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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Locating the Periodic Transient GRO J1849-03; Gamma-Ray Luminous Supernovae Remnants

We obtained one 50 ks observation of the Monoceros supernova remnant under this proposal. This supernova remnant was selected because it overlaps the error box of a gamma-ray source. Much to our surprise, we discovered a hard x-ray point source instead of the diffuse hard x-ray emission we expected from the supernova remnant. A paper on the discovery of the hard x-ray source and on follow-up optical observations identifying a likely Bestar companion was published in the Astrophysical Journal. Subsequently, a reanalysis of the same data yielded the detection of pulsations from the x-ray source. These results were also published in the Astrophysical Journal. Subsequent x-ray observations, which we performed under later proposals, have shown that the x-ray pulsar has a characteristic spin-down age of less than 1400 years in a binary system. The system is likely the first discovered very young, highly-energetic, rotation-powered pulsar in a binary system and offers an exciting opportunity to study the infancy and early evolution of neutron-star binaries.

Kaaret, P.↗
NASA NTRS2000

A Study of the Planetary Nebula M57

We present an overview of the objects known as planetary nebulae. These emission nebulae are the end-product of the evolution of a dying star. our ground-based imagery is of the most famous of these objects, M57, also known as the Ring Nebula. Taken with the 2.12-meter telescope at San Pedro Matir in Baja, Mexico, these seeing-limited images show variations in ionization, density and temperature as a function of position in the nebula. Our ground-based imagery is compared to similar HST archival images.

Archie, Deithra↗
NASA NTRS2003

Isotopic Composition of Silicon Carbide in the CO3 Chondrite Colony

Presolar grains have been identified in primitive members of all chondrite classes. The isotopic compositions of presolar grains provide probes of galactic evolution and nucleosynthesis in stars, while the abundances and characteristics of presolar grains contain a record of thermal processing in the solar system. Most of the detailed isotopic work has been done on SiC from Murchison and Orgueil, supplemented by a few studies of ordinary and enstatite chondrites. This work investigates SiC in the Colony CO3.O meteorite. SiC is present in Colony at a matrix-normalized abundance of approximately 3.7 ppm, much less than in CI chondrites and the matrixes of CM and primitive ordinary and enstatite chondrites. The abundances of SiC and other presolar grains in Colony seem to correlate with the chemical processing that produced CO3 chondrites. This implies that the known presolar grains experienced the same processing as the bulk CO3 material and assumes that the parent material was the same as that for other chondrites, including CI. That parent material is most plausibly the average material in the sun s parent molecular cloud. One test of this idea is to look for primary differences between SiC in Colony (and other meteorites) and that in CI and CM chondrites. True differences not related to thermal processing would falsify the assumption that all chondrite classes originated from the same reservoir of presolar dust.

Smith, J. B.↗
NASA NTRS2004

Nitrogen and Carbon Isotopic Composition of Silicon Carbide in the CO3.0 Meteorite ALHA 77307, a NanoSIMS Study

Presolar grains have been identified in primitive members of all chondrite classes [1, 2]. The study of the isotopic compositions of presolar grains provides information on galactic evolution and nucleosynthesis in stars [3, 4], while the abundances and characteristics of presolar grains contain a record of thermal processing in the solar system [2, 5]. Much of the detailed work on presolar silicon carbide grains has focused on Murchison [e.g., 2] and Orgueil [4], but several other carbonaceous [6, 7], ordinary, and enstatite chondrites [8-11] have also been studied. This study investigates the isotopic composition of silicon carbide from the CO3.0 carbonaceous chondrites ALHA77307 and Colony. SiC is present in ALHA77307 at a matrix normalized abundance of ~8.8 ppm [5], which is approximately twice the abundance of Colony [5], but less than in CI chondrites and the matrices of CM and primitive ordinary and enstatite chondrites [3]. The abundances of SiC and other presolar grains in ALHA77307 seem to correlate with the degree of chemical processing that produced CO3 chondrites [2, 5]. This implies that the same nebular processing that produced the bulk composition of the CO3 chondrite class also modified the assemblage of known presolar grains [5]. To test whether all chondrite classes originated from the same reservoir of presolar dust it is necessary to look for primary differences, not related to thermal processing, between SiC in CO3 chondrites and other chondritic meteorites.

Smith, J. B.↗
NASA NTRS2004

The Generation-X X-ray Observatory Vision Mission and Technology Study

The new frontier in astrophysics is the study of the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy opens a window into these objects by studying the emission from black holes, supernova explosions and the gamma-ray burst afterglows of massive stars. However, such objects are beyond the grasp of current or near-future observatories. X-ray imaging and spectroscopy of such distant objects will require an X-ray telescope with large collecting area and high angular resolution. Our team has conceived the Generation-X Vision Mission based on an X-ray observatory with 100 sq m collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such an observatory would be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. NASA has selected the Generation-X mission for study under its Vision Mission Program. We describe the studies being performed to develop the mission concept and define candidate technologies and performance requirements for Generation-X. The baseline Generation-X mission involves four 8m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required aerial density of at least 100 times lower than in Chandra, we will study 0.1mm thick mirrors which have active on-orbit figure control. We discuss the suite of required detectors, including a large FOV high angular resolution imager, a cryogenic imaging spectrometer and a grating spectrometer. We outline the development roadmap to confront the many technological challenges far implementing the Generation-X mission.

Figueroa-Feliciano, Enectali↗
NASA NTRS2005

Mission Study for Generation-X: A Large Area and High Angular Observatory to Study the Early Universe

In this report we provide a summary of the technical progress achieved during the last year Generation-X Vision Mission Study. In addition, we provide a brief programmatic status. The Generation-X (Gen-X) Vision Mission Study investigates the science requirements, mission concepts and technology drivers for an X-ray telescope designed to study the new frontier of astrophysics: the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy offers an opportunity to detect these via the activity of the black holes, and the supernova explosions and gamma-ray burst afterglows of the massive stars. However, such objects are beyond the grasp of current missions which are operating or even under development. Our team has conceived a Gen-X Vision Mission based on an X-ray observatory with 100 m2 collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such a high energy observatory will be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. In our study we develop the mission concept and define candidate technologies and performance requirements for Gen-X. The baseline Gen-X mission involves four 8 m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26 m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required areal density of at least 100 times lower than for Chandra, we study 0.2 mm thick mirrors which have active on-orbit figure control. We also study the suite of required detectors, including a large FOV high angular resolution imager, a cryogenic imaging spectrometer and a reflection grating spectrometer.

Brissenden, Roger↗
NASA NTRS2004

Chondrites and the Protoplanetary Disk, Part 1

The papers discussed the following: The Formation Process of Adhering and Consorting Compound Chondrules Inferred Their Petrology and Major-Element Composition. The Prospect of High-Precision Pb Isotopic Dating of Meteorites. Evolution of UV-Irradiated Protoplanetary Disks. A Model for the Formation of E Chondrites. Oxygen Isotopic Diffusion and Exchange Experiments on Olivine and Chondrule Melts: Preliminary Results. Shock Heating: Origin of Shock Waves in the Protoplanetary Disk. Thermal Structures of Protoplanetary Disks. Meteoritical Astrophysics: A New Subdiscipline. Origin and Thermal History of FeNi-Metal in Primitive Chondrites. The Collisions of Chondrules Behind Shock Waves. Primary Signatures of the Nebular Dust Preserved in Accretionary Rims and Matrices of CV Chondrites. History of Thermally Processed Solids in the Protoplanetary Disk: Reconciling Theoretical Models and Meteoritical. Evidence Evaporation and Condensation During CAI and Chondrule Formation. Shock Heating: Effects on Chondritic Material. Rhounite-bearing Inclusions E201 and E202 from Efremovka: Constraints from Trace. Element Measurements Element Mapping in Anhydrous IDPs: Identification of the Host Phases of Major/Minor Elements as a Test of Nebula Condensation Models. Theoretical Studies of Disk Evolution Around Solar Mass Stars. Chemical Effects of High-Temperature Processing of Silicates. I-Xe and the Chronology of the Early Solar System. The Effects of X-Rays on the Gas and Dust in Young Stellar Objects. Origin of Short-lived Radionuclides in the Early Solar System. On Early Solar System Chronology: Implications of an Initially Heterogeneous Distribution of Short-lived Radionuclides. The Origin of Short-lived Radionuclides and Early Solar System Irradiation. Disequilibrium Melting and Oxygen Isotope Exchange of CAIs and Chondrules in the Solar Nebula. Mineralogy and Chemistry of Fine-grained Matrices, Rims, and Dark Inclusions in the CR Carbonaceous Chondrites Acfer/El Djouf 001 and the Ungrouped Carbonaceous Chondrites Acfer 094 and Adelaide. Oxygen Isotopes of Aluminum-rich Chondrules from Unequilibrated Enstatite Chondrites.

Source record↗
NASA NTRS2012

Microlensing Signature of Binary Black Holes

We calculate the light curves of galactic bulge stars magnified via microlensing by stellar-mass binary black holes along the line-of-sight. We show the sensitivity to measuring various lens parameters for a range of survey cadences and photometric precision. Using public data from the OGLE collaboration, we identify two candidates for massive binary systems, and discuss implications for theories of star formation and binary evolution.

Schnittman, Jeremy↗
NASA NTRS2012

The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

The light emitted by stars and accreting compact objects through the history of the universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL isimportant to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited by galactic and other foreground emissions. Here, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z approx. 1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to ultraviolet frequencies and allowed us to measure the EBL flux density in this frequency band.

background↗
NASA NTRS2014

The Origin of the Local 1/4-KeV X-Ray Flux in Both Charge Exhange and a Hot Bubble

The solar neighbourhood is the closest and most easily studied sample of the Galactic interstellar medium, an understanding of which is essential for models of star formation and galaxy evolution. Observations of an unexpectedly intense diffuse flux of easily absorbed 1/4-kiloelectronvolt X-rays coupled with the discovery that interstellar space within about a hundred parsecs of the Sun is almost completely devoid of cool absorbing gas, led to a picture of a 'local cavity' filled with X-ray-emitting hot gas, dubbed the local hot bubble. This model was recently challenged by suggestions that the emission could instead be readily produced within the Solar System by heavy solar-wind ions exchanging electrons with neutral H and He in interplanetary space, potentially removing the major piece of evidence for the local existence of million-degree gas within the Galactic disk. Here we report observations showing that the total solar wind charge-exchange contribution is approximately 40 percent of the 1/4-keV flux in the Galactic plane. The fact that the measured flux is not dominated by charge exchange supports the notion of a million-degree hot bubble extending about a hundred parsecs from the Sun.

Charge exhange and a hot bubble↗
NASA NTRS2016

Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

Aller, Monique C.↗
NASA NTRS2016

Optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): Delay Lines and Alignment

We present the optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) as it gets ready for launch. BETTII is an 8-meter baseline far-infrared (30-90 microns) interferometer mission with capabilities of spatially resolved spectroscopy aimed at studying star formation and galaxy evolution. The instrument collects light from its two arms, makes them interfere, divides them into two science channels (30-50 microns and 60-90 microns), and focuses them onto the detectors. It also separates out the NIR light (1-2.5 microns) and uses it for tip-tilt corrections of the telescope pointing. Currently, all the optical elements have been fabricated, heat treated, coated appropriately and are mounted on their respective assemblies. We are presenting the optical design challenges for such a balloon borne spatio-spectral interferometer, and discuss how they have been mitigated. The warm and cold delay lines are an important part of this optics train. The warm delay line corrects for path length differences between the left and the right arm due to balloon pendulation, while the cold delay line is aimed at introducing a systematic path length difference, thereby generating our interferograms from where we can derive information about the spectra. The details of their design and the results of the testing of these opto-mechanical parts are also discussed. The sensitivities of different optical elements on the interferograms produced have been determined with the help of simulations using FRED software package. Accordingly, an alignment plan is drawn up which makes use of a laser tracker, a CMM, theodolites and a LUPI interferometer.

Dhabal, Arnab↗
NASA NTRS2019

Near-infrared Spectroscopy of Galaxies During Reionization: Measuring C III] in a Galaxy at z = 7.5

We present Keck/MOSFIRE H-band spectroscopy targeting C III] λ1907, 1909 in a z = 7.5056 galaxy previously identified via Lyα emission. We detect strong line emission at 1.621 ± 0.002 mm with a line flux of (2.63 ± 0.52) × 10−18 erg s−1cm−2. We tentatively identify this line as [C III] λ1907, but we are unable to detect C III] λ1909 owing to sky emission at the expected location. This gives a galaxy systemic redshift, zsys = 7.5032 ± 0.0003, with a velocity offset to Lyα of DvLya = 88 ± 27 km s−1. The ratio of combined C III]/Lyα is 0.30–0.45, one of the highest values measured for any z > 2 galaxy. We do not detect Si III] λλ1883, 1892, and place an upper limit on Si III]/C III] < 0.35 (2σ). Comparing our results to photoionization models, the C III] equivalent width (WC III] = 16.23 ± 2.32 Å), low Si III]/C III] ratio, and high implied [O III] equivalent width (from the Spitzer/IRAC [3.6]–[4.5] ~- 0.8 mag color) require subsolar metallicities (Z ~- 0.1–0.2 Zsun) and a high ionization parameter, log U >~ 1.5. These results favor models that produce higher ionization, such as the BPASS models for the photospheres of high-mass stars, and that include both binary stellar populations and/or an IMF that extends to 300 Me. The combined C III] equivalent width and [3.6]–[4.5] color are more consistent with ionization from young stars than active galactic nuclei (AGNs); however, we cannot rule out ionization from a combination of an AGN and young stars. We make predictions for James Webb Space Telescope spectroscopy using these different models, which will ultimately test the nature of the ionizing radiation in this source.

reionization↗
NASA NTRS2022

Exploring the MeV Sky With A Combined Coded Mask and Compton Telescope: the Galactic Explorer With A Coded Aperture Mask Compton Telescope (GECCO)

The sky at MeV energies is currently poorly explored. Here we present an innovative mission concept that builds upon the heritage of past and current missions improving the sensitivity and, very importantly, the angular resolution. This consists in combining a Compton telescope and a coded-mask telescope. We delineate the motivation for such a concept and we define the scientific goals for such a mission. The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel concept for a next-generation telescope covering hard X-ray and soft gamma-ray energies. The potential and importance of this approach that bridges the observational gap in the MeV energy range are presented. With the unprecedented angular resolution of the coded mask telescope combined with the sensitive Compton telescope, a mission such as GECCO can disentangle the discrete sources from the truly diffuse emission. Individual Galactic and extragalactic sources are detected. This also allows to understand the gamma-ray Galactic center excess and the Fermi Bubbles, and to trace the low-energy cosmic rays, and their propagation in the Galaxy. Nuclear and annihilation lines are spatially and spectrally resolved from the continuum emission and from sources, addressing the role of low-energy cosmic rays in star formation and galaxy evolution, the origin of the 511 keV positron line, fundamental physics, and the chemical enrichment in the Galaxy. Such an instrument also detects explosive transient gamma-ray sources, which, in turn, enables identifying and studying the astrophysical objects that produce gravitational waves and neutrinos in a multi-messenger context. By looking at a poorly explored energy band it also allows discoveries of new astrophysical phenomena.

Elena Orlando↗
NASA NTRSDate not supplied

A New Era of Astrophysics with NASA’s JWST

JWST - launched December 25, 2021 - is poised to change the way we understand the universe, and we are already making some groundbreaking discoveries in just the first several months of operations. I will discuss the engineering milestones that made the mission possible, as well as the over-arching scientific themes/goals of the telescope: first galaxies around the time of cosmic reionization, galaxy assembly and evolution, the birth of stars & protoplanetary systems, and study of planets (both within the solar system and exoplanets). I will also discuss specific scientific programs approved for Cycle 1, as well as early results from the mission.

James Webb Space Telescope↗
NASA NTRS2023

A Hunting Expedition For High-Order Hierarchies

Stellar hierarchical systems of high order containing more than three stars are rare and fascinating objects; their disco v ery and study highlight still unknown aspects of star formation and early evolution. We matched eclipsing binaries disco v ered by Transiting Exoplanet Surv e y Satellite with a Gaia catalogue of wide binaries and selected candidate quadruple (or higher order) systems based on e xcessiv e astrometric noise. A subset of 192 southern candidates located within 500 pc was observed by speckle interferometry, and we resolved for the first time 50 close pairs, confirming their high-order (from four to five components) multiplicity. These observations are reported, and some remarkable hierarchical systems are discussed.

Brian P Powell↗
DOE OSTI2021

Successive common envelope events from multiple planets

ABSTRACT Many stars harbour multiplanet systems. As these stars expand late in their evolutions, the innermost planet may be engulfed, leading to a common envelope (CE) event. Even if this is insufficient to eject the envelope, it may expand the star further, causing additional CE events, with the last one unbinding what remains of the envelope. This multiplanet CE scenario may have broad implications for stellar and planetary evolution across a range of systems. We develop a simplified version and show that it may be able to explain the recently observed planet WD 1856 b.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1986

UV observations of blue stragglers and population 2 K dwarfs

Blue stragglers are stars, found usually in either open or globular clusters, that appear to lie on the main sequence, but are brighter and bluer than the cluster turn-off. Currently, two rival models are invoked to explain this apparently pathological behavior: internal mixing (so that fresh fuel is brought into the stellar core); and mass transfer (by which a normal main sequence star acquires mass from an evolving nearby companion and so moves up the main sequence). The latter model predicts that in the absence of complete mass transfer (i.e., coalescence), blue stragglers should be binary systems with the fainter star in a post-main sequence evolutionary state. It is important to ascertain the cause of this phenomenon since stellar evolution models of main sequence stars play such a vital role in astronomy. If mass transfer is involved, one may easily exclude binaries from age determinations of clusters, but if mixing is the cause, our age determinations will be much less accurate unless we can determine whether all stars or only some mix, and what causes the mixing to occur at all.

Carney, B. W.↗