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17321. WD+dMs from the SUPERBLINK proper motion survey
ID:
ivo://CDS.VizieR/J/AJ/154/118
Title:
WD+dMs from the SUPERBLINK proper motion survey
Short Name:
J/AJ/154/118
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV-optical-IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use H{alpha} chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population.
17322. WD luminosity functions from the PS1 3pi Survey
ID:
ivo://CDS.VizieR/J/MNRAS/482/715
Title:
WD luminosity functions from the PS1 3pi Survey
Short Name:
J/MNRAS/482/715
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3{pi} Steradian Survey Processing Version 2 to construct the white dwarf luminosity functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalized maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833sr, which is 83 per cent of the 3{pi} sky and 62 per cent of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100.
17323. WDMS from LAMOST DR1
ID:
ivo://CDS.VizieR/J/A+A/570/A107
Title:
WDMS from LAMOST DR1
Short Name:
J/A+A/570/A107
Date:
21 Oct 2021
Publisher:
CDS
Description:
White dwarf-main sequence (WDMS) binaries are used to study several different important open problems in modern astrophysics. The Sloan Digital Sky Survey (SDSS) identified the largest catalogue of WDMS binaries currently known. However, this sample is seriously affected by selection effects and the population of systems containing cool white dwarfs and early-type companions is under-represented. Here we search for WDMS binaries within the spectroscopic data release 1 of the LAMOST (Large sky Area Multi-Object fiber Spectroscopic Telescope) survey. LAMOST and SDSS follow different target selection algorithms. Hence, LAMOST WDMS binaries may be drawn from a different parent population and thus help in overcoming the selection effects incorporated by SDSS on the current observed population. We develop a fast and efficient routine based on the wavelet transform to identify LAMOST WDMS binaries containing a DA white dwarf and a M dwarf companion, and apply a decomposition/fitting routine to their LAMOST spectra to estimate their distances and measure their stellar parameters, namely the white dwarf effective temperatures, surface gravities and masses, and the secondary star spectral types. We identify 121 LAMOST WDMS binaries, 80 of which are new discoveries, and estimate the sample to be about 90 per cent complete. The LAMOST and SDSS WDMS binaries are found to be statistically different. However, this result is not due to the different target selection criteria of both surveys, but likely a simple consequence of the different observing conditions. Thus, the LAMOST population is found at considerably shorter distances (50-450pc) and is dominated by systems containing early-type companions and hot white dwarfs. Even though WDMS binaries containing cool white dwarfs are also missed by the LAMOST survey, the LAMOST WDMS binary sample dominated by systems containing early-type companions is an important addition to the current known spectroscopic catalogue. Future LAMOST observations however are required to increase the small number of LAMOST WDMS binaries.
17324. WD within 20pc of the Sun
ID:
ivo://CDS.VizieR/J/AJ/138/1681
Title:
WD within 20pc of the Sun
Short Name:
J/AJ/138/1681
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition of five new stars to the 20pc sample yields a revised local space density of white dwarfs of (4.9+/-0.5)x10^-3^pc^-3^ and a corresponding mass density of (3.3+/-0.3)x10^-3^M_{sun}_pc^-3^. We find that at least 15% of the white dwarfs within 20 parsecs of the Sun (the DAZ and DZ stars) have photospheric metals that possibly originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, this suggests the possibility that the same percentage have planets or asteroid-like bodies orbiting them.
17325. Weak Galactic radio sources spectral indices
ID:
ivo://CDS.VizieR/J/MNRAS/473/1685
Title:
Weak Galactic radio sources spectral indices
Short Name:
J/MNRAS/473/1685
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the next few years the classification of radio sources observed by the large surveys will be a challenging problem and spectral index is a powerful tool for addressing it. Here we present an algorithm to estimate the spectral index of sources from multiwavelength radio images. We have applied our algorithm to SCORPIO, a Galactic plane survey centred around 2.1GHz carried out with Australian Telescope Compact Array and found we can measure reliable spectral indices only for sources stronger than 40 times the rms noise. Above a threshold of 1mJy, the source density in SCORPIO is 20 per cent greater than in a typical extragalactic field, like Australia Telescope Large Area Survey because of the presence of Galactic sources. Among this excess population, 16 sources per square degree have a spectral index of about zero suggesting optically thin thermal emission such as HII regions and planetary nebulae, while 12 per square degree present a rising spectrum, suggesting optically thick thermal emission such as stars and UCHII regions.
17326. weak G-band stars abundances
ID:
ivo://CDS.VizieR/J/A+A/587/A42
Title:
weak G-band stars abundances
Short Name:
J/A+A/587/A42
Date:
21 Oct 2021
Publisher:
CDS
Description:
Weak G-band (wGb) stars are a very peculiar class of red giants; they are almost devoided of carbon and often present mild lithium enrichment. Despite their very puzzling abundance patterns, very few detailed spectroscopic studies existed up to a few years ago, which prevented any clear understanding of the wGb phenomenon. We recently proposed the first consistent analysis of published data for a sample of 28 wGb stars and were able to identify them as descendants of early A-type to late B-type stars, although we were not able to conclude on their evolutionary status or the origin of their peculiar abundance pattern. Using new high-resolution spectra, we present the study of a new sample of wGb stars with the aim of homogeneously deriving their fundamental parameters and surface abundances for a selected set of chemical species that we use to improve our insight on this peculiar class of objects. We obtained high-resolution and high signal-to-noise spectra for 19 wGb stars in the southern and northern hemisphere that we used to perform consistent spectral synthesis to derive their fundamental parameters and metallicities, as well as the spectroscopic abundances for Li, C, ^12^C/^13^C, N, O, Na, Sr, and Ba. We also computed dedicated stellar evolution models that we used to determine the masses and to investigate the evolutionary status and chemical history of the stars in our sample. We confirm that the wGb stars are stars with initial masses in the range 3.2 to 4.2M_{sun}_. We suggest that a large fraction could be mildly evolved stars on the subgiant branch currently undergoing the first dredge-up, while a smaller number of stars are more probably in the core He burning phase at the clump. After analysing their abundance pattern, we confirm their strong nitrogen enrichment anti-correlated with large carbon depletion, characteristic of material fully processed through the CNO cycle to an extent not known in evolved intermediate-mass stars in the field and in open clusters. However, we demonstrate here that such a pattern is very unlikely owing to self-enrichment. In the light of the current observational constraints, no solid self-consistent pollution scenario can be presented either, leaving the wGb puzzle largely unsolved.
17327. Weak-line T Tauri in Spitzer c2d Survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/667/308
Title:
Weak-line T Tauri in Spitzer c2d Survey. II.
Short Name:
J/ApJ/667/308
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the central goals of the Spitzer Legacy Project "From Cores to Disks" (c2d) is to determine the frequency of circumstellar disks around weak-line T Tauri stars (WTTSs) and to study the properties and evolutionary status of these disks. Here we present a census of disks for a sample of over 230 WTTSs located in the c2d IRAC and MIPS maps of the Ophiuchus, Lupus, and Perseus Molecular Clouds.
17328. Weak metal line absorbers sample
ID:
ivo://CDS.VizieR/J/MNRAS/476/4965
Title:
Weak metal line absorbers sample
Short Name:
J/MNRAS/476/4965
Date:
15 Dec 2021 07:14:57
Publisher:
CDS
Description:
We present a sample of 34 weak metal line absorbers at z<0.3 selected by the simultaneous >3{sigma} detections of the SiII{lambda}1260 and CII{lambda}1334 absorption lines, with W_r_(SiII)<0.2 {AA} and W_r_(CII)<0.3{AA}, in archival HST/COS spectra. Our sample increases the number of known low-z 'weak absorbers' by a factor of >5. The column densities of HI and low-ionization metal lines obtained from Voigt profile fitting are used to build simple photoionization models. The inferred densities and line-of-sight thicknesses of the absorbers are in the ranges of -3.3<logn_H_/cm^-3^<-2.4 and ~1pc-50kpc (median ~=500pc), respectively. Most importantly, 85 per cent (50 per cent) of these absorbers show a metallicity of [Si/H]>-1.0(0.0). The fraction of systems showing near-/supersolar metallicity in our sample is significantly higher than in the HI-selected sample of Wotta et al., and the galaxy-selected sample of Prochaska et al., of absorbers probing the circum-galactic medium at similar redshift. A search for galaxies has revealed a significant galaxy-overdensity around these weak absorbers compared to random positions with a median impact parameter of 166 kpc from the nearest galaxy. Moreover, we find the presence of multiple galaxies in ~=80 per cent of the cases, suggesting group environments. The observed dN/dz of 0.8+/-0.2 indicates that such metal-enriched, compact, dense structures are ubiquitous in the haloes of low-z group galaxies. We suggest that these are transient structures that are related to galactic outflows and/or stripping of metal-rich gas from galaxies.
17329. Weak MgII absorbers at 0.4<z<2.4
ID:
ivo://CDS.VizieR/J/ApJ/660/1093
Title:
Weak MgII absorbers at 0.4<z<2.4
Short Name:
J/ApJ/660/1093
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a survey of weak MgII absorbers in the VLT/UVES spectra of 81 QSOs obtained from the ESO archive. In this survey, we identified 112 weak MgII systems within the redshift interval 0.4<z<2.4 with 86% completeness down to a rest-frame equivalent width of Wr(2796)=0.02{AA}, overing a cumulative redshift path length of {DELTA}Z~77.3.
17330. W51/e2 and G34.3+0.2 IRAM spectra
ID:
ivo://CDS.VizieR/J/A+A/582/A64
Title:
W51/e2 and G34.3+0.2 IRAM spectra
Short Name:
J/A+A/582/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
With only a few low- and high-mass star-formation regions studied in detail so far, it is unclear what role the environment plays in complex molecule formation. In this light, a comparison of relative abundances of related species between sources might be useful for explaining any observed differences. We seek to measure the relative abundance between three important complex organic molecules, ethylene glycol ((CH_2_OH)_2_), glycolaldehyde (CH_2_OHCHO) and methyl formate (HCOOCH_3_), toward high-mass protostars and thereby provide additional constraints on their formation pathways. We use IRAM30 m single-dish observations of the three species toward two high-mass star-forming regions - W51/e2 and G34.3+0.2 - and report a tentative detection of (CH_2_OH)_2_ toward both sources.

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