Astronomy and Astrophysics, volume 490, 1055-1070 (2008/11-2)
An X-ray survey of low-mass stars in Trumpler 16 with Chandra.
ALBACETE-COLOMBO J.F., DAMIANI F., MICELA G., SCIORTINO S. and HARNDEN F.R.Jr
Abstract (from CDS):
We identify and characterize low-mass stars in the ∼3Myr old Trumpler 16 region by means of a deep Chandra X-ray observation, and study their optical and near-IR properties. We compare the X-ray activity of Trumpler 16 stars with the known characteristics of Orion and Cygnus OB2 stars. We analyzed a 88.4ks Chandra ACIS-I observation pointed at the center of Trumpler 16. Because of diffuse X-ray emission, source detection was performed using the PWDetect code for two different energy ranges: 0.5-8.0keV and 0.9-8.0keV.
Result. were merged into a single final list. We positionally correlated X-ray sources with optical and 2MASS catalogs. Source events were extracted with the IDL-based routine ACIS-Extract. X-ray variability was characterized using the Kolmogorov-Smirnov test and spectra were fitted by using XSPEC. The X-ray spectra of early-type, massive stars were analyzed individually. Our list of X-ray sources consists of 1035 entries, 660 of which have near-IR counterparts and are probably associated with Trumpler 16 members. From near-IR, color-color, and color-magnitude diagrams we compute individual masses of stars and their Av values. The cluster median extinction is Av=3.6mag, while OB-type stars appear less absorbed, having Av=2.0mag. About 15% of the near-IR counterparts show disk-induced excesses. X-ray variability is found in 77 sources, and typical X-ray spectral parameters are NH∼5.37x1021cm–2 and kT∼1.95keV. The OB stars appear, softer with a median kT∼ 0.65 keV. The median X-ray luminosity is 6.3x1030erg/s, while variable sources show a larger median Lx value of 13x1030erg/s. OB-stars have an even higher median Lx of 80x1030erg/s, about 10 times that of the low-mass stars. The Trumpler 16 region has a very rich population of low-mass X-ray emitting stars. A large fraction of its circumstellar disks have survived the intense radiation field of its massive stars. Stars with masses 1.5-2.5M☉ display X-ray activity similar to the Cyg OB2 stars, but much less intense than observed for Orion nebula cluster members.
stars: formation - stars: early-type - stars: pre-main sequence - X-rays: stars
VizieR on-line data:
<Available at CDS (J/A+A/490/1055): table1.dat table2.dat table3.dat>
Table 1, col(1): [ADM2008] NNNN (Nos 1-1035) = Table 1, col(2): CXOTr16 JHHMMSS.ss+DDMMSS.s N=1035.
Status in Simbad:
could be processed
Table 1, col(2): the ID CXOCYG (ID for sources in the Association Cyg OB 2) is a misprint, we have created CXOTr16 for sources in Cl Trumpler 16.
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