0 Assigned ID: 998 ----- Attempting Submission 1 (Sat Mar 07 00:21:50 GMT 2020) ----- All 18 orbits should be executed consecutively, but we've divided the 18 orbits into three visits of 6 orbits each so that the APT could run more efficiently and reliably. -1822327582 ----- Attempting Submission 1 (Mon Jun 29 22:01:40 GMT 2020) ----- We request 18 orbits of HST time to observe the transit of HIP 41378 f, a Jovian planet (9.2 Earth radii) in a long-period orbit (542 days = 1.5 years) in a multi-planet system. The host star HIP 41378 is bright (Ks = 7.7, V=8.9), Sun-like (1.2 solar masses, 1.3 solar radii), and known to host at least five transiting planets. Two transits of HIP 41378 f were observed by the NASA K2 mission during non-consecutive three-month observing campaigns in 2015 and 2018, restricting the set of possible periods to a set of harmonics with a maximum period of roughly 1000 days and a minimum period near 50 days. An intensive radial velocity campaign (464 observations spanning four years) has just ruled out the remaining possibilities, revealing that the HIP 41378 f has an orbital period of 542 days and an unexpectedly low mass of 12 Earth masses. HIP 41378 f is predicted to transit on 20 May 2021 and will not transit again until November 2022. We propose to observe the 2021 transit event with WFC3/G141 to accomplish three goals: (1) probe the atmospheric composition of a cool Jovian planet; (2) investigate the possible presence of rings; (3) place constraints on the presence of exomoons. HIP 41378 f occupies a poorly-probed region of parameter space and bridges the gap between the hotter planets previously studied via transmission spectroscopy and the cooler Jovian planets in our own solar system. HST transmission spectroscopy of HIP 41378 f would provide an opportunity to investigate the influence of stellar irradiation on giant planet atmospheres and inform efforts to detect Jupiter analogs with direct imaging surveys. The transit of HIP 41378 f will last 19 hours (roughly 12 orbits). We request 18 consecutive HST orbits to observe the transit of HIP 41378 f . These observations will provide high phase coverage during the transit event as well as the pre-transit and post-transit baselines necessary for precisely determining the transit depth and constraining atmospheric properties. We will use WFC3 with the G141 (1.0 - 1.7 micron) grism. Our proposed observational design mimics that of numerous successful previous transmission spectroscopy observations with WFC/G141 (e.g., Knutson et al. 2014a,b; Kreidberg et al. 2014, 2015, 2018; Benneke et al. 2018, 2019). Specifically, we will perform time series spectroscopy just before, during, and just after transit. We will utilize the spatial scan observing mode to permit longer exposure times, thus reducing read noise without saturating the detector. In addition, we will use the 256 x 256 subarray to facilitate longer spatial scans and further improve observational efficiency for our bright target star. We used the open-source PandExo_HST tool to identify the optimal sampling sequence and scan rate. PandExo maximizes observational efficiency while ensuring that the peak photon counts are roughly 30,000 photoelectrons per pixel. We will further increase the efficiency of our observations by alternating between forward and revere scanning along the detector. At the start of the visit, we will acquire a direct image of HIP 41378 for wavelength calibration. In consecutive orbits, we will use the Hydrogen Paschen line at 1.28 m as a wavelength reference. Our PandExo simulations indicated that the ideal observation parameters are NSAMP = 8 and SAMP SEQ = SPARS10. We will scan at a rate of 0.418629 "/s using a scan size of 179 pixels and an exposure time of 51.7 seconds. These observations are predicted to result in a transit depth uncertainty of 23 ppm per channel when subdividing the spectrum into 30 wavelength channels. All team members are exoplanet scientists who have experience working with transit and radial velocity data. Dressing helped establish the HIP 41378 collaboration and was a Co-I on Cycle 24 Program GO #14682 (transmission spectroscopy using WFC3/G141). Along with Lopez-Morales, Crossfield, and PhD students in her research group (Fleming, Giacalone, Mayo, & Turtelboom), she will reduce, analyze, and interpret the HST data. Santerne led the multi-collaboration analysis of the HIP 41378 RV data and determined the transit ephemeris. Marley is an expert on the atmospheres of Jovian planets and brown dwarfs. Lopez-Morales is an expert in space-based and ground-based transmission spectroscopy. She was PI of Cycle 23 GO Proposal #14464 and is Co-PI of the HST Panchromatic Comparative Exoplanet Treasury (PanCET) program (GO #14767). Crossfield has been PI or co-PI of three previous HST programs on exoplanet atmosphere characterization, including a large program in Cycle 25 (GO #15333), which employs the same observational strategy as this proposal. Dai has expertise in transit modeling and hydrodynamic simulation. He has recently written a paper about "super-puff" planets and will assist with modeling the evolution of HIP 41378 f. Akinsanmi, Barros, and Santos have developed a code to fit exoplanetary rings. They will inspect the data for evidence of rings. Wheatley is PI for 2 HST programs on exoplanets (HD189733 and TRAPPIST-1), and has been Co-I of 13 other HST programs, mostly concerning atmospheric escape from giant exoplanets. He has also carried out a number of ground-based transmission spectroscopy studies of hot Jupiters. Lillo-Box has experience in ground-based transmission spectroscopy observations as well as high-resolution spectrographs for radial velocity monitoring and high-precision photometry both from the ground and from space. Deleuil is an expert in high-precision photometry and planetary interior modeling. Kirk is practiced in analyzing and interpreting transmission spectra both from the ground and space. Vanderburg discovered the system and is an experienced transit modeler. Mortier scheduled HARPS-N observations of HIP 41378 and has expertise in Bayesian analysis, stellar activity, and stellar characterization. Collier Cameron is a leading member of the SuperWASP transit search team and an expert on transiting planets as well as radial velocities and stellar activity. Exoplanets and Exoplanet Formation 6 false false false false false false false SUPPORTED STAR EXTRA-SOLAR PLANETARY SYSTEM ICRS coordinates, proper motions, parallax, and radial velocity are from Gaia DR2 and were retrieved from SIMBAD. J2000 J2000 B = 9.42 +/- 0.02, G = 8.81 +/- 0.0004, J = 7.982 +/- 0.026, H = 7.786 +/- 0.038, K = 7.722 +/- 0.031 WFC3/IR Spectroscopic No No G141 1619015835647 /System/Volumes/Data/solaris/user1/royle/OP-cache/16267-v01.xml The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. First of three consecutive visits covering pre-transit baseline, the transit, and post-transit baseline. 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