标题： X-Shooting ULLYSES：低金属丰度的大质量星 VII. 小麦哲伦云中B超巨星的恒星和风的性质 显示英文标题

标题： X-Shooting ULLYSES: Massive stars at low metallicity VII. Stellar and wind properties of B supergiants in the Small Magellanic Cloud

摘要： 大背景。 超巨星（BSGs）代表了主序星与大质量恒星更极端演化阶段之间的重要联系。此外，由于它们位于热星区域的较冷一端，确定它们的风特性对于限制大质量恒星的演化和反馈至关重要，例如，它们可能表现出双稳定跳跃现象。 目标。 我们对ULLYSES和XShootU数据集中的18个小型麦哲伦云（SMC）BSG样本进行了详细分析。我们的UV和光学分析涵盖了从B0到B8的BSG——包括双稳定跳跃区域。我们的目标是评估它们的演化状态，并验证它们的风特性如何反映低金属丰度环境中的双稳定跳跃现象。 方法。 我们使用CMFGEN模型化了我们样本的光谱和测光数据（从UV到红外）。我们将结果与不同的演化模型、文献中OB星的先前测定以及双稳定跳跃处不同的质量损失配方进行了比较。此外，我们提供了SMC中包括X射线的第一组BSG模型。 结果。 （i）在一个单一恒星演化的框架内，早期BSG的演化状态似乎不如晚期BSG那样明确，后者与氢壳燃烧模型一致。 （ii）UV分析显示证据表明BSG大气中含有X射线，我们为此提供了约束条件。总的来说，我们发现早期BSG的X射线亮度更高（接近标准log(L_X/L) ~ -7）。对于较冷的BSG，较低值更优选，log(L_X/L) ~ -8.5。 （iii）获得的质量损失率既没有显示出跳跃也没有单调地随温度下降。相反，观察到了相当恒定的趋势，这与银河系BSG中发现的增加相矛盾。 （iv）风速随温度的变化在~19kK处表现出急剧下降，这与银河系BSG中观察到的情况相似。 显示英文摘要

摘要： Context. B supergiants (BSGs) represent an important connection between the main sequence and more extreme evolutionary stages of massive stars. Additionally, lying toward the cool end of the hot star regime, determining their wind properties is crucial to constrain the evolution and feedback of massive stars as, for instance, they might manifest the bi-stability jump phenomenon. Aims. We undertake a detailed analysis of a representative sample of 18 Small Magellanic Cloud (SMC) BSGs within the ULLYSES and XShootU datasets. Our UV and optical analysis spans BSGs from B0 to B8 - covering the bi-stability jump region. We aim to evaluate their evolutionary status and verify what their wind properties say about the bi-stability jump in a low-metallicity environment. Methods. We used the CMFGEN to model the spectra and photometry (from UV to infrared) of our sample. We compare our results with different evolutionary models, with previous determinations in the literature of OB stars, and with diverging mass-loss recipes at the bi-stability jump. Additionally, we provide the first BSG models in the SMC including X-rays. Results. (i) Within a single-stellar evolution framework, the evolutionary status of early BSGs seem less clear than that of late BSGs, which agree with H-shell burning models. (ii) UV analysis shows evidence that BSGs contain X-rays in their atmospheres, for which we provide constraints. In general, we find higher X-ray luminosity (close to the standard log(L_X/L) ~ -7) for early BSGs. For cooler BSGs, lower values are preferred, log(L_X/L) ~ -8.5. (iii) The obtained mass-loss rates suggest neither a jump nor a monotonic decrease with temperature. Instead, a rather constant trend is observed, which is at odds with the increase found for Galactic BSGs. (iv) The wind velocity behavior with temperature shows a sharp drop at ~19 kK, similar to what is observed for Galactic BSGs.