Signs of interaction of the NGC 1275 nucleus with the high-velocity system according to 0.7 sec seeing observations

The nucleus of the Seyfert galaxy NGC 1275 was observed in the B system on 1 December 1989 with seeing 0, 7 seconds using the Zeiss-1000 telescope on Mount Majdanak in Central Asia. Special methods of processing reveal low-contrast details. The nucleus and circumnucleus are stretched in NW-SE direction. There are two narrow filaments near the nucleus in position angles roughly 340 degrees and 320 degrees. The first is directed near the radio jet of the nucleus, the second has broken details curved to the NW or toward the high-velocity system of NGC 1275

Observed and Physical Properties of Core-Collapse Supernovae

I use photometry and spectroscopy data for 24 Type II plateau supernovae to examine their observed and physical properties. This dataset shows that these objects encompass a wide range of ~5 mag in their plateau luminosities, their expansion velocities vary by x5, and the nickel masses produced in these explosions go from 0.0016 to 0.26 Mo. From a subset of 16 objects I find that the explosion energies vary between 0.6x and 5.5x10^51 ergs, the ejected masses encompass the range 14-56 Mo, and the progenitors' radii go from 80 to 600 Ro. Despite this great diversity several regularities emerge, which reveal that there is a continuum in the properties of these objects from the faint, low-energy, nickel-poor SNe 1997D and 1999br, to the bright, high-energy, nickel-rich SN 1992am. This study provides evidence that more massive progenitors produce more energetic explosions, thus suggesting that the outcome of the core collapse is somewhat determined by the envelope mass. I find also that supernovae with greater energies produce more nickel. Similar relationships appear to hold for Type Ib/c supernovae, which suggests that both Type II and Type Ib/c supernovae share the same core physics. When the whole sample of core collapse objects is considered, there is a continous distribution of energies below 8x10^51 ergs. Far above in energy scale and nickel production lies the extreme hypernova 1998bw, the only supernova firmly associated to a GRB.Comment: 25 pages, 7 figures, accepted for Part 1 of Astrophysical Journa

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A Thirteen-Year Study of Spectral Variability in NGC 5548

We present the final installment of an intensive 13-year study of variations of the optical continuum and broad H-beta emission line in the Seyfert 1 galaxy NGC 5548. The data base consists of 1530 optical continuum measurements and 1248 H-beta measurements. The H-beta variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction that the size of the broad-line region is proportional to the square root of the ionizing luminosity. Moreover, the apparently linear nature of the correlation between the H-beta response time and the nonstellar optical continuum arises as a consequence of the changing shape of the continuum as it varies, specifically with the optical (5100 A) continuum luminosity proportional to the ultraviolet (1350 A) continuum luminosity to the 0.56 power.Comment: 20 pages plus 4 figures. Accepted for publication in The Astrophysical Journa

BLR kinematics and Black Hole Mass in Markarian 6

We present results of the optical spectral and photometric observations of the nucleus of Markarian 6 made with the 2.6-m Shajn telescope at the Crimean Astrophysical Observatory. The continuum and emission Balmer line intensities varied more than by a factor of two during 1992-2008. The lag between the continuum and Hbeta emission line flux variations is 21.1+-1.9 days. For the Halpha line the lag is about 27 days but its uncertainty is much larger. We use Monte-Carlo simulation of the random time series to check the effect of our data sampling on the lag uncertainties and we compare our simulation results with those obtained by random subset selection (RSS) method of Peterson et al. (1998). The lag in the high-velocity wings are shorter than in the line core in accordance with the virial motions. However, the lag is slightly larger in the blue wing than in the red wing. This is a signature of the infall gas motion. Probably the BLR kinematic in the Mrk 6 nucleus is a combination of the Keplerian and infall motions. The velocity-delay dependence is similar for individual observational seasons. The measurements of the Hbeta line width in combination with the reverberation lag permits us to determine the black hole mass, M_BH=(1.8+-0.2)x10^8 M_sun. This result is consistent with the AGN scaling relationships between the BLR radius and the optical continuum luminosity (R_BLR is proportional to L^0.5) as well as with the black-hole mass-luminosity relationship (M_BH-L) under the Eddington luminosity ratio for Mrk 6 to be L_bol/L_Edd ~ 0.01.Comment: 17 pages, 10 figures, accepted for publication in MNRA

NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.Comment: 24 pages, 3 tables, 7 figures, accepted for publication in Ap

The Mass of the Black Hole in the Seyfert 1 Galaxy NGC 4593 from Reverberation Mapping

We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the H_beta emission-line light curve with the optical continuum light curve reveals an emission-line time delay of 3.73 (+-0.75) days. By combining this time delay with the H_beta line width, we derive a central black hole mass of M_BH = 9.8(+-2.1)x10^6 M_sun, an improvement in precision of a factor of several over past results.Comment: 22 pages, 3 tables, 5 figures, accepted for publication in Ap

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548

We present the results of three years of ground-based observations of the Seyfert 1 galaxy NGC 5548, which combined with previously reported data, yield optical continuum and broad-line H-beta light curves for a total of eight years. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this eight-year period, the nuclear continuum has varied by more than a factor of seven, and the H-beta emission line has varied by a factor of nearly six. The H-beta emission line responds to continuum variations with a time delay or lag of 10-20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.Comment: 29 pages, 6 figures. Accepted for publication in ApJ (1999 Jan 10

A Spectroscopic and Photometric Study of Short-Timescale Variability in NGC5548

Results of a ground-based optical monitoring campaign on NGC5548 in June 1998 are presented. The broad-band fluxes (U,B,V), and the spectrophotometric optical continuum flux F_lambda(5100 A) monotonically decreased in flux while the broad-band R and I fluxes and the integrated emission-line fluxes of Halpha and Hbeta remained constant to within 5%. On June 22, a short continuum flare was detected in the broad band fluxes. It had an amplitude of about ~18% and it lasted only ~90 min. The broad band fluxes and the optical continuum F_lambda(5100 A) appear to vary simultaneously with the EUV variations. No reliable delay was detected for the broad optical emission lines in response to the EUVE variations. Narrow Hbeta emission features predicted as a signature of an accretion disk were not detected during this campaign. However, there is marginal evidence for a faint feature at lambda = 4962 A with FWHM=~6 A redshifted by Delta v = 1100 km/s with respect to Hbeta_narrow.Comment: 12 pages, 7 figures, accepted for publishing in A&

A Reverberation-Based Mass for the Central Black Hole in NGC 4151

We have undertaken a new ground-based monitoring campaign to improve the estimates of the mass of the central black hole in NGC 4151. We measure the lag time of the broad H beta line response compared to the optical continuum at 5100 A and find a lag of 6.6 (+1.1/-0.8) days. We combine our data with the recent reanalysis of UV emission lines by Metzroth et al. to calculate a weighted mean of the black hole mass, M_BH = 4.57 (+0.57/-0.47) x 10^7 M_sun. The absolute calibration of the black hole mass is based on normalization of the AGN black hole mass - stellar velocity dispersion (M_BH - sigma_*) relationship to that of quiescent galaxies by Onken et al. The scatter in the M_BH - sigma_* relationship suggests that reverberation-mapping based mass measurements are typically uncertain by a factor of 3-4.Comment: 17 pages, 3 tables, 3 figures, accepted for publication in Ap