2018A&A...619A..71H

Query : 2018A&A...619A..71H

2018A&A...619A..71H - Astronomy and Astrophysics, volume 619A, 71-71 (2018/11-1)

The γ-ray spectrum of the core of Centaurus A as observed with H.E.S.S. and Fermi-LAT.

HESS COLLABORATION, ABDALLA H., ABRAMOWSKI A., AHARONIAN F., AIT BENKHALI F., ANGUNER E.O., ARAKAWA M., ARMAND C., ARRIETA M., BACKES M., BALZER A., BARNARD M., BECHERINI Y., BECKER TJUS J., BERGE D., BERNHARD S., BERNLOHR K., BLACKWELL R., BOTTCHER M., BOISSON C., BOLMONT J., BONNEFOY S., BORDAS P., BREGEON J., BRUN F., BRUN P., BRYAN M., BUCHELE M., BULIK T., CAPASSO M., CAROFF S., CAROSI A., CASANOVA S., CERRUTI M., CHAKRABORTY N., CHAVES R.C.G., CHEN A., CHEVALIER J., COLAFRANCESCO S., CONDON B., CONRAD J., DAVIDS I.D., DECOCK J., DEIL C., DEVIN J., DEWILT P., DIRSON L., DJANNATI-ATAI A., DONATH A., DRURY L.O., DYKS J., EDWARDS T., EGBERTS K., EMERY G., ERNENWEIN J.-P., ESCHBACH S., FARNIER C., FEGAN S., FERNANDES M.V., FIASSON A., FONTAINE G., FUNK S., FUSSLING M., GABICI S., GALLANT Y.A., GARRIGOUX T., GATE F., GIAVITTO G., GLAWION D., GLICENSTEIN J.F., GOTTSCHALL D., GRONDIN M.-H., HAHN J., HAUPT M., HAWKES J., HEINZELMANN G., HENRI G., HERMANN G., HINTON J.A., HOFMANN W., HOISCHEN C., HOLCH T.L., HOLLER M., HORNS D., IVASCENKO A., IWASAKI H., JACHOLKOWSKA A., JAMROZY M., JANKOWSKY D., JANKOWSKY F., JINGO M., JOUVIN L., JUNG-RICHARDT I., KASTENDIECK M.A., KATARZYNSKI K., KATSURAGAWA M., KATZ U., KERSZBERG D., KHANGULYAN D., KHELIFI B., KING J., KLEPSER S., KLOCHKOV D., KLUZNIAK W., KOMIN N., KOSACK K., KRAKAU S., KRAUS M., KRUGER P.P., LAFFON H., LAMANNA G., LAU J., LEFAUCHEUR J., LEMIERE A., LEMOINE-GOUMARD M., LENAIN J.-P., LESER E., LOHSE T., LORENTZ M., LIU R., LOPEZ-COTO R., LYPOVA I., MALYSHEV D., MARANDON V., MARCOWITH A., MARIAUD C., MARX R., MAURIN G., MAXTED N., MAYER M., MEINTJES P.J., MEYER M., MITCHELL A.M.W., MODERSKI R., MOHAMED M., MOHRMANN L., MORA K., MOULIN E., MURACH T., NAKASHIMA S., DE NAUROIS M., NDIYAVALA H., NIEDERWANGER F., NIEMIEC J., OAKES L., O'BRIEN P., ODAKA H., OHM S., OSTROWSKI M., OYA I., PADOVANI M., PANTER M., PARSONS R.D., PEKEUR N.W., PELLETIER G., PERENNES C., PETRUCCI P.-O., PEYAUD B., PIEL Q., PITA S., POIREAU V., PROKHOROV D.A., PROKOPH H., PUHLHOFER G., PUNCH M., QUIRRENBACH A., RAAB S., RAUTH R., REIMER A., REIMER O., RENAUD M., DE LOS REYES R., RIEGER F., RINCHIUSO L., ROMOLI C., ROWELL G., RUDAK B., RULTEN C.B., SAHAKIAN V., SAITO S., SANCHEZ D.A., SANTANGELO A., SASAKI M., SCHLICKEISER R., SCHUSSLER F., SCHULZ A., SCHWANKE U., SCHWEMMER S., SEGLAR-ARROYO M., SEYFFERT A.S., SHAFI N., SHILON I., SHININGAYAMWE K., SIMONI R., SOL H., SPANIER F., SPIR-JACOB M., STAWARZ L., STEENKAMP R., STEGMANN C., STEPPA C., SUSHCH I., TAKAHASHI T., TAVERNET J.-P., TAVERNIER T., TAYLOR A.M., TERRIER R., TIBALDO L., TIZIANI D., TLUCZYKONT M., TRICHARD C., TSIROU M., TSUJI N., TUFFS R., UCHIYAMA Y., VAN DER WALT D.J., VAN ELDIK C., VAN RENSBURG C., VAN SOELEN B., VASILEIADIS G., VEH J., VENTER C., VIANA A., VINCENT P., VINK J., VOISIN F., VOLK H.J., VUILLAUME T., WADIASINGH Z., WAGNER S.J., WAGNER P., WAGNER R.M., WHITE R., WIERZCHOLSKA A., WILLMANN P., WORNLEIN A., WOUTERS D., YANG R., ZABOROV D., ZACHARIAS M., ZANIN R., ZDZIARSKI A.A., ZECH A., ZEFI F., ZIEGLER A., ZORN J., ZYWUCKA N. (The Fermi-LAT Collaboration), MAGILL J.D., BUSON S., CHEUNG C.C., PERKINS J.S. and TANAKA Y.

Abstract (from CDS):

Centaurus A (Cen A) is the nearest radio galaxy discovered as a very-high-energy (VHE; 100GeV-100TeV) γ-ray source by the High Energy Stereoscopic System (H.E.S.S.). It is a faint VHE γ-ray emitter, though its VHE flux exceeds both the extrapolation from early Fermi-LAT observations as well as expectations from a (misaligned) single-zone synchrotron-self Compton (SSC) description. The latter satisfactorily reproduces the emission from Cen A at lower energies up to a few GeV. New observations with H.E.S.S., comparable in exposure time to those previously reported, were performed and eight years of Fermi-LAT data were accumulated to clarify the spectral characteristics of the γ-ray emission from the core of Cen A. The results allow us for the first time to achieve the goal of constructing a representative, contemporaneous γ-ray core spectrum of Cen A over almost five orders of magnitude in energy. Advanced analysis methods, including the template fitting method, allow detection in the VHE range of the core with a statistical significance of 12σ on the basis of 213 hours of total exposure time. The spectrum in the energy range of 250GeV-6TeV is compatible with a power-law function with a photon index Γ=2.52±0.13_stat±0.20_sys. An updated Fermi-LAT analysis provides evidence for spectral hardening by ΔΓ~=0.4±0.1 at γ-ray energies above 2.8^+1.0_–0.6GeV at a level of 4.0σ. The fact that the spectrum hardens at GeV energies and extends into the VHE regime disfavour a single-zone SSC interpretation for the overall spectral energy distribution (SED) of the core and is suggestive of a new γ-ray emitting component connecting the high-energy emission above the break energy to the one observed at VHE energies. The absence of significant variability at both GeV and TeV energies does not yet allow disentanglement of the physical nature of this component, though a jet-related origin is possible and a simple two-zone SED model fit is provided to this end.

Abstract Copyright: © ESO 2018

Journal keyword(s): gamma rays: galaxies - radiation mechanisms: non-thermal

Simbad objects: 3

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Number of rows : 3

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag B	Mag V	Mag R	Sp type	#ref 1850 - 2024	#notes
1	M 1	SNR	05 34 30.9	+22 00 53				~	6199	1
2	NAME Cen A Core	PoG	13 25 27.6039817176	-43 01 09.493008456				~	37	0
3	NAME Centaurus A	Sy2	13 25 27.61521044	-43 01 08.8050291	8.18	6.84	6.66	~	4489	3

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