Table 2.
Comparison of the best-fitting spectral parameters when a power-law model is fit to different datasets within the 2021 periastron passage of PSR B1259–63/LS 2883.
| Dataset | Time − tp | Spectral index (Γ) | Normalisation (ϕ0) | Normalisation (ϕ0) |
|---|---|---|---|---|
| decorrelation | ||||
| energy (E0) | (1 TeV) | |||
| days | 10−12 TeV−1 cm−2 s−1 | 10−12 TeV−1 cm−2 s−1 | ||
| Total 2021 | −23.58 to +127.26 | 2.65 ± 0.04stat ± 0.10sys | 1.28 ± 0.05stat ± 0.26sys | 1.13 ± 0.04stat ± 0.23sys |
| (0.27 − 33.6 TeV) | (0.95 TeV) | |||
| Total 2021 | −23.58 to +127.26 | 2.78 ± 0.05stat ± 0.10sys | 1.31 ± 0.05stat ± 0.26sys | 1.15 ± 0.04stat ± 0.23sys |
| (0.4 − 10 TeV) | (0.95 TeV) | |||
| 2021 Periastron period (Dataset A) | −3.9 to +15.3 | 2.75 ± 0.11stat ± 0.10sys | 1.52 ± 0.12stat ± 0.30sys | 1.34 ± 0.10stat ± 0.27sys |
| (0.4 − 10 TeV) | (0.95 TeV) | |||
| 2021 Peak TeV flux (Dataset B) | +25 to +36 | 2.98 ± 0.07stat ± 0.10sys | 5.00 ± 0.22stat ± 1.00sys | 2.45 ± 0.12stat ± 0.49sys |
| (0.4 − 10 TeV) | (0.79 TeV) | |||
| 2021 GeV flare period (Dataset C) | +55 to +108 | 2.42 ± 0.10stat ± 0.10sys | 0.38 ± 0.03stat ± 0.08sys | 0.68 ± 0.06stat ± 0.14sys |
| (0.4 − 10 TeV) | (1.27 TeV) | |||
| TeV Low flux period (Dataset D) | +81 to +127 | 2.42 ± 0.17stat ± 0.10sys | 0.17 ± 0.02stat ± 0.03sys | 0.37 ± 0.05stat ± 0.07sys |
| (0.4 − 10 TeV) | (1.40 TeV) | |||
| Average of previous periastron passages | −106 to +98 | 2.76 ± 0.09stat ± 0.10sys | – | 1.55 ± 0.12stat ± 0.31sys |
Notes. Γ represents the best-fit photon index of the power law dN/dE = ϕ0(E/E0)−Γ, with ϕ0 denoting the best-fit normalisation level, and E0 being the decorrelation energy (Abdo et al. 2009b). Presented here are the spectral properties of the total dataset of the periastron passage (for both fixed and unfixed energy ranges), as well as four additional sub-orbital periods from the 2021 dataset. All 2021 spectra in this table (with the exception of the total periastron passage spectrum marked “unfixed energy range”) are calculated using an energy range of (0.4–10.0) TeV to enable comparison. The average spectral properties of H.E.S.S. stereo analysis from previous periastron passages (2004, 2007, 2011 and 2014, taken from H.E.S.S. Collaboration 2020) are also included for comparison, from an averaging of the values reported in these papers. The spectra of previous periastron passages, however, do not use the same fixed energy values as the 2021 data. The two errors associated with each value are representative of, first, the magnitude of the statistical uncertainty in the value at a 95% confidence level, and secondly the systematic error in the measurements as adopted from Aharonian et al. (2006).
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