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
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
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
67841979
Carbon monoxide in low-mass dwarf stars
We compare high resolution infrared observations of the CO 3-1 bands in the 2.297– 2.310 µm region of M dwarfs and one L dwarf with theoretical expectations. We find a good match between the observational and synthetic spectra throughout the 20003500K temperature regime investigated. Nonetheless, for the 2500-3500 K temperature range the temperatures that we derive from synthetic spectral fits are higher than expected from more empirical methods by several hundred K. In order to reconcile our findings with the empirical temperature scale it is necessary to invoke warming of the model atmosphere used to construct the synthetic spectra. We consider that the most likely reason for the back-warming is missing high temperature opacity due to water vapour. We compare the water vapour opacity of the Partridge & Schwenke (1997) line list used for the model atmosphere with the output from a preliminary calculation by Barber & Tennyson (2004). While the Partridge & Schwenke line list is a reasonable spectroscopic match for the new line list at 2000 K, by 4000 K it is missing around 25% of the water vapour opacity. We thus consider that the offset between empirical and synthetic temperature scales is explained by the lack of hot water vapour used for computation of the synthetic spectra. For our coolest objects with temperatures below 2500 K we find best fits when using synthetic spectra which include dust emission. Our spectra also allow us to constrain the rotational velocities of our sources, and these velocities are consistent with the broad trend of rotational velocities increasing from M to L.
16341718
A Neptune-mass Planet Orbiting the Nearby G Dwarf HD 16417
Original article can be found at: http://www.iop.org/EJ/journal/1538-3881 Copyright IOP Publishing / American Astronomical Society. DOI: 10.1088/0004-637X/697/2/1263 [Full text of this article is not available in the UHRA]
13106340
The Prospects for Finding Brown Dwarfs in Eclipsing Binary Systems and Measuring Brown Dwarf Properties
We present the results of a simulation to investigate the prospects of measuring mass, age, radius, metallicity, and luminosity data for brown dwarfs in fully eclipsing binary systems around dwarf spectral types from late K to early M that could be identified by ultra-wide-field transit surveys such as SuperWASP. These surveys will monitor approximately a million K and M dwarfs with (where blending of sources is not FbF 1 20 a significant problem) at a level sufficient to detect transits of low-luminosity companions. We look at the current observational evidence for such systems and suggest that ∼1% of late K and early-to-mid M dwarfs could have a very close (∼0.02 AU) brown dwarf companion. With this assumption, and using SuperWASP as an example, our simulation predicts that ∼400 brown dwarfs in fully eclipsing binary systems could be discovered. All of these eclipsing binaries could yield accurate brown dwarf mass and radius measurements from radial velocity and follow-up light curve measurements. By inferring the brown dwarf effective temperature distribution, assuming a uniform age spread and an companion brown dwarf mass function, the simulation estimates that brown a p 0.5 dwarf brightness could also be measurable (at the 10% level) for ∼60 of these binary systems from near-infrared follow-up light curves of the secondary eclipse. We consider irradiation of these brown dwarfs by their primary stars and conclude that it would be below the 10% level for ∼70% of them. This means that in these cases, the measured brown dwarf brightnesses should essentially be the same as those of free-floating counterparts. The predicted age distribution of the primaries is dominated by young systems, and ∼20 binaries could be younger than 1 Gyr. Irradiation will be below the 10% level for ∼80% of these. We suggest that many of these young binary systems will be members of "kinematic moving groups," allowing their ages to be accurately constrained.
121035972
s-Channel helicity conservation, fixed poles and dip mechanisms
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.
123586127
Variational approach to the SU(2) mass gap on the lattice
A brief introduction is given to the basic idea of the linear delta expansion, which is illustrated in the case of a simple integral. The method is then applied to the calculation of the scalar glueball mass in lattice SU(2).
120811155
INVARIANT AMPLITUDES AND THIRD-ORDER LOW-ENERGY THEOREM FOR NUCLEON COMPTON SCATTERING.
Abstract Invariant amplitudes free of kinematic singularities and constraints are found for nucleon Compton scattering. Using these amplitudes and exploiting crossing symmetry it is shown that the low-energy theorem can be extended through third order in the photon energy.
119298480
Interactions of Hermitian and non-Hermitian Hamiltonians
The coupling of non-Hermitian -symmetric Hamiltonians to standard Hermitian Hamiltonians, each of which individually has a real energy spectrum, is explored by means of a number of soluble models. It is found that in all cases the energy remains real for small values of the coupling constant, but becomes complex if the coupling becomes stronger than some critical value. For a quadratic non-Hermitian -symmetric Hamiltonian coupled to an arbitrary real Hermitian -symmetric Hamiltonian, the reality of the ground-state energy for small enough coupling constant is established up to second order in perturbation theory.