DUST AROUND R CORONAE BOREALIS STARS. I. SPITZER/INFRARED SPECTROGRAPH OBSERVATIONS
DUST AROUND R CORONAE BOREALIS STARS. I. SPITZER/INFRARED SPECTROGRAPH OBSERVATIONS
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DOI：
10.1088/0004-637x/739/1/37
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发表时间：
2011-07
期刊：
影响因子：
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通讯作者：
D. Aníbal García-Hernández;N. Kameswara Rao;D. Lambert
中科院分区：
文献类型：
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作者：
D. Aníbal García-Hernández;N. Kameswara Rao;D. Lambert
本文给出了31颗R型北冕恒星(RCB)的斯皮策红外光谱(5~37μm)。这些光谱与每个RCB在最大光下的光学和近红外光度学相结合，以汇编光谱能量分布(SED)。用黑体通量分布对SEDS进行了拟合，并估计了来自星际尘埃的红外通量与恒星发射的通量之比。31颗恒星中的29颗恒星与30年前的红外天文卫星(IRAS)的通量进行了比较：除了少数样本外，斯皮策和IRAS在12μm和25μm的通量基本上是相等的。对于这少数人来说，IRA与Spitzer流量之比超过三倍。异常值被认为是恒星，在那里尘埃云或尘埃喷发的形成是罕见的事件。在IRAS观测之前喷出的一次喷雾可能被斯皮策重新观测到，因为它是在距离RCB更远的地方喷出的较冷的喷雾。通常，经历更频繁的光学衰落的RCB具有一个星周环境，其中包含在恒星处隐含更大立体角的喷雾和准恒定的红外通量。然而，估计的对角和尘埃的黑体温度表明，在IRAS和Spitzer之间的时间间隔内，系统地演变为较低的固体角和较低的温度。这些RCB和LMC的尘埃排放在总光度24μm和颜色指数[8.0]−[24.0]方面是相似的。
Spitzer/infrared spectrograph (IRS) spectra from 5 to 37 μm for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at maximum light to compile a spectral energy distribution (SED). The SEDs are fitted with blackbody flux distributions and estimates are made of the ratio of the infrared flux from circumstellar dust to the flux emitted by the star. Comparisons for 29 of the 31 stars are made with the Infrared Astronomical Satellite (IRAS) fluxes from three decades earlier: Spitzer and IRAS fluxes at 12 μm and 25 μm are essentially equal for all but a minority of the sample. For this minority, the IRAS to Spitzer flux ratio exceeds a factor of three. The outliers are suggested to be stars where formation of a dust cloud or dust puff is a rare event. A single puff ejected prior to the IRAS observations may have been reobserved by Spitzer as a cooler puff at a greater distance from the RCB. RCBs which experience more frequent optical declines have, in general, a circumstellar environment containing puffs subtending a larger solid angle at the star and a quasi-constant infrared flux. Yet, the estimated subtended solid angles and the blackbody temperatures of the dust show a systematic evolution to lower solid angles and cooler temperatures in the interval between IRAS and Spitzer. Dust emission by these RCBs and those in the LMC is similar in terms of total 24 μm luminosity and [8.0]−[24.0] color index.