Terzan 5 transient IGR J17480-2446: variation of burst and spectral properties with spectral states

Abstract

We study the spectral state evolution of the Terzan 5 transient neutron star low-mass X-ray binary IGR J17480-2446, and how the best-fit spectral parameters and burst properties evolved with these states, using the Rossi X-ray Timing Explorer data. As reported by other authors, this is the second source which showed transitions between atoll state and `Z' state. We find large scale hysteresis in the almost `C'-like hardness-intensity track of the source in the atoll state. This discovery is likely to provide a missing piece of the jigsaw puzzle involving various types of hardness-intensity tracks from `q'-shaped for Aquila X-1, 4U 1608-52, and many black holes to `C'-shaped for many atoll sources. Furthermore, the regular pulsations, a diagonal transition between soft and hard states, and the large scale hysteresis observed from IGR J17480-2446 argue against some of the previous suggestions involving magnetic field about atolls and millisecond pulsars. Our results also suggest that the nature of spectral evolution throughout an outburst does not, at least entirely, depend on the peak luminosity of the outburst. Besides, the source took at least a month to trace the softer banana state, as opposed to a few hours to a day, which is typical for an atoll source. In addition, while the soft colour usually increases with intensity in the softer portion of an atoll source, IGR J17480-2446 showed an opposite behaviour. From the detailed spectral fitting we conclude that a blackbody+powerlaw model is the simplest one, which describes the source continuum spectra well throughout the outburst. We find that these two spectral components were plausibly connected with each other, and they worked together to cause the source state evolution. (Truncated).

16 pages, 8 figures, 2 tables, accepted for publication in MNRAS

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Cited by in corpus (18)

• Accreting Millisecond X-Ray Pulsars
• Discovery of the Third Transient X-ray Binary in the Galactic Globular Cluster Terzan 5
• Common Patterns in the Evolution between the Luminous Neutron Star Low-Mass X-ray Binary Subclasses
• Low-frequency QPO from the 11 Hz accreting pulsar in Terzan 5: not frame dragging
• Dense Matter in Neutron Stars with eXTP
• Rapid X-ray variability properties during the unusual very hard state in neutron-star low-mass X-ray binaries
• The pulse profile and spin evolution of the accreting pulsar in Terzan 5, IGR J17480-2446, during its 2010 outburst
• The accretion/ejection link in the neutron star X-ray binary 4U 1820-30 I: A boundary layer-jet coupling?
• Chandra identification of 26 new black hole candidates in the central region of M31
• 50 M31 black hole candidates identified by Chandra and XMM-Newton
• The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars
• Discovery of Polarized X-Ray Emission from the Accreting Millisecond Pulsar SRGA J144459.2-604207
• Nuclear-powered X-ray millisecond pulsars
• X-ray burst ignition location on the surface of accreting X-ray pulsars: Can bursts preferentially ignite at the hotspot?
• Broadband time-resolved spectroscopy of thermonuclear X-ray bursts from 4U 1636-536 using AstroSat
• AstroSat view of the neutron star low-mass X-ray binary GX 340+0
• Broadband spectro-temporal investigation of neutron star low-mass X-ray binary GX 349+2
• AstroSat View of Transient Low-mass X-ray Binary XTE J1701-462: Spectral and Temporal Evolution along the Z-track