CaltechAUTHORS
Published July 20, 2022 | Version Published + Accepted Version
Journal Article Open

The Mysterious Affair of the H₂ in AU Mic

Creators

  • 1. ROR icon Rice University
  • 2. ROR icon Cornell University
  • 3. ROR icon Laboratory for Atmospheric and Space Physics
  • 4. ROR icon Peking University
  • 5. ROR icon NOIRLab
  • 6. ROR icon California Institute of Technology
  • 7. ROR icon Atacama Large Millimeter Submillimeter Array
  • 8. ROR icon Smithsonian Astrophysical Observatory
  • 9. ROR icon Dartmouth College

Abstract

Molecular hydrogen is the most abundant molecule in the galaxy and plays important roles in planets, their circumstellar environments, and many of their host stars. We have confirmed the presence of molecular hydrogen in the AU Mic system using high-resolution FUV spectra from HST-STIS during both quiescence and a flare. AU Mic is a ∼23 Myr M dwarf that hosts a debris disk and at least two planets. We estimate the temperature of the gas at 1000–2000 K, consistent with previous detections. Based on the radial velocities and widths of the H₂ line profiles and the response of the H₂ lines to a stellar flare, the H₂ line emission is likely produced in the star, rather than in the disk or the planet. However, the temperature of this gas is significantly below the temperature of the photosphere (∼3650 K) and the predicted temperature of its starspots (≳2650 K). We discuss the possibility of colder starspots or a cold layer in the photosphere of a pre-main-sequence M dwarf.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 17; revised 2022 June 1; accepted 2022 June 2; published 2022 July 20. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Support for program number (GO-15310) was provided through a grant from the STScI under NASA contract NAS5-26555. G.J.H. is supported by by general grant 12173003 awarded by the National Science Foundation of China. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. The original description of the VizieR service was published by Wenger et al. (2000). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Facility: HST (STIS). - Software: SpecTres (Carnall 2017), NumPy (Oliphant 2006; Van Der Walt et al. 2011), Pandas (pandas development team 2020), Matplotlib (Hunter 2007), LMFIT (Newville et al. 2014), emcee (Foreman-Mackey et al. 2013).

Attached Files

Published - Flagg_2022_ApJ_934_8.pdf

Accepted Version - 2206.02636.pdf

Files

2206.02636.pdf

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Additional details

Identifiers

Eprint ID
116112
Resolver ID
CaltechAUTHORS:20220804-249921000

Related works

Describes
https://arxiv.org/abs/2206.02636 (URL)

Funding

NASA
NAS5-26555
NASA
HST-GO-15310
National Natural Science Foundation of China
12173003

Dates

Created
2022-08-09
Created from EPrint's datestamp field
Updated
2022-08-09
Created from EPrint's last_modified field