Pub Date : 2024-08-09DOI: 10.1051/0004-6361/202450496
M. Hajduk, P. A. M. van Hoof, A. A. Zijlstra, G. Van de Steene, S. Kimeswenger, D. Barría, D. Tafoya, J. A. Toalá
Context. The very late thermal pulse (VLTP) affects the evolution of ∼20% of 1–8 M⊙ stars, repeating the last red giant phases within a few years and leading to the formation of a new, but hydrogen-poor, nebula within the old planetary nebula. The strong dust formation in the latter obscures the optical and near-infrared radiation of the star.Aims. We aimed to determine the reheating timescale of the central star in Sakurai’s Object, which is an important constraint for the poorly understood VLTP evolution.Methods. We observed the radio continuum emission of Sakurai’s Object for almost 20 years, from 2004 to 2023. Continuous, multi-frequency observations proved to be essential for distinguishing between phases dominated by photoionization and shock ionization.Results. The flux density fluctuates by more than a factor of 40 within months to years. The spectral index remained negative between 2006 and 2017 and has been close to zero since 2019. The emission region has been only barely resolved since 2021.Conclusions. Non-thermal radio emission observed from 2004 to 2017 traces shocks induced by wind interactions due to discrete mass-loss events. Thermal emission dominates from 2019 to 2023 and may indicate photoionization of the nebula by the central star.
{"title":"Non-thermal radio emission in Sakurai’s Object","authors":"M. Hajduk, P. A. M. van Hoof, A. A. Zijlstra, G. Van de Steene, S. Kimeswenger, D. Barría, D. Tafoya, J. A. Toalá","doi":"10.1051/0004-6361/202450496","DOIUrl":"https://doi.org/10.1051/0004-6361/202450496","url":null,"abstract":"<i>Context.<i/> The very late thermal pulse (VLTP) affects the evolution of ∼20% of 1–8 <i>M<i/><sub>⊙<sub/> stars, repeating the last red giant phases within a few years and leading to the formation of a new, but hydrogen-poor, nebula within the old planetary nebula. The strong dust formation in the latter obscures the optical and near-infrared radiation of the star.<i>Aims.<i/> We aimed to determine the reheating timescale of the central star in Sakurai’s Object, which is an important constraint for the poorly understood VLTP evolution.<i>Methods.<i/> We observed the radio continuum emission of Sakurai’s Object for almost 20 years, from 2004 to 2023. Continuous, multi-frequency observations proved to be essential for distinguishing between phases dominated by photoionization and shock ionization.<i>Results.<i/> The flux density fluctuates by more than a factor of 40 within months to years. The spectral index remained negative between 2006 and 2017 and has been close to zero since 2019. The emission region has been only barely resolved since 2021.<i>Conclusions.<i/> Non-thermal radio emission observed from 2004 to 2017 traces shocks induced by wind interactions due to discrete mass-loss events. Thermal emission dominates from 2019 to 2023 and may indicate photoionization of the nebula by the central star.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-08DOI: 10.1051/0004-6361/202450489
Daniel Hey, Conny Aerts
Context. The Gaia mission has delivered hundreds of thousands of variable star light curves in multiple wavelengths. Recent work demonstrates that these light curves can be used to identify (non-)radial pulsations in OBAF-type stars, despite their irregular cadence and low light curve precision, of the order of a few millimagnitudes. With the considerably more precise TESS photometry, we revisited these candidate pulsators to conclusively ascertain the nature of their variability.Aims. We seek to re-classify the Gaia light curves with the first two years of TESS photometry for a sample of 58 970 p- and g-mode pulsators, encompassing γ Dor, δ Scuti, slowly pulsating B, and β Cep variables. From the TESS data, we seek to assess the quality of Gaia’s classification of non-radial pulsators, which is based on sparse, years-long light curves of millimagnitude precision. We also supply four new catalogues containing the confirmed pulsators, along with their dominant and secondary pulsation frequencies, the number of independent mode frequencies, and a ranking according to their usefulness for future asteroseismic ensemble analysis.Methods. We first analysed the TESS light curves independent of their Gaia classification by pre-whitening all dominant pulsation modes down to a 1% false alarm probability. Using this, in combination with a feature-based random forest classifier, we identified different variability types across the sample.Results. We find that the Gaia photometry is exceptionally accurate for detecting the dominant and secondary frequencies, reaching approximately 80% accuracy in frequency for p- and g-mode pulsators. The majority of Gaia classifications are consistent with the classifications from the TESS data, illustrating the power of the low-cadence Gaia photometry for pulsation studies. We find that the sample of g-mode pulsators forms a continuous group of variable stars along the main sequence across B, A, and F spectral types, implying that the mode excitation mechanisms for all these pulsators need to be updated with improved physics. Finally, we provide a rank-ordered table of pulsators according to their asteroseismic potential for follow-up studies, based on the number of sectors they have been observed in, their classification probability, and the number of independent modes found in the TESS light curves from the nominal mission.Conclusions. Our catalogue offers a major increase in the number of confirmed g-mode pulsators with an identified dominant mode suitable for follow-up TESS ensemble asteroseismology of such stars.
背景盖亚任务提供了数十万条多波长变星光曲线。最近的研究表明，这些光曲线可以用来识别 OBAF 型恒星的（非）径向脉动，尽管它们的周期不规则，光曲线的精度也很低，只有几毫微米的数量级。有了更为精确的 TESS 光度计，我们重新研究了这些候选脉冲星，以最终确定它们的变率性质。我们试图用前两年的 TESS 测光数据对 58 970 个 p 模式和 g 模式脉冲星样本的 Gaia 光曲线进行重新分类，其中包括 γ Dor、δ Scuti、慢脉冲 B 和 β Cep 变量。根据 TESS 数据，我们试图评估 Gaia 对非径向脉动器分类的质量，该分类是基于稀疏的、长达数年的、精度为毫磁级的光变曲线。我们还提供了四个新的目录，其中包含已确认的脉冲星，以及它们的主要和次要脉冲频率、独立模式频率的数量，并根据它们对未来小行星地震集合分析的有用性进行了排序。我们首先分析了独立于盖亚分类的 TESS 光曲线，将所有主要脉动模式预先白化到 1%的误报概率。利用这种方法，结合基于特征的随机森林分类器，我们确定了整个样本的不同变异类型。我们发现盖亚光度计在检测主频和副频方面异常准确，p 模和 g 模脉冲星的频率准确率达到约 80%。盖亚的大部分分类与 TESS 数据的分类一致，这说明盖亚的低信噪比光度测量在脉冲研究中的强大功能。我们发现，g模式脉冲星样本形成了一个连续的变星群，沿着主序分布在B、A和F光谱型中，这意味着所有这些脉冲星的模式激发机制都需要通过改进物理学来更新。最后，我们根据脉冲星被观测到的扇区数量、其分类概率以及在 TESS 名义任务光曲线中发现的独立模式数量，提供了一个脉冲星排序表，以根据它们的小行星地震潜力进行后续研究。我们的目录大大增加了已确认的 g 模式脉冲星的数量，这些脉冲星的主导模式已被确定，适合对这类恒星进行 TESS 组合小行星震后续研究。
{"title":"Confronting sparse Gaia DR3 photometry with TESS for a sample of around 60 000 OBAF-type pulsators★★★","authors":"Daniel Hey, Conny Aerts","doi":"10.1051/0004-6361/202450489","DOIUrl":"https://doi.org/10.1051/0004-6361/202450489","url":null,"abstract":"<i>Context.<i/> The <i>Gaia<i/> mission has delivered hundreds of thousands of variable star light curves in multiple wavelengths. Recent work demonstrates that these light curves can be used to identify (non-)radial pulsations in OBAF-type stars, despite their irregular cadence and low light curve precision, of the order of a few millimagnitudes. With the considerably more precise TESS photometry, we revisited these candidate pulsators to conclusively ascertain the nature of their variability.<i>Aims.<i/> We seek to re-classify the <i>Gaia<i/> light curves with the first two years of TESS photometry for a sample of 58 970 <i>p<i/>- and <i>g<i/>-mode pulsators, encompassing <i>γ<i/> Dor, <i>δ<i/> Scuti, slowly pulsating B, and <i>β<i/> Cep variables. From the TESS data, we seek to assess the quality of <i>Gaia<i/>’s classification of non-radial pulsators, which is based on sparse, years-long light curves of millimagnitude precision. We also supply four new catalogues containing the confirmed pulsators, along with their dominant and secondary pulsation frequencies, the number of independent mode frequencies, and a ranking according to their usefulness for future asteroseismic ensemble analysis.<i>Methods.<i/> We first analysed the TESS light curves independent of their <i>Gaia<i/> classification by pre-whitening all dominant pulsation modes down to a 1% false alarm probability. Using this, in combination with a feature-based random forest classifier, we identified different variability types across the sample.<i>Results.<i/> We find that the <i>Gaia<i/> photometry is exceptionally accurate for detecting the dominant and secondary frequencies, reaching approximately 80% accuracy in frequency for <i>p<i/>- and <i>g<i/>-mode pulsators. The majority of <i>Gaia<i/> classifications are consistent with the classifications from the TESS data, illustrating the power of the low-cadence <i>Gaia<i/> photometry for pulsation studies. We find that the sample of <i>g<i/>-mode pulsators forms a continuous group of variable stars along the main sequence across B, A, and F spectral types, implying that the mode excitation mechanisms for all these pulsators need to be updated with improved physics. Finally, we provide a rank-ordered table of pulsators according to their asteroseismic potential for follow-up studies, based on the number of sectors they have been observed in, their classification probability, and the number of independent modes found in the TESS light curves from the nominal mission.<i>Conclusions.<i/> Our catalogue offers a major increase in the number of confirmed <i>g<i/>-mode pulsators with an identified dominant mode suitable for follow-up TESS ensemble asteroseismology of such stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-07DOI: 10.1051/0004-6361/202450177
Ryushi Miyayama, Hiroshi Kobayashi
To investigate impact vaporization for planetary atmosphere formation, we have studied the thermodynamic state generated by the shock wave due to a high-velocity impact, called the shock field. We have carried out iSALE simulations for high-velocity vertical impacts using ANEOS for an equation-of-state (EoS) model. To understand the shock fields obtained from simulations, we have investigated the contribution of the thermal and cold terms in the EoS model on the Hugoniot curves. Although the thermal and cold terms are important for the pressure, the internal energy is mainly determined by the thermal term. We thus assume a simple EoS determined by the thermal term and then analytically derive the shock internal-energy field, which reproduces the results of simulations well. Using the analytical solution of internal energy and the Hugoniot curve, we have derived the shock pressure field analytically as well. The analytical solutions for internal energy and pressure are valid even for impact velocities as low as the sound speed. The solution is good for the vertical direction or within the angles of about 60 degrees. We have applied the solution to impact vaporization for the formation of planetary atmospheres. This gives good estimation of reformation of the planetary atmospheres of Earth sized planet.
{"title":"Formation of planetary atmospheres","authors":"Ryushi Miyayama, Hiroshi Kobayashi","doi":"10.1051/0004-6361/202450177","DOIUrl":"https://doi.org/10.1051/0004-6361/202450177","url":null,"abstract":"To investigate impact vaporization for planetary atmosphere formation, we have studied the thermodynamic state generated by the shock wave due to a high-velocity impact, called the shock field. We have carried out iSALE simulations for high-velocity vertical impacts using ANEOS for an equation-of-state (EoS) model. To understand the shock fields obtained from simulations, we have investigated the contribution of the thermal and cold terms in the EoS model on the Hugoniot curves. Although the thermal and cold terms are important for the pressure, the internal energy is mainly determined by the thermal term. We thus assume a simple EoS determined by the thermal term and then analytically derive the shock internal-energy field, which reproduces the results of simulations well. Using the analytical solution of internal energy and the Hugoniot curve, we have derived the shock pressure field analytically as well. The analytical solutions for internal energy and pressure are valid even for impact velocities as low as the sound speed. The solution is good for the vertical direction or within the angles of about 60 degrees. We have applied the solution to impact vaporization for the formation of planetary atmospheres. This gives good estimation of reformation of the planetary atmospheres of Earth sized planet.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1051/0004-6361/202450559
L. Acuña, L. Kreidberg, M. Zhai, P. Mollière
The metal mass fractions of gas giants are a powerful tool for constraining their formation mechanisms and evolution. The metal content is inferred by comparing mass and radius measurements with interior structure and evolution models. In the midst of the JWST, CHEOPS, TESS, and the forthcoming PLATO era, we are at the brink of obtaining unprecedented precision in radius, age, and atmospheric metallicity measurements. To prepare for this wealth of data, we present the GAS gianT modeL for Interiors (GASTLI), an easy-to-use, publicly available Python package. The code is optimized to rapidly calculate mass-radius relations, and radius and luminosity thermal evolution curves for a variety of envelope compositions and core mass fractions. Its applicability spans planets with masses of 17 M⊕ < M < 6 MJup, and equilibrium temperatures of Teq< 1000 K. The interior model is stratified in a core composed of water and rock, and an envelope constituted by H/He and metals (water). The interior is coupled to a grid of self-consistent, cloud-free atmospheric models to determine the atmospheric and boundary interior temperature, as well as the contribution of the atmosphere to the total radius. We successfully validate GASTLI by comparing it to previous work and data of the gas giants of the Solar System and Neptune. We also test GASTLI on the Neptune-mass exoplanet HAT-P-26 b, finding a bulk metal mass fraction of between 0.60 and 0.78 and a core mass of 8.5–14.4 M⊕. Finally, we explore the impact of different equations of state and assumptions, such as C/O ratio and transit pressure, in the estimation of bulk metal mass fraction. These differences between interior models entail a change in radius of up to 2.5% for Jupiter-mass planets, but of more than 10% for Neptune-mass. These are equivalent to variations in core mass fraction of 0.07, or 0.10 in envelope metal mass fraction.
气态巨行星的金属质量分数是制约其形成机制和演化的有力工具。金属含量是通过将质量和半径测量结果与内部结构和演化模型进行比较而推断出来的。在JWST、CHEOPS、TESS和即将到来的PLATO时代，我们即将获得前所未有的半径、年龄和大气金属度测量精度。为了准备这些丰富的数据，我们推出了 GAS gianT modeL for Interiors (GASTLI)，这是一个易于使用、公开可用的 Python 软件包。该代码经过优化，可以快速计算各种包层成分和内核质量分数的质量-半径关系以及半径和光度热演化曲线。其适用范围包括质量为 17 M⊕ < M 6 MJup、平衡温度为 Teq 1000 K 的行星。内部模型分层为由水和岩石组成的内核以及由 H/He 和金属（水）组成的包层。内部模型与自洽无云大气模型网格耦合，以确定大气和边界内部温度，以及大气对总半径的贡献。我们将 GASTLI 与以前的工作以及太阳系气态巨行星和海王星的数据进行比较，成功地验证了 GASTLI。我们还在海王星质量的系外行星HAT-P-26 b上测试了GASTLI，发现其主体金属质量分数介于0.60和0.78之间，核心质量为8.5-14.4 M⊕。最后，我们探讨了不同状态方程和假设（如 C/O 比率和过境压力）对估计块状金属质量分数的影响。这些内部模型之间的差异会导致木星质量的行星半径发生最多 2.5%的变化，而海王星质量的行星半径则会发生 10%以上的变化。这相当于内核质量分数变化 0.07 或包层金属质量分数变化 0.10。
{"title":"GASTLI","authors":"L. Acuña, L. Kreidberg, M. Zhai, P. Mollière","doi":"10.1051/0004-6361/202450559","DOIUrl":"https://doi.org/10.1051/0004-6361/202450559","url":null,"abstract":"The metal mass fractions of gas giants are a powerful tool for constraining their formation mechanisms and evolution. The metal content is inferred by comparing mass and radius measurements with interior structure and evolution models. In the midst of the JWST, CHEOPS, TESS, and the forthcoming PLATO era, we are at the brink of obtaining unprecedented precision in radius, age, and atmospheric metallicity measurements. To prepare for this wealth of data, we present the GAS gianT modeL for Interiors (GASTLI), an easy-to-use, publicly available Python package. The code is optimized to rapidly calculate mass-radius relations, and radius and luminosity thermal evolution curves for a variety of envelope compositions and core mass fractions. Its applicability spans planets with masses of 17 <i>M<i/><sub>⊕<sub/> < <i>M <<i/> 6 <i>M<i/><sub>Jup<sub/>, and equilibrium temperatures of <i>T<i/><sub>eq<sub/> <i><<i/> 1000 K. The interior model is stratified in a core composed of water and rock, and an envelope constituted by H/He and metals (water). The interior is coupled to a grid of self-consistent, cloud-free atmospheric models to determine the atmospheric and boundary interior temperature, as well as the contribution of the atmosphere to the total radius. We successfully validate GASTLI by comparing it to previous work and data of the gas giants of the Solar System and Neptune. We also test GASTLI on the Neptune-mass exoplanet HAT-P-26 b, finding a bulk metal mass fraction of between 0.60 and 0.78 and a core mass of 8.5–14.4 <i>M<i/><sub>⊕<sub/>. Finally, we explore the impact of different equations of state and assumptions, such as C/O ratio and transit pressure, in the estimation of bulk metal mass fraction. These differences between interior models entail a change in radius of up to 2.5% for Jupiter-mass planets, but of more than 10% for Neptune-mass. These are equivalent to variations in core mass fraction of 0.07, or 0.10 in envelope metal mass fraction.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141891838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1051/0004-6361/202450085
Erick Nagel, Jerome Bouvier, Adrián E. Duarte
Context. The so-called “dippers” are young stellar objects that exhibit dimming episodes in their optical light curves. The common interpretation for the occurrence of these dips is that dusty regions periodically or quasi-periodically cross the line of sight toward the object.Aims. We develop a model where we assume that these regions are located at the intersection of the magnetospheric stream with the disk. The stream is fed by gas and dust coming from the disk. As the material follows the magnetic field lines above the disk plane, it forms an opaque screen that partially blocks the stellar emission. The amount of extinction caused by the material crossing the line of sight depends on the abundance and location of the dust along the stream, which depends on the degree of dust evaporation due to the heating by the star.Methods. We run hydrodynamical simulations of dusty accretion streams to produce synthetic dipper light curves for a sample of low-mass young stars still accreting from their disk according to evolutionary models. We compare the distribution of the light curve amplitudes between the synthetic sample and observed samples of dippers from various star-forming regions.Results. Dust evaporation along the accretion column drives the distribution of photometric amplitudes. Our results suggest that most of the observed dippers correspond to systems seen at high inclination. However, dust survival within accretion columns may also produce dippers at lower inclination, down to about 45°. We find that the dust temperature arising from stellar irradiation should be increased by a factor 1.6 to find consistency between the fraction of dippers our model predicts in star-forming regions and the observed fraction of 20–30%.Conclusions. Transient dust survival in accretion columns appear as an alternative (or complementary) mechanism to inner disk warp occultation in order to account for low-inclination dippers in star-forming regions.
{"title":"A dusty magnetospheric stream explaining the light curves of the dipper objects: Finding a new inclination threshold to produce dippers","authors":"Erick Nagel, Jerome Bouvier, Adrián E. Duarte","doi":"10.1051/0004-6361/202450085","DOIUrl":"https://doi.org/10.1051/0004-6361/202450085","url":null,"abstract":"<i>Context<i/>. The so-called “dippers” are young stellar objects that exhibit dimming episodes in their optical light curves. The common interpretation for the occurrence of these dips is that dusty regions periodically or quasi-periodically cross the line of sight toward the object.<i>Aims<i/>. We develop a model where we assume that these regions are located at the intersection of the magnetospheric stream with the disk. The stream is fed by gas and dust coming from the disk. As the material follows the magnetic field lines above the disk plane, it forms an opaque screen that partially blocks the stellar emission. The amount of extinction caused by the material crossing the line of sight depends on the abundance and location of the dust along the stream, which depends on the degree of dust evaporation due to the heating by the star.<i>Methods<i/>. We run hydrodynamical simulations of dusty accretion streams to produce synthetic dipper light curves for a sample of low-mass young stars still accreting from their disk according to evolutionary models. We compare the distribution of the light curve amplitudes between the synthetic sample and observed samples of dippers from various star-forming regions.<i>Results<i/>. Dust evaporation along the accretion column drives the distribution of photometric amplitudes. Our results suggest that most of the observed dippers correspond to systems seen at high inclination. However, dust survival within accretion columns may also produce dippers at lower inclination, down to about 45°. We find that the dust temperature arising from stellar irradiation should be increased by a factor 1.6 to find consistency between the fraction of dippers our model predicts in star-forming regions and the observed fraction of 20–30%.<i>Conclusions<i/>. Transient dust survival in accretion columns appear as an alternative (or complementary) mechanism to inner disk warp occultation in order to account for low-inclination dippers in star-forming regions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141891848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.1051/0004-6361/202450460
Daniel Marín Pina, Sara Rastello, Mark Gieles, Kyle Kremer, Laura Fitzgerald, Bruno Rando Forastier
Context. The star–black hole (S–BH) binary known as Gaia BH3, discovered by the Gaia Collaboration is chemically and kinematically associated with the metal-poor ED-2 stream in the Milky Way halo.Aims. We explore the possibility that Gaia BH3 was assembled dynamically in the progenitor globular cluster (GC) of the ED-2 stream.Methods. We used a public suite of star-by-star dynamical Monte Carlo models to identify S–BH binaries in GCs with different initial masses and (half-mass) radii.Results. We show that a likely progenitor of the ED-2 stream was a relatively low-mass (≲105M⊙) GC with an initial half-mass radius of ∼4 pc. Such a GC can dynamically retain a large fraction of its BH population and dissolve on the orbit of ED-2. From the suite of models we find that GCs produce ∼3 − 30 S–BH binaries, approximately independently of initial GC mass and inversely correlated with initial cluster radius. Scaling the results to the Milky Way GC population, we find that ∼75% of the S–BH binaries formed in GCs are ejected from their host GC, all in the early phases of evolution (≲1 Gyr); these are expected to no longer be close to streams. The ∼25% of S–BH binaries retained until dissolution are expected to form part of streams, such that for an initial mass of the progenitor of ED-2 of a few 104M⊙, we expect ∼2 − 3 S–BH to end up in the stream. GC models with metallicities similar to Gaia BH3 (≲1% solar) include S–BH binaries with similar BH masses (≳30 M⊙), orbital periods, and eccentricities.Conclusion. We predict that the Galactic halo contains of order 105 S–BH binaries that formed dynamically in GCs, a fraction of which may readily be detected in Gaia DR4. The detection of these sources provides valuable tests of BH dynamics in clusters and their contribution to gravitational wave sources.
{"title":"Dynamical formation of Gaia BH3 in the progenitor globular cluster of the ED-2 stream","authors":"Daniel Marín Pina, Sara Rastello, Mark Gieles, Kyle Kremer, Laura Fitzgerald, Bruno Rando Forastier","doi":"10.1051/0004-6361/202450460","DOIUrl":"https://doi.org/10.1051/0004-6361/202450460","url":null,"abstract":"<i>Context.<i/> The star–black hole (S–BH) binary known as <i>Gaia<i/> BH3, discovered by the <i>Gaia<i/> Collaboration is chemically and kinematically associated with the metal-poor ED-2 stream in the Milky Way halo.<i>Aims.<i/> We explore the possibility that <i>Gaia<i/> BH3 was assembled dynamically in the progenitor globular cluster (GC) of the ED-2 stream.<i>Methods.<i/> We used a public suite of star-by-star dynamical Monte Carlo models to identify S–BH binaries in GCs with different initial masses and (half-mass) radii.<i>Results.<i/> We show that a likely progenitor of the ED-2 stream was a relatively low-mass (≲10<sup>5<sup/> <i>M<i/><sub>⊙<sub/>) GC with an initial half-mass radius of ∼4 pc. Such a GC can dynamically retain a large fraction of its BH population and dissolve on the orbit of ED-2. From the suite of models we find that GCs produce ∼3 − 30 S–BH binaries, approximately independently of initial GC mass and inversely correlated with initial cluster radius. Scaling the results to the Milky Way GC population, we find that ∼75% of the S–BH binaries formed in GCs are ejected from their host GC, all in the early phases of evolution (≲1 Gyr); these are expected to no longer be close to streams. The ∼25% of S–BH binaries retained until dissolution are expected to form part of streams, such that for an initial mass of the progenitor of ED-2 of a few 10<sup>4<sup/> <i>M<i/><sub>⊙<sub/>, we expect ∼2 − 3 S–BH to end up in the stream. GC models with metallicities similar to <i>Gaia<i/> BH3 (≲1% solar) include S–BH binaries with similar BH masses (≳30 <i>M<i/><sub>⊙<sub/>), orbital periods, and eccentricities.<i>Conclusion.<i/> We predict that the Galactic halo contains of order 10<sup>5<sup/> S–BH binaries that formed dynamically in GCs, a fraction of which may readily be detected in <i>Gaia<i/> DR4. The detection of these sources provides valuable tests of BH dynamics in clusters and their contribution to gravitational wave sources.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.1051/0004-6361/202450711
M. Skarka, Z. Henzl
Aims. Our primary objective is to accurately identify and classify the variability of A-F stars in the southern continuous viewing zone of the TESS satellite. The brightness limit was set to 10 mag to ensure the utmost reliability of our results and allow for spectroscopic follow-up observations using small telescopes. We aim to compare our findings with existing catalogues of variable stars.Methods. The light curves from TESS and their Fourier transform were used to manually classify stars in our sample. Cross-matching with other catalogues was performed to identify contaminants and false positives.Results. We have identified 1171 variable stars (51% of the sample). Among these variable stars, 67% have clear classifications, which includes δ Sct and γ Dor pulsating stars and their hybrids, rotationally variables, and eclipsing binaries. We have provided examples of the typical representatives of variable stars and discussed the ambiguous cases. We found 20 pairs of stars with the same frequencies and identified the correct source of the variations. Additionally, we found that the variations in 12 other stars are caused by contamination from the light of faint nearby large-amplitude variable stars. To compare our sample with other variable star catalogues, we have defined two parameters reflecting the agreement in identification of variable stars and their classification. This comparison reveals intriguing disagreements in classification ranging from 52 to 100%. However, if we assume that stars without specific types are only marked as variable, then the agreement is relatively good, ranging from 57 to 85% (disagreement 15–43%). We have demonstrated that the TESS classification is superior to the classification based on other photometric surveys.Conclusions. The classification of stellar variability is complex and requires careful consideration. Caution should be exercised when using catalogue classifications.
{"title":"Periodic variable A-F spectral type stars in the southern TESS continuous viewing zone","authors":"M. Skarka, Z. Henzl","doi":"10.1051/0004-6361/202450711","DOIUrl":"https://doi.org/10.1051/0004-6361/202450711","url":null,"abstract":"<i>Aims<i/>. Our primary objective is to accurately identify and classify the variability of A-F stars in the southern continuous viewing zone of the TESS satellite. The brightness limit was set to 10 mag to ensure the utmost reliability of our results and allow for spectroscopic follow-up observations using small telescopes. We aim to compare our findings with existing catalogues of variable stars.<i>Methods<i/>. The light curves from TESS and their Fourier transform were used to manually classify stars in our sample. Cross-matching with other catalogues was performed to identify contaminants and false positives.<i>Results<i/>. We have identified 1171 variable stars (51% of the sample). Among these variable stars, 67% have clear classifications, which includes <i>δ<i/> Sct and <i>γ<i/> Dor pulsating stars and their hybrids, rotationally variables, and eclipsing binaries. We have provided examples of the typical representatives of variable stars and discussed the ambiguous cases. We found 20 pairs of stars with the same frequencies and identified the correct source of the variations. Additionally, we found that the variations in 12 other stars are caused by contamination from the light of faint nearby large-amplitude variable stars. To compare our sample with other variable star catalogues, we have defined two parameters reflecting the agreement in identification of variable stars and their classification. This comparison reveals intriguing disagreements in classification ranging from 52 to 100%. However, if we assume that stars without specific types are only marked as variable, then the agreement is relatively good, ranging from 57 to 85% (disagreement 15–43%). We have demonstrated that the TESS classification is superior to the classification based on other photometric surveys.<i>Conclusions<i/>. The classification of stellar variability is complex and requires careful consideration. Caution should be exercised when using catalogue classifications.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449145
Olena Shubina, Evgenij Zubko, Valerii Kleshchonok, Oleksandra V. Ivanova, Marek Husárik, Gorden Videen
Context. We analyze the results of photometric monitoring of comet C/2013 X1 (PANSTARRS) from December 2015 until January 2016 obtained within B, V, and R Johnson–Cousins filters.Aims. The main objective is to investigate the dust coma and to obtain the physical characteristics of its dust particles.Methods. We analyzed our observations using model-agglomerated debris particles, and we constrained the microphysical properties of the dust in comet C/2013 X1 (PANSTARRS) on the pre-outburst and post-outburst epochs. Moreover, we applied a geometrical model to the images processed by digital filters to estimate the rotational period of the nucleus.Results. Our campaign revealed a sharp increase in the comet brightness on January 1, 2016. The B − V and V − R colors calculated within an aperture size of 17 000 km appear to be mostly red, except for the outburst date. The dust production (A f ρ proxy) and normalized spectral gradient S′ (B − R) dramatically changed on January 2 as compared to what was seen in December 2015. According to this model, the C/2013 X1 coma was populated by 70% organic-matter particles by volume and by two types of silicate particles together, constituting the other 30%. One type of silicate particles was composed of Mg-rich silicates, whereas the other type was composed of both Mg-rich and Fe-poor silicates. Using the geometrical model, we estimate the nucleus rotational period to be (24.02 ± 0.02) h. We interpret the observed coma morphology by two jet structures, one structure that formed by the near-pole active area at a latitude of (85+5−3)°, and the other structure formed by an active area at a latitude of (+40 ± 5)°.
背景。我们分析了2015年12月至2016年1月期间在B、V和R约翰逊-考辛斯滤光片内获得的C/2013 X1彗星（PANSTARRS）的测光监测结果。主要目的是研究尘埃彗星并获得其尘埃粒子的物理特征。我们利用模型聚合的碎片颗粒对观测结果进行了分析，并对彗星C/2013 X1 (PANSTARRS)爆发前和爆发后的尘埃微物理特性进行了约束。此外，我们还对数字滤波器处理过的图像应用了几何模型，以估算彗核的旋转周期。我们的研究发现，2016 年 1 月 1 日彗星亮度急剧上升。在 17000 千米的孔径范围内计算出的 B - V 和 V - R 颜色似乎大多为红色，爆发日期除外。与2015年12月相比，1月2日的尘埃产生量（A f ρ代理）和归一化光谱梯度S′（B - R）发生了巨大变化。根据这一模型，按体积计算，C/2013 X1彗星彗尾由70%的有机物质粒子和两种类型的硅酸盐粒子共同构成，分别占另外的30%。其中一种硅酸盐颗粒由富含镁的硅酸盐组成，而另一种则由富含镁和贫铁的硅酸盐组成。我们用两个喷流结构来解释观测到的彗星形态，一个结构是由纬度为（85+5-3）°的近极活动区形成的，另一个结构是由纬度为（+40±5）°的活动区形成的。
{"title":"Dust properties and their variations in comet C/2013 X1 (PANSTARRS)","authors":"Olena Shubina, Evgenij Zubko, Valerii Kleshchonok, Oleksandra V. Ivanova, Marek Husárik, Gorden Videen","doi":"10.1051/0004-6361/202449145","DOIUrl":"https://doi.org/10.1051/0004-6361/202449145","url":null,"abstract":"<i>Context.<i/> We analyze the results of photometric monitoring of comet C/2013 X1 (PANSTARRS) from December 2015 until January 2016 obtained within <i>B, V<i/>, and <i>R<i/> Johnson–Cousins filters.<i>Aims.<i/> The main objective is to investigate the dust coma and to obtain the physical characteristics of its dust particles.<i>Methods.<i/> We analyzed our observations using model-agglomerated debris particles, and we constrained the microphysical properties of the dust in comet C/2013 X1 (PANSTARRS) on the pre-outburst and post-outburst epochs. Moreover, we applied a geometrical model to the images processed by digital filters to estimate the rotational period of the nucleus.<i>Results.<i/> Our campaign revealed a sharp increase in the comet brightness on January 1, 2016. The <i>B − V<i/> and <i>V − R<i/> colors calculated within an aperture size of 17 000 km appear to be mostly red, except for the outburst date. The dust production (<i>A f ρ<i/> proxy) and normalized spectral gradient <i>S′<i/> (<i>B − R<i/>) dramatically changed on January 2 as compared to what was seen in December 2015. According to this model, the C/2013 X1 coma was populated by 70% organic-matter particles by volume and by two types of silicate particles together, constituting the other 30%. One type of silicate particles was composed of Mg-rich silicates, whereas the other type was composed of both Mg-rich and Fe-poor silicates. Using the geometrical model, we estimate the nucleus rotational period to be (24.02 ± 0.02) h. We interpret the observed coma morphology by two jet structures, one structure that formed by the near-pole active area at a latitude of (85<sub>+5<sub/><sup>−3<sup/>)°, and the other structure formed by an active area at a latitude of (+40 ± 5)°.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141755430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-17DOI: 10.1051/0004-6361/202348808
A. de Burgos, S. Simón-Díaz, M. A. Urbaneja, J. Puls
Context. Blue supergiants (BSGs) are key objects for understanding the evolution of massive stars, which play a crucial role in the evolution of galaxies. However, discrepancies between theoretical predictions and empirical observations have opened up important questions yet to be answered. Studying statistically significant and unbiased samples of these objects can help to improve the situation.Aims. We perform a homogeneous and comprehensive quantitative spectroscopic analysis of a large sample of Galactic luminous blue stars (a majority of which are BSGs) from the IACOB spectroscopic database, providing crucial parameters to refine and improve theoretical evolutionary models.Methods. We derived the projected rotational velocity (υ sin i) and macroturbulent broadening (υmac) using IACOB-BROAD, which combines Fourier transform and line-profile fitting techniques. We compared high-quality optical spectra with state-of-the-art simulations of massive star atmospheres computed with the FASTWIND code. This comparison allowed us to derive effective temperatures (Teff), surface gravities (log 𝑔), microturbulences (ξ), surface abundances of silicon and helium, and to assess the relevance of stellar winds through a wind-strength parameter (log Q).Results. We provide estimates and associated uncertainties of the above-mentioned quantities for the largest sample of Galactic luminous O9 to B5 stars spectroscopically analyzed to date, comprising 527 targets. We find a clear drop in the relative number of stars at Teff ≈ 21 kK, coinciding with a scarcity of fast rotating stars below that temperature. We speculate that this feature (roughly corresponding to B2 spectral type) might be roughly delineating the location of the empirical terminal-age main sequence in the mass range between 15 and 85 M⊙. By investigating the main characteristics of the υ sin i distribution of O stars and BSGs as a function of Teff, we propose that an efficient mechanism transporting angular momentum from the stellar core to the surface might be operating along the main sequence in the high-mass domain. We find correlations between ξ,υmac and the spectroscopic luminosity 𝓛 (defined as Teff4 / g). We also find that no more than 20% of the stars in our sample have atmospheres clearly enriched in helium, and suggest that the origin of this specific subsample might be in binary evolution. We do not find clear empirical evidence of an increase in the wind strength over the wind bi-stability region toward lower Teff.
背景。蓝超巨星（BSG）是了解大质量恒星演化的关键天体，在星系演化过程中起着至关重要的作用。然而，理论预测与经验观测之间的差异提出了一些尚待解答的重要问题。研究这些天体中具有统计意义且无偏见的样本有助于改善这种状况。我们对来自IACOB光谱数据库的大量银河系发光蓝星样本（其中大部分是BSG）进行了均匀而全面的定量光谱分析，为完善和改进理论演化模型提供了重要参数。我们利用 IACOB-BROAD，结合傅立叶变换和线轮廓拟合技术，得出了投影旋转速度（υ sin i）和大扰动展宽（υmac）。我们将高质量的光学光谱与用 FASTWIND 代码计算的最先进的大质量恒星大气模拟进行了比较。通过比较，我们得出了有效温度（Teff）、表面引力（log 𝑔）、微扰动（ξ）、硅和氦的表面丰度，并通过风强度参数（log Q）评估了恒星风的相关性。我们提供了迄今为止通过光谱分析的银河系发光 O9 到 B5 星的最大样本（包括 527 个目标）的上述数量的估计值和相关不确定性。我们发现在 Teff ≈ 21 kK 时恒星的相对数量明显下降，这与低于该温度的快速旋转恒星的稀缺性相吻合。我们推测，这一特征（大致对应于B2光谱型）可能大致划定了质量范围在15到85 M⊙之间的经验末龄主序的位置。通过研究O星和BSG的υ sin i分布作为Teff函数的主要特征，我们提出了一种有效的机制，将角动量从恒星内核传输到表面，这种机制可能在高质域的主序上运行。我们发现ξ,υmac 与光谱光度𝓛（定义为 Teff4 / g）之间存在相关性。我们还发现，样本中不超过 20% 的恒星的大气层明显富含氦，这表明这一特定子样本的起源可能是双星演化。我们并没有发现明确的经验证据表明，在风的双稳态区域，风的强度会随着 Teff 值的降低而增加。
{"title":"The IACOB project","authors":"A. de Burgos, S. Simón-Díaz, M. A. Urbaneja, J. Puls","doi":"10.1051/0004-6361/202348808","DOIUrl":"https://doi.org/10.1051/0004-6361/202348808","url":null,"abstract":"<i>Context<i/>. Blue supergiants (BSGs) are key objects for understanding the evolution of massive stars, which play a crucial role in the evolution of galaxies. However, discrepancies between theoretical predictions and empirical observations have opened up important questions yet to be answered. Studying statistically significant and unbiased samples of these objects can help to improve the situation.<i>Aims<i/>. We perform a homogeneous and comprehensive quantitative spectroscopic analysis of a large sample of Galactic luminous blue stars (a majority of which are BSGs) from the IACOB spectroscopic database, providing crucial parameters to refine and improve theoretical evolutionary models.<i>Methods<i/>. We derived the projected rotational velocity (<i>υ<i/> sin <i>i<i/>) and macroturbulent broadening (<i>υ<i/><sub>mac<sub/>) using IACOB-BROAD, which combines Fourier transform and line-profile fitting techniques. We compared high-quality optical spectra with state-of-the-art simulations of massive star atmospheres computed with the FASTWIND code. This comparison allowed us to derive effective temperatures (<i>T<i/><sub>eff<sub/>), surface gravities (log <i>𝑔<i/>), microturbulences (<i>ξ<i/>), surface abundances of silicon and helium, and to assess the relevance of stellar winds through a wind-strength parameter (log <i>Q<i/>).<i>Results<i/>. We provide estimates and associated uncertainties of the above-mentioned quantities for the largest sample of Galactic luminous O9 to B5 stars spectroscopically analyzed to date, comprising 527 targets. We find a clear drop in the relative number of stars at T<sub>eff<sub/> ≈ 21 kK, coinciding with a scarcity of fast rotating stars below that temperature. We speculate that this feature (roughly corresponding to B2 spectral type) might be roughly delineating the location of the empirical terminal-age main sequence in the mass range between 15 and 85 <i>M<i/><sub>⊙<sub/>. By investigating the main characteristics of the <i>υ<i/> sin <i>i<i/> distribution of O stars and BSGs as a function of <i>T<i/><sub>eff<sub/>, we propose that an efficient mechanism transporting angular momentum from the stellar core to the surface might be operating along the main sequence in the high-mass domain. We find correlations between <i>ξ<i/>,<i>υ<i/><sub>mac<sub/> and the spectroscopic luminosity <i>𝓛<i/> (defined as <i>T<i/><sub>eff<sub/><sup>4<sup/> / <i>g<i/>). We also find that no more than 20% of the stars in our sample have atmospheres clearly enriched in helium, and suggest that the origin of this specific subsample might be in binary evolution. We do not find clear empirical evidence of an increase in the wind strength over the wind bi-stability region toward lower <i>T<i/><sub>eff<sub/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141725805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-17DOI: 10.1051/0004-6361/202449999
T. Nagao, K. Maeda, S. Mattila, H. Kuncarayakti, C. P. Gutiérrez, A. Cikota
Context. A peculiar subtype of Type Ia supernovae (SNe), 03fg-like (super-Chandrasekhar) SNe, show different observational properties from prototypical Type Ia SNe: they typically have high luminosities at the light-curve peak, low expansion velocities, and strong carbon features. The origin of this class of Type Ia SNe has been actively debated. Recent nebular-phase infrared observations of the 03fg-like Type Ia SN 2022pul using the James Webb Space Telescope revealed large-scale asymmetries in the ejecta and the presence of the strong [Ne II] line at 12.81 μm, suggesting a violent merger of two white dwarfs as its origin.Aims. Polarimetry is another powerful tool for studying the overall ejecta asymmetries of spatially unresolved SNe. Here, we aim to check the universality of the violent merger scenario as the origin of 03fg-like Type Ia SNe, by studying their explosion geometries using polarimetry.Methods. In this Letter we present imaging-polarimetric observations of the two 03fg-like Type Ia SNe 2021zny and 2022ilv.Results. SNe 2021zny and 2022ilv show high intrinsic polarization (∼1%–∼2%), which might be composed of multiple components with different polarization angles. This indicates that they have complex aspherical structures in their ejecta, supporting the violent merger scenario for their origin. Our observations provide the first clear evidence from polarimetry for such aspherical structures.
{"title":"The aspherical explosions of the 03fg-like Type Ia supernovae 2021zny and 2022ilv revealed by polarimetry","authors":"T. Nagao, K. Maeda, S. Mattila, H. Kuncarayakti, C. P. Gutiérrez, A. Cikota","doi":"10.1051/0004-6361/202449999","DOIUrl":"https://doi.org/10.1051/0004-6361/202449999","url":null,"abstract":"<i>Context.<i/> A peculiar subtype of Type Ia supernovae (SNe), 03fg-like (super-Chandrasekhar) SNe, show different observational properties from prototypical Type Ia SNe: they typically have high luminosities at the light-curve peak, low expansion velocities, and strong carbon features. The origin of this class of Type Ia SNe has been actively debated. Recent nebular-phase infrared observations of the 03fg-like Type Ia SN 2022pul using the <i>James Webb<i/> Space Telescope revealed large-scale asymmetries in the ejecta and the presence of the strong [Ne II] line at 12.81 μm, suggesting a violent merger of two white dwarfs as its origin.<i>Aims.<i/> Polarimetry is another powerful tool for studying the overall ejecta asymmetries of spatially unresolved SNe. Here, we aim to check the universality of the violent merger scenario as the origin of 03fg-like Type Ia SNe, by studying their explosion geometries using polarimetry.<i>Methods.<i/> In this Letter we present imaging-polarimetric observations of the two 03fg-like Type Ia SNe 2021zny and 2022ilv.<i>Results.<i/> SNe 2021zny and 2022ilv show high intrinsic polarization (∼1%–∼2%), which might be composed of multiple components with different polarization angles. This indicates that they have complex aspherical structures in their ejecta, supporting the violent merger scenario for their origin. Our observations provide the first clear evidence from polarimetry for such aspherical structures.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141725804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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