Search for: All records

The gamma-ray emitting narrow-line Seyfert 1 galaxies are a unique class of objects that launch powerful jets from relatively lower-mass black hole systems compared to the Blazars. However, the black hole masses estimated from the total flux spectrum suffer from the projection effect, making the mass measurement highly uncertain. The polarized spectrum provides a unique view of the central engine through scattered light. We performed spectropolarimetric observations of the gamma-ray emitting narrow-line Seyfert 1 galaxy 1H0323 + 342 using SPOL/MMT. The degree of polarization and polarization angle are 0.122 $\pm$ 0.040 per cent and 142 $\pm$ 9 degrees, while the H $\alpha$ line is polarized at 0.265 $\pm$ 0.280 per cent. We decomposed the total flux spectrum and estimated broad H $\alpha$ full width at half maximum of 1015 km s$^{-1}$. The polarized flux spectrum shows a broadening similar to the total flux spectrum, with a broadening ratio of 1.22. The Monte Carlo radiative transfer code ‘STOKES’ applied to the data provides the best fit for a small viewing angle of 9–24 deg and a small optical depth ratio between the polar and the equatorial scatters. A thick broad-line region with significant scale height can explain a similar broadening of the polarized spectrum compared to the total flux spectrum with a small viewing angle.

To understand the mass distribution and co-evolution of supermassive black holes with their host galaxy, it is crucial to measure the black hole mass of AGN. Reverberation mapping is a unique tool to estimate the black hole masses in AGN. We performed spectroscopic reverberation study using long-term monitoring data with more than 100 spectra of a radio-loud quasar PKS 0736 + 017 to estimate the size of the broad-line region (BLR) and black hole mass. The optical spectrum shows strong H β and H γ emission lines. We generated the light curves of 5100 Å continuum flux (f5100), H β, and H γ. All the light curves are found to be strongly variable with fractional variability of 69 per cent, 21 per cent, 30 per cent for V-band, H β, and H γ light curves, respectively. Along with the thermal contribution, non-thermal emission contributes to the estimated continuum luminosity at 5100 Å. Using different methods, e.g. CCF, JAVELIN, von-neumann, we estimated the size of the BLR, which is found to be 66.4$^{+6.0}_{-4.2}$ light days in the rest frame. The BLR size combined with the line width of H β provides a black hole mass of 7.32$^{+0.89}_{-0.91} \times 10^{7}M_{\odot }$. The source closely follows the BLR size–luminosity relation of AGN.