56 research outputs found
Preparing an unsupervised massive analysis of SPHERE high contrast data with the PACO algorithm
We aim at searching for exoplanets on the whole ESO/VLT-SPHERE archive with
improved and unsupervised data analysis algorithm that could allow to detect
massive giant planets at 5 au. To prepare, test and optimize our approach, we
gathered a sample of twenty four solar-type stars observed with SPHERE using
angular and spectral differential imaging modes. We use PACO, a new generation
algorithm recently developed, that has been shown to outperform classical
methods. We also improve the SPHERE pre-reduction pipeline, and optimize the
outputs of PACO to enhance the detection performance. We develop custom built
spectral prior libraries to optimize the detection capability of the ASDI mode
for both IRDIS and IFS. Compared to previous works conducted with more
classical algorithms than PACO, the contrast limits we derived are more
reliable and significantly better, especially at short angular separations
where a gain by a factor ten is obtained between 0.2 and 0.5 arcsec. Under good
observing conditions, planets down to 5 MJup, orbiting at 5 au could be
detected around stars within 60 parsec. We identified two exoplanet candidates
that require follow-up to test for common proper motion. In this work, we
demonstrated on a small sample the benefits of PACO in terms of achievable
contrast and of control of the confidence levels. Besides, we have developed
custom tools to take full benefits of this algorithm and to quantity the total
error budget on the estimated astrometry and photometry. This work paves the
way towards an end-to-end, homogeneous, and unsupervised massive re-reduction
of archival direct imaging surveys in the quest of new exoJupiters.Comment: Accepted for publication in A&
The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986
Transiting planets with orbital periods longer than 40 d are extremely rare
among the 5000+ planets discovered so far. The lack of discoveries of this
population poses a challenge to research into planetary demographics,
formation, and evolution. Here, we present the detection and characterization
of HD88986b, a potentially transiting sub-Neptune, possessing the longest
orbital period among known transiting small planets (< 4 R) with a
precise mass measurement ( > 25%). Additionally, we identified the
presence of a massive companion in a wider orbit around HD88986. Our analysis
reveals that HD88986b, based on two potential single transits on sector 21 and
sector 48 which are both consistent with the predicted transit time from the RV
model, is potentially transiting. The joint analysis of RV and photometric data
show that HD88986b has a radius of 2.490.18 R, a mass of
17.2 M, and it orbits every 146.05
d around a subgiant HD88986 which is one of the closest and brightest exoplanet
host stars (G2V type, R=1.543 0.065 R, V= mag,
distance=33.370.04 pc). The nature of the outer, massive companion is
still to be confirmed; a joint analysis of RVs, Hipparcos, and Gaia astrometric
data shows that with a 3 confidence interval, its semi-major axis is
between 16.7 and 38.8 au and its mass is between 68 and 284 M.
HD88986b's wide orbit suggests the planet did not undergo significant mass loss
due to extreme-ultraviolet radiation from its host star. Therefore, it probably
maintained its primordial composition, allowing us to probe its formation
scenario. Furthermore, the cold nature of HD88986b (4608 K), thanks to its
long orbital period, will open up exciting opportunities for future studies of
cold atmosphere composition characterization.Comment: 37 pages, accepted to be published in A&
Direct discovery of the inner exoplanet in the HD206893 system. Evidence for deuterium burning in a planetary-mass companion
Long term precise radial velocity (RV) monitoring of the nearby star
HD206893, as well as anomalies in the system proper motion, have suggested the
presence of an additional, inner companion in the system. Here we describe the
results of a multi-epoch search for the companion responsible for this RV drift
and proper motion anomaly using the VLTI/GRAVITY instrument. Utilizing
information from ongoing precision RV measurements with the HARPS spectrograph,
as well as Gaia host star astrometry, we report a high significance detection
of the companion HD206893c over three epochs, with clear evidence for Keplerian
orbital motion. Our astrometry with 50-100 arcsec precision afforded
by GRAVITY allows us to derive a dynamical mass of 12.7 M and an orbital separation of 3.53 au for HD206893c. Our
fits to the orbits of both companions in the system utilize both Gaia
astrometry and RVs to also provide a precise dynamical estimate of the
previously uncertain mass of the B component, and therefore derive an age of
Myr. We find that theoretical atmospheric/evolutionary models
incorporating deuterium burning for HD206893c, parameterized by cloudy
atmospheres provide a good simultaneous fit to the luminosity of both HD206893B
and c. In addition to utilizing long-term RV information, this effort is an
early example of a direct imaging discovery of a bona fide exoplanet that was
guided in part with Gaia astrometry. Utilizing Gaia astrometry is expected to
be one of the primary techniques going forward to identify and characterize
additional directly imaged planets. Lastly, this discovery is another example
of the power of optical interferometry to directly detect and characterize
extrasolar planets where they form at ice-line orbital separations of 2-4\,au.Comment: Accepted to A&
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