II型超新星SN2025abyc中延长的平台期到尾部过渡
A prolonged plateau-to-tail transition in the Type II supernova SN2025abyc
- Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）
- International Centre of Supernovae (ICESUN), Yunnan Key Laboratory of Supernova Research（超新星国际研究中心（ICESUN），云南省超新星研究重点实验室）
- University of Chinese Academy of Sciences（中国科学院大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过测光和光谱观测发现II型超新星SN2025abyc存在约30天的延长平台期到尾部过渡，并指出星周环境、镍分布和氢包层结构共同影响其光变演化。
AI中文摘要：
我们展示了II型超新星SN2025abyc的光学测光和光谱观测。在爆炸后约10至70天的光学厚阶段，其光变曲线在g、c、r和o波段分别显示出约2.7、2.1、0.9和0.8 mag/100天的强烈波长依赖的衰减率。在约70天时，光变曲线开始偏离其近乎线性的平台演化，并逐渐向放射性尾部过渡。对采样良好的ATLAS o波段光变曲线进行费米-狄拉克拟合，得到过渡中点t_PT约100.5天。线性平台结束与该过渡中点之间的间隔约为30天，表明存在一个延长的平台期到尾部过渡。这一时间尺度与SN2013by、SN2013ej和SN2014G的测量结果相当。在光谱上，爆炸后+13天时，Halpha轮廓显得微弱且宽，而Hbeta和Hgamma则显示出清晰的P-Cygni轮廓。这种形态可以通过II型超新星正常的早期光谱演化来解释，尽管不能排除与星周物质相互作用相关的发射对Halpha吸收槽的部分填充。SN2025abyc在其他方面遵循II型超新星的一般光球速度演化，同时在Halpha、Hbeta和FeII的比较分布中保持在高速侧。探索性的光变曲线建模表明，合成的镍质量约为0.03-0.04太阳质量。我们认为，扩展的星周环境、镍分布和氢包层结构都可能在塑造观测到的光变曲线演化中发挥作用，特别是延长的平台期到尾部过渡。
英文摘要：
We present optical photometric and spectroscopic observations of the Type II supernova SN2025abyc. During the optically thick phase between approximately 10 and 70 d after explosion, its light curves show strongly wavelength-dependent decline rates of approximately 2.7, 2.1, 0.9, and 0.8 mag/100d in the g, c, r, and o bands, respectively. At approximately 70 d, the light curves begin to depart from their nearly linear plateau evolution and gradually transition toward the radioactive tail. A Fermi-Dirac fit to the well-sampled ATLAS o-band light curve yields a transition midpoint of t_PT ~ 100.5d. The interval between the end of the linear plateau and this transition midpoint is approximately 30 d, indicating a prolonged plateau-to-tail transition. This timescale is comparable to those measured for SN2013by, SN2013ej, and SN2014G. Spectroscopically, at +13 d post-explosion, the Halpha profile appears weak and broad, whereas Hbeta and Hgamma display clear P-Cygni profiles. This morphology can be explained by the normal early spectroscopic evolution of SNe II, although partial filling of the Halpha absorption trough by emission associated with circumstellar interaction cannot be excluded. SN2025abyc otherwise follows the general photospheric velocity evolution of SNe II, while remaining toward the high-velocity side of the comparison distribution in Halpha, Hbeta, and FeII. Exploratory light-curve modelling suggests a synthesized Ni mass of approximately 0.03-0.04 solar mass. We suggest that the extended circumstellar environment, Ni distribution, and hydrogen-envelope structure could all play a role in shaping the observed light-curve evolution, particularly the prolonged plateau-to-tail transition.
