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

Eötvös Loránd University (ELTE)

Slovenská akadémia Vied

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

Eötvös Loránd University (ELTE)

Magyar Tudomanyos Akademia

The University of Sydney

A. L. des Etangs

Institut d 'Astrophysique de Paris

P. Maxted

Keele University

I. Ribas

Institut de Ciències de l'Espai (ICE) - CSIC

Institut d'Estudis Espacials de Catalunya (IEEC)

Y. Alibert

Universität Bern

R. Alonso

Instituto de Astrofísica de Canarias

Universidad de la Laguna

G. A. Escudé

Institut de Ciències de l'Espai (ICE) - CSIC

Institut d'Estudis Espacials de Catalunya (IEEC)

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

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

Università di Padova

J. Laskar

Observatoire de Paris

M. Lendl

Université de Genève

C. Lovis

Université de Genève

A. Luntzer

Universität Wien

D. Magrin

Osservatorio Astronomico di Padova

Valerio Nascimbeni

Osservatorio Astronomico di Padova

G. Olofsson

Stockholms universitet

H. P. Osborn

Universität Bern

Massachusetts Institute of Technology (MIT)

R. Ottensamer

Universität Wien

I. Pagano

Osservatorio Astrofisico di Catania

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

Osservatorio Astronomico di Padova

Università di Padova

Don L. Pollacco

The University of Warwick

D. Queloz

University of Cambridge

Université de Genève

Roberto Ragazzoni

Osservatorio Astronomico di Padova

Università di Padova

N. Rando

European Space Research and Technology Centre (ESA ESTEC)

H. Rauer

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Technische Universität Berlin

Freie Universität Berlin

N. C. Santos

Universidade do Porto

Gaetano Scandariato

Osservatorio Astrofisico di Catania

D. Segransan

Université de Genève

L. M. Serrano

Universita degli Studi di Torino

D. Sicilia

Osservatorio Astrofisico di Catania

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 A159

Ämneskategorier

Astronomi, astrofysik och kosmologi

Annan fysik

Den kondenserade materiens fysik

DOI

10.1051/0004-6361/202140345

Mer information

Senast uppdaterat

2021-11-12