18026( 6) - 21-Jan-2026 09:37:43 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18026 Version: 6 Check-in Time: 21-Jan-2026 09:37:43 STScI Edit Number: 0 Title Testing Volatile Transportation in the Epoch of Terrestrial Planet Formation ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Cicero Lu NOIRLab - Gemini North (HI) Y CoI: Isabel Rebollido ESA, European Space Astronomy Centre N CoI: Dr. Christine Chen The Johns Hopkins University N CoI: Dr. Chen Xie The Johns Hopkins University N CoI: Dr. Sarah Betti Space Telescope Science Institute N CoI: Dr. Sean Brittain Clemson University N CoI: Kadin Worthen Space Telescope Science Institute N CoI: Dr. Tracy Beck Space Telescope Science Institute N CoI: Dr. Aki Roberge NASA Goddard Space Flight Center N CoI: Prof. Kevin France University of Colorado at Boulder N CoI: Dr. John Henry Debes Space Telescope Science Institute - ESA - N JWST CoI: Prof. Luca Matra Trinity College Dublin N CoI: Aoife Brennan Trinity College Dublin N CoI: Dr. Marshall Perrin Space Telescope Science Institute N CoI: Dr. Joan Najita NOIRLab - (AZ) N CoI: Dr. Bin Ren Observatoire de la Cote d'Azur N CoI: Dr. Andre-Nicolas Chene NOIRLab - Gemini North (HI) N ------------------------------------------------------------------------------------ Abstract Debris disks offer a unique laboratory to test theories of volatile transport in the epoch of terrestrial planet formation. The leading hypothesis posits that exocomets can deliver water-ice stored in exo-Kuiper belts and the inner regions of a young planetary system in the form of water vapor via sublimation. However, liquid water remains elusive in debris disks to date. We propose to observe OH fluorescence emission as a tracer for H2O in liquid and vapor phases with HST STIS/NUV E230H and definitively to decipher whether water vapor exists in the inner regions in three young planetary systems (HD 131488, beta Pictoris, and HD 181327). These targets are most suitable because they contain water-rich exo-Kuiper belts newly discovered with JWST/NIRSpec observations and have also been identified with exocometary activities from past multi-wavelength studies. We aim to constrain the OH gas temperature, emission mechanism, and radial velocity for any detected OH line velocity to examine whether the OH gas origin is consistent with exocometary. While JWST provides new clues to the composition of planetesimal reservoirs, our proposed HST observation will provide the most direct and definitive clue for the existence of liquid H2O in debris disks. A non-detection will allow us to place the first constraints on OH dissociation rates based on observed H2O-ice column densities, providing a new benchmark for comparison with younger, gas-rich protoplanetary disks. Our proposed observation across our sample of early A to mid-F type stars will benchmark our understanding of the volatile transportation in these exoplanetary systems. ------------------------------------------------------------------------------------ 18026( 6) - 21-Jan-2026 09:37:43 - [ 2] Observations Description ------------------------ We aim to observe 3 debris disks, beta Pictoris, HD 131488, and HD 181327 with STIS/NUV MAMA E230H/c3012 with longslits. The objective of this program is to detect OH molecules resulting from exocometary outgassing and/or photoevaporation from the surface of planetesimals. Since beta Pic is very bright (V~3.86), we follow previous successful observations from PID 14735 and choose to use the 31x0.05 NDA slit to prevent saturating the detector. For HD 131488 and HD 181327, we chose to use 6 x0.2 arcsec slits. In the phase I proposal stage, we specified that a 0.2x0.2 arcsec square slit, but we have now realized that 6 x0.2 arcsec is a better choice because the extent of the slit can capture the entire disk in the FOV. Since we are using narrow slits with widths of 0.05 and 0.2, we add a acquisition/peak-up sequence after the standard acquisition (STIS-CCD) of the target to optimize the centering of the target in the slit. We also add a wavelength cal sequence prior to our science observation. For beta Pic, we use a 0.2x0.09 arcsec slit, and for the rest two, we use 0.2 x0.2 arcsec as recommended by HST/STIS docs for longslit echelle spectrograph (https://hst-docs.stsci.edu/stisihb/chapter-12-special-uses-of-stis/12-2-long-s lit-echelle-spectroscopy). We plan to observe the beta Pic for 2210 seconds to achieve an SNR of 50. Similarly, we plan to observe 3695s for HD 131488 and 2600s for HD 181327. These numbers differ a little bit from our specified exposure in the phase 1 proposal (3875s, 1580s, and 1798s for HD 131488, HD 181327, and beta Pictoris) due to re-running the ETC. But the new numbers are still within the allocated 5-orbit limitation. Additionally, we add position angle constraints to the science target to ensure alignment between the disk PA and slit PA. A misalignment between the two PAs will likely result in any possible emission falling outside of the slit. ------------------------------------------------------------------------------------ 18026( 6) - 21-Jan-2026 09:37:43 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-131488 STAR, A0-A3 V-IV, DISK RA=14H55M8.0288S, J2000 V = 8.0 DEC=-41D07'13.40" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0016282385564562042 -0.022276000026977272 0.006568399999999999 ------------------------------------------------------------------------------------------------------------------------------------ 2 -BET-PIC EXT-STAR, A4-A9 V-IV, RA=05H47M17.0877S, J2000 V = 3.86 DISK DEC=-51D03'59.44" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 5.474064950875862E-4 0.08404099999999999 0.0509307 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-181327 EXT-STAR, DISK, F3-F9 RA=19H22M58.9437S, J2000 V = 7.04 DEC=-54D32'16.98" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0028041584503067023 -0.08218600000873266 0.020930599999999997 ------------------------------------------------------------------------------------------------------------------------------------ 18026( 6) - 21-Jan-2026 09:37:43 - [ 4] Visit: 01 (beta Pic) Visit Requirements: ORIENT 75.8D TO 77 D; ORIENT 255.8D TO 257 D On Hold Comments: Additional Comments: The ETC gave a warning on buffer time being too short. Would this affect the science data? The STIS handbook says for a time-tag obs, the buffer time must be over 99 seconds. This observation is MAMA ACCUM mode, can we safely ignore the warnings? My alternative solution is to use 31x0.05NDC which would drop SNR by a factor of 2.5 but keep the buffer time long enough. Thank you for your time and help. 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 -BET-PIC STIS/CCD ACQ F25ND5 MIRROR 1 3.1 S (3.1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 -BET-PIC STIS/CCD ACQ/PEA 31X0.05ND G430M 4451 1 1 S (1 S) K A ------------------------------------------------------------------------------------------------------------------------------------ 3 -BET-PIC STIS/NUV ACCUM 31X0.05ND E230H 3012 WAVECAL=NO 1 1679 S -MAMA A (1679 S) Comments: The ETC gave a warning on buffer time being too short. Would this affect the science data? The STIS handbook says for a time-tag obs, the buffer time must be over 99 seconds. This observation is MAMA ACCUM mode, can we safely ignore the warnings? My alternative solution is to use 31x0.05NDC which would drop SNR by a factor of 2.5 but keep the buffer time long enough. Thank you for your time and help. ------------------------------------------------------------------------------------------------------------------------------------ 4 WAVE STIS/NUV ACCUM 0.2X0.09 E230H 3012 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ -BET-PIC 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A -BET-PIC 2 STIS/CCD ACQ/PEA 31X0.05N G430M 4451 none none none none 1 N/A K DA -BET-PIC 3 STIS/NUV ACCUM 31X0.05N E230H 3012 none none none none 1 N/A -MAMA DA WAVE 4 STIS/NUV ACCUM 0.2X0.09 E230H 3012 none none none none 1 N/A -MAMA 18026( 6) - 21-Jan-2026 09:37:43 - [ 5] Visit: 02 (HD 131488) Visit Requirements: ORIENT 128D TO 136 D; ORIENT 308D TO 316 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 HD-131488 STIS/CCD ACQ F25ND3 MIRROR 1 1 S (1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-131488 STIS/NUV ACCUM 6X0.2 E230H 3012 WAVECAL=NO 1 2111 S -MAMA (2111 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/NUV ACCUM 0.2X0.2 E230H 3012 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-131488 STIS/NUV ACCUM 6X0.2 E230H 3012 WAVECAL=NO 1 2543 S -MAMA (2543 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE STIS/NUV ACCUM 0.2X0.2 E230H 3012 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD-131488 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A HD-131488 2 STIS/NUV ACCUM 6X0.2 E230H 3012 none none none none 1 N/A -MAMA WAVE 3 STIS/NUV ACCUM 0.2X0.2 E230H 3012 none none none none 1 N/A -MAMA HD-131488 4 STIS/NUV ACCUM 6X0.2 E230H 3012 none none none none 2 N/A -MAMA WAVE 5 STIS/NUV ACCUM 0.2X0.2 E230H 3012 none none none none 2 N/A -MAMA 18026( 6) - 21-Jan-2026 09:37:43 - [ 6] Visit: 03 (HD 181327) Visit Requirements: 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 HD-181327 STIS/CCD ACQ F25ND3 MIRROR 1 1 S (1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-181327 STIS/NUV ACCUM 6X0.2 E230H 3012 WAVECAL=NO 1 2070 S -MAMA (2070 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/NUV ACCUM 0.2X0.2 E230H 3012 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-181327 STIS/NUV ACCUM 6X0.2 E230H 3012 WAVECAL=NO 1 2568 S -MAMA (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE STIS/NUV ACCUM 0.2X0.2 E230H 3012 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD-181327 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A HD-181327 2 STIS/NUV ACCUM 6X0.2 E230H 3012 none none none none 1 N/A -MAMA WAVE 3 STIS/NUV ACCUM 0.2X0.2 E230H 3012 none none none none 1 N/A -MAMA HD-181327 4 STIS/NUV ACCUM 6X0.2 E230H 3012 none none none none 2 N/A -MAMA WAVE 5 STIS/NUV ACCUM 0.2X0.2 E230H 3012 none none none none 2 N/A -MAMA 18026( 6) - 21-Jan-2026 09:37:43 - [ 7] Summary Form for Proposal 18026 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.09, 0.2X0.2, 31X0.05NDA, 6X0.2, F25ND3, F25ND5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 128D TO 136 D, ORIENT 255.8D TO 257 D, ORIENT 308D TO 316 D, ORIENT 75.8D TO 77 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E230H, G430M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names -BET-PIC, HD-131488, HD-181327, WAVE ------------------------------------------------------------------------------------------------------------------------------------