小麦哲伦云中6.85 s X射线脉冲星XTE J0103-728的脉冲射电辐射上限
Upper Limits on Pulsed Radio Emission from the 6.85 s X-ray Pulsar XTE J0103-728 in the Small Magellanic Cloud
摘要：
最近在SMC中检测到周期为6.85 s的X射线脉动，随后被确定为来自Be/X射线二元系统XTE J 0103 -728。最近对X射线发射源的定位使得有针对性地搜索来自该源的无线电脉动成为可能。XTE J 0103 -728的脉冲射电辐射的探测将使其成为继PSR B 1259 -63之后第二个既是Be/X射线双星又是射电脉冲星的系统。2008年2月，在XTE J 0103 -728的X射线脉冲源被发现后不久，我们用Parkes 64-m射电望远镜对XTE J 0103 -728进行了观测，以寻找相应的射电脉冲。我们使用了一个连续的6.4小时的观察与256 MHz的带宽集中在1390 MHz使用中心光束的Parkes多波束接收器。在随后的数据分析中，包括折叠搜索、傅立叶搜索、快速折叠算法搜索和单脉冲搜索，在0 ~ 800 pc cm^-3范围内的试验色散测量（DM）中没有发现脉冲信号。这个DM范围很容易包含SMC中源的预期值。我们将XTE J 0103 -728在观测时期的周期性射电辐射的光度上限定为~45 mJy kpc ^2，并将此上限与PSR B 1259 -63的测量光度范围进行比较，PSR B 1259 -63是目前已知的唯一能发射射电脉冲的Be/X射线双星。我们还比较了我们的极限的射电光度的中子星具有类似的长自旋周期XTE J 0103 -728。由于PSR B1259-63的无线电脉冲在近星点附近的轨道部分被遮蔽且无法检测到，如果XTE J 0103 -728正在经历类似的遮蔽，并且如果这些观测能够很好地采样该系统的轨道相位，则重复进行额外的无线电搜索观测可能是有价值的。
英文摘要：
X-ray pulsations with a 6.85 s period were recently detected in the SMC and were subsequently identified as originating from the Be/X-ray binary system XTE J0103-728. The recent localization of the source of the X-ray emission has made a targeted search for radio pulsations from this source possible. The detection of pulsed radio emission from XTE J0103-728 would make it only the second system after PSR B1259-63 that is both a Be/X-ray binary and a radio pulsar. We observed XTE J0103-728 in Feb 2008 with the Parkes 64-m radio telescope soon after the identification of the source of X-ray pulsations was reported in order to search for corresponding radio pulsations. We used a continuous 6.4 hour observation with a 256 MHz bandwidth centered at 1390 MHz using the center beam of the Parkes multibeam receiver. In the subsequent data analysis, which included a folding search, a Fourier search, a fast-folding algorithm search, and a single-pulse search, no pulsed signals were found for trial dispersion measures (DMs) between 0 and 800 pc cm^-3. This DM range easily encompasses the expected values for sources in the SMC. We place an upper limit of ~45 mJy kpc^2 on the luminosity of periodic radio emission from XTE J0103-728 at the epoch of our observation, and we compare this limit to a range of luminosities measured for PSR B1259-63, the only Be/X-ray binary currently known to emit radio pulses. We also compare our limit to the radio luminosities of neutron stars having similarly long spin periods to XTE J0103-728. Since the radio pulses from PSR B1259-63 are eclipsed and undetectable during the portion of the orbit near periastron, repeated additional radio search observations of XTE J0103-728 may be valuable if it is undergoing similar eclipsing and if such observations are able to sample the orbital phase of this system well.
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