ar X iv : a st ro - p h / 02 02 15 4 v 1 7 F eb 2 00 2 Study of the Largest Multiwavelength Campaign of the Microquasar GRS 1915 + 105

We present the results from a multiwavelength campaign of GRS 1915+105 performed from 2000 April 16 to 25. This is one of the largest coordinated set of observations ever performed for this source, covering the wide energy band in radio (13.3–0.3 cm), near-infrared (J-H-K), X-rays and Gamma-rays (from 1 keV to 10 MeV). During the campaign GRS 1915+105 was predominantly in the “plateau” (or low/hard) state but sometimes showed soft X-ray oscillations: before April 20.3, rapid, quasi-periodic (≃45 min) flare-dip cycles were observed. In the Institute of Space and Astronautical Science, Sagamihara 229-8510, Japan Institute of Physical and Chemical Research (RIKEN), Wako 351-01, Japan LAEFF-INTA, Madrid, Spain NRAO, USA Department of Physics and Astronomy, The Open University, UK Naval Research Lab, USA MSFC/NASA, USA IAA-CSIC, Granada, Spain Service d’Astrophysique, Saclay, France IAFE/CONICET, Argentina Nobeyama Radio Observatory, NAO, Japan Institute of Astronomy, The University of Tokyo, Japan Istituto di Astrofisica Spaziale, C.N.R., Italy SAO, Russia Observatorio Astronomico Nacional de Mexico, Mexico GSFC/NASA, USA