Regular radial velocity variations in nine G- and K-type giant stars: Eight planets and one planet candidate
Regular radial velocity variations in nine G- and K-type giant stars: Eight planets and one planet candidate
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九颗 G 型和 K 型巨星的径向速度规则变化：八颗行星和一颗候选行星
DOI：
10.1093/pasj/psab112
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发表时间：
2021
影响因子：
2.3
通讯作者：
Kokubo Eiichiro
中科院分区：
文献类型：
--
作者：
Teng Huan-Yu;Sato Bun’ei;Takarada Takuya;Omiya Masashi;Harakawa Hiroki;Izumiura Hideyuki;Kambe Eiji;Takeda Yoichi;Yoshida Michitoshi;Itoh Yoichi;Ando Hiroyasu;Kokubo Eiichiro
我们报告了在九个演化的 G 型和 K 型巨星中检测到的径向速度 (RV) 变化。观测是在冈山天体物理观测站进行的。行星或候选行星最能解释这些规律性的变化。然而，其中五颗恒星之间近 280 天的变化的巧合使我们无法完全排除某些变化的恒星起源，因为所有九颗恒星的恒星特性都相似。在 RV 变体的行星假说中，行星（包括一颗候选行星）可能生存在靠近演化恒星周围所谓“行星沙漠”边界的地方，其轨道周期在 255 天到 555 天之间。此外，它们是在G型和K型巨星周围检测到的质量最小的巨行星，最小质量在0.45MJ到1.34MJ之间。我们进一步研究了其他假设来进行检测，但没有一个可以更好地解释常规的 RV 变化。通过我们的检测，我们可以确信，对于 G 型和 K 型巨星，振幅低至 15 m s−1 的长达一年的规则变化是可以检测到的。此外，我们还进行了模拟，以进一步确认这些恒星周围行星的可探测性。最后，我们探索了中等质量恒星周围的巨行星，同样发现了一个四木星质量的间隙（例如，Santos et al. 2017, A&A, 603, A30），这可能是巨行星群的边界。
We report the detection of radial velocity (RV) variations in nine evolved G- and K-type giant stars. The observations were conducted at Okayama Astrophysical Observatory. Planets or planet candidates can best explain these regular variations. However, a coincidence of near 280 d variability among five of them prevents us from fully ruling out stellar origins for some of the variations, since all nine stars behave similarly in stellar properties. In the planet hypotheses for the RV variations, the planets (including one candidate) may survive close to the boundary of the so-called “planet desert” around evolved stars, having orbital periods between 255 and 555 d. Besides, they are the least-massive giant planets detected around G- and K-type giant stars, with minimum masses between 0.45MJand 1.34MJ. We further investigated other hypotheses for our detection, yet none of them can better explain regular RV variation. With our detection, we can be convinced that year-long regular variation with amplitude down to 15 m s−1for G- and K-type giant stars is detectable. Moreover, we performed simulations to further confirm the detectability of planets around these stars. Finally, we explored giant planets around intermediate-mass stars, and likewise found a four-Jupiter-mass gap (e.g., Santos et al. 2017, A&A, 603, A30), which is probably a boundary of the giant planet population.