2007A&A...470...83G


Query : 2007A&A...470...83G

2007A&A...470...83G - Astronomy and Astrophysics, volume 470, 83-95 (2007/7-4)

The IDV source J1128+5925, a new candidate for annual modulation?

GABANYI K.E., MARCHILI N., KRICHBAUM T.P., BRITZEN S., FUHRMANN L., WITZEL A., ZENSUS J.A., MUELLER P., LIU X., SONG H.G., HAN J.L. and SUN X.H.

Abstract (from CDS):

Short time-scale radio variations of compact extragalactic radio sources, known as IntraDay Variability (IDV), can be explained in at least some sources by a source-extrinsic effect, in which the variations are interpreted as scintillation of radio waves caused by the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favour of propagation-induced variability is the so-called ``annual modulation'' of the characteristic variability time-scale, which is due to the orbital motion of the Earth. So far there are only two sources known which show such a well-defined seasonal cycle, a few more sources with fewer data can be regarded as possible candidates for this effect. However, source-intrinsic effects, such as structural variations, can also cause the observed changes of the variability time-scale. Data for the new, recently discovered, and highly variable IDV source J1128+5925 are presented. We study the frequency and time dependence of the IDV in this compact quasar. We measure the characteristic variability time-scale of the IDV throughout the year, and analyze whether the observed changes in the variability time-scale are consistent with annual modulation. Assuming a radio wave propagation effect as origin, we are able to constrain some physical properties (such as distance, scattering-strength, and possible anisotropy) of the ``plasma'' screen, which may cause the scintillation. We monitored the flux density variability of J1128+5925 with dense time sampling between 2.7 and 10.45GHz. We observed with the 100m Effelsberg radio telescope of the Max-Planck-Institut fuer Radioastronomie (MPIfR) at 2.70GHz, 4.85GHz, and 10.45GHz, as well as with the 25m Urumqi radio telescope (China) at 4.85GHz. From ten observing sessions, each of which lasted several days during the period between 2004-2006, we determine the variability characteristics and time-scales which we investigate in view of possible scintillation and annual modulation. The observed pronounced changes of the variability time-scale of J1128+5925 are modelled with an anisotropic annual modulation model. The observed frequency dependence of the variation is in good agreement with the prediction from interstellar scintillation. Adopting a simple model for the annual modulation model and also using the frequency dependence of the IDV, we derive a lower limit to the distance the scattering screen and an upper limit for the scintillating source size. The latter is found to be consistent with the measured core size from Very Long Baseline Interferometry (VLBI).

Abstract Copyright:

Journal keyword(s): quasars: individual: J1128+5925 - scattering - radio continuum: galaxies - ISM: structure

Simbad objects: 17

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Number of rows : 17
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 3C 48 QSO 01 37 41.2996631208 +33 09 35.080388820   16.62 16.20     ~ 2708 2
2 QSO B0405-385 QSO 04 06 59.03533781 -38 26 28.0423651   19.55 18.0     ~ 221 2
3 8C 0716+714 BLL 07 21 53.4482942664 +71 20 36.363846516   15.5 14.17 14.27   ~ 1232 1
4 4C 71.07 QSO 08 41 24.36528508 +70 53 42.1730435     16.5 16.8   ~ 737 1
5 6C 091739+622838 QSO 09 21 36.23107643 +62 15 52.1803510   19.76 19.26 18.96   ~ 338 1
6 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5657 6
7 6C 095456+654857 BLL 09 58 47.2451872176 +65 33 54.819354600     17.0 15.75   ~ 666 1
8 6C 112519+594222 Bla 11 28 13.34067181 +59 25 14.7985568   19.78 19.56 19.33   ~ 78 1
9 6C 112856+453123 QSO 11 31 38.9 +45 14 51   20.0       ~ 29 1
10 3C 268.3 Sy1 12 06 24.70656 +64 13 36.8760   21.847 20.790 19.910   ~ 185 1
11 QSO J1300-3253 QSO 13 00 42.4259780568 -32 53 12.114395844     18.70 18   ~ 83 1
12 ICRF J131327.9+673550 G 13 13 27.98902761 +67 35 50.3599652           ~ 55 1
13 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4147 2
14 3C 295 Sy2 14 11 20.467 +52 12 09.52   22.34 20.80 18.54   ~ 949 5
15 QSO B1519-273 BLL 15 22 37.67599511 -27 30 10.7855131   18.72 18.5 17.42   ~ 276 1
16 ICRF J181926.5+384501 SyG 18 19 26.54735971 +38 45 01.7860362           ~ 116 0
17 NGC 7027 PN 21 07 01.571952 +42 14 10.47120   10.358 8.831 10.157   ~ 2412 1

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2022.12.01-12:34:39

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