SOFIA/EXES红外荧光法检测狮子座红蜘蛛体内二氧化碳
Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES
摘要：
我们报告的检测热CO2在富O AGB星R狮子座的基础上进行的高光谱分辨率观测范围为12.8-14.3微米的梯形交叉梯形光谱仪（EXES）安装在平流层红外天文台（SOFIA）。我们在几个振动带中发现了~240条CO_2发射线。由于有利的多普勒频移，这些检测是可能的，这使我们能够避免大地CO2特征的污染。最高激发线涉及能量为~7000 K的能级。探测到的谱线很窄（平均去卷积宽度约为2.5 km/s）且很弱（通常小于连续谱的10%）。振转图显示，有三种不同的人口，温暖，热，非常热，与旋转温度约550，1150和1600 K，分别。从该图中，我们得出柱密度的下限为~2.2E+16 cm^{-2}。基于狮子座R包络模型的进一步计算表明，总柱密度可以高达7.0E+17 cm^{-2}，相对于H2的丰度约为2.5E-05。探测到的谱线可能是由于CO2分子从高能振动态去激发而形成的，这些振动态基本上由2.7和4.2 μ m处的强R Leo连续谱填充。
英文摘要：
We report on the detection of hot CO2 in the O-rich AGB star R Leo based on high spectral resolution observations in the range 12.8-14.3 um carried out with the Echelon-cross-Echelle Spectrograph (EXES) mounted on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We have found ~240 CO2 emission lines in several vibrational bands. These detections were possible thanks to a favorable Doppler shift that allowed us to avoid contamination by telluric CO2 features. The highest excitation lines involve levels at an energy of ~7000 K. The detected lines are narrow (average deconvolved width ~2.5 km/s) and weak (usually <10% the continuum). A ro-vibrational diagram shows that there are three different populations, warm, hot, and very hot, with rotational temperatures of ~550, 1150, and 1600 K, respectively. From this diagram, we derive a lower limit for the column density of ~2.2E+16 cm^{-2}. Further calculations based on a model of the R Leo envelope suggest that the total column density can be as large as 7.0E+17 cm^{-2} and the abundance with respect to H2 ~2.5E-05. The detected lines are probably formed due to de-excitation of CO2 molecules from high energy vibrational states, which are essentially populated by the strong R Leo continuum at 2.7 and 4.2 um.
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