Volume 441, Number 1, October I 2005
|Page(s)||283 - 287|
|Section||Stellar structure and evolution|
|Published online||13 September 2005|
Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24
Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Milano “G.Occhialini” – INAF, via Bassini 15, Milano 20133, Italy e-mail: email@example.com
2 Università degli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano, Italy
3 Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
4 Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy
5 SRON, National Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
6 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
7 NSF Astronomy and Astrophysics Fellow
8 Astronomical Institute “Anton Pannekoek”, University of Amsterdam and Center for High-Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
Accepted: 22 June 2005
We present the spectral analysis of an XMM-Newton observation of the X-ray binary 4U 1700+24, performed during an outburst in August 2002. The EPIC-PN spectrum above 1 keV can be modeled by a blackbody plus Comptonization model, as in previous observations. At lower energies, however, we detect a prominent soft excess, which we model with a broad Gaussian centered at ∼0.5 keV. In the high resolution RGS spectrum we detect a single emission line, centered at 19.19 Å. We discuss two possible interpretations for this line: O VIII at redshift or Ne IX at redshift .
Key words: X-rays: individuals: 4U 1700+24 / stars: neutron / stars: binaries: symbiotic / line: identification
© ESO, 2005
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