2009A&A...503..817A

Query : 2009A&A...503..817A

2009A&A...503..817A - Astronomy and Astrophysics, volume 503, 817-825 (2009/9-1)

Spectrum and variability of the galactic center VHE γ-ray source HESS J1745-290.

AHARONIAN F., AKHPERJANIAN A.G., ANTON G., BARRES DE ALMEIDA U., BAZER-BACHI A.R., BECHERINI Y., BEHERA B., BERNLOEHR K., BOISSON C., BOCHOW A., BORREL V., BRAUN I., 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., 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., 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., JUNG I., KATARZYNSKI K., KATZ U., KAUFMANN S., KENDZIORRA E., KERSCHHAGGL M., KHANGULYAN D., KHELIFI B., KEOGH D., 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., 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., ROLLAND 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., 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., 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):

A detailed study of the spectrum and variability of the source HESS J1745-290 in the Galactic Center (GC) region using new data from the H.E.S.S. array of Cherenkov telescopes is presented. Flaring activity and quasi periodic oscillations (QPO) of HESS J1745-290 are investigated. The image analysis is performed with a combination of a semi-analytical shower model and the statistical moment-based Hillas technique. The spectrum and lightcurves of HESS J1745-290 are derived with a likelihood method based on a spectral shape hypothesis. Rayleigh tests and Fourier analysis of the H.E.S.S. GC signal are used to study the periodicity of the source. With a three-fold increase in statistics compared to previous work, a deviation from a simple power law spectrum is detected for the first time. The measured energy spectrum over the three years 2004, 2005 and 2006 of data taking is compatible with both a power law spectrum with an exponential cut-off and a broken power law spectrum. The curvature of the energy spectrum is likely to be intrinsic to the photon source, as opposed to effects of interstellar absorption. The power law spectrum with an exponential cut-off is characterized by a photon index of 2.10±0.04stat±0.10syst and a cut-off energy at 15.7±3.4stat±2.5systTeV. The broken power law spectrum exhibits spectral indices of 2.02±0.08stat±0.10syst and 2.63±0.14stat±0.10syst with a break energy at 2.57±0.19stat±0.44systTeV. No significant flux variation is found. Increases in the γ-ray flux of HESS J1745-290 by at least a factor of two would be required for a 3σ detection of a flare with time scales of an hour. Investigation of possible QPO activity at periods claimed to be detected in X-rays does not show any periodicities in the H.E.S.S. signal.

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Journal keyword(s): Galaxy: center - gamma rays: observations - methods: data analysis

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 [KRL2007b] 270 gam 17 45 38.5 -29 01 15           ~ 26 0
2 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14407 0
3 CXOGC J174539.7-290022 Psr 17 45 39.80 -29 00 19.9           ~ 51 1
4 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4388 3
5 0FGL J1746.0-2900 gam 17 45 41 -29 00.8           ~ 493 2

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