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Precise Dynamical Masses and Orbital Fits for β Pic b and β Pic c
The Astronomical Journal ( IF 5.1 ) Pub Date : 2021-03-12 , DOI: 10.3847/1538-3881/abdc2e
G. Mirek Brandt 1 , Timothy D. Brandt 1 , Trent J. Dupuy 2 , Yiting Li 1 , Daniel Michalik 3
Affiliation  

We present a comprehensive orbital analysis to the exoplanets β Pictoris b and c that resolves previously reported tensions between the dynamical and evolutionary mass constraints on β Pic b. We use the Markov Chain Monte Carlo orbit code orvara to fit 15 years of radial velocities and relative astrometry (including recent GRAVITY measurements), absolute astrometry from Hipparcos and Gaia, and a single relative radial velocity measurement between β Pic A and b. We measure model-independent masses of ${9.3}_{-2.5}^{+2.6}$ M Jup for β Pic b and 8.3 1.0 M Jup for β Pic c. These masses are robust to modest changes to the input data selection. We find a well-constrained eccentricity of 0.119 0.008 for β Pic b, and an eccentricity of ${0.21}_{-0.09}^{+0.16}$ for β Pic c, with the two orbital planes aligned to within ∼0.5. Both planets’ masses are within ∼1σ of the predictions of hot-start evolutionary models and exclude cold starts. We validate our approach on N-body synthetic data integrated using REBOUND. We show that orvara can account for three-body effects in the β Pic system down to a level ∼5 times smaller than the GRAVITY uncertainties. Systematics in the masses and orbital parameters from orvara’s approximate treatment of multiplanet orbits are a factor of ∼5 smaller than the uncertainties we derive here. Future GRAVITY observations will improve the constraints on β Pic c’s mass and (especially) eccentricity, but improved constraints on the mass of β Pic b will likely require years of additional radial velocity monitoring and improved precision from future Gaia data releases.



中文翻译:

β Pic b 和β Pic c 的精确动力学质量和轨道拟合

我们对系外行星β Pictoris b 和 c 进行了全面的轨道分析,以解决先前报道的β Pic b上动力学和进化质量约束之间的紧张关系。我们使用马尔可夫链蒙特卡罗轨道代码orvara来拟合 15 年的径向速度和相对天体测量(包括最近的重力测量)、来自 Hipparcos 和 Gaia 的绝对天体测量以及β Pic A 和 b之间的单个相对径向速度测量。我们衡量的模型独立群众${9.3}_{-2.5}^{+2.6}$ 中号 杰普β产品图B和8.3 1.0中号 杰普β图 C. 这些质量对于输入数据选择的适度变化是稳健的。我们找到的0.119 0.008的良好约束偏心β产品图b和偏心率${0.21}_{-0.09}^{+0.16}$β产品图C,与内〜0.5对准两个轨道平面。两颗行星的质量都在热启动进化模型预测的约1 σ以内,并且不包括冷启动。我们在使用REBOUND集成的N体合成数据上验证了我们的方法。我们表明,orvara可以将β Pic 系统中的三体效应解释到比 GRAVITY 不确定性小约 5 倍的水平。来自orvara的质量和轨道参数的系统学对多行星轨道的近似处理比我们在这里推导出的不确定性小约 5 倍。未来的 GRAVITY 观测将改进对β Pic c 质量和(特别是)偏心率的约束,但改进对β Pic b质量的约束可能需要数年的额外径向速度监测和未来 Gaia 数据发布的精度提高。

更新日期:2021-03-12
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