论文标题
HD 213258：一种新的快速振荡，超慢的旋转，强烈磁性AP在光谱二进制中
HD 213258: a new rapidly oscillating, super-slowly rotating, strongly magnetic Ap star in a spectroscopic binary
论文作者
论文摘要
我们报告有关HD 213258的AP恒星，我们最近确定为呈现出罕见，非凡的特性的独特组合。我们对这颗星的研究基于espadons stokes I和V数据，在7个时期获得的时间间隔略短于2年，苔丝数据和径向速度测量值略短。我们确认HD 213258绝对是AP明星。我们发现，在其频谱中，将FeIIλ6149.2Å线解析为两个磁性分裂的组件。 HD 213258，<b> 〜3.8 kg的平均磁场模量不会在〜2年内显示出显着变化。将我们的平均纵向野外测定与文献的几个测量值进行比较，我们表明恒星旋转周期可能必须达到50年的阶段，并且逆转了场极性。此外，HD 213258是迅速振荡的AP（ROAP）恒星，其中检测到高蒸汽脉动，周期为7.58分钟。最后，我们确认HD 213258的平均径向速度超过了至少99％的AP恒星（绝对值）。径向速度显示出低振幅变化，这表明恒星是单线光谱二元。它也是已知的天文二进制。虽然其轨道元素仍有待确定，但其轨道时期可能是二元ROAP恒星最短的元素之一。它的次要接近恒星和替代物体之间的边界。它可能是棕色矮人的可能性。虽然在整个AP恒星中的一小部分中观察到了大多数上述特性，但单颗恒星拥有所有恒星的可能性极低。这使得HD 213258成为异常有趣的对象，将来值得详细研究。
We report about HD 213258, an Ap star that we recently identified as presenting a unique combination of rare, remarkable properties. Our study of this star is based on ESPaDOnS Stokes I and V data obtained at 7 epochs spanning a time interval slightly shorter than 2 years, on TESS data, and on radial velocity measurements from the CORAVEL data base. We confirm that HD 213258 is definitely an Ap star. We found that, in its spectrum, the Fe II λ6149.2 Å line is resolved into its two magnetically split components. The mean magnetic field modulus of HD 213258, <B> ~ 3.8 kG does not show significant variations over ~2 years. Comparing our mean longitudinal field determinations with a couple of measurements from the literature, we show that the stellar rotation period must likely be of the order of 50 years, with a reversal of the field polarity. Moreover, HD 213258 is a rapidly oscillating Ap (roAp) star, in which high overtone pulsations with a period of 7.58 min are detected. Finally, we confirm that HD 213258 has a mean radial velocity exceeding (in absolute value) that of at least 99% of the Ap stars. The radial velocity shows low amplitude variations, which suggests that the star is a single-line spectroscopic binary. It is also a known astrometric binary. While its orbital elements remain to be determined, its orbital period likely is one of the shortest known for a binary roAp star. Its secondary is close to the borderline between stellar and substellar objects. There is a significant probability that it may be a brown dwarf. While most of the above-mentioned properties, taken in isolation, are observed in a small fraction of the whole population of Ap stars, the probability that a single star possesses all of them is extremely low. This makes HD 213258 an exceptionally interesting object that deserves to be studied in detail in the future.
