We present the discovery of ASASSN-18jd ( AT 2018bcb ) , a luminous optical/UV/X-ray transient located in the nucleus of the galaxy 2MASX J22434289–1659083 at z = 0.1192 . Swift UVOT photometry shows the UV SED of the transient to be well modeled by a slowly shrinking blackbody with temperature T \sim 2.5 \times 10 ^ { 4 } ~ { } K , a maximum observed luminosity of L _ { \text { max } } = 4.5 ^ { +0.6 } _ { -0.3 } \times 10 ^ { 44 } ~ { } erg~ { } s ^ { -1 } , and a total radiated energy of E = 9.6 ^ { +1.1 } _ { -0.6 } \times 10 ^ { 51 } ~ { } erg .
X-ray data from Swift XRT and XMM-Newton show a transient , variable X-ray flux with blackbody and power-law components .
Optical spectra show strong , roughly constant broad Balmer emission as well as transient features attributable to \ion Heii , \ion Niii-v , \ion Oiii , and coronal Fe .
While ASASSN-18jd shares similarities with Tidal Disruption Events ( TDEs ) , it is also similar to the ‘ ‘ rapid turn-on ’ ’ events seen in quiescent galaxies and in faint Active Galactic Nuclei ( AGNs ) .