SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS
SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS
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A 型和晚期 B 型恒星周围尘埃碎片的斯皮策中红外光谱：小行星带类似物和幂律尘埃分布
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发表时间：
2009
期刊：
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通讯作者：
S. Wolf
中科院分区：
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作者：
F. Morales;M. W. Werner;G. Bryden;P. Plavchan;K. Stapelfeldt;G. Rieke;K. Su;C. Beichman;C.;K. Grogan;S. Kenyon;A. Moro;S. Wolf
利用Spitzer/红外光谱仪（IRS）低分辨率组件，观测到52颗主序星A型和晚B型恒星在5 ~ 35 μm波段的红外辐射，这些恒星在24 μm波段的红外辐射超过了预期值。除了两种情况外，在所有情况下都证实了中红外过量。虽然突出的光谱特征在任何光谱中都不明显，但我们观察到光谱能量分布的整体形状存在显著的多样性。大多数的IRS多余的光谱是一致的单温度黑体发射，暗示尘埃位于一个单一的轨道半径-一个狭窄的环。假设过量的排放源自人口的大黑体颗粒，尘埃温度范围从70至324 K，与190 K的中位数对应的距离为10 Au。然而，有13颗恒星的尘埃排放遵循幂律分布，Fν = F0λα，指数α在1.0到2.9之间。这些系统中的温暖尘埃必须跨越更大范围的轨道位置-一个扩展的磁盘。所有的恒星都被斯皮策/MIPS在70 μm波段观测到，50个多余的源中有27个被探测到（信噪比> 3）。大多数70 μm的通量暗示着一个较冷的、类似柯伊伯带的成分，它可能完全独立于IRS波长处探测到的类似小行星带的暖辐射。在70 μm波段，37个类黑体拟合源中有14个被探测到。然而，用幂律圆盘模型拟合的13个具有IRS过量发射的物体都在70 μm处被探测到（4个在外推幂律之上，3个在外推幂律之上，6个在外推幂律之下），这表明中红外IRS发射和远红外70 μm发射可能与这些源有关。总的来说，观测到的黑体和幂律热分布图显示碎片分布在各种各样的径向结构中，这些结构似乎与光谱类型或恒星年龄无关。另外43颗较暗的A型和晚期B型星也没有70 μm光度测定，斯皮策/IRS也观测到了;结果总结在附录B中。
Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 μm, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) to have excess infrared emission at 24 μm above that expected from the stellar photosphere. The mid-IR excess is confirmed in all cases but two. While prominent spectral features are not evident in any of the spectra, we observed a striking diversity in the overall shape of the spectral energy distributions. Most of the IRS excess spectra are consistent with single-temperature blackbody emission, suggestive of dust located at a single orbital radius—a narrow ring. Assuming the excess emission originates from a population of large blackbody grains, dust temperatures range from 70 to 324 K, with a median of 190 K corresponding to a distance of 10 AU. Thirteen stars however, have dust emission that follows a power-law distribution, Fν = F0λα, with exponent α ranging from 1.0 to 2.9. The warm dust in these systems must span a greater range of orbital locations—an extended disk. All of the stars have also been observed with Spitzer/MIPS at 70 μm, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 μm fluxes are suggestive of a cooler, Kuiper Belt-like component that may be completely independent of the asteroid belt-like warm emission detected at the IRS wavelengths. Fourteen of 37 sources with blackbody-like fits are detected at 70 μm. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 μm (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 μm emission may be related for these sources. Overall, the observed blackbody and power-law thermal profiles reveal debris distributed in a wide variety of radial structures that do not appear to be correlated with spectral type or stellar age. An additional 43 fainter A and late B type stars without 70 μm photometry were also observed with Spitzer/IRS; results are summarized in Appendix B.