Results for "R. J. Foley"

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On Spectral Line Profiles in Type Ia Supernova SpectraDec 26 2012Jan 02 2013We present a detailed analysis of spectral line profiles in Type Ia supernova (SN Ia) spectra. We focus on the feature at ~3500 - 4000 A, which is commonly thought to be caused by blueshifted absorption of Ca H&K. Unlike some other spectral features in ... More
The Relation Between Ejecta Velocity, Intrinsic Color, and Host-Galaxy Mass for High-Redshift Type Ia SupernovaeJan 31 2012Recently, using a large low-redshift sample of Type Ia supernovae (SNe Ia), we discovered a relation between SN Ia ejecta velocity and intrinsic color that improves the distance precision of SNe Ia and reduces potential systematic biases related to dust ... More
Habitability of Earth-like stagnant lid planets: Climate evolution and recovery from snowball statesMar 28 2019Coupled models of mantle thermal evolution, volcanism, outgassing, weathering, and climate evolution for Earth-like (in terms of size and composition) stagnant lid planets are used to assess their prospects for habitability. The results indicate that ... More
Kinematics and Host-Galaxy Properties Suggest a Nuclear Origin for Calcium-Rich Supernova ProgenitorsJan 29 2015Calcium-rich supernovae (Ca-rich SNe) are peculiar low-luminosity SNe Ib with relatively strong Ca spectral lines at ~2 months after peak brightness. This class also has an extended projected offset distribution, with several members of the class offset ... More
The Role of Plate Tectonic-Climate Coupling and Exposed Land Area in the Development of Habitable Climates on Rocky PlanetsSep 01 2015The long-term carbon cycle is vital for maintaining liquid water oceans on rocky planets due to the negative climate feedbacks involved in silicate weathering. Plate tectonics plays a crucial role in driving the long-term carbon cycle because it is responsible ... More
Polarised correlators at finite temperatureJul 28 2010Sep 30 2010QCD undergoes a deconfining transition at high temperature to a "quark-gluon plasma" phase where hadrons may become unbound. In this work, meson correlation functions at non-zero momentum are studied both in the confined and plasma phases using the Maximum ... More
No X-rays from the very nearby Type Ia SN2014J: constraints on its environmentMay 07 2014Deep X-ray observations of the post-explosion environment around the very nearby Type Ia SN\,2014J (Dl=3.5 Mpc) reveal no X-ray emission down to a luminosity L<7x10^{36} erg/s (0.3-10 keV) at t~20 days after the explosion. We interpret this limit in the ... More
Scaling Laws for Convection with Temperature-dependent Viscosity and Grain-damageOct 28 2014Numerical experiments of convection with grain-damage are used to develop scaling laws for convective heat flow, mantle velocity, and plate velocity across the stagnant lid and plate-tectonic regimes. Three main cases are presented in order of increasing ... More
Measuring Ejecta Velocity Improves Type Ia Supernova DistancesNov 19 2010We use a sample of 121 spectroscopically normal Type Ia supernovae (SNe Ia) to show that their intrinsic color is correlated with their ejecta velocity, as measured from the blueshift of the Si II 6355 feature near maximum brightness, v_Si. The SN Ia ... More
Classifying Supernovae Using Only Galaxy DataSep 10 2013Oct 23 2013We present a new method for probabilistically classifying supernovae (SNe) without using SN spectral or photometric data. Unlike all previous studies to classify SNe without spectra, this technique does not use any SN photometry. Instead, the method relies ... More
A Definitive Measurement of Time Dilation in the Spectral Evolution of the Moderate-Redshift Type Ia Supernova 1997exApr 21 2005We have obtained high-quality Keck optical spectra at three epochs of the Type Ia supernova 1997ex, whose redshift z is 0.361. The elapsed calendar time between the first two spectra was 24.88 d, and that between the first and third spectra was 30.95 ... More
Very different X-ray to optical column density ratios in gamma-ray burst afterglows: ionisation in GRB environmentsFeb 20 2007Mar 22 2007We compare the HI column densities from Ly-alpha absorption to the metal column densities from X-ray absorption in gamma-ray burst (GRB) afterglows. Eight bursts of seventeen entering the sample, have significant extragalactic X-ray absorptions. Of these ... More
High-resolution X-ray spectroscopy of Procyon by Chandra and XMM-NewtonApr 23 2002We report the analysis of the high-resolution soft X-ray spectrum of the nearby F-type star Procyon in the wavelength range from 5 to 175 Angstrom obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board Chandra and with the Reflection ... More
Carbon cycling and habitability of Earth-size stagnant lid planetsDec 11 2017Models of thermal evolution, crustal production, and CO$_2$ cycling are used to constrain the prospects for habitability of rocky planets, with Earth-like size and composition, in the stagnant lid regime. Specifically, we determine the conditions under ... More
Large deviations of a modified Jackson network: stability and rough asymptoticsMar 23 2005Consider a modified, stable, two node Jackson network where server 2 helps server 1 when server 2 is idle. The probability of a large deviation of the number of customers at node one can be calculated using the flat boundary theory of Schwartz and Weiss ... More
Bridges and networks: Exact asymptoticsMar 23 2005We extend the Markov additive methodology developed in [Ann. Appl. Probab. 9 (1999) 110-145, Ann. Appl. Probab. 11 (2001) 596-607] to obtain the sharp asymptotics of the steady state probability of a queueing network when one of the nodes gets large. ... More
A Study of the Coronal Plasma in RS CVn binary systems: HR 1099 and coSep 17 2001XMM-Newton has been performing comprehensive studies of X-ray luminous RS CVn binary systems in its calibration and guaranteed time programs. We present results from ongoing investigations in the context of a systematic study of coronal emission from ... More
Complexity, economic science and possible economic benefits of climate change mitigation policyOct 16 2013Jan 28 2015Conventional economic analysis of stringent climate change mitigation policy generally concludes various levels of economic slowdown as a result of substantial spending on low carbon technology. Equilibrium economics however could not explain or predict ... More
The dynamics of technology diffusion and the impacts of climate policy instruments in the decarbonisation of the global electricity sectorSep 29 2013Jun 22 2014This paper presents an analysis of climate policy instruments for the decarbonisation of the global electricity sector in a non-equilibrium economic and technology diffusion perspective. Energy markets are driven by innovation, path-dependent technology ... More
Metallicity Differences in Type Ia Supernova Progenitors Inferred from Ultraviolet SpectraFeb 18 2013Apr 08 2013Two "twin" Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and spectra, yet have different ultraviolet (UV) continua as measured in Hubble Space Telescope spectra and measurably different ... More
On the Interpretation of Supernova Light Echo Profiles and SpectraApr 21 2010Feb 04 2011The light echo systems of historical supernovae in the Milky Way and local group galaxies provide an unprecedented opportunity to reveal the effects of asymmetry on observables, particularly optical spectra. Scattering dust at different locations on the ... More
A Study of the Coronal Plasma in RS CVn binary systemsSep 17 2001XMM-Newton has been performing comprehensive studies of X-ray bright RS CVn binaries in its Calibration and Guaranteed Time programs. We present results from ongoing investigations in the context of a systematic study of coronal emission from RS CVns. ... More
The Dusty Progenitor Star of the Type II Supernova 2017eawJun 01 2018We present pre-explosion photometry of the likely progenitor star of the Type II supernova (SN II) 2017eaw in NGC 6946. We use a Hubble Space Telescope (HST) image of SN 2017eaw to perform relative astrometry with HST and Spitzer Space Telescope (Spitzer) ... More
Whole planet coupling between climate, mantle, and core: Implications for the evolution of rocky planetsNov 18 2017Earth's climate, mantle, and core interact over geologic timescales. Climate influences whether plate tectonics can take place on a planet, with cool climates being favorable for plate tectonics because they enhance stresses in the lithosphere, suppress ... More
SN2008am: A Super-Luminous Type IIn SupernovaJan 18 2011We present observations and interpretation of the Type IIn supernova SN 2008am discovered by the ROTSE Supernova Verification Project (RSVP). SN 2008am peaked at approximately -22.3 mag at a redshift of z=0.2338, giving it a peak luminosity of 3 x 10^{44}erg/s ... More
Optical and infrared observations of the Type IIP SN2002hh from day 3 to 397Feb 16 2006Feb 17 2006We present optical and infrared (IR) observations of the type IIP SN2002hh from 3 to 397 days after explosion. The optical spectroscopic (4-397d) and photometric (3-278d) data are complemented by spectroscopic (137-381d) and photometric (137-314d) data ... More
A Sample of Type II-L SupernovaeAug 28 2014What are Type II-Linear supernovae (SNe II-L)? This class, which has been ill defined for decades, now receives significant attention -- both theoretically, in order to understand what happens to stars in the ~15-25Mo range, and observationally, with ... More
The Type II Supernova Rate in z~0.1 Galaxy Clusters from the Multi-Epoch Nearby Cluster SurveyApr 30 2012We present 7 spectroscopically confirmed Type II cluster supernovae (SNeII) discovered in the Multi-Epoch Nearby Cluster Survey, a supernova survey targeting 57 low redshift 0.05 < z < 0.15 galaxy clusters with the Canada-France-Hawaii Telescope. We find ... More
The Spectroscopic Classification and Explosion Properties of SN2009nz Associated with GRB091127 at z=0.490Jun 15 2011We present spectroscopic observations of GRB091127 (z=0.490) at the peak of the putative associated supernova, SN2009nz. Subtracting a late-time spectrum of the host galaxy, we isolate the contribution of SN2009nz and uncover broad features typical of ... More
Rotational Dynamics of Organic Cations in CH3NH3PbI3 PerovskiteJun 07 2015Sep 14 2015Methylammonium lead iodide (CH3NH3PbI3) based solar cells have shown impressive power conversion efficiencies of above 20%. However, the microscopic mechanism of the high photovoltaic performance is yet to be fully understood. Particularly, the dynamics ... More
On the Incidence of Strong MgII Absorbers Along GRB SightlinesMay 02 2006Jun 19 2006We report on a survey for strong (rest equivalent width W_r >= 1A), intervening MgII systems along the sightlines to long-duration gamma-ray bursts (GRBs). The GRB spectra which comprise the survey have a heterogeneous mix of resolution and wavelength ... More
Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the Spectrometer aboard INTEGRALFeb 28 2007Mar 12 2007The spectrometer aboard INTEGRAL, SPI, has the capability to detect the signature of polarised emission from a bright gamma-ray source. GRB 041219a is the most intense burst localised by INTEGRAL and is an ideal candidate for such a study. Polarisation ... More
In search of progenitors for supernova-less GRBs 060505 and 060614: re-examination of their afterglowsDec 04 2008Jan 31 2009GRB060505 and GRB060614 are nearby long-duration gamma-ray bursts (LGRBs) without accompanying supernovae (SNe) down to very strict limits. They thereby challenge the conventional LGRB-SN connection and naturally give rise to the question: are there other ... More
High energy emission and polarisation limits for the INTEGRAL burst GRB 061122Mar 30 2009(Abridged) GRB 061122 is one of the brightest GRBs detected within INTEGRAL's field of view to date. The two gamma-ray detectors on INTEGRAL were used to investigate the spectral characteristics of GRB 061122. A search for linear polarisation in the prompt ... More
The properties of V838 Mon in 2002 NovemberSep 08 2006We present the results of modelling the 0.45--1 micron spectral energy distribution of V838 Mon for 2002 November. Synthetic spectra were calculated using the NextGen model atmospheres of Hauschildt et al. (1999), which incorporate line lists for H2O, ... More
Intracluster supernovae in the Multi-epoch Nearby Cluster SurveyNov 05 2010Oct 07 2011The Multi-Epoch Nearby Cluster Survey (MENeaCS) has discovered twenty-three cluster Type Ia supernovae (SNe) in the 58 X-ray selected galaxy clusters (0.05 < z < 0.15) surveyed. Four of our SN Ia events have no host galaxy on close inspection, and are ... More
On the Progenitor of the Type II-Plateau SN 2008cn in NGC 4603Oct 13 2009Through comparison of pre- and post-explosion images obtained with the Wide Field and Planetary Camera 2 onboard the Hubble Space Telescope, we have isolated a supergiant star prior to explosion at nearly the same position as the high-luminosity SN II-P ... More
Circumstellar absorption in double detonation Type Ia supernovaeFeb 12 2013May 06 2013Upon formation, degenerate He core white dwarfs are surrounded by a radiative H-rich layer primarily supported by ideal gas pressure. In this Letter, we examine the effect of this H-rich layer on mass transfer in He+C/O double white dwarf binaries that ... More
Extending Supernova Spectral Templates for Next-Generation Space Telescope ObservationsAug 07 2018Nov 03 2018Empirical models of supernova (SN) spectral energy distributions (SEDs) are widely used for SN survey simulations and photometric classifications. The existing library of SED models has excellent optical templates but limited, poorly constrained coverage ... More
Lensed Image Angles: New Statistical Evidence for SubstructureJun 17 2008We introduce a novel statistical way of analyzing the projected mass distribution in galaxy lenses based solely on the angular distribution of images in quads around the lens center. The method requires the knowledge of the lens center location, but the ... More
Gradient Flow Analysis on MILC HISQ EnsemblesNov 01 2014Nov 14 2014We report on a preliminary scale determination with gradient-flow techniques on the $N_f = 2 + 1 + 1$ HISQ ensembles generated by the MILC collaboration. The ensembles include four lattice spacings, ranging from 0.15 to 0.06 fm, and both physical and ... More
Linking Type Ia Supernova Progenitors and their Resulting ExplosionsMar 13 2012Apr 19 2012Comparing the ejecta velocities at maximum brightness and narrow circumstellar/interstellar Na D absorption line profiles of a sample of 23 Type Ia supernovae (SNe Ia), we determine that the properties of SN Ia progenitor systems and explosions are intimately ... More
PKS 2123-463: a confirmed gamma-ray blazar at high redshiftSep 03 2012The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the First Fermi-LAT source catalog with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position ... More
Update on the 2+1+1 flavor QCD equation of state with HISQDec 18 2013We present recent results on the QCD equation of state with 2+1+1 flavors of highly improved staggered quarks (HISQ). We focus on three sets of ensembles with temporal extent 6, 8 and 10, that reach up to temperatures of 967, 725 and 580 MeV, respectively. ... More
A Spectroscopic Study of Type Ibc Supernova Host Galaxies from Untargeted SurveysJun 12 2012Sep 16 2012We present the largest spectroscopic study of the host environments of Type Ibc supernovae (SN Ibc) discovered exclusively by untargeted SN searches. Past studies of SN Ibc host environments have been biased towards high-mass, high-metallicity galaxies ... More
On the Progenitor of the Type IIb Supernova 2016gkgOct 14 2016We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck Adaptive Optics system was used to ... More
Dipolar and scalar $^{3}$He-$^{129}$Xe frequency shifts in stemless cellsMay 03 2019We study nuclear spin frequency shifts in a $^{3}$He-$^{129}$Xe comagnetometer caused by spin polarization of $^{3}$He. We use stemless cylindrical cells to systematically vary the cell geometry and separately measure the cell shape-dependent and shape-independent ... More
Growing evidence that SNe Iax are not a one-parameter family: the case of PS1-12bwhJan 19 2017In this study, we present observations of a type Iax supernova, PS1-12bwh, discovered during the Pan-STARRS1 3$\pi$-survey. Our analysis was driven by previously unseen pre-maximum, spectroscopic heterogeneity. While the light curve and post-maximum spectra ... More
Luminosity Indicators in the Ultraviolet Spectra of Type Ia SupernovaeMar 07 2008May 02 2008We present a complete sample of International Ultraviolet Explorer and Hubble Space Telescope ultraviolet (UV) spectra of Type Ia supernovae (SNe Ia) through 2004. We measure the equivalent width (EW) and blueshifted velocity of the minimum of the one ... More
Symanzik flow on HISQ ensemblesNov 06 2013We report on a scale determination with gradient-flow techniques on the $N_f = 2 + 1 + 1$ HISQ ensembles generated by the MILC collaboration. The lattice scale $w_0/a$, originally proposed by the BMW collaboration, is computed using Symanzik flow at four ... More
Initiation of Plate Tectonics from Post-Magma Ocean Thermo-Chemical ConvectionOct 28 2014Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable ... More
Investigating the Diversity of Type Ia Supernova Spectra with the Open-Source Relational Database KaeporaMay 06 2019We present a public, open-source relational database (we name kaepora) containing a sample of 4975 spectra of 777 Type Ia supernovae (SNe Ia). Since we draw from many sources, we significantly improve the spectra by inspecting these data for quality, ... More
Dust Formation and He II 4686 emission in the Dense Shell of the Peculiar Type Ib Supernova 2006jcApr 17 2007Feb 25 2008We present evidence for the formation of dust grains in an unusual Type Ib SN based on late-time spectra of SN 2006jc. The progenitor suffered an LBV-like outburst just 2 yr earlier, and we propose that the dust formation is a consequence of the SN blast ... More
Type Ia Supernova Colors and Ejecta Velocities: Hierarchical Bayesian Regression with Non-Gaussian DistributionsFeb 27 2014Nov 27 2014We investigate the statistical dependence of the peak intrinsic colors of Type Ia supernovae (SN Ia) on their expansion velocities at maximum light, measured from the Si II 6355 spectral feature. We construct a new hierarchical Bayesian regression model, ... More
Velocity Evolution and the Intrinsic Color of Type Ia SupernovaeJul 18 2011Sep 14 2011To understand how best to use observations of Type Ia supernovae (SNe Ia) to obtain precise and accurate distances, we investigate the relations between spectra of SNe Ia and their intrinsic colors. Using a sample of 1630 optical spectra of 255 SNe, based ... More
An Empirical Study of Contamination in Deep, Rapid, and Wide-Field Optical Follow-Up of Gravitational Wave EventsOct 05 2017Oct 09 2017We present an empirical study of contamination in deep, rapid, and wide-field optical follow-up searches of GW sources from aLIGO. We utilize dedicated observations during four nights of imaging with DECam. Our search covered $\sim56$ deg$^2$, with two ... More
The Interstellar Medium of GRB Host Galaxies I. Echelle Spectra of Swift GRB AfterglowsNov 02 2006Jan 04 2007We present optical echelle spectra of four gamma-ray burst (GRB) afterglows (GRB 050730, GRB 050820, GRB 051111, and GRB 060418) discovered during the first 1.5 years of operation of the Swift satellite and localized by either the Swift telescope or follow-up ... More
The Foundation Supernova Survey: Measuring Cosmological Parameters with Supernovae from a Single TelescopeNov 22 2018Measurements of the dark energy equation-of-state parameter, $w$, have been limited by uncertainty in the selection effects and photometric calibration of $z<0.1$ Type Ia supernovae (SNe Ia). The Foundation Supernova Survey is designed to lower these ... More
Improved Distances to Type Ia Supernovae with Two Spectroscopic SubclassesJun 09 2009We study the observables of 158 relatively normal Type Ia supernovae (SNe Ia) by dividing them into two groups in terms of the expansion velocity inferred from the absorption minimum of the Si II 6355 line in their spectra near B-band maximum brightness. ... More
A Survey for Supernovae in Massive High-Redshift ClustersNov 29 2006We describe our ongoing program designed to measure the SN-Ia rate in a sample of massive z=0.5-0.9 galaxy clusters. The SN-Ia rate is a poorly known observable, especially at high z, and in cluster environments. The SN rate and its redshift dependence ... More
Nano-optical imaging of WSe2 waveguide modes revealing light-exciton interactionsJan 09 2016Sep 27 2016We report on nano-optical imaging study of WSe2 thin flakes with the scanning near-field optical microscopy (NSOM). The NSOM technique allows us to visualize in real space various waveguide photon modes inside WSe2. By tuning the excitation laser energy, ... More
Should Type Ia Supernova Distances be Corrected for their Local Environments?May 15 2018Sep 18 2018Recent analyses suggest that distance residuals measured from Type Ia supernovae (SNe Ia) are correlated with local host galaxy properties within a few kpc of the SN explosion. However, the well-established correlation with global host galaxy properties ... More
An Intermediate Luminosity Transient in NGC300: The Eruption of a Dust-Enshrouded Massive StarJan 07 2009[abridged] We present multi-epoch high-resolution optical spectroscopy, UV/radio/X-ray imaging, and archival Hubble and Spitzer observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy NGC300. We find that ... More
Radio observations of candidate magnetic O starsDec 16 2010Context: Some O stars are suspected to have to have (weak) magnetic fields because of the observed cyclical variability in their UV wind-lines. However, direct detections of these magnetic fields using optical spectropolarimetry have proven to be very ... More
Gradient flow and scale setting on MILC HISQ ensemblesMar 10 2015May 30 2016We report on a scale determination with gradient-flow techniques on the $N_f=2+1+1$ highly improved staggered quark ensembles generated by the MILC Collaboration. The ensembles include four lattice spacings, ranging from approximately 0.15 to 0.06 fm, ... More
The soft X-ray blast in the apparently sub-luminous GRB 031203Sep 15 2005GRB031203 was a very low apparent luminosity gamma-ray burst (GRB). It was also the first GRB with a dust-scattered X-ray halo. The observation of the halo allowed us to infer the presence of a large soft X-ray fluence in the total burst output. It has, ... More
A Search for Fast Optical Transients in the Pan-STARRS1 Medium-Deep Survey: M Dwarf Flares, Asteroids, Limits on Extragalactic Rates, and Implications for LSSTJul 19 2013[Abridged] We present a search for fast optical transients (~0.5 hr-1 day) using repeated observations of the Pan-STARRS1 Medium-Deep Survey (PS1/MDS) fields. Our search takes advantage of the consecutive g/r-band observations (16.5 min in each filter), ... More
The Unexpected, Long-Lasting, UV Rebrightening of the Super-Luminous Supernova ASASSN-15lhMay 02 2016ASASSN-15lh is the most luminous supernova (SN) ever discovered (Dong et al. 2016), based on its peak bolometric luminosity. Here we report a UV rebrightening of ASASSN-15lh observed with {\it Swift} during our follow-up photometric campaign. The rebrightening ... More
The Galaxy Hosts and Large-Scale Environments of Short-Hard Gamma-Ray BurstsOct 02 2005Feb 11 2006The rapid succession of discovery of short--duration hard--spectrum GRBs has led to unprecedented insights into the energetics of the explosion and nature of the progenitors. Yet short of the detection of a smoking gun, like a burst of coincident gravitational ... More
The Unexpected, Long-Lasting, UV Rebrightening of the Super-Luminous Supernova ASASSN-15lhMay 02 2016Feb 13 2017Given its peak luminosity and early-time spectra, ASASSN-15lh was classified as the most luminous supernova (SN) ever discovered (Dong et al. 2016). Here we report a UV rebrightening of ASASSN-15lh observed with Swift during our follow-up campaign. The ... More
The Unexpected, Long-Lasting, UV Rebrightening of the Super-Luminous Supernova ASASSN-15lhMay 02 2016Nov 29 2016Given its peak luminosity and early-time spectra, ASASSN-15lh was classified as the most luminous supernova (SN) ever discovered (Dong et al. 2016). Here we report a UV rebrightening of ASASSN-15lh observed with Swift during our follow-up campaign. The ... More
Evidence for a Photospheric Component in the Prompt Emission of the Short GRB120323A and its Effects on the GRB Hardness-Luminosity RelationOct 26 2012Apr 07 2013The short GRB 120323A had the highest flux ever detected with the Fermi/GBM. Here we study its remarkable spectral properties and their evolution using two spectral models: (i) a single emission component scenario, where the spectrum is modeled by the ... More
The Aspherical Properties of the Energetic Type Ic SN 2002ap as Inferred from its Nebular SpectraAug 07 2007The nebular spectra of the broad-lined, SN 1998bw-like Type Ic SN 2002ap are studied by means of synthetic spectra. Two different modelling techniques are employed. In one technique, the SN ejecta are treated as a single zone, while in the other a density ... More
The Young, Massive, Star Cluster Sandage-96 After the Explosion of SN 2004dj in NGC 2403Dec 08 2008The bright Type II-plateau supernova (SN) 2004dj occurred within the young, massive stellar cluster Sandage-96 in a spiral arm of NGC 2403. New multi-wavelength observations obtained with several ground-based and space-based telescopes are combined to ... More
Supernova 2007bi as a pair-instability explosionJan 07 2010Stars with initial masses 10 M_{solar} < M_{initial} < 100 M_{solar} fuse progressively heavier elements in their centres, up to inert iron. The core then gravitationally collapses to a neutron star or a black hole, leading to an explosion -- an iron-core-collapse ... More
The Foundation Supernova Survey: Motivation, Design, Implementation, and First Data ReleaseNov 06 2017The Foundation Supernova Survey aims to provide a large, high-fidelity, homogeneous, and precisely-calibrated low-redshift Type Ia supernova (SN Ia) sample for cosmology. The calibration of the current low-redshift SN sample is the largest component of ... More
Identification of Electron Donor States in N-doped Carbon NanotubesNov 20 2000Nitrogen doped carbon nanotubes have been synthesized using pyrolysis and characterized by Scanning Tunneling Spectroscopy and transmission electron microscopy. The doped nanotubes are all metallic and exhibit strong electron donor states near the Fermi ... More
Ultraviolet Diversity of Type Ia SupernovaeApr 04 2016Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) probe the outermost layers of the explosion, and UV spectra of SNe Ia are expected to be extremely sensitive to differences in progenitor composition and the details of the explosion. Here we ... More
An Asymmetric, Energetic Type Ic Supernova Viewed Off-Axis, and a Link to Gamma-Ray BurstsMay 10 2005Type Ic supernovae, the explosions following the core collapse of massive stars that have previously lost their hydrogen and helium envelopes, are particularly interesting because of the link with long-duration gamma-ray bursts. Although indications exist ... More
Nebular Spectroscopy of Kepler's Brightest SupernovaNov 30 2018Dec 15 2018We present late-time ($\sim$240-260 days after peak brightness) optical photometry and nebular (+236 and +264 days) spectroscopy of SN 2018oh, the brightest Type Ia supernova (SN Ia) observed by the Kepler telescope. The Kepler/K2 30-minute cadence observations ... More
Distance determination to 12 Type II-P Supernovae using the Expanding Photosphere MethodMar 08 2009We use early-time photometry and spectroscopy of 12 Type II plateau supernovae (SNe IIP) to derive their distances using the expanding photosphere method (EPM). We perform this study using two sets of Type II supernova (SN II) atmosphere models, three ... More
Searching for Highly Magnified Stars at Cosmological Distances: Discovery of a Redshift 0.94 Blue Supergiant in Archival Images of the Galaxy Cluster MACS J0416.1-2403Feb 14 2019Individual highly magnified stars have been recently discovered at lookback times of more than half the age of the Universe, in lensed galaxies that straddle the critical curves of massive galaxy clusters. Having confirmed their detectability, it is now ... More
Explainable Agreement through Simulation for Tasks with Subjective LabelsJun 13 2018The field of information retrieval often works with limited and noisy data in an attempt to classify documents into subjective categories, e.g., relevance, sentiment and controversy. We typically quantify a notion of agreement to understand the difficulty ... More
The Troublesome Broadband Evolution of GRB 061126: Does a Grey Burst Imply Grey Dust?Mar 20 2007Jun 27 2007We report on observations of a gamma-ray burst (GRB 061126) with an extremely bright (R ~ 12 mag at peak) early-time optical afterglow. The optical afterglow is already fading as a power law 22 seconds after the trigger, with no detectable prompt contribution ... More
The Fast and Furious Decay of the Peculiar Type Ic Supernova 2005ekJun 10 2013Jul 11 2013We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova, SN 2005ek. Reaching a peak magnitude of M_R = -17.3 and decaying by ~3 mag in the first 15 days post-maximum, SN 2005ek is among the fastest Type ... More
Cosmology with Contaminated Samples: Methods of Measuring Dark Energy with Photometrically Classified Pan-STARRS SupernovaeNov 21 2016The Pan-STARRS (PS1) Medium Deep Survey discovered over 5,000 likely supernovae (SNe) but obtained spectral classifications for just 10% of its SN candidates. We measured spectroscopic host galaxy redshifts for 3,073 of these likely SNe and estimate that ... More
Phase Shift with LapH PropagatorsNov 24 2010The pion-pion scattering phase shift is computed using LapH propagators. The LapH method for computing quark propagators is used to form two-particle correlation functions with a number of different operators. Excited state energies of two-particle states ... More
Multi-hadron states in Lattice QCD spectroscopyMar 10 2010The ability to reliably measure the energy of an excited hadron in Lattice QCD simulations hinges on the accurate determination of all lower-lying energies in the same symmetry channel. These include not only single-particle energies, but also the energies ... More
Progress Report on Computing Excited-State Hadron Masses in Lattice QCDMar 14 2011Our progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Sets of spatially-extended hadron operators with a variety of different momenta are used. A new method of stochastically estimating the low-lying effects ... More
Excited-State Hadrons using the Stochastic LapH MethodJan 27 2011Progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Large sets of spatially-extended hadron operators are used. A new method of stochastically estimating the low-lying effects of quark propagation is utilized ... More
Connecting the progenitors, pre-explosion variability, and giant outbursts of luminous blue variables with Gaia16cfrJun 29 2017Oct 12 2017We present multi-epoch, multi-colour pre-outburst photometry and post-outburst light curves and spectra of the luminous blue variable (LBV) outburst Gaia16cfr discovered by the Gaia satellite on 1 December 2016. We detect Gaia16cfr in 13 epochs of Hubble ... More
EVN Observations of GRS1915+105Sep 21 2000Oct 11 2000We obtained EVN observations of the X-ray transient source GRS1915+105 in its radio-loud state. In 2 images obtained before a major flare, the source is resolved, showing two opposite asymmetric jets. This indicates that steady jets exist also before ... More
Measuring the Properties of Dark Energy with Photometrically Classified Pan-STARRS Supernovae. I. Systematic Uncertainty from Core-Collapse Supernova ContaminationNov 21 2016Jun 19 2017The Pan-STARRS (PS1) Medium Deep Survey discovered over 5,000 likely supernovae (SNe) but obtained spectral classifications for just 10% of its SN candidates. We measured spectroscopic host galaxy redshifts for 3,147 of these likely SNe and estimate that ... More
The Complete Light-curve Sample of Spectroscopically Confirmed Type Ia Supernovae from Pan-STARRS1 and Cosmological Constraints from The Combined Pantheon SampleOct 02 2017Mar 26 2018We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the PS1 SN photometry, astrometry and calibration ... More
SN 2012au: A Golden Link Between Superluminous Supernovae and Their Lower-Luminosity CounterpartsMar 30 2013Jun 04 2013We present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest a link between subsets of energetic and H-poor SNe and superluminous SNe. SN 2012au exhibited conspicuous SN Ib-like He I lines ... More
The Transitional Stripped-Envelope SN 2008ax: Spectral Evolution and Evidence for Large AsphericityJan 16 2010Jul 07 2011Supernova (SN) 2008ax in NGC 4490 was discovered within hours after shock breakout, presenting the rare opportunity to study a core-collapse SN beginning with the initial envelope-cooling phase immediately following shock breakout. We present an extensive ... More
First-Year Sloan Digital Sky Survey-II (SDSS-II) Supernova Results: Constraints on Non-Standard Cosmological ModelsAug 28 2009Sep 01 2009We use the new SNe Ia discovered by the SDSS-II Supernova Survey together with additional supernova datasets as well as observations of the cosmic microwave background and baryon acoustic oscillations to constrain cosmological models. This complements ... More
The Changing Fractions of Type Ia Supernova NUV-Optical Subclasses with RedshiftAug 07 2014UV and optical photometry of Type Ia supernovae (SNe Ia) at low redshift have revealed the existence of two distinct color groups, NUV-red and NUV-blue events. The color curves differ primarily by an offset, with the NUV-blue u- color curves bluer than ... More
Electromagnetic effects on the light hadron spectrumOct 16 2015For some time, the MILC Collaboration has been studying electromagnetic effects on light mesons. These calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in XPT. That is, the sea quarks are electrically neutral, while ... More
Charmed and light pseudoscalar meson decay constants from four-flavor lattice QCD with physical light quarksJul 14 2014Nov 18 2014We compute the leptonic decay constants $f_{D^+}$, $f_{D_s}$, and $f_{K^+}$, and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD using the experimentally determined value of $f_{\pi^+}$ for normalization. We use the MILC highly ... More