检索结果-内蒙古大学图书馆

The Astrophysical Journal 2019年第2期883卷

作者： Dongdong Yan Jianheng Guo Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming 650011 People's Republic of China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing People's Republic of China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 People's Republic of China

Observation of Cassini's Entry into Saturn: No Detection, and Lessons Learned

学校读者我要写书评

暂无评论

Research Notes of the AAS 2021年第6期5卷

作者： Ralph D. Lorenz Frank Crary Laurent Lamy Peter Jenniskens Liang Ge Xi-Liang Zhang Jian-Yang Li Masataka Imai Tatsuharu Ono Matthew R. Arnison Lee Spitler Johns Hopkins Applied Physics Laboratory Laurel MD 20723 USA University of Colorado Laboratory for Space and Atmospheric Science CO USA LESIA Observatoire de Paris PSL CNRS Meudon France LAM Pythéas Univ. Aix-Marseille CNES CNRS Marseille France SETI Institute Mountain View CA 94043 USA NASA Ames Research Center Moffett Field CA 94035 USA Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Science Beijing People's Republic of China Yunnan Observatories Chinese Academy of Sciences Kunming 650216 People's Republic of China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kuming 650216 People's Republic of China Planetary Science Institute Tucson AZ 85719 USA Faculty of Science Kyoto Sangyo University Kyoto Japan Department of Cosmosciences Graduate School of Science Hokkaido University Hokkaido Japan Canon Australia Sydney NSW 2113 Australia Bandicoot Imaging Sciences Sydney NSW 2101 Australia Research Centre in Astronomy Astrophysics & Astrophotonics Macquarie University Sydney NSW 2109 Australia Ralph.Lorenz@jhuapl.edu

The mission of the 2000 kg Cassini spacecraft concluded on 2017 September 15, by its deliberate entry into Saturn's atmosphere at some 31.1 km s−1. Observations, using Hubble and groundbased observatories, to attempt optical detection of this 0.25 kT 'artificial meteor' are summarized. No signatures were identified. A challenge with observing the event is that due to atmospheric drag, its timing was not completely deterministic months or even days in advance, a particular problem for space observatories. While imaging observations needed no geometric specification more than 'Saturn,' observations with spectrometers required pointing the instrument aperture or slit at the specific impact site. Since giant planet longitude systems are not always familiar, distribution of an unambiguous 'finder chart' showing the location of the predicted entry site on the disk is essential, as is clarity on whether stated times are spacecraft event time, or Earth received time (light-travel time, 83 minutes, later).

关键词： Space vehicles Meteors Meteoroids

Alma imaging of the CO (7−6) line emission in the submillimeter galaxy less 073 at redshift 4.755

学校读者我要写书评

暂无评论

arXiv 2020年

作者： Zhao, Yinghe Lu, Nanyao Díaz-Santos, Tanio Gao, Yu Xu, C. Kevin Charmandaris, Vassilis Inami, Hanae Rigopoulou, Dimitra Sanders, David B. Huang, Jiasheng Wang, Zhong Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science CAS 20A Datun Road Chaoyang District Beijing100012 China National Astronomical Observatories of China Chinese Academy of Sciences Beijing100012 China China-Chile Joint Center for Astronomy Chinese Academy of Sciences Camino El Observatorio 1515 Las Condes Santiago Chile Núcleo de Astronomía de la Facultad de Ingeniería Universidad Diego Portales Av. Ejército Libertador 441 Santiago Chile Department of Astronomy Xiamen University XiamenFujian361005 China Department of Physics University of Crete HeraklionGR-71003 Greece IAASARS National Observatory of Athens PenteliGR-15236 Greece Hiroshima Astrophysical Science Center Hiroshima University 1-3-1 Kagamiyama Higashi-HiroshimaHiroshima739-8526 Japan Department of Physics University of Oxford Keble Road OxfordOX1 3RH United Kingdom University of Hawaii Institute for Astronomy 2680 Wood-lawn Drive HonoluluHI96822 United States

In this paper we present our imaging observations on the CO (7−6) line and its underlying continuum emission of the young submillimeter galaxy LESS 073 at redshift 4.755, using the Atacama Large Millimeter/submillimeter Array (ALMA). At the achieved resolution of ∼1′′.2 × 0′′.9 (8 × 6 kpc2), the CO (7−6) emission is largely unresolved (with a deconvolved size of 1′′.1(±0′′.5) × 0′′.9(±0′′.8).), and the continuum emission is totally unresolved. The CO (7−6) line emission has an integrated flux of 0.86 ± 0.08 Jy km s−1, and a line width of 343 ± 40 km s−1. The continuum emission has a flux density of 0.51 mJy. By fitting the observed far-infrared (FIR) spectral energy distribution of LESS 073 with a single-temperature modified blackbody function, we obtained a dust temperature Tdust = 57.6 ± 3.5 K, 60-to-100 µm flux density ratio f60/f100 = 0.86 ± 0.08, and total infrared luminosity LIR = (5.8 ± 0.9) × 1012 L☉. The SED-fit-based f60/f100 is consistent with those estimated from various line ratios as advocated by our earlier work, indicating that those proposed line-ratio-based method can be used to practically derive f60/f100 for high-z sources. The total molecular gas mass of LESS 073 is (3.3 ± 1.7) × 1010 M☉, and the inferred gas depletion time is about 43 Myr. Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

Evolving ONe WD+He star systems to intermediate-mass binary pulsars

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Liu, D. Wang, B. Chen, W. Zuo, Z. Han, Z. Key Laboratory for Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China School of Physics and Electrical Information Shangqiu Normal University Shangqiu476000 China School of Science Xi'an Jiaotong University Xi'an710049 China

It has been suggested that accretion-induced collapse (AIC) is a non-negligible path for the formation of the observed neutron stars (NSs). An ONe white dwarf (WD) that accretes material from a He star may experience AIC process and eventually produce intermediate-mass binary pulsars (IMBPs), named as the ONe WD+He star scenario. Note that previous studies can only account for part of the observed IMBPs with short orbital periods. In this work, we investigate the evolution of about 900 ONe WD+He star binaries to explore the distribution of IMBPs. We found that the ONe WD+He star scenario could form IMBPs including pulsars with 5-340ms spin periods and 0.75-1.38Mo WD companions, in which the orbital periods range from 0.04 to 900 d. Compared with the 20 observed IMBPs, this scenario can cover the parameters of 13 sources in the final orbital period-WD mass plane and the Corbet diagram, most of which has short orbital periods. We found that the ONe WD+He star scenario can explain almost all the observed IMBPs with short orbital periods. This work can well match the observed parameters of PSR J1802-2124 (one of the two precisely observed IMBPs), providing a possible evolutional path for its *** also speculate that the compact companion of HD 49798 (a hydrogen depleted sdO6 star) may be not a NS based on the present work. Copyright © 2018, The Authors. All rights reserved.

关键词： White dwarfs

An extreme X-ray variability event of a weak-line quasar

学校读者我要写书评

暂无评论

arXiv 2020年

作者： Ni, Q. Brandt, W.N. Yi, W. Luo, B. Timlin, J.D. Hall, P.B. Liu, Hezhen Plotkin, R.M. Shemmer, O. Vito, F. Wu, Jianfeng Department of Astronomy & Astrophysics Pennsylvania State University Davey Lab University ParkPA16802 United States Institute for Gravitation and the Cosmos Pennsylvania State University University ParkPA16802 United States Department of Physics Pennsylvania State University University ParkPA16802 United States Yunnan Observatories Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Science Nanjing University Nanjing Jiangsu210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education Nanjing Jiangsu210093 China Collaborative Innovation Center of Modern Astronomy and Space Exploration Nanjing210093 China Department of Physics & Astronomy York University 4700 Keele Street TorontoONM3J 1P3 Canada Department of Physics University of Nevada 1664 N. Virginia St RenoNV89557 United States Department of Physics University of North Texas DentonTX76203 United States Instituto de Astrofísica Centro de Astroingeniería Facultad de Física Pontificia Universidad Católica de Chile Casilla 306 Santiago 22 Chile Chinese Academy of Sciences South America Center for Astronomy National Astronomical Observatories CAS Beijing100012 China Department of Astronomy Xiamen University Xiamen Fujian361005 China

We report the discovery of an extreme X-ray ux rise (by a factor of 20) of the weak-line quasar SDSS J153913.47+395423.4 (hereafter SDSS J1539+3954) at z = 1.935. SDSS J1539+3954 is the most-luminous object among radio-quiet type 1 AGNs where such dramatic X-ray variability has been observed. Before the X-ray ux rise, SDSS J1539+3954 appeared X-ray weak compared with the expectation from its UV ux;after the rise, the ratio of its X-ray ux and UV ux is consistent with the majority of the AGN population. We also present a contemporaneous HET spectrum of SDSS J1539+3954, which demonstrates that its UV continuum level remains generally unchanged despite the dramatic increase in the X-ray ux, and its C iv emission line remains weak. The dramatic change only observed in the X-ray ux is consistent with a shielding model, where a thick inner accretion disk can block our line of sight to the central X-ray source. This thick inner accretion disk can also block the nuclear ionizing photons from reaching the high-ionization broad emission-line region, so that weak high-ionization emission lines are observed. Under this scenario, the extreme X-ray variability event may be caused by slight variations in the thickness of the disk. This event might also be explained by gravitational light-bending effects in a reection model. Copyright © 2020, The Authors. All rights reserved.

关键词： Electromagnetic wave emission

The physical characteristics of interstellar medium in NGC 3665 with herschel observations

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Xiao, Meng-Yuan Zhao, Yinghe Gu, Qiu-Sheng Shi, Yong School of Astronomy and Space Science Nanjing University Nanjing210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Nanjing210093 China Yunnan Observatories CAS Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China Collaborative Innovation Center of Modern Astronomy and Space Exploration Nanjing210093 China Center for Astronomical Mega-Science CAS 20A Datun Road Chaoyang District Beijing100012 China

We present the analysis of the physical properties of the interstellar medium (ISM) in the nearby early-type galaxy NGC 3665, based on the far-infrared (FIR) photometric and spectroscopic data as observed by the Herschel Space Observatory. The fit to the spectral energy distribution reveals a high dust content in the galaxy, with the dust-to-stellar mass ratio of Mdust/M∗ ∼ 1.1 × 10−4 that is nearly three times larger than the mean value of local S0+S0a galaxies. For the ionized regions (H ii regions), the electron density (ne) is around 49.5 ± 11.9 cm−3 based on the [N ii] 122 µm/[N ii] 205 µm ratio. For the photodissociation regions, the heating efficiency is in the range of 1.26 × 10−3 and 1.37 × 10−3 based on the ([C ii] + [O i] 63 µm)/LTIR, which is slightly lower than other local galaxies;the hydrogen nucleus density and the strength of FUV radiation field are n ∼ 104 cm−3 and G0 ∼ 10−0.25, respectively. The above results are consistent with the presence of weak AGN and a low level of star-forming activity in NGC 3665. Our results give strong support to the 'morphological quenching' scenario, where a compact, massive bulge can stabilize amount of cool gas against star formation. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Which evolutionary status does the Blue Large-Amplitude Pulsators stay at?

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Wu, Tao Li, Yan Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

Asteroseismology is a very useful tool for exploring the stellar interiors and evolution- ary status and for determining stellar fundamental parameters, such as stellar mass, radius, surface gravity, and the stellar mean density. In the present work, we use it to preliminarily analyze the 14 new-type pulsating stars: Blue Large-Amplitude Pulsators (BLAPs) which is observed by OGLE project, to roughly analyze their evolutionary status. We adopt the theory of single star evolution and artificially set the mass loss rate of M = -2 × 10-4Mo/year and mass loss beginning at the radius of R = 40 Ro on red giant branch to generate a series of theoretical models. Based on these theoretical models and the corresponding observations, we find that those BLAP stars are more likely to be the core helium burning stars. Most of them are in the middle and late phase of the helium burning. Copyright © 2018, The Authors. All rights reserved.

关键词： Gravitation

SN 2017fgc: A fast-expanding Type Ia supernova exploded in massive shell galaxy NGC 474

学校读者我要写书评

暂无评论

arXiv 2021年

作者： Zeng, Xiangyun Wang, Xiaofeng Esamdin, Ali Pellegrino, Craig Burke, Jamison Stahl, Benjamin E. Zheng, Weikang Filippenko, Alexei V. Howell, D. Andrew Sand, D.J. Valenti, Stefano Mo, Jun Xi, Gaobo Liu, Jialian Zhang, Jujia Li, Wenxiong Iskandar, Abdusamatjan Zhang, Mengfan Lin, Han Sai, Hanna Xiang, Danfeng Wei, Peng Zhang, Tianmeng Reichart, D.E. Brink, Thomas G. McCully, Curtis Hiramatsu, Daichi Hosseinzadeh, Griffin Jeffers, Benjamin T. Ross, Timothy W. Stegman, Samantha Wang, Lifan Zhang, Jicheng Ma, Shuo Xinjiang Astronomical Observatory Chinese Academy of Sciences Xinjiang Urumqi830011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Science of Technology Beijing100044 China Department of Physics University of California Santa BarbaraCA93106-9530 United States Las Cumbres Observatory 6740 Cortona Drive GoletaCA93117-5575 United States Department of Astronomy University of California BerkeleyCA94720-3411 United States Department of Physics University of California BerkeleyCA94720-7300 United States Marc J. Staley Graduate Fellow Miller Senior Fellow Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Department of Physics University of California DavisCA95616 United States Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China Department of Physics and Astronomy University of North Carolina at Chapel Hill Chapel HillNC27599 United States Center for Astrophysics Harvard and Smithsonian 60 Garden Street CambridgeMA02138-1516 United States Las CumbresObservatory 6740 Cortona Drive GoletaCA9311-5575 United States Department of Chemistry University of Wisconsin MadisonWI53706 United States George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy Texas AandM University Department of Physics and A

We present extensive optical photometric and spectroscopic observations of the high-velocity (HV) Type Ia supernova (SN Ia) 2017fgc, covering the phase from ∼12 d before to ∼ 389 d after maximum brightness. SN 2017fgc is similar to normal SNe Ia, with an absolute peak magnitude of MB max ≈ -19:32 ± 0:13 mag and a post-peak decline of Δm15(B) = 1:05 ± 0:07 mag. Its peak bolometric luminosity is derived as (1:32 ± 0:13) × 1043erg s-1, corresponding to a 56Ni mass of 0:51 ± 0:03Mo. The light curves of SN 2017fgc are found to exhibit excess emission in the UBV bands in the early nebular phase and pronounced secondary shoulder/maximum features in the RrIi bands. Its spectral evolution is similar to that of HV SNe Ia, with a maximum-light Si II velocity of 15;000 ± 150 km s-1and a post-peak velocity gradient of ∼ 120 ± 10 km s-1d-1. The Fe II and Mg II lines blended near 4300 Å and the Fe II, Si II, and Fe III lines blended near 4800 Åare obviously stronger than those of normal SNe Ia. Inspecting a large sample reveals that the strength of the two blends in the spectra, and the secondary peak in the i=r-band light curves, are found to be positively correlated with the maximum-light Si II velocity. Such correlations indicate that HV SNe Ia may experience more complete burning in the ejecta and/or that their progenitors have higher metallicity. Examining the birthplace environment of SN 2017fgc suggests that it likely arose from a stellar environment with young and high-metallicity populations. © 2021, CC BY.

关键词： Supernovae

Vertical structure of radiation-pressure-dominated thin disks: Link between vertical advection and convective stability

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Gong, Hong-Yu Gu, Wei-Min Department of Astronomy Xiamen University Xiamen Fujian361005 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

In the classic picture of standard thin accretion disks, the viscous heating is balanced by the radiative cooling through the diffusion process, and the radiation-pressure-dominated inner disk suffers convec-tive instability. However, recent simulations have shown that the vertical advection process owing to the magnetic buoyancy can make significant contribution to the energy transport. In addition, no convective instability has been found by comparing the simulation results with the local convective stability criterion. In this work, following the spirit of simulations, we revisit the vertical structure of radiation-pressure-dominated thin disks by including the vertical advection process. Our study indicates a link between the additional energy transport and the convectively stable property. Thus, the vertical advection not only has significant contribution to the energy transport, but also plays an important role to make the disk convectively stable. Our analyses may be helpful to understand the discrepancy between the classic theory and simulations on standard thin disks. Copyright © 2017, The Authors. All rights reserved.

关键词： Stability criteria

The Radio and -ray variability analysis of S5 0716+714

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Li, H.Z. Jiang, Y.G. Yi, T.F. Guo, D.F. Chen, X. Zhang, H.M. Gao, Q.G. Lu, F.W. Ren, J.Y. Physics Department Yuxi Normal University Yuxi653100 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Sciences Shandong University Weihai264209 China Physics Department Yunan Normal University Kunming Yunnan650092 China GXU-NAOC Center for Astrophysics and Space Sciences Department of Physics Guangxi University Nanning530004 China Guangxi Key Laboratory for the Relativistic Astrophysics Nanning530004 China

We have studied the variability of S5 0716+714 at radio 15 GHz and -ray band using three different methods. A possible periodicity of P15GHz = 266.0 ± 11.5 and P = 344.0 ± 16.4 days are obtained for radio 15 GHz and -ray light curves, respectively. The variability may be related to the intrinsically emission mechanism. The difference between the variability timescales of radio 15 GHz and -ray may be due to that the emission of radio 15 GHz is produced via the synchrotron process, while the -ray is produced by both the SSC and EC processes. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies