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15 February 2025
 
  » arxiv » astro-ph/0107075

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Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. III. Optical Observations and the Optical--UV--X-ray Connection
O.Shemmer ; P.Romano ; R.Bertram ; W.Brinkmann ; S.Collier ; K.A.Crowley ; E.Detsis ; A.V.Filippenko ; C.M.Gaskell ; T.A.George ; M.Gliozzi ; M.E.Hiller ; T.L.Jewell ; S.Kaspi ; E.S.Klimek ; M.H.Lannon ; W.Li ; P.Martini ; S.Mathur ; H.Negoro ; H.Netzer ; I.Papadakis ; I.Papamastorakis ; B.M.Peterson ; B.W.Peterson ; R.W.Pogge ; V.I.Pronik ; K.S.Rumstay ; S.G.Sergeev ; E.A.Sergeeva ; G.M.Stirpe ; C.J.Taylor ; R.R.Treffers ; T.J.Turner ; P.Uttley ; M.Vestergaard ; K.von Braun ; R.M.Wagner ; Z.Zheng ;
Date 4 Jul 2001
Subject astro-ph
AbstractWe present the results of a two-year long optical monitoring program of the narrow-line Seyfert 1 galaxy Akn 564. The majority of this monitoring project was also covered by X-ray observations (RXTE) and for a period of ~50 days, we observed the galaxy in UV (HST) and X-rays (RXTE & ASCA) simultaneously with the ground-based observations. Rapid and large-amplitude variations seen in the X-ray band, on a daily and hourly time-scale, were not detected at optical and UV wavelengths, which in turn exhibited much lower variability either on short (one day) or long (several months) time-scales. The only significant optical variations can be described as two 2--4 day events with ~10% flux variations. We detect no significant optical line variations and thus cannot infer a reverberation size for the broad-line region. Similarly, the large X-ray variations seem to vanish when the light curve is smoothed over a period of 30 days. The UV continuum follows the X-rays with a lag of ~0.4 days, and the optical band lags the UV band by ~2 days. No significant correlation was found between the entire X-ray dataset and the optical band. Focusing on a 20-day interval around the strongest optical event we detect a significant X-ray--optical correlation with similar events seen in the UV and X-rays. Our data are consistent with reprocessing models on the grounds of the energy emitted in this single event. However, several large X-ray flares produced no corresponding optical emission.
Source arXiv, astro-ph/0107075
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