Twelve-hour spikes from the Crab Pevatron

Balbo, Matteo; Walter, R.; Ferrigno, C.; Bordas, P.

doi:10.1051/0004-6361/201015980

Cited by 46 publications

(56 citation statements)

References 15 publications

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“…On 22 September 2010, a gamma-ray flare was discovered for the first time from the direction of the Crab nebula with the AGILE pairproduction telescope (Tavani et al 2011), offering a rare opportunity to follow in detail the evolution of a flaring region in the nebula. The flare was confirmed with Fermi/LAT (Abdo et al 2011) indicating a variability time-scale as short as 12 h (Balbo et al 2011). …”

Section: Introductionmentioning

confidence: 80%

“…The observed variability time-scale of about 24 h (Balbo et al 2011) constrains the size of the emitting region to be smaller than r < t var c = 3 × 10 15 cm (t var /10 5 s) = 0 . 1 (t var /10 5 s).…”

Section: Connection To the High-energy Flarementioning

confidence: 86%

“…The exact mechanism by which the spin-down energy is released, transported, and dissipated remains poorly understood (cf., Chedia et al 1997;Hester et al 1998;Begelman 1999;Lyutikov 2003;Spitkovsky & Arons 2004;Komissarov & Lyubarsky 2004) -with shocks, plasma instabilities, pair acceleration, Poynting flux, and magnetic field all suggested to affect the evolution of the wind.…”

Section: Introductionmentioning

confidence: 99%

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VLBI imaging of a flare in the Crab nebula: more than just a spot

Lobanov

Horns

Muxlow

2011

A&A

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We report on very long baseline interferometry (VLBI) observations of the radio emission from the inner region of the Crab nebula, made at 1.6 GHz and 5 GHz after a recent high-energy flare in this object. The 5 GHz data have provided only upper limits of 0.4 milli-Jansky (mJy) on the flux density of the pulsar and 0.4 mJy/beam on the brightness of the putative flaring region. The 1.6 GHz data have enabled imaging the inner regions of the nebula on scales of up to ≈40 . The emission from the inner "wisps" is detected for the first time with VLBI observations. A likely radio counterpart (designated "C1") of the putative flaring region observed with Chandra and HST is detected in the radio image, with an estimated flux density of 0.5 ± 0.3 mJy and a size of 0 . 2-0 . 6. Another compact feature ("C2") is also detected in the VLBI image closer to the pulsar, with an estimated flux density of 0.4 ± 0.2 mJy and a size smaller than 0 . 2. Combined with the broad-band SED of the flare, the radio properties of C1 yield a lower limit of ≈0.5 mG for the magnetic field and a total minimum energy of 1.2 × 10 41 erg vested in the flare (corresponding to using about 0.2% of the pulsar spin-down power). The 1.6 GHz observations provide upper limits for the brightness (0.2 mJy/beam) and total flux density (0.4 mJy) of the optical Knot 1 located at 0 . 6 from the pulsar. The absolute position of the Crab pulsar is determined, and an estimate of the pulsar proper motion (μ α = −13.0 ± 0.2 mas/yr, μ δ = +2.9 ± 0.1 mas/yr) is obtained.

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Section: Introductionmentioning

confidence: 80%

Section: Connection To the High-energy Flarementioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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VLBI imaging of a flare in the Crab nebula: more than just a spot

Lobanov

Horns

Muxlow

2011

A&A

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“…New puzzles for our understanding of the Crab have been posed by the detection of three bright gamma-ray flares by the AGILE satellite and the Large Area Telescope (LAT) on board the Fermi satellite between 2007 and 2010 ( Abdo et al 2011a; Tavani et al 2011). During these flares the unpulsed component of the gamma-ray flux increased by a factor of ≈10 on timescales as short as 12 hr (Balbo et al 2011), while the period and flux of the pulsed component remained stable.…”

Section: Introductionmentioning

confidence: 99%

Gamma-Ray Activity in the Crab Nebula: The Exceptional Flare of 2011 April

Buehler

Scargle

Blandford

et al. 2012

ApJ

198

256

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The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab Nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of ≈11 lt-yr across, doubled its gamma-ray flux within eight hours. The peak photon flux was (186 ± 6) × 10 −7 cm −2 s −1 above 100 MeV, which corresponds to a 30-fold increase compared to the average value. During the flare, a new component emerged in the spectral energy distribution, which peaked at an energy of (375 ± 26) MeV at flare maximum. The observations imply that the emission region was likely relativistically beamed toward us and that variations in its motion are responsible for the observed spectral variability.

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“…PeV photons, on the other hand, have an absorption length considerably larger than the neutron decay distance and will maintain an unmodified energy spectrum that more resembles the injected spectrum at the source. PeV photons could still plausibly be produced by nonhadronic processes, such as inverse-Compton scattering from a high-energy electron population in or near Galactic sources (see, e.g., Schlickeiser 1989;Balbo et al 2011;Nozawa et al 2011;Kohri et al 2012), although there are flux upper limits in the northern (Chantell et al 1997;Borione et al 1998;Feng et al 2015b;Kang et al 2015aKang et al , 2015b and southern (Aartsen et al 2013c) hemispheres. These photon limits, except for (Kang et al 2015a), are for energies of order 1 PeV or below, whereas this analysis is most sensitive at energies above 100 PeV.…”

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confidence: 99%

Search for Sources of High-Energy Neutrons With Four Years of Data From the Icetop Detector

Aartsen¹,

Abraham²,

Ackermann³

et al. 2016

ApJ

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IceTop is an air-shower array located on the Antarctic ice sheet at the geographic South Pole. IceTop can detect an astrophysical flux of neutrons from Galactic sources as an excess of cosmic-ray air showers arriving from the source direction. Neutrons are undeflected by the Galactic magnetic field and can typically travel 10 (E/PeV) pc before decay. Two searches are performed using 4 yr of the IceTop data set to look for a statistically significant excess of events with energies above 10 PeV (10 16 eV) arriving within a small solid angle. The all-sky search method covers from −90°to approximately −50°in declination. No significant excess is found. A targeted search is also performed, looking for significant correlation with candidate sources in different target sets. This search uses a higher-energy cut (100 PeV) since most target objects lie beyond 1 kpc. The target sets include pulsars with confirmed TeV energy photon fluxes and high-mass X-ray binaries. No significant correlation is found for any target set. Flux upper limits are determined for both searches, which can constrain Galactic neutron sources and production scenarios.

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Twelve-hour spikes from the Crab Pevatron

Cited by 46 publications

References 15 publications

VLBI imaging of a flare in the Crab nebula: more than just a spot

VLBI imaging of a flare in the Crab nebula: more than just a spot

Gamma-Ray Activity in the Crab Nebula: The Exceptional Flare of 2011 April

Search for Sources of High-Energy Neutrons With Four Years of Data From the Icetop Detector

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