A new CCD （V） light curve is presented for the semi-detached binary system FU Ara. The light curve, obtained in 2007, is the first one since the last 50 years. With our data we were able to determine six new times o...A new CCD （V） light curve is presented for the semi-detached binary system FU Ara. The light curve, obtained in 2007, is the first one since the last 50 years. With our data we were able to determine six new times of minimum light and refined the period of the system to 0.8645049 days. A Wilson-Devinney analysis leads to a solution of a semi- detached configuration, composed of a main-sequence primary component of spectral type F5, fractionally smaller than its Roche lobe, and an evolved secondary component of spectral type K1 which fills its Roche lobe, and which is overluminous and oversized as compared with the main-sequence. The two components of FU Ara differ considerably in effective temperature. It is classified as an FO Virginis type of near-contact binary system. Assuming a reasonable value for the mass of the primary component, an estimate of the absolute elements of FU Ara has been made, on the assumption that the primary has a mass corresponding to its spectral type according to Svechnikov ＆ Taidakova.展开更多
CCD photometric observations of the short-period eclipsing binary DZ Lyn were obtained during seven nights in March-April 2008 in the B, V, Rc and Ic bands; these observations confirm the short-period （P = 0.378 d） ...CCD photometric observations of the short-period eclipsing binary DZ Lyn were obtained during seven nights in March-April 2008 in the B, V, Rc and Ic bands; these observations confirm the short-period （P = 0.378 d） of the system. The presented light curves are analyzed by means of the 2003 version of the Wilson-Devinney （WD） program. A grid of solutions for several fixed values of mass ratio was calculated. The best fitting possible is for a mass ratio of q -- 0.885, a degree of contact f = 0.18 and a low orbital inclination of i = 57.6°. The results show that DZ Lyn is an A-subtype W Ursae Majoris contact binary in poor thermal contact; in fact the difference between the mean temperatures of the components is about 1800 K. The star DZ Lyn seems to be another member of the class of poorly understood close binaries in or near geometrical contact but far from thermal contact. The absolute dimensions are estimated and its dynamical evolution is inferred.展开更多
We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS VS2443858,NSVS 780649 and V1098 Her.The absolute astrophysical parameters of the stellar components were determined by means of Ga...We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS VS2443858,NSVS 780649 and V1098 Her.The absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve solutions.The results show that:(ⅰ)Two of the systems,NSVS 2443858 and V1098 Her,are of A subtype while the obtained temperature of the secondary component of NSVS 780649 indicates that it is a W-subtype system;(ⅱ)The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary(EMRB)systems;(ⅲ)All the systems have deep contact configurations,so they also are deep low mass ratio(DLMR)systems;(ⅳ)The components of our systems are stars of F and G spectral type and undergo total eclipses;(ⅴ)The sum 0.871 M⊙of the component masses of NSVS 780649 is below the mass limit of 1.0-1.2 M⊙assumed for the known contact binary stars.展开更多
We present CCD B and V light curves,obtained in the year 2006,and a photometric solution of the low-mass ratio contact binary ASAS 021209＋2708.3. With our data we were able to determine six new times of minimum light...We present CCD B and V light curves,obtained in the year 2006,and a photometric solution of the low-mass ratio contact binary ASAS 021209＋2708.3. With our data we were able to determine six new times of minimum light and refine the orbital period of the system to 0.3181963 days.The light curves are analyzed using the 2003 version of the Wilson-Devinney program and the analysis was performed with and without adding a spot on the surface of one star because the light curves appear to exhibit a typical O’Connell effect,with Maximum I brighter than Maximum II.The results show that ASAS 021209＋2708.3 may be classified as an A-subtype W Ursae Majoris system with a small mass ratio q=0.1889,a large over-contact degree of f= 0.587,a very small difference between the component temperatures of Δ T=53 K and an orbital inclination of i=81°.It is known that deep（f50%） ,low-mass ratio（q0.25） overcontact binary stars are a very important resource for understanding the phenomena of Blue Straggler/FK Com-type stars.The formations of Blue Straggler stars and FK Com-type stars are unsolved problems in stellar astrophysics.One of the possible explanations for their formation is from the coalescence of W UMa-type overcontact binary systems.The absolute dimensions of ASAS 021209＋2708.3 are estimated and its dynamical evolution is inferred.展开更多
文摘A new CCD （V） light curve is presented for the semi-detached binary system FU Ara. The light curve, obtained in 2007, is the first one since the last 50 years. With our data we were able to determine six new times of minimum light and refined the period of the system to 0.8645049 days. A Wilson-Devinney analysis leads to a solution of a semi- detached configuration, composed of a main-sequence primary component of spectral type F5, fractionally smaller than its Roche lobe, and an evolved secondary component of spectral type K1 which fills its Roche lobe, and which is overluminous and oversized as compared with the main-sequence. The two components of FU Ara differ considerably in effective temperature. It is classified as an FO Virginis type of near-contact binary system. Assuming a reasonable value for the mass of the primary component, an estimate of the absolute elements of FU Ara has been made, on the assumption that the primary has a mass corresponding to its spectral type according to Svechnikov ＆ Taidakova.
文摘CCD photometric observations of the short-period eclipsing binary DZ Lyn were obtained during seven nights in March-April 2008 in the B, V, Rc and Ic bands; these observations confirm the short-period （P = 0.378 d） of the system. The presented light curves are analyzed by means of the 2003 version of the Wilson-Devinney （WD） program. A grid of solutions for several fixed values of mass ratio was calculated. The best fitting possible is for a mass ratio of q -- 0.885, a degree of contact f = 0.18 and a low orbital inclination of i = 57.6°. The results show that DZ Lyn is an A-subtype W Ursae Majoris contact binary in poor thermal contact; in fact the difference between the mean temperatures of the components is about 1800 K. The star DZ Lyn seems to be another member of the class of poorly understood close binaries in or near geometrical contact but far from thermal contact. The absolute dimensions are estimated and its dynamical evolution is inferred.
基金supported partly by project DN08/20 of Scientific Foundation of the Bulgarian Ministry of Education and Scienceproject RD 0-92/2019 of Shumen Universitythe support of the private IRIDA OBSERVATORY。
文摘We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS VS2443858,NSVS 780649 and V1098 Her.The absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve solutions.The results show that:(ⅰ)Two of the systems,NSVS 2443858 and V1098 Her,are of A subtype while the obtained temperature of the secondary component of NSVS 780649 indicates that it is a W-subtype system;(ⅱ)The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary(EMRB)systems;(ⅲ)All the systems have deep contact configurations,so they also are deep low mass ratio(DLMR)systems;(ⅳ)The components of our systems are stars of F and G spectral type and undergo total eclipses;(ⅴ)The sum 0.871 M⊙of the component masses of NSVS 780649 is below the mass limit of 1.0-1.2 M⊙assumed for the known contact binary stars.
文摘We present CCD B and V light curves,obtained in the year 2006,and a photometric solution of the low-mass ratio contact binary ASAS 021209＋2708.3. With our data we were able to determine six new times of minimum light and refine the orbital period of the system to 0.3181963 days.The light curves are analyzed using the 2003 version of the Wilson-Devinney program and the analysis was performed with and without adding a spot on the surface of one star because the light curves appear to exhibit a typical O’Connell effect,with Maximum I brighter than Maximum II.The results show that ASAS 021209＋2708.3 may be classified as an A-subtype W Ursae Majoris system with a small mass ratio q=0.1889,a large over-contact degree of f= 0.587,a very small difference between the component temperatures of Δ T=53 K and an orbital inclination of i=81°.It is known that deep（f50%） ,low-mass ratio（q0.25） overcontact binary stars are a very important resource for understanding the phenomena of Blue Straggler/FK Com-type stars.The formations of Blue Straggler stars and FK Com-type stars are unsolved problems in stellar astrophysics.One of the possible explanations for their formation is from the coalescence of W UMa-type overcontact binary systems.The absolute dimensions of ASAS 021209＋2708.3 are estimated and its dynamical evolution is inferred.
