Table 1: Photometry and membership for the observed sample stars in the $\sigma $ Ori cluster.

ID		 Namea RA b Decb Ic R-Ic Ref.c Jb $H-K_{\rm s}^{b}$ SpTd $v_{\rm r}$ $v \sin~(i)$ Li pEWe Membership Xf Notes
    (J2000)             (km s-1) (km s-1) (mÅ) $v_{\rm r}$ Li H$\alpha $ Tot    
S01 p053834-0239 5 38 34.79 -2 39 30.0 11.91 1.04 2 10.44 0.25 M1.0 $46.21\pm0.64$   $72\pm6$ N N N N N  
S02 r053838-0236 5 38 38.22 -2 36 38.4 12.38 0.86 2 11.16 0.15 K8.0* $30.93\pm0.33$ <17.8 $551\pm12$ Y Y Y Y Y  
S03 r053835-0231 5 38 35.47 -2 31 51.7 12.45 0.79 2 11.30 0.17 K7.5 $30.60\pm0.29$ <17.0 $582\pm4$ Y Y Y Y Y  
S04 4771-1097 5 38 35.87 -2 30 43.3 12.47 0.81 2 11.24 0.17 K8.0* ?   $338\pm32$ ? Y Y Y? Y SB
S05 4771-0910 5 39 18.83 -2 30 53.1 12.58 0.84 2 11.40 0.30 K9.0 $29.14\pm0.65$ $\rm 42.7^{+1.6}_{-3.1}$ $524\pm39$ Y Y Y Y Y  
S06 4771-1092 5 39 07.61 -2 32 39.2 12.63 0.81 2 11.30 0.31 K8.0 $30.27\pm0.32$ <17.0 $532\pm8$ Y Y Y Y Y  
S07 4771-1075 5 39 05.41 -2 32 30.3 12.66 0.87 2 11.55 0.19 K7.0* $30.40\pm0.20$ <17.4 $593\pm12$ Y Y Y Y Y  
S08 4771-0579 5 39 30.43 -2 35 07.3 12.71 0.74 2 11.61 0.15 K6.5 $80.50\pm0.80$   $30\pm5$ N N N N N  
S09 p053933-0236 5 39 33.44 -2 36 41.9 12.73 0.64 2 11.85 0.14 K5.0 $-14.01\pm1.15$   $29\pm3$ N N N N N  
S10 r053841-0237 5 38 41.29 -2 37 22.6 12.77 0.87 2 11.46 0.21 K9.5 $30.89\pm0.30$ <17.0 $592\pm9$ Y Y Y Y Y  
S11 SWW166 5 38 53.07 -2 38 53.6 12.78 1.07 1 11.62 0.21 M1.0 $-0.10\pm0.52$   $35\pm7$ N N N N Y  
S12 r053840-0230 5 38 40.27 -2 30 18.5 12.80 0.94 2 11.51 0.37 M0.0* $31.51\pm0.36$ <17.0 $552\pm19$ Y Y Y Y Y  
S13 4771-0041 5 38 27.26 -2 45 09.7 12.82 0.82 2 11.95 0.85 K7.0* $30.00\pm0.49$ <17.0 $431\pm11$ Y Y Y Y Y  
S14 SWW135 5 39 25.20 -2 38 22.0 12.83 0.95 1 11.31 0.45 M0.5 $30.10\pm0.46$ <17.0 $480\pm7$ Y Y Y Y Y  
S15 SWW78 5 38 47.46 -2 35 25.2 12.86 0.99 1 - 0.25 M1.0 $30.32\pm0.40$ <17.0 $589\pm6$ Y Y Y Y Y  
S16 r053832-0235b 5 38 32.84 -2 35 39.2 12.88 0.83 2 11.54 0.17 K8.5 $30.12\pm0.27$ <17.0 $576\pm6$ Y Y Y Y Y  
S17 4771-0080 5 38 52.01 -2 46 43.7 12.91 0.85 3 11.52 0.35 K9.0 $30.51\pm0.36$ <17.0 $551\pm10$ Y Y Y Y Y  
S18 4771-1038 5 39 11.63 -2 36 02.9 12.93 0.95 1 11.62 0.22 K8.0* $30.13\pm0.28$ <17.0 $590\pm6$ Y Y Y Y Y  
S19 r053849-0238 5 38 49.17 -2 38 22.2 12.96 1.03 1 11.39 0.15 M0.5* $30.79\pm0.28$ <17.0 $623\pm5$ Y Y Y Y Y  
S20 4771-0961 5 38 02.21 -2 29 55.6 12.99 0.69 2 11.83 0.19 K6.0 $21.24\pm0.69$   $32\pm4$ N N N N N  
S21 SWW102 5 38 47.92 -2 37 19.2 13.02 1.18 1 - - M1.0 $31.77\pm0.51$ <17.0 $481\pm8$ Y Y Y Y Y  
S22 r053830-0241 5 38 30.60 -2 41 18.8 13.06 0.47 2 12.42 0.12 K2.0 $29.17\pm0.83$   $22\pm5$ Y N N N N  
S23 SWW48 5 38 42.28 -2 37 14.8 13.06 0.98 1 11.77 0.22 M0.5 $30.42\pm0.43$ <17.0 $568\pm39$ Y Y Y Y N  
S24 SWW36 5 38 43.55 -2 33 25.4 13.09 1.06 1 11.72 0.24 M1.0 $31.63\pm0.33$ <17.0 $620\pm23$ Y Y Y Y Y  
S25 4771-1090 5 38 46.05 -2 43 47.8 13.12 0.74 2 11.97 0.16 K6.5 $8.38\pm0.60$   $39\pm4$ N N N N N  
S26 SWW205 5 38 49.22 -2 41 25.1 13.23 1.50 1 11.67 0.27 M3.5 ?   $442\pm57$ ? Y Y Y? Y SB
S27 r053838-0226 5 38 38.56 -2 26 44.8 13.30 0.71 3 12.30 0.16 K6.0 $91.40\pm0.68$   $33\pm2$ N N N N N  
S28 SWW35 5 38 48.68 -2 36 16.2 13.37 0.87 1 12.11 0.20 K9.5 $32.53\pm0.46$ <17.0 $590\pm4$ Y Y Y Y Y  
S29 r053851-0236 5 38 51.45 -2 36 20.6 13.38 0.87 2 12.44 0.26 K9.5 $32.06 \pm 0.73$   Y Y Y Y Y Y SB2
S30 K3.01-170 5 38 15.90 -2 34 41.2 13.42 0.64 3 12.37 0.15 K5.0 $-30.56\pm0.70$   $47\pm2$ N N N N N  
S31 r053812-0232 5 38 12.60 -2 33 01.5 13.44 0.62 3 12.46 0.16 K5.0 $33.15\pm0.71$   $21\pm4$ Y N N N N  
S32 SWW195 5 39 11.52 -2 31 06.6 13.45 0.95 1 11.99 0.46 M0.5 $30.91\pm0.79$ <17.0 $263\pm4$ Y Y Y Y Y  
S33 SWW97 5 38 45.38 -2 41 59.4 13.46 1.16 1 11.99 0.29 M1.0 $31.86\pm0.57$ <17.0 $482\pm10$ Y Y Y Y Y  
S34 r053831-0235 5 38 31.58 -2 35 14.9 13.49 1.11 1 11.52 0.35 M0.0* $32.13\pm0.55$ <19.2 $479\pm6$ Y Y Y Y Y  
S35 SWW47 5 38 53.17 -2 43 52.8 13.49 1.08 1 12.23 0.20 M1.0 $30.48\pm0.49$ <17.0 $561\pm8$ Y Y Y Y Y  
S36 K4.03-511 5 38 19.15 -2 35 27.9 13.51 0.74 3 12.31 0.18 K6.5 $121.73\pm0.67$   $59\pm17$ N N N N N  
S37 J053920.5-022737 5 39 20.44 -2 27 36.8 13.52 1.29 1 12.15 0.26 M2.0* $23.73\pm0.45$   $581\pm7$ N Y Y N? Y  
S38 SWW71 5 38 55.44 -2 41 29.7 13.59 1.39 1 12.17 0.28 M3.0 $3.53\pm0.54$   $78\pm5$ N N N N N  
S39 SWW87 5 38 27.74 -2 43 01.0 13.67 1.33 1 12.19 0.16 M2.5 $29.91\pm0.58$ $\rm 21.9^{+0.5}_{-3.1}$ $549\pm32$ Y Y Y Y Y  
S40 p053902-0238 5 39 02.16 -2 38 38.2 13.69 1.67 2 12.40 0.16 M4.0 $61.34\pm0.71$   $33\pm4$ N N N N N  
S41 r053833-0236 5 38 34.06 -2 36 37.5 13.72 1.52 1 11.98 0.25 M3.5* $34.12\pm2.21$ $\rm 45.7^{+1.1}_{-5.3}$ $424\pm56$ Y Y Y Y Y  
S42 p053925-0231 5 39 25.34 -2 31 43.7 13.75 0.81 2 12.43 0.26 K8.0 $103.44\pm0.61$   $65\pm6$ N N N N N  
S43 SWW41 5 38 08.27 -2 35 56.3 13.76 1.32 1 12.14 0.33 M2.5 ?   $518\pm4$ ? Y Y Y? Y SB
S44 SWW50 5 38 31.41 -2 36 33.8 13.80 1.29 1 12.17 0.49 M2.0 $30.81\pm0.88$ <17.0 $342\pm2$ Y Y Y Y N  
S45 K1.02-7 5 38 48.29 -2 36 41.0 13.83 1.74 3 12.04 0.26 M4.5 $30.21\pm1.38$ $\rm 32.1^{+12.4}_{-7.1}$ $510\pm60$ Y Y Y Y Y  
S46 r053832-0235a 5 38 32.60 -2 35 04.1 13.86 0.47 3 13.27 0.17 K2.0 $51.92\pm1.49$   $23\pm6$ N N N N N  
S47 r053834-0234 5 38 34.31 -2 35 00.1 13.88 0.43 2 - - K1.0 $30.37\pm0.38$ $\rm 29.3^{+2.8}_{-5.6}$ $542\pm34$ Y Y Y Y Y  
S48 r053814-0235 5 38 14.23 -2 35 07.3 13.99 0.59 3 13.11 0.11 K4.5 $48.50\pm0.71$   $42\pm13$ N N N N N  
S49 SWW177 5 38 29.12 -2 36 02.7 14.04 1.18 1 - - M1.0 $32.46\pm0.43$ <17.0 $604\pm7$ Y Y Y Y Y  
S50 SWW88 5 38 05.67 -2 40 19.4 14.07 1.27 1 12.77 0.28 M2.0 ?   $94\pm5$ ? N N N N SB
S51 SE34 5 38 50.39 -2 26 47.7 14.10 1.48 1 12.50 0.29 M3.5 $30.48\pm0.57$ $\rm 21.5^{+6.3}_{-4.5}$ $582\pm23$ Y Y Y Y Y  
S52 SE3 5 38 13.20 -2 26 08.8 14.10 1.57 1 12.48 0.27 M4.0 $32.07\pm0.52$ <17.0 $633\pm14$ Y Y Y Y Y  
S53 SWW144 5 38 43.34 -2 32 00.8 14.12 1.75 1 12.24 0.28 M4.5 $30.61 \pm 1.06$   Y Y Y Y Y Y SB2
S54 SWW101 5 38 49.64 -2 45 26.9 14.15 1.23 1 13.15 0.19 M1.5 $41.57\pm0.57$   $88\pm7$ N N N N -  
S55 SE51 5 39 17.17 -2 25 43.4 14.18 1.15 1 12.90 0.19 M1.0 $29.47\pm0.48$ <17.0 $133\pm8$ Y N Y Y Y  
S56 r053923-0233 5 39 22.87 -2 33 33.1 14.19 1.21 1 12.83 0.26 M2.0* $30.26\pm0.37$ <17.0 $584\pm7$ Y Y Y Y Y  
S57 SWW200 5 38 49.93 -2 41 22.8 14.21 1.37 1 12.75 0.22 M3.0 $31.35\pm0.49$ <17.0 $604\pm5$ Y Y Y Y Y  
S58 SWW28 5 39 02.77 -2 29 55.8 14.21 1.51 1 12.61 0.31 M3.5 $31.77\pm0.49$ <17.0 $603\pm9$ Y Y Y Y Y  
S59 SWW127 5 39 24.36 -2 34 01.4 14.28 1.25 1 12.98 0.21 M2.0 $33.18\pm0.45$ <17.0 $47\pm21$ Y N Y Y Y  
S60 J053836.7-024414 5 38 36.69 -2 44 13.7 14.32 1.76 1 12.54 0.27 M4.5 $30.57\pm0.75$ <17.0 $570\pm3$ Y Y Y Y N  
S61 4771-1099 5 39 07.81 -2 40 09.1 14.32 0.60 2 13.57 0.10 K4.5 $45.54\pm1.07$   $42\pm16$ N N N N N  
S62 J053820.1-023802 5 38 20.22 -2 38 01.6 14.33 1.69 1 12.58 0.25 M4.0* $33.92\pm2.54$ $\rm 56.2^{+7.0}_{-9.8}$ $480\pm36$ Y Y Y Y Y  
S63 J053827.5-023504 5 38 27.51 -2 35 04.2 14.35 1.36 3 12.83 0.25 M3.5* $29.72\pm0.63$ <17.0 $516\pm8$ Y Y Y Y Y  
S64 r053907-0228 5 39 07.59 -2 28 23.4 14.37 1.45 1 12.88 0.19 M3.0* $31.48\pm0.46$ <17.0 $615\pm11$ Y Y Y Y Y  
S65 SWW25 5 38 41.60 -2 30 28.9 14.39 1.45 1 12.84 0.21 M3.5 $31.01\pm0.51$ <17.0 $588\pm14$ Y Y Y Y N  
S66 K1.01-114 5 39 36.06 -2 36 31.0 14.43 0.76 3 13.07 0.22 K7.0 $48.55\pm0.63$   $56\pm23$ N N N N N  
S67 p053841-0236 5 38 41.36 -2 36 44.5 14.49 1.46 3 12.99 0.22 M3.5 $31.92\pm0.51$ <17.0 $577\pm14$ Y Y Y Y Y  
S68 SWW86 5 38 40.54 -2 33 27.6 14.54 1.65 1 12.80 0.27 M4.0 $31.79\pm0.73$ <17.0 $522\pm11$ Y Y Y Y N  
S69 SWW31 5 38 39.03 -2 45 32.2 14.58 1.34 1 12.91 0.30 M2.5 $30.67\pm0.56$ <17.0 $551\pm10$ Y Y Y Y N  
S70 K1.02-91 5 38 56.23 -2 31 15.4 14.58 0.76 3 13.42 0.25 K7.0 $69.74\pm0.63$   $37\pm9$ N N N N N  
S71 SWW29 5 38 47.19 -2 34 36.8 14.64 1.45 1 12.56 0.48 M3.5 $31.87\pm1.15$ <17.0 $306\pm9$ Y Y Y Y N  
S72 J053834.5-024109 5 38 34.60 -2 41 08.8 14.72 1.46 1 13.10 0.33 M3.5 $30.88\pm0.59$ <17.0 $547\pm3$ Y Y Y Y N  
S73 SWW15 5 38 43.87 -2 37 06.8 14.80 1.79 1 12.84 0.37 M4.5 $31.23\pm0.69$ <17.0 $453\pm7$ Y Y Y Y N  
S74 SWW227 5 38 59.23 -2 33 51.4 14.83 1.26 1 12.89 0.58 M2.0 $31.58\pm0.70$ <17.0 $395\pm33$ Y Y Y Y Y  
S75 J053914.5-022834 5 39 14.47 -2 28 33.3 14.85 1.52 1 13.34 0.31 M3.5* $29.19\pm0.53$ <17.0 $61\pm6$ Y N Y Y Y  
S76 K1.02-4 5 39 15.83 -2 36 50.7 14.86 1.50 3 13.25 0.32 M3.5 $31.27\pm0.60$ <17.0 $579\pm14$ Y Y Y Y Y  
S77 SWW230 5 38 42.86 -2 38 52.5 14.92 1.11 1 13.68 0.27 M1.0 $41.98\pm0.50$   $70\pm6$ N N N N N  
S78 SWW129 5 39 08.78 -2 31 11.5 14.97 1.63 1 13.04 0.45 M4.0 $31.91\pm0.64$ <17.0 $470\pm13$ Y Y Y Y N  
S79 K1.02-19 5 38 51.74 -2 36 03.3 14.97 1.87 3 12.91 0.26 M5.0 $30.81\pm0.76$ <17.0 $524\pm10$ Y Y Y Y Y  
S80 K3.01-167 5 38 49.70 -2 34 52.6 15.03 1.81 3 12.98 0.25 M4.5 $31.15\pm0.80$ <17.0 $483\pm4$ Y Y Y Y N  
S81 K8 5 38 50.78 -2 36 26.8 15.06 2.00 3 13.11 0.24 M5.0 $31.09\pm1.51$ $\rm 24.5^{+6.9}_{-2.1}$ $442\pm37$ Y Y Y Y N  
S82 K12 5 39 13.48 -2 23 51.9 15.18 1.41 3 13.95 0.24 M3.0 $40.63\pm0.63$   $135\pm57$ N N N N -  
S83 B3.01-67 5 38 46.85 -2 36 43.5 15.28 1.88 3 13.22 0.33 M5.0 $30.22\pm1.39$ $\rm 18.8^{+2.7}_{-1.4}$ $502\pm3$ Y Y Y Y N  
S84 SWW222 5 39 30.56 -2 38 27.0 15.30 1.32 3 13.81 0.22 M2.5 $23.43 \pm 0.69$   N N N Y N Y SB2
S85 K1.02-156 5 38 51.01 -2 27 45.7 15.51 1.00 3 14.28 0.23 M1.0 $72.34 \pm 0.88$   N N N N N Y SB2
S86 K3.01-263 5 38 28.25 -2 32 27.4 15.62 0.53 3 14.86 0.15 K3.5 $113.37\pm1.07$   $43\pm13$ N N N N Y  
S87 K4.03-422 5 38 45.28 -2 37 29.3 15.67 1.79 3 13.37 0.51 M4.5 $30.19\pm0.91$ <17.0 $402\pm3$ Y Y Y Y N  
S88 K3.01-226 5 38 35.29 -2 33 13.1 15.96 1.62 3 13.91 0.32 M4.0 $31.03\pm0.98$   $582\pm7$ Y Y Y Y N  
S89 r053808-0235b 5 38 08.66 -2 35 41.4 15.99 0.47 3 15.23 0.14 K2.0 $16.54 \pm 2.02$   N N N N N N SB2
S90 p053840-0232 5 38 40.89 -2 32 59.8 16.00 0.50 3 15.36 0.14 K3.0 $62.12\pm1.50$   $64\pm6$ N N N N N  
S91 p053902-0222 5 39 02.94 -2 22 41.8 16.02 1.36 3 14.79 0.17 M3.0 ?   $139\pm8$ ? N N N N SB
S92 J053826.8-022846 5 38 26.84 -2 38 46.0 16.12 1.91 3 14.11 0.28 M5.0 $30.66\pm0.94$ <17.0 $494\pm9$ Y Y Y Y N  
S93 K1.02-18 5 38 42.39 -2 36 04.4 16.26 1.49 3 14.26 0.38 M3.5 $29.66\pm1.26$ <17.0 $272\pm20$ Y Y Y Y N  
S94 K4.03-1807 5 38 41.46 -2 35 52.3 16.32 2.25 3 14.00 0.37 M6.0 $30.40\pm1.48$ <17.0 $322\pm27$ Y Y Y Y N  
S95 2MJ05391483-0244415 5 39 14.83 -2 44 41.6 - - - 12.34 0.19 - $61.23\pm0.59$   $32\pm3$ N N N N N  
S96 K3.01-325 5 38 32.68 -2 31 15.6 - - - 12.55 0.08 - - $34.79 \pm 1.19$   $9 \pm 4$ N N N N Y SB1
S97 2MJ05391003-0242425 5 39 10.04 -2 42 42.5 - - - 12.97 0.24 - $78.96\pm0.68$   $70\pm6$ N N N N N  
S98 2MJ05390458-0241493 5 39 04.59 -2 41 49.4 - - - 13.96 0.69 - $31.61\pm0.73$ <17.0 $443\pm57$ Y Y Y Y N  
a Star names are from the following sources: 4771-..., r05..., p05... = Wolk (1996); SE = Scholz & Eislöffel (2004); SWW = Sherry et al. (2004); J05... = Béjar et al. (2004); Zapatero Osorio et al. (2002): note that we have dropped the S Ori prefix in front of the J05... names; K = Kenyon et al. (2005); B = Burningham et al. (2005); 2M = 2MASS catalogue; b coordinates and infrared photometry are from the 2MASS catalogue; c optical photometric data are taken from the following sources: (1) Sherry et al. (2004), (2) Wolk (1996), (3) Kenyon et al. (2005); d spectral types marked with asterisk have been derived spectroscopically by Zapatero Osorio et al. (2002). The other spectral types have been derived from photometry (see Sect. 2.1); e for double-lined spectroscopic binaries, we only indicate whether the line is identified (Y) or not (N) f: Y = detected, N = undetected, - = outside the XMM field of view.


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