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We present the results of an intensive ground-based spectrophotometric monitoring campaign of the Seyfert galaxy NGC~4151 for a period of over two months, with a typical temporal resolution of one day. Light curves for four optical continuum bands and the H$\alpha$ and H$\beta$ emission lines are given. During the monitoring period, the continuum at 6925~\AA\ varied by $\sim$17\% while the continuum at 4600~\AA\ varied by $\sim$35\%, with larger variations in the near UV. The wavelength dependence of the variation amplitude also extends into the far UV. The dependence in the 2700$-$7200~\AA\ range can be explained by the different relative starlight contributions at different wavelengths, but the large variability at 1275~\AA\ cannot be explained in this way. The continuum variability timescale is of order 13 days and is similar at all optical wavelength bands. No evidence for a time lag between the optical continuum and the UV continuum and emission lines was found. The H$\alpha$ emission line flux varied by about 12\% with a gradual rise throughout the campaign. Its cross correlation with the continuum light curve gives a lag of $0-2$ days. The variations in the H$\beta$ emission line flux are about 30\% and lag the continuum by 0$-$3 days. This is in contrast to past results where a time lag of 9$\pm$2 days was found for both emission lines. This may be due to a different variability timescale of the {\em{ionizing}} continuum, or to a real change in the BLR gas distribution in the 5.5 years interval between the two campaigns., Comment: 16 pages, LaTeX (including aas2pp4 and epsf), including 10 PostScript figures; To appear in the ApJ (October 20, 1996) Vol. 470

We present the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short time-scale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the {\it International Ultraviolet Explorer} (IUE) for 9.3 days, yielding a pair of LWP and SWP spectra every $\sim$70 minutes, and during four-hour periods for 4 days prior to and 5 days after the continuous monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 \AA\ to 2688 \AA\ went through four significant and well-defined ``events'' of duration 2 -- 3 days during the continuous monitoring period. We find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller time scales (i.e., a few days). The continuum variations in all of the UV bands are {\it simultaneous} to within an accuracy of about 0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip), and do not correlate well with continuum light curves over the (short) duration of the campaign, because the time scale for continuum variations is apparently smaller than the response times of the emission lines., Comment: 39 pages, LaTeX, including 7 PostScript figures; To appear in the ApJ (October 20, 1996) Vol. 470

We present the data and initial results from a combined Hubble Space Telescope (HST)/IUE/ground-based spectroscopic monitoring campaign on the Seyfert 1 galaxy NGC 5548 that was undertaken in order to address questions that require both higher temporal resolution and higher signal-to-noise ratios than were obtained in our previous multiwavelength monitoring of this galaxy in 1988-1989. IUE spectra were obtained once every 2 days for a period of 74 days beginning on 1993 March 14. During the last 39 days of this campaign, spectroscopic observations were also made with the HST Faint Object Spectrograph (FOS) on a daily basis. Ground-based observations, consisting of 165 optical spectra and 77 photometric observations (both CCD imaging and aperture photometry), are reported for the period 1992 October-1993 September, although many of the data are concentrated around the time of the satellite-based program. These data constitute a fifth year of intensive optical monitoring of this galaxy. In this contribution we describe the acquisition and reduction of all of the satellite and ground-based data obtained in this program. We describe in detail various photometric problems with the FOS and explain how we identified and corrected for various anomalies.

We report on the results of a continuation of a large monitoring program of optical spectroscopy of the Seyfert 1 galaxy NGC 5548. The new observations presented here were obtained between 1990 December and 1992 October, and extend the existing database to nearly 1400 days, dating back to 1988 December. The continuum variations are generally smooth and well-resolved, except during the third year of this 4 year project, when the variations were apparently more rapid and of lower amplitude than observed at other times. The broad H(beta) emission line is found to vary in response to the continuum variations with a lag of about 18 days, but with some changes from year to year. The H(beta) transfer functions for each of the 4 yr and for the entire 4 yr database are derived by using a maximum entropy method.

After a minimum in the spring of 1984, when the broad permitted lines were found to become much weaker, the spectrum of NGC 4151 became much more like a Sy 2 (Lyutyi et al., 1984; Chuvaev and Oknyanskij, 1989; Penston and Perez, 1984). Recently, this object returned to the high state after about 8 yr in the semiquiescent phase (Oknyanskij et al., 1991).

The star HD 215441 has the largest magnetic field ever recorded, about 34 Kgauss (1), varying without change of polarity. There are some indications of smooth brightness variations of this star with amplitude ∆m = 0.2 mag. as well as of small smooth variations of linear polarisation correlated with the brightness variations (2-4).

Since there is sufficiently detailed information on the observed galaxies listed in the notes to Table 1, we briefly summarize the main results. From the observations of 94 objects, emission lines are discovered in 64; in one, Markaryan 396, hydrogen absorption lines are observed (this is a white dwarf, probably type DA, and possibly a weak radio source [23]). In the red region there are no lines detected in the objects Markaryan 422(3), 425(3), 431(4), 433(3), 616(3), 621(5), 643(4), 655(5), 656(4), and 658(3); the number of spectrograms is indicated in parentheses; it is possible that Markaryan 643 is a galactic cluster. The objects Markaryan 595, 609, 622, 688, 699, and 700 have broad, hydrogen emission lines and can be attributed to the Seyfert class of galaxies. Markaryan 609, 622, and 699, plus, probably, Markaryan 423, possess moderate Seyfert characteristics. Furthermore, in Markaryan 414, 584, 612, 617, 646, 670, 684, and 693 broad emission lines are observed or suspected. Markaryan 586 is probably similar to a QSO. Further observations are advisable for all these objects. In conclusion, the authors express their gratitude to A. L. Shcherbanovskii for help in the treatment of the spectrograms on the M-222 computer.

U, B, V, J, H, K photometry, polarimatry and spectroscopy of this peculiar object was made from August 1979 to December 1980.

This paper combines data from the three preceding papers in order to analyze the multi-waveband variability and spectral energy distribution of the Seyfert~1 galaxy NGC~4151 during the December 1993 monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium energy ($\sim$1.5~keV) X-rays, with a normalized variability amplitude (NVA) of 24\%. Weaker (NVA = 6\%) variations (uncorrelated with those at lower energies) were seen at soft $\gamma$-ray energies of $\sim$100~keV. No significant variability was seen in softer (0.1--1~keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9\% to 1\% as the wavelength increased from 1275~\AA\ to 6900~\AA. These data do not probe extreme ultraviolet (1200~\AA\ to 0.1~keV) or hard X-ray (2--50~keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of $\ls$0.15~day between 1275~\AA\ and the other ultraviolet bands, $\ls$0.3~day between 1275~\AA\ and 1.5~keV, and $\ls$1~day between 1275~\AA\ and 5125~\AA. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-waveband AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well-fitted with a very steep, red power-law ($ a = -2.5 $). If photons emitted at a ``primary" waveband are absorbed by nearby material and ``reprocessed" to produce emission at a secondary waveband, causality arguments require that variations in the secondary band follow those in the primary band. The tight interband correlation and limits on the ultraviolet and, Comment: 35 pages, LaTeX (including aaspp4), including 7 PostScript figures; To appear in the ApJ (October 20, 1996) Vol. 470

The results of an investigation of a close pair of compact galaxies in the northern sky are reported including the spectra, luminosity, and stability of the system. (JFP)