17789( 3) - 08-Nov-2024 22:13:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17789 Version: 3 Check-in Time: 08-Nov-2024 22:13:04 STScI Edit Number: 0 Title NUV observations of transiting exoplanetary debris in a 10-hr orbit around a white dwarf ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Joseph Alexander Guidry Boston University Y CoI: Dr. JJ Hermes Boston University N CoI: Dr. Zachary Vanderbosch California Institute of Technology N CoI: Prof. Boris T. Gaensicke University of Warwick N ------------------------------------------------------------------------------------ Abstract The atmospheres of white dwarfs that are accreting a tidally disrupted planetesimal are powerful tools for deriving the bulk chemical composition of exoplanets. Ultraviolet (UV) spectroscopy is necessary to extract the most accurate abundances of these polluted white dwarfs, due to the high temperatures of most white dwarfs and the higher density of metal lines in the UV compared to the optical. Recent studies have discovered several metal-rich white dwarfs that show transits from tidally disrupted debris, but only two such systems have been extensively studied in the UV. We propose near-ultraviolet spectroscopy of ZTF J0328-1219, a newly discovered remnant planetary system that shows persistent transits from a planetary debris disk that repeat every 10 hours. Our proposal is designed to obtain the near-UV (NUV) spectra required to most accurately derive the abundances of the disrupted rocky material in orbit around the white dwarf and create a time-tagged NUV light curve to constrain the possible wavelength dependence of the transit depths. Our observations will put ZTF J0328-1219 into the broader context of other transiting debris systems, marking a crucial step in understanding the relationship between the orbital periods and eccentricities and observed properties. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this HST program is to obtain time-resolved STIS near-ultraviolet spectroscopy of the white dwarf ZTFJ0328-1219 to (1) detect the photospheric metal absorption lines in this wavelength range and (2) to probe for color-dependence of the transit depth. The orbital period of the debris is 9.94h. The observations will be done using the G230L grating, TIME-TAG mode, and the 52x0.5 aperture. The target acquisition will be performed via a CCD image taken with the FP28x50LP broad-band filter. We used a Teff=7630K blackbody scaled to SDSS g=16.7 for the acquisition ETC run. For the ETC simulation of the STIS TIME-TAG spectrophotometry, we used a white dwarf model spectrum computed with the parameters from Table 6 of Vanderbosch et al. 2021 (ApJ 917, 41), i.e. Teff=7630K, log g=8.245, log(C/He)=-9.55, and 17789( 3) - 08-Nov-2024 22:13:04 - [ 2] we scaled all other elements to Bulk Earth abundances. As per our Phase I proposal, the observations have to be carried in a single 5-orbit visit, which will cover nearly a full orbital cycle of the debris. ------------------------------------------------------------------------------------ 17789( 3) - 08-Nov-2024 22:13:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTFJ0328-121 STAR, DC RA=03H28M33.5150S +/- 0.05", J2000 V = 16.6 Gaia G=16.6, GALEX NUV=18.91, 9 DEC=-12D19'45.26" +/- 0.05" SDSS g=16.7 Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.007556886478124577 -0.014392999969459197 0.0230377 ------------------------------------------------------------------------------------------------------------------------------------ 17789( 3) - 08-Nov-2024 22:13:04 - [ 4] Visit: 01 (ZTFJ0328-1219) Visit Requirements: SCHED 100%; BETWEEN 01-SEP-2025:00:00:00 AND 28-DEC-2025:00:00:00 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 ZTFJ0328-12 STIS/CCD ACQ F28X50LP MIRROR 1 2 S (2 S) 19 Comments: We used a T=7630K blackbody scaled to SDSS g=16.7 for the acquisition ETC run. ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTFJ0328-12 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=450 1 2042 S 19 -MAMA G see below (1940 S) Comments: We computed a white dwarf model spectrum with the parameters in Table 6 of Vanderbosch et al. 2021 (ApJ 917, 41) as input for the ETC calculation. ------------------------------------------------------------------------------------------------------------------------------------ 3 ZTFJ0328-12 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=450 1 2584 S 19 -MAMA G see below (2505 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ZTFJ0328-12 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=450 1 2584 S 19 -MAMA G see below (2482 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ZTFJ0328-12 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=450 1 2584 S 19 -MAMA G see below (2482 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ZTFJ0328-12 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=450 1 2584 S 19 -MAMA G see below (2482 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTFJ0328-1219 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A ZTFJ0328-1219 2 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 1 1940.0 S -MAMA G ZTFJ0328-1219 3 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 2 2505.0 S -MAMA G ZTFJ0328-1219 4 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 3 2482.0 S -MAMA G 17789( 3) - 08-Nov-2024 22:13:04 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTFJ0328-1219 5 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 4 2482.0 S -MAMA G ZTFJ0328-1219 6 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 5 2482.0 S -MAMA G 17789( 3) - 08-Nov-2024 22:13:04 - [ 6] Summary Form for Proposal 17789 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=450 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-SEP-2025:00:00:00 AND 28-DEC-2025:00:00:00, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names ZTFJ0328-1219 ------------------------------------------------------------------------------------------------------------------------------------