Open AccessOptical spectroscopy of GX 339−4 during the high–soft and low–hard states – II. Line ionization and emission region
Author(s) -
Wu Kinwah,
Soria Roberto,
Hunstead Richard W.,
Johnston Helen M.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.03915.x
Subject(s) - physics , astrophysics , emission spectrum , spectral line , line (geometry) , ionization , spectroscopy , orbital plane , orbital period , stars , astronomy , geometry , ion , mathematics , quantum mechanics
We have carried out observations of the X‐ray transient GX 339−4 during its high–soft and low–hard X‐ray spectral states. Our high‐resolution spectroscopic observation in 1999 April suggests that the H α line has a single‐peaked profile in the low–hard state as speculated in our previous paper. The He ii λ 4686 line, however, has a double‐peaked profile in both the high–soft and low–hard states. This suggests that the line‐emission mechanism is different in the two states. Our interpretation is that double‐peaked lines are emitted from a temperature‐inversion layer on the accretion disc surface when it is irradiatively heated by soft X‐rays. Single‐peaked lines may be emitted from outflow/wind matter driven by hard X‐ray heating. We have constructed a simple plane‐parallel model and we use it to illustrate that a temperature‐inversion layer can be formed at the disc surface under X‐ray illumination. We also discuss the conditions required for the formation of temperature inversion and line emission. Based on the velocity separations measured for the double‐peaked lines in the high–soft state, we propose that GX 339−4 is a low‐inclination binary system. The orbital inclination is about 15° if the orbital period is 14.8 h.