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The first photometric study of the short period shallow contact system LO Comae

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arXiv 2017年

作者： Zhang, Y. Han, Q.W. Liu, J.Z. Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi830011 China Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China

In this paper, the first complete photometric light curves in the B, V, and R passbands for an eclipsing binary LO Com are presented, and the photometric solution for the LO Com is derived by analyzing these light curves by using the Wilson and Devinney code. From the photometric solution, it is found that the LO Com is a W-type W UMa binary with a mass ratio of q = m2=m1= 2:478 and a contact degree of f = (3.2±0.25)%. By combining the two new minimum times with those published earlier in the literature, we have found that the (O-C) curve shows a downward parabolic variation corresponding to a long-term decrease in the orbital period with a rate of dP/dt = -1.18×10-7days yr-1. This long-term decrease in its orbital period may be caused by mass transfer from the more massive component to the less massive one. Copyright © 2017, The Authors. All rights reserved.

关键词： Photometry

Physical parameters and orbital period variation of a newly discovered cataclysmic variable GSC 4560-02157

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Research in Astronomy and Astrophysics 2016年第10期16卷 55-62页

作者： Zhong-Tao Han Sheng-Bang Qian Irina Voloshina Vladimir G. Metlov Li-Ying Zhu Lin-Jia Li Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216China University of Chinese Academy of Sciences Beijing 100049 China Sternberg Astronomical Institute Moscow State University Universitetskij prospect 13 Moscow 119992 Russia

GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V- and R-band data together with our observations, we discovered that the O - C curve of GSC 4560-02157 may show a cyclic variation with a period of 3.51 years and an amplitude of 1.40 min. If this variation is caused by a light travel-time effect via the existence of a third body, then its mass can be derived as M3 sin i1≈ 91.08 Mjup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V - R = 0.77（±0.03） which corresponds to a spectral type of K2-3. The secondary star＇s mass was estimated as M2 = 0.73（±0.02） Mo by combing the derived V - R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass-period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf＇s radius corresponding to a lower limit on mass of M1 ≈ 0.501 M⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.

关键词： techniques： photometric -- stars： binaries： cataclysmic variables -- stars： individual：GSC 4560-02157

Accreting CO material onto ONe white dwarfs towards accretion-induced collapse

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arXiv 2017年

作者： Wu, C. Wang, B. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

The final outcomes of accreting ONe white dwarfs (ONeWDs) have been studied for several decades, but there are still some issues not resolved. Recently, some studies suggested that the deflagration of oxygen would occur for accreting ONe WDs with Chandrasekhar masses. In this paper, we aim to investigate whether ONe WDs can experience accretion-induced collapse (AIC) or explosions when their masses approach the Chandrasekhar limit. Employing the stellar evolution code modules for experiments in stellar astrophysics (MESA), we simulate the long-Term evolution of ONe WDs by accreting CO material. The ONe WDs undergo weak multicycle carbon flashes during the mass-Accretion process, leading to the mass increase of the WDs. We found that different initialWDmasses and mass-Accretion rates have influence on the evolution of central density and temperature. However, the central temperature cannot reach the explosive oxygen ignition temperature due to the neutrino cooling. This work implies that the final outcome of accreting ONe WDs is electron-capture induced collapse rather than thermonuclear explosion. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631: Forbidden hugs in pandemic times - III

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arXiv 2022年

作者： Cai, Yong Zhi Pastorello, A. Fraser, M. Wang, X.-F. Filippenko, A.V. Reguitti, A. Patra, K.C. Goranskij, V.P. Barsukova, E.A. Brink, T.G. Elias-Rosa, N. Stevance, H.F. Zheng, W. Yang, Y. Atapin, K.E. Benetti, S. De Boer, T.J.L. Bose, S. Burke, J. Byrne, R. Cappellaro, E. Chambers, K.C. Chen, W.-L. Emami, N. Gao, H. Hiramatsu, D. Howell, D.A. Huber, M.E. Kankare, E. Kelly, P.L. Kotak, R. Kravtsov, T. Lander, V.Yu. Li, Z.-T. Lin, C.-C. Lundqvist, P. Magnier, E.A. Malygin, E.A. Maslennikova, N.A. Matilainen, K. Mazzali, P.A. McCully, C. Mo, J. Moran, S. Newsome, M. Oparin, D.V. Padilla Gonzalez, E. Reynolds, T.M. Shatsky, N.I. Smartt, S.J. Smith, K.W. Stritzinger, M.D. Tatarnikov, A.M. Terreran, G. Uklein, R.I. Valerin, G. Vallely, P.J. Vozyakova, O.V. Wainscoat, R. Yan, S.-Y. Zhang, J.-J. Zhang, T.-M. Zheltoukhov, S.G. Dastidar, R. Fulton, M. Galbany, L. Gangopadhyay, A. Ge, H.-W. Gutiérrez, C.P. Lin, H. Misra, K. Ou, Z.-W. Salmaso, I. Tartaglia, L. Xiao, L. Zhang, X.-H. Tsinghua University Beijing100084 China Inaf - Osservatorio Astronomico di Padova Vicolo dell'Osservatorio 5 Padova35122 Italy School of Physics O'Brien Centre for Science North University College Dublin Dublin 4 Belfield Ireland Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Departamento de Ciencias Fisicas Universidad Andres Bello Fernandez Concha 700 Santiago Las Condes Chile Nuncio Monsenor Sòtero Sanz 100 Santiago Providencia8320000 Chile Nagaraj-Noll-Otelline Sternberg Astronomical Institute of the Moscow State University Moscow119234 Russia Special Astrophysical Observatory Russian Academy of Sciences Nizhnij Arkhyz 369167 Russia Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain The Department of Physics The University of Auckland Private Bag 92019 Auckland New Zealand Astrophysics Research Centre School of Mathematics and Physics Queen's University Belfast Northern Ireland BelfastBT7 1NN United Kingdom Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States Department of Astronomy The Ohio State University 140 W. 18th Avenue ColumbusOH43210 United States The Ohio State University 191 W.Woodruff Avenue ColumbusOH43210 United States Las Cumbres Observatory 6740 Cortona Dr. Suite 102 GoletaCA93117 United States Department of Physics University of California Santa Barbara Santa BarbaraCA93106 United States Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138-1516 United States The Nsf Ai Institute for Artificial Intelligence and Fundamental Interactions United States School of Physics and Astronomy University of Minnesota 116 Church Street SE MinneapolisMN55455 United States Department of Physics and Astronomy University of Turku TurkuFI-20014 Finland Turku Collegium for Science Medicine and Technology University

We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from ∼ 231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼ 1.6×1041erg s-1, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (TBB≈ 2050 K) with molecular features (e.g. TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival Hubble Space Telescope data taken on 2003 August 3 reveals a ∼ 20 Moprogenitor candidate with log (L/Lo) = 5.0 dex and Teff= 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17-24 Moprimary component. Copyright © 2022, The Authors. All rights reserved.

关键词： Luminance

A mixture evolution scenario of the agn radio luminosity function. II. Do low- and high-power radio-loud agns evolve differently

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arXiv 2017年

作者： Yuan, Zunli Wang, Jiancheng Zhou, Ming Qin, Longhua Mao, Jirong Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

Following previous work, we further confirm that the cosmic evolution of steep-spectrum radio-loud AGNs (active galactic nuclei) can be reproduced by a simple combination of density evolution (DE) and luminosity evolution (LE). This mixture evolution scenario can naturally explain the luminosity-dependent evolution of radio-loud AGNs. Our models successfully fitted a large amount of data on radio luminosity functions (RLFs) of steep-spectrum sources and multi-frequency source counts. The modeling indicates that the DE slowly increase as (1 + z)0.3∼1.3 out to z ∼ 0.8, and then rapidly decreases as (1 + z)−6.8∼−5.7, while the LE rapidly increase as (1 + z)4.8 out to a higher redshift (at least z > 3.5). We find a high-redshift decline (i.e. redshift cutoff) in the number density of steep-spectrum radio sources, but we cannot conclude whether such decline is sharp or shallow. We believe that whether a redshift cutoff occurs or not depends mainly on DE, while its steepness is decided by LE, which, however, cannot be well constrained due to the lack of high-redshift samples. Most intriguingly, according to our mixture evolution scenario, there appears to be no need for different evolution for the low- and high-power radio-loud AGNs. Both types of sources experience the same combined evolution of DE and LE. Copyright © 2017, The Authors. All rights reserved.

关键词： Luminance

Merging of a CO WD and a He-rich white dwarf to produce a type Ia supernovae

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arXiv 2017年

作者： Liu, D. Wang, B. Wu, C. Han, Z. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Context. Although type Ia supernovae (SNe Ia) play a key role in astrophysics, the companions of the exploding carbon-oxygen white dwarfs (CO WDs) are still not completely identified. It has been suggested recently that a He-rich WD (a He WD or a hybrid HeCO WD) that merges with a CO WD may produce an SN Ia. This theory was based on the double-detonation model, in which the shock compression in the CO core caused by the surface explosion of the He-rich shell might lead to the explosion of the whole CO WD. However, so far, very few binary population synthesis (BPS) studies have been made on the merger scenario of a CO WD and a He-rich WD in the context of SNe Ia. Aims. We aim to systematically study the Galactic birthrates and delay-time distributions of SNe Ia based on the merger scenario of a CO WD and a He-rich WD. Methods. We performed a series of Monte Carlo BPS simulations to investigate the properties of SNe Ia from the merging of a CO WD and a He-rich WD based on the Hurley rapid binary evolution code. We also considered the influence of different metallicities on the final results. Results. From our simulations, we found that no more than 15% of all SNe Ia stem from the merger scenario of a CO WD and a He-rich WD, and their delay times range from ∼110 Myr to the Hubble time. This scenario mainly contributes to SN Ia explosions with intermediate and long delay times. The present work indicates that the merger scenario of a CO WD and a He-rich WD can roughly reproduce the birthrates of SN 1991bg-like events, and cover the range of their delay times. We also found that SN Ia birthrates from this scenario would be higher for the cases with low metallicities. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

Multi-color blackbody emission in GRB 081221

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arXiv 2018年

作者： Hou, Shu-Jin Zhang, Bin-Bin Meng, Yan-Zhi Wu, Xue-Feng Liang, En-Wei Lu, Hou-Jun Liu, Tong Liang, Yun-Feng Lin, Lin Lu, Rui-Jing Huang, Jin-Shu Zhang, Bing College of Physics and Electronic Engineering Nanyang Normal University Nanyang Henan473061 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Department of Physics GXU-NAOC Center for Astrophysics and Space Sciences Guangxi University Nanning530004 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China School of Astronomy and Space Science Nanjing University Nanjing210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education China Department of Astronomy Xiamen University Xiamen Fujian361005 China Department of Astronomy Beijing Normal University Beijing100875 China Department of Physics and Astronomy University of Nevada Las VegasNV89154 United States

The radiation mechanism of the prompt emission of gamma-ray bursts (GRBs) remains an open question. Although their spectra are usually well fitted with the empirical Band function, which is widely believed to be fully nonthermal and interpreted as an optically thin synchrotron emission, accumulating evidence shows that a thermal component actually exists. In this paper, a multicolor blackbody (mBB) model is proposed for the time-integrated spectrum of GRB 081221 by assuming a power-law distribution of the thermal luminosities with temperature, which manifests photospheric emissions from a different radius and/or angle. The effects of the minimum temperature kTmin, the maximum temperature kTmax and the power law index m of the luminosity distribution of an mBB are discussed. The fitting to the time-integrated spectrum during the bright phase (from 20s to 30s since the trigger) of GRB 081221 by the mBB model yields kTmin = 4.4± 0.3 keV, kTmax = 57.0 +1.6-1.4 keV, and m =-0.46+0.05-0.06. When the time bin is small enough, the time-resolved spectra of GRB 081221 are well fitted with a series of single-temperature blackbodies. Our results imply the prompt emission of GRB 081221 is dominated by the photosphere emission and its time-integrated spectrum is a superposition of pure blackbody components at different times, indicating that some empirical Band spectra may be interpreted as mBB if the temperature is widely distributed. Copyright © 2018, The Authors. All rights reserved.

关键词： Gamma rays

Populations of accreting white dwarfs

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arXiv 2018年

作者： Chen, Hai-Liang Woods, Tyrone E. Yungelson, Lev Gilfanov, Marat Han, Zhanwen Yunnan Observatories CAS Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Science Beijing100012 China Institute of Gravitational Wave Astronomy School of Physics and Astronomy University of Birmingham BirminghamB15 2TT United Kingdom Institute of Astronomy RAS 48 Pyatnitskaya Str. Moscow119017 Russia Max Planck Institute for Astrophysics Karl-Schwarzschild-Str. 1 Garching b. München85741 Germany Space Research Institute of Russian Academy of Sciences Profsoyuznaya 84/32 Moscow117997 Russia

Using a hybrid binary population synthesis approach, we modelled the formation and evolution of populations of accreting WDs for differing star formation histories. We found that the delay time distribution of SNe Ia in the single degenerate scenario is inconsistent with observations. Additionally, we found that our predicted X-ray and UV emission of populations of accreting WDs are consistent with the X-ray luminosities of early-type galaxies observed by Chandra and the HeII 4686Å/Hβ line ratio measured in stacked SDSS spectra of passively evolving galaxies. Moreover, we found that the majority of current novae in elliptical-like galaxies have low-mass WDs, long decay times, long recurrence periods and are relatively faint. In contrast, the majority of current novae in spiral-like galaxies have massive WDs, short decay times, short recurrence periods and are relatively bright. Our predicted distribution of mass-loss timescales in an M31-like galaxy is consistent with observations for Andromeda. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Revealing two radio active galactic nuclei extremely near PSR J0437-4715

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arXiv 2018年

作者： Li, Zhixuan Yang, Jun An, Tao Paragi, Zsolt Deller, Adam Reynolds, Cormac Hong, Xiaoyu Wang, Jiancheng Ding, Hao Xia, Bo Yan, Zhen Guo, Li Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650216 China Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-43992 Sweden Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China Postbus 2 DwingelooNL-7990 AA Netherlands Centre for Astrophysics & Supercomputing Swinburne University of Technology John St HawthornVIC3122 Australia CSIRO Astronomy and Space Science KensingtonWA6151 Australia University of Chinese Academy of Sciences 19A Yuquan Road Shijingshan District Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 Key Laboratory of Radio Astronomy Chinese Academy of Sciences Nanjing210009

Newton's gravitational constant G may vary with time at an extremely low level. The time variability of G will affect the orbital motion of a millisecond pulsar in a binary system and cause a tiny difference between the orbital period-dependent measurement of the kinematic distance and the direct measurement of the annual parallax distance. PSR J0437-4715 is the nearest millisecond pulsar and the brightest at radio. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, we searched for compact radio sources quite close to PSR J0437-4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, we detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and separations of 13 and 45 arcsec. With a network consisting of the Long Baseline Array and the Kunming 40-m radio telescope, we found that both sources have a point-like structure and a brightness temperature of >107K. According to these radio inputs and the absence of counterparts in the other bands, we argue that they are most likely the compact radio cores of extragalactic active galactic nuclei rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable us to achieve a sub-pc distance accuracy with the in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of G in the near future. Copyright © 2018, The Authors. All rights reserved.

关键词： Geometrical optics