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arXiv 0806.0067astro-ph
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探索低至~ 550 K的亚恒星温度状态

Exploring the substellar temperature regime down to ~550K

Ben Burningham, D. J. Pinfield, S. K. Leggett, M. Tamura, P. W. Lucas, D. Homeier, A. Day-Jones, H. R. A. Jones, J. R. A. Clarke, M. Ishii, M. Kuzuhara, N. Lodi… 展开作者

Ben Burningham, D. J. Pinfield, S. K. Leggett, M. Tamura, P. W. Lucas, D. Homeier, A. Day-Jones, H. R. A. Jones, J. R. A. Clarke, M. Ishii, M. Kuzuhara, N. Lodieu, M. R. Zapatero Osorio, B. P. Venemans, D. J. Mortlock, D. Barrado y Navascues, E. L. Martin, A. Magazzu

备注：
MNRAS accepted. 17 pages, 15 figures. Abstract abridged. Revised to reflect referees comments. Revisions include: slightly revised Teff estimate for ULAS1335; additional figure demonstrating spectral type index degeneracy; revised discussion of NH3-H index; revised IRAC photometry based on re-reduction (small changes)
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摘要：

我们在UKIRT红外深空巡天（UKIDSS）第三次数据发布中发现了三颗非常晚的T矮星：ULAS J101721.40+011817.9（ULAS 1017），ULAS J123828.51+095351.3（ULAS 1238）和ULAS J133553.45+113005.2（ULAS 1335）。我们详细介绍了所有三种光源的光学和近红外测光，以及ULAS 1335的中红外测光。我们使用每个源的近红外光谱将光谱类型T8 p（ULAS 1017），T8.5（ULAS 1228）和T9（ULAS 1335）分配给这些对象。我们估计ULAS 1017具有750 < Teff <850 K，5.0 < log g < 5.5，假设太阳金属丰度，年龄为1.6-15 Gyr，质量为33-70 MJ，距离为31-54 pc。我们将Burgasser等人（2006）的统一方案扩展到T9型，并建议包括WJ指数来取代现在饱和的J带指数。ULAS 1335与ULAS J003402.77-005206.7和CFBDS J005910.90-011401.3的光谱类型相同。与ULAS 1335的光谱比较表明，温度低于600 K。我们发现ULAS 1335在近红外到中红外的颜色非常红，H-[4.49]=4.34+/-0.04。这是T矮星观测到的最红的近中红外颜色，支持Teff <600 K，我们估计ULAS 1335的Teff约为550- 600 K。我们估计ULAS 1335的年龄为0.6-5.3 Gyr，质量为15-31 MJ，距离为8-12 pc。

英文摘要：

We report the discovery of three very late T dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS) Third Data Release: ULAS J101721.40+011817.9 (ULAS1017), ULAS J123828.51+095351.3 (ULAS1238) and ULAS J133553.45+113005.2 (ULAS1335).We detail optical and near-infrared photometry for all three sources, and mid-infrared photometry for ULAS1335. We use near-infrared spectra of each source to assign spectral types T8p (ULAS1017), T8.5 (ULAS1228) and T9 (ULAS1335) to these objects. We estimate that ULAS1017 has 750 < Teff < 850K, and 5.0 < log g < 5.5, assuming solar metallicity, an age of 1.6-15 Gyr, a mass of 33-70 MJ and lies at a distance of 31-54 pc. We extend the unified scheme of Burgasser et al. (2006) to the type T9 and suggest the inclusion of the WJ index to replace the now saturated J-band indices. ULAS1335 is the same spectral type as ULAS J003402.77-005206.7 and CFBDS J005910.90-011401.3. Comparison of model spectra with that of ULAS1335 suggest a temperature below 600K. We find ULAS1335 to be extremely red in near to mid-infrared colours, with H-[4.49]=4.34+/-0.04. This is the reddest near to mid-infrared colour yet observed for a T dwarf, which supports Teff < 600K, and we estimate Teff ~550-600K for ULAS1335. We estimate that ULAS1335 has an age of 0.6-5.3 Gyr, a mass of 15-31 MJ and lies at a distance of 8-12 pc.

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