A Spectacularly Polluted White Dwarf with Transits

0 Assigned ID: 6217 ----- Attempting Submission 1 (Wed Apr 09 10:53:02 GMT 2025) ----- For the best data quality, it is generally required to use all four FP-POS positions at a given COS cenwave (or 2 positions for certain exception cases). See extended explanation in the diagnostic browser. For the best data quality, it is generally required to use all four FP-POS positions at a given COS cenwave (or 2 positions for certain exception cases). See extended explanation in the diagnostic browser. We fixed FP-POS=4 in Visit 2, and fixed the exposure-level labels. -2027338815 ----- Attempting Submission 1 (Thu Jul 31 12:35:20 GMT 2025) ----- ----- Attempting Submission 2 (Fri Nov 14 14:05:41 GMT 2025) ----- ----- Attempting Submission 3 (Thu Nov 20 16:21:30 GMT 2025) ----- The two warnings are about the use of only one FP-POS setting in Visit 01 and 02. However, we use both FP-POS=3 and 4 across the two visits, and will combine all the data in post-processing. A Spectacularly Polluted White Dwarf with Transits Planetary systems orbiting white dwarfs offer not only a glimpse into the future solar system, but also a test of long-term dynamical processes spanning major stellar evolutionary transitions. These dynamical changes are epitomized by ubiquitous dust variability in the infrared, and via rapidly evolving transits detected now in at least 14 systems. Critically, the polluted stellar atmospheres distill entire exoplanetary bodies into their bulk chemical compositions, a phenomenon that is unavailable for main-sequence stars, and currently the only means to acquire empirical insight into exoplanetary surfaces and interiors. Here, we propose to study an unprecedented source with long-term transits, extreme pollution, gaseous disk emission, and a color term in multi-band light curves. The near record-breaking abundances determined from low-resolution spectroscopy imply that myriad lines of many metal species will be detected in the ultraviolet. These include but are not limited to C, N, O, Al, Si, P, S, Cr, Mn, Fe, and Ni. Multiple lines of oxygen and carbon will be detected with high confidence, and possibly nitrogen if present in sufficient quantities. These abundances directly constrain the volatile content of the parent body, and to some degree, its birthplace in this exoplanetary system, in turn constraining its origin and nature. The observed, several year transit duration suggests the parent body was initially in a relatively distant orbit where water and other ices may persist. Volatile-rich debris pollution has only been observed previously in a single case, and requires the ultraviolet capacity of Hubble for an assessment of the bulk chemical composition. The goal is simply deep spectroscopy of this relatively faint targets, with the aim to detect myriad metal absorption lines from the stellar atmosphere and possbily from circumstellar material. We use two central wavelngth settings: 1222A and 1291A. The program is split into three visits: 4 orbits at 1222A, one orbit per FP-POS setting, 3 orbits at 1291A and FP-POS=3 and 3 orbits at 1291A and FP-POS=4 (for 1291A only FP-POS=3,4 are allowed). The warning that comes up is a result of having the FP-POS=3 and 4 split over two visits, however, we will combine all spectroscopy in post-processing. Farihi and Gaensicke are leaders in the observations of circumstellar debris disks and white dwarf pollution. Together, they have discovered the majority of disks at white dwarfs, led several key studies on how the accretion takes place, and in the past several years have published nine papers based on Hubble results, including: detailed abundance studies confirming Earth-like debris at numerous polluted white dwarfs; the first (indirect) identification of water in the otherwise-rocky debris orbiting a GD 61; and the detection of rocky debris in two Hyades white dwarfs. Redfield is a leading expert in the observation of circumstellar, interstellar, and planetary atmosphere absorption, and was the first to detect Na in ground-based observations of exoplanet transits, as well as the first to demonstrate the circumstellar gas transiting WD1145+017 has an eccentric orbit. The team have the necessary resources and experience to analyze, interpret, and scientifically exploit the requested data. 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