Evidence of an evolved nature of MWC 349A

The Galactic emission-line object MWC 349A is one of the brightest radio stars in the sky. The central object is embedded in an almost edge-on oriented Keplerian rotating thick disc that seems to drive a rotating bipolar wind. The dense disc is also the site of hot molecular emission such as the CO...

Full description

Saved in:
Bibliographic Details
Published inarXiv.org
Main Authors Kraus, Michaela, Arias, Maria Laura, Cidale, Lydia S, Torres, Andrea F
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 18.02.2020
Subjects
Astrochemistry
Carbon monoxide
Emission
Galactic evolution
Gas temperature
Infrared spectra
Isotope ratios
Massive stars
Near infrared radiation
Physics - Astrophysics of Galaxies
Physics - Solar and Stellar Astrophysics
Pre-main sequence stars
Radio stars
Rotation
Stellar evolution
Online AccessGet full text

Cover

More Information
Summary:The Galactic emission-line object MWC 349A is one of the brightest radio stars in the sky. The central object is embedded in an almost edge-on oriented Keplerian rotating thick disc that seems to drive a rotating bipolar wind. The dense disc is also the site of hot molecular emission such as the CO bands with its prominent band heads in the near-infrared spectral range. Despite numerous studies, the nature of MWC 349A is still controversial with classifications ranging from a pre-main sequence object to an evolved supergiant. We collected new high-resolution near-infrared spectra in the K- and L-bands using the GNIRS spectrograph at Gemini-North to study the molecular disc of MWC 349A, and in particular to search for other molecular species such as SiO and the isotope 13CO. The amount of 13CO, obtained from the 12CO/13CO ratio, is recognized as an excellent tool to discriminate between pre-main sequence and evolved massive stars. We find no signatures of SiO band emission, but detect CO band emission with considerably lower intensity and CO gas temperature compared to previous observations. Moreover, from detailed modelling of the emission spectrum, we derive an isotope ratio of 12CO/13CO = 4 +- 1. Based on this significant enrichment of the circumstellar environment in 13CO we conclude that MWC 349A belongs to the group of B[e] supergiants, and we discuss possible reasons for the drop in CO intensity.
ISSN:2331-8422
DOI:10.48550/arxiv.2002.07780