منابع مشابه
The 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 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...
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 کاملProbing the Circumstellar Structure of Pre-main Sequence Stars
We present Hα spectropolarimetry of a large sample of pre-main sequence (PMS) stars of low and intermediate mass, and argue that the technique is a powerful tool in studying the circumstellar geometry around these objects. For the intermediate mass (2 – 15 M⊙) Herbig Ae/Be stars we find that 16 out of 23 show a line effect, which immediately implies that flattening is common among these objects...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 1999
ISSN: 0035-8711,1365-2966
DOI: 10.1046/j.1365-8711.1999.02987.x