Emission from thermonuclear explosions in white dwarf tidal disruption events

TYPEAstrophysics Seminar
Speaker:Kojiro Kawana
Affiliation:Tokyo U.
Time:11:30 - 12:30
Location:Lidow 605

In tidal disruption events (TDEs) of a white dwarf (WD) by a black hole (BH), the WD is not only tidally disrupted but possibly ignites nuclear burning with the help of tidal compression. We study properties of the emission from thermonuclear explosions in a helium WD TDE where a 0.2 M⊙ WD is dirsupted by a 10^2.5 M⊙ intermediate-mass BH. We perform hydrodynamic simulations coupled with nuclear reactions, post-process detailed nucleosynthesis calculations, and then radiative transfer simulations. We thus derive multi-band light curves and spectra. The helium WD TDE shows rapid and relatively faint light curves, because the ejecta mass and 56Ni mass are low. The spectra show strong calcium and Fe-peak features and very weak silicon features, reflecting the peculiar elemental abundance. Our model matches well with some rapid transients recently found by DES. The particular model presented here does not match with observed supernovae Iax, calcium-rich transients, nor .Ia explosion candidates, either in the spectra or light curves. However, we expect a large variety of the observational signatures once a wide range of the WD/BH masses and orbital parameters are considered. This study helps to search for WD TDEs with current and upcoming surveys, and to identify IMBHs as disrupters in the TDEs.