LMC脉冲星PSR B0540-69的HST/WFPC2观测
HST/WFPC2 observations of the LMC pulsar PSR B0540-69
摘要：
对更年轻、更明亮的脉冲星的研究对于了解孤立中子星的光学发射特性非常重要。PSRB 0540 - 69是第二亮（V~22）的光学脉冲星，是一个非常有意义的研究对象。这项工作有三个目的：通过光学天体测量限制脉冲星自行及其在天空平面上的速度，通过一组一致的多波段、高分辨率成像测光观测获得脉冲星光谱能量分布（SED）的更精确表征，测量脉冲星光学相位平均线性偏振，到目前为止，从地面观测中只获得了初步和不确定的测量结果。我们在直接成像和偏振测量模式下使用HST上的WFPC 2对PSRB 0540 - 69进行了高分辨率观测。根据多历元天体测量，我们将脉冲星自行的3 σ上限设定为1 mas/yr，这意味着在50 kpc LMC距离处的横向速度<250 km/s。此外，我们确定了脉冲星的绝对位置，前所未有的精度为70 mas。从多波段测光，我们表征了脉冲星的幂律光谱，并得出了光谱指数（0.70 +/-0.07）的最准确测量值，这表明光学和X射线波段之间的光谱转换。最后，从偏振测量中，我们获得了脉冲星相位平均偏振度的新测量值（16 +/-4%），与磁层模型一致，取决于实际的内在偏振度和去偏振因子，我们发现极化矢量（22 +/-12度位置角）可能与脉冲星的半长轴对齐-风星云和其明亮的发射结的视自行方向。
英文摘要：
The study of the younger, and brighter, pulsars is important to understand the optical emission properties of isolated neutron stars. PSRB0540-69, the second brightest (V~22) optical pulsar, is obviously a very interesting target for these investigations. The aim of this work is threefold: constraining the pulsar proper motion and its velocity on the plane of the sky through optical astrometry, obtaining a more precise characterisation of the pulsar optical spectral energy distribution (SED) through a consistent set of multi-band, high-resolution, imaging photometry observations, measuring the pulsar optical phase-averaged linear polarisation, for which only a preliminary and uncertain measurement was obtained so far from ground-based observations. We performed high-resolution observations of PSRB0540-69 with the WFPC2 aboard the HST, in both direct imaging and polarimetry modes. From multi-epoch astrometry we set a 3sigma upper limit of 1 mas/yr on the pulsar proper motion, implying a transverse velocity <250 km/s at the 50 kpc LMC distance. Moreover, we determined the pulsar absolute position with an unprecedented accuracy of 70 mas. From multi-band photometry we characterised the pulsar power-law spectrum and we derived the most accurate measurement of the spectral index (0.70+/-0.07) which indicates a spectral turnover between the optical and X-ray bands. Finally, from polarimetry we obtained a new measurement of the pulsar phase-averaged polarisation degree (16+/-4%),consistent with magnetosphere models depending on the actual intrinsic polarisation degree and depolarisation factor, and we found that the polarisation vector (22+/-12deg position angle) is possibly aligned with the semi-major axis of the pulsar-wind nebula and with the apparent proper motion direction of its bright emission knot.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
