CANGAROO‐III Observations of the 2006 Outburst of PKS 2155−304

Sakamoto, Yoshitaka; Nishijima, K.; Mizukami, Taku; Yamazaki, E.; Kushida, J.; Enomoto, R.; Ohishi, M.; Bicknell, G. V.; Clay, R. W.; Edwards, Philip; Gunji, Shuichi; Hara, Shinji; Hattori, Takahiro; Hayashi, S.; Higashi, Y.; Hirai, Y.; Inoue, Kenji; Itoh, C.; Kabuki, S.; Kajino, F.; Kawachi, A.; Kifune, T.; Kiuchi, R.; Kubo, H.; Mizuniwa, R.; Mori, M.; Muraishi, H.; Naito, T.; Nakamori, Takeshi; Nakano, S.; Nishida, D.; Seki, A.; Stamatescu, V.; Suzuki, Takeshi; Swaby, D. L.; Tanimori, T.; Thornton, G.; Tokanai, Fuyuki; Tsuchiya, Ken; Watanabe, S.; Yamada, Yukiko; Yanagita, S.; Yoshida, Tatsuo; Yoshikoshi, T.; Yukawa, Y.

doi:10.1086/528369

Cited by 22 publications

(23 citation statements)

References 67 publications

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“…Observations with Cangaroo-III confirmed the detection of a very active state with variability on sub-hour time scales (Sakamoto et al 2008). The very fast variability seen by H.E.S.S.…”

Section: Introductionmentioning

confidence: 61%

“…All data have been binned in 10 min bins, with the exception of the light curve in the uppermost panel, which provides the nightly averaged flux observed with the H.E.S.S. telescopes and the average fluxes detected with the CANGAROO experiment, which correspond to a livetime of typically a few hours (Sakamoto et al 2008). Only the nightly averaged three-fold triggers are shown for CANGAROO.…”

Section: Flux Evolution In Different Energy Bands and Correlationsmentioning

confidence: 99%

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A multiwavelength view of the flaring state of PKS 2155-304 in 2006

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

A&A

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Context. Multiwavelength (MWL) observations of the blazar PKS 2155-304 during two weeks in July and August 2006, the period when two exceptional flares at very high energies (VHE, E 100 GeV) occurred, provide a detailed picture of the evolution of its emission. The complete data set from this campaign is presented, including observations in VHE γ-rays (H.E.S.S.), X-rays (RXTE, Chandra, Swift XRT), optical (Swift UVOT, Bronberg, Watcher, ROTSE), and in the radio band (NRT, HartRAO, ATCA). Optical and radio light curves from 2004 to 2008 are compared to the available VHE data from this period, to put the 2006 campaign into the context of the long-term evolution of the source. Aims. The data set offers a close view of the evolution of the source on different time scales and yields new insights into the properties of the emission process. The predictions of synchrotron self-Compton (SSC) scenarios are compared to the MWL data, with the aim of describing the dominant features in the data down to the hour time scale. Methods. The spectral variability in the X-ray and VHE bands is explored and correlations between the integral fluxes at different wavelengths are evaluated. SSC modelling is used to interpret the general trends of the varying spectral energy distribution. Results. The X-ray and VHE γ-ray emission are correlated during the observed high state of the source, but show no direct connection with longer wavelengths. The long-term flux evolution in the optical and radio bands is found to be correlated and shows that the source reaches a high state at long wavelengths after the occurrence of the VHE flares. Spectral hardening is seen in the Swift XRT data. Conclusions. The nightly averaged high-energy spectra of the non-flaring nights can be reproduced by a stationary one-zone SSC model, with only small variations in the parameters. The spectral and flux evolution in the high-energy band during the night of the second VHE flare is modelled with multi-zone SSC models, which can provide relatively simple interpretations for the hour time-scale evolution of the high-energy emission, even for such a complex data set. For the first time in this type of source, a clear indication is found for a relation between high activity at high energies and a long-term increase in the low frequency fluxes.

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“…Observations with Cangaroo-III confirmed the detection of a very active state with variability on sub-hour time scales (Sakamoto et al 2008). The very fast variability seen by H.E.S.S.…”

Section: Introductionmentioning

confidence: 61%

Section: Flux Evolution In Different Energy Bands and Correlationsmentioning

confidence: 99%

A multiwavelength view of the flaring state of PKS 2155-304 in 2006

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…Aharonian et al 2005;Marshall et al 2001;Piner et al 2004Piner et al , 2008Piner et al , 2010. Many researchers have also found evidence of ultra-relativistic outflows (Aharonian et al 2007, Foschini et al 2007, Sakamoto et al 2008.…”

Section: Introductionmentioning

confidence: 98%

On the Radio and Near-Infrared Jet of PKS 2155–304 and Its Close Environment

Liuzzo

Falomo

Treves

et al. 2013

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PKS 2155-304 is one of the brightest BL Lac object in the sky and a very well studied target from radio to TeV bands. We report on high resolution (∼0.12 arcsec) direct imaging of the field of PKS 2155-304 using adaptive optics near-IR observations in J and Ks bands obtained with the ESO multi-conjugate adaptive optic demonstrator (MAD) at the Very Large Telescope. These data are complemented with archival VLA images at various frequencies to investigate the properties of the close environment of the source. We characterized the faint galaxies that form the poor group associated to the target. No radio emission is present for these galaxies, while an old radio jet at ∼20 kpc from the nucleus of PKS 2155-304 and a jet-like structure of ∼2 kpc (∼1 arcsec) in the eastern direction are revealed. No counterparts of these radio jets are found in the NIR or in archival Chandra observations.

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“…Although it has been observed since the seventies (earliest observations are from Ariel V, Cooke et al 1978) with many space and ground observatories at all wavelengths, it still shows unexpected behaviour, like the giant TeV flares, which occurred at the end of July 2006 (Aharonian et al 2007;Foschini et al 2007;Mazin & Lindfors 2007;Sakamoto et al 2008). The largest outburst, recorded on July 28, was characterized by an average flux -in the E > 200 GeV energy band -7 times the Crab flux and several peaks that doubled the mean value on timescales of the order of a few minutes (Aharonian et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Infrared to X-ray observations of PKS 2155–304 in a low state

Foschini¹,

Treves

Tavecchio

et al. 2008

A&A

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Aims. Our goal is to understand the nature of blazars and the mechanisms for the generation of high-energy γ-rays, through the investigation of the prototypical blazar PKS 2155−304, which shows complex behaviour. Methods. We analyze simultaneous infrared-to-X-ray observations obtained with XMM-Newton and REM on November 7, 2006, when the source was in a low X-ray state. We perform a comparative analysis of these results with those obtained from previous observations in different brightness states. Results. We found that the peak of the synchrotron emission moved from ultraviolet to optical wavelengths and the X-ray spectrum is best fit with a broken power law model with Γ 2 ∼ 2.4 harder than Γ 1 ∼ 2.6 and a break at about 3.5 keV. This suggests that the soft X-rays (E < 3.5 keV) are related to the high-energy tail of the synchrotron emission, while the hard X-rays (E > 3.5 keV) are from the energy region between the synchrotron and inverse-Compton humps. The different variability at energies below and above the break strengthens this hypothesis. Our results also stress the importance of monitoring this source at both low and high energies to better characterize its variability behaviour.

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CANGAROO‐III Observations of the 2006 Outburst of PKS 2155−304

Cited by 22 publications

References 67 publications

A multiwavelength view of the flaring state of PKS 2155-304 in 2006

A multiwavelength view of the flaring state of PKS 2155-304 in 2006

On the Radio and Near-Infrared Jet of PKS 2155–304 and Its Close Environment

Infrared to X-ray observations of PKS 2155–304 in a low state

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