DDO spectroscopic survey of MOST variable starsa Pribulla, Theodor; Rucinski, Slavek M; Kuschnig, Rainer ...
Monthly notices of the Royal Astronomical Society,
01/0001, Letnik:
392
Journal Article
Recenzirano
A spectroscopic support survey of 103 objects observed by the Microvariability and Oscillations of STars (MOST) satellite is presented; 96 are variable stars with 83 of them being new MOST ...variable-star detections or stars with variability types verified and/or modified on the basis of the MOST data. The analysis of 241 medium-resolution spectra using the broadening-function formalism yielded radial velocities, projected rotational velocities (for 31 targets for which it was possible) and spectral-type estimates. Seven new spectroscopic binaries were discovered; orbital solutions are given for two of them (HD 73709 and GSC 0814-0323). The visual binary HD 46180 was found to be composed of two close binary stars (eclipsing and non-eclipsing one), very probably forming a physical quadruple system.
ABSTRACTMicrovariability & Oscillations of STars (MOST) and All Sky Automated Survey (ASAS) observations have been used to characterize photometric variability of TW Hya on time-scales from a ...fraction of a day to 7.5 weeks and from a few days to 8 yr, respectively. The two data sets have very different uncertainties and temporal coverage properties and cannot be directly combined, nevertheless, they suggest a global variability spectrum with 'flicker-noise' properties, that is with amplitudes , over >4 decades in frequency, in the range f = 0.0003-10cd-1. A 3.7d period is clearly present in the continuous 11d, 0.07d time resolution, observations by MOST in 2007. Brightness extrema coincide with zero-velocity crossings in periodic (3.56d) radial-velocity variability detected in contemporaneous spectroscopic observations of Setiawan et al. and interpreted as caused by a planet. The 3.56/3.7d periodicity was entirely absent in the second, 4 times longer MOST run in 2008, casting doubt on the planetary explanation. Instead, a spectrum of unstable single periods within the range of 2-9d was observed; the tendency of the periods to progressively shorten was well traced using the wavelet analysis. The evolving periodicities and the overall flicker-noise characteristics of the TW Hya variability suggest a combination of several mechanisms, with the dominant ones probably related to the accretion processes from the disc around the star.
Echography of young stars reveals their evolution Zwintz, K.; Fossati, L.; Ryabchikova, T. ...
Science (American Association for the Advancement of Science),
08/2014, Letnik:
345, Številka:
6196
Journal Article
Recenzirano
Odprti dostop
We demonstrate that a seismic analysis of stars in their earliest evolutionary phases is a powerful method with which to identify young stars and distinguish their evolutionary states. The early star ...that is born from the gravitational collapse of a molecular cloud reaches at some point sufficient temperature, mass, and luminosity to be detected. Accretion stops, and the pre–main sequence star that emerges is nearly fully convective and chemically homogeneous. It will continue to contract gravitationally until the density and temperature in the core are high enough to start nuclear burning of hydrogen. We show that there is a relationship for a sample of young stars between detected pulsation properties and their evolutionary status, illustrating the potential of asteroseismology for the early evolutionary phases.
We demonstrate that a seismic analysis of stars in their earliest evolutionary phases is a powerful method with which to identify young stars and distinguish their evolutionary states. The early star ...that is born from the gravitational collapse of a molecular cloud reaches at some point sufficient temperature, mass, and luminosity to be detected. Accretion stops, and the pre-main sequence star that emerges is nearly fully convective and chemically homogeneous. It will continue to contract gravitationally until the density and temperature in the core are high enough to start nuclear burning of hydrogen. We show that there is a relationship for a sample of young stars between detected pulsation properties and their evolutionary status, illustrating the potential of asteroseismology for the early evolutionary phases.
We demonstrate that a seismic analysis of stars in their earliest evolutionary phases is a powerful method to identify young stars and distinguish their evolutionary states. The early star that is ...born from the gravitational collapse of a molecular cloud reaches at some point sufficient temperature, mass and luminosity to be detected. Accretion stops and the pre-main sequence star that emerges is nearly fully convective and chemically homogeneous. It will continue to contract gravitationally until the density and temperature in the core are high enough to start nuclear burning of hydrogen. We show that there is a relationship between detected pulsation properties for a sample of young stars and their evolutionary status illustrating the potential of asteroseismology for the early evolutionary phases.
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