Astrophysical lasers in optical Fe II lines in gas condensations near η Carinae

• We report here on the discovery of laser action in the range 0.9-2 μm in several spectral lines of Fe II, which are associated with transitions from "pseudo-metastable" states populated by spontaneous transitions from Lyα pumped Fe II levels. The intense Lyα radiation is formed in the HII region of gas condensations close to the star η Car. The laser transitions form together with spontaneous transitions closed radiative cycles, one of which includes the extremely bright 2507/09 Å lines. This fact, together with an accidental mixing of energy levels, may provide an explanation of the abnormal intensities of these UV non-lasing lines. Using the complicated energy level diagram of Fe II we present those peculiar features, which are essential for the inverted population and laser effect: the pumping, the level mixing, and the "bottle neck" for spontaneous decay. The laser action is a new indicator of non-equilibrium and spatially non-homogeneous physical conditions as well as a high brightness temperature of Lyα in ejecta from eruptive stars. Such conditions are very difficult to probe by existing methods

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

spontaneous transitions

intense radiation

laser transitions

radiative cycles

abnormal intensities

UV nonlasing lines

energy level diagram

laser effect

optical pumping

level mixing

spontaneous decay

Fe

0.9 to 2 micron

stellar radiation

stimulated emission

astrophysical plasma

brightness temperature

eruptive stars

pseudometastable states

laser action

η Carinae

gas condensations

astrophysical lasers

optical Fe II lines

Publikations- och innehållstyp

kon (ämneskategori)

ref (ämneskategori)