Variability of extragalactic sources at 2.7 GHz. I - Results of a 2-yr monitoring program

Kesteven, M. J.; Bridle, A. H.; Brandie, G. W.

doi:10.1086/111971

Cited by 34 publications

(32 citation statements)

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“…Kesteven, Bridle, and Brandie [35], and Fanti et al [36] considered a source to be possibly and If we base our analysis on the average probabilities p listed in Table 2 In conclusion, we summarize the main results of our search for variable sources reported in this and our earlier paper [13].…”

Section: Variable Sources Of the Rcr Catalogmentioning

confidence: 85%

Search for variable sources using data of “Cold” surveys

Majorova

Желенкова

2013

Astrophys. Bull.

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We search for variable sources, using the data of the surveys conducted on the RATAN-600 radio telescope in 1980-1994 at 3.94 GHz. To test the radio sources of the RCR (RATAN Cold Refined) catalog for variability, we estimated the long-term variability indices V of the studied objects, their relative variability amplitudes V χ , and the χ 2 probabilities p. Out of about two hundred considered sources, 41 proved to have positive long-term variability indices, suggesting that these sources may be variable. Fifteen objects can be considered to be reliably variable according to the χ 2 criterion p > 0.98, three of these sources have χ 2 probabilities p ≥ 0.999. The corresponding probabilities for six sources lie in the 0.95 < p < 0.98 interval, and those of the remaining 20 objects in the 0.73 ≤ p < 0.95 interval. Twenty-four of 41 objects are variable or possibly variable in the optical range, and five objects are known variable radio sources. We construct the light curves and spectra for the sources with positive long-term variability indices.

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Section: Variable Sources Of the Rcr Catalogmentioning

confidence: 85%

Search for variable sources using data of “Cold” surveys

Majorova

Желенкова

2013

Astrophys. Bull.

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“…The source is considered to be variable only if both the F values are greater than F α ν . We also used χ 2 -statistics (Kesteven et al 1976) to characterize INOV. According to this, if the χ 2 value of a DLC exceeds the critical value, χ 2 α,ν , with significance α = 0.01, then the source is considered variable.…”

Section: Intra-night Optical Variability (Inov)mentioning

confidence: 99%

Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst

Rakshit

Stalin

Muneer

et al. 2017

ApJ

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The gamma-ray blazar OJ 287 was in a high activity state during December 2015 -February 2016 Coinciding with this high brightness state, we observed this source for photometry on 40 nights in R-band and for polarimetry on 9 epochs in U BV RI bands. During the period of our observations, the source brightness varied between 13.20 ± 0.04 to 14.98 ± 0.04 mag and the degree of polarization (P ) fluctuated between 6.0 ± 0.3% and 28.3 ± 0.8% in R-band. Focusing on intra-night optical variability (INOV), we find a duty cycle of about 71% using χ 2 -statistics, similar to that known for blazars. From INOV data, the shortest variability time scale is estimated to be 142 ± 38 min yielding a lower limit of the observed Doppler factor δ 0 = 1.17, the magnetic field strength B ≤ 3.8 G and the size of the emitting region R s < 2.28 × 10 14 cm. On inter-night timescales, a significant anti-correlation between R-band flux and P is found. The observed P at U -band is generally larger than that observed at longer wavelength bands suggesting a wavelength dependent polarization. Using V -band photometric and polarimetric data from Steward Observatory obtained during our monitoring period we find a varied correlation between P and V -band brightness. While an anticorrelation is seen between P and V -band mag at sometimes, no correlation is seen at other times, thereby, suggesting the presence of more than one short-lived shock components in the jet of OJ 287.

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“…To confirm the variability of the objects with positive V , we performed computations similar to those made by Gorshkov and Konnikova [6], Kesteven et al [39], Fanti et al [40], and Seielstad et al [38].…”

Section: Analysis Of Statistical Properties Of Suspected Variable Soumentioning

confidence: 99%

“…Column 2 gives the parameter V χ , which characterizes the relative variation amplitude, and column 3 gives the probability p of variability according to the A comparison of the data listed in Tables 3 and 4 shows that the weighted average source flux densities F computed using formula (11) practically coincide with the mean values F (formula (8) Let us now see which objects among those listed in Tables 3 and 4 can be considered variable. Kesteven et al [39] and Fanti et al [40] considered a source to be possibly variable if its χ 2 probability satisfied the condition of 0.1% ≤ 1 − p ≤ 1% and reliably variable if…”

Section: Analysis Of Statistical Properties Of Suspected Variable Soumentioning

confidence: 99%

On possibility of detection of variable sources using the data of “Cold” surveys carried out on RATAN-600

Majorova

Желенкова

2012

Astrophys. Bull.

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In this study we attempt to assess the possibility of detection of variable sources using the data of the 7.6-cm wavelength surveys carried out on the RATAN-600 radio telescope in the period from 1980 through 1994. Objects selected according to certain criteria from the RCR catalog are used to construct the calibration curves and to estimate the accuracy of the resulting calibration curves and determine the r.m.s. errors for the measured source flux densities. To check the calibration sources for the presence of variable objects, quantitative estimates are performed for a number of parameters that characterize variability, in particular, for the long-term variability index V and the χ 2 (chi-square) probability p. The long-term variability index was found to be positive for 14 out of approximately 80 calibration sources, possibly indicating that these sources are variable. The most likely candidate variables are the three sources with the χ 2 probability p > 0.95. Five sources have χ 2 probabilities in the 0.85 < p < 0.95 interval, and the remaining six in the 0.6 < p < 0.8 interval.Nine out of 14 objects are possibly variable in the optical range. The light curves and spectra are determined for possible variable sources and a number of "non-variable" objects. We plan to use the results of this study in our future searches for variable radio sources using the data of the "Cold" surveys.

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Variability of extragalactic sources at 2.7 GHz. I - Results of a 2-yr monitoring program

Cited by 34 publications

References 0 publications

Search for variable sources using data of “Cold” surveys

Search for variable sources using data of “Cold” surveys

Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst

On possibility of detection of variable sources using the data of “Cold” surveys carried out on RATAN-600

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