1999/11/12 by Simon Casassus, Simón Casassus, P. F. Roche +3 · 4 citations
Chemistry · Physics and Astronomy · #Astrophysics and Star Formation Studies #Spectroscopy and Laser Applications #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.2000.03208.x
Accepted for publication in MNRAS
arxiv created 1999/11/12 · openalex publication_date 2000/06/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report on advances in the study of the cores of NGC 6302 and 6537 using infrared grating and echelle spectroscopy. In NGC 6302, emission lines from species spanning a large range of ionization potential, and in particular [Si ix] 3.934 μm, are interpreted using photoionization models (including cloudy), which allow us to re-estimate the temperature of the central star to be about 250 000 K. All of the detected lines are consistent with this value, except for [Al v] and [Al vi]. Aluminium is found to be depleted to one hundredth of the solar abundance, which provides further evidence for some dust being mixed with the highly ionized gas (with photons harder than 154 eV). A similar depletion pattern is observed in NGC 6537. Echelle spectroscopy of IR coronal ions in NGC 6302 reveals a stratified structure in ionization potential, which confirms photoionization to be the dominant ionization mechanism. The lines are narrow (<22 km s−1 FWHM), with no evidence of the broad wings found in optical lines from species with similar ionization potentials, such as [Ne v] 3426 Å. We note the absence of a hot bubble, or a wind-blown bipolar cavity filled with a hot plasma, at least on 1 arcsec and 10 km s−1 scales. The systemic heliocentric velocities for NGC 6302 and 6537, measured from the echelle spectra of IR recombination lines, are found to be −34.8±1 km s−1 and −17.8±3 km s−1. We also provide accurate new wavelengths for several of the infrared coronal lines observed with the echelle.