星团AgeS实验（CASE）：在球状星团中观测到矮新星的不足
Cluster AgeS Experiment (CASE): Deficiency of observed dwarf novae in globular clusters
摘要：
本文介绍了在球状星团中寻找矮新星的结果。它是基于现有的最大同质样本的观察，在时间跨度，观察的数量和集群的数量。它包括16个银河系GC，并产生了两个新的确定DNe：M55-CV1和M22-CV 2。所有以前已知的系统位于我们的领域也被恢复。我们观测了M4，M5，M10，M12，M22，M30，M55，NGC 288，NGC 362，NGC 2808，NGC 3201，NGC 4372，NGC 6362，NGC 6752，omega Cen（NGC 5139）和47 Tuc（NGC 104）。Kaluzny等人（2005）和Pietrukowicz等人（2005）已经分别报道了两种DNe的发现，即M55-CV1和M22-CV 2。在剩下的14个GC中，我们没有发现某些新的DNe。我们的结果使银河系球状星团中已知的DNe总数增加到12个，分布在7个星团中。我们的调查恢复了位于我们领域的所有三个已知的爆发灾难性变量（CV），即M5-V101，M22-CV1和M30前景中的V4。为了评估调查的效率，我们分析了插入人造恒星的图像，模拟了原型矮新星SS Cyg和U Gem的爆发。根据不同的条件，我们恢复了16%到100%的人造恒星。效率似乎主要受占空比/时间采样的影响，而受距离/幅度的影响要小得多。除了M30、NGC 362和NGC 6752（以及NGC 2808的致密核）的饱和小坍缩核外，我们的图像相减技术加上辅助的不饱和B带图像，避免了V带的拥挤效应。我们的研究结果清楚地表明，在GC中常见类型的DNe确实非常罕见。然而，在将这些结论扩展到GC中的CV人群之前，必须非常小心。
英文摘要：
We present the results of a search for dwarf novae (DNe) in globular clusters (GCs). It is based on the largest available homogeneous sample of observations, in terms of the time span, number of observations and number of clusters. It includes 16 Galactic GCs and yielded two new certain DNe: M55-CV1 and M22-CV2. All previously known systems located in our fields were recovered, too. We surveyed M4, M5, M10, M12, M22, M30, M55, NGC 288, NGC 362, NGC 2808, NGC 3201, NGC 4372, NGC 6362, NGC 6752, omega Cen (NGC 5139) and 47 Tuc (NGC 104). The discovery of two DNe, namely M55-CV1 and M22-CV2, was already reported by Kaluzny et al. (2005) and Pietrukowicz et al. (2005), respectively. In the remaining 14 GCs we found no certain new DNe. Our result raises the total number of known DNe in the Galactic globular clusters to 12 DNe, distributed among 7 clusters. Our survey recovered all three already known erupting cataclysmic variables (CVs) located in our fields, namely M5-V101, M22-CV1, and V4 in the foreground of M30. To assess the efficiency of the survey, we analyzed images with inserted artificial stars mimicking outbursts of the prototype dwarf novae SS Cyg and U Gem. Depending on the conditions, we recovered between 16-100 percent of these artificial stars. The efficiency seems to be predominantly affected by duty cycle/time sampling and much less by distance/magnitude. Except for saturated tiny collapsed cores of M30, NGC 362 and NGC 6752 (and also the dense core of NGC 2808) crowding effects in the V band were avoided by our image subtraction technique augmented with auxiliary unsaturated B-band images. Our results clearly demonstrate that in GCs common types of DNe are very rare indeed. However, great care must be taken before these conclusions can be extended to the CV population in GCs.
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