Table 3: Colour and extinction characteristics for the LMC lines of sight. The B and V photometric data were combined with intrinsic colours for LMC supergiants (Fitzpatrick 1988) to obtain the total \ensuremath {E_{B-V}} for the line of sight towards the LMC targets. To derive the reddening within the LMC ( \ensuremath {E_{B-V}} $_{\rm , LMC}$) the combined foreground contribution of both the Milky Way (MW) and intermediate velocity clouds (VC) were subtracted. All values are in magnitudes. Fitzpatrick & Savage (1984) derive \ensuremath {E_{B-V}} $_{\rm , total} = 0.34$ mag, and \ensuremath {E_{B-V}} $_{\rm , LMC} = 0.27$ mag for Sk -69 243, consistent with the value derived below. Smith et al. (1990) derive \ensuremath {E_{B-V}} $_{\rm , total} = 0.39$ and 0.41 mag for Sk -69 223 and Sk -69 243, respectively.
    Sk -69 223 Sk -69 243 Sk -67 2 Sk -68 135 Sk -67 5 Sk -70 120
Sp type (UV)   WC4+OB WN4.5+OB B2 Ia ON9.7 Ia O9.7 Ib B1 Ia
Sp type (optical)a   B1 Ia O3 If B1.5 Ia B0 Ia B0 Ia B1.5 Ia
B-V ($\pm$0.01)   0.11 0.13 0.048 0.00 -0.12 -0.06
(B-V)0a ($\pm$0.02)   -0.16 -0.27 -0.16 -0.22 -0.22 -0.16
Reddening:          
\ensuremath {E_{B-V}} $_{\rm , total}$ (E02)   0.42 0.30 0.35 0.27 - 0.06
\ensuremath {E_{B-V}} $_{\rm , total}$b ($\pm$0.03)   0.27 0.40 0.21 0.22 0.10 0.10
\ensuremath {E_{B-V}} $_{\rm , FG}$c ($\pm$0.02)   0.07 0.14 0.11 0.09 0.04 0.09
\ensuremath {E_{B-V}} $_{\rm , LMC}$c ($\pm$0.03)   0.20 0.26 0.10 0.13 0.06 0.01
\ensuremath {E_{B-V}} $_{\rm , LMC}$d ($\pm$0.03)   0.19 0.32 0.13 0.14 0.02 0.02
Adopted              
\ensuremath {E_{B-V}} $_{\rm , LMC}$   0.20 0.29 0.12 0.14 0.04 0.02
$\sigma $ \ensuremath {E_{B-V}}   0.06 0.04 0.04 0.02 0.03 -
a Spectral types from Table 1. (B-V)0 adopted from Fitzpatrick (1988) for LMC supergiants of corresponding optical spectral type. Intrinsic colour for WR/WN/WC stars from Smith et al. (1990): (B-V) $_0 = -0.27 \pm 0.05$. b \ensuremath {E_{B-V}} $_{\rm , total}$ = (B-V) $_{\rm observed} - (B-V)_0$. c  \ensuremath {E_{B-V}} $_{\rm , LMC}$ =  \ensuremath {E_{B-V}} $_{\rm , total}$ - \ensuremath {E_{B-V}} $_{\rm , FG}$. The foreground reddening \ensuremath {E_{B-V}} $_{\rm , FG}$ (=MW + VC reddening) towards the LMC lines of sight was estimated by applying the relation N(Na I) =  $1.7 \times 10^{14}$ \ensuremath {E_{B-V}}1.8 (Hobbs 1974b), to the observed Na I column densities. d \ensuremath {E_{B-V}} $_{\rm , LMC}$ =  \ensuremath {E_{B-V}} $_{\rm , total}$ - \ensuremath {E_{B-V}} $_{\rm , FG}$, with \ensuremath {E_{B-V}} $_{\rm , FG}$ =  \ensuremath {E_{B-V}} $_{\rm , MW}$ +  \ensuremath {E_{B-V}} $_{\rm , VC} \approx 0.08$ mag. \ensuremath {E_{B-V}} $_{\rm , MW} \sim 0.07$ mag, estimated from the Galactic extinction map by Drimmel et al. (2003), \ensuremath {E_{B-V}} $_{\rm , VC} \sim 0.01$ mag, derived via N(Na I). The foreground reddening map based on H I by Staveley-Smith gives a similar value of \ensuremath {E_{B-V}} $_{\rm , FG} = 0.08$ mag.

Source LaTeX | All tables | In the text