Astron. Astrophys. 358, 117-124 (2000)

BeppoSAX observations of Mrk 509 and MCG +8-11-11

G.C. Perola ¹, G. Matt ¹, F. Fiore ², P. Grandi ³, M. Guainazzi ⁴, F. Haardt ⁵, L. Maraschi ⁶, T. Mineo ⁷, F. Nicastro ⁸ and L. Piro <sup>3

1</sup> Dipartimento di Fisica, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
² Osservatorio Astronomico di Roma, Via dell'Osservatorio, 00044 Monteporzio Catone, Italy
³ Istituto di Astrofisica Spaziale, C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy
⁴ XMM SOC, VILSPA-ESA, Apartado 50727, 28080 Madrid, Spain
⁵ Dipartimento di Scienze, Università dell'Insubria, Via Lucini 3, 22100 Como, Italy
⁶ Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
⁷ Istituto di Fisica Cosmica ed Applicazioni all'Informatica, C.N.R., Via U. La Malfa 153, 90146 Palermo, Italy
⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

Received 9 February 2000 / Accepted 31 March 2000

Abstract

BeppoSAX observations of the Seyfert galaxies Mrk 509 and MCG +8-11-11 are presented. Earlier evidence of a soft excess in Mrk 509 is confirmed. This excess is found to be better represented by a power law than by a black body: with a photon slope of 2.5, its extrapolation matches the flux recorded in the far UV. An ASCA observation, which appeared to exclude the presence of the excess while showing instead evidence of a warm absorber, turns out to be compatible with the coexistence of the excess seen with BeppoSAX and of the warm absorber. The hard power law of Mrk 509 is seen for the first time to be affected by a cut-off at high energies, with an e-folding energy of about 70 keV. In MCG +8-11-11 the cut-off is found at about 170 keV, consistent within the combined errors with a previous estimate from a ASCA+OSSE/CGRO observation. In both objects the reflection component is clearly detected. In Mrk 509 its strength, together with that of the iron K line, indicates a solid angle , subtended by the reprocessing gas in the accretion disk, much less than 2, but lacking a valid constraint on the inclination angle this evidence is not as convincing as that found with BeppoSAX in IC 4329A. In MCG +8-11-11 the same parameters are instead consistent with =2, but the comparison with an ASCA observation, when the flux level was about 2.5 times weaker, suggests that a substantial fraction of the angle might be associated with gas farther out than the accretion disk.

Key words: galaxies: individual: Mrk 509, MCG+8-11-11 galaxies: Seyfert X-rays: galaxies

Send offprint requests to: G.C. Perola (perola@fis.uniroma3.it)

© European Southern Observatory (ESO) 2000

Online publication: June 26, 2000

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