Proper motions of thermally emitting isolated neutron stars measured with Chandra
Proper motions of thermally emitting isolated neutron stars measured with Chandra
复制标题
用钱德拉测量的热发射孤立中子星的自行
DOI：
10.1051/0004-6361/200811052
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发表时间：
2009
影响因子：
6.5
通讯作者：
V. Zavlin
中科院分区：
文献类型：
--
作者：
C. Motch;A. Pires;F. Haberl;A. Schwope;V. Zavlin
钱德拉天文台卓越的天体测量能力提供了在这个波长范围内以前所未有的精度测量X射线源自行的可能性。我们最近完成了一个自行调查的七个热发射无线电安静的孤立中子星（INS）在ROSAT全天巡天发现的。这些INS（RX J0420.0−5022、RX J0806.4−4123和RX J1308.6+2127）要么缺乏光学对应物，要么有一个非常微弱的光学对应物，以至于地面或空间光学观测将目前仪器的可能性推向了极限。每隔3至5年获得一对ACIS观测数据，以测量X射线源在X射线天空中的位移，并以河外或遥远的银河X射线源的背景作为参考。我们推导出RX J0420.0−5022和RX J0806.4−4123自行的2σ上限分别为123 mas yr −1和86 mas yr −1。RX J1308.6+2127显示出非常显著的位移（109 σ），产生μ = 220 ± 25 mas yr −1，是所有ROSAT发现的INS中第二快的。这个源可能正以一种速度迅速远离银河平面，这种速度排除了星际介质中任何重要的物质吸积。它的横向速度为10740（d/700 pc）km s −1，可能是所有ROSAT INS中最大的，其相应的空间速度也是中子星记录中最快的。因此RX J1308.6+2127是一颗中年（年龄约为1 My）的高速冷却中子星星。我们调查其可能的起源在附近的OB协会或从一个领域OB星星。在大多数情况下，从出生地开始的飞行时间明显短于从自旋下降率得出的特征年龄。总的来说，ROSAT INS的横向速度分布与正常无线电导航卫星的横向速度分布没有统计学差异。
The remarkable astrometric capabilities of the Chandra Observatory offer the possibility to measure proper motions of X-ray sources with an unprecedented accuracy in this wavelength range. We recently completed a proper motion survey of three of the seven thermally emitting radio-quiet isolated neutron stars (INSs) discovered in the ROSAT all-sky survey. These INSs (RX J0420.0−5022, RX J0806.4−4123 and RX J1308.6+2127) either lack an optical counterpart or have one so faint that ground based or space born optical observations push the current possibilities of the instrumentation to the limit. Pairs of ACIS observations were acquired 3 to 5 years apart to measure the displacement of the sources on the X-ray sky using as a reference the background of extragalactic or remote Galactic X-ray sources. We derive 2σ upper limits of 123 mas yr −1 and 86 mas yr −1 on the proper motion of RX J0420.0−5022 and RX J0806.4−4123, respectively. RX J1308.6+2127 exhibits a very significant displacement (∼9σ) yielding μ = 220 ± 25 mas yr −1 , the second fastest measured among all ROSAT-discovered INSs. The source is probably moving away rapidly from the Galactic plane at a speed which precludes any significant accretion of matter from the interstellar medium. Its transverse velocity of ∼740 (d/700 pc) km s −1 might be the largest of all ROSAT INSs and its corresponding spatial velocity lies among the fastest recorded for neutron stars. RX J1308.6+2127 is thus a middle-aged (age ∼1 My) high velocity cooling neutron star. We investigate its possible origin in nearby OB associations or from a field OB star. In most cases, the flight time from birth place appears significantly shorter than the characteristic age derived from spin down rate. Overall, the distribution in transverse velocity of the ROSAT INSs is not statistically different from that of normal radio pulsars.