An Investigation into the Reddening of M22
Abstract
The foreground reddening of M22 has been redetermined using the Balmer lines in cool horizontal-branch stars in the cluster itself. Spectroscopy of these stars is used to match a temperature determined from Hβ, Hγ, and Hδ to one derived from the Paschen continuum using various dereddenings. Results for six stars show the best agreement when E(B-V) = 0.42 with a mean error of ±0.016. An exact value for the reddening is important because of the availability of a statistical parallax for M22, which opens up the possibility of determining an accurate value for the absolute magnitude of the horizontal branch. Variations in the reddening across the cluster are also investigated.
- Publication:
-
The Astronomical Journal
- Pub Date:
- November 1988
- DOI:
- 10.1086/114916
- Bibcode:
- 1988AJ.....96.1649C
- Keywords:
-
- Balmer Series;
- Globular Clusters;
- Red Shift;
- Stellar Spectrophotometry;
- Blue Stars;
- H Alpha Line;
- H Beta Line;
- H Gamma Line;
- Stellar Temperature;
- Ubv Spectra;
- Astrophysics;
- CLUSTERS: GLOBULAR