We report the results of long-term simultaneous X-ray and UV monitoring of the nearby ( z = 0.03145 ) Seyfert 1.5 galaxy Mrk 817 using the Neil Gehrels Swift Observatory XRT and UVOT .
Prior work has revealed that the X-ray flux from Mrk 817 has increased by a factor of 40 over the last 40 years , whereas the UV emission has changed by a factor of 2.3 .
The X-ray emission of Mrk 817 now compares to some of the brightest Seyferts , but it has been poorly studied in comparison .
We find that the X-ray ( 0.3-10.0 keV ) and the UVM2 ( roughly 2000–2500Å ) fluxes have fractional variability amplitudes of 0.35 and 0.18 , respectively , over the entire monitoring period ( 2017 Jan. 2 to 2018 Apr .
20 ) .
A cross-correlation analysis is performed on the X-ray ( 0.3-10.0 keV ) and UVM2 light curves over the entire monitoring period , a period of less frequent monitoring ( 2017 Jan. 2 to 2017 Dec. 11 ) , and a period of more frequent monitoring ( 2018 Jan. 12 to 2018 Apr .
20 ) .
The analysis reveals no significant correlation between the two at any given lag for all monitoring periods .
Especially given that reverberation studies have found significant lags between optical/UV continuum bands and broad optical lines in Mrk 817 , the lack of a significant X-ray–UV correlation may point to additional complexities in the inner or intermediate disk .
Mechanical ( e.g. , a funnel in the inner disk ) and/or relativistic beaming of the X-ray emission could potentially explain the lack of a correlation .
Alternatively , scattering in an equatorial wind could also diminish the ability of more isotropic X-ray emission to heat the disk itself .