Luminosity dependence of the cyclotron line and evidence for the accretion regime transition in V 0332+53
Abstract
We report on the analysis of NuSTAR observations of the Be-transient X-ray pulsar V 0332+53 during the giant outburst in 2015 and another minor outburst in 2016. We confirm the cyclotron-line energy–luminosity correlation previously reported in the source and the line energy decrease during the giant outburst. Based on 2016 observations, we find that a year later the line energy has increased again essentially reaching the pre-outburst values. We discuss this behaviour and conclude that it is likely caused by a change of the emission region geometry rather than previously suggested accretion-induced decay of the neutron stars magnetic field. At lower luminosities, we find for the first time a hint of departure from the anticorrelation of line energy with flux, which we interpret as a transition from super- to sub-critical accretion associated with the disappearance of the accretion column. Finally, we confirm and briefly discuss the orbital modulation observed in the outburst light curve of the source.
Additional Information
© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 December 9. Received 2016 December 6; in original form 2016 April 29. Published: 14 December 2016. Authors thank E. M. Churazov, who developed the INTEGRAL/SPI data analysis methods and provided the software. This research has made use of data provided by HEASARC (NASA/GSFC and Smithsonian Astrophysical Observatory). This work is based on observations with INTEGRAL, an ESA project with instruments and a science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland and Spain), and with the participation of Russia and the USA. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. The authors acknowledge support from the Deutsches Zentrum für Luft- und Raumfahrt (DLR) through DLR-PT grant 50 OR 0702 (VD), Deutsche Forschungsgemeinschaft (DFG) through WE 1312/48-1 (VFS), the Russian Science Foundation through grant 14-12-01287 (AAM, SST and AAL), the Academy of Finland through grant 268740 and the Foundations' Professor Pool, the Finnish Cultural Foundation (JP).Attached Files
Submitted - 1607.03933v1.pdf
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Additional details
- Alternative title
- Luminosity dependence of the cyclotron line and the accretion regime transition in 2015 giant outburst of V 0332+53
- Eprint ID
- 69049
- DOI
- 10.1093/mnras/stw3236
- Resolver ID
- CaltechAUTHORS:20160715-085654157
- Created
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2016-07-15Created from EPrint's datestamp field
- Updated
-
2021-11-11Created from EPrint's last_modified field
- Caltech groups
- NuSTAR