Limits on the mass and initial entropy of 51 Eri b from Gaia EDR3 astrometry
Limits on the mass and initial entropy of 51 Eri b from Gaia EDR3 astrometry
复制标题
Gaia EDR3 天体测量中 51 Eri b 的质量和初始熵的限制
DOI：
10.1093/mnras/stab3148
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Dupuy T
中科院分区：
文献类型：
--
作者：
Dupuy T
Eri 51 B是唯一一颗年轻的行星，它与各种可能的初始熵状态相一致，包括与一些通过核心吸积形成行星的模型有关的冷启动情景。限制行星初始熵的最直接方法是在足够年轻的时候测量它的光度和质量，这样初始条件仍然重要。利用Hipparco和GaiaEDR3天体测量的交叉校准和轨道拟合程序orvara，我们给出了迄今为止51 Eri B质量的最严格上限（2σ时M<11 MdR）。我们还重新评估它的光度使用直接的光度方法，findingdex。结合这个光度与β Pic移动群的2400万年± 300万年的年龄，51 Eri是其中的一员，我们从跨越广泛初始熵的演化模型网格中推导出质量分布。我们发现51 Eri B与最冷启动的情况不一致，需要在97%的置信度下初始熵> 8kB重子− 1。这一结果代表了对潜在冷启动行星初始熵的第一个观测约束，并且它延续了直接成像行星指向暖启动或热启动形成情景的动态质量趋势。
51 Eri b is one of the only young planets consistent with a wide range of possible initial entropy states, including the cold-start scenario associated with some models of planet formation by core accretion. The most direct way to constrain the initial entropy of a planet is by measuring its luminosity and mass at a sufficiently young age that the initial conditions still matter. We present the tightest upper limit on 51 Eri b’s mass yet (M< 11MJupat 2σ) using a cross-calibration ofHipparcosandGaiaEDR3 astrometry and the orbit-fitting codeorvara. We also reassess its luminosity using a direct, photometric approach, findingdex. Combining this luminosity with the 24 ± 3 Myr age of the β Pic moving group, of which 51 Eri is a member, we derive mass distributions from a grid of evolutionary models that spans a wide range of initial entropies. We find that 51 Eri b is inconsistent with the coldest-start scenarios, requiring an initial entropy of >8kBbaryon−1at 97 per cent confidence. This result represents the first observational constraint on the initial entropy of a potentially cold-start planet, and it continues the trend of dynamical masses for directly imaged planets pointing to warm- or hot-start formation scenarios.