Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)

We report on the discovery of recently ionized hydrogen-deficient gas in the immediate circumstellar environment of the final helium shell flash star V4334 Sgr (Sakurai's object). On spectra obtained with FORS2 multi-object spectroscopy we have found spatially extended (about 2") emission from [N II], [O I], [O II] and very faint Halpha and [S II]. In the [N II] (ll6548,83) lines we have identified two components located at velocities -350 +/-50 and +200 +/-50 km/s, relative to V4334 Sgr itself. The full width of the [N II] l6583 feature at zero intensity corresponds to a velocity spread of about 1500 km/s. Based on the available data it is not possible to conclusively determine the mechanism of ionization. Both photo-ionization, from a rapidly evolving central star, and shock excitation, as the result of the collision of the fast ouflows with slower circumstellar matter, could account for the observed lines. The central star is still hidden behind strong dust absorption, since only a faint highly reddened continuum is apparent in the spectra. Theory states that it will become hotter and will retrace its post-asymptotic giant branch evolution towards the planetary nebula domain. Our detection of the ionized ejecta from the very late helium shell flash marks the beginning of a new phase in this star's amazingly rapid evolution.Comment: 11 pages, 2 figures. Accepted by ApJ

Bridge over troubled gas: clusters and associations under the SMC and LMC tidal stresses

We obtained SOAR telescope B and V photometry of 14 star clusters and 2 associations in the Bridge tidal structure connecting the LMC and SMC. These objects are used to study the formation and evolution of star clusters and associations under tidal stresses from the Clouds. Typical star clusters in the Bridge are not richly populated and have in general relatively large diameters (~30-35 pc), being larger than Galactic counterparts of similar age. Ages and other fundamental parameters are determined with field-star decontaminated photometry. A self-consistent approach is used to derive parameters for the most-populated sample cluster NGC 796 and two young CMD templates built with the remaining Bridge clusters. We find that the clusters are not coeval in the Bridge. They range from approximately a few Myr (still related to optical HII regions and WISE and Spitzer dust emission measurements) to about 100-200 Myr. The derived distance moduli for the Bridge objects suggests that the Bridge is a structure connecting the LMC far-side in the East to the foreground of the SMC to the West. Most of the present clusters are part of the tidal dwarf candidate D 1, which is associated with an H I overdensity. We find further evidence that the studied part of the Bridge is evolving into a tidal dwarf galaxy, decoupling from the Bridge.Comment: 15 pages, 15 figures, MNRAS, Accepted 2015 July 2

V605 Aql: The Older Twin of Sakurai's Object

New optical spectra have been obtained with VLT/FORS2 of the final helium shell flash (FF) star, V605 Aql, which peaked in brightness in 1919. New models suggest that this star is experiencing a very late thermal pulse. The evolution to a cool luminous giant and then back to a compact hot star takes place in only a few years. V605 Aql, the central star of the Planetary Nebula (PN), A58, has evolved from T$_{eff}\sim$5000 K in 1921 to $\sim$95,000 K today. There are indications that the new FF star, Sakurai's Object (V4334 Sgr), which appeared in 1996, is evolving along a similar path. The abundances of Sakurai's Object today and V605 Aql 80 years ago mimic the hydrogen deficient R Coronae Borealis (RCB) stars with 98% He and 1% C. The new spectra show that V605 Aql has stellar abundances similar to those seen in Wolf-Rayet [WC] central stars of PNe with ~55% He, and ~40% C. The stellar spectrum of V605 Aql can be seen even though the star is not directly detected. Therefore, we may be seeing the spectrum in light scattered around the edge of a thick torus of dust seen edge-on. In the present state of evolution of V605 Aql, we may be seeing the not too distant future of Sakurai's Object.Comment: 12 pages, 1 figure, ApJ Letters in pres

CG J1720-67.8: A Detailed Analysis of Optical and Infrared Properties of a New Ultracompact Group of Galaxies

We present here optical spectroscopy and BVRJHK(s) photometry of the recently discovered ultra-compact group of galaxies CG J1720-67.8. This work represents a considerable extension of the preliminary results we presented in a previous paper. Despite the complicated morphology of the group, a quantitative morphological classification of the three brightest members of the group is attempted based on photometric analysis. We find that one galaxy is consistent with a morphological type S0, while the other two are most probably late-type spirals that are already losing their identity due tothe interaction process. Information on the star formation activity and dust content derived from both spectroscopic data and optical and near-infrared colors are complemented with a reconstruction of far-infrared (FIR) maps from IRAS raw data. Enhanced star formation activity is revealed in all the group's members, including the early-type galaxy and the extended tidal tail, along which several tidal dwarf galaxy candidates are identified. The metallicity of the gaseous component is investigated and photoionization models are applied to the three main galaxies of the group, while a detailed study of the tidal dwarf candidates will appear in a companion paper. Subsolar metal abundances are found for all the three galaxies, the highest values being shown by the early-type galaxy (Z ~ 0.5 Zsolar).Comment: Accepted for publication in The Astrophysical Journa

A novel, aerosol-nanocrystal floating-gate device for non-volatile memory applications

This paper describes the fabrication, and structural and electrical characterization of a new, aerosol-nanocrystal floating-gate FET, aimed at non-volatile memory (NVM) applications. This aerosol-nanocrystal NVM device features program/erase characteristics comparable to conventional stacked gate NVM devices, excellent endurance (>l0^5 P/E cycles), and long-term non-volatility in spite of a thin bottom oxide (55-60Å). In addition, a very simple fabrication process makes this aerosol-nanocrystal NVM device a potential candidate for low cost NVM applications

Analytical Investigation of Innovation Dynamics Considering Stochasticity in the Evaluation of Fitness

We investigate a selection-mutation model for the dynamics of technological innovation,a special case of reaction-diffusion equations. Although mutations are assumed to increase the variety of technologies, not their average success ("fitness"), they are an essential prerequisite for innovation. Together with a selection of above-average technologies due to imitation behavior, they are the "driving force" for the continuous increase in fitness. We will give analytical solutions for the probability distribution of technologies for special cases and in the limit of large times. The selection dynamics is modelled by a "proportional imitation" of better technologies. However, the assessment of a technology's fitness may be imperfect and, therefore, vary stochastically. We will derive conditions, under which wrong assessment of fitness can accelerate the innovation dynamics, as it has been found in some surprising numerical investigations.Comment: For related work see http://www.helbing.or

High-resolution FUSE and HST ultraviolet spectroscopy of the white dwarf central star of Sh 2-216

LS V +4621 is the DAO-type central star of the planetary nebula Sh 2-216. We perform a comprehensive spectral analysis of high-resolution, high-S/N ultraviolet observations obtained with FUSE and STIS aboard the HST as well as the optical spectrum of LS V +4621 by means of state-of-the-art NLTE model-atmosphere techniques in order to compare its photospheric properties to theoretical predictions from stellar evolution theory as well as from diffusion calculations. From the N IV - NV, O IV - O VI, Si IV - Si V, and Fe V - Fe VII ionization equilibria, we determined an effective temperature of 95 +/- 2 kK with high precision. The surface gravity is log g = 6.9 +/- 0.2. An unexplained discrepancy appears between the spectroscopic distance d = 224 +46/-58 pc and the parallax distance d = 129 +6/-5 pc of LS V +4621. For the first time, we have identified Mg IV and Ar VI absorption lines in the spectrum of a hydrogen-rich central star and determined the Mg and Ar abundances as well as the individual abundances of iron-group elements (Cr, Mn, Fe, Co, and Ni). With the realistic treatment of metal opacities up to the iron group in the model-atmosphere calculations, the so-called Balmer-line problem (found in models that neglect metal-line blanketing) vanishes. Spectral analysis by means of NLTE model atmospheres has presently arrived at a high level of sophistication, which is now hampered largely by the lack of reliable atomic data and accurate line-broadening tables. Strong efforts should be made to improve upon this situation.Comment: 13 pages, 20 figure

IRAS 06562-0337, The Iron Clad Nebula: A New Young Star Cluster

IRAS 06562-0337 has been the recent subject of a classic debate: proto-planetary nebula or young stellar object? We present the first 2 micron image of IRAS 06562-0337, which reveals an extended diffuse nebula containing approximately 70 stars inside a 30 arcsec radius around a bright, possibly resolved, central object. The derived stellar luminosity function is consistent with that expected from a single coeval population, and the brightness of the nebulosity is consistent with the predicted flux of unresolved low-mass stars. The stars and nebulosity are spatially coincident with strong CO line emission. We therefore identify IRAS 06562-0337 as a new young star cluster embedded in its placental molecular cloud. The central object is likely a Herbig Be star, M approx 20 M_sun, which may be seen in reflection. We present medium resolution, high S/N, 1997 epoch optical spectra of the central object. Comparison with previously published spectra shows new evidence for time variable permitted and forbidden line emission, including SiII, FeII, [FeII], and [OI]. We suggest the origin is a dynamic stellar wind in the extended, stratified atmosphere of the massive central star in IRAS 06562-0337.Comment: 25 pages (4 figures) using aaspp4.sty. Accepted for publication in A

Digital relief generation from 3D models

It is difficult to extend image-based relief generation to high-relief generation, as the images contain insufficient height information. To generate reliefs from three-dimensional (3D) models, it is necessary to extract the height fields from the model, but this can only generate bas-reliefs. To overcome this problem, an efficient method is proposed to generate bas-reliefs and high-reliefs directly from 3D meshes. To produce relief features that are visually appropriate, the 3D meshes are first scaled. 3D unsharp masking is used to enhance the visual features in the 3D mesh, and average smoothing and Laplacian smoothing are implemented to achieve better smoothing results. A nonlinear variable scaling scheme is then employed to generate the final bas-reliefs and high-reliefs. Using the proposed method, relief models can be generated from arbitrary viewing positions with different gestures and combinations of multiple 3D models. The generated relief models can be printed by 3D printers. The proposed method provides a means of generating both high-reliefs and bas-reliefs in an efficient and effective way under the appropriate scaling factors