激变变星中的白矮星

仅在过去的10年中,由于采用了地面和空同时的光谱观测激变变星中正处于吸积过程的白矮星,在激变变星（CV）的研究方面出现了全新的途径。这些光谱探测开拓了恒星包层、角动量团儿CV演化中吸积物理学研究的新前没中。这篇评论包括了激变变星中的白矮星研究的方方面面：（1）表面温度;（2）吸积加热和冷却的不;(3)在高度倾斜的CV中吸收幕帘（盘的上面的大气）的影响和特点;（4）白矮星光球的化学丰度;（6）吸积带;（7）吸积的模拟。     

激变变星中吸积盘的边界问题

边界层是介于吸积盘和吸积星之间的非常狭窄的区域，在该区域中随着盘物质接近星面，它的角速度从开普勒角速度下降至恒星自转角速度。边界区因释放的能量接近吸积光度的一半，并且为确定吸积盘微分方程提供内边界条件而显示出它的重要性。本文综述了激变变星中吸积盘边界层的研究进展。     

激变食变星Ⅲ.AC Cancri

AC Cnc是周期为7~h13~m的类新星食变星。由于AC Cnc是双谱食双星,而且具有较对称的食,所以在对激变食变星的系统研究中,我们选择了该双星来进行观测。本文利用拟合光变曲线的方法对AC Cnc进行了测光解分析、并得到轨道倾角i=74.5°±0.8°,白矮星质量M_1=0.74±0.07M_⊙,晚型星质量M_2=0.97±0.08M_⊙。AC Cnc中吸积盘的径向温度分布可以近似地表示为T(r)∝r~(-0.5),吸积盘边缘温度为7600K。晚型星向白矮星的质量转移率大约为7×10~(-9)M_⊙yr~(-1)。AC Cnc的距离近似地等于500±100pc。     

短周期激变变星周期分布的新统计

我们对周期小于周期分布空缺段的激变变星，重新进行了周期分布统计，使用了比Ｗａｒｎｅｒ等人更多，更新的资料，统计中发现一个ＡＭＨｅｒ型ＣＶｓ：ＧＲＵＶ１偏离了Ｗａｒｎｅｒ等人的统计结果，我们给出了ＣＶＳ新的周期分布图和相应于此分布的随机概率。虽然结果与Ｗａｒｎｅｒ等人的不同，但周期分布同磁场仍呈现一定的相关性，磁激变变星与非磁激变变星同样显示出成团趋势。     

短周期激变变星周期分布的新统计

我们对周期小于周期分布空缺段的激变变星(CVs),重新进行了周期分布统计,使用了比Warner等人更多、更新的资料.统计中发现一个AM Her型CVs:GRU V1偏离了Warner等人的统计结果.我们给出了CVs 新的周期分布图和相应于此分布的随机概率.虽然结果与Warner等人的不同,但周期分布同磁场仍呈现一定的相关性,磁激变变星(MCVs)与非磁激变变星(NMCVS)同样显示出成团趋势.     

激变食变星PG0027+260的CCD光变曲线

我们于1989年11月30日晚对PG0027+260进行了时间分辨率为108秒的高速CCD测光,得到了一条完整的光变曲线,从而确认其为激变食变星系统,轨道周期0.146~d     

吸积盘边缘的质量和角动量损失与激变双星的演化

本给出了计算吸积盘边缘物质和角动量损失，以及它们对激变双星演化影响的理论模型。计算结果表明，紫外天卫星（ＩＵＥ）观测到的高速物质流是来源于吸积盘边缘，吸积盘边缘的角动量损失可以成为周期大于３小时的激变双星演化的物理机制。     

Cataclysmic variables III. AC Cancri

AC Cnc is a nova-like, eclipsing binary of period 7^h13^m. I chose it for observation because its eclipses are rather symmetrical. A photometric solution gives inclination i = 74.5° ± 0.8°, mass of white dwarf M₁ = 0.74 ± 0.07 M, mass of the late-type companion, M₂ = 0.97 ± 0.8 M. Temperature of the accretion disk varies approximately as inverse half-power of the radial distance, the temperature at the edge of the disk is 7600 K. Rate of mass transfer from the late-type star to the white dwarf is 7(−9) M/yr. The distance of AC Cnc is 500 ± 100 pc.     

The mass of the white dwarf in the old nova BT Mon

We present spectrophotometry of the eclipsing old nova BT Mon (Nova Mon 1939). By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be K _R = 205 ± 5 km s⁻¹ and its rotational velocity to be v  sin  i  = 138 ± 5 km s⁻¹. We also measure the radial velocity semi-amplitude of the primary star to be K _R = 170 ± 10 km s⁻¹. From these parameters we obtain a mass of 1.04 ± 0.06 M⊙ for the white dwarf primary star and a mass of 0.87 ⊙ 0.06 M⊙ for the G8 V secondary star. The inclination of the system is found to be 82^°_.2 ± 32^°_.2 and we estimate that the system lies at a distance of 1700 ± 300 pc. The high mass of the white dwarf and our finding that BT Mon was probably a fast nova together constitute a new piece of evidence in favour of the thermonuclear runaway model of classical nova outbursts. The emission lines are single-peaked throughout the orbital cycle, showing absorption around phase 0.5, high-velocity S-wave components and large phase offsets in their radial velocity curves. In each of these respects, BT Mon is similar to the SW Sex stars. We also find quasi-periodic flaring in the trailed spectra, which makes BT Mon a candidate intermediate polar.     

Indirect imaging of the accretion stream in eclipsing polars – III. HU Aquarii low state

We apply our technique for indirect imaging of the accretion stream to the polar HU Aqr, using eclipse profiles observed when the system was in a low-accretion state. The eclipse profile is different from that in the high state, and more variable from cycle to cycle. We find that the stream maps are brightest near the white dwarf and there is no significant brightening in the threading region. In the low state the stream threads on to the magnetic field closer to the L₁ point than in the high state, with a footpoint of the accreting field line at high latitude. We then produce maps of the accretion region from polarimetry using Stokes imaging. These show that the majority of the accretion occurs near the equator. The difference between the maps may be explained if most of the stream material is not emitting significantly in the low state. If so, neither the stream eclipse mapping nor Doppler tomography techniques will trace the bulk of the accretion flow between the two stars.     

A spatially resolved 'inside-out' outburst of IP Pegasi

We present a comprehensive photometric data set taken over the entire outburst of the eclipsing dwarf nova IP Peg in 1997 September/October. Analysis of the light curves taken over the long rise to the peak-of-outburst shows conclusively that the outburst started near the centre of the disc and moved outwards. This is the first data set that spatially resolves such an outburst. The data set is consistent with the idea that long rise times are indicative of such 'inside-out' outbursts. We show how the thickness and the radius of the disc, along with the mass transfer rate, change over the whole outburst. In addition, we show evidence of the secondary and the irradiation thereof. We discuss the possibility of spiral shocks in the disc; however, we find no conclusive evidence of their existence in this data set.     

Discovery of irradiation-induced variations in the light curve of the classical nova V2275 Cyg (N Cyg 2001 No. 2)

We present charge-coupled device (CCD) photometry, light curve and time-series analysis of the classical nova V2275 Cyg (N Cyg 2001 No. 2). The source was observed for 14 nights in total in 2002 and 2003 using an R filter with the 1.5-m Russian–Turkish joint telescope (RTT150) at the TUBITAK National Observatory in Antalya, Turkey, as part of a large programme on the CCD photometry of cataclysmic variables. We report the detection of two distinct periodicities in the light curve of the nova: (a)   P ₁= 0.314 49(15) d [7.6 h]  , and (b)   P ₂= 0.017 079(17) d [24.6 min]  . The first period is evident in both 2002 and 2003 whereas the second period is only detected in the 2003 data set. We interpret the first period as the orbital period of the system and attribute the orbital variations to aspect changes of the secondary irradiated by the hot white dwarf (WD). We suggest that the nova was a supersoft X-ray source in 2002 and, perhaps, in 2003. The second period could be a quasi-periodic oscillation originating from the oscillation of the ionization front (due to a hot WD) below the inner Lagrange point or a beat frequency in the system as a result of the magnetic nature of the WD if steady accretion has already been re-established.