We study properties of the emission from thermonuclear explosions in a helium white dwarf ( WD ) tidal disruption event ( TDE ) .
The helium WD is not only tidally disrupted but is detonated by the tidal compression and by succeeding shocks .
We focus on the emission powered by radioactive nuclei in the unbound ejecta of the TDE debris .
We consider a TDE where a 0.2 \mathrm { M } _ { \sun } helium WD is disrupted by a 10 ^ { 2.5 } \mathrm { M } _ { \sun } intermediate-mass black hole ( IMBH ) .
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 ( \Delta t _ { 1 \mathrm { mag } } \simeq 5 \text { - - } 10 d ) and relatively faint ( L _ { \mathrm { peak } } \simeq 10 ^ { 42 } \mathrm { erg } \mathrm { s } ^ { -1 } ) light curves , because the ejecta mass and ^ { 56 } Ni mass are low ( 0.12 \mathrm { M } _ { \sun } and 0.03 \mathrm { M } _ { \sun } , respectively ) .
The spectra show strong calcium and Fe-peak features and very weak silicon features , reflecting the peculiar elemental abundance .
The key feature is the Doppler shift of the spectral lines up to \simeq \pm 12 , 000 km s ^ { -1 } , depending on the viewing angle , due to the bulk motion of the ejecta .
Our model matches well with some rapid transients .
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 .