18138( 6) - 09-Mar-2026 12:04:42 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18138 Version: 6 Check-in Time: 09-Mar-2026 12:04:42 STScI Edit Number: 1 Title For Whom the Metal Flows: an FUV transit of the young AU Mic c ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Keighley Elizabeth Rockcliffe University of Maryland Baltimore County Y CoI: Dr. Elisabeth R. Newton Dartmouth College N CoI: Dr. Allison Youngblood NASA Goddard Space Flight Center N CoI: Dr. Girish M. Duvvuri Vanderbilt University N CoI: Pa Chia Thao University of North Carolina at Chapel N Hill CoI: Dr. Andrew Withycombe Mann University of North Carolina at Chapel N Hill CoI: Dr. Hans-Reinhard Mueller Dartmouth College N CoI: Dr. Thomas Barclay NASA Goddard Space Flight Center N CoI: Dr. Eric David Lopez NASA Goddard Space Flight Center N CoI: Prof. Adina Feinstein Michigan State University N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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. ------------------------------------------------------------------------------------ 18138( 6) - 09-Mar-2026 12:04:42 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 AU-MIC STAR, EXTRA-SOLAR RA=20H45M9.5325S +/- 0.0173", J2000 V = 8.627 PLANET, M V-IV, DEC=-31D20'27.24" +/- 0.0113" PRE-MAIN SEQUENCE STAR Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.021958633407246034 -0.360148 0.1029432 ------------------------------------------------------------------------------------------------------------------------------------ 18138( 6) - 09-Mar-2026 12:04:42 - [ 3] Visit: 01 (Pre-transit) Visit Requirements: On Hold Comments: Additional Comments: Two exposures 8 - 12 hours before transit to observe the unocculted star. 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 AU-MIC STIS/CCD ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S (0.1 SEQ 1-3 NON-INT S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S -MAMA G see below (2160 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S SEQ 4-5 NON-INT -MAMA G see below (2577 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AU-MIC 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A AU-MIC 2 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 2160.0 S -MAMA G WAVE 3 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA AU-MIC 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2577.0 S -MAMA G WAVE 5 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA 18138( 6) - 09-Mar-2026 12:04:42 - [ 4] Visit: 02 (In-transit) Visit Requirements: AFTER 01 BY 8 H TO 24 H; Period 18.85902 D AND ZERO-PHASE HJD2460850.477303652 On Hold Comments: Additional Comments: Five exposures starting about 1 hour prior to the predicted white-light mid-transit of the planet. 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 AU-MIC STIS/CCD ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S (0.1 PHASE 0.992267458620299 S) TO 0; SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S -MAMA G see below (2160 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S SEQ 4-5 NON-INT -MAMA G see below (2577 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 6 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S SEQ 6-7 NON-INT -MAMA G see below (2577 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 8 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S SEQ 8-9 NON-INT -MAMA G see below (2577 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 10 AU-MIC STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=13000, WAVECAL=NO 1 3000 S SEQ 10-11 NON-INT -MAMA G see below (2577 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 WAVE STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 18138( 6) - 09-Mar-2026 12:04:42 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AU-MIC 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A AU-MIC 2 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 2160.0 S -MAMA G WAVE 3 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA AU-MIC 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2577.0 S -MAMA G WAVE 5 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA AU-MIC 6 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 3 2577.0 S -MAMA G WAVE 7 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 3 N/A -MAMA AU-MIC 8 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 4 2577.0 S -MAMA G WAVE 9 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 4 N/A -MAMA AU-MIC 10 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 5 2577.0 S -MAMA G WAVE 11 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 5 N/A -MAMA 18138( 6) - 09-Mar-2026 12:04:42 - [ 6] Summary Form for Proposal 18138 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, F25ND3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=13000, WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 8 H TO 24 H, PHASE 0.992267458620299 TO 0, Period 18.85902 D AND ZERO-PHASE HJD2460850.477303652, SEQ 1-3 NON-INT, SEQ 10-11 NON-INT, SEQ 4-5 NON-INT, SEQ 6-7 NON-INT, SEQ 8-9 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names AU-MIC, WAVE ------------------------------------------------------------------------------------------------------------------------------------