Messier 51中超新星2011 dh/ PTF11eon的前身
The Progenitor of Supernova 2011dh/PTF11eon in Messier 51
摘要：
我们已经在超新星（SN）2011 dh/PTF 11 eon的位置发现了一颗发光的恒星，在SN之前的档案中，附近的Messier 51（M51）星系的多波段图像，几乎面对面，由哈勃太空望远镜与高级巡天相机获得。这一识别已被证实，以最高的天体测量精度，使用一个自适应光学图像的ESPRIK-II。早期的光谱和光度测量表明，这个SN是一个剥层的、核心塌陷的IIb型，其前身星（半径约为1 e11 cm）比研究充分的SN IIb 1993 J更致密。我们推断SN 2011 dh及其祖先的灭绝来自于低银河前景贡献，SN环境大致为太阳金属丰度。探测到的天体绝对星等M_V^0 ~ -7.7，有效温度~6000 K。这颗恒星的半径约为1 e13厘米，比SN祖先的半径更大。我们推测，检测到的恒星是一个不相关的恒星非常接近的实际祖星的位置，或者，更有可能的是，祖星的同伴在一个质量转移双星系统。在赫兹-罗素图中被探测到的恒星的位置与初始质量17- 19 Msun一致。即使在紫外线下，这颗恒星的光也可以轻易地掩盖一颗剥离的、紧凑的、非常热（~ 1 e5 K）的、富含氮的沃尔夫-拉叶星祖星的存在。
英文摘要：
We have identified a luminous star at the position of supernova (SN) 2011dh/PTF11eon, in pre-SN archival, multi-band images of the nearby, nearly face-on galaxy Messier 51 (M51) obtained by the Hubble Space Telescope with the Advanced Camera for Surveys. This identification has been confirmed, to the highest available astrometric precision, using a Keck-II adaptive-optics image. The available early-time spectra and photometry indicate that the SN is a stripped-envelope, core-collapse Type IIb, with a more compact progenitor (radius ~1e11 cm) than was the case for the well-studied SN IIb 1993J. We infer that the extinction to SN 2011dh and its progenitor arises from a low Galactic foreground contribution, and that the SN environment is of roughly solar metallicity. The detected object has absolute magnitude M_V^0 ~ -7.7 and effective temperature ~6000 K. The star's radius, ~1e13 cm, is more extended than what has been inferred for the SN progenitor. We speculate that the detected star is either an unrelated star very near the position of the actual progenitor, or, more likely, the progenitor's companion in a mass-transfer binary system. The position of the detected star in a Hertzsprung-Russell diagram is consistent with an initial mass of 17--19 Msun. The light of this star could easily conceal, even in the ultraviolet, the presence of a stripped, compact, very hot (~1e5 K), nitrogen-rich Wolf-Rayet star progenitor.
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