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Register a new userURAT South Parallax Results: Discovery of New Nearby Stars
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We present 916 trigonometric parallaxes and proper motions of newly discovered nearby stars from the United States Naval Observatory (USNO) Robotic Astrometric Telescope (URAT). Observations were taken at the Cerro Tololo Interamerican Observatory (CTIO) over a 2 year period from Oct 2015 to Oct 2017 covering the entire sky south of about +25 deg declination. SPM4 and UCAC4 early epoch catalog data were added to extend the temporal coverage for the parallax and proper motion fit up to 48 years. Using these new URAT parallaxes, optical and near-IR photometry from the APASS and 2MASS catalogs, we identify possible new nearby dwarfs, young stars, low-metallicity subdwarfs and white dwarfs. Comparison to known trigonometric parallaxes show a high quality of the URAT-based results confirming the error in parallax of the URAT south parallaxes reported here to be between 2 and 13 mas. We also include additional 729 trigonometric parallaxes from the URAT north 25 pc sample published in Finch & Zacharias (2016) here after applying the same criterion as for the southern sample to have a complete URAT 25 pc sample presented in this paper.
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We present 1103 trigonometric parallaxes and proper motions from the United States Naval Observatory (USNO) Robotic Astrometric Telescope (URAT) observations taken at the Naval Observatory Flagstaff Station (NOFS) over a 3 year period from April 2012 to June 2015 covering the entire sky north of about minus 10 deg declination. We selected 2 samples previously suspected nearby stars from known photometric distances and stars showing a large, significant parallax signature in URAT epoch data without any prior selection criteria. All systems presented in this paper have an observed parallax greater than equal to 40 mas with no previous published trigonometric parallax. The formal errors on these weighted parallax solutions are mostly between 4 and 10 mas. This sample gives a significant (order 50%) increase to the number of known systems having a trigonometric parallax to be within 25 pc of the Sun (without applying Lutz Kelker bias corrections). A few of these are found to be within 10 pc. Many of these new nearby stars display a total proper motion of less than 200 mas per year. URAT parallax results have been verified against Hipparcos and Yale data for stars in common. The publication of all significant parallax observations from URAT data is in preparation for CDS.
The URAT Parallax Catalog (UPC) consists of 112,177 parallaxes. The catalog utilizes all Northern Hemisphere exposures from the United States Naval Observatory (USNO) Robotic Astrometric Telescope (URAT) obtained between April 2012 and June 2015. Relative parallaxes are converted to absolute using photometric distance estimates of UCAC4 reference stars. There are 2 groups of stars in this catalog: 1) 58,677 stars with prior published trigonometric parallax (Hipparcos, Yale Parallax Catalog, MEarth project and SIMBAD), and 2) 53,500 stars with first time trigonometric parallaxes as obtained from URAT data. More stringent selection criteria have been applied for group 2 then for group 1 in order to keep the rate of false detections low. The mean error in UPC parallaxes is 10.8 and 4.3 mas for groups 1 and 2, respectively. All stars in UPC are north of -13 deg Dec and between 6.5 and 17 mag. The UPC is published by CDS as catalog I/333 and the acronym has been registered with the IAU. The Finch & Zacharias (2016, in press with AJ) paper describes the data, reductions, and results of an about 1000 star subset (stars within 40 pc of the Sun) of the entire UPC. The UPC also provides accurate positions and proper motions on the ICRS. This is the largest parallax catalog published since the Hipparcos Catalog.
Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar systems counterparts are the asteroid and Edgeworth-Kuiper belts. The DUNES survey aims at detecting extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the solar system into context. The survey allows us to address some questions related to the prevalence and properties of planetesimal systems. We used {it Herschel}/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 $mu$m were obtained, complemented in some cases with observations at 70 $mu$m, and at 250, 350 and 500 $mu$m using SPIRE. The observing strategy was to integrate as deep as possible at 100 $mu$m to detect the stellar photosphere. Debris discs have been detected at a fractional luminosity level down to several times that of the Edgeworth-Kuiper belt. The incidence rate of discs around the DUNES stars is increased from a rate of $sim$ 12.1% $pm$ 5% before emph{Herschel} to $sim$ 20.2% $pm$ 2%. A significant fraction ($sim$ 52%) of the discs are resolved, which represents an enormous step ahead from the previously known resolved discs. Some stars are associated with faint far-IR excesses attributed to a new class of cold discs. Although it cannot be excluded that these excesses are produced by coincidental alignment of background galaxies, statistical arguments suggest that at least some of them are true debris discs. Some discs display peculiar SEDs with spectral indexes in the 70-160$mu$m range steeper than the Rayleigh-Jeans one. An analysis of the debris disc parameters suggests that a decrease might exist of the mean black body radius from the F-type to the K-type stars. In addition, a weak trend is suggested for a correlation of disc sizes and an anticorrelation of disc temperatures with the stellar age.
We have conducted a novel search of most of the southern sky for nearby red dwarfs having low proper motions, with specific emphasis on those with proper motion < 0.18 arcsec yr-1, the lower cutoff of Luytens classic proper motion catalog. We used a tightly constrained search of the SuperCOSMOS database and a suite of photometric distance relations for photographic BRI and 2MASS JHKs magnitudes to estimate distances to more than fourteen million red dwarf candidates. Here we discuss 29 stars in 26 systems estimated to be within 25 parsecs, all of which have pm < 0.18 arcsec yr-1, which we have investigated using milliarcsecond astrometry, VRI photometry, and low-resolution spectroscopy. In total, we present the first parallaxes of 20 star systems, nine of which are within 25 parsecs. We have additionally identified eight young M dwarfs, of which two are new members of the nearby young moving groups, and 72 new giants, including two new carbon stars. We also present the entire catalog of 1215 sources we have identified by this means.
We report the discovery of a nearby star with a very large proper motion of 5.06 +/- 0.03 arcsec/yr. The star is called SO025300.5+165258 and referred to herein as HPMS (high proper motion star). The discovery came as a result of a search of the SkyMorph database, a sensitive and persistent survey that is well suited for finding stars with high proper motions. There are currently only 7 known stars with proper motions > 5 arcsec/yr. We have determined a preliminary value for the parallax of 0.43 +/- 0.13 arcsec. If this value holds our new star ranks behind only the Alpha Centauri system (including Proxima Centauri) and Barnards star in the list of our nearest stellar neighbors. The spectrum and measured tangential velocity indicate that HPMS is a main-sequence star with spectral type M6.5. However, if our distance measurement is correct, the HPMS is underluminous by 1.2 +/- 0.7 mag.
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