0 Assigned ID: 614 ----- Attempting Submission 1 (Fri Apr 08 17:27:31 GMT 2016) ----- HST Phase I Proposal 614 (Ou4_Cycle24.apt) successfully submitted. Receipt: # 614-1 This Phase II proposal is the resubmission for Cycle 26 and second epoch observation with smaller exposure times to take into account extra times for GS (Re)Acquisition. -601818460 ----- Attempting Submission 1 (Tue Jul 12 11:33:55 GMT 2016) ----- ----- Attempting Submission 2 (Wed Sep 07 16:28:20 GMT 2016) ----- ----- Attempting Submission 3 (Wed Jul 25 15:54:43 GMT 2018) ----- ----- Attempting Submission 4 (Fri Dec 07 16:33:05 GMT 2018) ----- Ou4 is a giant bipolar outflow with a total length of 1.2 degrees on the sky that was discovered in the optical in the direction of the blister HII region Sh2-129. The distance, the nature, and the driving source of Ou4 are, however, not known. Ou4 is relevant for the study of the eruptive phenomena producing collimated outflows from evolved low-mass binary stars and young, massive stellar systems. Our morpho-kinematics study of the Ou4 south bow-shock has allowed us to predict its expansion proper motion that is directly related to its distance. We propose to image the brightest [O III] emission of this bow-shock with the UVIS channel of the WFC3 in Cycle 24 and 26 in order to determine the distance of this largest known stellar bipolar outflow from its expansion proper motions. This measurement is crucial to determine the true nature of Ou4: either a foreground planetary nebula or a giant bipolar outflow launched ~90,000 years ago by HR 8119, the young massive triple system ionising Sh2-129. The first epoch observation was obtained on 2016-10-23 with ORIENT=78.8 degrees. To increase the time separation between the first and this second observation, we increase ORIENT of about 180 degrees to allow scheduling in May 2019 and consequently change the pointing to survey the same area of the bow shock. We use the observing strategy of the first epoch observation. We use the WFC3/UVIS channel with the F502N narrow filter to survey the brightest emission of the 5007 A line of the [O III] doublet in the Ou4 giant bipolar outflow. We execute dithered exposures using the B6 pattern (pre-defined WFC3-UVIS-MOS-DITH-LINE pattern has been modified), which combines two step over the chip gap to maximize the surveyed area and sub-pixel steps to improve the PSF sampling (WFC3 ISR 2010-09). The six frames are executed inside the same orbit for the best dither pointing accuracy. We use parallel buffer dumps. We add a flash at the end of each exposure (12 electrons) to reduce the charge losses during the detector readouts. Stellar Physics 6 false false false false false false false SUPPORTED ISM BIPOLAR OUTFLOW EMISSION LINE NEBULA HII REGION SHOCK FRONT WIND YES The target is extended and has a very small expansion proper motion. The pointing coordinates are optimized to maximize the emission survey. The flux is our surface brightness threshold in erg/s/cm2/arcsec2. J2000 J2000 2.25E-16 WFC3/UVIS Imaging No No F502N POS-TARG DITHER DITHER 2 2.632 Pre-defined WFC3-UVIS-MOS-DITH-LINE pattern has been modified to obtain B6 pattern (WFC3 ISR 2010-09). WFC3-UVIS-MOS-DITH-LINE false true 0.119 3 47.134 POS-TARG WFC3-UVIS-MOS-DITH-LINE 33.715 1 true /home/ngrosso/Documents/HST/Cycle_26/Phase_II/OP-cache/Ou4_Cycle_26_Phase_II_revised-v01.xml 1544197958506 The scheduling data was generated by CASM 26.2.2. CASM was run in Phase II mode. Two consecutive orbits. We require a specific orientation to maximize the time baseline, to survey the same area of the bow shock that was observed in 2016, and to put a V=10.7-mag star in quadrant C to prevent any filter and window ghost artifacts (the latter being produced in a such narrow filter image by star with V<12 mag in quadrant D; WFC3 ISR 2011-16) that would disturb our proper motion measurement. We use an angle tolerance to increase the schedulability (16-26 May 2019). (Tic-Visit :proposal-id 15511 :visit-id "01" :proposal-version -1 :trans-version "20181130" :date "07-Dec-2018 16:52:38.0" :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 3465008 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15511 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15511 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3056 :al-overhead-at-end 123 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3389 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15511 :visit-id "01" :orbit-number 2 :pcs-time 302 :si-vis-utilization 3087 :al-overhead-at-end 123 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3389 :pcs-gap 0 ) true 2 0 We add a flash at the end of each exposure (12 electrons) to reduce the charge losses during the detector readouts. We add a flash at the end of each exposure (12 electrons) to reduce the charge losses during the detector readouts.