Fitting the light curves of tidal disruption events with non-parabolic model

TL;DR

This paper introduces a non-parabolic model for fitting TDE light curves that accounts for the orbital energy of the star, improving SMBH mass estimates and understanding of stellar dynamics.

Contribution

The work develops a novel non-parabolic TDE model incorporating orbital energy as a free parameter, applied to real data for improved parameter estimation.

Findings

Neglecting orbital energy biases SMBH mass estimates.

Most TDEs originate from two-body relaxation in star clusters.

High-eccentricity, high-penetration events suggest alternative origins.

Abstract

Tidal disruption events (TDEs) are powerful probes of supermassive black hole (SMBH) properties and accretion physics. The existing light curve fitting tools assume that the disrupted stars are on parabolic orbits, which may introduce systematic biases in derived parameters. In this work, we develop a non-parabolic TDE model that incorporates orbital energy of the disrupted star as a free parameter ($\tilde{\epsilon}_{\rm orb}$) to modify the debris mass distribution and mass fallback rate. We apply this model to 30 TDEs from the ZTF-I survey and compare the results with those from a standard parabolic model. We find that neglecting orbital energy leads to biased black hole mass estimates: for eccentric (hyperbolic) orbits, parabolic models systematically underestimate (overestimate) the black hole mass. Additionally, we measure orbital eccentricities ($e$) and penetration factors ($\beta$) of the disrupted stars in this sample, enabling an investigation of their origins via the $e$-$\beta$ parameter space. Most events (24/30) are consistent with production via two-body relaxation in spherical nuclear star clusters, but six outliers with high $\beta$ and $e<1$ suggest alternative mechanisms. Our results highlight the importance of accounting for orbital energy in TDE modeling to improve the accuracy of SMBH mass measurements and to better understand the dynamical origin of the disrupted stars.