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2008A&A...478..387A - Astronomy and Astrophysics, volume 478, 387-393 (2008/2-1)

Upper limits from HESS active galactic nuclei observations in 2005-2007.

AHARONIAN F., AKHPERJANIAN A.G., BARRES DE ALMEIDA U., BAZER-BACHI A.R., BEHERA B., BEILICKE M., BENBOW W., BERNLOEHR K., BOISSON C., BOLZ O., BORREL V., BRAUN I., BRION E., BROWN A.M., BUEHLER R., BULIK T., BUESCHING I., BOUTELIER T., CARRIGAN S., CHADWICK P.M., CHOUNET L.-M., CLAPSON A.C., COIGNET G., CORNILS R., COSTAMANTE L., DALTON M., DEGRANGE B., DICKINSON H.J., DJANNATI-ATAIE A., DOMAINKO W., DRURY L.O'C., DUBOIS F., DUBUS G., DYKS J., EGBERTS K., EMMANOULOPOULOS D., ESPIGAT P., FARNIER C., FEINSTEIN F., FIASSON A., FOERSTER A., FONTAINE G., FUNK S., FUESSLING M., GALLANT Y.A., GIEBELS B., GLICENSTEIN J.F., GLUECK B., GORET P., HADJICHRISTIDIS C., HAUSER D., HAUSER M., 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., JUNG I., KATARZYNSKI K., KENDZIORRA E., KERSCHHAGGL M., KHELIFI B., KEOGH D., KOMIN N., KOSACK K., LAMANNA G., LATHAM I.J., LEMIERE A., LEMOINE-GOUMARD M., LENAIN J.-P., LOHSE T., MARTIN J.M., MARTINEAU-HUYNH O., MARCOWITH A., MASTERSON C., MAURIN D., MAURIN G., McCOMB T.J.L., MODERSKI R., MOULIN E., DE NAUROIS M., NEDBAL D., NOLAN S.J., OHM S., OLIVE J.-P., DE ONA WILHELMI E., ORFORD K.J., OSBORNE J.L., OSTROWSKI M., PANTER M., PEDALETTI G., PELLETIER G., PETRUCCI P.-O., PITA S., PUEHLHOFER G., PUNCH M., RANCHON S., RAUBENHEIMER B.C., RAUE M., RAYNER S.M., RENAUD M., RIPKEN J., ROB L., ROLLAND L., ROSIER-LEES S., ROWELL G., RUDAK B., RUPPEL J., SAHAKIAN V., SANTANGELO A., SCHLICKEISER R., SCHOECK F., SCHROEDER R., SCHWANKE U., SCHWARZBURG S., SCHWEMMER S., SHALCHI A., SOL H., SPANGLER D., STAWARZ L., STEENKAMP R., STEGMANN C., SUPERINA G., TAM P.H., TAVERNET J.-P., TERRIER R., VAN ELDIK C., VASILEIADIS G., VENTER C., 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):

Very high energy (VHE; E>100 GeV) γ-ray studies were performed for 18 active galactic nuclei (AGN) from a variety of AGN classes. VHE observations of a sample of 14 AGN, considered candidate VHE emitters, were made with the High Energy Stereoscopic System (HESS) between January 2005 and July 2007. Large-zenith-angle observations of three northern AGN (Mkn421, Mkn501, 1ES1218+304), known to emit VHE γ-rays, were also performed in order to sample their spectral energy distributions (SEDs) above 1TeV. In addition, the VHE flux from 1ES1101-232, previously detected by HESS in 2004-2005, was monitored during 2006 and 2007. As significant detections from the HESS observation program are reported elsewhere, the results reported here are primarily integral flux upper limits. The average exposure for each of the 14 VHE-candidate AGN is ∼7h live time, and the observations have an average energy threshold between 230GeV and 590GeV. Upper limits for these 14 AGN range from <0.9% to <4.9% of the Crab Nebula flux, and eight of these are the most constraining ever reported for the object. The brief (<2.2h each) large-zenith-angle observations yield upper limits for Mkn501 (<20% Crab above 2.5TeV) and 1ES1218+304 (<17% Crab above 1.0TeV), and a marginal detection (3.5σ) of Mkn421 (50% Crab above 2.1TeV). 1ES1101-232 was marginally detected (3.6σ, 1.7% Crab above 260GeV) during the 2006 (13.7h live time) observations, but not in the 2007 (4.6h live time) data. The upper limit in 2007 (<1.9% Crab above 260GeV) is below the average flux measured by HESS from 2004-2006.

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Journal keyword(s): galaxies: active - gamma rays: observations

Simbad objects: 29

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