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arXiv 2008.01108astro-ph.SRastro-ph.GA
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探索红超巨星的质量损失历史

Exploring the Mass Loss Histories of the Red Supergiants

Roberta M. Humphreys, Greta Helmel, Terry J. Jones, Michael S. Gordon

摘要:

我们报告中,以远红外成像和光度从7至37微米的SOFIA/FORCAST和2微米的自适应光学成像与LBTI/LMIRCam的大样本的红超巨星(RSG)在四个银河系的集群; RSGC 1,RSGC 2 =斯蒂芬森2,RSGC 3,和NGC 7419。这些星团中的红超巨星涵盖了它们的亮度和初始质量的预期范围,从大约9到超过25个太阳质量。这个星群包括了非常晚型的RSG,例如可能接近RSG阶段末期的MY Cep、高质量损失脉泽源、黄超巨星和后RSG候选者。许多恒星和几乎所有最明亮的恒星都具有光谱能量分布(SED),在最长波长处具有扩展的红外过量辐射。为了最好地模拟它们的SED,我们使用具有可变径向密度分布函数的DUSTY来估计它们的质量损失率。我们对42颗RSG的质量损失率-光度关系基本上遵循经典的德雅格曲线,但在光度低于10^5太阳光度时,我们发现大量的红超巨星的质量损失率低于德雅格关系。当光度高于10^5太阳光度时,会有一个快速的转变,向更高的质量损失率过渡,接近并与德雅格曲线重叠。我们建议不要使用线性关系或单一曲线,经验质量损失率-亮度关系可以用宽带更好地表示。有趣的是,在约10^5 Lsun时向更高质量损失率的转变大约对应于18 - 20 Msun的初始质量,这接近RSG变为II型SNe的上限。

英文摘要:

We report mid- to far-infrared imaging and photomety from 7 to 37 microns with SOFIA/FORCAST and 2 micron adaptive optics imaging with LBTI/LMIRCam of a large sample of red supergiants (RSGs) in four Galactic clusters; RSGC1, RSGC2=Stephenson 2, RSGC3, and NGC 7419. The red supergiants in these clusters cover their expected range in luminosity and initial mass from approximately 9 to more than 25 Solar masses. The population includes examples of very late-type RSGs such as MY Cep which may be near the end of the RSG stage, high mass losing maser sources, yellow hypergiants and post-RSG candidates. Many of the stars and almost all of the most luminous have spectral energy distributions (SEDs) with extended infrared excess radiation at the longest wavelengths. To best model their SEDs we use DUSTY with a variable radial density distribution function to estimate their mass loss rates. Our mass loss rate -- luminosity relation for 42 RSGs basically follows the classical de Jager curve, but at luminosities below 10^5 Solar luminosities we find a significant population of red supergiants with mass loss rate below the de Jager relation. At luminosities above 10^5 Solar luminosities there is a rapid transition to higher mass loss rates that approximates and overlaps the de Jager curve. We recommend that instead of using a linear relation or single curve, the empirical mass loss rate -- luminosity relation is better represented by a broad band. Interestingly, the transition to much higher mass loss rates at about 10^5 Lsun corresponds approximately to an initial mass of 18 --20 Msun which is close to the upper limit for RSGs becoming Type II SNe.

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