[论文解读] The carbon-rich type Ic supernova 2016adj in the iconic dust lane of Centaurus A: signatures of interaction with circumstellar hydrogen?

M. Stritzinger, E. Baron+25 more|arXiv (Cornell University)|Sep 10, 2023

Gamma-ray bursts and supernovae被引用 4

一句话总结

本研究基于光学与红外光谱，将天蝎座A中的SN 2016adj重新分类为富含碳的Ic型超新星，而非Ib/IIb型。研究发现，在+97天时检测到氢丰富壳层的星周相互作用，表现为H帕邢线和布拉开线发射线，表明喷流与激波发生相互作用。分析推断出⁵⁶Ni质量为0.5 M☉，喷流质量为4.2 M☉，但因消光与光回波效应，结果仍存在较大不确定性。

ABSTRACT

We present a comprehensive data set of supernova (SN) 2016adj located within the central dust lane of Centaurus A. SN 2016adj is significantly reddened and after correcting the peak apparent $B$-band magnitude ($m_B = 17.48\pm0.05$) for Milky Way reddening and our inferred host-galaxy reddening parameters (i.e., $R_{V}^{host} = 5.7\pm0.7$ and $A_{V}^{host} = 6.3\pm0.2$), we estimate it reached a peak absolute magnitude of $M_B \sim -18$. Detailed inspection of the optical/NIR spectroscopic time-series reveals a carbon-rich SN Ic and not a SN Ib/IIb as previously suggested in the literature. The NIR spectra shows prevalent carbon-monoxide formation occurring already by +41 days past $B$-band maximum, which is $\approx 11$ days earlier than previously reported in the literature for this object. Interestingly around two months past maximum, the NIR spectrum of SN~2016adj begins to exhibit H features, with a +97~d medium resolution spectrum revealing both Paschen and Bracket lines with absorption minima of $\sim 2000$ km/s, full-width-half-maximum emission velocities of $\sim 1000$ km/s, and emission line ratios consistent with a dense emission region. We speculate these attributes are due to circumstellar interaction (CSI) between the rapidly expanding SN ejecta and a H-rich shell of material formed during the pre-SN phase. A bolometric light curve is constructed and a semi-analytical model fit suggests the supernova synthesized 0.5 solar masses of $^{56}$Ni and ejected 4.2 solar masses of material, though these values should be approached with caution given the large uncertainties associated with the adopted reddening parameters, possible CSI contamination, and known light echo emission. Finally, inspection of Hubble Space Telescope archival data yielded no progenitor detection.

研究动机与目标

• 利用多 epoch 光学与红外光谱，将SN 2016adj从Ib/IIb型重新分类为富含碳的Ic型超新星。
• 通过晚期红外光谱中的H线发射，研究与富含氢物质的星周相互作用迹象。
• 构建光度曲线并拟合半解析模型，以推断⁵⁶Ni质量与喷流质量，同时考虑尘埃消光与光回波污染的影响。
• 利用差分成像与人工星测试，在预爆发的哈勃望远镜与VLT+NACO图像中搜索前身星。
• 评估宿主星系消光（RV_host = 5.7 ± 0.7，AV_host = 6.3 ± 0.2），及其对测光与光谱解释的影响。

提出的方法

• 利用地基与空间望远镜获取SN 2016adj的全面光学与红外光谱时序数据。
• 采用基于MCMC的建模方法拟合红外光谱中的CO发射特征，以确定形成 timescale 与激发条件。
• 基于多波段测光构建光度曲线，并应用半解析模型估算⁵⁶Ni质量与喷流质量。
• 对预爆发哈勃WFPC2/F555W与晚期WFC3/F555W图像进行差分成像，以搜索前身星消失的迹象。
• 在NACO自适应光学图像中进行人工星测试，以确定极限星等并评估前身星的可探测性。
• 使用标准星校准测光，并建模NACO视场中PSF的变化，以获得可靠的零点与深度极限。

Figure 1: Colored image of Centaurus A (NGC 5128) constructed from RGB images obtained with the Swope telescope located at the Las Campanas Observatory. SN 2016adj occurred within the central dust lane, just South-East of a very bright, and typically saturated foreground star.

实验结果

研究问题

• RQ1 SN 2016adj是否为富含碳的Ic型超新星，且是否表现出与富含氢物质的星周相互作用迹象？
• RQ2 在+97天红外光谱中观测到的H帕邢线与布拉开线的性质与起源为何？
• RQ3 SN 2016adj的⁵⁶Ni质量与喷流质量为何？消光与光回波效应如何影响这些估计值？
• RQ4 能否在预爆发的哈勃望远镜与VLT+NACO图像中探测到SN 2016adj的前身星？其光度的限制为何？
• RQ5 宿主星系消光参数（RV_host = 5.7 ± 0.7，AV_host = 6.3 ± 0.2）如何影响测光与光谱数据的解释？

主要发现

• 基于光学与红外光谱，SN 2016adj被重新分类为富含碳的Ic型超新星，CO形成最早可追溯至最大亮度后+41天。
• H帕邢线与布拉开线在+97天出现，吸收谷速率为~2000 km s⁻¹，发射线FWHM速度约为~1000 km s⁻¹，表明存在致密的星周相互作用。
• 发射线线比与致密、光致电离区域的特征一致，支持在超新星爆发前阶段形成富含氢的星周壳层。
• 光度曲线拟合表明⁵⁶Ni质量为0.5 M☉，喷流质量为4.2 M☉，但因消光与光回波污染，这些值存在较大不确定性。
• 在预爆发的哈勃望远镜或VLT+NACO图像中未探测到前身星，绝对星等极限分别为F814W > -5.7 mag 与 Ks > -7.5 mag，表明典型沃尔夫-拉叶星难以被探测到。
• 宿主星系消光极高（AV_host = 6.3 ± 0.2 mag，RV_host = 5.7 ± 0.7），显著影响测光校正与光谱解释。

Figure 2: Optical spectra of SN 2016adj from $-$ 7 d to $+$ 156 d. Phase and telescope facility are indicated on the right of each spectrum. Prevalent spectral features are marked with vertical dashed lines and labeled. Telluric absorption features are labeled with Earth symbols, while for the +43 d