We've been advised to not use the g' filter for SED fitting and have substituted the F475W filter with the F438W. Relevant personnel have been contacted about this substitution. Please advise if there are any problems reading the submission. This is a revised submission chaning aperture from UVIS1 to UVIS2. 1162714075 ----- Attempting Submission 1 (Wed Aug 07 12:48:10 GMT 2013) ----- ----- Attempting Submission 2 (Wed Aug 07 20:05:36 GMT 2013) ----- An unprecedented transient event has just been detected in a spiral arm of NGC 6984. Two H-poor supernovae - SN 2012im and 2013ek - both originating from massive stripped-envelope progenitor stars have been found at virtually the same location (< 0.4 arcsec). Interpretations have varied widely. Chance alignment of two completely independent supernovae of the same Type Ib/c class exploding within one year of each other from the same stellar cluster is statistically improbable. Thus, the two explosions are most likely physically related, and this has important ramifications in areas of high-mass binary star evolution and explosion mechanisms of core-collapse supernovae. High resolution HST images are the only means by which to probe the stellar environment of the progenitor system. To this end, we request WFC3/UVIS imaging in F336W, F475W, F555W, and F814W of SN 2013ek in the next month while SN 2013ek is still bright to pin down its precise location within a nearby cluster of stars visible in an archival plate of NGC 6984. Complementary follow-up images will be requested during regular GO proposals in Cycle 22 when the fading supernova reveals what is left behind. The proposed suite of images will allow us to model the cluster's broadband colors to determine properties of the progenitor star system's environment (e.g., mass, age, luminosity, star formation rate, metallicity) that will be used to constrain possible explosion scenarios. We request Director's Discretionary time for these observations as a non-disruptive TOO. We request two orbits to image the region of SN 2013ek and host galaxy NGC 6984 using WFC3/UVIS with the F336W, F475W, F555W, and F814W filters. Target is visible between August 7-22, for 57 mins per orbit. We estimate total integration times of ~25-30 mins per filter. Three- or four-point sub-pixel dithering will achieve the best resolution possible. NGC 6984 is at a distance of 65 Mpc. The 0.04" pixel scale of WFC3/UVIS will constrain the position of supernova and host cluster within ~12 pc. Default false false false false false SUPPORTED EXT-STAR SUPERNOVA J2000 POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 1 false 1375905712210 /Users/fesen/Desktop/OP-cache/13505_v2-v01.xml The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13505 :visit-id "01" :proposal-version -1 :trans-version "20130502" :date "07-Aug-2013 16:01:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 4620000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13505 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13505 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3084 :al-overhead-at-end 125 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13505 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3095 :al-overhead-at-end 125 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) true 2 0