Research Note

No apparent accretion mode changes detected in Centaurus X-3

¹ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
e-mail: daniela.mueller@astro.uni-tuebingen.de
² MAXI team, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

Received: 8 August 2011
Accepted: 30 September 2011

Abstract

Aims. Two distinct spectral states have previously been reported for Cen X-3 on the basis of RXTE/ASM observations. Intrigued by this result, we investigated the spectral properties of the source using the enhanced possibilities of the X-ray data now available with the aim to clarify and interpret the reported behavior.

Methods. To check the reported results, we used the same data set and followed the same analysis procedures as in the work that reported the two spectral states. Additionally, we repeated the analysis using the enlarged data sample including the newest RXTE/ASM observations as well as the data from the MAXI monitor and from the INTEGRAL/JEM-X and ISGRI instruments.

Results. We were unable to confirm the reported presence of the two spectral states in Cen X-3 either in the RXTE/ASM data or in the MAXI or INTEGRAL data. Our analysis shows that the flux variations in different energy bands are consistent with a spectral hardness that is constant over the entire time covered by observations.