Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud

Details Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud

2005-10-18

arxiv.org/abs/astro-ph/0510510v1

Astron.Astrophys.447:971-989,2006

Astronomy and Astrophysics

Astrophysics

Accepted for publication in Astronomy and Astrophysics. 20 pages. Figure 11 is degraded for posting on astro-ph

Scientific paper

10.1051/0004-6361:20054222

We present ESO/VLT spectra in the 2.9--4.1 micron range for a large sample of infrared stars in the Large Magellanic Cloud (LMC), selected on the basis of MSX and 2MASS colours to be extremely dust-enshrouded AGB star candidates. Out of 30 targets, 28 are positively identified as carbon stars, significantly adding to the known population of optically invisible carbon stars in the LMC. We also present spectra for six IR-bright stars in or near three clusters in the LMC, identifying four of them as carbon stars and two as oxygen-rich supergiants. We analyse the molecular bands of C2H2 at 3.1 and 3.8 micron, HCN at 3.57 micron, and sharp absorption features in the 3.70--3.78 micron region that we attribute to C2H2. There is evidence for a generally high abundance of C2H2 in LMC carbon stars, suggestive of high carbon-to-oxygen abundance ratios at the low metallicity in the LMC. The low initial metallicity is also likely to have resulted in less abundant HCN and CS. The sample of IR carbon stars exhibits a range in C2H2:HCN abundance ratio. We do not find strong correlations between the properties of the molecular atmosphere and circumstellar dust envelope, but the observed differences in the strengths and shapes of the absorption bands can be explained by differences in excitation temperature. High mass-loss rates and strong pulsation would then be seen to be associated with a large scale height of the molecular atmosphere.

Affiliated with

Also associated with

No associations

Rating

Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-193614