- ID:
- ivo://CDS.VizieR/I/323
- Title:
- International Celestial Reference Frame 2, ICRF2
- Short Name:
- I/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Technical Note describes the generation by an international team of the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry (VLBI) observations. ICRF2 contains precise positions of 3414 compact radio astronomical sources, more than five times the number as in the first ICRF, hereafter ICRF1. Further, the ICRF2 is found to have a noise floor of only 40{mu}as, some 5-6 times better than ICRF1, and an axis stability of 10{mu}as, nearly twice as stable as ICRF1. Alignment of ICRF2 with the International Celestial Reference System (ICRS) was made using 138 stable sources common to both ICRF2 and ICRF1-Ext2. Future maintenance of ICRF2 will be made using a set of 295 new "defining" sources selected on the basis of positional stability and the lack of extensive intrinsic source structure. The stability of these 295 defining sources, and their more uniform sky distribution eliminates the two largest weaknesses of ICRF1.
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- ID:
- ivo://CDS.VizieR/I/172
- Title:
- International Reference Stars (IRS)
- Short Name:
- I/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IRS is an all-sky catalog of positions and proper motions that is based on the AGK3R (Corbin 1977, 1978) in the Northern Hemisphere and on the newly completed SRS (Smith et al. 1990) in the south. The data for the 36027 stars of the IRS were compiled in B1950.0 FK4 and then transformed to J2000.0 FK5. The IRS was compiled by matching 122 meridian circle catalogs with the AGK3R and SRS to provide the data base. Catalogs whose stars had been observed using screens to minimize the magnitude equation and that contained FK4 (Fricke and Kopff 1963) stars were used to form a preliminary system. These catalogs were reduced to the FK4 by direct comparison; the resulting positions and proper motions were then used to reduce all of the other catalogs. Thus, the IRS is a differential catalog compiled from 164,917 positions reduced to the FK4 system. The IRS is divided into two parts. Part 1 contains the stars having better observational histories and, therefore, more reliable positions and proper motions. This part constitutes 81 percent of the catalog; mean errors of the proper motions are 0.43 and 0.44 seconds of arc/century (4.3 and 4.4 mas/yr) in right ascension and declination, respectively. The stars in Part 2 have poor observational histories and consist mostly of objects for which only two catalog positions in one or both coordinates were available when the proper motions were computed. Where accuracy is the primary consideration, it is best to use only the stars in Part 1, while if the highest possible density is desired, the two parts should be combined, as they are systematically the same. The data included are catalog part, IRS number, equatorial coordinates (equinox, equator, epoch B1950.0 and J2000.0), centennial proper motions (B1950.0 and J2000.0), original epochs, weights for right ascension and declination, and reference data such as DM numbers (BD, CD, CPD), AGK3 and CPC2 designations, and an IAU-recommended IRS identifier (based on coordinates).
- ID:
- ivo://CDS.VizieR/J/ApJS/191/179
- Title:
- IPN supplement to the BeppoSAX GRB catalog
- Short Name:
- J/ApJS/191/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Between 1996 July and 2002 April, one or more spacecraft of the interplanetary network detected 786 cosmic gamma-ray bursts that were also detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera experiments aboard the BeppoSAX spacecraft. During this period, the network consisted of up to six spacecraft, and using triangulation, the localizations of 475 bursts were obtained. We present the localization data for these events.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/65
- Title:
- Keck/NIRC2 obs. of the Galactic Center
- Short Name:
- J/ApJ/873/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession. One of the largest systematic uncertainties in the measured orbits has been errors in the astrometric reference frame, which is derived from seven infrared-bright stars associated with SiO masers that have extremely accurate radio positions, measured in the Sgr A*-rest frame. We have improved the astrometric reference frame within 14" of the Galactic Center by a factor of 2.5 in position and a factor of 5 in proper motion. In the new reference frame, Sgr A* is localized to within a position of 0.645mas and proper motion of 0.03mas/yr. We have removed a substantial rotation (2.25{deg} per decade), that was present in the previous less-accurate reference frame used to measure stellar orbits in the field. With our improved methods and continued monitoring of the masers, we predict that orbital precession predicted by general relativity will become detectable in the next ~5yr.
- ID:
- ivo://CDS.VizieR/J/AJ/156/234
- Title:
- KELT transit false positive catalog for TESS
- Short Name:
- J/AJ/156/234
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey of transiting planets orbiting bright stars for over 10 years. The KELT images have a pixel scale of ~23"/pixel very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS) - as well as a large point-spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with spatial resolution, cadence, and photometric precision higher than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1128 bright stars (6<V<13) that show transit-like features in the KELT light curves, but which were subsequently determined to be astrophysical false positives (FPs) after photometric and/or spectroscopic follow-up observations. The KELT-FUN team continues to pursue KELT and other planet candidates and will eventually follow up certain classes of TESS candidates. The KELT FP catalog will help minimize the duplication of follow-up observations by current and future transit surveys such as TESS.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A21
- Title:
- KiDS Survey for solar system objects mining
- Short Name:
- J/A+A/610/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The search for minor bodies in the Solar System promises insights into its formation history. Wide imaging surveys offer the opportunity to serendipitously discover and identify these traces of planetary formation and evolution. We present a method to acquire position, photometry, and proper motion measurements of Solar System objects in surveys using dithered image sequences. The application of this method on the Kilo-Degree Survey is demonstrated. Optical images of 346deg^2^ fields of the sky are searched in up to four filters using the AstrOmatic software suite to reduce the pixel to catalog data. The Solar System objects within the acquired sources are selected based on a set of criteria depending on their number of observation, motion, and size. The Virtual Observatory SkyBoT tool is used to identify known objects. We observed 20,221 SSO candidates, with an estimated false-positive content of less than 0.05%. Of these SSO candidates, 53.4% are identified by SkyBoT. KiDS can detect previously unknown SSOs because of its depth and coverage at high ecliptic latitude, including parts of the Southern Hemisphere. Thus we expect the large fraction of the 46.6% of unidentified objects to be truly new SSOs. Our method is applicable to a variety of dithered surveys such as DES, LSST, and Euclid. It offers a quick and easy-to-implement search for Solar System objects. SkyBoT can then be used to estimate the completeness of the recovered sample.
- ID:
- ivo://CDS.VizieR/J/A+AS/105/433
- Title:
- Kinematical data of 14 early-type galaxies
- Short Name:
- J/A+AS/105/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJ/783/131
- Title:
- Kinematic of stars in Galactic center
- Short Name:
- J/ApJ/783/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new kinematic measurements and modeling of a sample of 116 young stars in the central parsec of the Galaxy in order to investigate the properties of the young stellar disk. The measurements were derived from a combination of speckle and laser guide star adaptive optics imaging and integral field spectroscopy from the Keck telescopes. Compared to earlier disk studies, the most important kinematic measurement improvement is in the precision of the accelerations in the plane of the sky, which have a factor of six smaller uncertainties ({sigma}~10{mu}as/yr2). We have also added the first radial velocity measurements for eight young stars, increasing the sample at the largest radii (6''-12'') by 25%. We derive the ensemble properties of the observed stars using Monte Carlo simulations of mock data. There is one highly significant kinematic feature (~20{sigma}), corresponding to the well-known clockwise disk, and no significant feature is detected at the location of the previously claimed counterclockwise disk. The true disk fraction is estimated to be ~20%, a factor of ~2.5 lower than previous claims, suggesting that we may be observing the remnant of what used to be a more densely populated stellar disk. The similarity in the kinematic properties of the B stars and the O/WR stars suggests a common star formation event. The intrinsic eccentricity distribution of the disk stars is unimodal, with an average value of <e> =0.27+/-0.07, which we show can be achieved through dynamical relaxation in an initially circular disk with a moderately top-heavy mass function.
- ID:
- ivo://CDS.VizieR/J/A+A/404/913
- Title:
- Kinematics and HR Diagrams of Southern Young Stars
- Short Name:
- J/A+A/404/913
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial distribution, the space velocities and age distribution of the pre-main sequence (PMS) stars belonging to Ophiuchus, Lupus and Chamaeleon star-forming regions (SFRs), and of the young early-type star members of the Scorpius-Centaurus (Sco-Cen) OB association. These young stellar associations extend over the galactic longitude range from 280 to 360 degrees, and are at a distance interval of around 100 and 200pc. We present a compilation of PMS and early-type stars members of the investigated SFRs and OB associations. For these lists of stars we give the data used for the study of kinematic properties: positions, adopted distances, proper motions and radial velocities (whenever available), and the basic stellar data, used for the construction of Hertzsprung-Russel diagrams. All data have been taken from the literature. We also present the derived XYZ positions on the Galactic system, UVW components of the space velocities, visual extinction, and bolometric luminosity.
- ID:
- ivo://CDS.VizieR/J/ApJS/96/175
- Title:
- Kinematics of Metal-Poor Stars. I.
- Short Name:
- J/ApJS/96/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the kinematic properties of a sample of 1936 Galactic stars, selected without kinematic bias, and with abundances [Fe/H] <= -0.6. The stars selected for this study all have measured radial velocities, and the majority have abundances determined from spectroscopic and narrow-/intermediate-band photometric techniques. In contrast to previous examinations of the kinematics of the metal-poor stars in the Galaxy, our sample contains large numbers of stars that are located at distances in excess of 1 kpc from the Galactic plane. Thus, a much clearer picture of the nature of the metal-deficient populations in the Galaxy can now be drawn. Our present data can be well described in terms of a two-component kinematic model consisting of a thick disk, rotating at roughly 200 km/s (independent of metal abundance), and an essentially nonrotating halo. The kinematics of these two components suggest a very broad overlap in metallicity; the thick disk is shown to possess an extremely metal-weak tail, extending to abundances even lower than previously reported, down to at least [Fe/H] ~ -2.0. A "minimal-assumptions" maximum-likelihood model is used to show that below [Fe/H] = -1.5 roughly 30% of stars in the solar neighbourhood can be kinematically associated with the thick disk. Over the metallicity interval -1.6 <= [Fe/H] <= -1.0, the thick-disk proportion rises to 60%. This fraction is only slightly smaller than contribution of thick-disk stars derived by Morrison, Flynn, and Freeman in the same metallicity interval (80%). Our confirmation that significant numbers of stars with thick-disk-like kinematics exist in the solar neighbourhood at arbitrarily low metal abundance suggests that previous disagreements about the correlation of population rotation velocities and metal abundance (e.g. Sandage & Fouts vs. Norris) may be due primarily to the selection criteria employed, and the resulting different contribution of metal-weak thick-disk stars to the respective data sets. The non-Gaussian nature of the velocity distribution of extremely metal-poor stars ([Fe/H] <= -1.5) in the directions of the Galactic poles reported by previous workers can also be understood as a consequence of the overlap between a cold metal-weak thick-disk population and a hot halo population. A maximum-likelihood technique has been developed in order to estimate the velocity ellipsoids of the thick-disk and halo components of the Galaxy. From the 349 stars in our sample with -1.0 <= [Fe/H] <= -0.6 and |z| <= 1 kpc, the velocity ellipsoid of the thick disk is (sigma_U, sigma_V, sigma_W) = (63 +/- 7, 42 +/- 4, 38 +/- 4) km/s. These values are in remarkably good accord with the predicted thick-disk velocity ellipsoid obtained by Quinn, Hernquist, and Fullagar from simulations of a satellite-merger formation scenario. Based on this velocity ellipsoid, a radial scale length for thick-disk stars of h_R = 4.7 +/- 0.5 kpc is obtained, larger than reported by Morrison, and similar to the value obtained for the old-disk population. However, the apparent equality of sigma_V and sigma_W is evidence that the thick disk is kinematically distinct from the old-disk population, where sigma_V:sigma_W ~ 2^{1/2}:1. We find a substantially smaller asymmetric-drift velocity gradient for presumed thick-disk stars (delta Vrot/delta |z| = -13 +/- 6 km/s/kpc) than reported by Majewski (delta Vrot/delta |z| = -21 +/- 1 km/s/kpc). From 887 stars in our sample with [Fe/H] <= -1.5 the local velocity ellipsoid of the halo is (sigma_r, sigma_phi, sigma_theta) = (153 +/- 10, 93 +/- 18, 107 +/- 7) km/s, that is, strongly radially peaked, as indicated by previous studies. We find little difference in the velocity ellipsoids of this sample when it is split into two roughly equal pieces with -2.2 <= [Fe/H] <= -1.5 and [Fe/H] <= -2.2, which indicates a lack of radial metallicity gradient in the halo, as found from studies of the Galactic globular cluster system. The velocity ellipsoid obtained from the small number of stars in our sample with Galactocentric distances r > 10 kpc (N = 61) is (sigma_r, sigma_phi, sigma_theta) = (115 +/- 18, 138 +/- 78, 110 +/- 24) km/s, much less radially elongated than found for the local sample.
