In the present paper, we study the thermal properties of the geometrically thin accretion disks surrounding the null naked singularity (NNS) and the first type of Joshi-Malafarina-Narayan (JMN1) spacetimes and compare the results with the accretion disk around equally massive Schwarzschild black hole. First, we examine the properties of the circular orbits in these spacetimes. The emitted flux, radiation spectra, disk efficiency, and temperature distribution on the disk surface are then investigated. The efficiency of the conversion of the accreting matter into radiation is found to be substantially higher for naked singularities than that for black holes. We also verify that the flux radiated from the disk surface is greater for null and JMN1 naked singularities than black holes. Hence, the accretion disks around naked singularities are much more luminous than the black holes of the same mass and accretion rate. In the luminosity spectra of the NNS, we find that the significant contribution of the low-frequency is coming from the nearby regions of the NNS. Furthermore, the spectral luminosity distribution for the “nonzero torque” at the inner boundary is also analyzed by the inclusion of the nonzero torque value at the inner edge of the disk. The slopes of the luminosity distribution with respect to frequency for naked singularity spacetimes differ significantly from those of black holes. These unique features of the naked singularities serve as an effective tool to distinguish them from the equally massive black holes.

中文翻译：

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比较裸奇点和黑洞的薄吸积盘性质

在本文中，我们研究了空裸奇点 (NNS) 和第一类 Joshi-Malafarina-Narayan (JMN1) 时空周围的几何薄吸积盘的热特性，并将结果与​​同样质量的史瓦西周围的吸积盘进行了比较黑洞。首先，我们检查这些时空中圆形轨道的性质。然后研究磁盘表面上的发射通量、辐射光谱、磁盘效率和温度分布。吸积物质转化为辐射的效率被发现裸奇点比黑洞高得多。我们还验证了从磁盘表面辐射的通量对于空奇点和 JMN1 裸奇点比黑洞更大。因此，裸奇点周围的吸积盘比相同质量和吸积率的黑洞要亮得多。在NNS的光度谱中，我们发现低频的显着贡献来自NNS的附近区域。此外，还通过包含圆盘内边缘的非零扭矩值来分析内边界处“非零扭矩”的光谱光度分布。裸奇点时空的光度分布斜率相对于频率的斜率与黑洞的斜率显着不同。裸奇点的这些独特特征是区分它们与同等质量黑洞的有效工具。我们发现低频的显着贡献来自NNS的附近区域。此外，还通过包含圆盘内边缘的非零扭矩值来分析内边界处“非零扭矩”的光谱光度分布。裸奇点时空的光度分布斜率相对于频率的斜率与黑洞的斜率显着不同。裸奇点的这些独特特征是区分它们与同等质量黑洞的有效工具。我们发现低频的显着贡献来自NNS的附近区域。此外，还通过包含圆盘内边缘的非零扭矩值来分析内边界处“非零扭矩”的光谱光度分布。裸奇点时空的光度分布斜率相对于频率的斜率与黑洞的斜率显着不同。裸奇点的这些独特特征是区分它们与同等质量黑洞的有效工具。还通过包含圆盘内边缘的非零扭矩值来分析内边界处“非零扭矩”的光谱光度分布。裸奇点时空的光度分布斜率相对于频率的斜率与黑洞的斜率显着不同。裸奇点的这些独特特征是区分它们与同等质量黑洞的有效工具。还通过包含圆盘内边缘的非零扭矩值来分析内边界处“非零扭矩”的光谱光度分布。裸奇点时空的光度分布斜率相对于频率的斜率与黑洞的斜率显着不同。裸奇点的这些独特特征是区分它们与同等质量黑洞的有效工具。