60% of the A star members of the 12 Myr old beta Pictoris moving group (BPMG) show significant excess emission in the mid-infrared, several million years after the proto-planetary disk is thought to disperse. Theoretical models suggest this peak may coincide with the formation of Pluto-sized planetesimals in the disk, stirring smaller bodies into collisional destruction. Here we present resolved mid-infrared imaging of the disk of eta Tel (A0V in the BPMG) and consider its implications for the state of planet formation in this system. eta Tel was observed at 11.7 and 18.3um using T-ReCS on Gemini South. The resulting images were compared to simple disk models to constrain the radial distribution of the emitting material. The emission observed at 18.3um is shown to be significantly extended beyond the PSF along a position angle 8 degrees. This is the first time dust emission has been resolved around eta Tel. Modelling indicates that the extension arises from an edge-on disk of radius 0.5 arcsec (~24 AU). Combining the spatial constraints from the imaging with those from the spectral energy distribution shows that >50% of the 18um emission comes from an unresolved dust component at ~4 AU. The radial structure of the eta Tel debris disk is reminiscent of the Solar System, suggesting that this is a young Solar System analogue. For an age of 12Myr, both the radius and dust level of the extended cooler component are consistent with self-stirring models for a protoplanetary disk of 0.7 times minimum mass solar nebula. The origin of the hot dust component may arise in an asteroid belt undergoing collisional destruction, or in massive collisions in ongoing terrestrial planet formation.
The Insignificance of P-R Drag in Detectable Extrasolar Planetesimal Belts
本文考虑了一个简单的模型，在这个模型中，在一个小行星带中产生的尘埃由于P-R阻力而向恒星迁移，并在途中与其他尘埃颗粒发生破坏性碰撞。假设尘埃都是相同大小的，那么得到的表面密度分布可以通过解析推导出来，并且只取决于参数eta 0 = 5000 τ *sqrt（Mstar/r）/beta;这个参数可以通过假设beta=0.5的观测来确定。对于大质量的带，其中eta 0>>1的尘埃被限制在微行星带，而更纤细的带，其中eta 0 <<1，其表面密度随着与恒星的距离而恒定。从距离不同质量恒星不同距离的星子带尘埃的发射光谱可以看出，迄今为止探测到的尘埃带应该是eta 0>>1，eta 0 <<1 are hard to detect as they are much fainter than the stellar photosphere. This is confirmed for a sample of 37 debris disk candidates for which eta0 was determined to be >10。这意味着这些盘如此巨大，以至于相互碰撞会阻止尘埃到达这些系统的内部区域，并且在研究它们的动力学时可以忽略P-R阻力。应重新考虑通过P-R阻力将粒子捕获到行星共振中而在碎片盘中形成结构的模型。然而，由于碰撞并不能100%地阻止尘埃，这就意味着，…
We report the first scattered light detection of a dusty debris disk surrounding the F2V star HD 15115 using the Hubble Space Telescope in the optical, and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detected to ~315 AU radius, whereas the west side of the disk has radius >550 AU. We find a blue optical to near-infrared scattered light color relative to the star that indicates grain scattering properties similar to the AU Mic debris disk. The existence o…
The Complete Census of 70-um-Bright Debris Disks within the FEPS (Formation and Evolution of Planetary Systems) Spitzer Legacy Survey of Sun-like Stars
Spitzer Observations of G Dwarfs in the Pleiades: Circumstellar Debris Disks at 100 Myr Age
从斯皮策太空望远镜的波长范围从3.6到70微米的通量和上限提供了20个太阳质量的昴星团成员。其中一颗恒星可能有中红外线过剩，另外两颗可能有过剩，可能是由于星周碎片盘。对于在MIPS波长处具有最大、最安全的过量通量的恒星HII 1101，我们导出Log（L[尘埃]/L[太阳]）~ -3.8，碎片盘质量估计为4.2 x 10^-5 M（地球），假设尘埃颗粒大小均匀，为10微米。大型碰撞事件产生了短暂的过量的小尘埃颗粒，对于我们的大约1亿年前的昴星团G矮星样本来说，这种盘状瞬态的频率大约是10%。对于没有检测到24-70微米超差的恒星，其通量的上限对应于其盘质量的约3 sigma上限，使用MIPS 24微米上限为6 x 10^-6 M（地球），或使用MIPS 70微米上限为2 x 10^-4 M（地球）。这些上限盘质量（分别为“暖”和“冷”尘埃）大致一致，但略低于启发式模型的预测，该模型基于从太阳柯伊伯带的当前属性向后推断的“平均”太阳质量恒星碎片盘的演化。
