A&A 411, L415-L419 (2003)
DOI: 10.1051/0004-6361:20031444

Letter

First INTEGRAL observations of GRS 1915+105

D. C. Hannikainen¹, O. Vilhu^{1, 2}, J. Rodriguez^{3, 2}, S. Brandt⁴, N. J. Westergaard⁴, N. Lund⁴, I. Mocoeur³, Ph. Durouchoux³, T. Belloni⁵, A. Castro-Tirado⁶, P. A. Charles⁷, A. J. Dean⁷, R. P. Fender⁸, M. Feroci⁹, P. Hakala¹, R. W. Hunstead¹⁰, C. R. Kaiser⁷, A. King¹¹, I. F. Mirabel³, G. G. Pooley¹², J. Poutanen¹³, K. Wu¹⁴ and A. A. Zdziarski<sup>15

1</sup>  Observatory, PO Box 14, 00014, University of Helsinki, Finland
²  INTEGRAL Science Data Center, Chemin d'Écogia 16, 1290 Versoix, Switzerland
³  Centre d'Études de Saclay, DAPNIA/Service d'Astrophysique (CNRS FRE 2591), Bât. 709, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
⁴  Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
⁵  INAF - Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
⁶  Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 03004, 18080 Granada, Spain
⁷  Dept. of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
⁸  Astronomical Institute, "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
⁹  Istituto Astrofisica Spaziale e Fisica Cosmica, Sezione di Roma, CNR, via Fosso del Cavaliere, 00133 Roma, Italy
¹⁰  School of Physics, University of Sydney, NSW 2006, Australia
¹¹  Theoretical Astrophysics Group, University of Leicester, Leicester LE1 7RH, UK
¹²  Astrophysics Group, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK
¹³  Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland
¹⁴  MSSL, University College London, Holmbury St. Mary, Surrey RH5 6NT, UK
¹⁵  Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warszawa, Poland

(Received 7 July 2003 / Accepted 16 September 2003)

Abstract
We present data from the first of six monitoring Open Time observations of GRS 1915+105 undertaken with the orbiting INTEGRAL satellite. The source was clearly detected with all three X-ray and gamma-ray instruments on board. GRS 1915+105 was in a highly variable state, as demonstrated by the JEM X-2 and ISGRI lightcurves. These and simultaneous RXTE/PCA lightcurves point to a novel type of variability pattern in the source. In addition, we fit the combined JEM X-2 and ISGRI spectrum between 3-300 keV with a disk blackbody + powerlaw model leading to typical parameter values found earlier at similar luminosity levels. A new transient, IGR J19140+098, was discovered during the present observation.

Key words: X-rays: binaries -- X-rays: GRS 1915+105

Offprint request: D. Hannikainen, diana@astro.helsinki.fi

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