arXiv 0812.27882008-12-15astro-ph

M 33中第二颗食高质量X射线双星的探测

Detection of the second eclipsing high mass X-ray binary in M 33

W. Pietsch, F. Haberl, T. J. Gaetz, J. D. Hartman, P. P. Plucinsky, R. Tüllmann, B. F. Williams, A. Shporer, T. Mazeh, T. G. Pannuti

备注：: 19 pages, 9 figures, ApJ accepted
发表信息：: Astrophys.J.694:449-458,2009
DOI：: 10.1088/0004-637X/694/1/449

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摘要：

X射线源的钱德拉数据[PMH 2004] 47是在2006年对M 33（ChASeM 33）进行的ACIS调查中获得的。在其中一次观测中，源从高状态变化到低状态，然后返回，在另外两次观测中，它从低状态变化到相应的中间状态。这些转变被解释为在一个高质量的X射线双星系统中的一个紧凑的对象的食入口和出口。月食中期的相位由HJD 2453997.476 ± 0.006给出，月食半角为30.6 ± 1.2度。加上2001年[PMH 2004] 47的XMM-牛顿观测，我们确定双星周期为1.732479+-0.000027 d。这一时期也与ROSAT HRI 1994年对来文方的观测相一致。没有检测到与紧凑对象的旋转周期兼容的短期周期性。有迹象表明，长期变异性与Her X-1检测到的变异性相似。在高态期间，源的光谱是硬的（光子指数~0.85的幂律光谱），具有2 E37 erg/cm 2/s（0.2-4.5 keV）的未吸收光度。我们确认了一颗V ~ 21.0等的恒星，T_eff > 19000 K，log（g）> 2.5。CFHT的光学光变曲线显示出与X射线光变曲线相同的椭圆变化。光学光变曲线和X射线食可以用一个质量与中子星或高质量X射线双星中的黑洞一致的致密天体来模拟。然而，硬幂律X射线光谱倾向于中子星作为M 33中第二个食X射线双星的致密天体。假设中子星的正则质量为1.4 M太阳，最佳拟合伴星温度为33000 K，则系统倾角i = 72 °，伴星质量为10.9 M太阳。

英文摘要：

Chandra data of the X-ray source [PMH2004] 47 were obtained in the ACIS Survey of M 33 (ChASeM33) in 2006. During one of the observations, the source varied from a high state to a low state and back, in two other observations it varied from a low state to respectively intermediate states. These transitions are interpreted as eclipse ingress and egresses of a compact object in a high mass X-ray binary system. The phase of mid eclipse is given by HJD 2453997.476+-0.006, the eclipse half angle is 30.6+-1.2 degree. Adding XMM-Newton observations of [PMH2004] 47 in 2001 we determine the binary period to be 1.732479+-0.000027 d. This period is also consistent with ROSAT HRI observations of the source in 1994. No short term periodicity compatible with a rotation period of the compact object is detected. There are indications for a long term variability similar to that detected for Her X-1. During the high state the spectrum of the source is hard (power law spectrum with photon index ~0.85) with an unabsorbed luminosity of 2E37 erg/cm2/s (0.2-4.5 keV). We identify as an optical counterpart a V ~ 21.0mag star with T_eff > 19000 K, log(g) > 2.5. CFHT optical light curves for this star show an ellipsoidal variation with the same period as the X-ray light curve. The optical light curve together with the X-ray eclipse can be modeled by a compact object with a mass consistent with a neutron star or a black hole in a high mass X-ray binary. However, the hard power law X-ray spectrum favors a neutron star as the compact object in this second eclipsing X-ray binary in M 33. Assuming a neutron star with a canonical mass of 1.4 M_sun and the best fit companion temperature of 33000 K, a system inclination i = 72 degree and a companion mass of 10.9 M_sun are implied.

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