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Table 2.

Summary of the spectral analysis of nine NuSTAR observations of Her X-1.

35 d Max. flux Observed Line Line Ecyc Ecut Efold Power-
cycle of 35 d line width strength (a) norm. to 6.8 law
no. (e) cycle energy σ ASM-cts s−1 index
[ASM-cts s−1] [keV] [keV] [keV] [keV] [keV] [keV] Γ
427 6.60 ± 0.37 37.40 ± 0.25 (b) 5.76 ± 0.29 8.86 ± 0.87 37.54 ± 0.25 20.68 ± 0.27 9.95 ± 0.13 0.920 ± 0.004
457 2.96 ± 0.20 34.79 ± 0.22 4.46 ± 0.22 4.70 ± 0.70 37.38 ± 0.24 (c) 19.86 ± 0.12 9.37 ± 0.09 0.929 ± 0.003
468 6.50 ± 0.20 37.18 ± 0.14 5.97 ± 0.18 8.83 ± 0.44 37.38 ± 0.14 (c) 20.86 ± 0.15 10.16 ± 0.07 0.985 ± 0.001
478 4.10 ± 0.20 35.62 ± 0.18 4.94 ± 0.20 5.90 ± 0.40 37.44 ± 0.19 19.98 ± 0.16 9.79 ± 0.09 0.962 ± 0.002
484 4.09 ± 0.19 35.67 ± 0.29 4.84 ± 0.33 6.10 ± 0.70 37.50 ± 0.30 20.04 ± 0.11 10.16 ± 0.07 0.963 ± 0.002
490 5.60 ± 0.46 36.65 ± 0.16 5.61 ± 0.25 8.44 ± 0.59 37.46 ± 0.16 20.45 ± 0.23 9.79 ± 0.09 0.974 ± 0.002
494 5.02 ± 0.46 36.28 ± 0.22 5.26 ± 0.24 7.21 ± 0.53 37.48 ± 0.23 19.56 ± 0.12 9.65 ± 0.11 0.885 ± 0.002 (f)
495 3.72 ± 0.56 35.36 ± 0.41 4.76 ± 0.45 6.38 ± 0.98 37.44 ± 0.43 19.62 ± 0.29 9.49 ± 0.24 0.934 ± 0.005
498 (d) 4.00 ± 0.37 35.65 ± 0.21 5.01 ± 0.25 7.02 ± 0.50 37.54 ± 0.22 19.81 ± 0.16 9.38 ± 0.09 0.932 ± 0.001

Notes. The spectral parameters were found by applying the XSPEC-function highecut (see text). Uncertainties are at the 1 sigma (68%) level. The maximum flux of the respective 35-day cycle is given in units of (ASM-cts s−1), referring to the All Sky Monitor of RXTE. The corresponding physical flux in units of (keV cm−2 s) is found by multiplying with 0.2367. The flux was measured by Swift/BAT and converted according to (2–10 keV) (ASM-cts s−1) = 93.0 × (15–50 keV) (BAT-cts cm−2 s) (Staubert et al. 2016). The observed line energy was normalized to an ASM count rate of 6.8 cts s−1 using a slope of (0.675 ± 0.075) keV/(ASM-cts s−1) (see Fig. 1).

(a)

We note that strength = ;

(b)

the values for the CRSF are from Fürst et al. (2013), Obs. II (Table 3, HighE);

(c)

in Staubert et al. (2016, 2017) the flux normalization was done with a slope of 0.44 (instead of 0.675);

(d)

for the June 2019 observation only data from detector B have been used (see text);

(e)

35-day cycle numbering is according to Staubert et al. (1983);

(f)

observation at a high 35-day phase, Γ expected to be lower (Vasco 2012).

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