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Table 1

Summary of RV models and adopted priors.

Parameter Prior

Model 1
(2 planets + GP trained on y = K2 photometry)
GP hyperparameters
Covariance amplitude, a [m s-1]
Exponential timescale, λ [days] p(λ | y)
Coherence, Γ p(Γ | y)
Periodic timescale, PGP [days] p(PGP | y)
Additive jitter, s [m s-1]
Keplerian parameters
γ0 [m s-1]
Pb [days]
T0,b [BJD-2 450 000]
Kb [m s-1]
Pc [days]
T0,c [BJD-2 450 000]
Kc [m s-1]
Model 2
(2 planets + GP trained on y = BIS)
see Model 1
Model 3
(2 planets + untrained GP)
see Model 1 with the
following modifications:
ln Exponential timescale, lnλ [days]
ln Coherence, lnΓ
ln Periodic timescale, lnPGP [days]
Model 4
(2 planets)
see Keplerian parameters in Model 1

Notes. refers to a non-informative Jeffreys prior which is scale invariant; equal probability per decade which is necessary to sample multiple orders of magnitude (Gregory 2005). (◦) based on the transit light curve measurements from B17. (∗) m s-1 refers to a modified Jefferys prior on a parameter A which behaves like a uniform prior for A the knee at k m s-1 and behaves like a Jeffreys prior at Ak up to l. We use a modified Jeffreys prior on the RV semi-amplitudes K to sample multiple decades as a Jeffreys prior but also include K = 0 m s-1 which a Jeffreys prior does not (Gregory 2005). (†) We further insist that e = h2 + k2 < 1.

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