0 Assigned ID: 74 ----- Attempting Submission 1 (Mon Apr 03 17:52:50 GMT 2017) ----- HST Phase I Proposal 74 (what_is_14hls.apt) successfully submitted. Receipt: # 74-1 ----- Attempting Submission 2 (Mon Apr 03 17:54:24 GMT 2017) ----- HST Phase I Proposal 74 (what_is_14hls.apt) successfully submitted. Receipt: # 74-2 ----- Attempting Submission 3 (Fri Apr 07 18:05:59 GMT 2017) ----- Re-submitting with new dither pattern (increased step to cover chip gap) 1293080407 ----- Attempting Submission 1 (Wed Jul 12 21:24:40 GMT 2017) ----- HST Phase II Proposal 15222 (what_is_14hls_phase_ii.apt) successfully submitted. Receipt: # 15222-1 ----- Attempting Submission 2 (Wed Jul 12 21:58:11 GMT 2017) ----- iPTF14hls is an onging nearby supernova with spectral features identical to those of the common Type IIP class but more slowly evolving, remaining luminous for over 600 days with at least five distinct peaks in its light curve and showing evidence for multiple pre-explosion eruptions. The observed properties of iPTF14hls are unique among all known supernovae, challenge all existing explosion models and likely indicate pre-explosion eruptions with time scales and energies never observed before. Such eruptions are theorized to occur in ~95-130 solar mass stars which experience the pulsational pair instability. If iPTF14hls is indeed the first observed case of such a supernova, then determining its progenitor mass and metallicity will provide the first observational constraints of stellar evolutionary models in these mass ranges. Since no pre-explosion high-resolution imaging of the location of iPTF14hls exist, the only way to constrain the progenitor properties (independent of the supernova) is through HST studies of the site after the event fades. Such studies will require knowing the position of iPTF14hls to few-parsec precision. We propose a single-orbit HST observation to obtain high resolution localization of iPTF14hls before it fades. These images will serve as registration anchors for future post-event observations at the required precision (not possible with ground-based AO imaging). These observations will also allow us to measure the very late-time decline rate of iPTF14hls, constraining possible power sources, and to test an alternative explanation for iPTF14hls as a lensed normal supernova, by constraining any departure from point-source emission. This is a single orbit imaging observation of a supernova in two filters (F475W and F625W) with UVIS. We implement a 3-point dither patern for each exposure to improve spatial resolution while still maintaining a minimum exposure time above 350s (to enable buffer readout during the next exposure). We also wish to capture the overall morphology of the host galaxy, which is approximately 10 arcseconds across. In addition, we require a large number of sources around the supernova to be able to register the current images to any future HST images taken of the host galaxy after the supernova fades, in order to study the supernova's immediate environment. To make sure that the galaxy is far enough from any chip edge and that we have enough registration sources in all directions around the supernova, we choose the UVIS2 aperture. Stellar Physics 0 false false false false false false SUPPORTED EXT-STAR SUPERNOVA TYPE II The magnitude estimate depends on the epoch of observations as the supernova continues to fade. J2000 J2000 WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W POS-TARG DITHER 1.813 We choose a dither pattern that will also cover the chip gap to increase the availability of registration stars in that area. LINE false true 3 85.759 WFC3-UVIS-DITHER-LINE-3PT 3 false 1499896659029 /private/var/folders/mg/myjgy5ns1195d0dnr3v0sf9w0000gn/T/OPVisit4068332163281705981.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15222 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "12-Jul-2017 14:57:38.0" :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 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15222 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15222 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3059 :al-overhead-at-end 119 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3393 :pcs-gap 0 ) true 1 0