15 research outputs found
Observational effects of interaction in the Seyfert galaxy NGC 7469
Some pecularities of the circummucleus of the Seyfert galaxy NGC 7469 were revealed, plausibly caused by interaction with the satellite IC 5283 and a starlike detail, situated on the edge of the west spiral branch 14 seconds from the nucleus. Shock excited H II regions were noted in the part of NGC 7469 turned toward the satellite IC 5283. The galaxy's central radio structure (lambda approx. 6 cm) stretches in the direction toward the satellite IC 5283 and the starlike detail. The spectum and color index of the starlike detail suggest that it is a cluster of early type stars (M sub V = -19 sup m) and dust clouds (A sub V = 3 sup m), in NGC 7469
The peculiar galaxy Mkn 298 revisited through integral field spectroscopy
Spectroscopic and imaging data of the peculiar galaxy Mkn 298 are presented
in this paper. Narrow-band Halpha and broad-band R images are used to study the
star formation rate in the galaxy and its morphology, which is typical of a
merging system. Long-slit and integral field spectra are used to assess the
kinematics of gas and stars, and the nature of the ionizing source at different
distances from the nucleus. In particular, the nucleus of Mkn 298 is
characterized by peculiar line ratios: [NII] 6583/Halpha is typical of HII-like
regions, while [OI] 6300/Halpha could indicate the presence of an active
galactic nucleus. We show that models where a shock component is added to
photoionization from a starburst allow to reproduce the observed line ratios.
Mkn 298 is thus most likely a star forming galaxy, rather than a galaxy hosting
an active nucleus.Comment: 9 figures, 12 pages, accepted for publication on Astronomy &
Astrophysic
Multiwavelength observations of short time-scale variability in NGC 4151. I. Ultraviolet observations
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 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. 47
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Multiwavelength Observations of Short-Timescale Variability in NGC 4151. I. Ultraviolet Observations
We present the results of an intensive ultraviolet monitoring campaign on the Seyfert I galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously With the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr 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 to 2688 A 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 timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~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 timescale for continuum variations is apparently smaller than the response times of the emission lines.Astronom
The Extraordinary Optical Brightening of the Seyfert Galaxy NGC 4151 Nucleus in 1989-1996 in Frame of Synchrotron Jet Model
Data on continuum variability of the Seyfert galaxy
NGC 4151 nucleus are compiled. The most of them related to new
cycle of the nucleus activity in 1989-1996. X-ray through the UV and
optical data show remarkable similarity in variability characteristics to
those of blazars and do not contradict the supposition that new cycle
of activity mainly caused by synchrotron jet
Characteristics of the continuum variability of the nucleus of
The Structure Function (SF) analysis of variable fluxes of the Seyfert galaxy
NGC 415