THE SPECTRAL TYPES OF WHITE DWARFS IN MESSIER 4
- University of British Columbia, Vancouver (Canada)
- Division of Astronomy University of California at Los Angeles, Los Angeles, CA 90095 (United States)
We present the spectra of 24 white dwarfs in the direction of the globular cluster Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs. Determining the spectral types of the stars in this sample, we find 24 type DA and 0 type DB (i.e., atmospheres dominated by hydrogen and helium, respectively). Assuming the ratio of DA/DB observed in the field with effective temperature between 15,000-25,000 K, i.e., 4.2:1, holds for the cluster environment, the chance of finding no DBs in our sample simply due to statistical fluctuations is only 6 x 10{sup -3}. The spectral types of the approx100 white dwarfs previously identified in open clusters indicate that DB formation is strongly suppressed in that environment. Furthermore, all the approx10 white dwarfs previously identified in other globular clusters are exclusively type DA. In the context of these two facts, this finding suggests that DB formation is suppressed in the cluster environment in general. Though no satisfactory explanation for this phenomenon exists, we discuss several possibilities.
- OSTI ID:
- 21378370
- Journal Information:
- Astrophysical Journal, Vol. 705, Issue 1; Other Information: DOI: 10.1088/0004-637X/705/1/398; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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