60 research outputs found
Reliability of instrumental recording of the natural gas
The comparison of industrial natural gas flow meters, functioning of which is based on different metering methods usage, was made, recommendations on the optimization of choice of the meter's type in accordance with operation conditions were given
Spectroscopy of Stellar-Like Objects Contained in the Second Byurakan Survey. I
The results of spectroscopic observations of 363 star-like objects from the
Second Byurakan Survey (SBS) are reported. This SBS's subsample has proven to
be a rich source of newly identified quasars, Seyfert type galaxies, degenerate
stars and hot subdwarfs. In the subsample here studied, we identified 35 new
QSOs, 142 White Dwarfs (WDs) the majority of which, 114 are of DA type, 55
subdwarfs (29 of which are sdB-type stars), 10 HBB, 16 NHB, 54 G-type and 25
F-type stars, two objects with composite spectra, four Cataclismic Variables
(CV), two peculiar emission line stars, 17 objects with continuous spectra, as
well as one planetary nebula. Among the 35 QSOs we have found two Broad
Absorption Line (BAL) QSOs, namely SBS 1423+500 and SBS 1435+500A. Magnitudes,
redshifts, and slit spectra for all QSOs, also some typical spectra of the
peculiar stars are presented. We estimate the minimum surface density of bright
QSOs in redshift range 0.3<z<2.2 to be 0.05 per sq. deg. for B<17.0 and 0.10
per sq. deg. for B<17.5.Comment: 22 pages, 3 tables, 4 figures, PASP in pres
Lenticular galaxies with UV-rings
By using the public UV imaging data obtained by the GALEX (Galaxy Ultraviolet
Explorer) for nearby galaxies, we have compiled a list of lenticular galaxies
possessing ultraviolet rings - starforming regions tightly confined to
particular radial distances from galactic centers. We have studied large-scale
structure of these galaxies in the optical bands by using the data of the SDSS
(Sloan Digital Sky Survey): we have decomposed the galactic images into
large-scale disks and bulges, have measured the ring optical colours from the
residual images after subtracting model disks and bulges, and have compared the
sizes of the rings in the optical light and in the UV-band. The probable origin
of the outer starforming ring appearances in unbarred galaxies demonstrating
otherwise the regular structure and homogeneously old stellar population beyond
the rings is discussed.Comment: 9 pages plus one big colour figure in the Appendix; the slightly
expanded version of the paper accepted to Astronomy Letter
Long-term variability of the optical spectra of NGC 4151: I. Light curves and flux correlations
Results of a long-term spectral monitoring of the active galactic nucleus of
NGC 4151 are presented (11 years, from 1996 to 2006). High quality spectra
(S/N>50 in the continuum near Halpha and Hbeta) were obtained in the spectral
range ~4000 to 7500 \AA, with a resolution between 5 and 15 A, using the 6-m
and the 1-m SAO's telescopes (Russia), the GHAO's 2.1-m telescope (Cananea,
Mexico), and the OAN-SPM's 2.1-m telescope (San-Pedro, Mexico). The observed
fluxes of the Halpha, Hbeta, Hgamma and HeII emission lines and of the
continuum at the observed wavelength 5117 A, were corrected for the position
angle, the seeing and the aperture effects.
We found that the continuum and line fluxes varied strongly (up to a factor
6) during the monitoring period. The emission was maximum in 1996-1998, and
there were two minima, in 2001 and in 2005. The Halpha, Hgamma and He II fluxes
were well correlated with the Hbeta flux. We considered three characteristic
periods during which the Hbeta and Halpha profiles were similar: 1996-1999,
2000-2001 and 2002-2006. The line to continuum flux ratios were different; in
particular during the first period, the lines were not correlated with the
continuum and saturated at high fluxes. In the second and third period, where
the continuum flux was small, the Halpha and Hbeta fluxes were well correlated
to the continuum flux, meaning that the ionizing continuum was a good
extrapolation of the optical continuum. The CCFs are often asymmetrical and the
time lags between the lines and the continuum are badly defined indicating the
presence of a complex BLR, with dimensions from 1 to 50 light-days.Comment: A&A, accepte
Spectral Observations of Faint Markarian Galaxies of the Second Byurakan Survey. II
We continue the program of spectroscopic observations of objects from the
Second Byurakan Survey (SBS). This survey contains more than 1300 galaxies and
1700 star-like objects with m(pg)<19.5. Our work is aimed towards the
construction of a complete sample of faint Markarian galaxies. Here, we present
spectroscopic data for 43 galaxies. Amongst them six new Seyfert galaxies are
found, namely two Sy 1 type (SBS 1343+544 and SBS 1433+500), one Sy 2 type (SBS
1620+545) and three likely Sy 2 type galaxies (SBS 1205+556, SBS 1344+527, SBS
1436+597). SBS 1343+544 falls into the luminosity gap between low-redshift QSOs
and high luminosity Sefert galaxies. In the sample studied here, another 36
emission-line galaxies were spectroscopically confirmed. Thus far, 102 SBS
galaxies brighter than m(pg)=17.5 have been observed with the Cananea 2.1m GHO
telescope. The apparent magnitude and redshift distributions, the spectral
classification, the relative intensities of emission lines, and other
parameters, as well as slit spectra for all 43 observed galaxies are presented.Comment: 7 pages, 7 figures, 2 tables, Latex, aaspp4.sty and aj_pt.sty,
Submitted to Astronomical Journa
Minor-axis velocity gradients in spirals and the case of inner polar disks
We measured the ionized-gas and stellar kinematics along the major and minor
axis of a sample of 10 early-type spirals. Much to our surprise we found a
remarkable gas velocity gradient along the minor axis of 8 of them. According
to the kinematic features observed in their ionized-gas velocity fields, we
divide our sample galaxies in three classes of objects. (i) NGC 4984, NGC 7213,
and NGC 7377 show an overall velocity curve along the minor axis without
zero-velocity points, out to the last measured radius, which is interpreted as
due to the warped structure of the gaseous disk. (ii) NGC 3885, NGC 4224, and
NGC 4586 are characterized by a velocity gradient along both major and minor
axis, although non-zero velocities along the minor axis are confined to the
central regions. Such gas kinematics have been explained as being due to
non-circular motions induced by a triaxial potential. (iii) NGC 2855 and NGC
7049 show a change of slope of the velocity gradient measured along the major
axis (which is shallower in the center and steeper away from the nucleus), as
well as non-zero gas velocities in the central regions of the minor axis. This
has been attributed to the presence of a kinematically-decoupled gaseous
component in orthogonal rotation with respect to the galaxy disk, namely an
inner polar disk. The case and origin of inner polar disks are discussed and
the list of their host galaxies is presented.Comment: 13 pages. 3 PostScript figures (Figs. 1 and 3 at lower resolution).
Accepted for publication in A&
Optical and Radio Variability of the Blazar S4 0954+658
We present an optical-to-radio study of the BL Lac object S4 0954+658
observations during 1998-2023. The measurements were obtained with the SAO RAS
Zeiss-1000 1-m and AS-500/2 0.5-m telescopes in 2003-2023, with the RATAN-600
radio telescope at 1.25 (0.96, 1.1), 2.3, 4.7 (3.7, 3.9), 8.2 (7.7), 11.2, 22.3
(21.7) GHz in 1998-2023, with the IAA RAS RT-32 Zelenchukskaya and Badary
telescopes at 5.05 and 8.63 GHz in 2020--2023, and with the RT-22 single-dish
telescope of CrAO RAS at 36.8 GHz in 2009-2023. In this period the blazar had
been showing extremely high broadband activity with the variability amplitude
of flux densities up to 70-100% both in the optical and radio domains. In the
period of 2014-2023 the blazar had been showing the historically highest
activity in the radio wavelengths, and we detected multiple radio flares of
varying amplitude and duration. The large flares last on average from 0.3 to 1
year at 22-36.8 GHz and slightly longer at 5-11.2 GHz. The optical flares are
shorter and last 7-50 days. In the most active epoch of 2018-2023 the
characteristic time scale of variation at 5-22 GHz is about 100 days and
about 1000 days for the state with lower activity in 2009-2014. We found a
general correlation between the optical, radio, and -ray flux
variations, which suggests that we observe the same photon population from
different emission regions. We estimated linear size of this region as 0.5-2 pc
for different epochs. A broadband two components radio spectrum of S4 0954+658
jet was modelled by using both electrons and protons as emitting particles. It
is shown that the synchrotron radio waves in this AGN may be generated by
relativistic protons.Comment: Published in Astrophysical Bulletin Vol.78, N4 (2023
The Leo I Cloud: Secular nuclear evolution of NGC 3379, NGC 3384, and NGC 3368?
The central regions of the three brightest members of the Leo I galaxy group
-- NGC 3368, NGC 3379, and NGC 3384 -- are investigated by means of 2D
spectroscopy. In all three galaxies we have found separate circumnuclear
stellar and gaseous subsystems -- more probably, disks -- whose spatial
orientations and spins are connected to the spatial orientation of the
supergiant intergalactic HI ring reported previously by Schneider et al. (1983)
and Schneider (1985, 1989). In NGC 3368 the global gaseous disk seems also to
be inclined to the symmetry plane of the stellar body, being probably of
external origin. Although the rather young mean stellar age and spatial
orientations of the circumnuclear disks in NGC 3379, NGC 3384, and NGC 3368
could imply their recent formation from material of the intergalactic HI cloud,
the time scale of these secondary formation events, of order 3 Gyr, does not
support the collision scenario of Rood & Williams (1985), but is rather in line
with the ideas of Schneider (1985, 1989) regarding tidal interactions of the
galaxies with the HI cloud on timescales of the intergroup orbital motions.Comment: Accepted to ApJ, 46 pages (figs 18 and 22 are low resolution
Intermediate resolution H-beta spectroscopy and photometric monitoring of 3C 390.3 I. Further evidence of a nuclear accretion disk
We have monitored the AGN 3C390.3 between 1995 and 2000.Two large amplitude
outbursts, of different duration, in continuum and H beta light were observed
ie.: in October 1994 a brighter flare that lasted about 1000 days and in July
1997 another one that lasted about 700 days were detected. The flux in the H
beta wings and line core vary simultaneously, a behavior indicative of
predominantly circular motions in the BLR.Important changes of the Hbeta
emission profiles were detected: at times, we found profiles with prominent
asymmetric wings, as those normaly seen in Sy1s, while at other times, we
observe profiles with weak almost symmetrical wings, similar to those seen in
Sy1.8s. We found that the radial velocity difference between the red and blue
bumps is anticorrelated with the light curves of H beta and continuum
radiation.e found that the radial velocity difference between the red and blue
bumps is anticorrelated with the light curves of H-beta and continuum
radiation. Theoretical H-beta profiles were computed for an accretion disk, the
observed profiles are best reproduced by an inclined disk (25 deg) whose region
of maximum emission is located roughly at 200 Rg. The mass of the black hole in
3C 390.3, estimated from the reverberation analysis is Mrev = 2.1 x 10^9 Msun,
ie. 5 times larger than previous estimatesComment: 18 pages, 13 figures, 4 tables. to appear in Astronomy and
Astrophysic
Star Formation History at the Centers of Lenticular Galaxies with Bars and Purely Exponential Outer Disks from SAURON Data
We have investigated the stellar population properties in the central regions
of a sample of lenticular galaxies with bars and single-exponential outer
stellar disks using the data from the SAURON integral-field spectrograph
retrieved from the open Isaac Newton Group Archive. We have detected chemically
decoupled compact stellar nuclei with a metallicity twice that of the stellar
population in the bulges in seven of the eight galaxies. A starburst is
currently going on at the center of the eighth galaxy and we have failed to
determine the stellar population properties from its spectrum. The mean stellar
ages in the chemically decoupled nuclei found range from 1 to 11 Gyr. The
scenarios for the origin of both decoupled nuclei and lenticular galaxies as a
whole are discussed.Comment: 10 pages, 4 figures, a slightly edited version of the paper published
by Astronomy Letters, v. 37, no.1, 201
- …