Volume 490, Number 3, November II 2008
|Page(s)||1055 - 1070|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||11 September 2008|
An X-ray survey of low-mass stars in Trumpler 16 with Chandra*
Centro Universitario Regional Zona Atlántica – Univ. COMAHUE, Monseñor Esandi y Ayacucho (CP 8500), Viedma, Argentina e-mail: email@example.com
2 INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
3 AF Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138, USA
Accepted: 23 July 2008
Aims. We identify and characterize low-mass stars in the ~3 Myr 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.
Methods. We analyzed a 88.4 ks 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: 0.5-8.0 keV and 0.9-8.0 keV. Results 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.
Results. 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 = 3.6 mag, while OB-type stars appear less absorbed, having Av = 2.0 mag. 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 5.37 1021 cm-2 and 1.95 keV. The OB stars appear, softer with a median 0.65 keV. The median X-ray luminosity is 6.3 1030 , while variable sources show a larger median Lx value of 13 1030 . OB-stars have an even higher median Lx of 80 1030 , about 10 times that of the low-mass stars.
Conclusions. 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 1.5-2.5 display X-ray activity similar to the Cyg OB2 stars, but much less intense than observed for Orion nebula cluster members.
Key words: stars: formation / stars: early-type / stars: pre-main sequence / X-rays: stars
© ESO, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.