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Astronomy Reports, Vol. 47, No. 6, 2003, pp. 458­466. Translated from Astronomicheski Zhurnal, Vol. 80, No. 6, 2003, pp. 499­507. i Original Russian Text Copyright c 2003 by Afanas'ev, Dodonov, Moiseev, Gorshkov, Konnikova, Mingaliev.

Radio and Optical Spectral Studies of Radio Sources
V. L. Afanas'ev1 , S. N. Dodonov1 , A. V. Moiseev1 , A. G. Gorshkov2 , V. K. Konnikova2 , and M. G. Mingaliev
1 2

1

Special Astrophysical Observatory, Nizhni i Arkhyz, Russia Sternberg Astronomical Institute, Universitetski i pr. 13, 119992 Moscow, Russia
Received March 26, 2002; in final form, January 15, 2003

Abstract--Optical identifications and an analysis of the radio spectra of eight radio sources from a fluxdensity-complete sample at declinations 4 ­6 (B1950) are presented. The observations were carried out ° at 4000­9000 A on the 6-m telescope of the Special Astrophysical Observatory and at 0.97­21.7 GHz on the RATAN-600 telescope. Five of the eight sources are quasars and three are emission-line radio galaxies. c 2003MAIK "Nauka/Interperiodica".

1. INTRODUCTION This paper presents results of optical identifications of radio sources from a sample complete to a specified fluxdensity. This work is targeted at deriving the radio luminosity function of the sample objects and its cosmological dependences. This requires that the redshifts of the majority of the sample objects be known. All the objects whose spectra are presented here are optical counterparts of radio sources from a complete sample derived from the Zelenchuk survey at 3.9 GHz. This sample, which we have studied since 1980, contains all sources with fluxes S3.9 > 200 mJy, declinations 4 ­6 (1950), right ascensions 0­24 h, and Galactic latitudes |b| > 10 [1­3]. Currently, approximately 75% of the flat-spectrum sources in the sample have been optically classified. Previous results on optical identifications of the sample objects are published in [4­6]. 2. RADIO AND OPTICAL OBSERVATIONS Optical spectra of the objects were obtained in June and November 2000 on the 6-m telescope of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences. The observations of 1522+0400 and 1600+0412 were obtained using a multipupil spectrograph (http://www.sao.ru/gafan/devices/mpfs/mpfs_main.htm) with a TK1024 CCD detector, which has 1024 â 1024 channels and a counting noise of three electrons. The wavelength ° range observed was 4000­9000 A, with a dispersion ° of 5 A/pixel. The effective instrumental resolution ° was about 15 A. The spectra of the remaining objects

were obtained using the multipurpose SCORPIO instrument (http://www.sao.ru/moisav/scorpio/scorpio.html) in its long-slit mode together with the same CCD detector; the wavelength range was 3800­ ° ° 9200 A, with a dispersion of about 6 A/pixel. The ° effective instrumental resolution was about 20 A. The spectra were reduced in the standard way using programs developed in the Laboratory of Spectroscopy and Photometry of the SAO. Radio observations of the sample sources were carried out on the Southern sector of the RATAN600 plane-reflector radio telescope at 3.9 and 7.5 GHz in 1980­1991 and on the Northern sector at 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz in 1996­1999. The parameters of the receivers used on the Southern and Northern sectors are described in [1, 7], respectively, and the characteristics of the antenna beams for the Northern and Southern sectors are presented in [2, 8]. In each series of observations, the sources were observed daily for from 15 to 100 days. The observations on the Northern sector of the RATAN-600 were obtained in a fixed-focus regime [9]. The position of the main mirror could be adjusted within elevations of ±1 from the center of the observation zone. An equal number of panels was used at all elevations, in order to reduce the influence of variations in the radiation of the edge panels in the presence of variations in the curvature of the circular reflector. The effective area of the antenna was taken to be constant at all elevations. The source 2128+048 was used as a calibrator for all observations at declinations 4 ­6 . The size of this radio source is much less than the horizontal section of the antenna beam at all frequencies, right up to 21.7 GHz. The flux density of 2128+048 was taken

1063-7729/03/4706-0458$24.00 c 2003 MAIK "Nauka/Interperiodica"


RADIO AND OPTICAL SPECTRAL STUDIES Table 1. Object coordinates Source name 0323+ 0323+ 0354+ 0357+ 0427+ 1522+ 1600+ 2301+ 0446 0534 0441 0542 0457 0400 0412 0609 03 03 03 03 04 15 16 23 Radio coordinates J2000.0 RA DEC 23 23 54 57 27 22 00 01 14. 20. 24. 46. 47. 32. 02. 53. 72 21 13 13 57 76 54 46 + + + + + + + + 04 05 04 05 04 04 04 06 46 34 41 42 57 00 12 09 12. 11. 07. 31. 08. 29. 57. 12. 59 20 27 28 34 70 84 84 Optical­radio RA DEC 0.02 0.05 -0.02 0 0.02 0.05 0 -0.02
s

459

Ref JVAS NVSS JVAS JVAS JVAS NVSS JVAS JVAS

0.01 1.10 0.21 -0.04 -0.10 0.18 0.03 0.03

to be 4.25, 3.07, 2.35, 1.57, 1.24, and 0.75 Jy at 0.97, 2.3, 3.8, 7.7, 11.1, and 21.7 GHz, respectively. The data were reduced using programs that enabled derivation of the flux density for an individual scan of a source, as well as determination of the mean fluxdensity over the entire series of observations. The basis of the data reduction was optimal filtration of the input data using the method described in detail in [10]. Before this filtration, nonlinear filters were used to clean the input data of impulsive interference, jumps, and trends with time scales longer than the scale of the antenna beam in right ascension. When obtaining the mean fluxdensities for the entire observation time, we used only those recordings for which the noise dispersion at the location of the source was consistent with the noise properties of the total dataset; the method used to identify such recordings is described in [11]. We derived the mean flux density by applying optimal filtration to the average of the recordings, with the ith point for the filtration being the median of all the ith points for the cleaned input recordings. As a check, we also determined the mean fluxdensity
n

which the antenna setup was incorrect. When significant flux-density differences were observed, we inspected all the corresponding recordings visually and removed any that appeared suspicious, then repeated the entire reduction procedure. The measurement errors were also determined in two ways: = where mean signal beam, /
i 2

A2 i

1 2

,

2 is the dispersion of the residual noise in the recordings after removing the detected source and Ai is the tabulated value of the antenna and
n

s =
i

¯ (Si - S )2

n(n - 1)

1 2

,

¯ S=(
i

Si )/n,

(1)

where Si is the flux density of the ith observation and n is the number of observations. There is no reason to introduce a weighting function here, since we are summing only those recordings that have already been determined to have noise characteristics consistent with those for the total dataset. It is clear that the flux densities obtained in these two ways should be close and that substantial differences indicate the presence of a bad recording that has not been removed by the preliminary filtering. Our experience shows that significant differences are encountered only rarely, testifying to the correctness of the filtration algorithm applied. The few bad recordings that were still present are primarily those in
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¯ where S is the mean fluxdensity derived using (1). These two estimates should also be quite similar. If they corresponded to different distributions according to the Fisher criterion, we searched for bad recordings. In any case, we adopted the larger of the two estimates as the uncertainty in the measured flux density. In this approach, the resulting errors include the rms error in the flux density due to variability of the source during the series of observations. 3. RADIO AND OPTICAL COORDINATES Table 1 presents the radio coordinates of the studied objects at epoch 2000.0 and the difference between the optical and radio coordinates for each object. We took the radio coordinates from the JVAS1 catalog at 8.4 GHz [12] (rms coordinate error 0.014 ) and the NVSS2 survey [13] at 1.4 GHz (average
1 2

Jodrell Bank­VLA Astrometric Survey. NRAO VLA Sky Survey.


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AFANAS'EV et al.

1.0 0.8 0.6 0.4 0.2 0
0323 + 0534 z = 0.184 Ly NV SiIV CIV

()
0323 + 0446 z = 2.322

CIII]

(b)

3 2 1 Flux, 10­15 erg/(cm2 s å)
[OII] H FeII

H [SII]

2.0 1.5 1.0 0.5 0
Ly

Ly

(c) 0354 + 0441 z = 3.263
SiIV CIV CIII]

Ly Ly

(d) 0357 + 0542 z = 2.170
CIV [Ne V] CIII]

1.0 0.5

NV

SiIV OIV]

(e) 0427 + 0457 z = 0.517 0.6 0.4 0.2 0 ­ 0.2 4000 5000 6000 7000 Wavelength, å 8000 9000
MgII [OII] H H [OIII]

Fig. 1. Optical spectra of 0323+0446, 0323+0534, 0454+0441, 0357+0542, and 0427+0457 obtained on the 6-m telescope of the SAO.

rms errors about 0.11 and 0.56 in right ascension and declination, respectively). The source names are comprised of the hours and minutes of right ascension and degrees and minutes of declination corresponding to their coordinates. We obtained the optical coordinates from the USNO astrometric survey [14] or the Palomar Sky Survey APM database [15]. Taking

into account the errors in both coordinates, the radio and optical coordinates for all the sources agree to within 3 . 4. RESULTS Figures 1­4 show optical and radio spectra of the objects.
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3.0 2.5 2.0 1.5 1.0 0.5 0 ­ 0.5 Flux, 10­16 erg/(cm2 s å) 0.6 0.4 0.2 0 ­ 0.5 0.6
CIII] Ly 1600 + 0412 [NeV] [OII] [NeIII]

()
1522 + 0400 z = 0.534 [OIII]

[OIII]

H

[OIII]

(b)
CIV

z = 3.11 CIII]

5000

6000 (c)

7000

8000

2301 + 0609 z = 1.089 MgII [NeV] [OII]

0.4 0.2 0 ­ 0.2

4000

5000

6000

7000 Wavelength, å

8000

9000

Fig. 2. Optical spectra of 1522+0400, 1600+0412, and 2301+0609 obtained on the 6-m telescope of the SAO.

Table 2 presents the optical data. The columns give (1) the source name, (2) lines present in the spectrum, (3) the rest-frame and observed wavelengths of these lines, (4) the corresponding redshift, (5) the classification of the object, (6) the observed B magnitude from [14, 15], (7) the observation date, and (8) the exposure in minutes. Table 3 presents the fluxdensities of all the sources shown in Figs. 3 and 4. The columns give (1) the source name, (2)­(7) the flux densities and corresponding rms errors for 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz in mJy, and (8) the observation epoch. We present comments on individual sources below.

4.1. 0323+0446 The radio spectrum of this source, obtained in 1998 (Fig. 3a), falls off and then flattens toward
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higher frequencies. It can be approximated by the logarithmic parabola log S = -0.652 - 0.512 log + 0.171 log 2 (with the flux density in Jy and the frequency in GHz). The source does not display significant variability; over ten years of observations at 7.7 GHz obtained roughly once per year, the measured flux densities ranged from 135 ± 30 to 104 ± 4 mJy (covering a factor of 1.3 ± 0.3). The optical spectrum had been obtained earlier ° at 4500­9000 A using the 2.1-m telescope of the Guillermo Haro Observatory in Mexico. Based on the ° ° two lines CIV 1549 A and CIII] 1909 A, the object was classified as a quasar with a redshift of 2.322 [6]. Sixlines can be identified in the optical spectrum obtained using the SAO 6-m telescope (Fig. 1a): a pow° ° erful, broad Ly 1216 A line (FWHM 130 A), the ° line, the blended SiIV 1394,1403 A dou° NV 1240 A ° ° blet and OIV] 1406 A line, and the CIV 1549 A and


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Flux density, Jy 0.4 0323 + 0446 0.2 0.1

()

Flux density, Jy 1

0427 + 0457

()

0.6 0.4 1522 + 0400 (b)

4 1 0.5 0.2

0323 + 0534

(b)

1 0.3 0.1 0.3

0.3 0.1 0.03 0354 + 0441

(c) 0.1 0.06 0.03 (d) 0.4

1600 + 0412

(c)

2301 + 0609

(d)

0.2 0.2 0.1 0357 + 0542 0.05 1 2 4 7 10 20 Frequency, GHz 0.1 1 2 4 7 10 20 Frequency, GHz

Fig. 3. Radio spectra of 0323+0446, 0323+0534, 0354+0441, and 0357+0542.

Fig. 4. Radio spectra of 0427+0457, 1522+0400, 1600+0412, and 2301+0609. The upper spectrum of 0427+0457 was obtained at epoch November 1997 and the lower at epoch July 1999.

° CIII] 1909 A lines. The redshift derived using all these lines is z = 2.322 ± 0.001, confirming that the object is a quasar.

4.2. 0323+0534
The flux densities at 0.97­21.7 GHz are not variable, and the radio spectrum at 2.3­21.7 GHz is approximated well by the power law S = 3976 -0.968 mJy (Fig. 3b). The spectrum flattens at lower frequencies. Based on the frequency of the turnover due to self-absorption (m 0.25 GHz) and the flux density at this frequency (Sm 8 Jy), we infer that the size of the radiating region exceeds 200 kpc (adopting the value H= 10-4 Oe for the magnetic field in the jet).

° Two Balmer lines--strong H 6563 A and weak ° --can be identified in the optical spectrum H 4861 A ° ° (Fig. 1b),as wellas the [OII] 3727 Aand FeII 4924 A ° lines and the [SII] 6717, 6731 A forbidden doublet. ° The widths of the hydrogen lines are FWHM 70 A. All these lines are visible in emission, and the redshift is z = 0.186 ± 0.005; the object is an emission-line radio galaxy.

4.3. 0354+0441 This source was observed in 1985 at 3.9 and 7.7 GHz.Figure5ashows the flux-density variations at 7.7 GHz. Beginning in 1980, the flux density gradually decreased, reaching a minimum in 1995, after which it began to grow. The characteristic time
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RADIO AND OPTICAL SPECTRAL STUDIES Table 2. Optical data Source name 0323+0446 Lines present Ly SiIV/OIV] CIV CIII] 0323+0534 [OII] H FeII H [SII] 0354+0441 Ly Ly Ly NV SiIV/OIV] CIV CIII] 0357+0542 Ly NV SiIV/OIV] CIV [NeV] CIII] 0427+0457 MgII [OII] H H [OIII] 1522+0400 [NeV] [OII] [NeIII] [OIII] H [OIII] [OIII] 1600+0412 Ly CIV CIII] 2301+0609 CIII] MgII [NeV] [OII]
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° Wavelength, A 1216/4040 1400/4650 1549/5145 1909/6340 3727/4400 4861/5820 4924/5890 6563/7760 6724/7960 973/4150 1026/4375 1216/5185 1240/5285 1400/5940 1549/6600 1909/8135 1216/3865 1240/3930 1400/4440 1549/4875 1575/4930 1909/6056 2798/4245 3727/5654 4340/6590 4861/7375 4959/7522 3426/5255 3727/5725 3869/5930 4363/6655 4861/7465 4959/7615 5007/7685 1216/5000 1549/6320 1909/7850 1909/4000 2798/5830 2973/6210 3727/7780
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z 2.322

Spectral classification QSO

B 19.1

Date Nov. 5, 2000

T ,min 8

0.184

EmG

19.6

Nov. 4, 2000

10

3.263

QSO

19.9

Nov. 4, 2000

10

2.170

QSO

19.6

Nov. 5, 2000

10

0.517

EmG

19.3

Nov. 5, 2000

10

0.534

EmG

20.9

June 6, 2000

40

3.11

QSO

21.1

June 6, 2000

40

1.089

QSO

19.1

Nov. 2, 2000

10


464 Table 3. Radio data Source name 0.97 GHz 0323+0446 0323+0534 0354+0441 0357+0542 0427+0457 1522+0400 1600+0412 2301+0609 230 21 3568 52 420 18 80 15 902 35 712 30 1010 33 289 15 177 16

AFANAS'EV et al.

Fluxdensities and their errors, mJy 2.3 GHz 149 06 1750 27 331 10 182 11 576 25 475 20 450 15 189 07 295 12 3.9 GHz 132 05 1070 10 344 08 232 09 534 20 460 15 284 08 159 05 322 10 7.7 GHz 105 06 556 06 278 08 220 07 504 20 412 10 147 07 163 06 336 12 11.1 GHz 97 05 380 07 252 10 181 06 498 22 418 12 104 05 172 07 324 12 21.7 GHz 95 06 190 12 146 17 112 15 577 25 442 22 58 08 182 16 235 18

Epoch 01.1998 07.1999 01.1998 07.1999 11.1997 07.1999 07.1999 01.1998 08.1997

scale for the variability (from maximum to minimum) is more than ten years. The 0.97­21.7 GHz spectrum in Fig. 3c was obtained in 1998 (diamonds). The spectrum is complex and cannot be approximated by a simple logarithmic parabola. ° ° Three Lyman lines--Ly 973 A, Ly 1026 A, and ° --can be identified in the optical powerful Ly 1216 A ° spectrum (Fig. 1c), as well as the NV 1240 A line, ° doublet and OIV] the blended SiIV 1394, 1403 A ° ° 1406 A line, and the CIV and CIII] 1549 and 1909 A lines. The redshift derived using all the lines is z = 3.263 ± 0.002, and we classified the object as a distant quasar.

4.5. 0427+0457
This source displays appreciable long-term variability. Figure 5b shows the flux-density variations at 7.7 GHz from 1980 to 1999. The maximum 7.7-GHz flux-density variation has an amplitude Smax /Smin = 2 ± 0.14. Figure 4a presents spectra obtained in November 1997 (upper) and July 1999 (lower). Both spectra have a minimum and can be approximated by the parabolas log S = -0.057 - 0.570 log +0.327 log 2 and log S = -0.165- 0.455 log +0.236 log 2 . Note the appreciable variability at low frequencies. Five weak emission lines can be identified in the ° optical spectrum (Fig. 1d): MgII 2798 A, the OII] ° 3727 A forbidden line, the two Balmer lines H ° and H 4861 A, and the [OIII] 4959 A line ° ° 4340 A at a redshift of z = 0.517 ± 0.008. The object is an emission-line radio galaxy.

4.4. 0357+0542
The 0.97­21.7 GHz spectrum of the source at epoch July 1999 can be well approximated with the logarithmic parabola log S = -1.076 + 1.266 log - 0.902 log 2 ; the spectral maximum is at 5.0 GHz, and the maximum flux density is 230 mJy (Fig. 3d). The source shows modest long-term variability. Observations at 7.7 GHz over 11 years obtained roughly once per year show flux-density variations from 275 ± 9 to 220 ± 5 mJy (covering a factor of 1.25 ± 0.05). The optical spectrum (Fig. 1d) shows strong Ly ° 1216 A emission and the nearby NV line, the SiIV ° ° 1394, 1403 A, doublet and the nearby OIV] 1406 A ° and NeV 1575 A lines, ° line, the blended CIV 1549 A ° and the semiforbidden CIII] 1909 A line at a redshift of z = 2.17 ± 0.007. The object was classified as a quasar.

4.6. 1522+0400
The radio spectrum is power-law from 0.97­ 11.1 GHz, S = 985 -0.927 mJy (Fig. 4b), and the flux density is not variable. ° ° A strong [OIII] 5007 A line, weaker OII] 3727 A, ° ° [OIII] 4363 A, and [OIII] 4959 A lines, and weak NeV ° ° ° 3426 A, [NeIII] 3869 A, and H 4861 A lines can be identified in the optical spectrum (Fig. 2a). With the exception of H , all these lines are forbidden and visible in emission. The redshift derived from all the lines is z = 0.534 ± 0.001, and we classified the object as an emission-line radio galaxy.
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Flux density, Jy 500 450 400 350 300 250

0354 + 0441

(a)

° of z = 3.11 ± 0.01. There are also weak CIV 1549 A ° lines present near the noise level. We and HeII 1640 A classified the object as a quasar.

4.8. 2301+0609
This source was observed at 3.9 and 7.5 GHz starting in 1980. Figure 5c presents the 7.7 GHz flux densities for 1980­1997. The flux density reached a minimum in 1987, after which it began to grow. The characteristic variability time scale (from maximum to minimum) is more than ten years, and the maximum flux-density variation at 7.7 GHz is Smax /Smin = 2.7 ± 0.5. The spectrum (Fig. 4d) for August 1997 is well approximated by the logarithmic parabola log S = -0.733 + 0.695 log - 0.456 log 2 , and has a maximum at 5.8 GHz, with the maximum fluxdensity being 340 mJy. Four emission lines can be identified in the optical ° ° spectrum (Fig. 2c): CIII] 1909 A, MgII 2798 A, and ° ° forbidden NeV 2973 Aand OII] 3727 A. The redshift derived from these lines is z = 1.089 ± 0.003, and the object was classified as a quasar.

900 800 700 600 500 400

0427 + 0457

(b)

2301 + 0609 350 300 250 200 150 100 01.1980 01.1985 01.1990

(c)

5. CONCLUSIONS Of the eight objects studied, five proved to be quasars (two with redshifts z > 3) and three to be emission-line radio galaxies. The radio galaxies 0323+0534 and 1522+0400 have constant flux densities and power-law spectra. The z = 0.517 emission-line radio galaxy 0427+0457 and z = 1.089 quasar 2301+0609 display appreciable radio variability. We did not detect any significant variability of the distant (z = 3.11) quasar 1600+0412 at 3.9 and 7.7 GHz over the ten years covered by our observations. As expected, long characteristic variability time scales are observed for all the objects with high redshifts. Nearly all the optical spectra show a rich selection of lines, enabling very accurate determinations of the corresponding redshifts.

01.1995

01.1200

Fig. 5. 7.7-GHz light curves of 0427+0457 and 2301+0609. The fluxdensities before 1991 were obtained on the Southern sector and those after 1995 on the Northern sector of the RATAN-600 telescope.

4.7. 1600+0412
Observations made from 1989 through 1999 roughly once per year at 3.9 and 7.7 GHz did not reveal any flux-density variations within the errors. The ratio of the maximum and minimum fluxdensities measured at 7.7 GHz is Smax /Smin = 1.1 ± 0.15.The spectrum (Fig. 4c) has a minimum near 6 GHz and can be approximated by the parabola log S = -0.553 - 0.617 log +0.384 log 2 at epoch January 1998. One broad line is clearly visible in the optical spectrum (Fig. 2b), which we have interpreted as a blend ° of Ly 1216 A and the nearby NV line at a redshift
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6. ACKNOWLEDGMENTS This work was supported by the Russian Foundation for Basic Research (project no. 01-02-16331), a Universities of Russia grant (project no. UR.02.03.005), and a grant of the State Science and Technology Program "Astronomy" (project no. 1.2.5.1).


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REFERENCES
1. A. G. Gorshkov and V. K. Konnikova, Astron. Zh. 72, 291 (1995) [Astron. Rep. 39, 257 (1995)]. 2. A. M. Botashov, A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev, Astron. Zh. 76, 723 (1999) [Astron. Rep. 43, 631 (1999)]. 3. A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev, Astron. Zh. 77, 407 (2000) [Astron. Rep. 44, 353 (2000)]. 4. V. Chavushyan, R. Mujica, A. G. Gorshkov, et al., Pis'ma Astron. Zh. 26, 403 (2000) [Astron. Lett. 26, 339 (2000)]. 5. V. Chavushyan, R. Mujica, A. G. Gorshkov, et al., Astron. Zh. 78, 99 (2001) [Astron. Rep. 45, 79 (2001)]. 6. V. Chavushyan, R. Mujica, R. Valdes, et al., Astron. Zh. 79, 771 (2002) [Astron. Rep. 46, 697 (2002)]. 7. A. B. Berlin, A. A. Maksyasheva, N. A. Nizhel'skii , et al., Abstracts of Papers, XXVII Radio Astronomy Conference (St. Petersburg, 1997), Vol. 3, p. 115 .

8. V. R. Amirkhanyan, A. G. Gorshkov, and V. K. Konnikova, Astron. Zh. 69, 225 (1992) [Sov. Astron. 36, 115 (1992)]. 9. N. S. Soboleva, A. V. Temirova, and T. V. Pyatunina, Preprint SAO (Spets. Astrofiz. Obs., Nizhnii Arkhyz, 1986), p. 32. 10. A. G. Gorshkov and O. I. Khromov, Astrofiz. Issled. (Izv. Spets. Astrofiz. Obs.) 14, 15 (1981). 11. A. G. Gorshkov and V. K. Konnikova, Astron. Zh. 73, 351 (1996) [Astron. Rep. 40, 314 (1996)]. 12. I. W. A. Browne, Mon. Not. R. Astron. Soc. 293, 257 (1998). 13. J. J. Condon, W. D. Cotton, E. W. Greisen, et al., Astron. J. 115, 1693 (1998). 14. D. Monet, A. Bird, B. Canzian, et al., USNO-SA 1.0 (U.S. Naval Observatory, Washington, 1996). 15. R. L. Pennington, R. M. Humphreys, S. C. Odewahn, et al., Pub. Astron. Soc. Pac. 105, 103 (1993).

Translated by D. Gabuzda

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