Hydrocarbon dust is one of the dominant components of interstellar dust, which mainly consists of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons. While hydrocarbon dust is thought to be processed in interstellar radiation fields or shocks, detailed processing mechanisms are not completely understood yet. We investigate the processing of hydrocarbon dust by analyzing the relation between the luminosities emitted by hydrocarbon dust and the total infrared luminosities $(L_{mathrm{IR}})$ for 138 star-forming galaxies at redshift $z lt 0.3$. Using near-infrared 2.5–5$, mu {rm m}$ spectra obtained with AKARI, we derived the luminosities of the aromatic hydrocarbon feature at 3.3$, mu {rm m}$ ($L_mathrm{aromatic}$) and the aliphatic hydrocarbon feature at 3.4–3.6$, mu {rm m}$ ($L_mathrm{aliphatic}$). We also derived $L_mathrm{IR}$ and the radiation field strength by modeling the spectral energy distributions of the 138 galaxies with AKARI, WISE, and IRAS photometry data. We find that galaxies with higher $L_mathrm{IR}$ tend to exhibit lower $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios. Furthermore, we find that there is an anti-correlation between $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios and the radiation field strength, and also that the galaxies with low $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios are dominated by merger galaxies. These results support the suggestion that hydrocarbon dust is processed through photodissociation in strong radiation fields and/or shocks during merging processes of galaxies; the $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratio is likely to decrease in such harsh interstellar conditions since the aliphatic bonds are known to be chemically weaker than the aromatic bonds.
碳氢化合物尘埃是星际尘埃的主要成分之一，主要由多环芳香烃和脂肪烃组成。虽然碳氢化合物尘埃被认为是在星际辐射场或冲击中被处理的，但详细的处理机制还不完全清楚。我们通过分析138个红移为$z lt 0.3$的恒星形成星系中碳氢化合物尘埃发出的光度与总红外光度$(L_{mathrm{IR}})$之间的关系来研究碳氢化合物尘埃的处理过程。利用AKARI获得的2.5-5, mu {rm m}$近红外光谱，我们得出了3.3, mu {rm m}$处的芳香烃特征（$L_mathrm{aromatic}$）和3.4-3.6, mu {rm m}$处的脂肪烃特征（$L_mathrm{aliphatic}$）的光度。我们还利用AKARI、WISE和IRAS的测光数据，对138个星系的光谱能量分布进行建模，得出了$L_mathrm{IR}$和辐射场强。我们发现$L_mathrm{IR}$较高的星系往往表现出较低的$L_mathrm{脂肪族}/L_mathrm{芳香族}$比率。此外，我们还发现$L_mathrm{aliphatic}/L_mathrm{aromatic}$比值与辐射场强之间存在反相关关系，而且低$L_mathrm{aliphatic}/L_mathrm{aromatic}$比值的星系主要是合并星系。这些结果支持这样一种观点，即碳氢化合物尘埃是在星系合并过程中，在强辐射场和/或冲击下通过光解离处理的；在这种恶劣的星际条件下，$L_mathrm{脂肪族}/L__mathrm{芳香族}$比值很可能会降低，因为众所周知脂肪族键的化学性质比芳香族键弱。
{"title":"Processing of hydrocarbon dust in star-forming galaxies revealed with AKARI","authors":"Tsubasa Kondo, Akino Kondo, Katsuhiro L Murata, Takuma Kokusho, Shinki Oyabu, Toyoaki Suzuki, Risako Katayama, Hidehiro Kaneda","doi":"10.1093/pasj/psae069","DOIUrl":"https://doi.org/10.1093/pasj/psae069","url":null,"abstract":"Hydrocarbon dust is one of the dominant components of interstellar dust, which mainly consists of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons. While hydrocarbon dust is thought to be processed in interstellar radiation fields or shocks, detailed processing mechanisms are not completely understood yet. We investigate the processing of hydrocarbon dust by analyzing the relation between the luminosities emitted by hydrocarbon dust and the total infrared luminosities $(L_{mathrm{IR}})$ for 138 star-forming galaxies at redshift $z lt 0.3$. Using near-infrared 2.5–5$, mu {rm m}$ spectra obtained with AKARI, we derived the luminosities of the aromatic hydrocarbon feature at 3.3$, mu {rm m}$ ($L_mathrm{aromatic}$) and the aliphatic hydrocarbon feature at 3.4–3.6$, mu {rm m}$ ($L_mathrm{aliphatic}$). We also derived $L_mathrm{IR}$ and the radiation field strength by modeling the spectral energy distributions of the 138 galaxies with AKARI, WISE, and IRAS photometry data. We find that galaxies with higher $L_mathrm{IR}$ tend to exhibit lower $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios. Furthermore, we find that there is an anti-correlation between $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios and the radiation field strength, and also that the galaxies with low $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratios are dominated by merger galaxies. These results support the suggestion that hydrocarbon dust is processed through photodissociation in strong radiation fields and/or shocks during merging processes of galaxies; the $L_mathrm{aliphatic}/L_mathrm{aromatic}$ ratio is likely to decrease in such harsh interstellar conditions since the aliphatic bonds are known to be chemically weaker than the aromatic bonds.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948816","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}
The IceCube Collaboration has reported possible detections of high-energy neutrinos from nearby Seyfert galaxies. While central hot coronae are proposed as the primary neutrino production site, the exact coronal cosmic ray energy budget has been loosely constrained. In this study, we propose a new stringent upper bound on the coronal cosmic ray energy budget of Seyfert galaxies, considering both accretion dynamics and observed properties of radio-quiet Seyfert galaxies. Notably, even under the calorimetric condition where cosmic rays lose all their energy, our limit indicates that the coronal neutrino flux of NGC 1068 is about an order of magnitude fainter than the observed levels. This discrepancy suggests the need for further theoretical and observational investigations on the IceCube signals from Seyfert galaxies.
{"title":"Upper limit on the coronal cosmic ray energy budget in Seyfert galaxies","authors":"Yoshiyuki Inoue, Shinsuke Takasao, Dmitry Khangulyan","doi":"10.1093/pasj/psae065","DOIUrl":"https://doi.org/10.1093/pasj/psae065","url":null,"abstract":"The IceCube Collaboration has reported possible detections of high-energy neutrinos from nearby Seyfert galaxies. While central hot coronae are proposed as the primary neutrino production site, the exact coronal cosmic ray energy budget has been loosely constrained. In this study, we propose a new stringent upper bound on the coronal cosmic ray energy budget of Seyfert galaxies, considering both accretion dynamics and observed properties of radio-quiet Seyfert galaxies. Notably, even under the calorimetric condition where cosmic rays lose all their energy, our limit indicates that the coronal neutrino flux of NGC 1068 is about an order of magnitude fainter than the observed levels. This discrepancy suggests the need for further theoretical and observational investigations on the IceCube signals from Seyfert galaxies.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769492","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}
We present an analysis of a stellar occultation event caused by a near-Earth asteroid (98943) 2001 CC21, an upcoming flyby target in the Hayabusa2 extended mission, on 2023 March 5. To determine the asteroid’s shape from diffraction-affected light curves accurately, we developed a novel data-reduction technique named the Diffracted Occultation’s United Simulator for Highly Informative Transient Explorations (DOUSHITE). Using DOUSHITE-generated synthetic models, we derived constraints on (98943) 2001 CC21’s shadow shape from the single-chord occultation data. Our results suggest a significant elongation of the shadow with an axis ratio of $b/a = 0.37pm 0.09$. This shape could be crucial for planning Hayabusa2’s high-speed flyby to optimise the limited imaging opportunities.
{"title":"Diffraction modelling of a 2023 March 5 stellar occultation by subkilometer-sized asteroid (98943) 2001 CC21","authors":"Ko Arimatsu, Fumi Yoshida, Tsutomu Hayamizu, Miyoshi Ida, George L Hashimoto, Takashi Abe, Hiroshi Akitaya, Akari Aratani, Hidekazu Fukuda, Yasuhide Fujita, Takao Fujiwara, Toshihiro Horikawa, Tamio Iihoshi, Kazuyoshi Imamura, Ryo Imazawa, Hisashi Kasebe, Ryosuke Kawasaki, Hiroshi Kishimoto, Kazuhisa Mishima, Machiko Miyachi, Masanori Mizutani, Maya Nakajima, Hiroyoshi Nakatani, Kazuhiko Okamura, Misaki Okanobu, Masataka Okuda, Yuji Suzuki, Naoto Tatsumi, Masafumi Uno, Hidehito Yamamura, Mikoto Yasue, Hideki Yoshihara, Masatoshi Hirabayashi, Makoto Yoshikawa","doi":"10.1093/pasj/psae060","DOIUrl":"https://doi.org/10.1093/pasj/psae060","url":null,"abstract":"We present an analysis of a stellar occultation event caused by a near-Earth asteroid (98943) 2001 CC21, an upcoming flyby target in the Hayabusa2 extended mission, on 2023 March 5. To determine the asteroid’s shape from diffraction-affected light curves accurately, we developed a novel data-reduction technique named the Diffracted Occultation’s United Simulator for Highly Informative Transient Explorations (DOUSHITE). Using DOUSHITE-generated synthetic models, we derived constraints on (98943) 2001 CC21’s shadow shape from the single-chord occultation data. Our results suggest a significant elongation of the shadow with an axis ratio of $b/a = 0.37pm 0.09$. This shape could be crucial for planning Hayabusa2’s high-speed flyby to optimise the limited imaging opportunities.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769494","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}
The north-west side of the disk of M 31 is known as the near side because of the differential reddening of globular clusters found from their photographic photometry. This paper reports a simple geometric model to evaluate the visibility of the effect and its application to published CCD photometry on globular cluster systems of three spiral galaxies, M 31, M 33, and NGC 253. The color difference of globular cluster systems due to differential reddening was confirmed for M 31 and NGC 253; however, the data for M 33 were insufficient. The analysis reaffirms the currently adopted interpretation that the side on the minor axis of the galactic disk, where more conspicuous dust features and interstellar reddening are visible, is the nearer side to us and provides an additional basis for using spiral galaxies with identified spiral windings, S-wise or Z-wise, to study the large-scale spin distribution of galaxies in the universe.
M 31圆盘的西北侧被称为近侧，因为从其摄影测光中发现了球状星团的不同变红现象。本文报告了一个简单的几何模型，用于评估该效应的可见度，并将其应用于已发表的关于三个螺旋星系（M 31、M 33 和 NGC 253）球状星团系统的 CCD 摄影测量。在 M 31 和 NGC 253 中，球状星团系统的色差是由不同的变红引起的，这一点得到了证实；但是 M 33 的数据不够充分。分析结果再次证实了目前所采用的解释，即星系盘小轴线上的一侧是离我们较近的一侧，在这一侧可以看到更明显的尘埃特征和星际变红现象，并为利用具有已识别螺旋缠绕（S 向或 Z 向）的螺旋星系来研究宇宙中星系的大尺度自旋分布提供了新的依据。
{"title":"Spin parity of spiral galaxies. IV. Differential reddening of globular cluster systems of nearby spiral galaxies","authors":"Masanori Iye, Masafumi Yagi","doi":"10.1093/pasj/psae064","DOIUrl":"https://doi.org/10.1093/pasj/psae064","url":null,"abstract":"The north-west side of the disk of M 31 is known as the near side because of the differential reddening of globular clusters found from their photographic photometry. This paper reports a simple geometric model to evaluate the visibility of the effect and its application to published CCD photometry on globular cluster systems of three spiral galaxies, M 31, M 33, and NGC 253. The color difference of globular cluster systems due to differential reddening was confirmed for M 31 and NGC 253; however, the data for M 33 were insufficient. The analysis reaffirms the currently adopted interpretation that the side on the minor axis of the galactic disk, where more conspicuous dust features and interstellar reddening are visible, is the nearer side to us and provides an additional basis for using spiral galaxies with identified spiral windings, S-wise or Z-wise, to study the large-scale spin distribution of galaxies in the universe.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769493","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}
Yao Li, Duo Cao, Yi Zhang, Xiaoyong He, Feng Liu, Wangzhou Shi, Chenggang Shu
The Leighton Chajnantor Telescope (LCT) is an international collaborative program among Caltech, Shanghai Normal University (ShNU), and Universidad de Concepción (UdeC), aiming at the refurbishment and relocation of the Caltech Submillimeter Observatory (CSO) telescope from Mauna Kea, Hawaii, to the Chajnantor Plateau, northern Chile. A suite of excellent-sensitivity heterodyne superconductor–insulator–superconductor (SIS) receivers will be deployed to the telescope as the first set of instrumentations for high-resolution spectral observation. However, the current refrigeration technology for this receiver utilizes liquid helium (LHe), which greatly increases the cost of cooling and labor. To address this problem, a new LHe-free cryostat for the LCT heterodyne SIS receiver has been designed, fabricated, and tested. Mechanical and thermal analyses were performed to ensure that the cryostat meets the requirements of the telescope pointing accuracy and the SIS junction working environment, respectively. The experiment testing results are in good agreement with the calculation and analysis, indicating that the proposed LHe-free cryostat meets the operational requirements of the telescope at the new site.
{"title":"A new LHe-free cryostat for the heterodyne SIS receiver for the Leighton Chajnantor Telescope","authors":"Yao Li, Duo Cao, Yi Zhang, Xiaoyong He, Feng Liu, Wangzhou Shi, Chenggang Shu","doi":"10.1093/pasj/psae063","DOIUrl":"https://doi.org/10.1093/pasj/psae063","url":null,"abstract":"The Leighton Chajnantor Telescope (LCT) is an international collaborative program among Caltech, Shanghai Normal University (ShNU), and Universidad de Concepción (UdeC), aiming at the refurbishment and relocation of the Caltech Submillimeter Observatory (CSO) telescope from Mauna Kea, Hawaii, to the Chajnantor Plateau, northern Chile. A suite of excellent-sensitivity heterodyne superconductor–insulator–superconductor (SIS) receivers will be deployed to the telescope as the first set of instrumentations for high-resolution spectral observation. However, the current refrigeration technology for this receiver utilizes liquid helium (LHe), which greatly increases the cost of cooling and labor. To address this problem, a new LHe-free cryostat for the LCT heterodyne SIS receiver has been designed, fabricated, and tested. Mechanical and thermal analyses were performed to ensure that the cryostat meets the requirements of the telescope pointing accuracy and the SIS junction working environment, respectively. The experiment testing results are in good agreement with the calculation and analysis, indicating that the proposed LHe-free cryostat meets the operational requirements of the telescope at the new site.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141739638","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}
Akihiro Suzuki, Christopher M Irwin, Keiichi Maeda
We present the results of a series of 3D special relativistic hydrodynamic simulations of a gamma-ray burst (GRB) jet in a massive circumstellar medium (CSM) surrounding the progenitor star. Our simulations reproduce the jet morphology transitioning from a well-collimated state to a thermal pressure-driven state for a range of CSM masses and outer radii. The jet–CSM interaction redistributes the jet energy to materials expanding into a wide solid angle and results in a quasi-spherical ejecta with four-velocities from $Gamma beta simeq 0.1$ to 10. The mass and kinetic energy of the ejecta with velocities faster than $0.1c$ are typically of the order of $0.1, M_{odot }$ and $10^{51}:mbox{erg}$ with only a weak dependence on the CSM mass and radius for the explored CSM parameter ranges. We find that the numerically obtained density structure of the mildly relativistic ejecta is remarkably universal. The radial density profile is well approximated as a power-law function of the radial velocity with an index of $-5$, $rho propto v^{-5}$, in agreement with our previous simulations and other studies, as well as those suggested from recent studies on early-phase spectra of supernovae associated with GRBs. Such fast ejecta rapidly becomes transparent following its expansion. Gradually releasing the trapped thermal photons, the ejecta gives rise to bright UV–optical emission within ${sim} 1:$d. We discuss the potential link of the relativistic ejecta resulting from jet–CSM interaction to GRB-associated supernovae as well as fast and blue optical transients.
{"title":"Dynamical properties of mildly relativistic ejecta produced by the mass-loading of gamma-ray burst jets in dense ambient media","authors":"Akihiro Suzuki, Christopher M Irwin, Keiichi Maeda","doi":"10.1093/pasj/psae055","DOIUrl":"https://doi.org/10.1093/pasj/psae055","url":null,"abstract":"We present the results of a series of 3D special relativistic hydrodynamic simulations of a gamma-ray burst (GRB) jet in a massive circumstellar medium (CSM) surrounding the progenitor star. Our simulations reproduce the jet morphology transitioning from a well-collimated state to a thermal pressure-driven state for a range of CSM masses and outer radii. The jet–CSM interaction redistributes the jet energy to materials expanding into a wide solid angle and results in a quasi-spherical ejecta with four-velocities from $Gamma beta simeq 0.1$ to 10. The mass and kinetic energy of the ejecta with velocities faster than $0.1c$ are typically of the order of $0.1, M_{odot }$ and $10^{51}:mbox{erg}$ with only a weak dependence on the CSM mass and radius for the explored CSM parameter ranges. We find that the numerically obtained density structure of the mildly relativistic ejecta is remarkably universal. The radial density profile is well approximated as a power-law function of the radial velocity with an index of $-5$, $rho propto v^{-5}$, in agreement with our previous simulations and other studies, as well as those suggested from recent studies on early-phase spectra of supernovae associated with GRBs. Such fast ejecta rapidly becomes transparent following its expansion. Gradually releasing the trapped thermal photons, the ejecta gives rise to bright UV–optical emission within ${sim} 1:$d. We discuss the potential link of the relativistic ejecta resulting from jet–CSM interaction to GRB-associated supernovae as well as fast and blue optical transients.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141575872","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}
Hsien-chieh Shen, Takanori Sakamoto, Motoko Serino, Yuri Sato
A new type of cosmological transient, dubbed fast radio bursts (FRBs), was recently discovered. The source of FRBs is still unknown. One possible scenario of an FRB is the collapse of a spinning supra-massive neutron star. Zhang (2014, ApJ, 780, L21) suggests that the collapse can happen shortly (hundreds to thousands of seconds) after the birth of supra-massive neutron stars. The signatures can be visible in X-ray afterglows of long and short gamma-ray bursts (GRBs). For instance, a sudden drop (decay index steeper than $-3$ to $-9$) from a shallow decay (decay index shallower than $-1$) in the X-ray afterglow flux can indicate such an event. We selected the X-ray afterglow light curves with a steep decay after the shallow decay phase from the Swift/XRT GRB catalog. We analyzed when the decay index changed suddenly by fitting these light curves to double power-law functions and compared them with the onset of FRBs. We found that none of our GRB samples match the onset of FRBs.
最近发现了一种新型宇宙学瞬变现象，被称为快速射电暴（FRBs）。FRB的来源仍然未知。FRB的一种可能情况是旋转的超大质量中子星的坍缩。Zhang（2014，ApJ，780，L21）认为，坍缩可能发生在超大质量中子星诞生后不久（几百到几千秒）。长伽玛射线暴和短伽玛射线暴（GRBs）的X射线余辉中都可以看到这种迹象。例如，X射线余辉通量从浅衰变（衰变指数小于$-1）突然下降（衰变指数从$-3陡降至$-9），就表明发生了这样的事件。我们从 Swift/XRT GRB 星表中选取了在浅衰变阶段之后出现陡峭衰变的 X 射线余辉光变曲线。通过对这些光曲线进行双幂律函数拟合，我们分析了衰变指数突然发生变化的时间，并将其与FRB的发生时间进行了比较。我们发现，我们的GRB样本中没有一个与FRB的发生时间相吻合。
{"title":"Searching for the signature of fast radio burst by Swift/XRT X-ray afterglow light curve","authors":"Hsien-chieh Shen, Takanori Sakamoto, Motoko Serino, Yuri Sato","doi":"10.1093/pasj/psae053","DOIUrl":"https://doi.org/10.1093/pasj/psae053","url":null,"abstract":"A new type of cosmological transient, dubbed fast radio bursts (FRBs), was recently discovered. The source of FRBs is still unknown. One possible scenario of an FRB is the collapse of a spinning supra-massive neutron star. Zhang (2014, ApJ, 780, L21) suggests that the collapse can happen shortly (hundreds to thousands of seconds) after the birth of supra-massive neutron stars. The signatures can be visible in X-ray afterglows of long and short gamma-ray bursts (GRBs). For instance, a sudden drop (decay index steeper than $-3$ to $-9$) from a shallow decay (decay index shallower than $-1$) in the X-ray afterglow flux can indicate such an event. We selected the X-ray afterglow light curves with a steep decay after the shallow decay phase from the Swift/XRT GRB catalog. We analyzed when the decay index changed suddenly by fitting these light curves to double power-law functions and compared them with the onset of FRBs. We found that none of our GRB samples match the onset of FRBs.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504306","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}
Cosmic very small dust grains (VSGs) contain 100 to 10000 atoms, making them a mesoscopic system with specific thermal and optical characteristics due to the finite number of atoms within each grain. This paper focuses on graphite VSGs which contain free electrons. The energy level statistics devised by Kubo (1962, J. Phys. Soc. Jpn., 17, 975) are used for the first time to understand the thermal properties of free electrons in graphite VSGs. We show that the shape irregularity of the grains allows graphite VSGs to absorb or emit photons at submillimeter wavelengths or longer; otherwise, the frequency is limited to above a few THz. Additionally, we consider the decrease in Debye temperature due to the surface effect. VSGs have an extremely small volume, resulting in limited thermal energy storage, especially at low temperatures. Since a VSG is able to emit a photon with energy smaller than its internal energy, this determines the maximum frequency of the emitted photon. We develop a Monte Carlo simulation code to track the thermal history of a dust grain, considering the stochastic heating from the absorption of ambient photons and radiative cooling. This approach is applied to the interstellar environment to compute the spectral energy distributions from the interstellar graphite dust grains. The results show that graphite VSGs emit not only the mid-infrared excess emission, but also a surplus emission from submillimeter to millimeter wavelengths.
{"title":"Cosmic very small dust grains as a natural laboratory of mesoscopic physics: Modeling thermal and optical properties of graphite grains","authors":"Kenji Amazaki, Masashi Nashimoto, Makoto Hattori","doi":"10.1093/pasj/psae050","DOIUrl":"https://doi.org/10.1093/pasj/psae050","url":null,"abstract":"Cosmic very small dust grains (VSGs) contain 100 to 10000 atoms, making them a mesoscopic system with specific thermal and optical characteristics due to the finite number of atoms within each grain. This paper focuses on graphite VSGs which contain free electrons. The energy level statistics devised by Kubo (1962, J. Phys. Soc. Jpn., 17, 975) are used for the first time to understand the thermal properties of free electrons in graphite VSGs. We show that the shape irregularity of the grains allows graphite VSGs to absorb or emit photons at submillimeter wavelengths or longer; otherwise, the frequency is limited to above a few THz. Additionally, we consider the decrease in Debye temperature due to the surface effect. VSGs have an extremely small volume, resulting in limited thermal energy storage, especially at low temperatures. Since a VSG is able to emit a photon with energy smaller than its internal energy, this determines the maximum frequency of the emitted photon. We develop a Monte Carlo simulation code to track the thermal history of a dust grain, considering the stochastic heating from the absorption of ambient photons and radiative cooling. This approach is applied to the interstellar environment to compute the spectral energy distributions from the interstellar graphite dust grains. The results show that graphite VSGs emit not only the mid-infrared excess emission, but also a surplus emission from submillimeter to millimeter wavelengths.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504307","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}
We performed a $^{12}$CO- and $^{13}$CO-line study of the “Brick” (G0.253+0.016) in the Galactic Center (GC) by analyzing archival data obtained with the Nobeyama 45 m telescope. We present kinematics and molecular gas distributions in the longitude–velocity diagram, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ), which yields a distance from the Sun of 8 kpc and a Galactocentric distance of 0.2 kpc. The major- and minor-axis diameters of the Brick are $D_xtimes D_y=8.4 times 4.1, {rm pc}$ at position angles of 40 and $130^circ$, respectively, and the scale radius is $r_{rm Bri}=sqrt{D_x D_y}=2.96, {rm pc}$. The molecular mass inferred from the $^{12}$CO-line integrated intensity is $M_{mathrm{Bri};X_mathrm{CO}}sim 5.1times 10^4, M_odot$ for a conversion factor $X_{rm CO;GC}=1.0times 10^{20}$ H$_2$ cm $^{-2}$ [K km s$^{-1}]^{-1}$. On the other hand, the dynamical (virial) mass for the measured velocity dispersion of $sigma _v=10.0, {rm km s^{-1}}$ is calculated to be $M_{rm Bri;vir}sim 6.8 times 10^4,M_odot$, which yields a new conversion factor of $X_{rm CO;Bri}=1.3times 10^{20}$ H$_2$ cm $^{-2}$ [K km s$^{-1}]^{-1}$. The Brick’s center has a cavity surrounded by a spherical molecular bubble of radius $r_{rm bub}=1.85$ pc and mass $sim 1.7times 10^4,M_odot$ expanding at $v_{rm exp}simeq 10 {rm km s^{-1}}$ with a kinetic energy of $E_0sim 1.7times 10^{49}$ erg. If the bubble is approximated by an adiabatic spherical shock wave, the age is estimated to be $tsim 2/5 r_{rm bub}/v_{rm exp}sim 7.2times 10^4$ yr. Neither non-thermal radio structures nor thermal radio emission indicative of the H ii region are found in the archival data from MeerKAT. We suggest that the molecular bubble is a dark supernova remnant buried in the Brick, which has therefore experienced past (${sim}0.1$ Myr ago) massive star formation with a supernova explosion.
{"title":"Dark supernova remnant buried in the Galactic Center “Brick” G0.253+0.016 revealed by an expanding CO-line bubble","authors":"Yoshiaki Sofue","doi":"10.1093/pasj/psae047","DOIUrl":"https://doi.org/10.1093/pasj/psae047","url":null,"abstract":"We performed a $^{12}$CO- and $^{13}$CO-line study of the “Brick” (G0.253+0.016) in the Galactic Center (GC) by analyzing archival data obtained with the Nobeyama 45 m telescope. We present kinematics and molecular gas distributions in the longitude–velocity diagram, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ), which yields a distance from the Sun of 8 kpc and a Galactocentric distance of 0.2 kpc. The major- and minor-axis diameters of the Brick are $D_xtimes D_y=8.4 times 4.1, {rm pc}$ at position angles of 40 and $130^circ$, respectively, and the scale radius is $r_{rm Bri}=sqrt{D_x D_y}=2.96, {rm pc}$. The molecular mass inferred from the $^{12}$CO-line integrated intensity is $M_{mathrm{Bri};X_mathrm{CO}}sim 5.1times 10^4, M_odot$ for a conversion factor $X_{rm CO;GC}=1.0times 10^{20}$ H$_2$ cm $^{-2}$ [K km s$^{-1}]^{-1}$. On the other hand, the dynamical (virial) mass for the measured velocity dispersion of $sigma _v=10.0, {rm km s^{-1}}$ is calculated to be $M_{rm Bri;vir}sim 6.8 times 10^4,M_odot$, which yields a new conversion factor of $X_{rm CO;Bri}=1.3times 10^{20}$ H$_2$ cm $^{-2}$ [K km s$^{-1}]^{-1}$. The Brick’s center has a cavity surrounded by a spherical molecular bubble of radius $r_{rm bub}=1.85$ pc and mass $sim 1.7times 10^4,M_odot$ expanding at $v_{rm exp}simeq 10 {rm km s^{-1}}$ with a kinetic energy of $E_0sim 1.7times 10^{49}$ erg. If the bubble is approximated by an adiabatic spherical shock wave, the age is estimated to be $tsim 2/5 r_{rm bub}/v_{rm exp}sim 7.2times 10^4$ yr. Neither non-thermal radio structures nor thermal radio emission indicative of the H ii region are found in the archival data from MeerKAT. We suggest that the molecular bubble is a dark supernova remnant buried in the Brick, which has therefore experienced past (${sim}0.1$ Myr ago) massive star formation with a supernova explosion.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504338","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}
Heating of charged particles via collisionless shocks, while ubiquitous in the universe, is an intriguing yet puzzling plasma phenomenon. One outstanding question is how electrons and ions approach an equilibrium after they were heated to different immediate-postshock temperatures. In order to fill the significant lack of observational information of the downstream temperature-relaxation process, we observe a thermal-dominant X-ray filament in the northwest of SN 1006 with Chandra. We divide this region into four layers with a thickness of $15^{prime prime }$ or $0.16:$pc each, and fit each spectrum by a non-equilibrium ionization collisional plasma model. The electron temperature was found to increase toward downstream from 0.52–0.62 to 0.82–$0.95:$keV on a length scale of $60^{prime prime }$ (or $0.64:$pc). This electron temperature is lower than thermal relaxation processes via Coulomb scattering, requiring some other effects such as plasma mixture due to turbulence and/or projection effects, etc., which we hope will be resolved with future X-ray calorimeter missions such as XRISM and Athena.
通过无碰撞冲击加热带电粒子的现象在宇宙中无处不在，是一种有趣而又令人费解的等离子现象。一个悬而未决的问题是，电子和离子在被加热到不同的冲击后即时温度后，是如何接近平衡的。为了填补关于下游温度缓和过程的观测信息的巨大缺失，我们用钱德拉观测到了 SN 1006 西北部的一个热主导 X 射线灯丝。我们把这个区域分成了四层，每层厚度为15^{prime prime }$或0.16:$pc，并用非平衡电离碰撞等离子体模型拟合了每一层的光谱。结果发现，在 60^{prime prime }$ （或 $0.64:$pc）的长度尺度上，电子温度从 0.52-0.62 keV 上升到 0.82-$0.95:$keV。这一电子温度低于通过库仑散射产生的热弛豫过程，需要一些其他效应，如湍流和/或投影效应导致的等离子体混合物等，我们希望未来的X射线量热计任务（如XRISM和雅典娜）能够解决这些问题。
{"title":"Measurement of temperature relaxation in the postshock plasma of the northwestern limb of SN 1006","authors":"Masahiro Ichihashi, Aya Bamba, Yuichi Kato, Satoru Katsuda, Hiromasa Suzuki, Tomoaki Kasuga, Hirokazu Odaka, Kazuhiro Nakazawa","doi":"10.1093/pasj/psae049","DOIUrl":"https://doi.org/10.1093/pasj/psae049","url":null,"abstract":"Heating of charged particles via collisionless shocks, while ubiquitous in the universe, is an intriguing yet puzzling plasma phenomenon. One outstanding question is how electrons and ions approach an equilibrium after they were heated to different immediate-postshock temperatures. In order to fill the significant lack of observational information of the downstream temperature-relaxation process, we observe a thermal-dominant X-ray filament in the northwest of SN 1006 with Chandra. We divide this region into four layers with a thickness of $15^{prime prime }$ or $0.16:$pc each, and fit each spectrum by a non-equilibrium ionization collisional plasma model. The electron temperature was found to increase toward downstream from 0.52–0.62 to 0.82–$0.95:$keV on a length scale of $60^{prime prime }$ (or $0.64:$pc). This electron temperature is lower than thermal relaxation processes via Coulomb scattering, requiring some other effects such as plasma mixture due to turbulence and/or projection effects, etc., which we hope will be resolved with future X-ray calorimeter missions such as XRISM and Athena.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504336","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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