13406335
A search for southern ultracool dwarfs and wide binary systems in young moving groups
We associate 135 low-mass ultracool dwarfs in the southern hemisphere as candidate members of five moving groups using photometric and astrometric selection techniques. Of these objects, three candidates possess published radial velocities allowing a galactic space motion to be calculated, and the kinematic membership of the moving groups to be assessed. One object is a possible member of the IC2391 or Hyades moving groups. We also re-identify a previously known member of the Castor moving group. Also identified is a possible member of the Pleiades moving group, although the large uncertainties associated with the space motion of this object mean that it remains unconfirmed kinematically. Possible membership of moving groups has allowed possible ages and metallicities to be constrained for these objects and evolutionary models have been used to estimate their mass. In addition, the SuperCOSMOS and Hipparcos catalogues were searched for common proper motion binary companions to the 135 candidate moving group members. Three potential binary systems have been found. Further investigation is required to determine if one of these is the widest double brown dwarf binary system known, and another may consist of a low-mass star and a dwarf carbon star. We estimate that up to ∼75 of our candidate moving group members should be genuine, and discuss future work that will confirm and exploit this major new sample.
7959093
Discovery of the First Very Wide WD LD Binary System
Original paper can be found at: http://www.astrosociety.org/pubs/cs/361.html--Copyright Astronomical Society of the Pacific
7248338
Selection functions in doppler planet searches
We present a preliminary analysis of the sensitivity of Anglo-Australian Planet Search data to the orbital parameters of extrasolar planets. To do so, we have developed new tools for the automatic analysis of large-scale simulations of Doppler velocity planet search data. One of these tools is the two-dimensional Keplerian Lomb-Scargle (LS) periodogram that enables the straightforward detection of exoplanets with high eccentricities (something the standard LS periodogram routinely fails to do). We used this technique to redetermine the orbital parameters of HD20782b, with one of the highest known exoplanet eccentricities (e = 0.97 +/- 0.01). We also derive a set of detection criteria that do not depend on the distribution functions of fitted Keplerian orbital parameters (which we show are non-Gaussian with pronounced, extended wings). Using these tools, we examine the selection functions in orbital period, eccentricity and planet mass of Anglo-Australian Planet Search data for three planets with large-scale Monte Carlo like simulations. We find that the detectability of exoplanets declines at high eccentricities. However, we also find that exoplanet detectability is a strong function of epoch-to-epoch data quality, number of observations and period sampling. This strongly suggests that simple parametrizations of the detectability of exoplanets based on `whole-of-survey' metrics may not be accurate. We have derived empirical relationships between the uncertainty estimates for orbital parameters that are derived from least-squares Keplerian fits to our simulations and the true 99 per cent limits for the errors in those parameters, which are larger than equivalent Gaussian limits by the factors of 5-10. We quantify the rate at which false positives are made by our detection criteria, and find that they do not significantly affect our final conclusions. And finally, we find that there is a bias against measuring near-zero eccentricities, which becomes more significant in
7184822
PARALLAXES OF SOUTHERN EXTREMELY COOL OBJECTS. I. TARGETS, PROPER MOTIONS, AND FIRST RESULTS
We present results from the PARallaxes of Southern Extremely Cool objects (PARSEC) program, an observational program begun in 2007 April to determine parallaxes for 122 L and 28 T southern hemisphere dwarfs using the Wide Field Imager on the ESO 2.2 m telescope. The results presented here include parallaxes of 10 targets from observations over 18 months and a first version proper motion catalog. The proper motions were obtained by combining PARSEC observations astrometrically reduced with respect to the Second US Naval Observatory CCD Astrograph Catalog, and the Two Micron All Sky Survey Point Source Catalog. The resulting median proper motion precision is 5 mas yr–1 for 195,700 sources. The 140 0.3 deg2 fields sample the southern hemisphere in an unbiased fashion with the exception of the galactic plane due to the small number of targets in that region. The proper motion distributions are shown to be statistically well behaved. External comparisons are also fully consistent. We will continue to update this catalog until the end of the program, and we plan to improve it including also observations from the GSC2.3 database. We present preliminary parallaxes with a 4.2 mas median precision for 10 brown dwarfs, two of which are within 10 pc. These increase the present number of L dwarfs by 20% with published parallaxes. Of the 10 targets, seven have been previously discussed in the literature: two were thought to be binary, but the PARSEC observations show them to be single; one has been confirmed as a binary companion and another has been found to be part of a binary system, both of which will make good benchmark systems. These results confirm that the foreseen precision of PARSEC can be achieved and that the large field of view will allow us to identify wide binary systems. Observations for the PARSEC program will end in early 2011 providing three to four years of coverage for all targets. The main expected outputs are: more than a 100% increase in the number of L dwarfs with parallaxes, increment in the number of objects per spectral subclass up to L9—in conjunction with published results—to at least 10, and to put sensible limits on the general binary fraction of brown dwarfs. We aim to contribute significantly to the understanding of the faint end of the H-R diagram and of the L/T transition region.
14166441
The Liverpool-Edinburgh high proper motion survey
We present a catalogue of 6206 stars which have proper motions exceeding 0.18 �� yr −1 with an R-band faint magni- tude limit of 19.5 mag. This catalogue has been produced using SuperCOSMOS digitized R-band ESO and UK Schmidt Plates in 131 Schmidt fields covering more than 3000 square degrees (>7.5% of the whole sky) at the South Galactic Cap. The survey is ≥90% complete within the nominal limits of the Luyten Two Tenths Catalogue of mR ≤ 18.5 mag and 0.2 ≤ µ ≤ 2.5 �� yr −1 , and is ≥80% complete for mR ≤ 19.5 mag and µ ≤ 2.5 �� yr −1 .
16852132
The discovery of an M4+T8.5 binary system
The original article can be found at: http://www3.interscience.wiley.com Copyright Blackwell Publishing / Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14620.x
121035972
s-Channel helicity conservation, fixed poles and dip mechanisms
117287068
A New Approach to QCD Sum Rules and Inclusive $\tau$ Decay
We show that renormalization group improvement, making use of analyticity and the structure of the operator product expansion, combined with a non-perturbative expansion method allows one to describe quarkonium states via QCD sum rules without the need for explicit power corrections. This technique also allows an accurate determination of parameters related to the inclusive decay of the $\tau$ lepton.
11004734
Complex extension of quantum mechanics.
Requiring that a Hamiltonian be Hermitian is overly restrictive. A consistent physical theory of quantum mechanics can be built on a complex Hamiltonian that is not Hermitian but satisfies the less restrictive and more physical condition of space-time reflection symmetry (PT symmetry). One might expect a non-Hermitian Hamiltonian to lead to a violation of unitarity. However, if PT symmetry is not spontaneously broken, it is possible to construct a previously unnoticed symmetry C of the Hamiltonian. Using C, an inner product whose associated norm is positive definite can be constructed. The procedure is general and works for any PT-symmetric Hamiltonian. Observables exhibit CPT symmetry, and the dynamics is governed by unitary time evolution. This work is not in conflict with conventional quantum mechanics but is rather a complex generalization of it.
123362359
Extension of PT -Symmetric Quantum Mechanics to Quantum Field Theory with Cubic Interaction
It has recently been shown that a non-Hermitian Hamiltonian H possessing an unbroken PT symmetry (i) has a real spectrum that is bounded below, and (ii) defines a unitary theory of quantum mechanics with positive norm. The proof of unitarity requires a linear operator C, which was originally defined as a sum over the eigenfunctions of H. However, using this definition to calculate C is cumbersome in quantum mechanics and impossible in quantum field theory. An alternative method is devised here for calculating C directly in terms of the operator dynamical variables of the quantum theory. This new method is general and applies to a variety of quantum mechanical systems having several degrees of freedom. More importantly, this method is used to calculate the C operator in quantum field theory. The C operator is a new time-independent observable in PT -symmetric quantum field theory.
120327115
Comment on a proposed three-dimensional wave equation for mesons
A proposed equation for bound states of confined quarks is shown to be invalid. Possible modifications are discussed.