Search results for " Stars: pre-main sequence"
showing 10 items of 36 documents
The Gaia-ESO Survey: membership and initial mass function of the. Velorum cluster
2016
Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, we derived the most complete list of candidate cluster members. Then, we considered photometry, gra…
The Gaia-ESO Survey: The present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters
2017
Full list of authors: Spina, L.; Randich, S.; Magrini, L.; Jeffries, R. D.; Friel, E. D.; Sacco, G. G.; Pancino, E.; Bonito, R.; Bravi, L.; Franciosini, E.; Klutsch, A.; Montes, D.; Gilmore, G.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C. Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Hourihane, A.; Jofré, P.; Lewis, J.; Lind, K.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.
GSC 07396-00759 = V4046 Sgr C[D]: A Wide-separation Companion to the Close T Tauri Binary System V4046 Sgr AB
2011
We explore the possibility that GSC 07396-00759 (spectral type M1e) is a widely separated (~2.82', or projected separation ~12,350 AU) companion to the "old" (age ~12 Myr) classical T Tauri binary system V4046 Sgr AB, as suggested by the proximity and similar space motions of the two systems. If the two systems are equidistant and coeval, then GSC 07396--00759, like V4046 Sgr AB, must be a spectroscopic binary with nearly equal-mass components, and V4046 Sgr must be at least ~8 Myr old. Analysis of a serendipitous Chandra X-ray gratings spectrum and light curve as well as XMM-Newton light curves and CCD spectra of GSC 07396-00759 obtained during long exposures targeting V4046 Sgr AB reveals…
X-ray optical depth diagnostics of T Tauri accretion shocks
2009
In classical T Tauri stars, X-rays are produced by two plasma components: a hot low-density plasma, with frequent flaring activity, and a high-density lower temperature plasma. The former is coronal plasma related to the stellar magnetic activity. The latter component, never observed in non-accreting stars, could be plasma heated by the shock formed by the accretion process. However its nature is still being debated. Our aim is to probe the soft X-ray emission from the high-density plasma component in classical T Tauri stars to check whether this is plasma heated in the accretion shock or whether it is coronal plasma. High-resolution X-ray spectroscopy allows us to measure individual line f…
X-ray emission from MP Muscae: an old classical T Tauri star
2007
We study the properties of X-ray emitting plasma of MP Mus, an old classical T Tauri star. We aim at checking whether an accretion process produces the observed X-ray emission and at deriving the accretion parameters and the characteristics of the shock-heated plasma. We compare the properties of MP Mus with those of younger classical T Tauri stars to test whether age is related to the properties of the X-ray emission plasma. XMM-Newton X-ray spectra allows us to measure plasma temperatures, abundances, and electron density. In particular the density of cool plasma probes whether X-ray emission is produced by plasma heated in the accretion process. X-ray emission from MP Mus originates from…
XMM-Newton spectroscopy of the metal depleted T Tauri star TWA 5
2005
We present results of X-ray spectroscopy for TWA 5, a member of the young TW Hydrae association, observed with XMM-Newton. TWA~5 is a multiple system which shows Halpha emission, a signature typical of classical T Tauri stars, but no infrared excess. From the analysis of the RGS and EPIC spectra, we have derived the emission measure distribution vs. temperature of the X-ray emitting plasma, its abundances, and the electron density. The characteristic temperature and density of the plasma suggest a corona similar to that of weak-line T Tauri stars and active late-type main sequence stars. TWA 5 also shows a low iron abundance (~0.1 times the solar photospheric one) and a pattern of increasin…
Spectroscopic observations of blue stars with infrared excesses in NGC 6611
2013
The young open cluster NGC 6611 includes among its candidate members a class of peculiar objects with interesting properties: blue stars with infrared IR excesses. These stars show excesses in IR bands, signature of the presence of a circumstellar disk, but optical colors typical of older field stars. In order to confirm their membership to the cluster, it is therefore important to use new spectroscopic observations, together with previous photometric data. We aim at confirming the membership of these objects and at investigating their physical properties to verify whether the observed colors are intrinsic or altered by the presence of the disk or by the accretion processes. We analyze the …
The diagnostic potential of Fe lines applied to protostellar jets
2013
We investigate the diagnostic capabilities of the iron lines for tracing the physical conditions of the shock-excited gas in jets driven by pre-main sequence stars. We have analyzed the 300-2500 nm X-shooter spectra of two jets driven by the pre-main sequence stars ESO-Halpha 574 and Par-Lup 3-4. Both spectra are very rich in [FeII] lines over the whole spectral range; in addition, lines from [FeIII] are detected in the ESO-H\alpha 574 spectrum. NLTE codes along with codes for the ionization equilibrium are used to derive the gas excitation conditions of electron temperature and density, and fractional ionization. The iron gas-phase abundance is provided by comparing the iron lines emissivi…
Activity and Rotation in the Young Cluster h Per
2013
We study the stellar rotation-activity relation in the crucial age at which stars reach the fastest rotation. To this aim we have analyzed data of the young cluster h Per, very rich and compact, located at 2300 pc, that at an age of 13 Myr should be mainly composed of stars that have ended their contraction phase and that have not lost significant angular momentum viamagnetic breaking. To constrain the activity level of h Per members we have analyzed a deep Chandra/ACIS-I observation. Rotational periods of h Per members have been derived by Moraux et al. (2013) in the framework of the MONITOR project (Aigrain et al. 2007; Irwin et al. 2007). In the Chandra observation we have detected 1010 …
XMM-Newton survey of two upper Scorpius regions
2006
We study X-ray emission from young stars by analyzing deep XMM-Newton observations of two regions of the Upper Scorpius association, having an age of 5 Myr. Based on near infrared and optical photometry we identify 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derive coronal properties of Upper Scorpius stars by performing X-ray spectral and timing analysis. The study of four strong and isolated stellar flares allows us to derive the length of the flaring loops. Among the 22 Upper Scorpius stars, 13 are identified as Upper Scorpius photometric members for the first time. The sample includes 7 weak-line T Tauri stars and 1 classical T Tauri star, while the na…