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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Constraints on core-collapse supernova progenitors from explosion site integral field spectroscopy

Observationally, supernovae (SNe) are divided into subclasses according to their distinct characteristics. This diversity naturally reflects the diversity in the progenitor stars. It is not entirely clear, however, how different evolutionary paths leading massive stars to become an SN are governed by fundamental parameters such as progenitor initial mass and metallicity. Furthermore, this paper places constraints on progenitor initial mass and metallicity in distinct core-collapse SN subclasses through a study of the parent stellar populations at the explosion sites. Integral field spectroscopy (IFS) of 83 nearby SN explosion sites with a median distance of 18 Mpc has been collected and analysed, enabling detection and spectral extraction of the parent stellar population of SN progenitors. From the parent stellar population spectrum, the initial mass and metallicity of the coeval progenitor are derived by means of comparison to simple stellar population models and strong-line methods. Additionally, near-infrared IFS was employed to characterise the star formation history at the explosion sites. No significant metallicity differences are observed among distinct SN types. The typical progenitor mass is found to be highest for SN type Ic, followed by type Ib, then types IIb and II. Type IIn is the least associated with young stellar populations and thus massive progenitors. However, statistically significant differences in progenitor initial mass are observed only when comparing SNe IIn with other subclasses. Stripped-envelope SN progenitors with initial mass estimates lower than 25 M ⊙ are found; they are thought to be the result of binary progenitors. Confirming previous studies, these results support the notion that core-collapse SN progenitors cannot arise from single-star channels only, and both single and binary channels are at play in the production of core-collapse SNe. Near-infrared IFS suggests that multiple stellar populations with different ages may be present in some of the SN sites. As a consequence, there could be a non-negligible amount of contamination from old populations, and therefore the individual age estimates are effectively lower limits.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

Estimates of surface roughness derived from synthetic aperture radar (SAR) data

Radar remote sensing data provide a unique perspective of the earth's crust and the processes that have influenced its evolution. Physically based models are required, however, to relate the geophysical quantities being measured by the radar sensor to useful geologic information. In this study, synthetic aperture radar (SAR) data over the Cima volcanic field in the Mojave Desert of California are quantitatively connected with microtopography through inversion of a radar backscatter model. Changes in surface roughness inferred from the derived microtopography are modeled and found to be consistent with aeolian mantling as surfaces age. Estimated rates of aeolian deposition for the Cima area are compared to the Lunar Crater volcanic field in Nevada. Rates of deposition appear to be higher at Cima volcanic field, most likely because of its proximity to Soda Lake, the main source of the aeolian material.

Evans, Diane L.↗
DOE OSTI2017

Nearby Young, Active, Late-type Dwarfs in Gaia's First Data Release

The Galex Nearby Young Star Survey (GALNYSS) has yielded a sample of ∼2000 UV-selected objects that are candidate nearby (D≲150 pc), young (age ∼ 10–100 Myr), late-type stars. Here, we evaluate the distances and ages of the subsample of (19) GALNYSS stars with Gaia Data Release 1 (DR1) parallax distances D⩽120 pc. The overall youth of these 19 mid-K to early-M stars is readily apparent from their positions relative to the loci of main-sequence stars and giants in Gaia-based color-magnitude and color-color diagrams constructed for all stars detected by Galex and the Wide-field Infrared Space Explorer for which parallax measurements are included in DR1. The isochronal ages of all 19 stars lie in the range ∼10–100 Myr. Comparison with Li-based age estimates indicates a handful of these stars may be young main-sequence binaries rather than pre-main sequence stars. Nine of the 19 objects have not previously been considered as nearby, young stars, and all but one of these are found at declinations north of +30°. The Gaia DR1 results presented here indicate that the GALNYSS sample includes several hundred nearby, young stars, a substantial fraction of which have not been previously recognized as having ages ≲100 Myr.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1981

The properties of close multiple stars

A reexamination of the properties of close multiple systems is conducted, taking into account recent numerical, analytical, and observational results. The orbital elements of 43 spectroscopic multiple systems are presented in a table. Tables with photometry data of the systems and data describing their properties are also provided. Attention is given to period ratios, mass ratios, orbital coplanarity, stability, lithium abundances and age estimates, and prospects of future observations. Numerical studies indicate that fragmentation produces binary components with mass ratios usually close to 1.0, while fission usually produces mass ratios in the range 0.1-0.5. Using analytical stability criteria, all 27 close multiple systems considered are stable if they are corotating. If they are counter-rotating, four systems are possibly unstable. However, other factors suggest that even these four are probably stable. The solar-type close multiple systems ranged in age from 100 million years to 2,000 million years.

Fekel, F. C., Jr.↗
NASA NTRS2017

Boulders on Ceres

Introduction: In December 2015 the Dawn spacecraft moved into the Low Altitude Mapping Orbit (LAMO) around Ceres, encircling the dwarf planet at a distance of 400 km to the surface below. At this altitude, images of the on-board framing camera have a resolution of 36 meters per pixel, high enough to distinguish large boulders on the surface. Indeed, LAMO images show a multitude of boulders around what seem to be fresh craters. The average life-time of boulders on Dawn's previous target, Vesta, was estimated to be similar to that of Lunar boulders, as may be expected from the basaltic surface composition. The bulk composition of Ceres may be carbonaceous chondrite-like with significant contributions of clays, salt, and water ice. As such, the abundance and distribution of boulders on Ceres may be different from that on Vesta. We mapped, counted, and measured the diameter of boulders over the entire surface of Ceres. Our analysis of the data in combination with crater age estimates may provide clues to the physical nature and composition of the surface.

Ceres↗
NASA NTRS2013

HST-WFC3 Near-Infrared Spectroscopy of Quenched Galaxies at zeta approx 1.5 from the WISP Survey: Stellar Populations Properties

We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3- UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 microns] photometry to assemble a sample of massive (log(Mstar/M solar mass) at approx 11.0) and quenched (specific star formation rate < 0.01 G/yr(exp −1) galaxies at zeta approx 1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local universe, zeta approx 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are well fitted with exponentially decreasing star formation histories and short star formation timescales (τau less than or equal to 100 M/yr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 G/yr. In the (u − r)0-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the zeta appro. 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 G/yr) than the quenched galaxies off the RS (1.5 G/yr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at zeta approx 1.5 to be <43%.We speculate that the young quenched galaxies off the RS are in a transition phase between vigorous star formation at zeta > 2 and the zeta approx 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z approx. 1.5 RS is of the order of approx. 1G/yr.

HST WFC#↗
NASA NTRS2004

Membership and Coronal Activity in the NGC 2232 and Cr 140 Open Clusters

Making use of eight archival ROSAT HRI images in the regions of the NGC 2232 and Cr 140, this project's primary focus is to identify X-ray sources and to extract net source counts for these sources in these two open clusters. These X-ray data would be combined with ground-based photometry and spectroscopy in order to identify G, K, and early-M type cluster members. Such membership data are important because, at present, no members later than spectral type approx. F5 are currently known for either cluster. With ages estimated to be approx. 25 Myr and at distances of just approx. 350 pc, the combined late-type membership of the NGC 2232 and Cr 140 clusters would yield an almost unique sample of solar-type stars in the post-T Tauri/pre-main sequence phase of evolution. These stars could be used to assess the level and dispersion of coronal activity levels, as a part of a probe of the importance of magnetic braking and the level of magnetic dynamo activity, for solar-type stars just before they reach the zero-age main sequence.

Oliversen, Ronald J.↗
DOE OSTI2020

Stable Rate of Slip Along the Karakax Section of the Altyn Tagh Fault from Observation of Interglacial and Postglacial Offset Morphology and Surface Dating

Digital elevation maps obtained using TanDEM-X and Pleiades data combined with newly obtained surface age estimates using cosmogenic radionuclide (CRN) and optically simulated luminescence (OSL) methods are used to quantify the slip rate along the western section of the Altyn Tagh Fault in southern Xinjiang. The reconstruction of the conical shape of massive alluvial fans inferred to be from the Eemian (115±7 ka) from CRN dating shows consistent left-lateral offsets of 300±20 m, yielding a slip rate of 2.6±0.3 mm/year. Successive episodes of incision have left cut terraces inset in wide canyons, 10–25 m below the fans' surface. The incision was followed by the deposition of a broad terrace of early Holocene age, which is reincised by modern stream channels. Near the village of Shanxili, a 200 m wide valley is partially dammed by a shutter ridge displaced by the fault. A fill terrace deposited upstream from the ridge has an OSL age of 8.8±0.6 ka. The 23±2 m offset of the riser incising the terrace indicates a minimum postdepositional movement on the fault, yielding a Holocene rate of 2.6±0.5 mm/year, consistent with the 115-ka average slip rate. Furthermore, scarp degradation analysis using mass diffusion reveals a nonlinear relationship between fault displacement and degradation coefficient along the progressively exposed fault scarp, a pattern suggesting either seismic clustering or variable diffusion rate since the Eemian. Together with the Gozha Co-Longmu Co fault to the south, the Karakax section of the Altyn Tagh Fault contributes to the eastward movement of the western corner of Tibet.

58 GEOSCIENCES↗
DOE OSTI2018

Evaluation of micromilling/conventional isotope ratio mass spectrometry and secondary ion mass spectrometry of δ 18 O values in fish otoliths for sclerochronology

Stable oxygen isotope ratios (δ 18 O values) measured in fish otoliths can provide valuable detailed information on fish life history, fish age determination, and ocean thermography. Traditionally, otoliths are sampled by micromilling followed by isotope ratio mass spectrometry (IRMS), but direct analysis by secondary ion mass spectrometry (SIMS) is becoming more common. However, these two methods have not been compared to determine which, if either, is better for fish age validation studies. Hence, the goals were to: (1) determine if the δ 18 O signatures from the two different methods are similar, (2) determine which method is better for fish age validation studies, and (3) examine biogeographic and migration history. Both analytical techniques, micromilling/IRMS and SIMS, were used to measure δ 18 O values in six Pacific cod (Gadus macrocephalus) otoliths. A series of measurements was made from the center of each otolith to its edge to develop a life-history δ 18 O signature for each fish. The sampling resolution of SIMS analyses was 2–3 times greater than that obtained by micromilling/IRMS. We found an offset between SIMS and micromilling/IRMS δ 18 O values, about 0.5‰ on average, with SIMS yielding lower values. However, the δ 18 O patterns from both methods (i.e., the number of δ 18 O maxima) correspond to the estimated age determined by otolith growth-zone counts, validating fish age determination methods. Both techniques resolved δ 18 O life-history signatures and showed patterns consistent with seasonal variation in temperatures and changes due to fish migration. When otoliths are large, micromilling/IRMS can provide adequate resolution for fish age validation. Finally, SIMS is the better option if greater sampling resolution is required, such as when otoliths are small or specimens are longer lived and have compact growth zones.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Cosmogenic surface exposure ( 10 Be) dating of raised beaches in Marguerite bay, Antarctic Peninsula: Implications for relative sea-level history

Understanding the dynamics of ice mass loss in polar regions is crucial for deciphering climate change and Glacio Isostatic Adjustment patterns. This study focuses on Marguerite Bay, located in the south-central Antarctic Peninsula. We dated raised beaches to investigate relative sea-level changes using the cosmogenic surface exposure ( 10 Be) method. Previous studies have provided valuable insights into the region's glacial history, but limitations in dating techniques and age estimates necessitate further investigation. By analysing raised shingle beaches in Gaul Cove of Horseshoe Island and the southern coast of Calmette Bay, this research aims to contribute relative sea-level change history for these areas. In Horseshoe Island's Gaul Cove, raised beaches clustered on prominent steps reveal a 15 m relative sea-level change over the last 3.31 ka. Differently, Calmette Bay exhibits a 36 m relative sea-level fall over the last 7.29 ka. Finally, these findings indicate significant and differential glacial-isostatic adjustments in both regions during the middle and late Holocene. Additionally, our data reveal accelerated sea-level fall periods corresponding to Holocene deglaciation and glacial advance events, indicating the shorelines' relative sea-level change sensitivity to climate change.

58 GEOSCIENCES↗
DOE OSTI2015

Using naturally occurring radionuclides to determine drinking water age in a community water system

Drinking water quality in a community water system is closely linked to the age of water from initial treatment to time of delivery. However, water age is difficult to measure with conventional chemical tracers; particularly in stagnant water, where the relationship between disinfectant decay, microbial growth, and water age is poorly understood. Using radionuclides that were naturally present in source water, we found that measured activity ratios of 90 Y/ 90 Sr and 234 Th/ 238 U in discrete drinking water samples of known age accurately estimated water age up to 9 days old (σ est : ± 3.8 h, P < 0.0001, r 2 = 0.998, n = 11) and 25 days old (σ est : ± 13.3 h, P < 0.0001, r 2 = 0.996, n = 12), respectively. Moreover, 90 Y-derived water ages in a community water system (6.8 × 10 4 m 3 d –1 capacity) were generally consistent with water ages derived from an extended period simulation model. Radionuclides differ from conventional chemical tracers in that they are ubiquitous in distribution mains and connected premise plumbing. The ability to measure both water age and an analyte (e.g., chemical or microbe) in any water sample at any time allows for new insight into factors that control drinking water quality.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

The Spitzer c2d survey of large, nearby, interstellar clouds. XII. The Perseus YSO population as observed with IRAC and MIPS

The Spitzer Space Telescope mapped the Perseus molecular cloud complex with the Infrared Array Camera (IRAC) and the Multi-Band Imaging Photometer for Spitzer (MIPS) as part of the c2d Spitzer Legacy project. This paper combines the observations from both instruments giving an overview of low-mass star formation across Perseus from 3.6 to 70 μm. We provide an updated list of young stellar objects (YSOs) with new classifications and source fluxes from previous works, identifying 369 YSOs in Perseus with the Spitzer data set. By synthesizing the IRAC and MIPS maps of Perseus and building on the work of previous papers in this series, we present a current census of star formation across the cloud and within smaller regions. Sixty-seven percent of the YSOs are associated with the young clusters NGC 1333 and IC 348. The majority of the star formation activity in Perseus occurs in the regions around the clusters to the eastern and western ends of the cloud complex. The middle of the cloud is nearly empty of YSOs despite containing regions of high visual extinction. The western half of Perseus contains three-quarters of the total number of embedded YSOs (Class 0+I and Flat spectral energy distribution sources) in the cloud and nearly as many embedded YSOs as Class II and III sources. Class II and III objects greatly outnumber Class 0+I objects in eastern Perseus and IC 348. These results are consistent with previous age estimates for the clusters. Across the cloud, 56% of YSOs and 91% of the Class 0+I and Flat sources are in areas where A v &NestedLessLess; 5 mag, indicating a possible extinction threshold for star formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Discovery and validation of Kepler-452b: A 1.6 R{sub ⨁} super earth exoplanet in the habitable zone of a G2 star

We report on the discovery and validation of Kepler-452b, a transiting planet identified by a search through the 4 years of data collected by NASA’s Kepler Mission. This possibly rocky 1.63{sub −0.20}{sup +0.23} R{sub ⊕} planet orbits its G2 host star every 384.843{sub −0.012}{sup +0.007} days, the longest orbital period for a small (R{sub P}<2 R{sub ⊕}) transiting exoplanet to date. The likelihood that this planet has a rocky composition lies between 49% and 62%. The star has an effective temperature of 5757 ± 85 K and a logg of 4.32 ± 0.09. At a mean orbital separation of 1.046{sub −0.015}{sup +0.019} AU, this small planet is well within the optimistic habitable zone of its star (recent Venus/early Mars), experiencing only 10% more flux than Earth receives from the Sun today, and slightly outside the conservative habitable zone (runaway greenhouse/maximum greenhouse). The star is slightly larger and older than the Sun, with a present radius of 1.11{sub −0.09}{sup +0.15} R{sub ⊙} and an estimated age of ∼6 Gyr. Thus, Kepler-452b has likely always been in the habitable zone and should remain there for another ∼3 Gyr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SEARCHING FOR PLANETS IN HOLEY DEBRIS DISKS WITH THE APODIZING PHASE PLATE

We present our first results from a high-contrast imaging search for planetary mass companions around stars with gapped debris disks, as inferred from the stars' bright infrared excesses. For the six considered stars, we model the disks' unresolved infrared spectral energy distributions in order to derive the temperature and location of the disk components. With VLT/NaCo Apodizing Phase Plate coronagraphic L'-band imaging, we search for planetary mass companions that may be sculpting the disks. We detect neither disks nor companions in this sample, confirmed by comparing plausible point sources with archival data. In order to calculate our mass sensitivity limit, we revisit the stellar age estimates. One target, HD 17848, at 540 ± 100 Myr old is significantly older than previously estimated. We then discuss our high-contrast imaging results with respect to the disk properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

MILLIMETER SOURCE 13 S IN R CrA: OBSERVATIONS OF A PROTO-HERBIG Ae SYSTEM CANDIDATE

Compelled to observe a young, intermediate mass (IM) protostar candidate, we image velocity structure in a variety of molecular lines toward a strong millimeter continuum peak, MMS 13, in the young stellar object cluster R Corona Australis. We report the detection of N{sub 2}H{sup +} (1–0) and C{sup 34}S (2–1) corresponding to a filamentary IM core coincident with a site of turbulent flow convergence and Spitzer infrared emission minimum. Several emission features including a central decay of turbulence, kinematic signatures of bulk infall, and strong winds support mass and age estimates in indicating the presence of a proto-Herbig Ae system in the region. Channeling of center velocity flow with turbulence amplification along the rotation axis drives wind generation in the system candidate.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

DISCOVERY OF A LOW-MASS COMPANION AROUND HR 3549

We report the discovery of a low-mass companion to HR 3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 μm (10σ significance). We imaged HR 3549 B in the L band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in 2015 January. The companion is at a projected separation of ≃80 AU and position angle of ≃157°, so it is orbiting well beyond the warm disk inner edge of r > 10 AU. Our age estimate for this system corresponds to a companion mass in the range 15–80 M{sub J}, spanning the brown dwarf regime, and so HR 3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR 3549 provides interesting empirical constraints on models of the formation of substellar companions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The Sloan Digital Sky Survey Reverberation Mapping project: Post-starburst signatures in quasar host galaxies at z < 1

Quasar host galaxies are key for understanding the relation between galaxies and the supermassive black holes (SMBHs) at their centers. We present a study of 191 broad-line quasars and their host galaxies at z<1, using high signal-to-noise ratio (S/N) spectra produced by the Sloan Digital Sky Survey Reverberation Mapping project. Clear detection of stellar absorption lines allows a reliable decomposition of the observed spectra into nuclear and host components, using spectral models of quasar and stellar radiations as well as emission lines from the interstellar medium. We estimate age, mass M{sub ∗}, and velocity dispersion σ{sub ∗} of the host stars, the star formation rate (SFR), quasar luminosity, and SMBH mass M{sub ∙}, for each object. The quasars are preferentially hosted by massive galaxies with M{sub ∗}∼10{sup 11} M{sub ⊙} characterized by stellar ages around 1 billion yr, which coincides with the transition phase of normal galaxies from the blue cloud to the red sequence. The host galaxies have relatively low SFRs and fall below the main sequence of star-forming galaxies at similar redshifts. These facts suggest that the hosts have experienced an episode of major star formation sometime in the past 1 billion yr, which was subsequently quenched or suppressed. The derived M{sub ∙}−σ{sub ∗} and M{sub ∙}−M{sub ∗} relations agree with our past measurements and are consistent with no evolution from the local universe. The present analysis demonstrates that reliable measurements of stellar properties of quasar host galaxies are possible with high-S/N fiber spectra, which will be acquired in large numbers with future powerful instruments such as the Subaru Prime Focus Spectrograph.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

PROBING THE FERMI BUBBLES IN ULTRAVIOLET ABSORPTION: A SPECTROSCOPIC SIGNATURE OF THE MILKY WAY'S BICONICAL NUCLEAR OUTFLOW

Giant lobes of plasma extend ≈55° above and below the Galactic center, glowing in emission from gamma rays (the Fermi Bubbles) to microwaves and polarized radio waves. We use ultraviolet absorption-line spectra from the Hubble Space Telescope to constrain the velocity of the outflowing gas within these regions, targeting the quasar PDS 456 (ℓ, b = 10.°4, +11.°2). This sightline passes through a clear biconical structure seen in hard X-ray and gamma-ray emission near the base of the northern Fermi Bubble. We report two high-velocity metal absorption components, at v {sub LSR} = –235 and +250 km s{sup –1}, which cannot be explained by co-rotating gas in the Galactic disk or halo. Their velocities are suggestive of an origin on the front and back side of an expanding biconical outflow emanating from the Galactic center. We develop simple kinematic biconical outflow models that can explain the observed profiles with an outflow velocity of ≳900 km s{sup –1} and a full opening angle of ≈110° (matching the X-ray bicone). This indicates Galactic center activity over the last ≈2.5-4.0 Myr, in line with age estimates of the Fermi Bubbles. The observations illustrate the use of UV spectroscopy to probe the properties of swept-up gas venting into the Fermi Bubbles.

79 ASTRONOMY AND ASTROPHYSICS↗