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Date and Time of the Query: 2019-08-17 T22:48:23 PDT
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For refcode 2002ApJ...577...98K:
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Copyright by American Astronomical Society. Reproduced by permission
2002ApJ...577...98K Variable Ultraviolet Absorption in the Seyfert 1 Galaxy NGC 3516: The Case for Associated Ultraviolet and X-Ray Absorption S. B. Kraemer, D. M. Crenshaw, I. M. George, H. Netzer, T. J. Turner, and J. R. Gabel Received 2002 April 1; accepted 2002 May 27 ABSTRACT We present observations of the UV absorption lines in the Seyfert 1 galaxy NGC 3516, obtained at a resolution of {lambda}/{DELTA}{lambda} ~ 40,000 with the Space Telescope Imaging Spectrograph (STIS) on 2000 October 1. The UV continuum was ~4 times lower than that observed during 1995 with the Goddard High Resolution Spectrograph (GHRS), and the X-ray flux from a contemporaneous Chandra X-Ray Observatory observation was a factor of ~8 below that observed with ASCA. The STIS spectra show kinematic components of absorption in Ly{alpha}, C IV, and N V at radial velocities of -376, -183, and -36 km s^-1^ (components 1, 2, and 3+4, respectively), which were detected in the earlier GHRS spectra; the last of these is a blend of two GHRS components that have increased greatly in column density. Four additional absorption components have appeared in the STIS spectra at radial velocities of -692, -837, -994, and -1372 km s^-1^ (components 5-8); these may also have been present in earlier low-flux states observed by the International Ultraviolet Explorer. Based on photoionization models, we suggest that the components are arranged in increasing radial distance in the order 3+4, 2, 1, followed by components 5-8. We have achieved an acceptable fit to the X-ray data using the combined X-ray opacity of the UV components 1, 2, and 3+4. By increasing the UV and X-ray fluxes of these models to match the previous high states, we are able to match the GHRS C IV column densities, the absence of detectable C IV absorption in components 5-8, and the 1994 ASCA spectrum. We conclude that variability of the UV and X-ray absorption in NGC 3516 is primarily due to changes in the ionizing flux. Subject headings: galaxies: individual (NGC 3516) - galaxies: Seyfert - ultraviolet: galaxies - X-rays: galaxies
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