Hayato Sugiyama, Masaki Ueda, Kotaro Fukushima, Shogo B Kobayashi, Noriko Y Yamasaki, Kosuke Sato, Kyoko Matsushita
Abstract Observations of the hot X-ray emitting interstellar medium in the Milky Way are important for studying the stellar feedback and for understanding the formation and evolution of galaxies. We present measurements of the soft X-ray background emission for 130 Suzaku observations at 75° < l < 285° and |b| > 15°. With the standard soft X-ray background model consisting of the local hot bubble and of the Milky Way halo, residual structures remain at 0.7–1 keV in the spectra of some regions. Adding a collisional-ionization-equilibrium component with a temperature of ∼0.8 keV, much higher than the virial temperature of the Milky Way, significantly reduces the derived C-statistic for 56 out of 130 observations. The emission measure of the 0.8 keV component varies by more than an order of magnitude: assuming the solar abundance, the median value is $3 times 10^{-4}, rm {cm^{-6} pc}$ and the 16th–84th percentile range is $(1!-!8) times 10^{-4}, rm {cm^{-6} pc}$. Regions toward the Orion–Eridanus superbubble, having a large cavity extending from the Ori OB1 association, have the highest emission measures of the 0.8 keV component. While the scatter is large, the emission measures tend to be higher toward lower galactic latitudes. We discuss possible biases caused by the solar wind charge exchange, stars, and background groups. The 0.8 keV component is probably heated by supernovae in the Milky Way disk, possibly related to Galactic fountains.
{"title":"The soft X-ray background with Suzaku. II. Supervirial temperature bubbles?","authors":"Hayato Sugiyama, Masaki Ueda, Kotaro Fukushima, Shogo B Kobayashi, Noriko Y Yamasaki, Kosuke Sato, Kyoko Matsushita","doi":"10.1093/pasj/psad073","DOIUrl":"https://doi.org/10.1093/pasj/psad073","url":null,"abstract":"Abstract Observations of the hot X-ray emitting interstellar medium in the Milky Way are important for studying the stellar feedback and for understanding the formation and evolution of galaxies. We present measurements of the soft X-ray background emission for 130 Suzaku observations at 75° &lt; l &lt; 285° and |b| &gt; 15°. With the standard soft X-ray background model consisting of the local hot bubble and of the Milky Way halo, residual structures remain at 0.7–1 keV in the spectra of some regions. Adding a collisional-ionization-equilibrium component with a temperature of ∼0.8 keV, much higher than the virial temperature of the Milky Way, significantly reduces the derived C-statistic for 56 out of 130 observations. The emission measure of the 0.8 keV component varies by more than an order of magnitude: assuming the solar abundance, the median value is $3 times 10^{-4}, rm {cm^{-6} pc}$ and the 16th–84th percentile range is $(1!-!8) times 10^{-4}, rm {cm^{-6} pc}$. Regions toward the Orion–Eridanus superbubble, having a large cavity extending from the Ori OB1 association, have the highest emission measures of the 0.8 keV component. While the scatter is large, the emission measures tend to be higher toward lower galactic latitudes. We discuss possible biases caused by the solar wind charge exchange, stars, and background groups. The 0.8 keV component is probably heated by supernovae in the Milky Way disk, possibly related to Galactic fountains.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"4 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134991480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Aya Bamba, Hidetoshi Sano, Ryo Yamazaki, Jacco Vink
Abstract The effect of the surrounding environment of supernova remnant shocks on nonthermal X-rays from accelerated electrons, with or without interacting dense material, is an open issue. We conduct spatially resolved X-ray spectroscopy of the shock–cloud interacting region of RCW 86 with XMM–Newton. It is found that bright soft X-ray filaments surround the dense cloud, observed with 12CO and H i emission lines. These filaments are brighter in thermal X-ray emission, and fainter and possibly softer in synchrotron X-rays, compared to those without interaction. Our results show that the shock decelerates due to the interaction with clouds, which results in an enhancement of thermal X-ray emission. This could possibly also explain the softer X-ray synchrotron component, because it implies that those shocks that move through a low-density environment, and therefore decelerate much less, can be more efficient accelerators. This is similar to SN 1006 and Tycho, and is in contrast to RX J1713.7−3946. This difference among remnants may be due to the clumpiness of dense material interacting with the shock, which should be examined in future observations.
{"title":"On the influence of shock–cloud interactions on the nonthermal X-ray emission from the supernova remnant RCW 86","authors":"Aya Bamba, Hidetoshi Sano, Ryo Yamazaki, Jacco Vink","doi":"10.1093/pasj/psad075","DOIUrl":"https://doi.org/10.1093/pasj/psad075","url":null,"abstract":"Abstract The effect of the surrounding environment of supernova remnant shocks on nonthermal X-rays from accelerated electrons, with or without interacting dense material, is an open issue. We conduct spatially resolved X-ray spectroscopy of the shock–cloud interacting region of RCW 86 with XMM–Newton. It is found that bright soft X-ray filaments surround the dense cloud, observed with 12CO and H i emission lines. These filaments are brighter in thermal X-ray emission, and fainter and possibly softer in synchrotron X-rays, compared to those without interaction. Our results show that the shock decelerates due to the interaction with clouds, which results in an enhancement of thermal X-ray emission. This could possibly also explain the softer X-ray synchrotron component, because it implies that those shocks that move through a low-density environment, and therefore decelerate much less, can be more efficient accelerators. This is similar to SN 1006 and Tycho, and is in contrast to RX J1713.7−3946. This difference among remnants may be due to the clumpiness of dense material interacting with the shock, which should be examined in future observations.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"126 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135540768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Abstract NGC 4151, a nearby Seyfert galaxy, has recently been reported to emit gamma-rays in the GeV range, posing an intriguing astrophysical mystery. The star formation rate of NGC 4151 is too low to explain the observed GeV flux, but the galaxy is known for its coronal activity in X-ray and jet activity in radio. We propose that either the combination of these two activities or the jet activity alone can account for the gamma-ray spectrum. An energy-dependent variability search will allow one to distinguish between the two scenarios, as the coronal component can only contribute at energies of ≲1 GeV. Our analysis also indicates that it might still be difficult to see coronal neutrinos from the apparently X-ray brightest Seyfert NGC 4151 with current-generation neutrino observatories.
最近有报道称，附近的Seyfert星系NGC 4151发射出GeV范围的伽马射线，这构成了一个有趣的天体物理学谜团。NGC 4151的恒星形成率太低，无法解释观测到的GeV通量，但该星系以其x射线的日冕活动和射电的喷流活动而闻名。我们认为，这两种活动的结合或单独的喷流活动都可以解释伽马射线谱。能量相关的变率搜索将允许人们区分这两种情况，因为日冕分量只能在能量小于1 GeV时起作用。我们的分析还表明，用当前一代的中微子天文台可能仍然很难看到来自x射线最亮的Seyfert NGC 4151的日冕中微子。
{"title":"Gamma-ray emission in the Seyfert galaxy NGC 4151: Investigating the role of jet and coronal activities","authors":"Yoshiyuki Inoue, Dmitry Khangulyan","doi":"10.1093/pasj/psad072","DOIUrl":"https://doi.org/10.1093/pasj/psad072","url":null,"abstract":"Abstract NGC 4151, a nearby Seyfert galaxy, has recently been reported to emit gamma-rays in the GeV range, posing an intriguing astrophysical mystery. The star formation rate of NGC 4151 is too low to explain the observed GeV flux, but the galaxy is known for its coronal activity in X-ray and jet activity in radio. We propose that either the combination of these two activities or the jet activity alone can account for the gamma-ray spectrum. An energy-dependent variability search will allow one to distinguish between the two scenarios, as the coronal component can only contribute at energies of ≲1 GeV. Our analysis also indicates that it might still be difficult to see coronal neutrinos from the apparently X-ray brightest Seyfert NGC 4151 with current-generation neutrino observatories.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136068192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Abstract H4-1 is a planetary nebula (PN) located in the Galactic halo, and is notably carbon-rich and one of the most metal-deficient PNe in the Milky Way. To unveil its progenitor evolution through accurate measurement of the gas mass, we conducted a comprehensive investigation of H4-1, using the newly obtained Seimei/KOOLS-IFU spectra and multiwavelength spectro-photometry data. The emission-line images generated from the KOOLS-IFU data cube successfully resolve the ellipsoidal nebula and the equatorial flattened disk that are frequently seen in bipolar PNe evolved from massive progenitors. By a fully data-driven method, we directly derived the seven elemental abundances, the gas-to-dust mass ratio, and the gas and dust masses based on our own distance scale. By comparing the observed quantities with both the photoionization model and the binary nucleosynthesis model, we conclude that the progenitors of initial masses of 1.87 M$_{odot }$ and 0.82 M$_{odot }$ are second-generation stars formed ∼4 Gyr after the Big Bang that have undergone mass transfers and a binary merger, and have ultimately evolved into a PN showing unique chemical abundances. Our binary model successfully reproduces the observed abundances and also explains the evolutionary time scale of H4-1.
{"title":"Seimei/KOOLS-IFU mapping of the gas and dust distributions in Galactic PNe: Unveiling the origin and evolution of the Galactic halo PN H4-1","authors":"Masaaki Otsuka, Toshiya Ueta, Akito Tajitsu","doi":"10.1093/pasj/psad069","DOIUrl":"https://doi.org/10.1093/pasj/psad069","url":null,"abstract":"Abstract H4-1 is a planetary nebula (PN) located in the Galactic halo, and is notably carbon-rich and one of the most metal-deficient PNe in the Milky Way. To unveil its progenitor evolution through accurate measurement of the gas mass, we conducted a comprehensive investigation of H4-1, using the newly obtained Seimei/KOOLS-IFU spectra and multiwavelength spectro-photometry data. The emission-line images generated from the KOOLS-IFU data cube successfully resolve the ellipsoidal nebula and the equatorial flattened disk that are frequently seen in bipolar PNe evolved from massive progenitors. By a fully data-driven method, we directly derived the seven elemental abundances, the gas-to-dust mass ratio, and the gas and dust masses based on our own distance scale. By comparing the observed quantities with both the photoionization model and the binary nucleosynthesis model, we conclude that the progenitors of initial masses of 1.87 M$_{odot }$ and 0.82 M$_{odot }$ are second-generation stars formed ∼4 Gyr after the Big Bang that have undergone mass transfers and a binary merger, and have ultimately evolved into a PN showing unique chemical abundances. Our binary model successfully reproduces the observed abundances and also explains the evolutionary time scale of H4-1.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136262217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Tsunefumi Mizuno, Hiroshi Ohno, Eri Watanabe, Niccolò Bucciantini, Shuichi Gunji, Sinpei Shibata, Patrick Slane, Martin C Weisskopf
Abstract We report a detailed study of the magnetic-field structure of the Crab pulsar wind nebula, using the X-ray polarization data in 2–8 keV obtained with the Imaging X-ray Polarimetry Explorer. Contamination of the data for the nebula region by the pulsar emission was removed through application of a stringent pulsation phase cut, extracting a phase range of 0.7–1.0 only. We found that the electric-field vector polarization angle (PA) was about 130○ from north to east with a polarization degree (PD) of about 25% at the pulsar position, indicating that the direction of the toroidal magnetic field is perpendicular to the pulsar spin axis in the region close to the termination shock. The PA gradually deviated from the angle as an increasing function of the distance from the pulsar. There was a region of low PD to the west of the X-ray torus. Although such a region is expected to be located at the torus edge, where geometrical depolarization due to a steep spatial variation of the PA is expected, the observed low-PD region positionally deviated from the edge. We found that the region of low PD positionally coincided with a dense filament seen in the optical band, and conjecture that the low-PD region may be produced through deflection of the pulsar wind. By comparing the values of the PD at the pulsar position between the data and a model, in which toroidal and turbulent magnetic fields were considered, we estimated the fractional energy of the turbulent magnetic field to be about 2$/$3 of the total. We also evaluated the potential polarization of the northern jet in the nebula and derived the PD and PA to be about 30% and 120○, respectively.
{"title":"Magnetic-field structure of the Crab pulsar wind nebula revealed with IXPE","authors":"Tsunefumi Mizuno, Hiroshi Ohno, Eri Watanabe, Niccolò Bucciantini, Shuichi Gunji, Sinpei Shibata, Patrick Slane, Martin C Weisskopf","doi":"10.1093/pasj/psad070","DOIUrl":"https://doi.org/10.1093/pasj/psad070","url":null,"abstract":"Abstract We report a detailed study of the magnetic-field structure of the Crab pulsar wind nebula, using the X-ray polarization data in 2–8 keV obtained with the Imaging X-ray Polarimetry Explorer. Contamination of the data for the nebula region by the pulsar emission was removed through application of a stringent pulsation phase cut, extracting a phase range of 0.7–1.0 only. We found that the electric-field vector polarization angle (PA) was about 130○ from north to east with a polarization degree (PD) of about 25% at the pulsar position, indicating that the direction of the toroidal magnetic field is perpendicular to the pulsar spin axis in the region close to the termination shock. The PA gradually deviated from the angle as an increasing function of the distance from the pulsar. There was a region of low PD to the west of the X-ray torus. Although such a region is expected to be located at the torus edge, where geometrical depolarization due to a steep spatial variation of the PA is expected, the observed low-PD region positionally deviated from the edge. We found that the region of low PD positionally coincided with a dense filament seen in the optical band, and conjecture that the low-PD region may be produced through deflection of the pulsar wind. By comparing the values of the PD at the pulsar position between the data and a model, in which toroidal and turbulent magnetic fields were considered, we estimated the fractional energy of the turbulent magnetic field to be about 2$/$3 of the total. We also evaluated the potential polarization of the northern jet in the nebula and derived the PD and PA to be about 30% and 120○, respectively.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"170 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136316799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Yuchen He, Jingjing Wu, Wenyu Wang, Bin Jiang, Yanxia Zhang
Abstract Blue horizontal-branch stars (BHBs) are ideal tracers for studying the Milky Way (MW) due to their bright and nearly constant magnitude. However, an incomplete screen of BHBs from a survey would result in bias of estimation of the structure or mass of the MW. With surveys of large sky telescopes like the Sloan Digital Sky Survey (SDSS), it is possible to obtain a complete sample. Thus, detecting BHBs from massive photometric images quickly and effectually is necessary. The current acquisition methods of BHBs are mainly based on manual or semi-automatic modes. Therefore, novel approaches are required to replace manual or traditional machine-learning detection. The mainstream deep-learning-based object-detection methods are often vanilla convolutional neural networks whose ability to extract global features is limited by the receptive field of the convolution operator. Recently, a new Transformer-based method has benefited from the global receptive field advantage brought by the self-attention mechanism, exceeded the vanilla convolution model in many tasks, and achieved excellent results. Therefore, this paper proposes a hybrid convolution and Transformer model called AstroYOLO to take advantage of the convolution in local feature representation and Transformer’s easier discovery of long-distance feature dependences. We conduct a comparative experiment on the 4799 SDSS DR16 photometric image dataset. The experimental results show that our model achieves 99.25% AP@50, 93.79% AP@75, and 64.45% AP@95 on the test dataset, outperforming the YOLOv3 and YOLOv4 object-detection models. In addition, we test on larger cutout images based on the same resolution. Our model can reach 99.02% AP@50, 92.00% AP@75, and 61.96% AP@95 respectively, still better than YOLOv3 and YOLOv4. These results also suggest that an appropriate size for cutout images is necessary for the performance and computation of object detection. Compared with the previous models, our model has achieved satisfactory object-detection results and can effectively improve the accuracy of BHB detection.
{"title":"AstroYOLO: A hybrid CNN–Transformer deep-learning object-detection model for blue horizontal-branch stars","authors":"Yuchen He, Jingjing Wu, Wenyu Wang, Bin Jiang, Yanxia Zhang","doi":"10.1093/pasj/psad071","DOIUrl":"https://doi.org/10.1093/pasj/psad071","url":null,"abstract":"Abstract Blue horizontal-branch stars (BHBs) are ideal tracers for studying the Milky Way (MW) due to their bright and nearly constant magnitude. However, an incomplete screen of BHBs from a survey would result in bias of estimation of the structure or mass of the MW. With surveys of large sky telescopes like the Sloan Digital Sky Survey (SDSS), it is possible to obtain a complete sample. Thus, detecting BHBs from massive photometric images quickly and effectually is necessary. The current acquisition methods of BHBs are mainly based on manual or semi-automatic modes. Therefore, novel approaches are required to replace manual or traditional machine-learning detection. The mainstream deep-learning-based object-detection methods are often vanilla convolutional neural networks whose ability to extract global features is limited by the receptive field of the convolution operator. Recently, a new Transformer-based method has benefited from the global receptive field advantage brought by the self-attention mechanism, exceeded the vanilla convolution model in many tasks, and achieved excellent results. Therefore, this paper proposes a hybrid convolution and Transformer model called AstroYOLO to take advantage of the convolution in local feature representation and Transformer’s easier discovery of long-distance feature dependences. We conduct a comparative experiment on the 4799 SDSS DR16 photometric image dataset. The experimental results show that our model achieves 99.25% AP@50, 93.79% AP@75, and 64.45% AP@95 on the test dataset, outperforming the YOLOv3 and YOLOv4 object-detection models. In addition, we test on larger cutout images based on the same resolution. Our model can reach 99.02% AP@50, 92.00% AP@75, and 61.96% AP@95 respectively, still better than YOLOv3 and YOLOv4. These results also suggest that an appropriate size for cutout images is necessary for the performance and computation of object detection. Compared with the previous models, our model has achieved satisfactory object-detection results and can effectively improve the accuracy of BHB detection.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"48 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136316801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Abstract Galactic winds play a crucial role in the ejection of the interstellar medium (ISM) into intergalactic space. This study presents a model that classifies possible transonic solutions of galactic winds in the gravitational potential of the dark matter halo and stellar component under spherically symmetric and steady assumptions. Our model includes injections of mass and energy resulting from supernova feedback along a flow line. The mass flux in galactic winds is a critical factor in determining the acceleration process of the flow and revealing the impact of galactic winds on galaxy evolution. We apply the transonic galactic wind model to the observed outflow velocities of star-forming galaxies to estimate the mass flux. Dividing the mass flux by the star formation rate (SFR) yields the mass loading rate (and mass loading factor), which indicates the entrainment effect of the ISM by the hot gas flow. Our results demonstrate that the mass loading rate is inversely correlated with galaxy mass and SFR. In less massive galaxies (stellar mass ∼107−8 M⊙), the mass loading rate exceeds unity, indicating effective ejection of the ISM into intergalactic space. However, in massive galaxies (stellar mass ∼1010−11 M⊙), the mass loading rate falls below unity, meaning that the mass flux cannot exceed the injected mass by supernovae, thus resulting in ineffective ejection of the ISM.
{"title":"Transonic galactic wind model including stellar feedbacks and application to outflows in high/low-<i>z</i> galaxies","authors":"Asuka Igarashi, Masao Mori, Shin-ya Nitta","doi":"10.1093/pasj/psad065","DOIUrl":"https://doi.org/10.1093/pasj/psad065","url":null,"abstract":"Abstract Galactic winds play a crucial role in the ejection of the interstellar medium (ISM) into intergalactic space. This study presents a model that classifies possible transonic solutions of galactic winds in the gravitational potential of the dark matter halo and stellar component under spherically symmetric and steady assumptions. Our model includes injections of mass and energy resulting from supernova feedback along a flow line. The mass flux in galactic winds is a critical factor in determining the acceleration process of the flow and revealing the impact of galactic winds on galaxy evolution. We apply the transonic galactic wind model to the observed outflow velocities of star-forming galaxies to estimate the mass flux. Dividing the mass flux by the star formation rate (SFR) yields the mass loading rate (and mass loading factor), which indicates the entrainment effect of the ISM by the hot gas flow. Our results demonstrate that the mass loading rate is inversely correlated with galaxy mass and SFR. In less massive galaxies (stellar mass ∼107−8 M⊙), the mass loading rate exceeds unity, indicating effective ejection of the ISM into intergalactic space. However, in massive galaxies (stellar mass ∼1010−11 M⊙), the mass loading rate falls below unity, meaning that the mass flux cannot exceed the injected mass by supernovae, thus resulting in ineffective ejection of the ISM.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135618427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Carbon-enhanced metal-poor (CEMP) stars in the Galactic halo have a wide range of neutron-capture element abundance patterns. To identify their origin, we investigated three modes of $s$-process nucleosynthesis that have been proposed to operate in extremely metal-poor (EMP) Asymptotic Giant Branch (AGB) stars: the convective 13C burning, which occurs when hydrogen is engulfed by the helium flash convection in low-mass AGB stars, the convective 22Ne burning, which occurs in the helium flash convection of intermediate-mass AGB stars, and the radiative 13C burning, which occurs in the $^{13}$C pocket that is formed during the inter-pulse periods. We show that the production of $s$-process elements per iron seed ($s$-process efficiency) does not depend on metallicity below $[{rm Fe}/{rm H}]=-2$, because 16O in the helium zone dominates the neutron poison. The convective 13C mode can produce a variety of $s$-process efficiencies for Sr, Ba and Pb, including the maxima observed among CEMP stars. The 22Ne mode only produce the lowest end of $s$-process efficiencies among CEMP models. We show that the combination of these two modes can explain the full range of observed enrichment of $s$-process elements in CEMP stars. In contrast, the 13C pocket mode can hardly explain the high level of enrichment observed in some CEMP stars, even if considering star-to-star variations of the mass of the 13C pocket. These results provide a basis for discussing the binary mass transfer origin of CEMP stars and their subgroups.
{"title":"A comparative study of three modes of <i>s</i>-process nucleosynthesis in extremely metal-poor AGB stars","authors":"Shimako Yamada, Takuma Suda, Yutaka Komiya, Masayuki Aikawa, Masayuki Y Fujimoto","doi":"10.1093/pasj/psad062","DOIUrl":"https://doi.org/10.1093/pasj/psad062","url":null,"abstract":"Carbon-enhanced metal-poor (CEMP) stars in the Galactic halo have a wide range of neutron-capture element abundance patterns. To identify their origin, we investigated three modes of $s$-process nucleosynthesis that have been proposed to operate in extremely metal-poor (EMP) Asymptotic Giant Branch (AGB) stars: the convective 13C burning, which occurs when hydrogen is engulfed by the helium flash convection in low-mass AGB stars, the convective 22Ne burning, which occurs in the helium flash convection of intermediate-mass AGB stars, and the radiative 13C burning, which occurs in the $^{13}$C pocket that is formed during the inter-pulse periods. We show that the production of $s$-process elements per iron seed ($s$-process efficiency) does not depend on metallicity below $[{rm Fe}/{rm H}]=-2$, because 16O in the helium zone dominates the neutron poison. The convective 13C mode can produce a variety of $s$-process efficiencies for Sr, Ba and Pb, including the maxima observed among CEMP stars. The 22Ne mode only produce the lowest end of $s$-process efficiencies among CEMP models. We show that the combination of these two modes can explain the full range of observed enrichment of $s$-process elements in CEMP stars. In contrast, the 13C pocket mode can hardly explain the high level of enrichment observed in some CEMP stars, even if considering star-to-star variations of the mass of the 13C pocket. These results provide a basis for discussing the binary mass transfer origin of CEMP stars and their subgroups.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135824264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Abstract The results of a Suzaku observation of the supernova remnant (SNR) Kesteven 69 = G21.8−0.6 are presented. To estimate the sky background precisely, we conducted a simultaneous fit of the source region spectrum with the background region spectrum and found that the SNR spectrum is well represented by a two-component ionizing plasma model composed of a low-temperature plasma at kTe = 0.80 ± 0.11 keV and a high-temperature plasma at kTe = 1.5 ± 0.4 keV. The existence of a low-ionized Fe K line at 6.49 ± 0.07 keV was confirmed. The center energy of the line is consistent with those of type Ia SNRs.
{"title":"Spectral analysis of the Galactic supernova remnant Kesteven 69 with Suzaku","authors":"Shigeo Yamauchi, Thomas G Pannuti","doi":"10.1093/pasj/psad068","DOIUrl":"https://doi.org/10.1093/pasj/psad068","url":null,"abstract":"Abstract The results of a Suzaku observation of the supernova remnant (SNR) Kesteven 69 = G21.8−0.6 are presented. To estimate the sky background precisely, we conducted a simultaneous fit of the source region spectrum with the background region spectrum and found that the SNR spectrum is well represented by a two-component ionizing plasma model composed of a low-temperature plasma at kTe = 0.80 ± 0.11 keV and a high-temperature plasma at kTe = 1.5 ± 0.4 keV. The existence of a low-ionized Fe K line at 6.49 ± 0.07 keV was confirmed. The center energy of the line is consistent with those of type Ia SNRs.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135141729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Mohamed Sedik, Abdelrazek M K Shaltout, Yuanyong Deng, Kiyoshi Ichimoto
Abstract We analyze the magnetism of the quiet Sun internetwork (IN) using high-spatial-resolution data obtained by the spectropolarimeter (SP) of the Solar Optical Telescope aboard the Hinode satellite near the disk center of the Sun. The SP data were inverted using the Stokes Inversion based on Response functions (SIR) inversion code with a single-component atmosphere with depth dependent in the solar photosphere, assuming gradients in physical parameters along the line of sight (LOS). To avoid the effect of noise, only pixels with Stokes U and/or Q signals above 4.5 times the noise level are considered. The inversion results show that the magnetic field of the IN has mainly hG field strength and the inclination distribution is quasi-isotropic at the solar surface. The field strength decreases with height and becomes predominantly horizontal at the upper layers. At the mid photosphere, the distributions of field strength and inclination are consistent with those derived by Milne–Eddington inversion. The mean transverse and longitudinal flux densities are 66 Mx cm−2 and 13 Mx cm−2 at log τ = −1.0; we also study the ratio between the transverse and longitudinal components in the IN region as a function of depth in the photosphere, finding that the ratio is almost 2.7 in the deep layer, increasing to 5.1 in the upper layer. The mean field strength is greater than 100 G in the upper photosphere, which is consistent with the results based on the Hanle effect. We present the LOS velocity probability distribution function for IN at different optical depths, where its distribution is mainly associated with upflow velocities of VLOS = 1.2 and 0.6 km s−1 in the deeper and upper layers, respectively. In addition, there exists a reliable inversion analysis, which is obvious from the comparison between the observed and calculated area asymmetries in both Fe i lines of Hinode SP data.
{"title":"Investigating the magnetic field of the quiet Sun internetwork","authors":"Mohamed Sedik, Abdelrazek M K Shaltout, Yuanyong Deng, Kiyoshi Ichimoto","doi":"10.1093/pasj/psad067","DOIUrl":"https://doi.org/10.1093/pasj/psad067","url":null,"abstract":"Abstract We analyze the magnetism of the quiet Sun internetwork (IN) using high-spatial-resolution data obtained by the spectropolarimeter (SP) of the Solar Optical Telescope aboard the Hinode satellite near the disk center of the Sun. The SP data were inverted using the Stokes Inversion based on Response functions (SIR) inversion code with a single-component atmosphere with depth dependent in the solar photosphere, assuming gradients in physical parameters along the line of sight (LOS). To avoid the effect of noise, only pixels with Stokes U and/or Q signals above 4.5 times the noise level are considered. The inversion results show that the magnetic field of the IN has mainly hG field strength and the inclination distribution is quasi-isotropic at the solar surface. The field strength decreases with height and becomes predominantly horizontal at the upper layers. At the mid photosphere, the distributions of field strength and inclination are consistent with those derived by Milne–Eddington inversion. The mean transverse and longitudinal flux densities are 66 Mx cm−2 and 13 Mx cm−2 at log τ = −1.0; we also study the ratio between the transverse and longitudinal components in the IN region as a function of depth in the photosphere, finding that the ratio is almost 2.7 in the deep layer, increasing to 5.1 in the upper layer. The mean field strength is greater than 100 G in the upper photosphere, which is consistent with the results based on the Hanle effect. We present the LOS velocity probability distribution function for IN at different optical depths, where its distribution is mainly associated with upflow velocities of VLOS = 1.2 and 0.6 km s−1 in the deeper and upper layers, respectively. In addition, there exists a reliable inversion analysis, which is obvious from the comparison between the observed and calculated area asymmetries in both Fe i lines of Hinode SP data.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135689971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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