M33中的至尊LBV之星GR290（罗马诺之星）。光学分光光度监测
The Extreme LBV Star GR290 (Romano's Star) in M33. Optical Spectrophotometric Monitoring
摘要：
我们研究了M33中的LBV星GR 290（罗马诺星）的长期S Dor型变率和目前的热相，以研究超大质量恒星的LBV和WNL阶段之间可能存在的联系。我们使用中分辨率光谱，获得WHT在2008年12月，当GR 290是在最小值（V = 18.6），以及新的低分辨率光谱和B V R I测光获得的Loiano和Cima Ekar望远镜在2007-2010年。我们确定了超过80个发射线在3100-10000 A的范围内，属于不同的物种和禁戒跃迁。许多谱线，特别是HeI三重谱线，都显示出天鹅座P的剖面，其a-e径向速度差为-300 ~-500 km/s。4630-4713 A的混合发射线和其他发射线的形状类似于WN 9星;混合反卷积显示HeII 4686 A有很强的宽分量，半高宽\simeq 1700 km/s。在2003年至2010年期间，这颗恒星经历了很大的光谱变化，在4630-4686 A的发射特征中看得最清楚。使用Crowther & Smith（1997）的晚WN光谱类型，GR 290明显地在WN 11和WN 8 -9光谱类型之间变化，越热的恒星其视星等越暗。GR 290的光谱-可见光光度关系让人想起了研究得最好的LBV的行为。在2008年的最低，我们发现显着减少的热光度，这可能是由于吸收新形成的拱星物质。我们认为，目前，宽的4686 A谱线和光学连续谱形成于中心WR区域，而窄的发射线光谱起源于一个延伸的、缓慢扩展的包层，该包层由之前高亮度阶段喷射的物质组成，并被电离。由中央核。GR 290可能刚刚进入从LBV状态到后期WN类型转换之前的阶段。
英文摘要：
We study the long term, S Dor-type variability and the present hot phase of the LBV star GR290 (Romano's Star) in M33 in order to investigate possible links between the LBV and WNL stages of very massive stars. We use intermediate resolution spectra, obtained with WHT in December 2008, when GR290 was at minimum (V = 18.6), as well as new low resolution spectra and B V R I photometry obtained with the Loiano and Cima Ekar telescopes during 2007-2010. We identify more than 80 emission lines in the 3100-10000 A range, belonging to different species and to forbidden transitions. Many lines, especially the HeI triplets, show a P Cygni profile with an a-e radial velocity difference from -300 to -500 km/s. The shape of the 4630-4713 A emission blend and of other emission lines resembles that of WN9 stars; the blend deconvolution shows that the HeII 4686 A has a strong broad component with FWHM \simeq 1700 km/s. During 2003-2010 the star underwent large spectral variations, best seen in the 4630-4686 A emission feature. Using the late-WN spectral types of Crowther & Smith (1997), GR290 apparently varied between the WN11 and WN8-9 spectral types, the hotter being the star the fainter its visual magnitude. This spectrum-visual luminosity anticorrelation of GR290 is reminiscent of the behaviour of the best studied LBVs. During the 2008 minimum we find a significant decrease in bolometric luminosity, which could be attributed to absorption by newly formed circumstellar matter. We suggest that, presently, the broad 4686 A line and the optical continuum are formed in a central WR region, while the narrow emission line spectrum originate in an extended, slowly expanding envelope, that is composed by matter ejected during previous high luminosity phases, and ionized by the central nucleus. GR290 could have just entered in a phase preceeding the transition from the LBV state to late WN type.
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