The results of a comprehensive analysis of continuous radio spectra of a sample of Gigahertz-Peaked Spectrum (GPS) sources are reported. The sources are selected from a flux-density-complete sample (Sν ≥ 200 mJy at 4.8 or 5 GHz) using multifrequency measurements of the RATAN-600 radio telescope and data from the CATS astrophysical catalogs support system. The analysis revealed a very small number (1–2%) of “classical” GPS objects, which is significantly less than the expected fraction of 10%. GPS galaxies are found to have narrower and steeper radio spectra than quasars. The low-frequency part of the spectrum is seen to become steeper with increasing redshift. Galaxies and quasars at the same z have comparable angular sizes, whereas their luminosities may differ by one order of magnitude. At large redshifts there is a deficit of objects with low (several GHZ) peak frequencies. The number of GPS galaxies decreases sharply with redshift, and most of them are found at z between 0.01 and 1.81. GPS quasars are found at large redshifts, from 0.11 to 3.99. A quarter of the sample consists of blazars whose spectra may temporarily have a convex shape when the object is in active state. 相似文献
We present the results from our timing of the millisecond pulsar B1937+21, performed jointly since 1997 on two radio telescopes: the RT-64 in Kalyazin (Russia) at a frequency of 0.6GHz and RT-34 in Kashima (Japan) at a frequency of 2.15 GHz. The rms value of the pulse time of arrival (TOA) residuals for the pulsar at the barycenter of the Solar system is 1.8 μs (the relative variation is ≈10?14 over the observing period). The TOA residuals are shown to be dominated by white phase noise, which allows this pulsar to be used as an independent time scale keeper. The upper limit for the gravitational background energy density Ωgh2 at frequencies ≈6.5 × 10?9 Hz is estimated to be no higher than 10?6. Based on the long-term timing of the pulsar, we have improved its parameters and accurately determined the dispersion measure and its time variation over the period 1984–2002, which was, on average, ?0.00114(3) pc cm?3 yr?1. 相似文献
We report here the results of observations of two BL Lacertae-type objects, J2005+77 and J2022+76, using the RATAN-600 at frequencies 11.2, 7.7, and 4.8 GHz. We found variations of radio emission on timescales of one day and we are the first to discover a variability of this type for J2022+76.We compare our observations with long-term multifrequency radio observations of the same sources performed on RATAN-600 within the framework of other observational programs. We analyze the behaviour of variability of the two sources and provide arguments in favour of the preferred emission generation mechanisms for the objects studied. 相似文献
Based on observational data obtained with the RT-22 Crimean Astrophysical Observatory radio telescope at frequencies of 8.6 and 15.4 GHz, we investigate the quasi-periodic variations of microwave emission from solar active regions with periods Tp<10 min. As follows from our wavelet analysis, the oscillations with periods of 3–5 min and 10–40 s have the largest amplitudes in the dynamic power spectra, while there are virtually no oscillations with Tp<10 s. Our analysis shows that acoustic modes with Tp?1 min strongly dissipate in the lower solar corona due to thermal conduction losses. The oscillations with Tp=10–40 s are associated with Alfvén disturbances. We analyze the influence of acoustic and Alfvén oscillations on the thermal mechanisms of microwave emission in terms of the homogeneous model. We discuss the probable coronal heating sources. 相似文献
The observational data for 24 stars toward the young cluster vdB 130 are analyzed. The spectroscopic and photometric BV RIJHK observations have been carried out with the following telescopes: 6-m at the Special Astrophysical Observatory of the Russian Academy of Sciences, 60-cm at the Southern Station of the Moscow State University, and 2.5-m at the Caucasus Observatory of the Sternberg Astronomical Institute of theMoscow State University. Nine stars previously selected as cluster members have been found to belong to different subtypes of type B. A minimum color excess toward the cluster, E(B ? V) = 0.9 mag, has been revealed for the vdB 130 stars lying outside the molecular cloud. Maximum color excesses, E(B ? V) = 1.3?1.4 mag, have been found in the spectra of cluster stars 1r and 5r observed in dust blobs. Inside the cluster Rv is shown to differ from the standard one. The overwhelming majority of the remaining investigated stars belong to late types and have minor color excesses (≤0.3) typical of close distances. 相似文献
We present the long-term light curve of the radio source J1603+1105 and results of the study of its variability on timescales from several days to several weeks. From 2007, a flare with the maximum in 2010 was observed for the object that earlier showed no significant variations of flux density. Three flares with a successively decreasing amplitude were detected at an active phase in the long-term light curve. The characteristic time of the first one was 2.5 yrs. In five sets of daily observations of 95 to 120 days, the flux density variability on scales from 9 to 32 days in 2011, 2012, 2015, and 2016 was detected; in 2015 it was detected at three frequencies simultaneously. In 2011, the variability was found at a single frequency of 4.8 GHz; in 2012—at two frequencies, 4.8 and 7.7 GHz; in 2015—at 4.6, 8.2, and 11.2 GHz.We present instant spectra of the source at different flare phases showing that the dynamics of the flare development is consistent with the model, in which the variability is the result of the shock wave evolution in the radio source jet. 相似文献
The results of spectroscopic observations of the star RY Tau in the ultraviolet based on IUE data and in the visual spectral range obtained at ShAO are presented. Despite significant brightness variability in 1983–1984, the Mg II λ2800 Å emission doublet showed no synchronous variation with the UBV photometric data. Periodic variability of the Mg II λ2800 Å emission intensity with a period of 23 days has been detected for the first time. The periodicity is also observed for a group of such lines as CIV λ1450 Å, He II λ1640 Å, and S II λ1756 Å. The equivalent widths and shifts of the individual components of the Hα, H + Hε, and CaII K lines also vary with the period found. The observed variability of the emission spectrum can be explained by the existence of a companion in the system in an orbit with a semimajor axis of about 0.13 AU. 相似文献
Based on our UBV RI observations and X-ray data from the RXTE satellite, we have investigated the variability of the galaxy 3C 120 over the period 1996–2008. The relative variability amplitude in the U and B bands without any subtraction of the contribution from the underlying galaxy is 23 and 22%, respectively, against 21% in the X-ray band. The autocorrelation function based on the B-band data is considerably wider than that based on the X-ray data. The structure functions on a time scale from 1 to ～100–300 days in the X-ray and optical spectral ranges have the form of a power law (SF ～ τb). However, their indices differ significantly: b = 0.42 in the X-ray band and b = 1.36 in the B band. Considering the X-ray and optical variabilities as a superposition of independent flares in a wide range of durations, we may conclude that the amplitudes of short flares in the X-ray band are higher than those in the optical one and, conversely, the relative amplitudes of long flares in the X-ray band are slightly lower than those in the optical one, i.e., short events dominate in the X-ray band. The optical flux variations in the Rc and Ic bands lag significantly behind those in the B band, by 3.9?0.7+1.0 and 6.2?0.6+1.1 days, respectively, if the lag is estimated from the centroid of the cross-correlation function. The X-ray variability on a time scale of about 1800 days (～5 yr) lags behind the B-band variations by 5.3?3.3+2.7 days, but the confidence level of this estimate is only 87%. A more detailed analysis of the correlation between the X-ray and optical emissions has revealed a fairly complex picture: different degrees of correlation between the optical and X-ray fluxes are observed at different times. 相似文献
The propagation of an instantaneous burst of isotropic radiation from the time of its onset at some redshift z0 to the time of its detection at the present epoch (at z = 0) is considered within the framework of a flat Universe. The Thomson scattering by free electrons and the scattering in the primordial hydrogen Lα and Lβ lines and in the He I 1s2–1s2p, 1s3p (1S–1P*) lines are taken into account. It is shown that the relative amplitude of the spectral distortions due to the scattering in these lines at the corresponding frequencies can be a factor of 103?104 greater than the maximum possible amplitude from the scattering in the subordinate hydrogen lines considered previously (Dubrovich and Grachev 2015). In the linear approximation in optical depth, the distortion profiles in the resonance lines turn out to be purely absorption ones and depend neither on the direction nor on the distance to the burst center, in contrast to the profiles in the subordinate lines. The profiles contain jumps at frequencies corresponding to the instant the source (burst) appears at a given redshift z0. For example, at z0 = 5000 the jumps in the hydrogen Lα and Lβ lines lie at frequencies of 493 and 584 GHz, respectively, while in the above two helium lines they lie at frequencies of 855 and 930 GHz at z0 = 6000. The relative magnitude of the jumps ranges from 10?4 to 3 × 10?3. 相似文献
We present photoelectric and spectral observations of a hot candidate proto-planetary nebula—early B-type supergiant with emission lines in spectrum—IRAS 19336-0400. The light and color curves display fast irregular brightness variations with maximum amplitudes \(\Delta V = 0_ \cdot ^m 30\), \(\Delta B = 0_ \cdot ^m 35\), \(\Delta U = 0_ \cdot ^m 40\) and color-brightness correlations. By the variability characteristics IRAS 19336-0400 appears similar to other hot proto-planetary nebulae. Based on low-resolution spectra in the range λ4000–7500 Å we have derived absolute intensities of the emission lines Hα, Hβ, Hγ, [S II], [N II], physical conditions in gaseous nebula: ne = 104 cm?3, Te = 7000 ± 1000 K. The emission line Hα, Hβ equivalent widths are found to be considerably variable and related to light changes. By UBV-photometry and spectroscopy the color excess has been estimated: EB-V = 0.50–0.54. Joint photometric and spectral data analysis allows us to assume that the star variability is caused by stellar wind variations. 相似文献
2MASS is the most complete, homogeneous, and least contaminated catalog among the deep all-sky catalogs of stellar data produced to date. These qualities allow it to be successfully used not only for astrophysical studies, but also for solving various problems of all-sky astrometry and for operational support of automated telescopes. However, the lack of optical photometry in the catalog prevents its potential from being completely unveiled. To overcome this shortcoming, we have developed a procedure for transforming the 2MASS near-infrared magnitudes to optical magnitudes RJ relative to the UCAC2 magnitudes RU. As a result of applying this procedure, all 2MASS objects have gotten optical magnitudes with effective wavelengths between the V and R bands of the Johnson system. The resulting transformation accuracy \(\varepsilon _{R_J } \) < 0.m5). We also give a brief overview of the present-day all-sky catalogs with emphasis on their photometric properties and completeness. 相似文献
Based on observations with the 6-m SAO RAS telescope, we have found that chemically peculiar star with a large depression of the continuum at λ5200 Å and strengthened silicon lines in the spectrum has a strong magnetic field. The longitudinal field component Be has a negative polarity and varies from ?300 G to ?2000 G with a period of 1.756 days. Photometric variations of brightness take place with the same period. We determined the variability of the radial velocity at times of about tens of years pointing to a possible binarity of the object. We have built a magnetic model of this star, determined the inclination angles of the rotation axis to the line of sight i = 20° and of the dipole axis to the rotation axis β = 116°, and the field strength at the pole is Bp = 10 kG. We carried out a chemical composition analysis and found a lack of helium for almost an order of magnitude, some overabundance of silicon and metal elements for more than an order of magnitude, particularly, cobalt for three orders of magnitude. 相似文献
For a sample of 8156 emission-line galaxies from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4), we have determined the current star formation rates (SFR) from three parameters: the Hα luminosity of H II regions corrected for the aperture and interstellar extinction (N = 7006 galaxies), the far-infrared luminosity (IRAS data, N = 350), and the monochromatic luminosity in the radio continuum at ν = 1.4 GHz (NVSS data, N = 475). A Salpeter initial mass function with the range of stellar masses 0.1–100 M⊙ was assumed in the SFRFIR calculations. In calculating SFR1.4, we assumed that the fraction of the thermal emission in the total radio continuum emission of the galaxy at 1.4 GHz was 10%. An upper limit for the starburst age has been determined for galaxies with known abundances of heavy elements. We compare our results with those of similar studies for isolated and Markarian H II galaxies. 相似文献
One-dimensional sections of WMAP maps—ILC and background components (synchrotron, free-free radiation and dust emission) are investigated and their correlation properties on various angular scales are analyzed. Sections of the ILC map are found to correlate significantly with the maps of Galactic background components at the δ = 41° declination of RATAN-600 survey. The confidence level of the correlations found is estimated by analyzing random realizations of the Gaussian process that describes the microwave background. A method for identifying correlated intervals from maps on the sphere as a function of angular scale is proposed. This method can be used to search for non-Gaussian features (spots) found in the distribution of microwave background and radio sources in the same coordinate areas. The approach described can also be used to search for such non-Gaussian sources in observational programs performed on the radio telescope RATAN-600. 相似文献
We study the correlation between the emission from the broad-line region (BLR) and the emission in other wavelength ranges (from radio to x-ray) for the sample of 37 blazars (25 flat-spectrum radio quasars (FSRQs) and 10 BLLac blazars). Studying the relation between luminosities in various wavebands and the BLR luminosity is an effective method to examine the connection between the accretion rate and the luminosity of the jet.We used simultaneous RATAN-600measurements of blazar flux densities at six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The observational data from other bands was taken from the literature. To determine the effect produced by the state of the object on the correlation, for the radio data we used the measurements obtained with the RATAN-600 in two states-namely, the maximum and minimum flux density values.We show that at some frequencies of the radio band, there exists a correlation of emission with the emission in the BLR for two types of blazars. In the FSRQ and BL Lac blazars, the correlation between the flux from the BLR and the flux in the radio band is indistinguishable in all cases, except for the case when a strong flux density variation was considered for the BL Lac-type of blazars (tens of percent). At the same time, the levels of significance for BL Lac (at certain frequencies p is worse than 0.05) in the active state indicate only the probable presence of connection. On the example of the sample, we show that the variability of emission significantly affects the level of correlation. Our results are consistent with the theoretical predictions about the close relationship of the accretion disk and the jet in blazars. 相似文献
We have analyzed the optical (U BV) and ultraviolet (λ1000–2700 Å) observations of the nuclear variability of the Seyfert galaxy NGC 4151 in the period 1987–2001 (the second cycle of activity). The fast (tens of days) and slow (～10 years) components of the nuclear variability, F and S, respectively, are shown to be completely different, but thermal in nature. We associate the S component with the formation and evolution of an accretion disk and the F component (flares) with instabilities in the accretion disk and their propagation over the disk in the form of a shock wave. The S component is present not only in the optical, but also in the ultraviolet range, with its amplitude being comparable over the entire range λ1000–5500 Å under study. The amplitude of the average flare (the F component) doubles as the wavelength decreases from 5500 to 1000 Å, while the rise time of the brightness to its maximum Δt (the variability time scale) decreases from
to 6d ± 2d. The brightness decline (flare decay) time decreases by a factor of 16. The extinction in the ultraviolet is shown to have been grossly underestimated: beginning from the first IUE data, only the extinction in our Galaxy,
leads to a large increase in the luminosity of the variable source in the nucleus of NGC 4151: L = (6–8) × 1046 erg s?1. The spectral energy distribution for the variable source (λ950–5500 Å) agrees well with two Planck distributions: Te = 65 000 (λmax = 450 Å) and 8000 K. The radiation with Te = 8000 K is the reprocessing of the bulk of the ultraviolet radiation by the accretion disk with a lag of 0.5–0.6 days in the V band. The lag in the U-B variability of the slow component revealed the existence of an extended broad line region (EBLR) at an effective distance of 1.5 lt-years, as confirmed by spectroscopic data obtained at the Crimean Astrophysical Observatory. This yields the following mass of the central object in NGC 4151: Mc = (1–3) × 109M⊙. The luminosity of the variable source then accounts for 50–60% of LEdd rather than 1–2%, as has been thought previously. In general, the pattern of ultraviolet and optical variability in NGC 4151 agrees excellently with the theory of disk accretion instability for a supermassive black hole suggested by N. Shakura and R. Sunyaev 30 years ago: the energy release is at a maximumin the ultraviolet (in the case under consideration, at λ450 Å), the luminosity is ～1047 erg s?1 for Mc ～ 109M⊙ (several tens of percent of LEdd), and the variability time scale ranges from several days to many years.
Observations of the circumstellar maser emission from the long-period variable star Y Cas in the 1.35-cm water-vapor line are presented. The observations were performed with the RT-22 radio telescope at the Pushchino Radio Astronomy Observatory (Astrospace Center, Lebedev Physical Institute, Russian Academy of Sciences) in the period 1982–2005. The variations in the integrated flux Fint in the H2O line correlate with the visual light curve of the star. The phase delay Δ? between the Fint variations and the light curve is 0.2–0.4P (P is the period of the star). The H2O maser Y Cas belongs to transient sources: peaks of high maser activity alternate with intervals of a low emission level when the H2O-line flux does not exceed (0.1–0.5) × 10?20 W m?2. A “superperiod” of ～5.7 yr was found in the occurrence of activity peaks. A particularly strong maximum of maser radio emission took place at the end of 1997, when the flux Fint reached 15.6 × 10?20 W m?2. A model for the H2O maser variability in Y Cas is discussed. The variability is caused by a periodic action of shock waves driven by stellar pulsations. The H2O maser flares may be associated with short-lived episodes of enhanced mass loss by the star or with the propagation of a particularly strong shock wave when a planet orbiting the star passes through its periastron. 相似文献
Multicolor photometric observations of the optical afterglow from GRB 060526 with the Russian-Turkish 1.5-m RTT-150 telescope (Mount Bakyrlytepe, Turkey) are presented. The afterglow light curve was measured in detail starting from about 5 h after the GRB and over five ensuing nights. In addition, upper limits were obtained on the rapid variability of the afterglow on the first night of observations and the history of afterglow color variations was measured in detail. In the time interval from 6 to 16 h after the burst, the flux gradually decreased approximately as a power law with a slope of ?1.14 ± 0.02. Subsequently, variability was observed on a time scale δt < t and the afterglow began to decay much faster. The afterglow color was approximately constant (V?R ≈ 0.5) throughout the observations, despite the flux variability. Variability time scales up to δt/t ≈ 0.0055 were observed at ΔFν/Fν ≈ 0.3, which violates many constraints on the variability of the observed emission from an ultrarelativistic jet obtained by Ioka et al. (2005). We suggest explaining this variability by the fact that the shell motion is no longer ultrarelativistic at this time. 相似文献
We present our synchronous spectroscopy and photometry of DI Cep, a classical T Tauri star. The equivalent widths and radial velocities of the individual components and Hα, Hβ, D1 and D2 Na I, and HeI λ5876 Å emission line profiles exhibit variability. We have found a clear positive correlation between the brightness and equivalent width for the Hα and Hβ emission lines. The photometric and spectroscopic data are satisfactorily described in phases of a 9-day period. The expected magnetic field of the star has been estimated using existing magnetospheric models to be 655–1000 G. The star is suspected to be a binary. 相似文献
We analyze the spectroscopic and photometric observations of the active galactic nucleus (AGN) 1E 0754.6+3928 performed at Crimean Astrophysical Observatory in 1998–2004. Based on formal spectroscopic criteria for the optical wavelength range, we can classify this object as a narrow-line Seyfert 1 (NLS1) galaxy. Over the period of its observations, the AGN 1E 0754.6+3928 showed a very low rms flux variability amplitude in both continuum and Hβ (～3%). The Hβ time lag relative to the continuum has been found from the cross-correlation function centroid to be τcent = 112?67+215 days. This result and the Hβ line dispersion estimate have allowed us to determine the central black hole mass by the reverberation method: 1.05 × 108M⊙. The position of 1E 0754.6+3928 in the black hole mass-luminosity diagram agrees with the positions of other NLS1 galaxies and can be explained by an enhanced mass accretion rate in the central source. 相似文献
