Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU
Observations of the millimeter wave emission variability of extragalactic radio sources may give an important information on active processes in their inner parts. The millimeter wave observations of extragalactic radio sources were started with the 22-m radio telescope of the Crimean Astrophysical...
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Головна астрономічна обсерваторія НАН України
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irk-123456789-796452015-04-04T03:02:12Z Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU Volvach, A.E. Ryabov, M.I. MS3: Physics of Stars and Galaxies Observations of the millimeter wave emission variability of extragalactic radio sources may give an important information on active processes in their inner parts. The millimeter wave observations of extragalactic radio sources were started with the 22-m radio telescope of the Crimean Astrophysical Observatory in 1973. Since 1973, over 10 000 observations of 140 sources have been obtained. As the extended monitoring programs have demonstrated, there are unpredictable outbursts, quiescent periods, minimum flux levels, and secular trends. As it follows from the analysis, the flare evolution can be divided in three phases: (1) a rapid flux increase; (2) a plateau when the flux relatively constant; (3) a slow intensity decrease. Significant differences in the flare evolution in various optical classes of radio sources were not found. The Odesa Observatory of the Institute of Radio Astronomy of NAS of Ukraine (IRA NASU) have performed a long-term flux monitoring of extragalactic radio sources at 102 MHz with the DKR–1000 radio telescope of the Pushchino Radio Astronomy Observatory of the Astro–Space Center of the Lebedev Physical Institute. About 20 observational sessions of over 80 compact and extended radio sources have been carried out in 1984–1985, 1988–1992, and 1996–1998. The variability of radio sources at meter wavelengths is caused by “scintillations” of the flux density of the inhomogeneity of the local interstellar medium. At the same time, many of sources are showed anomalous flux variations at meter wavelengths that do not correspond to the assumption about interstellar scintillations. In this paper, we present a comparison of the data of two independent observations programs. Own activity of radio sources has been taken into account and the flux variability with the time delay at millimeter and meter wavelengths has been considered. It was possible due to the longer time series of the RT-22 observations. 2005 Article Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU / A.E. Volvach, M.I. Ryabov // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 211-215. — Бібліогр.: 7 назв. — англ. 0233-7665 http://dspace.nbuv.gov.ua/handle/123456789/79645 en Кинематика и физика небесных тел Головна астрономічна обсерваторія НАН України |
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MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies |
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MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies Volvach, A.E. Ryabov, M.I. Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU Кинематика и физика небесных тел |
| description |
Observations of the millimeter wave emission variability of extragalactic radio sources may give an important information on active processes in their inner parts. The millimeter wave observations of extragalactic radio sources were started with the 22-m radio telescope of the Crimean Astrophysical Observatory in 1973. Since 1973, over 10 000 observations of 140 sources have been obtained. As the extended monitoring programs have demonstrated, there are unpredictable outbursts, quiescent periods, minimum flux levels, and secular trends. As it follows from the analysis, the flare evolution can be divided in three phases: (1) a rapid flux increase; (2) a plateau when the flux relatively constant; (3) a slow intensity decrease. Significant differences in the flare evolution in various optical classes of radio sources were not found. The Odesa Observatory of the Institute of Radio Astronomy of NAS of Ukraine (IRA NASU) have performed a long-term flux monitoring of extragalactic radio sources at 102 MHz with the DKR–1000 radio telescope of the Pushchino Radio Astronomy Observatory of the Astro–Space Center of the Lebedev Physical Institute. About 20 observational sessions of over 80 compact and extended radio sources have been carried out in 1984–1985, 1988–1992, and 1996–1998. The variability of radio sources at meter wavelengths is caused by “scintillations” of the flux density of the inhomogeneity of the local interstellar medium. At the same time, many of sources are showed anomalous flux variations at meter wavelengths that do not correspond to the assumption about interstellar scintillations. In this paper, we present a comparison of the data of two independent observations programs. Own activity of radio sources has been taken into account and the flux variability with the time delay at millimeter and meter wavelengths has been considered. It was possible due to the longer time series of the RT-22 observations. |
| format |
Article |
| author |
Volvach, A.E. Ryabov, M.I. |
| author_facet |
Volvach, A.E. Ryabov, M.I. |
| author_sort |
Volvach, A.E. |
| title |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU |
| title_short |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU |
| title_full |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU |
| title_fullStr |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU |
| title_full_unstemmed |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU |
| title_sort |
flux density monitoring of extragalactic radio sources. observations at 22, 37 ghz and 102 mhz within the research programs for the rt-22 crao and the odesa observatory "uran-4" ira nasu |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2005 |
| topic_facet |
MS3: Physics of Stars and Galaxies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79645 |
| citation_txt |
Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU / A.E. Volvach, M.I. Ryabov // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 211-215. — Бібліогр.: 7 назв. — англ. |
| series |
Кинематика и физика небесных тел |
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AT volvachae fluxdensitymonitoringofextragalacticradiosourcesobservationsat2237ghzand102mhzwithintheresearchprogramsforthert22craoandtheodesaobservatoryuran4iranasu AT ryabovmi fluxdensitymonitoringofextragalacticradiosourcesobservationsat2237ghzand102mhzwithintheresearchprogramsforthert22craoandtheodesaobservatoryuran4iranasu |
| first_indexed |
2025-07-06T03:40:17Z |
| last_indexed |
2025-07-06T03:40:17Z |
| _version_ |
1836867353968640000 |
| fulltext |
FLUX DENSITY MONITORING OF EXTRAGALACTIC RADIO SOURCES.
OBSERVATIONS AT 22, 37 GHz AND 102 MHz WITHIN THE RESEARCH
PROGRAMS FOR THE RT-22 CrAO AND THE ODESA OBSERVATORY
“URAN-4” IRA NASU
A. E. Volvach1, M. I. Ryabov2
1Laboratory of Radio Astronomy, Crimean Astrophysical Observatory
RT-22, Katsively, 98688 Yalta, Ukraine
e-mail: volvach@crao.crimea.ua
2Odesa Observatory, Institute of Radio Astronomy, NAS of Ukraine
37 Pushkinska Str., 65011 Odesa, Ukraine
Observations of the millimeter wave emission variability of extragalactic radio sources may give
an important information on active processes in their inner parts. The millimeter wave obser-
vations of extragalactic radio sources were started with the 22-m radio telescope of the Crimean
Astrophysical Observatory in 1973. Since 1973, over 10 000 observations of 140 sources have been
obtained. As the extended monitoring programs have demonstrated, there are unpredictable out-
bursts, quiescent periods, minimum flux levels, and secular trends. As it follows from the analysis,
the flare evolution can be divided in three phases: (1) a rapid flux increase; (2) a plateau when
the flux relatively constant; (3) a slow intensity decrease. Significant differences in the flare
evolution in various optical classes of radio sources were not found. The Odesa Observatory of
the Institute of Radio Astronomy of NAS of Ukraine (IRA NASU) have performed a long-term
flux monitoring of extragalactic radio sources at 102 MHz with the DKR–1000 radio telescope of
the Pushchino Radio Astronomy Observatory of the Astro–Space Center of the Lebedev Physical
Institute. About 20 observational sessions of over 80 compact and extended radio sources have
been carried out in 1984–1985, 1988–1992, and 1996–1998. The variability of radio sources at
meter wavelengths is caused by “scintillations” of the flux density of the inhomogeneity of the lo-
cal interstellar medium. At the same time, many of sources are showed anomalous flux variations
at meter wavelengths that do not correspond to the assumption about interstellar scintillations.
In this paper, we present a comparison of the data of two independent observations programs.
Own activity of radio sources has been taken into account and the flux variability with the time
delay at millimeter and meter wavelengths has been considered. It was possible due to the longer
time series of the RT-22 observations.
INTRODUCTION
Observations of the millimeter wave emission variability of extragalactic radio sources may give an important
information on active processes in their inner parts. The millimeter wave observations of extragalactic radio
sources were started with the 22-m radio telescope of the Crimean Astrophysical Observatory (CrAO) in 1973.
Since 1973, over 10 000 observations of 140 sources have been obtained.
As the extended monitoring programs have demonstrated, there are unpredictable outbursts, quiescent
periods, minimum flux levels, and secular trends. As it follows from the analysis, the flare evolution can be
divided in three phases: (1) a rapid flux increase; (2) a plateau when the flux relatively constant; (3) a slow
intensity decrease. Significant differences in the flare evolution in various optical classes of radio sources were
not found.
The Odesa Observatory of the Institute of Radio Astronomy of NAS of Ukraine (IRA NASU) have per-
formed a long-term flux monitoring of extragalactic radio sources at 102 MHz with the DKR-1000 radio tele-
scope of the Pushchino Radio Astronomy Observatory of the Astro–Space Center of the Lebedev Physical
Institute. About 20 observational sessions of over 80 compact and extended radio sources have been carried out
in 1984–1985, 1988–1992, and 1996–1998.
The variability of radio sources at meter wavelengths is caused by “scintillations” of the flux density of
the inhomogeneity of the local interstellar medium. At the same time, many of sources are showed anomalous
flux variations at meter wavelengths that do not correspond to the assumption about interstellar scintillations.
c© A. E. Volvach, M. I. Ryabov, 2004
211
In this paper, we present a comparison of the data of two independent observations programs. Own activity
of radio sources has been taken into account and the flux variability with the time delay at millimeter and meter
wavelengths has been considered. It was possible due to the longer series of the RT-22 observations.
OBSERVATIONS
RT-22 observations
The observations were carried out with the 22-m CrAO radio telescope. For our measurements, we used two
similar Dicke switched radiometers of 22 GHz and 37 GHz. Until the end of 1981, the receiver with a RF
pre-amplifier was used at 22 GHz. Characteristics of the receivers and telescopes are presented in Table 1.
Table 1. Parameters of the receiving systems
Frequency, Aperture HPBW Beam Sensitivity Detection level
GHz effic. separation [K], (t = 1 s)
22 0.43 2.6′ 18.3′ 0.20 0.08
37 0.40 1.6′ 8.3′ 0.15 0.06
The antenna temperatures from sources were measured using the standard ON–ON method described by
Efanov et al. [3]. Before measuring the intensity, we determined the source position by scanning. The radio
telescope was then pointed at the source alternately by the principal and reference (arbitrary) beam lobes formed
during beam modulation and having mutually orthogonal polarizations. The antenna temperature from a source
was defined as the difference between the radiometer responses averaged over 30 s at two different antenna
positions. Depending on the intensity of the emission from sources, we made a series of 6–20 measurements and
then calculated the mean signal intensity and estimated the rms error of the mean.
The gain of the receiver was monitored using a noise generator every 2–3 hours. The orthogonal polarization
of the lobes allowed us to measure the total intensity of the emission from sources, irrespective of the polarization
of this emission. Absorption in the Earth’s atmosphere was taken into account by using atmospheric scans made
every 3–4 hours. The errors of the calculated optical depths are believed to be less than 10%.
The errors of the measured flux densities include the uncertainties of (1) the detected mean value of the an-
tenna temperature of the sources, (2) the calibration source measurements, (3) the noise generator level mea-
surement, and (4) the atmosphere attenuation corrections, but the main contributions to the quoted errors are
due to the first two terms.
The RT–22 flux densities are presented in Fig. 1 [4–7]. The flux density scale of observations was calibrated
using DR 21, 3C 274, Jupiter, and Saturn. The adopted parameters of the calibrators are listed in Table 2.
Table 2. The flux density values and beam size correction factors C of the calibration sources
Source f , GHz S, Jy C
DR 21 22.2 19.0 1.023
DR 21 36.8 18.06 1.050
3C 274 22.2 21.68 1.059
3C 274 36.8 15.04 1.104
Jupiter 22.2 1373 1
Jupiter 36.8 4348 1
Saturn 22.2 887 1
Saturn 36.8 2730 1
1 Flux densities are given for the distance of 1 AU. Beam correction factors
are variable because of variability of the distance of planets.
DKR-1000 observations
With the radio telescope DKR-1000 at frequency 102 MHz, a long term observational program of variability in
extragalactic radio sources is carried out. The observations cover the period 1984–1985 and 1988–1992. During
this period, 15 cycles of observations were carried out. The authors used their own procedure for obtaining
“light” curves of relative variations in the flux density by using the “calibration” sources [1, 2].
212
1977 1979 1981 1983 1985 1987 1989 1991 1993 1995
1
2
3
4
5
3C 111
1977 1979 1981 1983 1985 1987 1989 1991 1993 1995
1
2
3
4
5
1982 1984 1986 1988 1990 1992 1994 1996
0
0.4
0.8
1.2 3C 216
1982 1984 1986 1988 1990 1992 1994 1996
0
0.4
0.8
1.2
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
20
30
40
50
60
3C 273
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
20
30
40
50
60
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
5
10
15
20
25
3C 279
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
5
10
15
20
25
1984 1986 1988 1990 1992 1994 1996
0
1
2
3
3C 380
1984 1986 1988 1990 1992 1994 1996
0
1
2
3
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
4
8
12
16
20
3C 454.3
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
4
8
12
16
20
Figure 1. The RT-22 flux density in the observed sources as a function of the time
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
3C 111
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
1
1.2
1.4 3C 216
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
1
1.2
1.4
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
3C 273
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
3C 279
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
3C 380
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1.3
3C 454.3
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
0.8
0.9
1
1.1
1.2
1.3
Figure 2. The DKR-1000 flux density in the observed sources as a function of the time
213
The sources which did not change their flux among observational cycles were used as the calibration ones.
Thus, for all the examined sources, the “standard” flux variations relative to their average magnitude were
obtained during the whole observational period.
Observations were carried out all days and nights, and, therefore, it was necessary to exclude the influence
of seasonal and daily effects because changes in the ionosphere state. This problem was successfully solved, and,
eventually, variations in source fluxes are “free” of the ionosphere influence. As a result, variations in source
fluxes have been revealed from cycle to cycle within 25% of their mean level during the whole observational
period. The results obtained indicate the presence of refractions scintillations in radio sources during 1–3 months.
A whole number of extended sources showed a flux stability throughout all these observational periods. These
sources were used as the reference ones to estimate variations in fluxes of the compact sources 3C 2, 3C 103,
3C 228. Of particular importance are observational findings of “light curve” variations in the flux density.
Each of them can yield a valuable information on the character of own variability radio sources, inhomo-
geneities and turbulence state of interstellar medium in these or those regions of LISM. The DKR-1000 flux
densities are presented in Fig. 2.
DISCUSSION
The 3C 111, 3C 216, 3C 273, 3C 279, 3C 380, and 3C 454.3 radio sources were most extensively observed at
high and low frequencies. They were in a various stage of activity. The data of the monitoring was the best
at high frequency. We have calculated the relative units of the flux density for comparison of observations of
sources with RT-22 and DKR-1000.
In Fig. 3, the measured flux densities of the observed radio sources are plotted as the relation of the common
period of observations of each source with RT-22 and DKR-1000. It gives a possibility to study variations of
the flux density at different frequencies.
Unfortunately, the monitoring of sources was not extensive. In this connection, it is possible to suggest flux
density variations only at low and high frequencies. At the same time, if there is a variation at a low frequency,
it should appear with a time delay at a high frequency.
• 3C 111. During 1984–1982, there was no variations at high and low frequencies. We have not the obser-
vations with RT-22 from 1988 until 1990.
• 3C 216. There are variations of the flux density in different periods, but the times of observations at low
and high frequencies do not coincide.
• 3C 380. The source showed an increase of the flux density for the period from 1986 until 1996. The small
bursts are registered at high frequencies. However, in this period, when the source was observed simultaneously
with RT-22 and DKR-1000, the flux density practically did not vary.
• 3C 273. The source is one of the best observed with RT-22 extragalactic object. The bursts were observed
in 1983 and 1991. The flux density twice increased. At the same time, we had the DKR-1000 observations for
the periods when the flux at high frequencies was at an average level.
• 3C 279. The source is a most observable source at different frequencies. We observed variations in
the radio intensity at high frequency. Since the early 1981, the flux density at a high frequency had increased,
having reached its highest value in the 1982. Then, the source flux density has decreased until 1984. At a low
frequency, the flux density had increased in 1984–1985, and then the flux has decreased until 1996. Probably,
such a variation of the flux density is the result of the activity of source at high frequencies with a shift of
two years.
• 3C 454.3. The source is a most observable source at different frequencies too. The bursts are registered
at high frequencies in 1981, 1989, 1991, and 1994. There were no variations in the radio intensity at low and
high frequencies from 1985 to 1988. In 1988 and 1990, the flux density had simultaneously increased at low and
high frequencies.
CONCLUSIONS
Using monitoring of sources at high and low frequencies, the preliminary analysis of variations in the radio
intensity show different changes. Probably, for each source depending on its structure and the activity, there
is a “script” of the development of bursts from high to low frequencies. There can be various displays of
the variations in the radio intensity at low and high frequencies:
1. the two-year delay in the flux density variations from high frequencies to low (source 3C 279).
2. the quasi-synchronous variations of the flux density, when the bursts are observed at high and low fre-
quencies (source 3C 454.3).
214
0
0.5
1
1.5
2
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 111 RT-22
0
0.5
1
1.5
2
3C 111 DKR-1000
0
0.5
1
1.5
2
1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 216 RT-22
0
0.5
1
1.5
2
3C 216 DKR-1000
0
0.5
1
1.5
2
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 273 RT-22
0
0.5
1
1.5
2
3C 273 DKR-1000
0
0.5
1
1.5
2
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 279 RT-22
0
0.5
1
1.5
2
3C 279 DKR-1000
0
0.5
1
1.5
2
1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 380 RT-22
0
0.5
1
1.5
2
3C 380 DKR-1000
0
0.5
1
1.5
2
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
0
0.5
1
1.5
2
3C 454.3 RT-22
0
0.5
1
1.5
2
3C 454.3 DKR-1000
Figure 3. Flux density in the observed sources as a function of the time
3. the independent displays of the flux density variations at low and high frequencies, when the variability
of radio sources at a low frequency is caused by “scintillations” of the flux density of the inhomogeneity
of the local interstellar medium.
A further joint program of the observations at meter, decimeter, centimeter, and millimeter wavelengths for
a detailed study of flux density variations of AGN is planned.
[1] Bochkarev N. G., Ryabov M. I. // Astron. and Astropys. Transactions.–1996.–12.–P. 1–11.
[2] Bochkarev N. G., Ryabov M. I. // New Astron. Rev.–2000.–44.–P. 375–377.
[3] Efanov V. A., Moiseev I. G., Nesterov N. S. // Izv. Krym. Astrofiz. Obs.–1979.–60.–P. 3.
[4] Nesterov N. S., Volvach A. E. // Astron. Lett.–2002.–28.–P. 656.
[5] Nesterov N. S., Volvach A. E. // Astron. Lett.–2002.–28.–P. 721.
[6] Salonen E., Terasranta H., Urpo S., et al. // Astron. and Astrophys. Suppl. Ser.–1987.–70.–P. 409.
[7] Terasranta H., Tornikovski M., Urpo S., et al. // AAPS.–1992.–94.–P. 121.
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