Spectrum Analysis of Eclipsing X-Ray Binary M33 X-7

• Main Author: Syafira, Weni
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/42425
• Institution: Institut Teknologi Bandung

M33 X-7 is the first X-ray binary system which shows an eclipse profile. M33 X-7 has a compact object that is thought to be a black hole and the normal star is thought to be a B0 I to O7 I spectral type star. Orbital period of M33 X-7 is 3,45 days and the eclipse duration is 9,6 hours. There are three arguments that support a black hole as a compact object in M33 X-7, which are the absence of pulsation, X-ray luminosity ~ 1039 ergs/s in accordance with X-ray luminosity range of stellar mass black hole, and estimated black hole mass MX> 2,4 . X-ray binaries are divided into 2 types, namely HMXB (High Mass Binary X-ray) in which the normal stars are massive stars and LMXB (Low Mass X-ray Binary) in which the normal stars are low mass star. Compact object in X-ray binary can also be classified into two classes, namely black hole and neutron star. The typical spectrum of a black hole system has a power law component that extends to very high energy and the thermal component of the accretion disk. On the other hand, the typical spectrum of neutron star system has two thermal components namely from accretion disk and the star?s surface. Spectral variability in black hole system can be grouped into three main states namely steep power law, thermal, and hard. Components of the power law and thermal spectrum will always be present in each state but in a different ratio. X-ray spectral analysis was carried out using Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray mission data. Before analyzing the X-ray spectra, the population of X-ray sources in the M33 galaxy was explore through literature studies. The results of population studies show that the contribution of HMXB sources is dominant in X-ray source populations in the M33 galaxy. In other words, the M33 galaxy is highly suitable for the formation of HMXB systems, such as the M33 X-7. Based on NuSTAR data analysis, it is found that the flux variability in M33 X-7 is originated from X-ray eclipses. In other words, M33 X-7 does not exhibit intrinsic variability in light curves, such as outburst commonly found in LMXB. The M33 X-7 spectrum is best described by using power law model. Due to low counts, the entire spectrum of M33 X-7 observations shows better statistics than the spectrum which is divided into before, during and after eclipse phase. Although the M33 X-7 spectrum is best described with power law, it is difficult to fit data at high energy. This is because the model is too simple for very wide energy range.