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arXiv 0806.4824astro-ph
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用INTEGRAL/IBIS对窄线Seyfert 1 s的首次高能观测

First high energy observations of Narrow Line Seyfert 1s with INTEGRAL/IBIS

A. Malizia, L. Bassani, A. J. Bird, R. Landi, N. Masetti, A. De Rosa, F. Panessa, M. Molina, A. J. Dean, M. Perri, J. Tueller

摘要:

窄线塞弗特1星系(NLS 1)是一个非常有趣的天体,与它们的宽线类似星系(BLS 1)相比,它显示出一些特殊的性质。虽然在许多波段得到了很好的研究,但它们在>10 keV的行为研究得很差,但对于区分用来解释在X射线波段观察到的复杂性的模型很重要。在这里,我们提出了第一次高能量观测(17-100千电子伏)的5个NLS 1星系(3个善意和2个候选人)检测的INTEGRAL/IBIS和提供所有的宽波段光谱分析使用的数据Swift/XRT低于10千电子伏。组合的积分谱被发现是陡峭的(伽玛=2.6 +/- 0.3)比经典的塞弗特1对象。这是由于高能量截止,这是需要在一些个别的配合,如在平均宽带光谱。这种高能截止的位置比典型的1型活动星系核的能量要低(E < 60 keV);反射成分也可能存在,但它的值(R < 0.8)与标准塞弗特1型活动星系核的反射成分一致。我们没有在单个物体中检测到软过量,而只是在它们的累积光谱中。我们的研究结果表明,较低的等离子体温度的吸积等离子体相结合的高吸积率(接近爱丁顿率)点不同的核条件,在宽和窄线塞弗特1星系,可能与不同的演化阶段。

英文摘要:

Narrow Line Seyfert 1 galaxies (NLS1) are very interesting objects which display peculiar properties when compared to their broad line analogues (BLS1). Although well studied in many wavebands, their behaviour at >10 keV is poorly studied and yet important to discriminate between models invoked to explain the complexity observed in the X-ray band. Here we present for the first time high energy observations (17-100 keV) of five NLS1 galaxies (3 bona fide and 2 candidates) detected by INTEGRAL/IBIS and provide for all of them a broad band spectral analysis using data obtained by Swift/XRT below 10 keV. The combined INTEGRAL spectrum is found to be steeper (Gamma=2.6 +/- 0.3) than those of classical Seyfert 1 objects. This is due to a high energy cutoff, which is required in some individual fits as in the average broad band spectrum. The location of this high energy cutoff is at lower energies (E < 60 keV) than typically seen in classical type 1 AGNs; a reflection component may also be present but its value (R < 0.8) is compatible with those seen in standard Seyfert 1s. We do not detect a soft excess in individual objects but only in their cumulative spectrum. Our results suggest a lower plasma temperature for the accreting plasma which combined to the high accretion rates (close to the Eddington rate) point to different nuclear conditions in broad and narrow line Seyfert 1 galaxies, likely related to different evolutionary stages.

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