1. Chandra Observations of Rho Oph Dark Cloud Cores Katsuji Koyama, Kyoto University In a 1pc x 2pc Regions, we found 195 X-ray sources above the detection limit of ~10 28 erg/s. One hundred and ten (60 %) have optical and/or infrared counterparts.

2. Summary of the Observations (100 k-sec each) Mean kT (keV) log(N H ) Quiescent Flare ( 10 22 ) 2.9 5.2 6.8 2.3 3.9 3.3 1.7 2.7 2.3

3. Low Mass YSOs Ｐｒｅ－Ｍａｉｎ Ｓｅｑuenｃｅ Ｃｌａｓｓ Ｉ Ｐｒｏｔｏｓｔａｒ Ｃｌａｓｓ ＩＩ ＣＴＴＳ Ｃｌａｓｓ ＩＩＩ ＷＴＴＳ Ｍａｉｎ Ｓｅｑｕｅｎｃｅ

4. Animation of Flares from Class Is and others. (1 step= 5000 sec, total=I day)

5. Class I source YLW16A exhibited a Giant Flare. Strong 6.4 keV line (EW~100eV) is found. Uniform Sphere: EW～10(Z Fe /0.3)(N H /5x10 22 )

6. We have detected X-rays from 5 Brown Dwarfs Out of 15 IR identified BDs M8.5 M６ kT=1.7 (0.9-2.2) kT=2.5 (>1.0)

7. 2.5 x10 23 5.4 x10 23 1 x10 23 New very young YSOs ? No IR counterpart (K >15 mag) but lie in the cloud core. Then we found 3 Sources (1) All have larger N H (1~5 x10 23 ) than those of Class Is (7x10 22 ) and are similar to X-ray detected class 0s (10 23 :OMC2/3, 5x10 23 :RcrA) (2) All show flares.

8. Luminosity as a Function of Mass in Quiescent and Flare States Luminosity Function in Quiescent and Flare States ● Class I ▲ Class II □ Class III ◇ UnClassified

9. Temperature Distribution in Quiescent and Flare

10. kT & E.M. τ rise τ decay Plasma Density (n) Magnetic field (B) Loop Length (L) Observed ValuesPredicted Values Flare Loop Analysis Using: kT, E.M. rise and decay

11. ∝ (n/10 9 ) -1/7 (L/10 11 ) 2/7 (B/10 2 ) 6/7 (1) (heating rate ～ loop conduction cooling: Shibata & Yokoyama ) τ r ∝ (n/10 9 ) 1/2 (L/10 11 )(B/10 2 ) -1 (2) τ d ∝ 10 4 (n/10 9 ) -1/4 (L/10 11 ) 1/2 (B/10 2 ) (3) (2)+(3) τ d =Aτ r 1/2, A～640(n/10 9 ) -1/2 (4) (1)+(2)+(4) τ r ∝ (B/10 2 ) -4 ( ) 7/2, τ r ∝ (L/10 11 ) 4/3 ( ) -6/7 (unit: keV, sec, cm, Gauss)

12. τ r -τ d relation Best-fit log-linear Best-fit Equation (4) ● Class I ▲ Class II □ Class III ◇ UnClassified Then the density (n) ~10 10 -10 11

13. Magnetic Field and Density Estimation For Flare Loop  Present Work Shibata and Yokoyama Smaller (less active) tends to have Smaller Loop Size Larger Loop Size

14. Ｔｈｅ Ｅｎｄ Ｔｈａｎｋｓ For your attention