We report on 75 mas resolution, near-IR imaging spectroscopy within the central 30 lt-days of the Galactic center, taken with the new adaptive optics-assisted integral-field spectrometer SINFONI on the ESO VLT. To a limiting magnitude of K ~ 16, 9 of 10 stars in the central 04, and 13 of 17 stars out to 07 from the central black hole have spectral properties of B0-B9 main-sequence stars. Based on the 2.1127 μm He I line width, all brighter early-type stars have normal rotation velocities, similar to solar neighborhood stars. We combine the new radial velocities with SHARP/NACO astrometry to derive improved three-dimensional stellar orbits for six of these "S stars" in the central 05. Their orientations in space appear random. Their orbital planes are not co-aligned with those of the two disks of massive young stars 1''-10'' from Sgr A*. We can thus exclude the hypothesis that the S stars as a group inhabit the inner regions of these disks. They also cannot have been located/formed in these disks and then migrated inward within their planes. From the combination of their normal rotation and random orbital orientations, we conclude that the S stars were most likely brought into the central light-month by strong individual scattering events. The updated estimate of distance to the Galactic center from the S2 orbit fit is R0 = 7.62 ± 0.32 kpc, resulting in a central mass value of (3.61 ± 0.32) × 106 M☉. We happened to catch two smaller flaring events from Sgr A* during our spectral observations. The 1.7-2.45 μm spectral energy distributions of these flares are fit by a featureless, "red" power law of spectral index α' = -4 ± 1 (Sν ~ ν). The observed spectral slope is in good agreement with synchrotron models in which the infrared emission comes from accelerated, nonthermal, high-energy electrons in a radiatively inefficient accretion flow in the central R ~ 10RS region.
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机译：我们报告了银河中心30 lt天以内75 mas分辨率，近红外成像光谱学，该光谱学是在ESO VLT上使用新型自适应光学辅助积分场光谱仪SINFONI拍摄的。从中心黑洞到07为止，在中心04的10个恒星中有10个恒星中的9个星和17个恒星中的13个恒星具有B0-B9主序星的光谱特性。以2.1127μmHe I线宽为基础，所有较亮的早期型恒星均具有正常的旋转速度，类似于太阳邻星。我们将新的径向速度与SHARP / NACO占星术相结合，得出了05中心这些“ S”星中六颗的改进的三维恒星轨道。它们在空间中的方向似乎是随机的。它们的轨道平面与来自Sgr A *的两个大质量年轻恒星1''-10''的盘的轨道平面不对齐。因此，我们可以排除S恒星作为一组居住在这些盘的内部区域这一假设。它们也不能在这些磁盘中定位/形成然后在其平面内向内迁移。从它们的正常自转和随机轨道方向的组合中，我们得出结论，很强的单个散射事件将S星带入了中心光月。从S2轨道拟合到银河系中心的更新距离估计为R0 = 7.62±0.32 kpc，因此中心质量值为（3.61±0.32）×106M☉。在我们的光谱观察过程中，我们偶然发现了来自Sgr A *的两个较小的耀斑事件。这些耀斑的1.7-2.45μm光谱能量分布符合光谱指数α'= -4±1（Sν〜ν）的无特征“红色”幂律。观测到的光谱斜率与同步加速器模型非常吻合，在同步辐射器模型中，红外辐射来自中心R〜10RS区域中辐射效率低的积积流中的加速，非热，高能电子。
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