COMPARATIVE STUDY BETWEEN SPECTRA OF ULTRALUMINOUS X-RAY PULSAR AND ACCRETION-POWERED PULSAR IN HIGH MASS X-RAY BINARY SYSTEM BY MEANS OF NUSTAR DATA

• Main Author: Iriana Putra, Yudisthira
• Format: Theses
• Language: Indonesia
• Subjects: Astronomi
• Online Access: https://digilib.itb.ac.id/gdl/view/80736
• Institution: Institut Teknologi Bandung

This research is motivated by the discovery of the new class of pulsar known as Ultraluminous X-ray Pulsar (ULXP), which produces luminosity much higher than the Eddington luminosity of neutron stars. The purpose of this research is to describe the observed X-ray characteristics of the selected objects which contain ULXP and HMXB, and also to identify the involved physical through X-ray spectral analysis by using accretion disk and other relevant models. The description of their X-ray characteristics can be used to study the mechanism which is responsible for the enormous energy production. This data analysis method is used in this research by utilizing NuSTARDAS tools. The selected objects consist of NGC 7793 P13 (P13) which is classified as a ULXP, Cen X-3, Vela X-1, and LMC X-4 which are classified as HMXB pulsars with some differences in terms of luminosity and the host galaxies. It has been shown by the previous studies that in the X-ray HMXB pulsar can be characterized with cyclotron, black body, and bremsstrahlung radiation. On the other hand, ULXP tend to be more similar to ultrauminous X-ray sources (ULX) which are in general contain a black hole as a compact object. Considering that ULXP and HMXB is powered by the same compact object, the spectral comparison is expected to give some insight into how the energy production processes in ULXP may be different if compared to those of HMXB pulsars. The result of the present study shows that both classes can equally be modeled by non thermal components POWERLAW ? HIGHECUT, with major differences in the existence of emission line features in the spectrum of each HMXB pulsars which are absent in that ULXP and the significance of the thermal component in the spectra of ULXP which are not necessary in those of HMXB pulsars. The fact that the same continuum component can be used to model the spectra of both classes support the idea that both are powered by the same object. The absence of the emission line features in the ULXP indicates the existence of mechanism which prevent the production of emission lines. On the other hand, the significance of the thermal component in the spectra of ULXP indicates that the inner radius of the disk is closer to the compact object as compared to that of the HMXB pulsars. It also indicates that the temperature of the disk of ULXP can be higher than that of HMXB pulsars which may surpress the emission line production.