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arXiv 0901.2447astro-ph.GA
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环绕着HR Car的尘埃星云:斯皮策观测

The dusty Nebula surrounding HR Car: a Spitzer view

G. Umana, C. S. Buemi, C. Trigilio, J. L. Hora, G. G. Fazio, P. Leto

摘要:

我们目前的中红外观测的银河系亮蓝变星(LBV)HR车及其相关的星云进行与斯皮策太空望远镜使用IRAC和IRS,作为GTO计划的一部分,旨在研究恒星喷出物从演化的恒星。我们的观测揭示了内部星云丰富的中红外光谱,显示了固态和原子气体的特征。强低激发原子精细结构线,如$ 26.0 μ$ m [ \ion{Fe}{2} ]和$ 34.8 μ$ m [ \ion{Si}{2} ],表明,第一次,在这个对象类的PDR的存在。虽然低激发气体的物理和化学似乎是由光解为主,可能的贡献,由于冲击可以推断出的证据,气相铁丰度增强。无定形硅酸盐的存在,推断从观测到的特征广泛的功能在$10 μ$ m位于内部星云,表明尘埃已经形成在LBV爆发。这与在其他可能更进化的银河系LBV中检测到的晶体尘埃形成对比,这与在红超巨星中观察到的晶体尘埃相似。这被认为是爆发前进化阶段产生尘埃的证据。

英文摘要:

We present mid-IR observations of the Galactic Luminous Blue Variable (LBV) HR Car and its associated nebula carried out with the Spitzer Space Telescope using both IRAC and IRS, as part of a GTO program aimed to study stellar ejecta from evolved stars. Our observations reveal a rich mid-IR spectrum of the inner nebula showing both solid state and atomic gas signatures. Strong low-excitation atomic fine structure lines such as $ 26.0 μ$m [\ion{Fe}{2}] and $ 34.8 μ$m [\ion{Si}{2}], indicate, for the first time, the presence of a PDR in this object class. While the physics and chemistry of the low-excitation gas appears to be dominated by photodissociation, a possible contribution due to shocks can be inferred from the evidence of gas phase Fe abundance enhancement. The presence of amorphous silicates, inferred from the observed characteristic broad feature at $10 μ$m located in the inner nebula, suggests that dust has formed during the LBV outburst. This is in contrast with the detection of crystalline dust in other probably more evolved Galactic LBVs, which is similar to the crystalline dust observed in red supergiants. This has been considered to be evidence of dust production during evolutionary phases prior to the outburst.

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