منابع مشابه
Magnetic 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 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 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 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 کاملDust disks around old Pre Main - Sequence stars : HST / NICMOS 2 scattered light images and modeling
We present recent near-infrared detections of circumstellar disks around the two old PMS Herbig stars HD141569 and HD100546 obtained with the HST/NICMOS2 camera. They reveal extended structures larger than 350–400 AU in radius. While the HD100546 disk appears as a continuous disk down to 40AU, the HD141569 environment seems more complex, splitted at least into two dust populations. As a convinc...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2014
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361/201423654