Asteroid family identification using the Hierarchical Clustering Method and WISE/NEOWISE physical properties

Using albedos from WISE/NEOWISE to separate distinct albedo groups within the Main Belt asteroids, we apply the Hierarchical Clustering Method to these subpopulations and identify dynamically associated clusters of asteroids. While this survey is limited to the ~35% of known Main Belt asteroids that were detected by NEOWISE, we present the families linked from these objects as higher confidence associations than can be obtained from dynamical linking alone. We find that over one-third of the observed population of the Main Belt is represented in the high-confidence cores of dynamical families. The albedo distribution of family members differs significantly from the albedo distribution of background objects in the same region of the Main Belt, however interpretation of this effect is complicated by the incomplete identification of lower-confidence family members. In total we link 38,298 asteroids into 76 distinct families. This work represents a critical step necessary to debias the albedo and size distributions of asteroids in the Main Belt and understand the formation and history of small bodies in our Solar system.Comment: Accepted to ApJ. Full version of Table 3 to be published electronically in Ap

Density distributions of superheavy nuclei

We employed the Skyrme-Hartree-Fock model to investigate the density distributions and their dependence on nuclear shapes and isospins in the superheavy mass region. Different Skyrme forces were used for the calculations with a special comparison to the experimental data in $^{208}$Pb. The ground-state deformations, nuclear radii, neutron skin thicknesses and $\alpha$-decay energies were also calculated. Density distributions were discussed with the calculations of single-particle wavefunctions and shell fillings. Calculations show that deformations have considerable effects on the density distributions, with a detailed discussion on the $^{292}$120 nucleus. Earlier predictions of remarkably low central density are not supported when deformation is allowed for.Comment: 7 pages, 10 figure

Lingering grains of truth around comet 17P/Holmes

Comet 17P/Holmes underwent a massive outburst in 2007 Oct., brightening by a factor of almost a million in under 48 hours. We used infrared images taken by the Wide-Field Survey Explorer mission to characterize the comet as it appeared at a heliocentric distance of 5.1 AU almost 3 years after the outburst. The comet appeared to be active with a coma and dust trail along the orbital plane. We constrained the diameter, albedo, and beaming parameter of the nucleus to 4.135 $\pm$ 0.610 km, 0.03 $\pm$ 0.01 and 1.03 $\pm$ 0.21, respectively. The properties of the nucleus are consistent with those of other Jupiter Family comets. The best-fit temperature of the coma was 134 $\pm$ 11 K, slightly higher than the blackbody temperature at that heliocentric distance. Using Finson-Probstein modeling we found that the morphology of the trail was consistent with ejection during the 2007 outburst and was made up of dust grains between 250 $\mu$m and a few cm in radius. The trail mass was $\sim$ 1.2 - 5.3 $\times$ 10$^{10}$ kg.Comment: Accepted to ApJ. 2 tables, 4 figure

Main Belt Asteroids with WISE/NEOWISE: Near-Infrared Albedos

We present revised near-infrared albedo fits of 2835 Main Belt asteroids observed by WISE/NEOWISE over the course of its fully cryogenic survey in 2010. These fits are derived from reflected-light near-infrared images taken simultaneously with thermal emission measurements, allowing for more accurate measurements of the near-infrared albedos than is possible for visible albedo measurements. As our sample requires reflected light measurements, it undersamples small, low albedo asteroids, as well as those with blue spectral slopes across the wavelengths investigated. We find that the Main Belt separates into three distinct groups of 6%, 16%, and 40% reflectance at 3.4 um. Conversely, the 4.6 um albedo distribution spans the full range of possible values with no clear grouping. Asteroid families show a narrow distribution of 3.4 um albedos within each family that map to one of the three observed groupings, with the (221) Eos family being the sole family associated with the 16% reflectance 3.4 um albedo group. We show that near-infrared albedos derived from simultaneous thermal emission and reflected light measurements are an important indicator of asteroid taxonomy and can identify interesting targets for spectroscopic followup.Comment: Accepted for publication in ApJ; full version of Table1 to be published electronically in the journa

Spin-Excitation Mechanisms in Skyrme-Force Time-Dependent Hartree-Fock

We investigate the role of odd-odd (with respect to time inversion) couplings in the Skyrme force on collisions of light nuclei, employing a fully three-dimensional numerical treatment without any symmetry restrictions and with modern Skyrme functionals. We demonstrate the necessity of these couplings to suppress spurious spin excitations owing to the spin-orbit force in free translational motion of a nucleus but show that in a collision situation there is a strong spin excitation even in spin-saturated systems which persists in the departing fragments. The energy loss is considerably increased by the odd-odd terms

A Mesolithic settlement site at Howick, Northumberland: a preliminary report

Excavations at a coastal site at Howick during 2000 and 2002 have revealed evidence for a substantial Mesolithic settlement and a Bronze Age cist cemetery. Twenty one radiocarbon determinations of the earlier eighth millennium BP (Cal.) indicate that the Mesolithic site is one of the earliest known in northern Britain. An 8m core of sediment was recovered from stream deposits adjacent to the archaeological site which provides information on local environmental conditions. Howick offers a unique opportunity to understand aspects of hunter-gatherer colonisation and settlement during a period of rapid palaeogeographical change around the margins of the North Sea basin, at a time when it was being progressively inundated by the final stages of the postglacial marine transgression. The cist cemetery will add to the picture of Bronze Age occupation of the coastal strip and again reveals a correlation between the location of Bronze Age and Mesolithic sites which has been observed elsewhere in the region

NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos

We present preliminary diameters and albedos for 7,959 asteroids detected in the first year of the NEOWISE Reactivation mission. 201 are near-Earth asteroids (NEAs). 7,758 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using WISE or NEOWISE thermal measurements. Diameters are determined to an accuracy of ~20% or better. If good-quality H magnitudes are available, albedos can be determined to within ~40% or better.Comment: 42 pages, 5 figure

Optimization of the visibility of graphene on poly-Si film by thin-film optics engineering

A multilayer optical system containing poly-Si film, SiO 2 film, and Si substrate (poly-Si substrate) has been designed to enhance the visibility of graphene in contact with poly-Si. Film thicknesses of poly-Si and SiO 2 have been optimized by parametric study of the integral contrast of single layer graphene using transfer matrix theory. The multilayer poly-Si substrate and the most commonly used 285 nm SiO 2 /Si substrate (SiO 2 substrate) have been fabricated. Graphene grown by chemical vapor deposition on Ni catalyst has been transferred to the substrates and the visibility of the graphene on the different substrates has been compared. The samples have been characterized by optical microscope, illuminated with light from halogen lamp, and/or filtered with a 600 nm narrow band optical filter. The contrast of graphene on poly-Si substrate has been increased to near 8.7 under 600 nm narrow band illumination from nearly invisible under ordinary illumination, while the contrast of graphene on SiO 2 remains almost the same. Raman spectroscopy has been used to verify the presence of the single layer graphene on the poly-Si substrate.</p

The unrestricted Skyrme-tensor time-dependent Hartree-Fock and its application to the nuclear response from spherical to triaxial nuclei

The nuclear time-dependent Hartree-Fock model formulated in the three-dimensional space,based on the full Skyrme energy density functional and complemented with the tensor force,is presented for the first time. Full self-consistency is achieved by the model. The application to the isovector giant dipole resonance is discussed in the linear limit, ranging from spherical nuclei (16O, 120Sn) to systems displaying axial or triaxial deformation (24Mg, 28Si, 178Os, 190W, 238U). Particular attention is paid to the spin-dependent terms from the central sector of the functional, recently included together with the tensor. They turn out to be capable of producing a qualitative change on the strength distribution in this channel. The effect on the deformation properties is also discussed. The quantitative effects on the linear response are small and, overall, the giant dipole energy remains unaffected. Calculations are compared to predictions from the (quasi)-particle random phase approximation and experimental data where available, finding good agreement

ULTRACAM photometry of the eclipsing cataclysmic variable OU Vir

We present high-speed, three-colour photometry of the faint eclipsing cataclysmic variable OU Vir. For the first time in OU Vir, separate eclipses of the white dwarf and bright spot have been observed. We use timings of these eclipses to derive a purely photometric model of the system, obtaining a mass ratio of q = 0.175 +/- 0.025, an inclination of i = 79.2 +/- 0.7 degrees and a disc radius of Rd/a = 0.2315 +/- 0.0150. We separate the white dwarf eclipse from the lightcurve and, by fitting a blackbody spectrum to its flux in each passband, obtain a white dwarf temperature of T = 21700 +/- 1200 K and a distance of D = 650 +/- 210 pc. Assuming that the primary obeys the Nauenberg (1972) mass-radius relation for white dwarfs and allowing for temperature effects, we also find a primary mass Mw/Msun = 0.90 +/- 0.19, primary radius Rw/Rsun = 0.0097 +/- 0.0031 and orbital separation a/Rsun = 0.75 +/- 0.05.Comment: 8 pages LaTeX, 6 figures. Accepted by MNRAS; erratum added at end. Mon.Not.Roy.Astron.Soc. 347 (2004) 1173, erratum in pres