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P Cygni line profile

A feature in a spectrum that indicates a strong outflow of matter from a star. It is named after P Cygni, a Be star whose spectrum shows strong hydrogen and helium emission lines with ...

P Cygni line profile

P Cygni line profile   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

... Cygni line profile A feature in a spectrum that indicates a strong outflow of matter from a star. It is named after P Cygni, a Be star whose spectrum shows strong hydrogen and helium emission lines with absorption lines on their blueward side. These dual characteristics are caused by an expanding shell or wind of material that is being blown off the star either by radiation pressure or rapid rotation. Where the expanding shell is directly between us and the star, it produces absorption at a velocity which is blueshifted relative to the star. The other parts...

P Cygni line profile

P Cygni line profile  

A feature in a spectrum that indicates a strong outflow of matter from a star. It is named after P Cygni, a Be star whose spectrum shows strong hydrogen and helium emission lines with absorption ...
S Doradus star

S Doradus star  

A type of extremely luminous, eruptive variable that ejects shells of material; abbr. SDOR. These stars include some of the most massive (over 30 solar masses) and most luminous (about 106 solar ...
S Doradus star

S Doradus star   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...irregular on a timescale of tens of years or even centuries, with amplitudes up to 10 magnitudes. Eta Carinae is a famous example. Alternative names are Hubble–Sandage variable , and luminous blue variable . The older term P Cygni star is now reserved for any star with spectral lines having a P Cygni line profile , indicative of emission from an expanding...

Herbig Ae/Be star

Herbig Ae/Be star   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...counterparts of the more common T Tauri stars . Being more massive than T Tauri stars, they are of earlier spectral type, B, A, or F. Like the classical T Tauri stars their spectra contain emission lines, especially the hydrogen Balmer series . The existence of P Cygni line profiles indicates mass outflow from the system. Excess infrared and millimetre emission shows that HAeBe stars are associated with abundant circumstellar dust. Significant variations in brightness indicate the existence of clumps in the dust, possibly protoplanets or...

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