3 research outputs found
Planetary system architectures with low-mass inner planets: Direct imaging exploration of mature systems beyond 1 au
The discovery of planets orbiting at less than 1 au from their host star and
less massive than Saturn in various exoplanetary systems revolutionized our
theories of planetary formation. The fundamental question is whether these
close-in low-mass planets could have formed in the inner disk interior to 1 au,
or whether they formed further out in the planet-forming disk and migrated
inward. Exploring the role of additional giant planets in these systems may
help us to pinpoint their global formation and evolution. We searched for
additional substellar companions by using direct imaging in systems known to
host close-in small planets. The use of direct imaging complemented by radial
velocity and astrometric detection limits enabled us to explore the giant
planet and brown dwarf demographics around these hosts to investigate the
potential connection between both populations. We carried out a direct imaging
survey with VLT/SPHERE to look for outer giant planets and brown dwarf
companions in 27 systems hosting close-in low-mass planets discovered by radial
velocity. Our sample is composed of very nearby (<20pc) planetary systems,
orbiting G-, K-, and M-type mature (0.5-10Gyr) stellar hosts. We performed
homogeneous direct imaging data reduction and analysis to search for and
characterize point sources, and derived robust statistical detection limits. Of
337 point-source detections, we do not find any new bound companions. We
recovered the emblematic very cool T-type brown dwarf GJ229B. Our typical
sensitivities in direct imaging range from 5 to 30 MJup beyond 2 au. The
non-detection of massive companions is consistent with predictions based on
models of planet formation by core accretion. Our pilot study opens the way to
a multi-technique approach for the exploration of very nearby exoplanetary
systems with future ground-based and space observatories.Comment: 49 pages including 31 pages of appendices and references, 31 figures,
A&A, accepte
Efficiently combining Alpha CenA multi-epoch high-contrast imaging data. Application of K-Stacker to the 80 hrs NEAR campaign
Keplerian-Stacker is an algorithm able to combine multiple observations
acquired at different epochs taking into account the orbital motion of a
potential planet present in the images to boost the ultimate detection limit.
In 2019, a total of 100 hours of observation were allocated to VLT VISIR-NEAR,
a collaboration between ESO and Breakthrough Initiatives, to search for low
mass planets in the habitable zone of the Alpha Cen AB binary system. A weak
signal (S/N = 3) was reported around Alpha Cen A, at a separation of 1.1 a.u.
which corresponds to the habitable zone. We have re-analysed the NEAR data
using K-Stacker. This algorithm is a brute-force method able to find planets in
time series of observations and to constrain their orbital parameters, even if
they remain undetected in a single epoch. We scanned a total of about 3.5e+5
independent orbits, among which about 15 % correspond to fast moving orbits on
which planets cannot be detected without taking into account the orbital
motion. We find only a single planet candidate, which matches the C1 detection
reported in Wagner et al. 2021. Despite the significant amount of time spent on
this target, the orbit of this candidate remains poorly constrained due to
these observations being closely distributed in 34 days. We argue that future
single-target deep surveys would benefit from a K-Stacker based strategy, where
the observations would be split over a significant part of the expected orbital
period to better constrain the orbital parameters. This application of
K-Stacker on high contrast imaging data in the mid-infrared demonstrates the
capability of this algorithm to aid in the search for Earth-like planets in the
habitable zone of the nearest stars with future instruments of the E-ELT such
as METIS.Comment: 9 pages, 11 figures, K-Stacker github lin
Reference-star differential imaging on SPHERE/IRDIS
International audienceContext. Reference-star differential imaging (RDI) is a promising technique in high-contrast imaging that is thought to be more sensitive to exoplanets and disks than angular differential imaging (ADI) at short angular separations (i.e., Aims: We characterize the performance of RDI on SPHERE/IRDIS data in direct imaging of exoplanets and disks. Methods: We made use of all the archival data in H23 obtained by SPHERE/IRDIS in the past 5 yr to build a master reference library and perform RDI. To avoid biases caused by limited test targets under specific conditions, 32 targets were selected to obtain the average performances of RDI under different conditions, and we compared the performances with those of ADI. Results: In the point-source detection, RDI can outperform ADI at small angular separations ( Conclusions: RDI is a promising imaging technique for ground-based instruments such as SPHERE. The master reference library we built in this work can be easily implemented into legacy or future SPHERE surveys to perform RDI, achieving better performance than that of ADI. To obtain optimal RDI gains over ADI, we recommend future observations be carried out under seeing conditions of 0.6'-0.8'