AR-2019-2020

Figure 15: Relationship between R f and Γ (for spin 0) for the NuSTAR sample Seyfert 1 galaxies. centroid frequency of ∼ 1 . 74 in the course of the observation, while the QPO detected at ∼ 6 . 6 Hz disappeared during hard flarings. The fractional rms at the QPO and the sub-harmonic frequencies increases with photon energy, while at the 2nd harmonic frequencies, the rms seems to be constant. In addition, a soft time lag at QPO and sub-harmonic frequencies is observed up to a time scale of ∼ 35 ms (see Fig. 16), however, at the 2nd harmonic frequencies, there is weak/zero time lag. The broadband X-ray spectral modelling in the 0.7–25 keV band using the doubly absorbed disk plus thermal Comptonization model identified the source to be in the hard intermediate state of black hole X-ray binaries. Using a single zone fluctuation propagation model, they quantified the frequency-dependent fractional rms and time lag. The energy-dependent temporal behaviour can be explained by the variation of the temperature of the corona and the disk with a time lag between them. Broadband X-ray spectral study of ultra-luminous X-ray source M81 X–6 Ultraluminous X-ray sources (ULXs) are a class of extragalactic, compact, non-nuclear X-ray sources with X-ray luminosities in the range of 10 39 − 10 41 erg s − 1 . Vadakkumthani Jithesh , C. Anjana and Ranjeev Misra investigated the temporal and broadband X-ray spectral properties of the ULX M81 X–6 using simultaneous Suzaku and NuSTAR observations. To understand the nature of the source, they first searched for pulsating signals from the source using the NuSTAR observation. However, the temporal analysis did not identify any strong pulsating signals from the source. Alternatively, the broadband spectral modelling with accreting magnetic neutron star continuum model provides a statistically acceptable fit for the broadband X-ray spectrum, and the inferred spectral parameters and X-ray colours are consistent with other pulsating ULXs. Thus, the spectral analysis suggests that M81 X–6 is another candidate ULX pulsar. A compact X-ray emitting binary and 4FGL J0935.3+0901 4FGL J0935.3+0901 is a γ -ray source detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope . Vadakkumthani Jithesh and collaborators have conducted detailed analysis of the LAT data for this source and multi-wavelength studies of the source field. Its γ -ray emission can be described with a power law (Γ = 2 . 0 ± 0 . 2) with an exponential cutoff ( E c = 2 . 9 ± 1 . 6 GeV), while the flux shows significant long-term variations. From analysis of archival Neil Gehrels Swift X-ray Telescope data, they find only one X-ray source in the LAT’s 2 σ error region. Within a 3.7 arcsec radius error circle of the X-ray source, there is only one optical object down to r ∼ 23 mag. Time-resolved photometry of the optical object indicates a likely 2.5 hr