0Assigned ID: 6629
----- Attempting Submission 1 (Thu Apr 10 19:28:29 GMT 2025) -----
HST Phase I Proposal 6629 successfully submitted.
Receipt: # 6629-1
----- Attempting Submission 2 (Thu Apr 10 22:45:42 GMT 2025) -----
HST Phase I Proposal 6629 successfully submitted.
Receipt: # 6629-2
----- Attempting Submission 3 (Thu Apr 10 23:53:33 GMT 2025) -----Non Disruptive: 0 is too small. It must be >= 1.
This target is not used in this proposal.update the buffer time for the trigger2037413433----- Attempting Submission 1 (Mon Aug 11 01:18:29 GMT 2025) -----
HST Phase II Proposal 18041 successfully submitted.
Receipt: # 18041-1
----- Attempting Submission 2 (Mon Aug 11 19:10:09 GMT 2025) -----
HST Phase II Proposal 18041 successfully submitted.
Receipt: # 18041-2
----- Attempting Submission 3 (Wed Aug 13 18:16:22 GMT 2025) -----
----- Attempting Submission 4 (Wed Jun 10 04:50:01 GMT 2026) -----
HST Phase II Proposal 18041 successfully submitted.
Receipt: # 18041-4
----- Attempting Submission 5 (Thu Jun 11 17:45:12 GMT 2026) -----
HST Phase II Proposal 18041 successfully submitted.
Receipt: # 18041-5
----- Attempting Submission 6 (Thu Jun 11 18:06:10 GMT 2026) -----This is a disruptive ToO program, so I'm not sure how to fix this errorUnveiling the Progenitors of Type Ibn Supernovae with Early UV SpectroscopyWe propose a disruptive ToO program with HST/STIS to obtain two epochs of UV spectra of a newly discovered Type Ibn supernova (SN) within 250 Mpc. Type Ibn SNe are a rare class of fast-evolving transients that exhibit strong interaction between SN ejecta and dense circumstellar material (CSM), as evidenced by their rapidly evolving light curves and narrow helium lines in their spectra. This dense CSM likely originates from enhanced mass loss during the final years of massive star evolution, but the physical mechanisms driving this remain poorly understood. Studying Type Ibn SNe offers valuable insights into the late stages of massive star evolution and the processes that lead to their explosions--fundamental questions in transient astronomy. UV spectroscopy provides critical diagnostics of the progenitor surface composition, mass, and ejecta geometry. These properties can only be precisely constrained through UV data, enabling a comprehensive exploration of progenitor diversity and offering deeper insight into the nature of Type Ibn explosions.We propose a disruptive ToO UV spectroscopic sequence of a newly discovered Type Ibn supernova within 250 Mpc using HST/STIS FUV and NUV MAMA detectors. The sequence will consist of two epochs separated by approximately 10 days, with the first epoch scheduled before or near the optical peak. The primary goal is to capture the UV line evolution of Type Ibn supernovae, providing insights into their progenitor systems and explosion mechanisms.
The first epoch will be a disruptive Target of Opportunity, using the G140L and G230L gratings, while the second epoch, taken about 10 days later, will use the G230L grating only.PI Y. Dong is a postdoctoral researcher at the Harvard \& Smithsonian Center for Astrophysics. His current research focus on understanding the progenitors of Type Ibn supernovae. The data obtained through this program will be used in papers led by him.
Co-I O. Fox is a Instrument Scientist at STScI. He is an expert on supernovae and their progenitors and has extensive experience with HST.
Co-I V. A. Villar is an assistant professor at Harvard and executive board member of YSE. She is an expert in statistical studies of core-collapse supernovae. She will assist in assembling data sets for the target, analysis and writing papers.
Co-I L. Dessart is an expert in the theoretical modeling of compact object collapse, stellar outflows, and related phenomena. He will help with the interpretation and modeling of the HST spectra.
Co-I A. Filippenko is a professor at UC Berkeley. He is an expert on a wide range of transient phenomena and has extensive experience with HST.
Co-I N. Smith is a professor at University of Arizona. He is an expert on interaction supernovae. He has extensive experience in interpreting observations of interacting supernovae, including SNe Ibn.
Co-I T. Szalai is an assistant professor at University of Szeged. He is an expert in infrared and optical observations of supernovae, with a focus on circumstellar interaction and dust formation.
Co-I J. Andrews has expertise observing with HST/STIS, and is an assistant astronomer at the Gemini Observatory. Her research focuses on characterizing the progenitors of core collapse SNe, specifically focusing on their mass-loss history via circumstellar interaction.
Co-I G. Hosseinzadeh is an Assistant Professor at UC San Diego. He is an expert on Type Ibn supernovae and will contribute to the analysis and publication of data collected through this program.
Co-I C. Pellegrino is an expert on the observational properties of SNe Ibn and their progenitor channels.
Co-I R. Foley is an expert in observational studies of supernovae, including core-collapse and thermonuclear explosions. He has extensive experience working with Gemini data.
Co-I S. Gomez is an expert in optical observations (both photometric and spectroscopic) of exotic transients such as superluminous supernovae and tidal disruption events, presented in multiple publications with data from approved programs on facilities such as: Gemini, \textit{HST}, MMT, Magellan, FLWO, McDonald Observatory, and LCO.
Co-I K. de Soto is a graduate student at Harvard University and an expert in ML methods and statistical studies of core-collapse supernovae. She will aid in target selection with Superphot+.
Co-I C. Ransome is a postdoctoral fellow at the Harvard \& Smithsonian Center for Astrophysics. He has extensive observational experience, including HET / Gemini spectroscopic followup programs and environmental surveys.
Co-I K. Yadavalli is a graduate student at the Harvard \& Smithsonian Center for Astrophysics, and a member of YSE. He is an observational astronomer, with expertise in photometric analysis of core collapse supernovae and in calcium rich transients. He has led 3 spectroscopic Target of Opportunity programs on the HET. He will assist in obtaining data, analysis, and paper writing.
Co-I A. Gagliano is an postdoctoral fellow at the NSF AI Institute for Artificial Intelligence and Fundamental Interactions MIT/Centre for Astrophysics, and an expert on the early-interaction signatures and host galaxies of core-collapse supernovae. He has been awarded over 52 hours of Gemini time as PI in past semesters. He will assist in data analysis and paper writing.
Co-I D. Farias is a graduate student working on interacting core-collapse (CC) SNe. He has been PI and Co-PI of proposals of several Type Ibn SNe, including SN~2021foa, a CC-supernova showing a unique transition between Type IIn and Ibn throughout its evolution.
Co-I D. Frostig is a postdoctoral fellow at the Harvard \& Smithsonian Center for Astrophysics. She is an expert in near-infrared instrumentation and observation, as the instrument scientist of a near-infrared photometric instrument and as a frequent user of photometric and spectroscopic near-infrared instruments on the Magellan and MMT telescopes.
Co-I K. Davis has $>$50 nights of experience with obtaining and reducing optical spectra. They are also PI of multiple past Gemini programs focused on observing Type Ibn/Icn supernovae. They published a paper on the Type Icn SN 2022ann, where they used late-time spectroscopy to constrain the progenitor system.
Co-I A. E. Nugent is a postdoctoral fellow at the Harvard \& Smithsonian Center for Astrophysics. She is an expert in host galaxy studies of various transients and has experience reducing photometric and spectroscopic data from GMOS.
Co-I Q. Wang is a postdoctoral fellow at MIT. He is an expert in observation of Type Ibn SNe. He will assist in assembling data sets for the target, analysis and writing papers.
Co-I K. Taggart is an expert on core-collapse supernovae and their host environments.Stellar Physics and Stellar Types6falsetruefalsefalsefalsefalsefalseSUPPORTEDEXT-STARSUPERNOVANOJ2000STARSUPERNOVAWe will trigger on a newly discovered Type Ibn supernovaSTIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/NUV-MAMASpectroscopicNoNoG230L2376/private/var/folders/st/zcll9lr10qd1d0jt8641mp0w0000gp/T/OPVisit8392680744542804936.xmlTiming link suitability includes constraints ([Sequence (01 02 03) within 2.0 days] [04 After 01 by 6.0 to 12.0 days])The scheduling data was generated by CASM 34.1.CASM was run in Phase II mode.We will trigger the program on a newly discovered Type Ibn supernova within 250 Mpc(Tic-Visit
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