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 obtained with the StellarBox code. The model has been used for determining statistical properties of the turbulent plasma and obtaining synthetic spectroscopic observations for several Fe I lines at different locations on the stellar disk to mimic high-resolution spectroscopic observations.
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。
Dark spots on the surface of active stars produce changes in the shapes of the spectral lines that mimic spurious Doppler shifts, compromising the detection of small planets by means of the radial velocity (RV) technique. Modelling the spot-driven RV variability (known as ``jitter'') and how it affects the RV data sets is therefore crucial to design efficient activity-filtering techniques and inform observing strategies. Here, we characterise starspots and simulate the radial velocity curves induced by them to determine typical jitter amplitudes for a representative sample of 15 known host sta…
Testing 3D hydrodynamic models of stellar atmospheres is feasible by retrieving spectral line shapes across stellar disks, using differential spectroscopy during exoplanet transits. From synthetic data at hyper-high spectral resolution, characteristic patterns for FeI and FeII lines were identified in Paper IV from 3D models spanning T=3964-6726K (spectral types approx. K8V-F3V). The observability of patterns among lines of different strength, excitation potential and ionization level are now examined, as observed at ordinary spectral resolutions and in the presence of noise. Time variability …
A breakthrough in exoplanet detections is foreseen with the unprecedented astrometric measurement capabilities offered by instrumentation aboard Gaia space observatory. Besides, astrometric discoveries of exoplanets are expected from the planned space mission, Small-JASMINE. In this setting, the present series of papers focuses on estimating the effect of magnetic activity of G2V-type host stars on the astrometric signal. This effect interferes with the astrometric detections of Earth-mass planets. While the first two papers considered stars rotating at the solar rotation rate, this paper focu…
Transit observations have found the majority of exoplanets to date. Spectroscopic observations of transits and eclipses are the most commonly used tool to characterize exoplanet atmospheres and will be used in the search for life. However, an exoplanet's orbit must be aligned with our line of sight to observe a transit. Here we ask, from which stellar vantage points would a distant observer be able to search for life on Earth in the same way? We use the TESS Input Catalog and data from Gaia DR2 to identify the closest stars that could see Earth as a transiting exoplanet: We identify 1,004 Main…
In the search for life in the cosmos, transiting exoplanets are currently our best targets. In the search for life in the cosmos, transiting exoplanets are currently our best targets. With thousands already detected, our search is entering a new era of discovery with upcoming large telescopes that will look for signs of life in the atmospheres of transiting worlds. However, the universe is dynamic, and which stars in the solar neighborhood have a vantage point to see Earth as a transiting planet and can identify its vibrant biosphere since early human civilizations are unknown. Here we show th…
The high-resolution, dual channel, visible and near-infrared spectrograph CARMENES offers exciting opportunities for stellar and exoplanetary research on M dwarfs. In this work we address the challenge of reaching the highest radial velocity precision possible with a complex, actively cooled, cryogenic instrument, such as the near-infrared channel. We describe the performance of the instrument and the work flow used to derive precise Doppler measurements from the spectra. The capability of both CARMENES channels to detect small exoplanets is demonstrated with the example of the nearby M5.0 V s…
In the next decades, the astrobiological community will debate whether the first observations of oxygen in an exoplanet$'$s atmosphere signifies life, so it is critical to establish procedures now for collection and interpretation of such data. We present a step-by-step observational strategy for using oxygen as a robust biosignature, to prioritize exoplanet targets and design future observations. It is premised on avoiding planets lacking subaerial weathering of continents, which would imply geochemical cycles drastically different from Earth$'$s, precluding use of oxygen as a biosignature. T…
Proton Irradiation of Primitive Atmospheres of Young Exoplanets and early Earth: $N_{\mathrm{2}}O$ Greenhouse Warming and Prebiotic Synthesis
Yokohama National University（横滨国立大学）；Institute of Science Tokyo（东京科学大学）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；American University（美利坚大学）；Kyoto University（京都大学）；Tokai-mura, Naka-gun, Ibaraki（茨城县那珂郡东海村）；Tokyo City University（东京都立大学）；Uppsala University（乌普萨拉大学）；NASA Langley Research Center（美国国家航空航天局兰利研究中心）
We demonstrate that the James Webb Space Telescope (JWST) can detect infrared (IR) excess from the blended light spectral energy distribution of spatially unresolved terrestrial exoplanets orbiting nearby white dwarfs. We find that JWST is capable of detecting warm (habitable-zone; T$_{\rm eq}$=287 K) Earths or super-Earths and hot (400-1000 K) Mercury analogs in the blended light spectrum around the nearest 15 isolated white dwarfs with 10 hrs of integration per target using MIRI's Medium Resolution Spectrograph (MRS). Further, these observations constrain the presence of a CO$_2$-dominated a…
The advent of Gaia, capable of measuring stellar wobbles caused by orbiting planets, raised an interest to the astrometric detection of exoplanets. Another source of such wobbles (often also called jitter) is stellar magnetic activity. A quantitative assessment of the stellar astrometric jitter is important for a more reliable astrometric detection and characterisation of exoplanets. We calculate the displacement of the solar photocentre due to the magnetic activity for an almost 16-year period (February 2, 1999 - August 1, 2014). We also investigate how the displacement depends on the spectra…
Cosmic rays may have contributed to the start of life on Earth. Here, we investigate the evolution of the Galactic cosmic ray spectrum at Earth from ages $t = 0.6-6.0\,$Gyr. We use a 1D cosmic ray transport model and a 1.5D stellar wind model to derive the evolving wind properties of a solar-type star. At $t=1\,$Gyr, approximately when life is thought to have begun on Earth, we find that the intensity of $\sim$GeV Galactic cosmic rays would have been $\sim10$ times smaller than the present-day value. At lower kinetic energies, Galactic cosmic ray modulation would have been even more severe. Mo…
Context: The stellar wind and the interplanetary magnetic field modify the topology of planetary magnetospheres. Consequently, the hazardous effect of the direct exposition to the stellar wind, for example regarding the integrity of satellites orbiting the Earth or the habitability of exoplanets, depend upon the space weather conditions. Aims: The aim of the study is to analyze the response of an Earth-like magnetosphere for various space weather conditions and interplanetary coronal mass ejections. The magnetopause stand off distance, open-close field line boundary and plasma flows towards th…
The search for life in the universe mainly uses modern Earth as a template. However, we know that Earth's atmospheric composition changed significantly through its geological evolution. Recent discoveries show that transiting, potentially Earth-like exoplanets orbit a wide range of host stars, which strongly influence their atmospheric composition and remotely detectable spectra. Thus, a database for transiting terrestrial exoplanet around different host stars at different geological times is a crucial missing ingredient to support observational searches for signs of life in exoplanet atmosphe…
Energetic particles may have been important for the origin of life on Earth by driving the formation of prebiotic molecules. We calculate the intensity of energetic particles, in the form of stellar and Galactic cosmic rays, that reach Earth at the time when life is thought to have begun ($\sim$3.8Gyr ago), using a combined 1.5D stellar wind model and 1D cosmic ray model. We formulate the evolution of a stellar cosmic ray spectrum with stellar age, based on the Hillas criterion. We find that stellar cosmic ray fluxes are larger than Galactic cosmic ray fluxes up to $\sim$4 GeV cosmic ray energ…
Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O$_\mathrm{2}$ Levels in Nearby Transiting Habitable Zone Exoplanets
When searching for exoplanets and ultimately considering their habitability, it is necessary to consider the planet's composition, geophysical processes, and geochemical cycles in order to constrain the bioessential elements available to life. Determining the elemental ratios for exoplanetary ecosystems is not yet possible, but we generally assume that planets have compositions similar to those of their host stars. Therefore, using the Hypatia Catalog of high-resolution stellar abundances for nearby stars, we compare the C, N, Si, and P abundance ratios of main sequence stars with those in ave…
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。
A major goal in the discovery and characterisation of exoplanets is to identify terrestrial-type worlds that are similar to (or otherwise distinct from) our Earth. Recent results have highlighted the importance of applying devolatilisation -- i.e. depletion of volatiles -- to the chemical composition of planet-hosting stars to constrain bulk composition and interiors of terrestrial-type exoplanets. In this work, we apply such an approach to a selected sample of 13 planet-hosting Sun-like stars, for which high-precision photospheric abundances have been determined in the first paper of the seri…
Star compositions are essential for examining densities and compositional ranges of rocky exoplanets, testing their similarity to Earth. Stellar elemental abundances and planetary orbital data show that of the ~5000 known minerals, exoplanetary silicate mantles will contain mostly olivine, orthopyroxene, and clinopyroxene, $\pm$ quartz, and magnesiuwustite at the extremes; wholly exotic mineralogies are likely absent. Understanding these exotic geological systems requires a better marriage of geological insights to astronomical data. The study of exoplanets is like a mirror, reflecting our inc…
