The search for planetary mass companions to field brown dwarfs with HST/NICMOS

We present the results of a high-resolution spectral differential imaging survey of 12 nearby, relatively young field L dwarfs (<1 Gyr) carried out with HST/NICMOS to search for planetary mass companions at small physical separations from their host. The survey resolved two brown dwarf binaries: the L dwarf system Kelu-1AB and the newly discovered L/T transition system 2MASS J031059+164815AB. For both systems common proper motion has already been confirmed in follow-up observations which have been published elsewhere. The derived separations of the binaries are smaller than 6 AU and consistent with previous brown dwarf binary statistics. Their mass ratios of q > 0.8 confirm the preference for equal mass systems similar to a large number of other surveys. Furthermore, we found tentative evidence for a companion to the L4 dwarf 2MASS W033703-175807, straddling the brown dwarf/planetary mass boundary and revealing an uncommonly low mass ratio system (q ~ 0.2) compared to the vast majority of previously found brown dwarf binaries. With a derived minimum mass of 10 - 15 Mjup, a planetary nature of the secondary cannot be ruled out yet. However, it seems more likely to be a very low mass brown dwarf secondary at the border of the spectral T/Y transition regime, primarily due to its similarities to recently found very cool T dwarfs. This would make it one of the closest resolved brown dwarf binaries (0.087" $/pm$ 0.015", corresponding to 2.52 $\pm$ 0.44 AU at a distance of 29 pc) with the coolest (Teff ~ 600-630 K) and least massive companion to any L or T dwarf.Comment: 33 pages, 8 figures, 2 tables, accepted for publication by Ap

Approximate Bayesian computation scheme for parameter inference and model selection in dynamical systems

Approximate Bayesian computation methods can be used to evaluate posterior distributions without having to calculate likelihoods. In this paper we discuss and apply an approximate Bayesian computation (ABC) method based on sequential Monte Carlo (SMC) to estimate parameters of dynamical models. We show that ABC SMC gives information about the inferability of parameters and model sensitivity to changes in parameters, and tends to perform better than other ABC approaches. The algorithm is applied to several well known biological systems, for which parameters and their credible intervals are inferred. Moreover, we develop ABC SMC as a tool for model selection; given a range of different mathematical descriptions, ABC SMC is able to choose the best model using the standard Bayesian model selection apparatus.Comment: 26 pages, 9 figure

Nanoscale periodicity in stripe-forming systems at high temperature: Au/W(110)

We observe using low-energy electron microscopy the self-assembly of monolayer-thick stripes of Au on W(110) near the transition temperature between stripes and the non-patterned (homogeneous) phase. We demonstrate that the amplitude of this Au stripe phase decreases with increasing temperature and vanishes at the order-disorder transition (ODT). The wavelength varies much more slowly with temperature and coverage than theories of stress-domain patterns with sharp phase boundaries would predict, and maintains a finite value of about 100 nm at the ODT. We argue that such nanometer-scale stripes should often appear near the ODT.Comment: 5 page

End-user interactions with intelligent and autonomous systems.

Systems that learn from or personalize themselves to users are quickly becoming mainstream yet interaction with these systems is limited and often uninformative for the end user. This workshop focuses on approaches and challenges to explore making these systems transparent, controllable and ultimately trustworthy to end users. The aims of the workshop are to help establish connections among researchers and industrial practitioners using real-world problems as catalysts to facilitate the exchange of approaches, solutions, and ideas about how to better support end users

Atomistic modelling of large-scale metal film growth fronts

We present simulations of metallization morphologies under ionized sputter deposition conditions, obtained by a new theoretical approach. By means of molecular dynamics simulations using a carefully designed interaction potential, we analyze the surface adsorption, reflection, and etching reactions taking place during Al physical vapor deposition, and calculate their relative probability. These probabilities are then employed in a feature-scale cellular-automaton simulator, which produces calculated film morphologies in excellent agreement with scanning-electron-microscopy data on ionized sputter deposition.Comment: RevTeX 4 pages, 2 figure