0 Assigned ID: 1031 ----- Attempting Submission 1 (Sat Feb 25 00:45:10 GMT 2012) ----- HST Phase I Proposal 1031 (HST_47tuc_2012.apt) successfully submitted. The warnings indicate that I should click "Increase Scheduling Flexibility". However, clicking this gives me an error, since I have no scheduling constraints. This submission includes addition of post-flashes to our ACS coordinated parallel observations, as suggested to benefit our program. -470049374 ----- Attempting Submission 1 (Tue Jul 10 21:43:01 GMT 2012) ----- ----- Attempting Submission 2 (Tue Jul 09 02:49:26 GMT 2013) ----- A Deep, Near-UV Probe of the Faint Cataclysmic Variable Population of 47 Tucanae Dense globular clusters are rich sites for the production of interacting binaries, such as cataclysmic variables (CVs), millisecond radio pulsars (MSPs), and double WD systems. Previous HST WFPC2 and Chandra X-ray observations have identified 22 CVs in 47 Tuc with M_V<10. The unprecedented near-UV sensitivity, field of view, and resolution of the WFC3, in combination with subarcsecond Chandra positions, will allow us to probe the faint CV population down to M_V=11.6, identifying a large population of CVs at very low mass-transfer rates. The distribution of CV mass transfer rates inferred will constrain models of CV evolution and dynamical formation. We will also survey the population of helium-core WDs, another window into binary evolution. Our goal is to reach U~24.8 in both F390W and F300X, sensitive to faint blue CVs. In this dense cluster core, we use 4x4 dithering to improve our spatial resolution, resulting in target exposure times of 3881 s in F390W and 14256 s in F300X, leading to 8 orbits. We actually achieve 4656 s in F390W, and 14736 s in F300X. We schedule our program in two visits, since no visit should be more than 5 orbits. Each visit starts with one orbit of F390W (4 exps of ~580 s, considering guide star acq), then 3 orbits of F300X (4 exps of 608 s each, considering shorter re-acq). Each orbit steps through a WFC3 DITHER-BOX pattern. The 3rd and 4th orbits are offset by (1.446", 2.926") and (-1.446",-2.926") to ensure that all parts of the chip gap get 2/3 coverage in F300X in each visit, and the 1st orbit of the 2nd visit is offset to ensure that the chip gap is covered in F390W. We set up our dithers as POS-TARGS (following details in the document WFC3-2010-09.pdf) to allow inclusion of parallel ACS WFC exposures (patterns can't be used since we don't use the same parallel ACS parameters for all WFC3 pointings in an orbit). Dumping two WFC3 exposures takes longer than a single WFC3 exposure, so can only be done at the end of an orbit. Since ACS must be dumped after each exposure, only the last two WFC3 exposures per orbit can have long (~500 s) ACS parallels, while the first two WFC3 exposures can have short (~200 s) parallels (allowing immediate buffer dump). This gives us sixteen ACS exposures per visit, which we divide into 3 short F438W, 3 short F625W (one only 65 s to correct saturated stars), 2 short F658N, and 8 long F658N exposures. We find that we reach R~23.9 in H-alpha, R~24.5 in B, and 25 in R. Since the ACS fields are two half-mass radii from the center, their crowding will not be severe, so we do not attempt detailed subpixel dithering, though our WFC3 dithering will be sufficient for hot pixel and bad column cleaning. We place no restrictions on the timing of the two visits, so the two WFC3 visits may be at different roll angles, and the two parallel ACS fields may overlap, or be two separate fields. We choose WFC3-CENTER and place the target point at the Goldsbury (2011) center of 47 Tuc. We choose a 10-photon post-flash to ensure that our F300X exposures have sufficient signal to avoid the worst CTE degradation. Existing WFC3/UVIS F390W exposures show that these exposures will easily attain sufficient electrons/pixel. We are willing to add post-flash electrons to our H-alpha ACS exposures. HOT STARS 12 false false 0.0 0.0 false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER NGC104 J2000 J2000 Resolved target. Faintest target CVs U=24.8. WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F390W ACS/WFC Imaging No No F435W ACS/WFC Imaging No No F658N ACS/WFC Imaging No No F625W /private/var/folders/Zy/ZykLH3gZG7mByzWdZSUcTk+++TI/-Tmp-/OPVisit6513984074030386518.xml The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. 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