Year: 2026
Type: preprint
Abstract: Constraining atmospheric loss is crucial for understanding the evolution of planetary atmospheres. We report the detection of an evaporating exosphere from TOI-3884b, a super-Neptune in a polar orbit around an M4 dwarf star. We infer this evaporation from a 6.8$\pm$0.27\% excess transit depth in the He I 10830 Å\, line, observed during five transits of TOI-3884b with the Habitable Zone Planet Finder spectrometer. While we observe outflow signatures starting as early as 5 hours before the onset of the planet's optical transit, no significant post-transit tail is detected. Hitherto, such a pre-transit headwind without a significant post-transit tail has only been detected from HAT-P-67b, a hot Saturn orbiting an F-type star. This asymmetric outflow morphology supports irradiation-driven mass loss over core-heated mass loss, and we explore whether this could be caused by sub-Alfvén star-planet interaction. The detection of such complex outflow morphologies is now opening a new window, enabling us to test theories of star-planet interactions and planetary magnetic fields with observations.
Source: arXiv (Cornell University)
Authors: Ninan, Joe P., Libby-Roberts, Jessica, Mahadevan, Suvrath, Kochukhov, Oleg, Krolikowski, Daniel M., Stefansson, Gudmundur, Kanodia, Shubham, Orell-Miquel, Jaume, Morley, Caroline V., France, Kevin, Duvvuri, Girish, Bender, Chad F., Cochran, William D., Delamer, Megan, Diddams, Scott A., Halverson, Samuel, Hearty, Fred, Hebb, Leslie, Monson, Andrew, Robertson, Paul, Roy, Arpita, Schwab, Christian
Institutions: Tata Institute of Fundamental Research, Pennsylvania State University, Uppsala University, University of Arizona, Schmidt Sciences, University of Amsterdam, The University of Texas at Austin, University of Colorado Boulder, Laboratory for Atmospheric and Space Physics, University of Colorado System, University of California, Berkeley, California Institute of Technology, Jet Propulsion Laboratory, Hobart and William Smith Colleges, Cornell University, University of California, Irvine, Macquarie University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Aeronautics and Space Administration, Pennsylvania Space Grant Consortium, California Institute of Technology, Tata Institute of Fundamental Research, Department of Atomic Energy, Government of India, Indian Council of Agricultural Research, Swedish National Space Agency, Vetenskapsrådet, Ludwig-Maximilians-Universität München, Jet Propulsion Laboratory, Institute for Computational and Data Sciences, Pennsylvania State University, Office of Advanced Cyberinfrastructure
OpenAlex ID: W7223387478