Magnetic cataclysmic variables （CVs） contain a white dwarf （WD） with a magnetic field strong enough to control the accretion flow from a late type secondary. In this paper, we identify a magnetic CV （CXOGSG J2155...Magnetic cataclysmic variables （CVs） contain a white dwarf （WD） with a magnetic field strong enough to control the accretion flow from a late type secondary. In this paper, we identify a magnetic CV （CXOGSG J215544.4＋380116） from the Chandra archive data. The X-ray light curves show a significant period of 14.1 ks, and the X-ray spectra can be described by a multi-temperature hot thermal plasma, suggesting the source is a magnetic CV. The broad dip in the X-ray light curve is due to the eclipse of the primary magnetic pole, and the additional dip in the bright phase of the soft and medium bands may be caused by the accretion stream crossing our line of sight to the primary pole. Follow-up optical spectra show features of an M2-M4 dwarf dominating the red band and a WD which is responsible for the weak upturn in the blue band. The mass （~ 0.4 34⊙） and radius （~0.4 R⊙） for the M dwarf are obtained using CV evolution models and empirical relations between the orbital period and the mass/radius. The estimated low X-ray luminosity and accretion rate may suggest the source is a low-accretion-rate polar. In addition, Very Large Array observations reveal a possible radio counterpart to the X-ray source, but with a low significance. Further radio observations with high quality are needed to confirm the radio counterpart and explore the properties of this binary system.展开更多
The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs...The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.展开更多
GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V- and R-band data together with our observations, we discovered that the O - C curve of GSC 4560-...GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V- and R-band data together with our observations, we discovered that the O - C curve of GSC 4560-02157 may show a cyclic variation with a period of 3.51 years and an amplitude of 1.40 min. If this variation is caused by a light travel-time effect via the existence of a third body, then its mass can be derived as M3 sin i1≈ 91.08 Mjup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V - R = 0.77（±0.03） which corresponds to a spectral type of K2-3. The secondary star＇s mass was estimated as M2 = 0.73（±0.02） Mo by combing the derived V - R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass-period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf＇s radius corresponding to a lower limit on mass of M1 ≈ 0.501 M⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.展开更多
This paper presents the results of optical spectroscopic observations of two ROSAT bright sources, 1RXS J020928.9+283243 and 1RXS J042332.8+745300. The low-dispersion spectra suggest the cataclysmic variable classific...This paper presents the results of optical spectroscopic observations of two ROSAT bright sources, 1RXS J020928.9+283243 and 1RXS J042332.8+745300. The low-dispersion spectra suggest the cataclysmic variable classification for the two objects. Further photometric observations are expected to reveal the variable features and to confirm the classifications.展开更多
Cataclysmic variables are special celestial bodies because they have particular light curves and spectra.The mechanisms for generating emission lines radiated from dwarf novae in their quiescent phases are studied.We ...Cataclysmic variables are special celestial bodies because they have particular light curves and spectra.The mechanisms for generating emission lines radiated from dwarf novae in their quiescent phases are studied.We assume that the incident radiation field which is emitted by a hot source（white dwarf and boundary layer）irradiates the gaseous layer evaporated from the accretion disk,and the emission lines are radiated from the gas.We model the fluxes of emission lines by using the photoionization code CLOUDY.Using this method,we input some reasonable parameters and get a series of simulated spectra.In order to find a simulated spectrum which is the best fit to an observed spectrum,we use a cross-correlation method to match them.After the calculation,we use the approximation that the parameters of the simulated spectrum can simulate the observed spectrum.Finally,we learn more about the physical conditions of the system.展开更多
Earthquake,tsunami,nuclear plantb reakdown.Each is a major catast rophe.But Japan has been hit by all of them.Homelessness,economic losses,release of radiation.Each is a huge challenge.Now Japan must face all three.Ho...Earthquake,tsunami,nuclear plantb reakdown.Each is a major catast rophe.But Japan has been hit by all of them.Homelessness,economic losses,release of radiation.Each is a huge challenge.Now Japan must face all three.How will Japan respond to the domino-like disaster展开更多
Pattern recognition algorithms are commonly utilized to discover certain patterns,particularly in image-based data.Our study focuses on quasiperiodic oscillations(QPO)in celestial objects referred to as cataclysmic va...Pattern recognition algorithms are commonly utilized to discover certain patterns,particularly in image-based data.Our study focuses on quasiperiodic oscillations(QPO)in celestial objects referred to as cataclysmic variables(CV).We are dealing with interestingly indistinct QPO signals,which we analyze using a power density spectrum(PDS).The confidence in detecting the latter using certain statistical approaches may come out with less significance than the truth.We work with real and simulated QPO data of a CV called MV Lyrae.Our primary statistical tool for determining confidence levels is sigma intervals.The aforementioned CV has scientifically proven QPO existence,but as indicated by our analysis,the QPO ended up falling below 1-σ,and such QPOs are not noteworthy based on the former approach.We intend to propose and ultimately train a convolutional neural network(CNN)using two types of QPO data with varying amounts of training dataset lengths.We aim to demonstrate the accuracy and viability of the classification using a CNN in comparison to sigma intervals.The resulting detection rate of our algorithm is very plausible,thus proving the effectiveness of CNNs in this scientific area.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11273028 and 11333004)support from National Astronomical Observatories,Chinese Academy of Sciences under the Young Researcher Grant
文摘Magnetic cataclysmic variables （CVs） contain a white dwarf （WD） with a magnetic field strong enough to control the accretion flow from a late type secondary. In this paper, we identify a magnetic CV （CXOGSG J215544.4＋380116） from the Chandra archive data. The X-ray light curves show a significant period of 14.1 ks, and the X-ray spectra can be described by a multi-temperature hot thermal plasma, suggesting the source is a magnetic CV. The broad dip in the X-ray light curve is due to the eclipse of the primary magnetic pole, and the additional dip in the bright phase of the soft and medium bands may be caused by the accretion stream crossing our line of sight to the primary pole. Follow-up optical spectra show features of an M2-M4 dwarf dominating the red band and a WD which is responsible for the weak upturn in the blue band. The mass （~ 0.4 34⊙） and radius （~0.4 R⊙） for the M dwarf are obtained using CV evolution models and empirical relations between the orbital period and the mass/radius. The estimated low X-ray luminosity and accretion rate may suggest the source is a low-accretion-rate polar. In addition, Very Large Array observations reveal a possible radio counterpart to the X-ray source, but with a low significance. Further radio observations with high quality are needed to confirm the radio counterpart and explore the properties of this binary system.
基金supported by the National Natural Science Foundation of China through Grant 11873029the National Key Research and Development Program of China(2016YFA0400803 and 2017YFA0402703)。
文摘The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.
基金partly supported by the National Natural Science Foundation of China(Nos.11133007 and 11325315)the Key Research Program of the Chinese Academy of Sciences(Grant No.KGZD-EW-603)+1 种基金the Science Foundation of Yunnan Province(Nos.2012HC011 and 2013FB084)by the Strategic Priority Research Program The Emergence of Cosmological Structures of the Chinese Academy of Sciences(No.XDB09010202)
文摘GSC 4560-02157 is a new eclipsing cataclysmic variable with an orbital period of 0.265359 days. By using the published V- and R-band data together with our observations, we discovered that the O - C curve of GSC 4560-02157 may show a cyclic variation with a period of 3.51 years and an amplitude of 1.40 min. If this variation is caused by a light travel-time effect via the existence of a third body, then its mass can be derived as M3 sin i1≈ 91.08 Mjup, and it should be a low-mass star. In addition, several physical parameters were measured. The color of the secondary star was determined to be V - R = 0.77（±0.03） which corresponds to a spectral type of K2-3. The secondary star＇s mass was estimated as M2 = 0.73（±0.02） Mo by combing the derived V - R value around phase 0 with the assumption that it obeys the mass-luminosity relation for main sequence stars. This mass is consistent with the mass-period relation for CV donor stars. For the white dwarf, the eclipse durations and contacts of the white dwarf yield an upper limit on the white dwarf＇s radius corresponding to a lower limit on mass of M1 ≈ 0.501 M⊙. The overestimated radius and previously published spectral data indicate that the boundary layer may have a very high temperature.
文摘This paper presents the results of optical spectroscopic observations of two ROSAT bright sources, 1RXS J020928.9+283243 and 1RXS J042332.8+745300. The low-dispersion spectra suggest the cataclysmic variable classification for the two objects. Further photometric observations are expected to reveal the variable features and to confirm the classifications.
基金Supported by the National Natural Science Foundation of China (Grant No. 11163005)the Foundation of Ministry of Education (No. 211198)the Foundation of Huoyingdong (No. 121107)
文摘Cataclysmic variables are special celestial bodies because they have particular light curves and spectra.The mechanisms for generating emission lines radiated from dwarf novae in their quiescent phases are studied.We assume that the incident radiation field which is emitted by a hot source（white dwarf and boundary layer）irradiates the gaseous layer evaporated from the accretion disk,and the emission lines are radiated from the gas.We model the fluxes of emission lines by using the photoionization code CLOUDY.Using this method,we input some reasonable parameters and get a series of simulated spectra.In order to find a simulated spectrum which is the best fit to an observed spectrum,we use a cross-correlation method to match them.After the calculation,we use the approximation that the parameters of the simulated spectrum can simulate the observed spectrum.Finally,we learn more about the physical conditions of the system.
文摘Earthquake,tsunami,nuclear plantb reakdown.Each is a major catast rophe.But Japan has been hit by all of them.Homelessness,economic losses,release of radiation.Each is a huge challenge.Now Japan must face all three.How will Japan respond to the domino-like disaster
文摘Pattern recognition algorithms are commonly utilized to discover certain patterns,particularly in image-based data.Our study focuses on quasiperiodic oscillations(QPO)in celestial objects referred to as cataclysmic variables(CV).We are dealing with interestingly indistinct QPO signals,which we analyze using a power density spectrum(PDS).The confidence in detecting the latter using certain statistical approaches may come out with less significance than the truth.We work with real and simulated QPO data of a CV called MV Lyrae.Our primary statistical tool for determining confidence levels is sigma intervals.The aforementioned CV has scientifically proven QPO existence,but as indicated by our analysis,the QPO ended up falling below 1-σ,and such QPOs are not noteworthy based on the former approach.We intend to propose and ultimately train a convolutional neural network(CNN)using two types of QPO data with varying amounts of training dataset lengths.We aim to demonstrate the accuracy and viability of the classification using a CNN in comparison to sigma intervals.The resulting detection rate of our algorithm is very plausible,thus proving the effectiveness of CNNs in this scientific area.
