L483中一个光度和形态可变的红外星云
A Photometrically and Morphologically Variable Infrared Nebula in L483
摘要：
我们提出了窄和宽K波段观测的0/I类源IRAS 18148-0440，跨度17年。与L483暗星云中的这颗原恒星相关的红外星云在形态和光度上都是可变的，时间尺度只有几个月。这个星云看起来像是其他与年轻恒星有关的著名光学可见光可变星云的红外模拟物，例如哈勃的可变星云。与仙王座A一样，这是第一个被发现的只有在红外线下才能看到的大型可变星云之一。这个星云的变化很可能是由于云的亮度变化，而不是星云结构的任何运动。观测到的形态变化和光度变化的时间尺度仅比星云的光穿越时间长几倍，这表明星云的亮度发生了非常迅速的内在变化。我们的窄带观测还发现，H_2结在源东侧的距离是其西侧的近两倍，H_2排放比以前已知的CO流出更远。
英文摘要：
We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a time scale of only a few months. This nebula appears to be an infrared analogue to other well-known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a time scale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrow-band observations also found that H_2 knots are found nearly twice as far to the east of the source as to its west, and that H_2 emission extends farther east of the source than the previously known CO outflow.
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