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arXiv 1004.0644astro-ph.EP
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温暖的尘埃盘:探索A星24 μ m碎片群

Warm dusty discs: Exploring the A star 24um debris population

R. Smith, M. C. Wyatt

摘要:

对碎片盘的研究表明,大多数系统都类似于EKB。在这项研究中,我们的目标是确定有多少IRAS 25 um对A星的过度是真实的,并调查尘埃的位置。我们用TIMMI 2、VISIR、Michelle和TReCS观测了一个A型和B型主序星的样本,这些恒星被报道为具有中红外过剩。我们通过对发射光谱进行综合建模,并采用旨在限制中红外成像辐射范围的建模技术,来限制碎片的位置。我们独立地确认了3个候选者周围的暖尘埃的存在:HD 3003,HD 80950和eta Tel。对于双星HD 3003的稳定性分析表明,尘埃要么是拱星的,位于约4天文单位,而双星的轨道大于14天文单位,要么尘埃位于不稳定的位置;有一些证据表明,它的过量发射在约20年的时间尺度上发生了时间演化。对于7个目标,我们提出了恒星周围尘埃位置的定量限制。我们证明了HD 71155周围的光盘必须有空间上不同的组件在2和60 AU。我们模拟目前的仪器的限制,并表明,大多数已知的A星碎片光盘,可以很容易地解决在18微米的8米仪器已经解决。来自未分辨成像的限制可以帮助区分椎间盘发射的竞争模型,但是分辨成像是确定椎间盘位置的关键。为扩展排放的探测极限建立模型,可有助于确定未来观测活动的目标。JWST上的MIRI将能够解决大多数已知的A星碎片盘人口。E-ELT上的METIS将提供机会,通过探测扩展发射来更彻底地探索热盘种群,其中校准精度限制了通过测光的盘探测,对于<10 pc的恒星,其水平低于1佐迪。

英文摘要:

(Abridged) Studies of debris discs have shown that most systems are analogous to the EKB. In this study we aim to determine how many IRAS 25um excesses towards A stars are real, and investigate where the dust lies. We observe with TIMMI2, VISIR, Michelle and TReCS a sample of A and B-type main sequence stars reported as having mid-IR excess. We constrain the location of the debris through combined modelling of the emission spectrum and a modelling technique designed to constrain the radial extent of emission in mid-IR imaging. We independently confirm the presence of warm dust around 3 of the candidates: HD3003, HD80950 and eta Tel. For the binary HD3003 a stability analysis indicates the dust is either circumstellar and lying at ~4 AU with the binary orbiting at >14AU, or the dust lies in an unstable location; there is some evidence for temporal evolution of its excess emission on a ~20 year timescale. For 7 of the targets we present quantitative limits on the location of dust around the star. We demonstrate that the disc around HD71155 must have spatially distinct components at 2 and 60AU. We model the limits of current instrumentation and show that most of the known A star debris discs which could be readily resolved at 18um on 8m instruments have been resolved. Limits from unresolved imaging can help distinguish between competing models of the disc emission, but resolved imaging is key to the determination of the disc location. Modelling of the detection limits for extended emission can be useful for targeting future observational campaigns. MIRI on the JWST will be able to resolve most of the known A star debris disc population. METIS on the E-ELT will provide the opportunity to explore the hot disc population more thoroughly by detecting extended emission where calibration accuracy limits disc detection through photometry, reaching levels below 1 zodi for stars at <10pc.

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