Статья

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor

I. M. McHardyDepartment of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UKStephen ConnollyDepartment of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UKK. HorneSUPA Physics and Astronomy, University of St. Andrews, North Haugh KY16 9SS, UKEdward M. CackettDepartment of Physics and Astronomy, Wayne State University, 666 W. Hancock Street, Detroit, MI 48201, USAJ. M. GelbordSpectral Sciences Inc, 4 Fourth Avenue, Burlington, MA 01803, USAB. M. PetersonDepartment of Astronomy, The Ohio State University, 140 W 18th Avenue, Columbus, OH 43210, USAMayukh PahariDepartment of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UKN. GehrelsAstrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAM. R. GoadDepartment of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UKP. LiraDepartamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago, ChileP. ArévaloFacultad de Ciencias, Instituto de Fsica y Astronoma, Universidad de Valparaíso, Gran Bretana N 1111, Playa Ancha, Valparaso, ChileR. D. BaldiDepartment of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UKN. BrandtDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAElmé BreedtInstitute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UKHum ChandAryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, IndiaG. C. DewanganInter-University Centre for Astronomy and Astrophysics, Pune 411007, IndiaChris DoneDepartment of Physics, University of Durham, South Road, Durham DH1 3LE, UKM. ElvisHarvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USAD. EmmanoulopoulosDepartment of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UKMichael FausnaughDepartment of Astronomy, The Ohio State University, 140 W 18th Avenue, Columbus, OH 43210, USAS. KaspiSchool of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, IsraelC. S. KochanekDepartment of Astronomy, The Ohio State University, 140 W 18th Avenue, Columbus, OH 43210, USAK. T. KoristaDepartment of Physics, Western Michigan University, 1120 Everett Tower, Kalamazoo, MI 49008-5252, USAI. E. PapadakisDepartment of Physics, Institute of Theoretical and Computational Physics, University of Crete, 71003 Heraklion, GreeceA. R. RaoDepartment of Astrophysics and Astronomy, Tata Institute of Fundamental Research, Mumbai 40005, IndiaP. UttleyAstronomical Institute ‘Anton Pannekoek,’ University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the NetherlandsM. VestergaardDark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, DenmarkM. J. WardHarvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

2018en

ABI

Аннотация

We report the results of intensive X-ray, UV and optical monitoring of the Seyfert 1 galaxy NGC 4593 with Swift. There is no intrinsic flux-related spectral change in the the variable components in any band with small apparent variations due only to contamination by a second constant component, possibly a (hard) reflection component in the X-rays and the (red) host galaxy in the UV/optical bands. Relative to the shortest wavelength band, UVW2, the lags of the other UV and optical bands are mostly in agreement with the predictions of reprocessing of high energy emission from an accretion disc. The U-band lag is, however, far larger than expected, almost certainly because of reprocessed Balmer continuum emission from the more distant broad line region gas. The UVW2 band is well correlated with the X-rays but lags by ~6x more than expected if the UVW2 results from reprocessing of X-rays on the accretion disc. However, if the lightcurves are filtered to remove variations on timescales >5d, the lag approaches the expectation from disc reprocessing. MEMEcho analysis shows that direct X-rays can be the driver of most of the variations in the UV/optical bands as long as the response functions for those bands all have long tails (up to 10d) in addition to a strong peak (from disc reprocessing) at short lag (<1d). We interpret the tails as due to reprocessing from the surrounding gas. Comparison of X-ray to UVW2 and UVW2 to V-band lags for 4 AGN, including NGC 4593, shows that all have UVW2 to V-band lags which exceed the expectations from disc resprocessing by factor < 2. However the X-ray to UVW2 lags are, mostly, in greater excess from the expectations from disc reprocessing and differ between AGN. The largest excess is in NGC 4151. Absorption and scattering may be affecting X-ray to UV lags.

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Идентификаторы

DOI: 10.1093/mnras/sty1983

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