Results for "H. R. A. Jones"

total 340102took 0.19s
Benchmark ultra-cool dwarfs in widely separated binary systemsNov 22 2009Jan 21 2010Ultra-cool dwarfs as wide companions to subgiants, giants, white dwarfs and main sequence stars can be very good benchmark objects, for which we can infer physical properties with minimal reference to theoretical models, through association with the primary ... More
The effect of M dwarf starspot activity on low-mass planet detection thresholdsNov 04 2010In light of the growing interest in searching for low mass, rocky planets, we investigate the impact of starspots on radial velocity searches for earth-mass planets in orbit about M dwarf stars. Since new surveys targeting M dwarfs will likely be carried ... More
The prospects for finding brown dwarfs in eclipsing binary systems and measuring brown dwarf propertiesDec 07 2004We 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 late K and early M dwarfs identified by ultra-wide-field transit ... More
Implementation of a Quantum Search Algorithm on a Nuclear Magnetic Resonance Quantum ComputerMay 22 1998We demonstrate an implementation of a quantum search algorithm on a two qubit NMR quantum computer based on cytosine.
An introduction to artificial neural networksFeb 13 2001Artificial neural networks are algorithms which have been developed to tackle a range of computational problems. These range from modelling brain function to making predictions of time-dependent phenomena to solving hard (NP-complete) problems. In this ... More
Quantum Logic Gates and Nuclear Magnetic Resonance Pulse SequencesMay 22 1998We demonstrate how NMR can in principle be used to implement all the elements required to build quantum computers, and briefly discuss the potential applications of insights from quantum logic to the development of novel pulse sequences with applications ... More
Exoplanets from the CHEPS: Discovery of the Double Planet System HD191760Nov 18 2008Nov 26 2008The paper was withdrawn due to another possible solution to the dataset that is significantly different in nature. This issue will be addressed shortly and clarified with an additional data point.
Ultra-cool Dwarfs from Large Area SurveysFeb 16 2009Jan 21 2010We selected brown dwarf candidates from the seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7) with new photometric selectioncriteria based on a parameteriaztion of well-known L and T dwarfs. Then we confirmed their status with SDSS spectra. ... More
The Calan-Hertfordshire Extrasolar Planet SearchDec 29 2009The detailed study of the exoplanetary systems HD189733 and HD209458 has given rise to a wealth of exciting information on the physics of exoplanetary atmospheres. To further our understanding of the make-up and processes within these atmospheres we require ... More
A Metal-biased Planet SearchOct 01 2008We have begun a metal-rich planet search project using the HARPS instrument in La Silla, Chile to target planets with a high potential to transit their host star and add to the number of bright benchmark transiting planets. The sample currently consists ... More
Lack of cooling flow clusters at z>0.5Nov 14 2006The goal of this work is to study the incidence rate of "cooling flows" in the high redshift clusters using Chandra observations of z>0.5 objects from a new large, X-ray selected catalog. We find that only a very small fraction of high-z objects have ... More
Identifying Ultra-Cool Dwarfs at Low Galactic Latitudes: A Southern Candidate CatalogueApr 19 2012We present an Ultra-Cool Dwarf (UCD) catalogue compiled from low southern Galactic latitudes and mid-plane, from a cross-correlation of the 2MASS and SuperCOSMOS surveys. The catalogue contains 246 members identified from 5042 sq. deg. within 220 deg. ... More
Cool dwarfs stars from the Torino Observatory Parallax ProgramMar 07 2010We investigate and parameterise high proper motion red stars in the Torino Observatory Parallax Program. Observations of 27 objects were made over the period 1994 - 2001 on the 1.05m Torino telescope. The trigonometric parallaxes and proper motions were ... More
A Goldilocks principle for modeling radial velocity noiseJun 16 2016The doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial ... More
Vsini-s for late-type stars from spectral synthesis in K-band regionFeb 20 2012We analyse medium-resolution spectra (R\sim 18000) of 19 late type dwarfs in order to determine vsini-s using synthetic rather than observational template spectra. For this purpose observational data around 2.2 $\mu$m of stars with spectral classes from ... More
Finding benchmark brown dwarfs to probe the IMF as a function of timeMar 13 2006Using a simulated disk brown dwarf (BD) population, we find that new large area infrared surveys are expected to identify enough BDs covering wide enough mass--age ranges to potentially measure the mass function down to ~0.03Mo, and the BD formation history ... More
Discovery of a widely separated UCD-WD binaryMay 30 2008We present the discovery of the widest known ultracool dwarf - white dwarf binary. This binary is the first spectroscopically confirmed widely separated system from our target sample. We have used the 2MASS and SuperCOSMOS archives in the southern hemisphere, ... More
Energy dispersion compensation and beam loading in X-band linacs for the JLC/NLCJul 04 2003The shape of an RF pulse is distorted upon propagating through an X-band accelerator structure due to dispersive effects. This distortion together with beam loading introduce energy spread between 192 bunches. In order to minimize this energy spread we ... More
A Catalog of 200 Galaxy Clusters Serendipitously Detected in the ROSAT PSPC Pointed ObservationsMar 10 1998We present a catalog of 200 clusters of galaxies serendipitously detected in 647 ROSAT PSPC pointings covering 158 square degrees. This is one of the largest X-ray selected cluster samples, comparable in size only to the ROSAT All-Sky Survey sample of ... More
A Richness Study of 14 Distant X-ray Clusters From the 160 Square Degree SurveyMay 14 2001We have measured the surface density of galaxies toward 14 X-ray-selected cluster candidates at redshifts greater than z=0.46, and we show that they are associated with rich galaxy concentrations. We find that the clusters range between Abell richness ... More
X-ray Over-Luminous Elliptical Galaxies: A New Class of Mass Concentrations in the Universe?Mar 02 1999We detect four isolated, X-ray over-luminous (Lx>2e43 [h/0.5]**-2 erg/s) elliptical galaxies (OLEGs) in our 160 square degree ROSAT PSPC survey. The extent of their X-ray emission, total X-ray luminosity, total mass, and mass of the hot gas in these systems ... More
Evolution of Cluster X-Ray Luminosities and Radii: Results from the 160 Square Degree ROSAT SurveyMar 10 1998We searched for cluster X-ray luminosity and radius evolution using our sample of 200 galaxy clusters detected in the 160 deg^2 survey with the ROSAT PSPC (Vikhlinin et al. 1998, astro-ph/9803099). With such a large area survey, it is possible, for the ... More
The nature and space density of fossil groups of galaxiesApr 14 2003We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one galaxy brighter ... More
Spectral imaging of the Central Molecular Zone in multiple 7-mm molecular linesApr 26 2013We have imaged 24 spectral lines in the Central Molecular Zone (CMZ) around the Galactic Centre, in the range 42 to 50 GHz. The lines include emission from the CS, CH3OH, HC3N, SiO, HNCO, HOCO+, NH2CHO, OCS, HCS+, CCS, C34S, 13CS, 29SiO, H13CCCN, HCC13CN ... More
A rotational and variability study of a large sample of PMS stars in NGC 2264Feb 09 2004We present the results of an extensive search for periodic and irregular variable pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC 2664, based on photometric monitoring using the Wide Field Imager (WFI) on the 2.2m telescope on La ... More
Experimental study of photon beam polarimeter based on nuclear e+e- pair production in an amorphous targetOct 16 2006The experimental method of the linearly polarized photons polarimetry,using incoherent e+e- pair production process has been investigated on the beam of coherent bremsstrahlung (CB) photons in the energy range of 0.9-1.1 GeV at the Yerevan synchrotron. ... More
Two new ultra-cool benchmark systems from WISE+2MASSMar 09 2013We have used the 2MASS all-sky survey and the WISE to look for ultracool dwarfs that are part of multiple systems containing main sequence stars. We cross-matched L dwarf candidates from the surveys with Hipparcos and Gliese stars, finding two new systems. ... More
Abacus models for parabolic quotients of affine Weyl groupsMay 26 2011Mar 09 2012We introduce abacus diagrams that describe minimal length coset representatives in affine Weyl groups of types B, C, and D. These abacus diagrams use a realization of the affine Weyl group of type C due to Eriksson to generalize a construction of James ... More
The WARPS survey for faint Clusters of GalaxiesDec 07 1995The WARPS cluster survey is based on the ROSAT PSPC archive of pointed observations. It includes extended X-ray sources, detected with the Voronoi Tessellation and Percolation algorithm (VTP), and point-like X-ray sources with non-stellar optical counterparts. ... More
The Impact of Stellar Oscillations on Doppler Velocity Planet SearchesJun 25 2007Feb 25 2008We present a quantitative investigation of the effect of stellar oscillations on Doppler velocity planet searches. Using data from four asteroseismological observation campaigns, we find a power law relationship between the noise impact of these oscillations ... More
Tetraphenyl Butadiene Emanation and Bulk Fluorescence from Wavelength Shifting Coatings in Liquid ArgonMar 30 2018Feb 10 2019We study the stability of three types of popularly employed TPB coatings under immersion in liquid argon. TPB emanation from each coating is quantified by fluorescence assay of molecular sieve filter material after a prolonged soak time. Two of the coatings ... More
Brown dwarfs and low-mass stars in the Pleiades and Praesepe:- Membership and binarityMar 27 2003Apr 29 2003We present near infrared J-, H- and K-band photometry and optical spectroscopy of low-mass star and brown dwarf (BD) candidates in the Pleiades and Praesepe open clusters. We find that Pleiades stars with K=10.5--13 are rather redder than the NextGen ... More
Cluster Evolution in the Wide Angle ROSAT Pointed Survey (WARPS)Jan 31 1997A new flux limited catalogue of low luminosity (Lx <= 10^44 erg/s) X-ray galaxy clusters and groups covering a redshift range of z~0.1 to z~0.7 has been produced from the WARPS project. We present the number counts of this low luminosity population at ... More
Spectral energy distribution for GJ406Oct 19 2005We present results of modelling the bulk of the spectral energy distribution (0.35 - 5 micron) for GJ406 (M6V). Synthetic spectra were calculated using the NextGen, Dusty and Cond model atmospheres and incorporate line lists for H2O, TiO, CrH, FeH, CO, ... More
The enumeration of fully commutative affine permutationsJul 03 2009Dec 11 2009We give a generating function for the fully commutative affine permutations enumerated by rank and Coxeter length, extending formulas due to Stembridge and Barcucci--Del Lungo--Pergola--Pinzani. For fixed rank, the length generating functions have coefficients ... More
The WARPS X-ray survey of galaxies, groups and clusters I: Method and first resultsAug 29 1996We have embarked on a survey of ROSAT PSPC archival data with the aim of detecting all significant surface brightness enhancements due to sources in the innermost 15 arcmin of the PSPC field of view (0.5-2.0 keV). This project is part of the Wide Angle ... More
Spectral imaging of the Sagittarius B2 region in multiple 7-mm molecular linesOct 12 2010We have undertaken a spectral-line imaging survey of a 6 x 6 arcmin^2 area around Sgr B2 near the centre of the Galaxy, in the range from 30 to 50 GHz, using the Mopra telescope. The spatial resolution varies from 1.0 to 1.4 arcmin and the spectral resolution ... More
Stellar activity as a tracer of moving groupsFeb 27 2013We present the results of a study of the stellar activity in the solar neighborhood using complete kinematics (galactocentric velocities U,V,W) and the chromospheric activity index $\log R'_{\rm{HK}}$. We analyzed the average activity level near the centers ... More
Merging Binary ClustersJun 26 2001Jun 29 2001We study three prominent bi-modal X-ray clusters: A3528, A1750 and A3395. Using observations taken with ROSAT and ASCA, we analyze the temperature and surface brightness distributions. We also analyze the velocity distributions of the three clusters using ... More
Abundances in the atmosphere of the metal-rich planet-host star HD 77338May 21 2015Abundances of Fe, Si, Ni, Ti, Na, Mg, Cu, Zn, Mn, Cr and Ca in the atmosphere of the K-dwarf HD 77338 are determined and discussed. HD 77338 hosts a hot Uranus-like planet and is currently the most metal-rich single star to host any planet. Determination ... More
Effective temperatures, rotational velocities, microturbulent velocities and abundances in the atmospheres of the Sun,. HD1835 and HD10700Jan 24 2012Feb 07 2012We 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 ... More
The identification of HCN and HNC in Carbon Stars: Model Atmospheres, Synthetic Spectra and Fits to Observations in the 2.7-4.0 micron RegionJun 06 2003Model carbon star atmospheres and synthetic spectra have been calculated using the recent HCN/HNC vibration rotation linelist of Harris et al. (2002) ApJ, 578, 657. The calculations are repeated using only HCN lines and show that HNC has a significant ... More
Reply to Millis et al. on "A Tale of Two Theories: Quantum Griffiths Effects in Metallic Systems"Dec 01 2004Jan 03 2005In a recent paper (cond-mat/0411197) we showed the equivalence of two seemingly contradictory theories on Griffiths-McCoy singularities (GMS) in metallic antiferromagnets close to a quantum critical point (QCP). In a recent comment, Millis {\it et al.} ... More
A potential new method for determining the temperature of cool starsMay 21 2008We present high resolution (R = 90,000) mid-infrared spectra of M dwarfs. The mid infrared region of the spectra of cool low mass stars contain pure rotational water vapour transitions that may provide us with a new methodology in the determination of ... More
Faint Extended X-ray Sources: A new Large Area SurveySep 11 1995We have searched for extended X-ray sources in the ROSAT PSPC archive using the Voronoi Tesslation and Percolation algorithm (VTP). This algorithm detects all significant sources regardless of shape or size, and is particularly suited to finding low surface ... More
Improved HCN/HNC linelist, model atmospheres and synthetic spectra for WZ CasDec 14 2005We build an accurate database of 5200 HCN and HNC rotation-vibration energy levels, determined from existing laboratory data. 20~000 energy levels in the Harris et al. (2002) linelist are assigned approximate quantum numbers. These assignments, lab determined ... More
A Tale of Two Theories: Quantum Griffiths Effects in Metallic SystemsNov 08 2004We show that two apparently contradictory theories on the existence of Griffiths-McCoy singularities in magnetic metallic systems [1,2] are in fact mathematically equivalent. We discuss the generic phase diagram of the problem and show that there is a ... More
The disappearing $Q$ operatorDec 11 2006In the Schroedinger formulation of non-Hermitian quantum theories a positive-definite metric operator $\eta\equiv e^{-Q}$ must be introduced in order to ensure their probabilistic interpretation. This operator also gives an equivalent Hermitian theory, ... More
Which Green Functions Does the Path Integral for Quasi-Hermitian Hamiltonians Represent?May 21 2009In the context of quasi-Hermitian theories, which are non-Hermitian in the conventional sense, but can be made Hermitian by the introduction of a dynamically-determined metric $\eta$, we address the problem of how the functional integral and the Feynman ... More
The discovery of a T6.5 subdwarfJan 23 2014We report the discovery of ULAS J131610.28+075553.0, a sdT6.5 dwarf in the UKIDSS Large Area Survey 2 epoch proper motion catalogue. This object displays significant spectral peculiarity, with the largest yet seen deviations from T6 and T7 templates in ... More
Is it possible to detect planets around young active G and K dwarfs?Nov 14 2013Theoretical predictions suggest that the distribution of planets in very young stars could be very different to that typically observed in Gyr old systems that are the current focus of radial velocity surveys. However, the detection of planets around ... More
The Gaia Ultra-Cool Dwarf Sample -- II: Structure at the end of the main sequenceFeb 20 2019We identify and investigate known late M, L and T dwarfs in the Gaia second data release. This sample is being used as a training set in the Gaia data processing chain of the ultra cool dwarfs work package. We find 695 objects in the optical spectral ... More
Lithium in LP 944-20Jul 04 2007Jul 14 2007We present a new estimate of the lithium abundance in the atmosphere of the brown dwarf LP 944-20. Our analysis is based on a self-consistent analysis of low, intermediate and high resolution optical and near-infrared spectra. We obtain log N(Li) = 3.25 ... More
Parallaxes of Southern Extremely Cool objects (PARSEC) II: Spectroscopic Follow-up and Parallaxes of 52 TargetsSep 25 2013We present near-infrared spectroscopy for 52 ultracool dwarfs, including two newly discovered late-M dwarfs, one new late-M subdwarf candidate, three new L and four new T dwarfs. We also present parallaxes and proper motions for 21 of them. Four of the ... More
Chandra Cluster Cosmology Project III: Cosmological Parameter ConstraintsDec 15 2008Chandra observations of large samples of galaxy clusters detected in X-rays by ROSAT provide a new, robust determination of the cluster mass functions at low and high redshifts. Statistical and systematic errors are now sufficiently small, and the redshift ... More
Chandra Cluster Cosmology Project II: Samples and X-ray Data ReductionMay 15 2008Dec 15 2008We discuss the measurements of the galaxy cluster mass functions at z=~0.05 and z=~0.5 using high-quality Chandra observations of samples derived from the ROSAT PSPC All-Sky and 400deg^2 surveys. We provide a full reference for the data analysis procedures, ... More
Resonance Offset Tailored Pulses for NMR Quantum ComputationAug 07 2000We describe novel composite pulse sequences which act as general rotors and thus are suitable for nuclear magnetic resonance (NMR) quantum computation. The Resonance Offset Tailoring To Enhance Nutations (ROTTEN) approach permits perfect compensation ... More
Non-Fermi Liquid Behavior in U and Ce Alloys: Criticality, Disorder, Dissipation, and Griffiths-McCoy singularitiesMar 06 2000In this paper we provide the theoretical basis for the problem of Griffiths-McCoy singularities close to the quantum critical point for magnetic ordering in U and Ce intermetallics. We show that the competition between Kondo effect and RKKY interaction ... More
z ~ 2.5 - 3 Ionizers in the GOODS-N FieldJun 22 2018We use deep F275W imaging from the $Hubble$ Deep UV Legacy Survey (HDUV) and G280 grism spectroscopy from $HST$/WFC3, along with new and archival optical spectra from Keck/DEIMOS, to search for candidate ionizing sources in the GOODS-N field at z ~ 2.5 ... More
Use of composite rotations to correct systematic errors in NMR quantum computationNov 16 1999We implement an ensemble quantum counting algorithm on three NMR spectrometers with 1H resonance frequencies of 500, 600 and 750 MHz. At higher frequencies, the results deviate markedly from naive theoretical predictions. These systematic errors can be ... More
Droplets in Disordered Metallic Quantum Critical SystemsJun 08 2001We present a field theory for a structurally disordered magnetic system coupled to a metallic environment near a quantum critical point. We show that close to the magnetic quantum critical point droplets are formed due to the disorder and undergo dissipative ... More
Probing M subdwarf metallicity with an esdK5+esdM5.5 binaryJul 28 2015We present a spectral analysis of the binary G 224-58 AB that consists of the coolest M extreme subdwarf (esdM5.5) and a brighter primary (esdK5). This binary may serve as a benchmark for metallicity measurement calibrations and as a test-bed for atmospheric ... More
Primeval very low-mass stars and brown dwarfs - II. The most metal-poor substellar objectFeb 07 2017Feb 22 2017SDSS J010448.46+153501.8 has previously been classified as an sdM9.5 subdwarf. However, its very blue $J-K$ colour ($-0.15 \pm 0.17$) suggests a much lower metallicity compared to normal sdM9.5 subdwarfs. Here, we re-classify this object as a usdL1.5 ... More
Spectroscopy and kinematics of low-mass members of young moving groupsJul 19 2010We study a target sample of 68 low-mass objects (with spectral types in the range M4.5-L1) previously selected via photometric and astrometric criteria, as possible members of five young moving groups: the Local Association (Pleiades moving group, age=20 ... More
Atomic lines in infrared spectra for ultracool dwarfsDec 22 2003We provide a set of atomic lines which are suitable for the description of ultracool dwarf spectra from 10000 to 25000 \AA. This atomic linelist was made using both synthetic spectra calculations and existing atlases of infrared spectra of Arcturus and ... More
A search for southern ultracool dwarfs in young moving groupsMay 30 2008Oct 21 2009We associate 132 low-mass ultracool dwarfs in the southern hemisphere as candidate members of five moving groups using photometric and astrometric selection techniques. Of these objects, we present high resolution spectroscopy for seven candidates and ... More
Hubble Space Telescope H-alpha imaging of star-forming galaxies at z = 1-1.5: evolution in the size and luminosity of giant HII regionsSep 25 2012We present HST/WFC3 narrowband imaging of the H-alpha emission in a sample of eight gravitationally-lensed galaxies at z = 1 - 1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360pc, ... More
Giant Radio Galaxies: I. Intergalactic BarometersMar 20 2013We present new wideband radio observations with the Australia Telescope Compact Array of a sample of 12 giant radio galaxies. The radio observations are part of a larger radio-optical study aimed at relating the radio structures with the ambient medium ... More
Rotation Velocities for M-dwarfsAug 27 2009We present spectroscopic rotation velocities (v sin i) for 56 M dwarf stars using high resolution HET HRS red spectroscopy. In addition we have also determined photometric effective temperatures, masses and metallicities ([Fe/H]) for some stars observed ... More
Metallicities & Activities of Southern StarsApr 08 2008Apr 14 2008We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in the southern hemisphere. We have measured the iron abundances ([Fe/H]) and chromospheric emission indices (logR'HK) of ... More
Probing the Intracluster star-light with ChandraMar 20 2002Mar 20 2002We propose a method to test for the presence of intracluster star-light using X-ray binaries as a trace population. We discuss a particular application of this method to observations of the Virgo cluster.
`Oumuamua as a messenger from the Local AssociationNov 23 2017Dec 23 2017With a hyperbolic trajectory around the Sun, `Oumuamua is the first confirmed interstellar object. However, its origin is poorly known. By simulating the orbits of 0.23 million local stars, we find 109 encounters with periastron less than 5 pc. `Oumuamua's ... More
Entanglement entropy and differential entropy for massive flavorsMay 28 2015Jun 09 2015In this paper we compute the holographic entanglement entropy for massive flavors in the D3-D7 system, for arbitrary mass and various entangling region geometries. We show that the universal terms in the entanglement entropy exactly match those computed ... More
Entanglement entropy in top-down modelsFeb 15 2016We explore holographic entanglement entropy in ten-dimensional supergravity solutions. It has been proposed that entanglement entropy can be computed in such top-down models using minimal surfaces which asymptotically wrap the compact part of the geometry. ... More
The extremely red L dwarf ULAS J222711$-$004547 - dominated by dustJan 02 2014We report the discovery of a peculiar L dwarf from the UKIDSS LAS, ULAS J222711-004547. The very red infrared photometry (MKO J-K = 2.79$\pm$0.06, WISE W1-W2 = 0.65$\pm$0.05) of ULAS J222711-004547 makes it one of the reddest brown dwarfs discovered so ... More
A Pathfinder Instrument for Precision Radial Velocities in the Near-InfraredJun 23 2008We have designed and tested an in-plane echelle spectrograph configured to investigate precision radial velocities from ground-based near-infrared observations. The spectrograph operates across the spectral range of 0.9-1.7 mm at a spectral resolution ... More
Holographic Graphene in a CavityJul 11 2014The effective strength of EM interactions can be controlled by confining the fields to a cavity and these effects might be used to push graphene into a strongly coupled regime. We study the similar D3/probe D5 system on a compact space and discuss the ... More
Probabilistic galactic dynamics I - the Sun and GJ 710 with Monte Carlo, linearised and unscented treatmentsJul 27 2018Deterministic galactic dynamics is impossible due to the space-time randomness caused by gravitational waves. Instead of treating stellar orbits deterministically, we integrate not only the mean but also the covariance of a stellar orbit in the Galaxy. ... More
Understanding Fomalhaut as a Cooper pairOct 19 2017Nov 27 2017Fomalhaut is a nearby stellar system and has been found to be a triple based on astrometric observations. With new radial velocity and astrometric data, we study the association between Fomalhaut A, B, and C in a Bayesian framework finding that the system ... More
Carbon Monoxide bands in M dwarfsOct 01 2002We compare the observational and theoretical spectra of the $\Delta v$ = 2 CO bands in a range of M dwarfs. We investigate the dependence of theoretical spectra on effective temperatures as well as carbon abundance. In general we find that the synthetic ... More
Spectral Classification Beyond MSep 16 2004Significant populations of field L and T dwarfs are now known, and we anticipate the discovery of even cooler dwarfs by Spitzer and ground-based infrared surveys. However, as the number of known L and T dwarfs increases so does the range in their observational ... More
The electronic bands of CrD, CrH, MgD and MgH: application to the "deuterium test"Oct 01 2007Oct 11 2007We compute opacities for the electronic molecular band systems A 6Sigma+ -- X 6Sigma+ of CrH and CrD, and A 2Pi -- X 2Sigma+ of MgH and MgD. The opacities are computed by making use of existing spectroscopic constants for MgH and CrH. These constants ... More
Primeval very low-mass stars and brown dwarfs. I. Six new L subdwarfs, classification and atmospheric propertiesSep 22 2016We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or near infrared ... More
Active Gel Model of Amoeboid Cell MotilityJan 31 2013Feb 01 2013We develop a model of amoeboid cell motility based on active gel theory. Modeling the motile apparatus of a eukaryotic cell as a confined layer of finite length of poroelastic active gel permeated by a solvent, we first show that, due to active stress ... More
Probabilities of exoplanet signals from posterior samplingsDec 27 2011Jun 25 2012Estimating the marginal likelihoods is an essential feature of model selection in the Bayesian context. It is especially crucial to have good estimates when assessing the number of planets orbiting stars when the models explain the noisy data with different ... More
Spectral evidence for dust in late-type M dwarfsFeb 13 1997We have found a dramatic change in the spectra of late-type M dwarfs at wavelengths shorter than 0.75 microns. Comparisons with synthetic spectra illustrate that this change is well explained by the presence of dust. It thus seems that a substantial part ... More
Was Proxima captured by alpha Centauri A and B?Sep 11 2017Sep 29 2017The nearest stellar system consists of the stars Proxima, alpha Centauri A and B and at least one planet Proxima b. The habitability of Proxima b and any other planets are likely to be significantly influenced by the orbital evolution of the system. To ... More
Primeval very low-mass stars and brown dwarfs. I. Six new L subdwarfs, classification and atmospheric propertiesSep 22 2016Nov 09 2016We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or near infrared ... More
The current population of benchmark brown dwarfsDec 29 2009The number of brown dwarfs (BDs) now identified tops 700. Yet our understanding of these cool objects is still lacking, and models are struggling to accurately reproduce observations. What is needed is a method of calibrating the models, BDs whose properties ... More
Localized standing waves in inhomogeneous Schrodinger equationsFeb 18 2010A nonlinear Schrodinger equation arising from light propagation down an inhomogeneous medium is considered. The inhomogeneity is reflected through a non-uniform coefficient of the non-linear term in the equation. In particular, a combination of self-focusing ... More
Atomic force microscope nanolithography of graphene: cuts, pseudo-cuts and tip current measurementsFeb 14 2011We investigate atomic force microscope nanolithography of single and bilayer graphene. In situ tip current measurements show that cutting of graphene is not current driven. Using a combination of transport measurements and scanning electron microscopy ... More
Cosmological constraints from evolution of cluster baryon mass function at z~0.5Dec 03 2002Mar 10 2003We present a new method for deriving cosmological constraints based on the evolution of the baryon mass function of galaxy clusters, and implement it using 17 distant clusters from our 160deg2 ROSAT survey. The method uses the cluster baryon mass as a ... More
A 1500 deg$^2$ Near Infrared Proper Motion Catalogue from the UKIDSS Large Area SurveyNov 05 2013The UKIDSS Large Area Survey (LAS) began in 2005, with the start of the UKIDSS program as a 7 year effort to survey roughly 4000 deg$^2$ at high galactic latitudes in Y, J, H and K bands. The survey also included a significant quantity of 2-epoch J band ... More
Energy spectrum and mass composition of primary cosmic radiation in the region above the knee from the GAMMA experimentDec 31 2011The energy spectrum of the primary cosmic radiation in the energy range 1 - 100 PeV and the extensive air shower (EAS) characteristics obtained on the basis of the expanded data bank of the GAMMA experiment (Mt. Aragats, Armenia) are presented. With increased ... More
A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space densityMar 17 2015We present the spectroscopic analysis of a large sample of late-M, L, and T dwarfs from UKIDSS. Using the YJHK photometry from ULAS and the red-optical photometry from SDSS we selected a sample of 262 brown dwarf candidates and we followed-up 196 of them ... More
Minimization of Transverse Wakefields in the NLC Accelerator StructuresAug 17 2002The progress of a multiple bunches of electrons through several thousand accelerator structures results in a wakefield which if left unchecked will kick successive bunches off the axis of the accelerator and can at the very least dilute the final luminosity ... More
Unstable gap solitons in inhomogeneous Schrodinger equationsJan 13 2012A periodically inhomogeneous Schrodinger equation is considered. The inhomogeneity is reflected through a non-uniform coefficient of the linear and non-linear term in the equation. Due to the periodic inhomogeneity of the linear term, the system may admit ... More
Mechanisms of doping grapheneMar 02 2010We distinguish three mechanisms of doping graphene. Density functional theory is used to show that electronegative molecule like F4-TCNQ and electropositive metals like K dope graphene p- and n-type respectively. These dopants are expected to lead to ... More
A H13CN/HN13C linelist, model atmospheres and synthetic spectra for carbon starsJul 04 2008A line list of vibration-rotation transitions for 13C substituted HCN is presented. The line list is constructed using known experimental levels where available, calculated levels and ab initio line intensities originally calculated for the major isotopologue. ... More
The brightest pure-H ultracool white dwarfSep 06 2012We report the identification of LSR J0745+2627 in the United Kingdom InfraRed Telescope Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) as a cool white dwarf with kinematics and age compatible with the thick-disk/halo population. LSR J0745+2627 ... More