Observations of the Galactic bulge revealed an excess of short-timescale gravitational microlensing events that are generally attributed to a large population of free-floating or wide-orbit exoplanets. However, in recent years, some authors suggested that planetary-mass primordial black holes (PBHs) comprising a substantial fraction (1%–10%) of the dark matter in the milky Way may be responsible for these events. If that was the case, a large number of short-timescale microlensing events should also be seen toward the Magellanic Clouds. Here, we report the results of a high-cadence survey of the Magellanic Clouds carried out from 2022 October through 2024 May as part of the Optical Gravitational Lensing Experiment. We observed almost 35 million source stars located in the central regions of the Large and Small Magellanic Clouds and found only one long-timescale microlensing event candidate. No short-timescale events were detected despite high sensitivity to such events. That allows us to infer the strongest available limits on the frequency of planetary-mass PBHs in dark matter. We find that PBHs and other compact objects with masses from 1.4 × 10−8M⊙ (half of the Moon mass) to 0.013 M⊙ (planet/brown dwarf boundary) may comprise at most 1% of dark matter. That rules out the PBH origin hypothesis for the short-timescale events detected toward the Galactic bulge and indicates they are caused by the population of free-floating or wide-orbit planets.

中文翻译：

---

来自 OGLE 麦哲伦星云高节奏巡天对行星质量原始黑洞的限制


对银河系隆起的观测揭示了过多的短时间尺度引力微透镜事件，这些事件通常归因于大量自由浮动或宽轨道系外行星。然而，近年来，一些作者提出，占银河系暗物质很大一部分 （1%-10%） 的行星质量原始黑洞 （PBH） 可能是造成这些事件的原因。如果是这样的话，也应该在麦哲伦星云附近看到大量的短时间尺度微透镜事件。在这里，我们报告了 2022 年 10 月至 2024 年 5 月对麦哲伦星云进行的高速巡天的结果，作为光学引力透镜实验的一部分。我们观测了近 3500 万颗位于大麦哲伦星云和小麦哲伦星中心区域的源星，只发现了一个长时间尺度的微透镜事件候选者。尽管对此类事件高度敏感，但未检测到短时间事件。这使我们能够推断出暗物质中行星质量 PBH 频率的最强可用极限。我们发现，PBHs和其他质量从1.4×10-8M⊙（月球质量的一半）到0.013 M⊙（行星/褐矮星边界）的致密天体可能最多占暗物质的1%。这排除了对银河系隆起探测到的短时间尺度事件的 PBH 起源假说，并表明它们是由自由浮动或宽轨道行星的数量引起的。