Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation M. Schubnell, C. W. Akerlof, M. F. Cawley, M. Chantell, D. J. Fegan, S. Fennell, K. S. O'Flaherty, J. A. Gaidos, J. Hagan, A. M. Hillas, Y. Jiang, A. D. Kerrick, R. C. Lamb, M. A. Lawrence, D. A. Lewis, D. I. Meyer, G. Mohanty, M. Punch, P. T. Reynolds, A. C. Rovero, G. Sembroski, T. C. Weekes, T. Whitaker, C. Wilson, The Whipple Colloboration; Detection of TeV gamma rays from the AGN Markarian 421. AIP Conf. Proc. 15 June 1993; 276 (1): 185–189. https://doi.org/10.1063/1.43879 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

10.1063/1.43879

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VERITAS: status c.2005

AIP conference proceedings (2006)

T. C. Weekes

VERITAS (Very Energetic Radiation Imaging Telescope Array System), is one of a new generation of TeV gamma‐ray observatories. The current status of its construction is described here. The first two telescopes and cameras have been completed and meet the design specifications; the full array of four telescopes could be operational by the end of 2006.

10.1063/1.2220439

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Citations (1)

Whipple Observations of BL Lac Objects

arXiv (Cornell University) (1999)

M. D’Vali I.H. Bond S. M. Bradbury J. Buckley A. M. Burdett

Only BL Lac objects have been detected as extragalactic sources of very high energy (E > 300 GeV) gamma rays. Using the Whipple Observatory Gamma-ray Telescope, we have attempted to detect more BL Lacs using three approaches. First, we have conducted surveys of nearby BL Lacs, which led to the detections of Mrk 501 and 1ES 2344+514. Second, we have observed X-ray bright BL Lacs when the RXTE All-Sky Monitor identifies high state X-ray emission in an object, in order to efficiently detect extended high emission states. Third, we have conducted rapid observations of several BL Lacs and QSOs located close together in the sky to search for very high flux, short time-scale flare states such as have been seen from Mrk 421. We will present the results of a survey using the third observational technique.

BL Lac object

QSOS

Flare

10.48550/arxiv.astro-ph/9907263

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DISCOVERY OF VERY HIGH ENERGY GAMMA-RAY RADIATION FROM THE BL LAC 1ES 0806+524

The Astrophysical Journal (2008)

V. A. Acciari E. Aliu T. Arlen M. A. Bautista M. Beilicke

The high-frequency-peaked BL Lacertae object 1ES 0806+524, at redshift z = 0.138, was observed in the very high energy (VHE) gamma-ray regime by VERITAS between 2006 November and 2008 April. These data encompass the two- and three-telescope commissioning phases, as well as observations with the full four-telescope array. 1ES 0806+524 is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly timescales is found. The photon spectrum for the period 2007 November to 2008 April can be characterized by a power law with photon index 3.6 ± 1.0stat ± 0.3sys between ∼ 300 GeV and ∼ 700 GeV. The integral flux above 300 GeV is (2.2 ± 0.5stat ± 0.4sys) × 10−12 cm−2 s−1 which corresponds to 1.8% of the Crab Nebula flux. Non-contemporaneous multiwavelength observations are combined with the VHE data to produce a broadband spectral energy distribution that can be reasonably described using a synchrotron--self-Compton model.

BL Lac object

Crab Nebula

Spectral energy distribution

10.1088/0004-637x/690/2/l126

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Citations (54)

THE JUNE 2008 FLARE OF MARKARIAN 421 FROM OPTICAL TO TeV ENERGIES

The Astrophysical Journal (2008)

I. Donnarumma V. Vittorini S. Vercellone E. Del Monte M. Feroci

We present optical, X-ray, high energy ($\lessapprox 30$ GeV) and very high energy ($\gtrapprox 100$ GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high energy $\gamma$-ray signal was detected by AGILE with \sqrt{TS}=4.5 on June 9--15, with $F(E>100 \mathrm{MeV})= 42^{+14}_{-12}\times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. This flaring state is brighter than the average flux observed by EGRET by a factor of $\sim$3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a 5-day flare (June 9-15) peaking at $\sim$ 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A Swift/XRT observation near the flaring maximum revealed the highest 2-10 keV flux ever observed from this source, of 2.6 $\times 10^{-9}$ erg cm$^{-2}$ s$^{-1}$ (i.e. > 100 mCrab). A peak synchrotron energy of $\sim$3 keV was derived, higher than typical values of $\sim$0.5-1 keV. VHE observations with MAGIC and VERITAS on June 6-8 show the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a twelve-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The $\gamma$-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet.

Flare

Spectral energy distribution

10.1088/0004-637x/691/1/l13

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Citations (100)

VERITAS OBSERVATIONS OF DAY-SCALE FLARING OF M 87 IN 2010 APRIL

The Astrophysical Journal (2012)

E. Aliu T. Arlen T. Aune M. Beilicke W. Benbow

VERITAS 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} at energies above 350GeV. In 2010 April, VERITAS detected a flare from M87 with peak flux of (2.71 +- 0.68) X 10^{-11} cm^{-2} s^{-1} for E>350GeV. The source was observed for six consecutive nights during the flare, resulting in a total of 21 hr of good quality data. The most rapid flux variation occurred on the trailing edge of the flare with an exponential flux decay time of 0.90^{+0.22}_{-0.15} days. The shortest detected exponential rise time is three times as long, at 2.87^{+1.65}_{-0.99} days. The quality of the data sample is such that spectral analysis can be performed for three periods: rising flux, peak flux, and falling flux. The spectra obtained are consistent with power-law forms. The spectral index at the peak of the flare is equal to 2.19 +- 0.07. There is some indication that the spectrum is softer in the falling phase of the flare than the peak phase, with a confidence level corresponding to 3.6 standard deviations. We discuss the implications of these results for the acceleration and cooling rates of VHE electrons in M87 and the constraints they provide on the physical size of the emitting region.

Flare

Spectral index

10.1088/0004-637x/746/2/141

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Citations (50)

VERITAS: Very LArge Energetic Radiation Imaging Telescope Array System

arXiv (Cornell University) (1997)

T. C. Weekes C. Akerlof S. D. Biller A. C. Breslin J. Buckley

A next generation atmospheric Cherenkov observatory is described based on the Whipple Observatory $\gamma$-ray telescope. A total of nine such imaging telescopes will be deployed in an array that will permit the maximum versatility and give high sensitivity in the 50 GeV - 50 TeV band (with maximum sensitivity from 100 GeV to 10 TeV).

Cherenkov Telescope Array

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An Observatory to Study 10 (10) to 10 (17) EV Gamma Rays

T. C. Weekes

A facility is described which incorporates many of the best features of existing gamma ray telescopes at a single site. In addition to reducing the flux sensitivity in some energy ranges, it permits the measurements of the energy spectrum over seven decades of energy.

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Astrogam: a Very Energetic Gamma-Ray Experiment

Bulletin of the American Astronomical Society (1989)

Jenni Adams S. P. Ahlen L. Barbier J. J. Beatty P. Carlson

Source

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Upper-Air Fluorescence as a Tool in X-ray Astronomy and Searches for X-rays from NP 0532 and Other Pulsars

Springer eBooks (1970)

W. N. Charman R. W. P. Drever J. H. Fruin J. V. Jelley J. L. Elliot

10.1007/978-94-010-3311-4_5

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Citations (1)