- ID:
- ivo://CDS.VizieR/J/AJ/142/89
- Title:
- Precise astrometry with VLBA (VIPS)
- Short Name:
- J/AJ/142/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate positions for 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5GHz (VIPS). Among the observed sources, positions of 430 objects were not previously determined at milliarcsecond-level accuracy. For 95% of the sources the uncertainty of their positions ranges from 0.3 to 0.9mas, with a median value of 0.5mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron content maps derived from GPS observations and only marginally affected estimates of source coordinates.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/2638
- Title:
- Precise CCD positions of Phoebe in 2011-2014
- Short Name:
- J/MNRAS/449/2638
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 346 new CCD observations during the years 2011-2014 have been reduced to derive the precise positions of Phoebe, the ninth satellite of Saturn. The observations were made by the 2.4 m telescope at Yunnan Observatory over nine nights. Due to the use of a focal-reducer on the telescope, its significant geometric distortion is solved for and removed for each CCD field of view. The positions of Phoebe are measured with respect to the stars in UCAC2 catalogue (Cat. I/289). The theoretical position of Phoebe was retrieved from the Institute de Mechanique Celeste et de Calcul des Ephemerides (IMCCE) ephemeris which includes the latest theory PH12 by Desmars et al. (2013, J/A+A/553/A36), while the position of Saturn was obtained from the Jet Propulsion Laboratory ephemeris DE431. Our results show that the mean O-Cs (observed minus computed) are -0.02 and -0.07 arcsec in right ascension and declination, respectively. The dispersions of our observations are estimated at about 0.04 arcsec in each direction.
- ID:
- ivo://CDS.VizieR/J/A+A/442/381
- Title:
- Precise positions of RR Lyrae Stars with Vmax>12.5
- Short Name:
- J/A+A/442/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RR Lyrae stars are of great importance for investigations of Galactic structure. However, a complete compendium of all RR-Lyraes in the solar neighbourhood with accurate classifications and coordinates does not exist to this day. Here we present a catalogue of 561 local RR-Lyrae stars (V_max_>=12.5mag) according to the magnitudes given in the Combined General Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue contains ~100 RR Lyr stars. However, many objects have inaccurate coordinates in the GCVS, the primary source of variable star information, so that a reliable cross-identification is difficult. We identified RR Lyrae from both catalogues based on an intensive literature search. In dubious cases we carried out photometry of fields to identify the variable. Mennessier & Colome (2002, Cat. <J/A+A/390/173>) have published a paper with Tyc2-GCVS identifications, but we found that many of their identifications are wrong.
- ID:
- ivo://CDS.VizieR/I/151
- Title:
- Precise Radio Source Positions from Mark III VLBI
- Short Name:
- I/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains observations from 600 Mark III VLBI experiments from conducted between 1979 to 1988. These experiments resulted in 237681 acceptable pairs of group delay and phase delay rate observations. These have been used to derive positions of 182 extra-galactic radio sources with typical formal standard errors less than 1 mas. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Also included are the Mark III VLBI stations and a summary of the analysis configuration.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/179
- Title:
- Precision meteor orbits
- Short Name:
- J/A+AS/128/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital elements, encounter data and other relevant information of 359 photographic meteors (Table 2 of the paper).
- ID:
- ivo://CDS.VizieR/J/AcA/68/351
- Title:
- Predicted Microlensing Events by nearby VLM objects
- Short Name:
- J/AcA/68/351
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Microlensing events can be used to directly measure the masses of single field stars to a precision of ~1-10%. The majority of direct mass measurements for stellar and sub-stellar objects typically only come from observations of binary systems. Hence microlensing provides an important channel for direct mass measurements of single stars. The Gaia satellite has observed ~1.7 billion objects, and analysis of the second data release has recently yielded numerous event predictions for the next few decades. However, the Gaia catalog is incomplete for nearby very-low-mass objects such as brown dwarfs for which mass measurements are most crucial. We employ a catalog of very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens stars, and we use the objects from Gaia data release 2 (GDR2) as potential source stars. We then search for future microlensing events up to the year 2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any that are present in both catalogs. This leaves a sample of 1718 possible lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry to estimate their masses. We then compute their paths on the sky, along with the paths of the GDR2 source objects, until the year 2070, and search for potential microlensing events. Source-lens pairs that will produce a microlensing signal with an astrometric amplitude of greater than 0.131mas, or a photometric amplitude of greater than 0.4mmag, are retained.
- ID:
- ivo://CDS.VizieR/J/AcA/68/183
- Title:
- Predicted Microlensing Events for the 21st Century
- Short Name:
- J/AcA/68/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Gaia data release 2 (GDR2, Cat. I/345), we present an almanac of 2509 predicted microlensing events, caused by 2130 unique lens stars, that will peak between July 25, 2026 and the end of the century. This work extends and completes a thorough search for future microlensing events initiated by Bramich and Nielsen using GDR2. The almanac includes 161 lenses that will cause at least two microlensing events each. All of the predicted microlensing events in the almanac will exhibit astrometric signals that are detectable by observing facilities with an angular resolution and astrometric precision similar to, or better than, that of the Hubble Space Telescope (e.g., NIRCam on the James Webb Space Telescope), although the events with the most extreme source-to-lens contrast ratios may be challenging. Ground-based telescopes of at least 1 m in diameter can be used to observe many of the events that are also expected to exhibit a photometric signal.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A44
- Title:
- Predicted microlensing events from Gaia DR2
- Short Name:
- J/A+A/618/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I search for source-lens pairs in Gaia Data Release 2 (GDR2, Cat. I/345) that could potentially lead to microlensing events between 25th July 2014 and 25th July 2026. I estimate the lens masses using GDR2 photometry and parallaxes, and appropriate model stellar isochrones. Combined with the source and lens parallax measurements from GDR2, this allows the Einstein ring radius to be computed for each source-lens pair. By considering the source and lens paths on the sky, I calculate the microlensing signals that are to be expected.
- ID:
- ivo://CDS.VizieR/J/AJ/161/179
- Title:
- Predicted positions of {beta}Pictoris b and c
- Short Name:
- J/AJ/161/179
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We present a comprehensive orbital analysis to the exoplanets {beta}Pictoris b and c that resolves previously reported tensions between the dynamical and evolutionary mass constraints on {beta}Picb. We use the Markov Chain Monte Carlo orbit code orvara to fit 15years of radial velocities and relative astrometry (including recent GRAVITY measurements), absolute astrometry from Hipparcos and Gaia, and a single relative radial velocity measurement between {beta}Pic A and b. We measure model-independent masses of 9.3_-2.5_^+2.6^M_Jup_ for {beta}Picb and 8.3{+/-}1.0M_Jup_ for {beta}Picc. These masses are robust to modest changes to the input data selection. We find a well-constrained eccentricity of 0.119{+/-}0.008 for {beta}Picb, and an eccentricity of 0.21_-0.09_^+0.16^ for {beta}Picc, with the two orbital planes aligned to within ~0.5{deg}. Both planets' masses are within ~1{sigma} of the predictions of hot-start evolutionary models and exclude cold starts. We validate our approach on N-body synthetic data integrated using REBOUND. We show that orvara can account for three-body effects in the {beta}Pic system down to a level ~5 times smaller than the GRAVITY uncertainties. Systematics in the masses and orbital parameters from orvara's approximate treatment of multiplanet orbits are a factor of ~5 smaller than the uncertainties we derive here. Future GRAVITY observations will improve the constraints on {beta}Picc's mass and (especially) eccentricity, but improved constraints on the mass of {beta}Picb will likely require years of additional radial velocity monitoring and improved precision from future Gaia data releases.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A37
- Title:
- Prediction of stellar occultations 2012.5-2014
- Short Name:
- J/A+A/561/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prediction tables of stellar occultations by 5 Centaurs and 34 TNOs (referred simply as TNOs hereafter) for the period 2012.5-2014 were built to support the investigation of the physical properties of (8405) Asbolus, (24835) 1995 SM55, (10199) Chariklo, (26375) 1999 DE9, (47171) 1999 TC36, (38628) Huya, (54598) Bienor, (55565) 2002 AW197, (55576) Amycus, (83982) Crantor, (119951) 2002 KX14, (307261) 2002 MS4, (84522) 2002 TC302, (55637) 2002 UX25, (55638) 2002 VE95, (119979) 2002 WC19, (120132) 2003 FY128, (174567) 2003 MW12, (120178) 2003 OP32, 2003 UZ413, (84922) 2003 VS2, (90568) 2004 GV9, 2004 NT33, (175113) 2004 PF115, (120347) Salacia, (120348) 2004 TY364, (144897) 2004 UX10, 2005 CC79 (2011 FX62), (303775) 2005 QU182, (145451) 2005 RM43, (145452) 2005 RN43, (145453) 2005 RR43, (202421) 2005 UQ513, 2007 JH43, (278361) 2007 JJ43, (225088) 2007 OR10, (229762) 2007 UK126, 2008 OG19, and 2010 EK139 for this period. These objects are important to understand the structure, origin, and evolution of the outer solar system. Our goal was to derive precise predictions. With this aim, we constructed astrometric star catalogues in the UCAC4 system covering their sky paths. For that, we carried out during 2011-2013 an observational program at the ESO2p2/WFI instrument covering the sky path of these 39 TNOs for the period 2012.5-2014. We made the astrometry of 550 GB of images with the Platform for Reduction of Astronomical Images Automatically (PRAIA). By relatively simple astrometric techniques, we treated the overlapping observations and derived a field distortion pattern for the WFI mosaic of CCDs to within 50mas precision. The catalogue star positions were obtained in the UCAC4 frame with uncertainties of 40mas for stars up to magnitude completeness (about R=19). New stellar proper motions were also determined with 2MASS and the USNO B1.0 catalogue positions as first epoch. The catalogues for all TNOs contain in all more than 12.4 million entries, covering the sky paths of the objects with 30 arcmin width. The magnitude completeness is about R=19 with a limit about R=21. Ephemeris offsets with about 10mas to 100mas precision were applied for each TNO orbit to improve the predictions. They were obtained during 2011-2013 from a parallel observational campaign carried out with telescope diameters from 0.6m to 2.2m. The 7343 candidate stars listed in the prediction tables were searched using a proximity radius of 650mas with the geocentric apparent orbit (corrected by ephemeris offsets) of the body considered. This radius is a little more than seven times the apparent radius of a body with Pluto's size (50mas) plus the apparent Earth radius (285 mas) as projected in the sky plane at 31AU (about the Pluto-Earth distance for 2008-2015). No threshold in R magnitude was used in the search for candidates, as relatively faint R objects may turn out to be bright infrared stars, perfect targets for the SOFIA observatory and for ground-based instruments well equipped with J, H, or K band detectors (J, H, and K magnitudes are promptly available in the tables if the star belongs to the 2MASS). Besides, events may be also favoured by slow shadow speeds of less than 20km/s. Also, no constraint on a geographic place was applied, as in principle SOFIA observations can be done from any sub-solar point on Earth. Events in daylight at sub-planet point were not excluded either, as they could yet be observable in the dark, right above the horizon, from places near the Earth terminator. We furnish here prediction tables for future and also for past stellar occultations covering the sky paths between 2012.5-2014. The importance of predictions for occultations still to come is obvious. But the predictions of past occultations are also useful for at least three reasons. First, they can be used by anyone as reference for ongoing fittings of light curves of recent past observed events. Second, they serve to derive ephemeris drifts by comparing expected and observed central instants and C/A values. Finally, they can be used as an external check for the accuracy and precision of our prediction tables. In all, for R=19 stars (catalogue magnitude completeness) and 40mas errors in the WFI positions, we may assume a bulk error of about 80mas for C/A, dominated by the ephemeris offsets errors of about 70mas. For about 40AU, this implies a shadow path uncertainty over the Earth of the order of 2300km. If the ephemeris offsets can be well determined to within 30mas precision, then a bulk error of 50mas in C/A can be achieved, leading to a precision of about 1400km for the WFI occultation path predictions. Thus, the probability of actually observing the occultation is not as high as hoped, but not despairingly small, especially if the event occurs above a dense, populated region in terms of astronomers, including amateurs, with access to telescopes.
