Letter to the Editor

Evidence for a 2:3 resonance in Sco X-1 kHz QPOs

¹ Visiting Professor, Institut d'Astrophysique de Paris, 98bis Bld. Arago, 75014 Paris, France
² Université Pierre & Marie Curie (Paris VI), France
³ Department of Astrophysics, Chalmers University, 412-96 Göteborg, Sweden, e-mail: marek@fy.chalmers.se
⁴ Copernicus Astronomical Centre, ul. Bartycka 18, 00-716 Warszawa, Poland, e-mail: bulik@camk.edu.pl
⁵ Astronomical Institute, Charles University Prague, V Holešovičkách 2 CZ-180 00 Praha 8, Czech Republic e-mail: bursa@sirrah.troja.mff.cuni.cz
⁶ Institute of Astronomy, Zielona Góra University, Lubuska 2, 65-265 Zielona Góra, Poland, e-mail: wlodek@camk.edu.pl
⁷ Centre d'Étude Spatiale des Rayonnements, 9 Av. Colonel-Roche, 31028 Toulouse Cedex 4, France

Corresponding author: W. Kluźniak, wlodek@camk.edu.pl

Received: 28 June 2002
Accepted: 25 April 2003

Abstract

We find evidence that the two high frequency QPOs in Sco X-1 are, more often than not, approximately in the 2:3 frequency ratio familiar from studies of black hole candidates (e.g., XTE J1550-564, Remillard et al. [CITE]). This implies that the double kHz QPO phenomenon in neutron stars has its origin in properties of strong-field gravity and has little to do with the rotation of a stellar surface or any magnetic field structure anchored in the star.