Observation and Spectral Measurements of the Crab Nebula With Milagro

Abdo, A. A.; Allen, B.; Atkins, R.; Aune, T.; Benbow, W.; Berley, D.; Blaufuss, E.; Bonamente, E.; Bussóns, J.; Chen, C.; Christopher, G.; Coyne, D. G.; DeYoung, T.; Dingus, B. L.; Dorfan, D. E.; Falcone, A.; Fleysher, Lazar; Fleysher, Roman; Galbraith-Frew, Jessica; González, M. M.; Goodman, J. A.; Haines, T. J.; Hays, E.; Hoffman, C. M.; Hüntemeyer, P.; Kelley, L. A.; Kolterman, B. E.; Lansdell, C. P.; Linnemann, J.; McCullough, J. F.; McEnery, J. E.; Morgan, T.; Mincer, A. I.; Morales, M. F.; Némethy, P.; Noyes, D.; Pretz, J.; Ryan, J. M.; Samuelson, F. W.; Parkinson, P. M. Saz; Shoup, A.; Sinnis, G.; Smith, A. J.; Sullivan, G. W.; Vasileiou, V.; Walker, G.; Wascko, M. O.; Williams, D. A.; Westerhoff, S.; Yodh, G.

doi:10.1088/0004-637x/750/1/63

Cited by 45 publications

(52 citation statements)

References 21 publications

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“…In particular, we use the Mrk 421 spectra measured by Milagro and HEGRA CT1 in the same observation period considered for the correlations (see Aharonian et al 2003;Abdo et al 2014). We also use the average Milagro and HEGRA CT1 Crab spectra reported in Abdo et al (2012)…”

Section: 2mentioning

confidence: 99%

“…In order to obtain the parameter values (a, b and σ A ) that reproduce the VHE γ-ray / X-ray lineal correlation (see Section 3), the power law ǫ syn γ,c < ǫ γ of the synchrotron spectrum is used to describe the X-ray flux and the power law ǫ ssc γ,c < ǫ γ of the inverse Compton spectrum to describe VHE γ-ray flux. In addition, the units of synchrotron spectrum are converted from erg/cm 2 /s to counts/s using the online WebPIMMS 7 tool for a hydrogen column density of 1.61 × 10 20 cm −28 , and the units of inverse Compton spectrum are converted to Crab units with the Crab spectrum as measured by Milagro (Abdo et al 2012). For the electron spectral index, p 2 , a value of 3.6 is assumed.…”

Section: X-ray / Tev γRay Correlationmentioning

confidence: 99%

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Reconcilement of VHE γ -ray/X-ray correlation studies in Mrk 421 and break-down at high fluxes

González

Patricelli

Fraija

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Multi-wavelength campaigns have been carried out to study the correlation between the very high energy (VHE) γ-ray and the X-ray emissions in blazars but, no conclusive results have been achieved yet. In this paper, we add Milagro data to the existing VHE γ-ray data from HEGRA-CT1 and Whipple and test the consistency and robustness of the reported correlation between VHE γ-ray and X-ray fluxes in Mrk 421. We found that at monthly time scale the correlation is robust, consistent between instruments and described as a linear function. Furthermore, most of the fluxes on shorter time scales are consistent with the correlation within 3 σ A even, where σ A is an estimated intrinsic scatter. However, a break-down of the correlation becomes clearly evident at high states of activity with fluxes 2.5 × 10 −10 cm −2 s −1 at energies above 400 GeV independently of the time scale, observational period or instrument, even for single flares, the X-ray and VHE γ-ray emissions lie on the correlation until the VHE γray flux reaches values higher than the one mentioned above. We have interpreted our results within the one-zone synchrotron self-Compton model. We found that describing a single and unique γ-ray/X-ray correlation strongly narrows the range of possible values of the magnetic field B when a constant value of the spectral index along the correlation is assumed.

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Section: 2mentioning

confidence: 99%

Section: X-ray / Tev γRay Correlationmentioning

confidence: 99%

Reconcilement of VHE γ -ray/X-ray correlation studies in Mrk 421 and break-down at high fluxes

González

Patricelli

Fraija

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The events in a circular area centered on each bin whin an angular radius of 2σ are summed after weighting. Then the significances can be obtained by substituting the weighted N on and N o f f into the Li-Ma formulae [3,4].…”

Section: The Weighted Methodsmentioning

confidence: 99%

“…To improve the sensitivity, weighted methods are adopted by MILAGRO and ARGO-YBJ experiments. MILAGRO adopted a extension of the Li-Ma formula (17) [3], while, ARGO-YBJ adopted a extension of the Li-Ma formula (9) [4] to calculate the significance. Recently, HAWC adopted the likelihood method to calculate the significance [5], and ARGO-YBJ also proposed the chi-squared method.…”

Section: Introductionmentioning

confidence: 99%

A study of the methods for signal significance estimation in ground-based gamma-ray detectors

Nan¹,

Chen²

2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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Searching for new astrophysical sources is an important physical goal of current and nearly further ground-based gamma-ray detectors, such as HAWC, LHAASO and CTA. The gamma-ray signal appears as an excess number of events. The significance of the excess is estimated using statistical method and is used to determine whether to accept the signal or not. Up to now, four main statistical methods, including the classical Li-Ma method, the weighted method, the likelihood method and the chi-squared method, have been used in the majority of ground-based extensive air shower (EAS) experiments, such as Tibet ASγ, MILAGRO, ARGO-YBJ and HAWC. While these methods are not well tested for the accuracy in previous works. In this work, we develop a standard to test the accuracy of different methods basing on different experimental conditions. We find some problems for some methods, which have been already used in experiment data analysis. Finally, we obtain the limitation of different methods and provide application conditions for different methods, respectively. Additionally, we also test the superiority of different statistical methods and provide our best recommendations for different physical analyses.

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“…A second method of observing TeV gamma rays, known as the water Cherenkov technique, was developed at the Milagro Observatory [6], which operated from 2000 to 2008 in the mountains above Los Alamos, NM. Rather than image the Cherenkov light from extensive air showers, the Milagro detector was designed to directly sample shower particles at ground level using a large pool of water in an optically isolated reservoir.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the high altitude water Cherenkov detector to sources of multi-TeV gamma rays

Abeysekara

Alfaro

Álvarez

et al. 2013

Astroparticle Physics

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199

163

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The High Altitude Water Cherenkov (HAWC) observatory is an array of large water Cherenkov detectors sensitive to gamma rays and hadronic cosmic rays in the energy band between 100 GeV and 100 TeV. The observatory will be used to measure high-energy protons and cosmic rays via detection of the energetic secondary particles reaching the ground when one of these particles interacts in the atmosphere above the detector. HAWC is under construction at a site 4100 meters above sea level on the northern slope of the volcano Sierra Negra, which is located in central Mexico at 19• N latitude. It is scheduled for completion in 2014. In this paper we estimate the sensitivity of the HAWC instrument to point-like and extended sources of gamma rays. The source fluxes are modeled using both unbroken power laws and power laws with exponential cutoffs. HAWC, in one year, is sensitive to point sources with integral powerlaw spectra as low as 5 × 10 −13 cm −2 sec −1 above 2 TeV (approximately 50 mCrab) over 5 sr of the sky. This is a conservative estimate based on simple event parameters and is expected to improve as the data analysis techniques are refined. We discuss known TeV sources and the scientific contributions that HAWC can make to our understanding of particle acceleration in these sources.

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Observation and Spectral Measurements of the Crab Nebula With Milagro

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

Cited by 45 publications

References 21 publications

Reconcilement of VHE γ -ray/X-ray correlation studies in Mrk 421 and break-down at high fluxes

Reconcilement of VHE γ -ray/X-ray correlation studies in Mrk 421 and break-down at high fluxes

A study of the methods for signal significance estimation in ground-based gamma-ray detectors

Sensitivity of the high altitude water Cherenkov detector to sources of multi-TeV gamma rays

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