We present a comprehensive analysis of BI CVn,an eclipsing overcontact binary system.New BVR photometric observations,combined with available spectroscopic data,were analyzed simultaneously using the Wilson–Devinney ...We present a comprehensive analysis of BI CVn,an eclipsing overcontact binary system.New BVR photometric observations,combined with available spectroscopic data,were analyzed simultaneously using the Wilson–Devinney method to derive the orbital and physical parameters of the system.The resulting stellar parameters are M1=0.58±0.01M⊙,M2=1.42±0.02M⊙,R1=0.88±0.01R⊙,R2=1.31±0.01R⊙,with an orbital separation of a=2.80±0.01R⊙.Based on all available CCD times of minimum light,including both ground-based and T ESS observations,the(O-C)diagram of BI CVn was analyzed.T he orbital period exhibits a long-term decrease at a rate of-2.3239(±0.0001)×10-8 day yr-1,likely due to mass transfer from the more massive to the less massive component.Superimposed on this trend is a cyclic variation with a period of 56.84±0.08 yr,indicative of a light-travel time effect caused by a third body,whose estimated mass is 0.63±0.02M⊙.Using these derived parameters,we modeled the binary’s evolution through non-conservative processes with the Binary Star Evolution code.The evolutionary tracks of the components were examined in multiple parameter planes,leading to an estimated merger timescale of approximately 2.70 Gyr.展开更多
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
The objective of this work is to verify the validity of the Spink's model at the lower shelf of the transition curve CVN-T.Knowing that in this field of temperatures,previous results have shown that CVN is sensiti...The objective of this work is to verify the validity of the Spink's model at the lower shelf of the transition curve CVN-T.Knowing that in this field of temperatures,previous results have shown that CVN is sensitive to the steel micro-structure of the steel,heat treatments and the existence of defects such as those caused by internal hydrogen.Mild steel,with and without internal hydrogen and a metastable austenitic 2404 alloyed steel transformed at-196℃to about 90%martensite are studied.Standard charpy specimens with different notch root radii varying from 0 to 1 mm are used to measure fracture toughness by applying j-integral and also to measure the impact energy CVN.For all,bending tests were performed and the tests temperature was-196℃.For mild steel without internal hydrogen,the changes in both fracture toughness and impact toughness as a function of notch acuity coincide perfectly and are,also,in good agreement with those obtained at the upper shelf by Ritchie et al in AISI 4340 steel in two different heat treatments.However;in the case of mild steel severely charged with internal hydrogen and containing more than 10 ppm H2,which promotes high density of defects in the grain boundaries,the two linear relations are not similar but for the two cases of zero notch radii are the same and equal to 0 mm.The bi-phases 2404 alloyed steel shows that the slopes and the critical notch root radii of the linear relations are also different.The strain induced martensite from the residual austenite,/during the fracture toughness measurements at-196℃,with low strain rate is assumed to be inhibited.Only the strain rate sensitivity is responsible for this difference.However;for all three cases studied at-196℃and for the results obtained at the upper shelf by Rithie et al,the effective notch root radii whether measured by fracture toughness or by impact energy tests are the same.The fracture type in mild steel free from internal hydrogen is by macro-cleavage,while in the presence of internal hydrogen,macro-cleavage and inter-granular feature,with large cracks are observed.After fracture toughness tests,the fracture surface of the aged martensite 2404 alloyed steel is by fine dimples"ductile-fragile"feature.The main conclusion is that by applying the Spink's model described above,large dimension specimens satisfying the standard LFEM criterion(AS TM E23-01,2001)are not necessary.展开更多
基金a project supported by the Scientific and Technological Research Council of Türkiye (TüB?TAK) under grant No.114F166
文摘We present a comprehensive analysis of BI CVn,an eclipsing overcontact binary system.New BVR photometric observations,combined with available spectroscopic data,were analyzed simultaneously using the Wilson–Devinney method to derive the orbital and physical parameters of the system.The resulting stellar parameters are M1=0.58±0.01M⊙,M2=1.42±0.02M⊙,R1=0.88±0.01R⊙,R2=1.31±0.01R⊙,with an orbital separation of a=2.80±0.01R⊙.Based on all available CCD times of minimum light,including both ground-based and T ESS observations,the(O-C)diagram of BI CVn was analyzed.T he orbital period exhibits a long-term decrease at a rate of-2.3239(±0.0001)×10-8 day yr-1,likely due to mass transfer from the more massive to the less massive component.Superimposed on this trend is a cyclic variation with a period of 56.84±0.08 yr,indicative of a light-travel time effect caused by a third body,whose estimated mass is 0.63±0.02M⊙.Using these derived parameters,we modeled the binary’s evolution through non-conservative processes with the Binary Star Evolution code.The evolutionary tracks of the components were examined in multiple parameter planes,leading to an estimated merger timescale of approximately 2.70 Gyr.
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.
文摘The objective of this work is to verify the validity of the Spink's model at the lower shelf of the transition curve CVN-T.Knowing that in this field of temperatures,previous results have shown that CVN is sensitive to the steel micro-structure of the steel,heat treatments and the existence of defects such as those caused by internal hydrogen.Mild steel,with and without internal hydrogen and a metastable austenitic 2404 alloyed steel transformed at-196℃to about 90%martensite are studied.Standard charpy specimens with different notch root radii varying from 0 to 1 mm are used to measure fracture toughness by applying j-integral and also to measure the impact energy CVN.For all,bending tests were performed and the tests temperature was-196℃.For mild steel without internal hydrogen,the changes in both fracture toughness and impact toughness as a function of notch acuity coincide perfectly and are,also,in good agreement with those obtained at the upper shelf by Ritchie et al in AISI 4340 steel in two different heat treatments.However;in the case of mild steel severely charged with internal hydrogen and containing more than 10 ppm H2,which promotes high density of defects in the grain boundaries,the two linear relations are not similar but for the two cases of zero notch radii are the same and equal to 0 mm.The bi-phases 2404 alloyed steel shows that the slopes and the critical notch root radii of the linear relations are also different.The strain induced martensite from the residual austenite,/during the fracture toughness measurements at-196℃,with low strain rate is assumed to be inhibited.Only the strain rate sensitivity is responsible for this difference.However;for all three cases studied at-196℃and for the results obtained at the upper shelf by Rithie et al,the effective notch root radii whether measured by fracture toughness or by impact energy tests are the same.The fracture type in mild steel free from internal hydrogen is by macro-cleavage,while in the presence of internal hydrogen,macro-cleavage and inter-granular feature,with large cracks are observed.After fracture toughness tests,the fracture surface of the aged martensite 2404 alloyed steel is by fine dimples"ductile-fragile"feature.The main conclusion is that by applying the Spink's model described above,large dimension specimens satisfying the standard LFEM criterion(AS TM E23-01,2001)are not necessary.
