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		| Paper: | 
		Time Resolved Spectroscopy of Balloon 090100001: Observations and Modelling of Variations in Atmospheric Parameters | 
	 
	
		| Volume: | 
		392, Hot Subdwarf Stars and Related Objects | 
	 
	
		| Page: | 
		301 | 
	 
	
		| Authors: | 
		Østensen, R.H.; Telting, J.H.; Heber, U.; Jeffery, C.S. | 
	 
	
	
		| Abstract: | 
		We present results from analysis of low-resolution time-series spectroscopy of Balloon 090100001, obtained with the Nordic Optical Telescope in August/September 2004. Variations in surface parameters for the four strongest pulsation periods are investigated by phase folding and fitting to model spectra. A detailed analysis of the dominant mode, together with modelling of the projection factors for a range of different modes, shows that only a radial mode is consistent with the observed velocity and gravity variations. We calculate a pulsational radius of 0.213 R⊙, which corresponds to a total mass of 0.443 M⊙ for the observed mean surface gravity. We warn that these derivations are very sensitive to the accuracy of the radial velocity and gravity variation measurements. | 
	 
	
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