58 research outputs found
The observed radio/gamma-ray emission correlation for blazars with the Fermi-LAT and the RATAN-600 data
We study the correlation between gamma-ray and radio band radiation for 123
blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data
obtained at the same period of time (within a few months). We found an apparent
positive correlation for BL Lac and flat-spectrum radio quasar (FSRQ) sources
from our sample through testing the value of the Pearson product-moment
correlation coefficient. The BL Lac objects show higher values of the
correlation coefficient than FSRQs at all frequencies, except 21.7 GHz, and at
all bands, except GeV, typically at high confidence level (> 99%). At
higher gamma-ray energies the correlation weakens and even becomes negative for
BL Lacs and FSRQs. For BL Lac blazars, the correlation of the fluxes appeared
to be more sensitive to the considered gamma-ray energy band, than to the
frequency, while for FSRQ sources the correlation changed notably both with the
considered radio frequency and gamma-ray energy band. We used a data
randomization method to quantify the significance of the computed correlation
coefficients. We find that the statistical significance of the correlations we
obtained between the flux densities at all frequencies and the photon flux in
all gamma-ray bands below 3 GeV is high for BL Lacs (chance probability ). The correlation coefficient is high and significant for
the GeV band and low and insignificant for the GeV band for
both types of blazars for all considered frequencies.Comment: 14 pages, 5 tables, 8 figures, accepted to MNRA
Simultaneous spectra and radio properties of BL Lac's
We present the results of nine years of the blazar observing programme at the
RATAN-600 radio telescope (2005-2014). The data were obtained at six frequency
bands (1.1, 2.3, 4.8, 7.7, 11.2, 21.7 GHz) for 290 blazars, mostly BL Lacs. In
addition, we used data at 37 GHz obtained quasi-simultaneously with the
Metsahovi radio observatory for some sources. The sample includes blazars of
three types: high-synchrotron peaked (HSP), low-synchrotron peaked (LSP), and
intermediate-synchrotron peaked (ISP). We present several epochs of flux
density measurements, simultaneous radio spectra, spectral indices and
properties of their variability. The analysis of the radio properties of
different classes of blazars showed that LSP and HSP BL Lac blazars are quite
different objects on average. LSPs have higher flux densities, flatter spectra
and their variability increases as higher frequencies are considered. On the
other hand, HSPs are very faint in radio domain, tend to have steep low
frequency spectra, and they are less variable than LSPs at all frequencies.
Another result is spectral flattening above 7.7 GHz detected in HSPs, while an
average LSP spectrum typically remains flat at both the low and high frequency
ranges we considered.Comment: 14 pages, 6 figures. Accepted for publication in Astronomische
Nachrichte
RATAN-600 multi-frequency data for the BL Lacertae objects
We present a new catalogue of the RATAN-600 multi-frequency measurements for BL Lac objects. The purpose of this catalogue is to compile the BL Lac multi-frequency data that is acquired with the RATAN-600 simultaneously at several frequencies. The BL Lac objects emit a strongly variable and polarized non-thermal radiation across the entire electromagnetic spectrum from radio to gamma rays and represent about 1% of known AGNs. They belong to the blazar population and differ from other blazars' featureless optical spectrum, which sometimes have absorption lines, or have weak and narrow emission lines. One of the most effective ways of studying the physics of BL Lacs is the use of simultaneous multi-frequency data.
The multi-frequency broadband radio spectrum was obtained simultaneously with an accuracy of up to 1-2 min for four to six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The catalogue is based on the RATAN-600 observations and on the data from: equatorial coordinate and redshift, R-band magnitude, synchrotron peak frequency, SED classes, and object type literature.
The present version of the catalogue contains RATAN-600 flux densities measurements over nine years (2006-2014), radio spectra at different epochs, and their parameters of the catalogue for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600.</p
Multifrequency quasi-simultaneous observations of six low-synchrotron peaked blazars
© Pleiades Publishing, Ltd., 2015. We made an estimation of the synchrotron peak frequency (νspeak) of the spectral energy distribution (SED) for six blazars. These objects were selected as very-low-synchrotron peaked (VLSP) blazar candidates (with νspeak ≤ 1013 Hz).We have built the SED of the studied objects using quasi-simultaneous observations on the SAO RAS Zeiss-1000 and RATAN-600 telescopes and made an estimation of the synchrotron peak frequency. As a result, three sources (PKS0446+11, [HB89] 1308+326, and 3C345) were confirmed as VLSP, for the three remaining blazars the calculations have shown νspeak > 1013 Hz
The RATAN-600 multi-frequency catalogue of blazars -- BLcat
In this paper we present the RATAN-600 multi-frequency catalogue of blazars,
an updated version of the BLcat: the RATAN-600 multi-frequency catalogue of BL
Lacertae objects. The main novelty in the catalogue is an extension of the
sample with flat-spectrum radio quasars (FSRQs), thus currently it contains
more than 1700 blazars of different types. The main feature of the BLcat is a
compilation of radio continuum data for blazars based on the RATAN-600
quasi-simultaneous measurements at frequencies of 1.1, 2.3, 4.7, 7.7/8.2, 11.2,
and 21.7/22.3 GHz. We additionally supplement the catalogue with the radio data
from external sources to provide an opportunity to more complete study of radio
spectra and radio light curves. For the convenience of users, we developed
tools to calculate the spectral index, variability index, and radio luminosity.
We briefly describe basic radio properties of blazar subsamples of the
catalogue: spectral classification, spectral indices, flux density variability,
and radio luminosity.Comment: 9 pages, 8 figure
Study of the relation between the jet and accretion-disk emission in Blazars using RATAN-600 multifrequency data
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. © 2014 Pleiades Publishing, Ltd
A systematic TMRT observational study of Galactic C/C ratios from Formaldehyde
We present observations of the C-band (4.8 GHz) and Ku-band
(14.5 GHz) K-doublet lines of HCO and the C-band
(4.6 GHz) line of HCO toward a large sample of
Galactic molecular clouds, through the Shanghai Tianma 65-m radio telescope
(TMRT). Our sample with 112 sources includes strong HCO sources from the
TMRT molecular line survey at C-band and other known HCO sources. All three
lines are detected toward 38 objects (43 radial velocity components) yielding a
detection rate of 34\%. Complementary observations of their continuum emission
at both C- and Ku-bands were performed. Combining spectral line parameters and
continuum data, we calculate the column densities, the optical depths and the
isotope ratio HCO/HCO for each source. To evaluate photon
trapping caused by sometimes significant opacities in the main isotopologue's
rotational mm-wave lines connecting our measured K-doublets, and to obtain
C/C abundance ratios, we used the RADEX non-LTE model accounting
for radiative transfer effects. This implied the use of the new collision rates
from \citet{Wiesenfeld2013}. Also implementing distance values from
trigonometric parallax measurements for our sources, we obtain a linear fit of
C/C = (5.081.10)D + (11.866.60), with a
correlation coefficient of 0.58. D refers to Galactocentric distances.
Our C/C ratios agree very well with the ones deduced from CN and
CO but are lower than those previously reported on the basis of HCO,
tending to suggest that the bulk of the HCO in our sources was formed on
dust grain mantles and not in the gas phase.Comment: 27 pages, 8 figures, 7 tables. Accepted for publication in The
Astrophysical Journa
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