2009A&A...502..749A

Query : 2009A&A...502..749A

2009A&A...502..749A - Astronomy and Astrophysics, volume 502, 749-770 (2009/8-2)

Simultaneous multiwavelength observations of the second exceptional γ-ray flare of PKS 2155-304 in July 2006.

AHARONIAN F., AKHPERJANIAN A.G., ANTON G., BARRES DE ALMEIDA U., BAZER-BACHI A.R., BECHERINI Y., BEHERA B., BENBOW W., BERNLOEHR K., BOISSON C., BOCHOW A., BORREL V., BRION E., BRUCKER J., BRUN P., BUEHLER R., BULIK T., BUESCHING I., BOUTELIER T., CHADWICK P.M., CHARBONNIER A., CHAVES R.C.G., CHEESEBROUGH A., CHOUNET L.-M., CLAPSON A.C., COIGNET G., COSTAMANTE L., DALTON M., DANIEL M.K., DAVIDS I.D., DEGRANGE B., DEIL C., DICKINSON H.J., DJANNATI-ATAIE A., DOMAINKO W., DRURY L.O'C., DUBOIS F., DUBUS G., DYKS J., DYRDA M., EGBERTS K., EMMANOULOPOULOS D., ESPIGAT P., FARNIER C., FEINSTEIN F., FIASSON A., FOERSTER A., FONTAINE G., FUESSLING M., GABICI S., GALLANT Y.A., GERARD L., GIEBELS B., GLICENSTEIN J.F., GLUECK B., GORET P., GOEHRING D., HAUSER D., HAUSER M., HEINZ S., HEINZELMANN G., HENRI G., HERMANN G., HINTON J.A., HOFFMANN A., HOFMANN W., HOLLERAN M., HOPPE S., HORNS D., JACHOLKOWSKA A., DE JAGER O.C., JAHN C., JUNG I., KATARZYNSKI K., KATZ U., KAUFMANN S., KENDZIORRA E., KERSCHHAGGL M., KHANGULYAN D., KHELIFI B., KEOGH D., KLUZNIAK W., KNEISKE T., KOMIN N., KOSACK K., LAMANNA G., LENAIN J.-P., LOHSE T., MARANDON V., MARTIN J.M., MARTINEAU-HUYNH O., MARCOWITH A., MAURIN D., McCOMB T.J.L., MEDINA M.C., MODERSKI R., MONARD L.A.G., MOULIN E., NAUMANN-GODO M., DE NAUROIS M., NEDBAL D., NEKRASSOV D., NIEMIEC J., NOLAN S.J., OHM S., OLIVE J.-F., DE ONA WILHELMI E., ORFORD K.J., OSTROWSKI M., PANTER M., PAZ ARRIBAS M., PEDALETTI G., PELLETIER G., PETRUCCI P.-O., PITA S., PUEHLHOFER G., PUNCH M., QUIRRENBACH A., RAUBENHEIMER B.C., RAUE M., RAYNER S.M., RENAUD M., RIEGER F., RIPKEN J., ROB L., ROSIER-LEES S., ROWELL G., RUDAK B., RULTEN C.B., RUPPEL J., SAHAKIAN V., SANTANGELO A., SCHLICKEISER R., SCHOECK F.M., SCHROEDER R., SCHWANKE U., SCHWARZBURG S., SCHWEMMER S., SHALCHI A., SIKORA M., SKILTON J.L., SOL H., SPANGLER D., STAWARZ L., STEENKAMP R., STEGMANN C., SUPERINA G., SZOSTEK A., TAM P.H., TAVERNET J.-P., TERRIER R., TIBOLLA O., TLUCZYKONT M., VAN ELDIK C., VASILEIADIS G., VENTER C., VENTER L., VIALLE J.P., VINCENT P., VIVIER M., VOELK H.J., VOLPE F., WAGNER S.J., WARD M., ZDZIARSKI A.A. and ZECH A.

Abstract (from CDS):

The X-ray-TeV connection and the evolution of the emitting particle population is studied in high-energy peaked BL Lac objects, by obtaining spectral information in both bands on sub-hour timescales. Simultaneous observations with HESS, Chandra and the Bronberg optical observatory were performed on the BL Lac object PKS2155-304 in the night of July 29-30 2006, when the source underwent a major γ-ray outburst during its high-activity state of Summer 2006. This event took place about 44 h after the other major outburst of the night of July 27-28, which is known for its ultrafast variability. An unprecedented 6 to 8 h of simultaneous, uninterrupted coverage was achieved, with spectra and light curves measured down to 7 and 2min timescales, respectively. The source exhibited one major flare along the night, at high energies. The γ-ray flux reached a maximum of ∼11 times the Crab flux (>400GeV), with rise/decay timescales of ∼1 h, plus a few smaller-amplitude flares superimposed on the decaying phase. The emission in the X-ray and VHE γ-ray bands is strongly correlated, with no evidence of lags. The spectra also evolve with similar patterns, and are always soft (photon index Γ>2), indicating no strong shift of the peaks in the spectral energy distribution towards higher energies. Only at the flare maximum is there evidence that the γ-ray peak is inside the observed passband, at ∼400-600GeV. The VHE spectrum shows a curvature that is variable with time and stronger at higher fluxes. The huge VHE variations (∼22x) are only accompanied by small-amplitude X-ray and optical variations (factor 2 and 15% respectively). The source has shown for the first time in a high-energy peaked BL Lac object a large Compton dominance (LC/LS∼10) - rapidly evolving - and a cubic relation between VHE and X-ray flux variations, during a decaying phase. These results challenge the common scenarios for the TeV-blazar emission.

Abstract Copyright: ∼

Journal keyword(s): galaxies: active - galaxies: BL Lacertae objects: individual: PKS2155-304 - gamma rays: observations - X-rays: galaxies

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 M 1 SNR 05 34 30.9 +22 00 53           ~ 6191 1
2 Mrk 421 BLL 11 04 27.3140835504 +38 12 31.798495872   13.50 12.90 8.31   ~ 2671 1
3 7C 165211.80+395026.00 BLL 16 53 52.21668403 +39 45 36.6088754 14.09 14.15 13.29 8.26   ~ 2160 2
4 QSO B1959+650 BLL 19 59 59.8520303688 +65 08 54.652536492     12.8 11.21   ~ 625 2
5 QSO B2155-304 BLL 21 58 52.0652249880 -30 13 32.118447792   13.36 13.09 12.62   ~ 1732 1

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