High-mass binaries - a unique laboratory to study the formation and evolution of stars and for measuring cosmic distances

大质量恒星似乎在所有恒星中具有最高的多重率，这增加了被观测为食双星(EB)系统的机会。因此，早期类型的EBS不仅是研究高质量恒星性质的独特实验室，而且由于它们的亮度，它们还有可能测量到附近星系的精确距离，从而显著改进基于造父变星和SNIa的哈勃常数测定。我们的档案包含大约3000个O星和5000个B星光谱，代表着一个固体-可能是最大的-大质量恒星的均匀、多历元、高S/N光谱的集合-其中约80个Sb2系统在O_3-O_9范围内，以及90个B-B星系范围内。同样，我们对南银河系的多波段光度测量银盘调查在近10年的时间里产生了高精度的光曲线，揭示了大约85,000个可变天体，其中超过85%是以前不知道的变星。这份光度学档案包括473颗O星和1000多颗B星，其中41颗O型EBS和约300颗B型EBS。在这个项目中，我们想要通过将我们的高质量EB光曲线和我们的多历元高分辨率光谱结合起来，对感兴趣的天体进行详细的调查，以解决与大质量恒星有关的主要问题，即：恒星参数，如质量、质量比、光度、半径、丰度、周期等。密切的多个相互作用系统的起源和演化-较高多样性系统的探测和研究-多个系统中单个组件的质量转移和自转。分离的双线光谱EBS提供了一个独特的机会，可以测量到附近星系的准确距离。通过早期EBS的高精度V-K测量，我们将解决与表面亮度-颜色关系技术校准有关的主要问题，使其成为目前2MPC体积的单个EB系统获得2%距离的优秀工具，随着未来极大望远镜的出现，距离将达到30MPC。在本项目中，我们将测量M31中两个系统的1.5-2%的几何距离，M33和IC1613各有一个系统，这将极大地提高基于EB值的这些星系的距离测定。特别是，我们将校准造父变星的P-L关系对金属丰度的依赖，这将是迈向精确到1%的哈勃常数测定的基本和必要的一步。两个团队的不同专业知识的结合将允许开发双星系统的巨大潜力来研究恒星的形成和演化，并改进河外距离尺度的校准。所获得的结果将对现代天体物理学的许多不同领域产生强烈影响：恒星形成、恒星演化、附近星系的研究和宇宙学。

High-mass stars seem to have the highest multiplicity rate among all stars which increases the chance to be observed also as eclipsing binary (EB) systems. As a consequence early-type EBs are not only a unique laboratory to study properties, of high-mass stars but – due to their brightness – they have also the potential for measuring accurate distances to nearby galaxies, and thus to significantly improve the Hubble constant determination based on Cepheids and SN Ia.Our archive, containing about 3000 O- and 5000 B-star spectra, represents a solid – probably the largest – collection of homogeneous, multi-epoch, high S/N spectra for high-mass stars – among them about 80 SB2 systems in the range O3 – O9 and 90 SB2 systems in the range B0 – B9. Likewise, our multiband photometric Galactic Disk Survey of the southern Milky Way has produced high-precision light curves over a period of almost 10 years and revealed about 85,000 variable objects of which more than 85% were not known previously as variables. This photometric archive comprises 473 O and more than 1000 B stars – among them 41 O-type EBs and about 300 B-type EBs.With the present project we want to go into a detailed investigation of interesting objects by combining our high-quality EB light curves with our multi-epoch high-resolution spectra to attack the major questions with respect to high-mass stars, i.e.- Stellar parameters like mass, mass-ratio, luminosity, radius, abundances, period, etc.- Origin and evolution of close multiple and interacting systems - Detection and investigation of higher multiplicity systems- Mass transfer and rotation of individual components in multiple systemsApart from exploring stellar properties, detached double-lined spectroscopic EBs offer a unique opportunity to measure accurate distances to nearby galaxies. By high-precision V – K measurements of early-type EBs we will solve the main problem related to the calibration of the surface brightness – color relation technique making it an excellent tool for obtaining 2% distances to individual EB systems in a volume of 2 Mpc now, and up to 30 Mpc with the advent of future extremely large telescopes.During the present project we will measure 1.5 – 2% geometrical distances to two systems in M31, one system in M33 and one in IC 1613 and thus will significantly improve distance determinations to these galaxies based on the EBs.In particular we will calibrate the dependence of P-L relations of Cepheids on metallicity which will be a fundamental and necessary step towards a Hubble constant determination accurate to 1%.The combination of different expertizes of both teams will allow to exploit huge potential of binary systems to study both star formation and evolution, and improve the calibration of the extragalactic distance scale. The obtained results will have strong impact on many different fields of modern astrophysics: star formation, stellar evolution, studies of nearby galaxies and cosmology.