Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

Journal Article · Wed May 10 00:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA6D77· OSTI ID:22663323

Lin, Da-Bin; Mu, Hui-Jun; Lu, Rui-Jing; Wang, Xiang-Gao; Liang, En-Wei ^[1]; Liang, Yun-Feng ^[2]; Liu, Tong; Gu, Wei-Min ^[3]

---

1. GXU-NAOC Center for Astrophysics and Space Sciences, Department of Physics, Guangxi University, Nanning 530004 (China)
2. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
3. Department of Astronomy, Xiamen University, Xiamen, Fujian 361005 (China)

We derive a simple analytical formula to describe the evolution of spectral index β in the steep decay phase shaped by the curvature effect with the assumption that the spectral parameters and Lorentz factor of the jet shell are the same for different latitudes. Here, the value of β is estimated in the 0.3−10 keV energy band. For a spherical thin shell with a cutoff power-law (CPL) intrinsic radiation spectrum, the spectral evolution can be read as a linear function of observer time. For the situation with the Band function intrinsic radiation spectrum, the spectral evolution may be complex. If the observed break energy of the radiation spectrum is larger than 10 keV, the spectral evolution is the same as that shaped by jet shells with a CPL spectrum. If the observed break energy is less than 0.3 keV, the value of β would be a constant. For others, the spectral evolution can be approximated as a logarithmal function of the observer time in general.

• OSTI ID: 22663323
• Journal Information: Astrophysical Journal, Vol. 840, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
APPROXIMATIONS
COSMIC GAMMA BURSTS
DECAY
GAMMA RADIATION
KEV RANGE
SPECTRA
SPHERICAL CONFIGURATION
STAR EVOLUTION