We present new Large Binocular Telescope, Hubble Space Telescope, and Spitzer Space Telescope data for the failed supernova candidate N6946-BH1. We also report an unsuccessful attempt to detect the candidate with Chandra. The ∼300 000 $\, \mathrm{L}_\odot$ red supergiant progenitor underwent an outburst in 2009 and has since disappeared in the optical. In the LBT data from 2008 May through 2019 October, the upper limit on any increase in the R-band luminosity of the source is $2000 \, \mathrm{L}_\odot$. HST and Spitzer observations show that the source continued to fade in the near-IR and mid-IR, fading by approximately a factor of 2 between 2015 October and 2017 September to 2900 $\, \mathrm{L}_\odot$ at Hband (F160W). Models of the spectral energy distribution are inconsistent with a surviving star obscured either by an ongoing wind or dust formed in the transient. The disappearance of N6946-BH1 remains consistent with a failed supernova, but the post-failure phenomenology requires further theoretical study.

中文翻译：

---

用大型双筒望远镜寻找失败的超新星：N6946-BH1，仍然没有恒星

我们为失败的超新星候选 N6946-BH1 提供了新的大型双筒望远镜、哈勃太空望远镜和斯皮策太空望远镜的数据。我们还报告了使用 Chandra 检测候选人的失败尝试。∼300 000 $\, \mathrm{L}_\odot$ 红超巨星祖先在 2009 年经历了一次爆发，​​此后在光学中消失了。在 2008 年 5 月至 2019 年 10 月的 LBT 数据中，光源 R 波段光度的任何增加上限为 $2000 \, \mathrm{L}_\odot$。HST 和 Spitzer 的观测表明，该源在近红外和中红外继续衰减，在 2015 年 10 月至 2017 年 9 月之间衰减了大约 2 倍，至 2900 $\, \mathrm{L}_\odot$ 在 Hband (F160W)。光谱能量分布模型与被持续风或瞬变形成的尘埃遮蔽的幸存恒星不一致。N6946-BH1的消失与失败的超新星保持一致，但失败后的现象学需要进一步的理论研究。