0 Assigned ID: 7042 ----- Attempting Submission 1 (Tue Apr 14 00:07:44 GMT 2026) ----- FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser We are FLASHing to a total of about 45-50 e/pix, including sky background, on advice of CoI Bellini, in order to reduce CTE as much as possible. We have also made several other updates, in accordance with emails from the proposal scientists. submitting with the relaxed link on visit 09 (reverted to no seq-non-int), submitting so the system will have its dates correct again. -1219534740 ----- Attempting Submission 1 (Wed Aug 12 17:26:30 GMT 2026) ----- HST Phase II Proposal 18430 successfully submitted. Receipt: # 18430-1 ----- Attempting Submission 2 (Mon Aug 24 18:50:31 GMT 2026) ----- ----- Attempting Submission 4 (Wed Aug 26 12:38:51 GMT 2026) ----- HST Phase II Proposal 18430 successfully submitted. Receipt: # 18430-4 We are FLASHing in order to reduce CTE Planetary Nebulae in Globular Clusters: Are They All Ejected by Binary Stars? Stars now evolving in globular clusters (GCs) have initial masses of ~0.8 Msun. Theory predicts that single stars in such ancient populations likely cannot produce planetary nebulae (PNe)--because their post-AGB evolutionary timescales are so long that by the time the star is hot enough to ionise the ejecta, the PN has already dissipated. Nevertheless, there are 3 PNe known in Milky Way GCs. The existence of these PNe likely requires an origin from binary stars, which either merged early in their evolution, or recently underwent a common-envelope (CE) interaction. In the latter case, the central star of the PN would now be a close binary. We propose an acid test of this hypothesis by obtaining photometry of the central star of the PN JaFu 2 in the Milky Way GC NGC 6441. An HST study shows it to have a relatively low mass, strongly suggesting that it has undergone a CE event. In such a binary containing the hot central star and a main-sequence companion, with an orbital period of a few hours to several days, there will be heating effects that produce periodic photometric variations. These would be detectable with high-S/N WFC3 imaging and an optimal scheduling sequence. Thus a stringent test of the prediction that it is a close binary is possible. Failure to demonstrate binarity would call into question theoretical timescales for post-AGB evolution. Success would strengthen the paradigm that binary interactions are a major formation channel for PNe, and the ONLY channel in the old populations of GCs. More broadly, CE interactions are important in a wide variety of astrophysical settings--e.g., SN Ia, CVs, and even LIGO events--so it is crucial to understand them. Photometric monitoring of the nucleus of the planetary nebula JaFu 2 in the Galactic globular cluster NGC 6441. Since its expected variations are due to a heated hemisphere on a cool, close companion of the hot nucleus, the photometric amplitude should be largest at longer wavelengths. The WFC3/UVIS channel I band (F814W) is ideal. A few broad-band observations will be taken at shorter optical wavelengths and in the NUV, to monitor colour variations as well as search for the anticipated two components in the SED of the central star. Exposure times are of order 125 sec; thus several dithered exposures in each filter can be obtained during each HST orbit, by using an appropriate small subarray. Cadence. We will use an optimal spacing of the epochs that samples as many different binary periods as possible in the minimum number of HST orbits. Figure 3 plots the largest orbital phase gap, as a function of assumed binary orbital period, for an observing sequence that covers HST orbits 0, 1, 2, 4, 7, 12, 20, 31, and 47, counting from an arbitrary starting point. Thus our total request is 9 orbits, over an interval of about 3.1 days. PI HOWARD E. BOND (Adjunct Professor of Practice, Pennsylvania State University; Astronomer Emeritus, Space Telescope Science Institute; Eureka Scientific Principal Invesigator) has extensive experience with HST observing. He specializes in stellar astronomy and has authored or coauthored over 280 refereed papers, with over 12,600 citations. CoI ANDREA BELLINI (Principal Staff Scientist, Space Telescope Science Institute) is an authority on astrometric and photometric analyses of HST images. He has authored or coauthored over 175 refereed publications, with over 11,000 citations. Stellar Physics and Stellar Types Stellar Populations and the Interstellar Medium 6 false false false false false false false SUPPORTED STAR INTERACTING BINARY PLANETARY NEBULA CENTRAL STAR POST-AGB STAR SDO J2000 J2000 WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F218W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F390W Timing link suitability includes constraints ([04 After 01 by 0.3 to 0.3 days] [05 After 01 by 0.5 to 0.5 days] [06 After 01 by 0.8 to 0.8 days] [07 After 01 by 1.3 to 1.3 days] [08 After 01 by 2.0 to 2.0 days] [09 After 01 by 3.1 to 3.1 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "01" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:10:43.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1126224 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "01" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2691 :al-overhead-at-end 172 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18430 :visit-id "01" :orbit-number 2 :pcs-time 301 :si-vis-utilization 2669 :al-overhead-at-end 172 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18430 :visit-id "01" :orbit-number 3 :pcs-time 301 :si-vis-utilization 2688 :al-overhead-at-end 172 :internal-dur-at-end 190 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 3 0 Timing link suitability includes constraints ([04 After 01 by 0.3 to 0.3 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "04" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:23.0" :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 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "04" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2691 :al-overhead-at-end 172 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([05 After 01 by 0.5 to 0.5 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "05" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:24.0" :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 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "05" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2691 :al-overhead-at-end 172 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([06 After 01 by 0.8 to 0.8 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "06" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:24.0" :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 351936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "06" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2691 :al-overhead-at-end 172 :internal-dur-at-end 421 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([07 After 01 by 1.3 to 1.3 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "07" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:24.0" :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 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "07" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2690 :al-overhead-at-end 172 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([08 After 01 by 2.0 to 2.0 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "08" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:24.0" :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 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "08" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2691 :al-overhead-at-end 172 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([09 After 01 by 3.1 to 3.1 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18430 :visit-id "09" :proposal-version -1 :trans-version "20260618" :date "24-Aug-2026 12:03:26.0" :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 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18430 :visit-id "09" :obset-id "09" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18430 :visit-id "09" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2690 :al-overhead-at-end 172 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 1 0