Tidal Disruption Flares from Stars on Marginally Bound and Unbound Orbits

Abstract

We study the mass fallback rate of tidally disrupted stars on marginally bound and unbound orbits around a supermassive black hole (SMBH) by performing three-dimensional smoothed particle hydrodynamic (SPH) simulations with three key parameters: the star is modeled by a polytrope with two different indexes ($n=1.5$ and $3$). The stellar orbital properties are characterized by five orbital eccentricities ranging from $e=0.98$ to $1.02$ and five different penetration factors ranging from $\beta =1$ to $3$, where $\beta$ represents the ratio of the tidal disruption to pericenter distance radii. We derive analytic formulae for the mass fallback rate as a function of the stellar density profile, orbital eccentricity, and penetration factor. Moreover, two critical eccentricities to classify tidal disruption events (TDEs) into five different types: eccentric ($e<e_{\mathrm{crit},1}$), marginally eccentric ($e_{\mathrm{crit},1}\lesssim e<1$), purely parabolic ($e=1$), marginally hyperbolic ($1<e<e_{\mathrm{crit},2}$), and hyperbolic ($e\gtrsim e_{\mathrm{crit},2}$) TDEs, are reevaluated as $e_{\mathrm{crit},1}=1-2q^{-1/3}{\beta }^{k-1}$ and $e_{\mathrm{crit},2}=1+2q^{-1/3}{\beta }^{k-1}$, where $q$ is the ratio of the SMBH to stellar masses and $0<k\lesssim 2$. We find the asymptotic slope of the mass fallback rate varies with the TDE type. The asymptotic slope approaches $-5/3$ for parabolic TDEs, is steeper for marginally eccentric TDEs, and is flatter for marginally hyperbolic TDEs. The mass fallback rates of the marginally eccentric TDEs are much larger than the parabolic TDE case, while those of marginally hyperbolic TDEs are much smaller. Marginally unbound TDEs could be an origin of a very low density gas disk around a dormant SMBH.

42 pages 11 figures, accepted for publication in ApJ

References in corpus (15)

• An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core
• A Continuum of H- to He-Rich Tidal Disruption Candidates With a Preference for E+A Galaxies
• Stellar disruption by a supermassive black hole: is the light curve really proportional to $t^{-5/3}$?
• General Relativistic Hydrodynamic Simulation of Accretion Flow from a Stellar Tidal Disruption
• UV/Optical Detections of Candidate Tidal Disruption Events by GALEX and CFHTLS
• Evolution of tidal disruption candidates discovered by XMM-Newton
• On the mass and luminosity functions of tidal disruption flares: rate suppression due to black hole event horizons
• Measurement of the rate of stellar tidal disruption flares
• Rates of Stellar Tidal Disruption
• A New Paradigm for Gamma Ray Bursts: Long Term Accretion Rate Modulation by an External Accretion Disk
• Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption Event
• Thawing the frozen-in approximation: implications for self-gravity in deeply plunging tidal disruption events
• Neutrino Emissions from Tidal Disruption Remnants
• Ultra-Close Encounters of Stars With Massive Black Holes: Tidal Disruption Events With Prompt Hyperaccretion
• Ultra-deep tidal disruption events: prompt self-intersections and observables

Cited by in corpus (13)

• The Process of Stellar Tidal Disruption by Supermassive Black Holes. The first pericenter passage
• Eccentric Tidal Disruption Event Disks around Supermassive Black Holes: Dynamics and Thermal Emission
• The Eccentric Nature of Eccentric Tidal Disruption Events
• Tidal disruption events from eccentric orbits and lessons learned from the noteworthy ASASSN-14ko
• Global Simulations of Tidal Disruption Event Disk Formation via Stream Injection in GRRMHD
• Repeating Partial Tidal Encounters of Sun-like Stars Leading to their Complete Disruption
• Demographics of Tidal Disruption Events with L-Galaxies: I. Volumetric TDE rates and the abundance of Nuclear Star Clusters
• Evolution of Tidal Disruption Event Disks with Magnetically Driven Winds
• Exploring the origin of stars on bound and unbound orbits causing tidal disruption events
• Stellar Stripping and Disruption in Disks around Supermassive Black Hole Binaries: Repeating nuclear transients prior to LISA events
• Partial tidal disruption of White Dwarfs in off-equatorial orbits around Kerr black holes
• Tidal disruptions of close white dwarf binaries by intermediate mass black holes
• On the origin of late-time X-ray flares in UV/optically-selected tidal disruption events