arXiv 1312.05082013-12-02astro-ph.SR

低光度激变变星V405 Pegasi的XMM-牛顿观测

XMM-Newton observations of the low-luminosity cataclysmic variable V405 Pegasi

A. D. Schwope, V. Scipione, I. Traulsen, R. Schwarz, T. Granzer, A. M. Pires, J. R. Thorstensen

备注：: A&A, in press
DOI：: 10.1051/0004-6361/201322662

摘要：

V405 Peg是一个低光度激变变星，被认为是明亮的高纬度ROSAT全天巡天源RBS 1955的光学对应物。该系统被怀疑属于一个基本上未被发现的冬眠CV种群。尽管进行了密集的光学随访，但其亚类仍未确定。我们想进一步对V405 Peg进行分类，并通过它的长期行为，光谱特性，能量分布和吸积光度来了解它在CV动物园中的作用。我们执行的\textit{XMM-Newton} X射线和紫外线数据的光谱和时序分析。档案WISE，HST，和斯威夫特观测被用来确定光谱能量分布和长期的变化特征。X射线光谱的特征在于来自多温度等离子体的发射。没有发现发光的软X射线成分的证据。由$\sim50\%$产生的轨道相位相关的X射线光度变化没有明显的光谱变化。在我们的X射线数据中没有进一步的周期性。XMM-牛顿观测期间的平均X射线光度为L_X，bol simeq 5e 30 erg/s，但基于Swift观测，相应的光度在5e 29 erg/s和2 e31 erg/s年时间尺度之间变化。这个对象的CV子类仍然难以捉摸。频谱和定时属性显示了磁性和非磁性CV的共性。吸积光度远低于在给定轨道周期的标准吸积CV的预期。像V405 Peg这样的天体可能代表冰山一角，因此可能是银河山脊X射线发射的重要贡献者。如果是这样，它们将在未来的X射线调查中被发现，例如使用eROSITA。

英文摘要：

V405 Peg is a low-luminosity cataclysmic variable (CV) that was identified as the optical counterpart of the bright, high-latitude ROSAT all-sky survey source RBS1955. The system was suspected to belong to a largely undiscovered population of hibernating CVs. Despite intensive optical follow-up its subclass however remained undetermined. We want to further classify V405 Peg and understand its role in the CV zoo via its long-term behaviour, spectral properties, energy distribution and accretion luminosity. We perform a spectral and timing analysis of \textit{XMM-Newton} X-ray and ultra-violet data. Archival WISE, HST, and Swift observations are used to determine the spectral energy distribution and characterize the long-term variability. The X-ray spectrum is characterized by emission from a multi-temperature plasma. No evidence for a luminous soft X-ray component was found. Orbital phase-dependent X-ray photometric variability by $\sim50\%$ occurred without significant spectral changes. No further periodicity was significant in our X-ray data. The average X-ray luminosity during the XMM-Newton observations was L_X, bol simeq 5e30 erg/s but, based on the Swift observations, the corresponding luminosity varied between 5e29 erg/s and 2e31 erg/son timescales of years. The CV subclass of this object remains elusive. The spectral and timing properties show commonalities with both classes of magnetic and non-magnetic CVs. The accretion luminosity is far below than that expected for a standard accreting CV at the given orbital period. Objects like V405 Peg might represent the tip of an iceberg and thus may be important contributors to the Galactic Ridge X-ray Emission. If so they will be uncovered by future X-ray surveys, e.g. with eROSITA.

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