**Table 1:** Results of the quantitative spectral analysis of the ESO SPY sdO stars sorted by increasing helium abundance ( $\log\left(y\right)$ ). "Outliers'', i.e. values with relative errors between two or more exposures above the 2- $\sigma$ level of the global relative error, are flagged by an asterisk.
Object	ICRS 2000.0	B	M_V	$T_{\rm eff}$	$\log\left(g\right)$	$\log\left(y\right)$	$\log~(L)$	CN	Rem.
		mag	mag	[K]	$[{\rm cm\ s^{-2}}]$		$[{L_{\odot}}]$	class
helium deficient:
HE 1059-2735	11:01:24.95 -27:51:42.9	15.21^a	3.11	40966	5.38	-3.62	2.16	0	2
HE 1130-0620	11:32:41.60 -06:36:54.4	15.76^a	4.05	48122	5.84	-3.07	1.98	0	1
HE 1237-1408	12:39:56.64 -14:24:48.4	15.97^a	3.02	39683	5.33	-2.99	2.15	0	1, 2, 5, 8
HE 1318-2111	13:21:15.66 -21:27:18.5	14.48^a	3.31	36254 $^{\ast}$	5.42	-2.91	1.92	0	2, 5
HE 1115-0631	11:18:11.69 -06:47:33.2	14.77^a	4.17	40443	5.80	-2.59	1.72	0	1
PG 0026+136	00:28:52.33 +13:54:45.8	15.74 $^{\rm 1}$	3.17	38830	5.38	-2.39	2.07	0	1
EC 09445-0905	09:47:03.39 -09:19:50.5	15.69^a	4.59	73862	6.22	-2.08	2.28	0	2, 4
HE 1423-0119	14:25:51.29 -01:33:17.4	16.56^a	3.12	52662	5.50	-1.61	2.48	0	1
HE 1513-0432	15:16:19.17 -04:43:58.0	16.04^a	4.41	42699	5.92	-1.36 $^{\ast}$	1.69	0	1, 7
HE 0040-4838	00:42:31.08 -48:22:16.2	16.07	3.79	41823	5.67	-1.35	1.91	0
HE 1047-0637	10:50:28.79 -06:53:25.9	14.42^a	1.49	60650	5.03	-1.34	3.39	0	1, 5
HE 1356-1613	13:59:12.52 -16:28:01.8	16.18	4.11	55925 $^{\ast}$	5.93	-1.30	2.15	0	5
HE 1106-0942	11:09:08.22 -09:58:48.6	16.34	4.92	79742 $^{\ast}$	6.40	-1.03	2.27	0	1
helium enriched:
HE 1238-1745	12:41:01.16 -18:01:59.0	14.31^a	3.83	38219	5.64	-0.55	1.78	N	2, 5
HE 1258+0113	13:00:59.23 +00:57:11.7	16.23^b	3.80	39359	5.64	-0.53	1.83	N	1, 5, 7
HE 2218-2026	22:21:13.02 -20:11:17.6	16.28	4.40	38330	5.87	-0.35	1.56	C&N
HE 1135-1134	11:38:10.66 -11:51:03.8	15.45	3.88	40079	5.68	-0.26	1.82	N	1
HE 1136-2504	11:39:10.21 -25:20:55.5	13.83^a	4.25	41381	5.84	-0.16	1.72	N	2, 5
HE 1310-2733	13:12:50.65 -27:49:03.1	14.38	3.76	40000	5.63	-0.15	1.87	N	2, 5
HE 2359-2844	00:01:38.48 -28:27:42.8	15.7	3.85	38325	5.65	-0.15	1.77	C&N	3
PG 2204+070	22:07:16.20 +07:18:36.0	15.74 $^{\rm 4}$	3.72	40606	5.62	0.07	1.90	N	1, 4, 8
HE 1256-2738	12:59:01.48 -27:54:19.3	16.29^a	4.04	40029	5.68	0.09	1.82	C&N	2, 5
HE 2203-2210	22:06:29.38 -21:56:00.0	15.04	4.95	47343	6.20	0.45	1.59	C&N
HE 1142-2311	11:44:50.15 -23:28:18.0	15.37^a	3.86	54718	5.80	0.68	2.21	C^d	2, 5, 6
HE 0111-1526	01:13:38.24 -15:11:02.6	14.59^a	3.86	39152	6.31	0.83	1.16	C&N	3, 8
HE 1251+0159	12:54:08.35 +01:43:24.0	15.24^a	4.47	48208	5.98	1.03	1.80	C	1
HE 1511-1103	15:14:17.04 -11:14:13.6	14.78^a	3.88	42298	5.68	1.10	1.91	C&N	1, 5
HE 1430-0815	14:33:36.93 -08:28:24.8	15.69^a	2.32	61011	5.26	1.17	2.97	C	1, 2, 7, 8
HE 1203-1048	12:05:56.59 -11:05:29.4	15.69	3.98	45439	5.91 $^{\ast}$	1.36 $^{\ast}$	1.91	C	1
HE 1446-1058	14:49:24.49 -11:11:19.0	15.00^a	3.91	45000	5.76	1.37	1.94	C&N	2
HE 0342-1702	03:44:58.82 -16:52:42.2	14.75	4.18	41914	5.78	1.40	1.79	N
HE 0952+0227	09:55:34.57 +02:12:47.9	14.72	3.84	46524 $^{\ast}$	5.75	1.41	2.00	C^d	1, 5
HE 2347-4130	23:50:19.70 -41:14:01.1	15.16	4.07	44875	5.83	1.44	1.88	C
HE 0414-5429	04:15:30.23 -54:21:58.7	14.60	3.86	44678	5.76	1.57 $^{\ast}$	1.96	C^d
HE 0914-0314	09:17:15.62 -03:53:57.3	14.93	3.97	45136	5.79	1.65	1.94	C^d	1
BPS CS 22955-0024	20:23:50.26 -25:08:28.8	15.50^c	4.04	44622	5.80	1.72	1.89	C&N	4
HE 0155-3710	01:58:01.44 -36:56:21.9	15.08	4.24	41405	5.77	1.76	1.76	N	3, 7
HE 1136-1641	11:38:54.62 -16:58:13.4	14.82^a	4.03	44646	5.80	1.81	1.88	C	2
HE 0958-1151	10:00:42.64 -12:06:00.0	13.81^a	3.29	44125	5.51 $^{\ast}$	1.85	2.18	C^d	1, 2, 4, 5
HE 0016-3212	00:18:53.22 -31:56:01.7	14.27	3.73	41674	5.70 $^{\ast}$	2.14	1.97	C&N	3, 6
HE 0031-5607	00:34:07.75 -55:51:05.9	15.45	5.37	41423	6.25	2.26 $^{\ast}$	1.31	N	8
HE 1316-1834	13:19:16.93 -18:49:52.0	16.24	3.55	42811	5.56	2.32	2.05	N	2, 8
PG 2258+155	23:00:57.75 +15:48:39.8	15.14^c	4.77	42084	6.08 $^{\ast}$	2.84 $^{\ast}$	1.56	N	1, 4
PG 1632+222	16:34:16.09 +22:11:40.9	15.13^b	4.77	39384	6.16	2.84	1.31	C	1, 4, 8
HE 0001-2443	00:04:31.01 -24:26:21.1	13.66	4.62	40975	5.94	2.97	1.60	N	3
HZ 1	04:50:13.52 +17:42:06.2	12.60^a	3.95	41344	5.68	3.00	1.87	N	3, 4

1: Also in PG survey (Green et al. 1986). 2: Also in EC survey (Stobie et al. 1987). 3: Also in MCT survey (Demers et al. 1987). 4: McCook & Sion (1999), misclassified as white dwarf. 5: Christlieb et al. (2001). 6: Possibly cool companion indicated by B-J, J-K colours. 7: Possibly cool companion indicated by B-J colour. 8: Only one spectrum available
^a From subdwarf data base (Østensen 2006). ^b From SDSS g' and r' using the calibration of Smith et al. (2002). ^c Photographic magnitude (SIMBAD). ^d Weak N lines also present.

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