Two giant outbursts of V 0332+53 observed with INTEGRAL

Abstract

In July 2015, the high-mass X-ray binary V 0332+53 underwent a giant outburst, a decade after the previous one. This system hosts a strongly magnetized neutron star. During the 2004--2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. The long ($\approx 100$ d) and bright ($L_{\mathrm{x}}\approx 10^{38}$ erg s${}^{-1}$) 2015 outburst offered the opportunity to study during another outburst the unique properties of the fundamental CRSF and its dependence on the X-ray luminosity. The source was observed by the INTEGRAL satellite for $\sim 330$ ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004--2005 and left unpublished so far. We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the $3-100$ keV luminosity of $E_1\propto -0.095(8)L_{37}$ keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004--2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data we also report on the detection of a $\sim 34$ d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.

arXiv commentAccepted for publication on A&A

References in corpus (29)

• The Swift/BAT Hard X-ray Transient Monitor
• The INTEGRAL Science Data Centre (ISDC)
• Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
• V0332+53 in the outburst of 2004--2005: luminosity dependence of the cyclotron line and pulse profile
• Discovery of a flux-related change of the cyclotron line energy in Her X-1
• A model for cyclotron resonance scattering features
• SPI/INTEGRAL in-flight performance
• A reflection model for the cyclotron lines in the spectra of X-ray pulsars
• NuSTAR discovery of a luminosity dependent cyclotron line energy in Vela X-1
• Completing the puzzle of the 2004-2005 outburst in V0332+53: the brightening phase included
• The Be/X-ray Transient V0332+53: Evidence for a tilt between the orbit and the equatorial plane?
• No anti-correlation between cyclotron line energy and X-ray flux in 4U 0115+634
• Outburst of GX 304-1 monitored with INTEGRAL: positive correlation between the cyclotron line energy and flux
• INTEGRAL observation of the high-mass X-ray transient V0332+53 during the 2005 outburst decline
• Outbursts Large and Small from EXO 2030+375
• The High Energy Emission of the Crab Nebula from 20 keV to 6 MeV with INTEGRAL
• Origin of Two Types of X-Ray Outbursts in Be/X-Ray Binaries. I. Accretion Scenarios
• RXTE Discovery of Multiple Cyclotron Lines during the 2004 December Outburst of V0332+53
• Cyclotron Line Variability
• The Spiros imaging software for the Integral SPI spectrometer
• INTEGRAL observations of V0332+53 in outburst
• GRO J1008-57: an (almost) predictable transient X-ray binary
• Effects of the Geometry of the Line-Forming Region on the Properties of Cyclotron Resonant Scattering Lines
• Timing and Spectral properties of Be/X-ray pulsar EXO 2030+375 during a Type I outburst
• An unexpected drop in the magnetic field of the X-ray pulsar V0332+53 after the bright outburst occurred in 2015
• Recovery of the orbital parameters and pulse evolution of V0332+53 during a huge outburst
• Orbital parameters of V 0332+53 from 2015 giant outburst data
• The reawakening of the sleeping X-ray pulsar XTE J1946+274
• Recent activity of the Be/X-ray binary system SAX J2103.5+4545

Cited by in corpus (5)

• Cyclotron lines in highly magnetized neutron stars
• Luminosity dependence of the cyclotron line and evidence for the accretion regime transition in V 0332+53
• Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions
• Inversion of the decay of the cyclotron line energy in Her X-1
• A broadband self-consistent modelling of the X-ray spectrum of 4U 1626--67