Issue |
A&A
Volume 638, June 2020
|
|
---|---|---|
Article Number | A120 | |
Number of page(s) | 11 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202037594 | |
Published online | 23 June 2020 |
Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT★,★★
1
INAF – Osservatorio Astronomico di Padova,
Italy
e-mail: raffaele.gratton@inaf.it
2
Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales,
Av. Ejercito 441,
Santiago,
Chile
3
Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales,
Av. Ejercito 441,
Santiago,
Chile
4
Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326,
13388
Marseille,
France
5
INAF – Osservatorio Astrofisico di Torino,
Italy
6
Institute of Astrophysics,
FORTH,
GR-71110 Heraklion,
Greece
7
Department of Physics, University of Crete,
70013
Heraklion,
Greece
8
CRAL, UMR 5574, CNRS, Université Lyon 1, ENS,
9 avenue Charles André,
69561
Saint Genis Laval Cedex,
France
9
European Southern Observatory,
Alonso de Cordova 3107, Casilla 19001 Vitacura,
Santiago 19,
Chile
10
Univ. Grenoble Alpes, CNRS, IPAG,
38000
Grenoble,
France
11
Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile,
Casilla 36-D,
Santiago,
Chile
12
Observatoire de Genève, Université de Genève, 51 Chemin des Mailletes,
1290
Sauverny,
Switzerland
13
Université Côte d’Azur, OCA, CNRS,
Lagrange,
France
14
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité,
5 place Jules Janssen,
92195
Meudon,
France
15
Max Planck Institute for Astronomy,
Königstuhl 17,
69117
Heidelberg,
Germany
16
Department of Astronomy, Stockholm University,
Stockholm,
Sweden
17
INAF – Osservatorio Astronomico di Brera,
Milano,
Italy
18
STAR Institute, Université de Liège, Allée du Six Août 19c,
4000
Liège,
Belgium
19
Department of Astronomy, University of Michigan, 1085 S. Univer-sity Ave,
Ann Arbor,
MI
48109-1107,
USA
20
ONERA (Office National d’Etudes et de Recherches Aérospatiales),
BP72,
92322
Chatillon,
France
21
Hamburger Sternwarte,
Gojenbergsweg 112,
21029
Hamburg,
Germany
22
Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich,
Zürich,
Switzerland
23
INAF – Osservatorio Astrofisico di Arcetri,
Largo E. Fermi 5,
50125
Firenze,
Italy
24
European Southern Observatory,
Karl-Schwarzschild-Strasse 2,
85748
Garching,
Germany
Received:
28
January
2020
Accepted:
14
April
2020
Context. Proxima Centauri is the closest star to the Sun and it is known to host an Earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities. At quadrature, the expected projected separation of this new candidate is larger than 1 arcsec, making it a potentially interesting target for direct imaging.
Aims. While identification of the optical counterpart of this planet is expected to be very difficult, successful identification would allow for a detailed characterization of the closest planetary system.
Methods. We searched for a counterpart in SPHERE images acquired over four years through the SHINE survey. In order to account for the expected large orbital motion of the planet, we used a method that assumes the circular orbit obtained from radial velocities and exploits the sequence of observations acquired close to quadrature in the orbit. We checked this with a more general approach that considers Keplerian motion, called K-stacker.
Results. We did not obtain a clear detection. The best candidate has signal-to-noise ratio (S∕N) = 6.1 in the combined image. A statistical test suggests that the probability that this detection is due to random fluctuation of noise is <1%, but this result depends on the assumption that the distribution of noise is uniform over the image, a fact that is likely not true. The position of this candidate and the orientation of its orbital plane fit well with observations in the ALMA 12 m array image. However, the astrometric signal expected from the orbit of the candidate we detected is 3σ away from the astrometric motion of Proxima as measured from early Gaia data. This, together with the unexpectedly high flux associated with our direct imaging detection, means we cannot confirm that our candidate is indeed Proxima c.
Conclusions. On the other hand, if confirmed, this would be the first observation in imaging of a planet discovered from radial velocities and the second planet (after Fomalhaut b) of reflecting circumplanetary material. Further confirmation observations should be done as soon as possible.
Key words: planets and satellites: detection / planets and satellites: individual: Proxima c / stars: individual: Proxima / planets and satellites: terrestrial planets / instrumentation: high angular resolution / techniques: image processing
The reduced images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A120
© ESO 2020
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