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Astron. Astrophys. 323, 235-242 (1997)


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Solar P-mode frequencies from the IRIS network

B. Gelly 1, D. Fierry-Fraillon 1, E. Fossat 1, P. Palle 2, A. Cacciani 3, S. Ehgamberdiev 4, G. Grec 5, J.T. Hoeksema 6, S. Khalikov 4, M. Lazrek 5, 7, S. Loudagh 1, A. Pantel 1, C. Regulo 2 and F.X. Schmider 1

1 Département d'Astrophysique, URA CNRS 709, Université des Sciences, F-06108 Nice Cedex 2, France
2 Instituto de Astrofisica de Canarias, E-38071 La Laguna, Tenerife, Spain
3 Dipartimento di Fisica dell'Università, Piazzale Aldo Moro 2, I-00185 Roma, Italia
4 Astronomical Institute of the Uzbek Academy of Sciences, Astronomicheskaya 33, Tashkent-700052, Uzbekistan
5 Département Cassini, URA CNRS 1362, Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice Cedex 4, France
6 Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305, USA
7 Laboratoire d'Astronomie du CNCPRST, BP 1346, Rabat, Morocco

Received 24 September 1996 / Accepted 23 December 1996

Abstract

The Iris network for helioseismology has operated since 1989. We present tables of solar p-mode frequencies for observations taken during the four summer seasons from 1989 to 1992. This analysis uses the technique of maximum likelihood fitting and a [FORMULA] model for the probability density function of the spectrum. The simultaneous fitting of odd and even pairs of peaks strengthens the identification of the [FORMULA] eigenmodes and improves the error bars on the 0-2 group. The frequencies are in good agreement with other observational results and with theoretical values for the [FORMULA] and the [FORMULA] parameters of the asymptotic approximation. A decrease of [FORMULA] [FORMULA] is seen between the 1989 and the 1992 data sets. The change is associated with the decrease of solar activity and is comparable with results of previous studies.

Key words: Sun: oscillations; activity

Send offprint requests to: gelly@irisalfa.unice.fr

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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