Accretion disks around supermassive black holes ( SMBH ) are promising sites for stellar mass black hole ( BH ) mergers due to mass segregation and merger acceleration by disk gas torques .
Here we show that a GW-kick at BH merger causes ram-pressure stripping of gas within the BH Hill sphere .
If R _ { H } \geq H , the disk height , an off-center UV flare at a _ { BH } \sim 10 ^ { 3 } r _ { g } emerges within t _ { UV } \simO ( 2 { days } ) ( a _ { BH } / 10 ^ { 3 } r _ { g } ) ( M _ { SMBH } / 10 ^ { 8 } M% _ { \odot } ) ( v _ { kick } / 10 ^ { 2 } km / s ) post-merger and lasts O ( R _ { H } / v _ { kick } ) \simO ( 5 t _ { UV } ) .
The flare emerges with luminosity O ( 10 ^ { 42 } { erg / s } ) ( t _ { UV } / 2 { days } ) ^ { -1 } ( M _ { Hill } / 1 M _ { \odot } ) ( v _ { % kick } / 10 ^ { 2 } { km / s } ) ^ { 2 } .
AGN optical/UV photometry alters and asymmetric broad emission line profiles can develop after weeks .
If R _ { H } < H , detectability depends on disk optical depth .
Follow-up by large optical sky surveys is optimized for small GW error volumes and for LIGO/Virgo triggers > 50 M _ { \odot } .