AKARI observations of circumstellar dust in the globular clusters NGC104 and NGC362

TL;DR

This study uses AKARI infrared observations to detect and analyze circumstellar dust emissions in globular clusters NGC104 and NGC362, revealing dust around certain variable stars and identifying unique sources in NGC362.

Contribution

First infrared imaging survey of these clusters detecting circumstellar dust, highlighting differences in dust emission among variable stars and identifying new dust sources.

Findings

Dust mainly detected around AGB variable stars

Some stars below the giant branch tip show dust emission

Eight red sources with high F24/F7 ratio found in NGC362

Abstract

We report preliminary results of AKARI observations of two globular clusters, NGC104 and NGC362. Imaging data covering areas of about 10x10 arcmin^2 centered on the two clusters have been obtained with InfraRed Camera (IRC) at 2.4, 3.2, 4.1, 7.0, 9.0, 11.0, 15.0, 18.0 and 24.0 mu. We used F11/F2 and F24/F7 flux ratios as diagnostics of circumstellar dust emission. Dust emissions are mainly detected from variable stars obviously on the asymptotic giant branch, but some variable stars that reside below the tip of the first-ascending giant branch also show dust emissions. We found eight red sources with F24/F7 ratio greater than unity in NGC362. Six out of the eight have no 2MASS counterparts. However, we found no such source in NGC104.