We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass(which approximates the Johnson V-b...We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass(which approximates the Johnson V-band). Our three systems are KIC 2715417, KIC 6050116 and KIC 6287172. The first system, KIC 2715417, is considered a semi-detached system with the secondary component filling its Roche lobe. The second system, KIC 6050116, is an overcontact system, while the third system, KIC 6287172, belongs to ellipsoidal variables as deduced from the Roche lobe geometry. For photometric analysis, we used the PHOEBE software package, which is based on the Wilson-Devinney code. Due to lack of spectroscopic data, the photometric mass ratios are determined from the analyses of light curves using the q-search method. The absolute parameters are determined using three different methods(Harmanec, Maceroni &Van'tVeer and Gazeas & Niarchos).展开更多
The LAMOST spectra and Kepler light curves are combined to investigate the detached eclipsing binary KIC 8098300,which shows the O’Connell effect caused by spot/facula modulation.The radial velocity(RV)measurements a...The LAMOST spectra and Kepler light curves are combined to investigate the detached eclipsing binary KIC 8098300,which shows the O’Connell effect caused by spot/facula modulation.The radial velocity(RV)measurements are derived by using the tomographic spectra disentangling technology.The mass ratio q=K1/K2=0.812±0.007,and the orbital semimajor axis a sin i=14.984±0.048 R_(⊙)are obtained by fitting the RV curves.We optimize the binary model concerning the spot/facula activity with the code PHOEBE and obtain precise parameters of the orbit including the eccentricity e=0.0217±0.0008,the inclination i=87°.71±0°.04,and the angle of periastronω=284°.1±0°.5.The masses and radii of the primary and secondary star are determined as M_(1)=1.3467±0.0001 M_(⊙),R_(1)=1.569±0.003 R_(⊙),and M_(2)=1.0940±0.0001 M_(⊙),R_(2)=1.078±0.002 R_(⊙),respectively.The ratio of temperatures of the two component stars is r_(teff)=0.924±0.001.We also obtain the periastron precession speed of 0.000024±0.000001 day cycle-l.The residuals of out-of-eclipse are analyzed using the auto-correlation function and the discrete Fourier transform.The spot/facula activity is relatively weaker,but the lifetime is longer than that of most single main sequence stars in the same temperature range.The average rotation period of the spots P_(rot)=4.32 days is slightly longer than the orbital period,which may be caused by either the migration of spots/faculae along the longitude or the latitudinal differential rotation.The activity may be spot-dominated for the secondary star and facula-dominated for the primary star.The method of this work can be used to analyze more eclipsing binaries with the O’Connell effect in the Kepler field to obtain the precise parameters and investigate the difference of spot behavior between binaries and single stars.It is helpful for a deeper understanding of the stellar magnetic activity and dynamo theory.展开更多
This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C d...This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C diagram is a straight line with a negative slope which means that its period is almost constant for about 2 yr.Frequency analyses are performed for the residual light curve after subtracting the binary variations.The frequency spectrum reveals that one component star is aδScuti variable.Large frequency separation is cross-identified with the histogram graph and the Fourier transform method.Based on the large separation and density relationship,the mean density of theδSct component is estimated to be 0.05 g·cm-3.Five frequencies with the same frequency spacing in the range of 25 d-1-34 d-1 are detected.Statistically,the pulsation amplitudes ofδSct stars increase with decreasing of rotations,so we propose that KIC 5197256 might have a relatively large rotational velocity,and the frequency f10 might be the rotation frequency.展开更多
KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the wint...KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.展开更多
We investigate a short-period W UMa binary KIC 9026766 with an orbital period of 0.2721278 d in the Kepler field of view.By applying an automated q-search for the folded light curve and producing a synthetic light cur...We investigate a short-period W UMa binary KIC 9026766 with an orbital period of 0.2721278 d in the Kepler field of view.By applying an automated q-search for the folded light curve and producing a synthetic light curve for this object based on the PHOEBE code,we calculate the fundamental stellar parameters.We also analyze the O-C curve of the primary minima.The orbital period changes can be attributed to the combination of an upward quadratic function and light-travel time effect(LTTE)due to a possible third body with a minimum mass of 0.029 M☉and an orbital period of 972.5866±0.0041 d.The relative luminosity of the primary and secondary eclipses(MinⅠ-MinⅡ)is calculated.The periodogram of the residuals of the LTTE and MinⅠ-MinⅡshow peaks with the same period of 0.8566 d.The background effect of two nearby stars on our target is the possible reason for this signal.By considering the amplitudes and periods of the remaining signals in the O-C curve of minima,spot motion is possible.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
文摘We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass(which approximates the Johnson V-band). Our three systems are KIC 2715417, KIC 6050116 and KIC 6287172. The first system, KIC 2715417, is considered a semi-detached system with the secondary component filling its Roche lobe. The second system, KIC 6050116, is an overcontact system, while the third system, KIC 6287172, belongs to ellipsoidal variables as deduced from the Roche lobe geometry. For photometric analysis, we used the PHOEBE software package, which is based on the Wilson-Devinney code. Due to lack of spectroscopic data, the photometric mass ratios are determined from the analyses of light curves using the q-search method. The absolute parameters are determined using three different methods(Harmanec, Maceroni &Van'tVeer and Gazeas & Niarchos).
基金the support from the National Natural Science Foundation of China (NSFC) through the grants 11833002, 12090040, and 12090042Guo Shou Jing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences+2 种基金Funding for the project has been provided by the National Development and Reform CommissionLAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of SciencesFunding for the Kepler mission is provided by the NASA Science Mission directorate。
文摘The LAMOST spectra and Kepler light curves are combined to investigate the detached eclipsing binary KIC 8098300,which shows the O’Connell effect caused by spot/facula modulation.The radial velocity(RV)measurements are derived by using the tomographic spectra disentangling technology.The mass ratio q=K1/K2=0.812±0.007,and the orbital semimajor axis a sin i=14.984±0.048 R_(⊙)are obtained by fitting the RV curves.We optimize the binary model concerning the spot/facula activity with the code PHOEBE and obtain precise parameters of the orbit including the eccentricity e=0.0217±0.0008,the inclination i=87°.71±0°.04,and the angle of periastronω=284°.1±0°.5.The masses and radii of the primary and secondary star are determined as M_(1)=1.3467±0.0001 M_(⊙),R_(1)=1.569±0.003 R_(⊙),and M_(2)=1.0940±0.0001 M_(⊙),R_(2)=1.078±0.002 R_(⊙),respectively.The ratio of temperatures of the two component stars is r_(teff)=0.924±0.001.We also obtain the periastron precession speed of 0.000024±0.000001 day cycle-l.The residuals of out-of-eclipse are analyzed using the auto-correlation function and the discrete Fourier transform.The spot/facula activity is relatively weaker,but the lifetime is longer than that of most single main sequence stars in the same temperature range.The average rotation period of the spots P_(rot)=4.32 days is slightly longer than the orbital period,which may be caused by either the migration of spots/faculae along the longitude or the latitudinal differential rotation.The activity may be spot-dominated for the secondary star and facula-dominated for the primary star.The method of this work can be used to analyze more eclipsing binaries with the O’Connell effect in the Kepler field to obtain the precise parameters and investigate the difference of spot behavior between binaries and single stars.It is helpful for a deeper understanding of the stellar magnetic activity and dynamo theory.
基金supported by the National Natural Science Foundation of China(Grant No.U2031209)。
文摘This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C diagram is a straight line with a negative slope which means that its period is almost constant for about 2 yr.Frequency analyses are performed for the residual light curve after subtracting the binary variations.The frequency spectrum reveals that one component star is aδScuti variable.Large frequency separation is cross-identified with the histogram graph and the Fourier transform method.Based on the large separation and density relationship,the mean density of theδSct component is estimated to be 0.05 g·cm-3.Five frequencies with the same frequency spacing in the range of 25 d-1-34 d-1 are detected.Statistically,the pulsation amplitudes ofδSct stars increase with decreasing of rotations,so we propose that KIC 5197256 might have a relatively large rotational velocity,and the frequency f10 might be the rotation frequency.
基金support from the National Natural Science Foundation of China(NSFC,Grant Nos.11403088,11873081,U2031209,11833002,12090040,12090042 and 12003020)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.
基金the Kepler mission is provided by the NASA Science Mission directorate。
文摘We investigate a short-period W UMa binary KIC 9026766 with an orbital period of 0.2721278 d in the Kepler field of view.By applying an automated q-search for the folded light curve and producing a synthetic light curve for this object based on the PHOEBE code,we calculate the fundamental stellar parameters.We also analyze the O-C curve of the primary minima.The orbital period changes can be attributed to the combination of an upward quadratic function and light-travel time effect(LTTE)due to a possible third body with a minimum mass of 0.029 M☉and an orbital period of 972.5866±0.0041 d.The relative luminosity of the primary and secondary eclipses(MinⅠ-MinⅡ)is calculated.The periodogram of the residuals of the LTTE and MinⅠ-MinⅡshow peaks with the same period of 0.8566 d.The background effect of two nearby stars on our target is the possible reason for this signal.By considering the amplitudes and periods of the remaining signals in the O-C curve of minima,spot motion is possible.
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.
