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Long-term photometric behaviour of the eclipsing Z Cam-type dwarf nova AY Psc

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arXiv 2017年

作者： Han, Zhong-Tao Qian, Sheng-Bang Voloshina, Irina Zhu, Li-Ying 7 P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Sternberg Astronomical Institute Moscow State University Universitetskij prospect 13 Moscow119992 Russia

New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. Based on the long-term AAVSO data, moreover, the outburst behaviors were also explored. Our analysis suggests that the normal outbursts are quasiperiodic, with an amplitude of ~ 2.5(±0.1) mag and a period of ~ 18.3(±0.7) days. The amplitude vs. recurrence-time relation of AY Psc is discussed, and we concluded that this relation may represents general properties of dwarf nova (DN) outbursts. The observed standstill ends with an outburst, which is inconsistent with the general picture of Z Cam-type stars. This unusual behavior was considered to be related to the mass-transfer outbursts. Moreover, the average luminosity is brighter during standstills than during outburst cycles. The changes in brightness marks the variations in M2due to the disc of AY Psc is nearly steady state.M2value was limited to the range from 6.35 × 10-9to 1.18 × 10-8Moyr-1. More detailed examination shows that there are a few small outbursts presence during standstills. These events with amplitudes of ~ 0.5 - 0.9 mag are very similar to the stunted outbursts reported in some *** discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate. Copyright © 2017, The Authors. All rights reserved.

关键词： Cams

Kerr-Newman-AdS black hole in quintessential dark energy

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Physical Review D 2017年第6期95卷 064015-064015页

作者： Zhaoyi Xu Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 People’s Republic of China University of Chinese Academy of Sciences Beijing 100049 People’s Republic of China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 People’s Republic of China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing 100012 People’s Republic of China

Quintessential dark energy with pressure p and density ρ is related by equation of state p=ωρ with the state parameter −1<ω<−1/3. The cosmological dark energy influence on black hole spacetime is interesting and important. In this paper, we study the Kerr-Newman-AdS solutions of the Einstein-Maxwell equation in quintessence field around a black hole by Newman-Janis algorithm and complex computations. From the horizon structure equation, we obtain the expression between quintessence parameter α and cosmological constant Λ if the black hole exists two cosmological horizon rq and rc when ω=−2/3, the result is different from rotational black hole in quintessence matter situation. Through analysis we find that the black hole charge cannot change the value of α. But the black hole spin and cosmological constant are opposite. The black hole spin and cosmological constant make the maximum value of α small. The existence of four horizon leads seven types of extremal black holes to constrain the parameter α. With the state parameter ω ranging from −1 to −1/3, the maximum value of α changes from Λ to 1. When ω→−1, the quintessential dark energy likes cosmological constant. The singularity of the black holes is the same with that of Kerr black hole. We also discuss the rotation velocity of the black holes on the equatorial plane for ω=−2/3, −1/2 and −1/3. For small value of α, the rotation velocity on the equatorial plane is asymptotically flat and it can explain the rotation curves in spiral galaxies.

关键词： Dark energy General relativity

Discovery of a deep, low mass ratio overcontact binary GSC 03517–00663

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Research in Astronomy and Astrophysics 2015年第6期15卷 889-895页

作者： Di-Fu Guo Kai Li Shao-Ming Hu Yun-Guo Jiang Dong-Yang Gao Xu Chen Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Sciences Shandong University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

When observing blazars, we identified a new eclipsing binary named GSC 03517-00663. The light curves of GSC 03517-00663 are typical of EW-type light curves. Based on the observation using the 1 m telescope at the Weihai Observatory of Shandong University, complete VRI light curves were determined. Then, we analyzed the multiple light curves using the Wilson-Devinney program. It was found that GSC 03517-00663 has a mass ratio of q = 0.164 and a degree of contact of f = 69.2%. GSC 03517-00663 is a deep, low mass ratio overcontact binary. The light curves of GSC 03517-00663 show a strong O＇Connell effect, which was explained by employing a dark spot on the secondary component.

关键词： stars binaries close -- stars binaries eclipsing -- stars individual （GSC 03517-00663）

A phenomenological model for the light curve of three quiescent low-inclination dwarf novae and one pre-cataclysmic variable

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arXiv 2018年

作者： Dai, Zhibin Szkody, Paula Kennedy, Mark Su, Jie Medagangoda, N. Indika Robinson, Edward L. Garnavich, Peter M. De Silva, L. Malith M. 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 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Yuquan Road Shijingshan District Beijing100049 China University of Washington SeattleWA98195 United States Jodrell Bank Centre for Astrophysics School of Physics and Astronomy University of Manchester ManchesterM13 9PL United Kingdom Arthur C. Clarke Institute for Modern Technologies Sri Lanka University of Texas at Austin AustinTX United States University of Notre Dame Notre DameIN46556 United States Sabaragamuwa University of Sri Lanka

We used the light curve code XRBinary to model the quiescent K2 light curves of three low-inclination cataclysmic variables (CVs): 1RXS J0632+2536 (J0632+2536), RZ Leo, TW Vir and the pre-CV WD 1144+011. Optimized light curve models were obtained using a nonlinear fitting code NMfit and visualized by Phoebe 2.0. The disk model of J0632+2536 shows that one hotspot at the edge of the disk is enough to describe its light curve, while the other two dwarf nova (DN): RZ Leo and TW Vir require two hotspots. A typical pre-CV model with a weak irradiation effect for WD 1144+011 can explain its single-hump modulation, and the newly observed spectrum confirms its previous classification. The synthetic analyses for the DN clearly indicate that phase zero of the double-hump modulations occurs around the secondary minimum and the primary hump is mainly caused by the hotspot at the edge of the disk. The quiescent disk has a flat temperature distribution with a power index of ∼ 0.11. The disk model of RZ Leo implies a truncated disk, supporting its previously speculated classification as an intermediate polar (IP). Except for the IP model of RZ Leo, which lacks a component related to the inferred accretion curtain, the models of J0632+2536, TW Vir and WD 1144+011 are consistent with results from the Gaia mission. The derived masses and radii of the secondaries of the three DN are consistent with the semiempirical relations for CV donor stars, while their effective temperatures are higher than the predictions. Irradiation of the donor stars is investigated to explain this discrepancy. Copyright © 2018, The Authors. All rights reserved.

关键词： Modulation

Rotational splitting and asteroseismic modelling of the Δ scuti star EE camelopardalis

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arXiv 2017年

作者： Chen, Xinghao Li, Yan Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

According to the rotational splitting law of g modes, the frequency spectra of EE Cam can be disentangled only with oscillation modes of l = 0, 1, and 2. Fifteen sets of rotational splits are found, containing five sets of l = 1 multiplets and ten sets of l = 2 multiplets. The rotational period of EE Cam is deduced to be Prot = 1.84+0.07 -0.05 days. When we do model fittings, we use two nonradial oscillation modes (f11and f32) and the fundamental radial mode f1. The fitting results show that X2 of the best-fitting model is much smaller than those of other theoretical models. The physical parameters of the best-fitting model are M = 2.04 Mo, Z = 0.028, Teff = 6433 K, log L/Lo = 1.416, R = 4.12 Ro, log g = 3.518, and X2 = 0.00035. Furthermore, we find f11and f32are mixed mode, which mainly characterize the features of the helium core. The fundamental radial mode f1mainly restrict the features of the stellar envelope. Finally, the acoustic radius t0 and the period separation 0 are determined to be 5.80 hr and 463.7 s respectively, and the size of the helium core of EE Cam is estimated to be MHe = 0.181Mo and RHe = 0.0796 Ro. Copyright © 2017, The Authors. All rights reserved.

关键词： Cams

Using the Markov Chain Monte Carlo method to study the physical properties GeV-TeV BL Lac objects

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arXiv 2017年

作者： Qin, Longhua Wang, Jiancheng Yang, Chuyuan Yuan, Zunli Kang, Shiju Mao, Jirong Yunnan Observatory Chinese Academy of Sciences KunmingYunnan Province650011 China University of Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China School of Electrical Engineering Liupanshui Normal University LiupanshuiGuizhou553004 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We fit the spectral energy distributions (SEDs) of 46 GeV - TeV BL Lac objects in the frame of leptonic one-zone synchrotron self-Compton (SSC) model and investigate the physical properties of these objects. We use the Markov Chain Monte Carlo (MCMC) method to obtain the basic parameters, such as magnetic field (B), the break energy of the relativistic electron distribution (γb′) and the electron energy spectral index. Based on the modeling results, we support the following scenarios on GeV-TeV BL Lac objects: (1) Some sources have large Doppler factors, implying other radiation mechanism should be considered. (2) Comparing with FSRQs, GeV-TeV BL Lac objects have weaker magnetic field and larger Doppler factor, which cause the ineffective cooling and shift the SEDs to higher bands. Their jet powers are around 4.0 × 1045 erg · s−1, comparing with radiation power, 5.0 × 1042 erg · s−1, indicating that only a small fraction of jet power is transformed into the emission power. (3) For some BL Lacs with large Doppler factors, their jet components could have two substructures, e.g., the fast core and the slow sheath. For most GeV-TeV BL Lacs, Kelvin-Helmholtz instabilities are suppressed by their higher magnetic fields, leading few micro-variability or intro-day variability in the optical bands. (4) Combined with a sample of FSRQs, an anti-correlation between the peak luminosity Lpk and the peak frequency νpk is obtained, favoring the blazar sequence scenario. In addition, an anti-correlation between the jet power Pjet and the break Lorentz factor γb also supports the blazar sequence. Copyright © 2017, The Authors. All rights reserved.

关键词： Gamma rays

WZ Sge: An eclipsing cataclysmic variable evolving towards the period minimum

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arXiv 2017年

作者： Han, Z.-T. Qian, S.-B. Voloshina, Irina Zhu, L.-Y. P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Sternberg Astronomical Institute Moscow State University Universitetskij prospect 13 Moscow119992 Russia

We present the photometric results of the eclipsing cataclysmic variable (CV) WZ Sge near the period minimum (Pmin). Eight new mid-eclipse times were determined and the orbital ephemeris was updated. Our result shows that the orbital period of WZ Sge is decreasing at a rate of P = -2.72(±0.23) × 10-13ss-1. This secular decrease, coupled with previous detection of its donor, suggest that WZ Sge is a pre-bounce system. Further analysis indicates that the observed period decrease rate is about 1.53 times higher than pure gravitational radiation (GR) driving. We constructed the evolutionary track of WZ Sge, which predicts that Pminof WZ Sge is ~ 77.98(±0.90) min. If the orbital period decreases at the current rate, WZ Sge will evolve past its Pminafter ~ 25.3 Myr. Based on the period evolution equation we find M2≈ 4.04(±0.10) × 10-11Moyr-1, which is compatible with the current concept of CV evolution at ultrashort orbital periods. Copyright © 2017, The Authors. All rights reserved.

关键词： Stars

TESS Asteroseismic analysis of the known exoplanet shost star HD 222076

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arXiv 2020年

作者： Jiang, Chen Bedding, Timothy R. Stassun, Keivan G. Veras, Dimitri Corsaro, Enrico Buzasi, Derek L. Mikolajczyk, Przemys law Zhang, Qian-sheng Ou, Jian-wen Campante, Tiago L. Rodrigues, Thaíse S. Nsamba, Benard Bossini, Diego Kane, Stephen R. Ong, Jia Mian Joel Yıldız, Mutlu Orhan, Zeynep Çeiik Örtel, Sibel Wu, Tao Zhang, Xinyi Li, Tanda Basu, Sarbani Cunha, Margarida S. Christensen-Dalsgaard, Jørgen Chaplin, William J. School of Physics and Astronomy Sun Yat-Sen University No. 135 Xingang Xi Road Guangzhou510275 China Department of Physics and Astronomy Aarhus University Ny Munkegade 120 Aarhus C8000 Denmark School of Physics University of Sydney NSW2006 Australia Vanderbilt University Department of Physics and Astronomy 6301 Stevenson Center Ln. NashvilleTN37235 United States 6301 Stevenson Center Ln. NashvilleTN37235 United States Centre for Exoplanets and Habitability University of Warwick CoventryCV4 7AL United Kingdom Department of Physics University of Warwick CoventryCV4 7AL United Kingdom INAF — Osservatorio Astrofisico di Catania via S. Sofia 78 Catania95123 Italy Department of Chemistry & Physics Florida Gulf Coast University 10501 FGCU Boulevard S. Fort MyersFL33965 United States Astronomical Institute University of Wroclaw Mikolaja Kopernika 11 Wroclaw51-622 Poland Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Rua das Estrelas Porto4150-762 Portugal Departamento de Física e Astronomia Faculdade de Ciências da Universidade do Porto Rua do Campo Alegre s/n Porto4169-007 Portugal Osservatorio Astronomico di PadovaINAF Vicolo dellOsservatorio 5 PadovaI-35122 Italy Max-Planck-Institut für Astrophysik Karl-Schwarzschild-Str. 1 GarchingD-85748 Germany Department of Earth and Planetary Sciences University of California RiversideCA92521 United States Department of Astronomy Yale University P.O. Box 208101 New HavenCT06520-8101 United States Department of Astronomy and Space Sci

The Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission aiming to search for exoplanets that transit bright stars. The high-quality photometric data of TESS are excellent for the asteroseismic study of solar-like stars. In this work, we present an asteroseismic analysis of the red-giant star HD 222076 hosting a long-period (2.4 yr) giant planet discovered through radial velocities. Solar-like oscillations of HD 222076 are detected around 203 µHz by TESS for the first time. Asteroseismic modeling, using global asteroseismic parameters as input, yields a determination of the stellar mass (M? = 1.12 ± 0.12M), radius (R? = 4.34 ± 0.21 R), and age (7.4 ± 2.7 Gyr), with precisions greatly improved from previous studies. The period spacing of the dipolar mixed modes extracted from the observed power spectrum reveals that the star is on the red-giant branch burning hydrogen in a shell surrounding the core. We find that the planet will not escape the tidal pull of the star and be engulfed into it within about 800 Myr, before the tip of the red-giant branch is reached. Copyright © 2020, The Authors. All rights reserved.

关键词： Extrasolar planets

Multi-color photometric investigation of the totally eclipsing binary NO Cam

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arXiv 2017年

作者： Xiao, Zhou Shengbang, Qian Bin, Zhang Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 Graduate University of the Chinese Academy of Sciences Yuquan Road 19 Sijingshang Block Beijing100049

Multi-color photometric light curves of NO Cam in V RCand ICbands are obtained and analyzed simultaneously using the Wilson-Devinney (W-D) program. The solutions suggest that NO Cam is an A-subtype overcontact binary with its mass ratio to be q = 0.439 and a contact degree of f = 55.5%. The small temperature difference (ΔT = 44K) between its two components indicates that the system is under thermal contact. The high orbital inclination (i = 84.5°) strengthens our confidence in the parameters determined from the light curves. All available times of minimum light are collected and period variations are analyzed for the first time. The O - C curve reveals that its period is increasing continuously at a rate of dP/dt = +1.46 × 10-9, which can be explained by mass transfer from the less massive component to the more massive one. After the upward parabolic variation is subtracted, the residuals suggest that there may be a cyclic variation with a period of 2.23 years and an amplitude of A3= 0.00153 days, which may due to the light-travel time effect (LTTE) arising from the gravitational influence of a close-in tertiary component. The close-in companion reveals that early dynamic interaction among triple system may have played very important role in the formation of the W UMa type binaries. Copyright © 2017, The Authors. All rights reserved.

关键词： Photometry