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DOE OSTI2020

Benchmark neutrinoless double- β decay matrix elements in a light nucleus

We compute nuclear matrix elements of neutrinoless double-β decay mediated by light Majorana-neutrino exchange in the $\textit{A}$ = 6 system. The goal for this work is to benchmark two many-body approaches, the no-core shell model and the multireference in-medium similarity renormalization group (SRG). We use a SRG-evolved next-to-next-to-next-to-leading chiral order two-body potential for the nuclear interaction, and make the approximation that the isospin is conserved. We compare the results of the two approaches as a function of the cutoff on the many-body basis space. Although differences are seen in the predicted nuclear radii, the ground-state energies and neutrinoless double-β decay matrix elements produced by the two approaches show significant agreement. We discuss the implications for calculations in heavier nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1997

Deep WFPC2 and Ground-Based Imaging of a Complete Sample of 3C Quasars and Galaxies

We present the results of an HST and ground-based imaging study of a complete 3C sample of zeta approx. equal to 1 sources, comprising 5 quasars and 5 radio galaxies. We have observed all of the sample in essentially line-free bands at rest-frame 0.33 micrometers with WFPC2 and in rest-frame 1 micrometer images from the ground; we have also observed most of the sample in narrow-band filters centered on [O II]. We resolve continuum structure around all of our quasars in the high-resolution WFPC2 images, and in four of the five ground-based K' images. All of the quasars have some optical continuum structure that is aligned with the radio axis. In at least 3 of these cases, some of this optical structure is directly coincident with a portion of the radio structure, including optical counterparts to radio jets in 3C212 and 3C245 and an optical counterpart to a radio lobe in 3C2. These are most likely due to optical synchrotron radiation, and the radio and optical spectral indices in the northern lobe of 3C2 are consistent with this interpretation. The fact that we see a beamed optical synchotron component in the quasars but not in the radio galaxies complicates both the magnitude and the alignment comparisons. Nonetheless, the total optical and K' flux densities of the quasar hosts are consistent with those of the radio galaxies within the observed dispersion in our sample. The distributions of K' flux densities of both radio galaxies and quasar hosts exhibit similar mean and dispersion to that found for other radio galaxies at this redshift, and the average host galaxy luminosity is equivalent to, or a little fainter than, L*. The formal determination of the alignment in the optical and infrared in the two subsamples yields no significant difference between the radio galaxy and quasar subsamples, and the quasars 3C 196 and 3C 336 have aligned continuum and emission-line structure that is probably not due to beamed optical synchrotron emission. Very blue and/or edge-brightened structures are present in some objects within the probable quasar opening angle; these are possibly the result of illumination effects from the active nucleus, i.e., scattered quasar light or photoionization. In 3C 212, we see an optical object that lies 3 min. beyond the radio lobe, but which looks morphologically quite similar to the radio lobe itself. This object is bright in the infrared and has a steep spectral gradient along its length. A striking, semi-circular arc seen associated with 3C 280 may possibly be a tidal tail from a companion, enhanced in brightness by scattering or photoionization. In the near-infrared, most of the radio galaxies have elliptical morphologies with profiles that are well-fit by de Vaucouleurs r(exp 1/4)-laws and colors that are consistent with an old stellar population. All components around the quasars have optical-infrared colors that are redder than or similar to the colors of their respective nuclei; this is more consistent with a stellar origin for the emission than with a dominant scattering contribution. From the correspondence between the total magnitudes in the galaxies and quasars and the detection of aligned components in the quasars, we conclude that this study provides general support for the unification of FR II radio galaxies and quasars. Some of the objects in the sample (e.g, 3C 212) have properties that may be difficult to explain with our current understanding of the nature of FR II radio sources and the alignment effect.

Ridgway, Susan E.↗

DOE OSTI2023

The active CGCG 077-102 NED02 galaxy within the Abell 2063 galaxy cluster

Context.Within the framework of investigating the link between the central super massive black holes in the cores of galaxies and the galaxies themselves, we detected a variable X-ray source in the center of CGCG 077-102 NED02, which is a member of the CGCG 077-102 galaxy pair within the Abell 2063 cluster of galaxies. Aims.Our goal is to combine X-ray and optical data to demonstrate that this object harbors an active super massive black hole in its core, and to relate this to the dynamical status of the galaxy pair within the Abell 2063 cluster. Methods.We usedChandraandXMM-Newtonarchival data to derive the X-ray spectral shape and variability. We also obtained optical spectroscopy to detect the expected emission lines that are typically found in active galactic nuclei. Finally, we used public ZTF imaging data to investigate the optical variability. Results.There is no evidence of multiple X-ray sources or extended components within CGCG 077-102 NED02. Single X-ray spectral models fit the source well. We detect significant, nonrandom inter-observation 0.5–10 keV X-ray flux variabilities, for observations separated by ∼4 days for short-term variations and by up to ∼700 days for long-term variations. Optical spectroscopy points toward a passive galaxy for CGCG 077-102 NED01 and a Seyfert for CGCG 077-102 NED02. The classification of CGCG 077-102 NED02 is also consistent with its X-ray luminosity of over 10 42 erg s −1 . We do not detect short-term variability in the optical ZTF light curves. However, we find a significant long-term stochastic variability in theg-band that can be well described by the damped random walk model with a best-fit characteristic damping timescale ofτ DRW = 30 −12 +28 days. Finally, the CGCG 077-102 galaxy pair is deeply embedded within the Abell 2063 potential, with a long enough history within this massive structure to have been affected by the influence of this cluster for a long time. Conclusions.Our observations point toward a moderately massive black hole in the center of CGCG 077-102 NED02 of ∼10 6 M ⊙ . As compared to another similar pair in the literature, CGCG 077-102 NED02 is not heavily obscured, perhaps because of the surrounding intracluster medium ram-pressure stripping.

Astronomy & Astrophysics↗

DOE OSTI2026

Glauber-theory analysis of nuclear reactions on a 12 C target with variational Monte Carlo wave functions

The application of Glauber theory has been playing an increasingly important role with the study of unstable or exotic nuclei. Its adaptation to medium and high-energy nucleus-nucleus collisions is severely limited because one has to evaluate the matrix elements of multiple-scattering operators. The extraction of physical observables has been done using ‘approximate’ Glauber theory whose validity is hard to evaluate. Here, we perform a full calculation of the matrix elements using Monte Carlo integration and analyze the elastic differential cross sections and the total reaction cross sections for p+¹²C, ⁴,⁶He+¹²C, and ¹²C+¹²C collisions. We use the variational Monte Carlo wave functions for ⁴,⁶He and ¹²C obtained by using realistic two- and three-nucleon potentials. We demonstrate the performance of the Glauber-theory calculations by comparing with available experimental data. We further discuss the accuracy of the conventional approximate methods in the light of the cumulant expansion for Glauber’s phase-shift function.

Horiuchi, W. [Osaka Metropolitan University (Japan↗

NASA NTRS1990

The nature of the emission-line nebulae in powerful far-infrared galaxies

The authors discuss their program of narrow-band (H alpha + (NII)) imaging of a sample of 30 powerful far-infrared galaxies (FIRG's) chosen to have far-infrared spectral energy distributions similar to the prototype FIRG's Arp 220, NGC 3690, NGC 6240, and M82. The emission-line nebulae of these IR color-selected sample (ICSS) galaxies as a class are both impressively large (mean half light radius, r approx. 1.3 Kpc, and mean diameter, D approx. 16 Kpc) and luminous (L sub TOT approx. 10(exp 8) solar lumninosity; uncorrected for internal extinction). The mean total H alpha + (NII) luminosity of the FIRG's is comparable to that found for pairs of optically selected interacting galaxies (Bushouse, Lamb, and Werner 1988), but is a factor of approx. 5 greater than that of isolated spirals (Kennicutt and Kent 1983). Only approx. 25 percent of the nearby (z approx. less than 0.10) FIRG's have morphologies suggesting that large HII-regions contribute significantly to their emission-line appearance. The broad-band morphologies of our IR color-selected galaxies fall into three major categories. Nearly 75 percent are single galaxy systems, with the remaining FIRG's being either multiple nuclei systems, or members of interacting pairs. Since the authors saw few (10 percent) currently interacting FIRG's, yet many (80 percent) with highly distorted continuum morphologies, their IR color criteria may be preferentially selecting galaxies that have undergone highly inelastic, rapidly merging interactions.

Armus, Lee↗

DOE OSTI2023

Energy dependence of light hypernuclei production in heavy-ion collisions from a coalescence and statistical-thermal model perspective

A comparison of light hypernuclei production, from Ultra-relativistic Quantum Molecular Dynamics (UrQMD)+coalescence and the thermal model, in heavy ion collisions over a wide range of beam energies and system sizes is presented. We find that both approaches provide generally similar results, with differences in specific details. Especially the ratios of hypertriton to Λ are affected by both the source radius Δr of the coalescence procedure as well as canonical effects. On the other hand, the double ratio S 3 is almost independent of canonical effects, which is in contrast to coalescence. Thus, both the beam energy dependence and centrality dependence of S 3 can be used to constrain the hypertriton source radius. To do so the currently available data are not yet sufficient. Elliptic flow is shown to be unaffected by the source size of the nuclei and an almost perfect mass scaling of the elliptic flow is observed. Furthermore, our predictions further suggest that the existence of the H-dibaryon(ΛΛ) seems ruled out by ALICE data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1990

Observations of anthropogenic cloud condensation nuclei

Cloud Condensation Nuclei (CCN) concentrations and spectral measurements obtained with the DRI instantaneous CCN spectrometer (Hudson, 1989) over the last few years are presented. The climatic importance of cloud microphysics has been pointed out. The particles which affect cloud microphysics are cloud condensation nuclei (CCN). The commonly-observed order of magnitude difference in cloud droplet concentrations between maritime and continental air masses (i.e., Squires, 1958) was determined to be caused by systematic differences in the concentrations of CCN between continental and maritime air masses (e.g., Twomey and Wojciechowski, 1969). Twomey (1977) first pointed out that cloud microphysics also affects the radiative properties of clouds. Thus continental and anthropogenic CCN could affect global temperature. Resolution of this Twomey effect requires answers to two questions - whether antropogenic CCN are a significant contribution to atmospheric CCN, and whether they are actually affecting cloud microphysics to an extent which is of climatic importance. The reasons for the contrast between continental and maritime CCN concentration are not understood. The question of the relative importance of anthropogenic CCN is addressed. These observations should shed light on this complex question although further research is being conducted in order to produce more quantitative answers. Accompanying CN measurements made with a TSI 3020 condensation nucleus (CN) counter are also presented.

Hudson, James G.↗

NASA NTRS2014

Musculoskeletal-induced Nucleation in Altitude Decompression Sickness

Musculoskeletal activity has the potential to both improve and compromise decompression safety. Exercise enhances inert gas elimination during oxygen breathing prior to decompression (prebreathe), but it may also promote bubble nuclei formation (nucleation), which can lead to gas phase separation and bubble growth and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity and the level of tissue supersaturation may be critical to the net effect. There are limited data available to evaluate cost-benefit relationships. Understanding the relationship is important to improve our understanding of the underlying mechanisms of nucleation in exercise prebreathe protocols and to quantify risk in gravity and microgravity environments. Data gathered during NASA's Prebreathe Reduction Program (PRP) studies combined oxygen prebreathe and exercise followed by low pressure (4.3 psi; altitude equivalent of 30,300 ft [9,235 m]) microgravity simulation to produce two protocols used by astronauts preparing for extravehicular activity. Both the Phase II/CEVIS (cycle ergometer vibration isolation system) and ISLE (in-suit light exercise) trials eliminated ambulation to more closely simulate the microgravity environment. The CEVIS results (35 male, 10 female) serve as control data for this NASA/Duke study to investigate the influence of ambulation exercise on bubble formation and the subsequent risk of DCS.

Pollock, N. W.↗

NASA NTRS2010

Active Galaxy Unification in the Era of X-Ray Polarimetry

Active galactic nuclei (AGNs), Seyfert galaxies, and quasars are powered by luminous accretion and often accompanied by winds that are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes that are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption (warm absorbers). Here, we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow and the gas responsible for launching and collimating it. We present calculations that show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance-line scattering, and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three-dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV energy range is dominated by the effects of resonance lines. We predict a 5%-25% X-ray polarization signature of type-2 objects in this energy range. These results are generalized to flows that originate from a cold torus-like structure, located approximately 1 pc from the BH, which wraps the BH and is ultimately responsible for the apparent dichotomy between type 1 and type 2 AGNs. Such signals will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism Small Explorer SMEX, "GEMS" Swank et al. (2008).

Dorodnitsyn, A.↗

NASA NTRS1997

Colloids and Nucleation

The objectives of the work funded under this grant were to develop a microphotographic technique and use it to monitor the nucleation and growth of crystals of hard colloidal spheres. Special attention is given to the possible need for microgravity studies in future experiments. A number of persons have been involved in this work. A masters student, Keith Davis, began the project and developed a sheet illumination apparatus and an image processing system for detection and analysis. His work on a segmentation program for image processing was sufficient for his master's research and has been published. A post doctoral student Bernie Olivier and a graduate student Yueming He, who originally suggested the sheet illumination, were funded by another source but along with Keith made photographic series of several samples (that had been made by Keith Davis). Data extraction has been done by Keith, Bernie, Yueming and two undergraduates employed on the grant. Results are published in Langmuir. These results describe the sheet lighting technique as one which illuminates not only the Bragg scattering crystal, but all the crystals. Thus, accurate crystal counts can be made for nucleation rate measurements. The strange crystal length scale reduction, observed in small angle light scattering (SALS) studies, following the initial nucleation and growth period, has been observed directly. The Bragg scattering (and dark) crystal size decreases in the crossover region. This could be an effect due to gravitational forces or due to over- compression of the crystal during growth. Direct observations indicate a complex morphology for the resulting hard sphere crystals. The crystal edges are fairly sharp but the crystals have a large degree of internal structure. This structure is a result of (unstable) growth and not aggregation. As yet unpublished work compares growth exponents data with data obtained by SALS. The nucleation rate density is determined over a broad volume fraction range (0.505 to 0.575) and compared to classical nucleation rate calculations. The experimental nucleation rate density varies with volume fraction more slowly than expected theoretically. Gravity may influence nucleation because crystal nuclei are more dense than the surrounding fluid and may be gravitationally convected. The largest observed crystal size was near volume fraction 0.52. Near the freezing point, crystals should grow to large size because nuclei are sparse and there is plenty of room to grow without contacting other crystals. Near melting the opposite is true, with crystals growing into one another shortly after nucleation. The maximum crystal size seen near 0.52 volume fraction suggests that gravitational stresses are limiting crystal growth near freezing.

Ackerson, Bruce↗

DOE OSTI2022

SCAT uncovers ATLAS’s first tidal disruption event ATLAS18mlw: a faint and fast TDE in a quiescent Balmer strong Galaxy

ABSTRACT We present the discovery that ATLAS18mlw was a tidal disruption event (TDE) in the galaxy WISEA J073544.83+663717.3, at a luminosity distance of 334 Mpc. Initially discovered by the Asteroid Terrestrial Impact Last Alert System (ATLAS) on 2018 March 17.3, the TDE nature of the transient was uncovered only recently with the re-reduction of a SuperNova Integral Field Spectrograph (SNIFS) spectrum. This spectrum, taken by the Spectral Classification of Astronomical Transients (SCAT) survey, shows a strong blue continuum and a broad H α emission line. Here, we present roughly 6 yr of optical survey photometry beginning before the TDE to constrain active galactic nucleus activity, optical spectroscopy of the transient, and a detailed study of the host galaxy properties through analysis of archival photometry and a host spectrum. ATLAS18mlw was detected in ground-based light curves for roughly 2 months. From a blackbody fit to the transient spectrum and bolometric correction of the optical light curve, we conclude that ATLAS18mlw is best explained by a low-luminosity TDE with a peak luminosity of log(L [erg s−1]) = 43.5 ± 0.2. The TDE classification is further supported by the quiescent Balmer strong nature of the host galaxy. We also calculated the TDE decline rate from the bolometric light curve and find ΔL40 = −0.7 ± 0.2 dex, making ATLAS18mlw a member of the growing class of ‘faint and fast’ TDEs with low peak luminosities and fast decline rates.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Multiple giant eruptions and X-ray emission in the recoiling AGN/LBV candidate SDSS1133

We present a comprehensive analysis of 20 yr worth of multicolour photometric light curves, multiepoch optical spectra, and X-ray data of an off-nuclear variable object SDSS1133 in Mrk 177 at z = 0.0079. The UV-optical light curves reveal that SDSS1133 experienced four outbursts in 2001, 2014, 2019, and 2021. The persistent UV-optical luminosity in the non-outbursting state is ~1041 erg s -1 with small-scale flux variations, and peak luminosities during the outbursts reach ~10 42 erg s -1 . The optical spectra exhibit enduring broad hydrogen Balmer P-Cygni profiles with the absorption minimum at ~-2000 km s -1 , indicating the presence of fast-moving ejecta. Chandra detected weak X-ray emission at a 0.3-10-keV luminosity of L X = 4 × 10 38 erg s -1 after the 2019 outburst. These lines of evidence suggests that SDSS1133 is an extreme luminous blue variable (LBV) star experiencing multiple giant eruptions with interactions of the ejected shell with different shells and/or circumstellar medium (CSM), and disfavours the recoiling active galactic nuclei scenario suggested in the literature. We suggest that pulsational pair-instability may provide a viable explanation for the multiple energetic eruptions in SDSS1133. If the current activity of SDSS1133 is a precursor of a supernova explosion, we may be able to observe a few additional giant eruptions and then the terminal supernova explosion or collapse to a massive black hole in future observations.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1995

The microbial community of Ophrydium versatile colonies: endosymbionts, residents, and tenants

Ophrydium versatile is a sessile peritrichous ciliate (Kingdom Protoctista, class Oligohymenophora, order Peritrichida, suborder Sessilina) that forms green, gelatinous colonies. Chlorophyll a and b impart a green color to Ophrydium masses due to 400-500 Chlorella-like endosymbionts in each peritrich. Ophrydium colonies, collected from two bog wetlands (Hawley and Leverett, Massachusetts) were analyzed for their gel inhabitants. Other protists include ciliates, mastigotes, euglenids, chlorophytes, and heliozoa. Routine constituents include from 50-100,000 Nitzschia per ml of gel and at least four other diatom genera (Navicula, Pinnularia, Gyrosigma, Cymbella) that may participate in synthesis of the gel matrix. Among the prokaryotes are filamentous and coccoid cyanobacteria, large rod-shaped bacteria, at least three types of spirochetes and one unidentified Saprospira-like organism. Endosymbiotic methanogenic bacteria, observed using fluorescence microscopy, were present in unidentified hypotrichous ciliates. Animals found inside the gel include rotifers, nematodes, and occasional copepods. The latter were observed in the water reservoir of larger Ophrydium masses. From 30-46% of incident visible radiation could be attenuated by Ophrydium green jelly masses in laboratory observations. Protargol staining was used to visualize the elongate macronuclei and small micronucleus of O. versatile zooids and symbiotic algal nuclei. Electron microscopic analysis of the wall of the Chlorella-like symbiont suggests that although the Ophrydium zooids from British Columbia harbor Chlorella vulgaris, those from Hawley Bog contain Graesiella sp. The growth habit in the photic zone and loose level of individuation of macroscopic Ophrydium masses are interpretable as extant analogs of certain Ediacaran biota: colonial protists in the Vendian fossil record.

Non-NASA Center↗

DOE OSTI2025

Lens Model Accuracy in the Expected LSST Lensed AGN Sample

Strong gravitational lensing of active galactic nuclei (AGN) enables measurements of cosmological parameters through time-delay cosmography (TDC). With data from the upcoming LSST survey, we anticipate using a sample of O(1000) lensed AGN for TDC. To prepare for this dataset and enable this measurement, we construct and analyze a realistic mock sample of 1300 systems drawn from the OM10 (Oguri & Marshall 2010) catalog of simulated lenses with AGN sources at $z<3.1$ in order to test a key aspect of the analysis pipeline, that of the lens modeling. We realize the lenses as power law elliptical mass distributions and simulate 5-year LSST i-band coadd images. From every image, we infer the lens mass model parameters using neural posterior estimation (NPE). Focusing on the key model parameters, $θ_E$ (the Einstein Radius) and $γ_{lens}$ (the projected mass density profile slope), with consistent mass-light ellipticity correlations in test and training data, we recover $θ_E$ with less than 1% bias per lens, 6.5% precision per lens and $γ_{lens}$ with less than 3% bias per lens, 8% precision per lens. We find that lens light subtraction prior to modeling is only useful when applied to data sampled from the training prior. If emulated deconvolution is applied to the data prior to modeling, precision improves across all parameters by a factor of 2. Finally, we combine the inferred lens mass models using Bayesian Hierarchical Inference to recover the global properties of the lens sample with less than 1% bias.

Venkatraman, Padmavathi [Illinois U., Urbana; KIPA↗

DOE OSTI2025

Joint Modeling of Quasar Variability and Accretion Disk Reprocessing Using Latent Stochastic Differential Equations

Quasars are bright active galactic nuclei powered by the accretion of matter around supermassive black holes at the center of galaxies. Their stochastic brightness variability depends on the physical properties of the accretion disk and black hole. The upcoming Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to observe tens of millions of quasars, so there is a need for efficient techniques like machine learning that can handle the large volume of data. Quasar variability is believed to be driven by an X-ray corona, which is reprocessed by the accretion disk and emitted as UV/optical variability. We are the first to introduce an auto-differentiable simulation of the accretion disk and reprocessing. We use the simulation as a direct component of our neural network to jointly model the driving variability and reprocessing, trained with supervised learning on simulated LSST-like 10 yr quasar light curves. We encode the light curves using a transformer encoder, and the driving variability is reconstructed using latent stochastic differential equations, a physically motivated generative deep learning method that can model continuous-time stochastic dynamics. By embedding the physical processes of the driving signal and reprocessing into our network, we achieve a model that is more robust and interpretable. We demonstrate that our model outperforms a Gaussian process regression baseline and can infer accretion disk parameters and time delays between wave bands, even for out-of-distribution driving signals. Our approach provides a powerful framework that can be adapted to solve other inverse problems in multivariate time series.

Fagin, Joshua [City Univ. of New York (CUNY), NY (↗

DOE OSTI2023

Microphysics of liquid water in sub-10 nm ultrafine aerosol particles

Abstract. Ultrafine aerosol particles with sizes smaller than 50 nm have been shown in recent studies to serve as a large source of cloud condensation nuclei that can promote additional cloud droplet formation under supersaturation conditions. Knowledge of the microphysics of liquid water in these droplets remains limited, particularly in the sub-10 nm particle size range, due to experimental and theoretical challenges associated with the complexity of aerosol components and the small length scales of interest (e.g., difficulty of precisely sampling the liquid–air interface, questionable validity of mean-field theoretical representations). Here, we carried out molecular dynamics (MD) simulations of aerosol particles with diameters between 1 and 10 nm and characterized atomistic-level structure and water dynamics in well-mixed and phase-separated systems with different particle sizes, NaCl salinities, and pimelic acid (PML) organic surface loadings as a function of distance from the time-averaged Gibbs dividing interface or instantaneous water–air interface. We define a sphericity factor (ϕ) that can shed light on the phase-mixing state of nanodroplets, and we reveal an unexpected dependence of mixing state on droplet size. Our results also evidence an ion concentration enhancement in ultrafine aerosols, which should modulate salt nucleation kinetics in sub-10 nm droplets, and provide detailed characterization of the influence of droplet size on surface tension and on water self-diffusivity near the interface. Analysis of water evaporation free energy and water activity demonstrates the validity of the Kelvin equation and Köhler theory at droplet sizes larger than 4 nm under moderate salinities and organic loadings and the need for further extension to account for ion concentration enhancement in sub-10 nm aerosols, droplet-size-dependent phase separation effects, and a sharp decrease in the cohesiveness of liquid water in sub-4 nm droplets. Finally, we show that an idealized fractional surface coating factor (fs) can be used to categorize and reconcile water accommodation coefficients (α*) observed in MD simulations and experimental results in the presence of organic coatings, and we resolve the droplet size dependence of α*.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1999

Interpreting Broad Double-Peaked Emission Lines in Active Galactic Nuclei

The principal objectives of this project were to probe the inner regions of active galactic nuclei and to test general relativity in the strong-field limit. The approach takes advantage of broad atomic line emission observed from material deep in the potential well of an active galactic nucleus which contains key information as to the physics of the system. Line profiles in a wide range of wavebands from optical to X-ray have provided compelling evidence of the existence of a relativistic accretion disk around a supermassive black hole in a number of galaxies. The simplest model posits a geometrically thin disk in Keplerian orbit, with general relativistic effects in evidence. This model is the point of departure for the proposed work. We developed a high-performance numerical code to calculate photon trajectories in a Schwarzschild or Kerr metric and implemented it on parallel supercomputers. This code includes a general purpose ray tracer that calculates line profiles, light curves, and other observable quantities for a wide variety of emitter configurations. The versatility comes from the fact that the ray tracing algorithm does not depend on any symmetries regarding emitter locations. The speed comes from parallel implementation which enables us to sample hitherto unattainable volumes of disk model parameter space. During the period 1 March 1997 through 28 February 1998, two papers, supported in whole or in part by this grant, were published in refereed journals. They are reproduced in their entirety in the next two sections of this report.

Halpern, Jules↗

DOE OSTI2020

Isotopic equilibrium constants for very low-density and low-temperature nuclear matter

Yields of equatorially emitted light isotopes, 1 ≤ Z ≤ 14, observed in ternary fission in the reaction 241 Pu(n th, f) are employed to determine apparent chemical equilibrium constants for low-temperature and low-density nuclear matter. The degree of equilibration and role of medium modifications are probed through a comparison of experimentally derived reaction quotients with equilibrium constants calculated using a relativistic mean-field model employing a universal medium modification correction for the attractive σ meson coupling. The results of these comparisons indicate that equilibrium is achieved for the lighter ternary fission isotopes. For the heavier isotopes experimental reaction quotients are well below calculated equilibrium constants. This is attributed to a dynamical limitation reflecting insufficient time for full equilibrium to develop. The role of medium effects leading to yield reductions is discussed as is the apparent enhancement of yields for 8 He and other very neutron rich exotic nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗