15934( 2) - 25-Jul-2019 12:25:48 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15934 Version: 2 Check-in Time: 25-Jul-2019 12:25:48 STScI Edit Number: 0 Title Far-ultraviolet exploration of nearby young exoplanet-hosting stars ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Leonardo Dos Santos Observatoire de Geneve Y CoI: Prof. David Ehrenreich Observatoire de Geneve N CoI: Dr. Vincent Bourrier Observatoire de Geneve N CoI: Dr. Baptiste Lavie Observatoire de Geneve N ------------------------------------------------------------------------------------ Abstract One of the proposed explanations for the observed lack of close-in exoplanets with sizes between 1.5 and 2.0 Earth-radii is that this valley is carved by atmospheric erosion: sub-Neptune-sized planets begin their lives with large H/He-rich envelopes, which are lost during their early ages due to photoevaporation. The recent discovery of the young exoplanetary systems in K2-136 and K2-233 provides an excellent opportunity to test this hypothesis using Lyman-alpha transmission spectroscopy, but first we need to evaluate the FUV flux of the stars, which is the main objective of this project. We realistically estimate that the Lyman-alpha emission of these K-type stars are promptly detectable with HST/STIS, despite their distance, owing to their young age. These observations will allow us to study the UV environment and evolution around young low-mass exoplanetary systems, and in the future could lead to the first evidence of atmospheric escape in a young sub- Neptune. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program aims to observe the Lyman-alpha emission (1215 A) of young planet-hosting K4-type stars (V mag ~ 11) using the FUV-MAMA detector and the G140M grating centered in 1222 A. We perform the ACQ/PEAK exposures in spectroscopic mode because the target stars are too bright in the visible to be observed with MIRROR + 52X0.05D1 aperture (the same as the science exposures). We moved the AUTO-WAVECAL to GO-WAVECAL during Earth occultation: the time gained for the scientific exposures would be very useful, since the stars are faint in the FUV. The Bright Object Tool says all targets in the field are safe, however there is one unknown in the field of K2-136 in the GSC II database. Since our program has only 2 orbits and we do not have strict time-window limits, the eventual failure of one of the gyros does not have a significant impact on our program and it can still be carried on whenever a feasible time window is available. ------------------------------------------------------------------------------------ 15934( 2) - 25-Jul-2019 12:25:48 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 K2-233 STAR, EXTRA-SOLAR RA=15H21M55.1981S +/- 0.0506", J2000 V = V = 10.88 +/- 0.09 B 11.81, G 10.4191, PLANETARY SYSTEM, K DEC=-20D13'53.99" +/- 0.0442" -10.2644 J 8.968, H 8.501, K 8.375 III-I 43704601 566 Reference Frame: ICRS Comments: Astrometric information obtained from Gaia and magnitudes from SIMBAD. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0014118410243825256 -0.031188 0.014785 ------------------------------------------------------------------------------------------------------------------------------------ 2 K2-136 STAR, EXTRA-SOLAR RA=04H29M38.9938S +/- 0.0473", J2000 V = V = 11.20 +/- 0.01 B 12.48, R 10.90, G PLANETARY SYSTEM, K DEC=+22D52'57.79" +/- 0.0238" 39.48474 10.8545, J 9.096, H 8.496, K 8.368 V-IV 48110252 94 Reference Frame: ICRS Comments: Astrometric information obtained from Gaia and magnitudes from SIMBAD. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.005996870720840334 -0.035616999999999996 0.016849678662681658 ------------------------------------------------------------------------------------------------------------------------------------ 15934( 2) - 25-Jul-2019 12:25:48 - [ 3] Visit: 01 (K2-233) Visit Requirements: 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 K2-233 STIS/CCD ACQ F28X50OII MIRROR 1 6 S (6 S) SEQ 1-4 NON-INT Comments: The target is too bright for the longpass filter, so the F28X50OII was selected instead. The time to reach signal to noise ratio of 40 is estimated at 6 s, with time to saturation 603 s. ------------------------------------------------------------------------------------------------------------------------------------ 2 K2-233 STIS/CCD ACQ/PEA 52X0.05D1 G430M 4451 1 12 S (12 K S) Comments: We need to use a grating instead of mirror because the target is too bright. 12 s allows to reach S/N=10 with STIS/CCD/G430M and aperture 52x0.05D1 (the same as the science observations), and is below the time to saturation (4000 s). The Spectroscopic ETC yields a warning about the issue with charge transfer efficiency for low background, but we are just using the CCD for the target acquisition, after which we switch to the MAMA. ------------------------------------------------------------------------------------------------------------------------------------ 3 K2-233 STIS/FUV TIME-TA 52X0.05D1 G140M 1222 BUFFER-TIME=900, WAVECAL=NO 1 1500 S -MAMA G see below (1664 S) Comments: We are photon-starved and set the exposure time to the maximum possible value. The star is later-type (K3) than the K0 stars HD189733 and HD97658, observed with the same settings in previous programs, and it is farther away and fainter. We thus expect lower count rates, and set the buffer-time as Texp/2. ------------------------------------------------------------------------------------------------------------------------------------ 4 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 | ------------------------------------------------------------------------------------------------------------------------------------ 15934( 2) - 25-Jul-2019 12:25:48 - [ 4] 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 | ------------------------------------------------------------------------------------------------------------------------------------ K2-233 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I K2-233 2 STIS/CCD ACQ/PEA 52X0.05D G430M 4451 none none none none 1 N/A K 1 K2-233 3 STIS/FUV TIME-TA 52X0.05D G140M 1222 none none none none 1 1664.0 S -MAMA G 1 WAVE 4 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 1 N/A -MAMA 15934( 2) - 25-Jul-2019 12:25:48 - [ 5] Visit: 02 (K2-136) Visit Requirements: 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 K2-136 STIS/CCD ACQ F28X50OII MIRROR 1 13 S (13 SEQ 1-4 NON-INT S) Comments: The target is too bright for the longpass filter, so the F28X50OII was selected instead. The time to reach signal to noise ratio of 40 is estimated at 13 s, with time to saturation 1286 s. ------------------------------------------------------------------------------------------------------------------------------------ 2 K2-136 STIS/CCD ACQ/PEA 52X0.05D1 G430M 4451 1 19 S (19 K S) Comments: We need to use a grating instead of mirror because the target is too bright. 19 s allows to reach over S/N=10 with STIS/CCD/G430M and aperture 52x0.05D1 (the same as the science observations), and is below the time to saturation (5800 s). The Spectroscopic ETC yields a warning about the issue with charge transfer efficiency for low background, but we are just using the CCD for the target acquisition, after which we switch to the MAMA. ------------------------------------------------------------------------------------------------------------------------------------ 3 K2-136 STIS/FUV TIME-TA 52X0.05D1 G140M 1222 BUFFER-TIME=900, WAVECAL=NO 1 1500 S -MAMA G see below (1524 S) Comments: We are photon-starved and set the exposure time to the maximum possible value. The star is later-type (K6) than the K0 stars HD189733 and HD97658, observed with the same settings in previous programs, and it is farther away and fainter. We thus expect lower count rates, and set the buffer-time as Texp/2. ------------------------------------------------------------------------------------------------------------------------------------ 4 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 | ------------------------------------------------------------------------------------------------------------------------------------ 15934( 2) - 25-Jul-2019 12:25:48 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ K2-136 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I K2-136 2 STIS/CCD ACQ/PEA 52X0.05D G430M 4451 none none none none 1 N/A K 1 K2-136 3 STIS/FUV TIME-TA 52X0.05D G140M 1222 none none none none 1 1524.0 S -MAMA G 1 WAVE 4 STIS/FUV ACCUM 52X0.05 G140M 1222 none none none none 1 N/A -MAMA 15934( 2) - 25-Jul-2019 12:25:48 - [ 7] Summary Form for Proposal 15934 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.05, 52X0.05D1, F28X50OII ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=900, WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 1-4 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140M, G430M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names K2-136, K2-233, WAVE ------------------------------------------------------------------------------------------------------------------------------------