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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Faint-Source-Star Planetary Microlensing: The Discovery of the Cold Gas-Giant Planet OGLE-2014-BLG-0676Lb

We report the discovery of a planet OGLE-2014-BLG-0676Lb via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics; Optical Gravitational Lensing Experiment; Wise Observatory; RoboNETLas Cumbres Observatory Global Telescope; Microlensing Network for the Detection of Small Terrestrial Exoplanets; and -FUN. All analyses of the light-curve data favoura lens system comprising a planetary mass orbiting a host star. The most-favoured binary lens model has a mass ratio between the two lens masses of (4.78 +/- 0.13) 10(exp -3). Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09(+1.02/-1.12) MJ planet orbiting a 0.62(+0.20/-0.22) solar mass host star at a deprojected orbital separation of 4.40(+2.16/-1.46) au. The distance to the lens system is 2.22(+0.96/-0.83) kpc. Planet OGLE-2014-BLG-0676Lb provides additional data to the growing number of cool planets discover redusing gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation.

OGLE-2014-BLG-0676Lb↗
DOE OSTI2011

PTF 10bzf (SN 2010ah): A BROAD-LINE Ic SUPERNOVA DISCOVERED BY THE PALOMAR TRANSIENT FACTORY

We present the discovery and follow-up observations of a broad-line Type Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient Factory (PTF) on 2010 February 23. The SN distance is {approx_equal}218 Mpc, greater than GRB 980425/SN 1998bw and GRB 060218/SN 2006aj, but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with Palomar 48 inch, Palomar 60 inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, Combined Array for Research in Millimeter-wave Astronomy, Westerbork Synthesis Radio Telescope, and Expanded Very Large Array. Here we compare the properties of PTF 10bzf with those of SN 1998bw and other broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf suggest that this SN is intermediate, in kinetic energy and amount of {sup 56}Ni, between non-GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe like 1998bw. No X-ray or radio counterpart to PTF 10bzf was detected. X-ray upper limits allow us to exclude the presence of an underlying X-ray afterglow as luminous as that of other SN-associated GRBs such as GRB 030329 or GRB 031203. Early-time radio upper limits do not show evidence for mildly relativistic ejecta. Late-time radio upper limits rule out the presence of an underlying off-axis GRB, with energy and wind density similar to the SN-associated GRB 030329 and GRB 031203. Finally, by performing a search for a GRB in the time window and at the position of PTF 10bzf, we find that no GRB in the interplanetary network catalog could be associated with this SN.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The three-dimensional orbit and physical parameters of 47 OPH

Although 47 Oph has been shown to be a binary with a period of ∼27 days using both spectroscopic and interferometric techniques, only a preliminary orbit has been obtained in the previous work due to the shortage of high precision measurements. Since 1997, new spectroscopic and interferometric measurements have been obtained with much higher precision by the spectrograph of the 2.16 m telescope at Xinglong station and the Navy Precision Optical Interferometer, respectively. Combining all of the measurements, a three-dimensional orbit is obtained with high precision in this work. Thus, the component masses are calculated to be 1.50 ± 0.06 and 1.34 ± 0.06 M{sub ⊙}, respectively. The orbital parallax is 32.6 ± 0.6 mas, which is consistent with the Hipparcos parallax. With the known apparent magnitudes and color indices of the components, the derived luminosities are 7.80 ± 0.36 and 3.41 ± 0.25 L{sub ⊙}. The estimated radii of the components are 2.06 ± 0.07 and 1.36 ± 0.06 R{sub ⊙}. Finally, the evolutionary status of the components are investigated with the help of a stellar evolution model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

THE GALACTIC BULGE SURVEY: OUTLINE AND X-RAY OBSERVATIONS

We introduce the Galactic Bulge Survey (GBS) and we provide the Chandra source list for the region that has been observed to date. Among the goals of the GBS are constraining the neutron star (NS) equation of state and the black hole (BH) mass distribution via the identification of eclipsing NS and BH low-mass X-ray binaries (LMXBs). The latter goal will, in addition, be obtained by significantly enlarging the number of BH systems for which a BH mass can be derived. Further goals include constraining X-ray binary formation scenarios, in particular the common envelope phase and the occurrence of kicks, via source-type number counts and an investigation of the spatial distribution of X-ray binaries, respectively. The GBS targets two strips of 6{sup 0} x 1{sup 0} (12 deg{sup 2} in total), one above (1{sup 0} < b < 2{sup 0}) and one below (-2{sup 0} < b < -1{sup 0}) the Galactic plane in the direction of the Galactic center at both X-ray and optical wavelengths. By avoiding the Galactic plane (-1{sup 0} < b < 1{sup 0}) we limit the influence of extinction on the X-ray and optical emission but still sample relatively large number densities of sources. The survey is designed such that a large fraction of the X-ray sources can be identified from their optical spectra. The X-ray survey, by design, covers a large area on the sky while the depth is shallow using 2 ks per Chandra pointing. In this way we maximize the predicted number ratio of (quiescent) LMXBs to cataclysmic variables. The survey is approximately homogeneous in depth to a 0.5-10 keV flux of 7.7 x 10{sup -14} erg cm{sup -2} s{sup -1}. So far, we have covered about two-thirds (8.3 deg{sup 2}) of the projected survey area with Chandra providing over 1200 unique X-ray sources. We discuss the characteristics and the variability of the brightest of these sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Bioactive Silver-Containing Compositions of Methyl Cellulose with a Natural Sorbent Zosterin: The Structure, Morphology, and Properties

The morphology, structure, and optical properties of polymeric compositions based on a natural sorbent Zosterin, methyl cellulose (MC), and a Poviargol (silver-containing preparation) are studied via atomic force microscopy (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). AFM studies show substantial changes in the morphology of the surface of obtained films from granular with different grain sizes (for Zosterin and an MC/Zosterin binary system) to spongy with nanopores and submicron pores on the surface (for an MC/Zosterin/Poviargol ternary system). Silver nanoparticles with different shapes and sizes are observed by TEM in the MC/Zosterin/Poviargol ternary system against the background of the MC/Zosterin polymer matrix which has fractal-type morphology. A reflection corresponding to zero-valent silver is found by XRD in the MC/Zosterin/Poviargol ternary composition.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Bayesian investigation of isochrone consistency using the old open cluster NGC 188

This paper provides a detailed comparison of the differences in parameters derived for a star cluster from its color–magnitude diagrams (CMDs) depending on the filters and models used. We examine the consistency and reliability of fitting three widely used stellar evolution models to 15 combinations of optical and near-IR photometry for the old open cluster NGC 188. The optical filter response curves match those of theoretical systems and are thus not the source of fit inconsistencies. NGC 188 is ideally suited to this study thanks to a wide variety of high-quality photometry and available proper motions and radial velocities that enable us to remove non-cluster members and many binaries. Our Bayesian fitting technique yields inferred values of age, metallicity, distance modulus, and absorption as a function of the photometric band combinations and stellar models. We show that the historically favored three-band combinations of UBV and VRI can be meaningfully inconsistent with each other and with longer baseline data sets such as UBVRIJHK{sub S}. Differences among model sets can also be substantial. For instance, fitting Yi et al. (2001) and Dotter et al. (2008) models to UBVRIJHK{sub S} photometry for NGC 188 yields the following cluster parameters: age = (5.78 ± 0.03, 6.45 ± 0.04) Gyr, [Fe/H] = (+0.125 ± 0.003, −0.077 ± 0.003) dex, (m−M){sub V} = (11.441 ± 0.007, 11.525 ± 0.005) mag, and A{sub V} = (0.162 ± 0.003, 0.236 ± 0.003) mag, respectively. Within the formal fitting errors, these two fits are substantially and statistically different. Such differences among fits using different filters and models are a cautionary tale regarding our current ability to fit star cluster CMDs. Additional modeling of this kind, with more models and star clusters, and future Gaia parallaxes are critical for isolating and quantifying the most relevant uncertainties in stellar evolutionary models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Efficient Quaternary Organic Solar Cells with Parallel‐Alloy Morphology

Abstract Two compatible donors (PBDB‐T and PTB7‐Th) and two miscible acceptors (ITIC and FOIC) are employed to deliver a parallel‐alloy morphology model in non‐fullerene‐based quaternary organic solar cells. PBDB‐T and PTB7‐Th form a parallel link with a slight adjustment of molecular packing into enhanced face‐on crystallites while ITIC disperses into discontinuous FOIC microcrystal regions to form continuous and ordered alloy‐like acceptor phases. Characterization of blend morphology highlights the parallel‐alloy model—enabled by the introduction of PBDB‐T and ITIC, which contributes to improved molecular packing and reduced domain size resulting in efficient charge generation and consistent transport channels. This successful parallel‐alloy quaternary blend morphology demonstrates an enhanced optical absorption, optimized domain size, and nanostructures toward simultaneous improvement in charge transfer and transport. Therefore, a power conversion efficiency of 12.52% is realized for a quaternary device which is 6% higher than the ternary device (PBDB‐T:PTB7‐Th:FOIC) and 12% higher than the binary device (PTB7‐Th:FOIC). Domination of quaternary devices over ternary and binary blends, which is another feasible way to realize highly efficient devices through further investigation of quaternary OSCs, is presented.

Bi, Zhaozhao↗
DOE OSTI2010

VLBI OBSERVATIONS OF THE TYPE I b/c SUPERNOVA 2009bb

We report on VLBI as well as Very Large Array radio observations of the Type I b/c supernova 2009bb. The high radio luminosity of this supernova seems to require relativistic outflow, implying that the early radio emission was 'engine-driven', that is, driven by collimated outflow from a compact object, even though no gamma-ray emission was seen. The radio light curve shows a general decline, with a 'bump' near t = 52 d, seen most prominently at 5 GHz. The light-curve bump could be either engine-driven or it might represent the turn-on of the normal radio emission from a supernova, driven by interaction with the circumstellar material rather than by the engine. We undertook VLBI observations to resolve SN 2009bb's relativistic outflow. Our observations constrain the angular outer radius at an age of 85 d to be <0.64 mas, corresponding to <4 x 10{sup 17} cm and an average apparent expansion speed of <1.74 c. This result is consistent with the moderately relativistic ejecta speeds implied by the radio luminosity and spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

NON-RELATIVISTIC RADIATION-MEDIATED SHOCK BREAKOUTS. I. EXACT BOLOMETRIC PLANAR BREAKOUT SOLUTIONS

The problem of a non-steady planar radiation-mediated shock (RMS) breaking out from a surface with a power-law density profile, {rho}{proportional_to}x{sup n} , is numerically solved in the approximation of diffusion with constant opacity. For an appropriate choice of time, length, and energy scales, determined by the breakout opacity, velocity, and density, the solution is universal, i.e., depends only on the density power-law index n. The resulting luminosity depends weakly on the value of n. An approximate analytic solution, based on the self-similar hydrodynamic solutions and on the steady RMS solutions, is constructed and shown to agree with the numerical solutions as long as the shock is far from the surface, {tau} >> c/v{sub sh}. Approximate analytic expressions, calibrated based on the exact solutions, are provided, which describe the escaping luminosity as a function of time. These results can be used to calculate the bolometric properties of the bursts of radiation produced during supernova shock breakouts. For completeness, we also use the exact breakout solutions to provide an analytic approximation for the maximum surface temperature for fast (v{sub sh} {approx}> 0.1) non-thermal breakouts and show that it is a few times smaller than inferred based on steady state RMS solutions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

COSMOLOGICAL-MODEL-INDEPENDENT TESTS FOR THE DISTANCE-DUALITY RELATION FROM GALAXY CLUSTERS AND TYPE Ia SUPERNOVA

We perform a cosmological-model-independent test for the distance-duality (DD) relation {eta}(z) = D{sub L} (z)(1 + z){sup -2}/D{sub A} (z), where D{sub L} and D{sub A} are the luminosity distance and angular diameter distance, respectively, with a combination of observational data for D{sub L} taken from the latest Union2 SNe Ia and that for D{sub A} provided by two galaxy cluster samples compiled by De Filippis et al. and Bonamente et al. Two parameterizations for {eta}(z), i.e., {eta}(z) = 1 + {eta}{sub 0} z and {eta}(z) = 1 + {eta}{sub 0} z/(1 + z), are used. We find that the DD relation can be accommodated at 1{sigma} confidence level (CL) for the De Filippis et al. sample and at 3{sigma} CL for the Bonamente et al. sample. We also examine the DD relation by postulating two more general parameterizations: {eta}(z) = {eta}{sub 0} + {eta}{sub 1} z and {eta}(z) = {eta}{sub 0} + {eta}{sub 1} z/(1 + z), and find that the DD relation is compatible with the results from the De Filippis et al. and the Bonamente et al. samples at 1{sigma} and 2{sigma} CLs, respectively. Thus, we conclude that the DD relation is compatible with present observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

ON THE MASS-LOSS RATE OF MASSIVE STARS IN THE LOW-METALLICITY GALAXIES IC 1613, WLM, AND NGC 3109

We present a spectroscopic analysis of Very Large Telescope/X-Shooter observations of six O-type stars in the low-metallicity (Z {approx} 1/7 Z {sub sun}) galaxies IC 1613, WLM, and NGC 3109. The stellar and wind parameters of these sources allow us, for the first time, to probe the mass loss versus metallicity dependence of stellar winds at metallicities below that of the Small Magellanic Cloud (at Z {approx} 1/5 Z {sub sun}) by means of a modified wind momentum versus luminosity diagram. The wind strengths that we obtain for the objects in WLM and NGC 3109 are unexpectedly high and do not agree with theoretical predictions. The objects in IC 1613 tend toward a higher than expected mass-loss rate, but remain consistent with predictions within their error bars. We discuss potential systematic uncertainties in the mass-loss determinations to explain our results. However, if further scrutinization of these findings point towards an intrinsic cause for this unexpected sub-SMC mass-loss behavior, implications would include a higher than anticipated number of Wolf-Rayet stars and Ib/Ic supernovae in low-metallicity environments, but a reduced number of long-duration gamma-ray bursts produced through a single-star evolutionary channel.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Probing the origin of the two-component structure of broad-line region by reverberation mapping of an extremely variable quasar

ABSTRACT The physical origins of quasar components, such as the broad-line region (BLR) and dust torus, remain under debate. To gain insights into them, we focused on changing-state quasars (CSQs) which provide a unique perspective through structural changes associated with accretion disc state transitions. We targeted SDSS J125809.31+351943.0, an extremely variable CSQ, to study its central core structure and kinematics. We conducted reverberation mapping with optical spectroscopy to explore the structure of the BLR and estimate the black hole mass. The results from Hβ reverberation mapping indicated a black hole mass of $10^{9.64^{+0.11}_{-0.20}}\rm {M_\odot }$. Additionally, we analysed variations in the optical to X-ray spectral indices, αox, before and after the state transition, to investigate the accretion disc. These variations in αox and the Eddington ratio (from 0.4 per cent to 2.4 per cent) exhibitied behaviour similar to state transitions observed in X-ray binary systems. Spectral analysis of Hβ revealed a predominantly double-peaked profile during dim periods, transitioning to include a single-peaked component as the quasar brightened, suggesting that Hβ contains a mixture of two components. Each of these components has its distinct characteristics: the first is a double-peaked profile that remains stable despite changes in the accretion rate, while the second is a variable single-peaked profile. Using time-lags from reverberation mapping, we estimated the spatial relationships between these BLR components, the accretion disc, and the dust torus. Our results suggest that the BLR consists of two distinct components, each differing in location and origin.

Nagoshi, Shumpei (ORCID:0000000326504322)↗
DOE OSTI2010

Most luminous supernovae produced by shocks

The extremely luminous supernova SN2006gy is explained as some other peculiar supernovae: light is produced by a radiative shock propagating in a dense circumstellar envelope. This envelope is formed by a previous weak explosion at a stage of hydrodynamic instability due to creation of electron-positron pairs in stellar interiors. The problems in the theory and observations of supernovae created by multiple explosions are briefly reviewed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Absolute Dimensions and Evolutionary Status of the Semi-detached Algol W Ursae Minoris

Double-lined eclipsing binaries allow accurate and direct determination of fundamental parameters such as mass and radius for each component, and they provide important constraints on the stellar structure and evolution models. In this study, we aim to determine a unique set of binary parameters for the Algol system W UMi and to examine its evolutionary status. New high-resolution time-series spectroscopic observations were carried out during 14 nights from 2008 April to 2011 March, and a total of 37 spectra were obtained using the Bohyunsan Optical Echelle Spectrograph. We measured the radial velocities (RVs) for both components, and the effective temperature of the primary star was found to be T {sub eff,1} = 9310 ± 90 K by a comparison of the observed spectra and the Kurucz models. The physical parameters of W UMi were derived by an analysis of our RV data together with the multi-band light curves of Devinney et al. The individual masses, radii, and luminosities of both components are M {sub 1} = 3.68 ± 0.10 M {sub ⊙} and M {sub 2} = 1.47 ± 0.04 M {sub ⊙}, R {sub 1} = 3.88 ± 0.03 R {sub ⊙} and R {sub 2} = 3.13 ± 0.03 R {sub ⊙}, and L {sub 1} = 102 ± 1 L {sub ⊙} and L {sub 2} = 7.3 ± 0.1 L {sub ⊙}, respectively. A comparison of these parameters with theoretical stellar models showed that the primary component lies in the main-sequence band, while the less massive secondary is noticeably evolved. The results indicate that the initially more massive star became the present secondary by losing most of its own mass via mass transfer to the companion (present primary).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Chandra Observation of Luminous and Ultraluminous X-ray Binaries in M101

X-ray binaries in the Milky Way are among the brightest objects on the X-ray sky. With the increasing sensitivity of recent missions, it is now possible to study X-ray binaries in nearby galaxies. We present data on six ultraluminous binaries in the nearby spiral galaxy, M101, obtained with Chandra ACIS-S. Of these, five appear to be similar to ultraluminous sources in other galaxies, while the brightest source, P098, shows some unique characteristics. We present our interpretation of the data in terms of an optically thick outflow, and discuss implications.

Mukai, K.↗
NASA NTRS2013

Contrasting Behaviour from Two Be/X-ray Binary Pulsars: Insights into Differing Neutron Star Accretion Modes

In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4 s and 85.4 s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and optical data available for this source suggest this spin-up is continuous during long phases of X-ray quiescence, where accretion driven spin-up of the neutron star should be minimal.

Magellanic Clouds↗
DOE OSTI2014

Synthesis of Bi{sub 2}S{sub 3} with different sulfur content by conventional high temperature solid state solvothermal route

Bismuth sulfide (Bi{sub 2}S{sub 3}) is a binary chalcogenide compound material belonging to V-VI group of semiconductors. Because of its direct band gap of 1.3 eV and high figure of merit (ZT) value, it is widely used as a thermo electronic-cooling material based on the Peltier effect. The electrical and optical property of Bi{sub 2}S{sub 3} material is strongly dependent on stoichiometric composition, defect chemistry and structure. In this study, we have synthesized Bi{sub 2}S{sub x} (x = 3.15, 3.30, 3.45) compound material with different sulfur content by conventional high temperature solid state solvothermal reaction of bismuth and sulfur. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDXS) analysis of synthesized compound materials were carried out to observe crystallinity, surface morphology and composition of elements in the compound. The optical analysis revealed that energy band gap decreases with increase of sulfur content.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗