11817( 6) - 23-Nov-2009 16:01:18 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11817 Version: 6 Check-in Time: 23-Nov-2009 16:01:18 STScI Edit Number: 2 Title Detecting the upper atmosphere of a transiting hot Neptune: A feasibility study ------------------------------------------------------------------------------------ Type Cycle GO/DD 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David Ehrenreich Universite de Grenoble I CoI: Dr. Xavier Bonfils Universite de Grenoble I N CoI: Dr. Xavier Delfosse Universite de Grenoble I N CoI: Dr. Jean-Michel Desert CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Roger D. Ferlet CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Thierry Forveille Universite de Grenoble I N CoI: Dr. Guillaume Hebrard CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Anne-Marie Lagrange Universite de Grenoble I N CoI: Dr. Alain Lecavelier des Etangs CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Nadege Meunier Universite de Grenoble I N CoI: Dr. David Kent Sing CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Alfred Vidal-Madjar CNRS, Institut d'Astrophysique de Paris N ------------------------------------------------------------------------------------ Abstract Atmospheric escape is a phenomenon that shapes planetary atmospheres, from telluric planets in the Solar System to extrasolar 'hot Jupiters'. It dramatically enhances the detectability of a heavily irradiated hydrogen atmosphere, providing the planet is transiting its star and the transits are observed in the ultraviolet, at Lyman alpha. The 'hot Neptune' transiting the M dwarf GJ436 is the best analog we have to a transiting super-Earth. Internal structure and atmospheric models predict that it bears an extended hydrogen/helium atmosphere subject to evaporation. It is detectable with the Space Telescope Imaging Spectrograph, providing the background Lyman-alpha source -- the star -- is bright enough or, alternatively, the emission line profile spans over a large velocity range. To date, no spectra of GJ436 exist at this wavelength. Using 1 orbit of Director's Discretionary Time, we aim at properly estimating the stellar Lyman-alpha flux and line profile. This DDT will serve as a basis for a Cycle-18 program aimed at detecting the atmosphere of hot-Neptune GJ436b and constraining both internal structure and atmospheric models. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe the exoplanet host-star GJ 436 (a M dwarf) during 1 visit of 1 HST orbit in order to quantify its Lyman alpha flux with the STIS/FUV-MAMA. We will use the thinnest first-order slit 52x0.05 and the G140M grating. The first two exposures (exp#01.001 and exp#01.002) are acquisition (ACQ and ACQ/PEAK). The target is to be acquired during the ACQ/PEAK exposure using the 52x0.05 first-order slit. The science exposure (exp#01.003) will then be performed after an auto-WAVECAL and will last for the remaining orbit time available. Real Time Justification ----------------------- 11817( 6) - 23-Nov-2009 16:01:18 - [ 2] Calibration Justification ------------------------- Additional Comments ------------------- The goal of this DD observation is to prepare a Cycle-18 program. Therefore, it has to be performed before Cycle-18 proposal submission deadline. This date is not known yet and so far we have based ourselves on the deadline for the Cycle 17 (beginning of March). The January window seems mostly appropriated for this purpose. ------------------------------------------------------------------------------------ 11817( 6) - 23-Nov-2009 16:01:18 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GJ-436 STAR, EXTRA-SOLAR RA=11H42M11.0941S +/- 0.02474", J2000 V = 10 V = 10.68 PLANETARY SYSTEM, M DEC=+26D42'23.65" +/- 0.01472" V-IV Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.059756 -0.81370 0.09773 ------------------------------------------------------------------------------------------------------------------------------------ 11817( 6) - 23-Nov-2009 16:01:18 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: This visit consists in 1 HST orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GJ-436 STIS/CCD ACQ F28X50OII MIRROR ACQTYPE=POINT 1 13 S Comments: Exposure time of 13s needed to reach S/N=40 with the F28X50OII aperture. ------------------------------------------------------------------------------------------------------------------------------------ 2 GJ-436 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 7 S K Comments: Exposure time of 7s (well below saturation) needed to reach S/N=40 with G430L grism and first-order slit 52x0.05 (total counts = 7e5 with gain=4 and cr-split=0). ------------------------------------------------------------------------------------------------------------------------------------ 3 GJ-436 STIS/FUV TIME-TA 52X0.05 G140M 1222 BUFFER-TIME=900 1 1762 S -MAMA G ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GJ-436 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I GJ-436 2 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 1 N/A K GJ-436 3 STIS/FUV TIME-TA 52X0.05 G140M 1222 none none none none 1 N/A -MAMA G 11817( 6) - 23-Nov-2009 16:01:18 - [ 5] Summary Form for Proposal 11817 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.05, F28X50OII ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=900 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140M, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names GJ-436 ------------------------------------------------------------------------------------------------------------------------------------