Results for "M. A. Rol"

total 349151took 0.21s
The prompt emission & peculiar break of GRB 060124Oct 03 2006Mar 15 2007Our multi-wavelength analysis of GRB 060124 shows the unusual behaviour of the decaying lightcurve as well as supporting the recently proposed phenomenon of long-lasting central engine activity. The prompt X-ray emission displays uncommonly well resolved ... More
Broadband modeling of gamma-ray burst afterglowsAug 18 2005According to the fireball model gamma-ray burst (GRB) afterglows are the result of a shock pushed into the surrounding medium by an extremely relativistic outflow from the GRB. By modeling the broadband spectrum, ranging from X-ray to radio wavelengths, ... More
How Special Are Dark Gamma-Ray Bursts: A Diagnostic ToolJan 18 2005We present here a comprehensive study of the optical/near-infrared (IR) upper limits for gamma-ray bursts that have an X-ray afterglow. We have extrapolated the X-ray afterglows to optical wavelengths based on the physics of the fireball blast wave model ... More
GRB060602B = Swift J1749.4-2807: an unusual transiently accreting neutron-star X-ray binarySep 01 2007Oct 30 2008We present an analysis of the Swift BAT and XRT data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type-I ... More
The radio afterglow of GRB 030329 at centimeter wavelengths: evidence for a structured jet or non-relativistic expansionAug 18 2005We present our centimeter wavelength (1.4, 2.3 and 4.8 GHz) light curves of the afterglow of GRB 030329, which were obtained with the Westerbork Synthesis Radio Telescope. Modeling the data according to a collimated afterglow results in a jet-break time ... More
SCUBA sub-millimeter observations of gamma-ray bursters III. GRB 030329: The brightest sub-millimeter afterglow to dateMar 26 2005We discuss our ongoing program of Target of Opportunity (ToO) sub-millimeter observations of gamma-ray bursts (GRBs) using the Sub-millimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). In this paper, we present all ... More
Independent, extensible control of same-frequency superconducting qubits by selective broadcastingAug 26 2015A critical ingredient for realizing large-scale quantum information processors will be the ability to make economical use of qubit control hardware. We demonstrate an extensible strategy for reusing control hardware on same-frequency transmon qubits in ... More
SCUBA sub-millimeter observations of gamma-ray bursters: II. GRB 991208, 991216, 000301C, 000630, 000911, 000926Nov 01 2001We discuss our ongoing program of Target of Opportunity sub-millimeter observations of gamma-ray bursts (GRBs) using the Sub-millimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Sub-millimeter observations of the ... More
Inelastic Neutron Scattering Studies of Phonon Spectra and Simulations in Tungstates, AWO4 (A = Ba, Sr, Ca and Pb)Jul 25 2014Lattice dynamics and high pressure phase transitions in AWO4 (A = Ba, Sr, Ca and Pb) have been investigated using inelastic neutron scattering experiments, ab-initio density functional theory calculations and extensive molecular dynamics simulations. ... More
Haydeeite: a spin-1/2 kagome ferromagnetMar 27 2015Jun 01 2015The mineral haydeeite, alpha-MgCu3(OD)6Cl2, is a S=1/2 kagome ferromagnet that displays long-range magnetic order below TC=4.2 K with a strongly reduced moment. Our inelastic neutron scattering data show clear spin-wave excitations that are well described ... More
Gamma-Ray Burst afterglows as probes of environment and blastwave physics I: absorption by host galaxy gas and dustOct 30 2006Dec 18 2006We use a new approach to obtain limits on the absorbing columns towards an initial sample of 10 long Gamma-Ray Bursts observed with BeppoSAX and selected on the basis of their good optical and nIR coverage, from simultaneous fits to nIR, optical and X-ray ... More
Spectroscopy of GRB 021004: a structured jet ploughing through a massive stellar windJan 07 2005Mar 23 2005We present spectra of the afterglow of GRB 021004 taken with WHT ISIS and VLT FORS1 at three epochs spanning 0.49--6.62 days after the burst. We observe strong absorption likely coming from the host galaxy, alongside absorption in HI, SiIV and CIV with ... More
A fast, low-leakage, high-fidelity two-qubit gate for a programmable superconducting quantum computerMar 06 2019A common approach to realize conditional-phase (CZ) gates in transmon qubits relies on flux control of the qubit frequency to make computational states interact with non-computational ones using a fast-adiabatic trajectory to minimize leakage. We develop ... More
GRB 030329: three years of radio afterglow monitoringJun 09 2007Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. ... More
Density of states in solid deuterium: Inelastic neutron scattering studyMay 25 2009The dynamics of solid deuterium (sD2) is studied by means of inelastic scattering (coherent and incoherent) of thermal and cold neutrons at different temperatures and para-ortho ratios. In this paper, the results for the generalized density of states ... More
GRB 030329: 3 years of radio afterglow monitoringJun 09 2007Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. ... More
Gamma-Ray Burst Afterglows as Probes of Environment and Blastwave Physics II: the Distribution of p and Structure of the Circumburst MediumApr 27 2007Jul 28 2007We constrain blastwave parameters and the circumburst media of a subsample of ten BeppoSAX Gamma-Ray Bursts. For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst ... More
Evolution of Nanowire Transmons and Their Quantum Coherence in Magnetic FieldNov 21 2017We present an experimental study of nanowire transmons at zero and applied in-plane magnetic field. With Josephson non-linearities provided by the nanowires, our qubits operate at higher magnetic fields than standard transmons. Nanowire transmons exhibit ... More
Optical Classification of Gamma-Ray Bursts in the Swift EraMay 05 2009We propose a new method for the classification of optically dark gamma-ray bursts (GRBs), based on the X-ray and optical-to-X-ray spectral indices of GRB afterglows, and utilizing the spectral capabilities of Swift. This method depends less on model assumptions ... More
Understanding the magnetism in noncentrosymmetric CeIrGe3: Muon spin relaxation and neutron scattering studiesFeb 01 2018The magnetic properties of a pressure induced noncentrosymmetric heavy-fermion superconductor CeIrGe$_3$ have been investigated by muon spin relaxation ($\mu$SR), powder neutron diffraction (ND) and inelastic neutron scattering (INS) techniques at ambient ... More
Phonons, Nature of Bonding and Their Relation to Anomalous Thermal Expansion Behavior of M2O (M=Au, Ag, Cu)Nov 19 2013We report a comparative study of the dynamics of Cu2O, Ag2O and Au2O (i.e. M2O with M = Au, Ag and Cu) using first principle calculations based on the density functional theory. Here for the first time we show that the nature of chemical bonding and open ... More
The host galaxy of GRB010222: The strongest damped Lyman-alpha system knownDec 04 2001Analysis of the absorption lines in the afterglow spectrum of the gamma-ray burst GRB010222 indicates that its host galaxy (at a redshift of z=1.476) is the strongest damped Lyman-alpha (DLA) system known, having a very low metallicity and modest dust ... More
Time-domain characterization and correction of on-chip distortion of control pulses in a quantum processorJul 10 2019We introduce Cryoscope, a method for sampling on-chip baseband pulses used to dynamically control qubit frequency in a quantum processor. We specifically use Cryoscope to measure the step response of the dedicated flux control lines of two-junction transmon ... More
Phonons and Thermodynamics of LiMPO4 (M=Mn, Fe)Dec 12 2013Lithium transition metal phospho-olivines are useful electrode materials, owing to their stability, high safety, low cost and cyclability. We report phonon studies using neutron inelastic scattering experiments, ab-initio density functional theory calculations ... More
The broadband afterglow of GRB 030328Jan 13 2006We here report on the photometric, spectroscopic and polarimetric monitoring of the optical afterglow of the Gamma-Ray Burst (GRB) 030328 detected by HETE-2. We found that a smoothly broken power-law decay provides the best fit of the optical light curves, ... More
Gas and dust properties in the afterglow spectra of GRB 050730Aug 10 2005Sep 12 2005We present early WHT ISIS optical spectroscopy of the afterglow of gamma-ray burst GRB 050730. The spectrum shows a DLA system with the highest measured hydrogen column to date: N(HI) = 22.1 +/- 0.1 at the third-highest GRB redshift z = 3.968. Our analysis ... More
Evidence for energy injection and a fine-tuned central engine at optical wavelengths in GRB 070419AMar 08 2009We present a comprehensive multiwavelength temporal and spectral analysis of the FRED GRB 070419A. The early-time emission in the $\gamma$-ray and X-ray bands can be explained by a central engine active for at least 250 s, while at late times the X-ray ... More
The submm properties of GRB host galaxiesJun 09 2004Long duration gamma-ray bursts (GRBs) accompany the deaths of some massive stars and hence, since massive stars are short lived, are a tracer of star formation activity. Given that GRBs are bright enough to be seen to very high redshifts, and detected ... More
Error Mitigation by Symmetry Verification on a Variational Quantum EigensolverFeb 28 2019Variational quantum eigensolvers offer a small-scale testbed to demonstrate the performance of error mitigation techniques with low experimental overhead. We present successful error mitigation by applying the recently proposed symmetry verification technique ... More
GRB 070125 and the environments of spectral-line poor afterglow absorbersJul 19 2011GRB 070125 is among the most energetic bursts detected and the most extensively observed so far. Nevertheless, unresolved issues are still open in the literature on the physics of the afterglow and on the GRB environment. In particular, GRB 070125 was ... More
Protecting quantum entanglement from qubit errors and leakage via repetitive parity measurementsMay 29 2019Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits, and performs parity measurements to identify errors without destroying ... More
SCUBA sub-millimeter observations of gamma-ray bursters IV. GRB 021004, 021211, 030115, 030226, 041006Mar 26 2005We discuss our ongoing program of Target of Opportunity (ToO) sub-millimeter observations of gamma-ray bursts (GRBs) using the Sub-millimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). In this paper, we present the ... More
SCUBA observations of the host galaxies of four dark gamma-ray burstsJul 31 2002We present the results of a search for submillimetre-luminous host galaxies of optically dark gamma-ray bursts (GRBs) using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). We made photometry measurements ... More
Discovery of the afterglow and host galaxy of the low redshift short GRB 080905AJun 02 2010Aug 26 2010We present the discovery of short GRB 080905A, its optical afterglow and host galaxy. Initially discovered by Swift, our deep optical observations enabled the identification of a faint optical afterglow, and subsequently a face-on spiral host galaxy underlying ... More
Detailed study of the GRB 030329 radio afterglow deep into the non-relativistic phaseJun 09 2007Jan 04 2008We explore the physics behind one of the brightest radio afterglows ever, GRB 030329, at late times when the jet is non-relativistic. We determine the physical parameters of the blast wave and its surroundings, in particular the index of the electron ... More
Crystal field investigation in the light rare earth R$_3$Pt$_{23}$Si$_{11}$ compoundsDec 12 2016The crystalline electric field (CEF) is investigated in Pr$_3$Pt$_{23}$Si$_{11}$ and Nd$_3$Pt$_{23}$Si$_{11}$ by neutron spectroscopy (NS). At low temperature, the number of observed CEF excitations is consistent with the orthorhombic symmetry at the ... More
Prompt and Afterglow Emission Properties of Gamma-Ray Bursts with Spectroscopically Identified SupernovaeJul 06 2006Aug 07 2006We present a detailed spectral analysis of the prompt and afterglow emission of four nearby long-soft gamma-ray bursts (GRBs 980425, 030329, 031203, and 060218) that were spectroscopically found to be associated with type Ic supernovae, and compare them ... More
PySE: Software for Extracting Sources from Radio ImagesFeb 26 2018PySE is a Python software package for finding and measuring sources in radio telescope images. The software was designed to detect sources in the LOFAR telescope images, but can be used with images from other radio telescopes as well. We introduce the ... More
The Early-time Optical Properties of Gamma-Ray Burst AfterglowsApr 04 2008We present a multiwavelength analysis of 63 Gamma-Ray Bursts observed with the world's three largest robotic optical telescopes, the Liverpool and Faulkes Telescopes (North and South). Optical emission was detected for 24 GRBs with brightnesses ranging ... More
Magnetic excitations and electronic interactions in Sr$_2$CuTeO$_6$: a spin-1/2 square lattice Heisenberg antiferromagnetMay 31 2016Sr$_2$CuTeO$_6$ presents an opportunity for exploring low-dimensional magnetism on a square lattice of $S=1/2$ Cu$^{2+}$ ions. We employ ab initio multi-reference configuration interaction calculations to unravel the Cu$^{2+}$ electronic structure and ... More
The faint afterglow and host galaxy of the short-hard GRB 060121Mar 11 2006We present optical and X-ray observations of the afterglow and host galaxy of the short-hard GRB 060121. The faint R-band afterglow is seen to decline as t^(-0.66) while the X-ray falls as t^-1.18, indicating the presence of the cooling break between ... More
Active resonator reset in the nonlinear dispersive regime of circuit QEDApr 04 2016Jun 27 2016We present two pulse schemes for actively depleting measurement photons from a readout resonator in the nonlinear dispersive regime of circuit QED. One method uses digital feedback conditioned on the measurement outcome while the other is unconditional. ... More
Magnetic excitations and electronic interactions in Sr$_2$CuTeO$_6$: a spin-1/2 square lattice Heisenberg antiferromagnetMay 31 2016Dec 06 2016Sr$_2$CuTeO$_6$ presents an opportunity for exploring low-dimensional magnetism on a square lattice of $S=1/2$ Cu$^{2+}$ ions. We employ ab initio multi-reference configuration interaction calculations to unravel the Cu$^{2+}$ electronic structure and ... More
The discovery of polarization in the afterglow of GRB 990510 with the ESO Very Large TelescopeJun 22 1999Following a BeppoSAX alert (Piro 1999a) and the discovery of the OT at SAAO (Vreeswijk et al. 1999a), we observed GRB 990510 with the FORS instrument on ESO's VLT Unit 1 (`Antu'). The burst is unremarkable in gamma rays, but in optical is the first one ... More
GRB990712: First Indication of Polarization Variability in a Gamma-ray Burst AfterglowJul 03 2000We report the detection of significant polarization in the optical afterglow of GRB990712 on three instances 0.44, 0.70 and 1.45 days after the gamma-ray burst, with (P, theta) being (2.9% +- 0.4%, 121.1 degr +- 3.5 degr), (1.2% +- 0.4%, 116.2 degr +- ... More
Spin-Phonon Coupling, High Pressure Phase Transitions and Thermal Expansion of Multiferroic GaFeO3: A Combined First Principles and Inelastic Neutron Scattering StudyJun 04 2014We have carried out an extensive phonon study on multiferroic GaFeO3 to elucidate its dynamical behavior. Inelastic neutron scattering measurements are performed over a wide temperature range, 150 to 1198 K. First principles lattice dynamical calculations ... More
An Experimental Microarchitecture for a Superconducting Quantum ProcessorAug 25 2017Quantum computers promise to solve certain problems that are intractable for classical computers, such as factoring large numbers and simulating quantum systems. To date, research in quantum computer engineering has focused primarily at opposite ends ... More
Lithium Diffusion in Li2X(X=O, S and Se): Ab-initio Simulations and Neutron Inelastic Scattering MeasurementsMar 21 2019We have performed ab-initio lattice dynamics and molecular dynamics studies of Li2X (X=O, S and Se) to understand the ionic conduction in these compounds. The inelastic neutron scattering measurements on Li2O have been performed across its superionic ... More
Capacity estimation and verification of quantum channels with arbitrarily correlated errorsNov 16 2016One of the main figures of merit for quantum memories and quantum communication devices is their quantum capacity. It has been studied for arbitrary kinds of quantum channels, but its practical estimation has so far been limited to devices that implement ... More
Lattice Dynamics and Thermal Expansion Behavior in Metal Cyanides, MCN (M=Cu, Ag, Au): Neutron Inelastic Scattering and First Principles CalculationsOct 29 2015We report measurement of temperature dependence of phonon spectra in quasi one-dimensional metal cyanides MCN (M=Cu, Ag and Au). Ab initio lattice dynamics calculations have been performed to interpret the phonon-spectra as well as to understand the anamolous ... More
The prompt to late-time multiwavelength analysis of GRB 060210Jan 04 2007Mar 15 2007We present our analysis of the multiwavelength photometric & spectroscopic observations of GRB 060210 and discuss the results in the overall context of current GRB models. All available optical data underwent a simultaneous temporal fit, while X-ray and ... More
Ab initio lattice dynamics simulations and inelastic neutron scattering spectra for studying phonons in BaFe2As2: Effect of structural phase transition, structural relaxation and magnetic orderingJul 28 2008Feb 03 2009We have performed extensive ab initio calculations to investigate phonon dynamics and their possible role in superconductivity in BaFe2As2 and related systems. The calculations are compared to inelastic neutron scattering data that offer improved resolution ... More
Spin-Lattice Coupling in K0.8Fe1.6Se2 and KFe2Se2: Inelastic Neutron Scattering and ab-initio Phonon CalculationsJan 23 2013We report measurements of the temperature dependence of phonon densities of states in K0.8Fe1.6Se2 using inelastic neutron scattering technique. While cooling down to 150 K, a phonon peak splitting around 25 meV is observed and a new peak appears at 31 ... More
Detailed Radio View on Two Stellar Explosions and Their Host Galaxy: XRF080109/SN2008D and SN2007uy in NGC2770Nov 10 2010The galaxy NGC2770 hosted two core-collapse supernova explosions, SN2008D and SN2007uy, within 10 days of each other and 9 years after the first supernova of the same type, SN1999eh, was found in that galaxy. In particular SN2008D attracted a lot of attention ... More
Variable polarization in the optical afterglow of GRB 021004May 13 2003Jul 01 2003We present polarimetric observations of the afterglow of gamma-ray burst (GRB) 021004, obtained with the Nordic Optical Telescope (NOT) and the Very Large Telescope (VLT) between 8 and 17 hours after the burst. Comparison among the observations shows ... More
Visualization of membrane loss during the shrinkage of giant vesicles under electropulsationMay 23 2008Jan 15 2010We study the effect of permeabilizing electric fields applied to two different types of giant unilamellar vesicles, the first formed from EggPC lipids and the second formed from DOPC lipids. Experiments on vesicles of both lipid types show a decrease ... More
Phonon Dynamics and Inelastic Neutron Scattering of Sodium NiobateDec 13 2013Sodium niobate (NaNbO3) exhibits most complex sequence of structural phase transitions in perovskite family and therefore provides as excellent model system for understanding the mechanism of structural phase transitions. We report temperature dependence ... More
New Understanding of Ultra-Cold Neutron Production in Solid DeuteriumOct 01 2009Jun 16 2010Our recent neutron scattering measurements of phonons and other quasi-particle excitations in solid deuterium (sD$_2$) and the extraction of the density of states for phonons and rotational transitions in sD2 have led us to a new understanding of the ... More
The extreme, red afterglow of GRB 060923A: Distance or dust?Mar 28 2008Gamma-ray bursts are powerful probes of the early universe, but locating and identifying very distant GRBs remains challenging. We report here the discovery of the K-band afterglow of Swift GRB 060923A, imaged within the first hour post-burst, and the ... More
Evidence for a supernova in reanalyzed optical and near-infrared images of GRB970228Jul 20 1999We present B-, V-, R_c-, I_c-, J-, H-, K- and K'-band observations of the optical transient (OT) associated with GRB970228, based on a reanalysis of previously used images and unpublished data. In order to minimize calibration differences we have collected ... More
GRB 070306: A Highly Extinguished AfterglowMar 28 2008We report on the highly extinguished afterglow of GRB 070306 and the properties of the host galaxy. An optical afterglow was not detected at the location of the burst, but in near-infrared a doubling in brightness during the first night and later power-law ... More
GRB 050505: A high redshift burst discovered by SwiftFeb 10 2006We report the discovery and subsequent multi-wavelength afterglow behaviour of the high redshift (z = 4.27) Gamma Ray Burst GRB 050505. This burst is the third most distant burst, measured by spectroscopic redshift, discovered after GRB 000131 (z = 4.50) ... More
Phonon dynamics in Sr0.6K0.4Fe2As2 and Ca0.6Na0.4Fe2As2Oct 24 2008We report inelastic neutron scattering measurements of the phonon density-of-states in superconducting Sr0.6K0.4Fe2As2 (Tc=30 K) and Ca0.6Na0.4Fe2As2 (Tc=18 K). Compared with the parent compound BaFe2As2 doping affects mainly the lower and intermediate ... More
Inelastic neutron scattering and lattice dynamical calculations in BaFe2As2Jul 21 2008We report here first extensive measurements of the temperature dependence of phonon density of states of BaFe2As2, the parent compound of the newly discovered FeAs-based superconductors, using inelastic neutron scattering. The experiments were carried ... More
The GRB 060218/SN 2006aj event in the context of other Gamma-Ray Burst SupernovaeMay 02 2006Jul 18 2006The supernova SN 2006aj associated with GRB 060218 is the second-closest GRB-SN observed to date (z=0.033). We present Very Large Telescope, Liverpool Telescope, and Katzman Automatic Imaging Telescope multi-color photometry of SN 2006aj. This supernova ... More
Probing exciton localization in non-polar GaN/AlN Quantum Dots by single dot optical spectroscopyNov 24 2006We present an optical spectroscopy study of non-polar GaN/AlN quantum dots by time-resolved photoluminescence and by microphotoluminescence. Isolated quantum dots exhibit sharp emission lines, with linewidths in the 0.5-2 meV range due to spectral diffusion. ... More
Low-resolution VLT spectroscopy of GRBs 991216, 011211 and 021211Oct 13 2005Oct 13 2005We present low-resolution VLT spectroscopy of the afterglow of the gamma-ray bursts (GRBs) 991216, 011211 and 021211. Our spectrum of GRB991216 is the only optical spectrum for this afterglow. It shows two probable absorption systems at z=0.80 and z=1.02, ... More
The first Swift X-ray Flash: The faint afterglow of XRF 050215BMay 10 2006We present the discovery of XRF 050215B and its afterglow. The burst was detected by the Swift BAT during the check-out phase and observations with the X-ray telescope began approximately 30 minutes after the burst. These observations found a faint, slowly ... More
The Remarkable Afterglow of GRB 061007: Implications for Optical Flashes and GRB FireballsOct 21 2006Jan 06 2007We present a multiwavelength analysis of Swift GRB 061007. The 2-m robotic Faulkes Telescope South (FTS) began observing 137 s after the onset of the gamma-ray emission, when the optical counterpart was already decaying from R 10.3 mag, and continued ... More
The circumburst environment of a FRED GRB: study of the prompt emission and X-ray/optical afterglow of GRB 051111Nov 23 2006We report a multi-wavelength analysis of the prompt emission and early afterglow of GRB051111 and discuss its properties in the context of current fireball models. The detection of GRB051111 by the Burst Alert Telescope on-board Swift triggered early ... More
The host of GRB 060206: kinematics of a distant galaxyAug 25 2007Jun 04 2008We present early (starting 1.6h after the burst) WHT/ISIS optical spectroscopy of the afterglow of the gamma-ray burst GRB 060206 detecting a range of metal absorption lines and their fine-structure transitions. Additional information is provided by the ... More
GRB050223: A faint Gamma-Ray Burst discovered by SwiftJul 30 2005GRB050223 was discovered by the Swift Gamma-Ray Burst Explorer on 23 February 2005 and was the first Gamma-Ray Burst to be observed by both Swift and XMM-Newton. At the time of writing (May 2005), it has one of the faintest GRB afterglows ever observed. ... More
The afterglow of the short/intermediate-duration gamma-ray burst GRB 000301C: A jet at z=2.04May 31 2000Mar 02 2001We present Ulysses and NEAR data from the detection of the short or intermediate duration (2 s) gamma-ray burst GRB000301C (2000 March 1.41 UT). The gamma-ray burst (GRB) was localised by the Inter Planetary Network (IPN) and RXTE to an area of 50 arcmin^2. ... More
VLT spectroscopy of GRB 990510 and GRB 990712; probing the faint and bright end of the GRB host galaxy populationSep 01 2000We present time-resolved optical spectroscopy of the afterglows of the gamma-ray bursts GRB 990510 and GRB 990712. Through the identification of several absorption lines in the first epoch GRB 990510 spectrum, we determine the redshift for this burst ... More
Rotational variation of the linear polarisation of the asteroid (3200) Phaethon as evidence for inhomogeneity in its surface propertiesJul 31 2018Asteroid (3200) Phaethon is a Near-Earth Apollo asteroid with an unusual orbit that brings it closer to the Sun than any other known asteroid. Its last close approach to the Earth was in mid-December 2017 and the next one will be on October 2026. Previous ... More
Very high column density and small reddening towards GRB 020124 at z = 3.20Jul 17 2003We present optical and near-infrared observations of the dim afterglow of GRB 020124, obtained between 2 and 68 hours after the gamma-ray burst. The burst occurred in a very faint (R > 29.5) Damped Ly-alpha Absorber (DLA) at a redshift of z = 3.198 +- ... More
Spectroscopy and multiband photometry of the afterglow of intermediate duration gamma-ray burst 040924 and its host galaxyJun 10 2007We present optical photometry and spectroscopy of the afterglow and host galaxy of gamma-ray burst 040924. This GRB had a rather short duration of T90 ~2.4s, and a well sampled optical afterglow light curve. We aim to use this dataset to find further ... More
GRB 011121: A collimated outflow into wind-blown surroundingsSep 26 2003We discover a break in the GRB 011121 afterglow light curve after 1.3 days, which implies an initial jet opening angle of about 9 deg. The SED during the first four days is achromatic, and supports the jet origin of this break. The SED during the supernova ... More
On the constraining observations of the dark GRB 001109 and the properties of a z = 0.398 radio selected starburst galaxy contained in its error boxJun 18 2004We present optical and NIR (near infrared) follow up observations of the GRB 001109 from 1 to 300 days after the burst. No transient emission was found at these wavelengths within this GRB's (Gamma Ray Burst) 50" radius BeppoSAX error box. Strong limits ... More
Multiwavelength analysis of the intriguing GRB 061126: the reverse shock scenario and magnetizationApr 10 2008Jul 29 2008We present a detailed study of the prompt and afterglow emission from Swift GRB 061126 using BAT, XRT, UVOT data and multi-color optical imaging from ten ground-based telescopes. GRB 061126 was a long burst (T_90=191 s) with four overlapping peaks in ... More
Structure and dynamics of the fullerene polymer Li4 C60 studied with neutron scatteringFeb 18 2015Jun 22 2015The two-dimensional polymer structure and lattice dynamics of the superionic conductor Li4 C60 are investigated by neutron diffraction and spectroscopy. The peculiar bonding architecture of this compound is definitely confirmed through the precise localisation ... More
The origin of the early time optical emission of Swift GRB 080310Jan 05 2012We present broadband multi-wavelength observations of GRB 080310 at redshift z = 2.43. This burst was bright and long-lived, and unusual in having extensive optical and near IR follow-up during the prompt phase. Using these data we attempt to simultaneously ... More
The Burst Cluster: Dark Matter in a Cluster Merger Associated with the Short Gamma Ray Burst, GRB 050509BMay 20 2013We have identified a merging galaxy cluster with evidence of two distinct sub-clusters. The X-ray and optical data suggest that the subclusters are moving away from each other after closest approach. This cluster merger was discovered from observations ... More
GRB 021004: Tomography of a gamma-ray burst progenitor and its host galaxyApr 07 2010We analyse the distribution of matter around the progenitor star of gamma-ray burst GRB 021004 as well as the properties of its host galaxy with high-resolution echelle as well as near-infrared spectroscopy. Observations were taken by the 8.2m Very Large ... More
Restless Tuneup of High-Fidelity Qubit GatesNov 15 2016We present a tuneup protocol for qubit gates with tenfold speedup over traditional methods reliant on qubit initialization by energy relaxation. This speedup is achieved by constructing a cost function for Nelder-Mead optimization from real-time correlation ... More
GRB 060206 and the quandary of achromatic breaks in afterglow light curvesJun 08 2007Jul 19 2007Gamma-ray burst afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX era. We present our multi-wavelength analysis of GRB 060206 as an illustrative example of how inferences of jet breaks from ... More
A multi-colour study of the dark GRB 000210 host galaxy and its environmentDec 13 2002We present UBVRIZJsHKs broad band photometry of the host galaxy of the dark gamma-ray burst (GRB) of February 10, 2000. These observations represent the most exhaustive photometry given to date of any GRB host galaxy. A grid of spectral templates have ... More
GRB051022: physical parameters and extinction of a prototype dark burstJun 11 2007Jul 02 2007GRB051022 was undetected to deep limits in early optical observations, but precise astrometry from radio and X-ray showed that it most likely originated in a galaxy at z~0.8. We report radio, optical, near infra-red and X-ray observations of GRB051022. ... More
The optical/near-IR spectral energy distribution of the GRB 000210 host galaxyJan 29 2003We report on UBVRIZJsHKs-band photometry of the dark GRB 000210 host galaxy. Fitting a grid of spectral templates to its Spectral Energy Distribution (SED), we derived a photometric redshift (z=0.842\+0.0540.042) which is in excellent agreement with the ... More
Strategies for prompt searches for GRB afterglows: the discovery of the GRB 001011 optical/near-infrared counterpart using colour-colour selectionSep 29 2001Nov 14 2001We report the discovery of the optical and near-infrared counterparts to GRB 001011. The GRB 001011 error box determined by Beppo-SAX was simultaneously imaged in the near-infrared by the 3.58-m New Technology Telescope and in the optical by the 1.54-m ... More
The blue host galaxy of the red GRB 000418Jul 08 2003Sep 23 2003We report on multi-band (UBVRIZJsKs) observations of the host galaxy of the April 18, 2000 gamma-ray burst. The Spectral Energy Distribution (SED) is analysed by fitting empirical and synthetic spectral templates. We find that: (i) the best SED fit is ... More
Phonon spectra in CaFe2As2 and Ca0.6Na0.4Fe2As2: Measurement of the pressure and temperature dependence and comparison with ab-initio and shell model calculationsFeb 26 2009We report the pressure and temperature dependence of the phonon density-of-states in superconducting Ca0.6Na0.4Fe2As2 (Tc=21 K) and the parent compound CaFe2As2, using inelastic neutron scattering. We observe no significant change in the phonon spectrum ... More
eQASM: An Executable Quantum Instruction Set ArchitectureAug 07 2018Mar 09 2019A widely-used quantum programming paradigm comprises of both the data flow and control flow. Existing quantum hardware cannot well support the control flow, significantly limiting the range of quantum software executable on the hardware. By analyzing ... More
The early X-ray emission from GRBsJan 06 2006Jun 30 2006We present observations of the early X-ray emission for a sample of 40 gamma-ray bursts (GRBs) obtained using the Swift satellite for which the narrow-field instruments were pointed at the burst within 10 minutes of the trigger. Using data from the Burst ... More
Probing Cosmic Chemical Evolution with Gamma-Ray Bursts: GRB060206 at z=4.048Feb 20 2006Apr 09 2006Aim: We present early optical spectroscopy of the afterglow of the gamma-ray burst GRB 060206 with the aim of determining the metallicity of the GRB absorber and the physical conditions in the circumburst medium. We also discuss how GRBs may be important ... More
Early spectroscopic identification of SN 2008DMay 08 2008Jan 26 2009SN 2008D was discovered while following up an unusually bright X-ray transient in the nearby spiral galaxy NGC 2770. We present early optical spectra (obtained 1.75 days after the X-ray transient) which allowed the first identification of the object as ... More
Controlled tuning of whispering gallery modes of GaN/InGaN microdisk cavitiesAug 24 2011Controlled tuning of the whispering gallery modes of GaN/InGaN {\mu}-disk cavities is demonstrated. The whispering gallery mode (WGM) tuning is achieved at room temperature by immersing the {\mu}-disks in water and irradiating with ultraviolet (UV) laser. ... More
Phonon dynamics in SrFe2As2 and SrFeAsF parent pnictide compounds: How different/similar when compared to Ca- and Ba-compounds?Dec 09 2009Aug 06 2010We report detailed measurements of temperature dependence and ab initio lattice dynamical calculations of the phonon density-of-states of two Sr based iron pnictide parent compounds; SrFe2As2 and SrFeAsF. Although both compounds undergo a magnetic as ... More
Effects of magnetic doping and temperature dependence on phonon dynamics in CaFe\_{1-x}Co\_{x}AsF compounds (x = 0, 0.06, 0.12)Apr 22 2009We report detailed measurements of composition as well as temperature dependence of the phonon density-of-states in a new series of FeAs compounds with composition CaFe1\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12). The composition as well as temperature dependence ... More
Probing a GRB progenitor at a redshift of z=2: a comprehensive observing campaign of the afterglow of GRB 030226Aug 03 2004Aug 13 2004We report results from a comprehensive follow-up observing campaign of the afterglow of GRB 030226, including VLT spectroscopy, VLT polarimetry, and Chandra X-ray observations. In addition, we present BOOTES-1 wide-field observations at the time of the ... More