- ID:
- ivo://CDS.VizieR/J/AJ/161/108
- Title:
- R-band light curve of Qatar-1
- Short Name:
- J/AJ/161/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motivated by the unsettled conclusion on whether there are any transit timing variations (TTVs) for the exoplanet Qatar-1b, 10 new transit light curves are presented and a TTV analysis with a baseline of 1400 epochs is performed. Because the linear model provides a good fit with a reduced chi-square of {chi}_red_^2^=2.59 and the false-alarm probabilities of the possible TTV frequencies are as large as 35%, our results are consistent with a null-TTV model. Nevertheless, a new ephemeris with a reference time of T0=2455647.63360{+/-}0.00008 (BJD) and a period of P=1.4200236{+/-}0.0000001day is obtained. In addition, the updated orbital semimajor axis and planetary radius in units of stellar radius are provided, and the lower limit of the modified stellar tidal quality factor is also determined.
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- ID:
- ivo://CDS.VizieR/J/ApJ/582/1011
- Title:
- Revised NLTT Catalog
- Short Name:
- J/ApJ/582/1011
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We complete construction of a catalog containing improved astrometry and new optical/infrared photometry for the vast majority of NLTT stars lying in the overlap of regions covered by POSS I and by the second incremental Two Micron All Sky Survey (2MASS) release, approximately 44% of the sky. The epoch 2000 positions are typically accurate to 130mas, the proper motions to 5.5mas/yr, and the V-J colors to 0.25mag. Relative proper motions of binary components are measured to 3mas/yr. The false-identification rate is ~1% for 11<=V<=18 and substantially less at brighter magnitudes. These improvements permit the construction of a reduced proper-motion diagram that, for the first time, allows one to classify NLTT stars into main-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We in turn use this diagram to analyze the properties of both our catalog and the NLTT catalog on which it is based. In sharp contrast to popular belief, we find that NLTT incompleteness in the plane is almost completely concentrated in MS stars, and that SDs and WDs are detected almost uniformly over the sky {delta}>-33{deg}. Our catalog will therefore provide a powerful tool to probe these populations statistically, as well as to reliably identify individual SDs and WDs.
- ID:
- ivo://CDS.VizieR/J/AJ/89/1897
- Title:
- Southern stars of high radial velocity
- Short Name:
- J/AJ/89/1897
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Slit spectra have been obtained for 82 stars for which the objective-prism radial-velocity catalogue of Stock lists velocities over 130km/s in magnitude. The slit spectra reveal that many of these objects are F-K stars of low metal abundance, including some stars apparently as metal weak as any presently known. Radial velocities were derived from the slit spectra to examine the reliability of the large objective-prism velocities. The slit results confirm that the majority of the stars are indeed of high velocity, but show that the objective-prism technique tends to produce velocities systematically too large in magnitude by about 40km/s. It was also found that a large objective-prism velocity that is of low weight or from spectra near a plate edge is likely spurious. A search of the 10000 entries in Stock's catalogue yields 205 objects with radial-velocity magnitudes over 130km/s. Sixty-three of these velocities are not suspect because of low weight or edge proximity. An additional 14 stars of lower quality prism velocities were confirmed to have high velocities from the slit spectra. The high-velocity stars appear to form two distinct groups: metal-weak F-K stars and spectroscopically normal main-sequence A stars. Slit spectra were obtained on six nights in April 1978 utilizing the Boller and Chivens spectrograph and the Carnegie image tube at the Cassegrain focus of the 1-m Yale telescope at CTIO.
- ID:
- ivo://CDS.VizieR/V/65
- Title:
- Spectroscopically Selected Halo K Giants
- Short Name:
- V/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog results from a survey for distant Field K giants in the Galactic halo made for purposes of locating a chemically and kinematically unbiased sample out to about 25 kpc from the Sun. The motivation for the study and sample selection are outlined by Ratnatunga & Freeman (1985ApJ...291..260R), while details and analysis of the results will be found in Ratnatunga & Freeman (1989). Three high-galactic latitude fields each of 20 square degrees, designated by their Selected-Area identifications, include the following: SA 141 (l=240,b=-85); SA 189 (277, -50); and SA 127 (272, +38), and have the apparent magnitude range 13 < V < 16 and color range (B-V) > 0.9. Stars were selected from PDS photographic photometry of Schmidt plates (see Ratnatunga 1983, catalog II/121). K-giant selection used the Mgb+MgH feature at 5100A from digital image analysis of PDS scans of ESO 1-m Schmidt telescope objective-prism spectra with 450 A/mm at H-gamma resolution on IIIa-J plates exposed through a Schott GG475 filter. Luminosity confirmation, line-of-sight velocities, and metallicity were determined from 2-A resolution slit spectra taken with the 4-m Anglo- Australian and 1.9-m Mount Stromlo telescopes. Cross identifications exist for some stars in the SA 141 SGP field only.
- ID:
- ivo://CDS.VizieR/J/AJ/98/1693
- Title:
- UBVRI photometry of NLTT stars
- Short Name:
- J/AJ/98/1693
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVRI photometry is presented for a sample of 1656 southern stars, including 1211, that were previously not measured, drawn from the NLTT (Luyten, 1979; catalogue I/98) proper-motion catalog; the catalog is shown to be a rich source of subdwarfs. The normalized UV excess, d(U-B)0.6, photometric parallax, and interstellar reddening are calculated for each star when possible. Residuals between the photometry and the magnitudes published in the NLTT catalog indicate that the latter have a large scatter (~0.6mag) and therefore the values tabulated in the NLTT catalog must be regarded as approximate only. The erratum (Astron. J. 99, 1336) which deals with position angles of proper motions (pmPA) has been taken into account.
- ID:
- ivo://CDS.VizieR/II/180
- Title:
- uvby-beta photometry of metal-poor stars
- Short Name:
- II/180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the calibrations derived by Schuster and Nissen (=1989A&A...221...65S), the interstellar color excesses, E(b-y), and the metallicities, [Fe/H], have been determined for the 711 high velocity and metal-poor stars in the catalogue of uvby-beta photometry (=1988A&AS...73..225S). 220 of these listed in table1 turn out to be halo stars according to the criterion [Fe/H] <= -1.0. About 15% of the halo stars have colors that are significantly affected by interstellar reddening, i.e. E(b-y) > 0.025. The distributions in the c0-(b-y)0 diagram of the halo stars grouped according to [Fe/H], have well defined turn-off points. From the Teff values of these points a minimum age of 18-20 Gyr for the halo stars is determined. However, this age may be 2-3 Gyr too high due to a possible systematic error in Teff for the stellar models used. Relative ages of 77 halo stars in the turn-off region of the c0-(b-y)0 diagram are derived using the isochrones VandenBerg and Bell (=1985ApJS...58..561V). Assuming that the O/Fe abundance ratio is constant in halo stars, evidence of a cosmic age scatter of +/-2.5Gyr at a given metallicity is found. Furthermore, the mean age of the halo stars is found to decrease smoothly by about 3 Gyr from [Fe/H]= -2.0 to -1.0. These results suggest that a pressure-supported slow uniform collapse controlled the formation and early evolution of the Galaxy. However, the scenario of Searle and Zinn (=1978ApJ...225..357S) is also compatible with the results.
- ID:
- ivo://CDS.VizieR/J/A+AS/117/317
- Title:
- uvby-beta photometry of metal-poor stars. VIII.
- Short Name:
- J/A+AS/117/317
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of uvby-{beta} photometry for 87 of the turn-off and subgiant stars from the HK survey of Beers et al. (1992AJ....103.1987B, BPSII) is given. Most of these stars have [Fe/H]<=2.5. These photometric data have been taken and reduced using the same techniques as in our previous two uvby-{beta} catalogues (Schuster et al., 1989, Cat. <II/180> and Schuster et al., 1993, Cat. <J/A+AS/97/951>). An error analysis has been made; typical mean observational errors for a star with V=14.2m are 0.008, 0.007, 0.011, 0.010 and 0.012 in V, (b-y), m_1_, c_1_ and {beta}, respectively. Our photometric data are also compared to the UBV photometry and spectral indices from the HK survey; satisfactory agreement is found indicating good quality for the two data sets. The stars are classified in reddening-free diagrams of the uvby-{beta} system; several of the stars are found to have been mis-classified in the HK survey. Two metal-poor supergiants, three (possibly four) horizontal branch stars, one blue subluminous star and two stars with ambiguous photometry have been identified. Stellar parameters, such as E(b-y), M_V_, {delta}M_V_, and T_eff_, plus error estimates for these parameters, are provided using our photometric calibrations. Although all stars have galactic latitudes |b|>=30{deg} many of them are significantly reddened with E(b-y) ranging from 0.02 to 0.15. The average reddening towards the South Galactic Pole region, b<-60{deg}, is E(b-y)=0.027+/-0.004 corresponding to E(B-V)=0.036+/-0.005 in contrast to the low value of E(B-V)~0.01 derived from the Burstein & Heiles (1982AJ.....87.1165B) maps. The stars are analyzed in the (b-y)_0_, [Fe/H] diagram, and individual ages estimated using the isochrones of VandenBerg & Bell (1985ApJS...58..561V) and of Bergbusch & VandenBerg (1992ApJS...81..163B). These very metal-poor stars are found to be coeval, within 1-2Gyr, with the halo and thick-disk stars studied previously, with a mean age in excess of 18Gyr. Several blue "thick-disk" stars, which are perhaps analogous to the "blue metal-poor" stars of Preston et al. (1994, Cat. <J/AJ/108/538>), have been identified.
