| 其他摘要 | Supersoft X-ray sources and recurrent novae are recognised candidates for Type Ia supernova progenitors. They are both cataclysmic binaries consisting of a massive white dwarf primary star and a main-sequence (or subgiant, etc.) companion star. The white dwarf increases its mass by continuously accreting material from the companion star through an accretion disk, and may eventually produce a Type Ia supernova explosion. These two types of strongly interacting binaries are of great scientific importance for studying the structure and evolution of Type Ia supernova progenitors, as well as for exploring astrophysical processes such as binary mass transfer and accretion. However, due to the limitations of measurements, not many Type Ia supernova progenitor candidates have been discovered, and even fewer have been studied in detail, severely limiting the progress of related studies. A detailed analysis of some special samples of Type Ia supernova progenitors is presented in this paper, for investigating the physical processes of binary mass transfer and white dwarf accretion, for exploring the physical characteristics of accretion disks and their evolutionary processes, and for estimating the timescale of the explosion of Type Ia supernovae. The main innovative research results are as follows:1. V Sge is the first Galactic optical counterpart of an supersoft X-ray source. The author has used the one-metre optical telescope of the Yunnan Observatories to make photometric observations of V Sge, and combined them with data from the TESS space telescope to derive a series of light minima of this eclipsing binary and construct its O-C diagram, finally confirming that its orbital period is continuously decreasing. Based on its light variability, it was found that circumstellar material is likely to be present around this binary system. In V Sge, the mass of the companion is slightly larger than that of the white dwarf, so the decreasing orbital period suggests that the more massive companion transfers material to the white dwarf on its thermal timescale. However, given its more massive white dwarf and high accretion rate, an accretion disk wind should be present in V Sge. The author therefore considers, for the first time, the effect of the consequential angular momentum loss (CAML) mechanism driven by a magnetic accretion disk wind on its orbital evolution. Eventually, based on such a physical picture, the author estimates an approximate range of the mass transfer rate in V Sge and an upper limit to its mass accretion rate. From this, it is estimated that its white dwarf is likely to reach Chandrasekhar mass in at least a million years, followed by a possible Type Ia supernova explosion.2. QR And (= RX J0019.8+2156) is one of the few persistent supersoft X-ray sources in the Milky Way. Using data obtained by the TESS space telescope and collected by the AAVSO database, the author has obtained a series of eclipse timings for this supersoft X-ray source. For the first time internationally, its orbital period is found to be increasing continuously. The masses of its two components have also been calculated from the results of previous analyses. The results show that the companion mass is smaller than the white dwarf mass in QR And, and that the long-term increasing orbital period reveals that the low-mass companion transfers matter to the white dwarf on its thermal timescale. The author also suggests that it is the CAML due to the magnetic accretion disk wind that drives the companion to continuously fill its Roche lobe, ensuring a constant mass transfer to the white dwarf. The author also speculates that there may be small short-term fluctuations of mass transfer, based on light characteristics.3. V617 Sgr is the Galactic optical counterpart of the supersoft X-ray source. Nearly decade-long photometric monitoring for V617 Sgr using the $2.15m$ telescope at the CASLEO in Argentina, together with archival light curves collected in the AAVSO database, have been fitted. A series of eclipse timings was obtained and confirmed that its orbital period is long-term increasing. It was also found that its increasing orbital period is superimposed on a periodic oscillation, which may be caused by the light-time effect of a third body or by the magnetic activity cycle of companion star. Like QR And, the companion in V617 Sgr is slightly less massive than the white dwarf, and the increase of the orbital period suggests that the low-mass companion is continuously transferring mass to the white dwarf. Similar to V Sge and QR And, the CAML mechanism driven by magnetic accretion disk winds in V617 Sgr also has an impact on its orbital evolution. Unlike V Sge, in V617 Sgr, it is this angular momentum loss of system that allows the low-mass companion to continuously fill its Roche lobe, making mass transfer possible.4. WX Cen is also the optical counterpart of an supersoft X-ray source, and the author has confirmed its long-term decreasing orbital period, also using data observed by the TESS space telescope and collected by the AAVSO database. The masses of two components have also been estimated from previous analyses, and the companion masses are found to be slightly smaller than the white dwarf masses, similar to the case of V617 Sgr and QR And. If angular momentum is conserved, the mass transfer from the low-mass companion to the massive white dwarf would have to cause a long-term increase in the orbital period, which is not consistent with the observed long-term decrease. For this reason, the author proposed that the orbital evolution and mass transfer of WX Cen is dominated by angular momentum loss of system, which is contributed by both the magnetic stellar wind from the companion star and the magnetic accretion disk wind, either alone or together. At the same time, the continuous contraction of the orbit allows the low-mass companion to fill its Roche lobe and transfer mass to the white dwarf.5. U Sco is a well-known recurrent nova in the Milky Way, while its white dwarf mass is close to the Chandrasekhar limit, and is an important object for the study of Type Ia supernova progenitors and their explosions. Through analysis, the author has confirmed that its orbital period is long-term decreasing in the interval between the two nova outbursts. Similar to the case of WX Cen, V617 Sgr and QR And, the companion mass of U Sco is slightly smaller than the white dwarf mass. The long-term decrease in orbital period cannot be explained by a conserved mass transfer either. The author proposed that the decreasing orbital period of U Sco in the interval between nova outbursts is produced by the angular momentum loss of the system caused by magnetic wind. The angular momentum loss drives the orbital evolution of the binary system, and the continued contraction of the orbit ensures that the low-mass companion always fills its Roche lobe and continuously transfers mass to the white dwarf, eventually producing a Type Ia supernova.From the above research results, one can see that both the supersoft X-ray sources and the recurrent novae have a long-term orbital evolution, accompanied by complex and variable light features. This confirms that the massive white dwarfs of these binaries have a high mass accretion rate, further revealing that they are the progenitor of Type Ia supernovae, which has important implications for the study of the origin of Type Ia supernovae, etc. In future studies, the author will continue observation analysis of supersoft X-ray sources and recurrent novae, and combine multi-wavelength data to determine the rotation of massive white dwarfs and further explore the interaction between white dwarf accretion and rotating white dwarfs. At the same time, multi-wavelength observations of other binary containing accreting compact objects will be carried out to investigate the accretion and orbital evolution of compact objects, as well as to understand the structural features and evolution of the progenitors of Type Ia supernovae. |
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