New light curves and photometric solutions of FP Lyn,FV CVn and V354 UMa are presented.We found that these three systems are W-subtype shallow contact binaries.In addition,it is obvious that the light curves of FP Lyn...New light curves and photometric solutions of FP Lyn,FV CVn and V354 UMa are presented.We found that these three systems are W-subtype shallow contact binaries.In addition,it is obvious that the light curves of FP Lyn and V354 UMa are asymmetric.Therefore,a hot spot was added on the primary star of FP Lyn and a dark spot was added on the secondary star of V354 UMa.At the same time,we added a third light to the photometric solution of FP Lyn for the final result.The obtained mass ratios and fill-out factors are q = 1.153 and f = 13.4% for FP Lyn,q = 1.075 and f = 4.6% for FV CVn,and q = 3.623 and f = 10.7% for V354 UMa respectively.The investigations of orbital period for these three systems indicate that the periods are variable.FP Lyn and V354 UMa were discovered to have secularly increasing components with rates of dp/dt = 4.19 ×10^-7 dyr^-1 and dp/dt = 7.70 ×10^-7 dyr^-1 respectively,which are feasibly caused by conservative mass transfer from the less massive component to the more massive component.In addition,some variable components were discovered for FV CVn,including a rate of dp/dt =-1.13 ×10^-6 dyr^-1 accompanied by a cyclic oscillation with amplitude and period of 0.0069 d and 10.65 yr respectively.The most likely explanation for the long-term decrease is angular momentum loss.The existence of an additional star is the most plausible explanation for the periodic variation.展开更多
Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the A...Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. The H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium.We reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, and discuss its potential for improving our description of the outer regions of circumstellar shells.展开更多
基金financial support from the Universidad Nacional Aut ónoma de México (UNAM) and DGAPA (PAPIIT IN 100918)supported by the National Natural Science Foundation of China (NSFC) (No. 11703016)+3 种基金by the Joint Research Fund in Astronomy (No. U1431105)by the Natural Science Foundation of Shandong Province (No. ZR2014AQ019)by the Young Scholars Program of Shandong University, Weihai (No. 20820171006)by the Open Research Program of Key Laboratory for the Structure and Evolution of Celestial Objects (No. OP201704)
文摘New light curves and photometric solutions of FP Lyn,FV CVn and V354 UMa are presented.We found that these three systems are W-subtype shallow contact binaries.In addition,it is obvious that the light curves of FP Lyn and V354 UMa are asymmetric.Therefore,a hot spot was added on the primary star of FP Lyn and a dark spot was added on the secondary star of V354 UMa.At the same time,we added a third light to the photometric solution of FP Lyn for the final result.The obtained mass ratios and fill-out factors are q = 1.153 and f = 13.4% for FP Lyn,q = 1.075 and f = 4.6% for FV CVn,and q = 3.623 and f = 10.7% for V354 UMa respectively.The investigations of orbital period for these three systems indicate that the periods are variable.FP Lyn and V354 UMa were discovered to have secularly increasing components with rates of dp/dt = 4.19 ×10^-7 dyr^-1 and dp/dt = 7.70 ×10^-7 dyr^-1 respectively,which are feasibly caused by conservative mass transfer from the less massive component to the more massive component.In addition,some variable components were discovered for FV CVn,including a rate of dp/dt =-1.13 ×10^-6 dyr^-1 accompanied by a cyclic oscillation with amplitude and period of 0.0069 d and 10.65 yr respectively.The most likely explanation for the long-term decrease is angular momentum loss.The existence of an additional star is the most plausible explanation for the periodic variation.
基金the Vietnam National Satellite Centre(VNSC/VAST)the NAFOSTED funding agency+3 种基金the World Laboratorythe Odon Vallet Foundationthe Rencontres du Viet Namthe PCMI programme of the CNRS for financial support
文摘Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. The H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium.We reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, and discuss its potential for improving our description of the outer regions of circumstellar shells.
