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":"31 1","pages":""},"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":"161 1","pages":""},"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":"159 1","pages":""},"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":"147 1","pages":""},"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":"6 1","pages":""},"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}
In our previous study (Tsukamoto et al. 2023b, PASJ, 75, 835), we investigated the formation and early evolution of protoplanetary disks with 3D non-ideal magnetohydrodynamics simulations considering dust growth, and found that the modified equations of the conventional steady accretion disk model that consider magnetic braking, dust growth, and ambipolar diffusion reproduce the disk structure (such as density and vertical magnetic field) obtained from simulations very well. In this paper, as a sequel to our previous study, we analytically investigate the structure and evolution of protoplanetary disks corresponding to Class 0/I young stellar objects using the modified steady accretion disk model combining an analytical model of envelope accretion. We estimate that the disk radius is several astronomical units at the disk formation epoch and increases to several hundred astronomical units at the end of the accretion phase. The disk mass is estimated to be $0.01 lesssim M_{rm disk} lesssim 0.1 , M_odot$ for a disk with a radius of several tens of astronomical units and a mass accretion rate of $dot{M}_{rm disk} sim 10^{-6} , M_odot ,, {rm yr^{-1}}$. These estimates seems to be consistent with recent observations. We also found that, with typical disk ionization rates (ζ ≳ 10−19 s−1) and a moderate mass accretion rate ($dot{M}_{rm disk}gtrsim 10^{-8} , M_odot ,, {rm yr^{-1}}$), magnetorotational instability is suppressed in the disk because of low plasma β and efficient ambipolar diffusion. We argue that the radial profile of specific angular momentum (or rotational velocity) at the disk outer edge should be continuously connected to that of the envelope if the disk evolves by magnetic braking, and should be discontinuous if the disk evolves by an internal angular momentum transport process such as gravitational instability or magnetorotational instability. Future detailed observations of the specific angular momentum profile around the disk outer edge are important for understanding the angular momentum transport mechanism of protoplanetary disks.
{"title":"Co-evolution of dust grains and protoplanetary disks. II. Structure and evolution of protoplanetary disks: An analytical approach","authors":"Yusuke Tsukamoto","doi":"10.1093/pasj/psae039","DOIUrl":"https://doi.org/10.1093/pasj/psae039","url":null,"abstract":"In our previous study (Tsukamoto et al. 2023b, PASJ, 75, 835), we investigated the formation and early evolution of protoplanetary disks with 3D non-ideal magnetohydrodynamics simulations considering dust growth, and found that the modified equations of the conventional steady accretion disk model that consider magnetic braking, dust growth, and ambipolar diffusion reproduce the disk structure (such as density and vertical magnetic field) obtained from simulations very well. In this paper, as a sequel to our previous study, we analytically investigate the structure and evolution of protoplanetary disks corresponding to Class 0/I young stellar objects using the modified steady accretion disk model combining an analytical model of envelope accretion. We estimate that the disk radius is several astronomical units at the disk formation epoch and increases to several hundred astronomical units at the end of the accretion phase. The disk mass is estimated to be $0.01 lesssim M_{rm disk} lesssim 0.1 , M_odot$ for a disk with a radius of several tens of astronomical units and a mass accretion rate of $dot{M}_{rm disk} sim 10^{-6} , M_odot ,, {rm yr^{-1}}$. These estimates seems to be consistent with recent observations. We also found that, with typical disk ionization rates (ζ ≳ 10−19 s−1) and a moderate mass accretion rate ($dot{M}_{rm disk}gtrsim 10^{-8} , M_odot ,, {rm yr^{-1}}$), magnetorotational instability is suppressed in the disk because of low plasma β and efficient ambipolar diffusion. We argue that the radial profile of specific angular momentum (or rotational velocity) at the disk outer edge should be continuously connected to that of the envelope if the disk evolves by magnetic braking, and should be discontinuous if the disk evolves by an internal angular momentum transport process such as gravitational instability or magnetorotational instability. Future detailed observations of the specific angular momentum profile around the disk outer edge are important for understanding the angular momentum transport mechanism of protoplanetary disks.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529029","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}
Odd radio circles (ORCs) are mysterious rings of faint, diffuse emission recently discovered in radio surveys, some of which may be associated with galaxies in relatively dense environments. We propose that such ORCs are synchrotron emission from remnants of explosive galactic outflows, calling them OGREs, and discuss their broad-band non-thermal emission and evolution. We posit that a large amount of energy was ejected from the central galaxy in the past, creating an outgoing shock that accelerates cosmic rays. Assuming plausible values for the density, temperature and magnetic field of the ambient medium, consistency with the observed spectral index, size, and power of the ORCs requires the energy to be as high as ∼1060 erg, suggesting that their sources could be active galactic nuclei. We calculate the spectral energy distributions (SEDs) of the OGREs and their evolution, including synchrotron, inverse Compton (IC), and bremsstrahlung emission from electrons, and pion-decay emission from protons. We find that the SEDs of the younger OGREs are not greatly different from those of older ones currently observable as ORCs if radiative cooling of electrons is effective. As such younger OGREs are expected to be rarer and smaller, they may not be readily observable. However, if radiative cooling of electrons is ineffective, younger OGREs may be detectable in X-rays.
古怪射电圈（ORCs）是最近在射电巡天中发现的神秘的微弱弥散发射环，其中一些可能与处于相对致密环境中的星系有关。我们认为这些射电怪圈是星系爆炸性流出的残余物发出的同步辐射，称之为射电怪圈（OGREs），并讨论了它们的宽波段非热辐射和演化。我们假设过去有大量的能量从中央星系喷射出来，形成了外流冲击，加速了宇宙射线。假定环境介质的密度、温度和磁场值是可信的，要与观测到的ORC的光谱指数、大小和功率相一致，其能量必须高达∼1060 erg，这表明它们的来源可能是活动星系核。我们计算了OGREs的光谱能量分布（SEDs）及其演化过程，包括电子的同步辐射、反康普顿辐射（IC）和轫致辐射，以及质子的先驱衰变辐射。我们发现，如果电子的辐射冷却是有效的，那么较年轻的 OGREs 的 SED 与目前作为 ORC 观测到的较老的 OGREs 的 SED 并无太大区别。由于较年轻的 OGREs 比较罕见，体积也较小，因此可能不容易观测到。不过，如果电子的辐射冷却无效，较年轻的 OGRE 可能会在 X 射线中被探测到。
{"title":"Broad-band non-thermal emission of odd radio circles induced by explosive galactic outflow remnants and their evolution","authors":"Yutaka Fujita, Norita Kawanaka, Susumu Inoue","doi":"10.1093/pasj/psae046","DOIUrl":"https://doi.org/10.1093/pasj/psae046","url":null,"abstract":"Odd radio circles (ORCs) are mysterious rings of faint, diffuse emission recently discovered in radio surveys, some of which may be associated with galaxies in relatively dense environments. We propose that such ORCs are synchrotron emission from remnants of explosive galactic outflows, calling them OGREs, and discuss their broad-band non-thermal emission and evolution. We posit that a large amount of energy was ejected from the central galaxy in the past, creating an outgoing shock that accelerates cosmic rays. Assuming plausible values for the density, temperature and magnetic field of the ambient medium, consistency with the observed spectral index, size, and power of the ORCs requires the energy to be as high as ∼1060 erg, suggesting that their sources could be active galactic nuclei. We calculate the spectral energy distributions (SEDs) of the OGREs and their evolution, including synchrotron, inverse Compton (IC), and bremsstrahlung emission from electrons, and pion-decay emission from protons. We find that the SEDs of the younger OGREs are not greatly different from those of older ones currently observable as ORCs if radiative cooling of electrons is effective. As such younger OGREs are expected to be rarer and smaller, they may not be readily observable. However, if radiative cooling of electrons is ineffective, younger OGREs may be detectable in X-rays.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"26 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504339","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}
Fumi Yoshida, Toshifumi Yanagisawa, Takashi Ito, Hirohisa Kurosaki, Makoto Yoshikawa, Kohki Kamiya, Ji-an Jiang, Alan Stern, Wesley C Fraser, Susan D Benecchi, Anne J Verbiscer
Observation datasets acquired by the Hyper Suprime-Cam (HSC) on the Subaru Telescope for NASA’s New Horizons mission target search were analyzed through a method devised by JAXA. The method makes use of Field Programmable Gate arrays and was originally used to detect fast-moving objects such as space debris or near-Earth asteroids. Here we present an application of the method to detect slow-moving Kuiper Belt Objects (KBOs) in the New Horizons target search observations. A cadence that takes continuous images of one HSC field of view for half a night fits the method well. The observations for the New Horizons Kuiper Belt Extended Mission (NH/KEM) using HSC began in 2020 May, and are ongoing. Here we show our result of the analysis of the dataset acquired from 2020 May through 2021 June that have already passed the proprietary period and are open to the public. We detected 84 KBO candidates in the 2020 June and 2021 June datasets, when the observation field was close to opposition.
{"title":"A deep analysis for New Horizons’ KBO search images","authors":"Fumi Yoshida, Toshifumi Yanagisawa, Takashi Ito, Hirohisa Kurosaki, Makoto Yoshikawa, Kohki Kamiya, Ji-an Jiang, Alan Stern, Wesley C Fraser, Susan D Benecchi, Anne J Verbiscer","doi":"10.1093/pasj/psae043","DOIUrl":"https://doi.org/10.1093/pasj/psae043","url":null,"abstract":"Observation datasets acquired by the Hyper Suprime-Cam (HSC) on the Subaru Telescope for NASA’s New Horizons mission target search were analyzed through a method devised by JAXA. The method makes use of Field Programmable Gate arrays and was originally used to detect fast-moving objects such as space debris or near-Earth asteroids. Here we present an application of the method to detect slow-moving Kuiper Belt Objects (KBOs) in the New Horizons target search observations. A cadence that takes continuous images of one HSC field of view for half a night fits the method well. The observations for the New Horizons Kuiper Belt Extended Mission (NH/KEM) using HSC began in 2020 May, and are ongoing. Here we show our result of the analysis of the dataset acquired from 2020 May through 2021 June that have already passed the proprietary period and are open to the public. We detected 84 KBO candidates in the 2020 June and 2021 June datasets, when the observation field was close to opposition.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"41 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141188934","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}
Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this context, we studied the X-ray emissions from ZTF J190132.9+145808.7 (hereafter ZTF J1901+14), a notable massive isolated WD in the Galaxy, using the Chandra X-ray observatory. Our results showed 3.5σ level evidence of X-ray signals, although it is marginal. Under the assumption of a photon index of 2, we derived its intrinsic flux to be 2.3 (0.9–4.7) × 10−15 erg cm−2 s−1 and luminosity 4.6 (2.0–9.5) × 1026 erg s−1 for a 0.5–7 keV band in the $90%$ confidence range, given its distance of 41 pc. We derived the X-ray efficiency (η) concerning the spin-down luminosity to be 0.012 (0.0022–0.074), a value comparable to that of ordinary neutron star pulsars. The inferred X-ray luminosity may be compatible with curvature radiation from sub-TeV electrons accelerated within open magnetic fields in the magnetosphere of ZTF J1901+14. Conducting more extensive X-ray observations is crucial to confirm whether ZTF J1901+14-like isolated WDs are also significant sources of X-rays and sub-TeV electron cosmic rays, similar to other WD pulsars in accreting systems.
强磁化、快速旋转的大质量白矮星（WDs）是双变性合并的潜在结果。这些白矮星可以作为非热辐射和宇宙射线的来源，作为白矮星脉冲星而受到关注。在这种情况下，我们利用钱德拉 X 射线天文台研究了银河系中一个著名的大质量孤立 WD--ZTF J190132.9+145808.7（以下简称 ZTF J1901+14）的 X 射线辐射。我们的研究结果显示了 3.5σ 级的 X 射线信号证据，尽管这种证据很微弱。在光子指数为2的假设下，我们推导出它的本征通量为2.3（0.9-4.7）×10-15 erg cm-2 s-1，光度为4.6（2.0-9.5）×1026 erg s-1，波段为0.5-7 keV，置信度范围为90%$，考虑到它的距离为41 pc。我们推导出有关自旋下降光度的X射线效率（η）为0.012（0.0022-0.074），这个值与普通中子星脉冲星的效率相当。推断出的X射线光度可能与ZTF J1901+14磁层中开放磁场内加速的亚TeV电子产生的曲率辐射相吻合。进行更广泛的X射线观测对于确认类似ZTF J1901+14的孤立WD是否也是X射线和亚TeV电子宇宙射线的重要来源至关重要，这一点与吸积系统中的其他WD脉冲星类似。
{"title":"On the X-ray efficiency of the white dwarf pulsar candidate ZTF J190132.9+145808.7","authors":"Aya Bamba, Yukikatsu Terada, Kazumi Kashiyama, Shota Kisaka, Takahiro Minami, Tadayuki Takahashi","doi":"10.1093/pasj/psae041","DOIUrl":"https://doi.org/10.1093/pasj/psae041","url":null,"abstract":"Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this context, we studied the X-ray emissions from ZTF J190132.9+145808.7 (hereafter ZTF J1901+14), a notable massive isolated WD in the Galaxy, using the Chandra X-ray observatory. Our results showed 3.5σ level evidence of X-ray signals, although it is marginal. Under the assumption of a photon index of 2, we derived its intrinsic flux to be 2.3 (0.9–4.7) × 10−15 erg cm−2 s−1 and luminosity 4.6 (2.0–9.5) × 1026 erg s−1 for a 0.5–7 keV band in the $90%$ confidence range, given its distance of 41 pc. We derived the X-ray efficiency (η) concerning the spin-down luminosity to be 0.012 (0.0022–0.074), a value comparable to that of ordinary neutron star pulsars. The inferred X-ray luminosity may be compatible with curvature radiation from sub-TeV electrons accelerated within open magnetic fields in the magnetosphere of ZTF J1901+14. Conducting more extensive X-ray observations is crucial to confirm whether ZTF J1901+14-like isolated WDs are also significant sources of X-rays and sub-TeV electron cosmic rays, similar to other WD pulsars in accreting systems.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"42 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141146902","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 correlation analyses between the 12CO and 13CO J = 1–0 line intensities in order to derive the variability of the CO-to-H2 conversion factor (XCO,iso) in the central molecular zone (CMZ) of our Galaxy. New high-resolution XCO,iso maps at a resolution of ∼30″ and a longitude–velocity diagram (LVD) at resolution ${sim }{30^{primeprime}}times 2$ km s−1 are presented using the 12CO and 13CO archival survey data obtained by the Nobeyama 45 m telescope. We revealed the variation of XCO,iso in the CMZ within the range of XCO,iso ∼ (0.2–1.3) × 1020 cm−2 (K km s−1)−1, if we assume a normalization value of 0.59 × 1020 cm−2 (K km s−1)−1. The mean value is obtained as XCO,iso = (0.48 ± 0.15) × 1020 cm−2 (K km s−1)−1 in the CMZ of our Galaxy.
我们对12CO和13CO J = 1-0线强度进行了相关分析，以得出银河系中央分子区（CMZ）的CO-H2转换因子（XCO,iso）的变化情况。我们利用野边山45米望远镜获得的12CO和13CO档案巡天数据，绘制了新的分辨率为30″的高分辨率XCO,iso图和分辨率为2$ km s-1的经向速度图（LVD）。如果假设归一化值为 0.59 × 1020 cm-2 (K km s-1)-1，我们揭示了 CMZ 中 XCO,iso ∼ (0.2-1.3) × 1020 cm-2 (K km s-1)-1 范围内的变化。在银河系的 CMZ 中，平均值为 XCO,iso = (0.48 ± 0.15) × 1020 cm-2 (K km s-1)-1。
{"title":"The CO-to-H2 conversion factor in the Central Molecular Zone of the Milky Way using CO isotopologues","authors":"Mikito Kohno, Yoshiaki Sofue","doi":"10.1093/pasj/psae033","DOIUrl":"https://doi.org/10.1093/pasj/psae033","url":null,"abstract":"We performed correlation analyses between the 12CO and 13CO J = 1–0 line intensities in order to derive the variability of the CO-to-H2 conversion factor (XCO,iso) in the central molecular zone (CMZ) of our Galaxy. New high-resolution XCO,iso maps at a resolution of ∼30″ and a longitude–velocity diagram (LVD) at resolution ${sim }{30^{primeprime}}times 2$ km s−1 are presented using the 12CO and 13CO archival survey data obtained by the Nobeyama 45 m telescope. We revealed the variation of XCO,iso in the CMZ within the range of XCO,iso ∼ (0.2–1.3) × 1020 cm−2 (K km s−1)−1, if we assume a normalization value of 0.59 × 1020 cm−2 (K km s−1)−1. The mean value is obtained as XCO,iso = (0.48 ± 0.15) × 1020 cm−2 (K km s−1)−1 in the CMZ of our Galaxy.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"48 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141146904","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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