Chromospheric and transition region structure of the Herbig emission stars HR 5999 and BN ORI

Details Chromospheric and transition region structure of the Herbig emission stars HR 5999 and BN ORI Chromospheric and transition region structure of the Herbig emission stars HR 5999 and BN ORI

Sep 1986

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986esasp.263..173b&link_type=abstract

In ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE p 173-17

Astronomy and Astrophysics

Astrophysics

6

Chromosphere, Irregular Variable Stars, Iue, Pre-Main Sequence Stars, Stellar Spectra, Interstellar Extinction, Stellar Luminosity, Stellar Mass, Stellar Spectrophotometry

Scientific paper

The IUE spectra of HR 5999 and BN Ori were analyzed, showing strong emission lines of C II, C IV, O I, and Si IV (also Mg II in HR 5999), indicating the presence of chromospheres and transition regions around these high mass premain sequence (PMS) stars. Infrared, optical, and ultraviolet observations show that BN Ori has a spectral type of FO-2 IIIe, a bolometric luminosity of 36 L, age 1.5 million yr, and mass 2 to 2.5 solar mass. As HR 5999 fades, the ratio of total to selective absorption increases indicating the appearance of larger grains or changes in grain alignment. Emission measure distributions are used to investigate the atmospheric structure of the stars. As HR 5999 fades the emission measure distribution rises systematically and the inferred transition region pressures increase. The transition region and chromospheric radiative losses are large and imply input mechanical energy fluxes similar to those of lower mass PMS stars.

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