The 2001 Superoutburst of WZ Sagittae-猫眼课题宝

DOI：

10.1086/341696

发表时间：

2002-04

期刊：

Publications of the Astronomical Society of the Pacific

影响因子：

3.5

通讯作者：

中科院分区：

物理与天体物理3区

文献类型：

作者：

J. Patterson;G. Masi;M. Richmond;B. Martin;E. Beshore;D. Skillman;J. Kemp;T. Vanmunster;R. Rea;W. Allen;Stacey E. Davis;Tracy Davis;A. Henden;D. Starkey;J. Foote;A. Oksanen;L. Cook;R. Fried;D. Husar;R. Novák;T. Campbell;J. Robertson;T. Krajci;E. Pavlenko;N. Mirabal;P. Niarchos;O. Brettman;Stan Walker

我们报道了2001年射手座超强爆发期间全球范围内的观测活动的结果。在V=15.5的情况下休眠23年后，这颗恒星在2天内上升到8.2的峰值亮度，并显示出持续25天的主喷发。在恢复平静的过程中，出现了12次小爆发，∼的幅度为1毫克，复发时间为2天；这些“回声爆发”的来源不明，但与矮新星的正常爆发有些相似。52天后，这颗恒星开始缓慢下降到静止状态。光曲线中的周期波与1978年的超暴相一致：前12天有一个强烈的轨道信号，然后是0.05721(5)天的一个强大的普通超峰，比PORT B长0.92(8)%。后者持续了至少90天，尽管很可能突变为平均周期稍长的“晚期”超级驼峰[0.05736(5)天]。对于矮新星中的这种现象，超峰似乎遵循着熟悉的规则，其分量由两个基本频率的线性组合给出：轨道频率ωo和一个看不见的低频Ω，据信代表了吸积盘的近端进动。长时间序列显示了一种复杂的精细结构，∼20的频率是不相称的。基本上所有分量都以nωo-mΩ的频率出现，其中m=1，…但在第一周，共同的超峰在nωo-Ω处表现出主要成分，n=1，2，3，4，5，6，7，8，9(即m=1)；一个月后，主导力量转移到m=n-1的成分上。这可能是由于盘的螺旋臂模式的变化，可能是超峰的根本原因。绝大多数频率分量从ωo的谐波红移，这与近端进动(进动)的假设一致。但35.42周−1处的分量表明可能存在不同速率的逆行进动，可能是N=0.13±0.02周−1。这些日食允许测量传质热点的位置和亮度。这个圆盘一定非常偏心，几乎和白矮星的罗氏叶一样大。热点光度超过其静态值高达60倍。这表明次生物质的强化传质在喷发中起主要作用。

We report the results of a worldwide campaign to observe WZ Sagittae during its 2001 superoutburst. After a 23 yr slumber at V = 15.5, the star rose within 2 days to a peak brightness of 8.2, and showed a main eruption lasting 25 days. The return to quiescence was punctuated by 12 small eruptions, of ∼1 mag amplitude and 2 day recurrence time; these “echo outbursts” are of uncertain origin, but somewhat resemble the normal outbursts of dwarf novae. After 52 days, the star began a slow decline to quiescence. Periodic waves in the light curve closely followed the pattern seen in the 1978 superoutburst: a strong orbital signal dominated the first 12 days, followed by a powerful common superhump at 0.05721(5) day, 0.92(8)% longer than Porb. The latter endured for at least 90 days, although probably mutating into a “late” superhump with a slightly longer mean period [0.05736(5) day]. The superhump appeared to follow familiar rules for such phenomena in dwarf novae, with components given by linear combinations of two basic frequencies: the orbital frequency ωo and an unseen low frequency Ω, believed to represent the accretion disk’s apsidal precession. Long time series reveal an intricate fine structure, with ∼20 incommensurate frequencies. Essentially all components occurred at a frequency nωo - mΩ, with m = 1, …, n. But during its first week, the common superhump showed primary components at nωo - Ω, for n = 1, 2, 3, 4, 5, 6, 7, 8, 9 (i.e., m = 1 consistently); a month later, the dominant power shifted to components with m = n - 1. This may arise from a shift in the disk’s spiral‐arm pattern, likely to be the underlying cause of superhumps. The great majority of frequency components are redshifted from the harmonics of ωo, consistent with the hypothesis of apsidal advance (prograde precession). But a component at 35.42 cycles day−1 suggests the possibility of a retrograde precession at a different rate, probably N = 0.13 ± 0.02 cycles day−1. The eclipses permit measuring the location and brightness of the mass‐transfer hot spot. The disk must be very eccentric and nearly as large as the white dwarf’s Roche lobe. The hot‐spot luminosity exceeds its quiescent value by a factor of up to 60. This indicates that enhanced mass transfer from the secondary plays a major role in the eruption.

The 2001 Superoutburst of WZ Sagittae

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