THE
29-30 August 2005,
The Fourth Annual Meeting of the Armenian
Astronomical Society was held on August 29-30, 2005, in Byurakan. It was
organized jointly by the Armenian Astronomical Society and the Byurakan
Astrophysical Observatory.
Some 40
astronomers participated in the Meeting, including scientists from Germany (T.Arshakian, V.Hambaryan, T.Khanzadyan), Yerevan State University (YSU), and some 35
scientists from the Byurakan Observatory, as well as 14 YSU students attending
the Summer School which was attached to the ArAS meeting (see "Second Byurakan Summer School").
The meeting
was opened with a welcome address by Haik Harutyunian,
ArAS Co-President, followed by a report by Areg
Mickaelian, another ArAS Co-President, who presented the
The Meeting
was sponsored by Mr. David Nelson (
ABSTRACTS OF
CONTRIBUTIONS IN
(brief texts for some of the
contributions)
The 3D structure of the magnetic field of the Galaxy
R.R. Andreasyan
Byurakan Astrophysical
The activity
of cosmic objects is associated in most cases with the presence of magnetic
fields of different scales, natures and strength. The large-scale magnetic
field in our Galaxy was found in 1950-th, and till now is studied hardly using
all available methods (Parker 1979), based on the analyses of optical and radio
polarization data and measurements of Rotation Measure (RM) of extragalactic
radio sources and pulsars etc. It seems to be very important to take into
account of magnetic field distribution in galaxies, and partially in our
Galaxy, when we study the formation and evolution of galactic structural
features as well as a whole morphology of optical and radio galaxies and
quasars. Many attempts have been made to find the distribution of the
large-scale magnetic field of our Galaxy. It was shown that three classes of
model are viable for the large-scale structure of magnetic field in the disk of
Galaxy: 1. a bisymmetric spiral (BSS),
in which the field direction reverses from arm to arm (Simard-Normandin
& Kronberg 1980; Sofue
& Fujimoto 1983, Andreasyan & Makarov 1989,
Han et.al., 2002); 2. an axisiymmetric spiral (ASS),
with two field reversals inside the Solar Circle, Vallee
(1991,1996), Poezd et al.,(1993); 3. a concentric ring model, Rand & Kulkarni
(1989), Rand & Lyne (1994).
In the recent
study by Indrani & Despande
(1998) a model was suggested involving a magnetic field with the spiral
structure lying in the inter arm regions. Studies of polarized radio emission
from spiral galaxies (Beck et. al.1996) show galactic-scale magnetic fields,
with a pitch angle similar to that, of the spiral arm. Observations by Beck
& Hoernes (1996) show that in the galaxy NGC 6946
also the magnetic spiral structure lies in the
inter-arm region.
Halo magnetic
fields also were observed in many galaxies. The Halo magnetic fields may be: 1.
Poloidal, as in NGC 4631 (Hummel, Beck & Dahlem 1991); 2. May be parallel to the galactic disk, as
in NGC 253 (Beck et. al.1994); 3. Show a filamentary structure, as in NGC 4666
(Dahlem et al.1997). The
Halo magnetic field of our Galaxy was studied by Andreasyan & Makarov (1988, 1989). It was suggested that the
distribution of RMs of pulsars and extragalactic radio sources are consistent
with a Halo magnetic field of opposite sign above and below the Galactic plane.
. Han et al. (1997) (1999) obtained a similar result for the Halo magnetic
field of the Galaxy, and estimated the vertical component of magnetic field to
be B=0.37 ?G, directed toward the North Galactic pole.
These results are in agreement with the dipole magnetic field model for the
Halo, but deformed by the differential rotation of the Galaxy, as proposed by
Andreasyan & Makarov (1988, 1989).
So, in spite
of a large number of papers studying the structure of galactic magnetic field,
there is no generally accepted model.
Here we study
the 3-dimensional distribution of Galactic magnetic field, using all available
rotation measure data of pulsars. Since
the time of our earlier studies, much more data has become available for this
investigation, particularly for more distant pulsars (e.g. Rand & Lyne 1994; Han et al. 1997). The total number of pulsars with known values
of the rotation measure -RM, now is 363. We use this improved database for the
study of 3-dimentional model for whole galactic magnetic field. We divide the
study on two part; 1. The study of the magnetic field in the region near to
galactic plane (plane component) with |z|<z_o pc,
where z – is the distance from the galactic plane, and the value of half
thickness of plane component zo can be changed in
different versions of calculation; 2. The second stage is the study of Halo
component of magnetic field with |z|>z_o pc.
It is well
known that pulsars are strongly concentrated to the galactic plane, and there
are not so many pulsars in the Halo region. Therefore we use different methods
for the study of magnetic fields of Plane component and Halo component. For the
Plane component, using data of much more pulsars, we construct the map of
distribution of magnetic field in the galactic plane. It is known that for
pulsars
RM = \alpha^RxInt(n_eB_LdL), (\alpha=8.1.10^5) (1)
DM = RxIntn_edL,
(2)
where DM – is
the dispersion measure of pulsar, which is known practically for all pulsars
from the observations, BL is the component of the magnetic field along the line
of sight (in G), R- the distance of pulsar from the Sun, ne is the electron
density (cm-3), and the integral is taken over a distance L (pc). Equation (1) and (2) yield
<B_L> = (1/\alpha)d(RM)/d(DM), (3)
and
B_L(DM) =
(1/\alpha)d(RM)/d(DM) (4)
B_L(R)n_e(R) = (1/\alpha)d(RM)/d(R) (5)
Here ‹BL› is
the magnetic field strength averaged along the line of sight, and BL(DM) is the line of sight component of magnetic field
strength at the point with a given value of
DM (unlike to averaged value of ‹BL›), BL(R) is the line of sight component of magnetic
field strength at the point with a distance R from the Sun. It means, that
using the RM-DM and RM-R dependences for a given direction, it is possible to
find BL(DM) for each value of DM, and BL(R)ne(R) for each value of R. We can find the RM-DM
dependence for all directions in the plan of Galaxy using averaging procedure
similar to one presented in Andreasyan et.al (2005). That is, we use the
method, when the coordinates (l;DM) of the center of averaging region (where - l
is the galactic longitude, DM – the dispersion measure), with the constant
number of pulsars, is changing smoothly in the plane of (l;DM).
So we find the dependence of average values of RM from the average value of DM
in every direction, and from the formula (4) find the BL(DM).
This is true also for the RM-R dependence, and from the formula (5) we find the
BL(R)ne(R). In fact we are solving the inverse problem
to construct 2-dimensional model for plane component of Galactic magnetic field
with coordinates (l;DM), or
(l;R).
Some of the
results of calculations are given on the maps of BL(R)ne(R) and BL(DM) (fig1
and fig.2), which are constructed for some restrictions on the z coordinate. In
the fig.1 we have the distribution of BL(R)ne(R) in
the galactic plane (l;R). The Sun is located in the
center of the distribution. The galactic longitude l increases opposite to the
clockwise, and the center of the galaxy is directed to the right (green point).
The distance of the sun from the center of Galaxy is accepted 8.5 kpc. On the
maps pulsars are marked by circles of different color. The blue color of
circles and averaging regions indicates that the magnetic field component is
directed to the observer (RM>0), and the red color we use for the magnetic
field component directed from the observer (RM<0). As dense is the color, as
large is the value of BL(R)ne(R). On the picture we
have the distribution of BL(R)ne(R): for all pulsars
with known RM (-1800<z<1800pc); for the plane component of magnetic field
(-400 <z<400pc, -400<z<0pc and (-0<z<400pc); and the
distribution for the Halo region -1800<z<-400pc and 400<z<1800pc.
The restriction ?z?<1800pc for Halo region comes
from the catalogues of pulsars. On the map with -400 <z<400pc we see the
reversals of magnetic field directions from one spiral arm to another, what is
consistent with the results of previous studies (for example, see Han et al.
2002). But in the maps with -400<z<0pc and -0<z<400pc we see large
differences. The main difference in the pictures for South and North
hemispheres is the magnetic field distribution in the direction of Sagittarius
spiral arm (l ? 55o). The very strong and homogeneous
magnetic field of Sagittarius spiral arm, directed to the observer (blue
color), appears only in the North hemispheres. This distribution is consistent
with the results of Andreasian et al (2003). There
are also other large scale features on the fig.1, the detail investigation of
which is in progress.
The study of
the magnetic field of Halo region (in fig.1 regions -1800<z<-400pc and
400<z<1800pc.), using relatively less observational data, is also in
progress, and gives preliminary results, that are consistent with the results
of Andreasyan & Makarov (1988,1989) and Han et
al. (1997,1999).
We must note
that the results, obtained from the fig.1 for Plane component of Galactic
magnetic field depends strongly from the method of estimation of pulsars
distances. It is obvious, that these results reflect the spiral arm model of
electron density distribution (Taylor & Cordes,
1993), used for the estimation of pulsar distances. It is the reason, that for
the detail investigation we use also the distribution of BL(DM).
We bring here, for example, one of these distributions (fig.2). In this
picture, as one of coordinates, we use the averaged dispersion measure instead
of averaged distance from the Sun. The galactic longitude increases opposite to
clockwise (the center of the galaxy is directed to the right). From the picture
we see, that the maps for pulsars with -20<K<20 (K=DM.Sinb
pc.cm-3, b is the galactic latitude), and for pulsars with -20<K<0 and
0<K<20 are different. The main difference in the pictures for South and
North hemispheres, as in the picture 1, is the magnetic field distribution in
the direction of Sagittarius spiral arm. Magnetic field of Sagittarius spiral
arm appears only in the North hemisphere.
From the
distribution of BL(DM) we can find the distribution of BL(R), using the new
distribution (DM)L-R (see Andreasyan et al. 2005, and Andreasyan 2004, “The
Progress Repor of ANSEF Grant No.
04-ps-astroph-812-73 “THE DISTRIBUTION OF FREE ELECTRONS IN THE GALAXY”;). The
investigation of all these problems is in progress.
L I T E R A T
U R E
Andreasyan,
R.R. & Makarov, A.N.,
1988, Astrophysics, 28, 247.
Andreasyan,
R.R. & Makarov, A.N.,
1989, Astrophysics, 30, 101.
Andreasyan,
R.R. & Makarov, A.N.,
1990, Astrophysics, 31, 560.
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R.R., Hovhannisyan, M.A. & Andreasyan, M.R., 2003, Astrophysics, 46, 341.
Andreasyan,
R.R., Balayan, S. & Mavsisyan, V. 2005, “The
distribution of free electrons in the Galaxy'' Astrophysics, in preparation.
Beck,
R., Carilli, C.L., Holdaway,
M.A., & Klein, U., 1994, A&A, 292, 409.
Beck,
R. & Hoernes, P., 1996, Nat., 379, 47.
Beck,
R.,
Dahlem,
M., Petr, M.B., Lehnert,
M.D., Heckman, T.M., & Ehle, M., 1997, A&A,
in press.
Indrani,
C. & Deshpande, A.A., 1998, New Astron., 4, 33.
Han,
J.L.,
Han,
J.L.,
Han, J.L.,
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A&A, 264, 500.
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E., Beck, R. & Dahlem, M., 1991, A&A, 248,
23.
Parker, E.N.,
1979, Cosmical magnetic fields, their origin and
their activity,
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Rand, R.J.
& Lyne, A.G., 1994, MNRAS, 268, 497.
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M. & Kronberg, P.P., 1980, ApJ,
242, 74.
Sofue,
Y. & Fujimoto, M., 1983, ApJ, 265, 722.
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& Cordes, J.M., 1993, ApJS,
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J.P., 1991, ApJ, 366, 450.
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J.P., 1996, A&A, 308, 433.
3C 390.3 radio galaxy:
the link between the compact jet and the variable optical continuum
T.G. Arshakian
Max-Planck-Institut fur Radioastronomie (MPIfR),
The
"central engine" of AGN is thought to be powered by accretion on a
central nucleus believed to be a super-massive black hole. The localization and
exact mechanism of the energy release in AGN are still not well understood. We
present observational evidence for the link between variability of the radio
emission of the compact jet, optical and X-ray continua emission and ejections
of new jet components in the radio galaxy 3C 390.3. The time delays between the
light curves of the individual jet components and the light curve of the
optical continuum are estimated by using minimization methods and the discrete
correlation function. We find that the variations of the optical continuum are
correlated with radio emission from a stationary feature in the jet. This
correlation indicates that the source of variable non-thermal continuum
radiation is located in the innermost part of the relativistic jet at a distance ~0.4 parsecs from the central engine. We
suggest that the continuum emission from the jet and counterjet
ionizes material in a subrelativistic outflow
surrounding the jet, which results in a formation of two conical regions with
broad emission lines (in addition to the conventional broad line region around
the central nucleus).
The large
distance of the continuum source from the central engine challenges the
existing models in which the broad-line emission is localized exclusively
around the disk or near the central engine. It also questions the assumption of
virialized motion in the BLR in radio-loud AGN, which
forms the foundation of the method for estimating black hole masses from
reverberation mapping.
Active dwarf galaxies as
circumnuclear regions of LSB-galaxies
L.K. Erastova
Byurakan Astrophysical
It is shown
that in their structure, morphology, sizes, and luminosities, the active dwarf
galaxies reveal a tight similarity to the nuclear regions of normal in size
galaxies with active nuclei. There are a number of examples, when a dwarf galaxy turn out to be an active nuclear region of an
extended LSB-galaxy if observed in deep images. On the basis of the abovementioned,
an assumption is made that active dwarf galaxies or some of their parts are
isolated naked nuclear regions of the LSB-galaxies having extended halos, which
may not be observed at present even with the largest telescopes. It may turn
out that all or most of the active dwarf galaxies are giant spiral galaxies
with peripheries or LSB-type host galaxies.
Cosmic expansion and phenomenon of activity
H.A. Harutyunian
Byurakan Astrophysical
Study of MgII 2800 h and k
line profiles
obtained with IUE in A-type stars
J.B. Hovhannesyan
Byurakan Astrophysical
Once more about Astroparticle
S.G. Iskudarian
Byurakan Astrophysical Observatory (BAO), Byurakan
378433, Province
During
1993-2000 years author has presented some short contributions to different
International workshops. There are observational facts in these contributions,
speaking in favour of the unity of micro and macro
worlds of the Universe: fact of the existence of closed looplike
superstring in Our Supergalaxy (1), fact that M87 is
the active nucleus of Our Supergalaxy (2), that M87
with its immediate environment is also the nearest "void" (3),
observational facts about existence of similar structures-similar formations of
large and small scales and later, fact also about similar phenomena of large
and small scales in the Universe (4,5), discovery of the observational facts
about similar behaviour of galaxies and elementary
particles (6), when last ones are in conditions of the beginning moment of the
Big-Bang, when high energies released at high temperatures, discovery of the
fundamental basis of author's idea about subordinating of micro and macro
worlds of the Universe to the same general regularity, in which, may be, is
hidden the most beautiful symmetry in the Universe (it is ejection of the first
type stellar population from the entrails of the second type one (in protogalactic stage, of course) (it is betta
decay in micro world).
All these
above mentioned observational facts,author's
scientific thoughts and ideas (7,8), author's new approaches to some aspects of
extragalactic astrophysics (9,10), all of these were presented to different
international workshops and helped to rise the new branch of science, which was
called by physicists-theoreticians very nice name "astroparticle".
It was found
also a very interesting from the sight of view of the new science observational
fact. One can see physical connection between groups N94 and N106 obviously
from (11) (look at Fig. 1a,b,c (2)). The brightest
members of N94 group show distribution, liking to closed looplike
superstring (fig.1c). There is a similar connection between NGC4038-39 and
NGC4027 in more small scale. Interesting fact is about the similar populations
of both loops-the loop of superstring and the loop of NGC4038-39. Both contain
only very late type population. The loop of superstring consists from late type
galaxies (Fig.1c), the loop of NGC4038-39 consists of
superassociations only. Such a similarity cannot be by chance. Sooner it is a
result of the same way of origin of the loops and strings, but on different
scales.
There has been
made three contributions already about astroparticle
(12-14) by author, that's why the last one has been called "Once more
about astroparticle".
R e f e r e n
c e s
1.S.G.Iskudarian,
"An Example of Closed Looplike
Superstring". Euroconference "The Evolution
of Galaxies on Cosmological Timescales", 30th November-5th December 1998,
Puerto de la Cruz,
2.S.G.Iskudarian,
"Is M87 the Active Nucleus of Our Supergalaxy?".
International workshop on "Galaxy Clusters and Large Scale Structures in
the Universe", Sesto Pusteria (
3.S.G.Iskudarian,
"The Nearest "Void?"", International workshop on
"Observational Cosmology: from Galaxies to Galaxy Systems" Sesto Pusteria (
4.S.G.Iskudarian,
"Similar Structures-Similar Formations of Large and Small Scales",International workshop on"Observational
Cosmology:from Galaxies to Galaxy Systems",Sesto
Pusteria (
5.S.G.Iskudarian,
"Is SN Phenomenon Micro Scale Form of the Big-Bang", International
workshop on"The Largest Explosions Since the
Big-Bang:Supernovae and Gamma Ray Bursts",hosted
by
6.S.G.Iskudarian,
"Similar Behaviour of Galaxies and Elementary Paricles" International workshop on"Hubble
Deep Fields", 9-12 October, 2000,
7.S.G.Iskudarian,"The
Unity of the Universe",International workshop on
"Hubble Deep Fields",6-9 May,1996,
8.S.G.Iskudarian,
"The Universe of Micro and Macro Scales", Astro
Meeting-4, 24-29 November, 1997,
9.S.G.Iskudarian,
"New Approaches in Astrophysics", JENAM-2000, May 29th
10.S.G.Iskudarian,"New Approaches in Astropysics",
Nomination for the Cosmology Prize of the Peter Gruber Foundation, March 2 -
11.M.J.Geller,J.P.Huchra, Astrophys.J.,Suppl.Ser.,
52, 61, 1983.
12.S.G.Iskudarian, "Astroparticle
is My Baby", Carolina Hershell Visitor Programme for Enhance Women,
13.S.G.Iskudarian, "Astroparticle
is My Baby", VAC-4,
14.S.G.Iskudarian, "How was born Astroparticle
- New Branch of Science", International workshop on"Very
High Energy Phenomena in the
Universe", Moriond, 12-19 March, 2005,
Imprints of Star-Formation
T.V. Khanzadyan
Max-Planck-Institut fur Astronomie (MPIA), Heidelberg, Germany
Jets in the HL/XZ Tau region
T.Yu. Magakian
Byurakan Astrophysical
Virtual Observatories
A.M. Mickaelian
Byurakan Astrophysical
The
Astrophysical Virtual Observatories (VOs) have been created for construction of
a modern system for data archiving, extraction, acquisition, reduction, use and
publication, and for establishment a new environment for modern research based
on all-sky, multiwavelength, and multiepoch
observations. The VOs work out standards for efficient work with the databases,
extraction, reduction and analysis of data, like Registries, Data Models,
Uniform Content Descriptors (UCD), Data Access Layer (DAL), VO Query Language
(ADQL), VOTable, VOPlot,
Simple Image Access Protocol (SIAP), Simple Spectral Access Protocol (SSAP),
etc. The Armenian Virtual Observatory (ArVO) project was created on the basis
of the Digitized First Byurakan Survey (DFBS) to make a system for its
efficient use and integrate the Armenian astronomy into the international one.
One of the
main tasks for the ArVO is to create an efficient user interface for the DFBS.
The usage of this database is being developed in the following way: the needed
region of the DFBS plate with given sizes, and the corresponding region from
DSS1 and DSS2 will be extracted, the 2D spectra of objects will be retrieved
and compared with templates, the 1D spectra of objects will be available too,
wavelength and intensity calibration, and a numerical classification will be
made, the DFBS catalog data for objects will be given (position, magnitude,
colors, types), other available data from web (SIMBAD/NED/MAPS/USNO-B1.0) will
be provided, cross-matching with other catalogs will be carried out, and
finally, the multiwavelength data for all objects of interest will be
available.
ArVO was
officially authorized as an International Virtual Observatories Alliance (IVOA)
project in July 2005. ArVO includes also science development, as it is the
actual goal of AVOs. It is the development of an automatic identification
procedure for X-ray, IR and radio sources using the low-dispersion spectra and
all other available databases; optical identification of ~100,000 X-ray, IR
& radio sources; development of an automatic search procedure for modeled
objects; automatic search for new bright AGN in DFBS/DSBS, etc.
Search for new bright QSOs by the core - host galaxy
ratio
A.M. Mickaelian
Byurakan Astrophysical
Though some
100,000 quasars are known, we are not complete with the bright ones. These are
especially important for detailed studies, including their core - host galaxy
relation. Surprisingly, 16th magnitude objects may still be found. The
discovery of all bright quasars is really a problem, as there is not a single
method allowing reveal them independent of their color, presence of radio and/or
X-ray, etc. However, it seems the only feature typical for all of them is the
presence of the host galaxy. We have studied the DSS2 BRI images for all 1193
objects having B<16.5 and/or z<0.3 from the Véron-Cetty and
Véron catalog (2003) and found that about 80% of them have a point-like
image in blue, but extended in red and IR, the host galaxies being mostly red.
Moreover, the core is so weak in IR that only the host galaxy is observable.
These objects may be easily distinguished by the core - host galaxy ratio if
compared from the three colors. The objects being extended in B too, anyway may be distinguished by this ratio. Thus, a
special technology using the multiband images allows reveal new quasars that
could not be found by radio, X-ray or other features. A search with a goal to
find all bright quasars in the region with DEC>0 and |b|>20 has been
undertaken in Byurakan. The 2.6m telescope with the SCORPIO system is being
used for the spectral identification of the candidates.
The inner structure of stellar jets
T.H. Movsessian
Byurakan Astrophysical
Line formation in multi-component stochastic media
A.G. Nikoghossian
Byurakan Astrophysical
Investigation of the large-scale space orientation
model of the
extragalactic double radiosources by the inverse problems
method
H.V. Pikichian, A.V. Kishinevskaya,
T. Hovhannesyan
Byurakan Astrophysical
In frame of
the symmetric model of the extragalactic double radiosources
(EDR), the inverse problem of revealing of the large-scale space orientation of
their radioaxes has been put forward and undergone analitical and numeric investigations. The simplifying
natural assumptions allowed to bring the problem to a
system of integral equations, which may be solved unanimously. In the simplest
case, when a centrisymmetric orientation of radioaxes is assumed, the problem goes to a solution of
simple non-linear system of ariphmetic equations.
First, a numerical modelling of real and observed
distributions of observable quantities has been done, then
the ariphmetic system has been solved for the given
model by the Monte-Carlo method. In a centrisymmetric
simplest model, in this way the accuracy of the searched values of the
derivable quantities has been estimated, depending on the degree of the
statistical richness of the modelled
"observational material". After such a test, the real observational
material was reduced with the same algorithm. It is worth mentioning that an
estimate close to one given formerly by Birch et al. was obtained for the
angular coordinates of the center of anisotropy, and for the third coordinate,
the distance of the center of anisotropy, all our calculations lead to
inaccurate values. The last fact, probably leads to a real necessity for
transition to calculations with axisymmetric model
rather than a simple centrisymmetric anisotropy
model.
Spectral studies of the FBS blue stellar objects
P.K. Sinamian, A.M. Mickaelian
Byurakan Astrophysical
Spectral
observations of the First Byurakan Survey (FBS) blue stellar objects have been
carried out since 1987 with a goal of classification, discovery of new
interesting objects and study of the FBS sample in total. In 1987-1991, the
Byurakan Observatory 2.6m telescope with the long-slit spectrograph UAGS was
used. These photographic spectra were digitized by means of a professional
scanner and reduced with MIDAS as for CCD spectra. Observations for new FBS
objects, as well as repeated observations for confirmation and clarification of
the classification were conducted in 1997-2000 with the BAO-2.6 and OHP-1.93
telescopes by means of modern equipment. Altogether, 485 spectra for 406
objects were obtained, mainly for objects in the FBS zones with central
declinations +35, +39, and +43, as well as a number of objects were observed in
zones with DEC>+61. The principles of digitization and follow-up automatic
reduction of photographic spectra are discussed. The
principles of object classification as for photographic spectra, so as for CCD
spectra are worked out. New white dwarfs, hot subdwarfs, HBB stars,
cataclysmic variables, planetary nebulae, as well as some extragalactic objects
are revealed. The continuation of the survey for blue stellar objects is being
carried out on the basis of the Digitized First Byurakan Survey (DFBS) spectra,
and the selection and the preliminary classification of objects is much more
efficient.