Galaxies最新文献_第2页

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

Galaxies Pub Date : 2023-11-07 DOI: 10.3390/galaxies11060109

Konstantin Belotsky, Maxim Solovyov

引用次数: 0

Fueling Processes on (Sub-)kpc Scales kpc以下尺度的燃料过程

IF 2.5

Galaxies Pub Date : 2023-11-06 DOI: 10.3390/galaxies11060120

F. Combes

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

Galaxies Pub Date : 2023-11-01 DOI: 10.3390/galaxies11060108

James R. Webb, Ivan Parra Sanz

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

Galaxies 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

{"title":"Reference Array and Design Consideration for the Next-Generation Event Horizon Telescope","authors":"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","doi":"10.3390/galaxies11050107","DOIUrl":"https://doi.org/10.3390/galaxies11050107","url":null,"abstract":"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.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135823850","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}

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

Galaxies Pub Date : 2023-10-15 DOI: 10.3390/galaxies11050106

Rabindra Mahato, Monmoyuri Baruah

{"title":"A Comprehensive Study of Soft X-ray Absorption Features in GX 13+1 Using XMM-Newton Observations","authors":"Rabindra Mahato, Monmoyuri Baruah","doi":"10.3390/galaxies11050106","DOIUrl":"https://doi.org/10.3390/galaxies11050106","url":null,"abstract":"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.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":"166 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136184494","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}

引用次数: 0

Three Dimensional Natures of Massive Star Envelopes 大质量恒星包层的三维特性

Galaxies Pub Date : 2023-10-11 DOI: 10.3390/galaxies11050105

Yan-Fei Jiang

{"title":"Three Dimensional Natures of Massive Star Envelopes","authors":"Yan-Fei Jiang","doi":"10.3390/galaxies11050105","DOIUrl":"https://doi.org/10.3390/galaxies11050105","url":null,"abstract":"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.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136097666","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}

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

Galaxies Pub Date : 2023-10-08 DOI: 10.3390/galaxies11050104

Sun Kwok

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

Galaxies Pub Date : 2023-10-01 DOI: 10.3390/galaxies11050103

Sudip Bhattacharyya

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!

Galaxies Pub Date : 2023-09-30 DOI: 10.3390/galaxies11050102

Robert R. J. Antonucci

{"title":"A Walk through AGN Country—For the Somewhat Initiated!","authors":"Robert R. J. Antonucci","doi":"10.3390/galaxies11050102","DOIUrl":"https://doi.org/10.3390/galaxies11050102","url":null,"abstract":"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.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136343714","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}

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

Galaxies Pub Date : 2023-09-22 DOI: 10.3390/galaxies11050101

Camila Sepúlveda, Grigoris Panotopoulos

引用次数: 0