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1301. BANYAN. VII. Candidate YMG members from BASS
ID:
ivo://CDS.VizieR/J/ApJS/219/33
Title:
BANYAN. VII. Candidate YMG members from BASS
Short Name:
J/ApJS/219/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a near-infrared (NIR) spectroscopic follow-up survey of 182 M4-L7 low-mass stars and brown dwarfs (BDs) from the BANYAN All-Sky Survey (BASS) for candidate members of nearby, young moving groups (YMGs). We confirm signs of low gravity for 42 new BD discoveries with estimated masses between 8 and 75M_Jup_ and identify previously unrecognized signs of low gravity for 24 known BDs. We refine the fraction of low-gravity dwarfs in the high-probability BASS sample to ~82%. We use this unique sample of 66 young BDs, supplemented with 22 young BDs from the literature, to construct new empirical NIR absolute magnitude and color sequences for low-gravity BDs. We show that low-resolution NIR spectroscopy alone cannot differentiate between the ages of YMGs younger than ~120Myr, and that the BT-Settl atmosphere models do not reproduce well the dust clouds in field or low-gravity L-type dwarfs. We obtain a spectroscopic confirmation of low gravity for 2MASS J14252798-3650229, which is a new ~27M_Jup_, L4 {gamma} bona fide member of AB Doradus. We identify a total of 19 new low-gravity candidate members of YMGs with estimated masses below 13M_Jup_, 7 of which have kinematically estimated distances within 40pc. These objects will be valuable benchmarks for a detailed atmospheric characterization of planetary-mass objects with the next generation of instruments. We find 16 strong candidate members of the Tucana-Horologium association with estimated masses between 12.5 and 14M_Jup_, a regime where our study was particularly sensitive. This would indicate that for this association there is at least one isolated object in this mass range for every 17.5_-5.0_^+6.6^ main-sequence stellar member, a number significantly higher than expected based on standard log-normal initial mass function, however, in the absence of radial velocity and parallax measurements for all of them, it is likely that this over-density is caused by a number of young interlopers from other associations.
1302. BANYAN. XIII. Nearby young assoc. with Gaia DR2
ID:
ivo://CDS.VizieR/J/ApJ/862/138
Title:
BANYAN. XIII. Nearby young assoc. with Gaia DR2
Short Name:
J/ApJ/862/138
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we examine the nearest 100pc entries in Data Release 2 of Gaia to identify previously unrecognized candidate members in young associations. We analyze 695952 stars with the BANYAN {Sigma} Bayesian classification software and discover 898 new high-likelihood candidate members that span a wide range of properties, from spectral types B9 to L2, including 104 comoving systems, 111 brown dwarfs, and 31 new bona fide members. Our sample is mostly composed of highly active M dwarfs and will be crucial in examining the low-mass end of the initial mass function of young associations. Our sample includes new candidate members near the Galactic plane where previous surveys suffered from a high rate of contamination. This paper represents the first step toward a full reassessment of young associations in the solar neighborhood with the second data release of the Gaia mission.
1303. BANYAN. XII. New members from Gaia-Tycho data
ID:
ivo://CDS.VizieR/J/ApJ/860/43
Title:
BANYAN. XII. New members from Gaia-Tycho data
Short Name:
J/ApJ/860/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a search for stellar members of young associations within 150pc of the Sun, based on TGAS and an updated version of the BANYAN {Sigma} software to determine Bayesian membership probabilities that includes Gaia-2MASS color-magnitude diagrams. We identify 32 new F0-M3-type bona fide members of the 10-200Myr old Sco-Cen, Carina, Tucana-Horologium, Columba, and Octans associations and the AB Doradus, {beta} Pictoris, and Carina-Near moving groups. These new bona fide members have measurements of their full kinematics and literature data consistent with a young age. We also confirm the membership of 66 previously known candidate members using their Gaia-Tycho trigonometric distances or new literature radial velocities, and identify 219 additional new candidate members, most of which do not yet have a radial velocity measurement. This work is the first step toward a completeness-corrected survey of young association members based on Gaia DR2 in the near future.
1304. BANYAN. XI. The BANYAN {Sigma} algorithm
ID:
ivo://CDS.VizieR/J/ApJ/856/23
Title:
BANYAN. XI. The BANYAN {Sigma} algorithm
Short Name:
J/ApJ/856/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
BANYAN {Sigma} is a new Bayesian algorithm to identify members of young stellar associations within 150pc of the Sun. It includes 27 young associations with ages in the range ~1-800Myr, modeled with multivariate Gaussians in six-dimensional (6D) XYZUVW space. It is the first such multi-association classification tool to include the nearest sub-groups of the Sco-Cen OB star-forming region, the IC2602, IC2391, Pleiades and Platais 8 clusters, and the {rho} Ophiuchi, Corona Australis, and Taurus star formation regions. A model of field stars is built from a mixture of multivariate Gaussians based on the Besancon Galactic model. The algorithm can derive membership probabilities for objects with only sky coordinates and proper motion, but can also include parallax and radial velocity measurements, as well as spectrophotometric distance constraints from sequences in color-magnitude or spectral type-magnitude diagrams. BANYAN {Sigma} benefits from an analytical solution to the Bayesian marginalization integrals over unknown radial velocities and distances that makes it more accurate and significantly faster than its predecessor BANYAN II. A contamination versus hit rate analysis is presented and demonstrates that BANYAN {Sigma} achieves a better classification performance than other moving group tools available in the literature, especially in terms of cross-contamination between young associations. An updated list of bona fide members in the 27 young associations, augmented by the Gaia-DR1 release, as well as all parameters for the 6D multivariate Gaussian models for each association and the Galactic field neighborhood within 300 pc are presented.
1305. Bar-induced strengths in spiral galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/355/1251
Title:
Bar-induced strengths in spiral galaxies
Short Name:
J/MNRAS/355/1251
Date:
21 Oct 2021
Publisher:
CDS
Description:
Bar-induced perturbation strengths are calculated for a well-defined magnitude-limited sample of 180 spiral galaxies, based on the Ohio State University Bright Galaxy Survey. We use a gravitational torque method, the ratio of the maximal tangential force to the mean axisymmetric radial force, as a quantitative measure of the bar strength.
1306. Barium abundance in Galactic Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/437/2106
Title:
Barium abundance in Galactic Cepheids
Short Name:
J/MNRAS/437/2106
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using an Non-Local Thermodynamic Equilibrium (NLTE) analysis and a homogenous spectral data base, we have determined Ba abundances in a sample of 210 Galactic Cepheids and related objects. We confirm the previous result reported in Andrievsky et al. that the barium distribution in the range of Galactocentric distances from 5 to 18kpc shows very small gradient value. The value determined here - d[Ba/H]/dR~-0.01dex/kpc - is smaller than that for other s-process elements, such as La, Pr, Nd and Sm (Luck & Lambert, 2011AJ....142..136L, Cat. J/AJ/142/136), that typically show gradients of -0.03dex/kpc.
1307. Barium abundances from Keck/HIRES high res. spectra
ID:
ivo://CDS.VizieR/J/ApJ/896/64
Title:
Barium abundances from Keck/HIRES high res. spectra
Short Name:
J/ApJ/896/64
Date:
15 Nov 2021 00:01:16
Publisher:
CDS
Description:
Based on the high-resolution, high signal-to-noise-ratio spectra from the Keck/HIRES, we have analyzed the barium abundances of 602 stars. The parameter space of our sample are in the range of 4700<Teff<6100K, -0.1<[Fe/H]<0.6dex, and 2<logg<5dex. It is found that the nonlocal thermodynamic equilibrium (NLTE) effects are large for barium, and the barium abundances can be underestimated by up to 0.2dex compared to the the local thermodynamic equilibrium analysis for lines at 5853 and 6141{AA}. In addition, the average barium abundances of the high- and low-{alpha} stars are -0.10 and 0.00dex, respectively, and higher [Ba/Fe] corresponds to a lower [Mg/Fe] ratio. We note that there are 18 Ba-rich stars (with [Ba/Fe]>0.3 in NLTE), which contains six dwarfs and 12 giants. The Ba-rich objects make up around 3% in our sample.
1308. Barium abundances in Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/428/3252
Title:
Barium abundances in Cepheids
Short Name:
J/MNRAS/428/3252
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derived the barium atmospheric abundances for a large sample of Cepheids, comprising 270 stars. The sample covers a large range of Galactocentric distances, from about 4 to 15kpc, so it is appropriate to investigate the existence of radial barium abundance gradients in the Galactic disc. In fact, this is the first time that such a comprehensive analysis of the distribution of barium abundances in the Galactic disc has been carried out. As a result, we conclude that the Ba abundance distribution can be characterized by a zero gradient. This result is compared with derived gradients for other elements, and some reasons are briefly discussed for the independence of the barium abundances from Galactocentric distances.
1309. Barium abundances of red giant branch stars
ID:
ivo://CDS.VizieR/J/ApJ/869/50
Title:
Barium abundances of red giant branch stars
Short Name:
J/ApJ/869/50
Date:
21 Oct 2021
Publisher:
CDS
Description:
There are many candidate sites of the r-process: core-collapse supernovae (CCSNe; including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies --specifically dwarf galaxies-- helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference --how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [{alpha}/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than CCSNe in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] versus [Fe/H] seen for [Fe/H]<~-1.6 when compared to the [Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely source of r-process enrichment in dwarf galaxies at early times.
1310. Barium and related stars and WD companions
ID:
ivo://CDS.VizieR/J/A+A/626/A127
Title:
Barium and related stars and WD companions
Short Name:
J/A+A/626/A127
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper provides long-period and revised orbits for barium and S stars adding to previously published ones. The sample of barium stars with strong anomalies comprise all such stars present in the Lu et al. catalogue. We find orbital motion for all barium and extrinsic S stars monitored. We obtain the longest period known so far for a spectroscopic binary involving an S star, namely 57 Peg with a period of the order of 100-500yr. We present the mass distribution for the barium stars, which ranges from 1 to 3M_{sun}_, with a tail extending up to 5M_{sun}_ in the case of mild barium stars. This high-mass tail comprises mostly high-metallicity objects ([Fe/H]>=-0.1). Mass functions are compatible with WD companions and we derive their mass distribution which ranges from 0.5 to 1 Msun. Using the initial - final mass relationship established for field WDs, we derived the distribution of the mass ratio q'=M_AGB,ini_/M_Ba_ (where M_AGB,ini_ is the WD progenitor initial mass, i.e., the mass of the system former primary component) which is a proxy for the initial mass ratio. It appears that the distribution of q' is highly non uniform, and significantly different for mild and strong barium stars, the latter being characterized by values mostly in excess of 1.4, whereas mild barium stars occupy the range 1-1.4. We investigate as well the correlation between abundances, orbital periods, metallicities, and masses (barium star and WD companion). The 105 orbits of post-mass-transfer systems presented in this paper pave the way for a comparison with binary-evolution models.

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