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arXiv 1306.1106astro-ph.HE
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CXOU J005047 .9-731817:小麦哲伦星云中的一颗292秒X射线脉冲双星

CXOU J005047.9-731817: a 292-s X-ray binary pulsar in the Small Magellanic Cloud

P. Esposito, G. L. Israel, L. Sidoli, G. A. Rodríguez Castillo, N. Masetti, P. D'Avanzo, S. Campana

摘要:

本文报道了在小麦哲伦星云中发现的一个脉冲周期为292秒的瞬变X射线双星。2010年4月至5月,一系列钱德拉指向偶然记录了一次长达两周的爆发,在此期间,源光度增加了约100倍,达到约1 E36 erg/s的峰值(距离为61 kpc)。复杂的形状和能量依赖的脉动被检测到接近爆发峰值,并在其衰减阶段的第一部分。在爆发过程中,脉冲星的相位平均光谱可以用光子指数约为0.6的吸收功率定律很好地描述,但相位的函数变化很大。钱德拉也多次探测到该源(在2002年、2003年、2006年和2010年期间),其静态水平约为1 E34 erg/s。2012年,我们用ESO/VLT对R ~ 15 mag光学对应物进行了红外测光跟踪,并利用CTIO望远镜进行了光谱观测。光谱显示这是一颗晚Oe或早Be V-III光度级的恒星,尽管我们的数据不能排除更演化的伴星(我们可以排除光度I和光谱类型比B2晚)。最后,我们表明,爆发的主要参数(持续时间和峰值亮度)可以解释的源瞬态活动的I型爆发在Be X射线二进制。

英文摘要:

We report on the discovery of a transient X-ray pulsars, located in the Small Magellanic Cloud, with a pulse period of 292 s. A series of Chandra pointings fortuitously recorded in 2010 April-May the occurrence of a two-weeks-long outburst, during which the source luminosity increased by a factor of about 100, reaching a peak of ~1E36 erg/s (for a distance of 61 kpc). Complex-shape and energy-dependent pulsations were detected close to the outburst peak and during the very first part of its decay phase. During the outburst, the phase-averaged spectrum of the pulsar was well described by an absorbed power law with photon index ~0.6, but large variations as a function of phase were present. The source was also detected by Chandra several times (during 2002, 2003, 2006, and 2010) at a quiescent level of ~1E34 erg/s. In 2012 we performed an infrared photometric follow-up of the R ~ 15 mag optical counterpart with the ESO/VLT and a spectroscopic observation by means of the CTIO telescope. The optical spectra suggest a late-Oe or early-Be V-III luminosity-class star, though a more evolved companion cannot be ruled out by our data (we can exclude a luminosity class I and a spectral type later than B2). Finally, we show that the outburst main parameters (duration and peak luminosity) can be accounted for by interpreting the source transient activity as a type I outburst in a Be X-ray binary.

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