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Maser effects in the recombination lines of Eta Carinae

Published online by Cambridge University Press:  03 August 2017

Zulema Abraham ,
Augusto Damineli ,
Philippe Durouchoux ,
Lars-Åke Nyman  and
Felipe McAuliffe
Zulema Abraham
Affiliation:
Instituto Astronômico e Geofísico, Universidade de São Paulo, Brazil
Augusto Damineli
Affiliation:
Instituto Astronômico e Geofísico, Universidade de São Paulo, Brazil
Philippe Durouchoux
Affiliation:
CE Saclay, France
Lars-Åke Nyman
Affiliation:
ESO, La Silla, Chile
Felipe McAuliffe
Affiliation:
ESO, La Silla, Chile

Abstract

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Eta Car is a variable star surrounded by a cloud of gas and dust that absorbs a large part of its optical emission and that showed, in the past two hundred years, several events of mass ejection. It presents a 5.52 year period in the high excitation Heλ 10830 line intensity, indicating periodic changes in the ionizing radiation. Changes in the central velocity of optical lines, with the same periodicity, suggests the presence of a companion star, in a binary orbit. At radio frequencies, the region shows an optically thick bremsstrahlung spectrum, extending to millimeter and submillimeter wavelengths, and strong recombination lines at low quantum numbers showing maser effects. The flux densities, both from the continuum and recombination lines show a periodic behavior similar to that observed at optical wavelengths. We present observations of radio continuum and recombination lines at different millimeter wavelengths for several epochs. Based on these observations we modeled the emitting region as a thin disk and determined its temperature, electron density and velocity distributions using the radiation transfer equations in NLTE.

Type
Part 1. Star Formation
Information
Symposium - International Astronomical Union , Volume 206: Cosmic Masers: From Protostars to Blackholes , 2002 , pp. 234 - 238
Copyright
Copyright © Astronomical Society of the Pacific 2002 

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