18427( 2) - 07-Aug-2026 19:48:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18427 Version: 2 Check-in Time: 07-Aug-2026 19:48:41 STScI Edit Number: 0 Title Post-periastron Evolution of Ejecta and Jet-precession in the R Aqr Symbiotic System ------------------------------------------------------------------------------------ Type Cycle GO 34 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Margarita Karovska Smithsonian Institution Astrophysical Y Observatory CoI: Mr. Warren J. Hack Eureka Scientific Inc. N ------------------------------------------------------------------------------------ Abstract We propose HST/WFC3 observations of the interacting symbiotic system R Aqr, as a followup to the HST archival observations obtained during the recent periastron (with the next periastron expected in about 40 years). Our principal goal is to use the HST unique high-angular resolution UV-optical imaging capability to obtain a detailed post-periastron time-lapse study of the new ejecta and jet/counter-jet propagation, and especially of the jet evolution and precession, at scales close to the binary itself, about 5 AU, to the extended jet-interaction region within 4000 AU from the central binary. The results will have a great impact on the understanding of other wind accreting, jet-producing systems (e.g., interacting binaries, YSOs, PN, AGN), whose close accreting and jet-forming environments cannot be currently resolved. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request a total of 6 orbits, in 2 visits, scheduled within a couple of weeks from each other. The HST high-angular resolution in the spectral regions (filters) that we selected is critical for achieving the science goals of this project. It is very important to have the images at different filters obtained close in time because the R Aqr periastron related outburst and jet structures evolve rapidly, The visits need to be scheduled as close together as possible to keep the orientation as similar as possible due to the HST orbit. This will minimize the errors in combining the exposures and allow us to recover the highest angular-resolution possible to study the origin of the jet of this active system. We also prefer that the observations are scheduled during Spring-Summer 2027 when the Mira is in the vicinity of (or at) its optical minimum (June-July 2027). The primary component should have a magnitude of V less than 10.5 mag based on the 2023-2026 light curves. This period around the Mira-star minimum starts roughly in April-2027 and goes through September 2027. This will allow the secondary and faint emission components in the core of this system to remain visible without the effects of saturation from the primary. The variable nature of the emission from R Aqr will require us to monitor the light curve and spectra closely, using ground based photometry and spectroscopy. Depending on when the observations are scheduled, we may need to 18427( 2) - 07-Aug-2026 19:48:41 - [ 2] adjust the exposures accordingly; specifically, in the month before the actual observations are taken. We plan to carry out most of the HST WFC3/UVIS imaging of R Aqr using the 4-point dither mode in several filters centered on spectral lines and the nearby continuum. This approach will allow us to reach 0.025''/pixel, and will also assist in cosmic ray removal. Combining the dithered images will result in improvement of the sampling of the PSF and will allow us to further enhance the (nominal 0.04'') resolution using deconvolution techniques such as Richardson-Lucy or EMC2 reaching 0.025''. This will nearly double the number of pixels covering the regions of interest. We also plan several long exposures to image the fainter outer lobes (about 20 arcseconds from the center) and determine their morphology and evolution when compared to the archival HST observations in the past decade. Most of the selected filters were used previously, including in the 2023 WFC3/UVIS observations. This will allow direct comparison and study of the dynamical evolution and proper motions of individual structures (inner jet, knots and blobs, outburst structures etc.). The images obtained in the spectral lines will provide information on the ionization state, temperature, and density of the gas. The full list of filters we plan to use can be found in the original Phase 1 proposal description. The F343N filter, for example, will provide the [NeV] line intensity and indicate whether temperatures significantly higher than $10^5$ K are present. The Mg II$\lambda$2800\AA\ line has a resonant scattering component and will provide information on the ionization state of the gas. The [OII]$\lambda$3726\AA\ line serves as a density indicator. Furthermore, the [SII]$\lambda$6731\AA/H$\alpha$ ratio will allow us to identify shocked vs. ionized gas emission. The [O III]4363\AA/5007\AA\ ratio gives the temperature which further constrains the shock speed and the ionizing spectrum. The F658N filter will provide an estimate of the [NII] emission and will allow us to calculate the [S II]/[N II] ratio, while also providing density diagnostics where the ratio gets suppressed in the inner regions of R Aqr. The H$\alpha$/H$\beta$ ratio will map the intrinsic reddening, i.e. dust regions/shells along the jet and counter-jet, and perpendicularly to the jet (eg, in the orbital plane). The exposure times used in this proposal are based on the online WFC3 ETC calculations as verified by the 2023 WFC3 observations of R Aqr. We optimize the efficiency of the observing time by using subarray readouts (1024x1024 readout) to minimize the overheads, while still providing a >=40''x 40'' field of view. Our observations also include post-flash exposure in order to partially remediate the effects of charge-transfer inefficiency due to the age of the detector. This proposal was generated using the latest APT based on the desired exposure times to avoid saturation and on the use of dither patterns, and makes the most efficient use of the observing time. A reduced gyro mode will not have any significant impact as long as the target is in the HST field-of-regard when the observations need to be taken. This will not require any explicit roll constraints for our observations. ------------------------------------------------------------------------------------ 18427( 2) - 07-Aug-2026 19:48:41 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-R-AQR STAR, ACCRETION DISK, RA=23H43M49.4634S +/- 0.1", J2000 V = 10 +/- 3.0 INTERACTING BINARY, DEC=-15D17'4.18" +/- 0.1" JET, SYMBIOTIC STAR Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 18427( 2) - 07-Aug-2026 19:48:41 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type SPIRAL Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.86 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18427( 2) - 07-Aug-2026 19:48:41 - [ 5] Visit: 01 Visit Requirements: BETWEEN 01-MAR-2027:00:00:00 AND 01-AUG-2027:00:00:00 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 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F502N FLASH=20 1 20 S (80 PATTERN 2 1 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 2 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F373N FLASH=20 1 100 S (400 PATTERN 2 2 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F487N FLASH=20 1 20 S (80 PATTERN 2 3 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F656N FLASH=20 1 2 S (8 S) PATTERN 2 4 S 1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 5 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F658N FLASH=20 1 5 S (20 S) PATTERN 2 5 S 1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 6 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F280N FLASH=20 1 140 S (560 PATTERN 2 6 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 7 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F673N FLASH=20 1 4 S (16 S) PATTERN 2 7 S 1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 8 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F547M FLASH=20 1 1 S (4 S) PATTERN 2 8 S 1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 9 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F280N FLASH=20 2 600 S S 1C-SUB (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F502N FLASH=20 2 500 S S 1C-SUB (1000 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F343N FLASH=20 1 90 S (360 PATTERN 2 11 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F502N 1 none none none 1 N/A S K1C-SUB 18427( 2) - 07-Aug-2026 19:48:41 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F502N 2 none none none 1 N/A S K1C-SUB V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F502N 3 none none none 1 N/A S K1C-SUB V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F502N 4 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F373N 1 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F373N 2 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F373N 3 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F373N 4 none none none 1 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F487N 1 none none none 1 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F487N 2 none none none 1 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F487N 3 none none none 1 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F487N 4 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F656N 1 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F656N 2 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F656N 3 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F656N 4 none none none 1 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F658N 1 none none none 1 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F658N 2 none none none 1 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F658N 3 none none none 1 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F658N 4 none none none 1 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F280N 1 none none none 2 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F280N 2 none none none 2 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F280N 3 none none none 2 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F280N 4 none none none 2 N/A S K1C-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS2-C1 F673N 1 none none none 2 N/A S K1C-SUB 18427( 2) - 07-Aug-2026 19:48:41 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-R-AQR 7 WFC3/UVI ACCUM UVIS2-C1 F673N 2 none none none 2 N/A S K1C-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS2-C1 F673N 3 none none none 2 N/A S K1C-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS2-C1 F673N 4 none none none 2 N/A S K1C-SUB V-R-AQR 8 WFC3/UVI ACCUM UVIS2-C1 F547M 1 none none none 2 N/A S K1C-SUB V-R-AQR 8 WFC3/UVI ACCUM UVIS2-C1 F547M 2 none none none 2 N/A S K1C-SUB V-R-AQR 8 WFC3/UVI ACCUM UVIS2-C1 F547M 3 none none none 2 N/A S K1C-SUB V-R-AQR 8 WFC3/UVI ACCUM UVIS2-C1 F547M 4 none none none 2 N/A S K1C-SUB V-R-AQR 9 WFC3/UVI ACCUM UVIS2-C1 F280N none none 1 none 2 N/A S K1C-SUB V-R-AQR 9 WFC3/UVI ACCUM UVIS2-C1 F280N none none 2 none 3 N/A S K1C-SUB V-R-AQR 10 WFC3/UVI ACCUM UVIS2-C1 F502N none none 1 none 3 N/A S K1C-SUB V-R-AQR 10 WFC3/UVI ACCUM UVIS2-C1 F502N none none 2 none 3 N/A S K1C-SUB V-R-AQR 11 WFC3/UVI ACCUM UVIS2-C1 F343N 1 none none none 3 N/A S K1C-SUB V-R-AQR 11 WFC3/UVI ACCUM UVIS2-C1 F343N 2 none none none 3 N/A S K1C-SUB V-R-AQR 11 WFC3/UVI ACCUM UVIS2-C1 F343N 3 none none none 3 N/A S K1C-SUB V-R-AQR 11 WFC3/UVI ACCUM UVIS2-C1 F343N 4 none none none 3 N/A S K1C-SUB 18427( 2) - 07-Aug-2026 19:48:41 - [ 8] Visit: 02 Visit Requirements: AFTER 01 BY 0 H TO 14 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 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F656N FLASH=20 2 575 S S 1C-SUB (1150 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F763M FLASH=20 1 1 S (4 S) PATTERN 2 2-4 S 1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 3 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=20 1 20 S (80 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=20 1 240 S (960 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 5 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F673N FLASH=20 2 620 S S 1C-SUB (1240 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 V-R-AQR WFC3/UVI ACCUM UVIS2-C1K F373N FLASH=20 2 600 S S 1C-SUB (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 V-R-AQR WFC3/UVI ACCUM UVIS-QUAD FQ437N FLASH=20 1 160 S (640 PATTERN 2 7 S -SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F656N none none 1 none 1 N/A S K1C-SUB V-R-AQR 1 WFC3/UVI ACCUM UVIS2-C1 F656N none none 2 none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F763M 1 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F763M 2 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F763M 3 none none none 1 N/A S K1C-SUB V-R-AQR 2 WFC3/UVI ACCUM UVIS2-C1 F763M 4 none none none 2 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 N/A S K1C-SUB 18427( 2) - 07-Aug-2026 19:48:41 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 1 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none none none 2 N/A S K1C-SUB V-R-AQR 3 WFC3/UVI ACCUM UVIS2-C1 F336W 4 none none none 2 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 2 N/A S K1C-SUB V-R-AQR 4 WFC3/UVI ACCUM UVIS2-C1 F275W 4 none none none 2 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F673N none none 1 none 2 N/A S K1C-SUB V-R-AQR 5 WFC3/UVI ACCUM UVIS2-C1 F673N none none 2 none 2 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F373N none none 1 none 3 N/A S K1C-SUB V-R-AQR 6 WFC3/UVI ACCUM UVIS2-C1 F373N none none 2 none 3 N/A S K1C-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS-QUA FQ437N 1 none none none 3 N/A S D-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS-QUA FQ437N 2 none none none 3 N/A S D-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS-QUA FQ437N 3 none none none 3 N/A S D-SUB V-R-AQR 7 WFC3/UVI ACCUM UVIS-QUA FQ437N 4 none none none 3 N/A S D-SUB 18427( 2) - 07-Aug-2026 19:48:41 - [ 10] Summary Form for Proposal 18427 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-QUAD-SUB, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 0 H TO 14 D, BETWEEN 01-MAR-2027:00:00:00 AND 01-AUG-2027:00:00:00, PATTERN 2 1, PATTERN 2 11, PATTERN 2 2, PATTERN 2 2-4, PATTERN 2 3, PATTERN 2 4, PATTERN 2 5, PATTERN 2 6, PATTERN 2 7, PATTERN 2 8 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W, F280N, F336W, F343N, F373N, F487N, F502N, F547M, F656N, F658N, F673N, F763M, FQ437N ------------------------------------------------------------------------------------------------------------------------------------ Target Names V-R-AQR ------------------------------------------------------------------------------------------------------------------------------------