Pub Date : 2024-10-20DOI: 10.3847/1538-4357/ad73d7
Jing-Qiang Peng, Shu Zhang, Qing-Cang Shui, Yu-Peng Chen, Shuang-Nan Zhang, Ling-Da Kong, A. Santangelo, Zhuo-Li Yu, Long Ji, Peng-Ju Wang, Zhi Chang, Jian Li and Zhao-sheng Li
We study the spectral properties of the black hole X-ray transient binary 4U 1630–472 during its 2022 and 2023 outbursts with Insight-HXMT observations. We find that the outbursts are in peculiar soft states. The effect of the hardening factor on the disk temperature is taken into account by the kerrbb model, and the flux and temperature of the disk are found to follow and for the two outbursts, respectively. The flux–temperature relation is roughly consistent with a standard disk. By fitting with a p-free model, the p-value, the exponent of the radial dependence of the disk temperature, is found to have an anticorrelation with disk temperature. Combining a joint diagnostic analysis with a diagram of the relation between the nonthermal fraction and luminosity, we find a possible scenario that the disk evolves from 2022 to 2023 toward a slim one with a decreasing radiation efficiency, where such an evolution may depend on the fraction of the nonthermal emission in the high soft state.
{"title":"The Peculiar Disk Evolution of 4U 1630-472 Observed by Insight-HXMT During its 2022 and 2023 Outbursts","authors":"Jing-Qiang Peng, Shu Zhang, Qing-Cang Shui, Yu-Peng Chen, Shuang-Nan Zhang, Ling-Da Kong, A. Santangelo, Zhuo-Li Yu, Long Ji, Peng-Ju Wang, Zhi Chang, Jian Li and Zhao-sheng Li","doi":"10.3847/1538-4357/ad73d7","DOIUrl":"https://doi.org/10.3847/1538-4357/ad73d7","url":null,"abstract":"We study the spectral properties of the black hole X-ray transient binary 4U 1630–472 during its 2022 and 2023 outbursts with Insight-HXMT observations. We find that the outbursts are in peculiar soft states. The effect of the hardening factor on the disk temperature is taken into account by the kerrbb model, and the flux and temperature of the disk are found to follow and for the two outbursts, respectively. The flux–temperature relation is roughly consistent with a standard disk. By fitting with a p-free model, the p-value, the exponent of the radial dependence of the disk temperature, is found to have an anticorrelation with disk temperature. Combining a joint diagnostic analysis with a diagram of the relation between the nonthermal fraction and luminosity, we find a possible scenario that the disk evolves from 2022 to 2023 toward a slim one with a decreasing radiation efficiency, where such an evolution may depend on the fraction of the nonthermal emission in the high soft state.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452290","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 : 2024-10-20DOI: 10.3847/1538-4357/ad7788
Linhao Ma, 林昊 马 and Jim Fuller
Hot subdwarf B (sdB) stars are stripped helium-burning stars that are often found in close binaries, where they experience strong tidal interactions. The dissipation of tidally excited gravity waves alters their rotational evolution throughout the sdB lifetime. While many sdB binaries have well-measured rotational and orbital frequencies, there have been few theoretical efforts to accurately calculate the tidal torque produced by gravity waves. In this work, we directly calculate the tidal excitation of internal gravity waves in realistic sdB stellar models and integrate the coupled spin–orbit evolution of sdB binaries. We find that for canonical sdB (MsdB = 0.47 M⊙) binaries, the transitional orbital period below which they could reach tidal synchronization in the sdB lifetime is ∼0.2 day, with weak dependence on the companion masses. For low-mass sdBs (MsdB = 0.37 M⊙) formed from more massive progenitor stars, the transitional orbital period becomes ∼0.15 day. These values are very similar to the tidal synchronization boundary (∼0.2 day) evident from observations. We discuss the dependence of tidal torques on stellar radii, and we make predictions for the rapidly rotating white dwarfs formed from synchronized sdB binaries.
{"title":"Tidal Spin-up of Subdwarf B Stars","authors":"Linhao Ma, 林昊 马 and Jim Fuller","doi":"10.3847/1538-4357/ad7788","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7788","url":null,"abstract":"Hot subdwarf B (sdB) stars are stripped helium-burning stars that are often found in close binaries, where they experience strong tidal interactions. The dissipation of tidally excited gravity waves alters their rotational evolution throughout the sdB lifetime. While many sdB binaries have well-measured rotational and orbital frequencies, there have been few theoretical efforts to accurately calculate the tidal torque produced by gravity waves. In this work, we directly calculate the tidal excitation of internal gravity waves in realistic sdB stellar models and integrate the coupled spin–orbit evolution of sdB binaries. We find that for canonical sdB (MsdB = 0.47 M⊙) binaries, the transitional orbital period below which they could reach tidal synchronization in the sdB lifetime is ∼0.2 day, with weak dependence on the companion masses. For low-mass sdBs (MsdB = 0.37 M⊙) formed from more massive progenitor stars, the transitional orbital period becomes ∼0.15 day. These values are very similar to the tidal synchronization boundary (∼0.2 day) evident from observations. We discuss the dependence of tidal torques on stellar radii, and we make predictions for the rapidly rotating white dwarfs formed from synchronized sdB binaries.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452292","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 : 2024-10-20DOI: 10.3847/1538-4357/ad76a2
Sal Wanying Fu, Daniel R. Weisz, Else Starkenburg, Nicolas Martin, Michelle L. M. Collins, Alessandro Savino, Michael Boylan-Kolchin, Patrick Côté, Andrew E. Dolphin, Nicolas Longeard, Mario L. Mateo, Francisco J. Mercado, Nathan R. Sandford and Evan D. Skillman
We present ∼300 stellar metallicity measurements in two faint M31 dwarf galaxies, Andromeda XVI (MV = −7.5) and Andromeda XXVIII (MV = –8.8), derived using metallicity-sensitive calcium H and K narrowband Hubble Space Telescope imaging. These are the first individual stellar metallicities in And XVI (95 stars). Our And XXVIII sample (191 stars) is a factor of ∼15 increase over literature metallicities. For And XVI, we measure , , and ∇[Fe/H] = −0.23 ± 0.15 dex . We find that And XVI is more metal-rich than Milky Way ultrafaint dwarf galaxies of similar luminosity, which may be a result of its unusually extended star formation history. For And XXVIII, we measure , , and ∇[Fe/H]= −0.46 ± 0.10 dex , placing it on the dwarf galaxy mass–metallicity relation. Neither galaxy has a metallicity distribution function (MDF) with an abrupt metal-rich truncation, suggesting that star formation fell off gradually. The stellar metallicity gradient measurements are among the first for faint (L ≲ 106L⊙) galaxies outside the Milky Way halo. Both galaxies’ gradients are consistent with predictions from the FIRE simulations, where an age–gradient strength relationship is the observational consequence of stellar feedback that produces dark matter cores. We include a catalog for community spectroscopic follow-up, including 19 extremely metal-poor ([Fe/H] < –3.0) star candidates, which make up 7% of And XVI’s MDF and 6% of And XXVIII’s.
我们利用对金属性敏感的 H 和 K 钙窄带哈勃太空望远镜成像技术，对两个暗弱的 M31 矮星系仙女座 XVI（MV = -7.5）和仙女座 XXVIII（MV = -8.8）进行了 300 ∼ 300 颗恒星的金属性测量。这是仙女座 XVI（95 颗恒星）中首次出现的单个恒星金属性。我们的 And XXVIII 样本（191 颗恒星）比文献中的金属性增加了 ∼ 15 倍。对于 And XVI，我们测量了 、 、 和 ∇[Fe/H] = -0.23 ± 0.15 dex 。我们发现，与光度相近的银河系超暗矮星系相比，安得十六星系的金属含量更高，这可能是其恒星形成历史异常延长的结果。对于 And XXVIII，我们测量到, , 和∇[Fe/H]=-0.46 ± 0.10 dex，将其置于矮星系质量-金属度关系中。这两个星系的金属性分布函数（MDF）都没有突然出现富金属截断，这表明恒星形成是逐渐下降的。这些恒星金属性梯度测量结果是首次对银河系光环之外的暗星系（L ≲ 106L⊙）进行的测量。这两个星系的梯度与 FIRE 模拟的预测一致，在 FIRE 模拟中，年龄-梯度强度关系是恒星反馈产生暗物质核心的观测结果。我们还提供了一份用于社区光谱跟踪的星表，其中包括 19 颗极度贫金属（[Fe/H] < -3.0）的候选恒星，它们占 And XVI MDF 的 7%，占 And XXVIII MDF 的 6%。
{"title":"Stellar Metallicities and Gradients in the Faint M31 Satellites Andromeda XVI and Andromeda XXVIII","authors":"Sal Wanying Fu, Daniel R. Weisz, Else Starkenburg, Nicolas Martin, Michelle L. M. Collins, Alessandro Savino, Michael Boylan-Kolchin, Patrick Côté, Andrew E. Dolphin, Nicolas Longeard, Mario L. Mateo, Francisco J. Mercado, Nathan R. Sandford and Evan D. Skillman","doi":"10.3847/1538-4357/ad76a2","DOIUrl":"https://doi.org/10.3847/1538-4357/ad76a2","url":null,"abstract":"We present ∼300 stellar metallicity measurements in two faint M31 dwarf galaxies, Andromeda XVI (MV = −7.5) and Andromeda XXVIII (MV = –8.8), derived using metallicity-sensitive calcium H and K narrowband Hubble Space Telescope imaging. These are the first individual stellar metallicities in And XVI (95 stars). Our And XXVIII sample (191 stars) is a factor of ∼15 increase over literature metallicities. For And XVI, we measure , , and ∇[Fe/H] = −0.23 ± 0.15 dex . We find that And XVI is more metal-rich than Milky Way ultrafaint dwarf galaxies of similar luminosity, which may be a result of its unusually extended star formation history. For And XXVIII, we measure , , and ∇[Fe/H]= −0.46 ± 0.10 dex , placing it on the dwarf galaxy mass–metallicity relation. Neither galaxy has a metallicity distribution function (MDF) with an abrupt metal-rich truncation, suggesting that star formation fell off gradually. The stellar metallicity gradient measurements are among the first for faint (L ≲ 106L⊙) galaxies outside the Milky Way halo. Both galaxies’ gradients are consistent with predictions from the FIRE simulations, where an age–gradient strength relationship is the observational consequence of stellar feedback that produces dark matter cores. We include a catalog for community spectroscopic follow-up, including 19 extremely metal-poor ([Fe/H] < –3.0) star candidates, which make up 7% of And XVI’s MDF and 6% of And XXVIII’s.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452291","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 : 2024-10-20DOI: 10.3847/1538-4357/ad7464
M. Kumar, K. Murawski, B. Kuźma, E. K. J. Kilpua, S. Poedts and R. Erdélyi
This paper offers a fresh perspective on solar chromosphere heating and plasma outflows, focusing on the contribution of waves generated by solar granulation. Utilizing a 2.5D numerical experiment for the partially ionized lower solar atmosphere, we investigate the dissipation of these waves and their impact on plasma outflows and chromospheric heating via ion-neutral collisions. Employing the JOint ANalytical and Numerical Approach code, we adopt two-fluid model equations, examining partially ionized hydrogen plasma dynamics, including protons+electrons and neutrals, treated as two separate fluids that are coupled through ion-neutral collisions. Our investigation focuses on a quiet solar chromosphere region characterized by gravitational stratification and magnetic confinement by an initially set single magnetic arcade. The primary source of the waves is the solar convection beneath the photosphere. Our results demonstrate that ion-neutral collisions result in the dissipation of such waves, releasing thermal energy that heats the chromosphere plasma. Notably, this is accompanied by upward-directed plasma flows. Finally, we conclude that wave dissipation due to ion-neutral collisions in the two-fluid plasma model induces chromosphere heating and plasma outflows.
本文提供了一个关于太阳色球加热和等离子体外流的全新视角，重点关注太阳粒化产生的波的贡献。利用部分电离的太阳下层大气的 2.5D 数值实验，我们研究了这些波的耗散及其通过离子-中性碰撞对等离子体外流和色球层加热的影响。利用 JOint ANalytical and Numerical Approach 代码，我们采用了双流体模型方程，研究了部分电离氢等离子体动力学，包括质子+电子和中子，它们被视为通过离子-中性碰撞耦合的两种独立流体。我们的研究重点是一个安静的太阳色球区域，该区域的特点是引力分层和最初设置的单一磁弧的磁约束。波的主要来源是光球下面的太阳对流。我们的研究结果表明，离子中性碰撞导致这种波的消散，释放出的热能加热了色球等离子体。值得注意的是，这还伴随着向上的等离子体流。最后，我们得出结论，在双流体等离子体模型中，离子中性碰撞导致的波耗散引起了色球层加热和等离子体外流。
{"title":"Numerical Experiment on the Influence of Granulation-induced Waves on Solar Chromosphere Heating and Plasma Outflows in a Magnetic Arcade","authors":"M. Kumar, K. Murawski, B. Kuźma, E. K. J. Kilpua, S. Poedts and R. Erdélyi","doi":"10.3847/1538-4357/ad7464","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7464","url":null,"abstract":"This paper offers a fresh perspective on solar chromosphere heating and plasma outflows, focusing on the contribution of waves generated by solar granulation. Utilizing a 2.5D numerical experiment for the partially ionized lower solar atmosphere, we investigate the dissipation of these waves and their impact on plasma outflows and chromospheric heating via ion-neutral collisions. Employing the JOint ANalytical and Numerical Approach code, we adopt two-fluid model equations, examining partially ionized hydrogen plasma dynamics, including protons+electrons and neutrals, treated as two separate fluids that are coupled through ion-neutral collisions. Our investigation focuses on a quiet solar chromosphere region characterized by gravitational stratification and magnetic confinement by an initially set single magnetic arcade. The primary source of the waves is the solar convection beneath the photosphere. Our results demonstrate that ion-neutral collisions result in the dissipation of such waves, releasing thermal energy that heats the chromosphere plasma. Notably, this is accompanied by upward-directed plasma flows. Finally, we conclude that wave dissipation due to ion-neutral collisions in the two-fluid plasma model induces chromosphere heating and plasma outflows.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452296","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 : 2024-10-20DOI: 10.3847/1538-4357/ad702e
M. Reshma, Aditi Agarwal, C. S. Stalin, Prajwel Joseph, Akanksha Dagore, Amit Kumar Mandal, Ashish Devaraj and S. B. Gudennavar
Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on timescales of hours is very limited. Here, we present the first UV flux variability study on intraday timescales of a sample of ten blazars comprising two flat-spectrum radio quasars (FSRQs) and eight BL Lacertae objects (BL Lacs). These objects, spanning a redshift (z) range of 0.034 ≤ z ≤ 1.003, were observed in the far-UV (1300−1800 Å) and near-UV (2000−3000 Å) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on timescales of hours were detected in nine sources out of the observed ten blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process.
{"title":"Ultraviolet Flux and Spectral Variability Study of Blazars Observed with UVIT/AstroSat","authors":"M. Reshma, Aditi Agarwal, C. S. Stalin, Prajwel Joseph, Akanksha Dagore, Amit Kumar Mandal, Ashish Devaraj and S. B. Gudennavar","doi":"10.3847/1538-4357/ad702e","DOIUrl":"https://doi.org/10.3847/1538-4357/ad702e","url":null,"abstract":"Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on timescales of hours is very limited. Here, we present the first UV flux variability study on intraday timescales of a sample of ten blazars comprising two flat-spectrum radio quasars (FSRQs) and eight BL Lacertae objects (BL Lacs). These objects, spanning a redshift (z) range of 0.034 ≤ z ≤ 1.003, were observed in the far-UV (1300−1800 Å) and near-UV (2000−3000 Å) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on timescales of hours were detected in nine sources out of the observed ten blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452289","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 : 2024-10-17DOI: 10.3847/1538-4357/ad5f1e
Alexander J. Dittmann, M. Coleman Miller, Frederick K. Lamb, Isiah M. Holt, Cecilia Chirenti, Michael T. Wolff, Slavko Bogdanov, Sebastien Guillot, Wynn C. G. Ho, Sharon M. Morsink, Zaven Arzoumanian and Keith C. Gendreau
PSR J0740+6620 is the neutron star with the highest precisely determined mass, inferred from radio observations to be 2.08 ± 0.07 M⊙. Measurements of its radius therefore hold promise to constrain the properties of the cold, catalyzed, high-density matter in neutron star cores. Previously, Miller et al. and Riley et al. reported measurements of the radius of PSR J0740+6620 based on Neutron Star Interior Composition Explorer (NICER) observations accumulated through 2020 April 17, and an exploratory analysis utilizing NICER background estimates and a data set accumulated through 2021 December 28 was presented in Salmi et al. Here we report an updated radius measurement, derived by fitting models of X-ray emission from the neutron star surface to NICER data accumulated through 2022 April 21, totaling ∼1.1 Ms additional exposure compared to the data set analyzed in Miller et al. and Riley et al., and to data from XMM-Newton observations. We find that the equatorial circumferential radius of PSR J0740+6620 is km (68% credibility), a fractional uncertainty ∼83% the width of that reported in Miller et al., in line with statistical expectations given the additional data. If we were to require the radius to be less than 16 km, as was done in Salmi et al., then our 68% credible region would become km, which is close to the headline result of Salmi et al. Our updated measurements, along with other laboratory and astrophysical constraints, imply a slightly softer equation of state than that inferred from our previous measurements.
PSR J0740+6620是精确测定质量最高的中子星，根据射电观测推断其质量为2.08 ± 0.07 M⊙。因此，对其半径的测量有望制约中子星内核中冷态、催化、高密度物质的特性。此前，Miller 等人和 Riley 等人根据中子星内部成分探测器（NICER）截至 2020 年 4 月 17 日的观测数据报告了 PSR J0740+6620 的半径测量结果，Salmi 等人利用 NICER 的背景估计值和截至 2021 年 12 月 28 日的数据集进行了探索性分析。在此，我们报告最新的半径测量结果，该结果是通过拟合中子星表面的 X 射线发射模型和 NICER 截至 2022 年 4 月 21 日的数据得出的，与 Miller 等人和 Riley 等人分析的数据集相比，总共增加了 1.1 Ms 的曝光量、以及 XMM-Newton 观测数据。我们发现，PSR J0740+6620 的赤道圆周半径为 km（可信度为 68%），与 Miller 等人报告的半径宽度相比，不确定性小于 83%，这符合额外数据的统计预期。如果我们像萨尔米等人那样要求半径小于16千米，那么我们的68%可信度区域将变为千米，这与萨尔米等人的标题结果接近。
{"title":"A More Precise Measurement of the Radius of PSR J0740+6620 Using Updated NICER Data","authors":"Alexander J. Dittmann, M. Coleman Miller, Frederick K. Lamb, Isiah M. Holt, Cecilia Chirenti, Michael T. Wolff, Slavko Bogdanov, Sebastien Guillot, Wynn C. G. Ho, Sharon M. Morsink, Zaven Arzoumanian and Keith C. Gendreau","doi":"10.3847/1538-4357/ad5f1e","DOIUrl":"https://doi.org/10.3847/1538-4357/ad5f1e","url":null,"abstract":"PSR J0740+6620 is the neutron star with the highest precisely determined mass, inferred from radio observations to be 2.08 ± 0.07 M⊙. Measurements of its radius therefore hold promise to constrain the properties of the cold, catalyzed, high-density matter in neutron star cores. Previously, Miller et al. and Riley et al. reported measurements of the radius of PSR J0740+6620 based on Neutron Star Interior Composition Explorer (NICER) observations accumulated through 2020 April 17, and an exploratory analysis utilizing NICER background estimates and a data set accumulated through 2021 December 28 was presented in Salmi et al. Here we report an updated radius measurement, derived by fitting models of X-ray emission from the neutron star surface to NICER data accumulated through 2022 April 21, totaling ∼1.1 Ms additional exposure compared to the data set analyzed in Miller et al. and Riley et al., and to data from XMM-Newton observations. We find that the equatorial circumferential radius of PSR J0740+6620 is km (68% credibility), a fractional uncertainty ∼83% the width of that reported in Miller et al., in line with statistical expectations given the additional data. If we were to require the radius to be less than 16 km, as was done in Salmi et al., then our 68% credible region would become km, which is close to the headline result of Salmi et al. Our updated measurements, along with other laboratory and astrophysical constraints, imply a slightly softer equation of state than that inferred from our previous measurements.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448721","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 : 2024-10-17DOI: 10.3847/1538-4357/ad6987
Gabriela Oliveira da Rosa, S. O. Kepler, L. T. T. Soethe, Alejandra D. Romero and Keaton J. Bell
We present a census of photometrically detected rotation periods for white dwarf (WD) stars. We analyzed the light curves of 9285 WD stars observed by the Transiting Exoplanet Survey Satellite up to Sector 69. Using Fourier transform analyses and the TESS_localize software, we detected variability periods for 318 WD stars. The 115 high-probability likely single WDs in our sample have a median rotational period of 3.9 hr and a median absolute deviation of 3.5 hr. Our distribution is significantly different from the distribution of the rotational period from asteroseismology, which exhibits a longer median period of 24.2 hr and a median absolute deviation of 12.1 hr. In addition, we reported nonpulsating periods for three known pulsating WDs with rotational periods previously determined by asteroseismology: NGC 1501, TIC 7675859, and G226-29. We also calculated evolutionary models including six angular momentum transfer mechanisms from the literature throughout evolution in an attempt to reproduce our findings. Our models indicate that the temperature–period relation of most observational data is best fitted by models with low metallicity, probably indicating problems with the computations of angular momentum loss during the high-mass-loss phase. Our models also generate internal magnetic fields through the Tayler–Spruit dynamo.
{"title":"Photometric White Dwarf Rotation","authors":"Gabriela Oliveira da Rosa, S. O. Kepler, L. T. T. Soethe, Alejandra D. Romero and Keaton J. Bell","doi":"10.3847/1538-4357/ad6987","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6987","url":null,"abstract":"We present a census of photometrically detected rotation periods for white dwarf (WD) stars. We analyzed the light curves of 9285 WD stars observed by the Transiting Exoplanet Survey Satellite up to Sector 69. Using Fourier transform analyses and the TESS_localize software, we detected variability periods for 318 WD stars. The 115 high-probability likely single WDs in our sample have a median rotational period of 3.9 hr and a median absolute deviation of 3.5 hr. Our distribution is significantly different from the distribution of the rotational period from asteroseismology, which exhibits a longer median period of 24.2 hr and a median absolute deviation of 12.1 hr. In addition, we reported nonpulsating periods for three known pulsating WDs with rotational periods previously determined by asteroseismology: NGC 1501, TIC 7675859, and G226-29. We also calculated evolutionary models including six angular momentum transfer mechanisms from the literature throughout evolution in an attempt to reproduce our findings. Our models indicate that the temperature–period relation of most observational data is best fitted by models with low metallicity, probably indicating problems with the computations of angular momentum loss during the high-mass-loss phase. Our models also generate internal magnetic fields through the Tayler–Spruit dynamo.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448723","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 : 2024-10-17DOI: 10.3847/1538-4357/ad7824
Hao-Ran Yang and Xiang-Dong Li
Swift J1858.6−0814 (hereafter J1858) is a transient neutron star (NS) low-mass X-ray binary (LMXB). There is controversy regarding its donor mass derived from observations and theoretical calculations. In this paper, we adopt seven magnetic braking (MB) prescriptions suggested in the literature and different metallicity Z to simulate the evolution of the LMXB. Our results show that, employing the MB model proposed by A. Reiners & S. Mohanty (“rm12”), the convection- and rotation-boosted (“carb”) model, and the intermediate (“inter”) and convection-boosted (“cboost”) models in K. X. Van et al. can match (part of) the observational parameters of J1858 well. We then apply our method to other observed LMXBs and find that the “rm12” and “inter” MB laws are most promising in explaining transient LMXBs. In comparison, the simulations with the “cboost” and “carb” MB laws are more inclined to reproduce persistent LMXBs and ultracompact X-ray binaries, respectively. Our results, though subject to computational and/or observational bias, show that it is challenging to find a unified MB law that applies to the NS LMXB subpopulations simultaneously, indicating our lack of understanding of the true MB law. In addition, we explore the influence of various MB laws on the magnitude of the bifurcation periods in LMXBs.
Swift J1858.6-0814（以下简称 J1858）是一颗瞬态中子星（NS）低质量 X 射线双星（LMXB）。根据观测和理论计算得出的供体质量存在争议。在本文中，我们采用了文献中提出的七种磁制动（MB）方案和不同的金属性 Z 来模拟 LMXB 的演化。我们的结果表明，采用 A. Reiners & S. Mohanty（"rm12"）提出的磁制动模型、K. X. Van 等人提出的对流和旋转增强（"carb"）模型以及中间（"inter"）和对流增强（"cboost"）模型，可以很好地匹配 J1858 的（部分）观测参数。然后，我们将我们的方法应用于其他观测到的 LMXB，发现 "rm12 "和 "inter "MB 规律最有希望解释瞬态 LMXB。相比之下，使用 "cboost "和 "carb "MB定律进行的模拟分别更倾向于重现持续存在的LMXB和超小型X射线双星。我们的结果虽然受到计算和/或观测偏差的影响，但也表明要找到一个同时适用于 NS LMXB 子群的统一 MB 规律是很有挑战性的，这说明我们对真正的 MB 规律还缺乏了解。此外，我们还探讨了各种 MB 规律对 LMXB 分叉期大小的影响。
{"title":"The Influence of the Magnetic Braking Laws on the Evolution of Persistent and Transient Low-mass X-Ray Binaries","authors":"Hao-Ran Yang and Xiang-Dong Li","doi":"10.3847/1538-4357/ad7824","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7824","url":null,"abstract":"Swift J1858.6−0814 (hereafter J1858) is a transient neutron star (NS) low-mass X-ray binary (LMXB). There is controversy regarding its donor mass derived from observations and theoretical calculations. In this paper, we adopt seven magnetic braking (MB) prescriptions suggested in the literature and different metallicity Z to simulate the evolution of the LMXB. Our results show that, employing the MB model proposed by A. Reiners & S. Mohanty (“rm12”), the convection- and rotation-boosted (“carb”) model, and the intermediate (“inter”) and convection-boosted (“cboost”) models in K. X. Van et al. can match (part of) the observational parameters of J1858 well. We then apply our method to other observed LMXBs and find that the “rm12” and “inter” MB laws are most promising in explaining transient LMXBs. In comparison, the simulations with the “cboost” and “carb” MB laws are more inclined to reproduce persistent LMXBs and ultracompact X-ray binaries, respectively. Our results, though subject to computational and/or observational bias, show that it is challenging to find a unified MB law that applies to the NS LMXB subpopulations simultaneously, indicating our lack of understanding of the true MB law. In addition, we explore the influence of various MB laws on the magnitude of the bifurcation periods in LMXBs.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448753","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 : 2024-10-17DOI: 10.3847/1538-4357/ad6cd0
Louis Amard, Allan Sacha Brun and Ana Palacios
The magnetic field of red giants is still poorly understood today. Close to the core, asteroseismology has revealed magnetic fields of several hundred thousand gauss, but close to the surface, spectropolarimetric observations of the red giant Pollux only showed an average field of the order of 1 G. Using the ASH code, we conduct a series of 3D nonlinear magnetohydrodynamical simulations aiming at modeling the dynamo process operating within the extended convective envelope of a star similar to the red giant Pollux. We find that the dynamo is efficient even for the slow rotation considered and that large-scale fields are generated and maintained. We further test the correlation between the scale of the convective motions and the surface magnetic field geometry by varying the Prandtl number in our simulations. We show in particular that the value and the geometry of the modeled surface field depend directly on the coupling scales between the magnetic and the velocity fields, with larger convective cells leading to a stronger large-scale magnetic field. We also verify that the dynamo and the geometry of the resulting field are robust against a change of the initial conditions. We then compare our simulations to the observed field and find average ∣Bℓ∣ of about 7 G for the simulation with large convective cells, and down to 2 G for the smaller-scale simulation, very close to the observed value. Finally, we suggest the possibility of the reversal of the red giant’s magnetic field.
{"title":"Understanding Post-main-sequence Stellar Magnetism: On the Origin of Pollux’s Weak Surface Magnetic Field","authors":"Louis Amard, Allan Sacha Brun and Ana Palacios","doi":"10.3847/1538-4357/ad6cd0","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6cd0","url":null,"abstract":"The magnetic field of red giants is still poorly understood today. Close to the core, asteroseismology has revealed magnetic fields of several hundred thousand gauss, but close to the surface, spectropolarimetric observations of the red giant Pollux only showed an average field of the order of 1 G. Using the ASH code, we conduct a series of 3D nonlinear magnetohydrodynamical simulations aiming at modeling the dynamo process operating within the extended convective envelope of a star similar to the red giant Pollux. We find that the dynamo is efficient even for the slow rotation considered and that large-scale fields are generated and maintained. We further test the correlation between the scale of the convective motions and the surface magnetic field geometry by varying the Prandtl number in our simulations. We show in particular that the value and the geometry of the modeled surface field depend directly on the coupling scales between the magnetic and the velocity fields, with larger convective cells leading to a stronger large-scale magnetic field. We also verify that the dynamo and the geometry of the resulting field are robust against a change of the initial conditions. We then compare our simulations to the observed field and find average ∣Bℓ∣ of about 7 G for the simulation with large convective cells, and down to 2 G for the smaller-scale simulation, very close to the observed value. Finally, we suggest the possibility of the reversal of the red giant’s magnetic field.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448883","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 : 2024-10-17DOI: 10.3847/1538-4357/ad73a1
David Bogensberger, Jon M Miller, Richard Mushotzky, W. N. Brandt, Elias Kammoun, Abderahmen Zoghbi and Ehud Behar
The structure of the jet in Cen A is likely better revealed in X-rays than in the radio band, which is usually used to investigate jet proper motions. In this paper, we analyze Chandra Advanced CCD Imaging Spectrometer observations of Cen A from 2000 to 2022 and develop an algorithm for systematically fitting the proper motions of its X-ray jet knots. Most of the knots had an apparent proper motion below the detection limit. However, one knot at a transverse distance of 520 pc had an apparent superluminal proper motion of 2.7 ± 0.4c. This constrains the inclination of the jet to be i < 41° ± 6° and the velocity of this knot to be β > 0.94 ± 0.02. This agrees well with the inclination measured in the inner jet by the Event Horizon Telescope but contradicts previous estimates based on jet and counterjet brightness. It also disagrees with the proper motion of the corresponding radio knot, of 0.8 ± 0.1c, which further indicates that the X-ray and radio bands trace distinct structures in the jet. There are four prominent X-ray jet knots closer to the nucleus, but only one of these is inconsistent with being stationary. A few jet knots also have a significant proper-motion component in the nonradial direction. This component is typically larger closer to the center of the jet. We also detect brightness and morphology variations at a transverse distance of 100 pc from the nucleus.
Cen A的喷流结构在X射线中可能比在射电波段中得到更好的揭示，而射电波段通常用于研究喷流的正常运动。在本文中，我们分析了钱德拉高级CCD成像分光计从2000年到2022年对Cen A的观测，并开发了一种算法来系统地拟合其X射线喷流节的适当运动。大多数喷流节的视近运动都低于探测极限。然而，横向距离为 520 pc 的一个星结的视超运动为 2.7 ± 0.4c。这就限定了喷流的倾角为 i < 41° ± 6°，这个星结的速度为 β > 0.94 ± 0.02。这与事件地平线望远镜在内部喷流中测得的倾角非常吻合，但与之前根据喷流和反喷流亮度做出的估计相矛盾。这也与相应的射电节（0.8 ± 0.1c）的正确运动不符，进一步表明 X 射线波段和射电波段追踪的是喷流中不同的结构。在离核更近的地方有四个突出的 X 射线喷流节，但其中只有一个不符合静止状态。少数几个喷流结在非径向也有明显的顺运动分量。这个分量通常在更靠近喷流中心的地方更大。我们还探测到在距离核 100 pc 的横向距离上的亮度和形态变化。
{"title":"Superluminal Proper Motion in the X-Ray Jet of Centaurus A","authors":"David Bogensberger, Jon M Miller, Richard Mushotzky, W. N. Brandt, Elias Kammoun, Abderahmen Zoghbi and Ehud Behar","doi":"10.3847/1538-4357/ad73a1","DOIUrl":"https://doi.org/10.3847/1538-4357/ad73a1","url":null,"abstract":"The structure of the jet in Cen A is likely better revealed in X-rays than in the radio band, which is usually used to investigate jet proper motions. In this paper, we analyze Chandra Advanced CCD Imaging Spectrometer observations of Cen A from 2000 to 2022 and develop an algorithm for systematically fitting the proper motions of its X-ray jet knots. Most of the knots had an apparent proper motion below the detection limit. However, one knot at a transverse distance of 520 pc had an apparent superluminal proper motion of 2.7 ± 0.4c. This constrains the inclination of the jet to be i < 41° ± 6° and the velocity of this knot to be β > 0.94 ± 0.02. This agrees well with the inclination measured in the inner jet by the Event Horizon Telescope but contradicts previous estimates based on jet and counterjet brightness. It also disagrees with the proper motion of the corresponding radio knot, of 0.8 ± 0.1c, which further indicates that the X-ray and radio bands trace distinct structures in the jet. There are four prominent X-ray jet knots closer to the nucleus, but only one of these is inconsistent with being stationary. A few jet knots also have a significant proper-motion component in the nonradial direction. This component is typically larger closer to the center of the jet. We also detect brightness and morphology variations at a transverse distance of 100 pc from the nucleus.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448945","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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