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On the Possible Asymmetry in Gamma Rays from Andromeda Due to Inverse Compton Scattering of Star Light on Electrons from Dark Matter Annihilation 由于恒星光对暗物质湮灭电子的逆康普顿散射,仙女座伽玛射线可能存在不对称性
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-11-07 DOI: 10.3390/galaxies11060109
Konstantin Belotsky, Maxim Solovyov
Dark matter is a popular candidate to a new source of primary-charged particles, especially positrons in cosmic rays, which are proposed to account for observable anomalies. While this hypothesis of decaying or annihilating DM is mostly applied for our Galaxy, it could possibly lead to some interesting phenomena when applied for the other ones. In this work, we look into the hypothetical asymmetry in gamma radiation from the upper and lower hemisphere of the dark matter halo of the Andromeda galaxy due to inverse Compton scattering of starlight on the DM-produced electrons and positrons. While our 2D toy model raises expectations for the possible effect, a more complex approach gives negligible effect for the dark halo case, but shows some prospects for a dark disk model.
暗物质是主要带电粒子(尤其是宇宙射线中的正电子)新来源的热门候选物质,它们被认为可以解释可观察到的异常现象。虽然这种DM衰变或湮灭的假设主要适用于我们的银河系,但当它应用于其他星系时,可能会导致一些有趣的现象。在这项工作中,我们研究了仙女座星系暗物质晕的上半球和下半球伽马辐射的假设不对称性,这是由于星光对dm产生的电子和正电子的反向康普顿散射。虽然我们的2D玩具模型提高了对可能效果的期望,但一个更复杂的方法对暗晕的情况几乎没有影响,但对暗盘模型显示了一些前景。
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引用次数: 0
Fueling Processes on (Sub-)kpc Scales kpc以下尺度的燃料过程
IF 2.5 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-11-06 DOI: 10.3390/galaxies11060120
F. Combes
Since the 1970s, astronomers have struggled with the issue of how matter can be accreted to promote black-hole growth. While low-angular-momentum stars may be devoured by a black hole, they are not a sustainable source of fuel. Gas, which could potentially provide an abundant fuel source, presents another challenge due to its enormous angular momentum. While viscous torques are not significant, gas is subject to gravity torques from non-axisymmetric potentials such as bars and spirals. Primary bars can exchange angular momentum with the gas within corotation, causing it to spiral inwards until reaching the inner Lindblad resonance. An embedded nuclear bar can then take over. As the gas reaches the black hole’s sphere of influence, the torque becomes negative, fueling the center. Dynamical friction also accelerates the infall of gas clouds closer to the nucleus. However, because of the Eddington limit, growing a black hole from a stellar-mass seed is a slow process. The existence of very massive black holes in the early universe remains a puzzle that could potentially be solved through direct collapse of massive clouds into black holes or super-Eddington accretion.
自 20 世纪 70 年代以来,天文学家一直在苦苦思索如何增殖物质以促进黑洞生长的问题。虽然低角动量恒星可能会被黑洞吞噬,但它们并不是可持续的燃料来源。气体有可能提供丰富的燃料来源,但由于其巨大的角动量,它也面临着另一个挑战。虽然粘滞力矩并不显著,但气体会受到非轴对称势能(如条状和螺旋状)产生的重力力矩的影响。原生条带可以与冠层内的气体交换角动量,导致气体向内螺旋,直至达到内部林德布拉德共振。然后,内嵌的核棒就会接替它。当气体到达黑洞的影响范围时,扭矩就会变成负值,为中心提供动力。动力摩擦也会加速气体云向更靠近核的方向下坠。然而,由于爱丁顿极限的存在,从恒星质量的种子生长出黑洞是一个缓慢的过程。早期宇宙中是否存在超大质量黑洞仍然是一个谜题,有可能通过大质量云直接坍缩成黑洞或超爱丁顿吸积来解决。
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引用次数: 0
The Structure of Micro-Variability in the WEBT BL Lacertae Observation WEBT BL观测中微变异性的结构
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-11-01 DOI: 10.3390/galaxies11060108
James R. Webb, Ivan Parra Sanz
We present the results of an in-depth analysis of the Whole Earth Blazar Telescope (WEBT) micro-variability observations made during a campaign done in 2020 on the blazar BL Lacertae. The data consisted of 231 days of optical imaging and we separated the long-term light curve into individual single-night light curves, and then chose 41 nights that contained over 100 individual observations and also showed micro-variations well above the noise. Micro-variability is defined as excursions in the order of 0.01–0.1 magnitudes over timescales of hours or minutes either above or below a linear background sampled over the entire night. We then fit each individual micro-variability curve with model pulses from turbulent cells using the turbulent jet model.. We present the results of the pulse fitting analysis, which yields turbulent cell sizes, amplitudes and turbulent plasma characteristics.
我们介绍了对全球Blazar望远镜(WEBT)在2020年对Blazar BL Lacertae进行的一次活动中进行的微变化观测进行深入分析的结果。数据由231天的光学成像组成,我们将长期光曲线分离为单个单夜光曲线,然后选择41个夜晚,其中包含超过100个单独的观测,并且也显示出远高于噪声的微变化。微变异性被定义为在整晚采样的线性背景之上或之下,在以小时或分钟为时间尺度的0.01-0.1量级的偏移。然后,我们使用湍流射流模型将每个个体的微变异性曲线与湍流细胞的模型脉冲拟合。我们提出了脉冲拟合分析的结果,它产生了湍流细胞的大小,振幅和湍流等离子体的特性。
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引用次数: 0
Reference Array and Design Consideration for the Next-Generation Event Horizon Telescope 新一代视界望远镜参考阵列及设计考虑
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-10-18 DOI: 10.3390/galaxies11050107
Sheperd S. Doeleman, John Barrett, Lindy Blackburn, Katherine L. Bouman, Avery E. Broderick, Ryan Chaves, Vincent L. Fish, Garret Fitzpatrick, Mark Freeman, Antonio Fuentes, José L. Gómez, Kari Haworth, Janice Houston, Sara Issaoun, Michael D. Johnson, Mark Kettenis, Laurent Loinard, Neil Nagar, Gopal Narayanan, Aaron Oppenheimer, Daniel C. M. Palumbo, Nimesh Patel, Dominic W. Pesce, Alexander W. Raymond, Freek Roelofs, Ranjani Srinivasan, Paul Tiede, Jonathan Weintroub, Maciek Wielgus
We describe the process to design, architect, and implement a transformative enhancement of the Event Horizon Telescope (EHT). This program—the next-generation Event Horizon Telescope (ngEHT)—will form a networked global array of radio dishes capable of making high-fidelity real-time movies of supermassive black holes (SMBH) and their emanating jets. This builds upon the EHT principally by deploying additional modest-diameter dishes to optimized geographic locations to enhance the current global mm/submm wavelength Very Long Baseline Interferometric (VLBI) array, which has, to date, utilized mostly pre-existing radio telescopes. The ngEHT program further focuses on observing at three frequencies simultaneously for increased sensitivity and Fourier spatial frequency coverage. Here, the concept, science goals, design considerations, station siting, and instrument prototyping are discussed, and a preliminary reference array to be implemented in phases is described.
我们描述了设计、构建和实施事件视界望远镜(EHT)变革性增强的过程。这个项目——下一代事件视界望远镜(ngEHT)——将形成一个联网的全球射电天线阵列,能够拍摄超大质量黑洞(SMBH)及其喷射流的高保真实时影像。这主要是建立在EHT的基础上,通过在优化的地理位置部署额外的中等直径天线来增强当前全球毫米/亚毫米波长甚长基线干涉(VLBI)阵列,该阵列迄今为止主要利用了现有的射电望远镜。ngEHT计划进一步侧重于同时观察三个频率,以提高灵敏度和傅里叶空间频率覆盖。在这里,讨论了概念、科学目标、设计考虑、站点选址和仪器原型,并描述了一个初步的参考阵列,将分阶段实施。
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引用次数: 5
A Comprehensive Study of Soft X-ray Absorption Features in GX 13+1 Using XMM-Newton Observations 利用XMM-Newton观测综合研究gx13 +1软x射线吸收特征
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-10-15 DOI: 10.3390/galaxies11050106
Rabindra Mahato, Monmoyuri Baruah
In this study, a comprehensive analysis of the reflection grating spectrometer (RGS) data (energy range 0.33 keV to 2.5 keV) of GX 13+1 from the XMM-Newton space observatory was conducted. Numerous absorption lines have been described in earlier publications, although the majority of these investigations focused on the energy range between 3 keV and 10 keV. We considered all ten on-axis observations for spectral analysis, but during timing analysis, off-axis observations were also analysed. A fresh dip in off-axis observation 0122340701(B) was observed together with the previously reported dip in on-axis observation 0505480501(F). No burst or eclipsing was observed in any of the observations. The spectral analysis revealed the presence of the highly ionized elements, Si XIII 1s2–1s2p and 1s2–1s3p transitions with energies of 2.02 keV and 2.24 keV, respectively, as well as Mg XII 1s–6p transitions with energies of 1.91 keV and Al XIII 1s–4p transitions with energies of 2.15 keV. Before this study, no analyses of XMM-Newton data reported Mg XII and Al XIII elements. Moreover, the 1s–6p transitions of Mg XII and 1s–4p transitions of Al XIII were not even reported in any Chandra data analysis. The equivalent hydrogen column densities obtained (2.35 × 1022 cm−2 to 4.18 × 1022 cm−2) are consistent with previously reported values. The equivalent widths of neighbouring observations are found to be nearly the same. This supports us in suggesting that the absorptions may be due to the presence of an interstellar medium (ISM) in the line of sight (LOS) of the source.
本文对xmm -牛顿空间天文台发射的GX 13+1反射光栅光谱仪(RGS)数据(能量范围0.33 ~ 2.5 keV)进行了综合分析。在早期的出版物中已经描述了许多吸收谱线,尽管这些研究大多集中在3 keV到10 keV之间的能量范围内。我们考虑了所有10个轴上观测值进行光谱分析,但在时序分析期间,也分析了离轴观测值。在离轴观测值0122340701(B)中观察到新的下降,同时在轴上观测值0505480501(F)中观察到先前报道的下降。在任何观测中都没有观测到爆发或日食。光谱分析表明,存在能量分别为2.02 keV和2.24 keV的高电离元素Si XII 1s - 1s2p和1s2-1s3p,以及能量为1.91 keV的Mg XII 1s-6p和能量为2.15 keV的Al XII 1s-4p。在本研究之前,XMM-Newton数据分析未报道Mg XII和Al XIII元素。此外,在任何Chandra数据分析中,Mg XII的1s-6p跃迁和Al XIII的1s-4p跃迁甚至没有报道。得到的等效氢柱密度(2.35 × 1022 cm−2至4.18 × 1022 cm−2)与先前报道的值一致。发现相邻观测值的等效宽度几乎相同。这支持了我们的观点,即吸收可能是由于在光源的视线(LOS)内存在星际介质(ISM)。
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引用次数: 0
Three Dimensional Natures of Massive Star Envelopes 大质量恒星包层的三维特性
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-10-11 DOI: 10.3390/galaxies11050105
Yan-Fei Jiang
In this paper, we review our current understanding of the outer envelope structures of massive stars based on three-dimensional (3D) radiation hydrodynamic simulations. We briefly summarize the fundamental issues in constructing hydrostatic one-dimensional (1D) stellar evolution models when stellar luminosity approaches the Eddington value. Radiation hydrodynamic simulations in 3D covering the mass range from 13M⊙ to 80M⊙ always find a dynamic envelope structure with the time-averaged radial profiles matching 1D models with an adjusted mixing-length parameter when convection is subsonic. Supersonic turbulence and episodic mass loss are generally found in 3D models when stellar luminosity is super-Eddington locally due to the opacity peaks and convection being inefficient. Turbulent pressure plays an important role in supporting the outer envelope, which makes the photosphere more extended than predictions from 1D models. Massive star lightcurves are always found to vary with a characteristic timescale consistent with the thermal time scale at the location of the iron opacity peak. The amplitude of the variability as well as the power spectrum can explain the commonly observed stochastic low-frequency variability of mass stars observed by TESS over a wide range of parameters in an HR diagram. The 3D simulations can also explain the ubiquitous macro-turbulence that is needed for spectroscopic fitting in massive stars. Implications of 3D simulations for improving 1D stellar evolution models are also discussed.
在本文中,我们回顾了目前基于三维(3D)辐射流体动力学模拟对大质量恒星外包膜结构的理解。本文简要总结了当恒星光度接近Eddington值时,建立流体静力一维(1D)恒星演化模型的基本问题。在质量范围从13M⊙到80M⊙的三维辐射流体动力学模拟中,当对流为亚音速时,总能发现一个动态包络结构,其时间平均径向轮廓与调整后的混合长度参数的一维模型相匹配。在三维模型中,由于不透明峰和对流效率低下,当恒星亮度局部超爱丁顿时,通常会发现超音速湍流和偶发质量损失。湍流压力在支持外包膜方面起着重要作用,这使得光球层比一维模型预测的范围更大。我们发现大质量恒星的光曲线在铁不透明峰位置的特征时间尺度上总是变化的,与热时间尺度一致。变异性的幅度和功率谱可以解释在HR图中,TESS观测到的大质量恒星在大范围参数范围内常见的随机低频变异性。三维模拟还可以解释大质量恒星的光谱拟合所需要的无处不在的宏观湍流。三维模拟对改进一维恒星演化模型的意义也进行了讨论。
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引用次数: 0
Complex Organics in Space: A Changing View of the Cosmos 太空中的复杂有机物:不断变化的宇宙观
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-10-08 DOI: 10.3390/galaxies11050104
Sun Kwok
Planetary explorations have revealed that complex organics are widely present in the solar system. Astronomical infrared spectroscopic observations have discovered that complex organics are synthesized in large quantities in planetary nebulae and distributed throughout the galaxy. Signatures of organics have been found in distant galaxies, as early as 1.5 billion years after the Big Bang. A number of unsolved spectral phenomena such as diffuse interstellar bands, extended red emissions, 220 nm feature, and unidentified infrared emission bands are likely to originate from organics. In this paper, we discuss the possible chemical structures of the carriers of these unexplained phenomena, and how these organics are synthesized abiotically in the universe. We raise the possibility that the primordial solar system was enriched by complex organics synthesized and ejected by evolved stars. The implications of possible stellar organics in primordial Earth are also discussed.
行星探测表明,复杂的有机物在太阳系中广泛存在。天文红外光谱观测发现,复杂有机物在行星状星云中大量合成并分布在整个星系中。早在宇宙大爆炸后15亿年,在遥远的星系中就发现了有机物的特征。一些尚未解决的光谱现象,如漫射星际带、扩展红发射、220纳米特征和未识别的红外发射带,很可能来自有机物。在本文中,我们讨论了这些无法解释的现象的载体可能的化学结构,以及这些有机物是如何在宇宙中非生物合成的。我们提出了一种可能性,即原始太阳系是由进化恒星合成和喷射的复杂有机物丰富的。还讨论了原始地球中可能存在的恒星有机物的含义。
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引用次数: 0
Spin Equilibrium of Rapidly Spinning Neutron Stars via Transient Accretion 瞬态吸积作用下快速旋转中子星的自旋平衡
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-10-01 DOI: 10.3390/galaxies11050103
Sudip Bhattacharyya
The concept of spin equilibrium due to an interaction between the stellar magnetosphere and a thin, Keplerian accretion disk, and a well-known formula of the corresponding equilibrium spin frequency, provide a key understanding of spin evolution and the distribution of rapidly spinning neutron stars, viz., millisecond pulsars. However, this concept and formula are for stable accretion, but the mass transfer to most accreting millisecond pulsars is transient and the accretion rate evolves by orders of magnitude during an outburst. In this short and focussed review, we briefly discuss a relatively new concept of the spin equilibrium condition and a new formula for the equilibrium spin frequency for transiently accreting millisecond pulsars. We also review a new method to estimate this equilibrium spin frequency for observed transiently accreting millisecond pulsars, even when a pulsar has not yet attained the spin equilibrium. These will be crucial to probe the spin evolution and distribution of millisecond pulsars, and should also be applicable to all magnetic stars transiently accreting via a thin, Keplerian accretion disk.
由于恒星磁层与薄的开普勒吸积盘之间的相互作用而产生的自旋平衡的概念,以及相应的平衡自旋频率的著名公式,为理解自旋演化和快速旋转的中子星(即毫秒脉冲星)的分布提供了关键的理解。然而,这个概念和公式是针对稳定吸积的,但大多数吸积毫秒脉冲星的传质是短暂的,在爆发期间吸积速率以数量级变化。在这篇简短而集中的综述中,我们简要地讨论了一个相对较新的自旋平衡条件的概念和瞬态吸积毫秒脉冲星平衡自旋频率的新公式。我们还回顾了一种估算瞬时吸积毫秒脉冲星平衡自旋频率的新方法,即使脉冲星尚未达到自旋平衡。这对于探测毫秒脉冲星的自旋演化和分布至关重要,也应该适用于所有通过薄的开普勒吸积盘瞬态吸积的磁性恒星。
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引用次数: 0
A Walk through AGN Country—For the Somewhat Initiated! 在AGN国家散步——为一些初学者!
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-09-30 DOI: 10.3390/galaxies11050102
Robert R. J. Antonucci
Key issues in AGN and galaxy formation are discussed. Very successful Unified Models explain much of the variety of AGN with orientation effects; the ingredients are shadowing by a dusty “torus” and relativistic beaming. A spinoff result is described which is important for the formation of massive elliptical galaxies, the most spectacular and unequivocal AGN feedback phenomenon known. This is the so-called “alignment effect” in powerful radio galaxies at z∼>1. One of them is a BAL radio galaxy! Next, I explain a very robust derivation of the reddening law for nuclear dust, which reveals a dearth of small grains on parsec scales. Then, the quasistatic thin accretion disk model, thought by many to explain the energetically dominant optical/UV continuum, is thoroughly debunked. Much of this was known when the model was proposed 35 years ago. A new argument is provided that trivially falsifies a huge superset of such models. I then show that it is possible to see the central engine spectrum with the atomic and dust emission surgically removed! Few have noticed this breakthrough work. Finally, the far IR dust emission in Cygnus A is 10% polarized; to date, high nuclear dust polarization has been seen in all radio loud objects and no radio quiet ones.
讨论了AGN和星系形成的关键问题。非常成功的统一模型解释了AGN的取向效应的许多变化;这些成分被布满灰尘的“环面”和相对论光束所遮蔽。描述了一个衍生结果,它对大质量椭圆星系的形成很重要,这是已知的最壮观和最明确的AGN反馈现象。这就是在z ~ >1强力射电星系中所谓的“对准效应”。其中一个是BAL射电星系!接下来,我解释了核尘埃变红定律的一个非常可靠的推导,它揭示了秒差距尺度上小颗粒的缺乏。然后,准静态薄吸积盘模型,被许多人认为可以解释能量上占主导地位的光学/紫外连续体,被彻底揭穿。当这个模型在35年前被提出时,人们已经知道了很多。提出了一个新的论证,简单地证伪了这些模型的一个巨大的超集。然后,我表明,它是可能看到中央发动机光谱与原子和尘埃发射手术去除!很少有人注意到这项突破性的工作。最后,天鹅座A的远红外尘埃发射是10%极化的;到目前为止,高核尘埃极化已经在所有无线电大声的物体中发现,而没有无线电安静的物体。
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引用次数: 0
On Exotic Objects Made of Dark Energy and Dark Matter: Mass-to-Radius Profiles and Tidal Love Numbers 关于由暗能量和暗物质组成的奇异物体:质量-半径剖面和潮汐爱数
Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2023-09-22 DOI: 10.3390/galaxies11050101
Camila Sepúlveda, Grigoris Panotopoulos
We investigate some properties of exotic spherical configurations made of dark matter and dark energy. For the former we adopt a polytropic equation-of-state, while for the latter we adopt the Extended Chaplygin gas equation-of-state. Solving the Tolman-Oppenheimer-Volkoff equations, within the 2-fluid formalism, we compute the factor of compactness, the mass-to-radius relationships, as well as the tidal Love numbers and dimensionless deformabilities. A comparison between single fluid objects and 2-fluid configurations is made as well.
我们研究了由暗物质和暗能量构成的奇异球面构型的一些性质。对于前者我们采用多向状态方程,而对于后者我们采用扩展的Chaplygin气体状态方程。在2流体形式下,求解Tolman-Oppenheimer-Volkoff方程,计算紧性因子、质量-半径关系、潮汐Love数和无量纲可变形性。并对单流体物体和双流体结构进行了比较。
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引用次数: 0
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Galaxies
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