FIRST RESULTS ON p MODES FROM GOLF EXPERIMENT M. LAZREK 27 , F. BAUDIN 18 , L. BERTELLO 3 , P. BOUMIER 5 , J. CHARRA 5 , D. FIERRY-FRAILLON 9 , E. FOSSAT 9 , A. H. GABRIEL 5 , R. A. GARC ´ IA 4 , B. GELLY 9 , C. GOUIFFES 4 , G. GREC 2 , P. L. PALL ´ E 1 , F. P ´ EREZ HERN ´ ANDEZ 1 , C. R ´ EGULO 1 , C. RENAUD 2 , J.-M. ROBILLOT 6 , T. ROCA CORT ´ ES 1 , S. TURCK-CHI ` EZE 4 and R. K. ULRICH 3 1 Instituto de Astrof´ ısica de Canarias, 38205 La Laguna, Tenerife, Spain 2 Observatoire de la Cˆ ote d’Azur, Lab. Cassini CNRS URA1362, 06304 Nice, France 3 Astronomy Department, University of California Los Angeles, U.S.A. 4 Service d’Astrophysique, DSM/DAPNIA, CE Saclay, 91191 Gif-sur-Yvette, France 5 Institut d’Astrophysique Spatiale, CNRS/Universit´ e Paris XI, 91405 Orsay, France 6 Observatoire de l’Universit´ e Bordeaux 1, BP 89, 33270 Floirac, France 7 Centre National de la Recherche, CNCPRST, Rabat, Morocco 8 National Solar Observatory, NOAO, PO Box 26732, Tucson AZ-85726, U.S.A. 9 U.M.R. 6525, C.N.R.S. et Universit´ e de Nice-Sophia Antipolis, F-06108 Nice Cedex 2, France (Received 19 March 1997; accepted 17 June 1997) Abstract. The GOLF experiment on the SOHO mission aims to study the internal structure of the Sun by measuring the spectrum of global oscillations in the frequency range 10 7 to 10 2 Hz. Here we present the results of the analysis of the first 8 months of data. Special emphasis is put into the frequency determination of the modes, as well as the splitting in the multiplets due to rotation. For both, we show that the improvement in S/N level with respect to the ground-based networks and other experiments is essential in achieving a very low-degree frequency table with small errors ( 2 parts in 10 5 ). On the other hand, the splitting found seems to favour a solar core which does not rotate slower than its surface. The line widths do agree with theoretical expectations and other observations. 1. Introduction Helioseismology uses the temporal and spatial properties of solar oscillations to study the solar interior. The quality of analysis as measured by the precision of the deductions and the ability to probe all parts of the Sun’s interior is dependent on the acquisition of observations of the widest possible range of solar oscillation modes and with the greatest precision possible. The SOHO satellite includes three helioseismology instruments which aim to cover in a complementary manner a wide range of oscillation measurements. GOLF is one of these helioseismology instruments and emphasizes the lower frequencies, utilising global oscillations of the line-of-sight velocity vector of the solar photosphere as measured by the full-disk integrated light. At present only higher radial orders of the pressure or modes have been well identified in the solar oscillation spectrum, whether the observation is spatially integrated (Claverie et al., 1979; Grec, Fossat, and Pomerantz, 1980) or spatially resolved (Duvall and Harvey, 1983). The mode amplitudes favour the observations of periods around 5 min, these resulting in some of the best data reported to date Solar Physics 175: 227–246, 1997. c 1997 Kluwer Academic Publishers. Printed in Belgium.