来自VPHAS +的Westerlund 2周围Carina臂的新OB明星候选人
New OB star candidates in the Carina Arm around Westerlund 2 from VPHAS+
摘要：
O型和早期B型恒星处于银河系生态的顶点，但在银河系中，可能只有少数恒星被发现。我们提出了一个试点研究的结果，以选择和parametrise OB恒星候选人在南银河平面，下降到一个极限的大小$g=20$。一个2平方度的领域捕捉船底座臂周围的年轻大质量星团，韦斯特伦德2，检查。确认OB星在这个集群被用来验证我们的识别方法，根据选择从$(u-g, g-r)$图的区域。我们的马尔可夫链蒙特卡罗拟合方法结合VPHAS+ $u, g, r, i$与公布的$J, H, K$测光，以获得后验概率分布的恒星参数$\log(\rm T_{\rm eff})$和距离模量，以及红化参数$A_0$和$R_V$。恒星参数足以确认OB状态，而红化参数的确定精度为$σ(A_0)\sim0.09$和$σ(R_V)\sim0.08$。有489个对象适合作为新的OB候选对象，早于$\sim$ B2。这个总数包括74颗可能的大质量O型星，5颗可能的蓝超巨星和32颗红次矮星。这使该区域先前已知和候选OB星的数量增加了近10倍。大多数新物体的距离可能在3到6千秒差距之间。我们已经证实了以前的研究结果，在这些较长的距离，这些视线需要与$3.5<R_V<4$的非标准红化的法律。
英文摘要：
O and early B stars are at the apex of galactic ecology, but in the Milky Way, only a minority of them may yet have been identified. We present the results of a pilot study to select and parametrise OB star candidates in the Southern Galactic plane, down to a limiting magnitude of $g=20$. A 2 square-degree field capturing the Carina Arm around the young massive star cluster, Westerlund 2, is examined. The confirmed OB stars in this cluster are used to validate our identification method, based on selection from the $(u-g, g-r)$ diagram for the region. Our Markov Chain Monte Carlo fitting method combines VPHAS+ $u, g, r, i$ with published $J, H, K$ photometry in order to derive posterior probability distributions of the stellar parameters $\log(\rm T_{\rm eff})$ and distance modulus, together with the reddening parameters $A_0$ and $R_V$. The stellar parameters are sufficient to confirm OB status while the reddening parameters are determined to a precision of $σ(A_0)\sim0.09$ and $σ(R_V)\sim0.08$. There are 489 objects that fit well as new OB candidates, earlier than $\sim$B2. This total includes 74 probable massive O stars, 5 likely blue supergiants and 32 reddened subdwarfs. This increases the number of previously known and candidate OB stars in the region by nearly a factor of 10. Most of the new objects are likely to be at distances between 3 and 6 kpc. We have confirmed the results of previous studies that, at these longer distances, these sight lines require non-standard reddening laws with $3.5<R_V<4$.
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