se objects, the authors could identify models reproducing the observed periods quite well while staying close to the spectroscopic stellar parameters, and also verified the credibility of the selected models in many other ways, including the investigation of rotationally split frequencies.

Acknowledgements {#acknowledgements .unnumbered}
================

The authors thank the anonymous referee for the constructive comments on the manuscript. The authors thank Agnès Bischoff-Kim for providing her version of the <span style="font-variant:small-caps;">wdec</span> and the <span style="font-variant:small-caps;">fitper</span> program. The authors also thank the contribution of E. Bokor, Á. Győrffy, Gy. Kerekes, A. Már and N. Sztankó to the observations of the stars. The financial support of the Hungarian National Research, Development and Innovation Office (NKFIH) grants K-115709 and PD-116175, and the LP2014-17 Program of the Hungarian Academy of Sciences are acknowledged. P.I.P. is a Postdoctoral Fellow of the The Research Foundation – Flanders (FWO), Belgium. L.M. and Á.S. was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.

 {#app:g207}

Normalized differential light curves of G 207-9 obtained in 2007 at Piszkéstető mountain station of Konkoly Observatory.

 {#app:lp133}

Normalized differential light curves of LP 133-144 obtained in 2007 at Piszkéstető mountain station of Konkoly Observatory.

\[lastpage\]

[^1]: E-mail: bognar.zsofia@csfk.mta.hu (Zs.B.)

[^2]: <span style="font-variant:small-caps;">iraf</span> is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

[^3]: http://astroutils.astronomy.ohio-state.edu/time/utc2bjd.html


---
abstract: 'We present an accurate and efficient method to calculate the gravitational potential of an isolated system in three-dimensional Cartesian and cylindrica