Open AccessSimultaneous EUV and X‐ray variability of NGC 4051
Author(s) -
Uttley P.,
M I. M.,
Papadakis I. E.,
Cagi I.,
Fruscione A.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03266.x
Subject(s) - physics , astrophysics , power law , schwarzschild radius , galaxy , extreme ultraviolet lithography , context (archaeology) , lag , flux (metallurgy) , astronomy , accretion (finance) , optics , paleontology , computer network , statistics , mathematics , materials science , computer science , metallurgy , biology
We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC 4051. We find a strong correlation between variability in the EUV and medium‐energy X‐ray bands, indicating that both are sampling the same power‐law continuum. The lag between the two bands is less than 20 ks and, depending on model assumptions, may be <1 ks. We examine the consequences of such a small lag in the context of simple Comptonization models for the production of the power‐law continuum. A lag of <1 ks implies that the size of the Comptonizing region is less than 20 Schwarzschild radii for a black hole of mass >10 6 M ⊙ .