On the masses, age, and architecture of the VHS J1256-1257AB b system
On the masses, age, and architecture of the VHS J1256-1257AB b system
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关于 VHS J1256-1257AB b 系统的质量、寿命和架构
DOI：
10.1093/mnras/stac3557
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发表时间：
2023
影响因子：
4.8
通讯作者：
Dupuy T
中科院分区：
文献类型：
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作者：
Dupuy T
VHS J1256−1257 AB是一颗超冷的矮双星，拥有一颗宽间隔的行星质量伴星，这是JWST系外行星早期释放科学计划的关键目标。利用Keck自适应光学成像和孔径掩模干涉技术，我们确定了主星双星的轨道（a= 1.96 ± 0.03 Au，P= 7.31 ± 0.02 yr，e= 0.883 ± 0.003），并测量了它的动力学总质量（0.141 ± 0.008 M）。这一总质量与VHS J1256−1257 AB是一颗褐矮星双星或一对质量非常低的恒星相一致。此外，我们测量了VHS J1256−1257 B b相对于VHS J1256−1257 AB重心的轨道运动，发现宽伴星的轨道也是偏心的（），相对于中央双星的相互倾角为115 ± 14。这种轨道结构与VHS J1256−1257 B通过动力散射获得显著的相互倾斜，然后驱动Kozai-Lidov循环来泵VHS J1256−1257 AB的偏心率是一致的。我们从低质量恒星/亚恒星演化模型中推导出VHS J1256−1257 AB的冷却年龄为140 ± 20百万年。在这个年龄，VHS J1256−1257 B的光度与氘惰性和氘融合的演化轨迹一致。因此，我们发现VHS J1256−1257 B的质量有一个双峰概率分布，即12.0 ± 0.1兆焦耳或16 ± 1兆焦耳。未来的光谱数据来测量同位素，如HDO和CH 3D可以打破这种简并，并提供一个强有力的测试亚恒星模型在氘聚变质量边界。
VHS J1256−1257 AB is an ultracool dwarf binary that hosts a wide-separation planetary-mass companion that is a key target of theJWSTExoplanet Early Release Science programme. Using Keck adaptive optics imaging and aperture masking interferometry, we have determined the host binary’s orbit (a= 1.96 ± 0.03 au,P= 7.31 ± 0.02 yr,e= 0.883 ± 0.003) and measured its dynamical total mass (0.141 ± 0.008 M⊙). This total mass is consistent with VHS J1256−1257 AB being a brown dwarf binary or pair of very low-mass stars. In addition, we measured the orbital motion of VHS J1256−1257 b with respect to the barycentre of VHS J1256−1257 AB, finding that the wide companion’s orbit is also eccentric (), with a mutual inclination of 115○± 14○with respect to the central binary. This orbital architecture is consistent with VHS J1256−1257 b attaining a significant mutual inclination through dynamical scattering and thereafter driving Kozai–Lidov cycles to pump the eccentricity of VHS J1256−1257 AB. We derive a cooling age of 140 ± 20 Myr for VHS J1256−1257 AB from low-mass stellar/substellar evolutionary models. At this age, the luminosity of VHS J1256−1257 b is consistent with both deuterium-inert and deuterium-fusing evolutionary tracks. We thus find a bimodal probability distribution for the mass of VHS J1256−1257 b, either 12.0 ± 0.1MJupor 16 ± 1MJup, from these models. Future spectroscopic data to measure isotopologues such as HDO and CH3D could break this degeneracy and provide a strong test of substellar models at the deuterium-fusion mass boundary.