Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy.
Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy.
Science. 2017 Feb 24;355(6327):817-819. doi: 10.1126/science.aai8635. Epub 2017 Feb 20.
Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of [Formula: see text]1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity [Formula: see text] 10 erg second[Formula: see text]) might harbor NSs.
近邻星系中的超高亮 X 射线源 (ULXs) 比我们银河系中的任何 X 射线源都要亮。ULXs 通常被建模为以非常高的速率吸积恒星质量黑洞 (BHs) 或中等质量 BHs。我们展示了观测结果，表明 NGC 5907 ULX 实际上是一个正在吸积的 X 射线中子星 (NS)，其自旋周期从 2003 年的 1.43 秒演化为 2014 年的 1.13 秒。它具有各向同性的峰值光度[Formula: see text]，是 17.1 百万秒差距处 NS 对应爱丁顿极限光度的 1000 倍。即使假设是定向发射，标准的吸积模型也无法解释其光度，但一个强大的多极磁场可以描述其性质。这些发现表明，其他极端 ULXs（X 射线光度[Formula: see text] 10 erg second[Formula: see text]）可能包含 NS。
