Results for "Ryan 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 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
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
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
Spectropolarimetry of the Peculiar Type Ia SN 2005hkMar 03 2006Mar 10 2006We present Keck spectropolarimetry of the unusual type Ia supernova (SN Ia) 2005hk several days before maximum light. An analysis of the high signal-to-noise-ratio total-flux spectrum shows the object's extreme similarity to the peculiar SN 2002cx. SN ... More
Spectral Evolution of the Extraordinary Type IIn Supernova 2006gyJun 11 2009Jun 13 2009We present a detailed analysis of the extremely luminous Type IIn supernova SN2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, expansion speeds, and bolometric ... More
The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian ModelSep 14 2016Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, ... More
Constraining Type Ia Supernova Progenitor Scenarios with Extremely Late-time Photometry of Supernova SN 2013aaFeb 06 2018We present Hubble Space Telescope observations and photometric measurements of the Type Ia supernova (SN Ia) SN 2013aa 1500 days after explosion. At this epoch, the luminosity is primarily dictated by the amounts of radioactive ${}^{57}\textrm{Co}$ and ... More
Constraining Type Ia Supernova Progenitor Scenarios with Extremely Late-time Photometry of Supernova SN 2013aaFeb 06 2018Feb 08 2018We present Hubble Space Telescope observations and photometric measurements of the Type Ia supernova (SN Ia) SN 2013aa 1500 days after explosion. At this epoch, the luminosity is primarily dictated by the amounts of radioactive ${}^{57}\textrm{Co}$ and ... More
Late-time Spectroscopy of Type Iax SupernovaeJan 22 2016We examine the late-time (t > 200 days after peak brightness) spectra of Type Iax supernovae (SNe Iax), a low-luminosity, low-energy class of thermonuclear stellar explosions observationally similar to, but distinct from, Type Ia supernovae. We present ... More
Possible Detection of the Stellar Donor or Remnant for the Type Iax Supernova 2008haAug 05 2014Type Iax supernovae (SNe Iax) are thermonuclear explosions that are related to SNe Ia, but are physically distinct. The most important differences are that SNe Iax have significantly lower luminosity (1% - 50% that of typical SNe Ia), lower ejecta mass ... More
SN 2006gy: Discovery of the most luminous supernova ever recorded, powered by the death of an extremely massive star like Eta CarinaeDec 21 2006May 22 2007(abridged) We report our discovery and observations of the peculiar Type IIn supernova SN2006gy in NGC1260, revealing that it reached a peak magnitude of -22, making it the most luminous supernova ever recorded. It is not yet clear what powers the total ... More
On the absence of Wind Signatures in GRB Afterglow Spectra: Constraints on the Wolf-Rayet Winds of GRB ProgenitorsNov 02 2006Apr 10 2007We investigate available constraints on the circumstellar medium (CSM) around long-duration gamma-ray burst (GRB) progenitors from afterglow spectra. We first establish a statistical sample of five GRB afterglow spectra that have been collected and analyzed ... More
Nearby Supernova Rates from the Lick Observatory Supernova Search. II. The Observed Luminosity Functions and Fractions of Supernovae in a Complete SampleJun 23 2010Dec 07 2010This is the second paper of a series in which we present new measurements of the observed rates of supernovae (SNe) in the local Universe, determined from the Lick Observatory Supernova Search (LOSS). In this paper, a complete SN sample is constructed, ... 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
The Diversity of Massive Star Outbursts I: Observations of SN 2009ip, UGC 2773 OT2009-1, and Their ProgenitorsFeb 03 2010Despite both being outbursts of luminous blue variables (LBVs), SN 2009ip and UGC 2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, and possibly physical mechanisms that generated the outbursts. From pre-eruption HST ... More
Significant Luminosity Differences of Two Twin Type Ia SupernovaeJun 21 2018The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical "twins," having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet ... More
The long-term evolution and appearance of Type Iax postgenitor starsDec 20 2018Type Iax supernovae may arise from failed explosions of white dwarfs that leave behind a bound remnant (i.e., a "postgenitor" star) that could be identified in wide field surveys. To understand their observational signatures, we simulate these white dwarf ... More
The long-term evolution and appearance of Type Iax postgenitor starsDec 20 2018Mar 01 2019Type Iax supernovae may arise from failed explosions of white dwarfs that leave behind a bound remnant (i.e., a "postgenitor" star) that could be identified in wide field surveys. To understand their observational signatures, we simulate these white dwarf ... More
Constraining Type Iax Supernova Progenitor Systems with Stellar Population AgingJan 16 2019Type Iax supernovae (SNe~Iax) are the most common class of peculiar SNe. While they are thought to be thermonuclear white-dwarf (WD) SNe, SNe~Iax are observationally similar to, but distinct from SNe~Ia. Unlike SNe~Ia, where roughly 30\% occur in early-type ... 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
A 2.4% Determination of the Local Value of the Hubble ConstantApr 05 2016Jun 09 2016We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to reduce the uncertainty in the local value of the Hubble constant (H_0) from 3.3% to 2.4%. Improvements come from new, near-infrared observations of Cepheid variables in 11 new ... More
A luminous, blue progenitor system for a type-Iax supernovaAug 05 2014Type-Iax supernovae (SN Iax) are stellar explosions that are spectroscopically similar to some type-Ia supernovae (SN Ia) at maximum light, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic ... More
Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011byAug 12 2014The nearby Type Ia supernovae (SNe Ia) 2011fe and 2011by had nearly identical photospheric phase optical spectra, light-curve widths, and photometric colours, but at peak brightness SN 2011by reached a fainter absolute magnitude in all optical bands and ... More
On the Progenitor and Supernova of the SN 2002cx-like Supernova 2008geAug 03 2010Sep 05 2010We present observations of supernova (SN) 2008ge, which is spectroscopically similar to the peculiar SN 2002cx, and its pre-explosion site that indicate that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN 2008ge, is an S0 galaxy ... 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
X-ray Limits on the Progenitor System of the Type Ia Supernova 2017ejbJun 21 2018We present deep X-ray limits on the presence of a pre-explosion counterpart to the low-luminosity Type Ia supernova (SN Ia) 2017ejb. SN 2017ejb was discovered in NGC 4696, a well-studied elliptical galaxy in the Centaurus cluster with 894 ks of Chandra ... More
After the Fall: Late-Time Spectroscopy of Type IIP SupernovaeOct 24 2016Herein we analyse late-time (post-plateau; 103 < t < 1229 d) optical spectra of low-redshift (z < 0.016), hydrogen-rich Type IIP supernovae (SNe IIP). Our newly constructed sample contains 91 nebular spectra of 38 SNe IIP, which is the largest dataset ... More
SN 2008ha: An Extremely Low Luminosity and Extremely Low Energy SupernovaFeb 16 2009Feb 23 2009We present ultraviolet, optical, and near-infrared photometry as well as optical spectra of the peculiar supernova (SN) 2008ha. SN 2008ha had a very low peak luminosity, reaching only M_V = -14.2 mag, and low line velocities of only ~2000 km/s near maximum ... 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 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
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
Dust and the type II-Plateau supernova 2004djMar 15 2011Apr 13 2011We present mid-infrared (MIR) spectroscopy of a Type II-plateau supernova, SN 2004dj, obtained with the Spitzer Space Telescope, spanning 106--1393 d after explosion. MIR photometry plus optical/near-IR observations are also reported. An early-time MIR ... More
Late-time observations of SN2006gy: Still Going StrongFeb 13 2008Jul 08 2008Owing to its extremely high luminosity and long duration, SN2006gy radiated more energy in visual light than any other known SN. Two hypotheses to explain its high luminosity -- that it was powered by shock interaction with CSM as implied by its Type ... More
Signatures of Delayed Detonation, Asymmetry, and Electron Capture in the Mid-Infrared Spectra of Supernovae 2003hv and 2005dfFeb 05 2007We present the first mid-infrared (5.2-15.2 micron) spectra of Type Ia supernovae (SNe 2003hv and 2005df). The detection of Ni emission in SN 2005df 135 days after the explosion provides direct observational evidence of high-density nuclear burning forming ... More
The Subluminous Supernova 2007qd: A Missing Link in a Family of Low-Luminosity Type Ia SupernovaeJul 16 2010We present multi-band photometry and multi-epoch spectroscopy of the peculiar Type Ia supernova (SN Ia) 2007qd, discovered by the SDSS-II Supernova Survey. It possesses physical properties intermediate to those of the peculiar SN 2002cx and the extremely ... More
A Potential Progenitor for the Type Ic Supernova 2017einAug 09 2018We report the first detection of a credible progenitor system for a Type Ic supernova (SN Ic), SN 2017ein. We present spectra and photometry of the SN, finding it to be similar to carbon-rich, low-luminosity SNe Ic. Using a post-explosion Keck adaptive ... More
The Type IIn Supernova 2002kg: The Outburst of a Luminous Blue Variable Star in NGC 2403Mar 01 2006We show that Supernova (SN) 2002kg in NGC 2403, initially classified as Type II-narrow (IIn), has photometric and spectroscopic properties unlike those of normal SNe. Its behavior, instead, is more typical of highly massive stars which experience the ... More
Excited-Nucleon Spectroscopy with 2+1 Fermion FlavorsNov 17 2009We present progress made by the Hadron Spectrum Collaboration (HSC) in determining the tower of excited nucleon states using 2+1-flavor anisotropic clover lattices. The HSC has been investigating interpolating operators projected into irreducible representations ... More
A Deep Search for Prompt Radio Emission from Thermonuclear Supernovae with the Very Large ArrayOct 26 2015Searches for circumstellar material around Type Ia supernovae (SNe Ia) are one of the most powerful tests of the nature of SN Ia progenitors, and radio observations provide a particularly sensitive probe of this material. Here we report radio observations ... More
Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova 2006X in M100Aug 01 2007Nov 16 2007We present extensive optical (UBVRI), near-infrared (JK) light curves and optical spectroscopy of the Type Ia supernova (SN) 2006X in the nearby galaxy NGC 4321 (M100). Our observations suggest that either SN 2006X has an intrinsically peculiar color ... More
Supernovae in the Subaru Deep Field: the rate and delay-time distribution of type Ia supernovae out to redshift 2Jan 31 2011Jun 20 2011The type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD) of SNe Ia, which can distinguish among progenitor models. We present the results of a SN survey in the ... More
A luminosity distribution for kilonovae based on short gamma-ray burst afterglowsNov 13 2018The combined detection of a gravitational-wave signal, kilonova, and short gamma-ray burst (sGRB) from GW170817 marked a scientific breakthrough in the field of multi-messenger astronomy. But even before GW170817, there have been a number of sGRBs with ... More
Dust and the type II-plateau supernova 2004etApr 23 2009Sep 08 2009We present mid-infrared (MIR) observations of the Type II-plateau supernova (SN) 2004et, obtained with the {\it Spitzer Space Telescope} between days 64 and 1406 past explosion. Late-time optical spectra are also presented. For the period 300-795 days ... 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
Very Early Ultraviolet and Optical Observations of the Type Ia Supernova 2009igSep 05 2011Nov 01 2011Supernova (SN) 2009ig was discovered 17 hours after explosion by the Lick Observatory Supernova Search, promptly classified as a normal Type Ia SN (SN Ia), peaked at V = 13.5 mag, and was equatorial, making it one of the foremost supernovae for intensive ... More
Detection of Circumstellar Helium in Type Iax Progenitor SystemsDec 31 2018We present direct spectroscopic modeling of 44 Type Iax supernovae (SNe Iax) using the spectral synthesis code SYNAPPS. We confirm detections of helium emission in the early-time spectra of two SNe Iax: SNe 2004cs and 2007J. These He I features are better ... More
The Berkeley Sample of Stripped-Envelope SupernovaeOct 08 2018Oct 10 2018We present the complete sample of stripped-envelope supernova (SN) spectra observed by the Lick Observatory Supernova Search (LOSS) collaboration over the last three decades: 888 spectra of 302 SNe, 652 published here for the first time, with 384 spectra ... More
Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia SupernovaeApr 30 2018Jul 18 2018Double detonations in double white dwarf (WD) binaries undergoing unstable mass transfer have emerged in recent years as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. One potential outcome of this "dynamically driven double-degenerate ... More
Variable Sodium Absorption in a Low-Extinction Type Ia SupernovaJul 07 2009Recent observations have revealed that some Type Ia supernovae exhibit narrow, time-variable Na I D absorption features. The origin of the absorbing material is controversial, but it may suggest the presence of circumstellar gas in the progenitor system ... More
The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational Wave SourceOct 16 2017We discovered Swope Supernova Survey 2017a (SSS17a) in the LIGO/Virgo Collaboration (LVC) localization volume of GW170817, the first detected binary neutron star (BNS) merger, only 10.9 hours after the trigger. No object was present at the location of ... More
Hubble Space Telescope and Ground-Based Observations of the Type Iax Supernovae SN 2005hk and SN 2008ASep 17 2013Apr 25 2014We present Hubble Space Telescope (HST) and ground-based optical and near-infrared observations of SN 2005hk and SN 2008A, typical members of the Type Iax class of supernovae (SNe). Here we focus on late-time observations, where these objects deviate ... More
Type IIb Supernova SN 2011dh: Spectra and Photometry from the Ultraviolet to the Near-InfraredMar 21 2013Dec 16 2013We report spectroscopic and photometric observations of the Type IIb SN 2011dh obtained between 4 and 34 days after the estimated date of explosion (May 31.5 UT). The data cover a wide wavelength range from 2,000 Angstroms in the UV to 2.4 microns in ... More
Low-lying Zeros of Number Field $L$-functionsMar 28 2010One of the most important statistics in studying the zeros of L-functions is the 1-level density, which measures the concentration of zeros near the central point. Fouvry and Iwaniec [FI] proved that the 1-level density for L-functions attached to imaginary ... More
The Generalized Lasso Problem and UniquenessMay 20 2018We study uniqueness in the generalized lasso problem, where the penalty is the $\ell_1$ norm of a matrix $D$ times the coefficient vector. We derive a broad result on uniqueness that places weak assumptions on the predictor matrix $X$ and penalty matrix ... 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
SN 2016esw: a luminous Type II supernova observed within the first day after the explosionMay 08 2018We present photometry, spectroscopy, and host-galaxy integral-field spectroscopy of the Type II supernova (SN) 2016esw in CGCG~229-009 from the first day after the explosion up to 120 days. Its light-curve shape is similar to that of a typical SN II; ... More
Fast and Flexible ADMM Algorithms for Trend FilteringJun 09 2014Aug 29 2015This paper presents a fast and robust algorithm for trend filtering, a recently developed nonparametric regression tool. It has been shown that, for estimating functions whose derivatives are of bounded variation, trend filtering achieves the minimax ... More
The solution path of the generalized lassoMay 11 2010Nov 20 2012We present a path algorithm for the generalized lasso problem. This problem penalizes the $\ell_1$ norm of a matrix D times the coefficient vector, and has a wide range of applications, dictated by the choice of D. Our algorithm is based on solving the ... More
The Type Ia Supernova Rate in Redshift 0.5--0.9 Galaxy ClustersJun 18 2010Supernova (SN) rates are potentially powerful diagnostics of metal enrichment and SN physics, particularly in galaxy clusters with their deep, metal-retaining potentials and relatively simple star-formation histories. We have carried out a survey for ... More
New Hubble Space Telescope Discoveries of Type Ia Supernovae at z > 1: Narrowing Constraints on the Early Behavior of Dark EnergyNov 17 2006Dec 20 2006We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion years. These objects, which include 13 spectroscopically confirmed SNe Ia ... More
The Effect of Host Galaxies on Type Ia Supernovae in the SDSS-II Supernova SurveyMay 25 2010Aug 10 2010We present an analysis of the host galaxy dependencies of Type Ia Supernovae (SNe Ia) from the full three year sample of the SDSS-II Supernova Survey. We rediscover, to high significance, the strong correlation between host galaxy typeand the width of ... More
CfAIR2: Near Infrared Light Curves of 94 Type Ia SupernovaeAug 03 2014Sep 01 2015CfAIR2 is a large homogeneously reduced set of near-infrared (NIR) light curves for Type Ia supernovae (SN Ia) obtained with the 1.3m Peters Automated InfraRed Imaging TELescope (PAIRITEL). This data set includes 4607 measurements of 94 SN Ia and 4 additional ... More
Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption EventMar 13 2019We report the discovery of non-stellar hydrogen Balmer and metastable helium absorption lines accompanying a transient, high-velocity (0.05$c$) broad absorption line (BAL) system in the optical spectra of the tidal disruption event (TDE) AT2018zr ($z=0.071$). ... More
Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia SupernovaeFeb 09 2012May 04 2012In this first paper in a series we present 1298 low-redshift (z\leq0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through 2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light ... More
The Nearby Type Ibn Supernova 2015G: Signatures of Asymmetry and Progenitor ConstraintsApr 14 2017Sep 04 2017We present the results of an extensive observational campaign on the nearby Type Ibn SN 2015G, including data from radio through ultraviolet wavelengths. SN 2015G was asymmetric, showing late-time nebular lines redshifted by ~1000 km/s. It shared many ... More
WFIRST: Enhancing Transient Science and Multi-Messenger AstronomyMar 11 2019Astrophysical transients have been observed for millennia and have shaped our most basic assumptions about the Universe. In the last century, systematic searches have grown from detecting handfuls of transients per year to over 7000 in 2018 alone. As ... More
Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy LensNov 21 2014Mar 05 2015In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, ... More
The structure Jacobi operator for hypersurfaces in CP^2 and CH^2Dec 24 2008Using the methods of moving frames, we study real hypersurfaces in complex projective space CP^2 and complex hyperbolic space CH^2 whose structure Jacobi operator has various special properties. Our results complement work of several other authors who ... More
Cauchy transforms arising from homomorphic conditional expectations parametrize free Pick functions but those arising from conditional expectations do notJul 22 2016Nevanlinna showed that Cauchy transforms of probability measures parametrize all functions from the upper half plane into itself satisfying a certain asymptotic condition at infinity. We show that the correspondence fails in general for the unbounded ... More
Illuminating a Dark Lens : A Type Ia Supernova Magnified by the Frontier Fields Galaxy Cluster Abell 2744May 22 2015Aug 16 2015SN HFF14Tom is a Type Ia Supernova (SN) discovered at z = 1.3457 +- 0.0001 behind the galaxy cluster Abell 2744 (z = 0.308). In a cosmology-independent analysis, we find that HFF14Tom is 0.77 +- 0.15 magnitudes brighter than unlensed Type Ia SNe at similar ... More
Induced Saturation NumberDec 08 2011Jun 14 2012In this paper, we discuss a generalization of the notion of saturation in graphs in order to deal with induced structures. In particular, we define ${\rm indsat}(n,H)$, which is the fewest number of gray edges in a trigraph so that no realization of that ... More
Metrical Characterizations of super weakly compact operatorsApr 06 2016We characterize super weakly compact operators as those through which binary tree and diamond and Laakso graphs may not be factored with uniform distortion.
Normal-mode-based analysis of electron plasma waves with second-order Hermitian formalismDec 27 2017The classic problem of the dynamic evolution of Langmuir electron waves in a collisionless plasma and their Landau damping is cast as a second-order, self-adjoint problem with a continuum spectrum of real and positive squared frequencies. The corresponding ... More
Free Pick functions: representations, asymptotic behavior and matrix monotonicity in several noncommuting variablesSep 06 2013Oct 16 2013We extend the study of the Pick class, the set of complex analytic functions taking the upper half plane into itself, to the noncommutative setting. R. Nevanlinna showed that elements of the Pick class have certain integral representations which reflect ... More
The First Maximum-Light Ultraviolet through Near-Infrared Spectrum of a Type Ia SupernovaFeb 23 2012We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan ... 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
Hopf Hypersurfaces of Small Hopf Principal Curvature in CH^2Dec 24 2008Using the methods of moving frames and exterior differential systems, we show that there exist Hopf hypersurfaces in complex hyperbolic space CH^2 with any specified value of the Hopf principal curvature less than or equal to the corresponding value for ... More
Hydrodynamics of circumbinary accretion: Angular momentum transfer and binary orbital evolutionOct 10 2018Jan 09 2019We carry out 2D viscous hydrodynamical simulations of circumbinary accretion using the AREPO code. We self-consistently compute the accretion flow over a wide range of spatial scales, from the circumbinary disk (CBD) far from the central binary, through ... More
The Normal Defect of Some Classes of MatricesNov 17 2012An n \times n matrix A has a normal defect of k if there exists an (n+k) \times (n+k) normal matrix A_{ext} with A as a leading principal submatrix and k minimal. In this paper we compute the normal defect of a special class of 4 \times 4 matrices, namely ... More
Multiwavelet troubled-cell indicator for discontinuity detection of discontinuous Galerkin schemesSep 12 2014Feb 02 2016In this paper, we introduce a new global troubled-cell indicator for the discontinuous Galerkin (DG) method in one- and two-dimensions. This is done by taking advantage of the global expression of the DG method and re-expanding it in terms of a multiwavelet ... More
Type Ia Supernovae Strongly Interacting with Their Circumstellar MediumApr 02 2013Owing to their utility for measurements of cosmic acceleration, Type Ia supernovae (SNe) are perhaps the best-studied class of SNe, yet the progenitor systems of these explosions largely remain a mystery. A rare subclass of SNe Ia show evidence of strong ... More
Prospects for detecting the Rossiter-McLaughlin effect of Earth-like planets: the test case of TRAPPIST-1b and cAug 03 2016The Rossiter-McLaughlin effect is the principal method of determining the sky-projected spin--orbit angle ($\beta$) of transiting planets. Taking the example of the recently discovered TRAPPIST-1 system, we explore how ultracool dwarfs facilitate the ... More
Using the CMB angular power spectrum to study Dark Matter-photon interactionsSep 29 2013Apr 25 2014In this paper, we explore the impact of Dark Matter-photon interactions on the CMB angular power spectrum. Using the one-year data release of the Planck satellite, we derive an upper bound on the Dark Matter-photon elastic scattering cross section of ... More
The Interstellar Formation and Spectra of the Noble Gas, Proton-Bound HeHHe+, HeHNe+, & HeHAr+ ComplexesNov 09 2017The sheer interstellar abundance of helium makes any bound molecules or complexes containing it of potential interest for astrophysical observation. This work utilizes high-level and trusted quantum chemical techniques to predict the rotational, vibrational, ... More
Rarita-Schwinger Type operators on CylindersNov 16 2011Here we define Rarita-Schwinger operators on cylinders and construct their fundamental solutions. Further the fundamental solutions to the cylindrical Rarita-Schwinger type operators are achieved by applying translation groups. In turn, a Borel-Pompeiu ... More
Automated parameters for troubled-cell indicators using outlier detectionApr 22 2015Nov 13 2015In Vuik and Ryan (2014) we studied the use of troubled-cell indicators for discontinuity detection in nonlinear hyperbolic partial differential equations and introduced a new multiwavelet technique to detect troubled cells. We found that these methods ... More
The galaxies in the field of the nearby GRB980425/SN1998bwOct 28 2005We present spectroscopic observations of ESO 184-G82, the host galaxy of GRB980425/SN1998bw, and six galaxies in its field. A host redshift of z=0.0087+/-0.0006 is derived, consistent with that measured by Tinney et al. (1998). Redshifts are obtained ... 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
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
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
PS1-10afx at z=1.388: Pan-STARRS1 Discovery of a New Type of Superluminous SupernovaJan 31 2013Mar 11 2013We present the Pan-STARRS1 discovery of PS1-10afx, a unique hydrogen-deficient superluminous supernova (SLSN) at z=1.388. The light curve peaked at z_P1=21.7 mag, making PS1-10afx comparable to the most luminous known SNe, with M_u = -22.3 mag. Our extensive ... More
First-year Sloan Digital Sky Survey-II (SDSS-II) Supernova Results: Hubble Diagram and Cosmological ParametersAug 28 2009We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift ... 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
On-sky single-mode fiber coupling measurements at the Large Binocular TelescopeSep 14 2016The demonstration of efficient single-mode fiber (SMF) coupling is a key requirement for the development of a compact, ultra-precise radial velocity (RV) spectrograph. iLocater is a next generation instrument for the Large Binocular Telescope (LBT) that ... More
Search for Cosmic Strings in the COSMOS SurveyAug 03 2010Apr 12 2011We search the COSMOS survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. The COSMOS survey imaged 1.64 square degrees using the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). ... More
A Continuous-Time View of Early Stopping for Least SquaresOct 23 2018Feb 23 2019We study the statistical properties of the iterates generated by gradient descent, applied to the fundamental problem of least squares regression. We take a continuous-time view, i.e., consider infinitesimal step sizes in gradient descent, in which case ... More
Exploring the Spectrum of QCD using the LatticeJul 26 2009The calculation of the spectrum of QCD is key to an understanding of the strong interactions, and vital if we are to capitalize on the experimental study of the spectrum. In this paper, we describe progress towards understanding the spectrum of resonances ... More
SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar MediumDec 27 2006Feb 21 2007We present optical photometry and spectra of the peculiar Type Ib supernova (SN) 2006jc. Strong and relatively narrow He I emission lines indicate the progenitor star exploded inside a dense circumstellar medium (CSM) rich in He. An exceptionally blue ... More