Mass and radius are fundamental stellar parameters most complex for
measurement. Meanwhile, these parameters are necessary for star modeling
and explaining physical processes in them and the evolution of these objects.
We evaluated the quality of flare activity forecasting in active regions
based on spectral-polarization observations at RATAN-600 in the wide
range of radio waves.
Evolutionary status of the high-luminous star V1302 Aql (associated with
the powerful IR source IRC+10420) has not been determined for a long time.
The nature of ultraluminous X-ray sources (ULXs) remains a subject of
controversy and debates for past two decades.
First temperature measurements over active regions have been obtained
based on an automatic iterative method applied to the data observed at
Currently, attempts are underway to establish a taxonomy of comets on
the basis of their composition and to link it to the place of their
Monitoring of the continuum of SETI candidates with RATAN-600 (SAO RAS
The on-sky position of GRB 160625B (Dirirsa et al., GCN Circ. 19580)
has been observed by Mini-MegaTORTORA
nine-channel wide-field monitoring system with high temporal
resolution before, during and just after the LAT trigger
time (T0 = 2016-06-25 22:43:24).
Using optical spectroscopy a nature of ultraluminous X-ray sources in
external galaxies whose X-ray luminosities exceed the luminosities of the
brightest black holes in our Galaxy by thousands of times was revealed.
The sample of the Local Volume galaxies (distance smaller than 10 Mpc)
gives a unique opportunity to study the properties of galaxies including
the weakest objects: the absolute magnitude MB
and the virial mass Mvir
Based on the magnetic field measurements of the chemically peculiar star
HD965, conducted in 2000-2015 with the SAO RAS 6-m telescope, we have found
that this object is an ultra slow magnetic rotator with a rotation period of
about 20 years. The obtained result is strong evidence in favor of the
so-called fossil theory of large-scale field formation in these objects.
On the detection of gravitational waves by the Laser Interferometer
Gravitational-Wave Obsevatory (LIGO)
The Galactic low-mass X-ray binary GS 2023+338 was discovered during
the burst on May 22, 1989 with the Japanise satellite Ginga (aka Galaxy).
The flux reached 17 crabs (this unit of flux measurement is an bright
X-ray source, Crab Nebula) at 10-35 keV.
Variability of emission at scales from fractions of a second to tens of
years is one of characteristic properties of different celestial objects.
Transient events are also the emission variability though not regularly
observed. Such events are difficult to detect for that reason. During
the analysis of the surveys carried out on RATAN-600, it was found that
almost one fifth of the detected sources shows significant radio flux
variations. We discovered three radio transients in our search.
Currently, there is very little information on comets which are
active beyond the orbit of Jupiter. Dust tails and comas of such
comets are observed at large distances from the Sun (greater than 5 au),
where water ice sublimation is inconsiderable.
Two new LBV stars have been discovered in the Andromeda Galaxy.
Since the middle of the last century, only four such objects had been
known in this galaxy, they were discovered by American scientists
Edwin Hubble and Allan Sandage with colleagues. Astronomers from SAO
added two more stars to this list in 2015.
The March 20 total solar eclipse was visible over the North Atlantic
and Arctic Oceans. The partial phases were observed in Europe, the
western regions of Russia, Central Asia, the Middle East and partially
in the North Africa. In the Special Astrophysical Observatory it was
also partial with the Moon coverage of the Sun of less than 40%.
In January 2015 using the Mini-MegaTORTORA multichannel optical
sky-monitoring system with subsecond temporal resolution, the observations
of comet C/2014 Q2 (Lovejoy) and asteroid 357439 2004 BL86 were carried out.
Our recent observations with the Hubble Space Telescope (August 29, 2014)
led to revealing a highly isolated dwarf spheroidal galaxy
a distance of 2.12±0.07 Mpc from the Milky Way. The dSph galaxy
locates on the southern sky
J2000.0) and has a stellar mass about 1/10000 of the Milky Way mass.
SS433 is a close binary system, one star is a supergiant, a second one is
a black hole. The supergiant's matter overflows to the neighbouring black
hole and floods the hole with a powerful mass flux: 6 millions of billions
tons per second (that is one Earth mass for 11 days). Even a black hole
cannot accept such an enormous mass flux, a supercritical accretion disk
The variability of the spectrum of the optical component of the IR-source
IRAS01005+7910 was discovered for the first time in the BTA spectra .
Long-term monitoring of the object was carried out during 2002-2013 with
a high spectral resolution (R=60000).
Astronomers of the SAO together with an international group of scientists
have proposed an explanation to the long-standing
mystery of why magnetic fields are more common amongst cool white dwarf
stars than amongst young and hotter ones.
According to the most popular cosmological paradigm, the greater part
of the galaxy mass is accumulated in the dark matter halo. The mass
value can be measured in terms of various model assumptions, analyzing
the available observational data, for example, the distribution of the
rotation velocity at large distances from the center (the rotation curve).
It is much more difficult to make an estimate of the shape of the dark
halo in a particular galaxy, i.e. to understand whether it is spherical,
flattened or triaxial.
SAO researchers have discovered that supercritical accretion disks eject
hot gas with a velocity of a few thousand kilometers per second.
The supercritical regime of accretion onto black holes is very important
In the first half-billion years just after our Universe was born,
supermassive black holes (quasars) began to appear and grow in centers
of young galaxies.
A unique set of linear polarization measurements in the spectrum of
the Seyfert galaxy Mkn 6 was obtained with the 6-meter telescope.
It was shown for the first time that the analysis of the polarization
angle dependence on the velocity across the hydrogen line profiles due
to the gas emission in the broad-line formation region near the massive
AGN allows to determine directly from observations the type of motion
in the broad-line formation region, which in the case of Mkn 6 turned
out to be Keplerian at distances less than 0.02 pc from the nucleus.
The lower mass limit determined for the supermassive black hole in
the center of the Mkn 6 galaxy is equal to 150 million solar masses.
High spectral resolution echelle spectroscopy of supergiants at the
post-ABG stage resulted in the formation of a sample of these objects
possessing a high infrared excess, an emission at 21 μm, and also large
overabundances of carbon and heavy metals, synthesized by the s-process
at the preceding AGB stage.
Among the newly observed objects, we discovered the galaxies UGC 2172
and NGC 3239 in the stage of a vigorous burst of star formation.
The spatially resolved structure near the hydrogen emission Hα
line was found in the spectrum taken with the BTA/SCORPIO in June, 2013.
It extendeds by 6.5 arcsec along the frame vertical, and by 2600 km/s
(radial velocity) along the centre line of the frame. The structure has
been formed by an empty spherical shell that has erupted during the
outburst 13.5 years ago, and is now expanding with the velocity of
1300 km/s. The expansion velocity of 0.24 arcsec/yr corresponds to
the distance to the nova of 1.2±0.2 kpc.
An estimate the rotation period of cometary nuclei is important for
understanding and describing the physical processes of the cometary activity.
Unfortunately, the measurements of the rotation periods of the comet
nucleus depend on the model assumptions and it is one of the main reasons
for the scatter of the estimates given in various articles for a given comet.
Ultraluminous X-ray sources (ULXs) are located in external galaxies, their
X-ray luminosities are thousand times greater than those of brightest black
holes in the Galaxy. It has been found in the VLT and BTA observations of
extragalactic stellar clusters related to the ULXs, that these objects are
stellar-mass black holes with supercritical accretion disks.
Recent studies indicate that stars are most likely forming within the
binary and multiple systems. In our Galaxy, according to various
estimates, at least 50 percent of stars have companions. Therefore,
the study of binary and multiple stars is important for understanding
the mechanisms of star formation in general.
We present a photometric and spectroscopic study of the unique
isolated nearby galaxy KKR25.
We find a transition of LBV star from the LBV instability strip to the
region of classical WN for the first time.
The HH flow associated with young stellar object HL Tau has an exciting
history and even until now the origin of some its features is not clear yet.
Flow starts as the relatively faint and narrow jet from HL Tau
but at distance of about 20" from the star it abruptly changes direction
by about 14 deg and becomes much brighter and appears complex knotty
Galaxies with polar rings (PRGs) are a unique class of extragalactic objects,
consisting of a ring or disk of gas, stars and dust orbiting in a plane
nearly perpendicular to the disk of a central galaxy.
The results of long-term monitoring of Gigahertz-Peaked Spectrum sources
were found the statistically significant differences (0.05 significance
level) in the high-frequency spectral index distribution between subgroups
of galaxies and quasars.
According to modern views on the evolution and origin of stars,
most of the stars are members of binary systems. If both
components are massive enough, they eventually go supernova one by
one, whereas their cores collapse, turning into black holes or
The history of star formation was successfully analyzed for the first
time based on the spectra of the stellar population of dwarf galaxies
of low surface brightness outside the Local Group.
We have investigated the stellar population of two dwarf spheroidal
galaxies KDG61 and KDG64 in the central part of a close group of
Solar flare activity is produced by the processes of accumulation and
release of energy in an active region. A complex magnetic structure is
formed over the spots, the reconnection of which leads to the generation
of a flare. The information about the magnetic field can be retrieved
from is polarized microwave radiation, the spectrum of which is correlated
with the flare activity.
As a result of BTA observations of 23 chemically peculiar stars with
strong magnetic fields, it was found that in 22 of them the longitudinal
magnetic field, measured from the hydrogen line cores are considerably
lower (by about 1/3) than the value measured from metal lines in the
According to the current estimates, a few percent of Main Sequence B5-F5
stars reveal strong surface magnetic fields reaching the values of tens
of kilogauss, which is an order of magnitude greater than the maximal
magnetic field in sunspots.
The close X-ray binary with relativisic jest, contained probably
a black hole, Cygnus X-3 has been detected in first time
in Gamma-rays at enegries higher 100 ķeV (AGILE, Tavani et al., Nature, 2009)
during the intense radio flares, monitored with RATAN-600 radio telecope.
By means of deep optical images obtained at the Special Astrophysical
Observatory 6-m telescope it was discovered that some Seyfert galaxies
that were earlier considered to be non-interacting objects displayed
signatures of elongated tidal envelopes belonging to satellite debris.
CH Cyg is one of the most fascinating as well as the brightest and closest
symbiotic stars. It's composed of an M7 giant and a hot companion, most
likely an accreting white dwarf.
A bright extended nebulosity around a lenticular galaxy NGC 4460 was
discovered by Igor Karachentsev and Serafim Kaisin (2008, A&A, 479, 603)
during the recent
nearby galaxies on the SAO RAS 6-m telescope.
In the spectral observations of stars with infrared circular nebulae,
found in the Spitzer survey (24 microns), a new LBV star was discovered
in the Galaxy.
The brightest of all GRBs known to date, GRB080319B, the "Naked-Eye Burst",
has been observed by our colleagues who acquired its detailed optical light
curve during the stage of gamma emission.
Dwarf galaxy DDO 68 is the closest to us galaxy (D=10Mpc) with the lowest
metal content known to date. In this galaxy, using the 6 m BTA
telescope, a new massive blue variable star with high luminosity
Sun's luminocities in visible light) was found.
New observations of the RC J0311+0507 radio source using the MERLIN
radio interferometer (UK) and the 6-m optical telescope, have added
new strokes to the "portrait" of this unusual object, - one of the most
powerful and distant radio galaxies (z=4.51), and raised new questions
about the origin of the first galaxies in the early Universe.
A new bright LBV (Luminous Blue Variable) star was found in M33 galaxy.
The most metal-poor system of four subdwarfs discovered in the solar
Identification and Early Spectroscopic Observations of the Optical
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Last update: 12/05/2017