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arXiv 1306.3100astro-ph.EP
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昴星团太阳系外行星的直接成像搜索

Direct Imaging Search for Extrasolar Planets in the Pleiades

Kodai Yamamoto, Taro Matsuo, Hiroshi Shibai, Yoichi Itoh, Mihoko Konishi, Jun Sudo, Ryoko Tanii, Misato Fukagawa, Takahiro Sumi, Tomoyuki Kudo, Jun Hashimoto, N… 展开作者

Kodai Yamamoto, Taro Matsuo, Hiroshi Shibai, Yoichi Itoh, Mihoko Konishi, Jun Sudo, Ryoko Tanii, Misato Fukagawa, Takahiro Sumi, Tomoyuki Kudo, Jun Hashimoto, Nobuhiko Kusakabe, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph Carson, Thayne Currie, Sebastian E. Egner, Markus Feldt, Miwa Goto, Carol Grady, Olivier Guyon, Yutaka Hayano, Masahiko Hayashi, Saeko Hayashi, Thomas Henning, Klaus Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Ryo Kandori, Gillian R. Knapp, Masayuki Kuzuhara, Jungmi Kwon, Mike McElwain, Shoken Miyama, Jun-Ichi Morino, Amaya Moro-Martin, June Nishikawa, Tetsuo Nishimura, Tae-Soo Pyo, Eugene Serabyn, Hiroshi Suto, Ryuji Suzuki, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, John Wisniewski, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda, Motohide Tamura

摘要:

我们在斯巴鲁望远镜上使用HiCIAO结合自适应光学AO 188,在$H$和$K_{S}$波段对昴星团(1.25亿年,1.35秒差距)中恒星周围的太阳系外行星进行了成像调查。我们在9颗恒星周围的$H$带中发现了13个亮度小于14.5等的伴星。这13颗恒星中有5颗被确认为背景星,通过测量它们的自行。其中一颗在第二个纪元的观测中没有发现,因此不是背景或伴星。一种是多历元图像,但其自行精度不足以判断其是否为背景物体。其他四个候选者正在等待第二个历元观测以确定它们的自行。最后,剩下的2颗被证实是分别围绕HD 23514(G 0)和HII 1348(K5)运行的60颗$M_{J}$褐矮星伴星,与先前的研究报告相同。在我们的观测中,在距离中心恒星1 ''.5以外的$H$波段中,点源的平均检测限为20.3等。在此探测极限的基础上,我们计算出对于质量为6 ~ 12木星质量、半长轴为50--1000天文单位的行星,探测效率为90%。为此,我们从RV观测中推断出行星质量和半长轴的分布,并采用了Baraffe等人(2003)的行星演化模型。由于没有探测到行星,我们估计这样的行星在昴星团一颗恒星周围的频率低于17.9%($2σ$)。

英文摘要:

We carried out an imaging survey for extrasolar planets around stars in the Pleiades (125 Myr, 135 pc) in the $H$ and $K_{S}$ bands using HiCIAO combined with the adaptive optics, AO188, on the Subaru telescope. We found 13 companion candidates fainter than 14.5 mag in the $H$ band around 9 stars. Five of these 13 were confirmed to be background stars by measurement of their proper motion. One was not found in the second epoch observation, and thus was not a background or companion object. One had multi-epoch image, but the precision of its proper motion was not sufficient to conclude whether it was background object. Four other candidates are waiting for second epoch observations to determine their proper motion. Finally, the remaining 2 were confirmed to be 60 $M_{J}$ brown dwarf companions orbiting around HD 23514 (G0) and HII 1348 (K5) respectively, as had been reported in previous studies. In our observations, the average detection limit for a point source was 20.3 mag in the $H$ band beyond 1''.5 from the central star. On the basis of this detection limit, we calculated the detection efficiency to be 90% for a planet with 6 to 12 Jovian masses and a semi-major axis of 50--1000 AU. For this we extrapolated the distribution of planet mass and semi-major axis derived from RV observations and adopted the planet evolution model of Baraffe et al. (2003). As there was no detection of a planet, we estimated the frequency of such planets to be less than 17.9% ($2σ$) around one star of the Pleiades cluster.

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