Letter to the Editor

First INTEGRAL observations of eight persistent neutron star low mass X-ray binaries^*

¹ Science Data Centre, Chemin d'Écogia 16, 1290 Versoix, Switzerland
² CNR-IASF, Sezione di Milano, via Bassini 15, 20133 Milano, Italy
³ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
⁴ Observatoire de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
⁵ Observatory PO Box 14, Tahtitorninmaki, 00014 University of Helsinki, Finland
⁶ Space Research Institute (IKI), High Energy Department, Ul. Profsojuznaya 84/32,117810 Moscow, Russia
⁷ CNRS, FRE 2591, CE Saclay DSM/DAPNIA/SAp, 91191 Gif sur Yvette Cedex, France
⁸ N. Copernicus Astronomical Ctr., Bartycka 18, 00716 Warsaw, Poland
⁹ CNR-IASF, Sezione di Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy
¹⁰ Research and Scientific Support Department of ESA, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
¹¹ Dipartimento di Fisica, Università di Ferrara, via Paradiso 12, 44100 Ferrara, Italy
¹² Instituto Nacional de Tecnica Aerospacial, Carretera de Ajalvir 4, 28850 Torrejon de Ardoz, Madrid, Spain
¹³ CEA Saclay, DSM/DAPNIA/SAp, 91191 Gif sur Yvette, France
¹⁴ CNR-IASF, Sezione di Palermo, via Ugo La Malfa 153, 90146 Palermo, Italy
¹⁵ Università di Bologna, via Ranzani 1, 40127 Bologna, Italy

Corresponding author: A. Paizis, Ada.Paizis@obs.unige.ch

Received: 15 July 2003
Accepted: 1 August 2003

Abstract

Early results from the INTEGRAL Core Program, for a sample of eight persistently bright neutron star low mass X-ray binaries in the energy range from 5 keV to 200 keV, are presented. It is shown that INTEGRAL efficiently detects sources and that spectra may be obtained up to several hundreds of keV by combining data from three of the four INTEGRAL instruments: JEM-X, IBIS and SPI. For the source GX 17+2 it is shown that the spectrum extends well above 100 keV with a flattening above 30 keV. This might suggest a non-thermal comptonisation emission, but uncertainties in the current data reduction and background determination do not allow firm conclusions to be drawn yet.