For Whom the Metal Flows: an FUV transit of the young AU Mic c

0 Assigned ID: 6869 ----- Attempting Submission 1 (Thu Apr 10 23:50:27 GMT 2025) ----- HST Phase I Proposal 6869 successfully submitted. Receipt: # 6869-1 Updated pre-transit to in-transit time constraint. Pre-transit can now be taken 8 - 24 hours prior to transit. -769976667 ----- Attempting Submission 1 (Wed Aug 13 17:36:02 GMT 2025) ----- HST Phase II Proposal 18138 successfully submitted. Receipt: # 18138-1 ----- Attempting Submission 2 (Wed Aug 13 20:07:54 GMT 2025) ----- ----- Attempting Submission 3 (Fri Oct 10 15:59:27 GMT 2025) ----- ----- Attempting Submission 4 (Fri Mar 06 20:28:05 GMT 2026) ----- For Whom the Metal Flows: an FUV transit of the young AU Mic c Atmospheric escape is theoretically a ubiquitous process among planets with atmospheres. It has the power to shape the entire exoplanet population, potentially leading to a lack of close-orbiting gaseous planets and creating the common sub-Neptune exoplanet type. Despite the impact of this process, questions like what variables control it and when it is the most efficient remain open. This motivates the search and characterization of atmospheric escape in young systems, where the process may be the most influential. We propose for one transit of AU Mic c, a sub-Neptune with an 18 day period, with HST/STIS E140M. This will allow us to investigate and confirm the young planet's potentially metallic outflow. Confirmation of the presence of metals will place strong constraints on AU Mic c's outflow structure and kinematics, providing an important test case for atmospheric escape models. We will observe 1 AU Mic c transit with STIS FUV-MAMA E140M. The transit will be composed of 2 HST visits with 7 total orbits. The first visit will comprise 2 orbits 8-12 hours before the white-light mid-transit, a baseline observation of the unocculted host star. The second visit will comprise 5 orbits starting ~1 hour before the white-light mid-transit and capturing five hours afterward. Five back-to-back orbits can be scheduled while avoiding the South Atlantic Anomaly. PI Rockcliffe has analyzed several Lyman-alpha transits of young exoplanets (GO-14615 and -15836) and is the PI of GO-17534 which will provide more AU Mic b Lyman-alpha transits. She is an expert in observationally characterizing atmospheric escape in young exoplanet systems, and the AU Mic system in particular. Co-I Newton is an expert on M dwarf systems, with a particular focus on young systems with exoplanets. Co-I Youngblood is the PI of multiple HST programs to study the UV emission from late-type stars, including a large survey of the UV emission from JWST Cycle 1 transiting exoplanet host stars (GO-16701) and a Lyman alpha transit of TOI-1231b (GO-16700). She is experienced in analyzing Lyman alpha emission from M dwarfs. Co-I Duvvuri has scientific and technical expertise in the time-series spectroscopy of cool dwarfs observed at X-ray + ultraviolet + optical wavelengths to characterize the variability of stellar activity and in modeling stellar X-ray and extreme ultraviolet radiation. Co-I Thao is a graduate student who has had extensive experience using ground- and space-based telescopes (HST, Spitzer) to study the transmission spectrum of young planets. Co-I Mann is an expert on the fundamental properties of late-type and young stars. He also has done extensive work on the discovery and characterization of young transiting planets. He is co-PI of the THYME survey and the PI of a JWST Cycle 1 program on the 17 Myr transiting planet HIP67522 b. Co-I Mueller has an extensive background in modeling plasma/neutral interaction regions like astrospheres carved out of the interstellar medium by stellar winds. He models the interaction of stellar winds with the neutral evaporating atmosphere of close-in exoplanets. Co-I Barclay has modeling data from space telescopes of planets orbiting active stars - including prior observations of AU Mic (https://ui.adsabs.harvard.edu/abs/2022AJ....163..147G). He has also previously led HST proposals to observe transiting exoplanets (https://ui.adsabs.harvard.edu/abs/2023arXiv230110866B). Co-I Lopez in an expert in atmospheric escape modeling and how it impacts exoplanet evolution and demographics. Co-I Feinstein is an expert in transit observations of young planets, stellar activity, and is the lead software developer for several time-series photometry extraction and analyses, and HST data reduction pipelines. PI Rockcliffe and Newton have institutional access to the 1.3 and 2.4m telescopes at MDM, Dartmouth has a 25% share of both telescopes. Newton has access to LCO as an "LCO extended family" member from TAC service. Team members Mann and Newton have had multiple successful LCO programs to support space-based observations with TESS and HST. Mann has institutional access to SOAR. Exoplanets and Exoplanet Formation 6 false false false false false false false SUPPORTED STAR EXTRA-SOLAR PLANET M V-IV PRE-MAIN SEQUENCE STAR J2000 J2000 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/FUV-MAMA Spectroscopic No No E140M 1425 1760111864435 Timing link suitability includes constraints ([02 After 01 by 0.3 to 1.0 days]) The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. Two exposures 8 - 12 hours before transit to observe the unocculted star. (Tic-Visit :proposal-id 18138 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "10-Oct-2025 11:57:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 313520 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18138 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18138 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 316 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18138 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 578 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) true 2 0 /private/var/folders/jj/gh_vs4h933g07vk6bs52gxnwf2ybxw/T/OPVisit10250661654593321206.xml 1772828745682 Timing link suitability includes constraints ([02 After 01 by 0.3 to 1.0 days]) The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. Five exposures starting about 1 hour prior to the predicted white-light mid-transit of the planet. (Tic-Visit :proposal-id 18138 :visit-id "02" :proposal-version -1 :trans-version "20250929" :date "06-Mar-2026 15:25:45.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 783152 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18138 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18138 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 316 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18138 :visit-id "02" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 316 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18138 :visit-id "02" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 316 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18138 :visit-id "02" :orbit-number 4 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 316 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18138 :visit-id "02" :orbit-number 5 :pcs-time 380 :si-vis-utilization 2607 :al-overhead-at-end 0 :internal-dur-at-end 578 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) true 5 0