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arXiv 1109.6019astro-ph.SR
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CGCS 5926是共生X射线双星吗?

Is CGCS 5926 a symbiotic X-ray binary?

N. Masetti, U. Munari, A. A. Henden, K. L. Page, J. P. Osborne, S. Starrfield

摘要:

本文报道了对碳星CGCS 5926的多波长(X射线到光学)跟踪观测。这些都是出于这样一个事实,这颗星是位置一致的一个微弱的X射线发射对象属于ROSAT目录的来源,从而表明可能的共生X射线二进制(SyXB)的性质为it. Our分光光度光学数据证实了巨大的碳星性质的对象,并允许我们将其光谱类型为C(6,2)。CGCS 5926距离地球约5千秒差距。BVRcIc测光显示,它在月的时间尺度上显示出约0.3等的变化,当它的亮度增加时,它会变得更蓝。我们的测光数据表明,周期为151天,我们解释为由于径向脉动的CGCS 5926的基础上,其全球性的特点。在0.3-10 keV波段光度约为3e 32 erg/s的Swift/XRT X射线下,没有检测到该源。这种nondetection显然是在对比与ROSAT数据,但我们表明,即使CGCS 5926可以是一个SyXB的概率似乎相当低,目前的信息并没有完全排除这种可能性,而它使其他解释更不可能,如果我们假设ROSAT检测是真实的。因此,这个问题可能通过未来更敏感的高能观测来解决。

英文摘要:

We here report on multiwavelength (X-ray to optical) followup observations of carbon star CGCS 5926. These were motivated by the fact that this star is positionally coincident with a faint X-ray emitting object belonging to the ROSAT catalog of sources, thus suggesting a possible symbiotic X-ray binary (SyXB) nature for it. Our spectrophotometric optical data confirm the giant carbon star nature of the object and allow us to classify its spectral type as C(6,2). This classification places CGCS 5926 at a distance of about 5 kpc from Earth. BVRcIc photometry of the star shows that it displays a variability of about 0.3 mag on timescales of months, with the star getting bluer when its brightness increases. Our photometric data indicate a periodicity of 151 days, which we explain as due to radial pulsations of CGCS 5926 on the basis of its global characteristics. The source is not detected at X-rays with Swift/XRT down to a 0.3-10 keV band luminosity of around 3e32 erg/s. This nondetection is apparently in contrast with the ROSAT data; however we show that, even if the probability that CGCS 5926 can be a SyXB appears quite low, the present information does not completely rule out such a possibility, while it makes other interpretations even more unlikely if we assume that the ROSAT detection was real. This issue might thus be settled by future, more sensitive, observations at high energies.

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