arXiv 0810.53192008-10astro-ph

孤立中子星RX J0720 .4-3125的光谱和时间变化：新的XMM-牛顿观测

Spectral and temporal variations of the isolated neutron star RX J0720.4-3125: new XMM-Newton observations

M. M. Hohle, F. Haberl, J. Vink, V. Hambaryan, R. Turolla, S. Zane, C. P. de Vries, M. Mendez

备注：: eight pages, submitted to A&A in August 15th, 2008 eleven pages, revised version submitted to A&A in December 15th, accepted by A&A February 14th
DOI：: 10.1051/0004-6361/200810812

摘要：

在过去，孤立的，无线电安静的中子星RX J 0720.4 -3125在X射线光谱中显示出光谱参数（视半径，发射区的温度和吸收特征的等效宽度）的变化，不仅在8.39秒的旋转周期内，而且在几年的时间尺度上。使用XMM Newton对RX J0720.4-3125进行的新的X射线观测将覆盖范围扩大到大约7.5年，最新的指向于2007年11月进行。在总共14个可用的EPIC-pn数据集中，有11个是用相同的仪器设置（带薄滤波器的全帧读出模式）获得的，并且最适合于对这颗神秘的X射线脉冲星的光谱和定时特性进行比较研究。我们分析了新的XMM牛顿观测数据以及存档数据，以跟踪RX J0720.4-3125的光谱和时间演变。为了尽可能减少系统误差，强调了对所有这些观测数据进行系统和一致的数据处理。我们调查的相位残差来自不同的能带的数据，使用不同的定时解决方案的自旋周期的演变，并确认硬和软光子之间的相位滞后。在硬光子和软光子之间的X射线脉冲中的相移随时间而变化，并且在MJD=52800天左右改变符号，而不管所选择的定时解决方案。相位残差[略]

英文摘要：

In the past, the isolated, radio-quiet neutron star RX J0720.4-3125 showed variations in the spectral parameters (apparent radius, temperature of the emitting area and equivalent width of the absorption feature) seen in the X-ray spectra, not only during the spin period of 8.39s, but also over time scales of years. New X-ray observations of RX J0720.4-3125 with XMM Newton extend the coverage to about 7.5 years with the latest pointing performed in November 2007. Out of a total of fourteen available EPIC-pn datasets, eleven have been obtained with an identical instrumental setup (full frame read-out mode with thin filter), and are best suited for a comparative investigations of the spectral and timing properties of this enigmatic X-ray pulsar. We analysed the new XMM Newton observations together with archival data in order to follow the spectral and temporal evolution of RX J0720.4-3125 All XMM-Newton data were reduced with the standard XMM-SAS software package. A systematic and consistent data reduction of all these observations was emphasised in order to reduce systematic errors as far as possible. We investigate the phase residuals derived from data from different energy bands using different timing solutions for the spin period evolution and confirm the phase lag between hard and soft photons. The phase shift in the X-ray pulses between hard and soft photons varies with time and changes sign around MJD=52800 days, regardless of the chosen timing solution. The phase residuals[abridge]

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