Exploring the Accretion disc/Corona Connection in NGC 6814: Insights from UV and X-ray spectral-timing studies
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arXiv
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| Natura: | Preprint |
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2025
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| author | Kumari, Kavita Papadakis, I. E. Dewangan, G. C. |
| author_facet | Kumari, Kavita Papadakis, I. E. Dewangan, G. C. |
| contents | 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 $\sim 15~\rm{ks}$ and $30~\rm{ks}$, 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 $θ=70^{\circ}$ (consistent with past estimates for this source) and for spin $\leq 0.5$, 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 $\sim 10-20$% of the accretion power transferred to the corona, $\dot{m}/\dot{m}_{\rm Edd}\sim 0.1$, corona radius of $\sim 6-10~r_g$, and height of $\sim7.5-35~r_g$. 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_21953 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Exploring the Accretion disc/Corona Connection in NGC 6814: Insights from UV and X-ray spectral-timing studies Kumari, Kavita Papadakis, I. E. Dewangan, G. C. High Energy Astrophysical Phenomena Astrophysics of Galaxies 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 $\sim 15~\rm{ks}$ and $30~\rm{ks}$, 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 $θ=70^{\circ}$ (consistent with past estimates for this source) and for spin $\leq 0.5$, 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 $\sim 10-20$% of the accretion power transferred to the corona, $\dot{m}/\dot{m}_{\rm Edd}\sim 0.1$, corona radius of $\sim 6-10~r_g$, and height of $\sim7.5-35~r_g$. 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. |
| title | Exploring the Accretion disc/Corona Connection in NGC 6814: Insights from UV and X-ray spectral-timing studies |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2505.21953 |