2011A&A...531A..70B


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.02CET03:22:40

2011A&A...531A..70B - Astronomy and Astrophysics, volume 531A, 70-70 (2011/7-1)

The hard X-ray emission of Centaurus A.

BECKMANN V., JEAN P., LUBINSKI P., SOLDI S. and TERRIER R.

Abstract (from CDS):

The radio galaxy Cen A has been detected all the way up to the TeV energy range. This raises the question about the dominant emission mechanisms in the high-energy domain. Spectral analysis allows us to put constraints on the possible emission processes. Here we study the hard X-ray emission, in order to distinguish between a thermal and a non-thermal inverse Compton process. Using hard X-ray data provided by INTEGRAL, we determined the cut-off of the power-law spectrum in the hard X-ray domain (3-1000keV). In addition, INTEGRAL data are used to study the spectral variability. The extended emission detected in the gamma-rays by Fermi/LAT is investigated using the data of the spectrometre SPI in the 40-1000keV range. The hard X-ray spectrum of Cen A shows a significant cut-off at energies EC=434+106^–73keV with an underlying power-law of photon index Γ=1.73±0.02. A more physical model of thermal Comptonisation (compPS) gives a plasma temperature of kTe=206±62keV within the optically thin corona with Compton parameter y=0.42+0.09^–0.06. The reflection component is significant at the 1.9σ level with R=0.12+0.09^–0.10, and a reflection strength R>0.3 can be excluded on a 3σ level. Time resolved spectral studies show that the flux, absorption, and spectral slope varied in the range f3–30keV=1.2-9.2x10–10erg/cm2/s, NH=7-16x1022cm–2, and Γ=1.75-1.87. Extending the cut-off power-law or the Comptonisation model to the gamma-ray range shows that they cannot account for the high-energy emission. On the other hand, a broken or curved power-law model can also represent the data, therefore a non-thermal origin of the X-ray to GeV emission cannot be ruled out. The analysis of the SPI data provides no sign of significant emission from the radio lobes and gives a 3σ upper limit of f40–1000keV≲1.1x10–3ph/cm2/s. While gamma-rays, as detected by CGRO and Fermi, are caused by non-thermal (jet) processes, the main process in the hard X-ray emission of Cen A is still not unambiguously determined, since it is either dominated by thermal inverse Compton emission or by non-thermal emission from the base of the jet.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: Seyfert - galaxies: individual: Cen A - X-rays: galaxies

CDS comments: Paragraph 5. 1FGL J1322.0-4545 is a probable misprint for 1FGL J1322.0-4515.

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 4151 Sy1 12 10 32.5771747733 +39 24 21.057727323   12.18 11.48     ~ 3435 2
2 3C 273 BLL 12 29 06.6996828061 +02 03 08.598846466   13.05 14.830 14.11   ~ 5404 1
3 NGC 4507 Sy2 12 35 36.6328010225 -39 54 33.661858548   12.95 13.54 11.70 12.4 ~ 446 0
4 NGC 4593 Sy1 12 39 39.4435521178 -05 20 39.035028119   13.95 13.15     ~ 972 0
5 ESO 323-77 Sy2 13 06 26.1213873662 -40 24 52.594127368   13.58 13.42 12.01   ~ 199 0
6 NAME Cen A Core PoG 13 25 27.61507 -43 01 08.8053           ~ 34 0
7 NAME Centaurus A Sy2 13 25 27.61509104 -43 01 08.8056025   8.18 6.84 6.66   ~ 4076 3
8 1FGL J1333.4-4036 gam 13 33 26 -40 36.2           ~ 7 0

    Equat.    Gal    SGal    Ecl

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2021.03.02-03:22:40

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