X-ray Study of Low-mass Young Stellar Objects in the ρ Ophiuchi ...

46 CHAPTER 5. CHANDRA OBSERVATIONS OF THE ρ OPHIUCHI CLOUD(footnotes for Table 5.2)* Background-subtracted X-ray counts in 0.5–2.0 keV, 2.0–9.0 keV, and 0.5–9.0 keV for soft-band, hard-band, and theother sources, respectively. (m) denotes sources with marginal detections (the confidence level < 99.9 %, see §5.2).Although the confidence levels of A-48 and A-H2 are significant enough, we regard them as marginal sources becauseof the larger source size (A-48) and severe contamination from A-2 (A-H2).† Right ascension and declination for all sources are 16h and −24 ◦ .‡ Parentheses indicate the 90 % confidence limits.§ Observed flux (10 −14 ergs s −1 cm −2 ) and absorption-corrected X-ray luminosity (10 29 ergs s −1 ; “< L X >” in thetext) in 0.5–9.0 keV.‖ Reduced-χ 2 for the spectral fittings. Parentheses indicate the degrees of freedom.# We determine spectral parameters with fixed temperatures of 1 keV and 5 keV (see text). For sources which onlyshow the parameters for kT = 1 or 5 keV, no good fitting is obtained for the other temperature.** We assume the same abundances as the “F2” phase in Table 6.3. The quiescent spectrum is not obtained becausethe decay phases of the two flares occupy all of the light curve.†† The pileup effect is not corrected.‡‡ No spectral fit is done due to the limited statistics.§§ Abundances are free parameters (§6.3.2, §6.3.3, and §6.3.7).‖‖ We make the flare spectra with a bit larger timescale in order to obtain as good statistics as possible. Errors of< EM > for A-29 in the quiescent are not determined because of the limited statistics.## The spectra show the possible absorption edge of neutral Ca or warm Ar. The non-thermal model also wellreproduces the spectra (§6.3.5, see also Hamaguchi et al. 2002).*** We assume the same temperature because of the limited statistics.† † † These show non-thermal spectra (§6.6.3).‡ ‡ ‡ These show two temperature model with an unusual abundance pattern (§6.2).§§§ Foreground star. The distance is 60 pc (Festin, 1998).‖‖‖ The best-fit value of < kT > is not determined (larger than 10 keV), hence we assume 10 keV temperature forthe estimation of the other parameters.### N H and reduced-χ 2 are estimated by the simultaneous fittings with the identical sources in obs-A.