The Invisible Monster Has Two Faces: Observations of Є Aurigae with the Herschel Space Observatory

We present Herschel Space Observatory photometric observations of the unique, long-period eclipsing binary star Є Aurigae. Its extended spectral energy distribution is consistent with our previously published cool (550 K) dust disk model. We also present an archival infrared spectral energy distribution of the side of the disk facing the bright F-type star in the binary, which is consistent with a warmer (1150 K) disk model. The lack of strong molecular emission features in the Herschel bands suggests that the disk has a low gas-to-dust ratio. The spectral energy distribution and Herschel images imply that the 250 GHz radio detection reported by Altenhoff et al. is likely contaminated by infrared-bright, extended background emission associated with a nearby nebular region and should be considered an upper limit to the true flux density of Є Aur

Natural language processing and advanced information management

Integrating diverse information sources and application software in a principled and general manner will require a very capable advanced information management (AIM) system. In particular, such a system will need a comprehensive addressing scheme to locate the material in its docuverse. It will also need a natural language processing (NLP) system of great sophistication. It seems that the NLP system must serve three functions. First, it provides an natural language interface (NLI) for the users. Second, it serves as the core component that understands and makes use of the real-world interpretations (RWIs) contained in the docuverse. Third, it enables the reasoning specialists (RSs) to arrive at conclusions that can be transformed into procedures that will satisfy the users' requests. The best candidate for an intelligent agent that can satisfactorily make use of RSs and transform documents (TDs) appears to be an object oriented data base (OODB). OODBs have, apparently, an inherent capacity to use the large numbers of RSs and TDs that will be required by an AIM system and an inherent capacity to use them in an effective way

Discovery of an Unusual High State in the Long-Term Light Curve of AM Herculis

The magnetic cataclysmic variable archetype AM Herculis is known to display high and low photometric states, in which it switches from Roche lobe-overflow accretion (high) to wind accretion (low). The origin of this behavior is still unknown (although it is believed to be linked to the presence of starspots located near the L1 point on the secondary star), as are the specifics of duration and frequency of the two states. During the recent (2007) transition from an exceptionally long period of persistent low state behavior back to the high state, AM Her entered a short (~2 month) intermediate state, in which its brightness remained at ~0.5 mag fainter than the normal high-state level. Within the recorded history of AM Her, this was the first time the system displayed such behavior. Using data from the American Association of Variable Star Observers, we compare the characteristics of this faint high state to the subsequent normal high state, and a prior "failed high state," in which the system briefly reached a brightness level near that of the normal high state before rapidly returning to the low state. The distribution of magnitude values attained during each state, along with the shapes of the orbital light curve in each state, support a scenario in which the specific configuration of the accretion flow between the secondary star and the white dwarf must be rapidly established at the end of a low state, even before the mass transfer rate has reached the normal high-state level

CSS091109:035759+102943 - a candidate polar

We report optical time-resolved photometry of the CRTS transient CSS091109:035759+102943. Pronounced orbital variability with a 114 min period, large X-ray variability and the IR to X-ray spectral energy distribution suggest a classification as a magnetic cataclysmic binary, a likely AM Herculis star or polar.Comment: Astronomische Nachrichten, in press (4 pages, 4 figures

White Dwarf - Red Dwarf Systems Resolved with the Hubble Space Telescope. II. Full Snapshot Survey Results

Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low mass stellar and substellar companions. Of the 72 targets which remain candidate and confirmed white dwarfs with near-infrared excess, 43 are spatially resolved into two or more components, and a total of 12 systems are potentially triples. There is a possible, slight deficit of earlier spectral types (bluer colors) among the spatially unresolved companions, exactly the opposite of expectations if significant mass is transferred to the companion during the common envelope phase. Using the best available distance estimates, the low mass companions to white dwarfs exhibit a bimodal distribution in projected separation. This result supports the hypothesis that during the giant phases of the white dwarf progenitor, any unevolved companions either migrate inward to short periods of hours to days, or outward to periods of hundreds to thousands of years. No intermediate projected separations of a few to several AU are found among these pairs. However, a few double M dwarfs (within triples) are spatially resolved in this range, empirically demonstrating that such separations were readily detectable among the binaries with white dwarfs. A straightforward and testable prediction emerges: all spatially unresolved, low mass stellar and substellar companions to white dwarfs should be in short period orbits. This result has implications for substellar companion and planetary orbital evolution during the post-main sequence lifetime of their stellar hosts.Comment: Accepted to ApJ Supplement Series, emulateapj format, 14 figures, 8 table

Recent Results from Infrared Observations of White Dwarfs, their Companions, and the Dust that Surrounds Them

Although "traditionally" observed at short wavelengths, white dwarfs have displayed many surprising features when probed in the infrared. We present an overview of recent results from ground- and space-based near- to mid-infrared observations of white dwarfs. These include the discovery of many new candidate binary stars containing low mass stellar or sub-stellar companions from a sample of objects previously thought to be single white dwarfs, and Spitzer Space Telescope observations that suggest that dust is common in the environs of white dwarfs in cataclysmic variables

Mid-Infrared Circumstellar Shell Sources Discovered with Spitzer: An Obscured Population of Massive Stars?

We have discovered a large number of circular and elliptical shells around luminous central sources at 24 μm with the MIPS instrument on board the Spitzer Space Telescope. Most of these shells are not visible in the shorter wavelengths bands of IRAC or archival 2MASS and optical images. On the other hand, many of the central stars are detected in the 2MASS catalog, but lack an optical counterpart, indicating that we are dealing with a population of highly obscured objects. Our archival follow-up effort has revealed 90% of these shell sources to be previously unknown

Modeling steric effects in antibody aggregation using rule-based methods

The allergic response is produced by the release of immune mediators by mast cells and basophils. This process, in turn, is initiated by the aggregation of antigens and IgE-FcεRI antibody-receptor complexes. Computational modeling of antibody- antigen aggregate formation as well as the size and structure of these aggregates is an important tool for greater understanding of the allergic response. In addition, the incorporation of molecular geometry into aggregation models can more accurately capture details of the aggregation process, and may lead to insights into how geom- etry affects aggregate formation. However, it is challenging to simulate aggregation due to the computational cost of simulating large molecules. Methods to geometri- cally model antibody aggregation inspired by rigid body robotic motion simulations have previously been developed; however, high computational cost mandates that the resolution of the 3D molecular models be reduced, which affects the results of the simulation. Rule-based modeling can be used to model aggregation with low computational cost, but traditional rule-based modeling approaches do not include details of molecular geometry. In this work, we propose a novel implementation of rule-based modeling that encodes details of molecular geometry into the rules and the binding rate constant associated with each rule. We demonstrate how the set of rules is constructed accord- ing to the curvature of the molecule. We then perform a study of antigen-antibody aggregation using our proposed method combined with a previously developed 3D rigid-body Monte Carlo simulation. We first simulate the binding of IgE antibodies bound to cell surface receptors FcεRI to various binding regions of the allergen Pen a 1 using the aforementioned Monte Carlo simulation, and we analyze the distribution of the sizes of the aggregates that form during the simulation. Then, using our novel rule-based approach, we optimize a rule-based model according to the geometry of the Pen a 1 molecule and the data from the Monte Carlo simulation. In particular, we use the distances between the binding regions of the Pen a 1 molecule to optimize the rules and associated binding rate constants. The optimized rule-based models provide information about the average steric hindrance between binding regions and the probability that IgE-FcεRI receptor complexes will bind to these regions. In ad- dition, the optimized rule-based models provide a means of quantifying the variation in aggregate size distribution that results from differences in molecular geometry. We perform this procedure for seven resolutions and three molecular conforma- tions of Pen a 1. We then analyze the impact of resolution and conformation on the aggregate size distribution and on the optimal rule-based model. In addition, we develop a predictive model by first fixing the rule set and varying only the binding rate constant for each resolution, and then fitting the resulting data to a function. This model is intended to enable the prediction of the aggregate size distribution for higher resolutions while requiring only data for lower resolution Monte Carlo models, thus enhancing computational efficiency. Finally, we use a simple rule-based model to fit experimental cell degranulation data for various concentrations of the shrimp allergen Pen a 1 and the IgE antibody