arXiv 1004.40862010-04-23astro-ph.HE

INTEGRAL对瞬变X射线爆源XTE J1810-189的观测结果

Results of INTEGRAL TOO observation of the transient X-ray burster XTE J1810-189

I. Chelovekov, S. Grebenev

备注：: Published in Proceedings of the Workshop "The Extreme sky: Sampling the Universe above 10 keV" (Otranto/Italy, October 13-17, 2009), PoS, 96, 66
发表信息：: PoS, 2009, 96, 66

摘要：

我们报告了瞬时X射线爆发源XTE J1810-189的积分机会目标观测结果。观测是在2008年4月3日至6日进行的，在发现源后不久，接近爆发的高峰。此时，源的通量约为50 mCrab，并显示出远高于100 keV的硬康普顿化X射线谱。在3- 100 keV的宽能带中用指数截止的幂律近似，它给出了平均光子指数$Γ\simeq 1.6$和$kT_{cutoff}\simeq 67$ keV。在观察期间，我们仅发现指数变化的轻微迹象（$Γ$首先从$\sim 2.0$稳定降低至$\sim1.3$，然后升高回$\sim 2.0$）。然而，通过在光谱的低能量部分中的吸收测量的$N_{\rmn H}$值急剧且非常不规则地变化（从$\sim 4\times 10^{22}$到$\sim 100\times 10^{22}$ cm $^{-2}$）。在这些TOO观测期间，从源检测到10个I型X射线爆发。假设在爆发期间达到爱丁顿光度，具有最高峰值通量，我们得到到源$D=6.4\pm0.6$ kpc的距离的上限估计。从X射线爆发参数，我们得出结论，这个LMXB窝藏一个进化的恒星。

英文摘要：

We report results of the INTEGRAL Target of Opportunity observations of the transient X-ray burster XTE J1810-189. The observations were performed on April 3--6, 2008, soon after the discovery of the source and near the peak of its outburst. That time the source had a flux of about 50 mCrab and exhibited a hard Comptonized X-ray spectrum extending well above 100 keV. Being approximated by a power law with an exponetial cut-off in the broad 3--100 keV energy band it gave the average photon index $Γ\simeq 1.6$ and $kT_{cutoff}\simeq 67$ keV. We found only slight indications for changes in the index during the observation ($Γ$ first steady decreased from $\sim 2.0$ to $\sim1.3$ and then increased back to $\sim 2.0$). However the $N_{\rmn H}$ value measured by absorption in the low energy part of the spectrum changed drastically and very irregularly (from $\sim 4\times 10^{22}$ till $\sim 100\times 10^{22}$ cm$^{-2}$). There were 10 type I X-ray bursts detected from the source during these TOO observations. Assuming that the Eddington luminosity was reached during the burst with the highest peak flux we get an upper estimate for a distance to the source $D=6.4\pm0.6$ kpc. From the X-ray burst parameters we conclude that this LMXB harboures an evolved star.

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