The analysis of the first solar-like targets done by CoRoT has shown that the oscillation amplitudes are about 25% below the theoretical amplitudes while the convective backgrounds are up to three times higher than in the solar case (Michel et al. 2008). In such conditions, the comb-like structure of the acoustic modes has smaller signal-to-noise ratios than initially expected complicating the characterization of individual modes. In the present work we apply the curvelet filtering to the solar-like targets already observed by CoRoT as well as a partial reconstruction of the signal from the obtained spacing of the comb-like structure of the acoustic modes. It enables us to enhance the signal-to-noise ratio of the ridges in the Echelle diagrams. Finally, we study how the analysis of the p modes can be improved.
We present the target list of solar-type stars to be observed in short-cadence (2-min) for asteroseismology by the NASA Transiting Exoplanet Survey Satellite (TESS) during its 2-year nominal survey mission. The solar-like Asteroseismic Target List (ATL) is comprised of bright, cool main-sequence and subgiant stars and forms part of the larger target list of the TESS Asteroseismic Science Consortium (TASC). The ATL uses Gaia DR2 and the Extended Hipparcos Compilation (XHIP) to derive fundamental stellar properties, calculate detection probabilities and produce a rank-ordered target list. We pro…
Amended results for hard X-ray emission by non-thermal thick target recombination in solar flares
Brown & Mallik 2008和Brown et al. 2010勘误表给出了薄靶和厚靶碰撞区域的非热复合（NTR）表达式，声称该过程可以解释通常完全归因于热和非热韧致辐射（NTB）的太阳耀斑中硬X射线连续谱的很大一部分。然而，我们已经发现，厚靶的表达，成为非物理的低截止注入电子能谱。我们追溯到推导中的一个错误，推导出一个修正的版本，它是实值和连续的所有光子能量和截止，并表明，对于厚的目标，布朗等人。高估NTR发射在小光子能量。小的截止值和大的光谱指数的制度涉及大的（减少）校正因子，但在其他一些厚目标参数制度NTR/NTB仍然可以是统一的顺序。我们评论这些结果的重要性耀斑和微耀斑建模和光谱拟合。对我们的结果的经验拟合表明，如果delta > 6（E_0c/4 keV）^（0.4），则峰值NTR贡献包括硬X射线信号的一半以上。
Solar flares are events of intense scientific interest. Although certain solar conditions are known to be associated with flare activity, the exact location and timing of an individual flare on the Sun cannot as yet be predicted with certainty. Missions whose science objectives depend on observing solar flares must often make difficult decisions on where to target their observations if they do not observe the full solar disk. Yet, little analysis exists in the literature which might guide these missions' operations to maximize their opportunities to observe flares. In this study we analyze and…
Spectroscopic observations of active solar-analog stars having high X-ray luminosity, as a proxy of superflare stars
最近对太阳型超级耀斑恒星的研究表明，即使是像太阳一样缓慢旋转的老恒星也可能有大的恒星黑子和超级耀斑。我们进行了高色散光谱的49个附近的太阳类似星（G型主序星与$T_{\rm{eff}}\approx5,600\sim6,000$ K）确定为ROSAT软X射线源，这不是从以前的研究双星。我们期望这些恒星可以被用作明亮的太阳类超耀斑恒星的替代物，因为超耀斑恒星被期望显示出强烈的X射线光度。在49颗目标星中，超过一半（37颗）没有双星的证据，它们的大气参数（$T_{\rm{eff}}$、$\log g$和[Fe/H]）都在普通太阳类星的范围内。我们测量了Ca II 8542和H $α$线，这是色球活动的良好指标。这些线的强度表明，所有的目标恒星都有大的星斑。我们还测量了目标恒星的$v\sin i$（投影旋转速度）和锂丰度。Li丰度是理解恒星对流带演化的关键，它反映了恒星的年龄、质量和自转历史。我们证实，许多目标恒星快速旋转，与太阳相比，锂丰度很高，正如许多以前的研究所表明的那样。然而，也有一些目标星旋转缓慢（$v\sin i$ =2 $\sim$ 3 km s $^{-1}$），像太阳一样锂丰度低。这些结果支持了类似太阳的古老而缓慢旋转的恒星可能具有高活动水平和大的星点。这与我们以前对太阳型超耀斑恒星的研究结果是一致的。今后，为了从恒星发电机理论的角度研究大星点的详细性质，对这些活跃的太…
We studied the presence and spatiotemporal evolution of the quasi-biennial oscillations (QBOs) in the rotation rate residuals at target depths of 0.90$R_{\odot}$, 0.95$R_{\odot}$, and 0.99$R_{\odot}$ and at low (0 -- 30$^{\circ}$), mid (30 -- 50$^{\circ}$), and high (50 -- 70$^{\circ}$) latitudinal bands. To achieve these objectives we used data from the Michelson Doppler Imager (MDI) on {\it the Solar and Heliospheric Observatory} ({\it SOHO}) and the Helioseismic and Magnetic Imager (HMI) on the {\it Solar Dynamics Observatory} ({\it SDO}), covering solar cycles 23 and 24, respectively. The …
Enhancing Image Resolution of Solar Magnetograms: A Latent Diffusion Model Approach
Institute for Data Science, University of Applied Sciences North Western Switzerland (FHNW)（数据科学研究所，北西瑞士应用科学大学）；Department of Computer Science, University of Geneva（计算机科学系，日内瓦大学）
Solar flare hard X-ray spectroscopy serves as a key diagnostic of the accelerated electron spectrum. However, the standard approach using the collisional cold thick-target model poorly constrains the lower-energy part of the accelerated electron spectrum, and hence the overall energetics of the accelerated electrons are typically constrained only to within one or two orders of magnitude. Here we develop and apply a physically self-consistent warm-target approach which involves the use of both hard X-ray spectroscopy and imaging data. The approach allows an accurate determination of the electro…
Studies of solar twins have key impacts on the astronomical community, but only $\sim$100--200 nearby solar twins ($<$ 1 kpc) have been reliably identified over the last few decades. The aim of our survey (SDST) is to identify $\sim$150--200 distant solar twins and analogues (up to $\lesssim$ 4 kpc) closer to the Galactic Centre. We took advantage of the precise Gaia and Skymapper surveys to select Sun-like candidates in a 2-degree field, which were observed with the HERMES spectrograph on the Anglo-Australian Telescope. We successfully built up the required signal-to-noise ratio (25-per-pixel…
Stars provide an enormous gain for interstellar communications at their gravitational focus, perhaps as part of an interstellar network. If the Sun is part of such a network, there should be probes at the gravitational foci of nearby stars. If there are probes within the solar system connected to such a network, we might detect them by intercepting transmissions from relays at these foci. Here, we demonstrate a search across a wide bandwidth for interstellar communication relays beyond the Sun's innermost gravitational focus at 550 AU using the Green Bank Telescope (GBT) and Breakthrough Liste…
