منابع مشابه
Luminous pre - main sequence stars in the LMC ?
We report the serendipitous discovery of seven luminous irregular variables in the LMC by the EROS project. The stars have V ' 15 to 17, (BE − RE) ' 0, and vary by about 0.4 on timescales of 10 to 40 days. The variations in BE and RE are about equal but the stars are slightly bluer when they are fainter. Medium resolution optical spectra show strong Hα emission, weak Hβ emission and absorption ...
متن کاملThe Ages of Pre-main-sequence Stars
The position of pre-main-sequence or protostars in the Hertzsprung–Russell diagram is often used to determine their mass and age by comparison with pre-main-sequence evolution tracks. On the assumption that the stellar models are accurate, we demonstrate that, if the metallicity is known, the mass obtained is a good estimate. However, the age determination can be very misleading because it is s...
متن کاملMagnetic flaring in pre-main sequence stars
Observations of nearby star forming clouds with imaging Xray telescopes have revealed that X-ray emission is elevated 10 − 10 above main sequence levels in low-mass pre-main sequence (PMS) stars. The variability and spectral X-ray evidence, together with circularly polarized radio continuum flares seen in a few cases, strongly argues for an origin in magnetic reconnection flares. These high lev...
متن کاملCircumstellar Disks in pre-Main–Sequence Stars
This review covers the properties of disks around pre-main– sequence stars. It is at this time in the evolution that planets form, and it is important to understand the properties of these disks to understand planet formation. I discuss disk shapes, masses and temperatures, the properties of the host stars, disk lifetimes and dissipation processes. Finally, evidence of grain growth during pre-m...
متن کاملCoronal Structure of Pre-Main Sequence Stars
The study of pre-main sequence stellar coronae is undertaken in many different wavelength regimes, with apparently conflicting results. X-ray studies of T Tauri stars suggest the presence of loops with a range of sizes ranging from less than a stellar radius to 10 stellar radii. Some of these stars show a clear rotational modulation in X-rays, but many do not and indeed the nature of this emiss...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1999
ISSN: 0074-1809
DOI: 10.1017/s0074180900118261