We report on XMM-Newton, NuSTAR, and NICER X-ray observations of CTCV J2056–3014, a cataclysmic variable (CV) with one of the fastest-spinning white dwarfs (WDs) at P = 29.6 s. While previously classified as an intermediate polar, CJ2056 also exhibits the properties of WZ Sge–type CVs, such as dwarf novae and superoutbursts. With XMM-Newton and NICER, we detected the spin period up to ∼2 keV with 7σ significance. We constrained its derivative to s s−1 after correcting for binary orbital motion. The pulse profile is characterized by a single broad peak with ∼25% modulation. NuSTAR detected a fourfold increase in unabsorbed X-ray flux coincident with an optical flare, in 2022 November. The XMM-Newton and NICER X-ray spectra at 0.310 keV are best characterized by an absorbed, optically thin three-temperature thermal plasma model (kT = 0.3, 1.0, and 4.9 keV), while the NuSTAR spectra at 3–30 keV are best fit by a single-temperature thermal plasma model (kT = 8.4 keV), both with Fe abundance ZFe/Z⊙ = 0.3. CJ2056 exhibits similarities to other fast-spinning CVs, such as low plasma temperatures and no significant X-ray absorption at low energies. As the WD’s magnetic field strength is unknown, we applied both nonmagnetic and magnetic CV spectral models (MKCFLOW and MCVSPEC) to determine the WD mass. The derived WD mass range (M = 0.7–1.0 M⊙) is above the centrifugal breakup mass limit of 0.56 M⊙ and consistent with the mean WD mass of local CVs (M ≈ 0.8–0.9 M⊙).

中文翻译：

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快速旋转中间极极 CTCV J2056–3014 的宽带 X 射线研究


我们报告了 CTCV J2056-3014 的 XMM-Newton、NuSTAR 和 NICER X 射线观测，CTCV J2056-3014 是一个灾难变星 （CV），在 P = 29.6 s 时具有最快的旋转白矮星 （WD） 之一。虽然 CJ2056 以前被归类为中间极地，但它也表现出 WZ Sge 型 CV 的特性，例如矮新星和超爆发。使用 XMM-Newton 和 NICER，我们检测到高达 ∼2 keV 的自旋周期，显著性为 7σ。在校正双轨道运动后，我们将其导数限制为 s s−1。脉冲曲线的特点是具有 ∼25% 调制的单个宽峰。NuSTAR 在 2022 年 11 月检测到与光学耀斑相吻合的未吸收 X 射线通量增加了四倍。0.310 keV 的 XMM-Newton 和 NICER X 射线光谱最能用吸收的光学薄型三温热等离子体模型（kT = 0.3、1.0 和 4.9 keV）来表征，而 3-30 keV 的 NuSTAR 光谱最能用单温度热等离子体模型（kT = 8.4 keV）来拟合，两者的铁丰度 ZFe/Z⊙ = 0.3。CJ2056 表现出与其他快速旋转 CV 的相似之处，例如等离子体温度低，在低能量下没有明显的 X 射线吸收。由于 WD 的磁场强度未知，我们应用了非磁性和磁性 CV 光谱模型（MKCFLOW 和 MCVSPEC）来确定 WD 质量。得出的 WD 质量范围 （M = 0.7–1.0 M⊙） 高于 0.56 M 的离心破裂质量限值⊙与局部 CV 的平均 WD 质量 （M ≈ 0.8–0.9 M⊙） 一致。