Pub Date : 2024-07-05DOI: 10.1051/0004-6361/202348992
Vinicius Branco, Paula R. T. Coelho, Ariane Lançon, Lucimara P. Martins, Philippe Prugniel
Most Galactic globular clusters (GCs) harbour multiple populations of stars (MPs) that are composed of at least two generations: the first generation is characterised by a standard α-enhanced metal mixture, as observed in field halo stars of the Milky Way, and the second generation displays an anti-correlated CN–ONa chemical abundance pattern in combination with an enhanced helium fraction. Adequate collections of stellar spectra are needed to characterize the effect of these changes in the stellar abundance on the integrated light of GCs. We present a grid of synthetic stellar spectra to cover the atmospheric parameters relevant to old stellar populations at four subsolar metallicities and two abundance patterns that are representative of the first and second generations of stars in GCs. The integrated spectra of the populations were computed using our stellar grid and empirical stellar populations, namely, colour-magnitude diagrams from the literature for Galactic GCs. The spectra range from 290 to 1000 nm, where we measured the effect on several spectrophotometric indices due to the surface abundance variations attributed to MPs. We find non-negligible effects of the MPs on the spectroscopic indices that are sensitive to C, N, Ca, or Na, and on the Balmer indices; we also describe how MPs modify specific regions in the near-UV and near-IR that can be measured with narrow or medium photometric passbands. The effects vary with metallicity. A number of these changes remain detectable even when we account for the stochastic fluctuations due to the finite nature of the stellar population cluster.
{"title":"Synthetic stellar spectra for studying multiple populations in globular clusters","authors":"Vinicius Branco, Paula R. T. Coelho, Ariane Lançon, Lucimara P. Martins, Philippe Prugniel","doi":"10.1051/0004-6361/202348992","DOIUrl":"https://doi.org/10.1051/0004-6361/202348992","url":null,"abstract":"Most Galactic globular clusters (GCs) harbour multiple populations of stars (MPs) that are composed of at least two generations: the first generation is characterised by a standard <i>α<i/>-enhanced metal mixture, as observed in field halo stars of the Milky Way, and the second generation displays an anti-correlated CN–ONa chemical abundance pattern in combination with an enhanced helium fraction. Adequate collections of stellar spectra are needed to characterize the effect of these changes in the stellar abundance on the integrated light of GCs. We present a grid of synthetic stellar spectra to cover the atmospheric parameters relevant to old stellar populations at four subsolar metallicities and two abundance patterns that are representative of the first and second generations of stars in GCs. The integrated spectra of the populations were computed using our stellar grid and empirical stellar populations, namely, colour-magnitude diagrams from the literature for Galactic GCs. The spectra range from 290 to 1000 nm, where we measured the effect on several spectrophotometric indices due to the surface abundance variations attributed to MPs. We find non-negligible effects of the MPs on the spectroscopic indices that are sensitive to C, N, Ca, or Na, and on the Balmer indices; we also describe how MPs modify specific regions in the near-UV and near-IR that can be measured with narrow or medium photometric passbands. The effects vary with metallicity. A number of these changes remain detectable even when we account for the stochastic fluctuations due to the finite nature of the stellar population cluster.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545974","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 : 2024-07-05DOI: 10.1051/0004-6361/202348948
L. Barquín-González, S. Mateos, F. J. Carrera, I. Ordovás-Pascual, A. Alonso-Herrero, A. Caccianiga, N. Cardiel, A. Corral, R. M. Domínguez, I. García-Bernete, G. Mountrichas, P. Severgnini
The optical spectroscopic classification of active galactic nuclei (AGN) into type 1 and type 2 can be understood in the frame of the AGN unification models. However, it remains unclear which physical properties are driving the classification into intermediate sub-types (1.0, 1.2, 1.5, 1.8, 1.9). To shed light on this issue, we present an analysis of the effect of extinction and AGN and host galaxy luminosities on sub-type determination for a sample of 159 X-ray selected AGN with a complete and robust optical spectroscopic classification. The sample spans a rest-frame 2–10 keV X-ray luminosity range of 1042–1046 erg s−1 and redshifts between 0.05 and 0.75. From the fitting of their ultraviolet-to-mid-infrared spectral energy distributions, we extracted the observed AGN over total AGN+galaxy contrast, optical/ultraviolet line-of-sight extinction, as well as host galaxy and AGN luminosities. The observed contrast exhibits a clear decline with sub-type, distinguishing two main groups: 1.0–5 and 1.8–2. This difference is partly driven by an increase in extinction following the same trend. Nevertheless, 50% of 1.9s and 2s lack sufficient extinction to explain the lack of detection of broad emission lines, unveiling the necessity of an additional effect. Our findings show that 1.8–2s preferentially live in host galaxies with higher luminosities while displaying similar intrinsic AGN luminosities to 1.0–5s. Consequently, the AGN to host galaxy luminosity ratio diminishes, hindering the detection of the emission of the broad emission lines, resulting in the 1.8–2 classification of those with insufficient extinction. Thus, the combination of increasing extinction and decreasing AGN over galaxy luminosity ratio, mainly driven by an increasing host galaxy luminosity, constitutes the main reasons behind the sub-type classification into 1.0–5 and 1.8–2.
{"title":"Extinction and AGN over host galaxy contrast effects on the optical spectroscopic classification of AGN⋆","authors":"L. Barquín-González, S. Mateos, F. J. Carrera, I. Ordovás-Pascual, A. Alonso-Herrero, A. Caccianiga, N. Cardiel, A. Corral, R. M. Domínguez, I. García-Bernete, G. Mountrichas, P. Severgnini","doi":"10.1051/0004-6361/202348948","DOIUrl":"https://doi.org/10.1051/0004-6361/202348948","url":null,"abstract":"The optical spectroscopic classification of active galactic nuclei (AGN) into type 1 and type 2 can be understood in the frame of the AGN unification models. However, it remains unclear which physical properties are driving the classification into intermediate sub-types (1.0, 1.2, 1.5, 1.8, 1.9). To shed light on this issue, we present an analysis of the effect of extinction and AGN and host galaxy luminosities on sub-type determination for a sample of 159 X-ray selected AGN with a complete and robust optical spectroscopic classification. The sample spans a rest-frame 2–10 keV X-ray luminosity range of 10<sup>42<sup/>–10<sup>46<sup/> erg s<sup>−1<sup/> and redshifts between 0.05 and 0.75. From the fitting of their ultraviolet-to-mid-infrared spectral energy distributions, we extracted the observed AGN over total AGN+galaxy contrast, optical/ultraviolet line-of-sight extinction, as well as host galaxy and AGN luminosities. The observed contrast exhibits a clear decline with sub-type, distinguishing two main groups: 1.0–5 and 1.8–2. This difference is partly driven by an increase in extinction following the same trend. Nevertheless, 50% of 1.9s and 2s lack sufficient extinction to explain the lack of detection of broad emission lines, unveiling the necessity of an additional effect. Our findings show that 1.8–2s preferentially live in host galaxies with higher luminosities while displaying similar intrinsic AGN luminosities to 1.0–5s. Consequently, the AGN to host galaxy luminosity ratio diminishes, hindering the detection of the emission of the broad emission lines, resulting in the 1.8–2 classification of those with insufficient extinction. Thus, the combination of increasing extinction and decreasing AGN over galaxy luminosity ratio, mainly driven by an increasing host galaxy luminosity, constitutes the main reasons behind the sub-type classification into 1.0–5 and 1.8–2.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545973","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 : 2024-07-05DOI: 10.1051/0004-6361/202449903
A. Schimek, C. Cicone, S. Shen, D. Decataldo, P. Klaassen, L. Mayer
Optical emission line diagnostics, which are a common tool for constraining the properties of the interstellar medium (ISM) of galaxies, become progressively inaccessible at higher redshifts for ground-based facilities. Far-infrared (FIR) emission lines, which are redshifted into atmospheric windows that are accessible for ground-based submillimetre facilities, could provide ISM diagnostics alternative to optical emission lines. We investigated FIR line ratios involving [CII] λ158 μm, [OIII] λ88 μm, [OIII] λ52 μm, [NII] λ122 μm, and [NIII] λ57 μm using synthetic emission lines applied to a high-resolution (mgas = 883.4 M⊙) cosmological zoom-in simulation, including radiative transfer post-processing with the code KRAMSES-RT at z = 6.5. We find that the [CII]/[NII]122 ratio is sensitive to the temperature and density of photodissociation regions. It might therefore be a useful tool for tracing the properties of this gas phase in galaxies. We also find that [NII]/[NIII] is a good tracer of the temperature and that [OIII]52/[OIII]88 is a good tracer of the gas density of HII regions. Emission line ratios containing the [OIII] λ88 μm line are sensitive to high-velocity outflowing gas.
{"title":"Constraining the physical properties of gas in high-z galaxies with far-infrared and submillimetre line ratios","authors":"A. Schimek, C. Cicone, S. Shen, D. Decataldo, P. Klaassen, L. Mayer","doi":"10.1051/0004-6361/202449903","DOIUrl":"https://doi.org/10.1051/0004-6361/202449903","url":null,"abstract":"Optical emission line diagnostics, which are a common tool for constraining the properties of the interstellar medium (ISM) of galaxies, become progressively inaccessible at higher redshifts for ground-based facilities. Far-infrared (FIR) emission lines, which are redshifted into atmospheric windows that are accessible for ground-based submillimetre facilities, could provide ISM diagnostics alternative to optical emission lines. We investigated FIR line ratios involving [CII] <i>λ<i/>158 μm, [OIII] <i>λ<i/>88 μm, [OIII] <i>λ<i/>52 μm, [NII] <i>λ<i/>122 μm, and [NIII] <i>λ<i/>57 μm using synthetic emission lines applied to a high-resolution (<i>m<i/><sub>gas<sub/> = 883.4 <i>M<i/><sub>⊙<sub/>) cosmological zoom-in simulation, including radiative transfer post-processing with the code KRAMSES-RT at <i>z<i/> = 6.5. We find that the [CII]/[NII]122 ratio is sensitive to the temperature and density of photodissociation regions. It might therefore be a useful tool for tracing the properties of this gas phase in galaxies. We also find that [NII]/[NIII] is a good tracer of the temperature and that [OIII]52/[OIII]88 is a good tracer of the gas density of HII regions. Emission line ratios containing the [OIII] <i>λ<i/>88 μm line are sensitive to high-velocity outflowing gas.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545975","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 : 2024-07-05DOI: 10.1051/0004-6361/202450374
Gordian Edenhofer, João Alves, Catherine Zucker, Laura Posch, Torsten A. Enßlin
Recent advancements in 3D dust mapping have transformed our understanding of the Milky Way’s local interstellar medium, enabling us to explore its structure in three spatial dimensions for the first time. In this Letter, we use the most recent 3D dust map by Edenhofer et al. to study the well-known Chameleon, Musca, and Coalsack cloud complexes, located about 200 pc from the Sun. We find that these three complexes are not isolated but rather connect to form a surprisingly well-defined half-ring, constituting a single C-shaped cloud with a radius of about 50 pc, a thickness of about 45 pc, and a total mass of about 5 × 104M⊙, or 9 × 104M⊙ if including everything in the vicinity of the C-shaped cloud. Despite the absence of an evident feedback source at its center, the dynamics of young stellar clusters associated with the C structure suggest that a single supernova explosion about 4 Myr–10 Myr ago likely shaped this structure. Our findings support a single origin story for these cloud complexes, suggesting that they were formed by feedback-driven gas compression, and offer new insights into the processes that govern the birth of star-forming clouds in feedback-dominated regions, such as the Scorpius-Centaurus association.
三维尘埃绘图技术的最新进展改变了我们对银河系本地星际介质的认识，使我们能够首次从三维空间探索其结构。在这封信中，我们利用 Edenhofer 等人绘制的最新三维尘埃地图，研究了距离太阳约 200 pc 的著名的 Chameleon、Musca 和 Coalsack 云复合体。我们发现，这三个复合体并不是孤立的，而是连接在一起，形成了一个定义惊人的半环，构成了一个单一的 C 形云，半径约为 50 pc，厚度约为 45 pc，总质量约为 5 × 104 M⊙，如果包括 C 形云附近的所有物质，则总质量为 9 × 104 M⊙。尽管其中心没有明显的反馈源，但与C型结构相关的年轻恒星簇的动力学表明，大约4 Myr-10 Myr前的一次超新星爆炸很可能形成了这一结构。我们的研究结果支持这些云团复合体的单一起源故事，认为它们是由反馈驱动的气体压缩形成的，并对反馈主导区域（如天蝎座-半人马座联合体）中恒星形成云团的诞生过程提供了新的见解。
{"title":"The “C”: The large Chameleon-Musca-Coalsack cloud","authors":"Gordian Edenhofer, João Alves, Catherine Zucker, Laura Posch, Torsten A. Enßlin","doi":"10.1051/0004-6361/202450374","DOIUrl":"https://doi.org/10.1051/0004-6361/202450374","url":null,"abstract":"Recent advancements in 3D dust mapping have transformed our understanding of the Milky Way’s local interstellar medium, enabling us to explore its structure in three spatial dimensions for the first time. In this Letter, we use the most recent 3D dust map by Edenhofer et al. to study the well-known Chameleon, Musca, and Coalsack cloud complexes, located about 200 pc from the Sun. We find that these three complexes are not isolated but rather connect to form a surprisingly well-defined half-ring, constituting a single C-shaped cloud with a radius of about 50 pc, a thickness of about 45 pc, and a total mass of about 5 × 10<sup>4<sup/> <i>M<i/><sub>⊙<sub/>, or 9 × 10<sup>4<sup/> <i>M<i/><sub>⊙<sub/> if including everything in the vicinity of the C-shaped cloud. Despite the absence of an evident feedback source at its center, the dynamics of young stellar clusters associated with the C structure suggest that a single supernova explosion about 4 Myr–10 Myr ago likely shaped this structure. Our findings support a single origin story for these cloud complexes, suggesting that they were formed by feedback-driven gas compression, and offer new insights into the processes that govern the birth of star-forming clouds in feedback-dominated regions, such as the Scorpius-Centaurus association.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141546323","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 : 2024-07-04DOI: 10.1051/0004-6361/202348574
H. Rousseau, S. Ertel, D. Defrère, V. Faramaz, K. Wagner
Context. Ground-based large-aperture telescopes, interferometers, and future extremely large telescopes equipped with adaptive optics (AO) systems provide angular resolution and high-contrast performance superior to space-based telescopes at thermal infrared wavelengths. Their sensitivity, however, is critically limited by the high thermal background inherent to ground-based observations in this wavelength regime.Aims. We aim to improve the subtraction quality of the thermal infrared background from ground-based observations using principal component analysis (PCA).Methods. We used data obtained with the Nulling-Optimized Mid-Infrared Camera on the Large Binocular Telescope Interferometer as a proxy for general high-sensitivity AO-assisted ground-based data. We applied both a classical background subtraction – using the mean of dedicated background observations – and a new background subtraction based on a PCA of the background observations. We compared the performances of these two methods in both high-contrast imaging and aperture photometry.Results. Compared to the classical approach for background subtraction, PCA background subtraction delivers up to two times better contrasts down to the diffraction limit of the LBT’s primary aperture (i.e., 350 mas in N-band), that is, in the case of high-contrast imaging. An improvement factor between two and three was obtained over the mean background retrieval within the diffraction limit in the case of aperture photometry.Conclusions. The PCA background subtraction significantly improves the sensitivity of ground-based thermal infrared imaging observations. When apply to LBTI’s nulling interferometry data, we expect the method to improve the sensitivity by a similar factor of two to three. This study paves the way to maximizing the potential of future infrared ground-based instruments and facilities, such as the future 30m-class telescopes.
{"title":"Improving mid-infrared thermal background subtraction with principal component analysis","authors":"H. Rousseau, S. Ertel, D. Defrère, V. Faramaz, K. Wagner","doi":"10.1051/0004-6361/202348574","DOIUrl":"https://doi.org/10.1051/0004-6361/202348574","url":null,"abstract":"<i>Context<i/>. Ground-based large-aperture telescopes, interferometers, and future extremely large telescopes equipped with adaptive optics (AO) systems provide angular resolution and high-contrast performance superior to space-based telescopes at thermal infrared wavelengths. Their sensitivity, however, is critically limited by the high thermal background inherent to ground-based observations in this wavelength regime.<i>Aims<i/>. We aim to improve the subtraction quality of the thermal infrared background from ground-based observations using principal component analysis (PCA).<i>Methods<i/>. We used data obtained with the Nulling-Optimized Mid-Infrared Camera on the Large Binocular Telescope Interferometer as a proxy for general high-sensitivity AO-assisted ground-based data. We applied both a classical background subtraction – using the mean of dedicated background observations – and a new background subtraction based on a PCA of the background observations. We compared the performances of these two methods in both high-contrast imaging and aperture photometry.<i>Results<i/>. Compared to the classical approach for background subtraction, PCA background subtraction delivers up to two times better contrasts down to the diffraction limit of the LBT’s primary aperture (i.e., 350 mas in <i>N<i/>-band), that is, in the case of high-contrast imaging. An improvement factor between two and three was obtained over the mean background retrieval within the diffraction limit in the case of aperture photometry.<i>Conclusions<i/>. The PCA background subtraction significantly improves the sensitivity of ground-based thermal infrared imaging observations. When apply to LBTI’s nulling interferometry data, we expect the method to improve the sensitivity by a similar factor of two to three. This study paves the way to maximizing the potential of future infrared ground-based instruments and facilities, such as the future 30m-class telescopes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545835","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 : 2024-07-03DOI: 10.1051/0004-6361/202449428
E. Kleisioti, D. Dirkx, X. Tan, M. A. Kenworthy
Aims. We investigate whether volcanic exomoons can be detected in thermal wavelength light curves due to their phase variability along their orbit. The method we use is based on the photometric signal variability that volcanic features or hotspots would cause in infrared (IR) wavelengths, when they are inhomogeneously distributed on the surface of a tidally heated exomoon (THEM).Methods. We simulated satellites of various sizes around an isolated planet and modeled the system’s variability in two IR wavelengths, taking into account photon shot noise. The moon’s periodic signal as it orbits the planet introduces a peak in the frequency space of the system’s time-variable flux. We investigated the THEM and system properties that would make a moon stand out in the frequency space of its host’s variable flux.Results. The moon’s signal can produce a prominent feature in its host’s flux periodogram at shorter IR wavelengths for hotspots with temperatures similar to the ones seen on the Jovian moon, Io, while the same moon would not be identifiable in longer IR wavelengths. By comparing observations at two different wavelengths, we are able to disentangle the signal of an exomoon with transiting and non-transiting orbital inclinations from the planet’s signal in the frequency domain for system distances up to ~10 pc for Mars-sized exomoons and even further for Earth-sized ones.Conclusions. This method enlarges the parameter space of detectable exomoons around isolated planetary mass objects and directly imaged exoplanets, as it is sensitive to Io- to Earth-sized exomoons with hot volcanic features for a wide range of non-transiting orbital inclinations. Exomoon transits and the detection of outgassed volcanic molecules can subsequently confirm a putative detection.
目的。我们研究是否可以通过热波长光曲线探测到沿轨道相位变化的火山外月。我们所使用的方法是基于火山特征或热点在红外波长（IR）中引起的光度信号变化，当它们不均匀地分布在潮汐加热外小行星（THEM）的表面时。我们模拟了一颗孤立行星周围不同大小的卫星，并模拟了该系统在两个红外波段的变化，同时考虑了光子射出噪声。月球绕行星运行的周期性信号在系统时变通量的频率空间中引入了一个峰值。我们研究了能使卫星在其宿主可变通量的频率空间中脱颖而出的 THEM 和系统特性。在较短的红外波长下，对于温度与木卫二上的热点相似的热点，月球的信号会在其宿主的通量周期图中产生一个突出的特征，而在较长的红外波长下则无法识别出同一个月球。通过比较两种不同波长下的观测结果，我们能够在频域中将具有凌日和非凌日轨道倾角的外小行星信号与行星信号区分开来，对于火星大小的外小行星，系统距离可达 ~10 pc，对于地球大小的外小行星，系统距离甚至更远。这种方法扩大了在孤立的行星质量天体和直接成像的系外行星周围可探测到的外小行星的参数空间，因为它对在广泛的非凌日轨道倾角范围内具有热火山特征的艾欧至地球大小的外小行星敏感。外小行星凌日和对排出气体的火山分子的探测可以随后确认推定的探测结果。
{"title":"Direct detectability of tidally heated exomoons by photometric orbital modulation","authors":"E. Kleisioti, D. Dirkx, X. Tan, M. A. Kenworthy","doi":"10.1051/0004-6361/202449428","DOIUrl":"https://doi.org/10.1051/0004-6361/202449428","url":null,"abstract":"<i>Aims<i/>. We investigate whether volcanic exomoons can be detected in thermal wavelength light curves due to their phase variability along their orbit. The method we use is based on the photometric signal variability that volcanic features or hotspots would cause in infrared (IR) wavelengths, when they are inhomogeneously distributed on the surface of a tidally heated exomoon (THEM).<i>Methods<i/>. We simulated satellites of various sizes around an isolated planet and modeled the system’s variability in two IR wavelengths, taking into account photon shot noise. The moon’s periodic signal as it orbits the planet introduces a peak in the frequency space of the system’s time-variable flux. We investigated the THEM and system properties that would make a moon stand out in the frequency space of its host’s variable flux.<i>Results<i/>. The moon’s signal can produce a prominent feature in its host’s flux periodogram at shorter IR wavelengths for hotspots with temperatures similar to the ones seen on the Jovian moon, Io, while the same moon would not be identifiable in longer IR wavelengths. By comparing observations at two different wavelengths, we are able to disentangle the signal of an exomoon with transiting and non-transiting orbital inclinations from the planet’s signal in the frequency domain for system distances up to ~10 pc for Mars-sized exomoons and even further for Earth-sized ones.<i>Conclusions<i/>. This method enlarges the parameter space of detectable exomoons around isolated planetary mass objects and directly imaged exoplanets, as it is sensitive to Io- to Earth-sized exomoons with hot volcanic features for a wide range of non-transiting orbital inclinations. Exomoon transits and the detection of outgassed volcanic molecules can subsequently confirm a putative detection.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495946","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 : 2024-07-02DOI: 10.1051/0004-6361/202449925
C. Bacchini, C. Nipoti, G. Iorio, F. Roman-Oliveira, F. Rizzo, P. E. Mancera Piña, A. Marasco, A. Zanella, F. Lelli
Local gravitational instability (LGI) is considered crucial for regulating star formation and gas turbulence in galaxy discs, especially at high redshift. Instability criteria usually assume infinitesimally thin discs or rely on approximations to include the stabilising effect of the gas disc thickness. We test a new 3D instability criterion for rotating gas discs that are vertically stratified in an external potential. This criterion reads Q3D < 1, where Q3D is the 3D analogue of the Toomre parameter Q. The advantage of Q3D is that it allows us to study LGI in and above the galaxy midplane in a rigorous and self-consistent way. We apply the criterion to a sample of 44 star-forming galaxies at 0 ≲ z ≲ 5 hosting rotating discs of cold gas. The sample is representative of galaxies on the main sequence at z ≈ 0 and includes massive star-forming and starburst galaxies at 1 ≲ z ≲ 5. For each galaxy, we first apply the Toomre criterion for infinitesimally thin discs, finding ten unstable systems. We then obtain maps of Q3D from a 3D model of the gas disc derived in the combined potential of dark matter, stars and the gas itself. According to the 3D criterion, two galaxies with Q < 1 show no evidence of instability and the unstable regions that are 20% smaller than those where Q < 1. No unstable disc is found at 0 ≲ z ≲ 1, while ≈60% of the systems at 2 ≲ z ≲ 5 are locally unstable. In these latter, a relatively small fraction of the total gas (≈30%) is potentially affected by the instability. Our results disfavour LGI as the main regulator of star formation and turbulence in moderately star-forming galaxies in the present-day Universe. LGI likely becomes important at high redshift, but the input by other mechanisms seems required in a significant portion of the disc. We also estimate the expected mass of clumps in the unstable regions, offering testable predictions for observations.
局部引力不稳定性（LGI）被认为是调节星系盘中恒星形成和气体湍流的关键，尤其是在高红移时。不稳定性标准通常假定圆盘无限薄，或者依赖近似值来包含气体圆盘厚度的稳定效应。我们针对在外部势能中垂直分层的旋转气体盘测试了一种新的三维不稳定标准。Q3D的优势在于，它允许我们以严格和自洽的方式研究星系中平面及以上的LGI。我们将这一标准应用于一个由 44 个恒星形成星系组成的样本中，这些星系在 0 ≲ z ≲ 5 时承载着旋转的冷气体盘。这个样本代表了 z ≈ 0 时主序列上的星系，也包括了 1 ≲ z ≲ 5 时的大质量恒星形成星系和星爆星系。对于每个星系，我们首先应用无限薄圆盘的托姆雷标准，找到十个不稳定系统。然后，我们根据暗物质、恒星和气体本身的综合势能推导出的气体盘三维模型，得到了 Q3D 的地图。根据三维标准，两个星系的Q Q z ≲1，而2 ≲ z ≲5的星系中有≈60%是局部不稳定的。在后一种情况下，气体总量中相对较小的一部分（≈30%）可能会受到不稳定性的影响。我们的研究结果不认为LGI是当今宇宙中中等恒星形成星系中恒星形成和湍流的主要调节因素。LGI很可能在高红移时变得重要，但在很大一部分圆盘中似乎需要其他机制的输入。我们还估算了不稳定区域团块的预期质量，为观测提供了可检验的预测。
{"title":"A 3D view on the local gravitational instability of cold gas discs in star-forming galaxies at 0 ≲ z ≲ 5","authors":"C. Bacchini, C. Nipoti, G. Iorio, F. Roman-Oliveira, F. Rizzo, P. E. Mancera Piña, A. Marasco, A. Zanella, F. Lelli","doi":"10.1051/0004-6361/202449925","DOIUrl":"https://doi.org/10.1051/0004-6361/202449925","url":null,"abstract":"Local gravitational instability (LGI) is considered crucial for regulating star formation and gas turbulence in galaxy discs, especially at high redshift. Instability criteria usually assume infinitesimally thin discs or rely on approximations to include the stabilising effect of the gas disc thickness. We test a new 3D instability criterion for rotating gas discs that are vertically stratified in an external potential. This criterion reads <i>Q<i/><sub>3D<sub/> < 1, where <i>Q<i/><sub>3D<sub/> is the 3D analogue of the Toomre parameter <i>Q<i/>. The advantage of <i>Q<i/><sub>3D<sub/> is that it allows us to study LGI in and above the galaxy midplane in a rigorous and self-consistent way. We apply the criterion to a sample of 44 star-forming galaxies at 0 ≲ <i>z<i/> ≲ 5 hosting rotating discs of cold gas. The sample is representative of galaxies on the main sequence at <i>z<i/> ≈ 0 and includes massive star-forming and starburst galaxies at 1 ≲ <i>z<i/> ≲ 5. For each galaxy, we first apply the Toomre criterion for infinitesimally thin discs, finding ten unstable systems. We then obtain maps of <i>Q<i/><sub>3D<sub/> from a 3D model of the gas disc derived in the combined potential of dark matter, stars and the gas itself. According to the 3D criterion, two galaxies with <i>Q<i/> < 1 show no evidence of instability and the unstable regions that are 20% smaller than those where <i>Q<i/> < 1. No unstable disc is found at 0 ≲ <i>z<i/> ≲ 1, while ≈60% of the systems at 2 ≲ <i>z<i/> ≲ 5 are locally unstable. In these latter, a relatively small fraction of the total gas (≈30%) is potentially affected by the instability. Our results disfavour LGI as the main regulator of star formation and turbulence in moderately star-forming galaxies in the present-day Universe. LGI likely becomes important at high redshift, but the input by other mechanisms seems required in a significant portion of the disc. We also estimate the expected mass of clumps in the unstable regions, offering testable predictions for observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489594","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 : 2024-07-02DOI: 10.1051/0004-6361/202449271
Wen-Han Zhou, Shang-Fei Liu, Douglas N. C. Lin
Context. About 25–50% of white dwarfs are found to be contaminated by heavy elements, which are believed to originate from external sources such as planetary materials. Elemental abundances suggest that most of the pollutants are rocky objects and only a small fraction of white dwarfs bear traces of volatile accretion.Aims. In order to account for the scarcity of volatile pollution, we investigate the role of the white dwarfs’ magnetospheres in shielding the volatile content of icy objects.Methods. We estimated the volatile sublimation of inward drifting exocomets. We assume the orbits of the exocomets are circularized by the Alfvén wing drag that is effective for long-period comets.Results. Volatile material can sublimate outside the corotation radius and be shielded by the magnetic field. The two conditions for this volatile-shielded mechanism are that the magnetosphere radius must be larger than the corotation radius and that the volatiles are depleted outside the corotation radius, which requires a sufficiently slow orbital circularization process. We applied our model to nine white dwarfs with known rotational periods, magnetic fields, and atmosphere compositions. Our volatile-shielded model may explain the excess of volatile elements such as C and S in the disk relative to the white dwarf atmosphere in WD2326+049 (G29-38). Nevertheless, given the sensitivity of our model to the circularization process and material properties of icy objects, there remains considerable uncertainty in our results.Conclusions. We emphasize the importance of white dwarfs’ magnetic fields in preventing the accretion of volatile gas onto them. Our work suggests a possible explanation for the scarcity of volatile-accretion signatures among white dwarfs. We also identify a correlation between the magnetic field strength, the spin period, and the composition of pollutants in white dwarf atmospheres. However, given the uncertainties in our model, more observations are necessary to establish more precise constraints on the relevant parameters.
{"title":"White dwarf magnetospheres: Shielding volatile content of icy objects and implications for volatile pollution scarcity","authors":"Wen-Han Zhou, Shang-Fei Liu, Douglas N. C. Lin","doi":"10.1051/0004-6361/202449271","DOIUrl":"https://doi.org/10.1051/0004-6361/202449271","url":null,"abstract":"<i>Context<i/>. About 25–50% of white dwarfs are found to be contaminated by heavy elements, which are believed to originate from external sources such as planetary materials. Elemental abundances suggest that most of the pollutants are rocky objects and only a small fraction of white dwarfs bear traces of volatile accretion.<i>Aims<i/>. In order to account for the scarcity of volatile pollution, we investigate the role of the white dwarfs’ magnetospheres in shielding the volatile content of icy objects.<i>Methods<i/>. We estimated the volatile sublimation of inward drifting exocomets. We assume the orbits of the exocomets are circularized by the Alfvén wing drag that is effective for long-period comets.<i>Results<i/>. Volatile material can sublimate outside the corotation radius and be shielded by the magnetic field. The two conditions for this volatile-shielded mechanism are that the magnetosphere radius must be larger than the corotation radius and that the volatiles are depleted outside the corotation radius, which requires a sufficiently slow orbital circularization process. We applied our model to nine white dwarfs with known rotational periods, magnetic fields, and atmosphere compositions. Our volatile-shielded model may explain the excess of volatile elements such as C and S in the disk relative to the white dwarf atmosphere in WD2326+049 (G29-38). Nevertheless, given the sensitivity of our model to the circularization process and material properties of icy objects, there remains considerable uncertainty in our results.<i>Conclusions<i/>. We emphasize the importance of white dwarfs’ magnetic fields in preventing the accretion of volatile gas onto them. Our work suggests a possible explanation for the scarcity of volatile-accretion signatures among white dwarfs. We also identify a correlation between the magnetic field strength, the spin period, and the composition of pollutants in white dwarf atmospheres. However, given the uncertainties in our model, more observations are necessary to establish more precise constraints on the relevant parameters.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489574","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 : 2024-07-02DOI: 10.1051/0004-6361/202449403
E. Magaudda, B. Stelzer, R. A. Osten, J. S. Pineda, St. Raetz, M. McKay
We aim to advance our understanding of magnetic activity and the underlying dynamo mechanism at the end of the main sequence. To this end, we have embarked on collecting simultaneous X-ray and radio observations for a sample of M7..L0 dwarfs in the solar neighborhood using XMM-Newton jointly with the Jansky Very Large Array (JVLA) and the Australia Telescope Compact Array (ATCA). We supplemented the data from these dedicated campaigns with X-ray data from the all-sky surveys of the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG). Moreover, we complement this multiwavelength data set with rotation periods that we measured from light curves acquired with the Transiting Exoplanet Survey Satellite (TESS). We limited the sample to objects with rotation period of < 1 day, focusing on the study of a transition in magnetic behavior suggested by a drastic change in the radio detection rate at υ sin i ≈ 38 km s−1, corresponding to Prot ≈ 0.2 day for a typical ultracool dwarf (UCD) radius of R★ = 0.15 R⊙. Finally, to enlarge the target list, we have compiled archival X-ray and radio data for UCDs from the literature, and we have analyzed the abovementioned ancillary eROSITA and TESS observations for these objects’ analogous to the targets from our dedicated X-ray/radio campaigns. We compiled the most up to date radio/X-ray luminosity (LR,ν − Lx) relation for 26 UCDs with rotation periods (Prot) lower than 1 day, finding that rapid rotators lie the furthest away from the “Güdel-Benz” relation previously studied for earlier-type stars. Radio bursts are mainly (although not exclusively) experienced by very fast UCDs (Prot ≤ 0.2 day), while X-ray flares are seen by objects spanning the whole range of rotation. Finally, we examined the Lx/Lbol versus Prot relation, where our sample of UCDs spans a large activity level range, that is log(Lx/Lbol) = −5.5 to log(Lx/Lbol) = −3. Although they are all fast rotating, X-ray activity evidently decouples from that of normal dynamos. In fact, we found no evident relation between the X-ray emission and rotation, reinforcing previous speculations on a bimodal dynamo across late-type dwarfs. One radio-detected object, 2MJ0838, has a rotation period consistent with the range of auroral bursting sources; while it displays moderately circularly polarized emission, there is no temporal variation in the polarized flux. A radio flare from this object is interpreted as gyrosynchrotron emission, and it displays X-ray and optical flares. Among the ten UCDs observed with the dedicated X-ray/radio campaigns, we found a slowly rotating apparent auroral emitter (2MJ0752) that is also o
我们的目标是加深对主序末期的磁活动和基本动力机制的理解。为此，我们开始利用XMM-牛顿与扬斯基甚大阵列（JVLA）和澳大利亚望远镜紧凑阵列（ATCA）联合收集太阳附近M7...L0矮星样本的X射线和无线电同步观测数据。我们利用俄罗斯 Spektrum-Roentgen-Gamma 飞行任务（SRG）上的成像望远镜阵列 ROentgen 巡天（eROSITA）的全天空巡天的 X 射线数据来补充这些专项活动的数据。此外，我们还利用我们从 Transiting Exoplanet Survey Satellite（TESS）获取的光变曲线中测量到的自转周期对这一多波长数据集进行了补充。我们将样本限制在自转周期小于 1 天的天体上，重点研究在 υ sin i ≈ 38 km s-1 时射电探测率的急剧变化所暗示的磁性行为的转变，对于典型的超酷矮星（UCD）半径 R★ = 0.15 R⊙，对应于 Prot ≈ 0.2 天。最后，为了扩大目标列表，我们汇编了文献中有关超酷矮星的 X 射线和无线电档案数据，并分析了上述 eROSITA 和 TESS 对这些天体的辅助观测数据，这些数据类似于我们专门的 X 射线/无线电活动中的目标。我们为自转周期（Prot）小于 1 天的 26 个 UCD 汇编了最新的射电/X 射线光度（LR,ν - Lx）关系，发现快速自转者与之前研究的早期类型恒星的 "居德尔-本茨 "关系相距最远。射电暴主要出现在（虽然并不完全出现在）极快的 UCD 星上（Prot ≤ 0.2 天），而 X 射线耀斑则出现在整个自转周期范围内的天体上。最后，我们研究了Lx/Lbol与Prot的关系，我们的UCD样本跨越了很大的活动水平范围，即log(Lx/Lbol)=-5.5到log(Lx/Lbol)=-3。事实上，我们发现 X 射线辐射和自转之间没有明显的关系，这加强了之前对晚型矮星双模动力的推测。一个被探测到的射电天体，2MJ0838，其自转周期与极光爆发源的范围一致；虽然它显示出中等程度的圆极化发射，但极化通量没有时间变化。该天体的射电耀斑被解释为陀螺同步辐射，它还显示出 X 射线和光学耀斑。在用专门的 X 射线/无线电活动观测到的 10 个 UCD 中，我们发现了一个缓慢旋转的视极光发射器（2MJ0752），它也是 X 射线最亮的无线电探测到的 UCD 之一。我们推测这颗 UCD 正在经历磁性行为的转变，因为它产生了预期来自质量更高的 M 矮星的特征以及新出现的极光发射证据。
{"title":"Transitions in magnetic behavior at the substellar boundary","authors":"E. Magaudda, B. Stelzer, R. A. Osten, J. S. Pineda, St. Raetz, M. McKay","doi":"10.1051/0004-6361/202449403","DOIUrl":"https://doi.org/10.1051/0004-6361/202449403","url":null,"abstract":"We aim to advance our understanding of magnetic activity and the underlying dynamo mechanism at the end of the main sequence. To this end, we have embarked on collecting simultaneous X-ray and radio observations for a sample of M7..L0 dwarfs in the solar neighborhood using <i>XMM-Newton<i/> jointly with the <i>Jansky<i/> Very Large Array (JVLA) and the Australia Telescope Compact Array (ATCA). We supplemented the data from these dedicated campaigns with X-ray data from the all-sky surveys of the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG). Moreover, we complement this multiwavelength data set with rotation periods that we measured from light curves acquired with the Transiting Exoplanet Survey Satellite (TESS). We limited the sample to objects with rotation period of < 1 day, focusing on the study of a transition in magnetic behavior suggested by a drastic change in the radio detection rate at <i>υ<i/> sin <i>i<i/> ≈ 38 km s<sup>−1<sup/>, corresponding to <i>P<i/><sub>rot<sub/> ≈ 0.2 day for a typical ultracool dwarf (UCD) radius of <i>R<i/><sub>★<sub/> = 0.15 <i>R<i/><sub>⊙<sub/>. Finally, to enlarge the target list, we have compiled archival X-ray and radio data for UCDs from the literature, and we have analyzed the abovementioned ancillary eROSITA and TESS observations for these objects’ analogous to the targets from our dedicated X-ray/radio campaigns. We compiled the most up to date radio/X-ray luminosity (<i>L<i/><sub>R,ν<sub/> − <i>L<i/><sub>x<sub/>) relation for 26 UCDs with rotation periods (<i>P<i/><sub>rot<sub/>) lower than 1 day, finding that rapid rotators lie the furthest away from the “Güdel-Benz” relation previously studied for earlier-type stars. Radio bursts are mainly (although not exclusively) experienced by very fast UCDs (<i>P<i/><sub>rot<sub/> ≤ 0.2 day), while X-ray flares are seen by objects spanning the whole range of rotation. Finally, we examined the <i>L<i/><sub>x<sub/>/<i>L<i/><sub>bol<sub/> versus <i>P<i/><sub>rot<sub/> relation, where our sample of UCDs spans a large activity level range, that is log(<i>L<i/><sub>x<sub/>/<i>L<i/><sub>bol<sub/>) = −5.5 to log(<i>L<i/><sub>x<sub/>/<i>L<i/><sub>bol<sub/>) = −3. Although they are all fast rotating, X-ray activity evidently decouples from that of normal dynamos. In fact, we found no evident relation between the X-ray emission and rotation, reinforcing previous speculations on a bimodal dynamo across late-type dwarfs. One radio-detected object, 2MJ0838, has a rotation period consistent with the range of auroral bursting sources; while it displays moderately circularly polarized emission, there is no temporal variation in the polarized flux. A radio flare from this object is interpreted as gyrosynchrotron emission, and it displays X-ray and optical flares. Among the ten UCDs observed with the dedicated X-ray/radio campaigns, we found a slowly rotating apparent auroral emitter (2MJ0752) that is also o","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489554","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 : 2024-06-28DOI: 10.1051/0004-6361/202347732
D. Weßmayer, M. A. Urbaneja, K. Butler, N. Przybilla
We present a quantitative spectral analysis of the extreme nitrogen-enhanced supergiant HD 93840 (BN1 Ib) at an intermediate galactic latitude. Based on an optical high-resolution spectrum and complementary ultraviolet and infrared (spectro-)photometry, in addition to Gaia data, we carried out a full characterisation of the star’s properties. We used both hydrostatic and unified (photosphere+wind) model atmospheres that account for deviations from local thermodynamic equilibrium. A highly unusual surface CNO-mixing signature and a marked stellar overluminosity compared to the mass imply a binary channel for the star’s past evolution. The kinematics shows that it has reached its current position above the Galactic plane as a runaway star, likely ejected by the supernova explosion of its former companion star. Its current bulk composition, with a notably increased mean molecular weight due to core He- and progressed shell H-burning, suggests an advanced evolutionary stage. It is poised to yield a rare core-collapse supernova of a blue supergiant about ten OB star population scale heights above the Galactic disk relatively soon, contributing to the metal enrichment of the circumgalactic medium.
我们对位于中银河纬度的极氮增强超巨星HD 93840（BN1 Ib）进行了光谱定量分析。除了盖亚数据之外，我们还根据光学高分辨率光谱和补充紫外线和红外线（光谱）测光数据，对这颗恒星的特性进行了全面描述。我们使用了静水模型大气和统一（光层+风）模型大气，以考虑偏离局部热力学平衡的情况。非常不寻常的表面 CNO 混合特征和与质量相比明显的恒星过光度意味着这颗恒星过去的演化是双星通道。运动学显示，它是作为一颗失控恒星到达银河系平面上方的，很可能是被其前伴星的超新星爆炸喷射出来的。它目前的主要成分是核心氦和外壳氢燃烧，平均分子量显著增加，这表明它处于高级演化阶段。它很快就会产生一颗罕见的蓝超巨星核心坍缩超新星，该超新星位于银河系盘面上方约十个 OB 星群尺度高度处，有助于环银河介质的金属富集。
{"title":"Runaway BN supergiant star HD 93840: Progenitor of an imminent core-collapse supernova above the Galactic plane","authors":"D. Weßmayer, M. A. Urbaneja, K. Butler, N. Przybilla","doi":"10.1051/0004-6361/202347732","DOIUrl":"https://doi.org/10.1051/0004-6361/202347732","url":null,"abstract":"We present a quantitative spectral analysis of the extreme nitrogen-enhanced supergiant HD 93840 (BN1 Ib) at an intermediate galactic latitude. Based on an optical high-resolution spectrum and complementary ultraviolet and infrared (spectro-)photometry, in addition to <i>Gaia<i/> data, we carried out a full characterisation of the star’s properties. We used both hydrostatic and unified (photosphere+wind) model atmospheres that account for deviations from local thermodynamic equilibrium. A highly unusual surface CNO-mixing signature and a marked stellar overluminosity compared to the mass imply a binary channel for the star’s past evolution. The kinematics shows that it has reached its current position above the Galactic plane as a runaway star, likely ejected by the supernova explosion of its former companion star. Its current bulk composition, with a notably increased mean molecular weight due to core He- and progressed shell H-burning, suggests an advanced evolutionary stage. It is poised to yield a rare core-collapse supernova of a blue supergiant about ten OB star population scale heights above the Galactic disk relatively soon, contributing to the metal enrichment of the circumgalactic medium.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462522","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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