SHORT TIMESCALE VARIATIONS OF THE H{alpha} DOUBLE-PEAKED PROFILE OF THE NUCLEUS OF NGC 1097
- Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Campus do Vale, Porto Alegre, RS (Brazil)
- NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland (United States)
- Gemini South Observatory, c/o AURA Inc., Casilla 603, La Serena (Chile)
- Department of Astronomy and Astrophysics, the Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
The broad (FWHM {approx} 10,000 km s{sup -1}) double-peaked H{alpha} profile from the LINER/Seyfert 1 nucleus of NGC 1097 was discovered in 1991 and monitored for the following 11 years. The profile showed variations attributed to the rotation of gas in a non-axisymmetric Keplerian accretion disk, ionized by a varying radiatively inefficient accretion flow (RIAF) located in the inner parts of the disk. We present and model 11 new spectroscopic observations of the double-peaked profile taken between 2010 March and 2011 March. This series of observations was motivated by the finding that in 2010 March the flux in the double-peaked line was again strong, indeed, in 2010 December, even stronger than in the observations of a decade ago. We also discovered shorter timescale variations than in the previous observations: (1) the first, of {approx}7 days, is interpreted as due to 'reverberation' of the variation of the ionizing source luminosity, and the timescale of 7 days as the light crossing time between the source and the accretion disk; this new timescale and its interpretation provides a distance between the emitting gas and the supermassive black hole and as such introduces a new constraint on its mass; (2) the second, of Almost-Equal-To 5 months, was attributed to the rotation of a spiral arm in the disk, which was found to occur on the dynamical timescale. We use two accretion disk models to fit theoretical profiles to the new data, both having non-axisymmetric emissivities produced by the presence of an one-armed spiral. Our modeling constrains the rotation period for the spiral to be Almost-Equal-To 18 months. This work supports our previous conclusion that the broad double-peaked Balmer emission lines in NGC 1097-and probably also in other low-luminosity active nuclei-originate from an accretion disk ionized by a central RIAF.
- OSTI ID:
- 22016063
- Journal Information:
- Astrophysical Journal, Vol. 748, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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