近日，意大利罗马第二大学的Yu-Han Yang&Eleonora Troja及其研究团队取得一项新进展。经过不懈努力，他们发现一颗富含镧系元素的千新星在长伽马射线爆发后形成。相关研究成果已于2024年2月21日在国际权威学术期刊《自然》上发表。

据悉，从观测角度来看，千新星是由比铁重的原子核的放射性衰变提供能量的天体物理瞬变，其被认为是在两个致密天体合并时合成的。在最初的几天里，千新星的演化主要由大量的放射性同位素主导，这些同位素有助于提高加热速率。在数周到数月的时间尺度上，它的行为预计会因喷射物组成和合并残留物而有所不同。先前的研究表明，与伽马射线爆发230307A相关的千新星与AT2017gfo相似，中红外光谱显示了一条2.15微米的发射线，这条发射线归因于碲。

该研究团队对同一伽马射线爆进行了多波长分析，包括公开可用的詹姆斯韦伯太空望远镜数据和他们自己的哈勃太空望远镜数据。研究人员模拟了它在爆发后两个月的演化，并表明，在这些后期，光球半径的衰退和快速衰减的放热光度(L_bol∝t^-2.7±0.4，其中t是时间)支持富镧元素喷射物在冷却时的复合。

附：英文原文

Title: A lanthanide-rich kilonova in the aftermath of a long gamma-ray burst

Author: Yang, Yu-Han, Troja, Eleonora, OConnor, Brendan, Fryer, Chris L., Im, Myungshin, Durbak, Joe, Paek, Gregory S. H., Ricci, Roberto, Bom, Clcio R., Gillanders, James H., Castro-Tirado, Alberto J., Peng, Zong-Kai, Dichiara, Simone, Ryan, Geoffrey, van Eerten, Hendrik, Dai, Zi-Gao, Chang, Seo-Won, Choi, Hyeonho, De, Kishalay, Hu, Youdong, Kilpatrick, Charles D., Kutyrev, Alexander, Jeong, Mankeun, Lee, Chung-Uk, Makler, Martin, Navarete, Felipe, Prez-Garca, Ignacio

Issue&Volume: 2024-02-21

Abstract: Observationally, kilonovae are astrophysical transients powered by the radioactive decay of nuclei heavier than iron, thought to be synthesized in the merger of two compact objects. Over the first few days, the kilonova evolution is dominated by a large number of radioactive isotopes contributing to the heating rate. On timescales of weeks to months, its behaviour is predicted to differ depending on the ejecta composition and the merger remnant. Previous work has shown that the kilonova associated with gamma-ray burst 230307A is similar to kilonova AT2017gfo  and mid-infrared spectra revealed an emission line at 2.15micrometres that was attributed to tellurium. Here we report a multi-wavelength analysis, including publicly available James Webb Space Telescope data and our own Hubble Space Telescope data, for the same gamma-ray burst. We model its evolution up to two months after the burst and show that, at these late times, the recession of the photospheric radius and the rapidly decaying bolometric luminosity (L_bol∝t^-2.7±0.4, where t is time) support the recombination of lanthanide-rich ejecta as they cool.

DOI: 10.1038/s41586-023-06979-5

Source: https://www.nature.com/articles/s41586-023-06979-5