The changing face of AU Mic b: Stellar spots, spin-orbit commensurability, and transit timing variations as seen by CHEOPS and TESS
Artikel i vetenskaplig tidskrift, 2021
AU Mic is a young planetary system with a resolved debris disc showing signs of planet formation and two transiting warm Neptunes near mean-motion resonances. Here we analyse three transits of AU Mic b observed with the CHaracterising ExOPlanet Satellite (CHEOPS), supplemented with sector 1 and 27 Transiting Exoplanet Survey Satellite (TESS) photometry, and the All-Sky Automated Survey from the ground. The refined orbital period of AU Mic b is 8.462995 ± 0.000003 d, whereas the stellar rotational period is Prot = 4.8367 ± 0.0006 d. The two periods indicate a 7:4 spin-orbit commensurability at a precision of 0.1%. Therefore, all transits are observed in front of one of the four possible stellar central longitudes. This is strongly supported by the observation that the same complex star-spot pattern is seen in the second and third CHEOPS visits that were separated by four orbits (and seven stellar rotations). Using a bootstrap analysis we find that flares and star spots reduce the accuracy of transit parameters by up to 10% in the planet-to-star radius ratio and the accuracy on transit time by 3-4 min. Nevertheless, occulted stellar spot features independently confirm the presence of transit timing variations (TTVs) with an amplitude of at least 4 min. We find that the outer companion, AU Mic c, may cause the observed TTVs.
Planetary systems
Författare
G.M. Szabó
Eötvös Loránd University (ELTE)
D. Gandolfi
Istituto nazionale di astrofisica (INAF)
A. Brandeker
Stockholms universitet
Szilard Csizmadia
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Z. Garai
Slovak Academy of Sciences
Eötvös Loránd University (ELTE)
N. Billot
Université de Genève
C. Broeg
Universität Bern
D. Ehrenreich
Université de Genève
A. Fortier
Universität Bern
L. Fossati
Institut fur Weltraumforschung
S. Hoyer
Laboratoire d'Astrophysique de Marseille
L. Kiss
The University of Sydney
Eötvös Loránd University (ELTE)
Magyar Tudomanyos Akademia
A. L. des Etangs
Institut d 'Astrophysique de Paris
P. Maxted
Keele University
I. Ribas
Consejo Superior de Investigaciones Científicas (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Y. Alibert
Universität Bern
R. Alonso
Instituto de Astrofísica de Canarias
Universidad de la Laguna
G. A. Escudé
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Consejo Superior de Investigaciones Científicas (CSIC)
T. Bárczy
Admatis
S.C.C. Barros
Universidade do Porto
D. Barrado
Centro de Astrobiologia (CAB)
W. Baumjohann
Institut fur Weltraumforschung
M. Beck
Université de Genève
T. Beck
Universität Bern
A. Bekkelien
Université de Genève
X. Bonfils
Université Grenoble Alpes
W. Benz
Universität Bern
L. Borsato
Istituto nazionale di astrofisica (INAF)
M.-D. Busch
Universität Bern
J. Cabrera
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
S. Charnoz
Institut de Physique du Globe de Paris
A. Collier Cameron
University of St Andrews
C. Corral Van Damme
European Space Research and Technology Centre (ESA ESTEC)
M. B. Davies
Lunds universitet
L. Delrez
Universite de Liège
M. Deleuil
Laboratoire d'Astrophysique de Marseille
O. Demangeon
Laboratoire d'Astrophysique de Marseille
Universidade do Porto
B.O. Demory
Universität Bern
Anders Erikson
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Malcolm Fridlund
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
Universiteit Leiden
D. Futyan
Université de Genève
A. Garciá Muñoz
Technische Universität Berlin
Michaël Gillon
Universite de Liège
M. Guedel
Universität Wien
P. Guterman
Institut National des Sciences de l'Univers
Laboratoire d'Astrophysique de Marseille
Kevin Heng
Universität Bern
The University of Warwick
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
G. Lacedelli
Istituto nazionale di astrofisica (INAF)
Università di Padova
J. Laskar
Observatoire de Paris
M. Lendl
Université de Genève
C. Lovis
Université de Genève
A. Luntzer
Universität Wien
D. Magrin
Istituto nazionale di astrofisica (INAF)
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
G. Olofsson
Stockholms universitet
H. P. Osborn
Massachusetts Institute of Technology (MIT)
Universität Bern
R. Ottensamer
Universität Wien
I. Pagano
Istituto nazionale di astrofisica (INAF)
Enric Palle
Instituto de Astrofísica de Canarias
Universidad de la Laguna
G. Peter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
D. Piazza
Universität Bern
Giampaolo P. Piotto
Università di Padova
Istituto nazionale di astrofisica (INAF)
Don L. Pollacco
The University of Warwick
D. Queloz
University of Cambridge
Université de Genève
Roberto Ragazzoni
Università di Padova
Istituto nazionale di astrofisica (INAF)
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Freie Universität Berlin
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Technische Universität Berlin
N. C. Santos
Universidade do Porto
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
D. Segransan
Université de Genève
L. M. Serrano
Universita degli Studi di Torino
D. Sicilia
Istituto nazionale di astrofisica (INAF)
A.E. Simon
Universität Bern
Alexis M. S. Smith
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
S.G. Sousa
Universidade do Porto
Manfred B. Steller
Institut fur Weltraumforschung
Nicolas Thomas
Universität Bern
S. Udry
Université de Genève
V. Van Grootel
Universite de Liège
N. A. Walton
University of Cambridge
T.G. Wilson
University of St Andrews
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 654 A159Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
Annan fysik
Den kondenserade materiens fysik
DOI
10.1051/0004-6361/202140345