We present Hubble Space Telescope imaging of a pre-explosion counterpart to SN 2019yvr obtained 2.6 yr before its explosion as a type Ib supernova (SN Ib). Aligning to a post-explosion Gemini-S/GSAOI image, we demonstrate that there is a single source consistent with being the SN 2019yvr progenitor system, the second SN Ib progenitor candidate after iPTF13bvn. We also analysed pre-explosion Spitzer/Infrared Array Camera (IRAC) imaging, but we do not detect any counterparts at the SN location. SN 2019yvr was highly reddened, and comparing its spectra and photometry to those of other, less extinguished SNe Ib we derive $E(B-V)=0.51\substack{+0.27\\ -0.16}$ mag for SN 2019yvr. Correcting photometry of the pre-explosion source for dust reddening, we determine that this source is consistent with a log (L/L⊙) = 5.3 ± 0.2 and $T_{\mathrm{eff}} = 6800\substack{+400\\ -200}$ K star. This relatively cool photospheric temperature implies a radius of 320$\substack{+30\\ -50}~\mathrm{ R}_{\odot}$, much larger than expectations for SN Ib progenitor stars with trace amounts of hydrogen but in agreement with previously identified SN IIb progenitor systems. The photometry of the system is also consistent with binary star models that undergo common envelope evolution, leading to a primary star hydrogen envelope mass that is mostly depleted but still seemingly in conflict with the SN Ib classification of SN 2019yvr. SN 2019yvr had signatures of strong circumstellar interaction in late-time (>150 d) spectra and imaging, and so we consider eruptive mass-loss and common envelope evolution scenarios that explain the SN Ib spectroscopic class, pre-explosion counterpart, and dense circumstellar material. We also hypothesize that the apparent inflation could be caused by a quasi-photosphere formed in an extended, low-density envelope, or circumstellar matter around the primary star.

中文翻译：

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爆炸前 2.6 年，Ib 型超新星 2019yvr 的一个凉爽且膨胀的前身候选者

我们展示了哈勃太空望远镜对 SN 2019yvr 爆炸前对应物的成像，该图像是在爆炸前 2.6 年作为 Ib 型超新星 (SN Ib) 获得的。与爆炸后的 Gemini-S/GSAOI 图像对齐，我们证明存在与 SN 2019yvr 祖系统一致的单一来源，这是继 iPTF13bvn 之后的第二个 SN Ib 祖系统候选者。我们还分析了爆炸前的斯皮策/红外阵列相机 (IRAC) 成像，但我们没有在 SN 位置检测到任何对应物。SN 2019yvr 高度变红，将其光谱和光度与其他较不熄灭的 SNe Ib 进行比较，我们得出 SN 2019yvr 的 $E(BV)=0.51\substack{+0.27\\ -0.16}$ mag。校正粉尘变红的爆炸前源的光度测量，我们确定该源与 log (L/L⊙) = 5.3 ± 0 一致。2 和 $T_{\mathrm{eff}} = 6800\substack{+400\\ -200}$K 星。这个相对较冷的光球温度意味着半径为 320$\substack{+30\\ -50}~\mathrm{ R}_{\odot}$，远大于对含有微量氢的 SN Ib 前身星的预期，但在与先前确定的 SN IIb 祖系统一致。该系统的光度测量也与经历共同包络演化的双星模型一致，导致主星氢包络质量大部分耗尽，但似乎仍与 SN 2019yvr 的 SN Ib 分类相冲突。SN 2019yvr 在后期（>150 天）光谱和成像中具有强烈的星际相互作用特征，因此我们考虑了解释 SN Ib 光谱类、爆炸前对应物的喷发质量损失和常见包络演化情景，和致密的星际物质。我们还假设，明显的暴胀可能是由在扩展的低密度包络中形成的准光球层或主星周围的星周物质引起的。