A planet within the debris disk around the pre-main-sequence star AU Microscopii

Peter Plavchan¹, Thomas Barclay^{2

3}, Jonathan Gagné⁴, Peter Gao⁵, Bryson Cale⁶, William Matzko⁶, Diana Dragomir^{7

8}, Sam Quinn⁹, Dax Feliz¹⁰, Keivan Stassun¹⁰, Ian J M Crossfield^{7

11}, David A Berardo⁷, David W Latham⁹, Ben Tieu⁶, Guillem Anglada-Escudé¹², George Ricker⁷, Roland Vanderspek⁷, Sara Seager⁷, Joshua N Winn¹³, Jon M Jenkins¹⁴, Stephen Rinehart³, Akshata Krishnamurthy⁷, Scott Dynes⁷, John Doty³, Fred Adams¹⁵, Dennis A Afanasev³, Chas Beichman^{16

17}, Mike Bottom¹⁸, Brendan P Bowler¹⁹, Carolyn Brinkworth²⁰, Carolyn J Brown²¹, Andrew Cancino²², David R Ciardi¹⁷, Mark Clampin³, Jake T Clark²¹, Karen Collins⁹, Cassy Davison²³, Daniel Foreman-Mackey²⁴, Elise Furlan¹⁶, Eric J Gaidos²⁵, Claire Geneser²⁶, Frank Giddens²², Emily Gilbert²⁷, Ryan Hall²³, Coel Hellier²⁸, Todd Henry²⁹, Jonathan Horner²¹, Andrew W Howard³⁰, Chelsea Huang⁷, Joseph Huber²², Stephen R Kane³¹, Matthew Kenworthy³², John Kielkopf³³, David Kipping³⁴, Chris Klenke²², Ethan Kruse³, Natasha Latouf⁶, Patrick Lowrance³⁵, Bertrand Mennesson¹⁶, Matthew Mengel²¹, Sean M Mills³⁰, Tim Morton³⁶, Norio Narita^{37

38

39

40

41}, Elisabeth Newton⁴², America Nishimoto²², Jack Okumura²¹, Enric Palle⁴¹, Joshua Pepper⁴³, Elisa V Quintana³, Aki Roberge³, Veronica Roccatagliata^{44

45

46}, Joshua E Schlieder³, Angelle Tanner²⁶, Johanna Teske⁴⁷, C G Tinney⁴⁸, Andrew Vanderburg¹⁹, Kaspar von Braun⁴⁹, Bernie Walp⁵⁰, Jason Wang^{5

30}, Sharon Xuesong Wang⁴⁷, Denise Weigand²², Russel White²³, Robert A Wittenmyer²¹, Duncan J Wright²¹, Allison Youngblood³, Hui Zhang⁵¹, Perri Zilberman⁵²

Affiliations

¹ Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA. pplavcha@gmu.edu.
² Center for Space Sciences and Technology, University of Maryland Baltimore County (UMBC), Baltimore, MD, USA.
³ Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁴ Institute for Research on Exoplanets, Département de Physique, Université de Montréal, Montréal, Quebec, Canada.
⁵ Department of Astronomy, University of California, Berkeley, CA, USA.
⁶ Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA.
⁷ Massachusetts Institute of Technology, Cambridge, MA, USA.
⁸ Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA.
⁹ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
¹⁰ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.
¹¹ Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA.
¹² School of Physics and Astronomy, Queen Mary, University of London, London, UK.
¹³ Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA.
¹⁴ SETI Institute, Mountain View, CA, USA.
¹⁵ Department of Astronomy, University of Michigan, Ann Arbor, MI, USA.
¹⁶ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
¹⁷ NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA, USA.
¹⁸ Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI, USA.
¹⁹ Department of Astronomy, University of Texas at Austin, Austin, TX, USA.
²⁰ University Corporation for Atmospheric Research, Boulder, CO, USA.
²¹ University of Southern Queensland, Centre for Astrophysics, Toowoomba, Queensland, Australia.
²² Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, MO, USA.
²³ Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA.
²⁴ Center for Computational Astrophysics, Flatiron Institute, New York, NY, USA.
²⁵ Department of Earth Sciences, University of Hawaii at Manoa, Honolulu, HI, USA.
²⁶ Department of Physics and Astronomy, Mississippi State University, Starkville, MS, USA.
²⁷ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
²⁸ Keele University, Keele, Staffordshire, UK.
²⁹ RECONS Institute, Chambersburg, PA, USA.
³⁰ Department of Astronomy, California Institute of Technology, Pasadena, CA, USA.
³¹ Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA.
³² Leiden Observatory, Leiden University, Leiden, The Netherlands.
³³ Department of Physics and Astronomy, University of Louisville, Louisville, KY, USA.
³⁴ Department of Astronomy, Columbia University, New York, NY, USA.
³⁵ IPAC, California Institute of Technology, Pasadena, CA, USA.
³⁶ Astronomy Department, University of Florida, Gainesville, FL, USA.
³⁷ Department of Astronomy, The University of Tokyo, Tokyo, Japan.
³⁸ JST, PRESTO, Tokyo, Japan.
³⁹ Astrobiology Center, NINS, Tokyo, Japan.
⁴⁰ National Astronomical Observatory of Japan, NINS, Tokyo, Japan.
⁴¹ Instituto de Astrofisica de Canarias (IAC), La Laguna, Tenerife, Spain.
⁴² Department of Physics and Astronomy, Dartmouth College, Hanover, NH, USA.
⁴³ Department of Physics, Lehigh University, Bethlehem, PA, USA.
⁴⁴ Dipartimento di Fisica "Enrico Fermi", Universita' di Pisa, Pisa, Italy.
⁴⁵ INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy.
⁴⁶ INFN, Sezione di Pisa, Pisa, Italy.
⁴⁷ Observatories of the Carnegie Institution for Science, Pasadena, CA, USA.
⁴⁸ Exoplanetary Science at UNSW, School of Physics, UNSW Sydney, New South Wales, Australia.
⁴⁹ Lowell Observatory, Flagstaff, AZ, USA.
⁵⁰ NASA Infrared Telescope Facility, Hilo, HI, USA.
⁵¹ School of Astronomy and Space Science, Key Laboratory of Ministry of Education, Nanjing University, Nanjing, China.
⁵² SUNY Stony Brook, Stony Brook, NY, USA.

PMID: 32581383
PMCID: PMC7323865
DOI: 10.1038/s41586-020-2400-z

A planet within the debris disk around the pre-main-sequence star AU Microscopii

Peter Plavchan et al. Nature. 2020 Jun.

. 2020 Jun;582(7813):497-500.

doi: 10.1038/s41586-020-2400-z. Epub 2020 Jun 24.

Authors

Affiliations

¹ Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA. pplavcha@gmu.edu.
² Center for Space Sciences and Technology, University of Maryland Baltimore County (UMBC), Baltimore, MD, USA.
³ Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁴ Institute for Research on Exoplanets, Département de Physique, Université de Montréal, Montréal, Quebec, Canada.
⁵ Department of Astronomy, University of California, Berkeley, CA, USA.
⁶ Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA.
⁷ Massachusetts Institute of Technology, Cambridge, MA, USA.
⁸ Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA.
⁹ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
¹⁰ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.
¹¹ Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA.
¹² School of Physics and Astronomy, Queen Mary, University of London, London, UK.
¹³ Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA.
¹⁴ SETI Institute, Mountain View, CA, USA.
¹⁵ Department of Astronomy, University of Michigan, Ann Arbor, MI, USA.
¹⁶ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
¹⁷ NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA, USA.
¹⁸ Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI, USA.
¹⁹ Department of Astronomy, University of Texas at Austin, Austin, TX, USA.
²⁰ University Corporation for Atmospheric Research, Boulder, CO, USA.
²¹ University of Southern Queensland, Centre for Astrophysics, Toowoomba, Queensland, Australia.
²² Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, MO, USA.
²³ Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA.
²⁴ Center for Computational Astrophysics, Flatiron Institute, New York, NY, USA.
²⁵ Department of Earth Sciences, University of Hawaii at Manoa, Honolulu, HI, USA.
²⁶ Department of Physics and Astronomy, Mississippi State University, Starkville, MS, USA.
²⁷ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
²⁸ Keele University, Keele, Staffordshire, UK.
²⁹ RECONS Institute, Chambersburg, PA, USA.
³⁰ Department of Astronomy, California Institute of Technology, Pasadena, CA, USA.
³¹ Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA.
³² Leiden Observatory, Leiden University, Leiden, The Netherlands.
³³ Department of Physics and Astronomy, University of Louisville, Louisville, KY, USA.
³⁴ Department of Astronomy, Columbia University, New York, NY, USA.
³⁵ IPAC, California Institute of Technology, Pasadena, CA, USA.
³⁶ Astronomy Department, University of Florida, Gainesville, FL, USA.
³⁷ Department of Astronomy, The University of Tokyo, Tokyo, Japan.
³⁸ JST, PRESTO, Tokyo, Japan.
³⁹ Astrobiology Center, NINS, Tokyo, Japan.
⁴⁰ National Astronomical Observatory of Japan, NINS, Tokyo, Japan.
⁴¹ Instituto de Astrofisica de Canarias (IAC), La Laguna, Tenerife, Spain.
⁴² Department of Physics and Astronomy, Dartmouth College, Hanover, NH, USA.
⁴³ Department of Physics, Lehigh University, Bethlehem, PA, USA.
⁴⁴ Dipartimento di Fisica "Enrico Fermi", Universita' di Pisa, Pisa, Italy.
⁴⁵ INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy.
⁴⁶ INFN, Sezione di Pisa, Pisa, Italy.
⁴⁷ Observatories of the Carnegie Institution for Science, Pasadena, CA, USA.
⁴⁸ Exoplanetary Science at UNSW, School of Physics, UNSW Sydney, New South Wales, Australia.
⁴⁹ Lowell Observatory, Flagstaff, AZ, USA.
⁵⁰ NASA Infrared Telescope Facility, Hilo, HI, USA.
⁵¹ School of Astronomy and Space Science, Key Laboratory of Ministry of Education, Nanjing University, Nanjing, China.
⁵² SUNY Stony Brook, Stony Brook, NY, USA.

PMID: 32581383
PMCID: PMC7323865
DOI: 10.1038/s41586-020-2400-z

Erratum in

Publisher Correction: A planet within the debris disk around the pre-main-sequence star AU Microscopii.
Plavchan P, Barclay T, Gagné J, Gao P, Cale B, Matzko W, Dragomir D, Quinn S, Feliz D, Stassun K, Crossfield IJM, Berardo DA, Latham DW, Tieu B, Anglada-Escudé G, Ricker G, Vanderspek R, Seager S, Winn JN, Jenkins JM, Rinehart S, Krishnamurthy A, Dynes S, Doty J, Adams F, Afanasev DA, Beichman C, Bottom M, Bowler BP, Brinkworth C, Brown CJ, Cancino A, Ciardi DR, Clampin M, Clark JT, Collins K, Davison C, Foreman-Mackey D, Furlan E, Gaidos EJ, Geneser C, Giddens F, Gilbert E, Hall R, Hellier C, Henry T, Horner J, Howard AW, Huang C, Huber J, Kane SR, Kenworthy M, Kielkopf J, Kipping D, Klenke C, Kruse E, Latouf N, Lowrance P, Mennesson B, Mengel M, Mills SM, Morton T, Narita N, Newton E, Nishimoto A, Okumura J, Palle E, Pepper J, Quintana EV, Roberge A, Roccatagliata V, Schlieder JE, Tanner A, Teske J, Tinney CG, Vanderburg A, von Braun K, Walp B, Wang J, Wang SX, Weigand D, White R, Wittenmyer RA, Wright DJ, Youngblood A, Zhang H, Zilberman P. Plavchan P, et al. Nature. 2020 Jul;583(7818):E31. doi: 10.1038/s41586-020-2516-1. Nature. 2020. PMID: 32665715

Abstract

AU Microscopii (AU Mic) is the second closest pre-main-sequence star, at a distance of 9.79 parsecs and with an age of 22 million years¹. AU Mic possesses a relatively rare² and spatially resolved³ edge-on debris disk extending from about 35 to 210 astronomical units from the star⁴, and with clumps exhibiting non-Keplerian motion^5-7. Detection of newly formed planets around such a star is challenged by the presence of spots, plage, flares and other manifestations of magnetic 'activity' on the star^8,9. Here we report observations of a planet transiting AU Mic. The transiting planet, AU Mic b, has an orbital period of 8.46 days, an orbital distance of 0.07 astronomical units, a radius of 0.4 Jupiter radii, and a mass of less than 0.18 Jupiter masses at 3σ confidence. Our observations of a planet co-existing with a debris disk offer the opportunity to test the predictions of current models of planet formation and evolution.

PubMed Disclaimer

Figures

**Extended Data Figure 1**
The TESS and Spitzer light curves for AU Mic centered on four transit events. a and b Two TESS transits for AU Mic b, with the model components plotted as indicated in the legend. A flare is present during the egress of the first transit of AU Mic b, and a flare is present just after the ingress during the second transit of AU Mic b. While unfortunate timing, flares of this amplitude are pervasive throughout the TESS light curve for AU Mic, and complicate the recovery of these events from automated transit search algorithms. c The Spitzer transit observation of AU Mic b. The deviations in transit are not instrumental and the subject of a future paper, and are likely related to the planet crossing large active regions on the stellar surface. d The ~1 ppt candidate single transit event seen in the TESS light curve. For all panels, 1-σ measurement uncertainties are suppressed for visual clarity and are <1 ppt. 1-σ model uncertainties in transit are shown as shaded regions.

**Extended Data Figure 2**
MCMC corner plot for custom combined Spitzer and TESS light curve analysis for AU Mic. The full set of model parameters are shown, with the posterior probability distributions along the diagonal and covariance plots between parameters off-axis.

**Extended Data Figure 3**
One season (July-Oct 2007) of SuperWASP light curve for AU Mic, from the NASA Exoplanet Archive, phase-folded to to the rotation period of the star. Measurements with large photometric uncertainties (>5%) have been excluded from the plot. 1-σ measurement uncertainties are suppressed for visual clarity and are typically <1% but occasionally up to 5% at phases where there is more apparent vertical scatter in the measurement values themselves.

**Extended Data Figure 4**
Correlation plots of the standard HARPS stellar activity indicators with the RVs. The bisector values for the cross-correlation function, but not the activity indicators, show a correlation with the RVs, with significant remaining scatter. Formal uncertainties are smaller than the plotted symbols.

**Extended Data Figure 5**
Correlation plots of the HARPS activity indicators with each other. The activity indicators Calcium II H&K, Hα, and Sodium D activity indicators are strongly correlated with one another, but not with the RVs nor the CCF bisector.

**Extended Data Figure 6**
The HARPS RVs (blue circles) and standard activity indicators (black circles), phase folded to the rotation period of the star. None of the activity indicators show a statistically significant trend with the period of AU Mic b. The Calcium and Sodium activity indicators do appear to show by eye some cyclic variation with the rotation period of the star, but it is not significant. Formal uncertainties are smaller than the plotted symbols.

**Extended Data Figure 7**
a RV time-series of AU Mic with data from the iSHELL (yellow circles), High Resolution Spectrograph (HIRES, black circles) and High Accuracy Radial velocity Planet Searcher (HARPS, red squares) spectrometers. Uncertainties shown are 1-σ for HARPS and iSHELL. For HIRES, a 5 m/s minimum 1-σ uncertainty is adopted although the formal 1-σ uncertainties are smaller for all but one epoch at 5.43 m/s. The maximum-likelihood best fit model is overlaid in blue, with shaded regions indicating the 1-σ model confidence interval, with a separate GP for each data set indicated with different colored shaded regions. b Model-subtracted residuals, with the same colors as in a. Because our RVs are undersampled with respect to the stellar rotation period, the Gaussian Process best-fit model overfits the AU Mic RV time-series. c RV measurements are phased to the orbital period of AU Mic b, and binned in phase (red circles). The blue curve is a maximum-likelihood best-fit circular orbit model, after subtracting the best fit GP model of stellar activity and the modeled instrument offsets. The plot is labeled with the best-fit orbital period and velocity semi-amplitude.

**Extended Data Figure 8**
RADVEL MCMC corner plot for the model parameters for the iSHELL, HARPS and HIRES RV data sets. Along the diagonal are the one-dimensional posterior probability distributions for a given model parameter; the others are the two-dimensional parameter covariance plots.

**Extended Data Figure 9**
Photometric variability amplitudes (black squares) observed by Ref obtained contemporaneously in four different bandpasses. The horizontal error bars correspond to the effective bandpass widths and the 1-σ vertical error bars are set to 1 mmag. A 1/λ trend is shown in red, as would be expected for cool starspots with relatively small temperature contrast.

**Figure 1**
TESS light curve for AU Mic. Black dots are plotted as normalized flux as a function of time, obtained from MAST archive. Transit ephemerides of AU Mic b are indicated in red. The double-humped sinusoidal-like pattern is due to the rotational modulation of starspots, with the 4.863d rotation period readily apparent. The large, brief vertical streaks of data points deviating upwards from this slower modulation are due to flares. Data with non-zero quality flags indicating the presence of spacecraft-related artifacts, such as momentum dumps, are removed. The gap at ~1339 days corresponds to the data downlink with Earth during the spacecraft’s perigee. A third transit of AU Mic b was missed during this data downlink data gap, and thus the orbital period of AU Mic b is one-half of period inferred from the two TESS transit events seen. AU Mic exhibited flaring activity with energies ranging from 10^31.6 to 10^33.7 ergs in the TESS bandpass over the 27 day light curve (+/− ~60%), with a mean flare amplitude of 0.01 relative flux units. 1-σ measurement uncertainties are smaller than the symbols shown (<1 ppt).

**Figure 2:**
TESS visible light (red and green circles) and Spitzer IRAC 4.5 μm (purple circles) light curves of the transits of AU Mic b and a separate, single candidate transit event. a The data for transits of AU Mic b are shown with an arbitrary vertical shift applied for clarity; flux units are parts per thousand, or ppt. The transit model (orange curve) includes a photometric model that accounts for the stellar activity modeled with a Gaussian Process, which is subtracted from the data before plotting. The frequent flares from the stellar surface are removed with an iterative sigma-clipping (see Methods). In particular, flares are observed during the egress of the both TESS transits of AU Mic b, and also just after the ingress of the second transit of AU Mic b. The presence of these flares in the light curve particularly impact our precision in measuring the transit duration and thus the mass/density of the host star AU Mic and consequently the impact parameter and eccentricity of the orbit of AU Mic b. Model uncertainties shown as shaded regions are 1-σ c.i.. The uncertainty in the out-of-transit baseline is ~0.5 ppt but not shown for clarity. b The AU Mic candidate single transit signal, identified by visual inspection of the *TESS* light curve. The change in noise before and after the candidate transit signal is due to a “dump” of angular momentum from the spacecraft reaction wheels which decreased the pointing jitter and improved the photometric precision; data points during the dump are not shown.

**Figure 3:**
Mass-radius diagram for AU Mic b in the context of “mature” exoplanets and known young exoplanets. AU Mic b is shown in blue. We compare it to the nominal best-fit mass-radius relationship from known exoplanets orbiting older main sequence stars shown as a red segmented line (dispersion not shown), and known exoplanets from the NASA Exoplanet Archive with measured masses or mass upper limits, radii, and estimated stellar host ages <=400 Myr: DS Tuc A b (mass is estimated from Ref and not measured), Kepler-51 bcd, 63 b, K2-33 b, Qatar-3 b,4 b, KELT-9 and WASP-52 b. By combining the radius measurement from *TESS*, and the mass upper limit from RVs, we can ascertain an upper limit to the planet density for AU Mic b to critically inform models for planet formation. Our current upper limit for the mass of AU Mic b cannot rule out a density consistent with Neptune-like planets orbiting older main sequence stars, but a more precise constraint or measurement in the future may show it to be inflated. Uncertainties shown are 1-σ for detections, and 3-σ for mass upper-limits.

See this image and copyright information in PMC

References

1. Mamajek EE Bell, Cameron PM; “On the age of the β Pictoris moving group.” Mon. Not. R. Astron. Soc 445, 3 (2014)
1. Plavchan P; Jura M; & Lipscy SJ; “Where Are the M Dwarf Disks Older Than 10 Million Years?” Astrophys. J, 631, 2 (2005)
1. Kalas P; Liu MC; Matthews BC; “Discovery of a Large Dust Disk Around the Nearby Star AU Microscopii.” Science, 303, 5666 (2004) - PubMed
1. Strubbe LE; & Chiang EI; “Dust Dynamics, Surface Brightness Profiles, and Thermal Spectra of Debris Disks: The Case of AU Microscopii.” Astrophys. J, 648, 1 (2006)
1. Boccaletti A; et al.; “Fast-moving features in the debris disk around AU Microscopii.” Nature, 526, 230 (2015) - PubMed

Save citation to file

Email citation

Add to Collections

Add to My Bibliography

Your saved search

Create a file for external citation management software

Your RSS Feed

A planet within the debris disk around the pre-main-sequence star AU Microscopii

Affiliations

A planet within the debris disk around the pre-main-sequence star AU Microscopii

Authors

Affiliations

Erratum in

Abstract

Figures

References

Publication types

Grants and funding

LinkOut - more resources

Full Text Sources