追赶银河系中最快的恒星：利用两次近心点通过的GRAVITY+巡天探测S301的史瓦西进动
Catching Up with the Fastest Star in the Galaxy: A Two-Passage GRAVITY+ Campaign to Detect S301's Schwarzschild Precession
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中文总结 AI 辅助
针对银河系最快恒星S301，设计覆盖两次近心点的GRAVITY+天体测量巡天，通过史瓦西进动检验广义相对论，预测可实现31西格玛探测。
中文摘要 AI 辅助
S301是已知银河系中运动最快的恒星。它每8.68年绕Sgr A*运行一圈，轨道偏心率为e = 0.9832，在距黑洞136个史瓦西半径处速度达到25,600 km/s（GRAVITY合作组2026）。这样的轨道必然会发生进动，其机制与导致水星近日点进动的史瓦西效应相同，且与黑洞的自转无关。我们探究一个仅基于天体测量的GRAVITY+巡天计划，覆盖2031.8年和2040.5年的两次近心点通过，是否能够探测到这一进动。我们验证了一个相对论性光变曲线模型，设计了一个包含131个历元、基于Fisher信息最优且设有近心点下限的观测节奏，拟合了一个包含光行时延的七参数轨道，并构建了系统误差预算。在S301上达到的207微角秒白噪声水平下，拟合恢复的注入进动率0.2307度/年为0.2324 ± 0.0023度/年（在预测的100微角秒精度下为±0.0012）。实际的天体测量噪声并非白噪声。我们加入了每次运行的校准偏移和GRAVITY已发表振幅下的Sgr A*光心漂移，对参考零点、质量和距离进行边缘化，将有限系统误差按平方和相加，并根据真实GRAVITY轨道拟合的额外离散度进行放大。最终保留下来的进动率为0.0074度/年，相当于31西格玛的探测显著性。太阳会遮挡第一次近心点通过长达153天，这会损失对轨道周期和近心点历时的测量精度，但不影响进动率的测定。在S301的星等下，视向速度无法测量；测光仅用于验证光变曲线模型。Sgr A*的自转可能使进动率产生5.17%至5.74%的偏移，且无法约束，因此该巡天计划是一项与自转无关的广义相对论检验，也是对这颗恒星下一次回归前的预测。
英文摘要
S301 is the fastest known star in the Galaxy. It orbits Sgr A* every 8.68 yr on an e = 0.9832 orbit that carries it within 136 Schwarzschild radii at 25,600 km/s (GRAVITY Collaboration 2026). An orbit like that must precess, by the same Schwarzschild effect that turns Mercury's perihelion, whatever the spin of the black hole. We ask whether an astrometry-only GRAVITY+ campaign covering the 2031.8 and 2040.5 periapsis passages can catch it. We validate a relativistic light-curve model, design a 131-epoch Fisher-optimal cadence with a periapsis floor, fit a seven-parameter orbit including the light-travel-time delay, and build a systematic error budget. With white noise at the 207 microarcseconds achieved on S301, the fit recovers the injected rate, 0.2307 deg/yr, as 0.2324 +/- 0.0023 deg/yr (+/-0.0012 at the forecast 100 microarcseconds). Real astrometric noise is not white. We add per-run calibration offsets and a wandering Sgr A* photocentre at GRAVITY's published amplitudes, marginalize over the reference zero point, mass and distance, add the bounded systematics in quadrature, and inflate by the excess scatter of real GRAVITY orbit fits. What survives is 0.0074 deg/yr, a 31 sigma detection. The Sun hides the first periapsis for 153 d, at a cost to the period and periapsis epoch but not to the precession rate. Radial velocities are out of reach at S301's magnitude; photometry only validates the light-curve model. The spin of Sgr A* could shift the rate by 5.17-5.74 per cent and cannot be bounded, so the campaign is a spin-agnostic test of general relativity, and a forecast until the star comes round.
发表机构
- Whiting School of Engineering, Johns Hopkins University（约翰斯·霍普金斯大学惠廷工程学院）
机构由 AI 辅助整理，请以论文原文为准。
