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Investigating Possible Correlations between Gamma-Ray and Optical Lightcurves for TeV-Detected Northern Blazars over 8 Years of Observations 在8年的观测中,研究tev探测到的北方耀变体的伽马射线和光曲线之间可能的相关性
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-07-01 DOI: 10.3390/galaxies11040081
A. Acharyya, A. Sadun
Blazars are a subclass of active galactic nuclei (AGN) having relativistic jets aligned within a few degrees of our line-of-sight and form the majority of the AGN detected in the TeV regime. The Fermi-Large Area Telescope (LAT) is a pair-conversion telescope, sensitive to photons having energies between 20 MeV and 2 TeV, and is capable of scanning the entire gamma-ray sky every three hours. Despite the remarkable success of the Fermi mission, many questions still remain unanswered, such as the site of gamma-ray production and the emission mechanisms involved. The Asteroid Terrestrial-impact Last Alert System (ATLAS) is a high cadence all sky survey system optimized to be efficient for finding potentially dangerous asteroids, as well as in tracking and searching for highly variable and transient sources, such as AGN. In this study, we investigate possible correlations between the Fermi-LAT observations in the 100 MeV–300 GeV energy band and the ATLAS optical data in the R-band, centered at 679 nm, for a sample of 18 TeV-detected northern blazars over 8 years of observations between 2015 and 2022. Under the assumption that the optical and gamma-ray flares are produced by the same outburst propagating down the jet, the strong correlations found for some sources suggest a single-zone leptonic model of emission.
耀变体是活动星系核(AGN)的一个子类,具有相对喷流,在我们的视线范围内几度内排列,形成了TeV系统中探测到的大部分活动星系核。费米大面积望远镜(LAT)是一个对转换望远镜,对能量在20 MeV到2 TeV之间的光子敏感,并且能够每三小时扫描整个伽马射线天空。尽管费米任务取得了显著的成功,但仍有许多问题没有得到解答,比如伽马射线产生的地点和所涉及的发射机制。小行星对地撞击最后警报系统(ATLAS)是一种高节奏的全天空调查系统,经过优化,可以有效地发现潜在危险的小行星,以及跟踪和搜索高度可变的瞬态源,如AGN。在这项研究中,我们研究了Fermi-LAT在100 MeV-300 GeV波段的观测结果与ATLAS在r波段(以679 nm为中心)的光学数据之间可能的相关性,该数据来自于2015年至2022年8年观测的18个tev探测到的北方blazars样本。假设光学和伽玛射线耀斑是由沿喷流传播的同一次爆发产生的,在某些源中发现的强相关性表明发射的单区轻子模型。
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引用次数: 0
Discovering New B[e] Supergiants and Candidate Luminous Blue Variables in Nearby Galaxies 在邻近星系中发现新的B[e]超巨星和候选亮蓝变量
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-19 DOI: 10.3390/galaxies11030079
G. Maravelias, Stephan de Wit, A. Bonanos, F. Tramper, G. Munoz-Sanchez, E. Christodoulou
Mass loss is one of the key parameters that determine stellar evolution. Despite the progress we have achieved over the last decades we still cannot match the observational derived values with theoretical predictions. Even worse, there are certain phases, such as the B[e] supergiants (B[e]SGs) and the Luminous Blue Variables (LBVs), where significant mass is lost through episodic or outburst activity. This leads to various structures forming around them that permit dust formation, making these objects bright IR sources. The ASSESS project aims to determine the role of episodic mass in the evolution of massive stars, by examining large numbers of cool and hot objects (such as B[e]SGs/LBVs). For this purpose, we initiated a large observation campaign to obtain spectroscopic data for ∼1000 IR-selected sources in 27 nearby galaxies. Within this project we successfully identified seven B[e] supergiants (one candidate) and four Luminous Blue Variables of which six and two, respectively, are new discoveries. We used spectroscopic, photometric, and light curve information to better constrain the nature of the reported objects. We particularly noted the presence of B[e]SGs at metallicity environments as low as 0.14 Z⊙.
质量损失是决定恒星演化的关键参数之一。尽管我们在过去几十年中取得了进展,但我们仍然无法将观测所得的值与理论预测相匹配。更糟糕的是,在某些阶段,如B[e]超巨星(B[e]SGs)和发光蓝变星(LBVs),在那里大量的质量会通过偶发或爆发活动而损失。这导致它们周围形成各种结构,允许尘埃形成,使这些物体成为明亮的红外光源。evaluate项目旨在通过检测大量的冷热天体(如B[e]SGs/ lbv)来确定偶发性质量在大质量恒星演化中的作用。为此,我们发起了一项大型观测活动,以获得27个附近星系中约1000个红外选择源的光谱数据。在这个项目中,我们成功地确定了七个B[e]超巨星(一个候选)和四个发光蓝变量,其中六个和两个分别是新发现的。我们使用光谱学、光度学和光曲线信息来更好地约束所报道物体的性质。我们特别注意到在金属丰度低至0.14 Z⊙的环境中存在B[e]SGs。
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引用次数: 0
On the Evolution of, and Hot Gas in, Wind-Blown Bubbles around Massive Stars - Wind Bubbles Are Not Energy-Conserving 关于大质量恒星周围风吹气泡的演化和热气体——风吹气泡并不节能
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-19 DOI: 10.3390/galaxies11030078
V. Dwarkadas
The structure and evolution of wind-blown bubbles (WBBs) around massive stars has primarily been investigated using an energy-conserving model of wind-blown bubbles. While this model is useful in explaining the general properties of the evolution, several problems remain, including inconsistencies between observed wind luminosities and those derived using this formulation. Major difficulties include the low X-ray temperature and X-ray luminosity, compared to the model. In this paper, we re-examine the evolution, dynamics, and kinematics of WBBs around massive stars, using published ionization gasdynamic simulations of wind-blown bubbles. We show that WBBs can cool efficiently due to the presence of various instabilities and turbulence within the bubble. The expansion of WBBs is more consistent with a momentum-conserving solution, rather than an energy-conserving solution. This compares well with the dynamics and kinematics of observed wind bubbles. Despite the cooling of the bubble, the shocked wind temperature is not reduced to the observed values. We argue that the X-ray emission arise mainly from clumps and filaments within the hot shocked wind region, with temperatures just above 106 K. The remainder of the plasma can contribute to a lesser extent.
大质量恒星周围的风吹气泡(WBBs)的结构和演化主要是用一种节能的风吹气泡模型来研究的。虽然这个模型在解释演化的一般性质方面是有用的,但仍然存在一些问题,包括观测到的风光度与使用这个公式得出的风光度之间的不一致。与模型相比,主要的困难包括低x射线温度和x射线亮度。在本文中,我们利用已发表的风吹气泡电离气体动力学模拟,重新研究了大质量恒星周围wbs的演化、动力学和运动学。我们表明,由于泡内存在各种不稳定性和湍流,wbs可以有效冷却。wbs的扩展更符合动量守恒解,而不是能量守恒解。这与观测到的风泡的动力学和运动学相比较。尽管气泡冷却了,但激波风温度并没有降低到观测值。我们认为,x射线辐射主要来自热激风区域的团块和细丝,温度略高于106 K。其余的血浆也能起到较小的作用。
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引用次数: 0
Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants B[e]超巨星和黄超巨星的密集分子环境
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-16 DOI: 10.3390/galaxies11030076
M. Kraus, Michalis Kourniotis, M. Arias, A. Torres, D. Nickeler
Massive stars expel large amounts of mass during their late evolutionary phases. We aim to unveil the physical conditions within the warm molecular environments of B[e] supergiants (B[e]SGs) and yellow hypergiants (YHGs), which are known to be embedded in circumstellar shells and disks. We present K-band spectra of two B[e]SGs from the Large Magellanic Cloud and four Galactic YHGs. The CO band emission detected from the B[e]SGs LHA 120-S 12 and LHA 120-S 134 suggests that these stars are surrounded by stable rotating molecular rings. The spectra of the YHGs display a rather diverse appearance. The objects 6 Cas and V509 Cas lack any molecular features. The star [FMR2006] 15 displays blue-shifted CO bands in emission, which might be explained by a possible close to pole-on oriented bipolar outflow. In contrast, HD 179821 shows blue-shifted CO bands in absorption. While the star itself is too hot to form molecules in its outer atmosphere, we propose that it might have experienced a recent outburst. We speculate that we currently can only see the approaching part of the expelled matter because the star itself might still block the receding parts of a (possibly) expanding gas shell.
大质量恒星在其进化后期排出大量质量。我们的目标是揭示B[e]超巨星(B[e]SG)和黄超巨星(YHG)温暖分子环境中的物理条件,这些超巨星已知嵌入星周壳和盘中。我们给出了来自大麦哲伦星云的两个B[e]SG和四个银河系YHG的K波段光谱。从B[e]SGs LHA 120-S 12和LHA 120-S134探测到的CO波段发射表明,这些恒星被稳定的旋转分子环包围。YHG的光谱显示出相当多样化的外观。对象6 Cas和V509 Cas缺乏任何分子特征。恒星[FMR206]15在发射中显示出蓝移的CO带,这可能是由可能接近极点的定向双极流出所解释的。相反,HD 179821在吸收中显示出蓝移的CO带。虽然恒星本身太热,无法在外层大气中形成分子,但我们认为它可能经历了最近的爆发。我们推测,我们目前只能看到被排出物质的接近部分,因为恒星本身可能仍会阻挡(可能)膨胀的气体外壳的后退部分。
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引用次数: 0
Cosmic Ray Processes in Galactic Ecosystems 银河生态系统中的宇宙射线过程
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-16 DOI: 10.3390/galaxies11040086
E. Owen, Kinwah Wu, Y. Inoue, H. Yang, A. Mitchell
Galaxy evolution is an important topic, and our physical understanding must be complete to establish a correct picture. This includes a thorough treatment of feedback. The effects of thermal–mechanical and radiative feedback have been widely considered; however, cosmic rays (CRs) are also powerful energy carriers in galactic ecosystems. Resolving the capability of CRs to operate as a feedback agent is therefore essential to advance our understanding of the processes regulating galaxies. The effects of CRs are yet to be fully understood, and their complex multi-channel feedback mechanisms operating across the hierarchy of galaxy structures pose a significant technical challenge. This review examines the role of CRs in galaxies, from the scale of molecular clouds to the circumgalactic medium. An overview of their interaction processes, their implications for galaxy evolution, and their observable signatures is provided and their capability to modify the thermal and hydrodynamic configuration of galactic ecosystems is discussed. We present recent advancements in our understanding of CR processes and interpretation of their signatures, and highlight where technical challenges and unresolved questions persist. We discuss how these may be addressed with upcoming opportunities.
星系演化是一个重要的话题,我们的物理理解必须是完整的,才能建立一个正确的图景。这包括对反馈的彻底处理。热-机械和辐射反馈的影响已被广泛考虑;然而,宇宙射线(CRs)也是银河系生态系统中强大的能量载体。因此,解决CRs作为反馈代理运行的能力对于提高我们对星系调节过程的理解至关重要。CRs的影响还没有被完全理解,它们复杂的多通道反馈机制在星系结构的层次上运作,构成了一个重大的技术挑战。本文综述了cr在星系中的作用,从分子云的尺度到环星系介质。概述了它们的相互作用过程,它们对星系演化的影响,以及它们的可观测特征,并讨论了它们改变星系生态系统的热和水动力配置的能力。我们介绍了我们对CR流程的理解和对其特征的解释的最新进展,并强调了技术挑战和未解决的问题。我们将讨论如何利用即将到来的机会来解决这些问题。
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引用次数: 2
Vertical Structure of the Milky Way Disk with Gaia DR3 用盖亚DR3观测银河系盘的垂直结构
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-16 DOI: 10.3390/galaxies11030077
K. Vieira, V. Korchagin, G. Carraro, Artem Lutsenko
Using a complete sample of about 330,000 dwarf stars, well measured by Gaia DR3, limited to the galactic north and south solid angles |b|<75° and up to a vertical distance of 2 kpc, we analyze the vertical structure of the Milky Way stellar disks, based on projected tangential velocities. From selected subsamples dominated by their corresponding population, we obtain the thin and thick disk scale heights as hZ=279.76±12.49 pc and HZ=797.23±12.34 pc, respectively. Then from the simultaneous fitting of the sum of two populations over the whole sample, assuming these scale heights, we estimate the thick-to-thin disk number density ratio at the galactic plane to be ρT/ρt=0.750±0.049, which is consistent with a previous result by the authors: in the galactic plane there is a significant number of thick disk stars, possibly as many as thin disk ones, which also points to the existence of more thick disk stars than generally thought. The overall fit does not closely follow the data for |Z|>700 pc and points to the presence of more stars beyond the thin disk that cannot be accounted for by the two-disk model.
盖亚DR3对大约33万颗矮星进行了完整的测量,仅限于银河系南北实体角bb| 700pc,并指出在薄盘之外存在着更多的恒星,而这些恒星无法用双盘模型来解释。
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引用次数: 0
The Dynamics and Energetics of Remnant and Restarting RLAGN 剩余和重新启动RLAGN的动力学和能量学
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-13 DOI: 10.3390/galaxies11030074
V. Mahatma
In this article, I review past, current, and future advances on the study of radio-loud AGN (RLAGN; radio-loud quasars and radio galaxies) lifecycles exclusively in the remnant and restarting phases. I focus on their dynamics and energetics as inferred from radio observations while discussing their radiative lifetimes, population statistics, and trends in their physical characteristics. I briefly summarise multi-wavelength observations, particularly X-rays, that have enabled studies of the large-scale environments of RLAGN in order to understand their role in feedback. Furthermore, I discuss analytic and numerical simulations that predict key properties of remnant and restarting sources as found in wide-area surveys, and discuss the prospects of future surveys that may shed further light on these elusive subpopulations of RLAGN.
在这篇文章中,我回顾了过去、现在和未来关于无线电大星系核(RLAGN;无线电大类星体和无线电星系)生命周期的研究进展,这些研究仅在残余和重启阶段。我专注于从无线电观测中推断出的它们的动力学和能量学,同时讨论它们的辐射寿命、种群统计和物理特征的趋势。我简要总结了多波长观测,特别是X射线,这些观测使我们能够研究RLAGN的大规模环境,以了解它们在反馈中的作用。此外,我讨论了分析和数值模拟,这些模拟预测了大面积调查中发现的残余物和重启源的关键特性,并讨论了未来调查的前景,这些调查可能会进一步揭示RLAGN的这些难以捉摸的亚群。
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引用次数: 1
New Insight into the FS CMa System MWC 645 from Near-Infrared and Optical Spectroscopy 从近红外光谱和光谱学对FS CMa系统MWC 645的新认识
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-10 DOI: 10.3390/galaxies11030072
A. Torres, M. Arias, M. Kraus, L. Mercanti, T. Eenmäe
The B[e] phenomenon is manifested by a heterogeneous group of stars surrounded by gaseous and dusty circumstellar envelopes with similar physical conditions. Among these stars, the FS CMa-type objects are suspected to be binary systems, which could be experiencing or have undergone a mass-transfer process that could explain the large amount of material surrounding them. We aim to contribute to the knowledge of a recently confirmed binary, MWC 645, which could be undergoing an active mass-transfer process. We present near-infrared and optical spectra, identify atomic and molecular spectral features, and derive different quantitative properties of line profiles. Based on publicly available photometric data, we search for periodicity in the light curve and model the spectral energy distribution. We have detected molecular bands of CO in absorption at 1.62 μm and 2.3 μm for the first time. We derive an upper limit for the effective temperature of the cool binary component. We found a correlation between the enhancement of the Hα emission and the decrease in optical brightness that could be associated with mass-ejection events or an increase in mass loss. We outline the global properties of the envelope, possibly responsible for brightness variations due to a variable extinction, and briefly speculate on different possible scenarios.
B[e]现象表现为一群不均匀的恒星被具有相似物理条件的气体和尘埃包围。在这些恒星中,FS cma型天体被怀疑是双星系统,它们可能正在经历或已经经历了一个质量传递过程,这可以解释它们周围的大量物质。我们的目标是为最近确认的双星MWC 645的知识做出贡献,它可能正在经历一个活跃的传质过程。我们给出了近红外光谱和光学光谱,确定了原子和分子的光谱特征,并得出了谱线的不同定量性质。基于公开可用的光度数据,我们在光曲线中寻找周期性并建立光谱能量分布模型。我们首次在1.62 μm和2.3 μm处检测到CO的吸收分子带。我们导出了冷二元组分有效温度的上限。我们发现了α辐射的增强与光学亮度的降低之间的相关性,这可能与质量抛射事件或质量损失的增加有关。我们概述了包络层的全局特性,可能是由于变量消光引起的亮度变化的原因,并简要地推测了不同的可能情况。
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引用次数: 0
Investigating Gravitationally Lensed Quasars Observable by Nancy Grace Roman Space Telescope 研究南希·格蕾丝·罗马太空望远镜观测到的引力透镜类星体
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.3390/galaxies11030071
L. Hamolli, M. Hafizi, F. De Paolis, Esmeralda Guliqani
In this work, we investigate the possibility of observing quasars, particularly lensed quasars, by the Nancy Grace Roman Space Telescope (Roman). To this aim, based on the capabilities of the Roman Space Telescope and the results from the quasar luminosity function (QLF) in the infrared band of the Spitzer Space Telescope imaging survey, we calculated the number of quasars expected to be in its field of view. In order to estimate the number of lensed quasars, we develop a Monte Carlo simulation to estimate the probability that a quasar is lensed once or more times by foreground galaxies. Using the mass–luminosity distribution function of galaxies and the redshift distributions of galaxies and quasars, we find that 1 per 180 observed quasars will be lensed by foreground galaxies. Further on, adopting a singular isothermal sphere (SIS) model for lens galaxies, we calculate the time delay between lensed images for single and multiple lensing systems and present their distributions. We emphasize that detailed studies of these lensing systems will provide a powerful probe of the physical properties of quasars and may allow testing the mass distribution models of galaxies in addition to being extremely helpful for constraining the cosmological parameters.
在这项工作中,我们研究了用Nancy Grace Roman太空望远镜(Roman)观测类星体,特别是透镜类星体的可能性。为此,根据罗马太空望远镜的能力和斯皮策太空望远镜成像调查红外波段类星体光度函数(QLF)的结果,我们计算了预计在其视野内的类星体数量。为了估计透镜类星体的数量,我们开发了一个蒙特卡罗模拟来估计一个类星体被前景星系透镜化一次或多次的概率。利用星系的质量-光度分布函数以及星系和类星体的红移分布,我们发现每180个观测到的类星体中就有1个会被前景星系透镜化。此外,我们采用透镜星系的奇异等温球(SIS)模型,计算了单透镜系统和多透镜系统透镜图像之间的时间延迟,并给出了它们的分布。我们强调,对这些透镜系统的详细研究将为类星体的物理性质提供一个强大的探针,并可能允许测试星系的质量分布模型,此外还有助于约束宇宙学参数。
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引用次数: 0
Hawking Radiation and Lifetime of Primordial Black Holes in Braneworld 霍金辐射与膜世界中原始黑洞的寿命
IF 2.5 Q2 Physics and Astronomy Pub Date : 2023-05-31 DOI: 10.3390/galaxies11030070
B. Turimov, A. Mamadjanov, Ozodbek Rahimov
The paper explores the thermodynamic properties of primordial black holes (PBHs) in the braneworld. Specifically, the researchers examined Hawking radiation and the lifetime of PBHs. Through their analysis, an exact analytical expression for the Bekenstein–Hawking entropy, temperature, and heat capacity was derived. Their findings suggest that the lifetime of PBHs in the early universe is reduced by at least one order of magnitude, ultimately leading to their evaporation. This could explain why we have not observed the final rapid evaporation of PBHs in the recent epoch of the universe.
本文研究了膜世界中原始黑洞的热力学性质。具体来说,研究人员检查了霍金辐射和PBH的寿命。通过他们的分析,导出了贝肯斯坦-霍金熵、温度和热容的精确解析表达式。他们的发现表明,早期宇宙中PBH的寿命至少减少了一个数量级,最终导致它们的蒸发。这可以解释为什么我们在最近的宇宙时代没有观察到PBH的最终快速蒸发。
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引用次数: 0
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Galaxies
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