Pub Date : 2020-11-20DOI: 10.22201/IA.01851101P.2021.57.01.12
O. Karakuş, F. Ekmekçi
Within the scope of extended matter research, we present new spectral analysis results of an active binary system AR Lac. The low and high resolution spectra of this system were taken during the period 2013-2016. The evaluation of low dispersion spectra together with the B, V, Rc, Ic and WISE photometric data showed that AR Lac has an excess radiation in W2 band. In addition, the spectral energy distribution and the minima depth ratios of the light curves of this active binary system were studied to examine the flux contributions of the components of the system depending on wavelengths and on orbital phase. Furthermore, high resolution spectral analysis showed evidence of prominence-like structures and a possible extended matter around the cooler component of AR Lac binary system.
{"title":"NEW SPECTRAL ANALYSIS RESULTS WITHIN THE SCOPE OF EXTENDED MATTER RESEARCH IN THE AR LACERTAE ACTIVE BINARY SYSTEM","authors":"O. Karakuş, F. Ekmekçi","doi":"10.22201/IA.01851101P.2021.57.01.12","DOIUrl":"https://doi.org/10.22201/IA.01851101P.2021.57.01.12","url":null,"abstract":"Within the scope of extended matter research, we present new spectral analysis results of an active binary system AR Lac. The low and high resolution spectra of this system were taken during the period 2013-2016. The evaluation of low dispersion spectra together with the B, V, Rc, Ic and WISE photometric data showed that AR Lac has an excess radiation in W2 band. In addition, the spectral energy distribution and the minima depth ratios of the light curves of this active binary system were studied to examine the flux contributions of the components of the system depending on wavelengths and on orbital phase. Furthermore, high resolution spectral analysis showed evidence of prominence-like structures and a possible extended matter around the cooler component of AR Lac binary system.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90556586","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}
Shuo Zhang, A. Luo, G. Comte, Rui Wang, Yin-Bi Li, B. Du, W. Hou, Li Qin, J. Gizis, Jian-Jun Chen, Xiang-Lei Chen, Yan Lu, Yi-Han Song, Hua-Wei Zhang, F. Zuo
Applying the revised M subdwarf classification criteria discussed in Paper I to LAMOST DR7, combining the M subdwarf sample from Savcheva et al, a new M subdwarf sample was constructed for further study. The atmospheric parameters for each object were derived fitting with the PHOENIX grid, combining with Gaia DR2, the relationship between the gravity and metallicity were explored according to the locus both in the color-absolute magnitude diagram and the reduced proper motion diagram. Objects that have both the largest gravity and the lowest metallicity are located away from the main-sequence cloud and may be considered as the intrinsic M subdwarfs, which can be classified as luminosity class VI. Another group of objects whose spectra show typical M subdwarf characters have lower gravity and relatively moderate metal deficiency and occupy part of the ordinary M dwarf region in both diagrams. The Galactic U , V , W space velocity components and their dispersion show that the local Galactic halo population sampled in the solar neighborhood is represented by objects of high gravity and an inconspicuous bimodal metallicity distribution, with a fraction of prograde orbits. The other M subdwarfs seem to partly belong to the thick disk component with a significant fraction of thin disk moderately metal-poor objects intricately mixed with them. However, the selection effects, especially the favored anti-center direction of investigation in the LAMOST sub-sample, but also contamination by multiplicity and parameter coupling could play important roles and need to be further investigated.
{"title":"M Subdwarf Research. II. Atmospheric Parameters and Kinematics","authors":"Shuo Zhang, A. Luo, G. Comte, Rui Wang, Yin-Bi Li, B. Du, W. Hou, Li Qin, J. Gizis, Jian-Jun Chen, Xiang-Lei Chen, Yan Lu, Yi-Han Song, Hua-Wei Zhang, F. Zuo","doi":"10.12149/101043","DOIUrl":"https://doi.org/10.12149/101043","url":null,"abstract":"Applying the revised M subdwarf classification criteria discussed in Paper I to LAMOST DR7, combining the M subdwarf sample from Savcheva et al, a new M subdwarf sample was constructed for further study. The atmospheric parameters for each object were derived fitting with the PHOENIX grid, combining with Gaia DR2, the relationship between the gravity and metallicity were explored according to the locus both in the color-absolute magnitude diagram and the reduced proper motion diagram. Objects that have both the largest gravity and the lowest metallicity are located away from the main-sequence cloud and may be considered as the intrinsic M subdwarfs, which can be classified as luminosity class VI. Another group of objects whose spectra show typical M subdwarf characters have lower gravity and relatively moderate metal deficiency and occupy part of the ordinary M dwarf region in both diagrams. The Galactic U , V , W space velocity components and their dispersion show that the local Galactic halo population sampled in the solar neighborhood is represented by objects of high gravity and an inconspicuous bimodal metallicity distribution, with a fraction of prograde orbits. The other M subdwarfs seem to partly belong to the thick disk component with a significant fraction of thin disk moderately metal-poor objects intricately mixed with them. However, the selection effects, especially the favored anti-center direction of investigation in the LAMOST sub-sample, but also contamination by multiplicity and parameter coupling could play important roles and need to be further investigated.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78324365","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 : 2020-11-20DOI: 10.1051/0004-6361/202039952
A. Pastorello, M. Fraser, G. Valerin, A. Reguitti, K. Itagaki, P. Ochner, S. Williams, S. Smartt, K. Smith, S. Srivastav, N. Elias-Rosa, E. Kankare, E. Karamehmetoglu, P. Lundqvist, P. Mazzali, U. Munari, M. Stritzinger, L. Tomasella, J. Anderson, K. Chambers, A. Rest
We present the follow-up campaign of the luminous red nova (LRN) AT~2019zhd, the third event of this class observed in M 31. The object was followed by several sky surveys for about five months before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from M_r=-2.8+-0.2 mag to M_r=-5.6+-0.1 mag. Then, over a four-five day period, AT 2019zhd experienced a major brightening, reaching at peak M_r=-9.61+-0.08 mag, and an optical luminosity of 1.4x10^39 erg/s. After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, Halpha becomes very weak, Hbeta is no longer detectable and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the post-plateau decline, show a very red continuum (T_eff ~ 3000 K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN V1309 Sco, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (M_F555W=0.21+-0.14 mag, with F555W-F814W = 2.96+-0.12 mag) at the position of AT 2019zhd, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.
{"title":"Luminous Red Nova AT 2019zhd, a new merger in M 31.","authors":"A. Pastorello, M. Fraser, G. Valerin, A. Reguitti, K. Itagaki, P. Ochner, S. Williams, S. Smartt, K. Smith, S. Srivastav, N. Elias-Rosa, E. Kankare, E. Karamehmetoglu, P. Lundqvist, P. Mazzali, U. Munari, M. Stritzinger, L. Tomasella, J. Anderson, K. Chambers, A. Rest","doi":"10.1051/0004-6361/202039952","DOIUrl":"https://doi.org/10.1051/0004-6361/202039952","url":null,"abstract":"We present the follow-up campaign of the luminous red nova (LRN) AT~2019zhd, the third event of this class observed in M 31. The object was followed by several sky surveys for about five months before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from M_r=-2.8+-0.2 mag to M_r=-5.6+-0.1 mag. Then, over a four-five day period, AT 2019zhd experienced a major brightening, reaching at peak M_r=-9.61+-0.08 mag, and an optical luminosity of 1.4x10^39 erg/s. After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, Halpha becomes very weak, Hbeta is no longer detectable and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the post-plateau decline, show a very red continuum (T_eff ~ 3000 K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN V1309 Sco, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (M_F555W=0.21+-0.14 mag, with F555W-F814W = 2.96+-0.12 mag) at the position of AT 2019zhd, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77751652","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}
A medium- and high-resolution spectroscopic survey of helium-rich hot subdwarfs is being carried out using the Southern African Large Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs and of sequences connecting chemically-peculiar subdwarfs of different types. The first phase consists of medium-resolution spectroscopy of over 100 stars selected from low-resolution surveys. This paper describes the selection criteria, and the observing, classification and analysis methods. It presents 107 spectral classifications on the MK-like Drilling system and 106 coarse analyses ($T_{rm eff}, log g, log y$) based on a hybrid grid of zero-metal non-LTE and line-blanketed LTE model atmospheres. For 75 stars, atmospheric parameters have been derived for the first time. The sample may be divided into 6 distinct groups including the classical `helium-rich' sdO stars with spectral types (Sp) sdO6.5 - sdB1 (74) comprising carbon-rich (35) and carbon-weak (39) stars, very hot He-sdO's with Sp $lesssim$ sdO6 (13), extreme helium stars with luminosity class $lesssim 5$ (5), intermediate helium-rich subdwarfs with helium class 25 -- 35 (8), and intermediate helium-rich subdwarfs with helium class $10 - 25$ (6). The last covers a narrow spectral range (sdB0 -- sdB1) including two known and four candidate heavy-metal subdwarfs. Within other groups are several stars of individual interest, including an extremely metal-poor helium star, candidate double-helium subdwarf binaries, and a candidate low-gravity He-sdO star.
{"title":"The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis","authors":"C. Jeffery, B. Miszalski, E. Snowdon","doi":"10.1093/mnras/staa3648","DOIUrl":"https://doi.org/10.1093/mnras/staa3648","url":null,"abstract":"A medium- and high-resolution spectroscopic survey of helium-rich hot subdwarfs is being carried out using the Southern African Large Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs and of sequences connecting chemically-peculiar subdwarfs of different types. The first phase consists of medium-resolution spectroscopy of over 100 stars selected from low-resolution surveys. This paper describes the selection criteria, and the observing, classification and analysis methods. It presents 107 spectral classifications on the MK-like Drilling system and 106 coarse analyses ($T_{rm eff}, log g, log y$) based on a hybrid grid of zero-metal non-LTE and line-blanketed LTE model atmospheres. For 75 stars, atmospheric parameters have been derived for the first time. The sample may be divided into 6 distinct groups including the classical `helium-rich' sdO stars with spectral types (Sp) sdO6.5 - sdB1 (74) comprising carbon-rich (35) and carbon-weak (39) stars, very hot He-sdO's with Sp $lesssim$ sdO6 (13), extreme helium stars with luminosity class $lesssim 5$ (5), intermediate helium-rich subdwarfs with helium class 25 -- 35 (8), and intermediate helium-rich subdwarfs with helium class $10 - 25$ (6). The last covers a narrow spectral range (sdB0 -- sdB1) including two known and four candidate heavy-metal subdwarfs. Within other groups are several stars of individual interest, including an extremely metal-poor helium star, candidate double-helium subdwarf binaries, and a candidate low-gravity He-sdO star.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87052687","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}
Observations in space plasmas reveal particle velocity distributions out of thermal equilibrium, with anisotropies (e.g., parallel drifts or/and different temperatures, $T_parallel$ - parallel and $T_perp$ - perpendicular, with respect to the background magnetic field), and multiple quasithermal and suprathermal populations with different properties. The recently introduced (isotropic) $kappa$-cookbook is generalized in the present paper to cover all these cases of anisotropic and multi-component distributions reported by the observations. We derive general analytical expressions for the velocity moments and show that the common (bi-)Maxwellian and (bi-)$kappa-$distributions are obtained as limiting cases of the generalized anisotropic $kappa$-cookbook (or recipes). Based on this generalization, a new 2D fitting procedure is introduced, with an improved level of confidence compared to the 1D fitting methods widely used to quantify the main properties of the observed distributions. The nonlinear least-squares fit is led{applied to electron data sets} measured by the Ulysses spacecraft confirming the existence of three different populations, a quasithermal core and two suprathermal (halo and strahl) components. In general, the best overall fit is given by the sum of a Maxwellian and two generalized $kappa$-distributions.
在空间等离子体中的观测揭示了热平衡之外的粒子速度分布，具有各向异性(例如，平行漂移或/和不同的温度，$T_parallel$ -平行和$T_perp$ -垂直，相对于背景磁场)，以及具有不同性质的多个准热和超热群。本文对最近引进的(各向同性)$kappa$ -cookbook进行了推广，以涵盖观测报告的各向异性和多分量分布的所有情况。我们推导了速度矩的一般解析表达式，并证明了一般的(bi-)麦克斯韦分布和(bi-) $kappa-$分布作为广义各向异性$kappa$ -食谱(或食谱)的极限情况。在此基础上，引入了一种新的二维拟合程序，与广泛用于量化观测分布的主要属性的一维拟合方法相比，该程序具有更高的置信度。尤利西斯航天器测量的非线性最小二乘拟合led{applied to electron data sets}证实了三个不同种群的存在，一个准热核心和两个超热(晕和斯特拉尔)成分。一般来说，最佳的总体拟合是由麦克斯韦分布和两个广义$kappa$ -分布的和给出的。
{"title":"Generalized anisotropic κ-cookbook: 2D fitting of Ulysses electron data","authors":"K. Scherer, E. Husidic, M. Lazar, H. Fichtner","doi":"10.1093/mnras/staa3641","DOIUrl":"https://doi.org/10.1093/mnras/staa3641","url":null,"abstract":"Observations in space plasmas reveal particle velocity distributions out of thermal equilibrium, with anisotropies (e.g., parallel drifts or/and different temperatures, $T_parallel$ - parallel and $T_perp$ - perpendicular, with respect to the background magnetic field), and multiple quasithermal and suprathermal populations with different properties. The recently introduced (isotropic) $kappa$-cookbook is generalized in the present paper to cover all these cases of anisotropic and multi-component distributions reported by the observations. We derive general analytical expressions for the velocity moments and show that the common (bi-)Maxwellian and (bi-)$kappa-$distributions are obtained as limiting cases of the generalized anisotropic $kappa$-cookbook (or recipes). Based on this generalization, a new 2D fitting procedure is introduced, with an improved level of confidence compared to the 1D fitting methods widely used to quantify the main properties of the observed distributions. The nonlinear least-squares fit is led{applied to electron data sets} measured by the Ulysses spacecraft confirming the existence of three different populations, a quasithermal core and two suprathermal (halo and strahl) components. In general, the best overall fit is given by the sum of a Maxwellian and two generalized $kappa$-distributions.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82068050","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}
G. Altavilla, S. Marinoni, E. Pancino, S. Galleti, M. Bellazzini, N. Sanna, M. Rainer, G. Tessicini, J. Carrasco, A. Bragaglia, W. Schuster, G. Cocozza, M. Gebran, H. Voss, L. Federici, E. Masana, C. Jordi, M. Mongui'o, A. Castro, M. Peña-Guerrero, A. Pérez-Villegas
We present Johnson-Kron-Cousins BVRI photometry of 228 candidate spectrophotometric standard stars for the external (absolute) flux calibration of Gaia data. The data were gathered as part of a ten-year observing campaign with the goal of building the external grid of flux standards for Gaia and we obtained absolute photometry, relative photometry for constancy monitoring, and spectrophotometry. Preliminary releases of the flux tables were used to calibrate the first two Gaia releases. This paper focuses on the imaging frames observed in good sky conditions (about 9100). The photometry will be used to validate the ground-based flux tables of the Gaia spectrophotometric standard stars and to correct the spectra obtained in non-perfectly photometric observing conditions for small zeropoint variations. The absolute photometry presented here is tied to the Landolt standard stars system to $simeq$1 per cent or better, depending on the photometric band. Extensive comparisons with various literature sources show an overall $simeq$1 per cent agreement, which appears to be the current limit in the accuracy of flux calibrations across various samples and techniques in the literature. The Gaia photometric precision is presently of the order of 0.1 per cent or better, thus various ideas for the improvement of photometric calibration accuracy are discussed.
{"title":"The Gaia spectrophotometric standard stars survey – IV. Results of the absolute photometry campaign","authors":"G. Altavilla, S. Marinoni, E. Pancino, S. Galleti, M. Bellazzini, N. Sanna, M. Rainer, G. Tessicini, J. Carrasco, A. Bragaglia, W. Schuster, G. Cocozza, M. Gebran, H. Voss, L. Federici, E. Masana, C. Jordi, M. Mongui'o, A. Castro, M. Peña-Guerrero, A. Pérez-Villegas","doi":"10.1093/mnras/staa3655","DOIUrl":"https://doi.org/10.1093/mnras/staa3655","url":null,"abstract":"We present Johnson-Kron-Cousins BVRI photometry of 228 candidate spectrophotometric standard stars for the external (absolute) flux calibration of Gaia data. The data were gathered as part of a ten-year observing campaign with the goal of building the external grid of flux standards for Gaia and we obtained absolute photometry, relative photometry for constancy monitoring, and spectrophotometry. Preliminary releases of the flux tables were used to calibrate the first two Gaia releases. This paper focuses on the imaging frames observed in good sky conditions (about 9100). The photometry will be used to validate the ground-based flux tables of the Gaia spectrophotometric standard stars and to correct the spectra obtained in non-perfectly photometric observing conditions for small zeropoint variations. The absolute photometry presented here is tied to the Landolt standard stars system to $simeq$1 per cent or better, depending on the photometric band. Extensive comparisons with various literature sources show an overall $simeq$1 per cent agreement, which appears to be the current limit in the accuracy of flux calibrations across various samples and techniques in the literature. The Gaia photometric precision is presently of the order of 0.1 per cent or better, thus various ideas for the improvement of photometric calibration accuracy are discussed.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89553819","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}
J. Echevarr'ia, J. V. Hernández Santisteban, O. Segura Montero, S. Ram'irez, A. Ruelas-Mayorga, L. S'anchez, R. Michel, R. Costero, D. González-Buitrago, J. Olivares
Spectroscopic observations of AH Herculis during a deep quiescent state are put forward. We found the object in a rare long minima, allowing us to derive accurately the semi-amplitudes: $K_1 =121 pm , 4$ kms and $K_2 =152 pm 2$ kms and its mass functions $M_W{ sin }^{ 3 }i=0.30 pm 0.01$ M$_{odot}$ and $M_R{ sin }^{ 3 }i=0.24 pm 0.02$ M$_{odot}$, while its binary separation is given by $a sin i =1.39 pm 0.02$~R$_{odot}$. The orbital period $P_{orb}$~=~ 0.25812~$pm~0.00032$~days was found from a power spectrum analysis of the radial velocities of the secondary star. These values are consistent with those determined by citet{Horne:1986}. Our observations indicate that K5 is the most likely spectral type of the secondary. We discuss why we favour the assumption that the donor in AH Her is a slightly evolved star, in which case we find that the best solution for the inclination yields $i = 48^circ pm 2^circ$. Nonetheless, should the donor be a ZAMS star, we obtain that the inclination is between $ i = 43^circ$ and $i = 44^circ$. We also present Doppler tomography of H$alpha$ and H$beta$, and found that the emission in both lines is concentrated in a large asymmetric region at low velocities, but at an opposite position to the secondary star, outside the tidal radius and therefore at an unstable position. We also analyse the H$alpha$ and H$beta$ line profiles, which show a single broad peak and compare it with the previous quiescent state study which shows a double-peaked profile, providing evidence for its transient nature.
提出了大力神星在深静止状态下的光谱观测结果。我们找到了一个罕见的长极小值，使我们能够准确地推导出半振幅:$K_1 =121 pm , 4$kms和$K_2 =152 pm 2$kms及其质量函数$M_W{ sin }^{ 3 }i=0.30 pm 0.01$ M $_{odot}$和$M_R{ sin }^{ 3 }i=0.24 pm 0.02$ M $_{odot}$，而其二进制分离由$a sin i =1.39 pm 0.02$ R $_{odot}$给出。轨道周期$P_{orb}$ = 0.25812 $pm~0.00032$天是通过对该副恒星径向速度的功率谱分析得出的。这些值与citet{Horne:1986}确定的值一致。我们的观察表明，K5是最可能的光谱型的次星系。我们讨论了为什么我们倾向于假设AH Her的供体是一颗稍微进化的恒星，在这种情况下，我们发现倾角的最佳解决方案是$i = 48^circ pm 2^circ$。然而，如果捐赠者是一颗ZAMS星，我们得到的倾斜度介于$ i = 43^circ$和$i = 44^circ$之间。我们还对H $alpha$和H $beta$进行了多普勒断层扫描，发现两条线的辐射在低速时集中在一个大的不对称区域，但在与副恒星相反的位置，在潮汐半径之外，因此处于不稳定的位置。我们还分析了H $alpha$和H $beta$线剖面，它们显示一个单一的宽峰，并将其与先前的静态状态研究结果进行了比较，该研究显示了双峰剖面，为其瞬态性质提供了证据。
{"title":"New radial velocity observations of AH Her: evidence for material outside the tidal radius","authors":"J. Echevarr'ia, J. V. Hernández Santisteban, O. Segura Montero, S. Ram'irez, A. Ruelas-Mayorga, L. S'anchez, R. Michel, R. Costero, D. González-Buitrago, J. Olivares","doi":"10.1093/mnras/staa3615","DOIUrl":"https://doi.org/10.1093/mnras/staa3615","url":null,"abstract":"Spectroscopic observations of AH Herculis during a deep quiescent state are put forward. We found the object in a rare long minima, allowing us to derive accurately the semi-amplitudes: $K_1 =121 pm , 4$ kms and $K_2 =152 pm 2$ kms and its mass functions $M_W{ sin }^{ 3 }i=0.30 pm 0.01$ M$_{odot}$ and $M_R{ sin }^{ 3 }i=0.24 pm 0.02$ M$_{odot}$, while its binary separation is given by $a sin i =1.39 pm 0.02$~R$_{odot}$. The orbital period $P_{orb}$~=~ 0.25812~$pm~0.00032$~days was found from a power spectrum analysis of the radial velocities of the secondary star. These values are consistent with those determined by citet{Horne:1986}. Our observations indicate that K5 is the most likely spectral type of the secondary. We discuss why we favour the assumption that the donor in AH Her is a slightly evolved star, in which case we find that the best solution for the inclination yields $i = 48^circ pm 2^circ$. Nonetheless, should the donor be a ZAMS star, we obtain that the inclination is between $ i = 43^circ$ and $i = 44^circ$. We also present Doppler tomography of H$alpha$ and H$beta$, and found that the emission in both lines is concentrated in a large asymmetric region at low velocities, but at an opposite position to the secondary star, outside the tidal radius and therefore at an unstable position. We also analyse the H$alpha$ and H$beta$ line profiles, which show a single broad peak and compare it with the previous quiescent state study which shows a double-peaked profile, providing evidence for its transient nature.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90453259","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}
An all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the IMF, mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the single-star Tycho-2 sample and successfully reproduces the observed magnitudes and angular separations. The projected separation distribution follows $f(s)sim s^{-1.2}$ in $10^2 - 2cdot10^3$ AU range for 1--4.5 $m_{odot}$ primary stars. Several algorithms are explored as pairing functions. Random pairing is confidently rejected. Primary-constrained (PCP) and split-core pairing (SCP), the scenarios adopting primary component's or total system's mass as fundamental, are considered. The preferred IMF slope is $alpha sim 2.8$ either way. A simple power-law mass ratio distribution is unlikely, but the introduction of a twin excess provides a favourable result. PCP with $f(q) sim q^{-1}$ is preferred with a tiny twin fraction, models with $f(q) sim q^{-1.5}$ are acceptable when a larger twin excess is allowed. SCP is similar to PCP when a larger slope of the power law is adopted: $f(q)sim q^{beta+0.7}$.
{"title":"Pairing function of visual binary stars","authors":"D. Chulkov","doi":"10.1093/mnras/staa3601","DOIUrl":"https://doi.org/10.1093/mnras/staa3601","url":null,"abstract":"An all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the IMF, mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the single-star Tycho-2 sample and successfully reproduces the observed magnitudes and angular separations. The projected separation distribution follows $f(s)sim s^{-1.2}$ in $10^2 - 2cdot10^3$ AU range for 1--4.5 $m_{odot}$ primary stars. Several algorithms are explored as pairing functions. Random pairing is confidently rejected. Primary-constrained (PCP) and split-core pairing (SCP), the scenarios adopting primary component's or total system's mass as fundamental, are considered. The preferred IMF slope is $alpha sim 2.8$ either way. A simple power-law mass ratio distribution is unlikely, but the introduction of a twin excess provides a favourable result. PCP with $f(q) sim q^{-1}$ is preferred with a tiny twin fraction, models with $f(q) sim q^{-1.5}$ are acceptable when a larger twin excess is allowed. SCP is similar to PCP when a larger slope of the power law is adopted: $f(q)sim q^{beta+0.7}$.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85400121","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}
The DAV star R808 was observed by 13 different telescopes for more than 170 hours in April 2008 on the WET run XCOV26. 25 independent pulsation frequencies were identified by this data set. We assumed 19 $m$ = 0 modes and performed an asteroseismological study on those 19 modes. We evolve grids of DAV star models by texttt{WDEC} adopting the element diffusion scheme with pure and screened Coulomb potential effect. The core compositions are from white dwarf models evolved by texttt{MESA}, which are thermal nuclear burning results. Our best fitting model is from the screened Coulomb potential scenario, which has parameters of log($M_{rm He}/M_{rm *}$) = -2.4, log($M_{rm H}/M_{rm *}$) = -5.2, $T_{rm eff}$ = 11100,K, $M_{rm *}$ = 0.710,$M_{odot}$, log$g$ = 8.194, and $sigma_{RMS}$ = 2.86,s. The value of $sigma_{RMS}$ is the smallest among the four existing asteroseismological work. The average period spacing is 46.299,s for $l$ = 1 modes and 25.647,s for $l$ = 2 modes. The other 6 observed modes can be fitted by $m$ $neq$ 0 components of some modes for our best fitting model. Fitting the 25 observed modes, we obtain a $sigma_{RMS}$ value of 2.59,s. Considering the period spacings, we also assume, that at least in one case, we detect an $l$ = 2 trapped mode.
{"title":"Asteroseismology of the DAV star R808","authors":"Yanhui Chen, H. Shu","doi":"10.1093/mnras/staa3572","DOIUrl":"https://doi.org/10.1093/mnras/staa3572","url":null,"abstract":"The DAV star R808 was observed by 13 different telescopes for more than 170 hours in April 2008 on the WET run XCOV26. 25 independent pulsation frequencies were identified by this data set. We assumed 19 $m$ = 0 modes and performed an asteroseismological study on those 19 modes. We evolve grids of DAV star models by texttt{WDEC} adopting the element diffusion scheme with pure and screened Coulomb potential effect. The core compositions are from white dwarf models evolved by texttt{MESA}, which are thermal nuclear burning results. Our best fitting model is from the screened Coulomb potential scenario, which has parameters of log($M_{rm He}/M_{rm *}$) = -2.4, log($M_{rm H}/M_{rm *}$) = -5.2, $T_{rm eff}$ = 11100,K, $M_{rm *}$ = 0.710,$M_{odot}$, log$g$ = 8.194, and $sigma_{RMS}$ = 2.86,s. The value of $sigma_{RMS}$ is the smallest among the four existing asteroseismological work. The average period spacing is 46.299,s for $l$ = 1 modes and 25.647,s for $l$ = 2 modes. The other 6 observed modes can be fitted by $m$ $neq$ 0 components of some modes for our best fitting model. Fitting the 25 observed modes, we obtain a $sigma_{RMS}$ value of 2.59,s. Considering the period spacings, we also assume, that at least in one case, we detect an $l$ = 2 trapped mode.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76355764","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}
Carina is a nearby young stellar association. So far, only a small number of stars have been clearly identified as members of this association. In this paper we reanalyse the membership of the association in light of Gaia DR2 data, in particular finding that HD 95086 is a potential member (probability of 71%). This star is noteworthy as one of the few stars that hosts both a detected debris disc and a directly imaged planet. It has previously only been considered as a potential member of the Lower Centaurus Crux (LCC) - part of the Scorpius-Centaurus association. We also reanalyse the age of the Carina association. Using a Bayesian inference code applied to infer a solution from stellar evolution models for the most probable (>99%) members of Carina, we infer an age for the association of 13.3$^{+1.1}_{-0.6}$ Myr, much younger than previous studies. Whilst we have revised HD 95086's association membership from LCC to Carina, the fact that we also find Carina to have a younger age, similar to that of LCC, means that the estimates of HD 95086b's mass remain unchanged. However, the younger age of Carina does mean that the companion to another Carina member, HD 44627 (or AB Pic), has a mass that is more clearly in the planet rather than brown dwarf range.
{"title":"The age of the carina young association and potential membership of HD 95086","authors":"M. Booth, C. del Burgo, V. Hambaryan","doi":"10.1093/mnras/staa3631","DOIUrl":"https://doi.org/10.1093/mnras/staa3631","url":null,"abstract":"Carina is a nearby young stellar association. So far, only a small number of stars have been clearly identified as members of this association. In this paper we reanalyse the membership of the association in light of Gaia DR2 data, in particular finding that HD 95086 is a potential member (probability of 71%). This star is noteworthy as one of the few stars that hosts both a detected debris disc and a directly imaged planet. It has previously only been considered as a potential member of the Lower Centaurus Crux (LCC) - part of the Scorpius-Centaurus association. We also reanalyse the age of the Carina association. Using a Bayesian inference code applied to infer a solution from stellar evolution models for the most probable (>99%) members of Carina, we infer an age for the association of 13.3$^{+1.1}_{-0.6}$ Myr, much younger than previous studies. Whilst we have revised HD 95086's association membership from LCC to Carina, the fact that we also find Carina to have a younger age, similar to that of LCC, means that the estimates of HD 95086b's mass remain unchanged. However, the younger age of Carina does mean that the companion to another Carina member, HD 44627 (or AB Pic), has a mass that is more clearly in the planet rather than brown dwarf range.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81676165","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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