The fine line between total and partial tidal disruption events

¹ Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
e-mail: d.mainetti1@campus.unimib.it
² INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
³ INFN, Sezione di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
⁴ Institut d’Astrophysique de Paris, Sorbonne Universités, UPMC Univ Paris 6 et CNRS, UMR 7095, 98 bis bd Arago, 75014 Paris, France
⁵ Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA
⁶ Harvard-Smithsonian Center for Astrophysics, The Institute for Theory and Computation, 60 Garden Street, Cambridge, MA-02138, USA
⁷ Department of Astronomy & Astrophysics, University of California, Santa Cruz, CA-95064, USA

Received: 18 November 2016
Accepted: 24 February 2017

Abstract

Flares from tidal disruption events are unique tracers of quiescent black holes at the centre of galaxies. The appearance of these flares is very sensitive to whether the star is totally or partially disrupted, and in this paper we seek to identify the critical distance of the star from the black hole (r_d) that enables us to distinguish between these two outcomes. We perform here mesh-free finite mass, traditional, and modern smoothed particle hydrodynamical simulations of star-black hole close encounters, with the aim of checking if the value of r_d depends on the simulation technique. We find that the critical distance (or the so-called critical disruption parameter β_d) depends only weakly on the adopted simulation method, being β_d = 0.92 ± 0.02 for a γ = 5/3 polytrope and β_d = 2.01 ± 0.01 for a γ = 4/3 polytrope.