17999( 4) - 12-Jun-2026 17:43:13 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17999 Version: 4 Check-in Time: 12-Jun-2026 17:43:13 STScI Edit Number: 0 Title Structure of the Extreme-UV Continuum Source in the Heavily Microlensed Quasar SDSS J1339+1310 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Christopher W. Morgan United States Naval Academy Y CoI: Prof. Xinyu Dai University of Oklahoma Norman Campus N CoI: Prof. Luis J Goicoechea University of Cantabria N CoI: Dr. George Chartas College of Charleston N CoI: Vyacheslav Shalyapin Kharkiv National University N ------------------------------------------------------------------------------------ Abstract We propose to image the gravitationally lensed quasar SDSS J1339+1310 using a total of 12 orbits during HST Cycles 32 & 33. These regular monitoring observations of this heavily microlensed system with WFC3-UVIS in the F275W band will enable two primary science objectives: (1) We will analyze the microlensing variability in the resulting HST UV light curves in conjunction with existing optical light curves to make a measurement of the size of this quasar's continuum emission source at extreme-UV (EUV) wavelengths (83.7 nm in the rest frame). Only one other empirical measurement of a quasar's accretion disk size has ever been made at these extremely short UV wavelengths. (2) Coupling the new EUV size measurement with an existing measurement in the rest-frame near-UV will permit an empirical constraint on the temperature profile in this quasar's accretion disk. Empirical measurements of temperature profiles in other systems are quite discrepant from the predictions of basic thin disk models. We have also requested one deep observation with WFC3-IR in the F160W (H-band) to permit accurate modeling of the lens galaxy's mass profile. HST is the only existing telescope capable of making these UV observations with the angular resolution required to separate the flux from this lensed quasar's individual images and its lens galaxy. ------------------------------------------------------------------------------------ Observations Description ------------------------ This obsering program was approved for 6 orbits in Cycle 32 and 6 orbits in Cycle 33. This Phase II proposal covers the 6 Cycle 32 observations; the Cycle 33 observations will be scheduled in a separate Phase II proposal prior to Cycle 33. During Cycle 32, we will conduct 6 orbits of WFC3 observations to monitor SDSS1339 in the UV (F275W), and we will collect 1 deep image in the IR (F160W). Since the size scale of the quasar's BLR is much larger than the accretion disk, it is important to avoid contaminating emission line flux. The bandwidth of F275W corresponds to 775 A < lambda_{rest} < 898 A in the rest frame, just short of the Lyman limit at 912 A, but well clear of the Lyman beta emission line at 1026 A. Exposure times were calculated using the WFC3-UVIS Exposure Time Calculator (ETC) by direct upload of the 2016 UVIS G280 grism spectra with the goal of achieving S/N = 100 for the fainter image (image A). Each F275W 17999( 4) - 12-Jun-2026 17:43:13 - [ 2] observing epoch must be separated from a previous epoch by the system's time delay of 47+/-5 days. The need to differentiate between intrinsic and extrinsic (microlensing) variability drives the requirement for a (loose) scheduled monitoring interval in our observations. In Cycle 32 we have scheduled 5 sequenced WFC3/UVIS observations separated by the 47+/-5 day time delay. Each WFC3/UVIS observation consists of a dithered F275W exposure, each of which is timed to accomplish S/N = 100 in the fainter of the two quasar images (image A) without saturating the brighter image (B). We made use of the WFC3-UVIS-DITHER-BOX pattern with default line and point spacing, comprising four 540 sec sub-exposures. The dithering scheme will allow for correction of cosmic rays and detector anomalies, while also sub-sampling the UVIS PSF. To minimize losses from charge transfer effeciency (CTE) we employed the UVIS2-C1K1C-CTE aperture in all F275W images. We will also conduct one deep observation of SDSS1339 using WFC3/IR in F160W to allow for an accurate photometric fit of the lens galaxy. We uploaded ground-based VLT-XSHOOTER spectra into the WFC3-IR ETC to develop the the observing scheme for this single deep observation, with a goal of accomplishing S/N =100 for the elliptical lens galaxy without saturating either of the quasar images. The lens galaxy has a half-light radius of 1 arcsec and the quasar images are separated by 1.7 arcsec, so we will use the WFC3-IR-DITHER-BLOB dither pattern with its larger point spacing. This ensures that the target will not overlap any of the same pixels during subexposures while also avoiding the IR dust blobs on the detector. To ensure adequate sub-PSF sampling, we used the WF3C-IR-DITHER-LINE-3POINT subpattern at each primary dither location. ------------------------------------------------------------------------------------ 17999( 4) - 12-Jun-2026 17:43:13 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J133907 GALAXY, ELLIPTICAL, RA=13H39M7.1409S, J2000 V = 19.13 F_{\lambda} = 6.76 \times .13+131039.6 GRAVITATIONAL LENS, DEC=+13D10'39.62" 10^{-17} erg cm^{-2} s^{-1} \AA^{-1} at QUASAR 2750 \AA as measured by HST WFC3/UVIS G280 Grism Spectroscopy. Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17999( 4) - 12-Jun-2026 17:43:13 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17999( 4) - 12-Jun-2026 17:43:13 - [ 5] Visit: 07 (Cycle 33 Visit 1) Visit Requirements: On Hold Comments: Additional Comments: Visits 2-6 from the Cycle 32 phase of this two-cycle program are all scheduled to occur in HST Cycle 33, with Cycle 32 visit 6 happening in the window May 27 - June 3 2026. Visits 7-12 need to be scheduled after the Cycle 32 observations, so the scheduling windows assigned by the APT visit planner will need to be manually modified before this program is flight ready. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 6] Visit: 08 (Cycle 33 Visit 2) Visit Requirements: AFTER 07 BY 42 D TO 52 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 7] Visit: 09 (Cycle 33 Visit 3) Visit Requirements: AFTER 08 BY 42 D TO 52 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 8] Visit: 10 (Cycle 33 Visit 4) Visit Requirements: AFTER 09 BY 42 D TO 52 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 9] Visit: 11 (Cycle 33 Visit 5) Visit Requirements: On Hold Comments: Additional Comments: Post TTRBHST-93558 by the PI: Note that to make this visit schedulable, I had to remove the timing requirement for 6-50 days following visit 4. Optimally, visits 5-7 will be "interlaced" between visits 1-4 to allow for the maximum number of visits separated by the 47\pm 5 day period. I think this may need to be done manually by the program coordinator prior to this being flight ready. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 10] Visit: 12 (Cycle 33 Visit 6) Visit Requirements: AFTER 11 BY 42 D TO 52 D On Hold Comments: Additional Comments: No "Timing Requirements" were assigned to Visit 12 (Cycle 33 Visit 6) since the 6 observation sequence was longer than the permissible window in Cycle 33. This visit will optimally be sequened manually 47+-5 days after Cycle 32 Visit 6 or Cycle 33 Visit 6. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 11] Visit: 13 (Cycle 33 Visit 7) Visit Requirements: AFTER 12 BY 42 D TO 52 D On Hold Comments: Additional Comments: This visit was added following approval of TTRBHST-93558. The approval message follows: "The issue (TTRBHST-93558) has been updated with the following decision: Issue Summary: HOPR for Program 17818 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Dear Christopher, You submitted HOPR 93558 for HST program 17818 on May 06, 2026. After review, the Telescope Time Review Board (TTRB) approves your request and awards one orbit to repeat the observations in Visit 05, which suffered a guide-star acquisition failure, leading to degraded data. We also approve scheduling this repeat as requested: along with next cycle's observations, by appending it to the Visits 11-12 (of PID 17999) sequence. However, we were unable to reschedule Visit 06 as that would disrupt the HST schedule. The request is within the 90-day limit, and the program is less than 90% complete. The failed data will be made public immediately. Laura Watkins, the Science Policy Division Head, has concurred in our recommendation. Please work with your Program Coordinator (PC) to prepare a revised Phase II file. With best regards, Debopam for the TTRB Space Telescope Science Institute e-mailed to PI/PC/CS Morgan/Skipper/Revalski cc: TTRB, HST Mission Office, WFC3 User Support, HST Program folder -- Dr. Debopam Som Senior Staff Scientist Space Telescope Science Institute Ph: 4103382405 dsom@stsci.edu" Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS-J13390 WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=21 1 540 S PATTERN 2 1 7.13+131039 S 1C-CTE (2160 S) .6 ------------------------------------------------------------------------------------------------------------------------------------ 17999( 4) - 12-Jun-2026 17:43:13 - [ 12] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A 039.6 S K1C-CTE SDSS-J133907.13+131 1 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 1 N/A 039.6 S K1C-CTE 17999( 4) - 12-Jun-2026 17:43:13 - [ 13] Summary Form for Proposal 17999 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=21 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 07 BY 42 D TO 52 D, AFTER 08 BY 42 D TO 52 D, AFTER 09 BY 42 D TO 52 D, AFTER 11 BY 42 D TO 52 D, AFTER 12 BY 42 D TO 52 D, PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSS-J133907.13+131039.6 ------------------------------------------------------------------------------------------------------------------------------------