Open AccessInterstellar CO towards X Persei (HD 24534) – II. Two‐component model
Author(s) -
Kaczmarczyk Grzegorz
Publication year - 2000
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.1365-8711.2000.03602.x
Subject(s) - physics , astrophysics , molecular cloud , space telescope imaging spectrograph , radiative transfer , spectral line , line (geometry) , spectrograph , astronomy , hubble space telescope , stars , geometry , mathematics , quantum mechanics
The observations made by the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope ( HST ) of molecular CO in absorbing gas towards X Persei are reported. The two‐component statistical equilibrium model incorporating radiative excitation of CO by line emission at the same velocity that originates in nearby molecular clouds has been used to reproduce high‐resolution GHRS spectra. Earlier analysis indicates that the cloud has a complex structure and at least a two‐component model should be used to obtain accurate results. The spectra obtained from the International Ultraviolet Explorer ( IUE ) were used to complement GHRS data and constrain the space of possible solutions. The new oscillator strengths recommended by Eidelsberg et al. for A–X bands have been used. The results show that one of the components may be attributed to the Perseus OB2 molecular cloud, and the other component to an extension of the Taurus dark cloud. The total CO column density N (CO)=(1.0±0.2)×10 16 cm −2 has been determined. According to the results about 85 per cent of the observed CO belongs to an extension of the Taurus dark cloud. The CO radiation that originates in nearby molecular clouds may be the dominant excitation mechanism of the observed CO. The early results of 13 CO line analysis indicate a 13 CO/ 12 CO ratio of about 40.