New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests...New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests that normal outbursts are quasi-periodic, with an amplitude of 2.5（4-0.1） mag and a period of - 18.3（4-0.7） d. The amplitude vs. recurrence-time relation ofAY Psc is discussed, and we conclude that this relation may represent general properties of dwarf nova 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 mass-transfer outbursts. Moreover, the average luminosity Is brighter during standstills than during outburst cycles. The changes in brightness mark variations in M2 due to the fact that the disk of AY Psc is nearly steady state.M2 value was limited to the range from 6.35 × 10-9 to 1.18 × 10-8 M yr-1. More detailed examination shows that there are a few small outbursts present during standstills. These events with amplitudes of - 0.5 - 0.9 mag are very similar to the stunted outbursts reported in some nova-like cataclysmic variables. We discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate.展开更多
We present eight sets of new light curves for binaries FG Sct,VZ Lib and VZ Psc,which are all contact eclipsing binaries with short orbital periods.We carried out our observations from 2016 to 2017 using the 60-cm tel...We present eight sets of new light curves for binaries FG Sct,VZ Lib and VZ Psc,which are all contact eclipsing binaries with short orbital periods.We carried out our observations from 2016 to 2017 using the 60-cm telescope administered by National Astronomical Observatories,Chinese Academy of Sciences,the Holcomb Observatory at Butler University and the SARA-CT telescope in Chile.We firstly determined the orbital parameters of FG Sct using the O-C method and obtained photometric solutions utilizing the updated W-D program.We also studied its period variation and discovered that its orbital period is decreasing at a rate of 6.39(±0.24)×10^-8 d yr-1,which was likely caused by mass transfer from the primary component to the secondary component or angular momentum interchange between the two components via magnetic interactions.For VZ Lib and VZ Psc,we simultaneously analyzed their BV RI light curves in conjunction with the published radial velocities.In order to obtain the orbital parameters of VZ Lib,we also analyzed its period variation and revised cyclic change,which could be attributed to either the light-time effect due to a tertiary companion or magnetic activity cycle mechanism.We derived the periods of the tertiary component of VZ Lib to be 48.7(±0.1) yr or magnetic cycle to be 46.9(±1.9) yr.Strong emission lines at Ca II H+K,Hα,Hβ,Hγ and Ca II IRT were detected in the LAMOST spectra of VZ Psc,which imply chromospheric activities in this binary system.展开更多
This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V4...This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V455 And were obtained at the 6-m BTA of the SAO RAS in the low state of these systems with the determination of white dwarf radiation.The theoretical spectra were calculated using the grid models of hydrogen dwarf atmospheres of white dwarfs by varying the parameters(T_(eff) and log g) to reach the best agreement with the observed ones.We highlight different effects of the parameters on the shape and intensity of the HI lines.Therefore,it is possible to unambiguously determine T_(eff) and log g from the analysis of observations.The fundamental parameters of white dwarfs(M and R) were found by comparing the parameters of atmospheres with theoretical models of the internal structure.The obtained parameters of the primaries of TY Psc,FL Psc and V455 And are consistent with the average values for SU UMa and WZ Sge systems.As a result,we demonstrate the efficiency of the method for determining the parameters of such systems based on the analysis of a limited set of observed optical spectra.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11325315,11611530685,11573063 and 11133007)the Strategic Priority Research Program “The Emergence of Cosmological Structure” of the Chinese Academy of Sciences(Grant No.XDB09010202)+1 种基金the Science Foundation of Yunnan Province(Grant No.2012HC011)supported by the Russian Foundation for Basic Research(project No.17-52-53200)
文摘New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests that normal outbursts are quasi-periodic, with an amplitude of 2.5（4-0.1） mag and a period of - 18.3（4-0.7） d. The amplitude vs. recurrence-time relation ofAY Psc is discussed, and we conclude that this relation may represent general properties of dwarf nova 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 mass-transfer outbursts. Moreover, the average luminosity Is brighter during standstills than during outburst cycles. The changes in brightness mark variations in M2 due to the fact that the disk of AY Psc is nearly steady state.M2 value was limited to the range from 6.35 × 10-9 to 1.18 × 10-8 M yr-1. More detailed examination shows that there are a few small outbursts present during standstills. These events with amplitudes of - 0.5 - 0.9 mag are very similar to the stunted outbursts reported in some nova-like cataclysmic variables. We discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate.
基金supported by the Joint Research Fund in Astronomy (U1631236 and U1431114) under cooperative agreement between the NSFC and CASpartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories, Chinese Academy of Sciences
文摘We present eight sets of new light curves for binaries FG Sct,VZ Lib and VZ Psc,which are all contact eclipsing binaries with short orbital periods.We carried out our observations from 2016 to 2017 using the 60-cm telescope administered by National Astronomical Observatories,Chinese Academy of Sciences,the Holcomb Observatory at Butler University and the SARA-CT telescope in Chile.We firstly determined the orbital parameters of FG Sct using the O-C method and obtained photometric solutions utilizing the updated W-D program.We also studied its period variation and discovered that its orbital period is decreasing at a rate of 6.39(±0.24)×10^-8 d yr-1,which was likely caused by mass transfer from the primary component to the secondary component or angular momentum interchange between the two components via magnetic interactions.For VZ Lib and VZ Psc,we simultaneously analyzed their BV RI light curves in conjunction with the published radial velocities.In order to obtain the orbital parameters of VZ Lib,we also analyzed its period variation and revised cyclic change,which could be attributed to either the light-time effect due to a tertiary companion or magnetic activity cycle mechanism.We derived the periods of the tertiary component of VZ Lib to be 48.7(±0.1) yr or magnetic cycle to be 46.9(±1.9) yr.Strong emission lines at Ca II H+K,Hα,Hβ,Hγ and Ca II IRT were detected in the LAMOST spectra of VZ Psc,which imply chromospheric activities in this binary system.
基金supported by the Ministry of Science and Higher Education of the Russian Federationfinancial support from the RFBR and the Government of the RT in the framework of scientific projects 18–42–160003funded by the subsidy 671–2020–0052 allocated to KFU for assignment in scientific activities。
文摘This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V455 And were obtained at the 6-m BTA of the SAO RAS in the low state of these systems with the determination of white dwarf radiation.The theoretical spectra were calculated using the grid models of hydrogen dwarf atmospheres of white dwarfs by varying the parameters(T_(eff) and log g) to reach the best agreement with the observed ones.We highlight different effects of the parameters on the shape and intensity of the HI lines.Therefore,it is possible to unambiguously determine T_(eff) and log g from the analysis of observations.The fundamental parameters of white dwarfs(M and R) were found by comparing the parameters of atmospheres with theoretical models of the internal structure.The obtained parameters of the primaries of TY Psc,FL Psc and V455 And are consistent with the average values for SU UMa and WZ Sge systems.As a result,we demonstrate the efficiency of the method for determining the parameters of such systems based on the analysis of a limited set of observed optical spectra.
