Photometric variability of a directly imaged exo-Earth conveys spatial information on its surface and can be used to retrieve a two-dimensional geography and axial tilt of the planet (spin-orbit tomography). In this study, we relax the assumption of the static geography and present a computationally tractable framework for dynamic spin-orbit tomography applicable to the time-varying geography. First, a Bayesian framework of static spin-orbit tomography is revisited using analytic expressions of the Bayesian inverse problem with a Gaussian prior. We then extend this analytic framework to a time-varying one through a Gaussian process in time domain, and present analytic expressions that enable efficient sampling from a full joint posterior distribution of geography, axial tilt, spin rotation period, and hyperparameters in the Gaussian-process priors. Consequently, it only takes 0.3 s for a laptop computer to sample one posterior dynamic map conditioned on the other parameters with 3,072 pixels and 1,024 time grids, for a total of $\sim 3 \times 10^6$ parameters. We applied our dynamic mapping method on a toy model and found that the time-varying geography was accurately retrieved along with the axial-tilt and spin rotation period. In addition, we demonstrated the use of dynamic spin-orbit tomography with a real multi-color light curve of the Earth as observed by the Deep Space Climate Observatory. We found that the resultant snapshots from the dominant component of a principle component analysis roughly captured the large-scale, seasonal variations of the clear-sky and cloudy areas on the Earth.
Modelling solar radial velocities and photometric variability with SOAPv4
Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto（空间科学与天体物理研究所，波尔图大学）；Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto（波尔图大学理学院物理与天文系）；Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM（巴黎萨克雷大学，巴黎西岱大学，法国原子能和替代能源委员会，法国国家科学研究中心）；Department of Physics, University of Coimbra（科英布拉大学物理系）；Departamento de Ciências da Terra, FCTUC, Universidade de Coimbra（科英布拉大学地球科学系）
The correlation between photometric variability and radial velocity jitter, based on TESS and HARPS observations
目前和即将到来的高精度测光调查，如TESS，CHEOPS和PLATO将为社区提供数千个新的系外行星候选者。因此，这种相关性的存在是至关重要的，在选择目标与最低的RV抖动的有效RV后续的系外行星候选人。这种类型的研究对于设计优化的观测策略以减轻搜索地球质量系外行星时的RV抖动也至关重要。我们的目标是评估高精度光度变化测量和高精度RV抖动在不同的时间尺度之间的相关性。我们分析了171 G，K和M星与现有的TESS高精度光度时间序列和HARPS精确的RV。我们推导出了样本中恒星的恒星参数，并测量了RV抖动和光度变化。我们还估计了色球Ca II H $\&$ K活动指标$log(R' _{HK})$，$\textit{v sin i}$和恒星自转周期。最后，我们评估如何不同的恒星参数和RV采样子集可以有潜在的相关性的影响。我们发现，作为TESS光度观测和HARPS RV之间的时间间隔的函数的光度变化和RV抖动之间的相关性。随着分析所考虑的观测时间间隔的增加，相关值和显著性变得更小和更弱，以至于可以忽略不计。我们还发现，对于光度变化超过6.5 ppt的恒星，相关性明显更强。我们表明，这样的结果可能是由于现场为主的和院系为主的政权之间的过渡。我们量化了相关性，并更新了色球Ca II H $\&$ K活性指标$log(R' _{HK})$和RV抖动之间的关系。
Scientific Validation of the SPARC4 Pipeline: Multi-band Imaging, Polarimetry, and Photometric Time Series for Improved Characterization of Transiting Exoplanets
Laboratório Nacional de Astrofísica（国家天体物理实验室）；Instituto Nacional de Pesquisas Espaciais（国家空间研究所）；Centro Federal de Educação Tecnológica Celso Suckow da Fonseca（塞尔索·苏科瓦·达丰塞卡联邦技术教育中心）
Prioritizing High-Precision Photometric Monitoring of Exoplanet and Brown Dwarf Companions with JWST -- Strategic Exoplanet Initiatives with HST and JWST White Paper
Revealing the Vertical Cloud Structure of a young low-mass Brown Dwarf, an analog to the beta-Pictoris b directly-imaged exoplanet, through Keck I/MOSFIRE spectro-photometric variability
年轻的褐矮星类似于巨大的系外行星，因为它们共享有效温度，近红外颜色和表面重力。因此，对年轻褐矮星的详细描述可能会为巨型系外行星的研究提供帮助，我们目前无法以足够的信噪比观察它们的大气层。2 MASS J22081363+2921215是一颗年轻的L3褐矮星，属于β-Pica-b年轻移动群（2300万年+/-300万年），与β-Pica-b巨型系外行星共享其有效温度和质量。我们用安装在凯克I望远镜上的MOSFIRE多目标摄谱仪对2 MASS J22081363+2921215进行了约2.5小时的J波段分光光度监测。我们测得其J波段光变曲线的最小变异幅度为3.22 +/-0.42%。2 MASS J22081363+2921215的最大和最小通量谱之间的比率显示出弱的波长依赖性和潜在的增强的变化幅度在碱性线。进一步分析表明，碱性线上的变异幅度高于整体变异幅度（4.5- 11%，取决于线）。如果我们将原始MOSFIRE光谱的分辨率降低到R~100，则这些谱线中的可变性幅度较低，这解释了为什么先前在HST/WFC 3光变曲线中没有发现这种潜在的碱性谱线增强的可变性。使用辐射传输模型，我们得到了不同的云层，可能会引入分光光度变化，我们观察到2 MASS J22081363+2921215，进一步支持测量增强的变化幅度在碱性线。我们提供了一个艺术的娱乐垂直云结构的β-Picadium b类似物…
Determining the Detectability of H2O with Photometric Observations using Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE)
NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；University of Oslo（奥斯陆大学）
