High-Resolution Measurements of Intersystem Bands of Carbon Monoxide toward X Persei
Abstract
In an echelle spectrum of X Per acquired with the Space Telescope Imaging Spectrograph, we have identified individual rotational lines of 11 triplet-singlet (intersystem) absorption bands of 12CO. Four bands provide first detections for interstellar clouds. From a comparison with the ζ Oph sight line, we find that X Per is obscured by a higher 12CO column density of 1.4×1016 cm-2. Together with the high spectral resolution of 1.3 km s-1, this allows (1) an improved measurement of previously published interstellar f-values for seven bands and (2) an extraction of the first astrophysical oscillator strengths for d-X (8-0), (9-0), and (10-0), as well as for e-X (12-0). The 13CO d-X (12-0) band, previously suspected to exist toward ζ Oph, is now readily resolved and modeled. Our derived intersystem f-values for 12CO include a few mild (<=34%) disagreements with recent predictions from a perturbation analysis calculated for the interstellar excitation temperature. Overall, the comparison confirms the superiority of employing multiple singlet levels in the calculations of mixing coefficients over previous single-level predictions. Based on observations obtained with the NASA/ESA Hubble Space Telescope through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2002
- DOI:
- 10.1086/341549
- arXiv:
- arXiv:astro-ph/0205082
- Bibcode:
- 2002ApJ...572L..95S
- Keywords:
-
- ISM: Abundances;
- ISM: Molecules;
- Molecular Data;
- Ultraviolet: ISM;
- Astrophysics
- E-Print:
- 11 pages (incl. 1 figure). Accepted by ApJ Letters