Full-polarization millimeter wavelength variability of Sagittarius A* during the 2018 EHT campaign

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Volume 708 (April 2026)

A&A, 708 (2026) A179

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Table 1.

Results from the time-series analysis of the ALMA Sgr A^* light curves in total flux density and polarized intensity.

Day	SPW	α_PSD	α_PSD	Timescale
(2018)		(SF)	(P(ω))	(h)

Stokes I
April 21	B1	−2.64 ± 0.04	−2.2 ± 0.2	$0 . 45_{- 0.08}^{+ 0.12}$ $Mathematical equation: $ 0.45^{+0.12}_{-0.08} $$
	B4	−2.59 ± 0.03	−2.2 ± 0.2	$0 . 36_{- 0.05}^{+ 0.07}$ $Mathematical equation: $ 0.36^{+0.07}_{-0.05} $$
April 22	B1	−2.235 ± 0.012	−2.19 ± 0.12	$0 . 26_{- 0.12}^{+ 0.14}$ $Mathematical equation: $ 0.26^{+0.14}_{-0.12} $$
		−1.947 ± 0.015	–	$1 . 78_{- 0.18}^{+ 0.24}$ $Mathematical equation: $ 1.78^{+0.24}_{-0.18} $$
	B4	−2.155 ± 0.013	−2.19 ± 0.11	$0 . 25_{- 0.14}^{+ 0.16}$ $Mathematical equation: $ 0.25^{+0.16}_{-0.14} $$
		−1.842 ± 0.017	–	$1 . 9_{- 0.3}^{+ 0.4}$ $Mathematical equation: $ 1.9^{+0.4}_{-0.3} $$
April 24	B1	−2.43 ± 0.03	−2.23 ± 0.13	$0 . 87_{- 0.13}^{+ 0.18}$ $Mathematical equation: $ 0.87^{+0.18}_{-0.13} $$
	B4	−2.33 ± 0.03	−2.22 ± 0.14	$0 . 87_{- 0.13}^{+ 0.19}$ $Mathematical equation: $ 0.87^{+0.19}_{-0.13} $$
April 25	B1	−2.85 ± 0.02	−2.3 ± 0.3	$0 . 42_{- 0.05}^{+ 0.06}$ $Mathematical equation: $ 0.42^{+0.06}_{-0.05} $$
	B4	−2.670 ± 0.019	−2.2 ± 0.3	$0 . 43_{- 0.04}^{+ 0.05}$ $Mathematical equation: $ 0.43^{+0.05}_{-0.04} $$
All days	B1	−2.659 ± 0.011	−2.42 ± 0.05	$0 . 64_{- 0.05}^{+ 0.06}$ $Mathematical equation: $ 0.64^{+0.06}_{-0.05} $$
	B4	−2.609 ± 0.012	−2.38 ± 0.06	$0 . 60_{- 0.05}^{+ 0.06}$ $Mathematical equation: $ 0.60^{+0.06}_{-0.05} $$

Polarized Intensity

April 21	B1	−2.34 ± 0.03	−2.66 ± 0.06	$0 . 52_{- 0.08}^{+ 0.11}$ $Mathematical equation: $ 0.52^{+0.11}_{-0.08} $$
	B4	−2.33 ± 0.02	−2.59 ± 0.08	$0 . 51_{- 0.08}^{+ 0.10}$ $Mathematical equation: $ 0.51^{+0.10}_{-0.08} $$
April 22	B1	−2.529 ± 0.008	−2.65 ± 0.05	$0 . 50_{- 0.03}^{+ 0.03}$ $Mathematical equation: $ 0.50^{+0.03}_{-0.03} $$
	B4	−2.530 ± 0.008	−2.61 ± 0.05	$0 . 50_{- 0.02}^{+ 0.03}$ $Mathematical equation: $ 0.50^{+0.03}_{-0.02} $$
April 24	B1	−2.336 ± 0.015	−2.83 ± 0.06	$0 . 51_{- 0.06}^{+ 0.08}$ $Mathematical equation: $ 0.51^{+0.08}_{-0.06} $$
	B4	−2.341 ± 0.013	−2.76 ± 0.06	$0 . 53_{- 0.05}^{+ 0.06}$ $Mathematical equation: $ 0.53^{+0.06}_{-0.05} $$
April 25	B1	−2.359 ± 0.018	−2.62 ± 0.08	$0 . 55_{- 0.06}^{+ 0.08}$ $Mathematical equation: $ 0.55^{+0.08}_{-0.06} $$
	B4	−2.328 ± 0.016	−2.59 ± 0.09	$0 . 60_{- 0.06}^{+ 0.08}$ $Mathematical equation: $ 0.60^{+0.08}_{-0.06} $$
All days	B1	−2.405 ± 0.010	−2.42 ± 0.05	$0 . 61_{- 0.04}^{+ 0.05}$ $Mathematical equation: $ 0.61^{+0.05}_{-0.04} $$
	B4	−2.388 ± 0.010	−2.61 ± 0.03	$0 . 60_{- 0.04}^{+ 0.05}$ $Mathematical equation: $ 0.60^{+0.05}_{-0.04} $$

Notes. The PSD slopes and timescales are estimated using the SF. For comparison, PSD slopes α_PSD from the HPF periodogram P(ω), described in Appendix G, are also included.

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