2009A&A...508..161G


Query : 2009A&A...508..161G

2009A&A...508..161G - Astronomy and Astrophysics, volume 508, 161-171 (2009/12-2)

Very Long Baseline Array observations of the intraday variable source J1128+592.

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

Abstract (from CDS):

Short timescale flux density variations in flat spectrum radio sources are often explained by the scattering of radio waves in the turbulent ionized interstellar medium of the Milky Way. One of the most convincing observational arguments in favor of this is the annual modulation of the variability timescale caused by the orbital motion of Earth around the Sun. J1128+5925 is a recently discovered IDV source with a possible annual modulation in its variability timescale. New observations suggest a change in its variability characteristics. We search for changes either in source structure or in the interstellar medium that can explain the variations in the IDV pattern of J1128+5925. Using Very Long Baseline Interferometry (VLBI), we study a possible relation between source orientation on the sky and anisotropy angle seen in the annual modulation. Additionally, obtaining a source size estimate from VLBI data enables us to calculate the distance to the screen causing the variations in J1128+5925. We observed the source in six consecutive epochs with the Very Long Baseline Array (VLBA) at three frequencies, 5GHz, 8GHz, and 15GHz in total intensity and polarization. This data are combined with our densely time-sampled flux-density monitoring performed with the radio telescopes at Effelsberg (Germany) and at Urumqi (China). The VLBA observations detected an east-west oriented core-jet structure with no significant motion in its jet. The expansion of the VLBI core leads to an estimate of mild relativistic speed (2.5c±1.4c). The position angle of the VLBI jet agrees with the angle of anisotropy derived from the annual modulation model. No significant long-term structural changes were observed with VLBI on mas-scales, although, the VLBI core-size expansion offers a possible explanation of the observed decrease in the strength of IDV. VLBI polarimetry measured significant changes in the electric vector position angle (EVPA) and rotation measure (RM) of the core and jet. Part of the observed RM variability could be attributed to a scattering screen (37pc distance) that covers the source (core and jet) and may be responsible for the IDV. Superposition of polarized subcomponents below the angular resolution limit may also affect the observed RM.

Abstract Copyright:

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

Simbad objects: 14

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Number of rows : 14
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 QSO B0405-385 QSO 04 06 59.03533781 -38 26 28.0423651   19.55 18.0     ~ 223 2
2 Mrk 1506 Sy1 04 33 11.0956735296 +05 21 15.619461552   15.72 15.05 10.08   ~ 1947 2
3 4C 71.07 QSO 08 41 24.36528508 +70 53 42.1730435     16.5 16.8   ~ 742 1
4 6C 091739+622838 QSO 09 21 36.23107643 +62 15 52.1803510   19.76 19.26 18.96   ~ 341 1
5 ICRF J092703.0+390220 Sy1 09 27 03.01394144 +39 02 20.8518067   17.17 17.00 16.486   ~ 972 1
6 QSO B1036+054 QSO 10 38 46.77987408 +05 12 29.0867216   20.21 19.45 19.53   ~ 96 1
7 QSO J1128+592 QSO 11 28 +59.2           ~ 8 0
8 3C 273 BLL 12 29 06.6998257176 +02 03 08.597629980   13.05 14.830 14.11   ~ 5638 1
9 3C 279 Bla 12 56 11.16657958 -05 47 21.5251510   18.01 17.75 15.87   ~ 2923 2
10 QSO J1300-3253 QSO 13 00 42.4259780568 -32 53 12.114395844     18.70 18   ~ 83 1
11 QSO B1519-273 BLL 15 22 37.67599511 -27 30 10.7855131   18.72 18.5 17.42   ~ 279 1
12 QSO B1622-253 QSO 16 25 46.89164287 -25 27 38.3268734   21.3 20.6 19.60   ~ 330 1
13 ICRF J181926.5+384501 SyG 18 19 26.54735971 +38 45 01.7860362           ~ 116 0
14 NAME Local Bubble ISM ~ ~           ~ 824 0

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2023.02.03-17:10:55

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