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Table 1

Observing log and surface average longitudinal magnetic field values.

Date HJD- # of Exp. SN
2 450 000 frames time
17/07/2017 57951.03705 8 3.0 2357
11/08/2017 57976.06673 8 8.0 3094
Date Bz Nz Bz Nz
Hydrogen All
17/07/2017 −283 ± 107(2.6) 37 ± 96(0.4) −128 ± 68(1.9) 5 ± 62(0.1)
11/08/2017 485 ± 84(5.7) −47 ± 86(0.5) 404 ± 55(7.3) −30 ± 58(0.5)

Notes. The heliocentric Julian date shown in column two is that of the beginning of the sequence of exposures. Column three gives the number of frames obtained during each night of observation, while column four shows the exposure time, in seconds, of each frame. Column five gives the S/N per pixel of Stokes I calculated at about 4950 Å over a wavelength range of 100 Å. ⟨Bz⟩ values (G) are obtained from the spectral regions covered by the hydrogen lines obtained from the Stokes V and N parameter spectrum, respectively. The value in parenthesis gives the detection level (e.g., ⟨Bz⟩/σBz⟩). The same is reported under columns All, when using the whole spectrum. The uncertainties are that scaled by the χ2 of the linearfit (see Sect. 3.4 of Bagnulo et al. 2012).

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