A Study of Spectral Variability between flaring and non-flaring state in M74 X-1

Abstract

We conducted an extensive long-term spectral and timing study of the ultraluminous X-ray source (ULX) M74 X-1, using data taken between 2001 and 2021 by Chandra and XMM-Newton X-ray observatories. Our analysis shows that flares are present in some observations, whereas they are absent in others. Flaring state exhibits two-component spectra at a lower average flux level, whereas the non-flaring state displays single-component spectra at a higher average flux level. The M74 X-1 spectra are best described by the combination of accretion disk and Comptonization components, a dual thermal disk blackbody model, and a modified multi-temperature disk blackbody model. Using the dual thermal disk blackbody model, we obtain cool and hot temperatures of $T_{in}$ (cool) = $0.38_{-0.06}^{+0.08}$ keV and $T_{in}$ (hot) = $1.67_{-0.13}^{+0.18}$ keV, respectively, suggesting two temperature emitting regions and indicating possible presence of outflowing wind along with the accretion disk. We found a Gaussian feature at $E_{line}$ = $0.96_{-0.11}^{+0.05}$ keV with $\sigma$ = $0.11_{-0.06}^{+0.13}$ keV in the spectra of the flaring state which can be interpreted as the unresolved wind feature in the system when compared to similar feature seen in other ULXs. Plotting the hardness luminosity diagram, we get a trend of increasing hardness with luminosity, suggesting the presence of geometrical beaming in a low-inclination system. Additionally, using the hot disk blackbody component from the dual thermal disk blackbody model, we estimate the mass of the compact object to be M = $7.1_{-1.3}^{+1.4}$ M${}_{\odot }$, classifying it as a stellar-mass black hole and confirming super-Eddington accretion in the system.

Published in The Astrophysical Journal

References in corpus (24)

• An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
• Super-critically accreting stellar-mass black holes as ultraluminous X-ray sources
• An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907
• Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13
• Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
• XMM-Newton observations of the brightest Ultraluminous X-ray sources
• Masses, Beaming and Eddington Ratios in Ultraluminous X-ray Sources
• A spectral-timing model for ULXs in the super-critical regime
• X-ray observations of ultraluminous X-ray sources
• The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2
• Ultraluminous X-ray sources
• M51 ULX-7: super-orbital periodicity and constraints on the neutron star magnetic field
• NuSTAR, XMM-Newton and Suzaku Observations of the Ultraluminous X-ray Source Holmberg II X-1
• Nature of the soft ULX in NGC 247: super-Eddington outflow and transition between the supersoft and soft ultraluminous regimes
• Ionised Emission and Absorption in a Large Sample of Ultraluminous X-ray Sources
• The slow heartbeats of an ultra-luminous X-ray source in NGC 3621
• Soft Extragalactic X-Ray Binaries at the Eddington Threshold
• The Ultraluminous X-ray sources population of the galaxy NGC 7456
• The rare X-ray flaring activity of the Ultraluminous X-ray source NGC 4559 X7
• Broadband X-ray spectral variability of the pulsing ULX NGC 1313 X-2
• Long-term Spectral Variability of the Ultra-luminous X-ray source Holmberg IX X--1
• Quasi periodic whispers from a transient ULX in M\,101: signatures of a fast-spinning neutron star?
• Investigation of the Connection Between X-ray Binaries and Compact Star Clusters in NGC 628
• Exploring the nature of an ultraluminous X-ray source in NGC 628