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Short and Medium term Variability study of NGC2516 late type stars with EPIC-XMM I. Pillitteri 1, G. Micela 2, A. Marino1 , S. Sciortino 2 1: Dip. Scienze Fisiche e Astronomiche, Universita` di Palermo 2: INAF - Osservatorio Astronomico di Palermo • • • • Outline: NGC 2516 characteristics and XMM observations. Short term Variability Medium term Variability Summary and Future Work. EPIC Meeting, Palermo 14-16 Ottobre 2003 NGC 2516 cluster • • • • Rich Open Cluster, distance 387 pc Age: ~140 Myr, slightly older than Pleiades Solar Metallicity (Terndrup et al. 2002) Optical catalog: Jeffries et al. (2001) EPIC Meeting, Palermo 14-16 Ottobre 2003 EPIC-XMM observations • 5 EPIC Calibration Observations, typical obs time: 20 ksec. • Time coverage: 19 months Rev. number RA (J2000) Dec (J2000) Obs Time (ksec) Filter M1 M2 PN Time after 1st obs (months) 0060 2 segm. 7:58:20 “ -60:52:13 “ 20 17 THICK THICK Y Y Y Y Y Y 0 0092 7:58:22.3 -60:45:36 27 THICK Y Y Y 2 0164 7:58:20 -60:52:13 22 MEDIUM Y Y N 7 0209 2 segm. 7:58:22.3 “ -60:45:36 “ 21.4 13.5 THICK THICK Y Y Y Y Y Y 10 0346 7:58:22.3 -60:45:36 21.2 THICK Y Y Y 19 EPIC Meeting, Palermo 14-16 Ottobre 2003 Previous pubblications based on EPIC data: •Sciortino et al. 2001: Analysis of rev. number 0060. •Ramsay et al. 2003: Study of variability of 4 sources. EPIC Meeting, Palermo 14-16 Ottobre 2003 Analysis steps: 1. 2. 3. 4. 5. Calibrated event files obtained with SAS5.3.3. Filtering: Energy band : 0.3-5.5 keV, “low” rate time intervals. Source detection with Wavelet Convolution based code (PWXDetect) on (MOS1 + MOS2 + PN) of each observation and cross-id. with optical catalog, selection of a sample of dG and dM type stars. Light curves and Kolmogorov-Smirnov test for short term variability. Lx Amplitude Variation distributions for medium term variability. SAS product ... EPIC Meeting, Palermo 14-16 Ottobre 2003 Filtering ... ...and Detection Criteria for selection of the sample 1. 2. 3. Color index isolated sources detected at least once in XMM observations. • • 11 dG type stars (B-V0 0.5 & V-I0 0.93) 11 dM type stars (2.2 V-I0 5.0) EPIC Meeting, Palermo 14-16 Ottobre 2003 Results I. Short term variability G sample: 11 stars observed 7 times. • Number of detections: 75/77 ~ 97.4% • K-S test constant source null hypothesis P0 < 1%: Variables: 10/75 ~ 13 % M sample: 11 stars observed 7 times. • Number of detections: 31/77 ~ 40% • Variables (K-S test P0 < 1%): 8/31 ~ 26 % Results similar to field dG and dM stars (Marino et al. 2000, 2002). Different from Pleiades case where dG and dM stars show similar variability properties. EPIC Meeting, Palermo 14-16 Ottobre 2003 Light curves. G type stars EPIC Meeting, Palermo 14-16 Ottobre 2003 M type stars X-ray spectral variability of a dG star between two observations. Star id. JTH 9465 from Jeffries et al.(2001) catalog: B-V 0.82. Red: obs nr. rev 60-A: quiescent, black: obs nr. rev. 346: flare “Bump” at ~1.8 keV in the flare spectrum EPIC Meeting, Palermo 14-16 Ottobre 2003 Results II. Medium term variability in dG stars Analysis Amplitude variation of log LX (ALX) of dG stars at ~10 and ~20 month time scales. •Cumulative Distributions of ALX of NGC2516 dG stars, compared with analogous Sun, Pleiades (Micela & Marino 2003, Marino et al. 2003 ) and Hyades (Marino, priv. comm.) distributions. Sun data from YOHKOH/SXT full disk images in 0.7-2.5 keV. Pleiades and Hyades data from ROSAT observations. EPIC Meeting, Palermo 14-16 Ottobre 2003 EPIC Meeting, Palermo 14-16 Ottobre 2003 Summary: 1. Short time scales: dG in NGC 2516 are less variables than dM, similar result in field stars but different from Pleiades case. 2. Medium time scales: no evidence of solar-like cycle in NGC 2516 at 10 and 20 month time scales. Future work: •Long term (~ yr) variability (XMM<>ROSAT data) •Analysis of all summed exposures to achieve the deepest X-ray sensitivity. EPIC Meeting, Palermo 14-16 Ottobre 2003