X‐Ray Observations of the Seyfert Galaxy LB 1727 (1H 0419−577)

We discuss the properties of the Seyfert 1.5 galaxy LB 1727, also known as 1H0419-577, from X-ray observations obtained by ASCA and ROSAT along with opticalobservations from earlier epochs. ASCA shows only modest (< 20%) variations inX-ray flux within or between the observations. In contrast, a daily monitoringcampaign over 1996 Jun - Sept by the ROSAT HRI instrument reveals the softX-ray (0.1-2 keV) flux to have increased by a factor ~3. The 2 - 10 keV continuum can be parameterized as a power-law with a photonindex Gamma ~ 1.45-1.68 across ~0.7 - 11 keV in the rest-frame. We also reportthe first detection of iron Kalpha line emission in this source. SimultaneousASCA and ROSAT data show the X-ray spectrum to steepen sharply at a rest-energy\~0.75 keV, the spectrum below this energy can be parameterized as a power-lawof slope Gamma ~3.6. We show that LB 1727 is one of the few Seyferts for whichwe can rule out the possibility that the presence of a warm absorber is solelyresponsible for the spectral steepening in the soft X-ray regime. Considerationof the overall spectral-energy-distribution for this source indicates thepresence of a pronounced XUV-bump visible in optical, ultraviolet and softX-ray data.Comment: 27 pages, 7 figures. LaTeX with encapsulated postscript. To appear in the Astrophysical Journa