标题： AstroSat 观测了在 2019 年爆发期间的吸积毫秒 X 射线脉冲星 SAX J1808.4-3658 显示英文标题

标题： The AstroSat observation of accreting millisecond X-ray pulsar SAX J1808.4-3658 during its 2019 outburst

摘要： 我们报告了对吸积毫秒X射线脉冲星SAX J1808.4-3658在2019年爆发期间的AstroSat数据集的分析。我们发现了频率为$\sim 401$赫兹的相干脉冲以及与先前研究一致的轨道解。3-20 keV能段的脉冲轮廓可以用三个谐波相关的正弦分量很好地拟合，背景校正后的振幅分别为$\sim 3.5 \%$、$\sim 1.2 \%$和$\sim 0.37 \%$，分别对应基频、二次谐波和三次谐波。我们的能量分辨脉冲轮廓演化研究表明存在强烈的能量依赖性。我们还观察到，在基频时存在软时滞，在谐波时存在硬时滞。SAX J1808.4-3658的宽带谱可以用一个热发射成分（$kT \sim 1$keV）、来自高温晕的热康普顿化（$\Gamma \sim 1.67$）以及由于铁元素引起的宽发射线很好地描述。 显示英文摘要

摘要： We report on the analysis of the AstroSat dataset of the accreting millisecond X-ray pulsar SAX J1808.4-3658, obtained during its 2019 outburst. We found coherent pulsations at $\sim 401$ Hz and an orbital solution consistent with previous studies. The 3-20 keV pulse profile can be well fitted with three harmonically related sinusoidal components with background-corrected fractional amplitude of $\sim 3.5 \%$, $\sim 1.2 \%$ and $\sim 0.37 \%$ for fundamental, second and third harmonic, respectively. Our energy-resolved pulse profile evolution study indicate a strong energy dependence. We also observed a soft lag in fundamental and hard lag during its harmonic. The broadband spectrum of SAX J1808.4-3658 can be well described with a combination of thermal emission component with $kT \sim 1$ keV, a thermal Comptonization ($\Gamma \sim 1.67$) from the hot corona and broad emission lines due to Fe.