Occultation Measurement of the Size of the X-Ray-emitting Region in the Active Galactic Nucleus of NGC 1365

By G. Risaliti, M. Elvis, G. Fabbiano, A. Baldi, A. Zezas, M. Salvati. 2007

195 citations recorded by the source corpus.

We present an occultation of the central X-ray-emitting region in the Seyfert galaxy NGC 1365. This extreme spectral variation (from Compton-thin to reflection-dominated and back to Compton-thin in 4 days) has been caught in a 10 day Chandra monitoring campaign consisting of six short (15 ks) observations performed every 2 days. We discuss the implications of this occultation within the scenario of a Compton-thick cloud crossing the line of sight of the X-ray source. We estimate a source size R ≤ 1014 cm and a distance of the cloud from the source D ≤ 1016 cm. This direct measurement confirms the theoretical expectations of an extremely compact X-ray source and shows that the Compton-thick circumnuclear gas is located at a distance from the center on the scale of the broad-line region.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/36cd081e69eeb02bc2ecad64d5285f230ce69480

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. D. M. Alexander
2. H. Netzer
3. Mara Salvato
4. W. N. Brandt
5. P. Hopkins
6. R. Hickox
7. L. Hernquist
8. A. Koekemoer

In Nuclear and High Energy Physics

1. H. Netzer
2. M. Elitzur
3. A. Merloni
4. Luis C. Ho
5. E. Treister
6. A. Comastri
7. Mara Salvato
8. G. Zamorani

Citations in the corpus

• Revisiting the Unified Model of Active Galactic Nuclei (2015, background): “There is now evidence from very detailed studies of a small number of type-I and type-II AGNs, for eclipses by large column density blobs (Risaliti et al. 2007, 2011).”
• AGN Dusty Tori. II. Observational Implications of Clumpiness (2008, background): “Extreme cases involve 4 hr variability (Elvis et al. 2004) and variations in absorbing column of more than 1024 cm 2 within 2 days, indicating Comptonthick X-ray absorption from a single cloud in the broad-line region (Risaliti et al. 2007).”
• The incidence of obscuration in active galactic nuclei (2013, background): “Variable X-ray absorbers on short time-scales are quite common (Risaliti, Elvis & Nicastro 2002; Elvis et al. 2004; Risaliti et al. 2007; Maiolino et al. 2010), and the variability time-scales clearly suggest that these absorbing structures lie within (or are part of) the BLR itself.”
• First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN (2014, background): “30 − 60Rg (Risaliti et al. 2007, 2009b).”
• THREE-YEAR SWIFT–BAT SURVEY OF ACTIVE GALACTIC NUCLEI: RECONCILING THEORY AND OBSERVATIONS? (2010, unknown): “This has been largely discussed in Risaliti et al. (2002, 2007).”
• Evolution of broad-line emission from active galactic nuclei (2013, background): “Risaliti et al. (2002) find obscuring cloud columns in the range ∼1022–1023 cm−2, although an exceptional case of a Compton thick cloud (NH,c > 1024 cm−2) has also been recorded (Risaliti et al. 2007).”
• The dusty heart of nearby active galaxies. II. From clumpy torus models to physical properties of dust around active galactic nuclei (2009, background): “Moreover, X-ray column density variability as seen in many AGN point to rather small clouds and column densities of the order of 1023 cm−2 per cloud (e.g. Risaliti et al. 2007).”