Astrometry from the Gaia mission was recently used to discover the two nearest known stellar-mass black holes (BHs), Gaia BH1 and Gaia BH2. These objects are among the first stellar-mass BHs not discovered via X-rays or gravitational waves. Both systems contain ∼1 M _⊙ stars in wide orbits (a ≈ 1.4 au, 4.96 au) around ∼9 M _⊙ BHs, with both stars (solar-type main sequence star, red giant) well within their Roche lobes in Gaia BH1 and BH2, respectively. However, the BHs are still expected to accrete stellar winds, leading to potentially detectable X-ray or radio emission. Here, we report observations of both systems with the Chandra X-ray Observatory, the Very Large Array (for Gaia BH1) and MeerKAT (for Gaia BH2). We did not detect either system, leading to X-ray upper limits of L _X < 9.4 × 10²⁸ and L _X < 4.0 × 10²⁹ erg s⁻¹ and radio upper limits of L _r < 1.6 × 10²⁵ and L _r < 1.0 × 10²⁶ erg s⁻¹ for Gaia BH1 and BH2, respectively. For Gaia BH2, the non-detection implies that the accretion rate near the horizon is much lower than the Bondi rate, consistent with recent models for hot accretion flows. We discuss implications of these non-detections for broader BH searches, concluding that it is unlikely that isolated BHs will be detected via interstellar medium accretion in the near future. We also calculate evolutionary models for the binaries’ future evolution using Modules for Experiments in Stellar Astrophysics, and find that Gaia BH1 will be visible as a symbiotic BH X-ray binary for 5–50 Myr. Since no symbiotic BH X-ray binaries are known, this implies either that fewer than ∼10⁴ Gaia BH1-like binaries exist in the Milky Way, or that they are common but have evaded detection.

中文翻译：

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没有来自最近黑洞的 X 射线或无线电波以及对未来搜索的影响

盖亚任务的天体测量最近被用来发现两个最近的已知恒星质量黑洞 (BH)：盖亚 BH1 和盖亚 BH2。这些天体是第一批未通过 X 射线或引力波发现的恒星质量黑洞。两个系统都包含~1中号 _⊙宽轨道上的恒星（A≈ 1.4 au, 4.96 au) 约 ∼9中号 _⊙ BH，两颗恒星（太阳型主序星、红巨星）分别位于盖亚 BH1 和 BH2 的洛希瓣内。然而，黑洞预计仍会积聚恒星风，从而产生可能可检测到的 X 射线或无线电发射。在这里，我们报告了钱德拉 X 射线天文台甚大阵列（针对盖亚 BH1）和 MeerKAT（针对盖亚 BH2）这两个系统的观测结果。我们没有检测到任何一个系统，导致 X 射线上限L _X < 9.4 × 10 ²⁸且L _X < 4.0 × 10 ²⁹ erg s ⁻¹和无线电上限L _r < 1.6 × 10 ²⁵和L _r 盖亚 BH1 和 BH2 分别< 1.0 × 10 ²⁶ erg s ^-1 。对于盖亚 BH2，未检测到地平线附近的吸积率远低于邦迪率，这与最近的热吸积流模型一致。我们讨论了这些未探测到的对更广泛的黑洞搜索的影响，得出的结论是，在不久的将来，通过星际介质吸积不太可能探测到孤立的黑洞。我们还使用恒星天体物理学实验模块计算了双星未来演化的演化模型，并发现盖亚 BH1 将作为 5-50 Myr 的共生 BH X 射线双星可见。由于尚无已知的共生 BH X 射线双星，这意味着银河系中存在的类似盖亚 BH1 的双星数量少于 ∼10 ^{4 ，或者它们很常见但未能被发现。}