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CORRELATION BETWEEN THE INFRARED AND OPTICAL VARIATIONS OF NGC 4151 IN 30 YEARS: CHANGE IN THE SIZES OF THE INFRARED SOURCEстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
- Авторы: Oknyanskij V.L., Lyuty V.M., Taranova O.G., Shenavrin V.I.
- Журнал: Astronomy Letters
- Том: 25
- Номер: 8
- Год издания: 1999
- Издательство: Maik Nauka/Interperiodica Publishing
- Местоположение издательства: Russian Federation
- Первая страница: 483
- Последняя страница: 492
- Аннотация: The correlation between infrared and optical nuclear variability of the Seyfert galaxy NGC4151 is analyzed by using partly published photometric monitoring data for the last 30 years. A cross-correlation analysis is performed both for the entire 30-year-long series and separately for the two states of high nuclear activity in 1969-1980 (cycle A) and in 1990-1998 (cycle B). The lag between the infrared variability (the K band, 2.2 micrometers) and the optical variability (the U band, 0.36 micrometers) in cycle B was found to be Delta t = 35 +/- 8 days, which is approximately twice that in cycle A (Delta t = 18 +/- 6 days). The increase in lag correlates with an increase in optical luminosity. The lag for cycle B was found to depend on wavelength: Delta t = 6 and 8 days in J (1.25 micrometers) and H (1.6 micrometers), respectively, while in L (3.5 micrometers) Delta t = 97 days, which is almost a factor of 3 larger than that in K. The K and L emission is interpreted as thermal dust reradiation of the ultraviolet emission from a region close to the central source. Numerical simulations lead us to conclude that an emission-line region in the shape of a thin ring (torus) seen nearly face-on is in better agreement with observational data than the model of a spherical layer or a torus with a large inclination to the line of sight. The effective torus radius depends on wavelength, which accounts for the larger lag in L than in K. The increase in lag during cycle B is attributable to an increase in nucleus luminosity, which was accompanied by partial sublimation of dust grains in a region closer to the center. The variable J and H emission is apparently determined not so much by dust radiation as by accretion disk (AD) radiation.
- Добавил в систему: Таранова Ольга Георгиевна