0 Assigned ID: 7552 ----- Attempting Submission 1 (Thu Apr 16 19:06:29 GMT 2026) ----- HST Phase I Proposal 7552 successfully submitted. Receipt: # 7552-1 ----- Attempting Submission 2 (Thu Apr 16 21:49:53 GMT 2026) ----- HST Phase I Proposal 7552 successfully submitted. Receipt: # 7552-2 FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser I am somewhat concerned about the longer single exposure times for the f390w filter in particular given both targets are in star formation regions but there are no particularly bright areas from what I can see in GALEX images. Additionally if there are any suggestions on how to make the total exposure times longer for the optical filters (F438W, F555W, and F814W) in particular, that would be amazing. None of the example APTs I pulled for similar programs had flash levels for F390W, F438W, and F555W so I have ommited it here as well. 108705144 ----- Attempting Submission 1 (Tue Aug 18 01:25:32 GMT 2026) ----- No flash entered for F390W, F438W, and F555W. Echoes of Dying Breaths: Measuring Mass Loss with Late-time Observations of SN 2023ixf and SN 2024ggi A growing number of Type IIP supernovae (SNe IIP) display early and sustained circumstellar medium (CSM) interaction, requiring CSM masses that challenge the observed mass-loss rates of their red supergiant progenitors. This suggests red supergiants may experience a period of enhanced mass loss at the end of their lives. SN 2023ixf and SN 2024ggi, the nearest and best-observed SNe IIP in the past decade, provide the ideal laboratory to understand this phenomenon. We propose multi-cycle HST imaging in the UV and optical to map the distribution and composition of the CSM surrounding SN 2023ixf and SN 2024ggi. These observations target two complementary probes: UV emission from ongoing ejecta-CSM interaction and optical light echoes from more distant material. Together, this data will constrain the geometry, radial extent, and density of the CSM, ultimately providing critical insight into the mechanisms that drive late-stage mass loss. Long-term HST imaging will add to existing and planned multi-wavelength observations and establish SN 2023ixf and SN 2024ggi as benchmark SNe IIP for decades to come. In order to moniter the evolution of SN 2023ixf and SN 2024ggi we request 4 orbits total of WFC3/UVIS imaging. One for each supernovae to get F275W and F390W imaging (therefore 2 total) that will assess the evolution of any Mg II resulting from interaction between the circumstellar material and supernova ejecta. An additional orbit for each supernovae (2 total) will be for F438W, F555W, and F814W imaging to map the optical evolution and the creation of any light echoes. Both SN 2023ixf and SN 2024ggi are located in star forming regions in their respective host galaxies, we therefore opt to use the sub array to allow for shorter exposures of the regions. J. Pearson is a final year graduate student at the University of Arizona. Her thesis work focuses on understanding the final moments of the lives of massive stars through the observation of nearby SNe. As part of this work she has extensively used HST, JWST, and ground-based observations. J. Andrews is an Associate Astronomer the Gemini Observatory. Her research focuses on core collapse (CC) SNe, specifically focusing on circumstellar interaction and dust formation. She has extensive experience working with HST observations. B. Hsu is a graduate student at the University of Arizona working on the intersection of observations and numerical simulations of CCSNe, with a current focus on the complex CSM environments of Type II SNe. G. Hosseinzadeh is an expert in is an expert in very early observations of both Type Ia and Type II SNe and has experience analyzing UV observations of SNe. S. Vasylyev is a Postdoctoral Research Associate at the University of California San Diego who specializes in multi-wavelength observations of core-collapse supernovae, particularly those with signs of CSM-interaction. D. Sand is the co-PI of the DLT40 survey (a targeted search of nearby galaxies that often finds the nearest and brightest SNe). He is a general transient observer with experience in most aspects of the field, including extensive experience with HST, JWST, Swift, and ground-based observations of SNe and their environments. K. A. Bostroem is an LSST Catalyst Fellow at the University of Arizona. Her research focuses on nearby core collapse SNe and their interaction with CSM. She has extensive experience with HST data reduction and analysis of SNe. B. Subrayan is a Postdoctoral Research Associate at the University of Arizona who specializes in multi-wavelength observations of exotic transients and supernovae, including their dust and remnants. She has an extensive background in applications of statistical and machine learning methods in time-domain astronomy. C. Ransome is a Postdoctoral Research Associate at the University of Arizona. His research focuses on unusual, and interacting supernovae, their progenitors and host environments. He has experience in many ground based facilities as well as HST and JWST. A. P. Ravi is a Postdoctoral Research Associate at the University of California Davis. He has a background in studying the late-time evolution and dust production in CCSNe. S. Valenti is the co-PI of the DLT40 survey and PI of HST Cycle 32 PID 17796 which uses similar methodology as the proposed work. He has worked comprehensively on core collapse supernovae (CC SNe). N. Meza-Retamal is a graduate student at University of California Davis. His work focuses on optical and near-infrared observations of SNe IIP showing signatures of interaction. D. Mehta is a graduate student at the University of California Davis whose work focuses on the analysis of nearby CCSNe. M. Shrestha is an expert in high-energy transients such as gamma-ray bursts, core-collapse (CC) SNe, and kilonovae. She has extensive experience reducing and analyzing JWST, HST, and ground-based observations. Stellar Physics and Stellar Types 0 false true false false false false false SUPPORTED STAR SUPERNOVA SUPERNOVA TYPE II This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STAR SUPERNOVA SUPERNOVA TYPE II This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F390W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 2 false /private/var/folders/fl/hj8fpnh14yvdhrc2jpr_vvh00000gn/T/OPVisit5206768984043311414.xml Timing link suitability includes constraints ([Group (01 02) Within 0.1 days]) The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. 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