A5086675661- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Photocathodes and Microchannel Plates
- Ocular and Laser Science Research
- Galaxies: Formation, Evolution, Phenomena
- Advanced Optical Sensing Technologies
- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
- Cosmology and Gravitation Theories
- Particle physics theoretical and experimental studies
- Astronomical Observations and Instrumentation
- Mediterranean and Iberian flora and fauna
- Historical Astronomy and Related Studies
- Nuclear Physics and Applications
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
Adler Planetarium
2008-2017
University of Delaware
2008
We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains largest number homogeneously observed reduced nearby SNe Ia (z ≲ 0.08) published to date. It more than doubles sample, bringing SN cosmology point where systematic uncertainties dominate. Our natural system has a precision ≲0.02 mag in BVRIr'i' ≲0.04...
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles energies exceeding 10^12 electron Volts (eV) and are bright sources very-high-energy (VHE) gamma-ray emission, it not yet known where VHE emission originates. Here we report on radio observations galaxy M87, revealing period extremely strong flares accompanied by increase flux from its nucleus. These results...
This detection constrains the mechanism and emission region of gamma-ray radiation in pulsar’s magnetosphere.
We report the discovery of TeV gamma-ray emission from Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's remnant. Observations performed in period 2008-2010 with VERITAS ground-based observatory reveal weak coming direction remnant, compatible a point source located at $00^{\rm h} \ 25^{\rm m} 27.0^{\rm s},\ +64^{\circ} 10^{\prime} 50^{\prime\prime}$ (J2000). The photon spectrum measured by can be described power-law $dN/dE = C(E/3.42\;\textrm{TeV})^{-\Gamma}$ $\Gamma 1.95 \pm...
LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very energy gamma-rays. The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array imaging air-Cherenkov telescopes. A signal gamma-rays energies above 300 GeV found statistical 8.4 standard deviations. flux measured to be strongly variable; maximum during most apastron. spectrum for period emission can characterized by power law...
We report on TeV γ-ray observations of the blazar Mrk 421 (redshift 0.031) with VERITAS observatory and Whipple 10 m Cherenkov telescope. The excellent sensitivity allowed us to sample fluxes energy spectra unprecedented accuracy where was detected in each pointings. A total 47.3 hr 96 data were acquired between 2006 January 2008 June. present results a study as function time for different flux levels. On May 2 3, bright flares reaching level Crab. complemented radio, optical, X-ray...
We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with supernova remnant IC 443 is extended. contains one of best studied sites remnant/molecular cloud interaction and pulsar wind nebula CXOU J061705.3+222127, both which are important targets for VHE observations. VERITAS observed 37.9 hr during 2007 detected above 300 GeV an excess 247 events, resulting in a significance 8.3 standard deviations (σ) before trials 7.5σ after point-source search....
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account weak energy losses, can accumulate, suggesting that may also sources very high (VHE; E > 100 GeV) gamma-ray emission. We report here VHE observations the Coma cluster with VERITAS array imaging Cerenkov telescopes, complementing Fermi Large Area Telescope at GeV energies. No significant emission from Cluster was detected. Integral flux...
The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report results nearly 48 hours good quality selected data, taken between January 2010 and May 2011. No significant $\ensuremath{\gamma}$-ray emission is detected at nominal position 1, upper limits integrated flux are derived. According to recent studies, 1 most dark matter-dominated currently known. derive stringent bounds various annihilating decaying...
We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae 2011 June 28 with Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during 34.6-minute exposure, when integral flux above 200 GeV reached $(3.4\pm0.6) \times 10^{-6} \;\text{photons}\;\text{m}^{-2}\text{s}^{-1}$, roughly 125% Crab Nebula measured by VERITAS. light curve indicates that observations missed rising phase but covered significant portion decaying...
The very high energy (VHE; E > 100 GeV) blazar Markarian 501 has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within jets active galactic nuclei. However, there are few detailed multiwavelength studies during its quiescent state, due to low luminosity. A short-term study was coordinated in March 2009, focusing around multi-day observation with Suzaku X-ray satellite including {\gamma}-ray data from VERITAS, MAGIC,...
Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints diffuse radiation fields that fill universe. The detection significant emission above 100 GeV a distant quasar would show some radiated gamma-rays escape pair-production interactions with low-energy photons, be it extragalactic background light (EBL), or near supermassive black hole lying at jet's base. VERITAS detected up to ∼200 PKS 1441+25 (z = 0.939) during 2015 April,...
The 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 used to place constraints on the intensity extragalactic background light and intergalactic magnetic field. A multi-wavelength study centered around very-high-energy observations by VERITAS presented. This obtained, over period three years,...
The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring active galactic nuclei from waves TeV γ-rays. Here we report detection γ-ray emission above 250 GeV spring 2007 with VERITAS atmospheric Cerenkov telescope array and discuss its correlation X-ray emission. is measured be pointlike an intrinsic source radius less than 4.5'. differential energy spectrum fitted well by power-law function: dΦ/dE = (7.4 ± 1.3stat...
We report results from an intensive multiwavelength campaign on the intermediate-frequency-peaked BL Lacertae object W Com (z=0.102) during a strong outburst of very high energy gamma-ray emission in June 2008. The signal was detected by VERITAS 2008 7-8 with flux F(>200 GeV) = (5.7+-0.6)x10^-11 cm-2s-1, about three times brighter than discovery March. initial detection this flare at energies above 200 GeV followed observations gamma-rays (AGILE, E>100 MeV), and X-rays (Swift XMM-Newton),...
The 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 1791 events detected, corresponding to a significance 21.2 standard deviations (sigma), these observations (32.8 hours live time). observed integral flux above 200 GeV 6% Crab Nebula's and shows evidence for variability on time-scale days. measured energy...
We report on observations of very high energy γ rays from the shell-type supernova remnant (SNR) Cassiopeia A with Very Energetic Radiation Imaging Telescope Array System stereoscopic array four imaging atmospheric Cherenkov telescopes in Arizona. The total exposure time for these is 22 hr, accumulated between September and November 2007. γ-ray source associated SNR was detected above 200 GeV a statistical significance 8.3σ. estimated integral flux this about 3% Crab-Nebula flux. photon...
VERITAS, 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 four telescopes. A number astrophysical gamma‐ray sources have been detected, both galactic and extragalactic, including previously unknown at TeV energies. We describe status some highlight results, assess technical performance, sensitivity shower reconstruction capabilities.
Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already detected at Observatory, Markarian 421, H1426+428, 501, 1ES 1959+650 and 2344+514, are monitored routinely each night they visible. We report on 421 observations taken from November 2005 to June 2006 in gamma-ray, X-ray, optical radio bands. During this time, was found be variable all wavelengths probed. Both variability...
The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in the very high-energy (VHE; E > 100 GeV) wave band by VERITAS array of atmospheric Cherenkov telescopes. observations, taken between 2008 December and 2009 March totaling 22.1 hr, yield discovery VHE gamma rays from source. is detected at a statistical significance 5.5 standard deviations (5.5σ) above background, corresponding to an integral flux (3.9 +/- 0.8) x 10-12 cm-2 s-1 (3% Crab Nebula's flux) 300 GeV....
We report the detection of very high energy γ-ray emission from intermediate-frequency-peaked BL Lacertae object W Comae (z = 0.102) by VERITAS. The source was observed between 2008 January and April. A strong outburst measured in middle March, lasting for only 4 days. spectrum during two highest flare nights is fit a power law found to be steep, with differential photon spectral index Γ 3.81 ± 0.35stat± 0.34syst. integral flux above 200 GeV those corresponds roughly 9% Crab Nebula....
We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with VERITAS atmospheric Cherenkov telescope resolve extended overlapping elongated radio SNR. The 7.3 sigma (pre-trials) has a full angular extent roughly 0.6deg by 0.4deg. Most notably, centroid VHE is centered near peak coincident 12CO (J = 1-0) emission, 0.4deg away pulsar PSR J2229+6114, situated at northern end Evidently current-epoch particles...
We report the first detection of very-high-energy (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum measured by VERITAS is well described power law index 3.8 +- 0.5_stat 0.3_syst and flux normalization at 200 (5.1 0.9_stat 0.5_syst) x 10^{-11} TeV^-1 cm^-2 s^-1, where stat syst denote statistical systematical uncertainty, respectively. VHE steady over observation period between MJD 54881 55003 (2009 February 19 to June...