Contrasting X-ray/UV time-lags in Seyfert 1 galaxies NGC 4593 and NGC 7469 using <i>AstroSat</i> observations

We study accretion disk-corona connection in Seyfert 1 galaxies using simultaneous UV/X-ray observations of NGC 4593 (July 14-18, 2016) and 7469 (October 15-19, 2017) performed with AstroSat. use the X-ray (0.5-7.0 keV) data acquired Soft Telescope (SXT) UV (FUV: 130-180 nm, NUV: 200-300 nm) obtained Ultra-Violet Imaging (UVIT). also contemporaneous Swift demonstrate AstroSat's capability for X-ray/UV correlation studies. cross-correlation analysis Interpolated Discrete Cross-Correlation Functions found similar results. In case 4593, we that variations X-rays lead to those FUV NUV bands by ~ 38 ks 44 ks, respectively. These lags favour disk reprocessing model, they are consistent previous results within uncertainties. contrast, an opposite trend where soft lag 41 49 The hard Thermal Comptonization model. Our may provide direct observational evidence variable intrinsic emission from which acts as seed thermal a hot corona lamp-post like geometry. non-detection reverberation photons 7469, AstroSat data, is most likely due high rate resulting large emission.