For the best data quality, it is generally required to use all four FP-POS positions when observing at a given COS cenwave. COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS For the best data quality, it is generally required to use all four FP-POS positions when observing at a given COS cenwave. COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS For the best data quality, it is generally required to use all four FP-POS positions when observing at a given COS cenwave. COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS For the best data quality, it is generally required to use all four FP-POS positions when observing at a given COS cenwave. COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS COS EXPOSURE TIME ROUNDED DOWN TO NEAREST 0.1 SECONDS Updated transit time and period based on more recent transit observations 545822253 ----- Attempting Submission 2 (Thu Apr 04 16:31:51 GMT 2024) ----- ----- Attempting Submission 3 (Tue May 07 23:48:19 GMT 2024) ----- ----- Attempting Submission 4 (Wed Apr 16 20:18:49 GMT 2025) ----- We received the warning that for the best data quality, it is generally required to use all four FP-POS positions. However, the configuration we have requested has had proven success (HST GO 16164). We request the same observing strategy as this previous program, as it will allow us to achieve our scientific objectives and make for an easier comparison between this new and the archival observations. The 23 Myr M star AU Mic and its transiting planets are an ideal laboratory for understanding the impact of stellar activity on young exoplanet atmospheres. Young planetary systems offer a unique advantage in that their spectral signatures are representative of primordial formation conditions. This is significantly advantageous when compared with more evolved planets which have experienced significant stellar irradiation, processing and pollution. The formation mechanism and subsequent evolution of massive, short-period planets is not currently well understood. For example, these planets may have formed at large distances and migrated inwards or alternatively formed in situ. Here, we propose to obtain spectra during 4 transits of AU Mic b, the innermost Neptune-sized planet in the system (Teq = 820K), with NIRCam F322W2/F444W (2.4 - 5 micron). Our primary objective is to measure atmospheric C/O and metallicity to constrain the formation location of the planet. We propose for simultaneous JWST + HST observations. The chemistry in the atmosphere of AU Mic b will be dictated by the environmental ultraviolet flux. Because AU Mic is both young and a flare-active star, we require FUV observations to (i) identify and remove stellar flares from our transmission spectrum and (ii) characterize the FUV environment, which will be crucial for interpreting our planet spectrum. These observations will also provide unique FUV - NIR measurements of flare events, furthering our understanding of stellar magnetism. These spectra will provide an important legacy for understanding young stars, planetary atmospheres, and combining NIR + FUV to mitigate stellar contamination. We will observe four transits of AU Mic b simultaneously with JWST in order to monitor for stellar flares which are likely to occur during these observations. We will use the COS G130M setting with CENWAVE=1222 angstroms. This provides coverage from approximately 1060 - 1360 angstroms with a detector gap from 1210-1225 angstroms. This setting includes several emission lines which will be used to identify and characterize stellar flares (e.g. C III at 1175.95 Angstrom and Si III at 1294.55 Angstrom). The same COS setting will be used for all observations. This observing mode and setup have been used in previously successful HST programs (e.g. HST GO 16164). AU Mic is visible for 3000 seconds during an HST orbit. Assuming a total exposure time of 3000 seconds, we expect to achieve a S/N of 75 - 100 in the C III lines. Our observations must occur during transits of AU Mic b, which has an orbital period of 8.46321 days and a transit duration of 3.5 hours. According to the APT visit planner, there are ~20 possible transits visible during Cycle 32 and JWST Cycle 3, during which our observations should be scheduled. This should be feasible to schedule our simultaneous observations. AU Mic b experiences transit timing variations. We are actively monitoring this system to account for these variations. The uncertainty on the period is 0.00004 days. The current uncertainty on the transit mid-point is 0.0007 days. In order to obtain the longest out-of-transit baseline for each transit, we will stagger the out-of-transit observations for each visit in the following way: for 2 out of 3 transits we will obtain 2 pre-transit exposures and for 1 out of 3 transits we will obtain 2 post-transit exposures. Each transit will have 3 in-transit exposures. We believe this strategy is optimal so that the out-of-transit baseline extends as far as possible from ingress or egress, minimizing the possibility of a highly extended atmosphere creating pre- or post-transit absorption that could skew the in-transit absorption depths. With this strategy in mind, each visit must be scheduled no earlier than planetary orbital phase 0.97 and no later than 0.99. AU Mic is a pre-main sequence M-star with effective temperature T=3700+-100 K and must be considered under the Bright Object Protection Considerations for M Dwarf Flare events (Osten 2017). It exhibits flares with energy <= 10^30 ergs twice an hour (Feinstein et al. 2022). This can be compared to the active flare star AD Leo which experiences a flare with the same energy 5 times per day. From three archival visits to AU Mic, the star did not exhibit a flare with energy > 10^30 ergs, and thus is unlikely to exhibit a superflare during these proposed observations. Our selected COS configuration does not include the strongest FUV lines (e.g. Ly-alpha) which would otherwise cause damage to the detector. All emission line fluxes in our configuration are within the safe range for active M dwarfs. Adina Feinstein is an expert in transit observations of young planets, stellar activity, and is the lead software developer for several time-series photometry extraction and analyses, and JWST data reduction pipelines. Additionally, she led the JWST ERS Transiting Exoplanet Community analysis of the transit observation of WASP-39b with NIRISS/SOSS. Additiona, PI Feinstein is an expert in identifying and characterizing stellar flares on young stars at both ultraviolet and optical wavelengths. Luis Welbanks is an expert in atmospheric modeling and the interpretation of atmospheric observations using inference tools known as retrievals. He is an expert in the interpretation of ground and space based observations at low and high resolution. Michael Zhang is the main developer of the atmosphere modelling code PLATON and has analyzed several JWST exoplanet observations, including three taken by NIRCam Dr. Andrew Mann is an expert on fundamental properties low-mass and young stars, methods for searching for young planetary systems, and the effect of spots and stellar activity on light curves. He is the PI of a Cycle 1 JWST program to gather transmission spectra of the young planet HIP67522. Kevin France is an expert in the UV and X-ray properties of M dwarf stars. He leads numerous observing programs to characterize the photo-catalyzing high-energy stellar spectra of planet hosting stars and their temporal variability. Nikole Lewis is an expert in JWST operations for high-precision time-series observations as well as exoplanet atmospheric theory. She has led and contributed to numerous observing programs that aim to characterize the atmospheres of exoplanets. Eva-Maria Ahrer has expertise in data reduction and analysis of transit observations in both low and high spectral resolution. She has previously led the analysis and interpretations of JWST NIRCam exoplanet observations, as well as several ground-based observing campaigns. Alastair Claringbold has experience with forward modelling of exoplanet atmospheres and assessing the detectability of prebiosignatures with JWST. Paul Rimmer is an expert in atmospheric chemistry, who specializes in chemical kinetics models that can be applied to planetary atmospheres over a wide range of chemical compositions and temperatures, and in using chemistry to constrain physical conditions and events. Peter Wheatley is an experienced exoplanet astronomer and user of HST, and was involved in the JWST ERS observation of WASP-39b. He also specialises in atmospheric evolution and evaporation, as well as X-Ray astronomy and ground-based optical transmission spectra. Everett Schlawin has expertise on JWST transiting planet observations and data anlysis with the NIRCam instrument. Keighley Rockcliffe has expertise on AU Mic b's atmospheric escape as observed in the far ultraviolet by HST/STIS. Catriona Murray is the lead developer of the spectrophotometric modelling code chromatic_fitting. She has analyzed several ERS JWST transiting planet observations, including those taken by the NIRCam instrument, and has expertise in low-mass stars and the effect of stellar activity on transit light curves. Zach Berta-Thompson has expertise in observations of transiting exoplanet atmospheres with Hubble/JWST, he works on characterizing the effect of stellar surface heterogeneities on inferred transmission spectra, and he is the lead developer for the spectrophotometric analysis and visualization code chromatic and a collaborator with Catriona Murray on chromatic-fitting. Annabella Meech is an expert in the detection of exoplanet atmospheres, particularly at high-resolution and associated data reduction. Benjamin Rackham is an expert in observations of exoplanet transmission spectra from space and the ground, as well as modeling and correcting for the impact of stellar photospheric heterogeneity on transmission spectra. He recently co-led Study Analysis Group 21 of NASA's ExoPAG, which was focused on understanding the challenge of stellar photospheric heterogeneity in space-based transmission spectra and identifying mitigation approaches. He is also the PI of the HST Stellar Treasure Trove Legacy Program (AR17551), which is focused on understanding the limits of stellar heterogeneity inferences and corrections from precise, space-based spectra. Darryl Seligman (DZS). DZS has broad theoretical expertise including dynamics, plasma physics, fluid dynamics and nonlinear dynamics. He has relevant expertise on solar and stellar physics. Pa Chia Thao is a graduate student who has had extensive experience on using space-based telescopes (HST, Spitzer) to study the transmission spectrum of young planets. Lili Alderson is an expert at data analysis and the interpretation of exoplanet atmospheric observations with space-based telescopes, and has particular experience with JWST transmission spectra. Hannah Wakeford is an expert in time series data analysis of transiting exoplanets across the mass range. She has led and contributed to numerous observing programs that aim to characterize the atmospheres of exoplanets including Hubble Space Telescope observations of the AU Mic planets. Girish M. Duvvuri has scientific and technical expertise in the emission spectra of dwarf stars observed at X-ray + ultraviolet + optical wavelengths to characterize the variability of stellar activity and has technical expertise in modeling stellar X-ray and extreme ultraviolet radiation. Monika Lendl is an expert in the reduction and analysis of low-resolution spectroscopy and photometry of exoplanets with space- and ground-based facilities. She has experience with atmospheric characterisation via transmission and emission spectroscopy as well as phase curves. David Wilson is an expert in ultraviolet and X-ray observations of exoplanet host stars and has lead multiple HST ultraviolet spectroscopy programs. Exoplanets and Exoplanet Formation 6 false false false false false false SUPPORTED STAR EXTRA-SOLAR PLANET EXTRA-SOLAR PLANETARY SYSTEM PRE-MAIN SEQUENCE STAR NO This object was generated by the target selector and retrieved from the SIMBAD database. J2000 J2000 COS/FUV Spectroscopic No No G130M 1222 1745258955805 The scheduling data was generated by CASM 33.0. 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