K. A. Ponder
A5058461893- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Adaptive optics and wavefront sensing
- Time Series Analysis and Forecasting
- Neutrino Physics Research
- Spectroscopy and Chemometric Analyses
- Astro and Planetary Science
- Machine Learning and Algorithms
- Radio Astronomy Observations and Technology
- Calibration and Measurement Techniques
- Analytical Chemistry and Chromatography
- Cardiovascular and exercise physiology
- Anomaly Detection Techniques and Applications
- Solar and Space Plasma Dynamics
- Engineering Applied Research
- Atmospheric Ozone and Climate
- Algorithms and Data Compression
- Cardiovascular Disease and Adiposity
- Scientific Research and Discoveries
- Protein Tyrosine Phosphatases
University of California, Berkeley
2018-2023
SLAC National Accelerator Laboratory
2021-2023
Lawrence Berkeley National Laboratory
2020-2023
University of Pittsburgh
2014-2021
We present reverberation mapping results from the first year of combined spectroscopic and photometric observations Sloan Digital Sky Survey Reverberation Mapping Project. successfully recover time delays between $g+i$-band emission broad H$\beta$ line for a total 44 quasars, H$\alpha$ in 18 quasars. Time are computed using JAVELIN CREAM software traditional interpolated cross-correlation function (ICCF): Using well defined criteria, we report measurements 32 13 lags with JAVELIN, 42 17...
The Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM) is a dedicated multi-object RM experiment that has spectroscopically monitored sample of 849 broad-line quasars in single 7 deg$^2$ field with the SDSS-III BOSS spectrograph. quasar flux-limited to i_psf=21.7 mag, and covers redshift range 0.1<z<4.5. Optical spectroscopy was performed during 2014 Jan-Jul dark/grey time, an average cadence ~4 days, totaling more than 30 epochs. Supporting photometric monitoring g i bands...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
We present reverberation-mapping lags and black-hole mass measurements using the CIV 1549 broad emission line from a sample of 349 quasars monitored as part Sloan Digital Sky Survey Reverberation Mapping Project. Our data span four years spectroscopic photometric monitoring for total baseline 1300 days. report significant time delays between continuum in 52 quasars, with an estimated false-positive detection rate 10%. analysis marginal lag indicates that there are on order 100 additional...
Abstract Next-generation surveys like the Legacy Survey of Space and Time (LSST) on Vera C. Rubin Observatory (Rubin) will generate orders magnitude more discoveries transients variable stars than previous surveys. To prepare for this data deluge, we developed Photometric LSST Astronomical Time-series Classification Challenge (PLAsTiCC), a competition that aimed to catalyze development robust classifiers under LSST-like conditions nonrepresentative training set large photometric test...
We present the Pmas/ppak Integral-field Supernova hosts COmpilation (PISCO) which comprises Integral Field Spectroscopy (IFS) of 232 supernova (SN) host galaxies, that hosted 272 SNe, observed over several semesters with 3.5m telescope at Calar Alto Observatory (CAHA). PISCO is largest collection SN galaxies wide-field IFS, totaling 466,347 individual spectra covering a typical spatial resolution $\sim$380 pc. While focused studies regarding specific Ia- related topics will be published...
We present the discovery of PS18kh, a tidal disruption event (TDE) discovered at center SDSS J075654.53+341543.6 ($d\simeq322$ Mpc) by Pan-STARRS Survey for Transients. Our dataset includes pre-discovery survey data from Pan-STARRS, All-Sky Automated Supernovae (ASAS-SN), and Asteroid Terrestrial-impact Last Alert System (ATLAS) as well high-cadence, multi-wavelength follow-up ground-based telescopes Swift, spanning 56 days before peak light until 75 after. The optical/UV emission PS18kh is...
We describe the simulated data sample for "Photometric LSST Astronomical Time Series Classification Challenge" (PLAsTiCC), a publicly available challenge to classify transient and variable events that will be observed by Large Synoptic Survey Telescope (LSST), new facility expected start in early 2020s. The was hosted Kaggle, ran from 2018 September 28 December 17, included 1,094 teams competing prizes. Here we provide details of 18 source models, which were not revealed until after...
Abstract We present a new empirical Type Ia supernova (SN Ia) model with three chromatic flux variation templates: one phase dependent and two independent. No underlying dust extinction or patterns of intrinsic variability are assumed. Implemented S tan trained using spectrally binned Nearby Supernova Factory spectrophotometry, we examine this model's 2D, phase-independent space motivated basis representations. In both, the first template captures that appears dust-like, while second...
We analyze 143 Type Ia supernovae (SNeIa) observed in $H$ band (1.6-1.8 $\mu$m) and find SNeIa are intrinsically brighter $H$-band with increasing host galaxy stellar mass. galaxies more massive than $10^{10.43} M_{\odot}$ $0.13 \pm 0.04$ mag less galaxies. The same set of at optical wavelengths, after width-color-luminosity corrections, exhibit a $0.10 0.03$ offset the Hubble residuals. observe an outlier population ($|\Delta H_{\rm max}| > 0.5$ mag) show that removing moves mass threshold...
We present the results of an extensive observational campaign on nearby Type Ibn SN 2015G, including data from radio through ultraviolet wavelengths. 2015G was asymmetric, showing late-time nebular lines redshifted by ~1000 km/s. It shared many features with prototypical In 2006jc, extremely strong He I emssion and a blue pseudocontinuum. The young showed narrow P-Cygni profiles I, but never in its evolution did it show any signature hydrogen - arguing for dense, ionized, hydrogen-free...
The Photometric LSST Astronomical Time Series Classification Challenge (PLAsTiCC) is an open data challenge to classify simulated astronomical time-series in preparation for observations from the Large Synoptic Survey Telescope (LSST), which will achieve first light 2019 and commence its 10-year main survey 2022. revolutionize our understanding of changing sky, discovering measuring millions time-varying objects. In this challenge, we pose question: how well can objects sky that vary...
As a candidate 'super-Chandrasekhar' or 09dc-like Type Ia supernova (SN Ia), SN 2012dn shares many characteristics with other members of this remarkable class objects but lacks their extraordinary luminosity. Here, we present and discuss the most comprehensive optical data set to date, comprised densely sampled series early-time spectra obtained within Nearby Supernova Factory project, plus photometry spectroscopy at VLT about 1 yr after explosion. The light curves, colour spectral time...
Abstract We calibrate spectrophotometric optical spectra of 32 stars commonly used as standard stars, referenced to 14 already on the Hubble Space Telescope–based CALSPEC flux system. Observations and non-CALSPEC were obtained with SuperNova Integral Field Spectrograph over wavelength range 3300–9400 Å calibration for Nearby Supernova Factory cosmology experiment. In total, this analysis 4289 standard-star taken photometric nights. As a modern analysis, all presubmission methodological...
We study the spectral diversity of Type Ia supernovae (SNe Ia) at maximum light using high signal-to-noise spectrophotometry 173 SNe from Nearby Supernova Factory. decompose these spectra into different extrinsic and intrinsic components, we construct a nonlinear parameterization that preserves pairings "twin" Ia. call this "Twins Embedding". Our methodology naturally handles highly variability in spectra, such as changes photosphere expansion velocity, uses full spectrum rather than being...
Type Ia Supernovae (SNe Ia) are widely used to measure the expansion of Universe. Improving distance measurements SNe is one technique better constrain acceleration and determine its physical nature. This document develops a new spectral energy distribution (SED) model, called SUpernova Generator And Reconstructor (SUGAR), which improves description Ia, consequently could improve measurements. model constructed from properties spectrophotometric data The Nearby Supernova Factory...
SweetSpot is a three-year National Optical Astronomy Observatory (NOAO) Survey program to observe Type Ia supernovae (SNe Ia) in the smooth Hubble flow with WIYN High-resolution Infrared Camera (WHIRC) on 3.5-m telescope. We here present data from first half of this survey, covering 2011B-2013B NOAO semesters, and consisting 493 calibrated images 74 SNe observed rest-frame near-infrared (NIR) $0.02 < z 0.09$. Because many require host galaxy subtraction templates taken later release contains...
Classification of transient and variable light curves is an essential step in using astronomical observations to develop understanding their underlying physical processes. However, upcoming deep photometric surveys, including the Large Synoptic Survey Telescope (LSST), will produce a deluge low signal-to-noise data for which traditional labeling procedures are inappropriate. Probabilistic classification more appropriate but incompatible with metrics used on deterministic classifications....
We apply the color-magnitude intercept calibration method (CMAGIC) to Nearby Supernova Factory SNe Ia spectrophotometric dataset. The currently existing CMAGIC parameters are slope and of a straight line fit first linear region in diagram, which occurs over span approximately 30 days after maximum brightness. define new parameter, $\omega_{XY}$, size ``bump'' feature near brightness for arbitrary filters $X$ $Y$. find significant correlation between region, $\beta_{XY, 1}$, diagram...
We investigate the effects of extended multi-year light curves (9-year photometry and 5-year spectroscopy) on detection time lags between continuum variability broad-line response quasars at z>~1.5, compare with results using 4-year photometry+spectroscopy presented in a companion paper. demonstrate benefits three cases: (1) that are too long to be detected by shorter-duration data but can data; (2) recovered missed due insufficient curve quality; (3) for different broad line species same...
Abstract The Nearby Supernova Factory presents an interim data release of spectrophotometric timeseries 210 SNe Ia. Two slightly different versions the are included, corresponding to training sets used for SNEMO and SUGAR Type Ia models. has been shifted restframe is blinded with respect cosmology.
The Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) program monitors 849 active galactic nuclei (AGN) both spectroscopically and photometrically. photometric observations used in this work span over four years provide an excellent baseline for variability studies of these objects. We present the light curves from 2014 to 2017 obtained by Steward Observatory's Bok telescope CFHT with MegaCam. details on data acquisition processing each telescope, difference imaging photometry produce...
Abstract We construct a physically parameterized probabilistic autoencoder (PAE) to learn the intrinsic diversity of Type Ia supernovae (SNe Ia) from sparse set spectral time series. The PAE is two-stage generative model, composed an that interpreted probabilistically after training using normalizing flow. demonstrate learns low-dimensional latent space captures nonlinear range features exists within population and can accurately model evolution SNe across full wavelength observation times...
The recent increase in volume and complexity of available astronomical data has led to a wide use supervised machine learning techniques. Active strategies have been proposed as an alternative optimize the distribution scarce labeling resources. However, due specific conditions which labels can be acquired, fundamental assumptions, such sample representativeness cost stability cannot fulfilled. Recommendation System for Spectroscopic followup (RESSPECT) project aims enable construction...
Traditional cosmological inference using Type Ia supernovae (SNe Ia) have used stretch- and color-corrected fits of SN light curves assumed a resulting fiducial mean symmetric intrinsic dispersion for the relative luminosity. As systematics become main contributors to error budget, it has imperative expand supernova cosmology analyses include more general likelihood model remove biases with losses in precision. To illustrate an example analysis, we use simple two populations luminosity...