M. Libralato, R. Gerasimov, L. Bedin, J. Anderson, D. Apai, A. Bellini, A. J. Burgasser, M. Griggio, D. Nardiello, M. Salaris, M. Scalco, E. Vesperini
We present observations of the two closest globular clusters, NGC 6121 and NGC 6397, taken with the NIRISS detector of JWST. The combination of our new JWST data with archival Hubble Space Telescope (HST) images allows us to compute proper motions, disentangle cluster members from field objects, and probe the main sequence (MS) of the clusters down to <0.1 $M_odot$ as well as the brighter part of the white-dwarf sequence. We show that theoretical isochrones fall short in modeling the low-mass MS and discuss possible explanations for the observed discrepancies. Our analysis suggests that the lowest-mass members of both clusters are significantly more metal-rich and oxygen-poor than their higher-mass counterparts. It is unclear whether the difference is caused by a genuine mass-dependent chemical heterogeneity, low-temperature atmospheric processes altering the observed abundances, or systematic shortcomings in the models. We computed the present-day local luminosity and mass functions of the two clusters; our data reveal a strong flattening of the mass function indicative of a significant preferential loss of low-mass stars in agreement with previous dynamical models for these two clusters. We have made our NIRISS astro-photometric catalogs and stacked images publicly available to the community.
我们将介绍利用 JWST 的近红外ISS 探测器对两个距离最近的球状星团 NGC 6121 和 NGC 6397 的观测结果。将JWST的新数据与哈勃太空望远镜（HST）的存档图像结合起来，我们就可以计算适当的运动，将星团成员从场天体中分离出来，并探测星团的主序列（MS），最小可达<0.1 $M_odot$，以及白矮星序列中较亮的部分。我们发现理论上的等距线并不能模拟低质量的主序，并讨论了观测到的差异的可能解释。我们的分析表明，这两个星团中质量最低的成员比质量较高的成员富含金属和贫氧。目前还不清楚造成这种差异的原因是与质量相关的真正的化学异质性，还是低温大气过程改变了观测到的丰度，或者是模型的系统性缺陷。我们计算了这两个星团现在的光度和质量函数；我们的数据显示质量函数的强烈扁平化，表明低质量恒星的大量优先损耗，这与这两个星团以前的动力学模型是一致的。我们已经向社会公开了我们的 NIRISS 天文光度目录和叠加图像。
{"title":"JWST imaging of the closest globular clusters -- IV. Chemistry, luminosity, and mass functions of the lowest-mass members in the NIRISS parallel fields","authors":"M. Libralato, R. Gerasimov, L. Bedin, J. Anderson, D. Apai, A. Bellini, A. J. Burgasser, M. Griggio, D. Nardiello, M. Salaris, M. Scalco, E. Vesperini","doi":"arxiv-2409.06774","DOIUrl":"https://doi.org/arxiv-2409.06774","url":null,"abstract":"We present observations of the two closest globular clusters, NGC 6121 and\u0000NGC 6397, taken with the NIRISS detector of JWST. The combination of our new\u0000JWST data with archival Hubble Space Telescope (HST) images allows us to\u0000compute proper motions, disentangle cluster members from field objects, and\u0000probe the main sequence (MS) of the clusters down to <0.1 $M_odot$ as well as\u0000the brighter part of the white-dwarf sequence. We show that theoretical\u0000isochrones fall short in modeling the low-mass MS and discuss possible\u0000explanations for the observed discrepancies. Our analysis suggests that the\u0000lowest-mass members of both clusters are significantly more metal-rich and\u0000oxygen-poor than their higher-mass counterparts. It is unclear whether the\u0000difference is caused by a genuine mass-dependent chemical heterogeneity,\u0000low-temperature atmospheric processes altering the observed abundances, or\u0000systematic shortcomings in the models. We computed the present-day local\u0000luminosity and mass functions of the two clusters; our data reveal a strong\u0000flattening of the mass function indicative of a significant preferential loss\u0000of low-mass stars in agreement with previous dynamical models for these two\u0000clusters. We have made our NIRISS astro-photometric catalogs and stacked images\u0000publicly available to the community.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217383","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}
W. Vlemmings, T. Khouri, B. Bojnordi Arbab, E. De Beck, M. Maercker
The transport of energy through convection is important during many stages of stellar evolution, and is best studied in our Sun or giant evolved stars. Features that are attributed to convection are found on the surface of massive red supergiant stars. Also for lower mass evolved stars, indications of convection are found, but convective timescales and sizes remain poorly constrained. Models indicate that convective motions are crucial for the production of strong winds that return the products of stellar nucleosynthesis into the interstellar medium. Here we report a series of reconstructed interferometric images of the surface of the evolved giant star R Doradus. The images reveal a stellar disc with prominent small scale features that provide the structure and motions of convection on the stellar surface. We find that the dominant structure size of the features on the stellar disc is $0.72pm0.05$ astronomical units (au). We measure the velocity of the surface motions to vary between $-18$ and $+20$ km s$^{-1}$, which means the convective timescale is approximately one month. This indicates a possible difference between the convection properties of low-mass and high-mass evolved stars.
通过对流进行能量传输在恒星演化的许多阶段都很重要，对太阳或巨型演化恒星的研究最为深入。在质量较低的演化恒星中，也发现了对流的迹象，但对流的时间尺度和大小仍然没有得到很好的约束。模型表明，对流运动是产生强风的关键，强风将恒星核合成的产物送回星际介质。在这里，我们报告了一系列对演化巨星 R Doradus 表面的干涉测量重建图像。这些图像揭示了一个具有突出小尺度特征的恒星盘，这些特征提供了恒星表面对流的结构和运动。我们发现恒星盘上特征的主要结构尺寸为0.72/pm0.05$天文单位（au）。我们测得的表面运动速度在$-18$和$+20$ km s$^{-1}$之间变化，这意味着对流时间尺度大约为一个月。这表明低质量和高 质量演化恒星的对流特性可能存在差异。
{"title":"One month convection timescale on the surface of a giant evolved star","authors":"W. Vlemmings, T. Khouri, B. Bojnordi Arbab, E. De Beck, M. Maercker","doi":"arxiv-2409.06785","DOIUrl":"https://doi.org/arxiv-2409.06785","url":null,"abstract":"The transport of energy through convection is important during many stages of\u0000stellar evolution, and is best studied in our Sun or giant evolved stars.\u0000Features that are attributed to convection are found on the surface of massive\u0000red supergiant stars. Also for lower mass evolved stars, indications of\u0000convection are found, but convective timescales and sizes remain poorly\u0000constrained. Models indicate that convective motions are crucial for the\u0000production of strong winds that return the products of stellar nucleosynthesis\u0000into the interstellar medium. Here we report a series of reconstructed\u0000interferometric images of the surface of the evolved giant star R Doradus. The\u0000images reveal a stellar disc with prominent small scale features that provide\u0000the structure and motions of convection on the stellar surface. We find that\u0000the dominant structure size of the features on the stellar disc is\u0000$0.72pm0.05$ astronomical units (au). We measure the velocity of the surface\u0000motions to vary between $-18$ and $+20$ km s$^{-1}$, which means the convective\u0000timescale is approximately one month. This indicates a possible difference\u0000between the convection properties of low-mass and high-mass evolved stars.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217382","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}
I have used the third data release of the Gaia mission to improve the reliability and completeness of membership samples in the beta Pic moving group (BPMG) and other nearby associations with ages of 20-50 Myr (Sco Body, Carina, Columba, chi1 For, Tuc-Hor, IC 2602, IC 2391, NGC 2547). I find that Carina, Columba, and chi1 For are physically related and coeval, and that Carina is the closest fringe of a much larger association. Similarly, Tuc-Hor and IC 2602 form a coeval population that is spatially and kinematically continuous. Both results agree with hypotheses from Gagne et al. (2021). I have used the new catalogs to study the associations in terms of their initial mass functions, X-ray emission, ages, and circumstellar disks. For instance, using the model for Li depletion from Jeffries et al. (2023), I have derived an age of 24.7+0.9/-0.6 Myr for BPMG, which is similar to estimates from previous studies. In addition, I have used infrared photometry from the Wide-field Infrared Survey Explorer to check for excess emission from circumstellar disks among the members of the associations, which has resulted in a dramatic increase in the number of known disks around M stars at ages of 30-50 Myr and a significant improvement in measurements of excess fractions for those spectral types and ages. Most notably, I find that the W3 excess fraction for M0-M6 initially declines with age to a minimum in BPMG <0.015), increases to a maximum in Carina/Columba chi1 For (0.041+0.009/-0.007, 34 Myr), and declines again in the oldest two associations (40-50 Myr). The origin of that peak and the nature of the M dwarf disks at >20 Myr are unclear.
{"title":"A Census of the beta Pic Moving Group and Other Nearby Associations with Gaia","authors":"K. L. Luhman","doi":"arxiv-2409.06092","DOIUrl":"https://doi.org/arxiv-2409.06092","url":null,"abstract":"I have used the third data release of the Gaia mission to improve the\u0000reliability and completeness of membership samples in the beta Pic moving group\u0000(BPMG) and other nearby associations with ages of 20-50 Myr (Sco Body, Carina,\u0000Columba, chi1 For, Tuc-Hor, IC 2602, IC 2391, NGC 2547). I find that Carina,\u0000Columba, and chi1 For are physically related and coeval, and that Carina is the\u0000closest fringe of a much larger association. Similarly, Tuc-Hor and IC 2602\u0000form a coeval population that is spatially and kinematically continuous. Both\u0000results agree with hypotheses from Gagne et al. (2021). I have used the new\u0000catalogs to study the associations in terms of their initial mass functions,\u0000X-ray emission, ages, and circumstellar disks. For instance, using the model\u0000for Li depletion from Jeffries et al. (2023), I have derived an age of\u000024.7+0.9/-0.6 Myr for BPMG, which is similar to estimates from previous\u0000studies. In addition, I have used infrared photometry from the Wide-field\u0000Infrared Survey Explorer to check for excess emission from circumstellar disks\u0000among the members of the associations, which has resulted in a dramatic\u0000increase in the number of known disks around M stars at ages of 30-50 Myr and a\u0000significant improvement in measurements of excess fractions for those spectral\u0000types and ages. Most notably, I find that the W3 excess fraction for M0-M6\u0000initially declines with age to a minimum in BPMG <0.015), increases to a\u0000maximum in Carina/Columba chi1 For (0.041+0.009/-0.007, 34 Myr), and declines\u0000again in the oldest two associations (40-50 Myr). The origin of that peak and\u0000the nature of the M dwarf disks at >20 Myr are unclear.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227208","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}
Recent detections of gravitational waves from mergers of binary black holes (BBHs) with pre-merger source-frame individual masses in the so-called upper mass-gap, expected due to (pulsational) pair instability supernova ((P)PISN), have created immense interest in the astrophysical production of high-mass black holes (BHs). Previous studies show that high-mass BHs may be produced via repeated BBH mergers inside dense star clusters. Alternatively, inside dense star clusters, stars with unusually low core-to-envelope mass ratios can form via mergers of high-mass stars, which then can avoid (P)PISN, but produce high-mass BHs via mass fallback. We simulate detailed star-by-star multi-physics models of dense star clusters using the Monte Carlo cluster evolution code, CMC, to investigate the role of primordial binary fraction among high-mass stars (>=15 Msun) on the formation of high-mass BHs. We vary the high-mass stellar binary fraction (fb_15_prime) while keeping all other initial properties, including the population of high-mass stars, unchanged. We find that the number of high-mass BHs, as well as the mass of the most massive BH formed via stellar core-collapse are proportional to fb_15_prime. In contrast, there is no correlation between fb_15_prime and the number of high-mass BHs formed via BH-BH mergers. Since the total production of high-mass BHs is dominated by BH-BH mergers in old clusters, the overall number of high-mass BHs produced over the typical lifetime of globular clusters is insensitive to fb_15_prime. Furthermore, we study the differences in the demographics of BH-BH mergers as a function of fb_15_prime.
{"title":"The Role of High-mass Stellar Binaries in the Formation of High-mass Black Holes in Dense Star Clusters","authors":"Ambreesh Khurana, Sourav Chatterjee","doi":"arxiv-2409.05947","DOIUrl":"https://doi.org/arxiv-2409.05947","url":null,"abstract":"Recent detections of gravitational waves from mergers of binary black holes\u0000(BBHs) with pre-merger source-frame individual masses in the so-called upper\u0000mass-gap, expected due to (pulsational) pair instability supernova ((P)PISN),\u0000have created immense interest in the astrophysical production of high-mass\u0000black holes (BHs). Previous studies show that high-mass BHs may be produced via\u0000repeated BBH mergers inside dense star clusters. Alternatively, inside dense\u0000star clusters, stars with unusually low core-to-envelope mass ratios can form\u0000via mergers of high-mass stars, which then can avoid (P)PISN, but produce\u0000high-mass BHs via mass fallback. We simulate detailed star-by-star\u0000multi-physics models of dense star clusters using the Monte Carlo cluster\u0000evolution code, CMC, to investigate the role of primordial binary fraction\u0000among high-mass stars (>=15 Msun) on the formation of high-mass BHs. We vary\u0000the high-mass stellar binary fraction (fb_15_prime) while keeping all other\u0000initial properties, including the population of high-mass stars, unchanged. We\u0000find that the number of high-mass BHs, as well as the mass of the most massive\u0000BH formed via stellar core-collapse are proportional to fb_15_prime. In\u0000contrast, there is no correlation between fb_15_prime and the number of\u0000high-mass BHs formed via BH-BH mergers. Since the total production of high-mass\u0000BHs is dominated by BH-BH mergers in old clusters, the overall number of\u0000high-mass BHs produced over the typical lifetime of globular clusters is\u0000insensitive to fb_15_prime. Furthermore, we study the differences in the\u0000demographics of BH-BH mergers as a function of fb_15_prime.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217389","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}
Hao Li, Tanausú del Pino Alemán, Javier Trujillo Bueno
The polarization of the Mg II h & k resonance lines is the result of the joint action of scattering processes and the magnetic field induced Hanle, Zeeman, and magneto-optical effects, thus holding significant potential for the diagnostic of the magnetic field in the solar chromosphere. The Chromospheric LAyer Spectro-Polarimeter sounding rocket experiment, carried out in 2019, successfully measured at each position along the 196 arcsec spectrograph slit the wavelength variation of the four Stokes parameters in the spectral region of this doublet around 280 nm, both in an active region plage and in a quiet region close to the limb. We consider some of these CLASP2 Stokes profiles and apply to them the recently-developed HanleRT Tenerife Inversion Code, which assumes a one-dimensional model atmosphere for each spatial pixel under consideration (i.e., it neglects the effects of horizontal radiative transfer). We find that the non-magnetic causes of symmetry breaking, due to the horizontal inhomogeneities and the gradients of the horizontal components of the macroscopic velocity in the solar atmosphere, have a significant impact on the linear polarization profiles. By introducing such non-magnetic causes of symmetry breaking as parameters in our inversion code, we can successfully fit the Stokes profiles and provide an estimation of the magnetic field vector. For example, in the quiet region pixels, where no circular polarization signal is detected, we find that the magnetic field strength in the upper chromosphere varies between 1 and 20 gauss.
{"title":"Full Stokes-vector inversion of the solar Mg II h & k lines","authors":"Hao Li, Tanausú del Pino Alemán, Javier Trujillo Bueno","doi":"arxiv-2409.05328","DOIUrl":"https://doi.org/arxiv-2409.05328","url":null,"abstract":"The polarization of the Mg II h & k resonance lines is the result of the\u0000joint action of scattering processes and the magnetic field induced Hanle,\u0000Zeeman, and magneto-optical effects, thus holding significant potential for the\u0000diagnostic of the magnetic field in the solar chromosphere. The Chromospheric\u0000LAyer Spectro-Polarimeter sounding rocket experiment, carried out in 2019,\u0000successfully measured at each position along the 196 arcsec spectrograph slit\u0000the wavelength variation of the four Stokes parameters in the spectral region\u0000of this doublet around 280 nm, both in an active region plage and in a quiet\u0000region close to the limb. We consider some of these CLASP2 Stokes profiles and\u0000apply to them the recently-developed HanleRT Tenerife Inversion Code, which\u0000assumes a one-dimensional model atmosphere for each spatial pixel under\u0000consideration (i.e., it neglects the effects of horizontal radiative transfer).\u0000We find that the non-magnetic causes of symmetry breaking, due to the\u0000horizontal inhomogeneities and the gradients of the horizontal components of\u0000the macroscopic velocity in the solar atmosphere, have a significant impact on\u0000the linear polarization profiles. By introducing such non-magnetic causes of\u0000symmetry breaking as parameters in our inversion code, we can successfully fit\u0000the Stokes profiles and provide an estimation of the magnetic field vector. For\u0000example, in the quiet region pixels, where no circular polarization signal is\u0000detected, we find that the magnetic field strength in the upper chromosphere\u0000varies between 1 and 20 gauss.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227211","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}
László Molnár, Henryka Netzel, Madeline Howell, Csilla Kalup, Meridith Joyce
Globular clusters offer a powerful way to test the properties of stellar populations and the late stages of low-mass stellar evolution. In this paper we study oscillating giant stars and overtone RR Lyrae-type pulsators in the nearest globular cluster, M4, with the help of high-precision, continuous light curves collected by the Kepler space telescope in the K2 mission. We determine the frequency composition of five RRc stars and model their physical parameters with a grid of linear pulsation models. We are able, for the first time, to compare seismic masses of RR Lyrae stars directly to the masses of the very similar red horizontal branch stars in the same stellar population, independently determined from asteroseismic scaling relations. We find a close match, with an average seismic mass of $0.651pm0.028,M_odot$ for RR Lyrae stars and $0.657pm0.034,M_odot$ for red horizontal-branch stars. While the validity of our RR Lyrae masses still relies on the similarity of neighboring horizontal branch subgroups, this result strongly indicates that RRc stars may indeed exhibit high-degree, $l = 8$ and 9 non-radial modes, and modeling these modes can provide realistic mass estimates. We also determine the He content of the cluster to be $Y = 0.266pm 0.008$, and compare the seismic masses for our sample of RR Lyrae to theoretical mass relations and highlight the limitations of these relations.
{"title":"Matching seismic masses for RR Lyrae-type and oscillating red horizontal-branch stars in M4","authors":"László Molnár, Henryka Netzel, Madeline Howell, Csilla Kalup, Meridith Joyce","doi":"arxiv-2409.05391","DOIUrl":"https://doi.org/arxiv-2409.05391","url":null,"abstract":"Globular clusters offer a powerful way to test the properties of stellar\u0000populations and the late stages of low-mass stellar evolution. In this paper we\u0000study oscillating giant stars and overtone RR Lyrae-type pulsators in the\u0000nearest globular cluster, M4, with the help of high-precision, continuous light\u0000curves collected by the Kepler space telescope in the K2 mission. We determine\u0000the frequency composition of five RRc stars and model their physical parameters\u0000with a grid of linear pulsation models. We are able, for the first time, to\u0000compare seismic masses of RR Lyrae stars directly to the masses of the very\u0000similar red horizontal branch stars in the same stellar population,\u0000independently determined from asteroseismic scaling relations. We find a close\u0000match, with an average seismic mass of $0.651pm0.028,M_odot$ for RR Lyrae\u0000stars and $0.657pm0.034,M_odot$ for red horizontal-branch stars. While the\u0000validity of our RR Lyrae masses still relies on the similarity of neighboring\u0000horizontal branch subgroups, this result strongly indicates that RRc stars may\u0000indeed exhibit high-degree, $l = 8$ and 9 non-radial modes, and modeling these\u0000modes can provide realistic mass estimates. We also determine the He content of\u0000the cluster to be $Y = 0.266pm 0.008$, and compare the seismic masses for our\u0000sample of RR Lyrae to theoretical mass relations and highlight the limitations\u0000of these relations.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217411","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}
V. M. Kalari, R. J. Diaz, G. Robertson, A. McConnachie, M. Ireland, R. Salinas, P. Young, C. Simpson, C. Hayes, J. Nielsen, G. Burley, J. Pazder, M. Gomez-Jimenez, E. Martioli, S. B. Howell, M. Jeong, S. Juneau, R. Ruiz-Carmona, S. Margheim, A. Sheinis, A. Anthony, G. Baker, T. A. M. Berg, T. Cao, E. Chapin, T. Chin, K. Chiboucas, V. Churilov, E. Deibert, A. Densmore, J. Dunn, M. L. Edgar, J. Heo, D. Henderson, T. Farrell, J. Font, V. Firpo, J. Fuentes, K. Labrie, S. Lambert, J. Lawrence, J. Lothrop, R. McDermid, B. W. Miller, G. Perez, V. M. Placco, P. Prado, C. Quiroz, F. Ramos, R. Rutten, K. M. G. Silva, J. Thomas-Osip, C. Urrutia, W. D. Vacca, K. Venn, F. Waller, L. Waller, M. White, S. Xu, R. Zhelem
The Gemini South telescope is now equipped with a new high-resolution spectrograph called GHOST (the Gemini High-resolution Optical SpecTrograph). This instrument provides high-efficiency, high-resolution spectra covering 347-1060 nm in a single exposure of either one or two targets simultaneously, along with precision radial velocity spectroscopy utilizing an internal calibration source. It can operate at a spectral element resolving power of either 76000 or 56000, and can reach a SNR$sim$5 in a 1hr exposure on a V$sim$20.8 mag target in median site seeing, and dark skies (per resolution element). GHOST was installed on-site in June 2022, and we report performance after full integration to queue operations in November 2023, in addition to scientific results enabled by the integration observing runs. These results demonstrate the ability to observe a wide variety of bright and faint targets with high efficiency and precision. With GHOST, new avenues to explore high-resolution spectroscopy have opened up to the astronomical community. These are described, along with the planned and potential upgrades to the instrument.
{"title":"Gemini High-resolution Optical SpecTrograph (GHOST) at Gemini-South: Instrument performance and integration, first science, and next steps","authors":"V. M. Kalari, R. J. Diaz, G. Robertson, A. McConnachie, M. Ireland, R. Salinas, P. Young, C. Simpson, C. Hayes, J. Nielsen, G. Burley, J. Pazder, M. Gomez-Jimenez, E. Martioli, S. B. Howell, M. Jeong, S. Juneau, R. Ruiz-Carmona, S. Margheim, A. Sheinis, A. Anthony, G. Baker, T. A. M. Berg, T. Cao, E. Chapin, T. Chin, K. Chiboucas, V. Churilov, E. Deibert, A. Densmore, J. Dunn, M. L. Edgar, J. Heo, D. Henderson, T. Farrell, J. Font, V. Firpo, J. Fuentes, K. Labrie, S. Lambert, J. Lawrence, J. Lothrop, R. McDermid, B. W. Miller, G. Perez, V. M. Placco, P. Prado, C. Quiroz, F. Ramos, R. Rutten, K. M. G. Silva, J. Thomas-Osip, C. Urrutia, W. D. Vacca, K. Venn, F. Waller, L. Waller, M. White, S. Xu, R. Zhelem","doi":"arxiv-2409.05855","DOIUrl":"https://doi.org/arxiv-2409.05855","url":null,"abstract":"The Gemini South telescope is now equipped with a new high-resolution\u0000spectrograph called GHOST (the Gemini High-resolution Optical SpecTrograph).\u0000This instrument provides high-efficiency, high-resolution spectra covering\u0000347-1060 nm in a single exposure of either one or two targets simultaneously,\u0000along with precision radial velocity spectroscopy utilizing an internal\u0000calibration source. It can operate at a spectral element resolving power of\u0000either 76000 or 56000, and can reach a SNR$sim$5 in a 1hr exposure on a\u0000V$sim$20.8 mag target in median site seeing, and dark skies (per resolution\u0000element). GHOST was installed on-site in June 2022, and we report performance\u0000after full integration to queue operations in November 2023, in addition to\u0000scientific results enabled by the integration observing runs. These results\u0000demonstrate the ability to observe a wide variety of bright and faint targets\u0000with high efficiency and precision. With GHOST, new avenues to explore\u0000high-resolution spectroscopy have opened up to the astronomical community.\u0000These are described, along with the planned and potential upgrades to the\u0000instrument.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227215","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}
S. M. Díaz-Castillo, C. E. Fischer, R. Rezaei, O. Steiner, S. Berdyugina
High-resolution solar observations have revealed the existence of small-scale vortices, as seen in chromospheric intensity maps and velocity diagnostics. Frequently, these vortices have been observed near magnetic flux concentrations, indicating a link between swirls and the evolution of the small-scale magnetic fields. Vortices have also been studied with magneto-hydrodynamic (MHD) numerical simulations of the solar atmosphere, revealing their complexity, dynamics, and magnetic nature. In particular, it has been proposed that a rotating magnetic field structure driven by a photospheric vortex flow at its footprint produces the chromospheric swirling plasma motion. We present a complete and comprehensive description of the time evolution of a small-scale magnetic flux concentration interacting with the intergranular vortex flow and affected by processes of intensification and weakening of its magnetic field. In addition, we study the chromospheric dynamics associated with the interaction, including the analysis of a chromospheric swirl and an impulsive chromospheric jet.
{"title":"Connectivity between the solar photosphere and chromosphere in a vortical structure. Observations of multi-phase, small-scale magnetic field amplification","authors":"S. M. Díaz-Castillo, C. E. Fischer, R. Rezaei, O. Steiner, S. Berdyugina","doi":"arxiv-2409.05769","DOIUrl":"https://doi.org/arxiv-2409.05769","url":null,"abstract":"High-resolution solar observations have revealed the existence of small-scale\u0000vortices, as seen in chromospheric intensity maps and velocity diagnostics.\u0000Frequently, these vortices have been observed near magnetic flux\u0000concentrations, indicating a link between swirls and the evolution of the\u0000small-scale magnetic fields. Vortices have also been studied with\u0000magneto-hydrodynamic (MHD) numerical simulations of the solar atmosphere,\u0000revealing their complexity, dynamics, and magnetic nature. In particular, it\u0000has been proposed that a rotating magnetic field structure driven by a\u0000photospheric vortex flow at its footprint produces the chromospheric swirling\u0000plasma motion. We present a complete and comprehensive description of the time\u0000evolution of a small-scale magnetic flux concentration interacting with the\u0000intergranular vortex flow and affected by processes of intensification and\u0000weakening of its magnetic field. In addition, we study the chromospheric\u0000dynamics associated with the interaction, including the analysis of a\u0000chromospheric swirl and an impulsive chromospheric jet.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217409","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}
Raghvendra Sahai, Javier Alcolea, Bruce Balick, Eric G. Blackman, Valentin Bujarrabal, Arancha Castro-Carrizo, Orsola De Marco, Joel Kastner, Hyosun Kim, Eric Lagadec, Chin-Fei Lee, Laurence Sabin, M. Santander-Garcia, Carmen Sánchez Contreras, Daniel Tafoya, Toshiya Ueta, Wouter Vlemmings, Albert Zijlstra
As mass-losing asymptotic giant branch (AGB) stars evolve to planetary nebulae (PNe), the mass outflow geometries transform from nearly spherical to extreme aspherical. The physical mechanisms governing this transformation are widely believed to be linked to binarity and the associated production of disks and fast jets during transitional (post-AGB) evolutionary stages. We are carrying out a systematic ALMA survey ($P$re-planet$A$ry $N$ebulae high-angular-res$O$lution su$R$vey with $A$L$MA$ or PANORAMA) of a representative sample of bipolar and multipolar post-AGB objects. We have obtained high angular-resolution (0".1-0".4) observations of the CO(3--2) and/or 6--5 emission in order to probe the spatio-kinematic structure of the collimated outflows and the central disk/torii. The results are remarkable, generally showing the presence of bipolar or multipolar high-velocity outflows, dense toroidal waists, and in one case, a geometrically-thin circular ring around the central bipolar nebula. A high degree of point-symmetry characterizes the morphology of the mass ejecta. In this contribution, we present these and other highlights from our survey. We aim to use 2D/3D radiative transfer modeling in order to derive accurate outflow momenta, masses and mass-loss rates for our sample, and build hydrodynamical models that can explain the observed spatio-kinematic structures. These results will then be used to distinguish between different classes of PN-shaping binary interaction models.
当质量损失的渐变巨枝（AGB）恒星演化成行星状星云（PNe）时，质量流出的几何形状会从近似球形转变为极端非球形。人们普遍认为这种转变的物理机制与二元性以及在过渡（后AGB）演化阶段产生的相关磁盘和快速喷流有关。我们正在对具有代表性的双极和多极后AGB天体样本进行系统的ALMA巡天（P$re-planet$A$ry $N$ebulaehigh-angular-res$O$lution su$R$vey with $A$L$MA$ or PANORAMA）。我们获得了 CO（3--2）和/或 6--5 辐射的高角分辨率（0".1-0".4）观测数据，以探测共轭外流和中心盘/蝶形的空间运动结构。结果非常显著，一般都显示出存在双极或多极高速外流和致密的环状腰带，在一个情况下，中央双极星云周围还有一个几何上很薄的圆形环。质量喷出物的形态具有高度的点对称性。在本文中，我们将介绍这些以及我们的观测中发现的其他亮点。我们的目标是利用二维/三维辐射传递建模，为我们的样本推导出精确的流出矩、质量和质量损失率，并建立能够解释观测到的空间运动学结构的流体力学模型。然后将利用这些结果来区分不同类别的 PN 塑造双星相互作用模型。
{"title":"High-Speed Outflows and Dusty Disks during the AGB to PN Transition: The PANORAMA survey","authors":"Raghvendra Sahai, Javier Alcolea, Bruce Balick, Eric G. Blackman, Valentin Bujarrabal, Arancha Castro-Carrizo, Orsola De Marco, Joel Kastner, Hyosun Kim, Eric Lagadec, Chin-Fei Lee, Laurence Sabin, M. Santander-Garcia, Carmen Sánchez Contreras, Daniel Tafoya, Toshiya Ueta, Wouter Vlemmings, Albert Zijlstra","doi":"arxiv-2409.06038","DOIUrl":"https://doi.org/arxiv-2409.06038","url":null,"abstract":"As mass-losing asymptotic giant branch (AGB) stars evolve to planetary\u0000nebulae (PNe), the mass outflow geometries transform from nearly spherical to\u0000extreme aspherical. The physical mechanisms governing this transformation are\u0000widely believed to be linked to binarity and the associated production of disks\u0000and fast jets during transitional (post-AGB) evolutionary stages. We are\u0000carrying out a systematic ALMA survey ($P$re-planet$A$ry $N$ebulae\u0000high-angular-res$O$lution su$R$vey with $A$L$MA$ or PANORAMA) of a\u0000representative sample of bipolar and multipolar post-AGB objects. We have\u0000obtained high angular-resolution (0\".1-0\".4) observations of the CO(3--2)\u0000and/or 6--5 emission in order to probe the spatio-kinematic structure of the\u0000collimated outflows and the central disk/torii. The results are remarkable,\u0000generally showing the presence of bipolar or multipolar high-velocity outflows,\u0000dense toroidal waists, and in one case, a geometrically-thin circular ring\u0000around the central bipolar nebula. A high degree of point-symmetry\u0000characterizes the morphology of the mass ejecta. In this contribution, we\u0000present these and other highlights from our survey. We aim to use 2D/3D\u0000radiative transfer modeling in order to derive accurate outflow momenta, masses\u0000and mass-loss rates for our sample, and build hydrodynamical models that can\u0000explain the observed spatio-kinematic structures. These results will then be\u0000used to distinguish between different classes of PN-shaping binary interaction\u0000models.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217388","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}
Fatemeh Fazel Hesar, Bernard Foing, Ana M. Heras, Mojtaba Raouf, Victoria Foing, Shima Javanmardi, Fons J. Verbeek
This study applied machine learning models to estimate stellar rotation periods from corrected light curve data obtained by the NASA Kepler mission. Traditional methods often struggle to estimate rotation periods accurately due to noise and variability in the light curve data. The workflow involved using initial period estimates from the LS-Periodogram and Transit Least Squares techniques, followed by splitting the data into training, validation, and testing sets. We employed several machine learning algorithms, including Decision Tree, Random Forest, K-Nearest Neighbors, and Gradient Boosting, and also utilized a Voting Ensemble approach to improve prediction accuracy and robustness. The analysis included data from multiple Kepler IDs, providing detailed metrics on orbital periods and planet radii. Performance evaluation showed that the Voting Ensemble model yielded the most accurate results, with an RMSE approximately 50% lower than the Decision Tree model and 17% better than the K-Nearest Neighbors model. The Random Forest model performed comparably to the Voting Ensemble, indicating high accuracy. In contrast, the Gradient Boosting model exhibited a worse RMSE compared to the other approaches. Comparisons of the predicted rotation periods to the photometric reference periods showed close alignment, suggesting the machine learning models achieved high prediction accuracy. The results indicate that machine learning, particularly ensemble methods, can effectively solve the problem of accurately estimating stellar rotation periods, with significant implications for advancing the study of exoplanets and stellar astrophysics.
这项研究应用机器学习模型从美国宇航局开普勒任务获得的校正光曲线数据中估算恒星的自转周期。工作流程包括使用 LS-Periodogram 和 Transit Least Squarestechniques 得出的初始周期估计值，然后将数据分成训练集、验证集和测试集。我们使用了几种机器学习算法，包括决策树、随机森林、K-近邻和梯度提升，还使用了投票集合方法来提高预测准确性和稳健性。分析包括来自多个开普勒 ID 的数据，提供了轨道周期和行星半径的详细指标。性能评估结果表明，投票集合模型产生了最准确的结果，其均方误差比决策树模型低约50%，比K-近邻模型好17%。随机森林模型的表现与投票集合模型相当，显示出较高的准确性。相比之下，梯度提升模型的均方根误差比其他方法要小。预测的旋转周期与光度参考周期的比较显示两者接近，表明机器学习模型达到了较高的预测精度。结果表明，机器学习，尤其是集合方法，可以有效地解决准确估计恒星旋转周期的问题，对推动系外行星和恒星天体物理学的研究具有重要意义。
{"title":"Advancing Machine Learning for Stellar Activity and Exoplanet Period Rotation","authors":"Fatemeh Fazel Hesar, Bernard Foing, Ana M. Heras, Mojtaba Raouf, Victoria Foing, Shima Javanmardi, Fons J. Verbeek","doi":"arxiv-2409.05482","DOIUrl":"https://doi.org/arxiv-2409.05482","url":null,"abstract":"This study applied machine learning models to estimate stellar rotation\u0000periods from corrected light curve data obtained by the NASA Kepler mission.\u0000Traditional methods often struggle to estimate rotation periods accurately due\u0000to noise and variability in the light curve data. The workflow involved using\u0000initial period estimates from the LS-Periodogram and Transit Least Squares\u0000techniques, followed by splitting the data into training, validation, and\u0000testing sets. We employed several machine learning algorithms, including\u0000Decision Tree, Random Forest, K-Nearest Neighbors, and Gradient Boosting, and\u0000also utilized a Voting Ensemble approach to improve prediction accuracy and\u0000robustness. The analysis included data from multiple Kepler IDs, providing detailed\u0000metrics on orbital periods and planet radii. Performance evaluation showed that\u0000the Voting Ensemble model yielded the most accurate results, with an RMSE\u0000approximately 50% lower than the Decision Tree model and 17% better than the\u0000K-Nearest Neighbors model. The Random Forest model performed comparably to the\u0000Voting Ensemble, indicating high accuracy. In contrast, the Gradient Boosting\u0000model exhibited a worse RMSE compared to the other approaches. Comparisons of\u0000the predicted rotation periods to the photometric reference periods showed\u0000close alignment, suggesting the machine learning models achieved high\u0000prediction accuracy. The results indicate that machine learning, particularly\u0000ensemble methods, can effectively solve the problem of accurately estimating\u0000stellar rotation periods, with significant implications for advancing the study\u0000of exoplanets and stellar astrophysics.","PeriodicalId":501068,"journal":{"name":"arXiv - PHYS - Solar and Stellar Astrophysics","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142217410","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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