| 其他摘要 | LAMOST is a survey telescope with a large field of view and the highest spectrum acquiring rate in the world. So far, many stellar atmospheric parameters of binary and variable stars have been obtained, which lays a solid foundation for the study of binary and variable stars fields. It was found from LAMOST data that there are some abnormal δ Scuti-type stars in the catalogue. They are far beyond the red edge of the pulsating instability strip in both the H-R diagram and the logg–T diagram. Most of the binary stars with EW-type light curve should be contact binaries. A contact binary is an interacting binary system in which both components fill their Roche lobes and share a convective common envelope. For contact binaries, there is a good relationship between the orbital period (P) and the surface effective temperature (T). However, LAMOST has found some samples of "special contact binary" which obviously do not conform to the P-T relationship. Their surface effective temperature is obviously higher than the period, which may be candidates for pulsating variable stars. In this paper, the classification information and physical characteristics of these special pulsating variables are verified and discussed by combining with the existing photometric survey data or subsequent observation data. At the same time, some δ Scuti-type pulsating variables in close binary systems are analyzed and studied, and obtain the results as follow:1. Our follow-up observations reveal that many of these abnormal δ Scuti-type stars in the catalogue are misclassified. For example, ASAS J174406+2446.8 was found to be an abnormal δ Scuti-type star by LAMOST. We used the 1.0-m Cassegrain reflecting telescope to obtain the multi-color light curves in BVRcIc, and found that it is a binary system with a EB-type curve and a orbital period of 0.3781 days rather than a δ Scuti star. It is a W-subtype contact binary with a mass ratio of 1.135(±0.019) and a fill-out factor of 10.4(±5.6)%. The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn, II Per and GW Tau. All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory. Its orbital period analysis shows the presence of a cool red dwarf with a period of 11.89 years. Our study also shows that a large part of these abnormal δ Scuti-type stars may be misclassified.2. By comparing the objects observed by LAMOST with the variable star database VSX, we found that more than 10000 (DR7 data) EW-type binaries have been observed by LAMOST, and 9149 of them have determined the stellar atmospheric parameters, which greatly cover the lack of spectral information of such variable stars. By analyzing these data, we find that the orbital period (P) and the surface effective temperature (T) shows an obvious increasing relationship. Meanwhile, there are some high temperature EW-type binaries which do not conform to the P-T relationship. According to the light curves obtained from the follow-up observations and some surveys, we have determined that many targets are δ Scuti-type stars rather than EW-type eclipsing binaries. For example, we used the Sino-Thai 70-cm telescope at the Lijiang station of Yunnan Observatories to make follow-up observation for CSS J213934.3-050020, and found that it is a double-mode high-amplitude high amplitude δ Scuti-type pulsating star. Its fundamental mode and first-order mode are f0 = 6.8195 d−1 and f1 = 8.8709 d−1, respectively. Its mass is estimated to be 1.83 times the mass of the sun, which is in the evoluting stage of main sequence, and the presence of a companion star with a period of about 12 years and a mass of 0.65 times the mass of the sun.3. In addition, we analyzed the oEA system KIC06852488 observed by LAMOST, and found that the magnitude changes of the two maxima on the light curves are related. The Max I and Max II vary with a same cycle length about 2000 days and a 180 degree phase difference, and the variation of the Max II coincides with the O-C curve of primary light minima. We use W-d program to analyze the Kepler and TESS light curves, and conclude that it is a semi-detached system with a mass ratio 0.4622(±0.0036). The secondary component is filling its critical Roche lobe, while the radius filling factor of the primary component is 50%. The variation of the O'Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component. It is found that their positions are symmetrical with the inner Lagrange L1 point, which is the evidence of the correlation between the mass transfer and the magnetic activity of secondary stars. After subtracting the binary brightness changes, six superflares are detected that come from the cool secondary. Pulsation analysis reveals that the primary component oscillates in two non-radial p-modes and one possible higher-order g-mode. For HL Dra, previous analysis shows that it is an oEA system with orbital period of 0.944276 days. By analyzing the TESS light curves, we find that it is Algol-like binary system with a mass ratio of 0.361, where the radius filling factor of the primary and secondary component are 87% and 98%, respectively. During TESS observation, both the variable O'Connell effect and the existence of superflares indicate that the secondary should have strong magnetic activities, and the correlations between the changes of the O-C diagrams and the variable O'Connell effect should be caused by the magnetic activity of the secondary (i.e. the Applegate mechanism). The O-C curve shows a sinusoidal variation with a period of 129.88 years, which should be caused by the light-travel-time effect via the presence of a cool red dwarf third body. A total of 252 pulsating frequencies are detected from the high-precision photometric data of TESS, including 28 multiplets of tidally split frequencies. We identify 2 radial modes, 21 non-radial p-modes, and 3 non-radial f-modes from the possible independent frequencies. The coexistence of various observational phenomena indicate that KIC 06852488 and HL Dra are very interesting objects for further investigations of binary formation and evolutions and tidal interactions on stellar pulsations and on magnetic activities. |
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