A Three-Dimensional Panchromatic View of Active Regions and CMEs on the Young Solar-Type Star AB Dor

none 3387192 Assigned ID: 6933 ----- Attempting Submission 1 (Wed Oct 29 15:07:41 GMT 2025) ----- HST Phase I Proposal 6933 successfully submitted. Receipt: # 6933-1 INEFFICIENT ORDERING OF FP-POS POSITIONS INEFFICIENT ORDERING OF FP-POS POSITIONS INEFFICIENT ORDERING OF FP-POS POSITIONS INEFFICIENT ORDERING OF FP-POS POSITIONS Submisssion 2, 11/27/25. Kevin France -212767743 ----- Attempting Submission 1 (Tue Nov 18 23:55:55 GMT 2025) ----- ----- Attempting Submission 2 (Thu Nov 27 11:24:12 GMT 2025) ----- A Three-Dimensional Panchromatic View of Active Regions and CMEs on the Young Solar-Type Star AB Dor The magnetically active regions on young solar-type stars often produce large stellar flares that are likely associated coronal mass ejections (CMEs). These transient phenomena are thought to be key drivers of atmospheric evolution on early Earth-like planets. However, little is known about how stellar active regions are heated, the three-dimensional (3D) struicture, and how CMEs are generated from them. We propose HST/COS observations of a 50 Myr-old solar-type star, AB Dor, to be conducted in coordination with an approved multi-observatory campaign to provide the first multi-wavelength, temporally- and spatially-resolved observations of active regions on a young solar-type star: X-ray spectroscopic observations by XRISM, optical photometry by TESS, and ground-based optical spectroscopic observations. Simultaneous X-ray/UV/optical spectroscopy will allow us to detect Doppler shifts associated with stellar flares, enabling us to capture multi-thermal 3D CME phenomena and assess their true impact on exoplanetary environments for the first time. Furthermore, by performing Doppler imaging across multiple wavelengths capable of resolving the star's rapid rotation, we aim to obtain the first comprehensive 3D view of an active region on a star other than the Sun. In combination with numerical modeling, the proposed program will provide a critical benchmark for understanding stellar active regions and space weather around young solar-type stars, offering high legacy value for studies of planetary habitability in the era of JWST and future UV missions. FUV Spectra: The HST data will use COS with G130M, CENWAVE=1309 to record the emission lines of C III (117.5 nm), Si III (120.6 nm), N V (123.8nm), Fe XII (124.2, 134.9nm), C I (132.9nm), C II (133.5 nm), Fe XXI (135.4nm), O V (137.1nm), O IV] (140.1nm), and Si IV (139.4, 140.3 nm). To resolve the physical processes relevant to chromospheric and coronal heating, we require R ~ 15,000. To constrain the stellar wind density of EK Dra, we require signal-to-noise ~ 10 at the peak of the O IV] 140.1 nm line. By comparing to archival HST FUV spectra of EK Dra (Ayres & France 2010; Ayres 2015), we estimate that three orbits per visit will be sufficient for detection of S/N > 10 per resolution element in the peak of the density-sensitive O IV] features (COS.sp.1684389). We calculate S/N between 10 and 20 in the peak of several C I lines and the coronal iron lines, S/N between 20 and 30 in Si IV and N V, and S/N > 30 in Si III and C II. This highfidelity spectrum will allow us to identify temporal variability and will provide robust line-fit measurements of thermal and non-thermal widths and line kinematics. Given the observed UV flare rate from EK Dra, we expect to observe 2 - 3 multi-wavelength flares in a 12 orbit HST campaign (3 orbits per visits x 4 visits). Each 3-orbit visit is sufficient for a high-S/N stellar spectrum (see next sub-section) that will provide the quiescent stellar baseline and rotational modulation between flare events. Target Acquisition: We performed a quantitative ETC target acquisition calculation using the STScI online tools, we scaled observed solar-type star to an average magnitude of V = 7.6, and we find that an exposure time of approximately 3.2s are required (COS.ta.1684394), using an imaging target acquisition in BOA+MIRRORA. Instrument Safety: An ETC calculation using the observed EK Dra Lyman-alpha flux (the brightest stellar line in the FUV spectrum of EK Dra; Ayres et al. 2015), multiplied by 1.5 for conservatism, find no bright object violations using the COS G130M mode (COS.sp.1895208), therefore these observations present no risk to the instrument and are consistent with the COS 2025 observing guidelines. Coordinated Observations: Simultaneous observations from space- and ground-based telescopes using X-ray spectroscopy (NICER), optical spectroscopy/photometry (TESS, Seimei telescope), and radio telescope (GMRT) will complement the HST time. TESS will be pivotal for the calculation of global energies. These observatories have a long record of providing flexible scheduling to provide supporting ground-based observations for approved space-based flare campaigns. PI: K. France - University of Colorado Co-I Kevin France is the PI of the HST MUSCLES Treasury (GO13650), MEATS (GO16166), and MALWARE (GO18030) Surveys to study the UV and X-ray spectral and temporal properties of exoplanet host stars (France et al. 2016, 2018, 2020; Loyd et al. 2016; Youngblood et al. 2016; Behr et al. 2023). He is the co-PI of the follow-on Mega-MUSCLES (GO15071; Brown et al. 2022; Wilson et al. 2025a) and Mega-MEATS (GO16701; France et al. 2025; Wilson et al. 2025b) Surveys that focused on activity in stars optimal for planetary characterization with JWST. He was a member of the COS instrument and science teams; he is intimately familiar with HST-COS and -STIS instrument, data, and analysis procedures. His research group has developed numerous community tools for spectral and temporal analysis of HST and X-ray observatory observations of cool stars. Dr France has authored over 100 refereed publications on exoplanets, cool stars, and planet-forming disks using UV spectra from HST. Dr. Kosuke Namekata is an expert in multi-wavelength observations and data analysis of flares and coronal mass ejections from young solar analogues and M-dwarfs. Dr. Adina Feinstein is an expert in HST data acquisition and stellar magnetic activity and its impact on exoplanets, and has guaranteed access to the LCO telescope in Chile for this project. Dr. Belinda Nicholson is an expert in observations of stellar magnetic activity and exoplanet around young stars, with extensive experience using the 3.9m Anglo-Australian Telescope (AAT), and with guaranteed access to Mt Kent Observatory and the AAT for this project. Prof. Brad Carter is an expert in ground-based spectroscopy, with extensive experience using the 3.9m Anglo-Australian Telescope (AAT), and with guaranteed access to Mt Kent Observatory and the AAT for this project. Dr. Ian Waite is an expert in ground-based spectroscopy, with extensive experience using the 3.9m Anglo-Australian Telescope (AAT), and with guaranteed access to Mt Kent Observatory and the AAT for this project. Dr. Petr Kabath is an expert in ground-based spectroscopic observations of exoplanet host stars, and has guaranteed access to the 1.5 m telescope in Chile for this project. Dr. Yusuke Tampo is an expert in ground-based observations of transients such as dwarf novae, and has guaranteed access to the 2m South African Astronomical Observatory (SAAO) telescope in South Africa for this project. Dr. Vladimir Airapetian is an expert in the theoretical study of CMEs using AWSoM, as well as in astrobiology and pre-biotic chemistry in the early Solar System. Stellar Physics and Stellar Types Exoplanets and Exoplanet Formation 0 false false SUPPORTED EXT-STAR K V-IV 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 COS/FUV Spectroscopic No No G130M 1291 1774550366786 /System/Volumes/Data/solaris/user1/armstrong/hst/working/OP-cache/18216-v01.xml Timing link suitability includes constraints ([02 After 01 by 0.5 to 2.5 days] [H2 After 01 by 0.5 to 2.5 days]) The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. While the observing coordination window for these observations extends through spring 2026, the optimial window is December 29th 2025 to January 4th 2026. 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