2025/05/28 by Kavita Kumari, Kumari, Kavita, I. E. Papadakis +3
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2505.21953
openalex publication_date 2025/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We conducted a comprehensive spectral and timing analysis of NGC 6814 using AstroSat's 2019 and XMM-Newton's 2021 observations. Cross-correlation analysis revealed a significant correlation between FUV (1541 Å)/X-ray and UVW1 (2910 Å)/X-ray variations, with delays of ∼ 15~\rmks and 30~\rmks, respectively. We constructed four broadband SEDs after applying aperture correction (for the UVIT filter), subtracting host galaxy and emission line contributions from UV flux, and using mean X-ray spectra alongside selected UV data points. First, we fitted the SEDs with KYNSED model assuming various combinations of inclination, θ, color correction factors, f\rm col, and BH spins. Best-fit models were achieved for θ=70∘ (consistent with past estimates for this source) and for spin ≤ 0.5, while f\rm col is not constrained. KYNSED provided satisfactory fit to all SEDs in the case when the corona is powered by the accretion process, with ∼ 10-20% of the accretion power transferred to the corona, m/m\rm Edd∼ 0.1, corona radius of ∼ 6-10~rg, and height of ∼7.5-35~rg. Model time-lags computed using the SED best-fit results are aligned well with the observed time-lags. Although some of the model parameters are not constrained, the important result of our work is that both the broadband X-ray/UV spectra and the X-ray/UV time-lags in NGC 6814 are consistent with the hypothesis of X-ray illumination of the disc in a lamp-post geometry framework. Within this model framework, we do not need to assume an outer or inner truncated disc.