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J/AJ/126/2562       Second VLBA calibrator survey: VCS2      (Fomalont+, 2003)

The second VLBA calibrator survey: VCS2. Fomalont E.B., Petrov L., Macmillan D.S., Gordon D., Ma C. <Astron. J., 126, 2562-2566 (2003)> =2003AJ....126.2562F
ADC_Keywords: Radio sources ; Surveys ; Positional data Keywords: astrometry - catalogs - quasars: general - radio continuum - reference systems - techniques: interferometric Abstract: This paper presents an extension of the Very Long Baseline Array Calibrator Survey, called VCS2, containing 276 sources. This survey fills in regions of the sky that were not completely covered by the previous VCS1 calibrator survey. The VCS2 survey includes calibrator sources near the Galactic plane, -30°<DE←45°, and VLA calibrators. The positions have been derived from astrometric analysis of the group delays measured at 2.3 and 8.4 GHz using the Goddard Space Flight Center CALC/SOLVE package. From the VLBA snapshot observations, images of the calibrators are available, and each source is given a quality code for anticipated use. The VCS2 catalog is available from the NRAO Web site. Description: The VCS2 observations were carried out in two 24hr sessions: 2002 January 31 and 2002 May 14. The observations used the VLBA dual-frequency geodetic mode, observing simultaneously at 2.3GHz (S band) and 8.4GHz (X band). The data for each of these two frequencies were separated into four 8MHz channels, which spanned 140MHz at 2.3GHz and 490MHz at 8.4GHz, in order to provide precise measurements of the group delays for astrometric processing. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 100 276 The VCS2 Source List
See also: VIII/60 : Interferometer phase calibration sources (Patnaik+ 1998) J/ApJS/141/13 : VLBA calibrator Survey - VCS1 catalog (Beasley+, 2002) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 10 A10 --- VCS2 Second VLBA Calibrator Survey J2000 source name 12- 19 A8 --- IVS The B1950 source name (1) 21- 22 I2 h RAh Hour of right ascension (J2000) 24- 25 I2 min RAm Minute of right ascension (J2000) 27- 34 F8.5 s RAs Second of right ascension (J2000) 36- 42 F7.5 s e_RAs The 1 σ error in RAs 44 A1 --- DE- Sign of the declination (J2000) 45- 46 I2 deg DEd Degree of declination (J2000) 48- 49 I2 arcmin DEm Arcminute of declination (J2000) 51- 57 F7.4 arcsec DEs Arcsecond of declination (J2000) 59- 64 F6.4 arcsec e_DEs The 1 σ error in DEs 66- 71 F6.3 --- Cor Correlation between RA and DE error estimate 73- 75 I3 --- Num Number of observations used from survey sessions 77- 80 A4 --- BCode Band code (2) 81- 85 F5.2 Jy SFlux S-band (2.3GHz) correlated flux density at 500km baseline 87 A1 --- q_SFlux Quality factor on SFlux (3) 89- 93 F5.2 --- XFlux X-band (8.4GHz) correlated flux density at 500km baseline 95 A1 --- q_XFlux Quality factor on XFlux (3) 97-100 A4 --- --- [vcs2] Catalog name
Note (1): In JHHMM+DD.d format. Note (2): Band code: X/S = An ionosphere-free linear combination of the X-band and S-band data used for the position determination; X+ = Only X-band group delays were used, because of the poor quality of the S-band data; X-o = Only X-band group delays were used, because no fringes at S band were detected. Note (3): Quality factor: 1 = Excellent quality. Little change of signal over all baselines and stronger than 0.4Jy. 2 = Good quality. Some decrease of signal at shorter baselines, but stronger than 0.2Jy at all baselines. 3 = Average quality. Decrease of signal at the shorter baselines, but stronger than 0.10Jy everywhere. 4 = Fair quality. Less than 0.10Jy on the longer baselines, but more signal on the shorter baselines. These calibrators should be checked before using. 5 = Poor quality. Less than 0.10Jy on most baselines. These calibrators should not be used. The positions could be even more in error than indicated. Most sources within about 10 degrees of the Galactic plane are significantly broadened by interstellar scattering at 2.3GHz. ? = Unknown quality.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 12-Jan-2004
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