14461( 5) - 11-Apr-2016 13:23:44 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14461 Version: 5 Check-in Time: 11-Apr-2016 13:23:44 STScI Edit Number: 0 Title Atmospheric Escape from the Closest Super-Earth ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David Ehrenreich Observatoire de Geneve Y CoI: Prof. David Charbonneau Harvard University N CoI: Dr. Vincent Bourrier Observatoire de Geneve N CoI: Dr. Mercedes Lopez-Morales Smithsonian Institution Astrophysical N Observatory CoI: Dr. Alain Lecavelier des Etangs CNRS, Institut d'Astrophysique de Paris N CoI: Lars Buchhave Harvard University N CoI: Dr. Christophe Lovis Observatoire de Geneve N CoI: Fatemeh Motalebi Observatoire de Geneve N CoI: Dr. Francesco Pepe Observatoire de Geneve N CoI: Dr. Dimitar D. Sasselov Harvard University N CoI: Laura Schaefer Harvard University N CoI: Dr. Alessandro Sozzetti Osservatorio Astronomico di Torino N CoI: Dr. Stephane Udry Observatoire de Geneve N ------------------------------------------------------------------------------------ Abstract In July 2015, we announced the discovery of the super-Earth HD 219134b, orbiting a V = 5.57 star 6.5-pc away from us (Motalebi et al. 2015). This is the brightest and closest transiting system known so far. With Spitzer and HARPS-N, we measured the density of HD 219134b, which is compatible with a rocky planet, possibly containing a large amount of volatile species. The planet receives high stellar irradiation, which could significantly erode its atmosphere. Preliminary estimates indicate that this 4.5 Earth-mass object should nonetheless retain a substantial atmosphere. HD 219134b lies sufficiently far from its star to allow the formation of a hydrogen cloud with a detectable coma. HST is the only telescope able to detect, for the first time, atmospheric escape from a super-Earth, by observing a Lyman-alpha transit. The detection of escaping hydrogen will represent a smoking gun for the presence of water vapor in the lower atmosphere. Constraining the mass-loss rate will allow us to probe the evolution of super-Earths and assess whether hotter super-Earths can be evaporation remnants. Resolving the Lyman-alpha absorption signal will also bring new insights on the dynamics in the exospheric clouds, revealing interaction between the host star and its super-Earth through radiation pressure and stellar wind. A non-detection could hint at a CO/CO2-rich 'super-Venus' and will prepare for adapted follow-up observations. Both outcomes will thus motivate new proposals in Cycle 24. ------------------------------------------------------------------------------------ Observations Description ------------------------ We are going to observe the UV transit of the brightest (V=5.6) and closest (6 pc) known transiting planet, which is a super-Earth. The star is a K2 dwarf and we estimated its Lyman-alpha emission line by scaling up the one of HD 189733 14461( 5) - 11-Apr-2016 13:23:44 - [ 2] (K dwarf at 19 pc), taking into account the flux dilution due to the distance and the interstellar hydrogen column. Our target should bear the brightest Lyman-alpha flux ever observed for an exoplanet host-star. It should be at similar flux levels, though, as previously observed targets such as active M dwarfs AD Leo or HD 32008, and less intense than other observed targets such as 70 Oph or Xi Boo (see Wood et al. 2005, ApJS 159, 118). We seize this opportunity to observe during one HST orbit, before the planetary transit, with the E140H echelle grating, to access 100, 000 spectral resolution and explore the FUV range to measure other possible chromospheric emission lines. The rest of the observations (4 HST orbits: 1 before, 1 during, and 2 after the optical transit) will be carried out with the more sensitive G140M grism. The peak flux is ~2.5x10-12 erg s-1 cm-2 A-1 at 1215.3 A: it is lower than the local limit point source flux for the MAMA with G140M (which is 9.4x10-11 erg s-1 cm-2 A-1 according to the Approximate MAMA Spectroscopic Bright-Object Limits, Table 13.45 of the STIS instrument handbook). The star is also well fainter than the bright object magnitude limit (V=1.3 for a K2V star) given for the MAMA/G140M. ------------------------------------------------------------------------------------ 14461( 5) - 11-Apr-2016 13:23:44 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HR-8832 STAR, EXTRA-SOLAR RA=23H13M16.9763S +/- 0.00290", J2000 V = 5.57 +/- 0.009 U=7.460, B=6.560 PLANETARY SYSTEM, K DEC=+57D10'6.08" +/- 0.0022" 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 0.25515501536484153 0.29545 0.15276 ------------------------------------------------------------------------------------------------------------------------------------ 14461( 5) - 11-Apr-2016 13:23:44 - [ 4] Visit: 01 Visit Requirements: SCHED 100%; Period 3.092926 D AND ZERO-PHASE HJD2457463.82884 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 HR-8832 STIS/CCD ACQ F28X50OII MIRROR 1 3 S (3 S) PHASE 0.945 TO 0.955; I SEQ 1-4 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 HR-8832 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 1 S (1 S) K ------------------------------------------------------------------------------------------------------------------------------------ 3 HR-8832 STIS/FUV TIME-TA 0.2X0.2 E140H 1271 BUFFER-TIME=900, WAVECAL=NO 1 1792 S -MAMA G (1792 S) Comments: Using our scaled Lyman-alpha line model, the count rate for the entire detector in 2127s is 182 counts/s. The maximum buffer time should thus be 2x10^6 / 182 ~ 11, 000s. Because of other chromospheric emission in the range of the echelle grism, we consider a factor of 10x as a margin, so we keep on using our "classic" 900-s buffer time setting. ------------------------------------------------------------------------------------------------------------------------------------ 4 WAVE STIS/FUV ACCUM 0.2X0.2 E140H 1271 1 100 S (100 -MAMA S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HR-8832 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 1 S (1 S) SEQ 5-7 NON-INT K ------------------------------------------------------------------------------------------------------------------------------------ 6 HR-8832 STIS/FUV TIME-TA 52X0.05 G140M 1222 BUFFER-TIME=900 1 2147 S -MAMA G (2147 S) Comments: The count rate on the entire detector is 200 counts/s. ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE STIS/FUV ACCUM 52X0.05 G140M 1222 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 8 HR-8832 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 1 S (1 S) SEQ 8-10 NON-INT K ------------------------------------------------------------------------------------------------------------------------------------ 9 HR-8832 STIS/FUV TIME-TA 52X0.05 G140M 1222 BUFFER-TIME=900 1 2171 S -MAMA G (2171 S) Comments: The count rate on the entire detector is 200 counts/s. ------------------------------------------------------------------------------------------------------------------------------------ 10 WAVE STIS/FUV ACCUM 52X0.05 G140M 1222 1 DEF (0 S) -MAMA 14461( 5) - 11-Apr-2016 13:23:44 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 11 HR-8832 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 1 S (1 S) SEQ 11-13 NON-INT K ------------------------------------------------------------------------------------------------------------------------------------ 12 HR-8832 STIS/FUV TIME-TA 52X0.05 G140M 1222 BUFFER-TIME=900 1 2171 S -MAMA G (2171 S) Comments: The count rate on the entire detector is 200 counts/s. ------------------------------------------------------------------------------------------------------------------------------------ 13 WAVE STIS/FUV ACCUM 52X0.05 G140M 1222 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 14 HR-8832 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 1 S (1 S) SEQ 14-16 NON-INT K ------------------------------------------------------------------------------------------------------------------------------------ 15 HR-8832 STIS/FUV TIME-TA 52X0.05 G140M 1222 BUFFER-TIME=900 1 2171 S -MAMA G (2171 S) Comments: The count rate on the entire detector is 200 counts/s. ------------------------------------------------------------------------------------------------------------------------------------ 16 WAVE STIS/FUV ACCUM 52X0.05 G140M 1222 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 | ------------------------------------------------------------------------------------------------------------------------------------ HR-8832 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A II HR-8832 2 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 1 N/A K HR-8832 3 STIS/FUV TIME-TA 0.2X0.2 E140H 1271 none none none none 1 N/A -MAMA G WAVE 4 STIS/FUV ACCUM 0.2X0.2 E140H 1271 none none none none 1 N/A -MAMA HR-8832 5 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 2 N/A K HR-8832 6 STIS/FUV TIME-TA 52X0.05 G140M 1222 none none none none 2 N/A -MAMA G WAVE 7 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 2 N/A -MAMA HR-8832 8 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 3 N/A K HR-8832 9 STIS/FUV TIME-TA 52X0.05 G140M 1222 none none none none 3 N/A -MAMA G 14461( 5) - 11-Apr-2016 13:23:44 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ WAVE 10 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 3 N/A -MAMA HR-8832 11 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 4 N/A K HR-8832 12 STIS/FUV TIME-TA 52X0.05 G140M 1222 none none none none 4 N/A -MAMA G WAVE 13 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 4 N/A -MAMA HR-8832 14 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 5 N/A K HR-8832 15 STIS/FUV TIME-TA 52X0.05 G140M 1222 none none none none 5 N/A -MAMA G WAVE 16 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 5 N/A -MAMA 14461( 5) - 11-Apr-2016 13:23:44 - [ 7] Summary Form for Proposal 14461 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, 52X0.05, F28X50OIII ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=900, WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PHASE 0.945 TO 0.955, Period 3.092926 D AND ZERO-PHASE HJD2457463.82884, SCHED 100%, SEQ 1-4 NON-INT, SEQ 11-13 NON-INT, SEQ 14-16 NON-INT, SEQ 5-7 NON-INT, SEQ 8-10 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140H, G140M, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HR-8832, WAVE ------------------------------------------------------------------------------------------------------------------------------------