR detectors, optical switches, photovoltaics, compound semiconductor heterosrtuctures etc. We have modified the Gurman's statistical thermodynamic model (STM) of binary covalent alloys. In the Gurman's model, entropy calculations are based on the number of structural units present. The need to modify this model arose due to the fact that it gives equal probability for all the tetrahedra present in the alloy. We have modified the Gurman's model by introducing the concept that the entropy is based on the bond arrangement rather than that on the structural units present. In the present work calculation based on this modification have been presented for optical properties, which find application in optical switching/memories, solar cells and other optical devices. It has been shown that the calculated optical parameters (for a typical case of GaxSe1-x) based on modified model are closer to the available experimental results. These parameters include refractive index, extinction coefficient, dielectric functions, optical band gap etc. GaxSe1-x has been found to be suitable for reversible optical memories also, where phase change (a yields c and vice versa) takes place at specified physical conditions. DTA/DSC studies also suggest the suitability of this material for optical switching/memory applications. We have also suggested possible use of GaxSe1-x (x = 0.4) in place of oxide layer in a Metal - Oxide - Semiconductor type solar cells. The new structure is Metal - Ga2Se3 - GaAs. The I-V characteristics and other parameters calculated for this structure are found to be much better than that for Si based solar cells. Maximum output power is obtained at the intermediate layer thickness approximately 40 angstroms for this typical solar cell.

Concentrating Solar Power Projects - Atacama-1 | Concentrating Solar Power

Science.gov Websites

Capacity: Net: 110.0 MW Gross: 110.0 MW Status: Under construction Start Year: 2018 Do you have more Contact(s): Luis Rejano Company: Abengoa Solar Break Ground: May 14, 2014 Start Production: June 2018

Development of a Thin-Film Solar Cell Interconnect for the Powersphere Concept

NASA Technical Reports Server (NTRS)

Simburger, Edward J.; Matsumoto, James H.; Giants, Thomas W.; Garcia, Alexander, III; Liu, Simon; Rawal, Suraj P.; Perry, Alan R.; Marshall, Craig; Lin, John K.; Scarborough, Stephen E.

2005-01-01

Dual junction amorphous silicon (a-Si) solar cells produced on polyimide substrate have been selected as the best candidate to produce a lightweight solar array for the PowerSphere program. The PowerSphere concept features a space-inflatable, geodetic solar array approximately 0.6 meters in diameter and capable of generating about 20W of electrical power. Trade studies of various wiring concepts and connection methods led to an interconnect design with a copper contact that wraps around the edge, to the back of the solar cell. Applying Plasma Vapor Deposited (PVD) copper film to both sides and the edge of the solar cell produces the wrap around contact. This procedure results in a contact pad on the back of the solar cell, which is then laser welded to a flex circuit material. The flex circuit is constructed of copper in a custom designed routing pattern, and then sandwiched in a Kapton insulation layer. The flex circuit then serves as the primary power distribution system between the solar cells and the spacecraft. Flex circuit material is the best candidate for the wiring harness because it allows for low force deployment of the solar cells by the inflatable hinges on the PowerSphere. An additional frame structure, fabricated and assembled by ILC Dover, will reinforce the wrap around contact-flex blanket connection, thus providing a mechanically robust solar cell interconnect for the PowerSphere multifunctional program. The PowerSphere team will use the wraparound contact design approach as the primary solution for solar cell integration and the flex blanket for power distribution.

Growth and Photovoltaic Properties of High-Quality GaAs Nanowires Prepared by the Two-Source CVD Method.

PubMed

Wang, Ying; Yang, Zaixing; Wu, Xiaofeng; Han, Ning; Liu, Hanyu; Wang, Shuobo; Li, Jun; Tse, WaiMan; Yip, SenPo; Chen, Yunfa; Ho, Johnny C

2016-12-01

Growing high-quality and low-cost GaAs nanowires (NWs) as well as fabricating high-performance NW solar cells by facile means is an important development towards the cost-effective next-generation photovoltaics. In this work, highly crystalline, dense, and long GaAs NWs are successfully synthesized using a two-source method on non-crystalline SiO2 substrates by a simple solid-source chemical vapor deposition method. The high V/III ratio and precursor concentration enabled by this two-source configuration can significantly benefit the NW growth and suppress the crystal defect formation as compared with the conventional one-source system. Since less NW crystal defects would contribute fewer electrons being trapped by the surface oxides, the p-type conductivity is then greatly enhanced as revealed by the electrical characterization of fabricated NW devices. Furthermore, the individual single NW and high-density NW parallel arrays achieved by contact printing can be effectively fabricated into Schottky barrier solar cells simply by employing asymmetric Ni-Al contacts, along with an open circuit voltage of ~0.3 V. All these results indicate the technological promise of these high-quality two-source grown GaAs NWs, especially for the realization of facile Schottky solar cells utilizing the asymmetric Ni-Al contact.

Comparison of a newly developed binary typing with ribotyping and multilocus sequence typing methods for Clostridium difficile.

PubMed

Li, Zhirong; Liu, Xiaolei; Zhao, Jianhong; Xu, Kaiyue; Tian, Tiantian; Yang, Jing; Qiang, Cuixin; Shi, Dongyan; Wei, Honglian; Sun, Suju; Cui, Qingqing; Li, Ruxin; Niu, Yanan; Huang, Bixing

2018-04-01

Clostridium difficile is the causative pathogen for antibiotic-related nosocomial diarrhea. For epidemiological study and identification of virulent clones, a new binary typing method was developed for C. difficile in this study. The usefulness of this newly developed optimized 10-loci binary typing method was compared with two widely used methods ribotyping and multilocus sequence typing (MLST) in 189 C. difficile samples. The binary typing, ribotyping and MLST typed the samples into 53 binary types (BTs), 26 ribotypes (RTs), and 33 MLST sequence types (STs), respectively. The typing ability of the binary method was better than that of either ribotyping or MLST expressed in Simpson Index (SI) at 0.937, 0.892 and 0.859, respectively. The ease of testing, portability and cost-effectiveness of the new binary typing would make it a useful typing alternative for outbreak investigations within healthcare facilities and epidemiological research. Copyright © 2018 Elsevier B.V. All rights reserved.

Two W-subtype contact binaries: GQ Boo and V1367 Tau

NASA Astrophysics Data System (ADS)

Zhang, Jia; Qian, Sheng-Bang; Han, Zhong-Tao; Wu, Yue

2017-04-01

Two contact binaries, GQ Boo and V1367 Tau, were observed and analysed with a new method to obtain the absolute parameters. The light-curve analysis shows that both of them are obvious W-subtype contact binaries, with much more massive but apparently cooler components (M2/M1 ≃ 2 and 4, T2/T1 ≃ 0.95 and 0.94). The orbital periods were studied using the O-C diagrams, and it is thought that the minima timings were heavily affected by the longstanding magnetic activities on the star surface, so the minima timings cannot represent the real period changes. The mass-radius relationships were proposed by the light-curve analysis alone, which is equivalent to the mean density. The density and temperature can determine the other absolute parameters in most of the time. With the almost complete star parameter space provided by PARSEC, approximate masses and radii were obtained (0.52 ± 0.08 M⊙ and 1.01 ± 0.15 M⊙ for GQ Boo, and 0.22 ± 0.01 M⊙ and 0.92 ± 0.06 M⊙ for V1367 Tau). The mass-radius relationship is a neglected useful tool to calculate the mass and radius, especially for the detached binaries.

A Search for Variable Stars in Ruprecht 134 (Abstract)

NASA Astrophysics Data System (ADS)

El Hamri, R.; Blake, M.

2018-06-01

(Abstract only) Contact binary stars have been found in many old open clusters. These stars are useful for obtaining the distances to these star clusters and for understanding the stellar populations and evolution of the old clusters. Ruprecht 134 is a relatively neglected, old open cluster with an age of about 1 Gyr. We have obtained observations of Ruprecht 134 using the 1-meter telescope at Cerro Tololo Interamerican Observatory for the purpose of identifying candidate contact binaries. We present the preliminary results of this search and discuss future observations.

Photometric investigation of a very short period W UMa-type binary - Does CE Leonis have a large superluminous area?

NASA Technical Reports Server (NTRS)

Samec, Ronald G.; Su, Wen; Terrell, Dirk; Hube, Douglas P.

1993-01-01

A complete photometric analysis of BVRI Johnson-Cousins photometry of the high northern latitude galactic variable, CE Leo is presented. These observations were taken at Kitt Peak National Observatory on May 31, 1989-June 7, 1989. Three new precise epochs of minimum light were determined and a linear and a quadratic ephemeris were computed from these and previous data covering 28 years of observation. The light curves reveal that the system undergoes a brief 20 min totality in the primary eclipse, indicating that CE Leo is a W UMa W-type binary. A systemic velocity of about -40 km/s was determined. Standard magnitudes were found and a simultaneous solution of the B, V, R, I light curves was computed using the new Wilson-Devinney synthetic light curve code which has the capability of automatically adjusting star spots. The solution indicates that the system consists of two early K-type dwarfs in marginal contact with a fill-out factor less than 3 percent. Evidence for the presence of a large (45 deg radius) superluminous area on the cooler component is given.

The multiplicity of T Tauri stars in the star forming regions Taurus-Auriga and Ophiuchus-Scorpius: A 2.2 micron speckle imaging survey

NASA Technical Reports Server (NTRS)

Ghez, A. M.; Neugebauer, G.; Matthews, K.

1993-01-01

We present the results of a magnitude limited (K less than = 8.5 mag) speckle imaging survey of 69 T Tauri stars in the star forming regions Taurus-Auriga and Ophiuchus-Scorpius. Thirty-three companion stars were found with separations ranging from 0.07 sec to 2.5 sec, nine are new detections. This survey reveals a distinction between the classical T Tauri stars (CTTS) and the weak-lined T Tauri stars (WTTS) based on the binary star frequency as a function of separation: the WTTS binary star distribution is enhanced at the closer separations (less than 50 AU) relative to the CTTS binary star distribution. We suggest that the nearby companion stars shorten the accretion time scale in multiple star systems, thereby accounting for the presence of WTTS that are coeval with many CTTS. The binary star frequency in the projected linear separation range 16 to 252 AU for T Tauri stars (60 (+/- 17)%) is a factor of 4 greater than that of the solar-type main-sequence stars (16(+/- 3)%). Given the limited separation range of this survey, the rate at which binaries are detected suggests that most, if not all, T Tauri stars have companions. We propose that the observed overabundance of companions of T Tauri stars is an evolutionary effect, in which triple and higher order T Tauri stars are disrupted by close encounters with another star or system of stars.

30+ New & Known SB2s in the SDSS-III/APOGEE M Dwarf Ancillary Science Project Sample

NASA Astrophysics Data System (ADS)

Skinner, Jacob; Covey, Kevin; Bender, Chad; De Lee, Nathan Michael; Chojnowski, Drew; Troup, Nicholas; Badenes, Carles; Mahadevan, Suvrath; Terrien, Ryan

2018-01-01

Close stellar binaries can drive dynamical interactions that affect the structure and evolution of planetary systems. Binary surveys indicate that the multiplicity fraction and typical orbital separation decrease with primary mass, but correlations with higher order architectural parameters such as the system's mass ratio are less well constrained. We seek to identify and characterize double-lined spectroscopic binaries (SB2s) among the 1350 M dwarf ancillary science targets with APOGEE spectra in the SDSS-III Data Release 13. We quantitatively measure the degree of asymmetry in the APOGEE pipeline cross-correlation functions (CCFs), and use those metrics to identify a sample of 44 high-likelihood candidate SB2s. Extracting radial velocities (RVs) for both binary components from the CCF, we then measure mass ratios for 31 SB2s; we also use Bayesian techniques to fit orbits for 4 systems with 8 or more distinct APOGEE observations. The (incomplete) mass ratio distribution of this sample rises quickly towards unity. Two-sided Kolmogorov-Smirnov (K-S) tests find probabilities of 13.8% and 14.2% that the M dwarf mass ratio distribution is consistent with those measured by Pourbaix et al. (2004) and Fernandez et al. (2017), respectively. The samples analyzed by Pourbaix et al. and Fernandez et al. are dominated by higher-mass solar type stars; this suggests that the mass ratio distribution of close binaries is not strongly dependent on primary mass.

Magnetic braking in Solar-type close binaries

NASA Astrophysics Data System (ADS)

Maceroni, C.; Rucinski, S. M.

In tidally locked binaries the angular momentum loss by magnetic braking affects the orbital period. While this effect is too small to be detected in individual systems, its signature can be seen in shape of the orbital period distribution of suitable samples. As a consequence information on the braking mechanisms can be obtained - at least in principle - from the analysis of the distributions, the main problems being the selection of a large and homogeneous sample of binaries and the appropriate treatment of the observational biases. New large databases of variable stars are becoming available as by-products of microlensing projects, which have the advantage of joining, for the first time, sample richness and homogeneity. We report the main results of the analysis of the eclipsing binaries in OGLE-I catalog, that contains several thousands variables detected in a pencil-beam search volume towards the Baade's Window. By means of an automatic filtering algorithm we extracted a sample of 74 detached, equal-mass, main-sequence binary stars with short orbital periods (i.e., in the range 0.19 < P < 8 days) and derived from the presently observed period distribution, after correction for selection effects, the expected slope of the braking law. The results suggest an AML braking law very close to the "saturated" one, with a very weak dependence on the period. However we are still far from constraining the precise value of the slope, because of the important role played by the observational bias.

Optical and UV spectroscopy of the black hole binary candidate LMC X-1

NASA Technical Reports Server (NTRS)

Hutchings, J. B.; Crampton, D.; Cowley, A. P.; Bianchi, L.; Thompson, I. B.

1987-01-01

Both further optical spectroscopy of the binary star identified with LMC X-1, obtained between 1983 and 1985, and a series of IUE UV spectra taken during a 5 day interval in 1984 are presented. The optical data are used to refine the orbital period to 4.2288 days, and improved orbital parameters are derived. The velocity of the optical emission lines is antiphased with the absorption lines and has twice the velocity amplitude. These new results support the estimates of the masses in the system given earlier. The most probable component masses are approximately 20 solar masses for the primary and near 6 solar masses (for the x-ray star), suggesting the the latter may be a black hole. The UV spectra show very weak, low-velocity stellar-wind lines. It is suggested that much of the surrounding medium is highly ionized by the X-ray flux. The 'nonwind' UV spectral lines and the UV continuum temperature are consistent with the optical data, indicating a late O type star of M(bol) = -8.5. There is a weak modulation of absorption-line strengths with orbital phase, suggestive of a lack of axisymmetry in the X-irradiation of the primary star and indicative of a fairly low orbital inclination.

Adhesion and friction of iron-base binary alloys in contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Single pass sliding friction experiments were conducted with various iron base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a single crystal silicon carbide /0001/ surface in vacuum. Results indicate that atomic size and concentration of alloying elements play an important role in controlling adhesion and friction properties of iron base binary alloys. The coefficient of friction generally increases with an increase in solute concentration. The coefficient of friction increases linearly as the solute to iron atomic radius ratio increases or decreases from unity. The chemical activity of the alloying elements was also an important parameter in controlling adhesion and friction of alloys, as these latter properties are highly dependent upon the d bond character of the elements.

The minimum mass ratio of W Ursae Majoris binaries

NASA Technical Reports Server (NTRS)

Rasio, Frederic A.

1995-01-01

The minimum mass ratio for tidal stability of a contact binary containing two unevolved main-sequence stars is calculated to be q(sub min) approximately =0.09 in the case of a mostly radiative primary, and it is higher if an appreciable fraction of the mass lies in a convective envelope. At least one observed system, AW UMa, has a mass ratio just below this value (q = 0.075), implying that, if the system is stable, the primary must be slightly evolved and must have a very shallow convective envelope. Contact binaries with mass ratios significantly below that of AW UMa should not be observed, since they are tidally unstable and quickly merge into a single, rapidly rotating object, on a timescale approximately 10(exp 3)-10(exp 4) yr.

Concentrating Solar Power Projects - KVK Energy Solar Project |

Science.gov Websites

%) Technology: Parabolic trough Turbine Capacity: Net: 100.0 MW Gross: 100.0 MW Status: Under construction Start °22' 55.0" North, 71°46' 23.0" East Contact(s): SolarPACES Start Production: March 2013 PPA

The extreme Kuiper Belt binary 2001 QW322.

PubMed

Petit, J-M; Kavelaars, J J; Gladman, B J; Margot, J L; Nicholson, P D; Jones, R L; Parker, J Wm; Ashby, M L N; Bagatin, A Campo; Benavidez, P; Coffey, J; Rousselot, P; Mousis, O; Taylor, P A

2008-10-17

The study of binary Kuiper Belt objects helps to probe the dynamic conditions present during planet formation in the solar system. We report on the mutual-orbit determination of 2001 QW322, a Kuiper Belt binary with a very large separation whose properties challenge binary-formation and -evolution theories. Six years of tracking indicate that the binary's mutual-orbit period is approximately 25 to 30 years, that the orbit pole is retrograde and inclined 50 degrees to 62 degrees from the ecliptic plane, and, most surprisingly, that the mutual orbital eccentricity is <0.4. The semimajor axis of 105,000 to 135,000 kilometers is 10 times that of other near-equal-mass binaries. Because this weakly bound binary is prone to orbital disruption by interlopers, its lifetime in its present state is probably less than 1 billion years.

Speckle interferometry applied to asteroids and other solar system objects

NASA Technical Reports Server (NTRS)

Drummond, J. D.; Hege, E. K.

1985-01-01

The application of speckle interferometry to asteroids and other solar system objects is discussed. The assumption of a triaxial ellipsoid rotating about its shortest axis is the standard model. Binary asteroids, 433 Eros, 532 Herculina, 511 Davida, and Pallas are discussed.

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

Tovmassian, G.; González–Buitrago, D.; Zharikov, S.

We studied two objects identified as cataclysmic variables (CVs) with periods exceeding the natural boundary for Roche-lobe-filling zero-age main sequence (ZAMS) secondary stars. We present observational results for V1082 Sgr with a 20.82 hr orbital period, an object that shows a low luminosity state when its flux is totally dominated by a chromospherically active K star with no signs of ongoing accretion. Frequent accretion shutoffs, together with characteristics of emission lines in a high state, indicate that this binary system is probably detached, and the accretion of matter on the magnetic white dwarf takes place through stellar wind from themore » active donor star via coupled magnetic fields. Its observational characteristics are surprisingly similar to V479 And, a 14.5 hr binary system. They both have early K-type stars as donor stars. We argue that, similar to the shorter-period prepolars containing M dwarfs, these are detached binaries with strong magnetic components. Their magnetic fields are coupled, allowing enhanced stellar wind from the K star to be captured and channeled through the bottleneck connecting the two stars onto the white dwarf’s magnetic pole, mimicking a magnetic CV. Hence, they become interactive binaries before they reach contact. This will help to explain an unexpected lack of systems possessing white dwarfs with strong magnetic fields among detached white+red dwarf systems.« less

Burst Oscillation Periods from 4U 1636-53: A Constraint on the Binary Doppler Modulation

NASA Technical Reports Server (NTRS)

Giles, A. B.; Hill, K. M.; Strohmayer, T. E.; Cummings, N.; White, Nicholas E. (Technical Monitor)

2002-01-01

The burst oscillations seen during Type 1 X-ray bursts from low mass X-ray binaries (LMXB) typically evolve in period towards an asymptotic limit that likely reflects the spin of the underlying neutron star. If the underlying period is stable enough, measurement of it at different orbital phases may allow a detection of the Doppler modulation caused by the motion of the neutron star with respect to the center of mass of the binary system. Testing this hypothesis requires enough X-ray bursts and an accurate optical ephemeris to determine the binary phases at which they occurred. We present here a study of the distribution of asymptotic burst oscillation periods for a sample of 26 bursts from 4U 1636-53 observed with the Rossi X-ray Timing Explorer (RXTE). The burst sample includes both archival and proprietary data and spans more than 4.5 years. We also present new optical light curves of V801 Arae, the optical counterpart of 4U 1636-53, obtained during 1998-2001. We use these optical data to refine the binary period measured by Augusteijn et al. to 3.7931206(152) hours. We show that a subset of approx. 70% of the bursts form a tightly clustered distribution of asymptotic periods consistent with a period stability of approx. 1 x 10(exp -4). The tightness of this distribution, made up of bursts spanning more than 4 years in time, suggests that the underlying period is highly stable, with a time to change the period of approx. 3 x 10(exp 4) yr. This is comparable to similar numbers derived for X-ray pulsars. We investigate the period and orbital phase data for our burst sample and show that it is consistent with binary motion of the neutron star with v(sub ns) sin i < 38 and 50 km/s at 90 and 99% confidence, respectively. We use this limit as well as previous radial velocity data to constrain the binary geometry and component masses in 4U 1636-53. Our results suggest that unless the neutron star is significantly more massive than 1.4 solar masses the secondary is unlikely to have a mass as large as 0.36 solar masses, the mass estimated assuming it is a main sequence star which fills its Roche lobe. We show that a factor of 3 increase in the number of bursts with asymptotic period measurements should allow a detection of the neutron star velocity.

BD -22 5866: A Low-Mass, Quadruple-lined Spectroscopic and Eclipsing Binary

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya; Liu, Michael C.; Reid, I. Neill; Hebb, Leslie; Cameron, Andrew C.; Torres, Carlos A.; Wilson, David M.

2008-08-01

We report our discovery of an extremely rare, low-mass, quadruple-lined spectroscopic binary BD -22 5866 (=NLTT 53279, integrated spectral type = M0 V), found during an ongoing search for the youngest M dwarfs in the solar neighborhood. From the cross-correlation function, we are able to measure relative flux levels, estimate the spectral types of the components, and set upper limits on the orbital periods and separations. The resulting system is hierarchical, composed of a K7 + K7 binary and an M1 + M2 binary with semimajor axes of aAsin iA <= 0.06 and aBsin iB <= 0.30 AU. A subsequent search of the SuperWASP photometric database revealed that the K7 + K7 binary is eclipsing with a period of 2.21 days and at an inclination angle of 85°. Within uncertainties of 5%, the masses and radii of both components appear to be equal (0.59 M⊙, 0.61 R⊙). These two tightly orbiting stars (a = 0.035 AU) are in synchronous rotation, causing the observed excess Ca II, Hα, X-ray, and UV emission. The fact that the system was unresolved with published adaptive optics imaging, limits the projected physical separation of the two binaries at the time of the observation to dABlesssim 4.1 AU at the photometric distance of 51 pc. The maximum observed radial velocity difference between the A and B binaries limits the orbit to aABsin iAB <= 6.1 AU. As this tight configuration is difficult to reproduce with current formation models of multiple systems, we speculate that an early dynamical process reduced the size of the system, such as the interaction of the two binaries with a circumquadruple disk. Intensive photometric, spectroscopic, and interferometric monitoring, as well as a parallax measurement of this rare quadruple system, is certainly warranted. Based on observations collected at the W. M. Keck Observatory and the Canada-France-Hawaii Telescope (CFHT). The Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. The CFHT is operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Repeatable electrical measurement instrumentation for use in the accelerated stress testing of thin film solar cells

NASA Technical Reports Server (NTRS)

Davis, C. W.; Lathrop, J. W.

1985-01-01

Attention is given to the construction, calibration, and performance of a repeatable measurement system for use in conjunction with the accelerated stress testing of a-Si:H cells. A filtered diode array is utilized to approximate the spectral response of any type of solar cell in discrete portions of the spectrum. It is noted that in order to achieve the necessary degree of overall repeatability, it is necessary to pay particular attention to methods of contacting and positioning the cells.

Post passivation light trapping back contacts for silicon heterojunction solar cells.

PubMed

Smeets, M; Bittkau, K; Lentz, F; Richter, A; Ding, K; Carius, R; Rau, U; Paetzold, U W

2016-11-10

Light trapping in crystalline silicon (c-Si) solar cells is an essential building block for high efficiency solar cells targeting low material consumption and low costs. In this study, we present the successful implementation of highly efficient light-trapping back contacts, subsequent to the passivation of Si heterojunction solar cells. The back contacts are realized by texturing an amorphous silicon layer with a refractive index close to the one of crystalline silicon at the back side of the silicon wafer. As a result, decoupling of optically active and electrically active layers is introduced. In the long run, the presented concept has the potential to improve light trapping in monolithic Si multijunction solar cells as well as solar cell configurations where texturing of the Si absorber surfaces usually results in a deterioration of the electrical properties. As part of this study, different light-trapping textures were applied to prototype silicon heterojunction solar cells. The best path length enhancement factors, at high passivation quality, were obtained with light-trapping textures based on randomly distributed craters. Comparing a planar reference solar cell with an absorber thickness of 280 μm and additional anti-reflection coating, the short-circuit current density (J SC ) improves for a similar solar cell with light-trapping back contact. Due to the light trapping back contact, the J SC is enhanced around 1.8 mA cm -2 to 38.5 mA cm -2 due to light trapping in the wavelength range between 1000 nm and 1150 nm.

Polycrystalline Thin Film Photovoltaics: Research, Development, and Technologies: Preprint

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

Ullal, H. S.; Zweibel, K.; von Roedern, B.

2002-05-01

II-VI binary thin-film solar cells based on cadmium telluride (CdTe) and I-III-VI ternary thin-film solar cells based on copper indium diselenide (CIS) and related materials have been the subject of intense research and development in the past few years. Substantial progress has been made thus far in the area of materials research, device fabrication, and technology development, and numerous applications based on CdTe and CIS have been deployed worldwide. World record efficiency of 16.5% has been achieved by NREL scientists for a thin-film CdTe solar cell using a modified device structure. Also, NREL scientists achieved world-record efficiency of 21.1% formore » a thin-film CIGS solar cell under a 14X concentration and AM1.5 global spectrum. When measured under a AM1.5 direct spectrum, the efficiency increases to 21.5%. Pathways for achieving 25% efficiency for tandem polycrystalline thin-film solar cells are elucidated. R&D issues relating to CdTe and CIS are reported in this paper, such as contact stability and accelerated life testing in CdTe, and effects of moisture ingress in thin-film CIS devices. Substantial technology development is currently under way, with various groups reporting power module efficiencies in the range of 7.0% to 12.1% and power output of 40.0 to 92.5 W. A number of lessons learned during the scale-up activities of the technology development for fabrication of thin-film power modules are discussed. The major global players actively involved in the technology development and commercialization efforts using both rigid and flexible power modules are highlighted.« less

Enhanced Contacts for Inverted Metamorphic Multi-Junction Solar Cells Using Carbon Nanotube Metal Matrix Composites

DTIC Science & Technology

2018-01-18

to a variety solar energy markets. For instance, micro-cracks have been shown to cause decreased power output in single- and multi-crystalline Si PV ...fingers in silicon wafer solar cells and PV modules," Solar Energy Materials and Solar Cells, vol. 108, pp. 78-81, 1// 2013. [4] T. H. Reijenga and H...AFRL-RV-PS- AFRL-RV-PS- TR-2017-0125 TR-2017-0125 ENHANCED CONTACTS FOR INVERTED METAMORPHIC MULTI-JUNCTION SOLAR CELLS USING CARBON NANOTUBE METAL

High-voltage solar-cell chip

NASA Technical Reports Server (NTRS)

Kapoor, V. J.; Valco, G. J.; Skebe, G. G.; Evans, J. C., Jr.

1985-01-01

Integrated circuit technology has been successfully applied to the design and fabrication of 0.5 x 0.5-cm planar multijunction solar-cell chips. Each of these solar cells consisted of six voltage-generating unit cells monolithically connected in series and fabricated on a 75-micron-thick, p-type, single crystal, silicon substrate. A contact photolithic process employing five photomask levels together with a standard microelectronics batch-processing technique were used to construct the solar-cell chip. The open-circuit voltage increased rapidly with increasing illumination up to 5 AM1 suns where it began to saturate at the sum of the individual unit-cell voltages at a maximum of 3.0 V. A short-circuit current density per unit cell of 240 mA/sq cm was observed at 10 AM1 suns.

Habitability in Binary Systems: The Role of UV Reduction and Magnetic Protection

NASA Astrophysics Data System (ADS)

Clark, Joni; Mason, P. A.; Zuluaga, J. I.; Cuartas, P. A.; Bustamonte, S.

2013-06-01

The number of planets found in binary systems is growing rapidly and the discovery of many more planets in binary systems appears inevitable. We use the newly refined and more restrictive, single star habitable zone (HZ) models of Kopparapu et al. (2013) and include planetary magnetic protection calculations in order to investigate binary star habitability. Here we present results on circumstellar or S-type planets, which are planets orbiting a single star member of a binary. P-type planets, on the other hand, orbit the center of mass of the binary. Stable planetary orbits exist in HZs for both types of binaries as long as the semi-major axis of the planet is either greater than (P-type) or less than (S-type) a few times the semi-major axis of the binary. We define two types of S-type binaries for this investigation. The SA-type is a circumstellar planet orbiting the binary’s primary star. In this case, the limits of habitability are dominated by the primary being only slightly affected by the presence of the lower mass companion. Thus, the SA-type planets have habitability characteristics, including magnetic protection, similar to single stars of the same type. The SB-type is a circumstellar planet orbiting the secondary star in a wide binary. An SB-type planet needs to orbit slightly outside the secondary’s single star HZ and remain within the primary’s single star HZ at all times. We explore the parameter space for which this is possible. We have found that planets lying in the combined HZ of SB binaries can be magnetically protected against the effects of stellar winds from both primary and secondary stars in a limited number of cases. We conclude that habitable conditions exist for a subset of SA-type, and a smaller subset of SB-type binaries. However, circumbinary planets (P-types) provide the most intriguing possibilities for the existence of complex life due to the effect of synchronization of binaries with periods in the 20-30 day range which allows for planets with significant magnetic protection.

The NASA Lewis Research Center program in space solar cell research and technology. [efficient silicon solar cell development program

NASA Technical Reports Server (NTRS)

Brandhorst, H. W., Jr.

1979-01-01

Progress in space solar cell research and technology is reported. An 18 percent-AMO-efficient silicon solar cell, reduction in the radiation damage suffered by silicon solar cells in space, and high efficiency wrap-around contact and thin (50 micrometer) coplanar back contact silicon cells are among the topics discussed. Reduction in the cost of silicon cells for space use, cost effective GaAs solar cells, the feasibility of 30 percent AMO solar energy conversion, and reliable encapsulants for space blankets are also considered.

Reduce on the Cost of Photovoltaic Power Generation for Polycrystalline Silicon Solar Cells by Double Printing of Ag/Cu Front Contact Layer

NASA Astrophysics Data System (ADS)

Peng, Zhuoyin; Liu, Zhou; Chen, Jianlin; Liao, Lida; Chen, Jian; Li, Cong; Li, Wei

2018-06-01

With the development of photovoltaic industry, the cost of photovoltaic power generation has become the significant issue. And the metallization process has decided the cost of original materials and photovoltaic efficiency of the solar cells. Nowadays, double printing process has been introduced instead of one-step printing process for front contact of polycrystalline silicon solar cells, which can effectively improve the photovoltaic conversion efficiency of silicon solar cells. Here, the relative cheap Cu paste has replaced the expensive Ag paste to form Ag/Cu composite front contact of silicon solar cells. The photovoltaic performance and the cost of photovoltaic power generation have been investigated. With the optimization on structure and height of Cu finger layer for Ag/Cu composite double-printed front contact, the silicon solar cells have exhibited a photovoltaic conversion efficiency of 18.41%, which has reduced 3.42 cent per Watt for the cost of photovoltaic power generation.

Types of Information Expected from a Photometric Search for Extra-Solar Planets

NASA Technical Reports Server (NTRS)

Borucki, William; Koch, David; Bell, James, III; Cuzzi, Jeffrey N. (Technical Monitor)

1994-01-01

The current theory postulates that planets are a consequence of the formation of stars from viscous accretion disks. Condensation from the hotter, inner portion of the accretion disk favors the formation of small rocky planets in the inner portion and the formation of gas giants in the cuter, cooler part. Consequently, terrestrial-type planets in inner orbits must be commonplace (Wetheril 1991). From the geometry of the situation (Borucki and Summers 1984), it can be shown that 1% of those planetary systems that resemble our solar system should show transits for Earth-sized (or larger) planets. Thus a photometric satellite that uses a wide field of view telescope and a large CCD array to simultaneously monitor 5000 target stars should detect 50 planetary systems. To verify that regularly recurring transits are occurring rather than statistical fluctuations of the stellar flux, demands observations that extend over several orbital periods so that the constancy of the orbital period, signal amplitude, and duration can be measured. Therefore, to examine the region from Mercury's orbit to that of the Earth requires a duration of three years whereas a search out to the orbit of mars requires about six years. The results of the observations should provide estimates of the distributions of planetary size and orbital radius, and the frequency of planetary systems that have Earth-sized planets in inner orbits. Because approximately one half of the star systems observed will be binary systems, the frequency of planetary systems orbit ' ing either one or both of the stars can also be determined. Furthermore, the complexity of the photometric signature of a planet transiting a pair of stars provides enough information to estimate the eccentricities of the planetary orbits. In summary, the statistical evidence from a photometric search of solar-like stars should be able to either confirm or deny the applicability of the current theory of planet formation and provide new information about the stability of planetary orbits in binary star systems.

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

Smith, Myron A.; Shiao, Bernard; Bianchi, Luciana, E-mail: myronmeister@gmail.com, E-mail: shiao@stsci.edu, E-mail: bianchi@pha.jhu.edu

We report on intriguing photometric properties of Galactic stars observed in the Galaxy Evolution Explorer (GALEX) satellite's far-UV (FUV) and near-UV (NUV) bandpasses, as well as from the ground-based Sloan Digital Sky Survey (SDSS) and the Kepler Input Catalog. The first property is that the (FUV – NUV) color distribution of stars in the Kepler field consists of two well-separated peaks. A second and more perplexing property is that for stars with spectral types G or later the mean (FUV – NUV) color becomes much bluer, contrary to expectation. Investigating this tendency further, we found in two samples of mid-Fmore » through K type stars that 17%-22% of them exhibit FUV excesses relative to their NUV fluxes and spectral types. A correction for FUV incompleteness of the FUV magnitude-limited star sample brings this ratio to 14%-18%. Nearly the same fractions are also discovered among members of the Kepler Eclipsing Binary Catalog and in the published list of Kepler Objects of Interest. These UV-excess ('UVe') colors are confirmed by the negative UV continuum slopes in GALEX spectra of members of the population. The SDSS spectra of some UVe stars exhibit metallic line weakening, especially in the blue. This suggests an enhanced contribution of UV flux relative to photospheric flux of a solar-type single star. We consider the possibility that the UV excesses originate from various types of hot stars, including white dwarf DA and sdB stars, binaries, and strong chromosphere stars that are young or in active binaries. The space density of compact stars is too low to explain the observed frequency of the UVe stars. Our model atmosphere-derived simulations of colors for binaries with main-sequence pairs with a hot secondary demonstrate that the color loci conflict with the observed sequence. As a preferred alternative we are left with the active chromospheres explanation, whether in active close binaries or young single stars, despite the expected paucity of young, chromospherically active stars in the field. We also address a third perplexing color property, namely, the presence of a prominent island of 'UV red' stars surrounded by 'UV blue' stars in the diagnostic (NUV–g), (g – i) color diagram. We find that the subpopulation composing this island is mainly horizontal branch stars. These objects do not exhibit UV excesses and therefore have UV colors typical for their spectral types. This subpopulation appears 'red' in the UV only because the stars' colors are not pulled to the blue by the inclusion of UVe stars.« less

The formation mechanism for printed silver-contacts for silicon solar cells.

PubMed

Fields, Jeremy D; Ahmad, Md Imteyaz; Pool, Vanessa L; Yu, Jiafan; Van Campen, Douglas G; Parilla, Philip A; Toney, Michael F; van Hest, Maikel F A M

2016-04-01

Screen-printing provides an economically attractive means for making Ag electrical contacts to Si solar cells, but the use of Ag substantiates a significant manufacturing cost, and the glass frit used in the paste to enable contact formation contains Pb. To achieve optimal electrical performance and to develop pastes with alternative, abundant and non-toxic materials, a better understanding the contact formation process during firing is required. Here, we use in situ X-ray diffraction during firing to reveal the reaction sequence. The findings suggest that between 500 and 650 °C PbO in the frit etches the SiNx antireflective-coating on the solar cell, exposing the Si surface. Then, above 650 °C, Ag(+) dissolves into the molten glass frit - key for enabling deposition of metallic Ag on the emitter surface and precipitation of Ag nanocrystals within the glass. Ultimately, this work clarifies contact formation mechanisms and suggests approaches for development of inexpensive, nontoxic solar cell contacting pastes.

The formation mechanism for printed silver-contacts for silicon solar cells

DOE PAGES

Fields, Jeremy D.; Ahmad, Md. Imteyaz; Pool, Vanessa L.; ...

2016-04-01

Screen-printing provides an economically attractive means for making Ag electrical contacts to Si solar cells, but the use of Ag substantiates a significant manufacturing cost, and the glass frit used in the paste to enable contact formation contains Pb. To achieve optimal electrical performance and to develop pastes with alternative, abundant, and non-toxic materials requires understanding the contact formation process during firing. Here, we use in-situ X-ray diffraction during firing to reveal the reaction sequence. The findings suggest that between 500 degrees C and 650 degrees C PbO in the frit etches the SiNx antireflective-coating on the solar cell, exposingmore » the Si surface. Then, above 650 degrees C, Ag+ dissolves into the molten glass frit -- key for enabling deposition of metallic Ag on the emitter surface and precipitation of Ag nanocrystals within the glass. Ultimately, this work clarifies contact formation mechanisms and suggests approaches for development of inexpensive, nontoxic solar cell contacting pastes.« less

How I Learned to Stop Worrying and Love Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Moe, Maxwell Cassady

Relatively massive B-type stars with closely orbiting stellar companions can evolve to produce Type Ia supernovae, X-ray binaries, millisecond pulsars, mergers of neutron stars, gamma ray bursts, and sources of gravitational waves. However, the formation mechanism, intrinsic frequency, and evolutionary processes of B-type binaries are poorly understood. As of 2012, the binary statistics of massive stars had not been measured at low metallicities, extreme mass ratios, or intermediate orbital periods. This thesis utilizes large data sets of eclipsing binaries to measure the physical properties of B-type binaries in these previously unexplored portions of the parameter space. The updated binary statistics provide invaluable insight into the formation of massive stars and binaries as well as reliable initial conditions for population synthesis studies of binary star evolution. We first compare the properties of B-type eclipsing binaries in our Milky Way Galaxy and the nearby Magellanic Cloud Galaxies. We model the eclipsing binary light curves and perform detailed Monte Carlo simulations to recover the intrinsic properties and distributions of the close binary population. We find the frequency, period distribution, and mass-ratio distribution of close B-type binaries do not significantly depend on metallicity or environment. These results indicate the formation of massive binaries are relatively insensitive to their chemical abundances or immediate surroundings. Second, we search for low-mass eclipsing companions to massive B-type stars in the Large Magellanic Cloud Galaxy. In addition to finding such extreme mass-ratio binaries, we serendipitously discover a new class of eclipsing binaries. Each system comprises a massive B-type star that is fully formed and a nascent low-mass companion that is still contracting toward its normal phase of evolution. The large low-mass secondaries discernibly reflect much of the light they intercept from the hot B-type stars, thereby producing sinusoidal variations in perceived brightness as they orbit. These nascent eclipsing binaries are embedded in the hearts of star-forming emission nebulae, and therefore provide a unique snapshot into the formation and evolution of massive binaries and stellar nurseries. We next examine a large sample of B-type eclipsing binaries with intermediate orbital periods. To achieve such a task, we develop an automated pipeline to classify the eclipsing binaries, measure their physical properties from the observed light curves, and recover the intrinsic binary statistics by correcting for selection effects. We find the population of massive binaries at intermediate separations differ from those orbiting in close proximity. Close massive binaries favor small eccentricities and have correlated component masses, demonstrating they coevolved via competitive accretion during their formation in the circumbinary disk. Meanwhile, B-type binaries at slightly wider separations are born with large eccentricities and are weighted toward extreme mass ratios, indicating the components formed relatively independently and subsequently evolved to their current configurations via dynamical interactions. By using eclipsing binaries as accurate age indicators, we also reveal that the binary orbital eccentricities and the line-of-sight dust extinctions are anticorrelated with respect to time. These empirical relations provide robust constraints for tidal evolution in massive binaries and the evolution of the dust content in their surrounding environments. Finally, we compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, lucky imaging, high-contrast photometry, and common proper motion. We combine the samples from the various surveys and correct for their respective selection effects to determine a comprehensive nature of the intrinsic binary statistics of massive stars. We find the probability distributions of primary mass, secondary mass, orbital period, and orbital eccentricity are all interrelated. These updated multiplicity statistics imply a greater frequency of low-mass X-ray binaries, millisecond pulsars, and Type Ia supernovae than previously predicted.

Stellar encounters involving neutron stars in globular cluster cores

NASA Technical Reports Server (NTRS)

Davies, M. B.; Benz, W.; Hills, J. G.

1992-01-01

Encounters between a 1.4 solar mass neutron star and a 0.8 solar mass red giant (RG) and between a 1.4 solar mass neutron star (NS) and an 0.8 solar mass main-sequence (MS) star have been successfully simulated. In the case of encounters involving an RG, bound systems are produced when the separation at periastron passage R(MIN) is less than about 2.5 R(RG). At least 70 percent of these bound systems are composed of the RG core and NS forming a binary engulfed in a common envelope of what remains of the former RG envelope. Once the envelope is ejected, a tight white dwarf-NS binary remains. For MS stars, encounters with NSs will produce bound systems when R(MIN) is less than about 3.5 R(MS). Some 50 percent of these systems will be single objects with the NS engulfed in a thick disk of gas almost as massive as the original MS star. The ultimate fate of such systems is unclear.

Evolution of redback radio pulsars in globular clusters

NASA Astrophysics Data System (ADS)

Benvenuto, O. G.; De Vito, M. A.; Horvath, J. E.

2017-02-01

Context. We study the evolution of close binary systems composed of a normal, intermediate mass star and a neutron star considering a chemical composition typical of that present in globular clusters (Z = 0.001). Aims: We look for similarities and differences with respect to solar composition donor stars, which we have extensively studied in the past. As a definite example, we perform an application on one of the redbacks located in a globular cluster. Methods: We performed a detailed grid of models in order to find systems that represent the so-called redback binary radio pulsar systems with donor star masses between 0.6 and 2.0 solar masses and orbital periods in the range 0.2-0.9 d. Results: We find that the evolution of these binary systems is rather similar to those corresponding to solar composition objects, allowing us to account for the occurrence of redbacks in globular clusters, as the main physical ingredient is the irradiation feedback. Redback systems are in the quasi-RLOF state, that is, almost filling their corresponding Roche lobe. During the irradiation cycle the system alternates between semi-detached and detached states. While detached the system appears as a binary millisecond pulsar, called a redback. Circumstellar material, as seen in redbacks, is left behind after the previous semi-detached phase. Conclusions: The evolution of binary radio pulsar systems considering irradiation successfully accounts for, and provides a way for, the occurrence of redback pulsars in low-metallicity environments such as globular clusters. This is the case despite possible effects of the low metal content of the donor star that could drive systems away from redback configuration.

Automatic Detection and Evaluation of Solar Cell Micro-Cracks in Electroluminescence Images Using Matched Filters

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

Spataru, Sergiu; Hacke, Peter; Sera, Dezso

A method for detecting micro-cracks in solar cells using two dimensional matched filters was developed, derived from the electroluminescence intensity profile of typical micro-cracks. We describe the image processing steps to obtain a binary map with the location of the micro-cracks. Finally, we show how to automatically estimate the total length of each micro-crack from these maps, and propose a method to identify severe types of micro-cracks, such as parallel, dendritic, and cracks with multiple orientations. With an optimized threshold parameter, the technique detects over 90 % of cracks larger than 3 cm in length. The method shows great potentialmore » for quantifying micro-crack damage after manufacturing or module transportation for the determination of a module quality criterion for cell cracking in photovoltaic modules.« less

Some practical considerations for economical back contact formation on high efficiency solar cells

NASA Technical Reports Server (NTRS)

Lesk, I. A.

1985-01-01

The back contact can detract from solar cell performance in a number of ways: high recombination, barrier, photovoltaic, minority carrier collection, resistance. These effects may act in a nonuniform fashion over the cell area, and complicate the analysis of photovoltaic performance aimed at a better understanding of the effects of device geometry and material and/or processing parameters. The back contact is tested by reproducing it on both sides of a substrate. The objective is to find a back contact which performs well as a back contact, can be applied cheaply to large area solar cells, fits well into a practical process sequence, does not introduce structural damage or undesirable impurities into the silicon substrate, is compatible with an effective front contact technology, permits low temperature solder contacting, adheres well to silicon, and is reliable.

New Eclipsing Contact Binary System in Auriga

NASA Astrophysics Data System (ADS)

Austin, S. J.; Robertson, J. W.; Justice, C.; Campbell, R. T.; Hoskins, J.

2004-05-01

We present data on a newly discovered eclipsing binary system. The serendipitous discovery of this variable star was made by J.W. Robertson analyzing inhomogeneous ensemble photometry of stars in the field of the cataclysmic variable FS Aurigae from Indiana University RoboScope data. We obtained differential time-series BVR photometry during 2003 of this field variable using an ensemble of telescopes including the university observatories at ATU, UCA and joint ventures with amateur observatories in the state of Arkansas (Whispering Pines Observatory and Nubbin Ridge Observatory). The orbital period of this eclipsing system is 0.2508 days. The B-V light curve indicates colors of 1.2 around quadrature, to nearly 1.4 at primary eclipse. Binary star light curve models that best fit the BVR differential photometry suggest that the system is a contact binary overfilling the inner Roche Lobe by 12%, a primary component with a temperature of 4350K, a secondary component with a temperature of 3500K, a mass ratio of 0.37, and an inclination of 83 degrees. We present BVR light curves, an ephemeris, and best fit model parameters for the physical characteristics of this new eclipsing binary system.

RS CVn binaries: Testing the solar-stellar dynamo connection

NASA Technical Reports Server (NTRS)

Dempsey, R.

1995-01-01

We have used the Extreme Ultraviolet Explorer satellite to study the coronal emission from the EUV-bright RS CVn binaries Sigma2 CrB, observed February 10-21, 1994, and II Peg, observed October 1-5, 1993. We present time-resolved and integrated EUV short-, medium-, and long-wavelength spectra for these binaries. Sigma2 CrB shows significant first-order emission features in the long-wavelength region. The coronal emission distributions and electron densities are estimated for those active coronae dominated by high temperature plasma.

Identification and design principles of low hole effective mass p-type transparent conducting oxides

PubMed Central

Hautier, Geoffroy; Miglio, Anna; Ceder, Gerbrand; Rignanese, Gian-Marco; Gonze, Xavier

2013-01-01

The development of high-performance transparent conducting oxides is critical to many technologies from transparent electronics to solar cells. Whereas n-type transparent conducting oxides are present in many devices, their p-type counterparts are not largely commercialized, as they exhibit much lower carrier mobilities due to the large hole effective masses of most oxides. Here we conduct a high-throughput computational search on thousands of binary and ternary oxides and identify several highly promising compounds displaying exceptionally low hole effective masses (up to an order of magnitude lower than state-of-the-art p-type transparent conducting oxides), as well as wide band gaps. In addition to the discovery of specific compounds, the chemical rationalization of our findings opens new directions, beyond current Cu-based chemistries, for the design and development of future p-type transparent conducting oxides. PMID:23939205

A Mechanistic Understanding of a Binary Additive System to Synergistically Boost Efficiency in All-Polymer Solar Cells

PubMed Central

Kim, Yu Jin; Ahn, Sunyong; Wang, Dong Hwan; Park, Chan Eon

2015-01-01

All-polymer solar cells are herein presented utilizing the PBDTTT-CT donor and the P(NDI2OD-T2) acceptor with 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN) binary solvent additives. A systematic study of the polymer/polymer bulk heterojunction photovoltaic cells processed from the binary additives revealed that the microstructures and photophysics were quite different from those of a pristine system. The combination of DIO and CN with a DIO/CN ratio of 3:1 (3 vol% DIO, 1 vol% CN and 96 vol% o-DCB) led to suitable penetrating polymer networks, efficient charge generation and balanced charge transport, which were all beneficial to improving the efficiency. This improvement is attributed to increase in power conversion efficiency from 2.81% for a device without additives to 4.39% for a device with the binary processing additives. A detailed investigation indicates that the changes in the polymer:polymer interactions resulted in the formation of a percolating nasnoscale morphology upon processing with the binary additives. Depth profile measurements with a two-dimensional grazing incidence wide-angle X-ray scattering confirm this optimum phase feature. Furthermore impedance spectroscopy also finds evidence for synergistically boosting the device performance. PMID:26658472

Fabrication of contacts for silicon solar cells including printing burn through layers

DOEpatents

Ginley, David S; Kaydanova, Tatiana; Miedaner, Alexander; Curtis, Calvin J; Van Hest, Marinus Franciscus Antonius Maria

2014-06-24

A method for fabricating a contact (240) for a solar cell (200). The method includes providing a solar cell substrate (210) with a surface that is covered or includes an antireflective coating (220). For example, the substrate (210) may be positioned adjacent or proximate to an outlet of an inkjet printer (712) or other deposition device. The method continues with forming a burn through layer (230) on the coating (220) by depositing a metal oxide precursor (e.g., using an inkjet or other non-contact printing method to print or apply a volume of liquid or solution containing the precursor). The method includes forming a contact layer (240) comprising silver over or on the burn through layer (230), and then annealing is performed to electrically connect the contact layer (240) to the surface of the solar cell substrate (210) through a portion of the burn through layer (230) and the coating (220).

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

Liu, L.; Qian, S.-B.; Zhu, L.-Y.

The secured four-color light curves of VW Boo were analyzed with the 2003 version of the Wilson-Devinney code. It is confirmed that VW Boo is a shallow W-type contact binary system with a degree of contact factor f = 10.8%({+-} 0.5%). Two dark spots were found on the massive cool component this time. They cause an unequal depth of the two maxima. A period investigation based on all available visual, photographic, CCD, and photoelectric data shows that the period of the system includes a long-term decrease (dP/dt = -1.454 x 10{sup -7} days yr{sup -1}) and an oscillation (A{sub 3}more » = 0.0059 days; T{sub 3} = 25.96 years). These may be caused by mass transfer, angular momentum loss, and cyclic magnetic activity.« less

Protostellar Interferometric Line Survey (PILS): Constraining the formation of complex organic molecules with ALMA

NASA Astrophysics Data System (ADS)

Jorgensen, Jes K.; Coutens, Audrey; Bourke, Tyler L.; Favre, Cecile; Garrod, Robin; Lykke, Julie; Mueller, Holger; Oberg, Karin I.; Schmalzl, Markus; van der Wiel, Matthijs; van Dishoeck, Ewine; Wampfler, Susanne F.

2015-08-01

Understanding how, when and where complex organic and potentially prebiotic molecules are formed is a fundamental goal of astrochemistry and an integral part of origins of life studies. Already now ALMA is showing its capabilities for studies of the chemistry of solar-type stars with its high sensitivity for faint lines, high spectral resolution which limits line confusion, and high angular resolution making it possible to study the structure of young protostars on solar-system scales. We here present the first results from a large unbiased survey “Protostellar Interferometric Line Survey (PILS)” targeting one of the astrochemical template sources, the low-mass protostellar binary IRAS 16293-2422. The survey is more than an order of magnitude more sensitive than previous surveys of the source and provide imaging down to 25 AU scales (radius) around each of the two components of the binary. An example of one of the early highlights from the survey is unambiguous detections of the (related) prebiotic species glycolaldehyde, ethylene glycol (two lowest energy conformers), methyl formate and acetic acid. The glycolaldehyde-ethylene glycol abundance ratio is high in comparison to comets and other protostars - but agrees with previous measurements, e.g., in the Galactic Centre clouds possibly reflecting different environments and/or evolutionary histories. Complete mapping of this and other chemical networks in comparison with detailed chemical models and laboratory experiments will reveal the origin of complex organic molecules in a young protostellar system and investigate the link between these protostellar stages and the early Solar System.

The challenge of screen printed Ag metallization on nano-scale poly-silicon passivated contacts for silicon solar cells

NASA Astrophysics Data System (ADS)

Jiang, Lin; Song, Lixin; Yan, Li; Becht, Gregory; Zhang, Yi; Hoerteis, Matthias

2017-08-01

Passivated contacts can be used to reduce metal-induced recombination for higher energy conversion efficiency for silicon solar cells, and are obtained increasing attentions by PV industries in recent years. The reported thicknesses of passivated contact layers are mostly within tens of nanometer range, and the corresponding metallization methods are realized mainly by plating/evaporation technology. This high cost metallization cannot compete with the screen printing technology, and may affect its market potential comparing with the presently dominant solar cell technology. Very few works have been reported on screen printing metallization on passivated contact solar cells. Hence, there is a rising demand to realize screen printing metallization technology on this topic. In this work, we investigate applying screen printing metallization pastes on poly-silicon passivated contacts. The critical challenge for us is to build low contact resistance that can be competitive to standard technology while restricting the paste penetrations within the thin nano-scale passivated contact layers. The contact resistivity of 1.1mohm-cm2 and the open circuit voltages > 660mV are achieved, and the most appropriate thickness range is estimated to be around 80 150nm.

New Evidence for a Black Hole in the Compact Binary Cygnus X-3

NASA Technical Reports Server (NTRS)

Shrader, Chris R.; Titarchuk, Lev; Shaposhnikov, Nikolai

2010-01-01

The bright and highly variable X-ray and radio source known as Cygnus X-3 was among the first X-ray sources discovered, yet it remains in many ways an enigma. Its known to consist of a massive. Wolf-Rayet primary in an extremely tight orbit with a compact object. Yet one of the most basic of pa.ranietern the mass of the compact object - is not known. Nor is it even clear whether its is a neutron star or a black hole. In this Paper we present our analysis of the broad-band high-energy continua covering a substantial range in luminosity and spectral morphology. We apply these results to a recently identified scaling relationship which has been demonstrated to provide reliable estimates of the compact object mass in a number of accretion powered binaries. This analysis leads us to conclude that the compact object in Cygnus X-3 has a mass greater than 4.2 solar mass thus clearly indicative of a black hole and as such resolving a longstanding issue. The full range of uncertainty in our analysis and from using a. range of recently published distance estimates constrains the compact object mass to lie between 4.2 solar mass and 14.4 solar mass. Our favored estimate, based on a 9.0 kpc distance estimate is approx. l0 solar mass, with the. error margin of 3.2 solar masses. This result may thus pose challenges to shared-envelope evolutionary models of compact binaries. as well as establishing Cygnus X-3 as the first confirmed accretion-powered galactic gamma: ray source.

Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable-zone Planets

NASA Astrophysics Data System (ADS)

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

2016-02-01

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.

CONSTRAINING THE RADIATION AND PLASMA ENVIRONMENT OF THE KEPLER CIRCUMBINARY HABITABLE-ZONE PLANETS

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

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation propertiesmore » as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.« less

Cannibals in the thick disk: the young α-rich stars as evolved blue stragglers

NASA Astrophysics Data System (ADS)

Jofré, P.; Jorissen, A.; Van Eck, S.; Izzard, R. G.; Masseron, T.; Hawkins, K.; Gilmore, G.; Paladini, C.; Escorza, A.; Blanco-Cuaresma, S.; Manick, R.

2016-10-01

Spectro-seismic measurements of red giants enabled the recent discovery of stars in the thick disk that are more massive than 1.4 M⊙. While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 "young" stars and 13 "old" stars with similar stellar parameters but with masses below 1.2 M⊙ and found that more of the young starsappear to be in binary systems with respect to the old stars.Furthermore, we show that the young stars do not follow the expected trend of [C/H] ratios versus mass for individual stars. However, with a population synthesis of low-mass stars including binary evolution and mass transfer, we can reproduce the observed [C/N] ratios versus mass. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study the evolution of field blue stragglers after they have left the main-sequence.

Novel Contact Materials for Improved Performance CdTe Solar Cells Final Report

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

Rockett, Angus; Marsillac, Sylvain; Collins, Robert

This program has explored a number of novel materials for contacts to CdTe solar cells in order to reduce the back contact Schottky barrier to zero and produce an ohmic contact. The project tested a wide range of potential contact materials including TiN, ZrN, CuInSe 2:N, a-Si:H and alloys with C, and FeS2. Improved contacts were achieved with FeS 2. As part of understanding the operation of the devices and controlling the deposition processes, a number of other important results were obtained. In the process of this project and following its conclusion it led to research that resulted in sevenmore » journal articles, nine conference publications, 13 talks presented at conferences, and training of eight graduate students. The seven journal articles were published in 2015, 2016, and 2017 and have been cited, as of March 2018, 52 times (one cited 19 times and two cited 11 times). We demonstrated high levels of doping of CIS with N but electrical activity of the resulting N was not high and the results were difficult to reproduce. Furthermore, even with high doping the contacts were not good. Annealing did not improve the contacts. A-Si:H was found to produce acceptable but unstable contacts, degrading even over a day or two, apparently due to H incorporation into the CdTe. Alloying with C did not improve the contacts or stability. The transition metal nitrides produced Schottky type contacts for all materials tested. While these contacts were found to be unsatisfactory, we investigated FeS 2 and found this material to be effective and comparable to the best contacts currently available. The contacts were found to be chemically stable under heat treatment and preferable to Cu doped contacts. Thus, we demonstrated an improved contact material in the course of this project. In addition, we developed new ways of controlling the deposition of CdTe and other materials, demonstrated the nature of defects in CdTe, and studied the distribution of conductivity and carrier type in CdTe devices. We demonstrated the conduction mechanism by which CdTe polycrystals improve the performance of the devices relative to single crystal devices. The mechanism shows that grain boundaries are conduction pathways for photogenerated electrons and that the corresponding holes are confined to the grains and therefore do not contribute to recombination.« less

Combining binary decision tree and geostatistical methods to estimate snow distribution in a mountain watershed

USGS Publications Warehouse

Balk, Benjamin; Elder, Kelly

2000-01-01

We model the spatial distribution of snow across a mountain basin using an approach that combines binary decision tree and geostatistical techniques. In April 1997 and 1998, intensive snow surveys were conducted in the 6.9‐km2 Loch Vale watershed (LVWS), Rocky Mountain National Park, Colorado. Binary decision trees were used to model the large‐scale variations in snow depth, while the small‐scale variations were modeled through kriging interpolation methods. Binary decision trees related depth to the physically based independent variables of net solar radiation, elevation, slope, and vegetation cover type. These decision tree models explained 54–65% of the observed variance in the depth measurements. The tree‐based modeled depths were then subtracted from the measured depths, and the resulting residuals were spatially distributed across LVWS through kriging techniques. The kriged estimates of the residuals were added to the tree‐based modeled depths to produce a combined depth model. The combined depth estimates explained 60–85% of the variance in the measured depths. Snow densities were mapped across LVWS using regression analysis. Snow‐covered area was determined from high‐resolution aerial photographs. Combining the modeled depths and densities with a snow cover map produced estimates of the spatial distribution of snow water equivalence (SWE). This modeling approach offers improvement over previous methods of estimating SWE distribution in mountain basins.

Observationally Testing the Triple Origin of Blue Straggler Stars with Near-Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Kohler, Jacob P.; Gosnell, Natalie M.; Sokal, Kimberly R.; Mace, Gregory N.

2018-01-01

Presented are results to constrain blue straggler star (BSS) formation mechanisms in open cluster NGC 188 using data from the Immersion Grating INfrared Spectrometer (IGRINS) while at the Discovery Channel Telescope. The majority (at least 16 of 21) of NGC 188s BSSs are binaries, and, to date, seven white dwarf (WD) companions have been detected. This leaves at least nine undetected companion stars. Observations show a sharp peak of the BSSs companion mass distribution at 0.5 solar masses, highly suggestive of a WD or M-type main sequence (MS) star. Under our tested formation mechanism, the progenitors of BSSs are arranged in primordial hierarchical triple star systems that dynamically evolve through the Kozai-cycle tidal friction (KCTF) process into a binary composed of a BSS and, statistically, an M dwarf companion. We test for the presence of an M dwarf by cross-correlating a near-IR spectrum with both a BSS template and an M dwarf template. We present, for the first time, a preliminary detection of a 3800K, 0.5 solar mass M dwarf companion in each of the long period (log[P(d)]=3), single-lined binaries WOCS 451 and WOCS 5671 in NGC 188. To assess the possibility of a false M dwarf detection, we carry out Monte Carlo simulations cross-correlating an M dwarf template with a BSS-only spectrum with a signal-to-noise ratio matching our observations. Theoretical detection limits for various BSS-M dwarf pairs are reported. In the case of a non-detection, such as in WOCS 4970, we are able to place an upper limit on the mass, and thus temperature, of the companion star. Current and future research goals aim for further insight into the BSS formation mechanism frequencies of NGC 188.

A Photometric Study of the Contact Binary System FU Dra

NASA Astrophysics Data System (ADS)

Kaitchuck, R. H.; Hill, R. L.; Corn, A. P.; Gevirtz, J.; Levell, K. L.; Valenti, T. L.

2006-12-01

This paper reports new four-filter CCD observations of the contact binary FU Dra. The Wilson and Devinney model was used to simultaneously fit these light curves and published radial velocity data. The stellar masses, sizes, and densities were calculated. Five additional models involving dark spots, hot spots, and accretion heating were considered as explanations for the light curve asymmetry known as the "O'Connell effect" in FU Dra. No conclusive spot model choice could be made but the Liu and Yang model for accretion heating is an unlikely explanation for the O'Connell effect in FU Dra.

Lifetime of binary asteroids versus gravitational encounters and collisions

NASA Technical Reports Server (NTRS)

Chauvineau, Bertrand; Farinella, Paolo; Mignard, F.

1992-01-01

We investigate the effect on the dynamics of a binary asteroid in the case of a near encounter with a third body. The dynamics of the binary is modeled as a two-body problem perturbed by an approaching body in the following ways: near encounters and collisions with a component of the system. In each case, the typical value of the two-body energy variation is estimated, and a random walk for the cumulative effect is assumed. Results are applied to some binary asteroid candidates. The main conclusion is that the collisional disruption is the dominant effect, giving lifetimes comparable to or larger than the age of the solar system.

Space solar cell technology development - A perspective

NASA Technical Reports Server (NTRS)

Scott-Monck, J.

1982-01-01

The developmental history of photovoltaics is examined as a basis for predicting further advances to the year 2000. Transistor technology was the precursor of solar cell development. Terrestrial cells were modified for space through changes in geometry and size, as well as the use of Ag-Ti contacts and manufacture of a p-type base. The violet cell was produced for Comsat, and involved shallow junctions, new contacts, and an enhanced antireflection coating for better radiation tolerance. The driving force was the desire by private companies to reduce cost and weight for commercial satellite power supplies. Liquid phase epitaxial (LPE) GaAs cells are the latest advancement, having a 4 sq cm area and increased efficiency. GaAs cells are expected to be flight ready in the 1980s. Testing is still necessary to verify production techniques and the resistance to electron and photon damage. Research will continue in CVD cell technology, new panel technology, and ultrathin Si cells.

Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

NASA Technical Reports Server (NTRS)

Lathrop, J. W.

1983-01-01

Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

Lightweight, low-cost solar energy collector

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Costen, Michael K. (Inventor)

2006-01-01

A lightweight solar concentrator of the reflecting parabolic or trough type is realized via a thin reflecting film, an inflatable structural housing and tensioned fibers. The reflector element itself is a thin, flexible, specularly-reflecting sheet or film. The film is maintained in the parabolic trough shape by means of a plurality of identical tensioned fibers arranged to be parallel to the longitudinal axis of the parabola. Fiber ends are terminated in two identical spaced anchorplates, each containing a plurality of holes which lie on the desired parabolic contour. In a preferred embodiment, these fibers are arrayed in pairs with one fiber contacting the front side of the reflecting film and the other contacting the back side of the reflecting film. The reflective surface is thereby slidably captured between arrays of fibers which control the shape and position of the reflective film. Gas pressure in the inflatable housing generates fiber tension to achieve a truer parabolic shape.

A FUSE Survey of Algol-Type Interacting Binary Systems

NASA Astrophysics Data System (ADS)

Peters, C.

We propose a survey of Algol-type interacting binaries with FUSE. The observing list contains 15 systems with deltage40o for which systemic parameters are known. The program stars span the range from early-type contact systems that will eventually become conventional Algols to wide binaries in an advanced evolutionary state with prominent accretion disks. Some physical parameters that can be obtained include the ionization temperature and density in the accretion disk, domain of infall (gas stream), high temperature plasma on the trailing side of the system, and in certain systems the splash zone. We will look for the presence of ionO6 absorption and assess the phase interval over which it is observed. Emission from this ion has already been found in FUSE observations of three Algols (V356Sgr, TTHya, and RYPer) during total eclipse and confirms the presence of a sim300,000K plasma abovebelow the orbital plane. In accordance with the policy on the FUSE Survey and Supplementary Program, the observations will be obtained at random phases, but we request 5 visits of each target in order to secure good phase coverage and maximize the probability of obtaining data at interesting phases, such as the interval containing the mass outflow in the splash region where a tangentially-impacting gas stream is deflected off of the mass gainers photosphere. The physical parameters that are obtained in this project will constrain future 3-D hydrodynamical simulations of mass flow in Algols. This project will build upon the successful one (Z902) carried through in FUSE Cycle3.

A strategy for tissue self-organization that is robust to cellular heterogeneity and plasticity

PubMed Central

Cerchiari, Alec E.; Garbe, James C.; Jee, Noel Y.; Todhunter, Michael E.; Broaders, Kyle E.; Peehl, Donna M.; Desai, Tejal A.; LaBarge, Mark A.; Thomson, Matthew; Gartner, Zev J.

2015-01-01

Developing tissues contain motile populations of cells that can self-organize into spatially ordered tissues based on differences in their interfacial surface energies. However, it is unclear how self-organization by this mechanism remains robust when interfacial energies become heterogeneous in either time or space. The ducts and acini of the human mammary gland are prototypical heterogeneous and dynamic tissues comprising two concentrically arranged cell types. To investigate the consequences of cellular heterogeneity and plasticity on cell positioning in the mammary gland, we reconstituted its self-organization from aggregates of primary cells in vitro. We find that self-organization is dominated by the interfacial energy of the tissue–ECM boundary, rather than by differential homo- and heterotypic energies of cell–cell interaction. Surprisingly, interactions with the tissue–ECM boundary are binary, in that only one cell type interacts appreciably with the boundary. Using mathematical modeling and cell-type-specific knockdown of key regulators of cell–cell cohesion, we show that this strategy of self-organization is robust to severe perturbations affecting cell–cell contact formation. We also find that this mechanism of self-organization is conserved in the human prostate. Therefore, a binary interfacial interaction with the tissue boundary provides a flexible and generalizable strategy for forming and maintaining the structure of two-component tissues that exhibit abundant heterogeneity and plasticity. Our model also predicts that mutations affecting binary cell–ECM interactions are catastrophic and could contribute to loss of tissue architecture in diseases such as breast cancer. PMID:25633040

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.

Rapid mitigation of carrier-induced degradation in commercial silicon solar cells

NASA Astrophysics Data System (ADS)

Hallam, Brett J.; Chan, Catherine E.; Chen, Ran; Wang, Sisi; Ji, Jingjia; Mai, Ly; Abbott, Malcolm D.; Payne, David N. R.; Kim, Moonyong; Chen, Daniel; Chong, CheeMun; Wenham, Stuart R.

2017-08-01

We report on the progress for the understanding of carrier-induced degradation (CID) in p-type mono and multi-crystalline silicon (mc-Si) solar cells, and methods of mitigation. Defect formation is a key aspect to mitigating CID. Illuminated annealing can be used for both mono and mc-Si solar cells to reduce CID. The latest results of an 8-s UNSW advanced hydrogenation process applied to industrial p-type Czochralski PERC solar cells are shown with average efficiency enhancements of 1.1% absolute from eight different solar cell manufacturers. Results from three new industrial CID mitigation tools are presented, reducing CID to 0.8-1.1% relative, compared to 4.2% relative on control cells. Similar advanced hydrogenation processes can also be applied to multi-crystalline silicon passivated emitter with rear local contact (PERC) cells, however to date, the processes take longer and are less effective. Modifications to the firing processes can also suppress CID in multi-crystalline cells during subsequent illumination. The most stable results are achieved with a multi-stage process consisting of a second firing process at a reduced firing temperature, followed by extended illuminated annealing.

Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process

DOEpatents

Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

2001-01-01

A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process

DOEpatents

Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

2001-01-01

A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

Laminated photovoltaic modules using back-contact solar cells

DOEpatents

Gee, James M.; Garrett, Stephen E.; Morgan, William P.; Worobey, Walter

1999-09-14

Photovoltaic modules which comprise back-contact solar cells, such as back-contact crystalline silicon solar cells, positioned atop electrically conductive circuit elements affixed to a planar support so that a circuit capable of generating electric power is created. The modules are encapsulated using encapsulant materials such as EVA which are commonly used in photovoltaic module manufacture. The module designs allow multiple cells to be electrically connected in a single encapsulation step rather than by sequential soldering which characterizes the currently used commercial practices.

Microcrystalline silicon growth for heterojunction solar cells

NASA Technical Reports Server (NTRS)

Iles, P. A.; Leung, D. C.; Fang, P. H.

1983-01-01

A total of sixteen runs of e-beam vacuum deposition of p type microcrystalline Si (m-Si) films were attempted on n type or p-n junction single crystalline Si (C-Si) substrates. The m-Si film thickness varied from .15 to .7 um and metal contacts were deposited after plasma hydrogenation. The p-m-Si on n-c-Si structure had a Voc of up to 490 m V while no Voc improvements were observed in the p-m-Si on p-n C-Si structure against p-n controls. Both CFF and Jsc were lower than control. Possible problem areas were interfaced between m-Si and C-si and the back contacts due to lack of sintering for fear of dehydrogenation.

Plastic Schottky barrier solar cells

DOEpatents

Waldrop, James R.; Cohen, Marshall J.

1984-01-24

A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.