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arXiv 0801.2976astro-ph
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Swift J1656 .3-3302的高红移耀变体识别

High-redshift blazar identification for Swift J1656.3-3302

N. Masetti, E. Mason, R. Landi, P. Giommi, L. Bassani, A. Malizia, A. J. Bird, A. Bazzano, A. J. Dean, N. Gehrels, E. Palazzi, P. Ubertini

摘要:

我们报告的高红移blazar识别的一个新的伽马射线源,斯威夫特J1656.3-3302,发现与BAT成像仪的斯威夫特卫星和IBIS仪器上的INTEGRAL卫星。后续的光学光谱学使我们能够将对应物识别为R波段19 mag源,其在红移z = 2.40+-0.01处显示宽的Lyman-α、Si IV、He II、C IV和C III]发射线。当INTEGRAL/IBIS数据与Swift/BAT结果进行比较时,在X射线中观察到光谱演化,当源变暗时,光谱变陡。用Swift/XRT和INTEGRAL/IBIS观测到的0.7-200 keV的X射线连续谱显示出射电强(宽发射线)活动星系核(光子指数约为1.6)的典型幂律形状和低于2 keV的光谱曲率,这可能是由于源局部的内禀吸收(N_H约为7 e22 cm-2)造成的。或者,2.7 keV附近的斜率变化(光子指数约为1)可以同样很好地描述X射线光谱。在这个红移下,观测到的20-100 keV源的光度约为1 e48 erg s-1(假设各向同性发射),使斯威夫特J1656.3-3302成为最明亮的X射线耀变体之一。这个源是另一个在20 keV以上发现的遥远伽马射线响亮类星体的例子。它也是最远的对象,在以前未确认的积分源,其性质已确定后,通过光谱学。

英文摘要:

We report on the high-redshift blazar identification of a new gamma-ray source, Swift J1656.3-3302, detected with the BAT imager onboard the Swift satellite and the IBIS instrument on the INTEGRAL satellite. Follow-up optical spectroscopy has allowed us to identify the counterpart as an R-band 19 mag source that shows broad Lyman-alpha, Si IV, He II, C IV, and C III] emission lines at redshift z = 2.40+-0.01. Spectral evolution is observed in X-rays when the INTEGRAL/IBIS data are compared to the Swift/BAT results, with the spectrum steepening when the source gets fainter. The 0.7-200 keV X-ray continuum, observed with Swift/XRT and INTEGRAL/IBIS, shows the power law shape typical of radio loud (broad emission line) active galactic nuclei (with a photon index around 1.6) and a hint of spectral curvature below 2 keV, possibly due to intrinsic absorption (N_H about 7e22 cm-2) local to the source. Alternatively, a slope change (of about 1 in terms of photon index) around 2.7 keV can describe the X-ray spectrum equally well. At this redshift, the observed 20-100 keV luminosity of the source is about 1e48 erg s-1 (assuming isotropic emission), making Swift J1656.3-3302 one of the most X-ray luminous blazars. This source is yet another example of a distant gamma-ray loud quasar discovered above 20 keV. It is also the farthest object, among the previously unidentified INTEGRAL sources, whose nature has been determined a posteriori through optical spectroscopy.

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