Planets around evolved intermediate-mass stars - I. Two substellar companions in the open clusters NGC 2423 and NGC 4349
Planets around evolved intermediate-mass stars - I. Two substellar companions in the open clusters NGC 2423 and NGC 4349
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DOI：
10.1051/0004-6361:20077375
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发表时间：
2007-06
影响因子：
6.5
通讯作者：
C. Lovis;M. Mayor
中科院分区：
文献类型：
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作者：
C. Lovis;M. Mayor
上下文人们正在作出许多努力来确定太阳系外行星系统的特征，并揭示行星形成的基本机制。这个问题的一个重要方面是了解行星的形成过程如何取决于母星星的质量，这一点在很大程度上仍然未知。特别是，由于迄今为止发现的大多数行星都围绕太阳质量的恒星运行，因此对更大质量恒星周围的行星形成知之甚少。目标。为了研究这一点，我们提出了第一个结果，从径向速度行星搜索周围的红巨星的丛中的中间年龄的疏散星团。我们选择了质量在1.5到4 M�之间的红巨星所在的星系团，使用众所周知的星系团参数来准确地确定恒星质量。因此，我们正在探索一个鲜为人知的领域的主要质量，这将带来新的见解太阳系外行星系统的属性。方法.我们用Coralie和HARPS光谱仪跟踪了大约115颗红巨星的样本，以获得高精度的径向速度（RV）测量值，并探测这些恒星周围的巨行星。我们使用平分线和活动指数诊断来区分行星引起的RV变化和恒星光球抖动。结果我们在疏散星团NGC 2423和NGC 4349中发现了一颗巨行星和一颗褐矮星，它们围绕着2.4 M的星星NGC 2423 No. 3（TYC 5409-2156-1）和3.9 M的星星NGC 4349 No. 127（TYC 8975-2606-1）运行。这些低质量伴星的轨道周期分别为714天和678天，最小质量分别为10.6和19.8兆焦耳。结合其他已知的行星系统，这些探测表明，大质量行星在中等质量恒星周围的频率较高，因此可能与原行星盘的质量成比例。
Context. Many efforts are being made to characterize extrasolar planetary systems and unveil the fundamental mechanisms of planet formation. An important aspect of the problem, which remains largely unknown, is to understand how the planet formation process depends on the mass of the parent star. In particular, as most planets discovered to date orbit a solar-mass primary, little is known about planet formation around more massive stars. Aims. To investigate this point, we present first results from a radial velocity planet search around red giants in the clump of intermediate-age open clusters. We choose clusters harbouring red giants with masses between 1.5 and 4 M� , using the well-known cluster parameters to accurately determine the stellar masses. We are therefore exploring a poorly-known domain of primary masses, which will bring new insights into the properties of extrasolar planetary systems. Methods. We follow a sample of about 115 red giants with the Coralie and HARPS spectrographs to obtain high-precision radial velocity (RV) measurements and detect giant planets around these stars. We use bisector and activity index diagnostics to distinguish between planetary-induced RV variations and stellar photospheric jitter. Results. We present the discoveries of a giant planet and a brown dwarf in the open clusters NGC 2423 and NGC 4349, orbiting the 2.4 M� -star NGC 2423 No. 3 (TYC 5409-2156-1) and the 3.9 M� -star NGC 4349 No. 127 (TYC 8975-2606-1). These low-mass companions have orbital periods of 714 and 678 days and minimum masses of 10.6 and 19.8 MJup, respectively. Combined with the other known planetary systems, these detections indicate that the frequency of massive planets is higher around intermediate-mass stars, and therefore probably scales with the mass of the protoplanetary disk.