16998( 7) - 03-Feb-2025 20:28:34 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16998 Version: 7 Check-in Time: 03-Feb-2025 20:28:34 STScI Edit Number: 4 Title A comparative study of atmospheric escape in the brightest system of super-earths straddling the evaporation valley ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. David Ehrenreich University of Geneva, Department of Y Astronomy CoI: Dr. Laetitia Delrez Universite de Liege N CoI: Dr. Malcolm Fridlund Universiteit Leiden N CoI: Dr. Leonardo Dos Santos Space Telescope Science Institute Y CoI: Dr. Vincent Bourrier University of Geneva, Department of Y Astronomy CoI: Prof. Monika Lendl University of Geneva, Department of N Astronomy CoI: Prof. Yann Alibert University of Bern N CoI: Dr. Isabella Pagano INAF, Osservatorio Astrofisico di Catania N CoI: Dr. Luca Fossati Space Research Institute, Austrian Academy N of Sciences CoI: Prof. Kevin Heng Ludwig Maximilian Universitat of Munich N CoI: Dr. Alexis Brandeker Stockholm University N CoI: Dr. Alfred Vidal-Madjar CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Baptiste Lavie University of Geneva, Department of N Astronomy CoI: Dr. Adrien Deline University of Geneva, Department of Y Astronomy CoI: Dr. Alain Lecavelier des Etangs CNRS, Institut d'Astrophysique de Paris N ------------------------------------------------------------------------------------ Abstract Photo-evaporation of planetary atmospheres plays a key role in the evolution of exoplanets, carving their whole population. However, direct observations of atmospheric escape are scarce and almost non-existent in the mass range of super-Earths and mini-Neptunes, while these planets are among the most impacted by the phenomenon. A huge step forward could be made by achieving a comparative study of several super-Earths, volatile-rich or not, in a single multi-planet system: such planets would indeed experience the same evolution of the stellar X and EUV flux that are driving atmospheric escape. The perfect system for such a study has just been identified: the nearby, solar-type, and naked-eye star nu^2 Lupi hosts transiting planets spanning a remarkably large range of insolation (~100 to ~5x the insolation of Earth). TESS found the transits of the two inner planets and CHEOPS detected the transit of planet d, a volatile-rich super-Earth with an exceptional period of 107 day. These super-Earths straddle the radius gap of the "evaporation valley" and could have retained different fractions of gas and volatiles. Like for previously observed warm Neptunes, they could be enshrouded in huge comet-like exospheric clouds of escaping gas, which could have built up in the mild radiative environment. The system unique combination of proximity, brightness and favorable planet characteristics offers a fantastic opportunity to exploit HST ultraviolet capabilities to search for the hydrogen, oxygen and carbon escaping three planets in 16998( 7) - 03-Feb-2025 20:28:34 - [ 2] whole new mass and irradiation regimes. It is the ideal testbed for advancing both observations and theories of atmospheric evaporation of exoplanets. ------------------------------------------------------------------------------------ Observations Description ------------------------ We are targetting transits of exoplanets in the Nu2 Lupi system at Lyman-alpha. Nu2 Lupi is a naked-eye star (V=5.65). We will observe it with COS/FUV/G130M using both segments B (incl. Lyman-alpha) and A. The Lyman-alpha airglow will be corrected using available airglow templates, as in programs GO14877 (Bourrier et al. 2018, A&A 615, A117) and GO14767 (Dos Santos et al. 2019, A&A 629, A47). We wish to use only one FP-POS setting per visit so we are not impacted by the restriction to FP-POS=3 or 4 that applies when using segment B. We have set FP-POS=3 through the whole program. Each visit will consist in 5 HST orbits, spent in a single, orbit-long exposure in time-tag mode. The first orbit in each visit additionally contains an acquisition performed with COS/NUV in imaging mode, using the Bright Object Aperture and MIRRORB. The transit observations are time-critical: we aim at obtaining two transits (2x5 orbits) of planet b, three transits (3x5 orbits) of planet c, and three transits (3x5 orbits) of planet d. Planet b transits every ~11 days and there is a dozen windows available until March 2023. Planets c and d have longer periods and they are much more constraining in terms of planning: with its ~27-day period, there are only 4 windows available for transits of c between now and March 2023, with a first opportunity on 21 September 2021 (still in Cycle 28) and two beyond Cycle 29. Finally, planet d has an even longer period of ~107 days; there are 3 opportunites: one on 11 August 2021 (Cycle 28), one on 14 March 2022 (Cycle 29) and one on 29 Jan 2023 (Cycle 30). The proposal anticipated that one visit (5 orbits) would be carried over in Cycle 30; it might actually be up to three visits (15 orbits). Besides, the visits have slightly difference phase constraints, set to cover different parts of the transits. ------------------------------------------------------------------------------------ 16998( 7) - 03-Feb-2025 20:28:34 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 -NU.02-LUP STAR, EXTRA-SOLAR RA=15H21M48.1511S +/- 0.0681", J2000 V = V = 5.65 PLANETARY SYSTEM, G DEC=-48D19'3.46" +/- 0.0570" -68.780 V-IV Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.16281157987735026 -0.276024 0.0680818 ------------------------------------------------------------------------------------------------------------------------------------ 16998( 7) - 03-Feb-2025 20:28:34 - [ 4] Visit: 03 (Planet d) Visit Requirements: Period 107.1360 D AND ZERO-PHASE HJD2459331.18760 On Hold Comments: Additional Comments: 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 -NU.02-LUP COS/NUV ACQ/IMA BOA MIRRORB 1 13 S (13 PHASE 0.0003 TO 0.0011 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 -NU.02-LUP COS/FUV TIME-TA PSA G130M 1327 BUFFER-TIME=3400, FP-POS=3, 1 2550 S G FLASH=YES, SEGMENT=BOTH, see below LIFETIME-POS=LP3 (2326 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 -NU.02-LUP COS/FUV TIME-TA PSA G130M 1327 BUFFER-TIME=3400, FP-POS=3, 1 2829 S G FLASH=YES, SEGMENT=BOTH, see below LIFETIME-POS=LP3 (2060 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 -NU.02-LUP COS/FUV TIME-TA PSA G130M 1327 BUFFER-TIME=3400, FP-POS=3, 1 2829 S G FLASH=YES, SEGMENT=BOTH, see below LIFETIME-POS=LP3 (2060 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 -NU.02-LUP COS/FUV TIME-TA PSA G130M 1327 BUFFER-TIME=3400, FP-POS=3, 1 2829 S G FLASH=YES, SEGMENT=BOTH, see below LIFETIME-POS=LP3 (2200 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 -NU.02-LUP COS/FUV TIME-TA PSA G130M 1327 BUFFER-TIME=3400, FP-POS=3, 1 2829 S G FLASH=YES, SEGMENT=BOTH, see below LIFETIME-POS=LP3 (2200 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ -NU.02-LUP 1 COS/NUV ACQ/IMA BOA MIRRORB none none none none 1 N/A GE -NU.02-LUP 2 COS/FUV TIME-TA PSA G130M 1327 none none none none 1 2326.0 S G -NU.02-LUP 3 COS/FUV TIME-TA PSA G130M 1327 none none none none 2 2060 S G -NU.02-LUP 4 COS/FUV TIME-TA PSA G130M 1327 none none none none 3 2060 S G -NU.02-LUP 5 COS/FUV TIME-TA PSA G130M 1327 none none none none 4 2200 S G -NU.02-LUP 6 COS/FUV TIME-TA PSA G130M 1327 none none none none 5 2200 S G 16998( 7) - 03-Feb-2025 20:28:34 - [ 5] Summary Form for Proposal 16998 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures BOA, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=3400, FLASH=YES, FP-POS=3, LIFETIME-POS=LP3, SEGMENT=BOTH ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PHASE 0.0003 TO 0.0011, Period 107.1360 D AND ZERO-PHASE HJD2459331.18760 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names -NU.02-LUP ------------------------------------------------------------------------------------------------------------------------------------