[论文解读] The progenitor and remnant of the helium nova V445 Puppis

V. P. Goranskij, S. Yu. Shugarov+3 more|arXiv (Cornell University)|Nov 28, 2010

Astrophysical Phenomena and Observations被引用 5

一句话总结

该论文将V445 Pup识别为一颗在碳氧白矮星上发生双引爆的氦新星，其前身星为具有周期性光变（P = 0.650654 ± 0.000011 d）的共转包层双星。2000–2001年爆发后，尘埃形成遮挡了残骸，但到2007年，光学与红外自适应光学成像中未检测到任何恒星残骸，表明白矮星已被完全摧毁，双星系统已不复存在，从而排除了其未来成为Ia型超新星的可能性。

ABSTRACT

V445 Pup was a peculiar nova with no hydrogen spectral lines during the outburst. The spectrum contained strong emission lines of carbon, oxygen, calcium, sodium, and iron. We have performed digital processing of photographic images of the V445 Pup progenitor using astronomical plate archives. The brightness of the progenitor in the B band was 14.3 mag. It was a periodic variable star, its most probable period being 0.650654+/-0.000011 day. The light curve shape suggests that the progenitor was a common-envelope binary with a spot on the surface and variable surface brightness. The spectral energy distribution of the progenitor between 0.44 and 2.2 micrometers was similar to that of an A0V type star. After the explosion in 2001, the dust was formed in the ejecta, and the star became a strong infrared source. This resulted in the star's fading below 20 mag in the V band. Our CCD BVR observations acquired between 2003 and 2009 suggest that the dust absorption minimum finished in 2004, and the remnant reappeared at the level of 18.5 mag V. The dust dispersed but a star-like object was absent in frames taken in the K band with the VLT adaptive optics. Only expanding ejecta of the explosion were seen in these frames till March 2007. No reddened A0V type star reappeared in the spectral energy distribution. The explosion of V445 Pup in 2000 was a helium flash on the surface of a CO-type white dwarf. Taking into account the results of modern dynamic calculations, we discuss the possibility of a white-dwarf core detonation triggered by the helium flash and the observational evidence for it. Additionally, the common envelope of the system was lost in the explosion. Destruction in the system and mass loss from its components exclude the future SN Ia scenario for V445 Pup.

研究动机与目标

• 确定氦新星V445 Pup前身系统的性质。
• 研究2000–2001年爆发后双星系统的演化命运。
• 基于观测与动力学约束，评估V445 Pup是否可能是未来Ia型超新星的前身。
• 分析光度与光谱数据，推断爆发期间及之后的物理过程。
• 检验在碳氧白矮星上由氦壳层点火引发双引爆的假设。

提出的方法

• 对档案照相底片进行数字处理，测定前身星在B波段的亮度及其周期性变化。
• 分析前身星的光变曲线，推断轨道周期与由黑子引起的亮度调制。
• 在0.44至2.2 μm波段范围内进行光谱能量分布（SED）拟合，将前身星分类为A0V型并具有微弱红外超量。
• 利用CCD BVR光度测量（2003–2009年）追踪爆发后的亮度衰减与尘埃消散过程。
• 利用甚大望远镜（VLT）在K波段进行自适应光学成像（2007年），以搜寻可能存在的恒星残骸。
• 比较星像轮廓形状与分辨率，检测拉长特征或未分辨点源。

实验结果

研究问题

• RQ1 V445 Pup的前身系统性质如何？其双星性质的证据是什么？
• RQ2 前身星光变曲线中观测到的光变由何引起？这对其系统结构有何含义？
• RQ3 2001年爆发后，光学与红外成像是否显示存在恒星残骸？
• RQ4 该爆发是否可用涉及氦壳层与碳氧核心的双引爆机制来解释？
• RQ5 V445 Pup是否是未来Ia型超新星的可行前身？

主要发现

• V445 Pup的前身星为周期性变星，最可能周期为0.650654 ± 0.000011 d，表明其为具有表面不均匀性的双星系统。
• 前身星的光谱能量分布与A0V型恒星相符，并具有微弱红外超量，暗示其为主序星或演化过的伴星。
• 喷流中的尘埃形成导致恒星在2001年10月后亮度衰减至V < 20 mag以下，尘埃吸收最小值在2004年结束。
• 至2009年，残骸在V ≈ 18.5 mag处重新出现，但K波段自适应光学成像中未检测到任何恒星天体。
• 在SED或高分辨率成像中均未观测到点源或红化A型星，表明不存在存活的白矮星或伴星。
• 未探测到残骸且爆发动力学特征支持双引爆情景，导致白矮星完全摧毁，从而排除其未来成为Ia型超新星的可能性。