This is the new Phase II for this program, originally to be performed with COS. We submitted a program change request, that was accepted, to switch the program to STIS. This Phase II has been reworked in consequence. ----- Attempting Submission 3 (Mon Nov 23 14:00:41 GMT 2009) ----- 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.

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. 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. EXTRA-SOLAR PLANETS 0 false 0.0 0.0 false false false false false false SUPPORTED STAR EXTRA-SOLAR PLANETARY SYSTEM M V-IV This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 11 42 11.0941 +26 42 23.65 J2000 COS/FUV Spectroscopic No No G130M 1291 The scheduling data was generated by CASM 17.5. CASM was run in Phase II mode. /Users/DavidEhrenreich/Documents/Travail/Propositions/HST Cycle 17/DD GJ436/OP-cache/DD_II_v4-v01.xml 1258984263481 This visit consists in 1 HST orbit. (Tic-Visit :proposal-id 11817 :visit-id "01" :proposal-version -1 :trans-version "20090915" :date "23-Nov-2009 14:51:03.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 157520 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11817 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11817 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2934 :al-overhead-at-end 0 :internal-dur-at-end 442 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) true 1 0 Exposure time of 13s needed to reach S/N=40 with the F28X50OII aperture. 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).