Search results for "stars : activity"
showing 4 items of 4 documents
New Pre-Main Sequence Candidates in the Taurus-Auriga Star Forming Region
2007
Aims. We have studied the X-ray source population of the Taurus Molecular Cloud (TMC) to search for new members of the Taurus-Auriga star forming region. Methods. Candidate members have been selected among the X-ray sources detected in 24 fields of the XMM-Newton Extended Survey of the Taurus Molecular Cloud, having an IR counterpart in the 2MASS catalog, based on color-magnitude and color-color diagrams. Their X-ray spectral properties have been compared with those of known members and other X-ray sources in the same fields but without a NIR counterpart. A search for flare-like variability in the time series of all new candidates and the analysis of the X-ray spectra of the brightest candi…
X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391
2005
We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have been detected, from the early-types to the late-M dwarfs. Despite the capability of the instrument to recognize up to 3 thermal components, the X-ray spectra of the G, K and M members of the cluster are well described with two thermal components (at kT$_1 \sim$ 0.3-0.5 keV and kT$_2 \sim$ 1.0-1.2 keV respectively) while the X-ray spectra of F members…
Coronal properties of active G-type stars in different evolutionary phases
2005
We report on the analysis of XMM-Newton observations of three G-type stars in very different evolutionary phases: the "weak-line" T Tauri star HD 283572, the Zero Age Main Sequence star EK Dra and the Hertzsprung-gap giant star 31 Corn. The X-ray luminosities of the three stars are all in the range 10(30) - 10(31) erg/s. We compare the Emission Measure Distributions of these bright sources, derived from high-resolution X-ray spectra, as well as the pattern of elemental abundances vs. First Ionization Potential (FIP). The results of our analysis suggest that the coronae of these stars are very similar in terms of dominant coronal magnetic structures, in spite of differences in their evolutio…
The structure of coronal plasma in active stellar coronae from density measurements
2005
We have analyzed high-resolution X-ray spectra of a sample of 22 active stars observed with the High Energy Transmission Grating Spectrometer (HETGS) on Chandra in order to investigate their coronal plasma density, using the lines of the He-like ions O VII, Mg XI, and Si XIII. Si XII lines in all stars of the sample axe compatible with the low-density limit (i.e. n(e) = 10(30) erg/s); O VII lines yield much lower densities of a few 10(10) cm(-3). Our results indicate that the "hot" and "cool" plasma resides in physically different structures. Our findings imply remarkably compact coronal structures, especially for the hotter (similar to 7 MK) plasma emitting the Mg xi lines characterized by…