During the course of the Catalina Real-time Transient Survey (CRTS) we have discovered an exceptionally luminous optical transient. The source of this event appears to be either the most luminous supernova ever discovered, or the first clear optical detection of the tidal disruption of a star by a massive black hole. In spite of numerous ground and space-based observations the exact nature of the event remains unclear. High spatial resolution observations with HST WFC3 are critical to solving this mystery.

We will use HST WFC3-UVIS channel subarray observations with F390W, F555W & F763M to image the target seven times with each filter during one orbit. Using HST WFC3 exposure calculator, along with our May 5th opitcal spectrum as input, we find that S/N > 200 observations can be achieved with F390W, F555W & F763M in 45, 35,and 75 seconds, respectively. Our observations will consist of seven exposures in each filter in a custom bulit pattern designed specifically to reconstruct the image with the best possible resolution will also mitigate the impact of hot pixels and cosmic rays. These images will be taken using F390W, F555W, and F763M. F390W will highlight the location of the hot blue host-AGN component. F555W will trace the continuum component and observations with F763M will highlight the location of the strongest (red-shifted) H_alpha emission (which lies at the center of this filter's transmission), without also including the significant continuum component of a broader filter. We will use 1kx1k pixel subarrays which will allow us to stack the images thus greatly decrease the readout overheads with the buffer dump occuring after occultation but with the orbit. This array size gives us a 40" field of view which contains the entire galaxy target plus a nearby star. The visit planner suggests such observation can be sheduled throughout May and Jun. May dates are perfered since the target is a fading transient source. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 0 false 0.0 0.0 false false false false false false SUPPORTED GALAXY SEYFERT STARBURST J2000 10 29 12.5800 +40 42 19.70 J2000 WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F763M The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12117 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "12-May-2010 10:53:24.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 365584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12117 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12117 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2990 :al-overhead-at-end 79 :internal-dur-at-end 438 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3341 :pcs-gap 0 ) false 1 0