Table 4: The observed H $\alpha$ data. The first column denotes whether or not a line-effect was detected; the second column shows the contrast between the line-peak and the continuum to an accuracy of 0.1; the equivalent-widths and FWHM are measured to an accuracy of $\sim$ 5%. The continuum polarization was measured from featureless sections either side of the emission line. As the R 40 data from consecutive nights showed no variability, the data was combined to improve the S/N. The quoted uncertainties do not include the external errors, which we estimate to be 0.1-0.2% (see Sect. 2).
Name Line- Line-cont. EW FWHM Cont. Pol. (R-band)

effect? contrast (Å) ( km s^-1) P (%) $\theta$ ( $^\circ$ )

Galactic

AG Car (6/5/94) Y 17.5 -80 117 0.95 $\pm$ 0.01 160.1 $\pm$ 0.2

'' (10/2/03) Y 25 -119 150 1.09 $\pm$ 0.01 132.6 $\pm$ 0.4

HR Car (16/3/92)
Y 16 -59 115 4.22 $\pm$ 0.01 129.7 $\pm$ 0.1

'' (10/2/03) Y 18 -90 95 3.37 $\pm$ 0.01 133.9 $\pm$ 0.1

$\eta$ Car
Y 100 -1480 450 5.71 $\pm$ 0.04 76.4 $\pm$ 0.2

Hen 3-519 (6/5/94)
N 17 -197 475 2.90 $\pm$ 0.02 97.6 $\pm$ 0.2

'' (10/2/03) Y 22 -220 435 3.05 $\pm$ 0.01 99.2 $\pm$ 0.1

WRA 751
N 4.2 -10 90 2.29 $\pm$ 0.01 58.7 $\pm$ 0.1

P Cyg (10/12/03) N 18 -63 167 0.99 $\pm$ 0.02 29.3 $\pm$ 0.4

'' (13/12/03) N 18 -64 170 0.93 $\pm$ 0.02 29.3 $\pm$ 0.6

HD 160529 N 2 -4.4 80 6.97 $\pm$ 0.01 21.2 $\pm$ 0.1

SMC

R 40
N 4.6 -15 87 0.28 $\pm$ 0.03 92.9 $\pm$ 2.6

LMC

S Dor ? 8.3 -34 100 0.24 $\pm$ 0.02 72.6 $\pm$ 2.6

R 71 N 2.0 -7.8 200 0.31 $\pm$ 0.03 60.1 $\pm$ 2.3

R 110 Y 26 -96 100 1.50 $\pm$ 0.03 32.1 $\pm$ 0.6

R 116 N 2.5 -6.6 130 0.51 $\pm$ 0.02 28.6 $\pm$ 1.0

R 127 Y 40 -114 78 0.50 $\pm$ 0.01 33.4 $\pm$ 0.5

R 143 N 6.4 -20 100 2.93 $\pm$ 0.02 73.3 $\pm$ 0.2

**Table 4:** The observed H $\alpha$ data. The first column denotes whether or not a line-effect was detected; the second column shows the contrast between the line-peak and the continuum to an accuracy of 0.1; the equivalent-widths and *FWHM* are measured to an accuracy of $\sim$ 5%. The continuum polarization was measured from featureless sections either side of the emission line. As the R 40 data from consecutive nights showed no variability, the data was combined to improve the *S/N*. The quoted uncertainties do not include the external errors, which we estimate to be 0.1-0.2% (see Sect. 2).
Name	Line-	Line-cont.	EW	FWHM	Cont. Pol. (R-band)
	effect?	contrast	(Å)	( km s^-1)	P (%)	$\theta$ ( $^\circ$ )
Galactic
AG Car (6/5/94)	Y	17.5	-80	117	0.95 $\pm$ 0.01	160.1 $\pm$ 0.2
'' (10/2/03)	Y	25	-119	150	1.09 $\pm$ 0.01	132.6 $\pm$ 0.4
HR Car (16/3/92)	Y	16	-59	115	4.22 $\pm$ 0.01	129.7 $\pm$ 0.1
'' (10/2/03)	Y	18	-90	95	3.37 $\pm$ 0.01	133.9 $\pm$ 0.1
$\eta$ Car	Y	100	-1480	450	5.71 $\pm$ 0.04	76.4 $\pm$ 0.2
Hen 3-519 (6/5/94)	N	17	-197	475	2.90 $\pm$ 0.02	97.6 $\pm$ 0.2
'' (10/2/03)	Y	22	-220	435	3.05 $\pm$ 0.01	99.2 $\pm$ 0.1
WRA 751	N	4.2	-10	90	2.29 $\pm$ 0.01	58.7 $\pm$ 0.1
P Cyg (10/12/03)	N	18	-63	167	0.99 $\pm$ 0.02	29.3 $\pm$ 0.4
'' (13/12/03)	N	18	-64	170	0.93 $\pm$ 0.02	29.3 $\pm$ 0.6
HD 160529	N	2	-4.4	80	6.97 $\pm$ 0.01	21.2 $\pm$ 0.1
SMC
R 40	N	4.6	-15	87	0.28 $\pm$ 0.03	92.9 $\pm$ 2.6
LMC
S Dor	?	8.3	-34	100	0.24 $\pm$ 0.02	72.6 $\pm$ 2.6
R 71	N	2.0	-7.8	200	0.31 $\pm$ 0.03	60.1 $\pm$ 2.3
R 110	Y	26	-96	100	1.50 $\pm$ 0.03	32.1 $\pm$ 0.6
R 116	N	2.5	-6.6	130	0.51 $\pm$ 0.02	28.6 $\pm$ 1.0
R 127	Y	40	-114	78	0.50 $\pm$ 0.01	33.4 $\pm$ 0.5
R 143	N	6.4	-20	100	2.93 $\pm$ 0.02	73.3 $\pm$ 0.2

Source LaTeX | All tables | In the text

	1 Introduction
	2 Observations and data reduction
	3 Results
	4 Discussion
	5 Conclusions
	Appendix A: Atlas of early-type supergiants
	References