Four-colour photometry of eclipsing binaries. XLI uvby light curves for AD Bootis, HW Canis Majoris, SW Canis Majoris, V636 Centauri, VZ Hydrae, and WZ Ophiuchi

CONTEXT: Accurate mass, radius, and abundance determinations from binaries provide important information on stellar evolution, fundamental to central fields in modern astrophysics and cosmology. AIMS: Within the long-term Copenhagen Binary Project, we aim to obtain high-quality light curves and standard photometry for double-lined detached eclipsing binaries with late A, F, and G type main-sequence components, needed for the determination of accurate absolute dimensions and abundances, and for detailed comparisons with results from recent stellar evolutionary models. METHODS: Between March 1985 and July 2007, we carried out photometric observations of AD Boo, HW CMA, SW CMa, V636 Cen, VZ Hya, and WZ Oph at the Str"omgren Automatic Telescope at ESO, La Silla. RESULTS: We obtained complete uvby light curves, ephemerides, and standard uvby\beta indices for all six systems.For V636 Cen and HW CMa, we present the first modern light curves, whereas for AD Boo, SW CMa, VZ Hya, and WZ Oph, they are both more accurate and more complete than earlier data. Due to a high orbital eccentricity (e = 0.50), combined with a low orbital inclination (i = 84.7), only one eclipse, close to periastron, occurs for HW CMa. For the two other eccentric systems, V636 Cen (e = 0.134) and SW CMa (e = 0.316), apsidal motion has been detected with periods of 5270 +/- 335 and 14900 +/- 3600 years, respectively.Comment: Only change is: Bottom lines (hopefully) not truncated anymore. Accepted for publication in Astonomy & Astrophysic

Universal Probability-Free Conformal Prediction

We construct universal prediction systems in the spirit of Popper's falsifiability and Kolmogorov complexity and randomness. These prediction systems do not depend on any statistical assumptions (but under the IID assumption they dominate, to within the usual accuracy, conformal prediction). Our constructions give rise to a theory of algorithmic complexity and randomness of time containing analogues of several notions and results of the classical theory of Kolmogorov complexity and randomness.Comment: 27 page

Quantum erasure within the Optical Stern-Gerlach Model

In the optical Stern-Gerlach effect the two branches in which the incoming atomic packet splits up can display interference pattern outside the cavity when a field measurement is made which erases the which-way information on the quantum paths the system can follow. On the contrary, the mere possibility to acquire this information causes a decoherence effect which cancels out the interference pattern. A phase space analysis is also carried out to investigate on the negativity of the Wigner function and on the connection between its covariance matrix and the distinguishability of the quantum paths.Comment: 7 pages, 3 figure

Absolute dimensions of eclipsing binaries. XXVI, Setting a new standard : masses, radii, and abundances for the F-type systems AD Bootis, VZ Hydrae, and WZ Ophiuchi

Context. Accurate mass, radius, and abundance determinations from binaries provide important information on stellar evolution, fundamental to central fields in modern astrophysics and cosmology. Aims. We aim to determine absolute dimensions and abundances for the three F-type main-sequence detached eclipsing binaries ADBoo, VZHya, and WZOph and to perform a detailed comparison with results from recent stellar evolutionary models. Methods. uvby light curves and uvbyβ standard photometry were obtained with the Strömgren Automatic Telescope at ESO, La Silla, radial velocity observations at CfA facilities, and supplementary high-resolution spectra with ESO’s FEROS spectrograph. State-ofthe-art methods were applied for the analyses: the EBOP andWilson-Devinney binary models, two-dimensional cross-correlation and disentangling, and the VWA abundance analysis tool. Results. Masses and radii that are precise to 0.5–0.7% and 0.4–0.9%, respectively, have been established for the components, which span the ranges of 1.1 to 1.4 M and 1.1 to 1.6 R. The [Fe/H] abundances are from –0.27 to +0.10, with uncertainties between 0.07 and 0.15 dex. We find indications of a slight α-element overabundance of [α/Fe] ∼ +0.1 for WZOph. The secondary component of ADBoo and both components of WZOph appear to be slightly active. Yale-Yonsai and Victoria-Regina evolutionary models fit the components of ADBoo and VZHya almost equally well, assuming coeval formation, at ages of about 1.75/1.50 Gyr (ADBoo) and 1.25/1.00 Gyr (VZHya). BaSTI models, however, predict somewhat different ages for the primary and secondary components. For WZOph, the models from all three grids are significantly hotter than observed. A low He content, decreased envelope convection coupled with surface activity, and/or higher interstellar absorption would remove the discrepancy, but its cause has not been definitively identified. Conclusions. We have demonstrated the power of testing and comparing recent stellar evolutionary models using eclipsing binaries, provided their abundances are known. The strongest limitations and challenges are set by Teff and interstellar absorption determinations, and by their effects on and correlation with abundance results

Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot

We present a detailed study of the F-type detached eclipsing binary BK Peg, based on new photometric and spectroscopic observations. The two components, which have evolved to the upper half of the main-sequence band, are quite different with masses and radii of (1.414 +/- 0.007 Msun, 1.988 +/- 0.008 Rsun) and (1.257 +/- 0.005 Msun, 1.474 +/- 0.017 Rsun), respectively. The 5.49 day period orbit of BK Peg is slightly eccentric (e = 0.053). The measured rotational velocities are 16.6 +/- 0.2 (primary) and 13.4 +/- 0.2 (secondary) km/s. For the secondary component this corresponds to (pseudo)synchronous rotation, whereas the primary component seems to rotate at a slightly lower rate. We derive an iron abundance of [Fe/H] =-0.12 +/- 0.07 and similar abundances for Si, Ca, Sc, Ti, Cr and Ni. Yonsei-Yale and Victoria-Regina evolutionary models for the observed metal abundance reproduce BK Peg at ages of 2.75 and 2.50 Gyr, respectively, but tend to predict a lower age for the more massive primary component than for the secondary. We find the same age trend for three other upper main-sequence systems in a sample of well studied eclipsing binaries with components in the 1.15-1.70 Msun range, where convective core overshoot is gradually ramped up in the models. We also find that the Yonsei-Yale models systematically predict higher ages than the Victoria-Regina models. The sample includes BW Aqr, and as a supplement we have determined a [Fe/H] abundance of -0.07 +/- 0.11 for this late F-type binary. We propose to use BK Peg, BW Aqr, and other well-studied 1.15-1.70 Msun eclipsing binaries to fine-tune convective core overshoot, diffusion, and possibly other ingredients of modern theoretical evolutionary models.Comment: Accepted for publication in Astronomy and Astrophysic

The Science of Phylogenetic Systematics: Explanation, Prediction, and Test

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73926/1/j.1096-0031.1999.tb00279.x.pd

Minimizing follow-up for space-based transit surveys using full lightcurve analysis

One of the biggest challenges facing large transit surveys is the elimination of false-positives from the vast number of transit candidates. We investigate to what extent information from the lightcurves can identify blend scenarios and eliminate them as planet candidates, to significantly decrease the amount of follow-up observing time required to identify the true exoplanet systems. If a lightcurve has a sufficiently high signal-to-noise ratio, a distinction can be made between the lightcurve of a stellar binary blended with a third star and the lightcurve of a transiting exoplanet system. We perform simulations to determine what signal-to-noise level is required to make the distinction between blended and non-blended systems as function of transit depth and impact parameter. Subsequently we test our method on real data from the first IRa01 field observed by the CoRoT satellite, concentrating on the 51 candidates already identified by the CoRoT team. About 70% of the planet candidates in the CoRoT IRa01 field are best fit with an impact parameter of b>0.85, while less than 15% are expected in this range considering random orbital inclinations. By applying a cut at b<0.85, meaning that ~15% of the potential planet population would be missed, the candidate sample decreases from 41 to 11. The lightcurves of 6 of those are best fit with such low host star densities that the planet-to-star size ratii imply unrealistic planet radii of R>2RJup. Two of the five remaining systems, CoRoT1b and CoRoT4b, have been identified as planets by the CoRoT team, for which the lightcurves alone rule out blended light at 14% (2sigma) and 31% (2sigma). We propose to use this method on the Kepler database to study the fraction of real planets and to potentially increase the efficiency of follow-up.Comment: 13 pages, 11 figures, 2 tables. Accepted for publication in A&

Passage of Time in a Planck Scale Rooted Local Inertial Structure

It is argued that the `problem of time' in quantum gravity necessitates a refinement of the local inertial structure of the world, demanding a replacement of the usual Minkowski line element by a 4+2n dimensional pseudo-Euclidean line element, with the extra 2n being the number of internal phase space dimensions of the observed system. In the refined structure, the inverse of the Planck time takes over the role of observer-independent conversion factor usually played by the speed of light, which now emerges as an invariant but derivative quantity. In the relativistic theory based on the refined structure, energies and momenta turn out to be invariantly bounded from above, and lengths and durations similarly bounded from below, by their respective Planck scale values. Along the external timelike world-lines, the theory naturally captures the `flow of time' as a genuinely structural attribute of the world. The theory also predicts expected deviations--suppressed quadratically by the Planck energy--from the dispersion relations for free fields in the vacuum. The deviations from the special relativistic Doppler shifts predicted by the theory are also suppressed quadratically by the Planck energy. Nonetheless, in order to estimate the precision required to distinguish the theory from special relativity, an experiment with a binary pulsar emitting TeV range gamma-rays is considered in the context of the predicted deviations from the second-order shifts.Comment: 17 pages; Diagram depicting "the objective flow of time" is replaced with a much-improved diagra

Realism and Objectivism in Quantum Mechanics

The present study attempts to provide a consistent and coherent account of what the world could be like, given the conceptual framework and results of contemporary quantum theory. It is suggested that standard quantum mechanics can, and indeed should, be understood as a realist theory within its domain of application. It is pointed out, however, that a viable realist interpretation of quantum theory requires the abandonment or radical revision of the classical conception of physical reality and its traditional philosophical presuppositions. It is argued, in this direction, that the conceptualization of the nature of reality, as arising out of our most basic physical theory, calls for a kind of contextual realism. Within the domain of quantum mechanics, knowledge of 'reality in itself', 'the real such as it truly is' independent of the way it is contextualized, is impossible in principle. In this connection, the meaning of objectivity in quantum mechanics is analyzed, whilst the important question concerning the nature of quantum objects is explored.Comment: 20 pages. arXiv admin note: substantial text overlap with arXiv:0811.3696, arXiv:quant-ph/0502099, arXiv:0904.2702, arXiv:0904.2859, arXiv:0905.013

Encouraging versatile thinking in algebra using the computer

In this article we formulate and analyse some of the obstacles to understanding the notion of a variable, and the use and meaning of algebraic notation, and report empirical evidence to support the hypothesis that an approach using the computer will be more successful in overcoming these obstacles. The computer approach is formulated within a wider framework ofversatile thinking in which global, holistic processing complements local, sequential processing. This is done through a combination of programming in BASIC, physical activities which simulate computer storage and manipulation of variables, and specific software which evaluates expressions in standard mathematical notation. The software is designed to enable the user to explore examples and non-examples of a concept, in this case equivalent and non-equivalent expressions. We call such a piece of software ageneric organizer because if offers examples and non-examples which may be seen not just in specific terms, but as typical, or generic, examples of the algebraic processes, assisting the pupil in the difficult task of abstracting the more general concept which they represent. Empirical evidence from several related studies shows that such an approach significantly improves the understanding of higher order concepts in algebra, and that any initial loss in manipulative facility through lack of practice is more than made up at a later stage