发稿时间:2019-01-03浏览次数:13

USTC Astronomy Seminar Series: Fall
Understanding the absorption line holiday in NGC 5548
Gary Ferland  教授
University of Kentucky
2019/01/07, 4:00pm , the 19th-floor Observatory Hall
This talk is a summary of the Dehghanian+19 paper that recently appeared on the arXiv as arXiv:1812.11578D. We are trying to understand the NGC 5548 emission line "holiday," a period when the broad lines did not respond to changes in the FUV continuum. We study the FUV absorption lines since these are simpler to model and they display similar behavior. We created physical models of the cloud producing absorption FUV lines. We showed that changes in the covering factor of the "obscurer," which heavily modifies the observed SED of NGC 5548, produces changes in the soft X-rays. This changes the ionization of the cloud in ways that reproduce the FUV observations. Other models which change the soft x-ray SED like the Mathur+ Comptonization or Sun+ Falling Corona Models might work as well.
 Gary Ferland is a Professor of Physics and Astronomy at University of Kentucky. He obtained his Ph.D. from the University of Texas in 1978, and he was an associate professor at Ohio State University (1985-1992) before moving to University of Kentucky. Dr. Ferland’s research focuses on theoretical analysis and numerical modeling of emission from HII regions, AGNs, etc. He developed the most popular spectral synthesis code – CLOUDY, which has been widely used to interpret emission-line spectra from various environments.