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
3184583
Carbon abundances and 12C/13C from globular cluster giants
The behaviour of the Δν = 2 CO bands around 2.3 μm was examined by comparing observed and synthetic spectra in stars in globular clusters of different metallicity. Changes in the 1 2 C/ 1 3 C isotopic ratio and the carbon abundances were investigated in stars from 3500-4900 K in the galactic globular clusters M71, M5, M3 and M13, covering the metallicity range from -0.7 to -1.6. We found relatively low carbon abundances that are not affected by the value of oxygen abundance. For most giants, the 1 2 C/ 1 3 C ratios determined are consistent with the equilibrium value for the CN cycle. This suggests complete mixing on the ascent of the red giant branch, in contrast to the substantially higher values predicted across this range of parameters by the current generation of models. We found some evidence for a larger dispersion of 1 2 C/ 1 3 C in giants of M71 of metallicity [μ] = [M/H] = -0.7 in comparison with the giants of M3, M5 and M13, which are more metal deficient. Finally, we show evidence for lower 1 2 C/ 1 3 C in giants of globular clusters with lower metallicities, as predicted by theory.
119068354
Spectral energy distribution for GJ406
Original article can be found at: http://www.aanda.org/----Copyright The European Southern Observatory
18728713
Effective temperatures, rotational velocities, microturbulent velocities and abundances in the atmospheres of the Sun, HD 1835 and HD 10700★
We describe our procedure to determine effective temperatures, rotational velocities, microturbulent velocities, and chemical abundances in the atmospheres of Sun-like stars. We use independent determinations of iron abundances using the fits to the observed Fe I and Fe II atomic absorption lines. We choose the best solution from the fits to these spectral features for the model atmosphere that provides the best confidence in the determined log N(Fe), Vt , and v sin i .Computations were done in the framework of LTE. Blending effects were accounted for explicitly. First, we compute the abundance of iron for a set of adopted microturbulent velocities. In some cases, a few points of log N(Fe I) = log N(Fe II) can be found. To determine the most selfconsistent effective temperature and microturbulent velocity in any star’s atmosphere, we used an additional constraint where we minimise the dependence of the derived abundances of Fe I and Fe II on the excitation potential of the corresponding lines. Using this procedure we analyse the spectra of the Sun and two well known solar type stars, HD1835 and HD10700 to determine their abundances, microturbulent velocity and rotational velocity. Our approach allows us to determine self-consistent values for the effective temperatures, abundances, Vt and v sin i . For the Sun we obtain the best agreement for a model atmosphere of Teff /log g/[Fe/H] = 5777/4.44/0.0, iron abundances and microturbulent velocities of log N(Fe) =4.44, Vt = 0.75 km/s, for the Fe I lines, and log N(Fe) = -4.47, Vt = 1.5 km/s for the Fe II lines. Furthermore, abundances of other elements obtained from the fits of their absorption features agree well enough (± 0.1 dex) with the known values for the Sun. We determined a rotational velocity of v sin i = 1.6 ± 0.3 km/s for the spectrum of the Sun as a star. For HD1835 the self-consistent solution for Fe I and Fe II lines log N(Fe)=+0.2 was obtained with a model atmosphere of 5807/4.47/+0.2 and microturbulent velocity Vt = 0.75 km/s, and leads to v sin i = 7.2 ± 0.5 km/s. For HD10700 the self-consistent solution log N(Fe) = -4.93 was obtained using a model atmosphere of 5383/4.59/-0.6 and microturbulent velocity Vt = 0.5 km/s. The Fe I and Fe II lines give rise to a v sin i = 2.4 ± 0.4 km/s. Using the Teff found from the ionisation equilibrium parameters for all three stars, we found abundances of a number of other elements: Ti, Ni, Ca, Si, Cr. We show that uncertainties in the adopted values of Teff of 100 K and Vt of 0.5 km/s change the abundances of elements up to 0.1 and 0.2 dex respectively. Galactic abundances variations can generally be larger than this measurement precision and therefore we can study abundance variations throughout the Galaxy.
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 .
8384149
Carbon monoxide bands in M dwarfs
We compare the observational and theoretical spectra of thev= 2 CO bands in a range of M dwarfs. We investigate the dependence of theoretical spectra on eective temperatures as well as carbon abundance. In general we find that the synthetic CO bands fit the observed data extremely well and are excellent diagnostics. In particular the synthetic spectra reasonably match observations and the best fit temperatures are similar to those found by empirical methods. We also examine the 12 C/ 13 C isotopic ratio. We find that fundamental 13 CO bands around 2.345 and 2.375m are good discriminators for the 12 C/ 13 C ratio in M dwarfs. The 2.375m band is more useful because it doesn't suer such serious contamination by water vapour transitions. Our current dataset does not quite have the wavelength coverage to perform a reliable determination of the 12 C/ 13 C ratio in M dwarfs. For this we recommend observing the region 2.31-2.40m at a resolution of better than 1000. Alternatively the observational problems of contamination by water vapour at 2.345m maybe solved by observing at resolutions of around 50 000. We also investigated the possibility of using thev= 1 CO bands around 4.5m. We find that the contamination due to water vapour is even more of a problem at these wavelengths.
15944115
Faster than Hermitian quantum mechanics.
Given an initial quantum state |psi(I)> and a final quantum state |psi(F)>, there exist Hamiltonians H under which |psi(I)> evolves into |psi(F)>. Consider the following quantum brachistochrone problem: subject to the constraint that the difference between the largest and smallest eigenvalues of H is held fixed, which H achieves this transformation in the least time tau? For Hermitian Hamiltonians tau has a nonzero lower bound. However, among non-Hermitian PT-symmetric Hamiltonians satisfying the same energy constraint, tau can be made arbitrarily small without violating the time-energy uncertainty principle. This is because for such Hamiltonians the path from |psi(I)> to |psi(F)> can be made short. The mechanism described here is similar to that in general relativity in which the distance between two space-time points can be made small if they are connected by a wormhole. This result may have applications in quantum computing.
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.
121068756
Phenomenological approach to chiral - symmetry breaking
It is shown that all meson-baryon and meson-meson $\ensuremath{\sigma}$ terms which can be extracted from experiment can be reconciled with the (3, \ifmmode\bar\else\textasciimacron\fi{}3) chiral-symmetry-breaking scheme, ${H}^{\ensuremath{'}}={u}_{0}+{\mathrm{cu}}_{8}$, provided that $c$ assumes the value $c\ensuremath{\sim}\ensuremath{-}1.0$.
119400599
Must a Hamiltonian be Hermitian
A consistent physical theory of quantum mechanics can be built on a complex Hamiltonian that is not Hermitian but instead satisfies the physical condition of space–time reflection symmetry (PT symmetry). Thus, there are infinitely many new Hamiltonians that one can construct that might explain experimental data. One would think that a quantum theory based on a non-Hermitian Hamiltonian violates unitarity. However, if PT symmetry is not broken, it is possible to use a previously unnoticed physical symmetry of the Hamiltonian to construct an inner product whose associated norm is positive definite. This construction is general and works for any PT-symmetric Hamiltonian. The dynamics is governed by unitary time evolution. This formulation does not conflict with the requirements of conventional quantum mechanics. There are many possible observable and experimental consequences of extending quantum mechanics into the complex domain, both in particle physics and in solid state physics.
116740407
T Decay and e^+e^- Annihilation at Low Energies in the Nonperturbative Approach to QCD
A brief review of a new nonperturbative expansion technique for QCD and itsapplication to the inclusive decay of the Г lepton and e^+e^- annihilation into hadrons at low energies is presented.