A Novel Method of Estimating GRB Peak Energies Beyond the \emph{Swift}/BAT Limit
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2024
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| _version_ | 1866917866124607488 |
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| author | Li, Liang Wang, Yu |
| author_facet | Li, Liang Wang, Yu |
| contents | The \emph{Swift} Burst Alert Telescope (BAT), operating in the 15--150 keV energy band, struggles to detect the peak energy ($E_{\rm p}$) of gamma-ray bursts (GRBs), as most GRBs have $E_{\rm p}$ values typically distributed between 200-300 keV, exceeding BAT's upper limit. To address this, we develop an innovative method to robustly estimate the lower limit of $E_{\rm p}$ for GRBs with $E_{\rm p}>150$ keV. This approach relies on the intrinsic curvature of GRB spectra, which is already evident within the BAT energy range for such GRBs. By fitting BAT spectra with a cutoff power-law model and extrapolating the spectral curvature beyond BAT's range, we, therefore, can estimate the cutoff energy ($E^{'}_{\rm c}$) beyond 150 keV and the corresponding peak energy ($E^{'}_{\rm p}$). We applied this method to 17 GRBs, categorizing them into two main groups. Group I (10 bursts) maintains $α$ within a typical range (from $\sim$ -0.8 to $\sim$ -1.20) with increasing $E_{\rm c}$; Group II (2 bursts) maintains $E_{\rm c}$ within a typical range (300-500 keV) but with varying $α$. Our results show that for $E_{\rm c}\lesssim $1000 keV, the estimated $E^{'}_{\rm c}$ aligns well with observed values. Moreover, the reliability of $E^{'}_{\rm c}$ also depends on $α$: bursts with harder $α$ (e.g., $α\gtrsim -2/3$) show reduced accuracy, while bursts with softer $α$ (e.g., $α\lesssim -2/3$) yield more precise estimates. In conclusion, this method is well-suited for GRB spectra with moderately observed $E_{\rm c}$ ($E_{\rm p}$) values and $α$ indices that are not too hard. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2412_08226 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A Novel Method of Estimating GRB Peak Energies Beyond the \emph{Swift}/BAT Limit Li, Liang Wang, Yu High Energy Astrophysical Phenomena The \emph{Swift} Burst Alert Telescope (BAT), operating in the 15--150 keV energy band, struggles to detect the peak energy ($E_{\rm p}$) of gamma-ray bursts (GRBs), as most GRBs have $E_{\rm p}$ values typically distributed between 200-300 keV, exceeding BAT's upper limit. To address this, we develop an innovative method to robustly estimate the lower limit of $E_{\rm p}$ for GRBs with $E_{\rm p}>150$ keV. This approach relies on the intrinsic curvature of GRB spectra, which is already evident within the BAT energy range for such GRBs. By fitting BAT spectra with a cutoff power-law model and extrapolating the spectral curvature beyond BAT's range, we, therefore, can estimate the cutoff energy ($E^{'}_{\rm c}$) beyond 150 keV and the corresponding peak energy ($E^{'}_{\rm p}$). We applied this method to 17 GRBs, categorizing them into two main groups. Group I (10 bursts) maintains $α$ within a typical range (from $\sim$ -0.8 to $\sim$ -1.20) with increasing $E_{\rm c}$; Group II (2 bursts) maintains $E_{\rm c}$ within a typical range (300-500 keV) but with varying $α$. Our results show that for $E_{\rm c}\lesssim $1000 keV, the estimated $E^{'}_{\rm c}$ aligns well with observed values. Moreover, the reliability of $E^{'}_{\rm c}$ also depends on $α$: bursts with harder $α$ (e.g., $α\gtrsim -2/3$) show reduced accuracy, while bursts with softer $α$ (e.g., $α\lesssim -2/3$) yield more precise estimates. In conclusion, this method is well-suited for GRB spectra with moderately observed $E_{\rm c}$ ($E_{\rm p}$) values and $α$ indices that are not too hard. |
| title | A Novel Method of Estimating GRB Peak Energies Beyond the \emph{Swift}/BAT Limit |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2412.08226 |