0 Assigned ID: 1216 ----- Attempting Submission 1 (Fri Jan 17 20:05:09 GMT 2020) ----- Added comment on using a narrow slit. Added ETC run ID for ACQ/PEAK. Removed ACQ exposures from orbits 2 and onwards. 1801009759 ----- Attempting Submission 1 (Tue Mar 10 09:29:10 GMT 2020) ----- HST Phase II Proposal 16085 successfully submitted. Receipt: # 16085-1 ----- Attempting Submission 2 (Tue May 12 10:52:28 GMT 2020) ----- The recent discovery of the transiting young (45 Myr) planet DS Tuc A b around a bright and nearby solar-type star provides a unique opportunity to study the role of atmospheric escape in the early lives of warm Neptunes. One of the explanations for the lack of hot Neptune-sized planets is atmospheric escape, which is expected to be most important during the first 100 Myr after formation. In this program, we aim to detect and interpret the atmospheric escape of DS Tuc A b using Lyman-alpha transmission spectroscopy. Owing to its strong irradiation at a young age, we estimate that the escape rate of this planet is orders of magnitude larger than other warm Neptunes with previous detections. The stellar Lyman-alpha emission can be readily observed by HST/STIS due to the short distance of the star and its young age. The outcomes of this program will provide the first observational constraints for atmospheric escape models in young Neptune-sized exoplanets, as well as the lower-atmosphere composition of DS Tuc A b. The results will also be fundamental to future efforts in characterizing the planet using JWST and ground-based facilities. We will observe one transit of DS Tuc A b using HST/STIS with the G140M grating centered on 122.2 nm. Since DS Tuc is a binary (separation = 5 arcsec = 100 pixels), it is imperative to insert the correct star in the slit. We already verified that, for most of the remaining time of Cycle 27, it is impossible to set the ORIENT constraint so that we have both stars in the slit. The target DS Tuc A is approximately 1 magnitude brighter than DS Tuc B at visible wavelengths, so the telescope should automatically center the correct target assuming everything goes well. There is also another bright star 3 arcmin east of the DS Tuc system. We will use the narrowest slit width (0.05") to minimize airglow contamination as much as possible. We understand that this choice can introduce slit losses, but we can correct for these losses when analyzing the data (on the other hand, the extra noise introduced by the airglow cannot be corrected). The ACQ exposure is performed following the recommendations from the ETC. Our target star is very bright, so we always get warnings for the ACQ/PEAK when running it in the ETC. We decided to use the same ACQ/PEAK configuration as in program GO#13820 (similarly bright star, similar science case and same instrumental configuration). We set the timing constraints in the SCIENCE exposure to match an observing window of 10 hours around the exoplanet transit midcenter (period = 8.138268 days), which roughly corresponds to 5 orbits and some "wiggle room" for flexibility; this timing constraint covers the transit and the baseline flux of the star in the most reliable, yet flexible way. We set the schedulability constraint to 100 in order to maximize observation opportunities. We understand that simultaneous observations of HST with other telescopes is not guaranteed, thus we do not include the following as a timing constraint. However, this program would significantly benefit from performing the HST visit at the same time as the ground-based facilities that we have access to in La Silla, Chile. Our plan is to use these facilities to measure the stellar activity index of DS Tuc A during the transit of the planet, as well as wide-band photometry. We will use these data to correct for potential stellar activity effects that can be present in the FUV data obtained with HST and create spurious planetary signals. If it is not possible to accomodate this request, another possibility is to execute the HST visit between July 4 and August 26 2020, since our target is going to be in the TESS field and we can obtain simultaneous space-based photometry. The potential impacts of not performing simultaneous observations or having bad weather in La Silla are: i) The interpretation of the results can be more complicated in case the stellar activity modulation is as strong as a planetary signal in UV (in the order of a few percent or more) -- neither of these are known at the moment; ii) In case the results render only a tentative detection, we may need to apply for another HST transit to repeat the experiment and draw a more definitive conclusion. With these considerations in mind, even if we cannot perform simultaneous observations, the objectives of this program can still be attained to the extent that previous Lyman-alpha transits did in the past. If possible we request that the observations are carried out in one of these windows (times are in UT): 25 Jul 2020 21:46 - 26 Jul 2020 07:46; priority 1 (full transit visible from La Silla and TESS) 03 Aug 2020 01:05 - 03 Aug 2020 11:05; priority 1 (full transit visible from La Silla and TESS) 07 Jun 2020 01:52 - 07 Jun 2020 11:52; priority 2 (full transit visible from La Silla) 20 Sep 2020 21:00 - 21 Sep 2020 07:00; priority 2 (full transit visible from La Silla) 29 Sep 2020 00:19 - 29 Sep 2020 10:19; priority 2 (full transit visible from La Silla) 11 Aug 2020 04:24 - 11 Aug 2020 14:24; priority 3 (partial transit visible from La Silla and full from TESS) 15 Jun 2020 05:11 - 15 June 2020 15:11; priority 4 (partial transit visible from La Silla) Any time between 4 Jul 2020 to 26 Aug 2020; priority 5 (full transit visible from TESS) No simultaneous observations; priority 6 L. dos Santos has experience in data reduction and interpretation of HST/STIS and COS stellar spectra, ground- based spectra, as well as transmission spectroscopy of exoplanets, interpretation and correction of instrumental systematics and stellar activity in the far-ultraviolet and visible wavelengths. D. Ehrenreich, V. Bourrier, and R. Allart have an extensive experience on UV data analysis of planet-hosting stars, space- and ground-based transmission spectra and have several publications on ground-breaking discoveries about exoplanetary atmospheres. Moreover, V. Bourrier developed empirical and analytical tools to analyze and interpret observations of atmospheric escape from exoplanets. M. Lendl and O. Turner are experts in ground-based photometric monitoring of exoplanet-host stars. L. Nielsen is an expert in stellar spectroscopy, radial velocity measurements and analysis of stellar activity indexes. Our team has guaranteed observation time available with the Euler telescope (ground-based photometry and high-resolution spectroscopy). Planets and Planet Formation Stellar Physics 3 false false true false false false false SUPPORTED STAR EXTRA-SOLAR PLANETARY SYSTEM G V-IV REGULAR VARIABLE RS CVN STAR Coordinates from Tycho-2 database. Proper motion from Gaia DR2. Radial velocity from Newton+2019. J2000 J2000 STIS/FUV-MAMA Spectroscopic No No G140M 1222 /private/var/folders/jp/y94kfdg15xjgpplw8yrqt3jc0000gn/T/OPVisit2762266792861848804.xml 1589280508663 The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. 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