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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The color of polarization in cuprate superconductors

A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed, using a xenon light source (600 K color temperature), a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. One of the members of the electron carrier cuprate superconductors (Nd(1.85)Ce(.15)CuO(4-x) was examined and found that it possesses the same color of polarization as all the electron hole carrier cuprate superconductors so far examined. The commonality of the characteristic color in the cuprate superconductors indicated that the presence of this color is independent of the nature of charge carriers. The correlation of this color with existence of superconductivity suggests that the origin of the color relates to the origin of superconductivity in the cuprate superconductors. Photometric techniques are also discussed.

Hoff, H. A.↗
DOE OSTI2022

A warm super-Neptune around the G-dwarf star TOI-1710 revealed with TESS, SOPHIE, and HARPS-N

We report the discovery and characterization of the transiting extrasolar planet TOI-1710 b. It was first identified as a promising candidate by the Transiting Exoplanet Survey Satellite. Its planetary nature was then established with SOPHIE and HARPS-N spectroscopic observations via the radial-velocity method. The stellar parameters for the host star are derived from the spectra and a joint Markov chain Monte-Carlo adjustment of the spectral energy distribution and evolutionary tracks of TOI-1710. A joint MCMC analysis of the TESS light curve and the radial-velocity evolution allows us to determine the planetary system properties. From our analysis, TOI 1710 b is found to be a massive warm super-Neptune (M p = 28.3 ± 4.7 M ⊕ and R p = 5.34 ± 0.11 R ⊕ ) orbiting a G5V dwarf star (T eff = 5665 ± 55 K) on a nearly circular 24.3-day orbit (e = 0.16 ± 0.08). The orbital period of this planet is close to the estimated rotation period of its host star P rot = 22.5 ± 2.0 days and it has a low Keplerian semi-amplitude K = 6.4 ± 1.0 m s -1 ; we thus performed additional analyses to show the robustness of the retrieved planetary parameters. With a low bulk density of 1.03 ± 0.23 g cm -3 and orbiting a bright host star (J = 8.3, V = 9.6), TOI-1710 b is one of the best targets in this mass-radius range (near the Neptunian desert) for atmospheric characterization via transmission spectroscopy, a key measurement in constraining planet formation and evolutionary models of sub-Jovian planets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The GAPS programme at TNG

Neptunes represent one of the main types of exoplanets and have chemical-physical characteristics halfway between rocky and gas giant planets. Therefore, their characterization is important for understanding and constraining both the formation mechanisms and the evolution patterns of planets. We investigate the exoplanet candidate TOI-1422 b, which was discovered by the TESS space telescope around the high proper-motion G2 V star TOI-1422 (V = 10.6 mag), 155 pc away, with the primary goal of confirming its planetary nature and characterising its properties. We monitored TOI-1422 with the HARPS-N spectrograph for 1.5 yr to precisely quantify its radial velocity (RV) variation. We analyse these RV measurements jointly with TESS photometry and check for blended companions through high-spatial resolution images using the AstraLux instrument. We estimate that the parent star has a radius of R$_\star$ = 1.019 -0.013 +0.014 R ⊙ , and a mass of M$_\star$ = 1.019 -0.013 +0.014 M ⊙ . Our analysis confirms the planetary nature of TOI-1422 b and also suggests the presence of a Neptune-mass planet on a more distant orbit, the candidate TOI-1422 c, which is not detected in TESS light curves. The inner planet, TOI-1422 b, orbits on a period of P b = 12.9972 ± 0.0006 days and has an equilibrium temperature of T eq,b = 867 ± 17 K. With a radius of R b = 3.96 -0.11 +0.13 R ⊕ , a mass of M b = 9.0 -2.0 +2.3 M ⊕ and, consequently, a density of ρ b = 0.795 -0.235 +0.290 g cm -3 , it can be considered a warm Neptune-sized planet. Compared to other exoplanets of a similar mass range, TOI-1422 b is among the most inflated, and we expect this planet to have an extensive gaseous envelope that surrounds a core with a mass fraction around 10% – 25% of the total mass of the planet. The outer non-transiting planet candidate, TOI-1422 c, has an orbital period of P c = 29.29 -0.20 +0.21 days, a minimum mass, M c sin i, of 11.1 -2.3 +2.6 M ⊕ , an equilibrium temperature of T eq,c = 661 ± 13 K and, therefore, if confirmed, could be considered as another warm Neptune.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Studying baryon acoustic oscillations using photometric redshifts from the DESI Legacy Imaging survey DR9

Context. The Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Survey DR9 (DR9 hereafter), with its extensive dataset of galaxy locations and photometric redshifts, presents an opportunity to study baryon acoustic oscillations (BAOs) in the region covered by the ongoing spectroscopic survey with DESI. Aims. We aim to investigate differences between different parts of the DR9 footprint. Furthermore, we want to measure the BAO scale for luminous red galaxies within them. Our selected redshift range of 0.6–0.8 corresponds to the bin in which a tension between DESI Y1 and eBOSS was found. Methods. We calculated the anisotropic two-point correlation function in a modified binning scheme to detect the BAOs in DR9 data. We then used template fits based on simulations to measure the BAO scale in the imaging data. Results. Our analysis reveals the expected correlation function shape in most of the footprint areas, showing a BAO scale consistent with Planck’s observations. Aside from identified mask-related data issues in the southern region of the South Galactic Cap, we find a notable variance between the different footprints. Conclusions. We find that this variance is consistent with the difference between the DESI Y1 and eBOSS data, and it supports the argument that that tension is caused by sample variance. Additionally, we also uncovered systematic biases not previously accounted for in photometric BAO studies. We emphasize the necessity of adjusting for the systematic shift in the BAO scale associated with typical photometric redshift uncertainties to ensure accurate measurements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry

Infrared observations of metastable 2{sup 3}S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet’s upper atmosphere. Here, we present a new photometric technique to measure metastable 2{sup 3}S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498% ± 0.045% (11.1σ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass-loss rate for WASP-69b to be 5.25{sub −0.46}{sup +0.65}×10{sup −4} M{sub J} Gyr{sup −1} (3.32{sub −0.56}{sup +0.67}×10{sup −3} M{sub J} Gyr{sup −1}) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of 2.1×10{sup −4} M{sub J} Gyr{sup −1} (2.1×10{sup −3} M{sub J} Gyr{sup −1}). These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

Particle and optical measurements in the magnetic noon sector of the auroral oval

Simultaneous airborne photometric and satellite particle measurements in the mid-day sector of the auroral oval, around magnetic local noon, are presented. The two sets of measurements are employed independently to delineate various magnetospheric boundaries. The results derived from the particle measurements are compared with those from the photometric observations to assess the reliability of the photometric technique in identifying various magnetospheric regions.

Sivjee, G. G.↗
NASA NTRS1980

An investigation of previously derived Hyades, Coma, and M67 reddenings

New Hyades polarimetry and field star photometry were obtained to check the Hyades reddening, which was found to be nonzero in a previous study (Taylor, 1978). The new Hyades polarimetry implies essentially zero reddening. Four photometric techniques which are assumed to be insensitive to blanketing are used to compare the Hyades to nearby field stars and are found to yield essentially zero reddening. A simultaneous solution for the Hyades, Coma, and M67 reddenings is made, and the results are E(B-V) = 3 plus or minus 2(sigma) mmag, -1 plus or minus 3(sigma) mmag, and 46 plus or minus 6(sigma) mmag, respectively.

Taylor, B. J.↗
NASA NTRS1981

Introductory remarks: Photometry section

The principal goals of photometry and polarimetry are summarized. These goals include studies of the emission features of gaseous species of comets, the wavelength depenence of albedo, the phase function of scatter distribution, and time variation of rotation. Recent advances in photometric techniques were reviewed and include: use of proper filters, extension to the shortest and longest wavelengths, higher spectral resolving power, and polarizaton techniques.

Ahearn, M. F.↗
NASA NTRS1981

Detection of a temperature deficit in magnetic faculae at the solar photosphere

A photometric technique is presented which allows the observation of faculae across the entire solar disk. A clean continuum was used and granular noise was reduced by subtracting simultaneous spectroheliograms taken at widely separated points of the photospheric radiation curve. Spectroheliographic observations taken from March 12-14, 1980, using two color-scans in the green at gamma 4980.96 and gamma 5256.31 in the fourth order resulted in observation of clean continua in the red at gamma 6641.85 and gamma 7008.8 in another slot of the magnetograph. Approximately 20 raster scans were obtained and indications were found that dark magnetic facular structures in the Delta signal were cooler than the photosphere at equal optical continuum depths

Foukal, P.↗
NASA NTRS1984

Discovery of the first carbon star in NGC 6822

A new photometric technique has been developed for detecting carbon and M stars in distant stellar systems, leading to isolation of carbon-star candidates in a number of Local-Group galaxies. One of the brighter candidates in NGC 6822 has been confirmed spectroscopically; at a distance of approximately 0.5 Mpc, it is the first truly extragalactic carbon star to be positively identified. The star has M(I) = about -5.7 mag, placing it near the upper-luminosity end of known carbon stars in the Magellanic Clouds.

Aaronson, M.↗
NASA NTRS1990

Outer planets; Proceedings of Symposium 4 and the Topical Meeting of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

Various papers on the magnetospheres, atmospheres, satellites, and rings of the outer planets are presented. Individual topics addressed include: thermal plasma in outer planet magnetospheres, neutral gas-plasma interaction in the Io plasma torus, satellite-plasma interactions, comparison of planetary magnetic fields, energization process of trapped particles in outer planets, remote sensing of planetary plasma, comparison of the deep atmospheres of the giant planets, seasonal thermal structure of giant planet atmospheres, CCD imaging of Neptune at methane-band wavelengths, physical parameters for the Uranus atmosphere, Uranus photochemistry, Uranus electroglow production, vibrationally excited H2 in Saturn's upper atmosphere, Titan, origin of outer planet satellite systems, microphysical modeling of Titan's aerosols, tectonics of icy satellites, geological evolution of Ganymede, photometric techniques for atmosphereless solar system bodies, the new rings, narrow rings, and time variability of the Jovian system.

Johnson, T. V.↗
NASA NTRS1993

Multi-filter spectrophotometry of quasar environments

A many-filter photometric technique for determining redshifts and morphological types, by fitting spectral templates to spectral energy distributions, has good potential for application in surveys. Despite success in studies performed on simulated data, the results have not been fully reliable when applied to real, low signal-to-noise data. We are investigating techniques to improve the fitting process.

Craven, Sally E.↗
NASA NTRS1993

Seeing ghosts - Photometry of Saturn's G Ring

Saturn's faint and narrow G Ring is only visible to the eye in two Voyager images, each taken at a rather high solar phase angle of about 160 deg. In this paper we introduce a new photometric technique for averaging across multiple Voyager images, and use it to detect the G Ring at several additional viewing geometries. The resultant phase curve suggests that the G Ring is composed of dust particles obeying a very steep power-law size distribution. The dust is generally smaller than that seen in other rings, ranging down to 0.03 micron. The G Ring occupies the region between orbital radii 166,000 and 173,000 km, and has a peak somewhat closer to the inner edge. Based on these limits, we demonstrate that Voyager 2 passed through and directly sampled this ring during its 1981 encounter with Saturn. Combined analysis of additional data sets suggests that a population of larger bodies is also present in the G Ring; these bodies occupy a narrower band near the observed peak and are likely the source for the visible dust. Based on some preliminary dynamical models, we propose that these larger bodies represent leftover debris from the collisional breakup of a small moon in Saturn's distant past.

Showalter, Mark R.↗
NASA NTRS2000

WFPC2 Stellar Photometry with HSTphot

HSTphot, a photometry package designed to handle the undersampled PSFs found in WFPC2 images, is introduced and described, as well as some of the considerations that have to be made in order to obtain accurate PSF-fitting stellar photometry with WFPC2 data. Tests of HSTphot's internal reliability are made using multiple observations of the same field, and tests of external reliability are made by comparing with DoPHOT reductions of the same data. Subject headz'ngs: techniques: photometric

Dolphin, Andrew E.↗
NASA NTRS2005

Lower Thermospheric Composition Studies in the Auroral Zone

This TIMED/CEDAR grant had two major objectives. The GUVI instrument on TIMED should routinely produces maps of the flux of energetic particles and their average energy. However, while those data will be available soon there were no plans to routinely produce the O/N2 ratio in the auroral. Ground-based photometric techniques have been available for years which routinely measure all three quantities in the auroral zone. The first objective of the previous proposal was to use these ground-based techniques to provide some validation for the routine measure of average energy. The second objective was to use the ground-based to data to validate GUVI algorithms for the measure of O/N2 in the auroral zone. We have made some progress to these goals while we await the release of the properly precessed GUVI data. For now these objectives are being addressed by making use of algorithms by one of us (Doug Strickland of CPI) that are being used for specific GUVI level 1B data sets that contain data coincident with the groundbased measurements. Also we have collected ground-based data from two Alaska sites and they are available on our web site and on the CEDAR website. The details of the progress we have made are discussed.

Hecht, James↗
NASA NTRS2006

Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441

We have applied Alard's image subtraction method (ISIS v2.1) to the observations of the globular clusters NGC 6388 and NGC 6441 previously analyzed using standard photometric techniques (DAOPHOT, ALLFRAME). In this reanalysis of observations obtained at CTIO, besides recovering the variables previously detected on the basis of our ground-based images, we have also been able to recover most of the RR Lyrae variables previously detected only in the analysis of Hubble Space Telescope WFPC2 observations of the inner region of NGC 6441. In addition, we report five possible new variables not found in the analysis of the EST observations of NGC 6441. This dramatically illustrates the capabilities of image subtraction techniques applied to ground-based data to recover variables in extremely crowded fields. We have also detected twelve new variables and six possible variables in NGC 6388 not found in our previous groundbased studies. Revised mean periods for RRab stars in NGC 6388 and NGC 6441 are 0.676 day and 0.756 day, respectively. These values are among the largest known for any galactic globular cluster. Additional probable type II Cepheids were identified in NGC 6388, confirming its status as a metal-rich globular cluster rich in Cepheids.

Corwin, Michael T.↗
NASA NTRS2010

Detection of Planetary Emission from the Exoplanet TrES-2 Using Spitzer/IRAC

We present here the results of our observations of TrES-2 using the Infrared Array Camera on Spitzer. We monitored this transiting system during two secondary eclipses, when the planetary emission is blocked by the star. The resulting decrease in flux is 0.127% +/- 0.021%, 0.230% +/- 0.024%, 0.199% +/- 0.054%, and 0.359% +/- 0.060% at 3.6 microns, 4.5 microns, 5.8 microns, and 8.0 microns, respectively. We show that three of these flux contrasts are well fit by a blackbody spectrum with T(sub eff) = 1500 K, as well as by a more detailed model spectrum of a planetary atmosphere. The observed planet-to-star flux ratios in all four lRAC channels can be explained by models with and without a thermal inversion in the atmosphere of TrES-2, although with different atmospheric chemistry. Based on the assumption of thermochemical equilibrium, the chemical composition of the inversion model seems more plausible, making it a more favorable scenario. TrES-2 also falls in the category of highly irradiated planets which have been theoretically predicted to exhibit thermal inversions. However, more observations at infrared and visible wavelengths would be needed to confirm a thermal inversion in this system. Furthermore, we find that the times of the secondary eclipses are consistent with previously published times of transit and the expectation from a circular orbit. This implies that TrES-2 most likely has a circular orbit, and thus does not obtain additional thermal energy from tidal dissipation of a non-zero orbital eccentricity, a proposed explanation for the large radius of this planet. Key words: eclipses - infrared: stars - planetary systems - stars: individual (OSC 03549-02811) - techniques: photometric

Donovan, Francis T.↗
NASA NTRS2014

The Flux of Large Meteoroids Observed with Lunar Impact Monitoring

The flux of large meteoroids is not well determined due to relatively low number statistics, due mainly to the lack of collecting area available to meteor camera systems (10(2)-10(5) km2). Larger collecting areas are needed to provide reasonable statistics for flux calculations. The Moon, with millions of square kilometers of lunar surface, can be used as a detector for observing the population of large meteoroids in the tens of grams to kilogram mass range. This is accomplished by observing the flash of light produced when a meteoroid impacts the lunar surface, converting a portion of its kinetic energy to visible light detectable from Earth. A routine monitoring program at NASA's Marshall Space Flight Center has recorded over 300 impact flashes since early 2006. The program utilizes multiple 0.35 m (14 inch) Schmidt-Cassegrain telescopes, outfitted with video cameras using the 1/2 inch Sony EXview HAD CCDTM chip, to perform simultaneous observations of the earthshine hemisphere of the Moon when the lunar phase is between 0.1 and 0.5. This optical arrangement permits monitoring of approximately 3.8x10(6) km2 of lunar surface. A selection of 126 flashes recorded in 266.88 hours of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques outlined in [1] were applied to the video to determine the luminous energy, kinetic energy, and mass for each impactor, considering a range of luminous efficiencies. The flux to a limiting energy of 2.5x10(-6) kT TNT or 1.05×10(7) J is 1.03×10(-7) km(-2) hr(-1) and the flux to a limiting mass of 30 g is 6.14×10(-10) m(-2) yr(-1). Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than the power law distribution determined for the near Earth object population by [2].

Cooke, W. J.↗