标题： Swift探测到2014年新星V745 Sco的超软相超级快速开启现象 显示英文标题

标题： Swift detection of the super-swift switch-on of the super-soft phase in nova V745 Sco (2014)

摘要： V745 Sco是一颗再发新星，最近一次爆发发生在2014年2月。 V745 Sco在光学发现宣布后仅仅3.7小时就被Swift观测到，超软X射线辐射大约四天后被探测到，并持续了约两天，这不仅使它成为Swift对新星最快的后续观测，也是迄今为止最早检测到的超软发射切换。 如此早的切换时间表明高速外流和低喷出质量的结合，同时与超软发射达到的有效温度一起，表明一颗高质量白矮星（>1.3 M_sun）。 X射线光谱演化从早期阶段开始跟踪，那时激波发射明显可见，贯穿整个超软相，显示出柱密度、发射线、吸收边以及热连续谱温度的变化。 在整个超软区间也获得了UV光栅数据，光谱主要显示来自较低电离跃迁的发射线和巴耳末连续谱的发射。 V745 Sco与V2491 Cyg（另一颗具有非常短的超软相的新星）和M31N 2008-12a（迄今为止发现的最快速复发的新星）进行了比较。 与M31N 2008-12a相比，较长的复发时间可能由于较低的质量吸积率，尽管系统的倾角也可能起到一定作用。 新星V745 Sco（2014）揭示了迄今为止发现的演化最快的超软源相位，提供了详细且信息丰富的研究数据集。 显示英文摘要

摘要： V745 Sco is a recurrent nova, with the most recent eruption occurring in February 2014. V745 Sco was first observed by Swift a mere 3.7 hr after the announcement of the optical discovery, with the super-soft X-ray emission being detected around four days later and lasting for only ~two days, making it both the fastest follow-up of a nova by Swift and the earliest switch-on of super-soft emission yet detected. Such an early switch-on time suggests a combination of a very high velocity outflow and low ejected mass and, together with the high effective temperature reached by the super-soft emission, a high mass white dwarf (>1.3 M_sun). The X-ray spectral evolution was followed from an early epoch where shocked emission was evident, through the entirety of the super-soft phase, showing evolving column density, emission lines, absorption edges and thermal continuum temperature. UV grism data were also obtained throughout the super-soft interval, with the spectra showing mainly emission lines from lower ionization transitions and the Balmer continuum in emission. V745 Sco is compared with both V2491 Cyg (another nova with a very short super-soft phase) and M31N 2008-12a (the most rapidly recurring nova yet discovered). The longer recurrence time compared to M31N 2008-12a could be due to a lower mass accretion rate, although inclination of the system may also play a part. Nova V745 Sco (2014) revealed the fastest evolving super-soft source phase yet discovered, providing a detailed and informative dataset for study.