MAPS: Constraining Serendipitous Time Variability in Protoplanetary Disk Molecular Ion Emission

The Astrophysical Journal, vol. 956, pp. 103

Abstract

Abstract Theoretical models and observations suggest that the abundances of molecular ions in protoplanetary disks should be highly sensitive to the variable ionization conditions set by the young central star. We present a search for temporal flux variability of HCO+ J = 1–0, which was observed as a part of the Molecules with Atacama Large Millimeter/submillimeter Array (ALMA) at Planet-forming Scales ALMA Large Program. We split out and imaged the line and continuum data for each individual day the five sources were observed (HD 163296, AS 209, GM Aur, MWC 480, and IM Lup, with between three and six unique visits per source). Significant enhancement (>3σ) was not observed, but we find variations in the spectral profiles in all five disks. Variations in AS 209, GM Aur, and HD 163296 are tentatively attributed to variations in HCO+ flux, while variations in IM Lup and MWC 480 are most likely introduced by differences in the uv coverage, which impact the amount of recovered flux during imaging. The tentative detections and low degree of variability are consistent with expectations of X-ray flare-driven HCO+ variability, which requires relatively large flares to enhance the HCO+ rotational emission at significant (>20%) levels. These findings also demonstrate the need for dedicated monitoring campaigns with high signal-to-noise ratios to fully characterize X-ray flare-driven chemistry.

Authors 15

1. Abygail R. Waggoner

   University of Virginia

   Affiliation as printed

   University of Virginia, Charlottesville, VA 22904, USA; arw6qz@virginia.edu

   University of Virginia, Charlottesville, VA 22904, USA

2. L. Ilsedore Cleeves

   University of Virginia

   Affiliation as printed

   University of Virginia, Charlottesville, VA 22904, USA; arw6qz@virginia.edu

   University of Virginia, Charlottesville, VA 22904, USA

3. Ryan A. Loomis

   National Radio Astronomy Observatory

   Affiliation as printed

   National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA

4. Yuri Aikawa

   The University of Tokyo

   Affiliation as printed

   Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan

5. Jaehan Bae

   University of Florida

   Affiliation as printed

   Department of Astronomy, University of Florida, Gainesville, FL 32611, USA

6. Jennifer B. Bergner

   University of California, Berkeley

   Affiliation as printed

   UC Berkeley Department of Chemistry, Berkeley, CA 94720, USA

7. Alice S. Booth Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands

8. Jenny K. Calahan

   University of Michigan

   Affiliation as printed

   Department of Astronomy, University of Michigan, 323 West Hall, 1085 South University Ave., Ann Arbor, MI 48109, USA

9. Gianni Cataldi

   National Astronomical Observatory of Japan · The University of Tokyo

   Affiliation as printed

   Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan

   National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan

10. Charles J. Law

    Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA

11. Romane Le Gal

    Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Ausonius Institut de Recherche sur l'Antiquité et le Moyen age · Université Grenoble Alpes

    Affiliation as printed

    IRAM, 300 rue de la Piscine, F-38406 Saint-Martin d’Hères, France

    University Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France

    IRAM, 300 rue de la Piscine, F-38406 Saint-Martin d'Hères, France

12. Feng Long

    University of Arizona

    Affiliation as printed

    Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA

13. Karin I. Öberg

    Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA

14. Richard D. Teague

    Center for Astrophysics Harvard & Smithsonian · Massachusetts Institute of Technology

    Affiliation as printed

    Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA

    Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

15. David J. Wilner

    Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA