Detection of TeV photons from the active galaxy Markarian 421

Punch, M.; Akerlof, C.; Cawley, M. F.; Chantell, M.; Fegan, D. J.; Fennell, S.; Gaidos, J. A.; Hagan, J.; Hillas, A. M.; Jiang, Yao; Kerrick, A. D.; Lamb, R. C.; Lawrence, M. A.; Lewis, D. A.; Meyer, D. I.; Mohanty, G.; O’Flaherty, K. S.; Reynolds, P. T.; Rovero, A. C.; Schubnell, M.; Sembroski, G. H.; Weekes, T. C.; Whitaker, T.; Wilson, C.

doi:10.1038/358477a0

Cited by 754 publications

(396 citation statements)

References 12 publications

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“…In addition, observations from ground-based airČerenkov telescopes indicate that in more than ten of these sources the γ-ray spectrum extends above a TeV [31]. The non-thermal emission of these powerful objects shows a triple-peak structure in the overall spectral energy distribution.…”

Section: A Active Galactic Nucleimentioning

confidence: 99%

High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

Anchordoqui

Hooper

Sarkar

et al. 2008

Astroparticle Physics

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Ongoing experimental efforts to detect cosmic sources of high energy neutrinos are guided by the expectation that astrophysical accelerators of cosmic ray protons would also generate neutrinos through interactions with ambient matter and/or photons. However there will be a reduction in the predicted neutrino flux if cosmic ray sources accelerate not only protons but also significant numbers of heavier nuclei, as is indicated by recent air shower data. We consider plausible extragalactic sources such as active galactic nuclei, gamma-ray bursts and starburst galaxies and demand consistency with the observed cosmic ray composition and energy spectrum at Earth after allowing for propagation through intergalactic radiation fields. This allows us to calculate the expected neutrino fluxes from the sources, normalized to the observed cosmic ray spectrum. We find that the likely signals are still within reach of next generation neutrino telescopes such as IceCube.PACS numbers: 95.85. Ry, 98.70.Rz, 98.54.Cm, 98.54.Ep

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Section: A Active Galactic Nucleimentioning

confidence: 99%

High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

Anchordoqui

Hooper

Sarkar

et al. 2008

Astroparticle Physics

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“…In the more general context of blazars, Mrk 421 belongs to a subclass of the so-called high-energypeaked BL Lac (HBL) objects, relatively low luminosity sources with both peaks located at relatively high energies (respectively at ∼1 keV and ∼100 GeV). Mrk 421 is among the closest and most comprehensively studied objects of the HBL class and is also the first extragalactic source detected in the very high energy (VHE) γ-ray band (E > 100GeV; Punch et al 1992).…”

Section: Introductionmentioning

confidence: 99%

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Baloković¹,

Paneque²,

Madejski³

et al. 2016

ApJ

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We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy(VHE) γ-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep 3 G » power law, with no evidence for an exponential cutoff or additional hard components up to ∼80keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure that relates to the two bumps of the broadband SED. In each bump, the variability increases with energy, which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in situ electron acceleration and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states.

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“…Since the discovery of TeV g-rays from BL Lac objects Mrk 421 (Punch et al 1992) and Mrk 501 (Quinn et al 1996), detailed very high energy observations of these nearby blazars (z p , ) have been made. Measurements of flux var-0.031 z p 0.034 iation with time, particularly simultaneous measurements at several wavelengths, constrain models of particle acceleration and g-ray production in the jets.…”

Section: Introductionmentioning

confidence: 99%

Cutoff in the T[CLC]e[/CLC]V Energy Spectrum of Markarian 421 during Strong Flares in 2001

Krennrich

Badran

Bond

et al. 2001

The Astrophysical Journal

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Exceptionally strong and long-lasting flaring activity of the blazar Mrk 421 occurred between 2001 January and March. Based on the excellent signal-to-noise ratio of the data, we derive the energy spectrum between 260 GeV and 17 TeV with unprecedented statistical precision. The spectrum is not well described by a simple power law even with a curvature term. Instead, the data can be described by a power law with exponential cutoff: with TeV. Mrk 421 is the second g-ray blazar thatunambiguously exhibits an absorption-like feature in its spectral energy distribution at 3-6 TeV. Subject headings: BL Lacertae objects: individual (Markarian 421) -gamma rays: observationsSince the discovery of TeV g-rays from BL Lac objects Mrk 421 (Punch et al. 1992) and Mrk 501 (Quinn et al. 1996), detailed very high energy observations of these nearby blazars (z p , ) have been made. Measurements of flux var-0.031 z p 0.034 iation with time, particularly simultaneous measurements at several wavelengths, constrain models of particle acceleration and g-ray production in the jets. Spectral energy density measurements constrain both the models of the jets and of the infrared photon density in the intervening intergalactic medium. The possibility of absorption of g-rays by IR radiation has been predicted for some time (Nikishov 1962;Gould & Schrèder 1967;Stecker, De Jager, & Salamon 1992), and implications of recent observations have been discussed (see, e.g., Biller et al. 1998;Stanev & Franceschini 1998;Vassiliev 1999).The general picture that has emerged for the spectral energy density of emitted radiation from BL Lac objects has two components: a lower one with energies extended up to about

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Detection of TeV photons from the active galaxy Markarian 421

Cited by 754 publications

References 12 publications

High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Cutoff in the T[CLC]e[/CLC]V Energy Spectrum of Markarian 421 during Strong Flares in 2001

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