Ionization is important for magnetohydrodynamics and chemistry in protoplanetary disks but known ionization sources are often weak along the midplane. We present, for the first time, data from a laboratory experiment, where we measure ions from colliding mm-basalt grains emitted into the surrounding gas phase. This positive detection implies that very basic collisions in early phases of planet formation are sources of ionization. The midplane of protoplanetary disks might be ionized despite the lack of intense radiation sources.
{"title":"Gas Phase Ions in Protoplanetary Disks from Collisions of Solids","authors":"Jakob Penner, G. Wurm, J. Teiser","doi":"10.1093/mnrasl/slae004","DOIUrl":"https://doi.org/10.1093/mnrasl/slae004","url":null,"abstract":"\u0000 Ionization is important for magnetohydrodynamics and chemistry in protoplanetary disks but known ionization sources are often weak along the midplane. We present, for the first time, data from a laboratory experiment, where we measure ions from colliding mm-basalt grains emitted into the surrounding gas phase. This positive detection implies that very basic collisions in early phases of planet formation are sources of ionization. The midplane of protoplanetary disks might be ionized despite the lack of intense radiation sources.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139444331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The jet composition of GRB plays an important role in understanding the energy dissipation and radiation mechanisms in GRB physics, but it is poorly constrained from the observational data. Recently, an interesting long-duration GRB 230307A with redshift z =0.065 has attracted great attention. The lack of detected thermal emission and mini-structure of prompt emission lightcurve of this burst suggest that the outflow is Poynting-flux-dominated and point towards the ICMART model. In this paper, we invoke two independent methods to investigate the jet composition of GRB 230307A. The high magnetization parameter (σ > 7 or ever large) forR0 = 1010 cm that is used to suppress thermal component, strongly suggests that a significant fraction of the outflow energy is likely in a Poynting flux entrained with the baryonic matter. Moreover, it is found that the radiation efficiency of this burst for typical values εe = 0.1 and εB = 0.01 can reach as high as 50% which disfavors the internal shock model, but is consistent with ICMART model. Finally, a possible unified picture to produce GRB 230307A originated from a compact star merger is also discussed.
GRB的射流成分对理解GRB物理中的能量耗散和辐射机制起着重要作用，但观测数据对它的约束很差。最近，一个有趣的红移 z =0.065 的长持续时间 GRB 230307A 引起了人们的极大关注。该爆发没有探测到热辐射，而且其瞬发光速曲线的小结构表明其外流是以 Poynting 流量为主的，并指向 ICMART 模型。在本文中，我们采用了两种独立的方法来研究 GRB 230307A 的喷流成分。用于抑制热成分的R0 = 1010 cm的高磁化参数（σ > 7或更大）强烈表明，外流能量的很大一部分可能是与重子物质夹杂在一起的Poynting通量。此外，研究还发现，在εe = 0.1和εB = 0.01的典型值下，该爆发的辐射效率可高达50%，这不利于内部冲击模型，但与ICMART模型一致。最后，还讨论了产生源于紧凑星合并的 GRB 230307A 的可能统一图景。
{"title":"The jet composition of GRB 230307A: Poynting-flux-dominated outflow?","authors":"Zhao-Wei Du, HouJun Lü, Xiaoxuan Liu, EnWei Liang","doi":"10.1093/mnrasl/slad203","DOIUrl":"https://doi.org/10.1093/mnrasl/slad203","url":null,"abstract":"\u0000 The jet composition of GRB plays an important role in understanding the energy dissipation and radiation mechanisms in GRB physics, but it is poorly constrained from the observational data. Recently, an interesting long-duration GRB 230307A with redshift z =0.065 has attracted great attention. The lack of detected thermal emission and mini-structure of prompt emission lightcurve of this burst suggest that the outflow is Poynting-flux-dominated and point towards the ICMART model. In this paper, we invoke two independent methods to investigate the jet composition of GRB 230307A. The high magnetization parameter (σ > 7 or ever large) forR0 = 1010 cm that is used to suppress thermal component, strongly suggests that a significant fraction of the outflow energy is likely in a Poynting flux entrained with the baryonic matter. Moreover, it is found that the radiation efficiency of this burst for typical values εe = 0.1 and εB = 0.01 can reach as high as 50% which disfavors the internal shock model, but is consistent with ICMART model. Finally, a possible unified picture to produce GRB 230307A originated from a compact star merger is also discussed.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"32 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139390380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Analyses are given on four recent gravitational millilensing claims on gamma-ray bursts (GRBs): GRB 081122A, GRB 081126A, GRB 110517B, and GRB 210812A. Two tests, a light curve similarity test and a hardness similarity test, compare different temporal sections of a single GRB to see if they are statistically similar. The hardness similarity test shows that the ratio between the second and the first emission episodes in each energy channel differed from the same ratio averaged over all energy channels at above 90 per cent confidence level in GRB 081122A. Additionally, the light curve similarity test applied to GRB 081122A, GRB 081126A, and GRB 110517B separately indicated a high likelihood that the two emission episodes in each GRB were not from the same parent emission episode. This conclusion was reached with confidence levels of 4.8 sigma for GRB 081122A, 3.08 sigma for GRB 081126A, and 8.45 sigma for GRB 110517B. However, these tests did not detect a significant difference between the pulses of GRB 210812A. Consequently, our results suggest that while GRB 210812A could not be conclusively ruled out, the other three GRBs do not show clear evidence of millilensing.
对最近四次关于伽马射线暴（GRB）的引力毫感应索赔进行了分析：GRB 081122A、GRB 081126A、GRB 110517B 和 GRB 210812A。光曲线相似性测试和硬度相似性测试这两项测试比较了单个伽马射线暴的不同时间截面，看它们在统计上是否相似。硬度相似性测试表明，在 GRB 081122A 中，每个能量通道的第二次和第一次发射事件之间的比率与所有能量通道平均值的相同比率之间的差异在 90% 以上的置信水平。此外，对 GRB 081122A、GRB 081126A 和 GRB 110517B 分别进行的光曲线相似性测试表明，每个 GRB 中的两个发射事件很可能不是来自同一个母发射事件。得出这一结论的置信度为：GRB 081122A 为 4.8 sigma，GRB 081126A 为 3.08 sigma，GRB 110517B 为 8.45 sigma。然而，这些测试并没有发现 GRB 210812A 的脉冲之间存在显著差异。因此，我们的结果表明，虽然不能最终排除 GRB 210812A 的可能性，但其他三个 GRB 并没有显示出明显的毫光证据。
{"title":"Light curve and hardness tests for millilensing in GRB 081122A, GRB 081126A, GRB 110517B, and GRB 210812A","authors":"O. Mukherjee, Robert Nemiroff","doi":"10.1093/mnrasl/slad202","DOIUrl":"https://doi.org/10.1093/mnrasl/slad202","url":null,"abstract":"Analyses are given on four recent gravitational millilensing claims on gamma-ray bursts (GRBs): GRB 081122A, GRB 081126A, GRB 110517B, and GRB 210812A. Two tests, a light curve similarity test and a hardness similarity test, compare different temporal sections of a single GRB to see if they are statistically similar. The hardness similarity test shows that the ratio between the second and the first emission episodes in each energy channel differed from the same ratio averaged over all energy channels at above 90 per cent confidence level in GRB 081122A. Additionally, the light curve similarity test applied to GRB 081122A, GRB 081126A, and GRB 110517B separately indicated a high likelihood that the two emission episodes in each GRB were not from the same parent emission episode. This conclusion was reached with confidence levels of 4.8 sigma for GRB 081122A, 3.08 sigma for GRB 081126A, and 8.45 sigma for GRB 110517B. However, these tests did not detect a significant difference between the pulses of GRB 210812A. Consequently, our results suggest that while GRB 210812A could not be conclusively ruled out, the other three GRBs do not show clear evidence of millilensing.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"153 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139145857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report on the discovery of the first ultra metal-poor (UMP) star 2MASS J20500194−6613298 (J2050−6613; [Fe/H] = −4.05) selected from the Gaia BP/RP spectral catalog that belongs to the ancient Atari disk component. We obtained a high-resolution spectrum for the star with the MIKE spectrograph on the Magellan-Clay telescope. J2050−6613 displays a typical chemical abundance pattern for UMP stars, including carbon and zinc enhancements. In contrast, J2050−6613 shows extremely high [Sr/Fe] and [Sr/Ba] ratios compared to other stars in the [Fe/H] <−4.0 regime. J2050−6613 is most likely an early Population II star that formed from a gas cloud that was chemically enriched by a massive Population III hypernova (E >1052 erg). Such a Population III core-collapse hypernova could simultaneously explain the origin of the abundance pattern of light and heavy elements of 2MASS J2050−6613 if a large amount of Sr of ∼10−5 M⊙ was produced, possibly by neutrino-driven (wind) ejecta. Therefore, the abundance pattern of 2MASS J2050−6613 places important constraints on Sr-producing nucleosynthesis sources operating in the Atari progenitor at the earliest times.
{"title":"A Strontium-rich Ultra Metal-poor Star in the Atari Disk Component","authors":"M. Mardini, A. Frebel, A. Chiti","doi":"10.1093/mnrasl/slad197","DOIUrl":"https://doi.org/10.1093/mnrasl/slad197","url":null,"abstract":"We report on the discovery of the first ultra metal-poor (UMP) star 2MASS J20500194−6613298 (J2050−6613; [Fe/H] = −4.05) selected from the Gaia BP/RP spectral catalog that belongs to the ancient Atari disk component. We obtained a high-resolution spectrum for the star with the MIKE spectrograph on the Magellan-Clay telescope. J2050−6613 displays a typical chemical abundance pattern for UMP stars, including carbon and zinc enhancements. In contrast, J2050−6613 shows extremely high [Sr/Fe] and [Sr/Ba] ratios compared to other stars in the [Fe/H] <−4.0 regime. J2050−6613 is most likely an early Population II star that formed from a gas cloud that was chemically enriched by a massive Population III hypernova (E >1052 erg). Such a Population III core-collapse hypernova could simultaneously explain the origin of the abundance pattern of light and heavy elements of 2MASS J2050−6613 if a large amount of Sr of ∼10−5 M⊙ was produced, possibly by neutrino-driven (wind) ejecta. Therefore, the abundance pattern of 2MASS J2050−6613 places important constraints on Sr-producing nucleosynthesis sources operating in the Atari progenitor at the earliest times.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"60 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139169362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose to employ emission line luminosities obtained via optical spectroscopy to estimate the content of neutral hydrogen (HI) in galaxies. We use the optical spectroscopy data from the Mapping of Nearby Galaxies at APO (MaNGA) survey released in the frames of public DR17 of the Sloan Digital Sky Survey (SDSS). We compare the HI mass estimated by us for a large sample of SDSS/MaNGA galaxies with direct HI measurements from the ALFALFA survey and find a tight correlation between the masses with the correlation coefficient (CC) of 0.91 and the r.m.s scatter of 0.15 dex for the logarithmic mass. The obtained relationship is verified via another sample of MaNGA galaxies with HI masses measured with the Green Bank Telescope. Despite the coarser angular resolution of the radio data, the relation between the estimated and measured directly HI mass is tight as well - in this case CC=0.74 and the r.nm.s. is 0.29 dex. The established relations allow us to estimate the total mass of neutral hydrogen as well as the spatial distribution of HI surface density in galaxies from optical spectroscopic observations only in a simple and efficient way.
我们建议利用光谱学获得的发射线光度来估计星系中中性氢的含量。我们使用了在斯隆数字巡天(SDSS)的公共DR17框架中发布的APO (MaNGA)巡天附近星系测绘(Mapping of Nearby Galaxies at APO)的光学光谱数据。我们将我们估计的SDSS/MaNGA星系大样本的HI质量与ALFALFA调查的直接HI测量结果进行了比较，发现质量之间的相关系数(CC)为0.91，对数质量的r.m.s散射指数为0.15。通过另一个用绿岸望远镜测量的具有HI质量的MaNGA星系样本，验证了所获得的关系。尽管射电数据的角分辨率较粗，但估算和直接测量的HI质量之间的关系也很紧密——在这种情况下，CC=0.74和r.nms。是0.29指数。建立的关系式使我们能够简单而有效地从光谱观测中估计出星系中中性氢的总质量和HI表面密度的空间分布。
{"title":"The Neutral Hydrogen Mass in Galaxies Estimated via Optical Spectroscopy","authors":"D. Bizyaev","doi":"10.1093/mnrasl/slad186","DOIUrl":"https://doi.org/10.1093/mnrasl/slad186","url":null,"abstract":"\u0000 We propose to employ emission line luminosities obtained via optical spectroscopy to estimate the content of neutral hydrogen (HI) in galaxies. We use the optical spectroscopy data from the Mapping of Nearby Galaxies at APO (MaNGA) survey released in the frames of public DR17 of the Sloan Digital Sky Survey (SDSS). We compare the HI mass estimated by us for a large sample of SDSS/MaNGA galaxies with direct HI measurements from the ALFALFA survey and find a tight correlation between the masses with the correlation coefficient (CC) of 0.91 and the r.m.s scatter of 0.15 dex for the logarithmic mass. The obtained relationship is verified via another sample of MaNGA galaxies with HI masses measured with the Green Bank Telescope. Despite the coarser angular resolution of the radio data, the relation between the estimated and measured directly HI mass is tight as well - in this case CC=0.74 and the r.nm.s. is 0.29 dex. The established relations allow us to estimate the total mass of neutral hydrogen as well as the spatial distribution of HI surface density in galaxies from optical spectroscopic observations only in a simple and efficient way.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"56 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138600590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The origin of repeating fast radio bursts (RFRBs) is still a mystery. We propose that short-lived RFRBs might be triggered from the tidal disruption of white dwarfs (WDs) by intermediate-mass black holes (BHs). In this model, we show that the remnant WD clusters after tidal collapse cuts the magnetic lines on the BH accretion discs, and during each fall of the clump, so that electrons are torn from the surface of the mass and instantly accelerated to the relativistic energy. The subsequent movement of these electrons along magnetic field lines will result in coherent curvature radiation. This short-lived radio transients might accompany with the accretion process. The luminosity and the timescale can be estimated to be Ltot ∼ 1.96 × 1040 erg s−1 and Δt ∼ 1.14 ms, respectively, which are consistent with the typical properties of RFRBs. Moreover, the total event rate of our model for generating RFRBs might be as high as $sim 10~rm {yr^{-1}~Gpc^{-3}}$.
{"title":"Short-lived repeating fast radio bursts from tidal disruption of white dwarfs by intermediate-mass black holes","authors":"Jing-Tong Xing, Tong Liu","doi":"10.1093/mnrasl/slad187","DOIUrl":"https://doi.org/10.1093/mnrasl/slad187","url":null,"abstract":"\u0000 The origin of repeating fast radio bursts (RFRBs) is still a mystery. We propose that short-lived RFRBs might be triggered from the tidal disruption of white dwarfs (WDs) by intermediate-mass black holes (BHs). In this model, we show that the remnant WD clusters after tidal collapse cuts the magnetic lines on the BH accretion discs, and during each fall of the clump, so that electrons are torn from the surface of the mass and instantly accelerated to the relativistic energy. The subsequent movement of these electrons along magnetic field lines will result in coherent curvature radiation. This short-lived radio transients might accompany with the accretion process. The luminosity and the timescale can be estimated to be Ltot ∼ 1.96 × 1040 erg s−1 and Δt ∼ 1.14 ms, respectively, which are consistent with the typical properties of RFRBs. Moreover, the total event rate of our model for generating RFRBs might be as high as $sim 10~rm {yr^{-1}~Gpc^{-3}}$.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"71 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138600518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we explore the dynamical stability of magnetar bursts within the context of the chaos-randomness phase space for the first time, aiming to uncover unique behaviors compared to various astrophysical transients, including fast radio bursts (FRBs). We analyze burst energy time series data from active magnetar sources SGR J1550−5418 and SGR J1935+2154, focusing on burst arrival time and energy differences between consecutive events. We find a distinct separation in the time domain, where magnetar bursts exhibit significantly lower randomness compared to FRBs, solar flares, and earthquakes, with a slightly higher degree of chaos. In the energy domain, magnetar bursts exhibit a broad consistency with other phenomena, primarily due to the wide distribution of chaos-randomness observed across different bursts and sources. Intriguingly, contrary to expectations from the FRB-magnetar connection, the arrival time patterns of magnetar bursts in our analysis do not exhibit significant proximity to repeating FRBs in the chaos-randomness plane. This finding may challenge the hypothesis that FRBs are associated with typical magnetar bursts but indirectly supports the evidence that FRBs may primarily be linked to special magnetar bursts like peculiar X-ray bursts from SGR J1935+2154 observed simultaneously with Galactic FRB 200428.
{"title":"Quantifying chaos and randomness in magnetar bursts","authors":"S. Yamasaki, E. Göğüş, T. Hashimoto","doi":"10.1093/mnrasl/slad184","DOIUrl":"https://doi.org/10.1093/mnrasl/slad184","url":null,"abstract":"\u0000 In this study, we explore the dynamical stability of magnetar bursts within the context of the chaos-randomness phase space for the first time, aiming to uncover unique behaviors compared to various astrophysical transients, including fast radio bursts (FRBs). We analyze burst energy time series data from active magnetar sources SGR J1550−5418 and SGR J1935+2154, focusing on burst arrival time and energy differences between consecutive events. We find a distinct separation in the time domain, where magnetar bursts exhibit significantly lower randomness compared to FRBs, solar flares, and earthquakes, with a slightly higher degree of chaos. In the energy domain, magnetar bursts exhibit a broad consistency with other phenomena, primarily due to the wide distribution of chaos-randomness observed across different bursts and sources. Intriguingly, contrary to expectations from the FRB-magnetar connection, the arrival time patterns of magnetar bursts in our analysis do not exhibit significant proximity to repeating FRBs in the chaos-randomness plane. This finding may challenge the hypothesis that FRBs are associated with typical magnetar bursts but indirectly supports the evidence that FRBs may primarily be linked to special magnetar bursts like peculiar X-ray bursts from SGR J1935+2154 observed simultaneously with Galactic FRB 200428.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":" 754","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138610563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Zheltobryukhov, E. Zubko, E. Chornaya, A. Kochergin, D. Hines, G. Videen
On September 6 and 7 of 2023, we measured the degree of linear polarization of Comet C/2023 P1 (Nishimura) with the R filter. Our observations reveal an extremely low amplitude of positive polarization. Our modeling suggests Mg-rich silicate dust particles are the dominant species in the coma; whereas, an alternative explanation is that such low positive polarization in comets is attributed to the depolarizing effect of their gaseous emission. These two alternative explanations predict dramatically different polarimetric responses at small phase angle that can be discriminated in future polarimetric observations of Comet C/2023 P1 (Nishimura).
{"title":"On the extremely low polarization in Comet C/2023 P1 (Nishimura)","authors":"M. Zheltobryukhov, E. Zubko, E. Chornaya, A. Kochergin, D. Hines, G. Videen","doi":"10.1093/mnrasl/slad181","DOIUrl":"https://doi.org/10.1093/mnrasl/slad181","url":null,"abstract":"On September 6 and 7 of 2023, we measured the degree of linear polarization of Comet C/2023 P1 (Nishimura) with the R filter. Our observations reveal an extremely low amplitude of positive polarization. Our modeling suggests Mg-rich silicate dust particles are the dominant species in the coma; whereas, an alternative explanation is that such low positive polarization in comets is attributed to the depolarizing effect of their gaseous emission. These two alternative explanations predict dramatically different polarimetric responses at small phase angle that can be discriminated in future polarimetric observations of Comet C/2023 P1 (Nishimura).","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"252 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139221560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By performing global hydrodynamical simulations of accretion discs with driven turbulence models, we demonstrate that elevated levels of turbulence induce highly stochastic migration torques on low-mass companions embedded in these discs. This scenario applies to planets migrating within gravito-turbulent regions of protoplanetary discs as well as stars and black holes embedded in the outskirts of active galactic nuclei (AGN) accretion discs. When the turbulence level is low, linear Lindblad torques persists in the background of stochastic forces and its accumulative effect can still dominate over relatively long timescales. However, in the presence of very stronger turbulence, classical flow patterns around the companion embedded in the disc are disrupted, leading to significant deviations from the expectations of classical Type I migration theory over arbitrarily long timescales. Our findings suggest that the stochastic nature of turbulent migration can prevent low-mass companions from monotonically settling into universal migration traps within the traditional laminar disc framework, thus reducing the frequency of three-body interactions and hierarchical mergers compared to previously expected. We propose a scaling for the transition mass ratio from classical to chaotic migration q∝αR, where αR is the Reynolds viscosity stress parameter, which can be further tested and refined by conducting extensive simulations over the relevant parameter space.
通过利用驱动湍流模型对吸积盘进行全局流体力学模拟，我们证明了高水平的湍流会对嵌入这些盘中的低质量伴星产生高度随机的迁移力矩。这种情况适用于在原行星盘重力湍流区域内迁移的行星，以及嵌入活动星系核（AGN）吸积盘外围的恒星和黑洞。当湍流水平较低时，线性林德布拉德力矩会在随机力的背景下持续存在，其累积效应在相对较长的时间尺度内仍会占主导地位。然而，在湍流非常强烈的情况下，嵌入圆盘的伴星周围的经典流动模式会被打乱，导致在任意长的时间尺度上严重偏离经典的 I 型迁移理论的预期。我们的研究结果表明，湍流迁移的随机性会阻止低质量伴星在传统层状圆盘框架内单调地沉降到普遍迁移陷阱中，从而降低三体相互作用和分层合并的频率，而这是之前所预期的。我们提出了一个从经典迁移到混沌迁移的质量过渡比q∝αR，其中αR是雷诺粘滞应力参数。
{"title":"Chaotic Type I Migration in Turbulent Discs","authors":"Yinhao Wu, Yi-Xian Chen, Douglas N C Lin","doi":"10.1093/mnrasl/slad183","DOIUrl":"https://doi.org/10.1093/mnrasl/slad183","url":null,"abstract":"By performing global hydrodynamical simulations of accretion discs with driven turbulence models, we demonstrate that elevated levels of turbulence induce highly stochastic migration torques on low-mass companions embedded in these discs. This scenario applies to planets migrating within gravito-turbulent regions of protoplanetary discs as well as stars and black holes embedded in the outskirts of active galactic nuclei (AGN) accretion discs. When the turbulence level is low, linear Lindblad torques persists in the background of stochastic forces and its accumulative effect can still dominate over relatively long timescales. However, in the presence of very stronger turbulence, classical flow patterns around the companion embedded in the disc are disrupted, leading to significant deviations from the expectations of classical Type I migration theory over arbitrarily long timescales. Our findings suggest that the stochastic nature of turbulent migration can prevent low-mass companions from monotonically settling into universal migration traps within the traditional laminar disc framework, thus reducing the frequency of three-body interactions and hierarchical mergers compared to previously expected. We propose a scaling for the transition mass ratio from classical to chaotic migration q∝αR, where αR is the Reynolds viscosity stress parameter, which can be further tested and refined by conducting extensive simulations over the relevant parameter space.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139233541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pengfei Jiang, Lang Cui, Xiang Liu, Bo Zhang, Yongfeng Huang, H. Cao, Tao An, Jun Yang, Fengchun Shu, Guiping Tan, J. Yuan
LAMOST J024048.51+195226.9 (J0240+1952) was recently identified as the second AE Aqr-type cataclysmic variable, possessing the fastest known rotating white dwarf. We performed a Very Long Baseline Interferometry (VLBI) observation of J0240+1952 utilizing the European VLBI Network at 1.7 GHz, to obtain the first view of the radio morphology on mas-scale. Our high-resolution VLBI image clearly shows that the radio emission is compact on mas-scale (≲ 2 AU), with no evidence for a radio jet or extended emission. The compact radio source has an average flux density of ∼0.37 mJy, and its brightness temperature is given at ≳ 2.3 × 107 K, confirming a non-thermal origin. The emission exhibits irregular variations on a timescale of tens of minutes, similar to the radio flares seen in AE Aqr. The measured VLBI position of J0240+1952 is consistent with that derived from Gaia. Our results favour the model in which the radio emission is attributed to a superposition of synchrotron radiation from expanding magnetized blobs of this system.
{"title":"VLBI detection of the AE Aqr twin, LAMOST J024048.51+195226.9","authors":"Pengfei Jiang, Lang Cui, Xiang Liu, Bo Zhang, Yongfeng Huang, H. Cao, Tao An, Jun Yang, Fengchun Shu, Guiping Tan, J. Yuan","doi":"10.1093/mnrasl/slad178","DOIUrl":"https://doi.org/10.1093/mnrasl/slad178","url":null,"abstract":"LAMOST J024048.51+195226.9 (J0240+1952) was recently identified as the second AE Aqr-type cataclysmic variable, possessing the fastest known rotating white dwarf. We performed a Very Long Baseline Interferometry (VLBI) observation of J0240+1952 utilizing the European VLBI Network at 1.7 GHz, to obtain the first view of the radio morphology on mas-scale. Our high-resolution VLBI image clearly shows that the radio emission is compact on mas-scale (≲ 2 AU), with no evidence for a radio jet or extended emission. The compact radio source has an average flux density of ∼0.37 mJy, and its brightness temperature is given at ≳ 2.3 × 107 K, confirming a non-thermal origin. The emission exhibits irregular variations on a timescale of tens of minutes, similar to the radio flares seen in AE Aqr. The measured VLBI position of J0240+1952 is consistent with that derived from Gaia. Our results favour the model in which the radio emission is attributed to a superposition of synchrotron radiation from expanding magnetized blobs of this system.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139248936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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