We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stell...We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.展开更多
The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here. We reconstruct the observed light curves with a two-starspot model by mea...The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here. We reconstruct the observed light curves with a two-starspot model by means of a light curve modeling technique, and find that the active regions shift oppositely along longitude on a time scale of one day. Combining with the observational data obtained by other groups, we discuss the evolution of spotted regions in the photosphere, and find that its starspots evolve not only on a short time scale but also on a long time scale. The pure chromospheric emissions for Ca IIHK and Hβ lines are derived by using the spectral subtraction technique. The variation of Ca IIHK lines＇ excess emission is spatially correlated to the starspot regions. There is no clear rotational modulation for the Hβ line＇s excess emission, probably due to the contamination of prominence emission.展开更多
A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its sup...A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its supper Eddington luminosity of PULX.NGC 7793 P13,which is the second confirmed PULX,can be easily studied due to its nearby position and isolation from other sources in its host galaxy.In this paper,we calculate its magnetic field to be∼1.0×10^(12) G based on the continued observations from 2016 to 2020.The magnetic field evolution of NGC 7793 P13 is analyzed,which shows that the source has spent about 10^(4) yr for the field decaying from the simulated initial strength 4.0×10^(14) G to the present value.In case of an assumed constant accretion and the limitation of the companion mass,it will be a recycled PSR whose magnetic field is ∼10^(9) G and spin period is a few hundred milliseconds.We estimate the field strength of the other confirmed PULXs and find main range is 10^(13)-10^(14) G.Their positions of the magnetic field and spin period are around or below the magnetars.This is because these PULXs are in the binary systems and are with the spin-up rate that are 2-3 orders higher than the normal binary pulsars.We suggest that PULXs are the accreting magnetars whose multi-pole strong magnetic field can support the supper Eddington luminosity.They would be helpful for studying the evolution of the magnetars,the formation of the binary PSRs above the Eddington spin-up line,and the millisecond PSRs with the magnetic field stronger than ∼10^(9) G.展开更多
恒星视界公司推出的一体机以“数字家庭体验中心”和PC作为家庭生活的核心，彻底改变了以前数字家庭产品停留在概念化的阶段。该公司最新推出的ALL IN ONE系列液晶多媒体一体机——PP19S-28H，同时兼备高效强悍运算处理能力与时尚轻巧...恒星视界公司推出的一体机以“数字家庭体验中心”和PC作为家庭生活的核心，彻底改变了以前数字家庭产品停留在概念化的阶段。该公司最新推出的ALL IN ONE系列液晶多媒体一体机——PP19S-28H，同时兼备高效强悍运算处理能力与时尚轻巧外观两大特性，完美演绎一体机的优势。展开更多
基金Funding for the TESS mission is provided by the NASA Explorer Program。
文摘We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.
基金supported by the National Natural Science Foundation of China(Grant Nos.10373023 and 10773027)a grant from the Sik Sik Yuen of Hong Kong,China
文摘The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here. We reconstruct the observed light curves with a two-starspot model by means of a light curve modeling technique, and find that the active regions shift oppositely along longitude on a time scale of one day. Combining with the observational data obtained by other groups, we discuss the evolution of spotted regions in the photosphere, and find that its starspots evolve not only on a short time scale but also on a long time scale. The pure chromospheric emissions for Ca IIHK and Hβ lines are derived by using the spectral subtraction technique. The variation of Ca IIHK lines＇ excess emission is spatially correlated to the starspot regions. There is no clear rotational modulation for the Hβ line＇s excess emission, probably due to the contamination of prominence emission.
基金supported by the National Natural Science Foundation of China(12130342,12273030 and U1938107)。
文摘A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its supper Eddington luminosity of PULX.NGC 7793 P13,which is the second confirmed PULX,can be easily studied due to its nearby position and isolation from other sources in its host galaxy.In this paper,we calculate its magnetic field to be∼1.0×10^(12) G based on the continued observations from 2016 to 2020.The magnetic field evolution of NGC 7793 P13 is analyzed,which shows that the source has spent about 10^(4) yr for the field decaying from the simulated initial strength 4.0×10^(14) G to the present value.In case of an assumed constant accretion and the limitation of the companion mass,it will be a recycled PSR whose magnetic field is ∼10^(9) G and spin period is a few hundred milliseconds.We estimate the field strength of the other confirmed PULXs and find main range is 10^(13)-10^(14) G.Their positions of the magnetic field and spin period are around or below the magnetars.This is because these PULXs are in the binary systems and are with the spin-up rate that are 2-3 orders higher than the normal binary pulsars.We suggest that PULXs are the accreting magnetars whose multi-pole strong magnetic field can support the supper Eddington luminosity.They would be helpful for studying the evolution of the magnetars,the formation of the binary PSRs above the Eddington spin-up line,and the millisecond PSRs with the magnetic field stronger than ∼10^(9) G.
