Simultaneous GINGA and IUE Observations of the Seyfert Galaxy NGC 3516
Abstract
Simultaneous X-ray and UV observations of the Seyfert 1 galaxy NGC 3516 were carried out to investigate the connection between the variable X-ray and ultraviolet absorption features. Over a 2 week period, X-ray spectra Were obtained with Ginga, simultaneously with UV spectra from IUE. The X-ray spectrum was complex and could be fitted satisfactorily with a warm absorber model, a partial covering model, or a cold reflector model, in addition to an overlying column density of NH ~4 x 10^22^ cm^-2^. The X-ray absorption remained unchanged (in all the spectral models), while the spectral index a changed significantly. The Fe Kα line was generally found to be strong (EW ~ 250-400 eV). The UV spectra displayed a significant variation in the continuum flux, while the absorption features in the C IV λ1550, N V λ1240, and Si IV λ1400 lines stayed constant. A common origin of the UV and X-ray absorption could not be established due to the absence of variability in either the X-ray or the UV absorption. A lower limit on the column densities of the UV absorber is ~2 x 10^19^ cm^-2^. Assuming that the variability in the C IV λ1550 absorption (as detected in the archival data) is due to changes in the ionization level, the UV absorbers should be located closer than 9 Pc from the ionizing source for log N_H_~20, and at smaller distances for higher column densities. Based on estimates of the absorbing properties of a low-luminosity AGN in the framework of broad absorption line (BAL) theories, we suggest that NGC 3516 is consistent with a low-luminosity equivalent of a BAL QSO. Finally, we discuss the likely location of the UV absorbers in optically thin clouds in the broad line region. A common origin of the UV and X-ray absorption in such clouds is probably ruled out.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1993
- DOI:
- 10.1086/172230
- Bibcode:
- 1993ApJ...403..592K
- Keywords:
-
- Ginga Satellite;
- Iue;
- Seyfert Galaxies;
- Spaceborne Astronomy;
- Absorption Spectra;
- Active Galactic Nuclei;
- Astronomical Models;
- Emission Spectra;
- Light Curve;
- X Ray Spectra;
- Astrophysics;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 3516;
- GALAXIES: NUCLEI;
- GALAXIES: SEYFERT;
- ULTRAVIOLET: GALAXIES;
- X-RAYS: GALAXIES