Best-fit values for radius and temperature of the BB component in the case of RX J0440.9+4431 (empty star), RX J1037.5-5647 (filled circles), 4U 0352+309 (filled squares), RX J0146.9+6121 (empty circle), 3A 0535+262 (empty square), SAX J2103.5+4545 (empty triangle), 4U 2206+54 (filled triangles), IGR J11215-5292 (asterisks), IGR J08408-4503 (cross), XTE J1739-302 (filled star), and SXP 1062 (empty diamonds). The continuous lines connect the black-body parameters corresponding to four different levels of luminosity (in erg s^-1). References: 0 – this work; 1– La Palombara et al. (2009); 2 – Reig & Roche (1999); 3 – Coburn et al. (2001); 4 – La Palombara & Mereghetti (2007); 5 – Mukherjee & Paul (2005); 6 – La Palombara & Mereghetti (2006); 7 – Masetti et al. (2004); 8 – Torrejón et al. (2004); 9 – Reig et al. (2009); 10 – İnam et al. (2004); 11 – Sidoli et al. (2007); 12 – Sidoli et al. (2009); 13 – Bozzo et al. (2010); 14 – Hénault-Brunet et al. (2012).