- ID:
- ivo://CDS.VizieR/J/AJ/143/128
- Title:
- High-metallicity M giant candidates from SDSS
- Short Name:
- J/AJ/143/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tidal stripping and three-body interactions with the central supermassive black hole may eject stars from the Milky Way. These stars would comprise a set of "intragroup" stars (IGS) that trace the past history of interactions in our galactic neighborhood. Using the Sloan Digital Sky Survey (SDSS) DR7 (Cat. II/294, superseded by Cat. V/139), we identify candidate solar-metallicity red giant intragroup stars using color cuts that are designed to exclude nearby M and L dwarfs. We present 677 intragroup candidates that are selected between 300kpc and 2Mpc, and are either the reddest intragroup candidates (M7-M10) or are L dwarfs at larger distances than previously detected.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/561/A7
- Title:
- High-precision abundances for stars with planets
- Short Name:
- J/A+A/561/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Elemental abundance studies of solar twin stars suggest that the solar chemical composition contains signatures of the formation of terrestrial planets in the solar system, namely small but significant depletions of the refractory elements. To test this hypothesis, we study stars which, compared to solar twins, have less massive convective envelopes (therefore increasing the amplitude of the predicted effect) or are, arguably, more likely to host planets (thus increasing the frequency of signature detections). We measure relative atmospheric parameters and elemental abundances of a late-F type dwarf sample (52 stars) and a sample of metal-rich solar analogs (59 stars). We detect refractory-element depletions with amplitudes up to about 0.15dex. The distribution of depletion amplitudes for stars known to host gas giant planets is not different from that of the rest of stars. The maximum amplitude of depletion increases with effective temperature from 5650K to 5950K, while it appears to be constant for warmer stars (up to 6300K). The depletions observed in solar twin stars have a maximum amplitude that is very similar to that seen here for both of our samples. Gas giant planet formation alone cannot explain the observed distributions of refractory-element depletions, leaving the formation of rocky material as a more likely explanation of our observations. More rocky material is necessary to explain the data of solar twins than metal-rich stars, and less for warm stars. However, the sizes of the stars' convective envelopes at the time of planet formation could be regulating these amplitudes. Our results could be explained if disk lifetimes were shorter in more massive stars, as independent observations indeed seem to suggest.
- ID:
- ivo://CDS.VizieR/J/AZh/83/158
- Title:
- High precision effective temperatures of giants
- Short Name:
- J/AZh/83/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral lines of high and low excitation potentials respond differently to the change in effective temperature (Teff). Therefore, the ratio of their depths (or equivalent widths) is a very sensitive temperature indicator. A set of 100 relations is obtained which rely Teff on line depth ratios, calibrated against previously published precise (one per cent) temperature estimates of giants. Highly precise temperatures have been determined from this relations for a set of 110 giants of about solar metallicity, based on high resolution (R=42000), high S/N echelle spectra. The application range of the calibrations is 4000-7000K (F2III-K4III). The internal error of a single calibration is less than 95K, while the combination of all calibrations for a spectrum of S/N=100 reduces uncertainty to only 5-25K (1{sigma}). The big advantage of using line-depth ratios is the independence on the interstellar reddening, spectral resolution, rotational and microturbulence broadening.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1293
- Title:
- High precision orbits of 5 SB2 stars
- Short Name:
- J/ApJ/719/1293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision radial velocities (RVs) of double-lined spectroscopic binary stars HD78418, HD123999, HD160922, HD200077, and HD210027. They were obtained based on the high-resolution echelle spectra collected with the Keck I/HIRES, Shane/CAT/Hamspec, and TNG/Sarge telescopes/spectrographs over the years 2003-2008 as part of the TATOOINE search for circumbinary planets. The RVs were computed using our novel iodine cell technique for double-line binary stars, which relies on tomographically disentangled spectra of the components of the binaries. The precision of the RVs is of the order of 1-10m/s, and to properly model such measurements one needs to account for the light-time effect within the binary's orbit, relativistic effects, and RV variations due to tidal distortions of the components of the binaries. With such proper modeling, our RVs combined with the archival visibility measurements from the Palomar Testbed Interferometer (PTI) allow us to derive very precise spectroscopic/astrometric orbital and physical parameters of the binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A46
- Title:
- High-precision polarimetry of nearby stars
- Short Name:
- J/A+A/635/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the linear polarization produced by interstellar dust aligned by the magnetic field in the solar neighborhood (d<50pc). We also look for intrinsic effects from circumstellar processes, specifically in terms of polarization variability and wavelength dependence. We aim to detect and map dust clouds which give rise to statistically significant amounts of polarization of the starlight passing through the cloud, and to determine the interstellar magnetic field direction from the position angle of the observed polarization. High-precision broad-band (BVR) polarization observations are made of 361 stars in spectral classes F to G, with detection sensitivity at the level of or better than 10E-5 (0.001%). The sample consists of 125 stars in the magnitude range 6-9 observed at the 2.2m UH88 telescope on Mauna Kea, 205 stars in the magnitude range 3-6 observed at the Japanese (Tohoku) T60 telescope on Haleakala, and 31 stars in the magnitude range 4-7 observed at the 1.27m H127 telescope of the Greenhill Observatory, Tasmania. Identical copies of the Dipol-2 polarimeter are used on these three sites. Statistically significant (>3sigma) polarization is found in 115 stars, and >2sigma detection in 178 stars, out of the total sample of 361 stars. Polarization maps based on these data show filament-like patterns of polarization position angles which are related to both the heliosphere geometry, the kinematics of nearby clouds, and the Interstellar Boundary EXplorer (IBEX) ribbon magnetic field. From long-term multiple observations, a number (18) of stars show evidence of intrinsic variability at the 10E-5 level. This can be attributed to circumstellar effects (e.g., debris disks and chromospheric activity). The star HD 101805 shows a peculiar wavelength dependence, indicating size distribution of scattering particles different from that of a typical interstellar medium. Our high-S/N measurements of nearby stars with very low polarization also provide a useful dataset for calibration purposes.
- ID:
- ivo://CDS.VizieR/J/A+AS/119/265
- Title:
- High probability quasar candidates
- Short Name:
- J/A+AS/119/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Automated Quasar Detection (AQD) technique has been applied to six connected fields near the South Galactic Pole. A comparison with the Veron & Veron catalogue (1993) <VII/188> and the Cristiani et al. compilation (1995A&AS..112..347C) shows that AQD rediscovered ~75% of the known quasars with non-overlapping objective-prism spectra present in these fields (~40% if considering only the high degree candidates). A list of 1592 high grade candidates is given, including the results of cross-correlation with X-ray and radio catalogues.
- ID:
- ivo://CDS.VizieR/J/AJ/159/30
- Title:
- High proper-motion M-type stars spectroscopic obs.
- Short Name:
- J/AJ/159/30
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Large numbers of low-to-medium-resolution spectra of M-type dwarf stars from both the local Galactic disk and halo are available from various surveys. In order to fully exploit these data, we develop a template-fit method using a set of empirically assembled M dwarf/subdwarf classification templates, based on the measurements of the TiO and CaH molecular bands near 7000{AA}, which are used to classify M dwarfs/subdwarfs by spectral type and metallicity class. We further present a pipeline to automatically determine the effective temperature Teff, metallicity [M/H], {alpha}-element to iron abundance ratio [{alpha}/Fe], and surface gravity logg of M dwarfs/subdwarfs using the latest version of BT-Settl model atmospheres. We apply these methods to a set of low-to-medium-resolution spectra of 1544 high proper-motion ({mu}>=0.4"/yr) M dwarfs/subdwarfs, collected at the MDM observatory, Lick Observatory, Kitt-Peak National Observatory, and Cerro-Tololo Interamerican Observatory.
- ID:
- ivo://CDS.VizieR/J/AJ/125/277
- Title:
- High proper motions in central Orion nebula
- Short Name:
- J/AJ/125/277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The brightest portion of the Orion Nebula has been reimaged with the Hubble Space Telescope in H{alpha}, [N II], and [O III]. Comparison with earlier Wide Field Planetary Camera 2 images going back as much as 8yr has allowed determination of tangential velocities (proper motions) down to about 10km/s for a variety of sources. Multiple outflow systems are found associated with individual proplyds in the ionized portion of the nebula (HH 518, HH 624, possibly HH 507). The Orion-S complex of radio and infrared sources is the source of multiple outflows. A new outflow system (HH 625) has been identified as coming from the blueshifted portion of the imbedded high velocity CO flow coming from the Orion-S region, this object having CO, H2, and low ionization optical components. The low velocity CO outflow originating from or near FIR 4 is the likely source of HH 530. A new imbedded source is inferred from this optical data to lie in Orion-S. This optical outflow source (OOS) clearly feeds the systems HH 269 and HH 529, which lie along a straight line. There is evidence that this is also the source for HH 528, HH 202, and HH 203/204, all of which are blueshifted (except possibly HH 528 whose radial velocity is unknown). There is no strong radio, infrared, or X-ray source within the positional ellipse of the OOS.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/4054
- Title:
- High proper motion sources from WISE
- Short Name:
- J/MNRAS/454/4054
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The census of the solar neighbourhood is almost complete for stars and becoming more complete in the brown dwarf regime. Spectroscopic, photometric and kinematic characterization of nearby objects helps us to understand the local mass function, the binary fraction, and provides new targets for sensitive planet searches. We aim to derive spectral types and spectrophotometric distances of a sample of new high proper motion sources found with the WISE (Wide-field Infrared Survey Explorer) satellite, and obtain parallaxes for those objects that fall within the area observed by the Vista Variables in the Via Lactea survey (VVV). We used low-resolution spectroscopy and template fitting to derive spectral types, multiwavelength photometry to characterize the companion candidates and obtain photometric distances. Multi-epoch imaging from the VVV survey was used to measure the parallaxes and proper motions for three sources. We confirm a new T2 brown dwarf within ~15pc. We derived optical spectral types for 24 sources, mostly M dwarfs within 50pc. We addressed the wide binary nature of 16 objects found by the WISE mission and previously known high proper motion sources. Six of these are probably members of wide binaries, two of those are new, and present evidence against the physical binary nature of two candidate binary stars found in the literature, and eight that we selected as possible binary systems. We discuss a likely microlensing event produced by a nearby low-mass star and a galaxy, that is to occur in the following five years.
- ID:
- ivo://CDS.VizieR/J/ApJ/562/337
- Title:
- High proper-motion stars from MACHO astrometry
- Short Name:
- J/ApJ/562/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the preliminary results of our astrometric study of stellar motions along the lines of sight of the Magellanic Clouds and the Galactic bulge. Using 5 years of MACHO project point-spread function photometry, we find that we can easily select stars with proper motions of 0.03"/yr from these very dense fields, using the characteristic shapes of their light curves. By performing astrometry on photometrically selected, candidate, high proper motion (HPM) stars in 50 deg^2^, we have discovered 154 new HPM stars from ~55 million stars monitored by the MACHO project. These new objects have proper motions as high as 0.5"/yr, brightnesses ranging from V ~13 to V~19, and V-R colors between 0.3 and 1.45.