- ID:
- ivo://CDS.VizieR/J/AJ/158/182
- Title:
- Discoveries from the NEOWISE proper motion survey
- Short Name:
- J/AJ/158/182
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present low-resolution near-infrared spectra of discoveries from an all-sky proper motion search conducted using multi-epoch data from the Wide-field Infrared Survey Explorer. Using the data from NEOWISE, along with the AllWISE catalog, Schneider et al. (2016, J/ApJ/817/112) conducted an all-sky proper motion survey to search for nearby objects with high proper motions. Here, we present a follow-up spectroscopic survey of 65 of their discoveries, which focused primarily on potentially nearby objects (d<25 pc), candidate late-type brown dwarfs (>=L7), and subdwarf candidates. We found 31 new M dwarfs, 18 new L dwarfs, and 11 new T dwarfs. Of these, 13 are subdwarfs, including one new sdL1 and two new sdL7s. Eleven of these discoveries, with spectral types ranging from M7 to T7 (including one subdwarf) are predicted to be within 25 pc, adding to the number of known objects in the solar neighborhood. We also discovered three new early-type T subdwarf candidates, one sdT1, one sdT2, and one sdT3, which would increase the number of known early-type T subdwarfs from two to five.
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- ID:
- ivo://CDS.VizieR/J/A+A/624/A8
- Title:
- Evolved Galactic open clusters dynamical properties
- Short Name:
- J/A+A/624/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of Galactic open clusters (OCs) is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of OCs are called open cluster remnants (OCRs).These are sparsely populated structures that can barely be distinguished from the field. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as OCRs or OCR candidates. The sample also includes 7 objects that are catalogued as dynamically evolved OCs for comparison purposes. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the GAIA DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes ({mu}_{alpha}, {mu}_{delta}, {varpi}) for stars in the objects' areas. The investigated OCRs present masses (M) and velocity dispersions ({sigma}_v_) within well-defined ranges: M between ~10-40M_{sun} and {sigma}_v_ between ~1-7km/s. Some objects in the remnant sample have a limiting radius R_lim_<~2pc, which means that they are more compact than the investigated OCs; other remnants have R_lim_ between ~2-7pc, which is comparable to the OCs. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Using results from N-body simulations, we conclude that the OCRs we studied are in fact remnants of initially very populous OCs (N_0_~10^3^-10^4^stars). The outcome of the long-term evolution is to bring the final residues of the OCs to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.
- ID:
- ivo://CDS.VizieR/V/137D
- Title:
- Extended Hipparcos Compilation (XHIP)
- Short Name:
- V/137D
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extended Hipparcos Compilation (XHIP) cross-references the New Hipparcos Reduction (HIP2, Cat. I/311) with relatable data from a broad survey of presently available sources. The resulting collection uniquely assigns 116,096 spectral classifications, 46,392 radial velocities, and 19,097 iron abundances [Fe/H] to Hipparcos stars. Stellar classifications from SIMBAD and indications of multiplicity from either CCDM (Cat. I/274) or WDS (Cat. B/wds) are provided. Parameters for solar encounters and Galactic orbits are calculated for a subset of stars that can be made kinematically complete. Memberships in open clusters and stellar associations are assigned. We also provide stellar ages from The Geneva-Copenhagen survey of the Solar neighbourhood III (Cat. V/130), identifications of exoplanet host stars, and supplemental photometry from 2MASS (Cat. II/246) and SIMBAD.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/19
- Title:
- First brown dwarfs discovered by WISE
- Short Name:
- J/ApJS/197/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ground-based spectroscopic verification of 6 Y dwarfs (see also Cushing et al., 2011ApJ...743...50C), 89 T dwarfs, 8 L dwarfs, and 1 M dwarf identified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these are cold brown dwarfs with spectral types >=T6, six of which have been announced earlier by Mainzer et al. (2011ApJ...726...30M) and Burgasser et al. (2011ApJ...735..116B). We present color-color and color-type diagrams showing the locus of M, L, T, and Y dwarfs in WISE color space. Near-infrared and, in a few cases, optical spectra are presented for these discoveries. Near-infrared classifications as late as early Y are presented and objects with peculiar spectra are discussed. Using these new discoveries, we are also able to extend the optical T dwarf classification scheme from T8 to T9. After deriving an absolute WISE 4.6um (W2) magnitude versus spectral type relation, we estimate spectrophotometric distances to our discoveries. We also use available astrometric measurements to provide preliminary trigonometric parallaxes to four of our discoveries, which have types of L9 pec (red), T8, T9, and Y0; all of these lie within 10pc of the Sun. The Y0 dwarf, WISE 1541-2250, is the closest at 2.8^+1.3^_-0.6_pc; if this 2.8pc value persists after continued monitoring, WISE 1541-2250 will become the seventh closest stellar system to the Sun. Another 10 objects, with types between T6 and >Y0, have spectrophotometric distance estimates also placing them within 10pc. The closest of these, the T6 dwarf WISE 1506+7027, is believed to fall at a distance of ~4.9pc. WISE multi-epoch positions supplemented with positional info primarily from the Spitzer/Infrared Array Camera allow us to calculate proper motions and tangential velocities for roughly one-half of the new discoveries.
- ID:
- ivo://CDS.VizieR/J/AJ/156/140
- Title:
- Four new eclipsing mid M-dwarf systems from MEarth
- Short Name:
- J/AJ/156/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using data from the MEarth-North and MEarth-South transit surveys, we present the detection of eclipses in four mid M-dwarf systems: LP 107-25, LP 261-75, LP 796-24, and LP 991-15. Combining the MEarth photometry with spectroscopic follow-up observations, we show that LP 107-25 and LP 796-24 are short-period (1.388 and 0.523 day, respectively) eclipsing binaries in triple-lined systems with substantial third-light contamination from distant companions. LP 261-75 is a short-period (1.882 day) single-lined system consisting of a mid M-dwarf eclipsed by a probable brown dwarf secondary, with another distant visual brown dwarf companion. LP 991-15 is a long-period (29.3 day) double-lined eclipsing binary on an eccentric orbit with a geometry that produces only primary eclipses. A spectroscopic orbit is given for LP 991-15, and initial orbits for LP 107-25 and LP 261-75.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/138
- Title:
- Gaia and LAMOST DR4 M giant members of Sgr stream
- Short Name:
- J/ApJ/874/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use LAMOST DR4 M giants combined with Gaia DR2 proper motions and ALLWISE photometry to obtain an extremely pure sample of Sagittarius (Sgr) stream stars. Using TiO5 and CaH spectral indices as indicators, we selected a large sample of M-giant stars from M-dwarf stars in LAMOST DR4 spectra. Considering the position, distance, proper motion, and angular momentum distribution, we obtained 164 pure Sgr stream stars. We find that the trailing arm has higher energy than the leading arm in the same angular momentum. The trailing arm we detected extends to a heliocentric distance of ~130kpc at {Lambda}_{sun}_~170{deg}, which is consistent with the feature found in RR Lyrae in Sesar+ (2017, J/ApJ/844/L4). Both of these detections of Sgr, in M-giants and in RR Lyrae, imply that the Sgr stream may contain multiple stellar populations with a broad metallicity range.
- ID:
- ivo://CDS.VizieR/J/AJ/161/87
- Title:
- Gaia data for members of {epsilon}Cha
- Short Name:
- J/AJ/161/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to reexamine the membership and ages of nearby young moving groups (NYMGs), i.e., loose groups of stars of age <~100Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the {epsilon}Cha Association ({epsilon}CA) which, at an estimated age of ~3-5Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of {epsilon}CA include MPMus and TCha, two of the nearest stars of roughly solar mass that are known to host primordial protoplanetary disks, and the Herbig Ae/Be star HD104237A. We have used Gaia DR2 data to ascertain the Galactic positions and kinematics and color-magnitude diagram positions of {epsilon}CA members and candidates so as to reassess their membership status and thereby refine estimates of the distance, age, multiplicity, and disk fraction of the group. Our analysis yields 36 bona fide {epsilon}CA members, as well as 20 provisional members, including 3 new members identified here as comoving companions to previously known {epsilon}CA stars. We determine a mean distance to {epsilon}CA of 101.0{+/-}4.6pc and confirm that, at an age of 5_-2_^+3^Myr, {epsilon}CA represents the youngest stellar group within ~100pc of Earth. We identify several new photometric binary candidates, bringing the overall multiplicity fraction (MF) of {epsilon}CA to 40%, intermediate between the MFs of young T associations and the field.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A81
- Title:
- Gaia DR2-based catalogue of 237 Ap stars
- Short Name:
- J/A+A/628/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the distribution of strongly magnetic Ap stars in the Hertzsprung-Russell diagram (HRD) allows us to study the evolution of their magnetic fields across the main sequence (MS). With a newly extended Ap star sample from APOGEE and available Gaia DR2 data, we can now critically review the results of previous studies based on Hipparcos data. To investigate our targets in the Gaia DR2 HRD, we need to define astrometric and photometric quality criteria to remove unreliable data from the HRD. We used the Gaia DR2 renormalised unit weight error RUWE as our main quality criterion. We considered known (close) binaries in our sample compared to their (partly affected) astrometry and used the Gaia DR2 data to find common parallax and proper motion (CPPM) wide companions and open cluster members. We studied G, BP and RP variability amplitudes and their significance as a function of magnitude. In colour-magnitude diagrams (CMDs) with absolute G magnitude (determined from inverted parallax) versus BP-RP colour and HRDs, where BP-RP is replaced by effective temperature, we studied the appearance of outliers with respect to their astrometric quality, binarity, and variability. We present a catalogue of 83 previously known and 154 new strongly magnetic Ap stars with Gaia DR2 data, including astrometric quality parameters, binary flags, information on cluster membership, variability amplitudes, and data from Hipparcos. Our astrometrically cleaned subsamples include 47 and 46 old and new Ap stars with parallaxes >2mas. Most of the known 26 binaries among all 237 stars and 14 out of 15 CMD/HRD outliers were excluded by astrometric criteria. The remaining 11 known binaries and a few highly variable objects mainly appear in the bright and red CMD/HRD parts. A CMD based on Hipparcos photometry and Gaia DR2 parallaxes shows a much more narrow distribution in the absolute V magnitudes of 75 common Ap stars over the full B-V colour range than the corresponding CMD based on Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/I/343
- Title:
- Gaia-PS1-SDSS (GPS1) proper motion catalog
- Short Name:
- I/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine Gaia DR1, PS1, Sloan Digital Sky Survey (SDSS), and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of m_r_~20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate its positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are linear. By simultaneously fitting the positions of stars at different epochs of-Gaia DR1, PS1, SDSS, and 2MASS-we construct an extensive catalog of proper motions dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3mas/yr and a typical precision of 1.5-2.0mas/yr. The proper motions have been validated using galaxies, open clusters, distant giant stars, and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error (<0.3mas/yr) should be nearly an order of magnitude better than that of PPMXL and UCAC4 (>2.0mas/yr). Similarly, its precision (~1.5mas/yr) is a four-fold improvement relative to PPMXL and UCAC4 (~6.0mas/yr). For QSOs, the precision of GPS1 is found to be worse (~2.0-3.0mas/yr), possibly due to their particular differential chromatic refraction.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A151
- Title:
- Galactic Bulge Type II Cepheids NIR data
- Short Name:
- J/A+A/625/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform parallel Lomb-Scargle and Generalized Lomb-Scargle periodogram analysis of the Ks-band time series of the VISTA Variables in the Via Lactea Survey, to detect periodicities. We take account of periods, light amplitudes, distances and proper motions to provide a classification of the candidate variables. We provide a catalog which will be the starting point for future spectroscopic surveys in the innermost regions of the Galaxy.