\item HD 36980 AB is a close binary with $\rho \approx 0.7$ arcsec, $\theta \approx 61$ deg (catalogue of Components of Double and Multiple stars; Dommanget & Nys 1994 - there are no fundamental differences between this edition and the second one (Dommanget & Nys 2002), except for the number of considered sources). \item RX J0535.6-0152 AB is a T Tauri star with a red $V_{\rm T}-K_{\rm s}$ colour. It is a G6V-type spectroscopic binary with lithium in absorption (pEW(Li I) = +0.32 Å), partially filled H$\alpha$ line (pEW(H$\alpha$) = +2.40 Å) and X-ray in emission (Alcalá et al. 1996, 2000). RX J0535.6-0152 AB was the third strongest X-ray source in the investigation of 40 weak-line T Tauri stars in Orion by Marilli et al. (2007), with $\log{L_{\rm X}} = 30.7^{+0.2}_-0.7$ ($erg/cm^{2}/s$). These authors found it to be a photometric variable with a period of 1.74 d. \item HD 37285 AB is a visual binary star with $\rho \approx 0.4$ arcsec, $\theta \approx 263$ deg (Dommanget & Nys 1994). \item HD 37389 is embedded in the Ori I-2 Cometary Globule (Ho et al. 1978; Cernicharo et al. 1992; Mader et al. 1999). Oudmaijer et al. (1992) and Coulson et al. (1998) have reported infrared and submillimetre flux excesses due to a Vega-like disc. The star has appreciable polarization in the optical (Bhatt & Manoj 2000). Some catalogues tabulate a hypothetical companion, BD-01 985B, at $\rho \sim 5.0$ arcsec, $\theta \sim 350$ deg. \item HD 37149 is a helium-weak star (Bernacca & Ciatti 1972; Renson 1988) with H$\alpha$ in medium emission (Bidelman 1965). It is likely the UV-emission source [SC93b] 328 (Schmidt & Carruthers 1993). \item HD 290770 was discovered as an emission-line star by Bidelman (1965) and has been classified as a B8-9Ve Herbig Ae/Be star by many other authors (Guetter 1976; Gieseking 1983; Dong & Hu 1991; Nesterov et al. 1995; Thé et al. 1994). Vieria et al. (2003) found [O I]+[S II] in emission and measured the H$\alpha$ line in double-peak emission, with the secondary peak having more than half the strength of the primary. Yudin & Evans (1998) found negligible polarization in the optical. Previously unnoticed, HD 290770 has one of the most apparent flux excesses at the IRAS passbands in the Ori OB 1 b association (Caballero & Solano, in prep.). Here we report a close visual companion to the star at $\rho \sim 6.8$ arcsec, $\theta \sim 340$ deg, and $\Delta K_{\rm s} = 4.46 \pm 0.03$ mag fainter. From its I-J and $J-K_{\rm s}$ colours from DENIS and 2MASS, it seems to be a F-G:-type star in the fore-/background. \item HD 37344 is embedded in the bright-rimmed cloud complex Ori I-2N, close to cloud [OS98] 40C (Ogura & Sugitani 1998). \item HD 290602 is also BD-01 947. \item HD 290674 is also BD-01 977. \item HD 37321 AB is a well-known helium-weak star with a high rotational velocity ( $v \sin{i} \approx 100$ km/s; Mermilliod 1983) and spectrum variability (Molnar 1972; Garrison 1994 - but see Pedersen & Thomsen 1977). Blaauw & van Albada (1963) proposed that the star is a long-period spectroscopic binary; Morrell & Levato (1991) measured, however, a constant radial velocity of $24 \pm 6$ km/s during their monitoring. It is a close binary with $\rho = 0.756\pm 0.002$ arcsec, $\theta =14 \pm 1$ deg ( $\Delta H_{\rm p} = 1.62\pm0.01$ mag; Perryman et al. 1987). It was only resolved by Tycho-2. We accounted for the $B_{\rm T} V_{\rm T}$ magnitude of the A component and the near infrared $K_{\rm s}$ magnitude of both A and B components as a single object. The system could have a faint, red, third component ( $H = 10.98\pm0.02$ mag), at $\rho \approx 17.7$ arcsec, $\theta \approx 32$ deg. HD 37321 AB may also be the far-ultraviolet emission source [SC93b] 341 (Schmidt & Carruthers 1993). \item HD 36955 is a peculiar magnetic star with abnormal abundances of Si, Cr, and Eu (Gray & Corbally 1993; Kudryavtsev et al. 2006). \item V1247 Ori is a Herbig He/Be star (García-Lario et al. 1997; Fujii et al. 2002) whose non-banded H$\alpha$ emission was found by McConell (1982). Spectral types from A5III, through A7, to F0V have been provided (Schild & Cowley 1971; Nesterov et al. 1995; Vieira et al. 2003). Vieira et al. (2003) found no forbidden lines in its optical spectrum, but identified an H$\alpha$ symmetric profile without, or with only very shallow, absorption features. No H2O, NH3 or CO radio lines were found by Wouterloot et al. (1986; 1988; 1989). V1247 Ori is, besides, a well-studied $\delta$ Scuti star, with P =0.096967 d and peak-to-peak amplitude in the V band of 0.050 mag (Lampens & Rufener 1990; García et al. 1995; Handler 1999). Its SED shows clear excesses from the J band to 60-100 $\mu$ (Caballero & Solano, in prep.), and is composed of two components, one warm (1.2-2.2 $\mu$m) and the other cool (12-100 $\mu$m). \item Alnilam ($\epsilon$ Ori, 46 Ori, HD 37128; V = 1.70 mag) is one of the brightest supergiants in the sky and, therefore, one of the best known stars. The first spectroscopic study was carried out more than a century ago by Campbell (1894) and Keeler (1894). It is a hot, massive, single star in the hydrogen shell-burning phase (Lamers 1974; Jarad et al. 1989) with photometric and spectroscopic variability (Stebbins 1915; Ebbets 1982; Prinja et al. 2004), H$\alpha$, X-ray and radio emission (Cherrington 1937; Abbott et al. 1980; Berghöfer et al. 1996; Blomme et al. 2002), and strong stellar wind and mass loss (Groenewegen & Lamers 1989; Prinja et al. 2001; Crowther et al. 2006). Alnilam is one of the few early-type stars with determination of the angular diameter using optical interferometry (Hanbury Brown et al. 1974). It illuminates the NGC 1990 reflection nebula. Last, it has been used as a bright spectrophotometric standard (B0Ia in the MK classification by Johnson & Morgan 1953), to investigate the interstellar extinction (e.g. Whitford 1958; Bohlin et al. 1978), and to compare with other early-type supergiants (Humphrey 1978). A review of ``classic'' works on Alnilam can be found in Lamers (1972). The status of ``Alnilam B'' (BD-01 969B; see Table A.11), at 3 arcmin to the northeast, is unknown. \item HD 37397 is a low-amplitude variable star ( P = 0.572885 d, A(V) = 0.00089 mag; Koen & Eyer 2002) with a constant radial velocity of 22-23 km/s (Morrell & Levato 1991; Duflot et al. 1995; Grenier et al. 1999). \item VV Ori AB is a double-lined eclipsing binary in a detached configuration (Miller Barr 1904; Adams 1912; Daniel 1916; Struve & Luyten 1949). The two early-type stars, B1.0V+B4.5V, are separated by $13.49 \pm 0.05~R_\odot$ ( $P \approx 1.48$ d; Terrell et al. 2007). The mid-infrared source IRAS 05309-0111 is located at $\rho \sim 16$ arcsec, $\theta \sim 180$ deg, to VV Ori. Friedemann et al. (1996) had been the only investigators before us to notice the IRAS thermal emission of VV Ori, and attributed it to circumstellar dust. This is very important, because: (i) stars with very early spectral types, just as the primary in VV Ori, are not expected to have circumstellar discs at the age of the Ori OB 1 b association, and (ii) the disc would surround the binary system (i.e. the inner part of the disc would be at several - tens - astronomical units, while the binary components are separated by $\sim$0.64 AU). VV Ori may also be associated to the X-ray sources [NYS99] A-01 and 1AXG J053331-0110 (Nakano et al. 1999; Ueda et al. 2001). \item HD 36684 AB is a close binary with $\rho \approx 0.2$ arcsec, $\theta \approx 200$ deg (Dommanget & Nys 1994). It also has a high rotational velocity ( $v \sin{i} \approx 160$ km/s; Sharpless 1974). \item HD 290750 is a low-amplitude suspected variable (Rufener & Bartholdi 1982). \item HD 36779 AC forms, together with the post-T Tauri star HD 36779 B, a likely Lindroos system (Lindroos 1985). HD 36779 AC is, in its turn, a spectroscopic binary (Morrell & Levato 1991). \item HD 37187 might form a new (very wide) Lindroos system, together with V583 Ori ( $\rho \approx 29.0$ arcsec, $\theta \approx 212$ deg). \item HD 37076 and HD 290671 form the STF 751 double system, with $\rho \approx 15.6$ arcsec, $\theta \approx 124$ deg (Dommanget & Nys 1994). They share Tycho-2 proper motion within the uncertainties. The X-ray emission found by ROSAT (with HRI and PSPC) is associated to the faintest component (HD 290671, B9.5V; Caballero et al. in prep.). \item HD 290665 is an SiCrEuSr chemically peculiar star (Bartaya 1974; Schild & Cowley 1971; Guetter 1976; Joncas & Borra 1981; Gieseking 1983). It is also a strong magnetic star ( $\langle B_z \rangle \approx -0.17$ T; Bagnulo et al. 2006). Last, HD 290665 has a radial velocity discordant with association membership (Gieseking 1983). It could be, however, a spectroscopic binary. \item V1379 Ori is a slowly pulsating B star (Waelkens et al. 1998). \item HD 290662, a peculiar Vega-like star, was proposed as a spectroscopic binary by Gieseking (1983) based on low quality data. \item HD 36954 AB is a spectroscopic binary (SB1) with a period $P \sim 4.6$ d (Neubauer 1936; Morrell & Levato 1991). \item HD 37235 is a spectroscopic variable B7-A0:V according to Bernacca & Ciatti (1972). Renson (1992) tabulates it as an He-weak star. The origin of the mid-infrared source IRAS 05344-0044, located at a separation $\rho \sim 35$ arcsec to the south of the star, probably lies on the extended source 2MASX J05365804-0042413, whose spectral energy distribution resembles those of starburst galaxies with large dust content (see, e.g., Chary & Elbaz 2001) \item HD 290648, HD 290660 and HD 290650 are also BD-00 1004, BD-00 1020 and BD-00 1012, respectively. \item HD 290515 is at a projected angular separation of 34 arcsec to the background RR Lyr star [VZA2004] 28 (Vivas et al. 2004). \item HD 290492 AB is a close binary with $\rho = 0.739 \pm 0.005$ arcsec, $\theta = 63.9\pm 1.9$ deg ( $\Delta b= 0.6\pm0.2$ mag - Rossiter 1955; Marchetti et al. 2001). It is a non-variable, mild $\lambda$ Boo star candidate (Paunzen & Gray 1997; Paunzen et al. 2002 - but see Gerbaldi et al. 2003 and Faraggiana et al. 2004). Paunzen (2001) derived a photometric distance of $d = 279\pm20$ pc, but he erroneously assumed no contamination by the secondary in the spectrum of the primary. HD 290492 AB and the G8III star GSC 04766-02124, which is $\sim$3 mag fainter in the V band and at $\sim$24 arcsec to the west, do not share a common proper motion, as has been proposed in the literature. \item SS 28 is a T Tauri star. It has been only investigated by Stephenson & Sanduleak (1977), Bopp (1988), Wiramihardja et al. (1989) and Kogure et al. (1989). It has a double-peaked H$\alpha$ emission line with intensity about three times that of the continuum, H$\beta$ also in emission and an apparently ``filled in'' Ca II H and K. According to Bopp (1988), SS 28 resembles some unusual interacting F+B binary systems. It is, besides, an Einstein Observatory soft X-ray source. The ROSAT Satellite afterwards measured 18 events associated to SS 28 (ROSAT 1955; White et al. 2000). SIMBAD tabulates a quadruple identification (it is also Kiso A-0904 6, Kiso A-0903 234 and 2E 1299). \item BD-00 984 is a chemically peculiar star based on their abnormal abundances of Hg, Mn (Woolf & Lambert 1999 - they classified it as one of the youngest HgMn stars) and Si (Brown & Shore 1986). It forms a curious perfect alignement with two nearby radio sources: [LPZ94] 147 ( $\rho \approx 31.5$ arcsec, $\theta \approx 177.0$ deg - $S_\nu$(3.9 GHz) = $48\pm 24$ mJy, Larionov et al. 1994) and TXS 0529-004 ( $\rho \approx$ 1.8 arcmin, $\theta \approx 178$ deg - $S_\nu$(1.4 GHz) = $82.2 \pm 2.5$ mJy, Condon et al. 1998; $S_\nu$ (0.365 GHz) = $214 \pm 24$ mJy, Douglas et al. 1996). The spectral index of TXS 0529-004 is -0.9, consistent within the uncertainties with thermal Bremsstrahlung emission. \item HD 290500 was classified as a Herbig Ae/Be star by Vieira et al. (2003). They derived A2 spectral type and detected H$\alpha$ in double-peaked emission, with the secondary peak having less than half the strength of the primary. No forbidden lines were identified. Codella et al. (1995) gave an upper limit for the 22.2 GHz H2O maser emission of the star. HD 290500 has a mid-infrared flux excess, as measured by IRAS (Caballero & Solano, in prep.). \item HD 36841 has been widely used for determining ultraviolet interstellar extinction curves (e.g. Savage et al. 1985; Barbaro et al. 2001). It was formerly considered a late-O-type star (Mannino & Humblet 1955; Goy 1973; Cruz-González et al. 1974). \item V1093 Ori AB (HD 36313) is a variable of $\alpha^2$ CVn type (North 1984; Catalano & Renson 1998), a helium-weak, silicon, magnetic peculiar (Guetter 1976; Borra 1981; Bychkov et al. 2005), and a close binary star ( $\rho \approx$ 0.22 arcsec, $\theta \approx 172.6$ deg - Couteau 1962; van Biesbroeck 1974). \item Mintaka AE-D ($\delta$ Ori, 34 Ori, HD 36486; V = 2.23 mag) is the most famous star in the Orion belt. It is a very bright triple within a hierarchical quintuple system. Mintaka D ($\delta$ Ori Ab) is an early-B-type star at $\rho$ = 0.267 arcsec, $\theta = 140$ deg ( $\Delta H_P = 1.35\pm0.02$ mag), from the tight AE binary (Heintz 1980; McCalister & Hendry 1982; Perryman et al. 1997), it may be a rapid rotator or a spectroscopic binary (Harvin et al. 2002). Mintaka A (O9.5II, $\delta$ Ori Aa1) and E (B0.5III, $\delta$ Ori Aa2) form an eclipsing spectroscopic binary with a peak-to-peak amplitude A(HP) = 0.01 mag and a period P = 5.7325 d (Hartmann 1904; Jordan 1914; Pismis et al. 1950; Koch & Hrivnak 1981; Harvey et al. 1987; Harvin et al. 2002; Kholtygin et al. 2006). The binary has suffered from an intense mass loss. The other two components, Mintaka B and C, are described below. \item Mintaka C ($\delta$ Ori C, HD 36485) is at $\rho \approx$ 52.2 arcsec, $\theta \approx 0.1$ deg to Mintaka AE ( $\Delta V_{\rm T} = 4.417\pm 0.012$ mag; Høg et al. 2000). It is a helium-strong star (Morgan et al. 1978; Walborn 1983; Bohlender 1989) with nonthermal radio emission (Drake et al. 1987). \item HD 290491 is also TYC 4766 2264 1. \item HD 36726 A is a $\lambda$ Boo star (Abt & Levato 1977; Paunzen 2001) and has quite high rotational velocity, $v \sin{i}$ (about 120 km/s; Abt 1979). It is the brightest component of a triple system tabulated by Aitken & Doolittle (1932). The secondary is BD-00 993B (Table A.11). The system could be quadruple, since there is an additional 2MASS source at $\rho \approx 5.7$ arcsec, $\theta \approx 3$ deg to HD 36726 A with $J = 15.109 \pm 0.137$ mag. \item HD 290572 is a B8V and a K0V (sic) according to Cannon & Pickering (1924) and Nesterov et al. (1995), respectively. An intermediate A spectral type matches the $B_{\rm T}-K_{\rm s}$ colour better. \item HD 290569 is an A0V according to Nesterov et al. (1995); however, the relatively red colour $B_{\rm T}-K_{\rm s} = 1.29\pm0.12$ mag matches a later spectral type better (i.e. intermediate A). \item HD 37038 AB is a binary whose components are separated by $\rho \approx 0.6$ arcsec, $\theta \approx 265$ deg. The secondary is 2 mag fainter than the primary (Dommanget & Nys 1994). It could actually be a hierarchical triple, since Nordström et al. (1997) found the F-type dwarf to be a double-lined spectroscopic binary with evident radial-velocity variations in scales of a few days (the resolved binary cannot be responsible for such variations). \item HD 36863 has a radial velocity that deviates more than 25 km/s from the average radial velocity of the association (Gieseking 1983). It satisfies, however, the photometric and proper motion criteria of very young stars in Orion. HD 36863 might be a very young single-line spectroscopic binary (SB1). Guetter (1976) classified it as an A7-type star. \item [NYS99] A-06 is an X-ray source identified by ASCA and ROSAT (1AXG J053448-0131, 1RXS J053450.5-013120). We estimate F: spectral type from its $V_{\rm T}-K_{\rm s}$ colour. \item HD 290673 is also BD-01 975. \item TYC 4767 1130 1 seems to be a close ( $\rho \sim 3$ arcsec) binary from the 2MASS data. \item HD 37172 is a probable non-member of the association according to Guetter (1976), although other authors consider it to be a real member (Warren & Hesser 1977, 1978; Hesser et al. 1977; Gieseking 1983; de Geus & van de Grift 1990). It has a peculiar Mn I $\lambda$4030-4035 Å blend (Gray & Corbally 1993) and falls slightly to the red of the association sequence in the $V_{\rm T}-K_{\rm s}$ vs. $V_{\rm T}$ diagram (Fig. 3). It is at $\rho \approx$ 5.0 arcmin, $\theta \approx 115$ deg, to Alnilam. \item TYC 4766 2371 1 is the third closest bright star to Alnilam ( $\rho \approx$ 6.0 arcmin, $\theta \approx 250$ deg). \item TYC 4766 2150 1 (CCDM J05375-0103B) has been repeatedly proposed to form a binary system together with HD 290749 ( $\rho \approx 29.0$ arcsec, $\theta \approx 344$ deg - Burnham 1906; Dommanget & Nys 1994). However, they do not share a common proper motion. \item TYC 4766 542 1 might be the X-ray source 1RXS J053447.9-010224 (1AXG J053446-0102; Ueda et al. 2001). The nearby binary 2MASS J05344642-0102340 ( $\rho \approx 4.0$ arcsec, $\theta \approx 220$ deg, $\Delta H = 1.89 \pm 0.05$ mag), at $\sim$35 arcsec to the west of TYC 4766 542 1 could also be the X-ray source. \item HD 290746 is a G0V according to Nesterov et al. (1995); however, the relatively blue colour $B_{\rm T}-K_{\rm s} = 1.38 \pm 0.09$ mag better matches with an earlier spectral type (i.e. late A or early F). \item HD 290585 has a debris disc according to MIPS/Spitzer observations at 24 $\mu$m by Hernández et al. (2006). It is a double binary resolved by 2MASS ( $\rho \approx 5.6$ arcsec, $\theta \approx 132$ deg, $\Delta H = 2.05 \pm 0.05$ mag); the secondary is not in the Tycho-2 catalogue. \item HD 290513 is an F0V dwarf according to Nesterov et al. (1995); a G-K spectral type matches the observed colours better. \item TYC 4766 790 1 has a visual companion at $\rho \approx 8.5$ arcsec, $\theta \approx 190$ deg ( $\Delta H = 0.69\pm0.04$ mag). \item HD 290583 A has a visual companion of roughly the same brightness. HD 290583 B, not identified by Tycho-2, is at $\rho \approx 7.44$ arcsec, $\theta \approx 3.8$ deg ( $\Delta H = 0.40 \pm 0.03$ mag). \item HD 290507 and HD 290504 are A5V dwarfs according to Nesterov et al. (1995); F-G spectral types match the observed colours better. \item TYC 4766 528 1 is the brightest component of a visual triple system. The other two components are located at $\rho \approx 3.4$ arcsec, $\theta \approx 165$ deg ( $\Delta H = 0.36\pm 0.07$ mag), and $\rho \approx$ 7.4 arcsec, $\theta \approx 195$ deg ( $\Delta H = 2.07 \pm 0.06$ mag). \item TYC 4766 1168 1 has a visual companion at $\rho \approx 9.4$ arcsec, $\theta \approx 10$ deg ( $\Delta H = 0.98\pm0.04$ mag). \item TYC 4766 2424 1 has a low proper motion of less than 5 mas/a and a blue colour $B_{\rm T}-K_{\rm s} = 0.63\pm0.09$ mag, typical of early A-type stars in the association. \item TYC 4753 49 1 is at $\rho \sim 46$ arcsec, $\theta \sim 288$ deg to the radio source [LPZ94] 146 (Larionov et al. 1994). \item IRAS 05354-0142 has the reddest $V_{\rm T}-K_{\rm s}$ colour among the $\sim$1500 Tycho-2/2MASS investigated stars in the survey area ( $V_{\rm T}-K_{\rm s} = 7.1\pm0.3$ mag). The closeness of IRAS 05354-0142 to the Ori I-2 globule may explain part of its reddening, but not all. It might be an S-type or a C-type giant with a very late spectral type and very low effective temperature. The absence of a mid-infrared excess (Kraemer et al. 2003) rules out the hypothesis of IRAS 05354-0142 being a protostar in the upper part of the Hayashi track of collapse associated to the Bok globule. \item HD 290680 has a $V_{\rm T}-K_{\rm s}$ colour that matches a K spectral type better. \item HD 290679 is also GSC 04766-01466. \item HD 36780 is a K5III giant as tabulated in SIMBAD. It has a (variable) radial velocity inconsistent with association membership ( $V_{\rm r} = +91$ km/s, Griffin 1972; $V_{\rm r} = +73.2$ km/s, Bois et al. 1988). The star has a Hipparcos distance of $260 \pm 50$ pc. \item HD 290675 has a discordant radial velocity (Gieseking 1983). It is also BD-01 967. \item HD 37491 is likely associated to the mid-infrared source IRAS 05363-0111. \item HD 290749 is a B8V star according to Nesterov et al. (1995). With proper motion of 13.8 mas/a and colour $V_{\rm T}-K_{\rm s} \sim$ 1.0 mag, it is likely a late A- or an early F-type star in the foreground. See also the note for TYC 4766 2150 1 (Table A.5). \item HD 36882 is at $d=220\pm50$ pc (Perryman et al. 1997). Because of a transcription error, SIMBAD tabulates HD 36882 as one of the early-type stars associated to the H II region Sh 2-264, close to $\lambda$ Ori, in Sharpless (1959); the actual early-type star is $\phi^01$ Ori (HD 36822, B0III). \item HD 290667 and StHA 46 were catalogued by Stephenson (1986) as H$\alpha$ emission stars. However, Downes & Keyes (1988) and Maheswar et al. (2003) failed to detect the (sporadic?) emission. StHA 46 is at 18 arcsec to the southwest of the early-A star AG-00 669. \item HD 290647 falls in the tiny overlapping region between the Alnilam and Mintaka fields. It is also BD-00 1001. \item TYC 4767 2257 1 has a colour $V_{\rm T}-K_{\rm s} > 4.5$ mag, typical of intermediate M stars. Its proper motion is, however, very low ( $\mu \lesssim 1$ mas/s). \item HD 290647 falls in the tiny overlapping region between Alnilam and Mintaka fields. It is also BD-00 1001. \item TYC 4766 516 1 has a very red colour of $V_{\rm T}-K_{\rm s} = 5.44 \pm 0.09$ mag and no IRAS excess. It could be a mid-M-type giant or subgiant in back-/foreground. \item HD 290576 is also BPM 71736. \item TYC 4766 2124 1 is also GSC 04766-02124. \item HD 290568 is also BD-00 987 and IRAS 05303-0009. \item HD 36117 is a nearby ( $d = 170\pm30$ pc; Perryman et al. 1997), peculiar, A-type star (Gray & Corbally 1993) with X-ray emission \item HD 36139 is a nearby ( $d = 124\pm13$ pc; Perryman et al. 1997), high rotation-velocity, radial-velocity variable (Morrell & Levato 1991), A-type star with no known companion. \item HD 36840 is at a Hipparcos distance of $d = 380 \pm 120$ pc, which is probably incorrect, given the spectral type of the star (G5V). \item HD 36558 has a discordant radial velocity of $V_{\rm r} = +42.1\pm4.8$ km/s (Nordström et al. 2004). \item HD 36443 (LHS 5107, G 99-16; Roman 1995) is a well-known, solar-like, high-velocity star at only $d = 38.2\pm1.9$ pc and with radial velocity $V_{\rm r} \approx -9.1$ km/s (Wilson 1953). \item HD 290486 AB is a visual binary star with $\rho \approx 1.7$ arcsec, $\theta \approx 304$ deg (Dommanget & Nys 1994). \item E Ori 2-1328 is a young M 4.5-type very low-mass star with lithium in absorption (pEW(Li I) = + $0.40 \pm 0.05$ Å) and Balmer lines in faint (chromospheric) emission (pEW(H $\alpha) = -8.2\pm0.5$ Å). The sodium line in the red optical is weak in comparison with field dwarfs of the same spectral type (pEW(Na I) = + $3.4 \pm 0.5$ Å; Béjar et al. 2003a). \item E Ori 2-1868 is a young M6.0-type very low-mass star with faint alkali lines (pEW(Na I) < 3 Å; Béjar et al. 2003b). The i-band magnitude has been taken from the SuperCOSMOS Science Archive (Hambly et al. 2001). \item E Ori 1-388 is a young M6.0-type very low-mass star with faint alkali lines (pEW(Na I) = + $3.9 \pm 0.5$ Å; Béjar et al. 2003a) and Balmer lines in faint (chromospheric) emission (pEW(H $\alpha) = -6.5\pm2.0$ Å). It is embedded in the [OS98] 40B remnant molecular cloud. \item E Ori 1-1644 is a young M5.0-type very low-mass star with Balmer lines in faint (chromospheric) emission (pEW(H $\alpha) = -7.6\pm1.0$ Å; Béjar et al. 2003a). \item E Ori 2-878 is a young M5.5-type very low-mass star with faint alkali lines (pEW(Na I) < 3 Å; Béjar et al. 2003b). \item E Ori 2-705 is a young M5.0-type very low-mass star with faint alkali lines (pEW(Na I) < 4 Å; Béjar et al. 2003b). The i-band magnitude is from SuperCOSMOS. \item E Ori 2-603 is a young M5.5-type very low-mass star with faint alkali lines (pEW(Na I) < 3 Å; Béjar et al. 2003b). \item Kiso A-0904 41 and Kiso A-0904 42 form a binary system with $\rho \approx 11.0$ arcsec, $\theta \approx 277$ deg. The i-band magnitudes are from SuperCOSMOS. They have been identified in XMM-Newton observations (Caballero et al., in prep). \item V469 Ori is proably associated to the [OS98] 29J, [OS98] 29H, and [OS98] 29K remnant molecular clouds. \item Kiso A-0904 76 is a K6-type variable ($\Delta V$ = 0.33 mag) star with pEW(H $\alpha) = -20.2$ Å and pEW(Li I) = +0.5 Å (Briceño et al. 2005). It has a visual companion at $\rho \approx 5.3$ arcsec, $\theta \approx 321$ deg ( $\Delta H = 2.91\pm 0.05$ mag). \item Haro 5-80 is a variable, emission-line star (Haro & Moreno 1953; Fedorovich 1960; Wiramihardja et al. 1989). It has a very nearby ( $\rho \sim 3$ arcsec, $\theta \sim 15$ deg) companion or a small jet (possibly associated to an unknown Herbig-Haro object) \item 2E 1398 is an X-ray source tabulated in at least six catalogues from Einstein, ROSAT and XMM-Newton data (Harris et al. 1994; McDowell 1994; Moran et al. 1996; Voges et al. 1999; ROSAT Consortium 2000; XMM-Newton Survey Science Centre Consortium 2007). It is located at 4.5 arcmin to the west of Alnilam. The i-band magnitude is from SuperCOSMOS. \item Kiso A-0904 37 has rather blue I-J and $J-K_{\rm s}$ colours. Besides, it has a faint, red, visual companion at $\rho \approx 5.6$ arcsec, $\theta \approx$ 144 deg, unresolved by Wiramihardja et al. (1989). It is likely that the actual emission-line star or brown dwarf (and the only truly young objects) is the visual companion (J2000 coordinates: 05 35 32.38 -01 12 08.2). \item StHA 47 is a mid-K-type T Tauri star according to Downes & Keyes (1988). It is the fourth strongest X-ray emitter at less than 20 arcmin to Alnilam, from XMM-Newton observations. \item CVSO 162 is an M1-type variable ( $\Delta V = 0.23$ mag) star with pEW(H $\alpha) = -3.9$ Å and pEW(Li I) = +0.5 Å (Briceño et al. 2005). \item Annizam 363062 is a visual binary with $\rho \approx 6.3$ arcsec, $\theta \approx 243$ deg ( $\Delta H = 2.41 \pm 0.06$ mag). Five X-ray events in the surrounding area were tabulated in the catalogue of ROSAT HRI Pointed Observations (ROSAT Team 2000). It might also be the Einstein source 2E B0534-0111. It is not known which component is the actual X-ray emitter. \item Haro 5-67 is a G:-type, photometrically variable, T Tauri star with strong Balmer emission detected by several H$\alpha$ objective-prism surveys (Haro & Moreno 1953; Sanduleak 1971; Stephenson 1986) and with IRAS flux excess (Weaver & Jones 1992). It has been spectroscopically followed up by Herbig & Kaneswara Rao (1972) and Downes & Keyes (1988). \item Kiso A-0904 50 has rather blue I-J and $J-K_{\rm s}$ colours. It might be a variable young star or an active object in the fore-/background. \item Kiso A-0904 61 could also be the H$\alpha$ emitter Haro 5-77 (suspected variable NSV 2465; Kukarkin et al. 1981). \item V583 Ori (Haro 5-74) is a variable, emission-line star (Haro & Moreno 1953; Fedorovich 1960; Wiramihardja et al. 1989). It is possibly the X-ray source 2E 1423 and might form a Lindroos system with the B9V star HD 37187 (Table A.3). \item HD 36779 B is a K5IV with Li I in absorption in a likely Lindroos system with the B-type star HD 36779 (Table A.3 - Lindroos 1985; Pallavicini et al. 1992; Martín et al. 1992), see, however, a brief discussion of the position in the H-R diagram and the radial velocity of HD 36779 B in Gerbaldi et al. (2001). \item 2E 1357 is a K3-type star with pEW(H $\alpha) = -2.75$ Å and pEW(Li I) = + $0.470\pm0.008$ Å (Alcalá et al. 1996, 2000). \item Kiso A-0904 28 is also the X-ray source 2E 1340 (McDowell 1994). The star was detected by Kraemer et al. (2003) at 8.3 $\mu$m, which suggests a possible flux excess in the mid-infrared. \item Kiso A-0904 30 was previously identified with a fainter, much bluer source 24 arcsec to the east. \item 2E 1449 is a K4-type star with pEW(H$\alpha$) = +0.35 Å and pEW(Li I) = + $0.410 \pm 0.010$ Å (Alcalá et al. 1996, 2000). \item Kiso A-0904 60 is a K6-type variable ( $\Delta V = 0.51$ mag) star with pEW(H $\alpha) = -61.9$ Å and pEW(Li I) = +0.3 Å (Briceño et al. 2005). It could be a tight binary ( $\rho \lesssim 1.0$ arcsec) based on the 2MASS photometry quality flags. \item Kiso A-0904 65 is a variable ( $\Delta V = 0.87$ mag) star with a very strong Balmer emission, pEW(H $\alpha) = -400$ Å, and lithium in absorption, pEW(Li I) = +0.3 Å (Briceño et al. 2005). \item CVSO 124 is an M3-type variable ( $\Delta V = 0.19$ mag) star with pEW(H$\alpha$) = -17.3 Å and pEW(Li I) = +0.4 Å (Briceño et al. 2005). It also falls in the Mintaka field. \item Kiso A-0904 34 is also [SE2005] 104. It does not show significant periodic variability. \item Kiso A-0904 33 has a faint, red, visual companion at $\rho \approx 4.9$ arcsec, $\theta \approx 14$ deg, with near-infrared magnitudes $J = 12.55\pm0.03$ mag and $K_{\rm s} = 11.55 \pm 0.03$ mag. \item PU Ori is a pre-main sequence star with H$\alpha$ in strong two-lobe emission (Haro & Moreno 1953; Herbig et al. 1972; Cohen & Kuhi 1979; Wiramihardja et al. 1989), photometric variability (Fedorovich 1960; Briceño et al. 2005), mid-infrared flux excess at the IRAS passbands (Weintraub 1990; Weaver & Jones 1992) and forbidden emission lines ([O I] $\lambda$ 6300.3 Å; Hirth et al. 1997). It has an extraordinarily red colour of $J-K_{\rm s} = 1.77 \pm 0.03$ mag. \item StHA 48 is a K4-type T Tauri star according to Maheswar et al. (2003). \item CVSO 124 is an M3-type variable ( $\Delta V = 0.19$ mag) star with pEW(H $\alpha) = -17.3$ Å and pEW(Li I) = +0.4 Å (Briceño et al. 2005). It also falls in the Alnilam field. \item Kiso A-0903 221 has a faint red visual companion at $\rho \approx$ 6.4 arcsec, $\theta \approx 49$ deg ( $\Delta H = 5.1 \pm 0.2$ mag). \item Kiso A-0904 4 is a K7-type variable ($\Delta V$ = 0.66 mag) star with pEW(H$\alpha$) = -34.2 Å and pEW(Li I) = +0.3 Å (Briceño et al. 2005). It is also Kiso A-0903 228. \item IRAS 05307-0038 (also known as YSO CB031YC1 and YSO-C CB031YC1-I) is a bright ( $K_{\rm s} = 8.63\pm 0.02$ mag) T Tauri star embedded in the IC 434 Bok globule/reflection nebula (Dreyer 1895; Hubble 1922; Cederblad 1946; Dorschner & Gürtler 1963; Magakian 2003). This star has an extended and fuzzy nebulosity in the J band and was classified as a Class II object because of a flux excess at 25 $\mu$m (Yun & Clemens 1994, 1995). Yun et al. (1997) measured H$\alpha$ and H$\beta$ in emission and Li I in absorption, and characterised its SED from the B band to the mid-infrared. Yun et al. (1996) discovered two nearby radio sources that could be associated to the star (there are other two additional radio sources in the surrounding area, found by Condon et al. 1998). Gómez et al. (2006), in a very sensitive survey using NASA 70 m antenna at Robledo de Chavela (Spain), failed to detect water maser emission from these sources. See Fig. A.1. \item Kiso A-0904 22 has a nearby visual companion identified as a photometric young star candidate, Mantaqah 2385113 (Table A.17). \item Kiso A-0904 13 is also Kiso A-0903 245. \item Mantaqah 487126 displayed 14 X-ray events during ROSAT observations (White et al. 2000 - 8 events -; ROSAT 2000 - 6 events -). \item 1AXG J053127-0021 appears in numerous X-ray catalogues from ROSAT and ASCA data. The i-band magnitude is from SuperCOSMOS. \item Mantaqah 148186 is an X-ray source in several catalogues (e.g. Voges et al. 1999). \item Mantaqah 400105 is an X-ray source in several catalogues (e.g. White et al. 2000). \item Mantaqah 320042 displayed 12 X-ray events during ROSAT observations (White et al. 2000 -5 events-; ROSAT 2000 -7 events-). \item Kiso A-0904 18 has a $J-K_{\rm s}$ colour redder than 2.0 mag. \item E Ori 2-1982 has no DENIS or SuperCOSMOS counterpart. The i-band magnitude (actually I) is from Béjar et al. (2003b). \item [OSP2002] OriI-2N 4 has a tiny (chromospheric?) Balmer emission (pEW(H$\alpha$) $\approx$-2.6 Å; Ogura et al. 2002). \item BD-01 969B (``Alnilam B'', $\epsilon$ Ori B; V = 10.5 mag) is located at $\rho \approx$ 179.0 arcsec, $\theta \approx58$ deg, to Alnilam (this value coincides with the original measurements by Burnham in 1879 - Burnham 1906). No spectral type has been tabulated or measured. \item AG-00 669 forms a visual double with the foreground solar-like star StHA 46 (Jeffers 1963). See Table A.7. \item BD-00 983B (``Mintaka B'', $\delta$ Ori B; V = 14.0 mag) is located at $\rho \approx$ 33.0 arcsec, $\theta \approx 229$ deg, to Mintaka AE-D (this value coincides with the original measurements by Burnham in 1878 - Burnham 1906). No spectral type has been tabulated or measured. The star shows no evidence of any significant X-ray emission in deep observations with the Chandra Space Telescope (Miller et al. 2002). \item BD-00 993B (``HD 36726 BC''; V = 13.7 mag) is located at $\rho \sim 19.8$ arcsec, $\theta \sim$ 213 deg ( $\Delta H = 1.30\pm 0.05$ mag) to the A0Vm-type star HD 36726 (Table A.4). BD-00 993B is, in its turn, a close binary with $\rho \sim 0.8$ arcsec, $\theta \sim 64$ deg (Dommanget & Nys 1994). \item X Ori is the reddest object in the studied area. It is an M8-9-type Mira Cet variable found by Wolf (1904) with $P = 424.15 \pm 1.77$ d (Templeton et al. 2005) and silicate dust emission (Sloan & Price 1998; Speck et al. 2000). Although X Ori is even brighter in the near- and mid-infrared than Alnilam and Mintaka ( $K_{\rm s} \sim$ 0.9 mag), its extremely red colours ( $V-K_{\rm s} >10$ mag) prevented its detection in the Tycho-2 catalogue. \item Ruber 1 has a proper motion of -$12 \pm 5$, -$49 \pm 2$ mas/s, measured by us using POSSI, UKST blue, red, and infrared, DENIS and 2MASS (the six epochs cover 47 years; see method details in Caballero 2007b). Ruber 1 probably is a late M dwarf in the foreground. \item G 99-18 is a high proper-motion star, with $\mu = 280$ mas/a. It falls in the tiny overlapping region between the Alnilam and Mintaka fields. \item Ruber 2 has very peculiar colours: the near-infrared colours are very red (e.g. $J-K_{\rm s} = 1.33 \pm 0.04$ mag), typical of early and intermediate L dwarfs, very late M giants or carbon stars. Its I-J colour is red enough, as well, to be selected as an association member candidate. The optical colours are, however, contradictory and variable. The SuperCOSMOS Science Archive tabulates photographic magnitudes B(1988.0) = 17.643 mag, R1(1951.9) = 19.148 mag and R2(1989.0) = 15.713 mag. Photographic R bands are separated by 37.1 years and probably reflect intrinsic (high-amplitude, long-time-scale) photometric variability of the object. SuperCOSMOS and USNO-B1 tabulate appreciable proper motions for Ruber 2. However, after a careful astrometric study using the original plate digitisations, DENIS and 2MASS, we conclude that the proper motion of the object is null within uncertainties of 10 mas/s. Ruber 2 is at a separation of only $\sim$9 arcmin to the core of the unusual Berkeley 20 cluster (see Sect. 1). Therefore, Ruber 2 probably is a pulsating late M giant of that cluster, at a heliocentric distance of 8.4 kpc. \item 2MASS J05345451-0143256 has a 2MASS double detection, with quality flags AUU and UEA. It is not in the NASA/IPAC Extragalactic Database (NED). It could be an unresolved stellar binary instead of a galaxy. \item 2MASX J05332498-0106242 is also the NED object LCSB S0895N (Monnier Ragaigne et al. 2003). \item 2MASX J05365804-0042413 is the infrared source IRAS 05344-0044, very close to the young early-type star HD 37235. \item 2MASX J05364723-0039144 is also the NED object LCSB S0899N (Monnier Ragaigne et al. 2003). \item 2MASS J05364746-0039110 is located at 4.3 arcsec to the centre of 2MASX J05364723-0039144 (see just above), in the plane of the galaxy. This source is probably an artifact. \item 2MASX J05322266-0000555 is also the NED object LEDA 147610 (Klemola et al. 1987; Paturel et al. 1989). \item 2MASS J05341337-0044087 is PMN J0534-0044, a powerful radio source discovered in many surveys (e.g. Becker et al. 1991; Griffith et al. 1995; Douglas et al. 1996; Condon et al. 1998). Its optical/near infrared counterpart is faint ( $i = 16.82 \pm 0.11$ mag) and relatively blue ( $i-K_{\rm s} = 1.2~\pm~~0.2$ mag). \item Annizam 2473146 is at $\sim$4 arcsec to the east of an extended source with a galactic appearance. \item Annizam 2464138 could be reddened by the nearby Ori I-2 Bok globule and be a background star. \item Annizam 1840146 was subject of a dedicated astrometric study using public data (plate digitisations, DENIS and 2MASS). There seems to be an artifact in the POSSI Schmidt plate of 1951 that causes a false proper motion of more than 100 mas/s in the astrometric catalogues USNO-B1 and SuperCOSMOS Science Archive. The very red object has, however, null proper motion within the uncertainty of 10 mas/s using seven astrometric epochs between 1987 and 2000 (see Caballero 2007b for details of the astrometric analysis). \item Annizam 1106127 has 2MASS photometry quality flags ``EEE''; it might indicate that it is an unresolved binary with $\rho \sim 1$-2 arcsec. \item Annizam 1415101 is surrounded by a galaxy arm-like structure. It could be the point-like core of a background galaxy. \item Annizam 2042095 has a bluer, fainter, visual companion at about 3 arcsec to the northeast. \item Annizam 2611268 is at $\sim$8 arcsec to the south of a probable foreground star, about $\sim$3.3 mag brighter in the i band. \item Annizam 123132 is in the glare of Alnilam ( $\rho \sim 2.0$ arcmin, $\theta \sim 130$ deg). \item Annizam 1751268 is probably the Einstein X-ray source 2E 1458. \item Annizam 1748267 is at only $\rho \sim 8.4$ arcsec, $\theta \sim 340$ deg to Annizam 1751268 (see just above). \item V993 Ori is a long-time-known variable star discovered by Luyten (1932). It has a very red colour $J-K_{\rm s} = 1.26 \pm 0.04$ mag for its brightness ( $H = 9.82 \pm 0.02$ mag). \item Annizam 798196 could be associated to the X-ray source 1WGA J0536.4-0059, found in several ROSAT HRI and PSPC catalogues (Moran et al. 1996; ROSAT Consortium 2000; Flesch & Hardcastle 2004). It might be a background source associated to the (extragalactic?) radio source NVSS 053627-005937 in the 1.4 GHz NRAO VLA Sky Survey (Condon et al. 1998), located at $\rho \sim 18$ arcsec, $\theta \sim 200$ deg. \item [SE2005] 120 (Mantaqah 1357158) is a photometric candidate member of the ``$\epsilon$ Orionis cluster'' firstly identified by Scholz & Eislöffel (2005). It is the most variable star of the five objects with high-amplitude ( AI = 0.952 mag), irregular variations. It also have a significant periodic variability of $P = 82 \pm 3$ h, with superimposed short-term fluctuations. Scholz & Eislöffel (2005) classified it as very low-mass analogue of the classical T Tau stars affected by intrinsic reddening. For explaining the large variations, they proposed two possible scenarios involving a eclipsing ``hot Jupiter'' in close orbit and ``hot spots formed by matter flow from an accretion disc onto the central object''. It might be, however, a typical eclipsing binary in the fore-/background. \item [SE2005] 126 (Mantaqah 1582164) is another photometric candidate member of the ``$\epsilon$ Orionis cluster'' with significant periodic variability in the work by Scholz & Eislöffel (2005). In this case, the object has a low-amplitude variability ( AI = 0.016 mag) with a very short period ( $P = 4.06\pm 0.05$ mag). The values are consistent with pulsations induced by deuterium-burning in young brown dwarfs (Caballero et al. 2004; Palla & Baraffe 2005). \item [SE2005] 71 (Annizam 2446149) is a non-variable photometric candidate member of the ``$\epsilon$ Orionis cluster'' (Scholz & Eislöffel 2005). It is located at $\rho \sim 14$ arcsec, $\theta \sim 270$ deg, to V472 Ori. \item Mantaqah 2041159 is surrounded by galaxy arm-like structures. It could be the point-like core of a background galaxy. \item [SE2005] 44 (Mantaqah 2627125) is a photometric candidate member of the ``$\epsilon$ Orionis cluster'' with significant periodic variability ( AI = 0.027 mag, $P = 31.0 \pm1.8$ h; Scholz & Eislöffel 2005). \item Mantaqah 2216132 has a fainter redder visual companion at $\rho \sim 5.6$ arcsec, $\theta \sim 210$ deg. \item Mantaqah 2385113 is at $\rho \approx 6.87$ arcsec, $\theta \approx 352$ deg to Kiso A-0904 22, together with it could form a $\sim$2700 AU-wide low-mass binary. \item Mantaqah 941101 has a brighter bluer visual companion at $\rho \sim 4.5$ arcsec, $\theta \sim 230$ deg. \item Mantaqah 1926266 is at $\rho \approx$ 15.1 arcmin, $\theta \approx 224$ deg, to Kiso A-0903 183. \item Mantaqah 161138 is in the glare of Mintaka ( $\rho \sim 2.7$ arcmin, $\theta \sim 140$ deg). \item Mantaqah 104142 is in the glare of Mintaka ( $\rho \sim 1.7$ arcmin, $\theta \sim 140$ deg). \item Mantaqah 67144 is in the glare of Mintaka ( $\rho \sim 1.1$ arcmin, $\theta \sim 145$ deg). Its J-band magnitude is strongly affected. \item Mantaqah 1982094 has a blue visual companion at $\rho \sim 6.6$ arcsec, $\theta \sim 60$ deg. \item Albus 1 has by far the bluest colour among all the investigated objects ( $V_{\rm T}- K_{\rm s} = -0.95\pm0.14$ mag) and a measurable proper motion $\mu = 19$ mas/a. Although Albus 1 was detected from the data presented in this work, it was followed-up with additional photometric data and discussed in detail in Caballero & Solano (2007). Very recently, Vennes et al. (2007) obtained a series of optical spectra, showing that it is a peculiar, bright, helium-rich B3 subdwarf ( $n_{\rm He} = 0.6\pm0.1$). \item TYC 5360 681 1, the stellar counterpart of an IRAS source, has an appreciable proper motion tabulated by Tycho-2: ( $\mu_\alpha \cos{\delta}$, $\mu_\delta) = (-4\pm2$, +$16\pm 3$) mas/a. Assuming an heliocentric distance of $d \gtrsim 1$ kpc, typical of a giant, it would have a very large tangential velocity of $V_{\rm t} \gtrsim 80$ km/s. \item BD-13 1293 is the reddest IRAS source in this list. The star, investigated here for the first time, displays very strong wide absorption bands, especially at $\sim$1 $\mu$m (between the i and J bands). It is a photometric variable: from the Hipparcos catalogue, its $V_{\rm T}$ magnitude varies between $V_{\rm T} = 9.41$ and 10.00 mag (15 and 85% percentiles, respectively).