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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Improved Constraints for the XUV Luminosity Evolution of Trappist-1

We re-examine the XUV luminosity evolution of TRAPPIST-1 utilizing new observational constraints of the current stellar parameters (XUV and bolometric luminosity) from multi-epoch X-ray/UV photometry. Following the formalism presented on Fleming et al. (2020), we infer that TRAPPIST-1maintained a saturated XUV luminosity, relative to the bolometric luminosity, of log10(LXUV/Lbol)=−3.03+0.25−0.23at early times for a period of tsat= 3.14+2.22−1.46Gyr. After the saturation phase, we find LXUV decayed over time by an exponential rate ofβXUV=−1.17+0.27−0.28. Compared to our inferred age of the system, age = 7.96+1.78−1.87Gyr, our result for tsat suggests that there is only a∼4% chance thatTRAPPIST-1 still remains in the saturated phase today, which is significantly lower than the previous estimate of 40%. Despite this reduction in tsat, our results remain consistent in the conclusion that the TRAPPIST-1 planets likely received an extreme amount XUV energy—an estimated integrated XUV energy of∼1030−1032erg over the star’s lifetime—that is∼15% lower than the original result.

Stellar evolution↗
NASA NTRS1991

Design of narrow band XUV and EUV coronagraphs using multilayer optics

A novel approach to the study of the solar corona is described, which enables observation of the soft X-ray (XUV), EUV, and FUV emission of the highly ionized ions present in the corona. The principal advantage of this approach is a relatively low contrast between the innner corona and the solar disk at the wavelengths involved; the contrast between coronal visible light and the XUV or EUV light is about 1. The design and the anticipated performances of the XUV and EUV coronagraphs using normal incidence multilayer optics are described.

Walker, A. B. C., Jr.↗
NASA NTRS2020

A Coupled Analysis of Atmospheric Mass Loss and Tidal Evolution in XUV Irradiated Exoplanets: The TRAPPIST-1 Case Study

Exoplanets residing close to their stars can experience evolution of both their physical structures and their orbits due to the influence of their host stars. In this work, we present a coupled analysis of dynamical tidal dissipation and atmospheric mass loss for exoplanets in X-ray and ultraviolet (XUV) irradiated environments. As our primary application, we use this model to study the TRAPPIST-1 system and place constraints on the interior structure and orbital evolution of the planets. We start by reporting on an ultraviolet continuum flux measurement (centered around ∼1900 Å) for the star TRAPPIST-1, based on 300 ks of Neil Gehrels Swift Observatory data, and which enables an estimate of the XUV-driven thermal escape arising from XUV photodissociation for each planet. We find that the X-ray flaring luminosity, measured from our X-ray detections, of TRAPPIST-1 is 5.6 × 10(exp −4) L(*), while the full flux including non-flaring periods is 6.1 × 10(exp −5) L*, when L(*) is TRAPPIST-1ʼs bolometric luminosity. We then construct a model that includes both atmospheric mass loss and tidal evolution and requires the planets to attain their present-day orbital elements during this coupled evolution. We use this model to constrain the ratio Q' = 3Q/2k2 for each planet. Finally, we use additional numerical models implemented with the Virtual Planet Simulator VPLanet to study ocean retention for these planets using our derived system parameters.

Juliette Becker↗
NASA NTRS1976

Space-resolved spectra of laser-produced plasmas in the XUV

The design and imaging properties of an XUV (extreme ultraviolet, 200-550 A) normal-incidence slitless spectrograph, the spectrum obtained from laser-generated plasmas, and the monochromatic plasma images are described. The electron temperature of the plasmas, electron density as a function of position in the plasma, and the thickness of material penetrated by the laser pulse are determined. Elements from Z = 6 to Z = 28 were investigated, in addition to Nb. Secondary plasma-emission regions were observed 2-3 mm from the flat (thick or thin) targets. Time-integrated photographs of the expanding plasmas were recorded by the slitless spectrograph. A technique for obtaining time-resolved images of the plasmas in picosecond time intervals is proposed, and problems in the design of a stigmatic XUV spectrograph are discussed.

Feldman, U.↗
NASA NTRS1975

The analysis of XUV emission lines

A technique for analyzing measurements of XUV spectral-line intensities is described. Application of the technique to OSO-4 and OSO-6 spectra indicates that the mean coronal temperature is 2.1 million K in typical active solar regions and that the mean coronal temperature in typical quiet regions ranges from 1.5 to 2.1 million K. One active-region spectrum shows evidence for substantial quantities of coronal material with temperatures between 2 and 3.5 million K. Measurements from limb spectra show evidence that (1) coronal abundances of N and O are low relative to heavier elements; or (2) that the ionization-equilibrium calculations used may contain systematic errors; or (3) that the XUV intensity measurements may be incorrectly calibrated.

Withbroe, G. L.↗
NASA NTRS1976

Channel electron multipliers - Detection efficiencies with opaque MgF2 photocathodes at XUV wavelengths

Detection efficiencies of channel electron multipliers (CEM) with opaque MgF2 photocathodes obtained in the extreme ultraviolet (XUV), 44 A to 990 A, are reported. A stable highly efficient response is reported for that interval, with no adverse effects on CEM performance. Efficiencies twice those of uncoated CEMs are obtained for 50 A to 350 A. The Mullard B419BL and Galileo 4510WL single-stage cone-cathode CEMs were used in the experiments. A rare-gas double ionization chamber was employed as absolute standard detector for 406 A to 990 A, and a flow Geiger counter filled with 96% argon and 4% isobutane for 44 A to 256 A. Absolute detection efficiencies are 10% higher from 67 A to 990 A when photocathodes are illuminated at an angle of incidence 45 deg. The photocathodes suffered no loss of response in storage (in vacuum or air) after an initial aging period. Effects of scattered UV radiation are greatly reduced when MgF2-coated CEMs are used in the XUV.

Lapson, L. B.↗
NASA NTRS1977

Thin aluminum filters for use on the Apollo Telescope Mount XUV spectrographs

Thin, unbacked, aluminum film filters were used on two extreme ultraviolet (XUV) instruments flown on the Apollo Telescope Mount of Skylab by the Naval Research Laboratory to transmit the XUV radiation while blocking the longer wavelength radiation that would saturate the detector. The requirements placed on these filters - large size, resistance to degradation by high acoustic and vibration fields, and low pinhole transmittances - were far more severe than those placed on any filters previously flown. Special techniques were developed for vacuum evaporation of the aluminum, removal of the films from the substrates, supporting the films and mounting them to obtain finished filters, and storing them so that no degradation took place. A description of these techniques will be given.

Schumacher, R. J.↗
NASA NTRS1977

Structure and dynamics of a solar flare - X-ray and XUV observations

Results are presented for an analysis of X-ray and XUV emission from the solar flare that occurred on September 5, 1973. X-ray emission was monitored by ionization chambers aboard the Solrad 9 satellite, and the XUV emission in the wavelength range 170-345 A was recorded by a slitless objective-grating spectroheliograph on Skylab. The physical parameters of the flare plasma, including temperature, density, volume, and magnetic-field configuration, are evaluated. A geometrical loop model is used to determine the volumes of the various emitting regions. The structure of the flare in the rise and decay phases is examined in detail, and conclusions about the effect of various dynamic processes in the flare plasma are made. A major finding is that continued energy release is required well into the flare decay phase. In the rise phase, energy is apparently released only along a small portion of a loop, and in the decay phase apparently throughout most of its length.

Dere, K. P.↗
NASA NTRS1981

Anti-Stokes scattering as an XUV radiation source

Harris (1977) has shown that laser induced scattering from atoms stored in a metastable level may be used to produce an XUV radiation source with several unique properties, including narrow linewidth, tunability, linear polarization, picosecond pulsewidth, and relatively high peak spectral brightness. The present investigation provides a summary concerning the progress made on the use of this radiation source as a unique instrument for XUV spectroscopy, and as a possible flashlamp for a 200 A laser. Zych et al. (1978) demonstrated that the maximum spectral brightness of the source is that of a blackbody with a temperature of the metastable storage level. The peak count rate and peak spectral brightness of the anti-Stokes emission at 569 A are 17 times and 139 times greater than those of the 584 A resonance line. The anti-Stokes process was employed as an external source of radiation for high resolution spectroscopy of the 3p6 shell of potassium. Attention is also given to emission spectroscopy of lithium, metastable levels which are appropriate for storage, and a hollow cathode discharge.

Harris, S. E.↗
NASA NTRS1984

Plasma diagnostics for the outer solar corona - UV and XUV Fe XII lines

The formation of the UV and XUV spectral lines of Fe XII in the outer corona was investigated. The results indicate that these lines can be an important tool for probing the physical conditions in the coronal regions where the solar wind is generated. The Fe XII lines can be particularly useful for determining outflow velocities of heavy ions in the solar wind and for providing critical empirical constraints on energy transport and dissipation mechanisms in the solar wind acceleration region. Application of the theoretical calculations to existing UV, EUV, and XUV observations of the low corona provide evidence that: (1) the inclusion of the effects of resonances in the collision strengths for the low-lying levels of Fe XII is important, (2) that the contributions of resonances for these levels are even larger than the estimates given in the present paper, and (3) that the collision strengths used here yield populations for these levels which are accurate to a factor of 2. These results have implications concerning the accuracy of abundances and densities derived from observations of the Fe XII lines in the low corona.

Withbroe, G. L.↗
NASA NTRS1990

The Ultra High Resolution XUV Spectroheliograph

The Ultra High Resolution XUV Spectroheliograph (UHRXS), a solar observatory planned for the Space Station Freedom, is described. The UHRXR instruments include nine XUV Ritchey-Chretien telescopes covering a spectral range of 70-350 A, which will provide images of solar atmosphere structures ranging in temperature from 50,000 to 20,000,000 K. The images will be obtained with spatial resolution that is an order of magnitude better than any other currently planned solar satellite experiment.

Walker, Arthur B. C., Jr.↗
NASA NTRS1992

The Ultra High Resolution XUV Spectroheliograph. III - A modified configuration for a free flying platform

The Ultra-High Resolution XUV Spectroheliograph (UHRXS) is a comprehensive solar observatory capable of studying solar phenomena at soft X-ray, XUV, EUV, and VUV wavelengths with normal incidence imaging multilayer telescopes capable of very high angular resolution (about 0.1 arcsec), and spectrographs able to achieve high spectral resolution. This instrument has been selected by NASA for flight as an attached payload on the Space Station Freedom. Recent developments have made it clear that accommodations for attached payloads on Freedom will not become available during the initial operations of Freedom and may never be available. We have studied the changes that must be made to place the UHRXS instrument on a Free Flying Plafform such as the Delta Launched Explorer Bus. We report on the configuration, performance, and accommodation on a free flying platform of the revised UHRXS concept.

Walker, Arthur B. C., Jr.↗
NASA NTRS1974

High angular resolution cosmic X-ray astronomy observations in the energy range 0.15-2 keV and XUV observations of nearby stars from an attitude controlled rocket

The construction of a two dimensional focusing Wolter Type I mirror system for X-ray and XUV astronomical observations from an Astrobee F sounding rocket is described. The mirror design goal will have a one degree field, a 20-arc seconds resolution, an effective area of about 50 sq cm at 1 keV and 10 sq cm at 0.25 keV on axis. A star camera provides aspect data to about 15-arc seconds. Two detectors are placed at the focus with an interchange mechanism to allow a detector change during flight. The following specific developments are reported: (1) position sensitive proportional counter development; (2) channel plate multiplier development; (3) telescope mirror development and payload structure; (4) Australian rocket flight results; (5) Comet Kohoutek He I observation; and (6) Vela, Puppis A, and Gem-Mon bright patch observations.

Garmire, G. P.↗
NASA NTRS1975

XUV results from Skylab

The extreme ultraviolet spectroheliograph of the Skylab-ATM experiment S082A recorded 1000 exposures during the mission, covering the wavelength range from 171 to 335 A or from 315 to 630 A. Each exposure recorded a spectrum of solar images with spatial resolution reaching 2 arc sec. Among the features observed were the chromospheric network, filaments, active regions, XUV bright points, the limb, spicules, prominences, coronal holes, and loops. During the mission, a number of flares were photographed; the images showed the changing form of a flare in different lines from the chromosphere to the corona as well as how this form changed during the course of the flare. The spectral images of a number of eruptive prominences were also recorded.

Tousey, R.↗