Galaxies最新文献_第7页

Infrared Spectroscopy of Be Stars: Influence of the Envelope Parameters on Brackett-Series Behaviour Be星的红外光谱：包络参数对Brackett级数行为的影响

IF 2.5

Galaxies Pub Date : 2023-08-17 DOI: 10.3390/galaxies11040090

Y. R. Cochetti, A. Granada, M. Arias, A. Torres, C. Arcos

{"title":"Infrared Spectroscopy of Be Stars: Influence of the Envelope Parameters on Brackett-Series Behaviour","authors":"Y. R. Cochetti, A. Granada, M. Arias, A. Torres, C. Arcos","doi":"10.3390/galaxies11040090","DOIUrl":"https://doi.org/10.3390/galaxies11040090","url":null,"abstract":"The IR spectra of Be stars display numerous hydrogen recombination lines, constituting a great resource for obtaining information on the physical and dynamic structures of different regions within the circumstellar envelope. Nevertheless, this spectral region has not been analysed in depth, and there is a lack of synthetic spectra with which to compare observations. Therefore, we computed synthetic spectra with the HDUST code for different disc parameters. Here, we present our results on the spectral region that includes lines of the Brackett series. We discuss the dependence of the line series strengths on several parameters that describe the structure of the disc. We also compared model line profiles, fluxes, and EWs with observational data for two Be stars (MX Pup and π Aqr). Even though the synthetic spectra adequately fit our observations of both stars and allow us to constrain the parameters of the disc, there is a discrepancy with the observed data in the EW and flux measurements, especially in the case of MX Pup. It is possible that by including Brackett lines of higher terms or adding the analysis of other series, we may be able to better constrain the parameters of the observed disc.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48905271","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

Gamma Ray Pulsars and Opportunities for the MACE Telescope 伽马射线脉冲星与MACE望远镜的机遇

IF 2.5

Galaxies Pub Date : 2023-08-17 DOI: 10.3390/galaxies11040091

A. Pathania, Krishna Kumar Singh, K. Yadav

引用次数: 0

Multidimensional Simulations of Core Convection 核心对流的多维模拟

IF 2.5

Galaxies Pub Date : 2023-07-28 DOI: 10.3390/galaxies11040089

D. Lecoanet, P. Edelmann

{"title":"Multidimensional Simulations of Core Convection","authors":"D. Lecoanet, P. Edelmann","doi":"10.3390/galaxies11040089","DOIUrl":"https://doi.org/10.3390/galaxies11040089","url":null,"abstract":"The cores of main sequence intermediate- and high-mass stars are convective. Mixing at the radiative–convective boundary, waves excited by the convection, and magnetic fields generated by convective dynamos all influence the main sequence and post-main sequence evolution of these stars. These effects must be understood to accurately model the structure and evolution of intermediate- and high-mass stars. Unfortunately, there are many challenges in simulating core convection due to the wide range of temporal and spatial scales, as well as many important physics effects. In this review, we describe the latest numerical strategies to address these challenges. We then describe the latest state-of-the-art simulations of core convection, summarizing their main findings. These simulations have led to important insights into many of the processes associated with core convection. Two outstanding problems with multidimensional simulations are, 1. it is not always straightforward to extrapolate from simulation parameters to the parameters of real stars; and 2. simulations using different methods sometimes appear to arrive at contradictory results. To address these issues, next generation simulations of core convection must address how their results depend on stellar luminosity, dimensionality, and turbulence intensity. Furthermore, code comparison projects will be essential to establish robust parameterizations that will become the new standard in stellar modeling.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46147784","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: 1

Searching for Short-Timescale Transients in Gamma-ray Telescope Data 伽玛射线望远镜数据中短时间尺度瞬变的搜索

IF 2.5

Galaxies Pub Date : 2023-07-24 DOI: 10.3390/galaxies11040088

Annanay Jaitly, D. Kostunin, Karin Cescon

{"title":"Searching for Short-Timescale Transients in Gamma-ray Telescope Data","authors":"Annanay Jaitly, D. Kostunin, Karin Cescon","doi":"10.3390/galaxies11040088","DOIUrl":"https://doi.org/10.3390/galaxies11040088","url":null,"abstract":"Astrophysical sources show variability in their emissions over a range of timescales, with transients such as fast radio bursts (FRBs) and magnetar giant flares (MGFs) showing variability on timescales as short as a few milliseconds. Recent advances in gamma-ray astronomy such as telescopes’ high temporal resolution and relatively high uptime, combined with follow-up programs between different facilities, should allow serendipitous observations of burst-like phenomena. Even so, no very-high-energy gamma-ray counterparts for FRBs have been detected so far, and there is a general lack of software tools suited to search for such phenomena. We present a tool capable of searching gamma-ray telescope data for transient phenomena over arbitrary timescales—it is based on the Gammapy package and recursively scans the given field of view for clusters of events within user-defined time and angular-separation intervals. The generalized implementation allows for its application in many other cases and multiple gamma-ray telescopes. The main features and methodology of the developed tool are presented here, along with an analysis of the open gamma ray telescope data performed using it.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41819535","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

Dynamics of Powerful Radio Galaxies 强大射电星系的动力学

IF 2.5

Galaxies Pub Date : 2023-07-17 DOI: 10.3390/galaxies11040087

R. Turner, S. Shabala

引用次数: 0

What Drives the Ionized Gas Outflows in Radio-Quiet AGN? 是什么驱动了AGN中电离气体的外流?

IF 2.5

Galaxies Pub Date : 2023-07-12 DOI: 10.3390/galaxies11040085

M. Singha, C. O’Dea, S. Baum

{"title":"What Drives the Ionized Gas Outflows in Radio-Quiet AGN?","authors":"M. Singha, C. O’Dea, S. Baum","doi":"10.3390/galaxies11040085","DOIUrl":"https://doi.org/10.3390/galaxies11040085","url":null,"abstract":"We review the mechanisms driving the ionized gas outflows in radio-quiet (RQ) AGN. Although it constitutes ∼90% of the AGN population, what drives these outflows in these AGNs remains an open question. High-resolution imaging and integral field unit (IFU) observation is key to spatially resolving these outflows, whereas radio observations are important to comprehend the underlying radiative processes. Radio interferometric observations have detected linear, collimated structures on the hundreds of pc scale in RQ AGN, which may be very similar to the extended radio jets in powerful galaxies. Proper motions measured in some objects are sub-relativistic. Other processes, such as synchrotron radiation from shock-accelerated gas around the outflows could give rise to radio emissions as well. Near the launching region, these outflows may be driven by the thermal energy of the accretion disk and exhibit free–free emission. IFU observations on the other hand have detected evidence of both winds and jets and the outflows driven by them in radio-quiet AGN. Some examples include nearby AGN such as Mrk 1044 and HE 1353-1917. An IFU study of nearby (z <0.06) RQ AGN has found that these outflows may be related to their radio properties on <100 pc scale, rather than their accretion properties. Recent JWST observations of RQ AGN XID 2028 have revealed that radio jets and wind could inflate bubbles, create cavities, and trigger star formation. Future high-resolution multi-wavelength observations and numerical simulations taking account of both jets and winds are hence essential to understand the complex interaction between radio-quiet AGN and the host from sub-pc to kpc scales.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43724849","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

Exoplanets around Red Giants: Distribution and Habitability 红巨星周围的系外行星：分布与宜居性

IF 2.5

Galaxies Pub Date : 2023-07-11 DOI: 10.3390/galaxies11060112

Ruixuan E. Chen, Jonathan H. Jiang, P. Rosen, Kristen A. Fahy, Yanbei Chen

引用次数: 0

Probing Neutrino Production in Blazars by Millimeter VLBI 用毫米VLBI探测Blazars中中微子的产生

IF 2.5

Galaxies Pub Date : 2023-07-05 DOI: 10.3390/galaxies11040084

Y. Kovalev, A. Plavin, A. Pushkarev, S. Troitsky

引用次数: 1

Searching for Phase-Locked Variations of the Emission-Line Profiles in Binary Be Stars 寻找双星Be发射线轮廓的锁相变化

IF 2.5

Galaxies Pub Date : 2023-07-04 DOI: 10.3390/galaxies11040083

A. Miroshnichenko, Raghav Chari, S. Danford, P. Prendergast, A. Aarnio, I. Andronov, Lidiia L. Chinarova, Aidan Lytle, Ainash Amantayeva, Ilfa A. Gabitova, Nadezhda L. Vaidman, Sayat S. Baktybayev, S. Khokhlov

{"title":"Searching for Phase-Locked Variations of the Emission-Line Profiles in Binary Be Stars","authors":"A. Miroshnichenko, Raghav Chari, S. Danford, P. Prendergast, A. Aarnio, I. Andronov, Lidiia L. Chinarova, Aidan Lytle, Ainash Amantayeva, Ilfa A. Gabitova, Nadezhda L. Vaidman, Sayat S. Baktybayev, S. Khokhlov","doi":"10.3390/galaxies11040083","DOIUrl":"https://doi.org/10.3390/galaxies11040083","url":null,"abstract":"There is growing evidence that many Be stars are parts of binary systems. As the B-type primaries are very fast rotators and their spectral lines may be distorted by the circumstellar material, it is not easy to measure their radial velocity directly from the spectral lines. It has been shown that some Be binaries exhibit peak intensity variations consisting of double-peaked Hα lines that are phase-locked with orbital periods. We searched for such variations in the spectra of 12 Be stars, including several known and suspected binaries. Our results include confirmation of the orbital periods in ν Geminorum, ϵ Capricorni, κ Draconis, 60 Cygni, and V2119 Cygni, its refinement in o Puppis, as well as suggesting hints for binarity in o Aquarii, BK Camelopardalis, and 10 Cassiopeae. Monitoring of the Hα line profile variations in β Canis Minoris for over the last 10 years gives further support to the existence of a 182.5-day period found earlier in a smaller set of data. A similar but still preliminary period (179.6 days) was found in the Hα line profile variations in ψ Persei. It is shown for the first time that ν Geminorum exhibits phase-locked variations in the Hα emission peak intensity ratio and, therefore, is a part of the inner binary in this triple system. Our results show that the mentioned phase-locked peak intensity variations are observed in more Be binary systems than previously known and can be used to search for binarity of Be stars when application of other methods is inconclusive.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45197716","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

Observational Implications of OJ 287’s Predicted 2022 Disk Impact in the Black Hole Binary Model OJ 287在黑洞二元模型中预测的2022年圆盘撞击的观测意义

IF 2.5

Galaxies Pub Date : 2023-07-03 DOI: 10.3390/galaxies11040082

M. Valtonen, L. Dey, A. Gopakumar, S. Zoła, A. Lähteenmäki, M. Tornikoski, Alok C. Gupta, T. Pursimo, E. Knudstrup, J. Gómez, R. Hudec, Martin Jelínek, J. Štrobl, A. Berdyugin, S. Ciprini, D. Reichart, V. Kouprianov, K. Matsumoto, M. Dróżdż, M. Mugrauer, A. Sadun, M. Zejmo, A. Sillanpää, H. Lehto, K. Nilsson, R. Imazawa, M. Uemura

{"title":"Observational Implications of OJ 287’s Predicted 2022 Disk Impact in the Black Hole Binary Model","authors":"M. Valtonen, L. Dey, A. Gopakumar, S. Zoła, A. Lähteenmäki, M. Tornikoski, Alok C. Gupta, T. Pursimo, E. Knudstrup, J. Gómez, R. Hudec, Martin Jelínek, J. Štrobl, A. Berdyugin, S. Ciprini, D. Reichart, V. Kouprianov, K. Matsumoto, M. Dróżdż, M. Mugrauer, A. Sadun, M. Zejmo, A. Sillanpää, H. Lehto, K. Nilsson, R. Imazawa, M. Uemura","doi":"10.3390/galaxies11040082","DOIUrl":"https://doi.org/10.3390/galaxies11040082","url":null,"abstract":"We present a summary of the results of the OJ 287 observational campaign, which was carried out during the 2021/2022 observational season. This season is special in the binary model because the major axis of the precessing binary happens to lie almost exactly in the plane of the accretion disc of the primary. This leads to pairs of almost identical impacts between the secondary black hole and the accretion disk in 2005 and 2022. In 2005, a special flare called “blue flash” was observed 35 days after the disk impact, which should have also been verifiable in 2022. We did observe a similar flash and were able to obtain more details of its properties. We describe this in the framework of expanding cloud models. In addition, we were able to identify the flare arising exactly at the time of the disc crossing from its photo-polarimetric and gamma-ray properties. This is an important identification, as it directly confirms the orbit model. Moreover, we saw a huge flare that lasted only one day. We may understand this as the lighting up of the jet of the secondary black hole when its Roche lobe is suddenly flooded by the gas from the primary disk. Therefore, this may be the first time we directly observed the secondary black hole in the OJ 287 binary system.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46916486","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: 1