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Space telescope and optical reverberation mapping project. III. Optical continuum emission and broadband time delays in NGC 5548

Space telescope and optical reverberation mapping project. III. Optical continuum emission and broadband time delays in NGC 5548
Space telescope and optical reverberation mapping project. III. Optical continuum emission and broadband time delays in NGC 5548
We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters (BVRI and ugriz). Combined with ultraviolet data from the Hubble Space Telescope and Swift, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from 1158 Å to the z band (~9160 Å). We find that the lags at wavelengths longer than the V band are equal to or greater than the lags of high-ionization-state emission lines (such as He II λ1640$ and λ 4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with γ α λ4/3. However, the lags also imply a disk radius that is 3 times larger than the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10% of the Eddington luminosity (L = 0.1LEdd). Using optical spectra from the Large Binocular Telescope, we estimate the bias of the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with high levels of BLR contamination (~20%) can be important for the shortest continuum lags and likely has a significant impact on the u and U bands owing to Balmer continuum emission.
0004-637X
1-25
Fausnaugh, M.M.
cfddf3bf-5915-45cc-8597-e27e496dfa60
Mchardy, Ian
4f215137-9cc4-4a08-982e-772a0b24c17e
et al.
Fausnaugh, M.M.
cfddf3bf-5915-45cc-8597-e27e496dfa60
Mchardy, Ian
4f215137-9cc4-4a08-982e-772a0b24c17e

Fausnaugh, M.M. and Mchardy, Ian , et al. (2016) Space telescope and optical reverberation mapping project. III. Optical continuum emission and broadband time delays in NGC 5548. The Astrophysical Journal, 821 (1), 1-25, [56]. (doi:10.3847/0004-637X/821/1/56).

Record type: Article

Abstract

We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters (BVRI and ugriz). Combined with ultraviolet data from the Hubble Space Telescope and Swift, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from 1158 Å to the z band (~9160 Å). We find that the lags at wavelengths longer than the V band are equal to or greater than the lags of high-ionization-state emission lines (such as He II λ1640$ and λ 4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with γ α λ4/3. However, the lags also imply a disk radius that is 3 times larger than the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10% of the Eddington luminosity (L = 0.1LEdd). Using optical spectra from the Large Binocular Telescope, we estimate the bias of the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with high levels of BLR contamination (~20%) can be important for the shortest continuum lags and likely has a significant impact on the u and U bands owing to Balmer continuum emission.

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SPACE TELESCOPE AND OPTICAL REVERBERATION MAPPING PROJECT. - Accepted Manuscript
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Accepted/In Press date: 25 February 2016
e-pub ahead of print date: 11 April 2016
Organisations: Astronomy Group

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Local EPrints ID: 411803
URI: http://eprints.soton.ac.uk/id/eprint/411803
ISSN: 0004-637X
PURE UUID: dcefcf45-26a4-40c8-8989-19364073d38c

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Date deposited: 26 Jun 2017 16:30
Last modified: 16 Dec 2019 18:56

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