论文标题
关于M型AGB恒星EP Aquarii I.高分辨率Alma和Sphere观测值的详细观察
A detailed view on the circumstellar environment of the M-type AGB star EP Aquarii I. High-resolution ALMA and SPHERE observations
论文作者
论文摘要
众所周知，凉爽进化的恒星是通过其密集而尘土飞扬的恒星风能富集星际介质的重要贡献者。对这些流出的高分辨率观察表明它们具有高度的形态复杂性。我们在四个过滤器中观察到带有ALMA的渐近巨型分支（AGB）恒星EP Aquarii，并在带6和VLT/Sphere/Zimpol中观察到可见的。两种乐器的角度分辨率均为0.025''。这些是对EP Aquarii的低分辨率2016 ALMA分析的后续观察，该观察结果表明，其风具有几乎面向的，螺旋式的赤道密度增强，并具有几乎极点双线性的双向外流。在螺旋的底部，SIO发射显示出在连续亮度峰的西部大约0.4''的明显发射空隙，并提议与同伴的存在有关。新的ALMA数据可以更好地解决内风，并揭示其在CO中观察到的形态与流体动力伴侣诱导的扰动一致。假设同伴的紫外线景点是SIO中发射空隙的原因，我们从孔的大小中推导了暂定伴侣的光谱特性。我们得出的结论是，最可能的伴侣候选人是白色矮人，质量在0.65至0.8 msol之间，尽管不能明确排除像太阳能伴侣。径向SIO发射显示周期性，低振幅扰动。我们暂时建议它们可能是AGB风与另一个更接近低质量伴侣的相互作用的结果。偏振球/Zimpol数据显示了围绕AGB恒星的圆形信号，半径为0.1'...
Cool evolved stars are known to be significant contributors to the enrichment of the interstellar medium through their dense and dusty stellar winds. High resolution observations of these outflows have shown them to possess high degrees of morphological complexity. We observed the asymptotic giant branch (AGB) star EP Aquarii with ALMA in band 6 and VLT/SPHERE/ZIMPOL in four filters the visible. Both instruments had an angular resolution of 0.025''. These are follow-up observations to the lower-resolution 2016 ALMA analysis of EP Aquarii, which revealed that its wind possesses a nearly face-on, spiral-harbouring equatorial density enhancement, with a nearly pole-on bi-conical outflow. At the base of the spiral, the SiO emission revealed a distinct emission void approximately 0.4'' to the west of the continuum brightness peak, which was proposed to be linked to the presence of a companion. The new ALMA data better resolve the inner wind and reveal that its morphology as observed in CO is consistent with hydrodynamical companion-induced perturbations. Assuming that photodissociation by the UV-field of the companion is responsible for the emission void in SiO, we deduced the spectral properties of the tentative companion from the size of the hole. We conclude that the most probable companion candidate is a white dwarf with a mass between 0.65 and 0.8 Msol , though a solar-like companion could not be definitively excluded. The radial SiO emission shows periodic, low-amplitude perturbations. We tentatively propose that they could be the consequence of the interaction of the AGB wind with another much closer low-mass companion. The polarised SPHERE/ZIMPOL data show a circular signal surrounding the AGB star with a radius of 0.1''...
