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Spectral state evolution of 4u 1820-30: the stability of the spectral index of comptonization tail
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Frontera, Filippo Seifina, Elena Titarchuk, Lev G. |
| Copyright Year | 2013 |
| Description | We analyze the X-ray spectra and their timing properties of the compact Xray binary 4U 1820-30. We establish spectral transitions in this source seen with BeppoSAX and the Rossi X-ray Timing Explorer (RXTE). During the RXTE observations (1996 - 2009), the source were approximately approximately 75% of its time in the soft state making the lower banana and upper banana transitions combined with long-term low-high state transitions. We reveal that all of the X-ray spectra of 4U 1820-30 are fit by a composition of a thermal (blackbody) component, a Comptonization component (COMPTB) and a Gaussian-line component. Thus using this spectral analysis we find that the photon power-law index Gamma of the Comptonization component is almost unchangeable (Gamma approximately 2) while the electron temperature kTe changes from 2.9 to 21 keV during these spectral events. We also establish that for these spectral events the normalization of COMPTB component (which is proportional to mass accretion rate ËM) increases by factor 8 when kTe decreases from 21 keV to 2.9 keV. Before this index stability effect was also found analyzing X-ray data for Z-source GX 340+0 and for atolls, 4U 1728-34, GX 3+1. Thus, we can suggest that this spectral stability property is a spectral signature of an accreting neutron star source. On the other hand in a black hole binary Î monotonically increases with ËMand ultimately its value saturates at large ËM. |
| File Size | 719245 |
| Page Count | 51 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20140011104 |
| Archival Resource Key | ark:/13960/t9k40sk5g |
| Language | English |
| Publisher Date | 2013-03-18 |
| Access Restriction | Open |
| Subject Keyword | Evolution Spectral State Comptonization Binary Stars Atolls Spectrum Analysis Spectral Signatures Color-color Diagram Photons X Ray Spectra X Ray Timing Explorer Accretion Disks Stellar Luminosity Black Holes Astronomy Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
