arXiv: Solar and Stellar Astrophysics最新文献_第9页

The Gaia-ESO Survey: Galactic evolution of lithium at high metallicity 盖亚- eso巡天:高金属丰度锂的星系演化

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-07-06 DOI: 10.1051/0004-6361/202038688

S. Randich, L. Pasquini, E. Franciosini, L. Magrini, R. Jackson, R. Jeffries, V. D’Orazi, D. Romano, N. Sanna, G. Tautvaisien.e, M. Tsantaki, N. Wright, G. Gilmore, T. Bensby, A. Bragaglia, E. Pancino, R. Smiljanic, A. Bayo, G. Carraro, A. Gonneau, A. Hourihane, L. Morbidelli, C. Worley

{"title":"The Gaia-ESO Survey: Galactic evolution of lithium at high metallicity","authors":"S. Randich, L. Pasquini, E. Franciosini, L. Magrini, R. Jackson, R. Jeffries, V. D’Orazi, D. Romano, N. Sanna, G. Tautvaisien.e, M. Tsantaki, N. Wright, G. Gilmore, T. Bensby, A. Bragaglia, E. Pancino, R. Smiljanic, A. Bayo, G. Carraro, A. Gonneau, A. Hourihane, L. Morbidelli, C. Worley","doi":"10.1051/0004-6361/202038688","DOIUrl":"https://doi.org/10.1051/0004-6361/202038688","url":null,"abstract":"Reconstructing the Galactic evolution of lithium (Li) is the main tool used to constrain the source(s) of Li enrichment in the Galaxy. Recent results have suggested a decline in Li at supersolar metallicities, which may indicate reduced production. We exploit the unique characteristics of the Gaia-ESO Survey open star cluster sample to further investigate this issue and to better constrain the evolution of Li at high metallicity. We trace the the upper envelope of Li abundance versus metallicity evolution using 18 clusters and considering members that should not have suffered any Li depletion. At variance with previous claims, we do not find any evidence of a Li decrease at high metallicity. The most metal-rich clusters in the sample ([Fe/H] about 0.3) actually show the highest Li abundances, with A(Li) > 3.4. Our results clearly show that previous findings, which were based on field stars, were affected by selection effects. The metal-rich population in the solar neighbourhood is composed of relatively old and cool stars that have already undergone some Li depletion; hence, their measured Li does not represent the initial interstellar medium abundance, but a lower limit to it.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75261504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 10

The flux-weighted gravity-luminosity relation of Galactic classical Cepheids 银河经典造父变星的通量加权引力光度关系

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-07-04 DOI: 10.1051/0004-6361/202038292

M. Groenewegen

{"title":"The flux-weighted gravity-luminosity relation of Galactic classical Cepheids","authors":"M. Groenewegen","doi":"10.1051/0004-6361/202038292","DOIUrl":"https://doi.org/10.1051/0004-6361/202038292","url":null,"abstract":"The flux-weighted gravity-luminosity relation (FWGLR) is investigated for a sample of 477 classical Cepheids (CCs), including stars that have been classified in the literature as such but are probably not. The luminosities are taken from the literature, based on the fitting of the spectral energy distributions (SEDs) assuming a certain distance and reddening. The flux-weighted gravity (FWG) is taken from gravity and effective temperature determinations in the literature based on high-resolution spectroscopy. \u0000There is a very good agreement between the theoretically predicted and observed FWG versus pulsation period relation that could serve in estimating the FWG (and $log g$) in spectroscopic studies with a precision of 0.1~dex. \u0000As was known in the literature, the theoretically predicted FWGLR relation for CCs is very tight and is not very sensitive to metallicity (at least for LMC and solar values), rotation rate, and crossing of the instability strip. The observed relation has a slightly different slope and shows more scatter (0.54~dex). This is due both to uncertainties in the distances and to the pulsation phase averaged FWG values. \u0000Data from future Gaia data releases should reduce these errors, and then the FWGLR could serve as a powerful tool in Cepheid studies.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85967738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Fundamental parameters of Ap-star HD 108662 Ap-star HD 108662的基本参数

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-29 DOI: 10.26087/INASAN.2020.5.4.010

A. Romanovskaya, T. Ryabchikova, D. Shulyak

引用次数: 0

Preflare very long-periodic pulsations observed in Hα emission before the onset of a solar flare 在太阳耀斑开始前，在α α辐射中观察到的耀斑前非常长周期的脉动

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-24 DOI: 10.1051/0004-6361/202038398

Dong Li, Song Feng, W. Su, Yu Huang

{"title":"Preflare very long-periodic pulsations observed in Hα emission before the onset of a solar flare","authors":"Dong Li, Song Feng, W. Su, Yu Huang","doi":"10.1051/0004-6361/202038398","DOIUrl":"https://doi.org/10.1051/0004-6361/202038398","url":null,"abstract":"Very long-periodic pulsations during preflare phases (preflare-VLPs) have been detected in the full-disk solar soft X-Ray (SXR) flux (see Tan et al. 2016). They may be regarded as precursors to solar flares and may help us better understand the trigger mechanism of solar flares. In this letter, we report a preflare-VLP event before the onset of an M1.1 circular-ribbon flare on 2015 October 16. It was simultaneously observed in Halpha, SXR, and extreme ultraviolet (EUV) wavelengths, which were recorded by the NVST, GOES, EVE, and AIA respectively. The preflare-VLP is identified as the repeat and quasi-periodic pulses in light curves during preflare phase, which might be modulated by LRC-circuit oscillation in the current-carrying plasma loop. The quasi-periodicity can be determined from the Fourier power spectrum with Markov chain Monte Carlo (MCMC)-based Bayesian (e.g., Liang et al. 2020), such as ~9.3 minutes. We present the first report of a preflare-VLP event in the local Halpha line and EUV wavelength, which could be considered a precursor of a solar flare. This finding should therefore prove useful for the prediction of solar flares, especially for powerful flares.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90040945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 21

Stellar coronal X-ray emission and surface magnetic flux 恒星日冕x射线发射和表面磁通量

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-24 DOI: 10.1051/0004-6361/202038022

J. Zhuleku, J. Warnecke, H. Peter

{"title":"Stellar coronal X-ray emission and surface magnetic flux","authors":"J. Zhuleku, J. Warnecke, H. Peter","doi":"10.1051/0004-6361/202038022","DOIUrl":"https://doi.org/10.1051/0004-6361/202038022","url":null,"abstract":"Observations show that the coronal X-ray emission of the Sun and other stars depends on the surface magnetic field. Using power-law scaling relations between different physical parameters, we build an analytical model to connect the observed X-ray emission to the magnetic flux. The basis for our model are the scaling laws of Rosner, Tucker & Vaiana (RTV) that connect the temperature and pressure of a coronal loop to its length and energy input. To estimate the energy flux into the upper atmosphere, we use scalings derived for different heating mechanisms, e.g. for field-line braiding or Alfven-wave heating. We supplement this by observed relations between active region size and magnetic flux and derive scalings of how X-ray emissivity depends on temperature. Based on our analytical model, we find a power-law dependence of the X-ray emission on the magnetic flux, $L_{rm X}propto Phi^m$, with a power-law index $m$ being in the range from about 1 to 2. This finding is consistent with a wide range of observations, from individual features on the Sun, e.g. bright points or active regions, to stars of different types and varying levels of activity. The power-law index $m$ depends on the choice of the heating mechanism, and our results slightly favour the braiding and nanoflare scenarios over Alfven wave heating. In addition, the choice of instrument will have an impact on the power-law index $m$, which is because of the sensitivity of the observed wavelength region to the temperature of the coronal plasma. Overall, our simple analytical model based on the RTV scaling laws gives a good representation of the observed X-ray emission. This underlines that we might be able to understand stellar coronal activity though a collection of basic building blocks, i.e. loops, that we can study in spatially resolved detail on the Sun.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79208890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 10

Unveiling the magnetic nature of chromospheric vortices 揭示色球涡旋的磁性本质

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-24 DOI: 10.1051/0004-6361/202038360

M. Murabito, J. Shetye, M. Stangalini, E. Verwichte, T. Arber, I. Ermolli, F. Giorgi, T. Goffrey

{"title":"Unveiling the magnetic nature of chromospheric vortices","authors":"M. Murabito, J. Shetye, M. Stangalini, E. Verwichte, T. Arber, I. Ermolli, F. Giorgi, T. Goffrey","doi":"10.1051/0004-6361/202038360","DOIUrl":"https://doi.org/10.1051/0004-6361/202038360","url":null,"abstract":"Vortex structures in the Sun's chromosphere are believed to channel energy between different layers of the solar atmosphere. We investigate the nature and dynamics of two small-scale quiet-Sun rotating structures in the chromosphere. We analyse two chromospheric structures that show clear rotational patterns in spectropolarimetric observations taken with the Interferometric Bidimensional Spectrometer (IBIS) at the Ca II 8542 A~ line. We present the detection of spectropolarimetric signals that manifest the magnetic nature of rotating structures in the chromosphere. Our observations show two long-lived structures of plasma that each rotate clockwise inside a 10 arcsec$^{2}$~ quiet-Sun region. Their circular polarization signals are 5-10 times above the noise level. Line-of-sight Doppler velocity and horizontal velocity maps from the observations reveal clear plasma flows at and around the two structures. An MHD simulation shows these two structures are plausibly magnetically connected. Wave analysis suggests that the observed rotational vortex pattern could be due to a combination of slow actual rotation and a faster azimuthal phase speed pattern of a magneto-acoustic mode. Our results imply that the vortex structures observed in the Sun's chromosphere are magnetic in nature and that they can be connected locally through the chromosphere.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90389680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

RASSINE: Interactive tool for normalising stellar spectra 用于规范化恒星光谱的交互工具

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-23 DOI: 10.1051/0004-6361/202037722

M. Cretignier, J. Francfort, X. Dumusque, R. Allart, F. Pepe

{"title":"RASSINE: Interactive tool for normalising stellar spectra","authors":"M. Cretignier, J. Francfort, X. Dumusque, R. Allart, F. Pepe","doi":"10.1051/0004-6361/202037722","DOIUrl":"https://doi.org/10.1051/0004-6361/202037722","url":null,"abstract":"Aims: We provide an open-source code allowing an easy, intuitive, and robust normalisation of spectra. Methods: We developed RASSINE, a Python code for normalising merged 1D spectra through the concepts of convex hulls. The code uses six parameters that can be easily fine-tuned. The code also provides a complete user-friendly interactive interface, including graphical feedback, that helps the user to choose the parameters as easily as possible. To facilitate the normalisation even further, RASSINE can provide a first guess for the parameters that are derived directly from the merged 1D spectrum based on previously performed calibrations. Results: For HARPS spectra of the Sun that were obtained with the HELIOS solar telescope, a continuum accuracy of 0.20% on line depth can be reached after normalisation with RASSINE. This is three times better than with the commonly used method of polynomial fitting. For HARPS spectra of $alpha$ Cen B, a continuum accuracy of 2.0% is reached. This rather poor accuracy is mainly due to molecular band absorption and the high density of spectral lines in the bluest part of the merged 1D spectrum. When wavelengths shorter than 4500 Aare excluded, the continuum accuracy improves by up to 1.2%. The line-depth precision on individual spectrum normalisation is estimated to be 0.15%, which can be reduced to the photon-noise limit (0.10%) when a time series of spectra is given as input for RASSINE. Conclusions: With a continuum accuracy higher than the polynomial fitting method and a line-depth precision compatible with photon noise, RASSINE is a tool that can find applications in numerous cases, for example stellar parameter determination, transmission spectroscopy of exoplanet atmospheres, or activity-sensitive line detection.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86779018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Comprehensive photometric investigation of an active early K-type contact system—IL Cancri 活跃的早期k型接触系统-巨蟹座il的综合光度研究

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-23 DOI: 10.1093/pasj/psaa062

N. Liu, T. Sarotsakulchai, S. Rattanasoon, Bin Zhang

{"title":"Comprehensive photometric investigation of an active early K-type contact system—IL Cancri","authors":"N. Liu, T. Sarotsakulchai, S. Rattanasoon, Bin Zhang","doi":"10.1093/pasj/psaa062","DOIUrl":"https://doi.org/10.1093/pasj/psaa062","url":null,"abstract":"Comprehensive photometric investigation was carried out to the early K-type contact binary - IL Cnc. A few light curves from both ground-based telescopes and the Kepler space telescope were obtained (or downloaded) and then analyzed in detail. They are mostly found to be asymmetric and there are even continuously changing O'Connell effect in the light curves from Kepler K2 data, suggesting the system to be highly active. Using the Wilson-Devinney code (version 2013), photometric solutions were derived and then compared. It is found that the calculation of the mass ratio is easily affected by the spot settings. Combining the radial velocities determined from LAMOST median resolution spectral data, the mass ratio of the binary components is found to be $M_2/M_1 = 1.76pm 0.05$. The components are in shallow contact ($fsim 9%$) and have a temperature difference about $T_2 - T_1 = -280pm 20$ K. The system is demonstrated to be W-subtype, which may be a common feature of K-type contact binaries. The masses of the binary components were estimated to be $M_1sim 0.51$ M$_{sun}$ and $M_2sim 0.90$ M$_{sun}$. The values are in good agreement with that deduced from the parallax data of Gaia. The results suggest that the primary component lacks luminosity compared with the zero main sequence. The H$alpha$ spectral line of the primary component is found to be peculiar. Combining newly determined minimum light times with those collected from literature, the orbital period of IL Cnc is studied. It is found that the (O$-$C)s of the primary minima show sinusoidal variation while the secondary do not. The oscillation is more likely to be caused by the starspot activities. Yet this assumption needs more data to support.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86174458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Prospects for radio detection of stellar plasma beams 恒星等离子体束的无线电探测前景

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-21 DOI: 10.1051/0004-6361/202038576

H. K. Vedantham

引用次数: 3

Three-component modelling of C-rich AGB star winds – V. Effects of frequency-dependent radiative transfer including drift★ 富c AGB星风的三分量模拟——V.含漂移的频率相关辐射传输效应

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-06-19 DOI: 10.1093/mnras/staa2714

C. Sandin, L. Mattsson

{"title":"Three-component modelling of C-rich AGB star winds – V. Effects of frequency-dependent radiative transfer including drift★","authors":"C. Sandin, L. Mattsson","doi":"10.1093/mnras/staa2714","DOIUrl":"https://doi.org/10.1093/mnras/staa2714","url":null,"abstract":"Stellar winds of cool carbon stars enrich the interstellar medium with significant amounts of carbon and dust. We present a study of the influence of two-fluid flow on winds where we add descriptions of frequency-dependent radiative transfer. Our radiation hydrodynamic models in addition include stellar pulsations, grain growth and ablation, gas-to-dust drift using one mean grain size, dust extinction based on both the small particle limit and Mie scattering, and an accurate numerical scheme. We calculate models at high spatial resolution using 1024 gridpoints and solar metallicities at 319 frequencies, and we discern effects of drift by comparing drift models to non-drift models. Our results show differences of up to 1000 per cent in comparison to extant results. Mass-loss rates and wind velocities of drift models are typically, but not always, lower than in non-drift models. Differences are larger when Mie scattering is used instead of the small particle limit. Amongst other properties, the mass-loss rates of the gas and dust, dust-to-gas density ratio, and wind velocity show an exponential dependence on the dust-to-gas speed ratio. Yields of dust in the least massive winds increase by a factor four when drift is used. We find drift velocities in the range 10-67 km/s, which is drastically higher than in our earlier works that use grey radiative transfer. It is necessary to include an estimate of drift velocities to reproduce high yields of dust and low wind velocities.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89278909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 10