Decametric survey of discrete sources in the northern sky

The data of the latest decametric band survey performed with the UTR-2 radio telescope are used along with other results obtained at higher frequencies (below 1415 MHz) for plotting spectra of 114 radio sources located in a sky strip between declinations 52° and 60°. Some parameters of the source spectra in the frequency range 12.6–1415 MHz are presented.     

Decametric survey of discrete sources in the northern sky

This paper presents results and describes the improved data processing algorithm of the low frequency sky survey of discrete sources carried out with the UTR-2 radio telescope. The measurements were conducted within the frequency range 10 to25 MHz. Coordinates and flux densities of the sources detected were obtained. Identification with sources from the 4C survey has been done. The resulting catalogue contains parameter estimates for 483 sources on a set of frequencies within the UTR-2 range. This revised version was published online in July 2006 with corrections to the Cover Date. This revised version was published online in July 2006 with corrections to the Cover Date.     

Decametric survey of discrete sources in the northern Sky

The latest data obtained in the course of the UTR-2 Very Low-Frequency Sky Survey within the declination zone 41° to 52° together with the data from a number of higher frequency surveys have been used to determine radio spectra for 194 radio sources in the frequency range 12.6 to 1400 MHz. The spectrum plots and parameters of the sources are presented.     

Correlated variations of planetary albedos and coincident solar-interplanetary variations

To locate two-dimensional positions of the solar decametric radio bursts a heliograph was developed on the basis of the UTR-2 radiotelescope (Khar'kov) operated in the range 10–26 MHz. The beamwidth of the heliograph rapid-scanning pencil-beam is 25 arc min at 25 MHz, and its field of view is about 3.5° (E-W) × 2.0° (N-S). The instrument yields rapidly forty records of the radio brightness of all (8 × 5) elementary parts (each 25 arc min in diameter) of the investigated sky area during every period of 1/4 s. Both coordinates of a burst center are measured with an accuracy 5 arc min. The bandwidth of the receiving system is 10 kHz. The heliograph operates in conjunction with a radiospectrograph connected to the output of a N-S arm of the UTR-2 array. The data observations with the UTR-2 correspond only to one linear polarized component.The ionospheric distortion of the test records of the radio source Cassiopeia-A that occurred sometimes is illustrated.First results of 25 MHz observations of the solar radio storm in August, 1976 with the heliograph are presented here. This storm is accompanied by the compact sunspot group travelling all over the optical disk. The type III and stria bursts were predominant during the storm. On the given day the scattering regions of their apparent centers were overlapped and the sizes of these regions were usually not more than 5 arc min. On some days there occurred additional burst sources displaced in position from the persistent storm region. It was found out that, as a rule, 25 MHz stria-bursts from the type IIIb chain coincided in position with the following type III burst at the same frequency. The difference of the daily averaged coordinates of both stria and type III bursts was considerably smaller than the mean diameter of their sources.The radial distance of the 25 MHz storm region from the solar center was calculated by using the three methods. The storm height was estimated as 1.8R from the rotation rate close to the central meridian of the storm center. Definite association of the spots with the storm near the limb allowed to determine the average value 2.1R for the height. The limb measurements give the mean height of 2.3R .The center-to-limb variation of the storm source height is a known fact in the meter-wavelength range. This is the evidence of the propagation effects in the solar corona being essential to interpret the results of the radio source location.     

Decametric survey of discrete sources

The recent data of the decametric survey carried out in Grakovo with the UTR-2 radio telescope and the data of a number of higher frequency surveys have been used for constructing the spectra of 147 discrete sources in the frequency range 12.6–1400 MHz.The analysis of the spectra shows that the mean value of the spectral index for galaxies in an interval of declinations –2° to –13° is somewhat higher than for those with declinations from –2° to +20°, while the mean spectral indices of quasars and unidentified sources for these two declination ranges coincide quite well.     

Decametric survey of discrete sources in the northern sky

Spectra of 197 discrete sources have been obtained in a frequency range 10–1400 MHz. The sources lie at declinations between 0° and +10° and right ascensions from 0–24 h. The spectra have been constructed on the basis of a decametric survey carried out at Grakovo with the UTR-2 radio-telescope, as well as a number of higher frequency surveys performed at Culgoora, Cambridge, Parkes and Ohio. Analysis of the spectrum plots shows that 84% of the spectra are linear (in the logarithmic scale), 11% are characterized by positive and 5% by negative curvature.     

Study of Extended Radio Galaxies at 151.6 MHz using the Mauritius Radio Telescope

The MRT survey will be by far one of the most extensive survey at low frequencies. This survey will provide a moderately deep radio catalog reaching a source density of about 2 × 10⁴ sr^-1over the southern sky with an angular resolution of 4' × 4' and a limiting flux density of 70 mJy (1 σ) at 151 MHz. The availability of zero spacing and short baselines in the MRT array will make it sensitive to the background temperature and to large scale features in the sky. In addition to this feature, the low frequency operation makes a study of continuum emission from large radio sources by MRT to have several interesting and important implications in the study of radio galaxies. This paper discusses the parameter space of radio galaxies which can be explored using the MRT. Images of a few extended radio galaxies are also presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of the RC catalog sample in the region overlapping with the regions of the FIRST and SDSS surveys: I. Identification of sources with the VLSS, TXS, NVSS, FIRST, and GB6 catalogs

Radio sources of the RC catalog produced in 1980–1985 at RATAN-600 radio telescope based on a deep survey of a sky strip centered on the declination of the SS433 source are optically identified in the region overlapping with FIRST and SDSS surveys (about 132?° large). The NVSS catalog was used as the reference catalog for refining the coordinates of the radio sources. The morphology is found for about 75% of the objects of the sample and the ratio of single, double and multicomponent radio sources is computed based on FIRST radio maps. The 74, 365, 1400, and 4850MHz data of the VLSS, TXS, NVSS, FIRST, and GB6 catalogs are used to analyze the shape of the spectra.     

A sharper view of the outer Galaxy at 1420 and 408 MHz from the Canadian Galactic Plane Survey – I. Revisiting the KR catalogue and new Gigahertz Peaked Spectrum sources

Arcminute-resolution radio continuum images at 408 and 1420 MHz from the Canadian Galactic Plane Survey (CGPS) have been used to re-examine radio sources listed in the Kallas & Reich catalogue. This catalogue is of particular interest to Galactic studies as it lists both extended and compact radio sources found in the second Galactic quadrant. We have determined the nature (extended versus compact, Galactic versus extragalactic) of all of these bright radio sources. A number of large H  ii regions with no optical counterparts are highlighted along with a sample of large radio galaxies. Many sources previously thought to be extended Galactic objects are shown to be point sources. A sample of point sources with flat or rising spectra between 408 and 1420 MHz has been compiled, and within this sample likely Gigahertz Peaked Spectrum sources have been identified.     

Decametric survey of discrete sources in the Northern sky

A new method was developed for comparing absolute flux scales of the decametric surveys. The absolute scales of the new survey performed with the UTR-2 in the 10 to 25 MHz frequency range are compared with UTR-1 data and surveys at 10.03, 22.25, 26.3 and 38 MHz operating frequencies.     

The second epoch Molonglo Galactic Plane Survey: compact source catalogue

We present the first data release from the second epoch Molonglo Galactic Plane Survey (MGPS-2). MGPS-2 was carried out with the Molonglo Observatory Synthesis Telescope at a frequency of 843 MHz and with a restoring beam of 45 × 45      arcsec², making it the highest resolution large-scale radio survey of the southern Galactic plane. It covers the range  | b | < 10° and 245° < l < 365°  , and is the Galactic counterpart to the Sydney University Molonglo Sky Survey (SUMSS) which covers the whole southern sky with  δ≤−30° (| b | > 10°  ).
In this paper, we present the MGPS-2 compact source catalogue. The catalogue has 48 850 sources above a limiting peak brightness of 10 mJy beam⁻¹. Positions in the catalogue are accurate to 1–2 arcsec. A full catalogue including extended sources is in preparation. We have carried out an analysis of the compact source density across the Galactic plane and find that the source density is not statistically higher than the density expected from the extragalactic source density alone.
We also present version 2.0 of the SUMSS image data and catalogue which is now available online. The data consist of 629 4.3°× 4.3° mosaic images covering the 8100 deg² of sky with  δ≤−30° and | b | > 10°  . The catalogue contains 210 412 radio sources to a limiting peak brightness of 6 mJy beam⁻¹ at  δ≤−50°  and 10 mJy beam⁻¹ at  δ > −50°  . We describe the updates and improvements made to the SUMSS cataloguing process.     

Low frequency observations of the scintillation of weak radio sources

Interplanetary scintillation observations of weak radio sources have been made at a frequency of 102.5 MHz. Sources have been chosen from the Bologna catalogue, with flux densities 0.5 Jy–4.0 Jy at 408 MHz.It has been found that the average scintillation visibility is in agreement with the results of the interferometer observations of Speed and Warwick (1978).A very wide spectral index distribution has been found for weak radio sources at low frequencies, perhaps indicating the presence of a new population of low luminosity, flat spectrum radio sources.     

The orientation of radio sources relative to the minor axes of their elliptical galaxies

The elliptical galaxies identified with 139 radio sources having double, wide-tail, twin-tail, or head-tail structures were examined on glass or film copies of Schmidt sky survey plates, and orientations were measured for 78 of them. The observed radio axes of well-collimated double sources are distributed over all possible orientations relative to their parent galaxies, but there is a significant preference for orientations within 30° of the projected minor axes of the galaxies. A similar minor-axis trend is found among wide-tail and twin-tail sources. The observed minor-axis peak is fairly broad. These results are consistent with either a very large dispersion in the ejection of radio components about the minor axes of oblate galaxies or a small dispersion about the equatorial planes of prolate galaxies. Other evidence indicates that both oblate and prolate radio galaxies exist. The minor-axis trend is stronger for large sources in the sample selected by Palimakaet al. (1979), but counter-examples to the minor-axis trend were found among other giant sources.     

Decametric survey of discrete sources in the northern sky

The region of the celestial sphere between declinations =52°.3 and =59° and right ascensions =1^h and =19^h has been surveyed with the UTR-2 radiotelescope. The results of the survey are presented.The catalogue contains the positions and flux densities of 313 radio-sources detected at 10, 12.6, 14.7, 16.7, 20, and 25 MHz.     

Harmonic components of decametric solar radio bursts

Type-IIIb, IIId, and III solar decametric radio bursts, being distinguished by the typical negative drift rate of their dynamic spectra, are compared. Observational data were obtained with a UTR-2 antenna during the period 1973–1982. During the analysis of the bursts of all these spectral varieties, the frequency drift time (drift delay) was measured in the ranges 25 to 12.5 MHz, 25 to 20 MHz, and 12.5 to 10 MHz. Durations of type-III bursts were determined at the harmonically-related frequencies of 25 and 12.5 MHz; radio source locations were also used.It is shown that these decametric bursts are distinctly divided into two groups: (1)type-IIIb chains of simple stria bursts and also normal type-III storm bursts observed at central regions constitute a group of events with a fast drifting spectrum; (2) type-III bursts from type-IIIb-III pairs and the limb variant of normal III bursts, as well as peculiar type-IIId chains of diffuse striae and related chains with an echo component, constitute a second group of events with comparatively slow drift rates.The first group of the phenomena is associated with the fundamental F frequency and the second one, with the harmonic H of the coronal plasma frequency. The results of the present investigation agree well with earlier conclusions on the harmonic origin of decametric chains and type-III bursts. Measurements of drift delays in narrow frequency ranges, an octave apart, as well as type-III burst durations at harmonically-related frequencies confirm the existence of both F and H components in the solar radiation. The essential result of 10 years of decametric observations is that the frequency drift rates and durations are rather stable parameters for the various type-III bursts and stria-burst chains. The stability characterizes some unspecified conditions of burst generation in the middle corona.     

A deep radio survey in the ISO-ELAIS fields: optical identification with the APM catalogue/atl>

The optical identification programme is presented for a complete sample of 867 radio sources that were observed with the Very Large Array (VLA) within 4.22 deg² to S _{1.4 GHz} ≥ 0.135 mJy (5 σ). The area covered by the VLA survey is part of the regions of the sky that have been surveyed in the mid and far Infrared over the wavelength range 6.7–175 μmwith ISO as part of the European Large Area ISO Survey (ELAIS). Optical identifications are made using the Automatic Plate-measuring Machine (APM) optical catalogue in E (∼ R) and O (∼ B) bands with approximate limiting magnitudes of ∼ 20.0 and 21.5 mag, respectively. For 220 out of the 867 radio sources, likely identifications are proposed with an a posteriori identification percentage of 25%. The sample of identification has a reliability of 96% and a completeness of 80%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Unusual Solar Radio Burst Observed at Decameter Wavelengths

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s^?1) at frequencies higher than 22 MHz and negative (100 kHz?s^?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈10³ s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.     

List of Participants

The possibility of obtaining information about small-scale inhomogenities of the electron component of the local interstellar medium (ISM) is investigated using interstellar scintillation of extragalactic radio sources. We analyze Culgoora array variability data at 80 and 160 MHz for 190 extragalactic radio sources distributed over most of the sky. The variability on time-scales of 1 month-15 years is interpreted as interstellar scintillations in rapidly-moving nearby (less than 150 pc) hot gas near shock waves in the local ISM. All-sky maps of scintillation index m averaged over 3-5 neighbouring sources and over m for time-scales of 1 month (m1) and one or several years (m12) show several maximum values for m. Locations of the maxima are insensitive to the method and number of points used for averaging. The positions of the maxima obtained in different ways agree to within 15-30 degrees on the sky; this is the angular resolution of this method. Two of the three most certain maxima are probably associated with Loop I, and the third coincides with a soft X-ray (0.1 - 0.3 keV) background maximum near the South Galactic Pole. Other less certain scintillation index maxima probably correspond to the Orion starformation region and to a soft X-ray maximum near the North Galactic Pole. A tunnel that is free of gas in the direction l = 240° is indicated by low values of m. The estimated time-scale for interstellar scintillations in these structures in the local ISM is in agreement with the time-scale for the observed radio source variations.     

IRAS F02044+0957: An interacting system

A list of 750 objects has been compiled using the Astrophysical CATalogs Support System (CATS) database, by cross-identifying sources in the IRAS catalogues and the catalogue of the Texas survey at 365 MHz. We have carried out a search for optical counterparts of those objects, where the difference in positions between the two catalogues and the APM is less than 3. One of these sources, IRAS F02044+0957, was observed with the RATAN-600 radio telescope at four frequencies in April 1999. Optical spectroscopy of the components of the system was made with the 2.1-m telescope of the Guillermo Haro Observatory. The radio and optical spectra, the NVSS radio map and the optical and infrared images allow us to conclude that the steep spectrum (=–0-94 ± 0-02) radio source IRAS F02044+0957 is a pair of interacting galaxies, a LINER and a HII galaxy, at z=0.093.Published in Astrofizika, Vol. 48, No. 1, pp. 113–124 (February 2005).     

A search for compact decametric radio sources in supernova remnants using the interplanetary scintillation technique

Interplanetary scintillation observations of eleven supernova remnants and the pulsar J1939+2134, around which the existence of a supernova remnant remains obscure, were carried out with the largest in the world decameter radio telescope UTR-2 at 20, 25 and 30 MHz to determine if any of them contain compact radio sources with the angular size θ<5″. The sample included the young Galactic remnants and the other powerful SNRs. The interplanetary scintillations of the compact radio source in the Crab Nebula associated with the well-known pulsar J0534+2200 and the pulsar J1939+2134 were observed. Apart from the Crab Nebula, we have not detected a compact radio source in supernova remnants with the angular size θ<5″ and the flux density more than 10 Jy. The observations do not confirm the existence of the low frequency compact source in Cassiopeia A that has remained controversial.