G. Valle, M. Dell'Omodarme, P. G. Prada Moroni, S. Degl'Innocenti
We compared stellar radii derived from asteroseismic scaling relations with those estimated using two independent surface brightness-colour relations (SBCRs) and Gaia DR3 parallaxes. We cross-matched asteroseismic and astrometric data for over 6,400 RGB and RC stars from the APO-K2 catalogue with the TESS Input Catalogue v8.2 to obtain precise V band magnitudes and E(B-V) colour excesses. We then adopted two different SBCRs from the literature to derive stellar radius estimates, denoted as $R^a$ and $R^b$, respectively. We analysed the ratio of these SBCR-derived radii to the asteroseismic radius estimates, $R$, provided in the APO-K2 catalogue. Both SBCRs exhibited good agreement with asteroseismic radius estimates. On average, $R^a$ was overestimated by 1.2% with respect to $R$, while $R^b$ was underestimated by 2.5%. For stars larger than 20 $R_{odot}$, SBCR radii are systematically lower than asteroseismic ones. The agreement with asteroseismic radii shows a strong dependence on the parallax. The dispersion is halved for stars with a parallax greater than 2.5 mas. In this subsample, $R^b$ showed perfect agreement with $R$, while $R^a$ remained slightly overestimated by 3%. A trend with [Fe/H] of 4% to 6% per dex was found. For stars less massive than about 0.95 $M_{odot}$, SBCR radii were significantly higher than asteroseismic ones, by about 6%. This overestimation correlated with the presence of extended helium cores in these stars' structures relative to their envelopes. Furthermore, radius ratios showed a dichotomous behaviour at higher masses, mainly due to the presence of several RC stars with SBCR radii significantly lower with respect to asteroseismology. This behaviour originates from a different response of asteroseismic scaling relations and SBCR to [$alpha$/Fe] abundance ratios for massive stars, both in RGB and RC phases, which is reported here for the first time.
{"title":"Testing the asteroseismic estimates of stellar radii with surface brightness-colour relations and Gaia DR3 parallaxes. Red giants and red clump stars","authors":"G. Valle, M. Dell'Omodarme, P. G. Prada Moroni, S. Degl'Innocenti","doi":"arxiv-2409.10050","DOIUrl":"https://doi.org/arxiv-2409.10050","url":null,"abstract":"We compared stellar radii derived from asteroseismic scaling relations with\u0000those estimated using two independent surface brightness-colour relations\u0000(SBCRs) and Gaia DR3 parallaxes. We cross-matched asteroseismic and astrometric\u0000data for over 6,400 RGB and RC stars from the APO-K2 catalogue with the TESS\u0000Input Catalogue v8.2 to obtain precise V band magnitudes and E(B-V) colour\u0000excesses. We then adopted two different SBCRs from the literature to derive\u0000stellar radius estimates, denoted as $R^a$ and $R^b$, respectively. We analysed\u0000the ratio of these SBCR-derived radii to the asteroseismic radius estimates,\u0000$R$, provided in the APO-K2 catalogue. Both SBCRs exhibited good agreement with\u0000asteroseismic radius estimates. On average, $R^a$ was overestimated by 1.2%\u0000with respect to $R$, while $R^b$ was underestimated by 2.5%. For stars larger\u0000than 20 $R_{odot}$, SBCR radii are systematically lower than asteroseismic\u0000ones. The agreement with asteroseismic radii shows a strong dependence on the\u0000parallax. The dispersion is halved for stars with a parallax greater than 2.5\u0000mas. In this subsample, $R^b$ showed perfect agreement with $R$, while $R^a$\u0000remained slightly overestimated by 3%. A trend with [Fe/H] of 4% to 6% per dex\u0000was found. For stars less massive than about 0.95 $M_{odot}$, SBCR radii were\u0000significantly higher than asteroseismic ones, by about 6%. This overestimation\u0000correlated with the presence of extended helium cores in these stars'\u0000structures relative to their envelopes. Furthermore, radius ratios showed a\u0000dichotomous behaviour at higher masses, mainly due to the presence of several\u0000RC stars with SBCR radii significantly lower with respect to asteroseismology.\u0000This behaviour originates from a different response of asteroseismic scaling\u0000relations and SBCR to [$alpha$/Fe] abundance ratios for massive stars, both in\u0000RGB and RC phases, which is reported here for the first time.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"206 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258036","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}
Thanawuth Thanathibodee, Connor Robinson, Nuria Calvet, Catherine Espaillat, Caeley Pittman, Nicole Arulanantham, Kevin France, Hans Moritz Günther, Seok-Jun Chang, P. Christian Schneider
The C IV doublet in the UV has long been associated with accretion in T Tauri stars. However, it is still unclear where and how the lines are formed. Here, we present a new C IV line model based on the currently available accretion shock and accretion flow models. We assume axisymmetric, dipolar accretion flows with different energy fluxes and calculate the properties of the accretion shock. We use Cloudy to obtain the carbon level populations and calculate the emerging line profiles assuming a plane-parallel geometry near the shock. Our model generally reproduces the intensities and shapes of the C IV emission lines observed from T Tauri stars. We find that the narrow component is optically thin and originates in the postshock, while the broad component is optically thick and emerges from the preshock. We apply our model to seven T Tauri stars from the Hubble Ultraviolet Legacy Library of Young Stars as Essential Standards Director's Discretionary program (ULLYSES), for which consistently determined accretion shock properties are available. We can reproduce the observations of four stars, finding that the accretion flows are carbon-depleted. We also find that the chromospheric emission accounts for less than 10 percent of the observed C IV line flux in accreting T Tauri stars. This work paves the way toward a better understanding of hot line formation and provides a potential probe of abundances in the inner disk.
紫外线中的 C IV 双线长期以来一直与金牛星的吸积有关。然而，目前还不清楚这些线是在哪里以及如何形成的。在此，我们根据现有的吸积冲击和吸积流模型，提出了一个新的C IV线模型。我们假设了具有不同能量通量的轴对称双极吸积流，并计算了吸积冲击的特性。我们使用 "云"（Cloudy）来获取碳水平种群，并假设冲击附近的几何形状是平面平行的，来计算新出现的线剖面。我们的模型基本再现了从金牛座恒星上观测到的 CIV 发射线的强度和形状。我们发现窄分量在光学上很薄，起源于冲击后，而宽分量在光学上很厚，出现于冲击前。我们将我们的模型应用于哈勃紫外线年轻恒星遗产图书馆作为基本标准主任自由裁量权计划（ULLYSES）中的七颗金牛座恒星，这些恒星的吸积冲击特性是一致确定的。我们可以再现对四颗恒星的观测结果，发现吸积流是碳耗尽的。我们还发现，在吸积金牛座恒星中，色球发射只占观测到的C IV线通量的不到10%。这项工作为更好地理解热线的形成铺平了道路，并为探测内盘的丰度提供了可能。
{"title":"A Model of the C IV $λλ$ 1548, 1550 Doublet Line in T Tauri Stars","authors":"Thanawuth Thanathibodee, Connor Robinson, Nuria Calvet, Catherine Espaillat, Caeley Pittman, Nicole Arulanantham, Kevin France, Hans Moritz Günther, Seok-Jun Chang, P. Christian Schneider","doi":"arxiv-2409.10361","DOIUrl":"https://doi.org/arxiv-2409.10361","url":null,"abstract":"The C IV doublet in the UV has long been associated with accretion in T Tauri\u0000stars. However, it is still unclear where and how the lines are formed. Here,\u0000we present a new C IV line model based on the currently available accretion\u0000shock and accretion flow models. We assume axisymmetric, dipolar accretion\u0000flows with different energy fluxes and calculate the properties of the\u0000accretion shock. We use Cloudy to obtain the carbon level populations and\u0000calculate the emerging line profiles assuming a plane-parallel geometry near\u0000the shock. Our model generally reproduces the intensities and shapes of the C\u0000IV emission lines observed from T Tauri stars. We find that the narrow\u0000component is optically thin and originates in the postshock, while the broad\u0000component is optically thick and emerges from the preshock. We apply our model\u0000to seven T Tauri stars from the Hubble Ultraviolet Legacy Library of Young\u0000Stars as Essential Standards Director's Discretionary program (ULLYSES), for\u0000which consistently determined accretion shock properties are available. We can\u0000reproduce the observations of four stars, finding that the accretion flows are\u0000carbon-depleted. We also find that the chromospheric emission accounts for less\u0000than 10 percent of the observed C IV line flux in accreting T Tauri stars. This\u0000work paves the way toward a better understanding of hot line formation and\u0000provides a potential probe of abundances in the inner disk.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257984","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}
We develop a theoretical framework and use two-dimensional hydrodynamical simulations to study the repulsive effect between two close orbiters embedded in an accretion disk. We consider orbiters on fixed Keplerian orbits with masses low enough to open shallow gaps. The simulations indicate that the repulsion is larger for more massive orbiters and decreases with the orbital separation and the disk's viscosity. We use two different assumptions to derive theoretical scaling relations for the repulsion. A first scenario assumes that each orbiter absorbs the angular momentum deposited in its horseshoe region by the companion's wake. A second scenario assumes that the corotation torques of the orbiters are modified because the companion changes the underlying radial gradient of the disk surface density. We find a substantial difference between the predictions of these two scenarios. The first one fails to reproduce the scaling of the repulsion with the disk viscosity and generally overestimates the strength of the repulsion. The second scenario, however, gives results that are broadly consistent with those obtained in the simulations.
{"title":"A close pair of orbiters embedded in a gaseous disk: the repulsive effect","authors":"F. J. Sanchez-Salcedo, F. S. Masset, S. Cornejo","doi":"arxiv-2409.10751","DOIUrl":"https://doi.org/arxiv-2409.10751","url":null,"abstract":"We develop a theoretical framework and use two-dimensional hydrodynamical\u0000simulations to study the repulsive effect between two close orbiters embedded\u0000in an accretion disk. We consider orbiters on fixed Keplerian orbits with\u0000masses low enough to open shallow gaps. The simulations indicate that the\u0000repulsion is larger for more massive orbiters and decreases with the orbital\u0000separation and the disk's viscosity. We use two different assumptions to derive\u0000theoretical scaling relations for the repulsion. A first scenario assumes that\u0000each orbiter absorbs the angular momentum deposited in its horseshoe region by\u0000the companion's wake. A second scenario assumes that the corotation torques of\u0000the orbiters are modified because the companion changes the underlying radial\u0000gradient of the disk surface density. We find a substantial difference between\u0000the predictions of these two scenarios. The first one fails to reproduce the\u0000scaling of the repulsion with the disk viscosity and generally overestimates\u0000the strength of the repulsion. The second scenario, however, gives results that\u0000are broadly consistent with those obtained in the simulations.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"48 Suppl 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257983","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}
Y. Sanjay, S. Krishna Prasad, R. Erdelyi, M. B. Korsos, D. Banerjee, P. S. Rawat
The multi-wavelength data from the Solar Dynamics Observatory (SDO) is extensively used in studying the physics of the Sun and its atmosphere. In this study, we estimate the formation heights of low-corona and chromospheric channels of the Atmospheric Imaging Assembly (AIA) over the atmospheres of sunspot umbrae during the quiet condition period within 20 different active regions. The upward propagating slow magnetoacoustic waves (slow MAWs) of 3-min period, which are perpetually present in sunspots, are utilized for this purpose. Employing a cross-correlation technique, the most frequent time lag between different channel pairs is measured. By combining this information with the local sound speed obtained from the characteristic formation temperatures of individual channels, we estimate the respective formation heights. The median values of formation heights obtained across all active regions in our sample are 356, 368, 858, 1180, and 1470 km, respectively, for the AIA 1600 {AA}, 1700 {AA}, 304 {AA}, 131 {AA}, and 171 {AA} channels. The corresponding ranges in the formation heights are 247 $--$ 453, 260 $--$ 468, 575 $--$ 1155, 709 $--$ 1937, and 909 $--$ 2585 km, respectively. These values are measured with respect to the HMI continuum. We find the formation height of UV channels is quite stable (between 250 $--$ 500 km) and displays only a marginal difference between the AIA 1600 {AA} and 1700 {AA} during quiet conditions. On the other hand, the formation height of coronal channels is quite variable.
{"title":"On the formation height of low-corona and chromospheric channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO)","authors":"Y. Sanjay, S. Krishna Prasad, R. Erdelyi, M. B. Korsos, D. Banerjee, P. S. Rawat","doi":"arxiv-2409.10451","DOIUrl":"https://doi.org/arxiv-2409.10451","url":null,"abstract":"The multi-wavelength data from the Solar Dynamics Observatory (SDO) is\u0000extensively used in studying the physics of the Sun and its atmosphere. In this\u0000study, we estimate the formation heights of low-corona and chromospheric\u0000channels of the Atmospheric Imaging Assembly (AIA) over the atmospheres of\u0000sunspot umbrae during the quiet condition period within 20 different active\u0000regions. The upward propagating slow magnetoacoustic waves (slow MAWs) of 3-min\u0000period, which are perpetually present in sunspots, are utilized for this\u0000purpose. Employing a cross-correlation technique, the most frequent time lag\u0000between different channel pairs is measured. By combining this information with\u0000the local sound speed obtained from the characteristic formation temperatures\u0000of individual channels, we estimate the respective formation heights. The\u0000median values of formation heights obtained across all active regions in our\u0000sample are 356, 368, 858, 1180, and 1470 km, respectively, for the AIA 1600\u0000{AA}, 1700 {AA}, 304 {AA}, 131 {AA}, and 171 {AA} channels. The\u0000corresponding ranges in the formation heights are 247 $--$ 453, 260 $--$ 468,\u0000575 $--$ 1155, 709 $--$ 1937, and 909 $--$ 2585 km, respectively. These\u0000values are measured with respect to the HMI continuum. We find the formation\u0000height of UV channels is quite stable (between 250 $--$ 500 km) and displays\u0000only a marginal difference between the AIA 1600 {AA} and 1700 {AA} during\u0000quiet conditions. On the other hand, the formation height of coronal channels\u0000is quite variable.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258037","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}
We investigate the evolutionary stages of four open clusters, Berkeley 39, Collinder 261, NGC 6819, and NGC 7789, of ages ranging from 1.6 -- 6 Gyr. These clusters have previously been classified into dynamically young and intermediate age groups based on the segregation level of BSS with respect to red giant branch stars and main sequence stars, respectively. We identify members of these four clusters using the ML-MOC algorithm on Gaia DR3 data. To examine the relative segregation of cluster members of different evolutionary stages, we utilize cumulative radial distributions, proper motion distributions, and spatial distributions in galactocentric coordinates. Our analysis shows that Berkeley 39 and NGC 6819 exhibit moderate signs of population-wise segregation from evolved to less-evolved members. NGC 7789 shows signs of mass segregation only in the cumulative radial distributions. On the other hand, Collinder 261 exhibits high segregation of BSS in the cumulative radial distribution, while other populations show the same level of segregation.
{"title":"Dynamical Evolution of Four Old Galactic Open Clusters traced by their constituent stars with textit{Gaia} DR3","authors":"Shanmugha Balan, Khushboo K Rao, Kaushar Vaidya, Manan Agarwal, Souradeep Bhattacharya","doi":"arxiv-2409.10186","DOIUrl":"https://doi.org/arxiv-2409.10186","url":null,"abstract":"We investigate the evolutionary stages of four open clusters, Berkeley 39,\u0000Collinder 261, NGC 6819, and NGC 7789, of ages ranging from 1.6 -- 6 Gyr. These\u0000clusters have previously been classified into dynamically young and\u0000intermediate age groups based on the segregation level of BSS with respect to\u0000red giant branch stars and main sequence stars, respectively. We identify\u0000members of these four clusters using the ML-MOC algorithm on Gaia DR3 data. To\u0000examine the relative segregation of cluster members of different evolutionary\u0000stages, we utilize cumulative radial distributions, proper motion\u0000distributions, and spatial distributions in galactocentric coordinates. Our\u0000analysis shows that Berkeley 39 and NGC 6819 exhibit moderate signs of\u0000population-wise segregation from evolved to less-evolved members. NGC 7789\u0000shows signs of mass segregation only in the cumulative radial distributions. On\u0000the other hand, Collinder 261 exhibits high segregation of BSS in the\u0000cumulative radial distribution, while other populations show the same level of\u0000segregation.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258045","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. R. Barnes, S. V. Jeffers, C. A. Haswell, M. Damasso, F. Del Sordo, F. Liebing, M. Perger, G. Anglada-Escudé
The radial velocity (RV) method of exoplanet detection requires mitigation of nuisance signals arising from stellar activity. Using analytic cool and facular spot models, we explore the use of central line moments (CLMs) for recovering and monitoring rotation induced RV variability. Different spot distribution patterns, photosphere-spot contrast ratios and the presence or absence of the convective blueshift lead to differences in CLM signals between M dwarfs and G dwarfs. Harmonics of the rotation period are often recovered with the highest power in standard periodogram analyses. By contrast, we show the true stellar rotation may be more reliably recovered with string length minimisation. For solar minimum activity levels, recovery of the stellar rotation signal from CLMs is found to require unfeasibly high signal-to-noise observations. The stellar rotation period can be recovered at solar maximum activity levels from CLMs for reasonable cross-correlation function (CCF) signal-to-noise ratios $> 1000 - 5000$. The CLMs can be used to recover and monitor stellar activity through their mutual correlations and correlations with RV and bisector inverse span. The skewness of a CCF, a measure of asymmetry, is described by the third CLM, $M_3$. Our noise-free simulations indicate the linear RV vs $M_3$ correlation is up to 10 per cent higher than the RV vs bisector inverse span correlation. We find a corresponding $sim 5$ per cent increase in linear correlation for CARMENES observations of the M star, AU Mic. We also assess the effectiveness of the time derivative of the second CLM, $M_2$, for monitoring stellar activity.
{"title":"Identifying activity induced RV periodicities and correlations using Central Line Moments","authors":"J. R. Barnes, S. V. Jeffers, C. A. Haswell, M. Damasso, F. Del Sordo, F. Liebing, M. Perger, G. Anglada-Escudé","doi":"arxiv-2409.10306","DOIUrl":"https://doi.org/arxiv-2409.10306","url":null,"abstract":"The radial velocity (RV) method of exoplanet detection requires mitigation of\u0000nuisance signals arising from stellar activity. Using analytic cool and facular\u0000spot models, we explore the use of central line moments (CLMs) for recovering\u0000and monitoring rotation induced RV variability. Different spot distribution\u0000patterns, photosphere-spot contrast ratios and the presence or absence of the\u0000convective blueshift lead to differences in CLM signals between M dwarfs and G\u0000dwarfs. Harmonics of the rotation period are often recovered with the highest\u0000power in standard periodogram analyses. By contrast, we show the true stellar\u0000rotation may be more reliably recovered with string length minimisation. For\u0000solar minimum activity levels, recovery of the stellar rotation signal from\u0000CLMs is found to require unfeasibly high signal-to-noise observations. The\u0000stellar rotation period can be recovered at solar maximum activity levels from\u0000CLMs for reasonable cross-correlation function (CCF) signal-to-noise ratios $>\u00001000 - 5000$. The CLMs can be used to recover and monitor stellar activity\u0000through their mutual correlations and correlations with RV and bisector inverse\u0000span. The skewness of a CCF, a measure of asymmetry, is described by the third\u0000CLM, $M_3$. Our noise-free simulations indicate the linear RV vs $M_3$\u0000correlation is up to 10 per cent higher than the RV vs bisector inverse span\u0000correlation. We find a corresponding $sim 5$ per cent increase in linear\u0000correlation for CARMENES observations of the M star, AU Mic. We also assess the\u0000effectiveness of the time derivative of the second CLM, $M_2$, for monitoring\u0000stellar activity.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269219","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}
Pulsating stars have been studied using non-linear hydrodynamic codes since the pioneering work of Robert Christy in the 1960s. Modern codes include improvements such as allowing for convection but there is a penalty in terms of computation speed and for some stars convection is not significant. In this work a new version of the Christy program has been developed which can run hundreds of star models to convergence in a day or two of computer time. This allows overall patterns of behaviour to be studied and suitable models for individual case stars to be identified. The star SZ Lyn was chosen as a test case for the model. Light curve and radial velocity data were obtained for this star using amateur equipment. A run of 625 parameter sets (mass, luminosity, effective temperature and hydrogen fraction) identified the best fit parameters for SZ Lyn. Model results show a good fit to the observed data in terms of amplitude, period and shape of the light and velocity curves. In this paper we report on the model developed by PM and radial velocity observations by RL.
{"title":"Modelling Pulsating Stars","authors":"Philip Masding, Robin Leadbeater","doi":"arxiv-2409.10116","DOIUrl":"https://doi.org/arxiv-2409.10116","url":null,"abstract":"Pulsating stars have been studied using non-linear hydrodynamic codes since\u0000the pioneering work of Robert Christy in the 1960s. Modern codes include\u0000improvements such as allowing for convection but there is a penalty in terms of\u0000computation speed and for some stars convection is not significant. In this\u0000work a new version of the Christy program has been developed which can run\u0000hundreds of star models to convergence in a day or two of computer time. This\u0000allows overall patterns of behaviour to be studied and suitable models for\u0000individual case stars to be identified. The star SZ Lyn was chosen as a test\u0000case for the model. Light curve and radial velocity data were obtained for this\u0000star using amateur equipment. A run of 625 parameter sets (mass, luminosity,\u0000effective temperature and hydrogen fraction) identified the best fit parameters\u0000for SZ Lyn. Model results show a good fit to the observed data in terms of\u0000amplitude, period and shape of the light and velocity curves. In this paper we\u0000report on the model developed by PM and radial velocity observations by RL.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"77 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257985","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}
Karl D. Gordon, G. C. Sloan, Macarena Garcia Marin, Mattia Libralato, George Rieke, Jonathan A. Aguilar, Ralph Bohlin, Misty Cracraft, Marjorie Decleir, Andras Gaspar, David R. Law, Alberto Noriega-Crespo, Michael Regan
The absolute flux calibration of the Mid-Infrared Instrument Imaging and Coronagraphy is based on observations of multiple stars taken during the first 2.5 years of JWST operations. The observations were designed to ensure that the flux calibration is valid for a range of flux densities, different subarrays, and different types of stars. The flux calibration was measured by combining observed aperture photometry corrected to infinite aperture with predictions based on previous observations and models of stellar atmospheres. A subset of these observations were combined with model point-spread-functions to measure the corrections to infinite aperture. Variations in the calibration factor with time, flux density, background level, type of star, subarray, integration time, rate, and well depth were investigated, and the only significant variations were with time and subarray. Observations of the same star taken approximately every month revealed a modest time-dependent response loss seen mainly at the longest wavelengths. This loss is well characterized by a decaying exponential with a time constant of ~200 days. After correcting for the response loss, the band-dependent scatter around the corrected average (aka repeatability) was found to range from 0.1 to 1.2%. Signals in observations taken with different subarrays can be lower by up to 3.4% compared to FULL frame. After correcting for the time and subarray dependencies, the scatter in the calibration factors measured for individual stars ranges from 1 to 4% depending on the band. The formal uncertainties on the flux calibration averaged for all observations are 0.3 to 1.0%, with longer-wavelength bands generally having larger uncertainties.
{"title":"The James Webb Space Telescope Absolute Flux Calibration. II. Mid-Infrared Instrument Imaging and Coronagraphy","authors":"Karl D. Gordon, G. C. Sloan, Macarena Garcia Marin, Mattia Libralato, George Rieke, Jonathan A. Aguilar, Ralph Bohlin, Misty Cracraft, Marjorie Decleir, Andras Gaspar, David R. Law, Alberto Noriega-Crespo, Michael Regan","doi":"arxiv-2409.10443","DOIUrl":"https://doi.org/arxiv-2409.10443","url":null,"abstract":"The absolute flux calibration of the Mid-Infrared Instrument Imaging and\u0000Coronagraphy is based on observations of multiple stars taken during the first\u00002.5 years of JWST operations. The observations were designed to ensure that the\u0000flux calibration is valid for a range of flux densities, different subarrays,\u0000and different types of stars. The flux calibration was measured by combining\u0000observed aperture photometry corrected to infinite aperture with predictions\u0000based on previous observations and models of stellar atmospheres. A subset of\u0000these observations were combined with model point-spread-functions to measure\u0000the corrections to infinite aperture. Variations in the calibration factor with\u0000time, flux density, background level, type of star, subarray, integration time,\u0000rate, and well depth were investigated, and the only significant variations\u0000were with time and subarray. Observations of the same star taken approximately\u0000every month revealed a modest time-dependent response loss seen mainly at the\u0000longest wavelengths. This loss is well characterized by a decaying exponential\u0000with a time constant of ~200 days. After correcting for the response loss, the\u0000band-dependent scatter around the corrected average (aka repeatability) was\u0000found to range from 0.1 to 1.2%. Signals in observations taken with different\u0000subarrays can be lower by up to 3.4% compared to FULL frame. After correcting\u0000for the time and subarray dependencies, the scatter in the calibration factors\u0000measured for individual stars ranges from 1 to 4% depending on the band. The\u0000formal uncertainties on the flux calibration averaged for all observations are\u00000.3 to 1.0%, with longer-wavelength bands generally having larger\u0000uncertainties.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258043","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}
Type IIn supernovae (SNeIIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here we systematically model the light curves of 142 archival SNeIIn using MOSFiT (the Modular Open Source Fitter for Transients). We find that the observed and inferred properties of SNIIn are diverse, but there are some trends. The typical SN CSM is dense ($sim$10$^{-12}$gcm$^{-3}$) with highly diverse CSM geometry, with a median CSM mass of $sim$1M$_odot$. The ejecta are typically massive ($gtrsim10$M$_odot$), suggesting massive progenitor systems. We find positive correlations between the CSM mass and the rise and fall times of SNeIIn. Furthermore there are positive correlations between the rise time and fall times and the $r$-band luminosity. We estimate the mass-loss rates of our sample (where spectroscopy is available) and find a high median mass-loss rate of $sim$10$^{-2}$M$_odot$yr$^{-1}$, with a range between 10$^{-4}$--1M$_odot$yr$^{-1}$. These mass-loss rates are most similar to the mass loss from great eruptions of luminous blue variables, consistent with the direct progenitor detections in the literature. We also discuss the role that binary interactions may play, concluding that at least some of our SNeIIn may be from massive binary systems. Finally, we estimate a detection rate of 1.6$times$10$^5$yr$^{-1}$ in the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory.
II型超新星（SNeIIn）是核心坍缩超新星的一个高度异质的亚类，其光谱特征是与致密周星际介质（CSM）的相互作用。在这里，我们使用 MOSFiT（瞬变模块化开源拟合器）对 142 个存档 SNeIIn 的光变曲线进行了系统建模。我们发现，SNIIn 的观测和推断属性各不相同，但存在一些趋势。典型的SN CSM是致密的（$sim$10$^{-12}$gcm$^{-3}$），CSM的几何形状多种多样，CSM的平均质量为$sim$1M$_odot$。喷出物通常是大质量的（$gtrsim10$M$_odot$），这表明它们是大质量的原生系统。我们发现SNeIIn的CSM质量与上升时间和下降时间之间存在正相关。我们估算了样本的质量损失率（在有光谱的情况下），发现质量损失率的中位数很高，为$sim$10$^{-2}$M$_odot$yr$^{-1}$，范围在10$^{-4}$--1M$_odot$yr$^{-1}$之间。这些质量损失率与发光蓝变星大爆发时的质量损失最为相似，与文献中的直接原生体探测结果一致。我们还讨论了双星相互作用可能扮演的角色，得出的结论是，我们的 SNeIIn 至少有一部分可能来自大质量双星系统。最后，我们估计即将在维拉-C-鲁宾天文台（Vera C. Rubin Observatory）进行的 "时空遗产巡天"（Legacy Survey of Space and Time）的探测率为1.6$times$10$^5$yr$^{-1}$。
{"title":"Unveiling the Diversity of Type IIn Supernovae via Systematic Light Curve Modeling","authors":"C. L. Ransome, V. A. Villar","doi":"arxiv-2409.10596","DOIUrl":"https://doi.org/arxiv-2409.10596","url":null,"abstract":"Type IIn supernovae (SNeIIn) are a highly heterogeneous subclass of\u0000core-collapse supernovae, spectroscopically characterized by signatures of\u0000interaction with a dense circumstellar medium (CSM). Here we systematically\u0000model the light curves of 142 archival SNeIIn using MOSFiT (the Modular Open\u0000Source Fitter for Transients). We find that the observed and inferred\u0000properties of SNIIn are diverse, but there are some trends. The typical SN CSM\u0000is dense ($sim$10$^{-12}$gcm$^{-3}$) with highly diverse CSM geometry, with a\u0000median CSM mass of $sim$1M$_odot$. The ejecta are typically massive\u0000($gtrsim10$M$_odot$), suggesting massive progenitor systems. We find positive\u0000correlations between the CSM mass and the rise and fall times of SNeIIn.\u0000Furthermore there are positive correlations between the rise time and fall\u0000times and the $r$-band luminosity. We estimate the mass-loss rates of our\u0000sample (where spectroscopy is available) and find a high median mass-loss rate\u0000of $sim$10$^{-2}$M$_odot$yr$^{-1}$, with a range between\u000010$^{-4}$--1M$_odot$yr$^{-1}$. These mass-loss rates are most similar to the\u0000mass loss from great eruptions of luminous blue variables, consistent with the\u0000direct progenitor detections in the literature. We also discuss the role that\u0000binary interactions may play, concluding that at least some of our SNeIIn may\u0000be from massive binary systems. Finally, we estimate a detection rate of\u00001.6$times$10$^5$yr$^{-1}$ in the upcoming Legacy Survey of Space and Time at\u0000the Vera C. Rubin Observatory.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269221","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}
We report analysis of photometry and spectroscopy of a deep Algol-like minimum of the pre-main-sequence star WW Vul in July and August 2016. This revealed substantial reddening due to absorption by circumstellar material. After dereddening, our spectra of WW Vul were consistent with spectral type A3V throughout the event. H{alpha} is normally in emission in WW Vul. During the minimum, H{alpha} emission dropped by ~30% and FWHM of the H{alpha} line reduced by ~15%.
{"title":"Photometry and spectroscopy of a deep Algol-like minimum of WW Vul in 2016","authors":"David Boyd","doi":"arxiv-2409.10073","DOIUrl":"https://doi.org/arxiv-2409.10073","url":null,"abstract":"We report analysis of photometry and spectroscopy of a deep Algol-like\u0000minimum of the pre-main-sequence star WW Vul in July and August 2016. This\u0000revealed substantial reddening due to absorption by circumstellar material.\u0000After dereddening, our spectra of WW Vul were consistent with spectral type A3V\u0000throughout the event. H{alpha} is normally in emission in WW Vul. During the\u0000minimum, H{alpha} emission dropped by ~30% and FWHM of the H{alpha} line\u0000reduced by ~15%.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269220","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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