Multiplanet system imaged at HR 8799

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Re: Multiplanet system imaged at HR 8799

Post by Led_Zep on 10th February 2016, 3:22 pm

http://arxiv.org/abs/1602.02856

High-Cadence, High-Contrast Imaging for Exoplanet Mapping: Observations of the HR 8799 Planets with VLT/SPHERE Satellite Spot-Corrected Relative Photometry


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Re: Multiplanet system imaged at HR 8799

Post by Lazarus on 17th March 2016, 7:43 pm

Booth et al. (2016) "Resolving the Planetesimal Belt of HR 8799 with ALMA"
http://arxiv.org/abs/1603.04853

Some tension between the derived location of the inner edge of the disc and the orbit of the outermost planet HR 8799 b. This could be resolved if the orbit of HR 8799 b reaches eccentricities of 0.3 (e.g. due to perturbations from the other planets), or if there is an additional planet located between HR 8799 b and the inner edge of the disc.
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Re: Multiplanet system imaged at HR 8799

Post by Sirius_Alpha on 27th April 2016, 8:38 pm

Astrometric Monitoring of the HR 8799 Planets: Orbit Constraints from Self-Consistent Measurements
http://arxiv.org/abs/1604.08157

More monitoring of their positions and orbits. They tentatively suggest that the planets may have higher inclinations than reported before, which might make it more consistent with the inclination of the disk from ALMA observations, as well as from asteroseismology results for the stellar inclination.

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Re: Multiplanet system imaged at HR 8799

Post by Lazarus on 18th October 2016, 5:41 pm

Another orbit analysis, this time allowing for both eccentric and misaligned orbits. Seems to be a 2-sigma case for a misalignment between b and c, and planet d appears to have a non-zero eccentricity.

Wertz et al. "VLT/SPHERE robust astrometry of the HR8799 planets at milliarcsecond-level accuracy Orbital architecture analysis with PyAstrOFit"
https://arxiv.org/abs/1610.04014
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Re: Multiplanet system imaged at HR 8799

Post by Led_Zep on 10th November 2016, 9:31 pm

http://subarutelescope.org/Topics/2016/11/09/index.html

First light of CHARIS (Coronagraphic High Angular Resolution Imaging Spectrograph),
a new instrument for the Subaru Telescope



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Re: Multiplanet system imaged at HR 8799

Post by Sirius_Alpha on 21st January 2018, 9:36 pm

Invoking a fifth, sub-Jovian planet outside the orbit of b could explain why the outer disk's inner edge is so far from the orbit of b.

Shaping HR8799's outer dust belt with an unseen planet
https://arxiv.org/abs/1801.06513

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Re: Multiplanet system imaged at HR 8799

Post by Lazarus on 24th April 2018, 1:27 pm

Greenbaum et al. "GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4μm with KLIP Forward Modeling"
https://arxiv.org/abs/1804.07774
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Re: Multiplanet system imaged at HR 8799

Post by Sirius_Alpha on 12th September 2018, 8:36 pm

Dynamical Constraints on the HR 8799 Planets with GPI
https://arxiv.org/abs/1809.04107

The HR 8799 system uniquely harbors four young super-Jupiters whose orbits can provide insights into the system's dynamical history and constrain the masses of the planets themselves. Using the Gemini Planet Imager (GPI), we obtained down to one milliarcsecond precision on the astrometry of these planets. We assessed four-planet orbit models with different levels of constraints and found that assuming the planets are near 1:2:4:8 period commensurabilities, or are coplanar, does not worsen the fit. We added the prior that the planets must have been stable for the age of the system (40 Myr) by running orbit configurations from our posteriors through N-body simulations and varying the masses of the planets. We found that only assuming the planets are both coplanar and near 1:2:4:8 period commensurabilities produces dynamically stable orbits in large quantities. Our posterior of stable coplanar orbits tightly constrains the planets' orbits, and we discuss implications for the outermost planet b shaping the debris disk. A four-planet resonance lock is not necessary for stability up to now. However, planet pairs d and e, and c and d, are each likely locked in two-body resonances for stability if their component masses are above 6 MJup and 7 MJup, respectively. Combining the dynamical and luminosity constraints on the masses using hot-start evolutionary models and a system age of 425~Myr, we found the mass of planet b to be 5.80.5 MJup, and the masses of planets c, d, and e to be 7.2+0.6−0.7 MJup each.

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