Errata: The X-Ray Emission Measure (EM) of the Young Stellar Objects   (YSOs) in the Rho Ophiuchi (Rho Oph) and Monoceros R2 Dark Clouds (Mon R2)
  Errors were made in the calculations of EMs using the best fit normalizations in XSPEC. Lists of the errors and corrections are as follows.   (1)Tables 1, 3, and 4 in ApJ, 557, 747 and astro-ph/0104190 (YSOs in Rho Oph): All the EMs in these tables should be multiplied by pi; the log(EM) in the first raw in Table 1, for example, is 52.6(52.2--53.2), not 52.1(51.7--52.7).   (2)Figures 7 and 9 in ApJ, 557, 747 and astro-ph/0104190 (YSOs in Rho Oph): The EM plots should be systematically up-shifted by the factor of pi.   (3)Table 3 in ApJ, 563, 361 and astro-ph/0108078 (young brown dwarfs in Rho Oph): All the EMs in this table should be multiplied by pi; the log(EM) in the first raw, for example, is 52.1(52.0--52.6), not 51.6(51.5--52.1).   (4)Table 1 in ApJ, 567, 423 and astro-ph/0110462 (YSOs in Mon R2): All the EMs in this table should be divided by 10; the log(EM) in the first raw, for example, is 52.5(52.1--52.9), not 53.5(53.1--53.9).   All the spectral parameters except EM are unchanged. These errors of EM do not affect any of the conclusions of the relevant papers.   In addition, Gregorio-Hetem, J., Montmerle, T., Casanova, S., and Feigelson, E. D.1998, A&A, 331, 193 should be included in the reference list of ApJ, 567, 423 (astro-ph/0110462). 
Kensuke Imanishi, Makoto Kohno, Katsuji Koyama (Kyoto University)