揭示激变变星的周期反弹星族：eROSITA选源的光谱与时域后续观测
Unveiling the period-bounce population of cataclysmic variables: Spectroscopic and time-domain follow-up of eROSITA-selected candidates
- Eberhard Karls Universität Tübingen（蒂宾根大学）
- Leibniz Institut für Astrophysik Potsdam (AIP)（波茨坦阿基米德天体物理研究所）
- University of Potsdam（波茨坦大学）
- University of Warwick（华威大学）
- Penn State University（宾夕法尼亚州立大学）
- University of Washington（华盛顿大学）
- University of Utah（犹他大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究对213个eROSITA选定的周期反弹星候选体开展光谱及时域后续观测，确认24个新激变变星，证实其符合周期反弹星特征，或使已确认的周期反弹星数量增约50%，并发现大量周期反弹星或仍隐藏在白矮星星表中。
AI中文摘要：
激变变星（CVs）在长期演化过程中，轨道周期（$P_{\rm orb}$）会逐渐缩短至约80分钟的最小值，之后又会向更长的周期演化；这类越过演化转折点的CVs被称为周期反弹星（PBs）。尽管理论预测所有CVs中应有40%-80%为PBs，但观测到的CV星族中仅3%-25%是PBs，这种差异很可能源于PBs本征光度较低。本研究旨在调查213个SRG/eROSITA选定的PB候选体的演化状态，样本还包含19个此前已确认的PBs，作为评估候选体的基准。我们通过识别斯隆数字巡天V（SDSS-V）光学光谱中的巴尔末发射线，以及存档测光巡天中的矮新星爆发，确认了24个新的CVs；通过将富氢大气模型拟合到SDSS-V光谱，估算了白矮星（WDs）的有效温度和长期吸积率；还测量了巴尔末减缩，将其作为吸积盘物理条件的诊断指标，以评估是否与已知PBs一致。此外，我们分析了凌日系外行星巡天卫星（TESS）的存档光变曲线，确定了部分系统的$P_{\rm orb}$，并编制多波段测光以构建和建模光谱能量分布（SEDs），由此推断出伴星的近似光谱型。对新发现CVs的分析表明，它们符合PBs的特征，可能使已确认的PB星族数量增加约50%；我们的结果显示，相当一部分PB星族可能仍隐藏在白矮星星表中。
英文摘要：
During their secular evolution, cataclysmic variable stars (CVs) evolve toward shorter orbital periods ($P_{\rm orb}$) until reaching a minimum near $P_{\rm orb}\sim80$ min, after which they evolve back toward longer periods. CVs that have evolved past this evolutionary turning point are known as period-bouncers (PBs). Despite predictions that 40-80% of all CVs should be PBs, only 3-25% of the observed CV population is composed of PBs, a discrepancy likely due to their intrinsic low luminosities. We aim to investigate the evolutionary status of 213 SRG/eROSITA-selected PB candidates. The sample also includes 19 previously confirmed PBs, which serve as benchmarks for evaluating the candidates. We confirmed 24 new CVs through the identification of Balmer emission lines in optical spectra from the Sloan Digital Sky Survey V (SDSS-V) and of dwarf-nova outbursts in archival photometric surveys. By fitting hydrogen-rich atmosphere models to the SDSS-V spectra, we estimated the effective temperature and secular mass accretion rate of the WDs. We also measured the Balmer decrements, used as diagnostics of the physical conditions of the accretion disc, to assess whether they are consistent with known PBs. In addition, we analysed archival light curves from the Transiting Exoplanet Survey Satellite (TESS) to determine $P_{\rm orb}$ for a subset of systems, and compiled multi-wavelength photometry to construct and model spectral energy distributions (SEDs), from which we inferred approximate donor spectral types. Our analysis of the new CVs indicates that they are consistent with being PBs, potentially increasing the population of confirmed PBs by $\sim 50\%$. Our results suggest that a substantial fraction of the PB population may remain hidden in WD catalogues.
