Melnick 34：已知最大的双星系统
Weighing Melnick 34: the most massive binary system known
摘要：
在这里，我们确认Melnick 34，一颗位于大麦云的剑鱼座30区域的X射线亮星，是一颗由WN 5 h + WN 5 h组成的SB 2双星。我们目前的轨道解决方案，使用26个历元的VLT/UVES光谱和22个历元的档案双子座/GMOS光谱。径向速度监测和自动模板拟合方法都揭示了一个类似的高偏心率系统，质量比接近1，轨道周期与Pollock等人先前推导的155.1 +/- 1天X射线光变曲线周期一致。我们赞成的解决方案推导出偏心率为0.68 +/- 0.02，质量比为0.92 +/- 0.07，给出最小质量Ma_sin^{3}（i）= 65 +/- 7 Msun和Mb_sin^{3}（i）= 60 +/- 7 Msun。使用WN 5 h模板和CMFGEN的光谱建模揭示了每个组分的T ~53 kK的温度和log（La/Lsun）= 6.43 +/- 0.08和log（Lb/Lsun）= 6.37 +/- 0.08的光度，由此BONSAI演化建模给出了Ma = 139（+21，-18）Msun和Mb = 127（+17，-17）Msun，年龄约为0.6百万年。如果Mk 34的倾角为i ~50°，光谱和动力学质量会一致，使Mk 34成为已知质量最大的双星，也是研究碰撞风双星性质的绝佳候选者。在2-3百万年内，Mk 34的两个组成部分预计都将演化成恒星质量的黑洞，假设双星系统幸存下来，Mk 34将成为潜在的双星黑洞合并的祖先和引力波源。
英文摘要：
Here we confirm Melnick 34, an X-ray bright star in the 30 Doradus region of the Large Magellanic Cloud, as an SB2 binary comprising WN5h+WN5h components. We present orbital solutions using 26 epochs of VLT/UVES spectra and 22 epochs of archival Gemini/GMOS spectra. Radial-velocity monitoring and automated template fitting methods both reveal a similar high eccentricity system with a mass ratio close to unity, and an orbital period in agreement with the 155.1 +/- 1 day X-ray light curve period previously derived by Pollock et al. Our favoured solution derived an eccentricity of 0.68 +/- 0.02 and mass ratio of 0.92 +/- 0.07, giving minimum masses of Ma_sin^{3}(i) = 65 +/- 7 Msun and Mb_sin^{3}(i) = 60 +/- 7 Msun. Spectral modelling using WN5h templates with CMFGEN reveals temperatures of T ~53 kK for each component and luminosities of log(La/Lsun) = 6.43 +/- 0.08 and log(Lb/Lsun) = 6.37 +/- 0.08, from which BONNSAI evolutionary modelling gives masses of Ma = 139 (+21,-18) Msun and Mb = 127 (+17,-17) Msun and ages of ~0.6 Myrs. Spectroscopic and dynamic masses would agree if Mk34 has an inclination of i ~50°, making Mk34 the most massive binary known and an excellent candidate for investigating the properties of colliding wind binaries. Within 2-3 Myrs, both components of Mk34 are expected to evolve to stellar mass black holes which, assuming the binary system survives, would make Mk34 a potential binary black hole merger progenitor and gravitational wave source.
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