A Caltech Library Service

The Mysterious Affair of the H₂ in AU Mic

Flagg, Laura and Johns-Krull, Christopher M. and France, Kevin and Herczeg, Gregory and Najita, Joan and Youngblood, Allison and Carvalho, Adolfo and Carptenter, John and Kenyon, Scott J. and Newton, Elisabeth and Rockcliffe, Keighley (2022) The Mysterious Affair of the H₂ in AU Mic. Astrophysical Journal, 934 (1). Art. No. 8. ISSN 0004-637X. doi:10.3847/1538-4357/ac7643.

[img] PDF - Published Version
Creative Commons Attribution.

[img] PDF - Accepted Version
Creative Commons Attribution Non-commercial Share Alike.


Use this Persistent URL to link to this item:


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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Flagg, Laura0000-0001-6362-0571
Johns-Krull, Christopher M.0000-0002-8828-6386
France, Kevin0000-0002-1002-3674
Herczeg, Gregory0000-0002-7154-6065
Youngblood, Allison0000-0002-1176-3391
Carvalho, Adolfo0000-0002-9540-853X
Carptenter, John0000-0003-2251-0602
Kenyon, Scott J.0000-0003-0214-609X
Newton, Elisabeth0000-0003-4150-841X
Rockcliffe, Keighley0000-0003-1337-723X
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).
Funding AgencyGrant Number
National Natural Science Foundation of China12173003
Subject Keywords:Exoplanet formation; Debris disks; Low mass stars; Starspots; Circumstellar gas; High resolution spectroscopy; Exoplanets; Pre-main sequence stars; Stellar atmospheres
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet formation (492); Debris disks (363); Low mass stars (2050); Starspots (1572); Circumstellar gas (238); High resolution spectroscopy (2096); Exoplanets (498); Pre-main sequence stars (1290); Stellar atmospher
Record Number:CaltechAUTHORS:20220804-249921000
Persistent URL:
Official Citation:Laura Flagg et al 2022 ApJ 934 8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116112
Deposited By: George Porter
Deposited On:09 Aug 2022 18:11
Last Modified:09 Aug 2022 18:11

Repository Staff Only: item control page