# Tidal disruption events: the role of stellar spin

## TL;DR

This paper investigates how stellar spin influences the fallback rate and lightcurve of tidal disruption events, revealing that stellar rotation can significantly alter the timing and magnitude of the resulting luminous flares.

## Contribution

It introduces analytical and numerical analysis of stellar spin effects on TDE fallback rates, highlighting the importance of stellar rotation in modeling observed TDE lightcurves.

## Key findings

- Fast prograde stellar spin leads to earlier and higher fallback rates.
- Retrograde spin causes delayed and sometimes partial disruptions.
- Fallback rate overshoots the canonical t^{-5/3} decay after peak.

## Abstract

The tidal force from a supermassive black hole can rip apart a star that passes close enough in what is known as a Tidal Disruption Event. Typically half of the destroyed star remains bound to the black hole and falls back on highly eccentric orbits, forming an accretion flow which powers a luminous flare. In this paper we use analytical and numerical calculations to explore the effect of stellar rotation on the fallback rate of material. We find that slowly spinning stars ($\Omega_* \lesssim 0.01 \Omega_{\rm{breakup}}$) provide only a small perturbation to fallback rates found in the non-spinning case. However when the star spins faster, there can be significant effects. If the star is spinning retrograde with respect to its orbit the tidal force from the black hole has to spin down the star first before disrupting it, causing delayed and sometimes only partial disruption events. However, if the star is spinning prograde this works with the tidal force and the material falls back sooner and with a higher peak rate. We examine the power-law index of the fallback curves, finding that in all cases the fallback rate overshoots the canonical $t^{-5/3}$ rate briefly after the peak, with the depth of the overshoot dependent on the stellar spin. We also find that in general the late time evolution is slightly flatter than the canonical $t^{-5/3}$ rate. We therefore conclude that considering the spin of the star may be important in modelling observed TDE lightcurves.