The expansion of the trinucleotide repeat (CGG)n in successive generations through maternal meiosis is the cause of fragile X syndrome. Analysis of CA repeat polymorphisms flanking the FMR-1 gene provides evidence of a limited number of "founder" chromosomes and predisposing high-risk haplotypes rel
Observational evidence for expansion in the SSS spectra of novae
✍ Scribed by J.-U. Ness
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 158 KB
- Volume
- 331
- Category
- Article
- ISSN
- 0004-6337
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
For several novae, a bright X‐ray source with a spectrum resembling the class of Super Soft X‐ray Sources (SSS) has been observed a few weeks to months after outburst. Novae are powered by explosive nuclear burning on the surface of a white dwarf, and enough energy is produced to power a radiatively driven wind. Owing to the evolution of the opacity of the ejecta, the observable spectrum gradually shifts from optical to soft X‐rays (SSS phase). It has sometimes been assumed that at the beginning of the SSS phase no more mass loss occurs. However, high‐resolution X‐ray spectra of some novae have shown highly blue‐shifted absorption lines, indicating a significant expansion. In this paper, I show that all novae that have been observed with X‐ray gratings during their SSS phase show significant blue shifts. I argue that all models that attempt to explain the X‐ray bright SSS phase have to accommodate the continued expansion of the ejecta (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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