Pub Date : 2020-09-11DOI: 10.1088/1361-6471/abb784
D. Vescovi, Carlo Mascaretti, F. Vissani, L. Piersanti, O. Straniero
The luminosity constraint is a very precise relationship linking the power released by the Sun as photons and the solar neutrino fluxes. Such a relation, which is a direct consequence of the physical processes controlling the production and the transport of energy in the solar interior, is of great importance for the studies of solar neutrinos and has a special role for the search of neutrinos from the CNO cycle, whose first detection with a 5$sigma$ significance has been recently announced by the Borexino collaboration. Here we revise the luminosity constraint, discussing and validating its underlying hypotheses, in the light of latest solar neutrino and luminosity measurements. We generalize the current formulation of the luminosity constraint relation so that it can be easily used in future analysis of solar neutrino data, and we provide a specific application showing the link between CNO and pp neutrino fluxes.
{"title":"The luminosity constraint in the era of precision solar physics","authors":"D. Vescovi, Carlo Mascaretti, F. Vissani, L. Piersanti, O. Straniero","doi":"10.1088/1361-6471/abb784","DOIUrl":"https://doi.org/10.1088/1361-6471/abb784","url":null,"abstract":"The luminosity constraint is a very precise relationship linking the power released by the Sun as photons and the solar neutrino fluxes. Such a relation, which is a direct consequence of the physical processes controlling the production and the transport of energy in the solar interior, is of great importance for the studies of solar neutrinos and has a special role for the search of neutrinos from the CNO cycle, whose first detection with a 5$sigma$ significance has been recently announced by the Borexino collaboration. Here we revise the luminosity constraint, discussing and validating its underlying hypotheses, in the light of latest solar neutrino and luminosity measurements. We generalize the current formulation of the luminosity constraint relation so that it can be easily used in future analysis of solar neutrino data, and we provide a specific application showing the link between CNO and pp neutrino fluxes.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74144013","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}
Pub Date : 2020-09-08DOI: 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
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.
{"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":null,"pages":null},"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}
Identifying the heating mechanisms of the solar corona and the driving mechanisms of solar wind are key challenges in understanding solar physics. A full three-dimensional compressible magnetohydrodynamic (MHD) simulation was conducted to distinguish between the heating mechanisms in the fast solar wind above the open field region. Our simulation describes the evolution of the Alfvenic waves, which includes the compressible effects from the photosphere to the heliospheric distance $s$ of 27 solar radii ($R_odot$). The hot corona and fast solar wind were reproduced simultaneously due to the dissipation of the Alfven waves. The inclusion of the transition region and lower atmosphere enabled us to derive the solar mass loss rate for the first time by performing a full three-dimensional compressible MHD simulation. The Alfven turbulence was determined to be the dominant heating mechanism in the solar wind acceleration region ($s>1.3 R_odot$), as suggested by previous solar wind models. In addition, shock formation and phase mixing are important below the lower transition region ($s<1.03R_odot$) as well.
{"title":"Full compressible 3D MHD simulation of solar wind","authors":"Takuma Matsumoto","doi":"10.1093/MNRAS/STAA3533","DOIUrl":"https://doi.org/10.1093/MNRAS/STAA3533","url":null,"abstract":"Identifying the heating mechanisms of the solar corona and the driving mechanisms of solar wind are key challenges in understanding solar physics. A full three-dimensional compressible magnetohydrodynamic (MHD) simulation was conducted to distinguish between the heating mechanisms in the fast solar wind above the open field region. Our simulation describes the evolution of the Alfvenic waves, which includes the compressible effects from the photosphere to the heliospheric distance $s$ of 27 solar radii ($R_odot$). The hot corona and fast solar wind were reproduced simultaneously due to the dissipation of the Alfven waves. The inclusion of the transition region and lower atmosphere enabled us to derive the solar mass loss rate for the first time by performing a full three-dimensional compressible MHD simulation. The Alfven turbulence was determined to be the dominant heating mechanism in the solar wind acceleration region ($s>1.3 R_odot$), as suggested by previous solar wind models. In addition, shock formation and phase mixing are important below the lower transition region ($s<1.03R_odot$) as well.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83374726","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}
Pub Date : 2020-09-07DOI: 10.1051/0004-6361/202038574
K. Werner, N. Reindl, L. Lobling, I. Pelisoli, V. Schaffenroth, A. Rebassa-Mansergas, P. Irawati, Juanjuan Ren
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)
UCAC2 46706450是一颗紫外线(UV)过剩的晚型恒星。它被认为是建立具有白矮星(WD)伴星的FGK恒星样本的候选者，可用于测试双星演化模型。为了验证伴星的WD性质，Parsons等人(2016)进行了紫外光谱分析。通过详细的模型-大气分析，我们发现紫外源是一个极热的WD，其有效温度$T_mathrm{eff}$ = $105,000pm5000$ K，质量$M/M_odot = 0.54pm0.02$，半径$R/R_odot = 0.040^{+0.005}_{-0.004}$，光度$L/L_odot= 176^{+55}_{-49}$，即致密物体即将进入WD冷却序列。研究这颗低温恒星($T_mathrm{eff}$ = $4945pm250$ K)的光谱，我们发现它是一颗K型亚巨星，拥有$M/M_odot = 0.8-2.4$、$R/R_odot = 5.9^{+0.7}_{-0.5}$和$L/L_odot= 19^{+5}_{-5}$，以$v sin(i)=81$ km s $^{-1}$的速度快速旋转。光学光曲线显示周期为2天，o波段峰对峰振幅为0.06等。我们认为，这是由恒星旋转与恒星黑子有关引起的。根据半径，我们推断出极高的旋转速度为$v_{mathrm{rot}}=151^{+18}_{-13}$ km s $^{-1}$，从而标志着这颗恒星是已知旋转速度最快的亚巨星之一。这解释了在CaII H和K的H $alpha$发射和发射在线岩心观测到的色球活动以及NUV通量过剩。从WD和K亚巨星的等速和恒定径向速度，以及与光谱能量分布的拟合，我们推断它们形成了一个物理上的、宽的、但尚未确定的双星系统。这两种成分都显示出相似的金属丰度，铁族元素的丰度略高于太阳(高达0.6指数)，这意味着由于残留的微弱辐射驱动的风，WD大气中的原子扩散尚未活跃。(节选)
{"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":null,"pages":null},"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}
Pub Date : 2020-09-07DOI: 10.1051/0004-6361/202039357
M. Soto, Mat'ias I. Jones, J. Jenkins
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.
{"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":null,"pages":null},"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}
Pub Date : 2020-08-26DOI: 10.1051/0004-6361/202038029
J. Wiegert, M. Groenewegen, A. Jorissen, L. Decin, T. Danilovich
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.
{"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":null,"pages":null},"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}
Pub Date : 2020-08-01DOI: 10.1051/0004-6361/201937237
M. Montes-Sol'is, I. Arregui
We use Coronal Multi-channel Polarimeter (CoMP) observations of propagating waves in the solar corona and Bayesian analysis to assess the evidence of models with resonant damping and foot-point wave power asymmetries. Two nested models are considered. The reduced model considers resonant damping as the sole cause of the measured discrepancy between outward and inward wave power. The larger model contemplates an extra source of asymmetry with origin at the foot-points. We first compute probability distributions of parameters conditional on the models and the observed data. The obtained constraints are then used to calculate the evidence for each model in view of data. We find that we need to consider the larger model to explain CoMP data and to accurately infer the damping ratio, hence, to better assess the possible contribution of the waves to coronal heating.
{"title":"Quantifying the evidence for resonant damping of coronal waves with foot-point wave power asymmetry","authors":"M. Montes-Sol'is, I. Arregui","doi":"10.1051/0004-6361/201937237","DOIUrl":"https://doi.org/10.1051/0004-6361/201937237","url":null,"abstract":"We use Coronal Multi-channel Polarimeter (CoMP) observations of propagating waves in the solar corona and Bayesian analysis to assess the evidence of models with resonant damping and foot-point wave power asymmetries. Two nested models are considered. The reduced model considers resonant damping as the sole cause of the measured discrepancy between outward and inward wave power. The larger model contemplates an extra source of asymmetry with origin at the foot-points. We first compute probability distributions of parameters conditional on the models and the observed data. The obtained constraints are then used to calculate the evidence for each model in view of data. We find that we need to consider the larger model to explain CoMP data and to accurately infer the damping ratio, hence, to better assess the possible contribution of the waves to coronal heating.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86847197","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}
Pub Date : 2020-07-27DOI: 10.1051/0004-6361/202038879
S. Blouin, J. Daligault, D. Saumon, A. Bédard, P. Brassard
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.
{"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":null,"pages":null},"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}
D. Chochol, S. Shugarov, vLubom'ir Hamb'alek, A. Skopal, vStefan Parimucha, P. Dubovsk'y
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$300 km/s around day 5 after the maximum was caused by the fast bipolar winds from the burning white dwarf after shrinking of its pseudophotosphere.
2018年4月29日，一颗明亮的古典新星(CN) Per 2018被发现。它的前身是一颗著名的矮新星V392 Per。在这篇文章中，我们分析了CN V392 Per的$UBVR_{C}I_{C}$光度和光谱学。从$V$光曲线(LC)中，我们得到了亮度衰减时间t $_{2,V}$ = 3 d, t $_{3,V}$ = 10 d，并利用新的$MV_{max}$ - t $_{3}$“普遍”衰减规律和$MV_{15}$关系，采用CNe的Gaia数据，计算出新星在最大时的绝对星等$MV_{max}$ = -9.30 ${pm}$ 0.57。我们确定了颜色过剩$E_{B-V}$ = 0.90 $pm$ 0.09和到新星的距离$d$ = 3.55 $pm$ 0.6 kpc。光谱的最大亮度与F2超巨星相似。通过大气和黑体模型拟合连续体计算出的它的放热光度与我们从光度学中得到的光度一致。我们估计V392 Per中的一颗白矮星的质量为$M_{wd}$ = 1.21 M $_{odot}$。CN Per 2018可以被归类为具有高原型爆发LC的快速超级爱丁顿新星。在衰退过程中，新星呈现出He/N光谱分类、大膨胀速度和三峰发射线分布，这可以用赤道环几乎正面指向和双极流几乎对准视线来解释。利用CN Per 2018的最大值后光谱和现有无线电数据估计系统的倾角为$isim$ 9 $^{circ}$。向蓝方向和向红方向发射凸点强度的差异可以用后退流出的密度高出1.5倍来解释。在最大值后第5天左右，双极出口径向速度迅速增加$sim$ 300 km/s，这是由燃烧的白矮星在其伪光球收缩后产生的快速双极风引起的。
{"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$300 km/s around day 5 after the maximum was caused by the fast bipolar winds from the burning white dwarf after shrinking of its pseudophotosphere.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81914712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-21DOI: 10.1051/0004-6361/202037913
C. Tappert, N. Vogt, A. Ederoclite, L. Schmidtobreick, M. Vučković, L. L. Becegato
We present a re-analysis of the H$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.
{"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":null,"pages":null},"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}
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