This is a resubmission (although I'm not getting the resubmit button) -- Knox Long found a way to use the built in dithers, which also squeezed in a little more integration time. This version implements that scheme. ----- Attempting Submission 1 (Sat Jul 17 12:28:24 GMT 2010) ----- ----- Attempting Submission 2 (Thu Jul 22 12:55:01 GMT 2010) ----- SN2008S in NGC6946 is the prototype of a new class of optical transients. Its luminosity was low for a Type II supernova, and the progenitor star was identified as a completely dust obscured log (L/Lsun)=4.5, T=440K massive star (~10 Msun) in archival Spitzer data. It is uncertain whether this is a new class of low−luminosity supernova (e.g. an electron capture supernova) or a new class of massive star outburst. The transient has now faded to the point where the source is again invisible in the optical. Near−IR detections are consistent with a somewhat hotter source, T~1200K, somewhat brighter than the progenitor and still fading at ~3 mag/year. Using two epochs of IRAC observations to constrain the mid−IR emission, and two epochs of HST H−band/J-band observations to constrain emission from cool stars, we will solve this mystery by either identifying and characterizing the surviving progenitor or ruling out its survival.

We will obtain two epochs of WFC3/IR images of the transient SN2008S in NGC6946 separated by at least 6 months. The goal is to identify the transient in the near-IR relative to our ground based images, determine it's magnitude and rate of fading compared to the estimated luminosity of massive stars, and characterize its environment (crowding). This will be matched to a set of Warm Spitzer observations at 3.6 and 4.5 to constrain the luminosity in emission by warm dust. The primary observations are the WFC3/IR H-band (F160W) observations. We will obtain 3 dithered MULTIACCUM H-band observations in each epoch. We also obtain a single J-band image. Given the overheads created by buffer dumps it was not possible to obtain multiple dithers in the second filter. However, by combining the J-band images from the two epochs we will obtain a high quality image. This J band data will be used to characterize the region around SN2008S and the other 3 SN in the WFC3/IR field of view. We also include ACS/WFC I (F184W) and V (F555W) parallels. The goal here is simply to build the archival data base for NGC6946 with deep, high quaility data. A loose orient restriction will keep the WFC on some part of the galaxy, and the epoch 1/2 orients are required to be the same. This seems to cause no scheduling difficulties given the timing requirement of the primary observations. For most possible orientations 1 or 2 of the addition SN in N6946 will lie in the ACS field of view. This revised version uses a 3pt line dither for F160W followed by a F110W exposure. A pos targ from the last H band observation is used in epoch 1 but not in epoch 2 to produce an effective dithering of the two J band observations. 12 false 0.0 0.0 false false false false false false SUPPORTED EXT-STAR SUPERNOVA J2000 00 00 0.0000 +00 00 0.00 J2000 WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.605 LINE false false 3 41.788 WFC3-IR-DITHER-LINE-3PT 1 false 1279802931964 Timing link suitability includes constraints ([02 After 01 by 180.0 to 365.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. /tmp/OPVisit3538.xml (Tic-Visit :proposal-id 12331 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "22-Jul-2010 08:48:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2129200 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12331 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12331 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3124 :al-overhead-at-end 0 :internal-dur-at-end 1060 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3516 :pcs-gap 0 ) true 1 0 1279802934210 Timing link suitability includes constraints ([02 After 01 by 180.0 to 365.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. /tmp/OPVisit3539.xml (Tic-Visit :proposal-id 12331 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "22-Jul-2010 08:48:54.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2129200 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12331 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12331 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3126 :al-overhead-at-end 0 :internal-dur-at-end 1060 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3516 :pcs-gap 0 ) true 1 0