标题： 用射电和X射线观测研究MAXI J1810-222的性质和特性 显示英文标题

标题： Investigating the nature and properties of MAXI J1810-222 with radio and X-ray observations

摘要： 我们展示了对X射线暂现源MAXI J1810-222的射电和X射线观测结果。该源中的吸积体性质尚未确定。在本文中，我们展示了使用澳大利亚望远镜紧凑阵列(ATCA)、尼尔·盖尔斯·斯威夫特观测站X射线望远镜(XRT)和斯威夫特爆发警报望远镜(BAT)进行的准同时射电和X射线监测活动的结果。我们还利用中子星内部组成探测器(NICER)的观测数据分析了X射线的时间行为。结果表明，在这次爆发期间，MAXI J1810-222表现出似乎奇特的X射线光谱演化，其中在爆发初期，该源仅在软X射线波段被探测到。然后，在MAXI J1810-222首次被探测到约200天后，硬X射线辐射增加，该源转变为一个持续时间较长（约1.5年）的明亮、更硬的X射线状态。在此硬态之后，MAXI J1810-222返回到较软的状态，随后逐渐变暗并再次转变为更硬的状态，然后似乎遵循更典型的爆发衰减过程。根据X射线光谱和时间特性以及源的射电行为，我们认为本研究的结果最符合MAXI J1810-222是一个相对较远（$\gtrsim$6 kpc）的黑洞X射线双星系统。足够大的源距离可以简单地解释观察到的看似异常的爆发演化，其中只有爆发最明亮的部分能够被全天X射线望远镜探测到。 显示英文摘要

摘要： We present results from radio and X-ray observations of the X-ray transient MAXI J1810-222. The nature of the accretor in this source has not been identified. In this paper, we show results from a quasi-simultaneous radio and X-ray monitoring campaign taken with the Australia Telescope Compact Array (ATCA), the Neil Gehrels Swift observatory X-ray telescope (XRT), and the Swift Burst Alert Telescope (BAT). We also analyse the X-ray temporal behaviour using observations from the Neutron star Interior Composition Explorer (NICER). Results show a seemingly peculiar X-ray spectral evolution of MAXI J1810-222 during this outburst, where the source was initially only detected in the soft X-ray band for the early part of the outburst. Then, ~200 days after MAXI J1810-222 was first detected the hard X-ray emission increased and the source transitioned to a long-lived (~1.5 years) bright, harder X-ray state. After this hard state, MAXI J1810-222 returned back to a softer state, before fading and transitioning again to a harder state and then appearing to follow a more typical outburst decay. From the X-ray spectral and timing properties, and the source's radio behaviour, we argue that the results from this study are most consistent with MAXI J1810-222 being a relatively distant ($\gtrsim$6 kpc) black hole X-ray binary. A sufficiently large distance to source can simply explain the seemingly odd outburst evolution that was observed, where only the brightest portion of the outburst was detectable by the all-sky X-ray telescopes.