Deciphering an Adolescent Warm Sub-Neptune to Unify Formation Models with Primordial Atmospheres

0 Assigned ID: 5479 ----- Attempting Submission 1 (Tue Mar 26 16:43:54 GMT 2024) ----- HST Phase I Proposal 5479 successfully submitted. Receipt: # 5479-1 ----- Attempting Submission 2 (Tue Mar 26 17:59:43 GMT 2024) ----- HST Phase I Proposal 5479 successfully submitted. Receipt: # 5479-2 POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE 0 ----- Attempting Submission 1 (Fri Aug 16 12:35:09 GMT 2024) ----- HST Phase II Proposal 17832 successfully submitted. Receipt: # 17832-1 ----- Attempting Submission 2 (Fri Oct 11 14:09:34 GMT 2024) ----- HST Phase II Proposal 17832 successfully submitted. Receipt: # 17832-2 ----- Attempting Submission 3 (Fri Feb 28 14:17:04 GMT 2025) ----- HST Phase II Proposal 17832 successfully submitted. Receipt: # 17832-3 ----- Attempting Submission 4 (Tue Mar 18 08:49:44 GMT 2025) ----- HST Phase II Proposal 17832 successfully submitted. Receipt: # 17832-4 ----- Attempting Submission 5 (Mon May 12 09:26:42 GMT 2025) ----- We believe the error about the target out of the aperture is for the WFC3 staring observations and refers only to the zeroth order. The first order, which will be used in the analysis, should be within the aperture. Deciphering an Adolescent Warm Sub-Neptune to Unify Formation Models with Primordial Atmospheres Prior observations of mature gas giants have shown evidence of metal-enhanced atmospheres with respect to their host-star. This enrichment could happen during the birth of the planet or it could be caused by atmospheric evolution. While formation and evolution models are able to provide various physical explanations, observational evidence to support any specific hypothesis is still missing due to an inability to distinguish the root-cause of metal-enhancement when studying evolved worlds. Atmospheric characterization of very young planets (<100 Myr), which are yet to experience significant atmospheric evolution, allows us to break the formation/evolution degeneracy and uncover the cause of metal-enrichment. We propose to observe the young (45 Myr) planet DS Tuc Ab using simultaneous transmission spectroscopy with HST WFC3 and JWST NIRSpec to measure the atmospheric metallicity and the carbon-to-oxygen ratio. Forward models show that water, methane, and carbon dioxide are the fundamental tracers of these characteristics, which are best distinguished by having a broad wavelength coverage. This can only be achieved by using both facilities. These data will also allow us to constrain the planet's mass which, in combination with the proposed STIS observations of the host star, will allow us to generate models of the planet's evolution to predict its final fate. Therefore, these observations will give us strict constraints on formation and evolution pathways for this adolescent world. By also using observations of analogue mature planets, we will be able to construct a timeline of atmospheric evolution and find the source of metal-enrichment in exoplanetary atmospheres. We will perform a time-series observation using WFC3 G141 to measure the transmission spectrum of DS Tuc A b. As the name suggests, DS Tuc A has a companion star (DS Tuc B) with a projected separation of 6.16". Due to the restraints of RGM, and the brightness of DS Tuc A, the spectra from these stars will overlap before the first NDR. Therefore, in order to correct for contamination from this companion star, each orbit contains a single G141 stare mode spectrum to measure the relative flux of the two stars. We have placed orient constraints such that the spectra of DS Tuc A and DS Tuc B do not overlap in this stare mode image. The scan observations will be taken with the 512x512 subarray. We will use the SPARS25, NSAMP=3 sampling sequence and the spatial scan mode with bi-directional scans to maximize the duty cycle. We will use a scan rate of ~0.93"/s, which will give peak counts of ~30K e-/pix from DS Tuc A and ~20K e-/pix from DS Tuc B. Hence,the regions in which these spectra overlap shall be <50K e-/pix. To mid-orbit avoid buffer dumps, each WFC3 orbit has been made into a different visit. Furthermore, we will utilise 3 orbits of time to observer DS Tuc A with COS and STIS to understand the planet's irradiation environment. We will take exposures with STIS G230L, G430L, and G750L as well as with COS G140L. Ms Amy Joan Louca specialises in producing disequlibrium chemistry models of exoplanetary atmospheres and evolution models for the atmospheres and interiors of gas giants. Dr Billy Edwards has substantial experience in characterizing exoplanetary atmospheres through transit and eclipse spectroscopy with space-based telescopes. He is the PI of the HST proposal GO-16457 and is part of the JWST MIRI GTO team. Dr Yamila Miguel is an expert in (exo)planet interiors and atmospheres. She has worked on the Juno mission as well as being a coordinator the the Chemistry Working Group for the ESA Ariel space mission. Dr Nestor Espinoza has significant expertise in the reduction and analysis of data from space-based telescopes for exoplanet science. He is the scientific lead of the Exoplanet Characterization Toolkit (ExoCTK) and part of the STScI JWST support team. Exoplanets and Exoplanet Formation 6 false true false false false false AVAILABLE STAR EXTRA-SOLAR PLANET NO This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. J2000 J2000 WFC3/IR Spectroscopic No No G141 STIS/CCD Spectroscopic No No G750L 7751 1747041928010 Timing link suitability includes constraints ([02 After 01 by 0.1 to 0.1 days]) The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 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