Revisiting Radial Velocity Measurements of the K2-18 System with the Line-by-Line Framework
Michael Radica, Étienne Artigau, David Lafrenière, Charles Cadieux, Neil J. Cook, René Doyon, Pedro J. Amado, José A Caballero, Thomas Henning, Andreas Quirrenb… 展开作者
Michael Radica, Étienne Artigau, David Lafrenière, Charles Cadieux, Neil J. Cook, René Doyon, Pedro J. Amado, José A Caballero, Thomas Henning, Andreas Quirrenbach, Ansgar Reiners, Ignasi Ribas
The cross-correlation function and template matching techniques have dominated the world of precision radial velocities for many years. Recently, a new technique, named line-by-line, has been developed as an outlier resistant way to efficiently extract radial velocity content from high resolution spectra. We apply this new method to archival HARPS and CARMENES datasets of the K2-18 system. After reprocessing the HARPS dataset with the line-by-line framework, we are able to replicate the findings of previous studies. Furthermore, by splitting the full wavelength range into sub-domains, we were able to identify a systematic chromatic correlation of the radial velocities in the reprocessed CARMENES dataset. After post-processing the radial velocities to remove this correlation, as well as rejecting some outlier nights, we robustly uncover the signal of both K2-18b and K2-18c, with masses that agree with those found from our analysis of the HARPS dataset. We then combine both the HARPS and CARMENES velocities to refine the parameters of both planets, notably resulting in a revised mass and period for K2-18c of $6.99^{+0.96}_{-0.99}$M$_{Earth}$ and $9.2072\pm0.0065$d, respectively. Our work thoroughly demonstrates the power of the line-by-line technique for the extraction of precision radial velocity information.
TRADES: A new software to derive orbital parameters from observed transit times and radial velocities. Revisiting Kepler-11 and Kepler-9
目的。为了从观测数据中确定系外行星系统的轨道参数,我们开发了一个名为TRADES(TRAnsits and Dynamics of Exoplanetary Systems)的软件,可以同时拟合观测到的径向速度和凌日时间数据。方法.我们实现了一个N体系统的动力学模拟器,它也适合在轨道集成过程中的可用数据,并确定最佳的轨道参数组合,使用网格搜索,$χ^2$最小化,遗传算法,粒子群优化,和引导分析。结果为了验证TRADES,我们在合成三体系统和开普勒任务发现的两个真实系统上测试了代码:开普勒-9和开普勒-11。这些系统是测试多个系外行星系统的良好基准,这些系统由于行星之间的引力相互作用而显示出过境时间变化(TTV)。我们发现开普勒-11行星的轨道参数与发现论文中提出的值以及同一作者最近的工作非常一致。我们分析了Kepler-9系统的前三个季度,发现与发现论文部分一致的参数。分析涵盖开普勒数据的12个季度的过境时间(T0),我们已经找到了一个新的最佳拟合解决方案。该解决方案输出的质量约为发现论文中提出的值的55%;这导致径向速度的半幅值降低约为12.80 m/s。
Future direct imaging missions such as HabEx and LUVOIR aim to catalog and characterize Earth-mass analogs around nearby stars. The exoplanet yield of these missions will be dependent on the frequency of Earth-like planets, and potentially the a priori knowledge of which stars specifically host suitable planetary systems. Ground or space based radial velocity surveys can potentially perform the pre-selection of targets and assist in the optimization of observation times, as opposed to an uninformed direct imaging survey. In this paper, we present our framework for simulating future radial velo…
The detection of Earth-size exoplanets is a technological and data analysis challenge. Future progress in Earth-mass exoplanet detection is expected from the development of extreme precision radial velocity measurements. Increasing radial velocity precision requires developing a new physics-based data analysis methodology to discriminate planetary signals from host-star-related effects, taking stellar variability and instrumental uncertainties into account. In this work, we investigate and quantify stellar disturbances of the planet-hosting solar-type star HD121504 from 3D radiative modeling o…
Characterisation of the radial velocity signal induced by rotation in late-type dwarfs
我们研究了晚型星(FGKM)中与自转相关的活动诱导信号。利用HARPS公共数据库的光谱和ASAS巡天提供的光变曲线,分析了55颗恒星的Ca II H&K、H α和视向速度时间序列。我们在活动指标的时间序列中以及在光度学光变曲线中寻找短期周期信号。然后分析径向速度数据集,以确定活动引起的信号的存在。我们测量了37颗恒星的径向速度信号,从晚F型到中期M型恒星的恒星表面特征的旋转调制引起的。我们报告的经验关系,与一定程度的光谱型依赖性,色球发射的平均水平测得的日志(Rhk)和测得的径向速度半振幅之间。我们还报道了色球测量信号的半幅值与径向速度感应信号的半幅值之间的关系,这种关系强烈地依赖于光谱型。我们发现,对于一个给定的色球活动强度(即一个给定的旋转周期)的M型星往往比G和K型星诱导更大的旋转相关的径向速度信号。
Activity-induced radial velocity jitter in a flaring M dwarf
我们调查的影响,恒星活动和耀斑的短期径向速度测量中M耀斑恒星CN狮子座。根据三个夜晚得到的181个UVES光谱计算了径向速度变化。我们搜索的光谱订单,包含很少的大气吸收线,并校准他们对大地A波段从O $_2$在地球大气中。在我们的观测过程中发生了一次巨大的耀斑,它对径向速度有很强的影响。耀斑引起的视径向速度移动为几百m/s $^{-1}$,并与H $α$辐射明显相关。耀斑外,只有光谱订单包含最突出的发射线的H,他,和钙显示相关的色球活动连同径向速度抖动超过几个10米秒$^{-1}$。我们确定了一些光谱订单,是免费的强发射线,并没有耀斑相关的径向速度抖动,虽然耀斑发生的归一化H $α$光度为0.4德克斯强。由于中等耀斑引起的平均径向速度抖动小于10 m s $^{-1}$。强烈的耀斑很容易在光谱中直接识别,在行星搜索中应该被忽略。
Minimizing the bias in exoplanet detection - application to radial velocities of LHS 1140
一颗围绕LHS 1140运行的周期为24.7d的岩石行星已经被发现,这是基于在其光和高精度径向速度数据中发现的凌日现象(Dittmann et al. 2017)。通过两种独立的方法得到的这一发现是一种观察性的尝试,然而,我们发现对数据的保守分析给出了不同的解决方案。根据我们对恒星活动的诊断,在径向速度数据中,一个三行星系统是显而易见的。我们鼓励进一步进行有针对性的光度和径向速度观测,以限制显然造成3.8天和90天径向速度信号的小型海王星和超级地球质量物体。我们使用我们的软件包Agatha(https://phillippro.shinyapps.io/Agatha/)提供一个全面的策略,从径向速度数据中的恒星活动中解开行星信号。
Orbital eccentricity of WASP-12 and WASP-14 from new radial-velocity monitoring with SOPHIE
作为对已知凌日行星进行长期径向速度监测的一部分-旨在测量轨道偏心率、自旋-轨道对准和其他行星伴星-我们获得了两个凌日系统WASP-12和WASP-14的径向速度数据,这两个系统都在近轨道上拥有气态巨星(轨道周期分别为1.09天和2.24天)。在这两种情况下,最初的轨道解都显示出很大的轨道偏心率,WASP-12为0.049+-0.015,WASP-14为0.091+-0.003。从那时起,对WASP-12的二次日食的红外测量表明,偏心率(e cos w)的一个投影非常接近于零,这对初始径向速度轨道的偏心率产生了怀疑。我们的测量证实,初始偏心检测可能是虚假的,并表明径向速度数据是兼容的圆形轨道。考虑到径向速度和光度数据中存在相关系统噪声,MCMC分析给出e=0.017(+0.015-0.011)。通过对比,我们确定了WASP-14的轨道偏心率,并将其值修正为e=0.088+-0.003。因此,WASP-14是目前已知的离地球最近的行星,并且有着确定的偏心轨道。
Context. Following the first discovery of a planet orbiting a giant star in 2002, we started the CORALIE radial-velocity search for companions around evolved stars (CASCADES). We present the observations of three stars conducted at the 1.2 m Leonard Euler Swiss telescope at La Silla Observatory, Chile, using the CORALIE spectrograph. Aims. We aim to detect planetary companions to intermediate-mass G- and K- type evolved stars and perform a statistical analysis of this population. We searched for new planetary systems around the stars HD22532 (TIC 200851704), HD64121 (TIC 264770836), and HD6912…
For many classes of astronomical and astrophysical binary systems, long observational records of their radial velocity $V$, which is their directly observable quantity, are available. For exoplanets close to their parent stars, they cover several full orbital revolutions, while for wide binaries like, e.g., the Proxima/$α$ Centauri AB system, only relatively short orbital arcs are sampled by existing radial velocity measurements. Here, the changes $ΔV$ induced on a binary's radial velocity by some long-range modified models of gravity are analytically calculated. In particular, extra-potential…