Five percent measurement of the gravitational constant in the Large Magellanic Cloud

Abstract

We perform a novel test of General Relativity by measuring the gravitational constant in the Large Magellanic Cloud (LMC). The LMC contains six well-studied Cepheid variable stars in detached eclipsing binaries. Radial velocity and photometric observations enable a complete orbital solution, and precise measurements of the Cepheids' periods permit detailed stellar modelling. Both are sensitive to the strength of gravity, the former via Kepler's third law and the latter through the gravitational free-fall time. We jointly fit the observables for stellar parameters and the gravitational constant. Performing a full Markov Chain Monte Carlo analysis of the parameter space including all relevant nuisance parameters, we constrain the gravitational constant in the Large Magellanic Cloud relative to the Solar System to be $G_\text{LMC}/G_\text{SS} = 0.93^{+0.05}_{-0.04}$. We discuss the implications of this 5% measurement of Newton's constant in another galaxy for dark energy and modified gravity theories. This result excludes one Cepheid, CEP-1812, which is an outlier and needs further study: it is either a highly unusual system to which our model does not apply, or it prefers $G_\text{LMC}

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大麦哲伦星云引力常数的5%测量

我们通过测量大麦哲伦星云(LMC)的引力常数，对广义相对论进行了新的检验。LMC包含六颗被充分研究过的造父变星，它们是分离的食双星。视向速度和光度观测可以得到完整的轨道解，对造父变星周期的精确测量可以建立详细的恒星模型。两者都对重力强度敏感，前者通过开普勒第三定律，后者通过重力自由落体时间。我们共同拟合了恒星参数和引力常数的观测值。对包含所有相关干扰参数的参数空间进行完整的马尔可夫链蒙特卡罗分析，我们约束大麦哲伦星云相对于太阳系的引力常数为$G_\text{LMC}/G_\text{SS} = 0.93^{+0.05}_{-0.04}$。我们讨论这5条的含义% measurement of Newton's constant in another galaxy for dark energy and modified gravity theories. This result excludes one Cepheid, CEP-1812, which is an outlier and needs further study: it is either a highly unusual system to which our model does not apply, or it prefers $G_\text{LMC}

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