193 results on '"Fleysher, L."'
Search Results
2. Observation and Spectral Measurements of the Crab Nebula with Milagro
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Abdo, A. A., Allen, B. T., Aune, T., Benbow, W., Berley, D., Chen, C., Christopher, G. E., DeYoung, T., Dingus, B. L., Ellsworth, R. W., Falcone, A., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Gordo, J. B., Hays, E., Hoffman, C. M., Huentemeyer, P. H., Kolterman, B. E., Linnemann, J. T., McEnery, J. E., Morgan, T., Mincer, A. I., Nemethy, P., Pretz, J., Ryan, J. M., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Vasileiou, V., Walker, G. P., Williams, D. A., and Yodh, and G. B.
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Astrophysics - High Energy Astrophysical Phenomena - Abstract
The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is believed to be caused by inverse-Compton up-scattering scattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fit. The fit is consistent with values measured by IACTs between 1 and 20 TeV. Fixing the spectral index to values that have been measured below 1 TeV by IACT experiments (2.4 to 2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20 to 40 TeV., Comment: Submitted to Astrophysical Journal
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- 2011
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3. The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro
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Abdo, A. A., Allen, B. T., Aune, T., Berley, D., Casanova, S., Chen, C., Dingus, B. L., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Hoffman, C. M., Hopper, B., Hüntemeyer, P. H., Kolterman, B. E., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Nemethy, P., Noyes, D., Pretz, J., Ryan, J. M., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Vasileiou, V., Walker, G. P., Williams, D. A., and Yodh, G. B.
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Astrophysics - Abstract
Results are presented of a harmonic analysis of the large scale cosmic-ray anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy pro jections in right ascension generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico. With a high duty cycle and large field-of-view, Milagro is an excellent instrument for measuring this anisotropy with high sensitivity at TeV energies. The analysis is conducted using a seven year data sample consisting of more than 95 billion events, the largest such data set in existence. We observe an anisotropy with a magnitude around 0.1% for cosmic rays with a median energy of 6 TeV. The dominant feature is a deficit region of depth (2.49 +/- 0.02 stat. +/- 0.09 sys.)x10^(-3) in the direction of the Galactic North Pole centered at 189 degrees right ascension. We observe a steady increase in the magnitude of the signal over seven years., Comment: 36 pages, 16 figures, submitted to ApJ
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- 2008
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4. A Measurement of the Spatial Distribution of Diffuse TeV Gamma Ray Emission from the Galactic Plane with Milagro
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Abdo, A. A., Allen, B., Aune, T., Berley, D., Blaufuss, E., Casanova, S., Chen, C., Dingus, B. L., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Hoffman, C. M., H"untemeyer, P. H., Kolterman, B. E., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Moskalenko, I. V., Nemethy, P., Noyes, D., Porter, T. A., Pretz, J., Ryan, J. M., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Strong, A. W., Sullivan, G. W., Vasileiou, V., Walker, G. P., Williams, D. A., and Yodh, G. B.
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Astrophysics - Abstract
Diffuse $\gamma$-ray emission produced by the interaction of cosmic-ray particles with matter and radiation in the Galaxy can be used to probe the distribution of cosmic rays and their sources in different regions of the Galaxy. With its large field of view and long observation time, the Milagro Gamma Ray Observatory is an ideal instrument for surveying large regions of the Northern Hemisphere sky and for detecting diffuse $\gamma$-ray emission at very high energies. Here, the spatial distribution and the flux of the diffuse $\gamma$-ray emission in the TeV energy range with a median energy of 15 TeV for Galactic longitudes between 30$^\circ$ and 110$^\circ$ and between 136$^\circ$ and 216$^\circ$ and for Galactic latitudes between -10$^\circ$ and 10$^\circ$ are determined. The measured fluxes are consistent with predictions of the GALPROP model everywhere except for the Cygnus region ($l\in[65^\circ,85^\circ]$). For the Cygnus region, the flux is twice the predicted value. This excess can be explained by the presence of active cosmic ray sources accelerating hadrons which interact with the local dense interstellar medium and produce gamma rays through pion decay., Comment: 15 pages, 3 figures, accepted by ApJ
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- 2008
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5. Discovery of Localized Regions of Excess 10-TeV Cosmic Rays
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Abdo, A. A., Allen, B., Aune, T., Berley, D., Blaufuss, E., Casanova, S., Chen, C., Dingus, B. L., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzales, M. M., Goodman, J. A., Hoffman, C. M., Hüntemeyer, P. H., Kolterman, B. E., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Nemethy, P., Noyes, D., Pretz, J., Ryan, J. M., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Vasileiou, V., Walker, G. P., Williams, D. A., and Yodh, G. B.
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Astrophysics - Abstract
An analysis of 7 years of Milagro data performed on a 10-degree angular scale has found two localized regions of excess of unknown origin with greater than 12 sigma significance. Both regions are inconsistent with gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6 sigma, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at ~10 TeV. Potential causes of these excesses are explored, but no compelling explanations are found., Comment: Submitted to PhysRevLett
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- 2008
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6. TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro
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Abdo, A. A., Allen, B., Berley, D., Casanova, S., Chen, C., Coyne, D. G., Dingus, B. L., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Hays, E., Hoffman, C. M., Hopper, B., Huntemeyer, P. H., Kolterman, B. E., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Nemethy, P., Noyes, D., Ryan, J. M., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Vasileiou, V., Walker, G. P., Williams, D. A., Xu, X. W., and Yodh, G. B.
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Astrophysics - Abstract
A survey of Galactic gamma-ray sources at a median energy of ~20 TeV has been performed using the Milagro Gamma Ray Observatory. Eight candidate sources of TeV emission are detected with pre-trials significance $>4.5\sigma$ in the region of Galactic longitude $l\in[30^\circ,220^\circ]$ and latitude $b\in[-10^\circ,10^\circ]$. Four of these sources, including the Crab nebula and the recently published MGRO J2019+37, are observed with significances $>4\sigma$ after accounting for the trials involved in searching the 3800 square degree region. All four of these sources are also coincident with EGRET sources. Two of the lower significance sources are coincident with EGRET sources and one of these sources is Geminga. The other two candidates are in the Cygnus region of the Galaxy. Several of the sources appear to be spatially extended. The fluxes of the sources at 20 TeV range from ~25% of the Crab flux to nearly as bright as the Crab., Comment: Submitted to ApJ
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- 2007
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7. Discovery of TeV Gamma-Ray Emission from the Cygnus Region of the Galaxy
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Abdo, A. A., Allen, B., Berley, D., Blaufuss, E., Casanova, S., Chen, C., Coyne, D. G., Delay, R. S., Dingus, B. L., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Hays, E., Hoffman, C. M., Kolterman, B. E., Kelley, L. A., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Moskalenko, I. V., Nemethy, P., Noyes, D., Ryan, J. M., Samuelson, F. W., Parkinson, P. M. Saz, Schneider, M., Shoup, A., Sinnis, G., Smith, A. J., Strong, A. W., Sullivan, G. W., Vasileiou, V., Walker, G. P., Williams, D. A., Xu, X. W., and Yodh, G. B.
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Astrophysics - Abstract
The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this paper we present spatial and flux measurements of TeV gamma-ray emission from the Cygnus Region. The TeV image shows at least one new source MGRO J2019+37 as well as correlations with the matter density in the region as would be expected from cosmic-ray proton interactions. However, the TeV gamma-ray flux as measured at ~12 TeV from the Cygnus region (after excluding MGRO J2019+37) exceeds that predicted from a conventional model of cosmic ray production and propagation. This observation indicates the existence of either hard-spectrum cosmic-ray sources and/or other sources of TeV gamma rays in the region., Comment: Submitted to Astrophysical Journal Letters
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- 2006
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8. Constraints on Very High Energy gamma-ray emission from Gamma-Ray Bursts
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Atkins, R., Benbow, W., Berley, D., Blaufuss, E., Coyne, D. G., DeYoung, T., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gonzalez, M. M., Goodman, J. A., Hays, E., Hoffman, C. M., Kelley, L. A., Lansdell, C. P., Linnemann, J. T., McEnery, J. E., Mincer, A. I., Morales, M. F., Nemethy, P., Noyes, D., Ryan, J. M., Samuelson, F. W., Parkinson, P. M. Saz, Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Williams, D. A., Wilson, M. E., Xu, X. W., and Yodh, G. B.
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Astrophysics - Abstract
The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high energy particles interacting in the Earth's atmosphere. Milagro has a wide field of view and high duty cycle, monitoring the northern sky almost continuously in the 100 GeV to 100 TeV energy range. Milagro is, thus, uniquely capable of searching for very high-energy emission from gamma-ray bursts (GRBs) during the prompt emission phase. Detection of >100 GeV counterparts would place powerful constraints on GRB mechanisms. Twenty-five satellite-triggered GRBs occurred within the field of view of Milagro between January 2000 and December 2001. We have searched for counterparts to these GRBs and found no significant emission from any of the burst positions. Due to the absorption of high-energy gamma rays by the extragalactic background light, detections are only expected to be possible for redshifts less than ~0.5. Three of the GRBs studied have measured redshifts. GRB 010921 has a redshift low enough (0.45) to allow an upper limit on the fluence to place an observational constraint on potential GRB models., Comment: submitted to ApJ
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- 2005
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9. Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro Observatory
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The Milagro Collaboration, Atkins, R., Benbow, W., Berley, D., Blaufuss, E., Bussons, J., Coyne, D. G., DeYoung, T., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Fleysher, L., Fleysher, R., Gisler, G., Gonzalez, M. M., Goodman, J. A., Haines, T. J., Hays, E., Hoffman, C. M., Kelley, L. A., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Noyes, D., Ryan, J. M., Samuelson, F. W., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Williams, D. A., Westerhoff, S., Wilson, M. E., Xu, X., and Yodh, G. B.
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Astrophysics - Abstract
The Milagro telescope monitors the northern sky for 100 GeV to 100 TeV transient emission through continuous very high energy wide-field observations. The large effective area and ~100 GeV energy threshold of Milagro allow it to detect very high energy (VHE) gamma-ray burst emission with much higher sensitivity than previous instruments and a fluence sensitivity at VHE energies comparable to that of dedicated gamma-ray burst satellites at keV to MeV energies. Even in the absence of a positive detection, VHE observations can place important constraints on gamma-ray burst (GRB) progenitor and emission models. We present limits on the VHE flux of 40 s -- 3 h duration transients nearby to earth, as well as sensitivity distributions which have been corrected for gamma-ray absorption by extragalactic background light and cosmological effects. The sensitivity distributions suggest that the typical intrinsic VHE fluence of GRBs is similar or weaker than the keV -- MeV emission, and we demonstrate how these sensitivity distributions may be used to place observational constraints on the absolute VHE luminosity of gamma-ray bursts for any GRB emission and progenitor model., Comment: Accepted for publication in ApJL, minor revisions to the text, retypeset in emulateapj style
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- 2003
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10. Exclusion regions and their power
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Fleysher, L., Fleysher, R., Haines, T. J., Mincer, A. I., and Nemethy, P.
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Physics - Data Analysis, Statistics and Probability - Abstract
The question of exclusion region construction in new phenomenon searches has been causing considerable discussions for many years and yet no clear mathematical definition of the problem has been stated so far. In this paper we formulate the problem in mathematical terms and propose a solution to the problem within the framework of statistical tests. The proposed solution avoids problems of the currently used procedures., Comment: 4 pages, 2 figures, submitted to PRD
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- 2003
11. The uniformly most powerful test of statistical significance for counting-type experiments with background
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Fleysher, L., Fleysher, R., Haines, T. J., Mincer, A. I., and Nemethy, P.
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Physics - Data Analysis, Statistics and Probability ,Astrophysics ,High Energy Physics - Experiment - Abstract
In this paper, after a discussion of general properties of statistical tests, we present the construction of the most powerful hypothesis test for determining the existence of a new phenomenon in counting-type experiments where the observed Poisson process is subject to a Poisson distributed background with unknown mean., Comment: 8 pages, 1 figure, submitted to PRD
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- 2003
12. Tests of Statistical Significance and Background Estimation in Gamma Ray Air Shower Experiments
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Fleysher, R., Fleysher, L., Nemethy, P., Mincer, A. I., and Haines, T. J.
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Astrophysics ,High Energy Physics - Experiment ,High Energy Physics - Phenomenology - Abstract
In this paper we discuss several methods of significance calculation and point out the limits of their applicability. We then introduce a self consistent scheme for source detection and discuss some of its properties. The method allows incorporating background anisotropies by vetoing existing small scale regions on the sky and compensating for known large scale anisotropies. By giving an example using Milagro gamma ray observatory we demonstrate how the method can be employed to relax the detector stability assumption. Two practical implementations of the method are discussed. The method is universal and can be used with any large field-of-view detector, where the object of investigation, steady or transient, point or extended, traverses its field of view., Comment: 12 pages, 7 figures. Submitted to ApJ, submission number: 58334
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- 2003
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13. The high-energy gamma-ray fluence and energy spectrum of GRB 970417a from observations with Milagrito
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Atkins, R., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Sanchez, M. M. Gonzalez, Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Klein, S., Leonor, I., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Samuelson, F. W., Shen, B., Shoup, A., Sinnis, C., Smith, A. J., Sullivan, G. W., Tumer, T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
Evidence of TeV emission from GRB970417a has been previously reported using data from the Milagrito detector. Constraints on the TeV fluence and the energy spectrum are now derived using additional data from a scaler system that recorded the rate of signals from the Milagrito photomultipliers. This analysis shows that if emission from GRB970417a has been observed, it must contain photons with energies above 650 GeV. Some consequences of this observation are discussed., Comment: Submitted to the Astrophysical Journal
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- 2002
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14. Evidence for TeV Emission from GRB 970417a
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The Milagro Collaboration, Atkins, R., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Shen, B., Shoup, A., Sinnis, C., Smith, A. J., Sullivan, G. W., Tumer, T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
Milagrito, a detector sensitive to very high energy gamma rays, monitored the northern sky from February 1997 through May 1998. With a large field of view and a high duty cycle, this instrument was well suited to perform a search for TeV gamma-ray bursts (GRBs). We report on a search made for TeV counterparts to GRBs observed by BATSE. BATSE detected 54 GRBs within the field of view of Milagrito during this period. An excess of events coincident in time and space with one of these bursts, GRB 970417a, was observed by Milagrito. The excess has a chance probability of $2.8 \times 10^{-5}$ of being a fluctuation of the background. The probability for observing an excess at least this large from any of the 54 bursts is $1.5 \times 10^{-3}$. No significant correlations were detected from the other bursts., Comment: 10 pages, 3 figures
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- 2000
15. First Results of a Study of TeV Emission from GRBs in Milagrito
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McEnery, J. E., Atkins, R., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., McConnell, M., McCullough, J. F., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Shen, B., Shoup, A., Sinnis, C., Smith, A. J., Sullivan, G. W., Tumer, T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
Milagrito, a detector sensitive to gamma-rays at TeV energies, monitored the northern sky during the period February 1997 through May 1998. With a large field of view and high duty cycle, this instrument was used to perform a search for TeV counterparts to gamma-ray bursts. Within the Milagrito field of view 54 gamma-ray bursts at keV energies were observed by the Burst And Transient Satellite Experiment (BATSE) aboard the Compton Gamma-Ray Observatory. This paper describes the results of a preliminary analysis to search for TeV emission correlated with BATSE detected bursts. Milagrito detected an excess of events coincident both spatially and temporally with GRB 970417a, with chance probability $2.8 \times 10^{-5}$ within the BATSE error radius. No other significant correlations were detected. Since 54 bursts were examined the chance probability of observing an excess with this significance in any of these bursts is $1.5 \times 10^{-3}$. The statistical aspects and physical implications of this result are discussed., Comment: 6 pages, 5 figures, to appear in "GeV-TeV Astrophysics: Toward a Major Atmospheric Cherenkov Telescope VI," Snowbird, Utah (August, 1999)
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- 1999
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16. Instrumented Water Tanks can Improve Air Shower Detector Sensitivity
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Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
Previous works have shown that water Cherenkov detectors have superior sensitivity to those of scintillation counters as applied to detecting extensive air showers (EAS). This is in large part due to their much higher sensitivity to EAS photons which are more than five times more numerous than EAS electrons. Large area water Cherenkov detectors can be constructed relatively cheaply and operated reliably. A sparse detector array has been designed which uses these types of detectors to substantially increase the area over which the Milagro Gamma Ray Observatory collects EAS information. Improvements to the Milagro detector's performance characteristics and sensitivity derived from this array and preliminary results from a prototype array currently installed near the Milagro detector will be presented., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
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- 1999
17. Calibration of the Milagro Cosmic Ray Telescope
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Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
The Milagro detector is an air shower array which uses the water Cherenkov technique and is capable of continuously monitoring the sky at energies near 1 TeV. The detector consists of 20000 metric tons of pure water instrumented with 723 photo-multiplier tubes (PMTs). The PMTs are arranged in a two-layer structure on a lattice of 3 m spacing covering 5000 $m^2$ area. The direction of the shower is determined from the relative timing of the PMT signals, necessitating a common time reference and amplitude slewing corrections to improve the time resolution. The calibration system to provide these consists of a pulsed laser driving 30 diffusing light sources deployed in the pond to allow cross-calibration of the PMTs. The system is capable of calibrating times and the pulse-heights from the PMTs using the time-over-threshold technique. The absolute energy scale is provided using single muons passing through the detector. The description of the calibration system of the Milagro detector and its prototype Milagrito will be presented., Comment: 4 pages, submitted to the XXVI International Cosmic Ray Conference
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- 1999
18. Study of the Shadows of the Moon and the Sun with VHE Cosmic Rays
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Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
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Astrophysics - Abstract
Milagrito, a prototype for the Milagro detector, operated for 15 months in 1997-8 and collected 8.9 billion events. It was the first extensive air shower (EAS) array sensitive to showers intiated by primaries with energy below 1 TeV. The shadows of the sun and moon observed with cosmic rays can be used to study systematic pointing shifts and measure the angular resolution of EAS arrays. Below a few TeV, the paths of cosmic rays coming toward the earth are bent by the helio- and geo-magnetic fields. This is expected to distort and displace the shadows of the sun and the moon. The moon shadow, offset from the nominal (undeflected) position, has been observed with high statistical significance in Milagrito. This can be used to establish energy calibrations, as well as to search for the anti-matter content of the VHE cosmic ray flux. The shadow of the sun has also been observed with high significance., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
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- 1999
19. Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope
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Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
The Milagrito water Cherenkov telescope operated for over a year. The most probable gamma-ray energy was ~1 TeV and the trigger rate was as high as 400 Hz. We have developed an efficient technique for searching the entire sky for short duration bursts of TeV photons. Such bursts may result from "traditional" gamma-ray bursts that were not in the field-of-view of any other instruments, the evaporation of primordial black holes, or some as yet undiscovered phenomenon. We have begun to search the Milagrito data set for bursts of duration 10 seconds. Here we will present the technique and the expected results. Final results will be presented at the conference., Comment: submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
20. Milagrito Detection of TeV Emission from Mrk 501
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
The Milagro water Cherenkov detector near Los Alamos, New Mexico, has been operated as a sky monitor at energies of a few TeV between February 1997 and April 1998. Serving as a test run for the full Milagro detector, Milagrito has taken data during the strong and long-lasting 1997 flare of Mrk 501. We present results from the analysis of Mrk 501 and compare the excess and background rates with expectations from the detector simulations., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
21. Search for a TeV Component of GRBs using the Milagrito Detector
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
Observing gamma ray bursts (GRBs) in the TeV energy range can be extremely valuable in providing insight to GRB radiation mechanisms and in constraining source distances. The Milagrito detector was an air shower array which used the water Cherenkov technique to search for TeV sources. Data from this detector was analyzed to look for a TeV component of GRBs coincident with low energy -rays detected by the BATSE instrument on the Compton Gamma Ray Observatory. A sample of 54 BATSE GRBs which were in the field of view of the Milagrito detector during its lifetime (February 1997 to May 1998) was used., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
22. Detection of 6 November 1997 Ground Level Event by Milagrito
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
Solar Energetic Particles from the 6 November 1997 solar flare/CME(coronal mass ejection) with energies exceeding 10 GeV have been detected by Milagrito, a prototype of the Milagro Gamma Ray Observatory. While particle acceleration beyond 1 GeV at the Sun is well established, few data exist for protons or ions beyond 10 GeV. The Milagro observatory, a ground based water Cherenkov detector designed for observing very high energy gamma ray sources, can also be used to study the Sun. Milagrito, which operated for approximately one year in 1997/98, was sensitive to solar proton and neutron fluxes above ~5- 10 GeV. Milagrito operated in a scaler mode, which was primarily sensitive to muons, low energy photons, and electrons, and the detector operated in a mode sensitive to showers and high zenith angle muons. In its scaler mode, Milagrito registered a rate increase coincident with the 6 November 1997 ground level event observed by Climax and other neutron monitors. A preliminary analysis suggests the presence of >10 GeV particles., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
23. Status of the Milagro Gamma Ray Observatory
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
24. An All-Sky Search for Steady VHE Gamma-Ray Sources
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Astrophysics - Abstract
The Milagrito water Cherenkov detector in the Jemez Mountains near Los Alamos, New Mexico took data from February 1997 to April 1998. Milagrito served as a prototype for the larger Milagro detector, which has just begun operations. Milagrito was the first large-aperture gamma-ray detector with sensitivity to gamma rays below 1 TeV. We report here on a search for steady emission from point sources over most of the northern sky using data from Milagrito., Comment: 4 pages
- Published
- 1999
25. First results of a study of TeV emission from GRBs in Milagrito
- Author
-
McEnery, JE, Atkins, R, Benbow, W, Berley, D, Chen, ML, Coyne, DG, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, McConnell, M, McCullough, JF, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Shen, B, Shoup, A, Sinnis, C, Smith, AJ, Sullivan, GW, Tumer, T, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Milagrito, a detector sensitive to gamma-rays at TeV energies, monitored thenorthern sky during the period February 1997 through May 1998. With a largefield of view and high duty cycle, this instrument was used to perform a searchfor TeV counterparts to gamma-ray bursts. Within the Milagrito field of view 54gamma-ray bursts at keV energies were observed by the Burst And TransientSatellite Experiment (BATSE) aboard the Compton Gamma-Ray Observatory. Thispaper describes the results of a preliminary analysis to search for TeVemission correlated with BATSE detected bursts. Milagrito detected an excess ofevents coincident both spatially and temporally with GRB 970417a, with chanceprobability $2.8 \times 10^{-5}$ within the BATSE error radius. No othersignificant correlations were detected. Since 54 bursts were examined thechance probability of observing an excess with this significance in any ofthese bursts is $1.5 \times 10^{-3}$. The statistical aspects and physicalimplications of this result are discussed.
- Published
- 2000
26. First results of a study of TeV emission from GRBs in Milagrito
- Author
-
Miller, RS, Atkins, R, Benbow, W, Berley, D, Chen, ML, Coyne, DG, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, McConnell, M, McCullough, JF, McEnery, JE, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Shen, B, Shoup, A, Sinnis, C, Smith, AJ, Sullivan, GW, Tumer, T, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Milagrito, a detector sensitive to gamma-rays at TeV energies, monitored thenorthern sky during the period February 1997 through May 1998. With a largefield of view and high duty cycle, this instrument was used to perform a searchfor TeV counterparts to gamma-ray bursts. Within the Milagrito field of view 54gamma-ray bursts at keV energies were observed by the Burst And TransientSatellite Experiment (BATSE) aboard the Compton Gamma-Ray Observatory. Thispaper describes the results of a preliminary analysis to search for TeVemission correlated with BATSE detected bursts. Milagrito detected an excess ofevents coincident both spatially and temporally with GRB 970417a, with chanceprobability $2.8 \times 10^{-5}$ within the BATSE error radius. No othersignificant correlations were detected. Since 54 bursts were examined thechance probability of observing an excess with this significance in any ofthese bursts is $1.5 \times 10^{-3}$. The statistical aspects and physicalimplications of this result are discussed.
- Published
- 2000
27. Instrumented Water Tanks can Improve Air Shower Detector Sensitivity
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Previous works have shown that water Cherenkov detectors have superiorsensitivity to those of scintillation counters as applied to detectingextensive air showers (EAS). This is in large part due to their much highersensitivity to EAS photons which are more than five times more numerous thanEAS electrons. Large area water Cherenkov detectors can be constructedrelatively cheaply and operated reliably. A sparse detector array has beendesigned which uses these types of detectors to substantially increase the areaover which the Milagro Gamma Ray Observatory collects EAS information.Improvements to the Milagro detector's performance characteristics andsensitivity derived from this array and preliminary results from a prototypearray currently installed near the Milagro detector will be presented.
- Published
- 1999
28. Calibration of the Milagro Cosmic Ray Telescope
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
The Milagro detector is an air shower array which uses the water Cherenkovtechnique and is capable of continuously monitoring the sky at energies near 1TeV. The detector consists of 20000 metric tons of pure water instrumented with723 photo-multiplier tubes (PMTs). The PMTs are arranged in a two-layerstructure on a lattice of 3 m spacing covering 5000 $m^2$ area. The directionof the shower is determined from the relative timing of the PMT signals,necessitating a common time reference and amplitude slewing corrections toimprove the time resolution. The calibration system to provide these consistsof a pulsed laser driving 30 diffusing light sources deployed in the pond toallow cross-calibration of the PMTs. The system is capable of calibrating timesand the pulse-heights from the PMTs using the time-over-threshold technique.The absolute energy scale is provided using single muons passing through thedetector. The description of the calibration system of the Milagro detector andits prototype Milagrito will be presented.
- Published
- 1999
29. Status of the Milagro Gamma Ray Observatory
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
The Milagro Gamma Ray Observatory is the world's first large-area waterCherenkov detector capable of continuously monitoring the sky at TeV energies.Located in northern New Mexico, Milagro will perform an all sky survey of theNorthern Hemisphere at energies between ~250 GeV and 50 TeV. With a high dutycycle, large detector area (~5000 square meters), and a wide field-of-view (~1sr), Milagro is uniquely capable of searching for transient and DC sources ofhigh-energy gamma-ray emission. Milagro has been operating since February,1999. The current status of the Milagro Observatory and initial results will bediscussed.
- Published
- 1999
30. Study of the Shadows of the Moon and the Sun with VHE Cosmic Rays
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Milagrito, a prototype for the Milagro detector, operated for 15 months in1997-8 and collected 8.9 billion events. It was the first extensive air shower(EAS) array sensitive to showers intiated by primaries with energy below 1 TeV.The shadows of the sun and moon observed with cosmic rays can be used to studysystematic pointing shifts and measure the angular resolution of EAS arrays.Below a few TeV, the paths of cosmic rays coming toward the earth are bent bythe helio- and geo-magnetic fields. This is expected to distort and displacethe shadows of the sun and the moon. The moon shadow, offset from the nominal(undeflected) position, has been observed with high statistical significance inMilagrito. This can be used to establish energy calibrations, as well as tosearch for the anti-matter content of the VHE cosmic ray flux. The shadow ofthe sun has also been observed with high significance.
- Published
- 1999
31. Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
The Milagrito water Cherenkov telescope operated for over a year. The mostprobable gamma-ray energy was ~1 TeV and the trigger rate was as high as 400Hz. We have developed an efficient technique for searching the entire sky forshort duration bursts of TeV photons. Such bursts may result from "traditional"gamma-ray bursts that were not in the field-of-view of any other instruments,the evaporation of primordial black holes, or some as yet undiscoveredphenomenon. We have begun to search the Milagrito data set for bursts ofduration 10 seconds. Here we will present the technique and the expectedresults. Final results will be presented at the conference.
- Published
- 1999
32. Detection of 6 November 1997 Ground Level Event by Milagrito
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Solar Energetic Particles from the 6 November 1997 solar flare/CME(coronalmass ejection) with energies exceeding 10 GeV have been detected by Milagrito,a prototype of the Milagro Gamma Ray Observatory. While particle accelerationbeyond 1 GeV at the Sun is well established, few data exist for protons or ionsbeyond 10 GeV. The Milagro observatory, a ground based water Cherenkov detectordesigned for observing very high energy gamma ray sources, can also be used tostudy the Sun. Milagrito, which operated for approximately one year in 1997/98,was sensitive to solar proton and neutron fluxes above ~5- 10 GeV. Milagritooperated in a scaler mode, which was primarily sensitive to muons, low energyphotons, and electrons, and the detector operated in a mode sensitive toshowers and high zenith angle muons. In its scaler mode, Milagrito registered arate increase coincident with the 6 November 1997 ground level event observedby Climax and other neutron monitors. A preliminary analysis suggests thepresence of >10 GeV particles.
- Published
- 1999
33. Milagrito Detection of TeV Emission from Mrk 501
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
The Milagro water Cherenkov detector near Los Alamos, New Mexico, has beenoperated as a sky monitor at energies of a few TeV between February 1997 andApril 1998. Serving as a test run for the full Milagro detector, Milagrito hastaken data during the strong and long-lasting 1997 flare of Mrk 501. We presentresults from the analysis of Mrk 501 and compare the excess and backgroundrates with expectations from the detector simulations.
- Published
- 1999
34. Search for a TeV Component of GRBs using the Milagrito Detector
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
Observing gamma ray bursts (GRBs) in the TeV energy range can be extremelyvaluable in providing insight to GRB radiation mechanisms and in constrainingsource distances. The Milagrito detector was an air shower array which used thewater Cherenkov technique to search for TeV sources. Data from this detectorwas analyzed to look for a TeV component of GRBs coincident with low energy-rays detected by the BATSE instrument on the Compton Gamma Ray Observatory. Asample of 54 BATSE GRBs which were in the field of view of the Milagritodetector during its lifetime (February 1997 to May 1998) was used.
- Published
- 1999
35. An All-Sky Search for Steady VHE Gamma-Ray Sources
- Author
-
Atkins, R, Benbow, W, Berley, D, Chen, M-L, Coyne, DG, Delay, RS, Dingus, BL, Dorfan, DE, Ellsworth, RW, Evans, D, Falcone, A, Fleysher, L, Fleysher, R, Gisler, G, Goodman, JA, Haines, TJ, Hoffman, CM, Hugenberger, S, Kelley, LA, Leonor, I, Macri, J, McConnell, M, McCullough, JF, McEnery, JE, Miller, RS, Mincer, AI, Morales, MF, Nemethy, P, Ryan, JM, Schneider, M, Shen, B, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Thompson, TN, Tumer, OT, Wang, K, Wascko, MO, Westerhoff, S, Williams, DA, Yang, T, and Yodh, GB
- Subjects
astro-ph - Abstract
The Milagrito water Cherenkov detector in the Jemez Mountains near LosAlamos, New Mexico took data from February 1997 to April 1998. Milagrito servedas a prototype for the larger Milagro detector, which has just begunoperations. Milagrito was the first large-aperture gamma-ray detector withsensitivity to gamma rays below 1 TeV. We report here on a search for steadyemission from point sources over most of the northern sky using data fromMilagrito.
- Published
- 1999
36. Sodium imaging as a marker of tissue injury in patients with multiple sclerosis
- Author
-
Inglese, M., Oesingmann, N., Zaaraoui, W., Ranjeva, J.P., and Fleysher, L.
- Published
- 2013
- Full Text
- View/download PDF
37. Lower cortical gamma-aminobutyric acid level contributes to connectivity in sensory-motor inter-connected regions in progressive MS
- Author
-
Droby, A, Fleysher, L, Petracca, M, Podranski, K, Xu, J, Fabian, M, Marjańska, M, and Inglese, M.
- Subjects
Multiple sclerosis ,Functional connectivity ,functional connectivity ,gamma-aminobutyric acid (GABA) ,multiple sclerosis ,rs-fMRI, MR spectroscopy ,Gamma-aminobutyric acid (GABA) ,MR spectroscopy ,rs-fMRI - Published
- 2020
38. Streamline density and lesion volume reveal a postero–anterior gradient of corpus callosum damage in multiple sclerosis
- Author
-
Petracca, M., primary, Schiavi, S., additional, Battocchio, M., additional, El Mendili, M. M., additional, Fleysher, L., additional, Daducci, A., additional, and Inglese, M., additional
- Published
- 2020
- Full Text
- View/download PDF
39. 0090 Stage-Specific Sleep Disruption and its Effect on Spatial Navigational Memory
- Author
-
Parekh, A A, primary, Kam, K, primary, Mullins, A, primary, Fakhoury, A, primary, Castillo, B, primary, Roberts, Z, primary, Fleysher, L, primary, Rapoport, D M, primary, Ayappa, I, primary, and Varga, A, primary
- Published
- 2020
- Full Text
- View/download PDF
40. Observation and Spectral Measurements of the Crab Nebula with Milagro
- Author
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Abdo, A. A, Allen, B. T, Aune, T, Benbow, W, Berley, D, Chen, C, Christopher, G. E, DeYoung, T, Dingus, B. L, Falcone, A, Fleysher, L, Fleysher, R, Gonzalez, M. M, Goodman, J. A, Gordo, J. B, Hays, E, Hoffman, C. M, Huntemeyer, P. H, Kolterman, B. E, Linnemann, J. T, McEnery, J. E, Morgan, T, Mincer, A. I, and Nemethy, P
- Subjects
Astrophysics - Abstract
The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is believed to be caused by inverse-Compton up-scattering scattering of ambient photons by an energetic electron population. The location of a Te V steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fit.
- Published
- 2011
41. Instrumented Water Tanks can Improve Air Shower Detector Sensitivity
- Author
-
Atkins, Robert W., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., Mcconnell, M., Mccullough, J. F., Mcenery, J. E., Miller, R. S., Allen Mincer, Morales, Miguel F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Physics::Instrumentation and Detectors ,astro-ph ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,FOS: Physical sciences ,High Energy Physics::Experiment ,Astrophysics - Abstract
Previous works have shown that water Cherenkov detectors have superior sensitivity to those of scintillation counters as applied to detecting extensive air showers (EAS). This is in large part due to their much higher sensitivity to EAS photons which are more than five times more numerous than EAS electrons. Large area water Cherenkov detectors can be constructed relatively cheaply and operated reliably. A sparse detector array has been designed which uses these types of detectors to substantially increase the area over which the Milagro Gamma Ray Observatory collects EAS information. Improvements to the Milagro detector's performance characteristics and sensitivity derived from this array and preliminary results from a prototype array currently installed near the Milagro detector will be presented., 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 2017
42. Detection of 6 November 1997 Ground Level Event by Milagrito
- Author
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Atkins, R., Benbow, W., Berley, D., Chen, M. -L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., McConnell, M., McCullough, J. F., McEnery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
astro-ph ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Physics::Space Physics ,FOS: Physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,High Energy Physics::Experiment ,Astrophysics ,Nuclear Experiment - Abstract
Solar Energetic Particles from the 6 November 1997 solar flare/CME(coronal mass ejection) with energies exceeding 10 GeV have been detected by Milagrito, a prototype of the Milagro Gamma Ray Observatory. While particle acceleration beyond 1 GeV at the Sun is well established, few data exist for protons or ions beyond 10 GeV. The Milagro observatory, a ground based water Cherenkov detector designed for observing very high energy gamma ray sources, can also be used to study the Sun. Milagrito, which operated for approximately one year in 1997/98, was sensitive to solar proton and neutron fluxes above ~5- 10 GeV. Milagrito operated in a scaler mode, which was primarily sensitive to muons, low energy photons, and electrons, and the detector operated in a mode sensitive to showers and high zenith angle muons. In its scaler mode, Milagrito registered a rate increase coincident with the 6 November 1997 ground level event observed by Climax and other neutron monitors. A preliminary analysis suggests the presence of >10 GeV particles., 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 2017
43. Cortical sensorimotor alterations classify clinical phenotype and putative genotype of spasmodic dysphonia
- Author
-
Battistella, G., primary, Fuertinger, S., additional, Fleysher, L., additional, Ozelius, L. J., additional, and Simonyan, K., additional
- Published
- 2016
- Full Text
- View/download PDF
44. A custom-made MR-compatible passive device for FMRI investigations in neural correlates of ankle movements during motor tasks
- Author
-
Levrero, F., primary, Bellini, A., additional, Iandolo, R., additional, Marre, I., additional, Bommarito, G., additional, Oesingmann, N., additional, Fleysher, L., additional, Mancardi, G., additional, Casadio, M., additional, and Inglese, M., additional
- Published
- 2016
- Full Text
- View/download PDF
45. Neural correlates of ankle movements during different motor tasks: A feasibility study
- Author
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Iandolo, R., primary, Marre, I., additional, Bellini, A., additional, Bommarito, G., additional, Oesingmann, N., additional, Fleysher, L., additional, Levrero, F., additional, Mancardi, G., additional, Casadio, M., additional, and Inglese, M., additional
- Published
- 2015
- Full Text
- View/download PDF
46. Ultra-High-Field MRI Visualization of Cortical Multiple Sclerosis Lesions with T2 and T2*: A Postmortem MRI and Histopathology Study
- Author
-
Jonkman, L.E., primary, Klaver, R., additional, Fleysher, L., additional, Inglese, M., additional, and Geurts, J.J.G., additional
- Published
- 2015
- Full Text
- View/download PDF
47. Discovery of TeV gamma-ray emission from the cygnus region of the galaxy
- Author
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Abdu, A. A., Gebauer, I., Linnemann, J. T., Allen, B., Chen, C., Delay, R. S., Yodh, G. B., Berley, D., Blaufuss, E., Goodman, J. A., Hays, E., Lansdell, C. P., Noyes, D., Smith, A. J., Sullivan, G. W., Vasileiou, V., Casanova, S., Dingus, B. L., Huffman, C. M., Samuelson, F. W., Sinnis, G., Walker, G. P., Xu, X. W., Coyne, D. G., Kelley, L. A., Saz Parkinson, P. M., Schneider, M., Williams, D. A., Ellsworth, R. W., Fleysher, L., Fleysher, R., Kolterman, B. E., Mincer, A. I., Nemethy, P., Gonzalez, M. M., Mcenery, J. E., Moskalenko, I. V., Ryan, J. M., Shoup, A., and Strong, A. W.
- Subjects
Acceleration of particles ,observations [Gamma rays] ,Physics ,ddc:530 ,Gamma rays: observations ,Cosmic rays - Published
- 2007
48. TeV Observations of Markarian 501 with the Milagrito Water Cerenkov Detector
- Author
-
Atkins, R., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Delay, R. S., Brenda Dingus, Dorfan, D. E., Ellsworth, R. W., Espinoza, C., Evans, D., Falcone, A., Fleysher, L., Pleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Mcconnell, M., Mccullough, J. F., Mcenery, J. E., Miller, R. S., Mincer, A. I., Morales, M. F., Murray, M. M., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, C., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Abstract
The Milagrito water Cerenkov detector near Los Alamos, New Mexico, was operated as a sky monitor at energies of a few TeV between 1997 February and 1998 May, including the period of the strong, long-lasting 1997 flare of Markarian 501. Milagrito served as a test run for the full Milagro detector. An event excess with a significance of 3.7 sigma from Markarian 501 was observed, in agreement with expectations.
- Published
- 1999
49. Calibration of the Milagro Cosmic Ray Telescope
- Author
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Atkins, Robert W., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., Mcconnell, M., Mccullough, J. F., Mcenery, J. E., Miller, R. S., Allen Mincer, Morales, Miguel F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
astro-ph ,Physics::Instrumentation and Detectors ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,High Energy Physics::Experiment ,Astrophysics - Abstract
The Milagro detector is an air shower array which uses the water Cherenkov technique and is capable of continuously monitoring the sky at energies near 1 TeV. The detector consists of 20000 metric tons of pure water instrumented with 723 photo-multiplier tubes (PMTs). The PMTs are arranged in a two-layer structure on a lattice of 3 m spacing covering 5000 $m^2$ area. The direction of the shower is determined from the relative timing of the PMT signals, necessitating a common time reference and amplitude slewing corrections to improve the time resolution. The calibration system to provide these consists of a pulsed laser driving 30 diffusing light sources deployed in the pond to allow cross-calibration of the PMTs. The system is capable of calibrating times and the pulse-heights from the PMTs using the time-over-threshold technique. The absolute energy scale is provided using single muons passing through the detector. The description of the calibration system of the Milagro detector and its prototype Milagrito will be presented., 4 pages, submitted to the XXVI International Cosmic Ray Conference
- Published
- 1999
50. Search for a TeV Component of GRBs using the Milagrito Detector
- Author
-
Atkins, Robert W., Benbow, W., Berley, D., Chen, M. L., Coyne, D. G., Delay, R. S., Dingus, B. L., Dorfan, D. E., Ellsworth, R. W., Evans, D., Falcone, A., Fleysher, L., Fleysher, R., Gisler, G., Goodman, J. A., Haines, T. J., Hoffman, C. M., Hugenberger, S., Kelley, L. A., Leonor, I., Macri, J., Mcconnell, M., Mccullough, J. F., Mcenery, J. E., Miller, R. S., Allen Mincer, Morales, Miguel F., Nemethy, P., Ryan, J. M., Schneider, M., Shen, B., Shoup, A., Sinnis, G., Smith, A. J., Sullivan, G. W., Thompson, T. N., Tumer, O. T., Wang, K., Wascko, M. O., Westerhoff, S., Williams, D. A., Yang, T., and Yodh, G. B.
- Subjects
Physics::Instrumentation and Detectors ,astro-ph ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,High Energy Physics::Experiment ,Astrophysics - Abstract
Observing gamma ray bursts (GRBs) in the TeV energy range can be extremely valuable in providing insight to GRB radiation mechanisms and in constraining source distances. The Milagrito detector was an air shower array which used the water Cherenkov technique to search for TeV sources. Data from this detector was analyzed to look for a TeV component of GRBs coincident with low energy -rays detected by the BATSE instrument on the Compton Gamma Ray Observatory. A sample of 54 BATSE GRBs which were in the field of view of the Milagrito detector during its lifetime (February 1997 to May 1998) was used., Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt Lake City
- Published
- 1999
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