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Astron. Astrophys. 339, L33-L36 (1998)


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Letter to the Editor

BeppoSAX detection of the Fe K line in the nearby starburst galaxy NGC 253

M. Persic 1, S. Mariani 2, M. Cappi 3, L. Bassani 3, L. Danese 4, A.J. Dean 5, G. Di Cocco 3, A. Franceschini 6, L.K. Hunt 7, F. Matteucci 8, E. Palazzi 3, G.G.C. Palumbo 2, 3, Y. Rephaeli 9, P. Salucci 4 and A. Spizzichino 3

1 Trieste Astronomical Observatory, via G.B.Tiepolo 11, I-34131 Trieste, Italy
2 Astronomy Department, University of Bologna, via Zamboni 33, I-40126 Bologna, Italy
3 ITeSRE/CNR, via Gobetti 101, I-40129 Bologna, Italy
4 SISSA/ISAS, via Beirut 2-4, I-34013 Trieste, Italy
5 Physics Department, Southampton University, Southampton SO9 5NH, UK
6 Astronomy Department, University of Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
7 CAISMI/CNR, Largo E.Fermi 5, I-50125 Firenze, Italy
8 Astronomy Department, University of Trieste, via Besenghi, I-34131 Trieste, Italy
9 School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel

Received 5 August 1998 / Accepted 22 September 1998

Abstract

We present BeppoSAX results on the nearby starburst galaxy NGC 253. Although extended, a large fraction of the X-ray emission comes from the nuclear region. Preliminary analysis of the LECS/MECS/PDS [FORMULA] 0.2-60 keV data from the central 4´ region indicates that the continuum is well fitted by two thermal models: a "soft" component with [FORMULA] keV, and a "hard" component with [FORMULA] keV absorbed by a column density of [FORMULA] 1.2 [FORMULA] 1022 cm-2. For the first time in this object, the Fe K line at 6.7 keV is detected, with an equivalent width of [FORMULA] 300 eV. This detection, together with the shape of the 2-60 keV continuum, implies that most of the hard X-ray emission is thermal in origin, and constrains the iron abundances of this component to be [FORMULA] 0.25 of solar. Other lines clearly detected are Si, S and Fe L/Ne, in agreement with previous ASCA results. We discuss our results in the context of the starburst-driven galactic superwind model.

Key words: galaxies: individual: NGC 253 – galaxies: spiral – galaxies: starburst

Send offprint requests to: Massimo Persic (e-mail: persic@oat.ts.astro.it)

© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998

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