Two cyclotron lines in Vela X-1?

We present the spectral analysis of our 35 ksec continuous RXTE observation of the High Mass X-ray Binary Vela X-1. The spectral models used normally to describe pulsar spectra like a power law with an exponential cutoff or the NPEX model (Negative Positive EXponential), do not work for our data. Our successful model consists of two NPEX components: one is heavily absorbed, while the other is due to reflection. But we still find large deviations around ∼21 keV and ∼50 keV. We interpret the feature at ∼55 keV as a cyclotron absorption line while the lower deviation might be due to instrument calibration problems around 25 keV in the PCA. [ABSTRACT FROM AUTHOR]