- ID:
- ivo://CDS.VizieR/J/ApJ/769/40
- Title:
- Potassium abundance in red giants of GCs
- Short Name:
- J/ApJ/769/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two independent studies recently uncovered two distinct populations among giants in the distant, massive globular cluster (GC) NGC 2419. One of these populations has normal magnesium (Mg) and potassium (K) abundances for halo stars: enhanced Mg and roughly solar K. The other population has extremely depleted Mg and very enhanced K. To better anchor the peculiar NGC 2419 chemical composition, we have investigated the behavior of K in a few red giant branch stars in NGC 6752, NGC 6121, NGC 1904, and {omega} Cen. To verify that the high K abundances are intrinsic and not due to some atmospheric features in giants, we also derived K abundances in less evolved turn-off and subgiant stars of clusters 47 Tuc, NGC 6752, NGC 6397, and NGC 7099. We normalized the K abundance as a function of the cluster metallicity using 21 field stars analyzed in a homogeneous manner. For all GCs of our sample, the stars lie in the K-Mg abundance plane on the same locus occupied by the Mg-normal population in NGC 2419 and by field stars. This holds for both giants and less-evolved stars. At present, NGC 2419 seems unique among GCs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/852/49
- Title:
- Properties of metal-poor stars in APOGEE DR13
- Short Name:
- J/ApJ/852/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We find two chemically distinct populations separated relatively cleanly in the [Fe/H]-[Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities [Fe/H]<-0.9) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the Sloan Digital Sky Survey. These two stellar populations show the most significant differences in their [X/Fe] ratios for the {alpha}-elements, C+N, Al, and Ni. In addition to these populations having differing chemistry, the low metallicity high-Mg population (which we denote "the HMg population") exhibits a significant net Galactic rotation, whereas the low-Mg population (or "the LMg population") has halo-like kinematics with little to no net rotation. Based on its properties, the origin of the LMg population is likely an accreted population of stars. The HMg population shows chemistry (and to an extent kinematics) similar to the thick disk, and is likely associated with in situ formation. The distinction between the LMg and HMg populations mimics the differences between the populations of low- and high-{alpha} halo stars found in previous studies, suggesting that these are samples of the same two populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/63
- Title:
- Properties of Sgr Stars
- Short Name:
- J/ApJ/889/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3D positions and kinematics of stars relative to the Sagittarius (Sgr) orbital plane and angular momentum, we identify 166 Sgr stream members observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) that also have Gaia DR2 astrometry. This sample of 63/103 stars in the Sgr trailing/leading arm is combined with an APOGEE sample of 710 members of the Sgr dwarf spheroidal core (385 of them newly presented here) to establish differences of 0.6dex in median metallicity and 0.1dex in [{alpha}/Fe] between our Sgr core and dynamically older stream samples. Mild chemical gradients are found internally along each arm, but these steepen when anchored by core stars. With a model of Sgr tidal disruption providing estimated dynamical ages (i.e., stripping times) for each stream star, we find a mean metallicity gradient of 0.12+/-0.03dex/Gyr for stars stripped from Sgr over time. For the first time, an [{alpha}/Fe] gradient is also measured within the stream, at 0.02_/-0.01dex/Gyr using magnesium abundances and at 0.04+/-0.01dex/Gyr^ using silicon, which imply that the Sgr progenitor had significant radial abundance gradients. We discuss the magnitude of those inferred gradients and their implication for the nature of the Sgr progenitor within the context of the current family of Milky Way satellite galaxies, and we suggest that more sophisticated Sgr models are needed to properly interpret the growing chemodynamical detail we have on the Sgr system.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/L8
- Title:
- Properties of TriAnd stars
- Short Name:
- J/ApJ/859/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy, or a distant extension of the Galactic disk. We test these hypotheses using the chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey-IV's (SDSS-IV's) 14th Data Release (DR14) of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about -0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H]~-0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity-i.e., past a Galactocentric radius of 24kpc-albeit vertically perturbed about 7kpc below the nominal disk midplane in this region of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/112/545
- Title:
- Proton capture chains in globular clusters. I.
- Short Name:
- J/AJ/112/545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sodium abundances have been derived for 130 giant stars in the globular cluster M13 from spectra of the Na I doublet at {lambda}5682 and 5685A obtained using the KPNO 4-m Hydra fiber positioner and bench spectrograph. Magnesium abundances have also been obtained for the brightest 98 stars in the sample from the nearby Mg I line at {lambda}5711A. The stars observed in M13 range from the faintest at M_V_~+1.0 and log(g)~2.6 up to the tip of the giant branch, and include 18 stars on the asymptotic giant branch. Among the lower luminosity giants, the sodium abundances have a large star-to-star range, approximately from -0.3<=[Na/Fe]<=+0.5. However, the sodium abundances of the most luminous giants (Mv<-1.7) are usually high; typically, [Na/Fe]>=+0.3, with a much smaller star-to-star scatter. The asymptotic giant branch stars have smaller sodium abundances on average than do the red giant branch tip stars. The spread in [Na/Fe] ratios is larger in M13 than it is among halo field giants of comparable metallicity; M13 contains many more stars with high [Na/Fe] ratios than can be found in the field, even at relatively low luminosities on the giant branch. Magnesium is uniformly overabundant ([Mg/Fe]~+0.3) in all stars with a low sodium abundance, but the [Mg/Fe] ratio ranges from approximately -0.3 to +0.3 in stars with a high sodium abundance. These sodium and magnesium abundance variations in M13 are discussed in the context of proton capture and deep mixing hypotheses. In addition to the CN and ON hydrogen burning chains previously discussed in the literature, the NeNa and MgAl burning chains have also contributed to the abundance mixture observed in M13 giants. At least some of the products of proton capture chains have been produced in situ in the giants, and brought to the surface, most probably via deep mixing. Evidence in support of the occurrence of proton capture nucleosynthesis and deep mixing among M13 stars includes (1) the absence of sodium-poor stars at the red giant tip, (2) the fact that asymptotic branch stars have lower sodium abundances on average than do stars near the red giant tip, and (3) the existence of a positive correlation between sodium and nitrogen abundances as well as a partial anti-correlation of sodium and magnesium abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/430/165
- Title:
- Radial velocities for 6691 K and M giants
- Short Name:
- J/A+A/430/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table provides Hipparcos positions, Hipparcos & Tycho-2 proper motions, and CORAVEL radial velocities for 6691 K and M giants in the solar neighbourhood, mostly from the Hipparcos survey. A bayesian maximum-likelihood approach has been used to derive the distances and space velocities. New V-I indices, computed from a color transformation based on Hp-V_T2_, are also provided. Spectroscopic binaries have been identified as well. These data may be used to study the kinematics of giant stars in the solar neighbourhood, and to correlate it with their location in the Hertzsprung-Russell diagram.
- ID:
- ivo://CDS.VizieR/J/A+A/485/303
- Title:
- Radial velocities for 1309 stars and 166 OCl
- Short Name:
- J/A+A/485/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the final catalogues of a long term observing program performed with the two Coravel spectrovelocimeters for red giants in open clusters. The main aims were to detect spectroscopic binaries and determine their orbital parameters, determine the membership, and compute mean velocities for the stars and open clusters. We computed weighted mean radial velocities for 1309 stars from 10517 individual observations, including the systemic radial velocities from spectroscopic orbits and for Cepheids. The final results are contained in three catalogues collecting 10517 individual radial velocities, mean radial velocities for 1309 red giants, and mean radial velocities for 166 open clusters, among which 57 are new determinations. We identify 891 members and 418 non-members. We discovered a total of 288 spectroscopic binaries, among which 57 were classified as non-members. In addition 27 stars were judged to be variable in radial velocities, all of them being red supergiants.
- ID:
- ivo://CDS.VizieR/J/AJ/151/106
- Title:
- Radial velocities in 2006-2014 for HD 89758
- Short Name:
- J/AJ/151/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report that the spectroscopic binary {mu} Ursae Majoris ({mu} UMa) has secondary RV variations of 471.2 days in addition to those of 230.0 days already known. Keplerian orbit analysis yields stellar mass companions of 1.6M_{sun}_ for the 230 day period and 0.14M_{sun}_for the 471 day period. However, the HIPPARCOS photometries show a period similar to the stellar rotational period, which is one-quarter of the RV period. Variations in the bisector velocity curvature show a period of 463.6 days. We also find ~473 day variations in the equivalent width (EW) measurements of the H_{alpha}_ and H_{beta}_ lines, whose origin is probably stellar activity. We note that the nature of 471 day variations is similar to one observed in "Sequence D" of Asymptotic Giant Branch pulsating stars. We therefore conclude that the RV and the EW variations in the spectroscopic binary M giant {mu} UMa A originate from the complex pulsations and the chromospheric activity.
- ID:
- ivo://CDS.VizieR/J/A+A/375/30
- Title:
- Radial velocities in open clusters
- Short Name:
- J/A+A/375/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate radial velocities and photoelectric UBV photometry for 73 and 57 red-giant candidates, respectively, in the intermediate-age open clusters NGC 2324, 2818, 3960 and 6259. These data confirm the membership of 47 stars, 12 of which (26% ) are spectroscopic binaries; three preliminary orbits have been determined in NGC 3960. From Washington photometry of 8 red giant members, the metallicity of NGC 6259 is found to be [Fe/H]=0.06+/-0.08. At the age of these clusters, most of the red giants are observed in the core-helium (clump) burning phase, the general morphology of which is well reproduced by theoretical models with convective overshooting. However, a number of bona fide cluster giant members are found significantly to the red of the isochrones fitting the rest of the CMD of these and a few other clusters. Some of these stars are binaries, but others seem to be single. In either case, their red colours and/or low luminosities remain unexplained by current stellar evolution theory.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A47
- Title:
- Radial velocities of 12 evolved stars
- Short Name:
- J/A+A/613/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and line bisectors for 12 giants with high Li abundance. We report the discovery of two new planetary systems around HD238914 and TYC3318-01333-1, reveal a binary Li-rich giant HD181368. Although our current phase coverage is not complete, we suggest the presence of planetary mass companions around TYC3663-01966-1 and TYC3105-00152-1. We confirm the previous result for BD+48 740 (Adamow et al, 2012ApJ...754L..15A).
