Results for "R. P. Butler"

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Quantitative Spectroscopy of BA-type SupergiantsSep 22 2005Luminous BA-SGs allow topics ranging from NLTE physics and the evolution of massive stars to the chemical evolution of galaxies and cosmology to be addressed. A hybrid NLTE technique for the quantitative spectroscopy of BA-SGs is discussed. Thorough tests ... More
Electromagnetic Moments of the Baryon DecupletAug 22 1993We compute the leading contributions to the magnetic dipole and electric quadrupole moments of the baryon decuplet in chiral perturbation theory. The measured value for the magnetic moment of the $\Omega^-$ is used to determine the local counterterm for ... More
The output distribution of important LULU-operatorsMar 23 2010Oct 28 2014Two procedures to compute the output distribution phi_S of certain stack filters S (so called erosion-dilation cascades) are given. One rests on the disjunctive normal form of S and also yields the rank selection probabilities. The other is based on inclusion-exclusion ... More
E2/M1 Mixing Ratio of $Δ\to Nγ$ and Hyperon Resonance Radiative DecayFeb 03 1993We compute the leading contribution to the E2/M1 mixing ratio of the decay $\Delta\rightarrow N\gamma$ in heavy baryon chiral perturbation theory. We find the mixing ratio to be $4\% \ltap |\delta_{\rm E2/M1}| \ltap 11\%$, much larger than estimates based ... More
Sub-Saturn Planet Candidates to HD 16141 and HD 46375Apr 24 2000Precision Doppler measurements from the Keck/HIRES spectrometer reveal periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD 16141 (G5 IV) has a period of 75.8 d and a velocity amplitude of 11 m/s, yielding a companion having Msini ... More
On the Early Time X-ray Spectra of Swift Afterglows I: Evidence for Anomalous Soft X-ray EmissionApr 04 2006Nov 03 2006We have conducted a thorough and blind search for emission lines in >70 Swift X-ray afterglows of total exposure ~10^7s. We find that most afterglows are consistent with pure power-laws plus extinction. Significant outliers to the population exist at ... More
Refined Astrometry and Positions for 179 Swift X-ray AfterglowsNov 01 2006Dec 22 2006We present a refined catalog for the positions of 179 Gamma-ray burst (GRB) X-ray afterglows observed by the X-ray Telescope (XRT) on Swift prior to November 1, 2006. The positions are determined by detecting X-ray field sources in the deep X-ray images ... 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
The Discovery of a Planetary Companion to 16 Cygni BNov 27 1996High precision radial velocity observations of the solar-type star 16 Cygni B taken at McDonald Observatory and at Lick Observatory, have each independently discovered periodic radial-velocity variations indicating the presence of a Jovian-mass companion ... More
X-ray Hardness Evolution in GRB Afterglows and Flares: Late Time GRB Activity Without N_H VariationsDec 19 2006Mar 10 2007We show that the X-ray and $\gamma$-ray spectra of Swift GRBs and their afterglows are consistent with the emission characteristic of an expanding, relativistic fireball. The classical afterglow due to the impact of the fireball on the external medium ... More
Previously Claimed(/Unclaimed) X-ray Emission Lines in High Resolution Afterglow SpectraJan 04 2004We review the significance determination for emission lines in the Chandra HETGS spectrum for GRB020813, and we report on a search for additional lines in high resolution Chandra spectra. No previously unclaimed features are found. We also discuss the ... More
Extragalactic Stellar Astronomy with Blue SupergiantsMar 14 2007The present generation of large telescopes facilitates spectroscopy of blue supergiants in galaxies out to distances beyond the Local Group. Recent developments in NLTE spectrum synthesis techniques allow for an accurate determination of stellar parameters ... More
Maximally Rotating Supermassive Stars at the Onset of Collapse: The Perturbative Effects of Gas Pressure, Magnetic Fields, Dark Matter and Dark EnergyFeb 02 2018Jul 26 2018The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors ... More
X-ray Hardness Variations as an Internal/External Shock DiagnosticFeb 23 2007Jun 22 2007The early, highly time-variable X-ray emission immediately following GRBs exhibits strong spectral variations that are unlike the temporally smoother emission which dominates after $t\sim 10^3$ s. The ratio of hard channel (1.3-10.0 keV) to soft channel ... More
Planetary Companions Around Two Solar Type Stars: HD 195019 and HD 217107Oct 26 1998We have enlarged the sample of stars in the planet search at Lick Observatory. Doppler measurements of 82 new stars observed at Lick Observatory, with additional velocities from Keck Observatory, have revealed two new planet candidates. The G3V/IV star, ... More
A SupergiantsSep 07 2004A-type supergiants are primary targets for quantitative spectroscopy of individual stars in nearby galaxies because of their intrinsic brightness. An overview is given on the non-LTE techniques required for their analysis. Applications concentrate on ... More
Maximally Rotating Supermassive Stars at the Onset of Collapse: The Perturbative Effects of Gas Pressure, Magnetic Fields, Dark Matter and Dark EnergyFeb 02 2018The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors ... More
Chandra Observations of the Optically Dark GRB030528Jan 04 2004The X-ray-rich GRB030528 was detected by the HETE satellite and its localization was rapidly disseminated. However, early optical observations failed to detect a counterpart source. In a 2-epoch ToO observation with Chandra, we discovered a fading X-ray ... More
A Planetary Companion to the Nearby M4 Dwarf, Gliese 876Jul 29 1998Doppler measurements of the M4 dwarf star, Gliese 876, taken at both Lick and Keck Observatory reveal periodic, Keplerian velocity variations with a period of 61 days. The orbital fit implies that the companion has a mass of, M = 2.1 MJUP /sin i, an orbital ... More
Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672Dec 17 2001Jan 23 2002We have found a very faint companion to the active solar analog HR 7672 (HD 190406; GJ 779; 15 Sge). Three epochs of high resolution imaging using adaptive optics (AO) at the Gemini-North and Keck II Telescopes demonstrate that HR 7672B is a common proper ... More
The Pan-Pacific Planet Search III: Five companions orbiting giant starsOct 14 2015We report a new giant planet orbiting the K giant HD 155233, as well as four stellar-mass companions from the Pan-Pacific Planet Search, a southern hemisphere radial velocity survey for planets orbiting nearby giants and subgiants. We also present updated ... More
Precise radial velocities of giant stars: I. Stable starsApr 25 2006Context: Future astrometric missions such as SIM PlanetQuest need very stable reference stars. K giants have large luminosities, which place them at large distances and thus the jitter of their photocenters by companions is relatively small. Therefore ... More
The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPSFeb 12 2012Apr 19 2012Doppler spectroscopy has uncovered or confirmed all the known planets orbiting nearby stars. Two main techniques are used to obtain precision Doppler measurements at optical wavelengths. The first approach is the gas cell method, which consists on the ... More
The long rapid decay phase of the extended emission from the short GRB 080503Nov 08 2009Feb 10 2010GRB080503 was classified as a short GRB with extended emission (Perley et al. 2009). The origin of such extended emission (found in about a quarter of Swift short GRBs) is still unclear and may provide some clues to the identity of the elusive progenitors ... More
Optical and X-ray Observations of the Afterglow to XRF030723Jan 04 2004The X-ray-flash XRF030723 was detected by the HETE satellite and rapidly disseminated, allowing for an optical transient to be detected ~1 day after the burst. We discuss observations in the optical with Magellan, which confirmed the fade of the optical ... More
The Jupiter Twin HD 154345bFeb 12 2008Jan 12 2009We announce the discovery of a twin of Jupiter orbiting the slightly metal-poor ([Fe/H] = -0.1) nearby (d = 18 pc) G8 dwarf HD 154345. This planet has a minimum mass of 0.95 Jupiter masses and a 9.2 year, circular orbit with radius 4.2 AU. There is currently ... More
Detection of new Optical Counterpart candidates to PSR B1951+32 with HST/WFPC2Jul 23 2002There remain several definitive gamma-ray pulsars that are as yet undetected in the optical regime. A classic case is the pulsar PSR B1951+32, associated with the complex CTB 80 SNR. Previous ground based high speed 2-d optical studies have ruled out ... More
Temperature and particle size dependence of equilibrium order parameter of FePtApr 27 2005First, second and third nearest neighbor pair mixing potentials for equiatomic FePt alloys were calculated from first principles by the Connolly-Williams method within the canonical cluster expansion formalism. Using the mixing potentials obtained in ... More
Magnetic flows on Sol-manifolds: dynamical and symplectic aspectsAug 14 2007Jul 08 2008We consider magnetic flows on compact quotients of the 3-dimensional solvable geometry Sol determined by the usual left-invariant metric and the distinguished monopole. We show that these flows have positive Liouville entropy and therefore are never completely ... More
A note on log-convexity of q-Catalan numbersJan 02 2007The q-Catalan numbers studied by Carlitz and Riordan are polynomials in q with nonnegative coefficients. They evaluate, at q=1, to the Catalan numbers: 1, 1, 2, 5, 14,..., a log-convex sequence. We use a combinatorial interpretation of these polynomials ... More
Towards a Real-time Transient Classification EngineFeb 15 2008Temporal sampling does more than add another axis to the vector of observables. Instead, under the recognition that how objects change (and move) in time speaks directly to the physics underlying astronomical phenomena, next-generation wide-field synoptic ... More
Up-dated opacities from the Opacity ProjectOct 29 2004Dec 18 2004Using the code AUTOSTRUCTURE, extensive calculations of inner-shell atomic data have been made for the chemical elements He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe and Ni. The results are used to obtain up-dated opacities from the Opacity ... More
The GJ 876 Planetary System -- A Progress ReportJul 21 2004We present an updated analysis of the GJ 876 planetary system based on an augmented data set that incorporates 65 new high-precision radial velocities obtained with the Keck telescope from 2001 to 2004. These new radial velocities permit a more accurate ... More
Self-Referential OrderMay 22 2013May 24 2013We introduce the concept of {\it self-referential order} which provides a way to quantify structural organization in non crystalline materials. The key idea consists in the observation that, in a disordered system, where there is no ideal, reference, ... More
Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange NMRAug 21 2001We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas ... More
Investigating signatures of cosmological time dilation in duration measures of prompt gamma-ray burst light curvesAug 27 2014We study the evolution with redshift of three measures of gamma-ray burst (GRB) duration ($T_{\rm 90}$, $T_{\rm 50}$ and $T_{\rm R45}$) in a fixed rest frame energy band for a sample of 232 Swift/BAT detected GRBs. Binning the data in redshift we demonstrate ... More
Integrated Polarization Properties of 3C48, 3C138, 3C147, and 3C286Feb 27 2013We present the integrated polarization properties of the four compact radio sources 3C48, 3C138, 3C147 and 3C286, from 1 to 50 GHz, over a 30-year time frame spanning 1982 to 2012. These four sources are commonly used as flux density and polarization ... More
High Resolution Gratings Spectroscopy of GRBs 030382 and 041006 with Chandra LETGSFeb 17 2005We present high resolution X-ray spectroscopy of two recent GRB afterglows observed with the Low Energy Transmission Gratings on Chandra. The afterglows to GRBs 030328 and 041006 are detected beginning 15.33 and 16.8 hours after each burst, respectively, ... More
An Accurate Flux Density Scale from 50 MHz to 50 GHzSep 19 2016The flux density scale of Perley and Butler (2013) is extended downwards to ~50 MHz by utilizing recent observations with the Karl G. Jansky Very Large Array (VLA) of 20 sources between 220 MHz and 48.1 GHz, and legacy VLA observations at 73.8 MHz. The ... More
Uncovering the Intrinsic Variability of Gamma-ray BurstsMar 17 2014Apr 11 2014We develop a robust technique to determine the minimum variability timescale for Gamma-ray Burst light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also ... More
Optimal Time-Series Selection of QuasarsAug 18 2010Jan 04 2011We present a novel method for the optimal selection of quasars using time-series observations in a single photometric bandpass. Utilizing the damped random walk model of Kelly et al. (2009), we parameterize the ensemble quasar structure function in Sloan ... More
Accurate fundamental parameters for 23 bright solar-type starsFeb 23 2010We combine results from interferometry, asteroseismology and spectroscopy to determine accurate fundamental parameters of 23 bright solar-type stars, from spectral type F5 to K2 and luminosity classes III to V. For some stars we can use direct techniques ... More
Planck LFI flight model feed hornsJan 26 2010this paper is part of the Prelaunch status LFI papers published on JINST: The Low Frequency Instrument is optically interfaced with the ESA Planck telescope through 11 corrugated feed horns each connected ... More
Solar-like oscillations in the metal-poor subgiant nu Indi: II. Acoustic spectrum and mode lifetimeJun 06 2007Convection in stars excites resonant acoustic waves which depend on the sound speed inside the star, which in turn depends on properties of the stellar interior. Therefore, asteroseismology is an unrivaled method to probe the internal structure of a star. ... More
Searching for Faint Comoving Companions to the $α$ Centauri system in the VVV Survey Infrared ImagesAug 17 2017The VVV survey has observed the southern disk of the Milky Way in the near infrared, covering 240 deg$^{2}$ in the $ZYJHK_S$ filters. We search the VVV Survey images in a $\sim$19 deg$^{2}$ field around $\alpha$ Centauri, the nearest stellar system to ... More
The Expanded Very Large ArraySep 08 2009In almost 30 years of operation, the Very Large Array (VLA) has proved to be a remarkably flexible and productive radio telescope. However, the basic capabilities of the VLA have changed little since it was designed. A major expansion utilizing modern ... More
Rotational Modulation of M/L Dwarfs due to Magnetic SpotsSep 07 2007We find periodic I-band variability in two ultracool dwarfs, TVLM 513-46546 and 2MASS J00361617+1821104, on either side of the M/L dwarf boundary. Both of these targets are short-period radio transients, with the detected I-band periods matching those ... More
The Frequency of Low-mass ExoplanetsJun 25 2009Jun 28 2009We report first results from the Anglo-Australian Telescope Rocky Planet Search - an intensive, high-precision Doppler planet search targeting low-mass exoplanets in contiguous 48 night observing blocks. On this run we targeted 24 bright, nearby and intrinsically ... More
Solar-Like Oscillations in beta Hydri: Evidence for Short-Lived High-Amplitude OscillationsFeb 26 2002Velocity measurements of the G2 subgiant beta Hyi with both UCLES and CORALIE show a clear excess of power centred at 1.0 mHz. In the UCLES data we find evidence for a short-lived, high-amplitude oscillation event. If confirmed as a feature of subgiants, ... More
An Activity Catalogue of Southern StarsJul 14 2006Jul 15 2006We have acquired high-resolution echelle spectra of 225 F6-M5 type stars in the southern hemisphere. The stars are targets or candidates to be targets for the Anglo-Australian Planet Search. CaII HK line cores were used to derive activity indices for ... More
The Anglo-Australian Planet Search XXIV: The Frequency of Jupiter AnalogsJan 20 2016We present updated simulations of the detectability of Jupiter analogs by the 17-year Anglo-Australian Planet Search. The occurrence rate of Jupiter-like planets that have remained near their formation locations beyond the ice line is a critical datum ... More
On the Frequency of Jupiter AnalogsNov 22 2010The Anglo-Australian Planet Search has now accumulated 12 years of radial-velocity data with long-term instrumental precision better than 3 m/s. In this paper, we expand on earlier simulation work, to probe the frequency of near-circular, long-period ... More
The thermal emission of Centaurs and Trans-Neptunian objects at millimeter wavelengths from ALMA observationsSep 20 2017The sensitivity of ALMA makes it possible to detect thermal mm/submm emission from small/distant Solar System bodies at the sub-mJy level. Measured fluxes are primarily sensitive to the objects' diameters, but deriving precise sizes is somewhat hampered ... More
Observing Strategies for the Detection of Jupiter AnalogsMar 14 2013To understand the frequency, and thus the formation and evolution, of planetary systems like our own solar system, it is critical to detect Jupiter-like planets in Jupiter-like orbits. For long-term radial-velocity monitoring, it is useful to estimate ... More
The Frequency of Low-Mass Exoplanets. III. Toward eta-Earth at Short PeriodsMar 22 2011Determining the occurrence rate of terrestrial-mass planets (m_p < 10M_earth) is a critically important step on the path towards determining the frequency of Earth-like planets (eta-Earth), and hence the uniqueness of our Solar system. Current radial-velocity ... More
The PLANCK LFI flight model ortho-mode transducersJan 26 2010The Low Frequency Instrument (LFI) of the ESA Planck CMB mission is an array of 22 ultra sensitive pseudocorrelation radiometers working at 30, 44, and 70 GHz. LFI has been calibrated and delivered for integration with the satellite to the European Space ... More
Observed Properties of Exoplanets: Masses, Orbits, and MetallicitiesApr 29 2005Jun 13 2005We review the observed properties of exoplanets found by the Doppler technique which has revealed 152 exoplanets to date. We focus on our ongoing 18-year survey of 1330 FGKM type stars at Lick, Keck, and the Anglo-Australian Telescopes carried out with ... More
Oscillations in alpha Cen A observed with UCLES at the AATSep 18 2002We report Doppler measurements of alpha Cen A from time-series spectroscopy made with UCLES at the 3.9-m AAT. Wavelength calibration using an iodine absorption cell produced high-precision velocity measurements, whose power spectrum shows the clear signature ... More
The Pan-Pacific Planet Search VI: Giant planets orbiting HD 86950 and HD 222076Nov 23 2016We report the detection of two new planets orbiting the K giants HD 86950 and HD 222076, based on precise radial velocities obtained with three instruments: AAT/UCLES, FEROS, and CHIRON. HD 86950b has a period of 1270$\pm$57 days at $a=2.72\pm$0.08 AU, ... More
Selection Functions in Doppler Planet SearchesOct 09 2008We 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 ... More
The M Dwarf GJ 436 and its Neptune-Mass PlanetAug 11 2006Dec 04 2006We determine stellar parameters for the M dwarf GJ 436 that hosts a Neptune-mass planet. We employ primarily spectral modeling at low and high resolution, examining the agreement between model and observed optical spectra of five comparison stars of type, ... More
The non-detection of oscillations in Procyon by MOST: is it really a surprise?Jan 31 2005We argue that the non-detection of oscillations in Procyon by the MOST satellite reported by Matthews et al. (2004) is fully consistent with published ground-based velocity observations of this star. We also examine the claims that the MOST observations ... More
Beyond the Iron Peak: r- and s-process Elemental Abundances in Stars with PlanetsApr 21 2008We present elemental abundances of 118 stars (28 of which are known extrasolar planetary host stars) observed as part of the Anglo-Australian Planet Search. Abundances of O, Mg, Cr, Y, Zr, Ba, Nd and Eu (along with previously published abundances for ... More
The Frequency of Low-Mass Exoplanets. II. The `Period Valley'Aug 31 2010Radial-velocity planet search campaigns are now beginning to detect low-mass "Super-Earth" planets, with minimum masses M sin i < 10 M_earth. Using two independently-developed methods, we have derived detection limits from nearly four years of the highest-precision ... More
The Stabilized Poincare-Heisenberg algebra: a Clifford algebra viewpointNov 02 2006The stabilized Poincare-Heisenberg algebra (SPHA) is the Lie algebra of quantum relativistic kinematics generated by fifteen generators. It is obtained from imposing stability conditions after attempting to combine the Lie algebras of quantum mechanics ... More
Chemical composition of Galactic OB stars I. CNO abundances in O9 starsApr 12 2002We present NLTE abundances of CNO for a sample of four O9 stars in the Galaxy, together with new determinations of their stellar parameters, $T_{\rm eff}$, $\log g$, $\epsilon$(He) and microturbulence. These new analyses take into account the effect of ... More
A Mass for the Extrasolar Planet Gl 876b Determined from Hubble Space Telescope Fine Guidance Sensor 3 Astrometry and High-Precision Radial VelocitiesDec 04 2002We report the first astrometrically determined mass of an extrasolar planet, a companion previously detected by Doppler spectroscopy. Radial velocities first provided an ephemeris with which to schedule a significant fraction of the {\it HST} observations ... More
In-flight verification of the FREGATE spectral responseMar 06 2002We present the first results of the in-flight validation of the spectral response of the FREGATE X/gamma detectors on-board the HETE-2 satellite. This validation uses the Crab pulsar and nebula as reference spectra.
FREGATE observation of a strong burst from SGR1900+14Mar 06 2002After a long period of quiescence, the soft gamma repeater SGR1900+14 was suddenly reactivated on April 2001. On July 2, 2001, a bright flare emitted by this source triggerred the WXM and FREGATE instruments onboard the HETE-2 satellite. Unlike typical ... More
Low Mass Companions for Five Solar-Type Stars from the Magellan Planet Search ProgramOct 29 2008We report low mass companions orbiting five Solar-type stars that have emerged from the Magellan precision Doppler velocity survey, with minimum (Msini) masses ranging from 1.2 to 25 Mjup. These nearby target stars range from mildly metal-poor to metal-rich, ... More
VLA Observations of Single Pulses from the Galactic Center MagnetarMay 02 2019We present the results of a 7-12 GHz phased-array study of the Galactic center magnetar J1745-2900 with the Karl G. Jansky Very Large Array (VLA). Using data from two 6.5 hour observations from September 2014, we find that the average profile is comprised ... More
The Low Frequency Instrument in the ESA Planck missionOct 02 2003Measurements of the cosmic microwave background (CMB) allow high precision observation of the cosmic plasma at redshift z~1100. After the success of the NASA satellite COBE, that in 1992 provided the first detection of the CMB anisotropy, results from ... More
Topological Modes in One Dimensional Solids and Photonic CrystalsOct 28 2014It is shown theoretically that a one-dimensional crystal with time reversal symmetry is characterized by a Z_{2} topological invariant that predicts the existence or otherwise of edge states. This is confirmed experimentally through the construction and ... More
Astrometry and radial velocities of the planet host M dwarf GJ 317: new trigonometric distance, metallicity and upper limit to the mass of GJ 317bNov 10 2011We have obtained precision astrometry of the planet hosting M dwarf GJ 317 in the framework of the Carnegie Astrometric Planet Search project. The new astrometric measurements give a distance determination of 15.3 pc, 65% further than previous estimates. ... More
Five Long-period Extrasolar Planets in Eccentric orbits from the Magellan Planet Search ProgramJan 22 2010Jan 26 2010Five new planets orbiting G and K dwarfs have emerged from the Magellan velocity survey. These companions are jovian-mass planets in eccentric (e \geq 0.24) intermediate and long-period orbits. HD 86226b orbits a solar metallicity G2 dwarf. The MP sin ... More
Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star ClassificationJun 14 2011Jun 18 2011Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest ... More
A ~ 7.5 Earth-Mass Planet Orbiting the Nearby Star, GJ 876Oct 18 2005Oct 18 2005High precision, high cadence radial velocity monitoring over the past 8 years at the W. M. Keck Observatory reveals evidence for a third planet orbiting the nearby (4.69 pc) dM4 star GJ 876. The residuals of three-body Newtonian fits, which include GJ ... More
Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass SubgiantsApr 19 2007Apr 19 2007We report precision Doppler measurements of three intermediate-mass subgiants from Lick and Keck Observatories. All three stars show variability in their radial velocities consistent with planet-mass companions in Keplerian orbits. We find a planet with ... More
Monte Carlo simulation of equilibrium L1_0 ordering in FePt nanoparticlesOct 22 2004First, second and third nearest neighbor mixing potentials for FePt alloys, were calculated from first principles using a Connolly-Williams approach. Using the mixing potentials obtained in this manner, the dependency of equilibrium L1_0 ordering on temperature ... More
GJ 581 update: Additional Evidence for a Super-Earth in the Habitable ZoneJul 18 2012We present an analysis of the significantly expanded HARPS 2011 radial velocity data set for GJ 581 that was presented by Forveille et al. (2011). Our analysis reaches substantially different conclusions regarding the evidence for a Super-Earth-mass planet ... More
Neutrino Lasing in the SunDec 23 1993Applying the phenomenon of neutrino lasing in the solar interior, we show how the rate for the generic neutrino decay process `\nu -> fermion + boson', can in principal be enhanced by many orders of magnitude over its normal decay rate. Such a large enhancement ... More
The Cosmic Rate, Luminosity Function and Intrinsic Correlations of Long GRBsOct 19 2009Jan 19 2010We calculate durations and spectral parameters for 207 Swift bursts detected by the BAT instrument from April 2007 to August 2009, including 67 events with measured redshifts. This is the first supplement to our catalog of 425 Swift GRBs (147 with redshifts) ... More
Generalized Tests for Selection Effects in GRB High-Energy CorrelationsFeb 22 2008Dec 12 2008Several correlations among parameters derived from modelling the high-energy properties of GRBs have been reported. We show that well-known examples of these have common features indicative of strong contamination by selection effects. We focus here on ... More
Non-LTE line-formation for CNODec 16 2002Accurate atomic data have become available in the recent past due to the demands of astrophysics and fusion research. We report on the impact of such data on non-LTE line-formation calculations for CNO in early-type stars. Considerable improvement is ... More
Four new planets around giant stars and the mass-metallicity correlation of planet-hosting starsMar 11 2016CONTEXT. Exoplanet searches have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. AIMS. During the past six years, we have conducted a radial velocity follow-up program ... More
Domain wall switching: optimizing the energy landscapeApr 06 2007It has recently been suggested that exchange spring media offer a way to increase media density without causing thermal instability (superparamagnetism), by using a hard and a soft layer coupled by exchange. Victora has suggested a figure of merit xi ... More
Gamma-ray Bursts, Classified PhysicallyApr 07 2008From Galactic binary sources, to extragalactic magnetized neutron stars, to long-duration GRBs without associated supernovae, the types of sources we now believe capable of producing bursts of gamma-rays continues to grow apace. With this emergent diversity ... More
The Lick Planet Search: Detectability and Mass ThresholdsJun 29 1999We analyse 11 years of precise radial velocities for 76 solar type stars from the Lick survey. Eight stars in this sample have previously reported planetary-mass companions, all with mass (m sin i) less than 8 Jupiter masses (MJ). For the stars without ... More
The Pan-Pacific Planet Search VII: The most eccentric planet orbiting a giant starNov 15 2017Radial velocity observations from three instruments reveal the presence of a 4 M_jup planet candidate orbiting the K giant HD 76920. HD 76920b has an orbital eccentricity of 0.856$\pm$0.009, making it the most eccentric planet known to orbit an evolved ... More
PSR B1951+32 and PSR J0537-6910 - where are the optical counterparts?Aug 29 2002Sep 09 2002There remain several definitive gamma-ray pulsars that are as yet undetected in the optical regime. A classic case is the pulsar PSR B1951+32, associated with the complex CTB 80 SNR. Previous ground based high speed 2-d optical studies have ruled out ... More
The Energy-Dependence of GRB Minimum Variability TimescalesJan 23 2015Jun 08 2015We constrain the minimum variability timescales for 938 GRBs observed by the Fermi/GBM instrument prior to July 11, 2012. The tightest constraints on progenitor radii derived from these timescales are obtained from light curves in the hardest energy channel. ... More
Probing Hadronic Structure with The Decay $Δ\rightarrow Nl^+l^-$Mar 18 1993We compute the branching ratio for $\Delta\rightarrow Ne^+e^-$ and $\Delta\rightarrow N\mu^+\mu^-$ in chiral perturbation theory and find that both decays should be observable at CEBAF. With sufficiently low thresholds on the $e^+e^-$ invariant mass a ... More
The effect of tow gaps on compression after impact strength of robotically laminated structuresMay 14 2013When (robotic) Automated Fibre Placement (AFP) is used to manufacture aerospace components with complex three dimensional geometries, gaps between fibre tows can occur. This paper is the first to explore the interaction under compressive load of these ... More
The Origin of the Magellanic Stream and Its Leading ArmJun 11 2007Feb 04 2008We explore the Magellanic Stream (MS) using a Gaussian decomposition of the HI velocity profiles in the Leiden-Argentine-Bonn (LAB) all-sky HI survey. This decomposition exposes the MS to be composed of two filaments distinct both spatially (as first ... More
3He Lung Imaging in an Open Access, Very-Low-Field Human MRI SystemMar 18 2004Dec 16 2004The human lung and its functions are extremely sensitive to gravity, however the conventional high-field magnets used for most laser-polarized 3He MRI of the human lung restrict subjects to lying horizontally. Imaging of human lungs using inhaled laser-polarized ... More
Magnetospherically driven optical and radio aurorae at the end of the stellar main sequenceJul 31 2015Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. ... More
Automating Discovery and Classification of Transients and Variable Stars in the Synoptic Survey EraJun 27 2011The rate of image acquisition in modern synoptic imaging surveys has already begun to outpace the feasibility of keeping astronomers in the real-time discovery and classification loop. Here we present the inner workings of a framework, based on machine-learning ... More
Don't Blink: Constraining the Circumstellar Environment of the Interacting Type Ia Supernova 2015cpDec 06 2018Despite their cosmological utility, the progenitors of Type Ia supernovae (SNe Ia) are still unknown, with many efforts focused on whether accretion from a nondegenerate companion can grow a carbon-oxygen white dwarf to near the Chandrasekhar mass. The ... More
The Hidden K-edge Signal in K-edge ImagingJun 13 2015K-edge imaging is commonly used for viewing contrast pharmaceuticals in a variety of multi-energy x-ray imaging techniques, ranging from dual-energy and spectral computed tomography to fluoroscopy. When looking for the K-edge signal of a specific contrast, ... More
SN 2008iy: An Unusual Type IIn Supernova with an Enduring 400 Day Rise TimeNov 25 2009Jan 26 2011We present spectroscopic and photometric observations of the Type IIn supernova (SN) 2008iy. SN 2008iy showed an unprecedentedly long rise time of ~400 days, making it the first SN to take significantly longer than 100 days to reach peak optical luminosity. ... More