arXiv: Solar and Stellar Astrophysics最新文献_第7页

The luminosity constraint in the era of precision solar physics 精确太阳物理时代的光度约束

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-09-11 DOI: 10.1088/1361-6471/abb784

D. Vescovi, Carlo Mascaretti, F. Vissani, L. Piersanti, O. Straniero

引用次数: 4

The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars 贫金属主序星中行星吞噬对恒星旋转的影响

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-09-08 DOI: 10.1051/0004-6361/202038653

A. Oetjens, L. Carone, M. Bergemann, A. S. M. F. Astronomy, Ruprecht-Karls-Universitat Heidelberg, Institute for Space Sciences, Institut d'Estudis Espacials de Catalunya

{"title":"The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars","authors":"A. Oetjens, L. Carone, M. Bergemann, A. S. M. F. Astronomy, Ruprecht-Karls-Universitat Heidelberg, Institute for Space Sciences, Institut d'Estudis Espacials de Catalunya","doi":"10.1051/0004-6361/202038653","DOIUrl":"https://doi.org/10.1051/0004-6361/202038653","url":null,"abstract":"The method of gyrochronology relates the age of its star to its rotation period. However, recent evidence of deviations from gyrochronology relations was reported in the literature. Here, we study the influence of tidal interaction between a star and its companion on the rotation velocity of the star, in order to explain peculiar stellar rotation velocities. The interaction of a star and its planet is followed using a comprehensive numerical framework that combines tidal friction, magnetic braking, planet migration, and detailed stellar evolution models from the GARSTEC grid. We focus on close-in companions from 1 to 20 M$_{Jup}$ orbiting low-mass, 0.8 and 1 M$_{odot}$, main-sequence stars with a broad metallicity range from [Fe/H] = -1 to solar. Our simulations suggest that the dynamical interaction between a star and its companion can have different outcomes, which depend on the initial semi-major axis and the mass of the planet, as well as the mass and metallicity of its host star. In most cases, especially in the case of planet engulfment, we find a catastrophic increase in stellar rotation velocity from 1 kms$^{-1}$ to over 40 kms$^{-1}$, while the star is still on the main-sequence. The main prediction of our model is that low-mass main-sequence stars with abnormal rotation velocities should be more common at low-metallicity, as lower [Fe/H] favours faster planet engulfment, provided occurrence rate of close in massive planets is similar at all metallicities. Our scenario explains peculiar rotation velocities of low-mass main-sequence stars by the tidal interaction between the star and its companion. Current observational samples are too small and incomplete, and thus do not allow us to test our model.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"122 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87773251","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: 3

Full compressible 3D MHD simulation of solar wind 全可压缩3D MHD模拟太阳风

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-09-07 DOI: 10.1093/MNRAS/STAA3533

Takuma Matsumoto

引用次数: 15

An extremely hot white dwarf with a rapidly rotating K-type subgiant companion: UCAC2 46706450 一颗极热的白矮星与一颗快速旋转的k型次巨星伴星:UCAC2 46706450

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-09-07 DOI: 10.1051/0004-6361/202038574

K. Werner, N. Reindl, L. Lobling, I. Pelisoli, V. Schaffenroth, A. Rebassa-Mansergas, P. Irawati, Juanjuan Ren

{"title":"An extremely hot white dwarf with a rapidly rotating K-type subgiant companion: UCAC2 46706450","authors":"K. Werner, N. Reindl, L. Lobling, I. Pelisoli, V. Schaffenroth, A. Rebassa-Mansergas, P. Irawati, Juanjuan Ren","doi":"10.1051/0004-6361/202038574","DOIUrl":"https://doi.org/10.1051/0004-6361/202038574","url":null,"abstract":"UCAC2 46706450 is a late-type star with an ultraviolet (UV) excess. It was considered a candidate to establish a sample of FGK stars with white dwarf (WD) companions that can be used to test binary evolution models. To verify the WD nature of the companion, UV spectroscopy was performed by Parsons et al. (2016). By a detailed model-atmosphere analysis we show that the UV source is an extremely hot WD with effective temperature $T_mathrm{eff}$ = $105,000pm5000$ K, mass $M/M_odot = 0.54pm0.02$, radius $R/R_odot = 0.040^{+0.005}_{-0.004}$, and luminosity $L/L_odot= 176^{+55}_{-49}$, i.e., the compact object is just about to enter the WD cooling sequence. Investigating spectra of the cool star ($T_mathrm{eff}$ = $4945pm250$ K) we found that it is a K-type subgiant with $M/M_odot = 0.8-2.4$, $R/R_odot = 5.9^{+0.7}_{-0.5}$, and $L/L_odot= 19^{+5}_{-5}$, that is rapidly rotating with $v sin(i)=81$ km s$^{-1}$. Optical light curves reveal a period of two days and an o-band peak-to-peak amplitude of 0.06 mag. We suggest, that it is caused by stellar rotation in connection with star spots. With the radius we infer an extremely high rotational velocity of $v_{mathrm{rot}}=151^{+18}_{-13}$ km s$^{-1}$, thus marking the star as one of the most rapidly rotating subgiants known. This explains chromospheric activity observed by H$alpha$ emission and emission-line cores in CaII H and K as well as NUV flux excess. From equal and constant radial velocities of the WD and the K subgiant as well as from a fit to the spectral energy distribution we infer that they form a physical, wide though unresolved binary system. Both components exhibit similar metal abundances and show iron-group elements with slightly oversolar (up to 0.6 dex) abundance, meaning that atomic diffusion in the WD atmosphere is not yet active due to a residual, weak radiation-driven wind. (abridged)","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90852837","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: 1

SPECIES II. Stellar parameters of the EXPRESS program giant star sample 物种II。EXPRESS项目巨星样本的恒星参数

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-09-07 DOI: 10.1051/0004-6361/202039357

M. Soto, Mat'ias I. Jones, J. Jenkins

{"title":"SPECIES II. Stellar parameters of the EXPRESS program giant star sample","authors":"M. Soto, Mat'ias I. Jones, J. Jenkins","doi":"10.1051/0004-6361/202039357","DOIUrl":"https://doi.org/10.1051/0004-6361/202039357","url":null,"abstract":"As part of the search for planets around evolved stars, we can understand planet populations around significantly higher-mass stars than the Sun on the main sequence. This population is difficult to study any other way, particularly with radial-velocities since these stars are too hot and rotate too fast to measure precise velocities. Here we estimate stellar parameters for all of the giant stars from the EXPRESS project, which aims to detect planets orbiting evolved stars, and study their occurrence rate as a function of stellar mass. We analyse high resolution echelle spectra of these stars, and compute the atmospheric parameters by measuring the equivalent widths for a set of iron lines, using an updated method implemented during this work. Physical parameters are computed by interpolating through a grid of stellar evolutionary models, following a procedure that carefully takes into account the post-MS evolutionary phases. Probabilities of the star being in the red giant branch (RBG) or the horizontal branch (HB) are estimated from the derived distributions. Results: We find that, out of 166 evolved stars, 101 of them are most likely in the RGB phase, while 65 of them are in the HB phase. The mean derived mass is 1.41 and 1.87 Msun for RGB and HB stars, respectively. To validate our method, we compared our results with interferometry and asteroseismology studies. We find a difference in the radius with interferometry of 1.7%. With asteroseismology, we find 2.4% difference in logg, 1.5% in radius, 6.2% in mass, and 11.9% in age. Compared with previous spectroscopic studies, and find a 0.5% difference in Teff, 1% in logg, and 2% in [Fe/H]. We also find a mean mass difference with respect to the EXPRESS original catalogue of 16%. We show that the method presented here can greatly improve the estimates of the stellar parameters for giant stars compared to what was presented previously.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76957357","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: 1

How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions 如何从agb星的光谱能量分布中分辨出几何形状和质量损失率

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-08-26 DOI: 10.1051/0004-6361/202038029

J. Wiegert, M. Groenewegen, A. Jorissen, L. Decin, T. Danilovich

{"title":"How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions","authors":"J. Wiegert, M. Groenewegen, A. Jorissen, L. Decin, T. Danilovich","doi":"10.1051/0004-6361/202038029","DOIUrl":"https://doi.org/10.1051/0004-6361/202038029","url":null,"abstract":"High-angular-resolution observations of asymptotic giant branch (AGB) stars often reveal non-spherical morphologies for the gas and dust envelopes. We aim to make a pilot study to quantify the impact of different geometries (spherically symmetric, spiral-shaped, and disc-shaped) of the dust component of AGB envelopes on spectral energy distributions (SEDs), mass estimates, and subsequent mass-loss rate (MLR) estimates. We also estimate the error made on the MLR if the SED is fitted by an inappropriate geometrical model. We use the 3D Monte-Carlo-based radiative-transfer code RADMC-3D to simulate emission from dusty envelopes with different geometries (but fixed spatial extension). We compare these predictions with each other, and with the SED of the AGB star EP Aqr that we use as a benchmark since its envelope is disc-like and known to harbour spiral arms, as seen in CO. The SEDs involving the most massive envelopes are those for which the different geometries have the largest impact, primarily on the silicate features at 10 and 18 um. These different shapes originate from large differences in optical depths. Massive spirals and discs appear akin to black bodies. Optically thick edge-on spirals and discs (with dust masses of 1e-4 and 1e-5 Msun) exhibit black-body SEDs that appear cooler than those from face-on structures and spheres of the same mass, while optically thick face-on distributions appear as warmer emission. We find that our more realistic models, combined spherical and spiral distributions, are 0.1 to 0.5 times less massive than spheres with similar SEDs. More extreme, less realistic scenarios give that spirals and discs are 0.01 to 0.05 times less massive than corresponding spheres. This means that adopting the wrong geometry for an AGB circumstellar envelope may result in a MLR that is incorrect by as much as 1 to 2 orders of magnitude when derived from SED fitting.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88996455","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: 3

Quantifying the evidence for resonant damping of coronal waves with foot-point wave power asymmetry 用足点波能不对称量化日冕波共振阻尼的证据

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-08-01 DOI: 10.1051/0004-6361/201937237

M. Montes-Sol'is, I. Arregui

引用次数: 6

Toward precision cosmochronology 走向精确的宇宙年代学

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-07-27 DOI: 10.1051/0004-6361/202038879

S. Blouin, J. Daligault, D. Saumon, A. Bédard, P. Brassard

{"title":"Toward precision cosmochronology","authors":"S. Blouin, J. Daligault, D. Saumon, A. Bédard, P. Brassard","doi":"10.1051/0004-6361/202038879","DOIUrl":"https://doi.org/10.1051/0004-6361/202038879","url":null,"abstract":"The continuous cooling of a white dwarf is punctuated by events that affect its cooling rate. Probably the most significant of those is the crystallization of its core, a phase transition that occurs once the C/O interior has cooled down below a critical temperature. This transition releases latent heat as well as gravitational energy due to the redistribution of the C and O ions during solidification, thereby slowing down the evolution of the white dwarf. The unambiguous observational signature of core crystallization - a pile-up of objects in the cooling sequence - was recently reported. However, existing evolution models struggle to quantitatively reproduce this signature, casting doubt on their accuracy when used to measure the ages of stellar populations. The timing and amount of the energy released during crystallization depend on the exact form of the C/O phase diagram. Using the advanced Gibbs-Duhem integration method and state-of-the-art Monte Carlo simulations of the solid and liquid phases, we have obtained a very accurate version of this phase diagram, allowing a precise modeling of the phase transition. Despite this improvement, the magnitude of the crystallization pile-up remains underestimated by current evolution models. We conclude that latent heat release and O sedimentation alone are not sufficient to explain the observations and that other unaccounted physical mechanisms, possibly $^{22}$Ne phase separation, play an important role.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80830713","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

Classical Nova Persei 2018 outburst from the dwarf nova V392 Per 经典新星英仙座2018从矮新星V392 Per爆发

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-07-27 DOI: 10.22323/1.368.0029

D. Chochol, S. Shugarov, vLubom'ir Hamb'alek, A. Skopal, vStefan Parimucha, P. Dubovsk'y

{"title":"Classical Nova Persei 2018 outburst from the dwarf nova V392 Per","authors":"D. Chochol, S. Shugarov, vLubom'ir Hamb'alek, A. Skopal, vStefan Parimucha, P. Dubovsk'y","doi":"10.22323/1.368.0029","DOIUrl":"https://doi.org/10.22323/1.368.0029","url":null,"abstract":"On 2018, April 29, a bright classical nova (CN) Per 2018 was discovered. Its progenitor is a well-known dwarf nova V392 Per. In this contribution, we analyze $UBVR_{C}I_{C}$ photometry and optical spectroscopy of the CN V392 Per. From the $V$ light curve (LC) we found the brightness decline times t$_{2,V}$ = 3 d, t$_{3,V}$ = 10 d and calculated absolute magnitude of the nova at maximum $MV_{max}$ = -9.30 ${pm}$0.57 using the new $MV_{max}$ - t$_{3}$ \"universal\" decline law and $MV_{15}$ relations, adopting the Gaia data for CNe. We determined the colour excess $E_{B-V}$ = 0.90$pm$0.09 and distance to the nova $d$ = 3.55$pm$0.6 kpc. The optical spectrum obtained in brightness maximum resembles that of the F2 supergiant. Its bolometric luminosity computed by fitting the continuum by atmospheric and black-body models is in agreement with the luminosity, that we have found from photometry. We estimated the mass of the ONe white dwarf in V392 Per as $M_{wd}$ = 1.21 M$_{odot}$. The CN Per 2018 can be classified as a fast super-Eddington nova with an outburst LC of plateau type. Nova displayed He/N spectrum classification, large expansion velocities, and triple-peaked emission-line profiles during the decline, explained by equatorial ring seen nearly face on and a bipolar flow aligned almost with the line of sight. The post maximum spectra of CN Per 2018 and available radio data were used to estimate the inclination angle of the system as $isim$ 9$^{circ}$. The difference in intensity of redward and blueward emission bumps is possible to explain by about 1.5 times higher density of the receding outtflow. The rapid increase of the bipolar outflow radial velocities by $sim$300 km/s around day 5 after the maximum was caused by the fast bipolar winds from the burning white dwarf after shrinking of its pseudophotosphere.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81914712","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: 2

The luminosity evolution of nova shells 新星壳的光度演化

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-07-21 DOI: 10.1051/0004-6361/202037913

C. Tappert, N. Vogt, A. Ederoclite, L. Schmidtobreick, M. Vučković, L. L. Becegato

{"title":"The luminosity evolution of nova shells","authors":"C. Tappert, N. Vogt, A. Ederoclite, L. Schmidtobreick, M. Vučković, L. L. Becegato","doi":"10.1051/0004-6361/202037913","DOIUrl":"https://doi.org/10.1051/0004-6361/202037913","url":null,"abstract":"We present a re-analysis of the H$alpha$ and [OIII] flux data from the only comprehensive study of the luminosity evolution of nova shells, undertaken almost two decades ago. We use newly available distances and extinction values, and include additional luminosity data of 'ancient' nova shells. We compare the long-term behaviour with respect to nova speed class and light curve type. We find that, in general, the luminosity as a function of time can be described as consisting of an initial shallow logarithmic decline or constant behaviour, followed by a logarithmic main decline phase, with a possible return to a shallow decline or constancy at very late stages. The luminosity evolution in the first two phases is likely to be dominated by the expansion of the shell and the corresponding changes in volume and density, while for the older nova shells, the interaction with the interstellar medium comes into play. The slope of the main decline is very similar for almost all groups for a given emission line, but it is significantly steeper for [OIII], compared to H$alpha$, which we attribute to the more efficient cooling provided by the forbidden lines. The recurrent novae are among the notable exceptions, along with the plateau light curve type novae and the nova V838 Her. We speculate that this is due to the presence of denser material, possibly in the form of remnants from previous nova eruptions, or of planetary nebulae, As a by-product of our study, we revised the identification of all novae included in our investigation with sources in the Gaia Data Release 2 catalogue.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":"385 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73234160","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