SPIRou detects two planets around the nearby M4.5V star GJ 4274

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Volume 705 (January 2026)

A&A, 705 (2026) A243

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Table 2

GP prior and fit parameters for GJ 4274 activity indicators B_ℓ & dTemp.

Parameters	Priors		Posterior

	B_ℓ	dT emp	B_ℓ	dT emp
a	ℳℒ𝒰(σ_y, y_ptp)		$203_{- 62}^{+ 158} (G)$ $203_{ - 62}^{ + 158}({\rm{G}})$	${3.00}_{- 0.68}^{+ 1.16} (K)$ $3.00_{ - 0.68}^{ + 1.16}({\rm{K}})$
λ_e (d)	ℒ𝒰(δ_tav, 1000)	200 (fixed)	$248_{- 72}^{+ 309}$ $248_{ - 72}^{ + 309}$	200
P_rot (d)	𝒩(4.6, 0.4)		${4.600}_{- 0.006}^{+ 0.011}$ $4.600_{ - 0.006}^{ + 0.011}$	${4.597}_{- 0.011}^{+ 0.014}$ $4.597_{ - 0.011}^{ + 0.014}$
λ_p	ℒ𝒰(0.5, 5)		${1.79}_{- 0.47}^{+ 0.95}$ $1.79_{ - 0.47}^{ + 0.95}$	${1.66}_{- 0.52}^{+ 0.87}$ $1.66_{ - 0.52}^{ + 0.87}$
Jitter	ℳℒ𝒰(σ_y, y_ptp)		$21_{- 8}^{+ 6} (G)$ $21_{ - 8}^{ + 6}({\rm{G}})$	${2.43}_{- 0.16}^{+ 0.18} (K)$ $2.43_{ - 0.16}^{ + 0.18}({\rm{K}})$

RMS			33.73 (G)	2.325 (K)
$χ_{r e d}^{2}$ $\chi _{red}^2$			1.25	0.91

Notes. We use δt_av to denote the average time between consecutive observations, while σ_y and y_ptp are the standard deviation and peak-to-peak difference of the activity indicator y, respectively. The uniform distribution ranging from a to b is given by (a, b). The notation ℒ(a, b) indicates the log-uniform (or Jeffrey) distribution with shape parameters a and b. Finally, ℳℒ(a, b) denotes the modified log-uniform (modified Jeffrey) distribution, which is a log-uniform distribution whose support includes zero.

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