Results for "L. Fortson"

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A Measurement of the Cosmic Ray Spectrum and Composition at the KneeMar 14 2000Jun 22 2000The energy spectrum and primary composition of cosmic rays with energy between $3\times 10^{14}$ and $3\times10^{16}\unit{eV}$ have been studied using the CASA-BLANCA detector. CASA measured the charged particle distribution of air showers, while BLANCA ... More
CASA-BLANCA: A Large Non-imaging Cherenkov Detector at CASA-MIAJul 02 1997The lateral distribution of Cherenkov light at ground level records important information on the development of the cosmic ray air shower which produces it. We have constructed an array of 144 non-imaging Cherenkov detectors at the CASA-MIA experiment ... More
Muon Hunter: a Zooniverse projectFeb 24 2018The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential ... More
Atomic Parity Nonconservation: Electroweak Parameters and Nuclear StructureNov 05 1992There have been suggestions to measure atomic parity nonconservation (PNC) along an isotopic chain, by taking ratios of observables in order to cancel complicated atomic structure effects. Precise atomic PNC measurements could make a significant contribution ... More
Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?Sep 18 2014Dec 19 2014We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S ... More
Constraints on Gamma-ray Emission from the Galactic Plane at 300 TeVMar 10 1997We describe a new search for diffuse ultrahigh energy gamma-ray emission associated with molecular clouds in the galactic disk. The Chicago Air Shower Array (CASA), operating in coincidence with the Michigan muon array (MIA), has recorded over 2.2 x 10^{9} ... More
Gamma-ray Signatures of Ultra High Energy Cosmic Ray Line-of-sight InteractionsMay 01 2013Sep 29 2013Ultra High Energy Cosmic Rays (UHECRs) interact en route to Earth, producing secondary gamma-rays. For the case of high cosmic ray power and weak intergalactic magnetic fields, the deflections of these UHECRs may be small leading to detectable gamma-ray ... More
TeV Gamma-Ray Observations of the Perseus and Abell 2029 Galaxy ClustersFeb 13 2006Galaxy clusters might be sources of TeV gamma rays emitted by high-energy protons and electrons accelerated by large scale structure formation shocks, galactic winds, or active galactic nuclei. Furthermore, gamma rays may be produced in dark matter particle ... More
Galaxy Zoo: Bars in Disk GalaxiesMar 01 2010Oct 09 2010We present first results from Galaxy Zoo 2, the second phase of the highly successful Galaxy Zoo project (www.galaxyzoo.org). Using a volume-limited sample of 13665 disk galaxies (0.01< z < 0.06 and M_r<-19.38), we study the fraction of galaxies with ... More
Galaxy Zoo: the effect of bar-driven fueling on the presence of an active galactic nucleus in disc galaxiesFeb 03 2015We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited ... More
Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES 1218+304 with VERITASJan 15 2010We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, ... More
Snowmass Cosmic Frontiers 6 (CF6) Working Group Summary --The Bright Side of the Cosmic Frontier: Cosmic Probes of Fundamental PhysicsOct 21 2013Oct 25 2013Report of the CF6 Working Group at Snowmass 2013. Topics addressed include ultra-high energy cosmic rays, neutrinos, gamma rays, baryogenesis, and experiments probing the fundamental nature of spacetime.
VERITAS contributions to the 35th International Cosmic Ray ConferenceSep 22 2017Compilation of papers presented by the VERITAS Collaboration at the 35th International Cosmic Ray Conference (ICRC), held July 12 through July 20, 2017 in Busan, South Korea.
Galaxy Zoo: Evidence for Diverse Star Formation Histories through the Green ValleyJan 23 2015Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary pathways between early- and late-type galaxies, we present results from a ... More
Gamma-ray Observations Under Bright Moonlight with VERITASMar 03 2017Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so ... More
A Multi-Component Measurement of the Cosmic Ray Composition Between 10^{17} eV and 10^{18} eVNov 09 1999The average mass composition of cosmic rays with primary energies between $10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been ... More
VERITAS observations of the BL Lac object TXS 0506+056Jul 12 2018On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event \icnu, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of the gamma-ray ... More
Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphologyFeb 11 2015We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z<0.085, using Galaxy~Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral ... More
Measurement of Cosmic-ray Electrons at TeV Energies by VERITASAug 29 2018Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation and inverse-Compton scattering processes while propagating within the Galaxy and these ... More
Measurement of the Iron Spectrum in Cosmic Rays by VERITASJul 20 2018We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 to 500 TeV. The measurement makes use of a template-based analysis method, which, for the first time, is applied to the energy reconstruction of iron-induced air ... More
A strong limit on the very-high-energy emission from GRB 150323AMar 03 2018On 2015 March 23, VERITAS responded to a $Swift$-BAT detection of a gamma-ray burst, with observations beginning 270 seconds after the onset of BAT emission, and only 135 seconds after the main BAT emission peak. No statistically significant signal is ... More
Integrating human and machine intelligence in galaxy morphology classification tasksFeb 23 2018Quantifying galaxy morphology is a challenging yet scientifically rewarding task. As the scale of data continues to increase with upcoming surveys, traditional classification methods will struggle to handle the load. We present a solution through an integration ... More
Direct measurement of stellar angular diameters by the VERITAS Cherenkov TelescopesApr 12 2019The angular size of a star is a critical factor in determining its basic properties. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. ... More
Galaxy Zoo: Finding offset discs and bars in SDSS galaxiesApr 28 2017We use multi-wavelength SDSS images and Galaxy Zoo morphologies to identify a sample of $\sim$$270$ late-type galaxies with an off-centre bar. We measure offsets in the range 0.2-2.5 kpc between the photometric centres of the stellar disc and stellar ... More
Very-high-energy observations of the binaries V 404 Cyg and 4U 0115+634 during giant X-ray outburstsAug 23 2016Transient X-ray binaries produce major outbursts in which the X-ray flux can increase over the quiescent level by factors as large as $10^7$. The low-mass X-ray binary V 404 Cyg and the high-mass system 4U 0115+634 underwent such major outbursts in June ... More
Search for Magnetically Broadened Cascade Emission From Blazars with VERITASJan 02 2017We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGN), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma rays from AGN interact with extragalactic background ... More
The Green Valley is a Red Herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxiesFeb 19 2014We use SDSS+\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram ... More
HESS J1943+213: An Extreme Blazar Shining Through The Galactic PlaneJun 11 2018HESS J1943+213 is a very-high-energy (VHE; $>$100 GeV) $\gamma$-ray source in the direction of the Galactic Plane. Studies exploring the classification of the source are converging towards its identification as an extreme synchrotron BL Lac object. Here ... More
VERITAS observations of the BL Lac 1ES 1218+304Jan 28 2009The VERITAS collaboration reports the detection of very-high-energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 1218+304 located at a redshift of z=0.182. A gamma-ray signal was detected with a statistical significance of ... More
Status of the VERITAS ObservatoryOct 02 2008VERITAS, an Imaging Atmospheric Cherenkov Telescope (IACT) system for gammma-ray astronomy in the GeV-TeV range, has recently completed its first season of observations with a full array of four telescopes. A number of astrophysical gamma-ray sources ... More
TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008Jun 06 2011Jun 09 2011We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV gamma-ray fluxes and energy spectra ... More
VERITAS Collaboration Contributions to the 32nd International Cosmic Ray ConferenceNov 10 2011Compilation of papers contributed by the VERITAS Collaboration to the 32nd International Cosmic Ray Conference, held 11-18 August 2011 in Beijing, China.
Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524Dec 04 2008The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope ... More
Detection of Pulsed Gamma Rays Above 100 GeV from the Crab PulsarAug 18 2011We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 Gigaelectronvolts (GeV) with the VERITAS array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon ... More
Long term observations of B2 1215+30 with VERITASOct 24 2013We report on VERITAS observations of the BL Lac object B2 1215+30 between 2008 and 2012. During this period, the source was detected at very high energies (VHE; E > 100 GeV) by VERITAS with a significance of $8.9\sigma$ and showed clear variability on ... More
VERITAS: Status and HighlightsNov 04 2011The VERITAS telescope array has been operating smoothly since 2007, and has detected gamma-ray emission above 100 GeV from 40 astrophysical sources. These include blazars, pulsar wind nebulae, supernova remnants, gamma-ray binary systems, a starburst ... More
The most powerful flaring activity from the NLSy1 PMN J0948+0022Oct 27 2014We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 ($z$ = 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi ... More
Discovery of a new TeV gamma-ray source: VER J0521+211Aug 22 2013We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov telescope array. These observations were motivated by the discovery of a cluster of >30GeV photons in the first ... More
Rapid TeV Gamma-Ray Flaring of BL LacertaeNov 13 2012We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6-minute exposure, when the integral ... More
Discovery of Very High Energy Gamma Rays from 1ES 1440+122Aug 09 2016The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 hours, resulted in the ... More
Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITASMay 20 2009We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar ... More
VERITAS Deep Observations of the Dwarf Spheroidal Galaxy Segue 1Feb 09 2012Jul 07 2015The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report on the results of nearly 48 hours of good quality selected data, taken between January 2010 and May 2011. No ... More
The impact of astrophysical particle acceleration on searches for beyond-the-Standard-Model physicsMay 01 2013Jul 28 2013A brief white paper is provided, discussing how the particle acceleration mechanisms taking place within astrophysical sources may mimic or mask signatures of new physics and the role that will be played by next-generation gamma-ray observatories, such ... More
Frequency doubling and stabilization of a Tm,Ho:YLF laser at 2051 nm to a high finesse optical cavityMay 23 2011Light from a Tm,Ho:YLF laser operating at 2051 nm is frequency doubled then coupled into a high Fabry-Perot cavity with manufacturer quoted finesse in excess of 300,000. The frequency of the laser is stabilized using the Pound-Drever-Hall (PDH) method. ... More
Modeling with the Crowd: Optimizing the Human-Machine Partnership with ZooniverseMar 19 2019LSST and Euclid must address the daunting challenge of analyzing the unprecedented volumes of imaging and spectroscopic data that these next-generation instruments will generate. A promising approach to overcoming this challenge involves rapid, automatic ... More
VERITAS detection of $γ$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observationsJun 20 2015During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, $E>100$ GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations ... More
Gamma-ray observations of the Be/pulsar binary 1A 0535+262 during a giant X-ray outburstMar 16 2011Jul 25 2011Giant X-ray outbursts, with luminosities of about $ 10^{37}$ erg s$^{-1}$, are observed roughly every 5 years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very-high energies (VHE; ... More
VERITAS Observations of the BL Lac Object PG 1553+113Nov 05 2014We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560\,GeV, is well described by a power law with a spectral index of $4.33 \pm 0.09$. ... More
Discovery of VHE $γ$-ray emission from the SNR G54.1+0.3Apr 30 2010Jul 06 2010We report the discovery of very high energy gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8$\sigma$ and appears point-like given the 5$^{arcminute}$ ... More
VERITAS Observations of Six Bright, Hard-Spectrum Fermi-LAT BlazarsOct 26 2012We report on VERITAS very-high-energy (VHE; E>100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray ... More
Search for a correlation between very-high-energy gamma rays and giant radio pulses in the Crab pulsarOct 17 2012We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays ($E_{\gamma} >$ 150 GeV) and ... More
A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852Feb 02 2016Feb 03 2016The F-type star KIC 8462852 has recently been identified as an exceptional target for SETI (search for extraterrestrial intelligence) observations. We describe an analysis methodology for optical SETI, which we have used to analyse nine hours of serendipitous ... More
Investigating Broadband Variability of the TeV Blazar 1ES 1959+650Dec 02 2014We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift UVOT, X-ray observations by the Swift X-ray Telescope (XRT), ... More
Discovery of High-energy and Very High Energy Gamma-ray Emission from the Blazar RBS 0413Apr 04 2012We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high-energy (VHE; E > 100 GeV) gamma-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based gamma-ray observatory, detected VHE gamma rays from RBS ... More
Science Highlights from VERITASOct 05 2015The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based array located at the Fred Lawrence Whipple Observatory in southern Arizona and is one of the world's most sensitive gamma-ray instruments at energies of 85 GeV to ... More
Investigating the TeV Morphology of MGRO J1908+06 with VERITASApr 28 2014We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy (VHE) gamma-ray observatory. Previously, the TeV emission has been attributed to the pulsar wind nebula (PWN) of the Fermi-LAT pulsar ... More
A Three-Year Multi-Wavelength Study of the Very High Energy Gamma-ray Blazar 1ES 0229+200Dec 23 2013The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blazar. Very-high-energy measurements of this active galactic nucleus have been ... More
Highlight Talk: Recent Results from VERITASDec 29 2009VERITAS is a state-of-the-art ground-based gamma-ray observatory that operates in the very high-energy (VHE) region of 100 GeV to 50 TeV. The observatory consists of an array of four 12m-diameter imaging atmospheric Cherenkov telescopes located in southern ... More
A connection between star formation activity and cosmic rays in the starburst galaxy M 82Nov 04 2009Although Galactic cosmic rays (protons and nuclei) are widely believed to be dominantly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery [1]. The active ... More
Discovery of TeV Gamma-ray Emission from CTA 1 by VERITASDec 19 2012We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and ... More
VERITAS Observations of the TeV Binary LS I +61 303 During 2008-2010May 02 2011We present the results of observations of the TeV binary LS I +61 303 with the VERITAS telescope array between 2008 and 2010, at energies above 300 GeV. In the past, both ground-based gamma-ray telescopes VERITAS and MAGIC have reported detections of ... More
VERITAS 2008 - 2009 monitoring of the variable gamma-ray source M87May 03 2010M87 is a nearby radio galaxy that is detected at energies ranging from radio to VHE gamma-rays. Its proximity and its jet, misaligned from our line-of-sight, enable detailed morphological studies and extensive modeling at radio, optical, and X-ray energies. ... More
A search for enhanced very high energy gamma-ray emission from the March 2013 Crab Nebula flareSep 23 2013Jan 08 2014In March 2013, a flaring episode from the Crab Nebula lasting ~2 weeks was detected by the Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). VERITAS provides simultaneous observations throughout this period. During the flare, ... More
Very High Energy outburst of Markarian 501 in May 2009Aug 04 2016The very high energy (VHE; E $>$ 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54938--54956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE $\gamma$-ray activity was detected on May ... More
Multiwavelength observations and modeling of 1ES 1959+650 in a low flux stateJul 25 2013We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (sigma) significance in 7.6 hours of observation in a ... More
Discovery of TeV Gamma-ray Emission Toward Supernova Remnant SNR G78.2+2.1May 28 2013We report the discovery of an unidentified, extended source of very-high-energy (VHE) gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hours of data taken by the VERITAS gamma-ray observatory ... More
VERITAS Observations of day-scale flaring of M87 in 2010 AprilDec 19 2011VERITAS has been monitoring the very-high-energy (VHE; >100GeV) gamma-ray activity of the radio galaxy M87 since 2007. During 2008, flaring activity on a timescale of a few days was observed with a peak flux of (0.70 +- 0.16) X 10^{-11} cm^{-2} s^{-1} ... More
Multiwavelength Observations of the Previously Unidentified Blazar RX J0648.7+1516Oct 26 2011Nov 09 2011We report on the VERITAS discovery of very-high-energy (VHE) gamma- ray emission above 200 GeV from the high-frequency-peaked BL Lac object RXJ0648.7+1516 (GBJ0648+1516), associated with 1FGLJ0648.8+1516. The photon spectrum above 200 GeV is fit by a ... More
Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J0632+057May 19 2009HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary ... More
The Composition of Cosmic Rays at the KneeFeb 07 2002The observation of a small change in spectral slope, or 'knee' in the fluxes of cosmic rays near energies 10^15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review ... More
A luminous and isolated gamma-ray flare from the blazar B2 1215+30Jan 04 2017B2 1215+30 is a BL Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes, and subsequently confirmed by the VERITAS observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected ... More
Multiwavelength Observations of LS I +61 303 with VERITAS, Swift and RXTEApr 28 2009We present results from a long-term monitoring campaign on the TeV binary LSI +61 303 with VERITAS at energies above 500 GeV, and in the 2-10 keV hard X-ray bands with RXTE and Swift, sampling nine 26.5 day orbital cycles between September 2006 and February ... More
VERITAS Observations of a Very High Energy Gamma-ray Flare from the Blazar 3C 66AJan 28 2009Dec 10 2010The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected during 2007 - 2008 in VHE (very high energy: E > 100 GeV) gamma-rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events ... More
The First VERITAS TelescopeApr 06 2006The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic Radiation Imaging Telescope Array System) has been in operation since February 2005. We present here a technical description of the instrument and a summary of its performance. The ... More
VERITAS Observations of the Nova in V407 CygniMay 23 2012We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging ... More
Multiwavelength Observations of Markarian 421 in 2005 - 2006Jan 09 2009Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421, H1426+428, Markarian 501, 1ES 1959+650 ... More
VERITAS Discovery of >200GeV Gamma-ray Emission from the Intermediate-frequency-peaked BL Lac Object W ComaeAug 06 2008Aug 07 2008We report the detection of very high-energy gamma-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae (z=0.102) by VERITAS. The source was observed between January and April 2008. A strong outburst of gamma-ray emission was ... More
A Search for Pulsations from Geminga Above 100 GeV with VERITASDec 15 2014We present the results of 71.6 hours of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between November 2007 and February 2013 were phase-folded using a Geminga ... More
Citizen Science: Contributions to Astronomy ResearchFeb 12 2012The contributions of everyday individuals to significant research has grown dramatically beyond the early days of classical birdwatching and endeavors of amateurs of the 19th century. Now people who are casually interested in science can participate directly ... More
Optical clocks based on ultra-narrow three-photon resonances in alkaline earth atomsSep 09 2004A sharp resonance line that appears in three-photon transitions between the $^{1}S_{0}$ and $^{3}P_{0}$ states of alkaline earth and Yb atoms is proposed as an optical frequency standard. This proposal permits the use of the even isotopes, in which the ... More
Precision measurement of light shifts at two off-resonant wavelengths in a single trapped Ba+ ion and determination of atomic dipole matrix elementsAug 13 2008We define and measure the ratio (R) of the vector ac-Stark effect (or light shift) in the 6S_1/2 and 5D_3/2 states of a single trapped barium ion to 0.2% accuracy at two different off-resonant wavelengths. We earlier found R = -11.494(13) at 514.531nm ... More
Optimizing the Human-Machine Partnership with ZooniverseSep 25 2018Over the past decade, Citizen Science has become a proven method of distributed data analysis, enabling research teams from diverse domains to solve problems involving large quantities of data with complexity levels which require human pattern recognition ... More
Multiwavelength Observations of the VHE Blazar 1ES 2344+514Jun 22 2011Multiwavelength observations of the high-frequency-peaked blazar 1ES2344+514 were performed from 2007 October to 2008 January. The campaign represents the first contemporaneous data on the object at very high energy (VHE, E >100 GeV) {\gamma}-ray, X-ray, ... More
Observation of Markarian 421 in TeV gamma rays over a 14-year time spanOct 30 2013The variability of the blazar Markarian 421 in TeV gamma rays over a 14-year time period has been explored with the Whipple 10 m telescope. It is shown that the dynamic range of its flux variations is large and similar to that in X-rays. A correlation ... More
A new limit on the permanent electric dipole moment of ^{199}HgDec 01 2000We present the first results of a new search for a permanent electric dipole moment of the ^{199}Hg atom using a UV laser. Our measurements give d(Hg)= - (1.06 +/- 0.49 +/- 0.40) 10^{-28} e cm. We interpret the result as an upper limit |d(Hg)| < 2.1 10^{-28} ... More
Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITASMar 15 2017May 08 2017We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves ... More
Upper limits from five years of blazar observations with the VERITAS Cherenkov telescopesMar 08 2016Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E>100 GeV) {\gamma}-ray sources. In this work, we ... More
A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITASSep 06 2016The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the study of high-energy non-thermal emission. It has been the subject of multi-wavelength ... More
Multiwavelength observations of the AGN 1ES 0414+009 with VERITAS, Fermi-LAT, Swift-XRT, and MDMJun 18 2012Jun 20 2012We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the VERITAS array of Cherenkov telescopes. 1ES 0414+009 was observed by VERITAS between January 2008 and February 2011, resulting in 56.2 hours of good quality ... More
VERITAS Upper Limit on the VHE Emission from the Radio Galaxy NGC 1275Nov 04 2009The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E > 100 GeV) part of its broadband spectrum particularly interesting, especially for ... More
Multiwavelength Observations of The TeV Binary LS I +61 303 with VERITAS, Fermi-LAT and Swift-XRT During a TeV OutburstOct 29 2013We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61 303 with the VERITAS telescope array (>200 GeV), Fermi-LAT (0.3-300 GeV), and Swift-XRT (2-10 keV). The data were taken from December 2011 through January ... More
Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITASFeb 15 2010We report on observations of very high-energy gamma rays from the shell-type supernova remnant Cassiopeia A with the VERITAS stereoscopic array of four imaging atmospheric Cherenkov telescopes in Arizona. The total exposure time for these observations ... More
Galaxy Zoo: Morphological Classifications for 120,000 Galaxies in HST Legacy ImagingOct 10 2016Oct 14 2016We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour composite images. Images ... More
Very-High-Energy $γ$-Ray Observations of the Blazar 1ES 2344+514 with VERITASAug 09 2017We present very-high-energy $\gamma$-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above ... More
Exceptionally bright TeV flares from the binary LS I +61$^\circ$ 303Jan 08 2016The TeV binary system LS I +61$^\circ$ 303 is known for its regular, non-thermal emission pattern which traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission ... More
Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky SurveyAug 15 2013Aug 19 2013We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304,122 galaxies drawn from the Sloan Digital Sky Survey. Morphology is a powerful probe for quantifying a galaxy's ... More
A Very High Energy $γ$-Ray Survey towards the Cygnus Region of the GalaxyMay 15 2018We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with the VERITAS Cherenkov telescope array and over seven years of high-energy $\gamma$-ray data taken with the Fermi ... More
Gamma rays from the quasar PKS 1441+25: story of an escapeDec 14 2015Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the Universe. The detection of significant emission above 100 GeV from a distant quasar would ... More
Galaxy Zoo SupernovaeNov 09 2010Nov 15 2010This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof of concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient surveys. ... More
The Real-Time Analysis of the Cherenkov Telescope Array ObservatoryJul 24 2013The Cherenkov Telescope Array (CTA) Observatory must be capable of issuing fast alerts on variable and transient sources to maximize the scientific return. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the ... More