X-Ray Properties of LINERs and Low-Luminosity Seyfert Galaxies Observed with ASCA. I. Observations and Results
X-Ray Properties of LINERs and Low-Luminosity Seyfert Galaxies Observed with ASCA. I. Observations and Results
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DOI：
10.1086/324373
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发表时间：
2002-03
期刊：
影响因子：
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通讯作者：
Y. Terashima;N. Iyomoto;L. Ho;A. Ptak
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文献类型：
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作者：
Y. Terashima;N. Iyomoto;L. Ho;A. Ptak
本文基于ASCA卫星的观测资料，对低电离核发射线区（liner）和低光度塞弗特星系的x射线特性进行了全面的研究。我们分析了21颗liner和17颗低光度seferts的53次观测数据。除了一个物体外，所有物体都探测到x射线辐射。在2-10 keV波段的x射线光度范围为4 × 1039至5 × 1041 ergs -1，比经典的Seyfert星系小1-3个数量级。大多数物体的x射线光谱可以用正则模型很好地描述，该模型包括：(1)来自kT < 1 keV的热等离子体的软组分和(2)由光子指数为Γ≈1.8的幂律或kT≈10 keV的热轫致辐射表示的硬组分。一些对象不需要软热分量，它们的连续体可以用一个幂律模型很好地拟合。有些物体表现出重吸收，柱密度超过1023 cm-2。我们在几个物体中检测到等效宽度从50 eV到2 keV不等的铁K线发射。在我们的样本中，少于一天的时间尺度变化并不常见。通过比较ASCA的多次观测结果或其他卫星发表的2-10 keV观测结果，我们发现至少有8个物体在一周到几年的时间尺度上是可变的。我们发现许多物体的形态，无论是在软带还是硬带，相对于望远镜的点扩展函数都是点状的；有一些在其中一个或两个能带上都有明显的延伸。本系列的第二篇论文将讨论x射线发射的物理解释及其对低光度活动星系核的影响。
This paper presents a comprehensive study of the X-ray properties of low-ionization nuclear emission-line regions (LINERs) and low-luminosity Seyfert galaxies based on observations obtained with the ASCA satellite. We analyzed data of 53 observations of 21 LINERs and 17 low-luminosity Seyferts. X-ray emission has been detected in all but one object. The X-ray luminosities in the 2-10 keV band range from 4 × 1039 to 5 × 1041 ergs s-1, which are 1-3 orders of magnitude smaller than in classical Seyfert galaxies. The X-ray spectra of most objects are well described by a canonical model which consists of (1) a soft component from a thermal plasma with kT < 1 keV and (2) a hard component represented by a power law with a photon index of Γ ≈ 1.8 or thermal bremsstrahlung emission with kT ≈ 10 keV. Several objects do not require the soft thermal component, and their continua are well fitted by a single power-law model. Some objects show heavy absorption with column densities in excess of 1023 cm-2. We detect in several objects Fe K line emission with equivalent widths ranging from 50 eV to 2 keV. Variability on timescales less than a day is uncommon in our sample. By comparing multiple observations made with ASCA or with published 2-10 keV observations from other satellites, we show that at least eight objects are variable on timescales of a week to several years. We find that the morphologies of many objects, both in the soft and hard bands, are consistent with being pointlike relative to the telescope point-spread function; a few are clearly extended in either or both energy bands. The second paper of this series will discuss the physical interpretation of the X-ray emission and its implications for low-luminosity active galactic nuclei.