[en] A study of active galactic nuclei using the Einstein Monitor Proportional Counter (MPC) is described. The MPC data analysis methods are described, including calibration, background subtraction, and spectral analysis. Spectral parameters in the 1-10 keV range are derived for 38 Seyfert or N galaxies and 14 QSOs which exceed a 2-10 keV flux limit of approx. = 9 x 10^-12 erg cm^-2 s^-1. The mean power law energy index [α] is 0.68 +/- 0.05 for the sample as a whole, with no significant dependence on luminosity or classification (Seyfert or QSO). The rms dispersion in α is 0.31, which is due both to measurement errors and real differences in spectral index. Absorbing columns of > 10²² cm^-2 are common among low luminosity (L/sub x/ < 10⁴⁴ erg s^-1) Seyfert galaxies, but relatively rare among higher luminosity objects. The low energy imaging instruments on Einstein are used in conjunction with the MPC to measure smaller column densities or soft excesses in several objects. The MPC data also reveal the ubiquity of variability on timescales of days to months, with lower luminosity Seyferts displaying the largest excursions. Several cases of variable column density have been found. The X-ray spectral results are discussed in terms of the synchrotron self-Compton mechanism and the nonthermal radio spectra which have similar power law indices of approx. = 0.7. The column densities are examined in terms of models for the optical emission line regions, and alternative models in which the X-ray flux actively regulates the ionization structure of a warmer medium. A generalized photoionization code has been developed with particular attention to X-ray effects and recent atomic data

[en] The results of the 9th and 10th IUE episode programs listed are summarized. Observations and basic data reductions were completed for 4 extragalactic programs which were allocated a total of 9 US1 shifts, and 2 stellar investigations which used 10 US2 shifts. Use was made of the Goddard RDAF to obtain better signal to noise ratio spectra using the Gaussian extraction routines. Highlights include the first IUE observations of H1821+643, the second brightest quasar in the sky, and the discovery of accretion disk emission line profiles in the elliptical Seyfert galaxy Arp 102B. Both of these observations were accompanied by nearly simultaneous optical spectrophotometry. As a result of the stellar programs, large amplitude variability associated with the rotation period of the Ap stars 78 Vir and 53 Cam was found

[en] A line due to Ni 2 7378 in the Seyfert galaxies NGC 1068, 2110, 3227, 4151, 5506, and Arp 102 B was detected. The average Ni abundance is about 2 times solar, which is 5 times less than in the filaments of the Crab Nebula. This argues for nucleosynthetic processing in the latter. The Ni 2 line is spatially revolved in NGC 1068, and shows at least a factor of 4 enhancement in the Ni abundance away from the nucleus. The off-nuclear abundance of Ni in NGC 1068 approaches that of the Crab, which strongly suggests that type supernovae enriched the off-nuclear gas clouds

[en] The first X-ray spectrum of a classical Seyfert 2 galaxy, NGC 1068, measured by the Einstein Observatory, is presented. The small soft X-ray luminosity of about 9 x 10 to the 41st ergs/s, the lack of variability, and the Compton temperature of less than 10 to the 6th K are all consistent with the model of Antonucci and Miller (1985); these authors have suggested that NGC 1068 contains a hidden Seyfert 1 nucleus seen indirectly through the electron scattering. However, the steep spectral slope (alpha = 2.0 + or - 0.3) distinguishes the NGC 1068 from the vast majority of Seyfert 1 galaxies. 30 references

[en] The previous unidentified hard X-ray source H 0253 + 193 is coincident with Lynds 1457, a dark nebula at high galactic latitude (l = 159 deg, b = -34 deg). The Einstein IPC position coincides with the peak in the CO map obtained by Hobbs, Blitz, and Magnani (1986). Using interstellar Na I absorption, these authors determined a distance to the cloud of 65 pc, making this the nearest known molecular cloud. The X-ray source can be explained as an embedded T Tauri star with a 2-10 keV luminosity of 1 x 10 to the 31st erg/s. 29 references

[en] Observational and theoretical investigations are reviving interest in the hypothesis that the broad emission lines in some AGN might arise in a relativistic accretion disk. But until now only one object, Arp 102B, has displayed the distinctive double-peaked, asymmetric line shape which is fitted well by the disk model. This paper reports the discovery of a line profile in a second radio galaxy, 3C 332 (z = 0.1511), which is so similar to that of Arp 102B as to suggest the existence of a small but distinct class of objects in which the broad emission lines arise largely in the disk. In the context of the model, the line-emitting region in 3C 332 lies between r1 of about 175 and r2 of about 525r(g). In comparison, the line profile of Arp 102B is fitted with r1 of about 350 and r2 of about 1000. All aspects of the model developed for Arp 102B are consistent with the properties of 3C 332. 24 refs

[en] A new phenomenon has been detected in observations of Hercules X-1 at times consistent with the preeclipse and anomalous dips. The X-ray intensity does not drop for the duration of the dip but is punctuated by short spikes that appear to repeat with a period of approximately 108 minutes. Spectral fits during the on-state, the spike-state, and the low-state suggest a single, constant intrinsic source spectrum which becomes partially covered by an absorbing medium during the spike and low states. All three states can be fitted with the same flat power law between 1 and 20 keV with an absorber of varying covering fraction. Since the morphology and spectrum of the spikes are similar during both the preeclipse and the anomalous dips, and the possible 108 minute period is seen in both states, there is for the first time strong support for a common origin for the preeclipse and anomalous dips. 56 references

[en] Based on optical photometry, the identification of the X-ray source 1E 0630+178 with a blue object inside the Einstein error circle is reported. The question of whether the X-rays could be thermal emission from the surface of a neutron star is addressed. The new optical data confirm that relative fluxes in the optical, X-ray, and gamma-ray bands closely match those of the Vela pulsar. The Vela pulsar is adopted as an observational model for Geminga, whereby only the lack of radio emission from Geminga remains to be accounted for. Previous observational results and theoretical models for Geminga are reviewed in light of the new findings. 47 references

[en] The rotation of a magnetized white dwarf or neutron star accidentally located within or behind the Lynds 1457 molecular cloud, is considered as a model for the hard X-ray source H0253 + 193. It is calculated that all models of this type have a low a priori probability because the positions are so remarkably coincident and because the objects involved are not sufficiently common. A neutron star accreting in a close binary is rejected because its likelihood is extremely small and because the observed position, luminosity, and spectrum of the object are all quite atypical for X-ray binaries. Two other possibilities are considered: (1) an isolated white dwarf or neutron star drifting accidentally into the cloud and accreting sufficient gas to power the X-ray source and (2) a white dwarf accreting in a close binary. 68 refs

[en] The prime objects of the present self-consistent model of a line-emitting accretion disk able to account for the properties observed in a small class of AGNs are Arp 102B and 3C 390.3, whose double-peaked emission lines have been attributed to a Keplerian disk. Improved calculations of the line profile of a relativistic Keplerian disk, generalized to include a variety of emissivity laws as well as local broadening due to electron scattering or turbulence, are noted to fit Arp 102B; analytic and numerical calculations of the solid angle presented by the outer thin disk to an extended isotropic source of illumination demonstrate that the energy budget requirements for line emission from the disk are also satisfied. 27 refs