In this study,we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June 2.We carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on...In this study,we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June 2.We carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of the outburst,which shows the presence of hydrogen absorption lines commonly found in dwarf nova outbursts.Analysis of photometric data reveals the occurrence of early superhumps in the initial days of observations,followed by ordinary and late superhumps.We have accurately calculated the period of the ordinary superhumps as Pord=0.05681(10)days and determined the periods at different stages,as well as the rate of change of the superhump period(P_(dot)=(5)P/P=8.1×10^(-5)).Additionally,we have derived the mass ratio of the components(q=0.09),and estimated the color temperature during the outburst as~11,000 K,the distance to the system(d=560 pc)and absolute magnitude of the system in outburst(MV=5.3).We have shown that outbursts of this star are very rare:based on brightness measurements on 600 archival photographic plates,we found only one outburst that occurred in 1984.This fact,as well as the properties listed above,convincingly shows that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.展开更多
G328 = A65 = L3314 （V = 13.83, B - V = 1.91） is a field star in the direction of the globular cluster M4. If we take E（B - V） = 0.40, then its （B - V）0 = 1.51, corresponding to a spectral type of K5Ⅲ if it is a...G328 = A65 = L3314 （V = 13.83, B - V = 1.91） is a field star in the direction of the globular cluster M4. If we take E（B - V） = 0.40, then its （B - V）0 = 1.51, corresponding to a spectral type of K5Ⅲ if it is a giant star; or of dM2 if it is a dwarf. Observations at both the MSSSO and Yunnan Observatory have shown that G328 is a new variable with peak to peak amplitude ≌ 0.05 mag in V. While it is not unusual for so red a star to be a variable, special attention must be paid to its short period of about one day. If the variability is due to pulsation, the spectral type and luminosity as well as effective temperature should be determined in order to compare it with Xiong＇s theory.展开更多
By means of a population synthesis code, we investigate the Mira variables. Their birth rate （over 0.65yr^-1） and their number （～ 130000） in the Galaxy are estimated. For all possible Mira variables, ranges of th...By means of a population synthesis code, we investigate the Mira variables. Their birth rate （over 0.65yr^-1） and their number （～ 130000） in the Galaxy are estimated. For all possible Mira variables, ranges of their initial masses,pulsating periods, mass losses and lifetimes are given. We check our model with the observed Mira variables near the Sun and our results prove to be valid.展开更多
New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests...New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests that normal outbursts are quasi-periodic, with an amplitude of 2.5（4-0.1） mag and a period of - 18.3（4-0.7） d. The amplitude vs. recurrence-time relation ofAY Psc is discussed, and we conclude that this relation may represent general properties of dwarf nova outbursts. The observed standstill ends with an outburst, which is inconsistent with the general picture of Z Cam- type stars. This unusual behavior was considered to be related to mass-transfer outbursts. Moreover, the average luminosity Is brighter during standstills than during outburst cycles. The changes in brightness mark variations in M2 due to the fact that the disk of AY Psc is nearly steady state.M2 value was limited to the range from 6.35 × 10-9 to 1.18 × 10-8 M yr-1. More detailed examination shows that there are a few small outbursts present during standstills. These events with amplitudes of - 0.5 - 0.9 mag are very similar to the stunted outbursts reported in some nova-like cataclysmic variables. We discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate.展开更多
We report on time-resolved spectroscopic observations of the SU Ursae Majoris dwarf nova, YZ Cnc for over llh on two nights during its 2002 January superoutburst. The spectra on the first day only showed absorption-li...We report on time-resolved spectroscopic observations of the SU Ursae Majoris dwarf nova, YZ Cnc for over llh on two nights during its 2002 January superoutburst. The spectra on the first day only showed absorption-line profiles, while on the second day the lines showed “W” profiles with blue and red troughs. The radial velocity curve of the absorption troughs and emission peaks of H/3 has an amplitude of 49±10 km s^-1 and a phase offset of -0.07±0.04, which are very similar to those measured in quiescence. However, the γ velocity deviates strongly from the systemic velocity measured in quiescence, by some ±60 km s^-1. Large shifts of -70 km s^-1 in the orbital-averaged velocity and -0.09 in the phase are also found in our observations. All these features can be well explained by a precessing, eccentric disk.展开更多
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
A new set of low-resolution spectral and UBVJHKL-photometric observations of the symbi- otic nova PU Vul is presented. The binary has been evolving after its symbiotic nova outburst in 1977 and now it is in the nebula...A new set of low-resolution spectral and UBVJHKL-photometric observations of the symbi- otic nova PU Vul is presented. The binary has been evolving after its symbiotic nova outburst in 1977 and now it is in the nebular stage. It is found that the third orbital cycle （after 1977） was characterized by great changes in associated light curves. Now, PU Vul exhibits a sine-wave shape in all the light curves （with an amplitude in the U band of about 0.7 mag）, which is typical for symbiotic stars in the quiescent state. Brightness variability due to pulsations of the cool component is now clearly visible in the VRI light curves. The amplitude of the pulsations increases from 0.5 mag in the V band to 0.8 mag in the I band. These two types of variability, as well as a very slow change in the physical parameters of the hot component due to evolution after the outburst of 1977, influence the spectral energy distribution （SED） of the system. The variability of emission lines is highly complex. Only hydrogen line fluxes vary with orbital phase. An important feature of the third orbital cycle is the first emergence of the OVI, 6828A Raman scattering line. We determine the temperature of the hot component by means of the Zanstra method applied to the He II, 4686A line. Our estimate is about 150000 K for the spectrum obtained near orbital maximum in 2014. The VO spectral index derived near pulsation minimum corresponds to M6 spectral class for the cool component of PU Vul.展开更多
In this Mini-Volume, seven papers written on the basis of talks selected from those presented at the scientific conference "Modern studies of variable stars," commemorating Prof. M. A. Svechnikov(1933–2011)...In this Mini-Volume, seven papers written on the basis of talks selected from those presented at the scientific conference "Modern studies of variable stars," commemorating Prof. M. A. Svechnikov(1933–2011), are published. The conference covered a variety of variable-star topics; the papers in this Mini-Volume deal with close, mainly eclipsing, binaries, Herbig Be stars and stellar molecular masers, with an accent on stellar catalogs of different kinds. We briefly review the contents of these papers.展开更多
The star 1-1-42 （=vZ1390）, a cluster member in M3, located near the red edge of the instability strip of the horizontal branch, was discovered by Roberts and Sandage as a low amplitude variable, it was designated as...The star 1-1-42 （=vZ1390）, a cluster member in M3, located near the red edge of the instability strip of the horizontal branch, was discovered by Roberts and Sandage as a low amplitude variable, it was designated as V204 in the ＂second catalogue of variable stars in globular clusters＂, but its coordinates given in all versions of this catalogue are wrong since 1955. We argue that V204 is indeed a low amplitude HB variable star, located near to the red edge of the instability strip, with a period of 0.74785d and an amplitude of about 0.04 mag in V. We also find that the red cluster member star 1-1-39 is a low amplitude variable with a period of 1.16^d and amplitude of about 0.03 mag in V which might be pulsating at the second overtone.展开更多
We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillati...We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillations of β Cephei stars which are often rapidly rotating stars. Our results show that the third-order perturbation formalism presented by Soufi et al. should be corrected for some missing terms and some misprints in the equations. As a first step in our study of β Cephei stars, we quantify by numerical calculations the effect of rotation on the oscillation frequencies of a uniformly rotating zero-age main-sequence star with 12 M⊙. For an equatorial velocity of 100 km s^-1, it is found that the second- and third-order corrections for （l, m） = （2, 2）, for instance, are of the order of 0.01% of the frequency for radial order n = 6 and reaches up to 0.5% for n = 14.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
Time-series photometric observations were made for the high amplitudeδScuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories,Chinese Academy of Sciences.After performin...Time-series photometric observations were made for the high amplitudeδScuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories,Chinese Academy of Sciences.After performing the frequency analysis of the light curves,we confirmed the fundamental frequency of f=5.28677 c d 1,together with seven harmonics of the fundamental frequency,which are newly detected.No additional frequencies were detected.The O C diagram,produced with the 21 newly determined times of maximum light combined with those provided in the literature,helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355±0.000000003 d.展开更多
We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys（CRTS,DASCH,NSVS,OMC and Super WASP）and our photometric observations.Combining with the data in literature,a ...We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys（CRTS,DASCH,NSVS,OMC and Super WASP）and our photometric observations.Combining with the data in literature,a total of 179 times of light maximum are used to analyze the O-C diagram of BO Lyn.We find that it can be described by an upward parabolic component and a periodic variation with a period of 34.5±0.1 yr.The latter could be caused by the light travel time effect as a result of an additional companion orbiting in a highly elliptical orbit（e=0.64±0.03）.Our study indicates that the companion’s luminosity cannot be ignored,and it should be a late A-type main-sequence star.The long-term period change of BO Lyn is also detected,and its value,1.52±0.26×10^（-3）d Myr^（-1）,is consistent with evolutionary models.We suggest that more spectroscopic and photometric observations are needed in the future to confirm the nature of the BO Lyn system.展开更多
This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by ...This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by Xinjiang Astronomical Observatory. 19 variable stars and three variable candi- dates were detected in a 45＇ - 48.75＇ field around the cluster. 12 of the variable stars are newly-discovered variable objects. The physical properties, classifications and memberships of these 22 objects are studied through their light curves, their positions on the color-magnitude diagram and with archival data from the Naval Observatory Merged Astrometric Dataset. Among these objects, five are eclipsing binary systems, six are pulsating variable stars including one known 6 Scuti star and one newly-discovered RR Lyrae star. The distance to the RR Lyrae star is estimated to be 7.9 - 0.3 kpc, indicating that the star is located far behind the cluster. Four variable stars are probable members of the cluster, and 13 of the 22 objects are confirmed to be field stars.展开更多
We present a progress of a long term project to obtain UBVI CCD photometry of open clusters which were little studied before, using the Doyak 1.8 m telecope of Bohyunsan Optical Astronomy Observatory operated by the K...We present a progress of a long term project to obtain UBVI CCD photometry of open clusters which were little studied before, using the Doyak 1.8 m telecope of Bohyunsan Optical Astronomy Observatory operated by the Korea Astronomical Observatory, in Korea. The primary goals of this project are (1) to make a catalog of UBVI photometry of open clusters, (2) to make an atlas of open clusters, and (3) to survey and monitor variable stars in open clusters.展开更多
We are playing a lead role for growth of astronomy and its quality teaching and research in Manipur, a State located at northeast India (longitude = 93°58'E;latitude = 24°44'N;altitude = 782 m). We h...We are playing a lead role for growth of astronomy and its quality teaching and research in Manipur, a State located at northeast India (longitude = 93°58'E;latitude = 24°44'N;altitude = 782 m). We have innovatively designed and constructed three cost effective observatories, each costing a few hundred USD. These observatories are completely different in design and are perfectly usable for doing serious work on astronomical observation and measurements, using small ground-based telescopes. One Celestron CGE1400 telescope is housed with equatorial mounting in one of three constructed observatories and the same observatory has been inducted, since January 2012, as one of the members of the “Orion Project”, which is an international project headquartered at Phoenix, Arizona, USA, dedicated for photometric and spectroscopic observations of five bright variable stars of the Orion constellation. We have been producing high precision BVRI photometric data that match well with those produced by other observatories enrolled in the Orion project. Our photometric data were presented and discussed in the 33rd Annual Conference of the Society for Astronomical Sciences: Symposium on Telescope Science, held at Ontario, California, USA during June 12 - 14, 2014. Further, we could successfully demonstrate them to the entire population of the State and play live shows of the observation of three spectacular astronomical events namely, solar eclipse of 15th January 2010, lunar eclipse of 10th December 2011 and Transit of Venus of June 6, 2012. We have conducted a number of seminars and workshops for training and research in astronomy. In the present paper, we would like describe our self-built observatories, our observational facilities, the BVRI photometric data that we acquired for the Orion project, and other activities undertaken for growth of astronomy activities in the State of Manipur, India.展开更多
This paper is devoted to binary stars belonging to the class of eclipsing-variable systems.Photometric and spectroscopic analysis of eclipses allows us to determine geometric parameters of the orbit and physical chara...This paper is devoted to binary stars belonging to the class of eclipsing-variable systems.Photometric and spectroscopic analysis of eclipses allows us to determine geometric parameters of the orbit and physical characteristics of stellar components as well as inclinations of stellar equators to the orbital plane. Estimations of inclinations can be obtained from measurement of the Rossiter-McLaughlin effect, which is discussed using examples of some eccentric binaries with an anomalous apsidal effect. Our task is to find the complete spectrum of solutions of the equation of apsidal motion, depending on the inclinations of the polar axes of the components to the orbital one for these systems, based on their individual spectroscopic and photometric observational data. The matrix of solutions allows us to select those pairs of polar inclinations that provide agreement with the observational apsidal period.展开更多
基金financial support of the APVV-20-0148,VEGA 2/0030/21 and VEGA 2/0031/22grantssupport from the Government Office of the Slovak Republic within EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No.09I03-03-V01-00002the private company 4pi Systeme GmbH for partial sponsorship。
文摘In this study,we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June 2.We carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of the outburst,which shows the presence of hydrogen absorption lines commonly found in dwarf nova outbursts.Analysis of photometric data reveals the occurrence of early superhumps in the initial days of observations,followed by ordinary and late superhumps.We have accurately calculated the period of the ordinary superhumps as Pord=0.05681(10)days and determined the periods at different stages,as well as the rate of change of the superhump period(P_(dot)=(5)P/P=8.1×10^(-5)).Additionally,we have derived the mass ratio of the components(q=0.09),and estimated the color temperature during the outburst as~11,000 K,the distance to the system(d=560 pc)and absolute magnitude of the system in outburst(MV=5.3).We have shown that outbursts of this star are very rare:based on brightness measurements on 600 archival photographic plates,we found only one outburst that occurred in 1984.This fact,as well as the properties listed above,convincingly shows that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.
文摘G328 = A65 = L3314 （V = 13.83, B - V = 1.91） is a field star in the direction of the globular cluster M4. If we take E（B - V） = 0.40, then its （B - V）0 = 1.51, corresponding to a spectral type of K5Ⅲ if it is a giant star; or of dM2 if it is a dwarf. Observations at both the MSSSO and Yunnan Observatory have shown that G328 is a new variable with peak to peak amplitude ≌ 0.05 mag in V. While it is not unusual for so red a star to be a variable, special attention must be paid to its short period of about one day. If the variability is due to pulsation, the spectral type and luminosity as well as effective temperature should be determined in order to compare it with Xiong＇s theory.
文摘By means of a population synthesis code, we investigate the Mira variables. Their birth rate （over 0.65yr^-1） and their number （～ 130000） in the Galaxy are estimated. For all possible Mira variables, ranges of their initial masses,pulsating periods, mass losses and lifetimes are given. We check our model with the observed Mira variables near the Sun and our results prove to be valid.
基金supported by the National Natural Science Foundation of China(Grant Nos.11325315,11611530685,11573063 and 11133007)the Strategic Priority Research Program “The Emergence of Cosmological Structure” of the Chinese Academy of Sciences(Grant No.XDB09010202)+1 种基金the Science Foundation of Yunnan Province(Grant No.2012HC011)supported by the Russian Foundation for Basic Research(project No.17-52-53200)
文摘New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. In addition, based on long-term AAVSO data, the outburst behaviors were also explored. Our analysis suggests that normal outbursts are quasi-periodic, with an amplitude of 2.5（4-0.1） mag and a period of - 18.3（4-0.7） d. The amplitude vs. recurrence-time relation ofAY Psc is discussed, and we conclude that this relation may represent general properties of dwarf nova outbursts. The observed standstill ends with an outburst, which is inconsistent with the general picture of Z Cam- type stars. This unusual behavior was considered to be related to mass-transfer outbursts. Moreover, the average luminosity Is brighter during standstills than during outburst cycles. The changes in brightness mark variations in M2 due to the fact that the disk of AY Psc is nearly steady state.M2 value was limited to the range from 6.35 × 10-9 to 1.18 × 10-8 M yr-1. More detailed examination shows that there are a few small outbursts present during standstills. These events with amplitudes of - 0.5 - 0.9 mag are very similar to the stunted outbursts reported in some nova-like cataclysmic variables. We discussed several possible mechanisms and suggested that the most reasonable mechanism for these stunted outbursts is a changing mass-transfer rate.
基金Supported by the National Natural Science Foundation of China.
文摘We report on time-resolved spectroscopic observations of the SU Ursae Majoris dwarf nova, YZ Cnc for over llh on two nights during its 2002 January superoutburst. The spectra on the first day only showed absorption-line profiles, while on the second day the lines showed “W” profiles with blue and red troughs. The radial velocity curve of the absorption troughs and emission peaks of H/3 has an amplitude of 49±10 km s^-1 and a phase offset of -0.07±0.04, which are very similar to those measured in quiescence. However, the γ velocity deviates strongly from the systemic velocity measured in quiescence, by some ±60 km s^-1. Large shifts of -70 km s^-1 in the orbital-averaged velocity and -0.09 in the phase are also found in our observations. All these features can be well explained by a precessing, eccentric disk.
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 RNF grant 17-12-01241(problem formulation and analysis)support from grants VEGA 2/0008/17 and APPV15-0458support from grant RFBR 15-07-04512-A
文摘A new set of low-resolution spectral and UBVJHKL-photometric observations of the symbi- otic nova PU Vul is presented. The binary has been evolving after its symbiotic nova outburst in 1977 and now it is in the nebular stage. It is found that the third orbital cycle （after 1977） was characterized by great changes in associated light curves. Now, PU Vul exhibits a sine-wave shape in all the light curves （with an amplitude in the U band of about 0.7 mag）, which is typical for symbiotic stars in the quiescent state. Brightness variability due to pulsations of the cool component is now clearly visible in the VRI light curves. The amplitude of the pulsations increases from 0.5 mag in the V band to 0.8 mag in the I band. These two types of variability, as well as a very slow change in the physical parameters of the hot component due to evolution after the outburst of 1977, influence the spectral energy distribution （SED） of the system. The variability of emission lines is highly complex. Only hydrogen line fluxes vary with orbital phase. An important feature of the third orbital cycle is the first emergence of the OVI, 6828A Raman scattering line. We determine the temperature of the hot component by means of the Zanstra method applied to the He II, 4686A line. Our estimate is about 150000 K for the spectrum obtained near orbital maximum in 2014. The VO spectral index derived near pulsation minimum corresponds to M6 spectral class for the cool component of PU Vul.
文摘In this Mini-Volume, seven papers written on the basis of talks selected from those presented at the scientific conference "Modern studies of variable stars," commemorating Prof. M. A. Svechnikov(1933–2011), are published. The conference covered a variety of variable-star topics; the papers in this Mini-Volume deal with close, mainly eclipsing, binaries, Herbig Be stars and stellar molecular masers, with an accent on stellar catalogs of different kinds. We briefly review the contents of these papers.
文摘The star 1-1-42 （=vZ1390）, a cluster member in M3, located near the red edge of the instability strip of the horizontal branch, was discovered by Roberts and Sandage as a low amplitude variable, it was designated as V204 in the ＂second catalogue of variable stars in globular clusters＂, but its coordinates given in all versions of this catalogue are wrong since 1955. We argue that V204 is indeed a low amplitude HB variable star, located near to the red edge of the instability strip, with a period of 0.74785d and an amplitude of about 0.04 mag in V. We also find that the red cluster member star 1-1-39 is a low amplitude variable with a period of 1.16^d and amplitude of about 0.03 mag in V which might be pulsating at the second overtone.
文摘We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillations of β Cephei stars which are often rapidly rotating stars. Our results show that the third-order perturbation formalism presented by Soufi et al. should be corrected for some missing terms and some misprints in the equations. As a first step in our study of β Cephei stars, we quantify by numerical calculations the effect of rotation on the oscillation frequencies of a uniformly rotating zero-age main-sequence star with 12 M⊙. For an equatorial velocity of 100 km s^-1, it is found that the second- and third-order corrections for （l, m） = （2, 2）, for instance, are of the order of 0.01% of the frequency for radial order n = 6 and reaches up to 0.5% for n = 14.
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.
基金Supported by the National Natural Science Foundation of China (Grant No. U1231202)partially supported by the National Basic Research Program of China (973 Program, 2013CB834900)the Fundamental Research Funds for Central Universities
文摘Time-series photometric observations were made for the high amplitudeδScuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories,Chinese Academy of Sciences.After performing the frequency analysis of the light curves,we confirmed the fundamental frequency of f=5.28677 c d 1,together with seven harmonics of the fundamental frequency,which are newly detected.No additional frequencies were detected.The O C diagram,produced with the 21 newly determined times of maximum light combined with those provided in the literature,helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355±0.000000003 d.
基金The DASCH project at Harvard is grateful for partial support from NSF grants AST-0407380,AST0909073 and AST-1313370partly supported by the West Light Foundation of Chinese Academy of Sciences+2 种基金the National Natural Science Foundation of China(Nos.11325315 and 11573063)the Yunnan Natural Science Foundation(Nos.2013FB084,2014FB187 and 2017FA001)the Strategic Priority Research Program “The Emergence of Cosmological Structures” of the Chinese Academy of Sciences(Grant No.XDB09010202)
文摘We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys（CRTS,DASCH,NSVS,OMC and Super WASP）and our photometric observations.Combining with the data in literature,a total of 179 times of light maximum are used to analyze the O-C diagram of BO Lyn.We find that it can be described by an upward parabolic component and a periodic variation with a period of 34.5±0.1 yr.The latter could be caused by the light travel time effect as a result of an additional companion orbiting in a highly elliptical orbit（e=0.64±0.03）.Our study indicates that the companion’s luminosity cannot be ignored,and it should be a late A-type main-sequence star.The long-term period change of BO Lyn is also detected,and its value,1.52±0.26×10^（-3）d Myr^（-1）,is consistent with evolutionary models.We suggest that more spectroscopic and photometric observations are needed in the future to confirm the nature of the BO Lyn system.
基金supported by the National Natural Science Foundation of China under Grant No.11273051the program of Light in China Western Region(LCWR,Grant Nos.XBBS201221 and 2015-XBQN-A-02)
文摘This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by Xinjiang Astronomical Observatory. 19 variable stars and three variable candi- dates were detected in a 45＇ - 48.75＇ field around the cluster. 12 of the variable stars are newly-discovered variable objects. The physical properties, classifications and memberships of these 22 objects are studied through their light curves, their positions on the color-magnitude diagram and with archival data from the Naval Observatory Merged Astrometric Dataset. Among these objects, five are eclipsing binary systems, six are pulsating variable stars including one known 6 Scuti star and one newly-discovered RR Lyrae star. The distance to the RR Lyrae star is estimated to be 7.9 - 0.3 kpc, indicating that the star is located far behind the cluster. Four variable stars are probable members of the cluster, and 13 of the 22 objects are confirmed to be field stars.
文摘We present a progress of a long term project to obtain UBVI CCD photometry of open clusters which were little studied before, using the Doyak 1.8 m telecope of Bohyunsan Optical Astronomy Observatory operated by the Korea Astronomical Observatory, in Korea. The primary goals of this project are (1) to make a catalog of UBVI photometry of open clusters, (2) to make an atlas of open clusters, and (3) to survey and monitor variable stars in open clusters.
文摘We are playing a lead role for growth of astronomy and its quality teaching and research in Manipur, a State located at northeast India (longitude = 93°58'E;latitude = 24°44'N;altitude = 782 m). We have innovatively designed and constructed three cost effective observatories, each costing a few hundred USD. These observatories are completely different in design and are perfectly usable for doing serious work on astronomical observation and measurements, using small ground-based telescopes. One Celestron CGE1400 telescope is housed with equatorial mounting in one of three constructed observatories and the same observatory has been inducted, since January 2012, as one of the members of the “Orion Project”, which is an international project headquartered at Phoenix, Arizona, USA, dedicated for photometric and spectroscopic observations of five bright variable stars of the Orion constellation. We have been producing high precision BVRI photometric data that match well with those produced by other observatories enrolled in the Orion project. Our photometric data were presented and discussed in the 33rd Annual Conference of the Society for Astronomical Sciences: Symposium on Telescope Science, held at Ontario, California, USA during June 12 - 14, 2014. Further, we could successfully demonstrate them to the entire population of the State and play live shows of the observation of three spectacular astronomical events namely, solar eclipse of 15th January 2010, lunar eclipse of 10th December 2011 and Transit of Venus of June 6, 2012. We have conducted a number of seminars and workshops for training and research in astronomy. In the present paper, we would like describe our self-built observatories, our observational facilities, the BVRI photometric data that we acquired for the Orion project, and other activities undertaken for growth of astronomy activities in the State of Manipur, India.
文摘This paper is devoted to binary stars belonging to the class of eclipsing-variable systems.Photometric and spectroscopic analysis of eclipses allows us to determine geometric parameters of the orbit and physical characteristics of stellar components as well as inclinations of stellar equators to the orbital plane. Estimations of inclinations can be obtained from measurement of the Rossiter-McLaughlin effect, which is discussed using examples of some eccentric binaries with an anomalous apsidal effect. Our task is to find the complete spectrum of solutions of the equation of apsidal motion, depending on the inclinations of the polar axes of the components to the orbital one for these systems, based on their individual spectroscopic and photometric observational data. The matrix of solutions allows us to select those pairs of polar inclinations that provide agreement with the observational apsidal period.
