标题： V39的性质：IC 1613星系中一个LBV候选体还是低金属量星系中的LBV假象？ 显示英文标题

标题： The nature of V39: an LBV candidate or LBV impostor in the very low metallicity galaxy IC 1613?

摘要： [删减] 上下文：已知的发光蓝变星（LBV）恒星或LBV候选体（LBVc）非常少，特别是在金属丰度低于大麦哲伦星云（SMC）的情况下。 LBV阶段对于大质量恒星的演化至关重要，但其与金属丰度的关系尚不清楚。 IC 1613中的V39是一个已知的光度变星，在B波段的变化超过1mag。 在其周期内。 这颗恒星之前被提议为银河系W Virginis和IC 1613红超巨星的投影，但其特征使其成为一个可能的LBVc。 方法：我们研究了V39的中分辨率蓝光和红光VLT-VIMOS光谱，覆盖了40天的时间跨度，并使用模型大气代码CMFGEN对综合光谱进行了定量分析。 结果：我们识别出强的巴尔末线和FeII P-Cygni轮廓，并且光谱呈现出一种混合特征，在蓝端类似于B-A超巨星，在红端类似于G型恒星。 没有检测到显著的Vrad变化，光谱变化在光度周期内很小。 我们的分析将V39置于LBV和LBVc区域的低光度部分，但它也与sgB[e]恒星一致。 结论：径向速度表明V39属于IC 1613。 缺乏Vrad变化和光谱变化排除了双星情景。 观测到的特征与W Virginis恒星不一致，这一可能性也被排除。 我们提出这颗恒星是一个B-A LBVc或sgB[e]恒星，周围有一个厚盘绕其旋转。 如果得到证实，V39将是目前已知的金属丰度最低的解析LBV候选体。 另外，它可能代表大质量恒星演化的新的瞬态阶段，即LBV伪装者。 显示英文摘要

摘要： [abridged] Context: Very few examples of luminous blue variable (LBV) stars or LBV candidates (LBVc) are known, particularly at metallicities below the SMC. The LBV phase is crucial for the evolution of massive stars, and its behavior with metallicity is poorly known. V39 in IC 1613 is a well-known photometric variable, with B-band changes larger than 1mag. over its period. The star, previously proposed to be a projection of a Galactic W Virginis and an IC 1613 red supergiant, shows features that render it a possible LBVc. Method: We investigate mid-resolution blue and red VLT-VIMOS spectra of V39, covering a time span of 40 days, and perform a quantitative analysis of the combined spectrum using the model atmosphere code CMFGEN. Results: We identify strong Balmer and FeII P-Cygni profiles, and a hybrid spectrum resembling a B-A supergiant in the blue and a G-star in the red. No significant Vrad variations are detected, and the spectral changes are small over the photometric period. Our analysis places V39 in the low-luminosity part of the LBV and LBVc region, but it is also consistent with a sgB[e] star. Conclusions: The radial velocity indicates that V39 belongs to IC 1613. The lack of Vrad changes and spectroscopic variations excludes binary scenarios. The features observed are not consistent with a W Virginis star, and this possibility is also discarded. We propose that the star is a B-A LBVc or sgB[e] star surrounded by a thick disk precessing around it. If confirmed, V39 would be the lowest metallicity resolved LBV candidate known to date. Alternatively, it could represent a new transient phase of massive star evolution, an LBV impostor.