论文标题
广泛的二进制物作为修饰的重力测试：检测三体系统污染的前景
Wide Binaries as a Modified Gravity test: prospects for detecting triple-system contamination
论文作者
论文摘要
最近的研究表明，用盖亚（Gaia）高精度的非常宽的二元恒星的速度差异可以为模拟暗物质的改良性用力理论提供有趣的测试。从本质上讲，类似于Mond的理论（包括外部效应）预测，对于类似的轨道，宽二进制（大于〜7 kau）的轨道应比牛顿快〜15％。在Pittordis和Sutherland（2022; PS22）中选择的9,000个候选系统的样本中，可以很容易地检测到这种转移。但是，目前的主要障碍是观察到的候选宽二元系统的“脂肪尾巴”，其速度差异为〜1.5-6倍圆速度。该尾巴不能绑定纯二进制系统，但是对尾巴的可能解释是三重或四倍的系统，其尚未解决或未被发现的附加恒星。虽然可以对此尾巴进行建模并统计上减去，但获得三重群体的精确模型对于改良重力的可靠测试至关重要。在本文中，我们探讨了观察限制三重人群的前景：我们模拟了在随机时期和查看角度的PS22中，“观察到”的层次三重系统的群体“观察到”；对于每个模拟系统，我们评估了检测第三颗恒星的各种可能方法，包括Gaia天体，径向速度漂移以及来自直接鲁宾图像，斑点成像和冠状图像成像的几种成像方法。结果通常是令人鼓舞的，因为可以检测到参数空间关键区域中90％的三重系统。在〜25-100 au分离时，有一个凉爽的棕色矮人同伴的中等“死区”，我们的任何基线方法都无法检测到。大型但可行的观察运动可以极大地阐明三重/四倍人口的效果，并使重力测试具有决定性的作用。
Recent studies have shown that velocity differences of very wide binary stars, measured to high precision with GAIA, can provide an interesting test for modified-gravity theories which emulate dark matter; in essence, MOND-like theories (with external field effect included) predict that wide binaries (wider than ~ 7 kAU) should orbit ~ 15% faster than Newtonian for similar orbits; such a shift is readily detectable in principle in the sample of 9,000 candidate systems selected from GAIA EDR3 by Pittordis and Sutherland (2022; PS22). However, the main obstacle at present is the observed "fat tail" of candidate wide-binary systems with velocity differences at ~1.5 - 6x circular velocity; this tail cannot be bound pure binary systems, but a possible explanation of the tail is triple or quadruple systems with unresolved or undetected additional star(s). While this tail can be modelled and statistically subtracted, obtaining an accurate model for the triple population is crucial for a robust test for modified gravity. In this paper we explore prospects for observationally constraining the triple population: we simulate a population of hierarchical triple systems "observed" as in PS22 at random epochs and viewing angles; for each simulated system we evaluate various possible methods for detecting the third star, including GAIA astrometry, radial velocity drift, and several imaging methods from direct Rubin images, speckle imaging and coronagraphic imaging. Results are generally encouraging, in that typically 90% of the triple systems in the key regions of parameter space are detectable; there is a moderate "dead zone" of cool brown-dwarf companions at ~ 25-100 AU separation which are not detectable with any of our baseline methods. A large but feasible observing campaign can greatly clarify the effect of the triple/quadruple population and make the gravity test decisive.
