论文标题
$ {\ bf ^3he ^{\ bf +}} $的绿色银行望远镜观察
Green Bank Telescope Observations of ${\bf ^3He^{\bf +}}$: Planetary Nebulae
论文作者
论文摘要
我们使用绿色银行望远镜从四个银河行星星云的样本中搜索$^3he^+$排放：NGC 3242，NGC 6543，NGC 6826和NGC 7009。此后，大量和这些丰度主要是由恒星修饰的。在整个银河系磁盘中，$^3he^+$ $^3he^+$的观察表明，$^3he/h $丰度比率很小的变化 - “ $^3he $ plateau” - 表明$^3He $生产在星星中的净效果忽略不可。这与某些行星星云报道的$^3he/h $丰度比率相反。这种差异被称为“ $^3he $问题”。我们使用与$^3he^+$过渡同时观察到的无线电重组线来对这些观察结果实现的光谱灵敏度进行强有力的评估。我们在$ \ sim $ 1-2 MK强度下检测光谱线，但是在这些级别下，仪器效应损害了我们测量准确光谱线参数的能力。我们没有确认NGC 3242中$^3he^+$的先前检测报告，也无法从我们的任何来源中检测到$^3he^+$。该结果受到质疑，所有报告的星云都报告了$^3he^+$排放的所有检测。 $^3he/h $丰富的上限我们在这里为NGC 3242提供了与标准出现的$^3He $相矛盾的，因此要求某种类型的额外混合过程在低质量恒星中运行。
We use the Green Bank Telescope to search for $^3He^+$ emission from a sample of four Galactic planetary nebulae: NGC 3242, NGC 6543, NGC 6826, and NGC 7009. During the era of primordial nucleosynthesis the light elements $^2H$, $^3He$, $^4He$, and $^7Li$ were produced in significant amounts and these abundances have since been modified primarily by stars. Observations of $^3He^+$ in H II regions located throughout the Milky Way disk reveal very little variation in the $^3He/H$ abundance ratio -- the "$^3He$ Plateau" -- indicating that the net effect of $^3He$ production in stars is negligible. This is in contrast to much higher $^3He/H$ abundance ratios reported for some planetary nebulae. This discrepancy is known as the "$^3He$ Problem". We use radio recombination lines observed simultaneously with the $^3He^+$ transition to make a robust assessment of the spectral sensitivity that these observations achieve. We detect spectral lines at $\sim$ 1 -- 2 mK intensities, but at these levels instrumental effects compromise our ability to measure accurate spectral line parameters. We do not confirm reports of previous detections of $^3He^+$ in NGC 3242 nor do we detect $^3He^+$ emission from any of our sources. This result calls into question all reported detections of $^3He^+$ emission from any planetary nebula. The $^3He/H$ abundance upper limit we derive here for NGC 3242 is inconsistent with standard stellar production of $^3He$ and thus requires that some type of extra mixing process operates in low-mass stars.
