14843( 4) - 29-Aug-2017 19:49:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14843 Version: 4 Check-in Time: 29-Aug-2017 19:49:04 STScI Edit Number: 0 Title Clouds in the Forecast? A Joint Spitzer and HST Investigation of Clouds and Hazes for Two Exo-Neptunes ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Laura Kreidberg Harvard University Y CoI: Dr. Caroline Morley Harvard University N CoI: Dr. Michael Line Arizona State University N CoI: Dr. Kevin B. Stevenson Space Telescope Science Institute N CoI: Dr. Diana Dragomir Massachusetts Institute of Technology N ------------------------------------------------------------------------------------ Abstract Recent observations of transiting planets have revealed that clouds and hazes are common in exoplanet atmospheres. Little is known, however, about how the clouds/hazes form, what their composition is, and how their properties vary with planet parameters. We propose to characterize the atmospheres of two exo-Neptunes, GJ 436b and GJ 3470b, both of which show evidence for clouds or hazes in their near-infrared spectra. We will measure precise 3.6 and 4.5 micron transit depths for these planets, to compare with existing high-precision data at shorter wavelengths. We will also obtain a UV spectrum for GJ 3470 with HST/COS to enable accurate models of the planet's photochemistry. These observations will enable us to distinguish at high confidence between a range of physically realistic models for the atmospheric chemistry, including methanogenic photochemical hazes and equilibrium salt/sulfide clouds. The measurements will enable comparative planetology with the handful of other small, cool worlds currently accessible to observation, and serve as a first assessment of the prevalence, origin, and composition of clouds and haze in metal-enriched atmospheres below 1000 K. Our findings will guide the design of future observations of increasingly Earth-like worlds with JWST. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe the spectrum of the M1.5-dwarf GJ 3470 with COS over the wavelength range 1150 - 3200 Angstroms. GJ 3470 is a faint target, so COS is superior to STIS at these wavelengths due to its greater sensitivity. We will use a combination of the G130M, G160M, and G230L gratings to acquire the complete spectrum. All data will be obtained in TIME-TAG mode so that we can constrain the star's flaring activity. We will use the FLASH=YES setting to maximize exposure time on target. These observations are based on the successful set-up used by the MUSCLES program to measure M-dwarf spectra (GO Programs 12464, 13640). We calculated exposure times needed to achieve a signal-to-noise SNR > 5 for major stellar emission lines in each grating (CII for G130M, C IV for G160M, and Mg II for G230L). We based our calculations on measurements of the spectrum of GJ 832 (an M-dwarf of similar spectral type) from the MUSCLES program (France et al. 2016). We assumed that GJ 3470 has the same instrinsic flux as 14843( 4) - 29-Aug-2017 19:49:04 - [ 2] GJ 832 and scaled the expected signal by the distance to the star (GJ 3470 is 6x more distant than GJ 832, so we expect a roughly 40x smaller signal). GJ 3470 is an active star, so these exposure times are conservative estimates and we expect the actual SNR to be greater than 5. The MUSCLES spectrum for GJ 832 has SNR of 75, 40, and 180, for the C IV, CII, and Mg II lines. These data were obtained with exposure times of 15119, 7671, and 2756s using the G160M, G160M, and G230L gratings, respectively. Based on these results and our expectations for the brightness of GJ 3470, we require 2419, 4310, and 77 s in G130M, G160M, and G230L for a total of 3 orbits accounting for time to acquire the target. ------------------------------------------------------------------------------------ 14843( 4) - 29-Aug-2017 19:49:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GJ-3470 STAR, EXTRA-SOLAR RA=07H59M5.8422S +/- 0.1", J2000 V = 12.332 PLANETARY SYSTEM, M DEC=+15D23'29.21" +/- 0.1" III-I Reference Frame: Other: SIMBAD Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2012 -0.012370328060074091 -0.0605 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14843( 4) - 29-Aug-2017 19:49:04 - [ 4] Visit: 01 Visit Requirements: Period 3.33665 D AND ZERO-PHASE HJD2456090.47701 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 GJ-3470 COS/NUV ACQ/IMA PSA MIRRORB 1 330. S PHASE 0.05 TO 0.95 GE (330 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GJ-3470 COS/NUV TIME-TA PSA G230L 2950 BUFFER-TIME=1750, FLASH=YES, 1 550 S (550 G FP-POS=4 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GJ-3470 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=3900, FLASH=YES, 1 1183 S G FP-POS=3, SEGMENT=BOTH (1183 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 GJ-3470 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=3900, FLASH=YES, 1 1029 S G FP-POS=4, SEGMENT=BOTH (1029 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 GJ-3470 COS/FUV TIME-TA PSA G160M 1611 BUFFER-TIME=10828, FLASH=YES, 1 1666 S G FP-POS=1, SEGMENT=BOTH (1666 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 GJ-3470 COS/FUV TIME-TA PSA G160M 1611 BUFFER-TIME=10828, FLASH=YES, 1 900 S (900 G FP-POS=2, SEGMENT=BOTH S) ------------------------------------------------------------------------------------------------------------------------------------ 7 GJ-3470 COS/FUV TIME-TA PSA G160M 1611 BUFFER-TIME=10828, FLASH=YES, 1 900 S (900 G FP-POS=3, SEGMENT=BOTH S) ------------------------------------------------------------------------------------------------------------------------------------ 8 GJ-3470 COS/FUV TIME-TA PSA G160M 1611 BUFFER-TIME=10828, FLASH=YES, 1 920 S (920 G FP-POS=4, SEGMENT=BOTH 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 | ------------------------------------------------------------------------------------------------------------------------------------ GJ-3470 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE GJ-3470 2 COS/NUV TIME-TA PSA G230L 2950 none none none none 1 N/A G GJ-3470 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G GJ-3470 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G GJ-3470 5 COS/FUV TIME-TA PSA G160M 1611 none none none none 2 N/A G GJ-3470 6 COS/FUV TIME-TA PSA G160M 1611 none none none none 3 N/A G 14843( 4) - 29-Aug-2017 19:49:04 - [ 5] 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-3470 7 COS/FUV TIME-TA PSA G160M 1611 none none none none 3 N/A G GJ-3470 8 COS/FUV TIME-TA PSA G160M 1611 none none none none 3 N/A G 14843( 4) - 29-Aug-2017 19:49:04 - [ 6] Summary Form for Proposal 14843 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=10828, BUFFER-TIME=1750, BUFFER-TIME=3900, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, SEGMENT=BOTH ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PHASE 0.05 TO 0.95, Period 3.33665 D AND ZERO-PHASE HJD2456090.47701 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G160M, G230L, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names GJ-3470 ------------------------------------------------------------------------------------------------------------------------------------