3. Results

3.1. The observational parameters

The observational parameters of the radio observations are summarized in Table 1 (click here).

   

Array Date Beam Comp. RA(1950) DEC(1950)

name (MHz) (mJy) (h) (m) (s) (mJy) (mJy)

VLA 90 May 17 8415 0.30 0.26 50 0.06 a 14 22 37.47 20 14 00.44 28.6 85.6

- - - - - - - b 14 22 37.51 20 13 57.50 26.6 26.6

- - - - - - - c 14 22 37.49 20 13 54.68 7.3 19.4

- - - - - - - d 14 22 37.48 20 13 52.44 2.4 4.6

- - - - - - - e 14 22 37.51 20 13 49.39 100.1 206.9

- - - - - - - f 14 22 37.75 20 13 47.90 0.8 13.6

VLA 90 May 17 14965 0.17 0.15 50 0.1 a 14 22 37.47 20 13 57.45 6.2 17.4

- - - - - - - b 14 22 37.51 20 13 57.51 15.1 18.7

- - - - - - - c 14 22 37.49 20 13 54.68 1.7 2.3

- - - - - - - e 14 22 37.51 20 13 49.40 31.4 92.4

EVN 87 Mar 01 1.666 0.15 0.15 - 0.5 b 14 22 37.49 20 13 57.35 14.7 15.1

- - - - - - - d 14 22 37.50 20 13 49.62 5.2 7.4

3.2. Source position

  The positions we obtained for the VLBI core component of 1422+202 are referred to those of OQ208. Before making any comparisons between the VLA and VLBI positions one has to take the following issues into consideration.

• The differences between the positions used as input at the VLBI correlator and the VLA positions for OQ208 give (VLBI-VLA): (B1950.0) and (B1950.0). This difference accounts for both the elliptical aberration ( and in R.A. and Dec. respectively; see for example Aoki et al. 1983) and the difference between the VLBI reference frame and the VLA we derived (<0.050.3 rms in B1950.0 coordinates). The elliptical aberration had to be corrected for, as source positions in b1950.0 coordinates were used in the correlator, which does not account for elliptical aberration.
• The positional accuracy for a VLA observation is estimated to be better than 0.1 (Perley et al. 1982).

The cross in Figs. 2 (click here)-3 (click here) marks the position of the optical counterpart for 1422+202 as given by Argue et al. (1973). Table 2 (click here) presents the differences between the VLBI, VLA, and optical positions.

   

(VLA-VLBI)core 0.02 +0.26

(VLA-VLBI)hot spot 0.01 -0.22

VLAcore-Optical 0.02 -0.03

We estimate the VLBI positional accuracy of 1422+202 to be about of the same order of magnitude as the VLA positional accuracy. This means that the positions derived from the VLBI, VLA, and optical observations do overlap inside the given errors.