Papers by Amanda Weinstein
The hunt for axionlike particles with the Cherenkov Telescope Array
Gamma-ray photons can convert into axion-like particles (ALPs) and vice versa when interacting wi... more Gamma-ray photons can convert into axion-like particles (ALPs) and vice versa when interacting with astrophysical magnetic fields. The conversions of ALPs may have important implications for astrophysics since they would imprint characteristic features on the spectra of gamma-ray sources. The features may be detected by the Fermi Gamma-ray Space Telescope and by current Imaging Atmospheric Cherenkov Telescopes (IACTs) or the future Cherenkov Telescope Array (CTA). Thus, gamma-ray observations can provide valuable constraints on the nature of ALPs, and represent an excellent complementary approach to laboratory searches for ALPs. CTA's twenty times larger collection area and improved sensitivity compared to current IACTs will make it an extraordinarily powerful instrument to search for signatures of ALPs imprinted in the spectra of gamma-ray sources in the energy range between a few tens of GeV up to a few dozen TeV. The US contribution of Medium Size Telescopes will be therefore...
Commissioning and performance of a fast level-2 trigger system at VERITAS
2012 18th IEEE-NPSS Real Time Conference, 2012
ABSTRACT
Snowmass Cosmic Frontiers 6 (CF6) Working Group Summary--The Bright Side of the Cosmic Frontier: Cosmic Probes of Fundamental Physics
ABSTRACT Report of the CF6 Working Group at Snowmass 2013. Topics addressed include ultra-high en... more ABSTRACT Report 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.
The topological trigger system for the VERITAS upgrade
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012
Discovery of TeV gamma-ray emission from CTA 1 by Veritas
Astrophysical Journal, 2013
ABSTRACT We report the discovery of TeV gamma-ray emission coincident with the shell-type radio s... more ABSTRACT We 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 shows an extended morphology, approximated by a two-dimensional Gaussian of semi-major (semi-minor) axis 0.30 degree (0.24 degree) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N_0 (E/3 TeV)^(-\Gamma), with a differential spectral index of \Gamma = 2.2 +- 0.2_stat +- 0.3_sys, and normalization N_0 = (9.1 +- 1.3_stat +- 1.7_sys) x 10^(-14) cm^(-2) s^(-1) TeV^(-1). The integral flux, F_\gamma = 4.0 x 10^(-12) erg cm^(-2) s^(-1) above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, co-location with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.
Illuminating Galactic Accelerators with CTA
Pulsar Wind Nebulae and Cosmic Rays: A Bedtime Story
Nuclear Physics B - Proceedings Supplements
The role pulsar wind nebulae play in producing our locally observed cosmic ray spectrum remains m... more The role pulsar wind nebulae play in producing our locally observed cosmic ray spectrum remains murky, yet intriguing. Pulsar wind nebulae are born and evolve in conjunction with SNRs, which are favored sites of Galactic cosmic ray acceleration. As a result they frequently complicate interpretation of the gamma-ray emission seen from SNRs. However, pulsar wind nebulae may also contribute directly to the local cosmic ray spectrum, particularly the leptonic component. This paper reviews the current thinking on pulsar wind nebulae and their connection to cosmic ray production from an observational perspective. It also considers how both future technologies and new ways of analyzing existing data can help us to better address the relevant theoretical questions. A number of key points will be illustrated with recent results from the VHE (E > 100 GeV) gamma-ray observatory VERITAS.
A prototype for the real-time analysis of the Cherenkov Telescope Array
Ground-based and Airborne Telescopes V, 2014
Journal of Instrumentation, 2007
The energy resolution of the barrel part of the CMS Electromagnetic Calorimeter has been studied ... more The energy resolution of the barrel part of the CMS Electromagnetic Calorimeter has been studied using electrons of 20 to 250 GeV in a test beam. The incident electron's energy was reconstructed by summing the energy measured in arrays of 3×3 or 5×5 channels. There was no significant amount of correlated noise observed within these arrays. For electrons incident at the centre of the studied 3×3 arrays of crystals, the mean stochastic term was measured to be 2.8% and the mean constant term to be 0.3%. The amount of the incident electrons' energy which is contained within the array depends on its position of incidence. The variation of the containment with position is corrected for using the distribution of the measured energy within the array. For uniform illumination of a crystal with 120 GeV electrons a resolution of 0.5% was achieved. The energy resolution meets the design goal for the detector.
Towards a global software architecture for operating and controlling the Cherenkov Telescope Array
Software and Cyberinfrastructure for Astronomy III, 2014
ABSTRACT The Cherenkov Telescope Array (CTA) is an international initiative to build the next gen... more ABSTRACT The Cherenkov Telescope Array (CTA) is an international initiative to build the next generation ground-based gamma-ray instrument. CTA will allow studying the Universe in the very-high-energy gamma-ray domain with energies ranging from a few tens of GeV to more than a hundred TeV. It will extend the currently accessible energy band, while increasing the sensitivity by a factor of 10 with respect to existing Cherenkov facilities. Furthermore, CTA will enhance other important aspects like angular and energy resolution. CTA will comprise two arrays, one in the Northern hemisphere and one in the Southern hemisphere, of in total more than one hundred of telescopes of three different sizes. The CTA performance requirements and the increased complexity in operation, control and monitoring of such a large distributed multi-telescope array leads to new challenges in designing and developing the CTA control software system. Indeed, the control software system must be flexible enough to allow for the simultaneous operation of multiple sub-arrays of different types of telescopes, to be ready to react in short timescales to changing weather conditions or to automatic alarms for transient phenomena, to be able to operate the observatory with a minimum personal effort on site, to cope with the malfunctioning of single telescopes or sub-arrays of telescopes, and to readout and control a large and heterogeneous set of devices. This report describes the preliminary architectural design concept for the CTA control software system that will be responsible to manage all the functionality of the CTA array, thereby enabling CTA to reach its scientific goals.
AIAA Infotech@Aerospace 2007 Conference and Exhibit, 2007
The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
Veritas: Status and Early Results
th-www.if.uj.edu.pl
... J. Grube, R. Guenette, G. Gyuk, D. Hanna E. Hays, J. Holder, D. Horan, SB Hughes, CM Hui, TB ... more ... J. Grube, R. Guenette, G. Gyuk, D. Hanna E. Hays, J. Holder, D. Horan, SB Hughes, CM Hui, TB Humensky A. Imran, P. Kaaret, GE ... It remains in question whether the gamma-ray emission is produced by inverse Compton scattering of accelerated electrons or is the result of pion ...
Physical Review Letters, 1982
Evidence for a new resonance 0 * nn in the process J/$ -t yrln is presented.
The European Physical Journal C, 2006
The amplitude of the signal collected from the PbWO 4 crystals of the CMS electromagnetic calorim... more The amplitude of the signal collected from the PbWO 4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.
The Astrophysical Journal, 2010
M 87 is a nearby radio galaxy that is detected at energies ranging from radio to very-high-energy... more M 87 is a nearby radio galaxy that is detected at energies ranging from radio to very-high-energy (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. Flaring activity was observed at all energies, and multiwavelength correlations would help clarify the origin of the VHE emission. In this paper, we describe a detailed temporal and spectral analysis of the VERITAS VHE gammaray observations of M87 in 2008 and 2009. In the 2008 observing season, VERITAS detected an excess with a statistical significance of 7.2 standard deviations (σ) from M 87 during a joint multi-wavelength monitoring campaign conducted by three major VHE experiments along with the Chandra X-ray Observatory. In February 2008, VERITAS observed a VHE flare from M 87 occurring over a 4-day timespan. The peak nightly flux above 250 GeV was (1.14 ± 0.26) × 10 −11 cm −2 s −1 , which corresponded to 7.7% of the Crab Nebula flux. M 87 was marginally detected before this 4-day flare period, and was not detected afterwards. Spectral analysis of the VERITAS observations showed no significant change in the photon index between the flare and pre-flare states. Shortly after the VHE flare seen by VERITAS, the Chandra X-ray Observatory detected the flux from the core of M 87 at a historical maximum, while the flux from the nearby knot HST-1 remained quiescent. presented the 2008 contemporaneous VHE gamma-ray, Chandra X-ray, and VLBA radio observations which suggest the core as the most likely source of VHE emission, in contrast to the 2005 VHE flare that was simultaneous with an X-ray flare in the HST-1 knot. In 2009, VERITAS continued its monitoring of M 87 and marginally detected a 4.2 σ excess corresponding to a flux of ∼ 1% of the Crab Nebula. No VHE flaring activity was observed in 2009.
The Astrophysical Journal, 2014
HESS J0632+057 is the only gamma-ray binary known so far whose position in the sky allows observa... more HESS J0632+057 is the only gamma-ray binary known so far whose position in the sky allows observations with ground-based observatories both in the northern and southern hemispheres. Here we report on long-term observations of HESS J0632+057 conducted with the VERITAS and H.E.S.S. Cherenkov Telescopes and the X-ray Satellite Swift, spanning a time range from 2004 to
The Astrophysical Journal, 2009
The recent detection by the Fermi γ-ray space telescope of high-energy γ-rays from the radio gala... more The recent detection by the Fermi γ-ray space telescope of high-energy γ-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 the understanding of active galactic nuclei (AGN) with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hours. No VHE γ-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope (LAT) result.
Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-Ray Observations of the Coma Cluster of Galaxies with Veritas and Fermi
The Astrophysical Journal, 2012
ABSTRACT Observations of radio halos and relics in galaxy clusters indicate efficient electron ac... more ABSTRACT Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated, suggesting that clusters may also be sources of very high-energy (VHE; E>100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cherenkov telescopes, with complementing Fermi-LAT observations at GeV energies. No significant gamma-ray emission from the Coma cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5)*10^-8\ ph. m^-2 s^-1 (VERITAS, >220 GeV} and ~2*10^-6 ph. m^-2 s^-1 (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain CRs and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be < 16% from VERITAS data and < 1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of (2 - 5.5) muG, depending on the radial magnetic-field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this {renders} the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark-matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally-averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, <\sigma v>. (abr.)
The Astrophysical Journal, 2012
We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the V... more We 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 2008 January and 2011 February, resulting in 56.2 hr of good quality pointed observations. These observations resulted in a detection of 822 events from the source corresponding to a statistical significance of 6.4 standard deviations (6.4σ ) above the background. The source flux, showing no evidence for variability, is measured as (5.2 ± 1.1 stat ± 2.6 sys )× 10 −12 photons cm −2 s −1 above 200 GeV, equivalent to approximately 2% of the Crab Nebula flux above this energy. The differential photon spectrum from 230 GeV to 850 GeV is well fit by a power law with a photon index of Γ = 3.4 ± 0.5 stat ± 0.3 sys and a flux normalization of (1.6 ± 0.3 stat ± 0.8 sys ) × 10 −11 photons cm −2 s −1 at 300 GeV. We also present multiwavelength results taken in the optical (MDM), x-ray (Swift-XRT), and GeV (Fermi-LAT) bands and use these results to construct a broadband spectral energy distribution (SED). Modeling of this SED indicates that homogenous one-zone leptonic scenarios are not adequate to describe emission from the system, with a lepto-hadronic model providing a better fit to the data.
The Astrophysical Journal, 2012
We present the results of a joint observational campaign between the Green Bank radio telescope a... more We 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 γ > 150 GeV) and Giant Radio Pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15366 GRPs were recorded during 11.6 hours of simultaneous observations, which were made across four nights in December 2008 and in November and December 2009. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, 8 different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Further, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period time scales. On ∼8-second time scales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.