We propose observations of the exceptional long duration transient GRB 111209A. Its long-lived gamma- and X-ray emission mark it apart from other GRBs, and are very similar to those of the Christmas day burst 2010, whose origin remains under debate, culminating in the publication of two competing scenarios in Nature earlier this month. Unlike the Christmas day burst, our deep VLT and Gemini spectroscopy has unveiled the redshift of GRB 111209A, and allows us to lauch a comprehensive campaign to understand its origin. Does it originate from a massive star collapse akin to long GRBs? Is it related to Galactic nuclei, as suggested for some other long lived gamma-ray transients discovered in 2011? By utilizing the exquisite HST PSF we will obtain a precise position of the afterglow with respect to its host galaxy. Coupled with this we will use the unique ability of WFC3 grism's to obtain good S/N across the 1 micron region to search at the expected peak of any supernova, and hence provide spectroscopic evidence for the presence (or absence) of an associated supernova. Ultimately these observations may show conclusively what these long duration transients are, and link them into the diverse populations of high energy transients that are now being uncovered.

We propose to obtain observations of the exceptional GRB 111209A. Our first epoch of observations will consist of two orbits, one of imaging and a second of grism spectroscopy. Our imaging will be split between the F336W and F125W filters on WFC3. We will use a 3 point dither for each filter to pack the orbit, with the F336W observations tracking the afterglow, and F125W providing a measure of any associated supernova. Our grism observations will utilize G102 to map the expected spectral peak of the supernova. We will use a 4-point dither pattern. HOT STARS 0 false 0.0 0.0 false false false false SUPPORTED UNIDENTIFIED ACCRETION DISK GAMMA RAY EMITTER X-RAY EMITTER J2000 WFC3/IR Imaging No No F125W WFC3/UVIS Imaging No No F336W WFC3/IR Imaging No No F125W WFC3/UVIS Imaging No No F336W WFC3/IR Imaging No No F125W WFC3/UVIS Imaging No No F336W WFC3/IR Spectroscopic No No G102 WFC3/IR Spectroscopic No No G102 WFC3/IR Spectroscopic No No G102 POS-TARG DITHER 0.145 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE 1 false POS-TARG DITHER 0.636 LINE false false 3 41.788 WFC3-IR-DITHER-LINE 2 false POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 3 false POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 4 false The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 1324376293000 62.27361669373499 (Tic-Visit :proposal-id 12786 :visit-id "01" :proposal-version -1 :trans-version "20110825" :date "14-Dec-2011 16:56:06.0" :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 1336288 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12786 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12786 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2686 :al-overhead-at-end 0 :internal-dur-at-end 597 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3029 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 1324382043000 62.32439428860121 (Tic-Visit :proposal-id 12786 :visit-id "02" :proposal-version -1 :trans-version "20110825" :date "14-Dec-2011 17:49:23.0" :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 992304 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12786 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12786 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2627 :al-overhead-at-end 0 :internal-dur-at-end 464 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3029 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12786 :visit-id "03" :proposal-version -1 :trans-version "20110825" :date "27-Dec-2011 22:43:01.0" :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 2008032 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12786 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12786 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2875 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12786 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3053 :al-overhead-at-end 116 :internal-dur-at-end 670 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) true 2 0