Dynamics of the boxy elliptical galaxy NGC 1600

We use three-integral models to infer the distribution function (DF) of the boxy E3-E4 galaxy NGC 1600 from surface brightness and line-profile data o n the minor and major axes. We assume axisymmetry and that the mass-to-ligh t ratio is constant in the central similar to 1R(e). Stars in the resulting gravitational potential move mainly on regular orbits. We use an approxima te third integral K from perturbation theory and write the DF as a sum of b asis functions in the three integrals E, L-z and K. We then fit the project ed moments of these basis functions to the kinematic observables and deproj ected density, using a non-parametric algorithm. The deduced dynamical stru cture is radially anisotropic, with sigma(theta)sigma(r)approximate to sigm a(phi)sigma(r)approximate to 0.7 on the major axis. Both on the minor axis and near the centre the velocity distribution is more isotropic; thus the m odel is flattened by equatorial radial orbits. The kinematic data are fitte d without the need for a central black hole; the central mass determined pr eviously from ground-based data therefore overestimates the actual black-ho le mass. The mass-to-light ratio of the stars is MLV=6 h(50). The anisotrop y structure of NGC 1600 with a radially anisotropic main body and more near ly isotropic centre is similar to that found recently in NGC 1399, 2434, 33 79 and 6703, suggesting that this pattern may be common amongst massive ell iptical galaxies. We discuss a possible merger origin of NGC 1600 in the li ght of these results.