论文标题
KMT-2017-BLG-2820和自由浮动行星种群的性质
KMT-2017-BLG-2820 and the Nature of the Free-Floating Planet Population
论文作者
论文摘要
我们报告了一个新的自由浮动星球(FFP)候选者,KMT-2017-BLG-2820,带有爱因斯坦半径$θ_\ e \ e \ simeq 6 \,\ muas $,镜头相对运动$μ_\ rel \ rel \ rel \ rel \ rel \ simeq 8 \ simeq 8 \ \ simeq 8 \,\ masyr $ $ $ $ $ $ $ = 6.这是对KMTNET数据库中的巨型源源源点透镜(FSPL)事件进行的第三次FFP候选者,以及第六次FSPL FFP候选人总体。我们没有发现主机的重要证据。根据它们的时间尺度分布和检测率,我们认为这六个FSPL FFP候选者中有五个是从OGLE-IV数据库中\ citet {Mroz17}发现的六点源点透镜(PSPL)FFP候选者的人口。 FSPL FFPS的$θ_\ e $分布意味着它们是凸起中的jovian行星,要么是磁盘中的超级地球。但是,明显的“爱因斯坦沙漠”($ 10 \laθ_\ e/\ muas \ la 30 $)会为后者争辩。是否可以在30m望远镜上的第一个自适应光学(AO)灯光下确定12个(6 fspl和6 PSPL)FFP候选者中的每个FFP候选者,还是仅仅是一个非常宽的行星。如果后者,AO观察值的第二个时期可以用精度$ {\ cal O}(10 \,\ au)$来测量投影的行星宿主分离。目前,证据平衡有利于未结合的假设。
We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius $θ_\e\simeq 6\,\muas$, lens-source relative proper motion $μ_\rel \simeq 8\,\masyr$, and Einstein timescale $t_\e=6.5\,$hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet data base, and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six point-source point-lens (PSPL) FFP candidates found by \citet{mroz17} in the OGLE-IV data base. The $θ_\e$ distribution of the FSPL FFPs implies that they are either sub-Jovian planets in the bulge or super-Earths in the disk. However, the apparent "Einstein Desert" ($10\laθ_\e/\muas\la 30$) would argue for the latter. Whether each of the 12 (6 FSPL and 6 PSPL) FFP candidates is truly an FFP, or simply a very wide-separation planet, can be determined at first adaptive optics (AO) light on 30m telescopes, and earlier for some. If the latter, a second epoch of AO observations could measure the projected planet-host separation with a precision ${\cal O}(10\,\au)$. At the present time, the balance of evidence favors the unbound-planet hypothesis.