K-Stacker: an algorithm to hack the orbital parameters of planets hidden in high-contrast imaging

Coroller, H. Le; Nowak, M.; Delorme, P.; Chauvin, G.; Gratton, R.; Devinat, M.; Bec-Canet, J.; Schneeberger, Antoine; Estevez, D.; Arnold, L.; Beust, H.; Bonnefoy, M.; Boccaletti, A.; Desgrange, C.; Desidera, S.; Galicher, R.; Lagrange, Anne-Marie; Langlois, M.; Maire, Anne-Lise; Ménard, F.; Vernazza, Pierre; Vigan, A.; Zurlo, A.; Fenouillet, T.; Lambert, Jean‐Charles; Bonavita, M.; Cheetham, A.; D’Orazi, V.; Feldt, M.; Janson, Markus; Ligi, R.; Mesa, D.; Meyer, Michael; Samland, M.; Sissa, E.; Beuzit, Jean-Luc; Dohlen, Kjetil; Fusco, Thierry; Mignant, D. Le; Mouillet, D.; Ramos, J.; Rochat, S.; Sauvage, Jean-François

doi:10.1051/0004-6361/202037605

Cited by 8 publications

(9 citation statements)

References 41 publications

(34 reference statements)

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“…An additional night of data was taken on 2019 June 27. Enough time separates the collection of these data from the initial observations such that orbital motion complicates combining these with the rest of the data 33 , 34 . However, this extra night provides a useful astrometric check for brighter planet candidates.…”

Section: Resultsmentioning

confidence: 99%

Imaging low-mass planets within the habitable zone of α Centauri

et al. 2021

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Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.

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Section: Resultsmentioning

confidence: 99%

Imaging low-mass planets within the habitable zone of α Centauri

et al. 2021

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“…We are then left with four epochs in which the planet is expected to be out of the coronagraph and sufficiently far from b: Feb. 2015 and Dec. 2018, when it should be NE of the star, as well as Dec. 2019 and Feb. 2020, when it is expected to be SW of the star. An examination of the corresponding images does not clearly reveal β Pictoris c. Further work will include the combination of all data set, for example, as done in Le Coroller et al (2020) to try and directly detect β Pictoris c in the SPHERE data.…”

Section: Discussionmentioning

confidence: 99%

“…However, the lower limits on β Pictoris b's eccentricity remained quite elusive. Finally, using the K-STacker algorithm, which is an approach that is fully different from the Markov-chain Monte Carlo (MCMC) based methods, Le Coroller et al (2020) derived an eccentricity of 0.07.…”

Section: Introductionmentioning

confidence: 99%

Unveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data

Lagrange

Rubini²,

Nowak³

et al. 2020

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Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. Aims. We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10–11 MJup range. Conversely, β Pictoris c’s mass is well constrained, at 7.8 ± 0.4 MJup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 MJup closer than 3 au, and more massive than 3.5 MJup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2 MJup. Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b.

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“…The existence of HD 95086 c has been investigated by Le Coroller et al (2020) using the K-Stacker algorithm (Nowak et al 2018). The code was applied to a combination of six IFS observations (median over Y-H wavelengths) obtained at different epochs (from February 2015 to May 2017).…”

Section: K-stacker Explorationmentioning

confidence: 99%

In-depth direct imaging and spectroscopic characterization of the young Solar System analog HD 95086

Desgrange

Chauvin

Christiaens

et al. 2022

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Context. HD 95086 is a young nearby Solar System analog hosting a giant exoplanet orbiting at 57 au from the star between an inner and outer debris belt. The existence of additional planets has been suggested as the mechanism that maintains the broad cavity between the two belts. Aims. We present a dedicated monitoring of HD 95086 with the VLT/SPHERE instrument to refine the orbital and atmospheric properties of HD 95086 b, and to search for additional planets in this system. Methods. SPHERE observations, spread over ten epochs from 2015 to 2019 and including five new datasets, were used. Combined with archival observations, from VLT/NaCo (2012-2013) and Gemini/GPI (2013-2016), the extended set of astrometric measurements allowed us to refine the orbital properties of HD 95086 b. We also investigated the spectral properties and the presence of a circumplanetary disk around HD 95086 b by using the special fitting tool exploring the diversity of several atmospheric models. In addition, we improved our detection limits in order to search for a putative planet c via the K-Stacker algorithm. Results. We extracted for the first time the JH low-resolution spectrum of HD 95086 b by stacking the six best epochs, and confirm its very red spectral energy distribution. Combined with additional datasets from GPI and NaCo, our analysis indicates that this very red color can be explained by the presence of a circumplanetary disk around planet b, with a range of high-temperature solutions (1400-1600 K) and significant extinction (A V 10 mag), or by a super-solar metallicity atmosphere with lower temperatures (800-1300 K), and small to medium amount of extinction (A V 10 mag). We do not find any robust candidates for planet c, but give updated constraints on its potential mass and location.

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K-Stacker: an algorithm to hack the orbital parameters of planets hidden in high-contrast imaging

Cited by 8 publications

References 41 publications

Imaging low-mass planets within the habitable zone of α Centauri

Imaging low-mass planets within the habitable zone of α Centauri

Unveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data

In-depth direct imaging and spectroscopic characterization of the young Solar System analog HD 95086

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