Similar ratios of rise timescale to decline timescale of optical light curves in common tidal disruption events

TL;DR

This study investigates the ratio of rise to decline timescales in optical light curves of tidal disruption events (TDEs) and suggests it could serve as a classification parameter to distinguish TDEs from other transients.

Contribution

The paper introduces the timescale ratio $R_{2/1,rd}$ as a potential new classification parameter for optical TDEs, supported by analysis of 34 events and additional transients.

Findings

$R_{2/1,rd}$ is approximately 0.6 for most optical TDEs.

AT2020wey's initial outlier ratio was revised to about 0.9 after model adjustments.

$R_{2/1,rd}$ differs significantly in some transients, indicating potential for classification.

Abstract

Totally similar physical process in tidal disruption events (TDEs) basically indicates that there should be potential parameter to distinguish variability properties of TDEs from the other transient events having different physical processes. Here, we try to report such a parameter, the timescale ratio $R_{2/1,rd}$ of rise timescale $t_{1/2,r}$ (from half-max to maximum) to decline timescale $t_{1/2,d}$ (from maximum to half-max), especially based on the 34 optical TDEs with reported $t_{1/2,r}$ and $t_{1/2,d}$. Among the 34 optical TDEs, AT2020wey is an outlier with $R_{2/1,rd}\sim2.7$ which is 4.5 times larger than the mean value 0.6 of the other optical TDEs. However, after considering similar but more flexible model functions, the re-determined $R_{2/1,rd}$ is $\sim$0.9 in AT2020wey, totally similar as the values of the other optical TDEs. Therefore, the parameter $R_{1/2,rd}\sim0.6$ could be a potential classification parameter for optical TDEs. Furthermore, $R_{1/2,rd}$ have been checked in the unique optical transients of AT2019avd, PS1-10adi, SDSS J0946+3512 and J2334+1457. We can find that the second flare with $R_{1/2,rd}\sim11$ in AT2019avd should be very different from the other optical TDEs, but PS1-10adi, SDSS J0946+3512, J2334+1457 and the first flare in AT2019avd should be similar as the other optical TDEs. In the near future, properties of $R_{1/2,rd}$ through large sample of optical transients could provide further clues to support whether $R_{1/2,rd}$ could be a better classification parameter to distinguish TDEs and the other transient events.