Faint Active Galactic Nuclei Favor Unexpectedly Long Inter-band Time Lags
نویسندگان
چکیده
Inconsistent conclusions are obtained from recent active galactic nuclei (AGNs) accretion disk inter-band time-lag measurements. While some works show that the measured time lags significantly larger (by a factor of $\sim 3$) than theoretical predictions Shakura \& Sunyaev (SSD) model, others find measurements consistent with (or only slightly than) SSD model. These conflicting observational results might be symptoms our poor understanding AGN physics. Here we sources larger-than-expected tend to less-luminous AGNs. Such dependence is unexpected if attributed light-travel-time delay illuminating variable X-ray photons static SSD. If, instead, related not but also outer broad emission-line regions (BLRs; e.g., blended emission lines and/or diffuse continua), result indicates contribution non-disk BLR observed UV/optical continuum decreases increasing luminosity ($L$), i.e., an anti-correlation resembling well-known Baldwin effect. Alternatively, argue coherent thermal fluctuations as relevant timescale, $\tau_{\mathrm{TH}}\propto L^{0.5}$. With future accurate lags, above two scenarios can distinguished by inspecting upon either components in spectra or timescales.
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ژورنال
عنوان ژورنال: The astrophysical journal
سال: 2021
ISSN: ['2041-8213', '2041-8205']
DOI: https://doi.org/10.3847/2041-8213/abf9aa