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Regular version of the site
Of all publications in the section: 29
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Article
Zheleznyakov V. V., Bespalov P. A. Astronomy Letters. 2018. Vol. 44. No. 7. P. 442-456.

A model for the source of microwave bursts from the Crab pulsar in the form of a current sheet with a transversemagnetic field has been investigated. The emission generation mechanism is based on the excitation of plasma waves at the double plasma resonance frequencies in a nonrelativistic nonequilibrium plasma followed by their scattering into electromagnetic waves that escape from the current sheet into the neutron star magnetosphere. The basic parameters of the source explaining the observed characteristics of quasi-harmonic bursts in the interpulses of radio emission from this pulsar have been established.

Added: Oct 19, 2018
Article
Struminskiy A., Belov A., Sadovski A. Astronomy Letters. 2018. Vol. 44. No. 5. P. 324-330.

The discovery of a terrestrial planet orbiting Proxima Centauri has led to a lot of papers discussing the possible conditions on this planet. Since the main factors determining space weather in the Solar System are the solar wind and cosmic rays (CRs), it seems important to understand what the parameters of the stellar wind, Galactic and stellar CRs near exoplanets are. Based on the available data, we present our estimates of the stellar wind velocity and density, the possible CR fluxes and fluences near Proxima b. We have found that there are virtually no Galactic CRs near the orbit of Proxima b up to particle energies ∼ 1 TeV due to their modulation by the stellar wind. Nevertheless, more powerful and frequent flares on Proxima Centauri than those on the Sun can accelerate particles to maximum energies ∼ 3150αβ GeV (α, β < 1). Therefore, the intensity of stellar CRs in the astrosphere may turn out to be comparable to the intensity of low-energy CRs in the heliosphere.

Added: Nov 2, 2018
Article
Bespalov P. A., O.N. Savina. Astronomy Letters. 2015. Vol. 41. No. 10. P. 601-605.

We discuss the connection of the formation and properties of solar atmosphere transition region characterized by a steep electron temperature gradient with electrostatic turbulence, which provides a high effective electron collision frequency and a low thermal conductivity of the medium. A simple dependence of the noise electric field in the transition region on the effective collision frequency has been derived. Based on known experimental models of the solar atmosphere, we have estimated the height dependence of the thermal conductivity and the strength of the noise electric fields for a tube with a relatively weak magnetic field passing from the chromosphere into the corona.

Added: Sep 30, 2015
Article
Petrukhin N. Astronomy Letters. 2014. Vol. 40. No. 6. P. 372-381.

The free oscillations of coronal loops with a constant density and a variable magnetic field

changing according to parabolic laws are investigated. Using our developed method, we derive the wave

equations with constant coefficients that describe the kink oscillations of symmetric and asymmetric

magnetic flux tubes. For such models, we obtain analytical expressions for the oscillation spectra and

amplitudes as well as the magnitudes and directions of the displacements of the extrema of the fundamental

and first modes relative to their values for homogeneous tubes. For the first mode of an asymmetric loop,

we have determined the dependence of the coordinate displacement for the internal node on the ratios of the

magnetic field strengths in its asymmetric parts and the ratio of the amplitudes at the extremum points

Added: Oct 27, 2015
Article
Kornilov V., Kornilov M.V., Shatsky N. et al. Astronomy Letters. 2016. Vol. 42. No. 9. P. 616-630.

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below −15°C. The typical ground wind speed is 3 m s−1; the probability of a wind stronger than 10 m s−1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.

Added: Feb 7, 2019
Article
Petrukhin N., Pelinovsky E., Batsyna E. K. Astronomy Letters. 2012. Vol. 38. No. 6. P. 388-393.

The possibility that vertical acoustic waves with frequencies lower than the cutofffrequency corresponding to the temperature minimum pass this minimum is investigated. It is shown that the averaged temperature profile in the solar atmosphere can be approximated by several so-called reflectionless profiles onwhich the acousticwaves propagate without internal reflection. The possibility of the penetration of vertical acoustic waves, including low-frequencyones, into the solar corona is explained in this way.

Added: Mar 23, 2014
Article
Петрухин Н. С., Пелиновский Е. Н., Бацына Е. К. Письма в Астрономический журнал. 2012. Т. 38. № 6. С. 439-445.

The possibility that vertical acoustic waves with frequencies lower than the cutoff frequency corresponding to the temperature minimum pass this minimum is investigated. It is shown that the averaged temperature profile in the solar atmosphere can be approximated by several so-called reflectionless profiles on which the acoustic waves propagate without internal reflection. The possibility of the penetration of vertical acoustic waves, including low-frequency ones, into the solar corona is explained in this way.

Added: May 3, 2012
Article
Беспалов П. А., Савина О. Н. Письма в Астрономический журнал. 2008. Т. 34. № 5. С. 378-386.

The generalized Wiedemann-Franz law for a nonisothermal quasi-neutral plasma with developedion-acoustic turbulence and Coulomb collisions has been proven. The results obtained are used  to explain the anomalously low thermal conductivity in the chromosphere-corona transition region of the solar atmosphere. Model temperature distributions in the lower corona and the transition region that correspond to well-known experimental data have been determined. The results obtained are useful for explaining the abrupt change in turbulent-plasma temperature at distances smaller than the particle mean free path.

Added: Dec 12, 2012
Article
Годенко Е. А., Измоденов В. В. Письма в Астрономический журнал. 2021. Т. 47. № 1. С. 53-65.

Interstellar dust (ISD) penetrates into the heliosphere due to the relative motion of the Sun and the local interstellar medium (LISM). Inside the heliosphere and at the boundaries, where solar wind interacts with the LISM, distribution of ISD is modified due to the action of the electromagnetic forces, the solar gravitation and the radiation pressure. These forces make the distribution of the ISD particles in the heliosphere inhomogeneous. In previous work we demonstrated the existence of singularities in the ISD density distribution at 0.03–10 AU north and south with respect to the heliospheric current sheet. In this paper we show that dispersion in the ISD velocity distribution strongly affects the singularities. Even small values of dispersion have the drastic impact on the density distribution and smooth the high density layers discovered previously.

Added: Oct 11, 2021
Article
Буренин Р. А., Ревнивцев М., Ткаченко А. и др. Письма в Астрономический журнал. 2016. Т. 42. С. 240-250.

A sample of cataclysmic variables (CVs) detected among the X-ray sources of the 400 square degree (400d) survey performed based on ROSAT pointings is presented. A technique for selecting CVs among the X-ray sources using additional optical and infrared data, based on Sloan Digital Sky Survey andWISE data, is described. We present the optical observations of the selected objects carried out mainly with the Russian-Turkish 1.5-m telescope (RTT-150) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (BTA). Some observations have also been performed with the 1.6-m AZT-33IK telescope of the Institute of Solar-Terrestrial Physics, the Siberian branch of the Russian Academy of Sciences. Eight CVs, four of which were detected in our work, have been selected by now. Based on this sample, we have obtained preliminary constraints on the X-ray luminosity function of CVs in the solar neighborhood in the range of low luminosities, L X ~ 1029-1030 erg s-1 (0.5-2 keV). The logarithmic slope of the CV luminosity function in this luminosity range is shown to become gentler than that at L X > 1031 erg s-1. It follows from our estimates of the CV luminosity function that several thousand CVs will be detected in the SRG all-sky survey at high Galactic latitudes, which will allow much more accurate measurements of their X-ray luminosity function to be obtained.

Added: Jan 28, 2018
Article
Петрухин Н. С. Письма в Астрономический журнал. 2014. Т. 40. № 6. С. 416-425.
Added: Nov 24, 2014
Article
Буренин Р. А., Сазонов С. Ю. Письма в Астрономический журнал. 2016. Т. 42. № 5. С. 277-294.

We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3 < z < 5.5 selected among the X-ray sources of the "serendipitous" XMM-Newton survey presented in the 3XMMDR4 catalog (the median X-ray flux is ≈5 × 10-15 erg s-1 cm-2 in the 0.5-2 keV energy band) and located at high Galactic latitudes | b| > 20° in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error δ mz' < 0.2 and a color i' - z' < 0.6 (to first eliminate the M-type stars). For the selected sources, we have calculated the dependences χ2( z) for various spectral templates from the library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z = 0 and obtained a sample of quasars with photometric redshift estimates 2.75 < z phot < 5.5. The selection completeness of known quasars at z spec > 3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation (Δ z = | z spec - z phot|) is σ Δ z /(1+ z spec) = 0.07, while the outlier fraction is η = 9% when Δ z/(1 + z cпek.) > 0.2. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3 < z < 5.5 will allow the purity of this sample to be estimated more accurately.

Added: Jan 27, 2018
Article
Садовский А. М., Струминский А. Б., Белов А. Письма в Астрономический журнал. 2018. Т. 44. № 5. С. 347-353.
Added: Nov 2, 2018
Article
Позаненко А. С., Минаев П. Ю., Гребенев С. А. и др. Письма в Астрономический журнал. 2019. Т. 45. № 11. С. 768-786.

Observations of the gravitational-wave (GW) event S190425z registered by the LIGO/Virgo detectors with the Anti-Coincidence Shield (ACS) of the gamma-ray spectrometer SPI aboard the INTEGRAL observatory are presented. With a high probability (>99%) it was associated with a neutron star (NS) merger in a close binary system. This is only the second event of such type in the history of GW observations (after GW170817). A weak gamma-ray burst, GRB190425, consisting of two pulses in ~0.5 and ~5.9 s after the NS merging in S190425z was detected by SPI-ACS. The pulses had a priori reliability of 3.5 and 4.4 sigma as single events and 5.5 sigma as a combined event. Analysis of the SPI-ACS count rate history recorded these days (~125 ks in total) has shown that the rate of appearance of two close pulses with characteristics of GRB190425 by chance does not exceed 6.4 x 10^{-5} s^{-1}. We note that the time profile of GRB190425 has a lot in common with the profile of the GRB170817A burst accompanying the GW170817 event; that both the NS mergers were the closest (<150 Mpc) of all the events registered by the LIGO/Virgo detectors; and that there were no confident excesses of gamma-ray emission over the background detected in any of >30 black hole merger events recorded to the moment by these detectors. No hard X-ray flares were detected in the field of view of the SPI and IBIS-ISGRI gamma-ray telescopes aboard INTEGRAL. This, as well as the lack of detection of gamma-ray emission from GRB190425 by the GBM monitor of the Fermi observatory assuming its occultation by the Earth, can significantly reduce the localization area for the source of this GW event. The estimates of the parameters E_{iso} and E_{p} for GRB190425 are obtained and compared with the similar parameters for GRB170817A.

Added: Feb 5, 2020
Article
Петрухин Н. С., Файнштейн С. Письма в Астрономический журнал. 1988. № 6(24).
Added: Nov 16, 2010
Article
Ледков А. А., Эйсмонт Н. А., Сюняев Р. А. и др. Письма в Астрономический журнал. 2012. Т. 38. № 9. С. 631-644.
Added: Dec 7, 2015
Article
Эйсмонт Н. А., Ледков А. А., Гребенев С. и др. Письма в Астрономический журнал. 2012. Т. 38. № 9. С. 631-644.
Added: Jan 31, 2013
Article
Петрухин Н. С., Островский Л. Письма в Астрономический журнал. 1981. № 58. С. 848-858.
Added: Nov 16, 2010
Article
Буренин Р. А., Сазонов С. Ю. Письма в Астрономический журнал. 2017. Т. 43. № 3. С. 159-169.

We present the results of optical spectroscopy for 19 quasar candidates at photometric redshifts z phot ≳ 3, 18 of which enter into the Khorunzhev et al. (2016) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for a quasi-random sample of new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. Fourteen of the 18 candidates actually have turned out to be quasars; 10 of them are at spectroscopic redshifts z spec > 3. The high purity of the sample of new candidates suggests that the purity of the entire K16 catalog of quasars is probably 70-80%. One of the most distant ( z spec = 5.08) optically bright ( i' ≲ 21) quasars ever detected in X-ray surveys has been discovered.

Added: Jan 27, 2018
Article
Накаряков В., Петрухин Н. С. Письма в Астрономический журнал. 1994. Т. 20. С. 431-434.
Added: Nov 16, 2010
Article
Хохрякова А. Д., Ляпина Д., Попов С. Б. Письма в Астрономический журнал. 2019. Т. 45. № 3. С. 163-169.

In this note we discuss the possibility of detecting accompanying  X-ray emission from sources of fast radio bursts with the eROSITA telescope onboard the Spektr-RG observatory. It is shown that during the four years of the survey program about 300 bursts are expected to appear in the field of view of eROSITA. About 1\% of them will be detected by ground based radio telescopes. For the total energy release $\sim~10^{46}$~ergs depending on spectral characteristics and absorption in the interstellar and intergalactic media, an X-ray flare can be detected from distances from $\sim 1$~Mpc (thermal spectrum with $kT=200$~keV and strong absorption) up to $\sim1$~Gpc (power-law spectrum with photon index $\Gamma=2 $ and realistic absorption). Thus, eROSITA observations might help to provide important constraints on  parameters of sources of fast radio bursts, or may even allow identification of X-ray transient counterparts, which will help to constrain models of fast radio bursts generation.

Added: Feb 20, 2019
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