NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154
NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154
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DOI：
10.3847/2041-8213/abc94c
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
G. Younes;T. Güver;C. Kouveliotou;M. Baring;Chin-Ping Hu;Z. Wadiasingh;Beste Begiçarslan;T. Enoto-T.-E
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作者：
G. Younes;T. Güver;C. Kouveliotou;M. Baring;Chin-Ping Hu;Z. Wadiasingh;Beste Begiçarslan;T. Enoto-T.-E
我们报告了对磁星SGR 1935+2154的NICER观测，涵盖了其2020年爆发风暴和爆发后90天的长期持续发射演变。在4月28日00:40:58 UTC拍摄的第一个1120秒内，我们检测到超过217次爆发，对应于>0.2次爆发s−1。3小时后，频率为0.008次s−1，此后一直保持在较低的水平。t90脉冲持续时间分布在840 ms处达到峰值；等待时间的分布符合对数正态分布，平均为2.1 s。1-10 keV爆发光谱与平均温度和面积为kT = 1.7 keV, r2 = 53 km2的黑体很好地拟合。约3个数量级的差分爆发通量分布可以用幂律形式dN/dF∝F−1.5±0.1很好地模拟。源持续发射脉冲剖面在暴发后数小时呈双峰。我们发现，尽管与源相关的快速射电暴与较亮的峰值在相位上对齐，但爆发峰值到达时间在脉冲相位上遵循均匀分布。我们从突出后21-39天的重节奏观测中测量了源自旋下降，Hz s - 1，比2014年突出后测量的值大2.7倍。最后，持续发射通量和黑体温度在爆发初期迅速下降，在40 d后达到静止状态，而发射区域的大小保持不变。
We report on NICER observations of the magnetar SGR 1935+2154, covering its 2020 burst storm and long-term persistent emission evolution up to ∼90 days postoutburst. During the first 1120 s taken on April 28 00:40:58 UTC, we detect over 217 bursts, corresponding to a burst rate of >0.2 bursts s−1. Three hours later, the rate was 0.008 bursts s−1, remaining at a comparatively low level thereafter. The T 90 burst duration distribution peaks at 840 ms; the distribution of waiting times to the next burst is fit with a lognormal with an average of 2.1 s. The 1–10 keV burst spectra are well fit by a blackbody, with an average temperature and area of kT = 1.7 keV and R 2 = 53 km2. The differential burst fluence distribution over ∼3 orders of magnitude is well modeled with a power-law form dN/dF ∝ F −1.5±0.1. The source persistent emission pulse profile is double-peaked hours after the burst storm. We find that the burst peak arrival times follow a uniform distribution in pulse phase, though the fast radio burst associated with the source aligns in phase with the brighter peak. We measure the source spin-down from heavy-cadence observations covering days 21–39 postoutburst, Hz s−1, a factor of 2.7 larger than the value measured after the 2014 outburst. Finally, the persistent emission flux and blackbody temperature decrease rapidly in the early stages of the outburst, reaching quiescence 40 days later, while the size of the emitting area remains unchanged.