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
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DOI：
10.3847/0004-637x/821/1/56
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
M. Fausnaugh;K. Denney;A. Barth;M. Bentz;M. Bottorff;M. Carini;K. Croxall;G. D. Rosa;M. Goad-M.-Go
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作者：
M. Fausnaugh;K. Denney;A. Barth;M. Bentz;M. Bottorff;M. Carini;K. Croxall;G. D. Rosa;M. Goad-M.-Go
我们提出了基于地面的光学光度监测数据NGC 5548，一个扩展的多波长混响映射活动的一部分。从2014年1月到7月，光变曲线在9个滤镜（BVRI和ugriz）中几乎每天都有节奏。结合哈勃太空望远镜和雨燕的紫外数据，我们确认了连续谱带之间的显着时间延迟作为波长的函数，将波长覆盖范围从1158 nm扩展到z波段（~9160 nm）。我们发现，在波长长于V波段的滞后等于或大于高电离态发射线（如He ii λ 1640和λ 4686）的滞后，这表明连续发射源的物理尺寸与内部宽线区（BLR）相当。滞后随波长的变化趋势与τ_λ = 4 / 3的吸积盘对连续谱后处理的预测基本一致。然而，滞后也意味着一个盘半径是3倍以上的预测从标准薄盘理论，假设测辐射热光度是10%的爱丁顿光度（L = 0.1 L Edd）。使用从大双目望远镜的光谱，我们估计的带间连续滞后的偏差，由于在过滤器中观察到的BLR发射。我们发现，具有高水平的BLR污染（~20%）的滤波器的偏差对于最短的连续滞后可能是重要的，并且由于Balmer连续发射，可能对u和U波段产生重大影响。
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 λ 1640 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 τ ∝ λ 4 / 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 = 0.1 L Edd ). 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.