Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1<sup>*</sup>

Bohn, A. J.; Kenworthy, Matthew A.; Ginski, C.; Rieder, Steven; Mamajek, Eric E.; Meshkat, Tiffany; Pecaut, Mark J.; Reggiani, Maddalena; Boer, J. de; Keller, Christoph U.; Snik, Frans; Southworth, J.

doi:10.3847/2041-8213/aba27e

Cited by 72 publications

(49 citation statements)

References 89 publications

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“…The newly discovered planetary companion to YSES 2 is among the lowest mass direct imaging companions known to date. The only objects of similar low mass are 51 Eri b (Macintosh et al 2015), HD 95086 b (Rameau et al 2013), HR8799 b (Marois et al 2008), PDS 70 b and c, (Keppler et al 2018;Haffert et al 2019;Wang et al 2020;Stolker et al 2020a), and YSES 1c (Bohn et al 2020b). Of these, only YSES 1c is located around a solar-mass star.…”

Section: Discussionmentioning

confidence: 99%

“…In our previous study we considered scattering or planet capturing events to explain the current large separation of YSES 1b. However, dynamic scattering by a third body in the system is expected to produce high eccentricities, inconsistent with orbital stability of both planetary components in the YSES 1 system (Bohn et al 2020b). 6 The new detection of YSES 2b in our small survey sample of 70 solar-type systems in Sco-Cen makes the hypothesis that we see captured free-floating planets unlikely.…”

Section: Discussionmentioning

confidence: 99%

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Discovery of a directly imaged planet to the young solar analog YSES 2

Bohn

Ginski

Kenworthy

et al. 2021

A&A

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Context. To understand the origin and formation pathway of wide-orbit gas giant planets, it is necessary to expand the limited sample of these objects. The mass of exoplanets derived with spectrophotometry, however, varies strongly as a function of the age of the system and the mass of the primary star. Aims. By selecting stars with similar ages and masses, the Young Suns Exoplanet Survey (YSES) aims to detect and characterize planetary-mass companions to solar-type host stars in the Scorpius-Centaurus association. Methods. Our survey is carried out with VLT/SPHERE with short exposure sequences on the order of 5 min per star per filter. The subtraction of the stellar point spread function (PSF) is based on reference star differential imaging using the other targets (with similar colors and magnitudes) in the survey in combination with principal component analysis. Two astrometric epochs that are separated by more than one year are used to confirm co-moving companions by proper motion analysis. Results. We report the discovery of YSES 2b, a co-moving, planetary-mass companion to the K1 star YSES 2 (TYC 8984-2245-1, 2MASS J11275535-6626046). The primary has a Gaia EDR3 distance of 110 pc, and we derive a revised mass of 1.1 M⊙ and an age of approximately 14 Myr. We detect the companion in two observing epochs southwest of the star at a position angle of 205° and with a separation of ~1.′′05, which translates to a minimum physical separation of 115 au at the distance of the system. Photometric measurements in the H and Ks bands are indicative of a late L spectral type, similar to the innermost planets around HR 8799. We derive a photometric planet mass of 6.3−0.9+1.6 MJup using AMES-COND and AMES-dusty evolutionary models; this mass corresponds to a mass ratio of q = (0.5 ± 0.1)% with the primary. This is the lowest mass ratio of a direct imaging planet around a solar-type star to date. We discuss potential formation mechanisms and find that the current position of the planet is compatible with formation by disk gravitational instability, but its mass is lower than expected from numerical simulations. Formation via core accretion must have occurred closer to the star, yet we do not find evidence that supports the required outward migration, such as via scattering off another undiscovered companion in the system. We can exclude additional companions with masses greater than 13 MJup in the full field of view of the detector (0.′′15<ρ<5.′′50), at 0.′′5 we can rule out further objects that are more massive than 6 MJup, and for projected separations ρ >2′′ we are sensitive to planets with masses as low as 2 MJup. Conclusions. YSES 2b is an ideal target for follow-up observations to further the understanding of the physical and chemical formation mechanisms of wide-orbit Jovian planets. The YSES strategy of short snapshot observations (≤5 min) and PSF subtraction based on a large reference library proves to be extremely efficient and should be considered for future direct imaging surveys.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Discovery of a directly imaged planet to the young solar analog YSES 2

Bohn

Ginski

Kenworthy

et al. 2021

A&A

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“…The β Pictoris system has only recently joined the selective group of multi-planet directly imaged systems, along with HR 8799 (Marois et al 2008(Marois et al , 2010, PDS 70 (Keppler et al 2018;Müller et al 2018;Haffert et al 2019), and TYC 8998-760-1 (Bohn et al 2020). Because of the lack of planet detection and the struggle to constrain long-period orbits, the formation and dynamical evolution of cold giant planets remain largely unconstrained.…”

Section: Stability Resonance and Evaporating Bodiesmentioning

confidence: 99%

The mass ofβPictoris c fromβPictoris b orbital motion

Lacour

Wang

Rodet

et al. 2021

A&A

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Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet. Methods. We combined previous astrometry of β Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of β Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, β Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations. Results. From the astrometry of planet b only, we can (i) detect the presence of β Pictoris c and (ii) constrain its mass to 10.04−3.10+4.53 MJup. If one adds the astrometry of β Pictoris c, the mass is narrowed down to 9.15−1.06+1.08 MJup. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89−0.75+0.75 MJup. With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters of β Pictoris c are now constrained as precisely as those of β Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets’ dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.

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“…In order to characterize the atmosphere of the planet, we performed a Bayesian retrieval analysis on the spectrum using the radiative transfer tool petitRADTRANS (pRT) 16 , connected to the nested sampling tool PyMultiNest 17 . We focus on revealing the presence of 13 CO, which is expected to be the most detectable isotopologue in atmospheres of gas giants 18 , and measuring the isotopologue abundance ratio 12 CO/ 13 CO. In addition, we aim to constrain atmospheric properties of the planet such as the carbon-to-oxygen ratio C/O, which may shed light on the conditions during the formation of the planet 19 .…”

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confidence: 99%

“…We set up the retrieval model in a similar way as used in previous work on HR 8799 e 20 (see Methods). The model consists of nine free parameters: the planet radius RP, surface gravity log(g), metallicity [Fe/H], carbon-to-oxygen ratio C/O, the isotopologue abundance ratio 12 CO/ 13 CO, three parameters for the Temperature-Pressure (T-P) profile, and a spectral slope correction factor fslope, arising from uncertainties in the calibration of the observed spectrum. We ran retrievals on the spectrum of TYC 8998 b using two sets of models: the full model including 13 CO and the reduced model excluding 13 CO.…”

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The 13CO-rich atmosphere of a young accreting super-Jupiter

Zhang

Snellen

Bohn

et al. 2021

Nature

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Isotope abundance ratios play an important role in astronomy and planetary sciences, providing insights in the origin and evolution of the Solar System, interstellar chemistry, and stellar nucleosynthesis 1,2 . In contrast to deuterium/hydrogen ratios, carbon isotope ratios are found to be roughly constant (~89) in the Solar System 1,3 , but do vary on galactic scales with 12 C/ 13 C~68 in the current local interstellar medium 4-6 . In molecular clouds and protoplanetary disks, 12 CO/ 13 CO isotopologue ratios can be altered by ice and gas partitioning 7 , low-temperature isotopic ion exchange reactions 8 , and isotope-selective photodissociation 9 . Here we report on the detection of 13 CO in the atmosphere of the young, accreting giant planet TYC 8998-760-1 b at a statistical significance of > 6σ. Marginalizing over the planet's atmospheric temperature structure, chemical composition, and spectral calibration uncertainties, suggests a 12 CO/ 13 CO ratio of ! $ (90% confidence), a significant enrichment in 13 C with respect to the terrestrial standard and the local interstellar value. Since the current location of TYC 8998 b at ≥160 au is far beyond the CO snowline, we postulate that it accreted a significant fraction of its carbon from ices enriched in 13 C through fractionation. Future isotopologue measurements in exoplanet atmospheres can provide unique constraints on where, when and how planets are formed.TYC 8998-760-1 b 10 is a widely-separated planetary mass companion around a young solar analog TYC 8998-760-1 (also known as 2MASS J13251211-6456207) with an age of ~17 Myr 11 . With the recent detection of a second planet 12 , it is part of the first directly imaged multiplanet system around a solar-type star. TYC 8998 b is located at a projected separation of 160 au, with an estimated mass of 14±3 MJ. We observed the planet on two nights, 2019 June 5 and June 19, using Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) 13,14 installed at the Cassegrain focus of UT3 of the Very Large Telescope of the European Southern Observatory at Cerro Paranal, Chile. The observations were performed in K-band (1.95 -2.45 μm), providing a spectral resolving power (λ/Δλ) of ~4500. We extracted the spectrum of TYC 8998 b from 2.10 to 2.45 μm as detailed in Methods.As shown in Figure 1, the planet spectrum is dominated by molecular features from H2O and CO. The 12 CO v=2-0, 3-1, 4-2 bandheads are visible at 2.2935, 2.3227, and 2.3535 μm respectively. When we compare the observed spectrum with the best-fit model obtained by atmospheric retrieval, an extra emission signature at 2.166 μm is seen in Figure 1c, which is identified as the hydrogen Brackett γ recombination line. This is likely an indication of ongoing accretion of circumplanetary material onto the planet. We estimated a mass accretion rate of 10 -9.4±1.3 M⊙ yr -1 using the Br γ line luminosity (see Methods). Future observations at longer wavelengths and polarimetric data can provide further insights into the circumplanetary disk and accret...

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Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1^*

Cited by 72 publications

References 89 publications

Discovery of a directly imaged planet to the young solar analog YSES 2

Discovery of a directly imaged planet to the young solar analog YSES 2

The mass ofβPictoris c fromβPictoris b orbital motion

The 13CO-rich atmosphere of a young accreting super-Jupiter

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Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1*

Cited by 72 publications

References 89 publications

Discovery of a directly imaged planet to the young solar analog YSES 2

Discovery of a directly imaged planet to the young solar analog YSES 2

The mass ofβPictoris c fromβPictoris b orbital motion

The 13CO-rich atmosphere of a young accreting super-Jupiter

Contact Info

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Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1^*