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681. VLBA observations of the AGN TXS 0128+554
ID:
ivo://CDS.VizieR/J/ApJ/899/141
Title:
VLBA observations of the AGN TXS 0128+554
Short Name:
J/ApJ/899/141
Date:
14 Mar 2022 07:07:50
Publisher:
CDS
Description:
We have carried out a Chandra X-ray and multifrequency radio Very Long Baseline Array study of the active galactic nucleus (AGN) TXS0128+554, which is associated with the Fermi {gamma}-ray source 4FGLJ0131.2+5547. The AGN is unresolved in a target 19.3ks Chandra image, and its spectrum is well fit by a simple absorbed power-law model, with no distinguishable spectral features. Its relatively soft X-ray spectrum compared to other compact symmetric objects (CSOs) may be indicative of a thermal emission component, for which we were able to obtain an upper temperature limit of kT=0.08keV. The compact radio morphology and measured advance speed of 0.32c{+/-}0.07c indicate a kinematic age of only 82yr{+/-}17yr, placing TXS0128+554 among the youngest members of the CSO class. The lack of compact, inverted spectrum hotspots and an emission gap between the bright inner jet and outer radio lobe structure indicate that the jets have undergone episodic activity, and were relaunched a decade ago. The predicted {gamma}-ray emission from the lobes, based on an inverse Compton-emitting cocoon model, is three orders of magnitude below the observed Fermi-LAT flux. A comparison to other Fermi-detected and non-Fermi-detected CSOs with redshift z<0.1 indicates that the {gamma}-ray emission likely originates in the inner jet/core region, and that nearby, recently launched AGN jets are primary candidates for detection by the Fermi-LAT instrument.
682. VLBI Ecliptic Plane Survey: VEPS-1
ID:
ivo://CDS.VizieR/J/ApJS/230/13
Title:
VLBI Ecliptic Plane Survey: VEPS-1
Short Name:
J/ApJS/230/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present here the results of the first part of the VLBI Ecliptic Plane Survey (VEPS) program. The goal of the program is to find all compact sources within 7.5{deg} of the ecliptic plane that are suitable as calibrators for anticipated phase referencing observations of spacecraft, and determine their positions with accuracy at the 1.5 nrad level. We run the program in two modes: search and refine. In the search mode, a complete sample of all sources brighter than 50mJy at 5GHz listed in the Parkes-MIT-NRAO and Green Bank 6cm (GB6) catalogs, except those previously detected with VLBI, is observed. In the refining mode, the positions of all ecliptic plane sources, including those found in the search mode, are improved. By 2016 October, thirteen 24hr sessions that targeted all sources brighter than 100mJy have been observed and analyzed. Among 3320 observed target sources, 555 objects have been detected. We also conducted a number of follow-up VLBI experiments in the refining mode and improved the positions of 249 ecliptic plane sources.
683. VLBI ICRF2
ID:
ivo://CDS.VizieR/J/AJ/150/58
Title:
VLBI ICRF2
Short Name:
J/AJ/150/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. ICRF2 contains precise positions of 3414 compact radio astronomical objects and has a positional noise floor of ~40{mu}as and a directional stability of the frame axes of ~10{mu}as. A set of 295 new "defining" sources was selected on the basis of positional stability and the lack of extensive intrinsic source structure. The positional stability of these 295 defining sources and their more uniform sky distribution eliminates the two greatest weaknesses of the first realization of the International Celestial Reference Frame (ICRF1). Alignment of ICRF2 with the International Celestial Reference System was made using 138 positionally stable sources common to both ICRF2 and ICRF1. The resulting ICRF2 was adopted by the International Astronomical Union as the new fundamental celestial reference frame, replacing ICRF1 as of 2010 January 1.
684. VLBI ICRF. II
ID:
ivo://CDS.VizieR/J/AJ/127/3587
Title:
VLBI ICRF. II
Short Name:
J/AJ/127/3587
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use very long baseline interferometry data obtained between mid-1995 and the end of 2002 May together with older data to extend and revise the International Celestial Reference Frame (ICRF). Revised positions of ICRF candidate and "other" sources, based on inclusion of the additional data, are presented. Positions, in the frame of the ICRF, for an additional 109 new sources are also presented. All but four of the new sources are located north of {delta}=-30{deg}. Positions of the ICRF defining sources remain unchanged. We present a summary of current astrometric and geodetic observing programs and discuss the evolution and future of the ICRF.
685. VLBI International Celestial Reference Frame (ICRF)
ID:
ivo://CDS.VizieR/I/251
Title:
VLBI International Celestial Reference Frame (ICRF)
Short Name:
I/251
Date:
21 Oct 2021
Publisher:
CDS
Description:
of the 1998AJ....116..516M paper: A quasi-inertial reference frame is defined based on the radio positions of 212 extragalactic sources distributed over the entire sky. The positional accuracy of these sources is better than about 1mas in both coordinates. The radio positions are based upon a general solution for all applicable dual-frequency 2.3 and 8.4GHz Mark III very long baseline interferometry data available through the middle of 1995, consisting of 1.6 million pairs of group delay and phase delay rate observations. Positions and details are also given for an additional 396 objects that either need further observation or are currently unsuitable for the definition of a high-accuracy reference frame. The final orientation of the frame axes has been obtained by a rotation of the positions into the system of the International Celestial Reference System and is consistent with the FK5 J2000.0 optical system, within the limits of the link accuracy. The resulting International Celestial Reference Frame has been adopted by the International Astronomical Union as the fundamental celestial reference frame, replacing the FK5 optical frame as of 1998 January 1.
686. VLBI Position Measurements
ID:
ivo://CDS.VizieR/J/AZh/81/1032
Title:
VLBI Position Measurements
Short Name:
J/AZh/81/1032
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large number (~2 million) of VLBI observations have been reduced in order to re ne the measured coordinates of the observed radio sources. The data reduction was carried out in the OCCAM package using the least squares colocation method. Corrections to the coordinates of 642 objects were derived. The accuracy of the catalog is no worse than 0.2 milliseconds of arc for stable sources.
687. WASHINGTON 20 Catalog
ID:
ivo://CDS.VizieR/I/40
Title:
WASHINGTON 20 Catalog
Short Name:
I/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalogue contains the two parts: the 9989 first stars are the standard and intermediary stars, +90 to -36 degrees of declination, observed in the years 1913 to 1926, and reduced without proper motion to the equinox 1920.0 ; the second part (stars numbered 9990 to 10571) are 582 miscellaneous stars.
688. Wide binaries in Tycho-Gaia: search method
ID:
ivo://CDS.VizieR/J/MNRAS/472/675
Title:
Wide binaries in Tycho-Gaia: search method
Short Name:
J/MNRAS/472/675
Date:
21 Oct 2021
Publisher:
CDS
Description:
We mine the Tycho-Gaia astrometric solution (TGAS) catalogue for wide stellar binaries by matching positions, proper motions and astrometric parallaxes. We separate genuine binaries from unassociated stellar pairs through a Bayesian formulation that includes correlated uncertainties in the proper motions and parallaxes. Rather than relying on assumptions about the structure of the Galaxy, we calculate Bayesian priors and likelihoods based on the nature of Keplerian orbits and the TGAS catalogue itself. We calibrate our method using radial velocity measurements and obtain 7108 high-confidence candidate wide binaries with projected separations s<~1pc. The normalization of this distribution suggests that at least 0.7 per cent of TGAS stars have an associated, distant TGAS companion in a wide binary. We demonstrate that Gaia's astrometry is precise enough that it can detect projected orbital velocities in wide binaries with orbital periods as large as 10^6^yr. For pairs with s<~4x10^4^au, characterization of random alignments indicates our contamination to be 5-10 per cent. For s<~5x10^3^au, our distribution is consistent with Opik's law. At larger separations, the distribution is steeper and consistent with a power-law P(s){propto}s^-1.6^; there is no evidence in our data of any bimodality in this distribution for s<~1pc. Using radial velocities, we demonstrate that at large separations, i.e. of order s~1pc and beyond, any potential sample of genuine wide binaries in TGAS cannot be easily distinguished from ionized former wide binaries, moving groups or contamination from randomly aligned stars.
689. Wide field imagers ground-based astrometry. V.
ID:
ivo://CDS.VizieR/J/A+A/563/A80
Title:
Wide field imagers ground-based astrometry. V.
Short Name:
J/A+A/563/A80
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-precision astrometry requires accurate point-spread function modeling and accurate geometric-distortion corrections. This paper demonstrates that it is possible to achieve both requirements with data collected at the High Acuity Wide-field K-band Imager (HAWK-I); a wide-field imager installed at the Nasmyth focus of UT4/VLT ESO 8m telescope. Our final astrometric precision reaches ~3mas per coordinate for a well exposed star in a single image, with a systematic error less than 0.1mas. We constructed calibrated astro-photometric catalogs and atlases of 7 fields: the Baade's window, NGC 6656, NGC 6121, NGC 6822, NGC 6388, NGC 104, and the James Webb Space Telescope calibration field (in the LMC). We make these catalogs and images electronically available to the community. Furthermore, as a demonstration of the efficacy of our approach, combining archival material taken with the optical wide-field imager at the MPI/ESO 2.2m with HAWK-I observations, we are able to achieve an excellent separation between cluster members and field objects for NGC 6656 and NGC 6121 with a time base-line of about 8 years. Using both HST and HAWK-I data, we also study the radial distribution of the SGB populations in NGC 6656 and conclude that the radial trend is flat, within our uncertains. We also provide membership probabilities for most of the stars in NGC 6656 and NGC 6121 catalogs and estimate membership for the published variable stars in these two fields.
690. W1J00 and W2J00 Transit Circle Catalogs
ID:
ivo://CDS.VizieR/I/334
Title:
W1J00 and W2J00 Transit Circle Catalogs
Short Name:
I/334
Date:
21 Oct 2021
Publisher:
CDS
Description:
W1J00. We present the result of observations made with the Six-inch Transit Circle in Washington, D.C., between September 1977 and July 1982. The catalog, called W1J00, contains mean positions of 7267 stars, all but five are north of -30 degrees declination, and 4383 observations of solar system objects. Positions of stars are for mean epoch of observation, on equator and equinox J2000.0. Positions of solar system objects are apparent places. Error estimates are about 100mas per coordinate for the majority of stars. W2J00. We present the result of observations made with the Six-inch Transit Circle in Washington, D.C. and the Seven-inch Transit Circle at the Black Birch station near Blenheim, New Zealand between April 1985 and February 1996. The catalog, called W2J00, contains mean positions of 44,395 globally distributed stars, 5048 observations of the planets, and 6518 observations of the brighter minor planets. Positions of stars are for mean epoch of observation, on equator and equinox J2000.0. Positions of solar system objects are apparent places. Error estimates are about 75mas per coordinate for the majority of stars.

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