- ID:
- ivo://CDS.VizieR/J/A+A/564/A60
- Title:
- NGC 4833 Na-O measured with FLAMES
- Short Name:
- J/A+A/564/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our FLAMES survey of Na-O anticorrelation in globular clusters (GCs) is extended to NGC 4833, a metal-poor GC with a long blue tail on the horizontal branch (HB). We present the abundance analysis (Na, O, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, La, Nd)for 78 red giants based on UVES and GIRAFFE spectra acquired at the ESO-VLT. NGC 4833 has [Fe/H]=-2.015+/-0.004+/-0.084dex (rms=0.014dex) from 12 stars observed with UVES; the iron abundance is homogeneous at better than 6%. The Na-O anticorrelation in NGC 4833 is quite extended, as expected from the high temperatures reached by stars on the HB, and NGC 4833 contains a conspicuous fraction of stars with extreme [O/Na] ratios. Large star-to-star variations are seen also for Mg, which spans a range of more than 0.5dex in this GC. Depletions in Mg are correlated to the abundances of O and anti-correlated with Na, Al, and Si abundances. This pattern suggests the action of nuclear processing at unusually high temperatures, producing the extreme chemistry observed in the stellar generations of NGC 4833. This extreme changes are also seen in giants of the much more massive GCs M 54 and omega Cen, and our conclusion is that NGC 4833 has probably lost a conpicuous fraction of its original mass due to bulge shocking, as also indicated by its orbit.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3130
- Title:
- NGC5694 radial velocities and metallicities
- Short Name:
- J/MNRAS/446/3130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the kinematics of the remote globular cluster NGC 5694 based on GIRAFFE@VLT medium-resolution spectra. A sample of 165 individual stars selected to lie on the red giant branch in the cluster colour-magnitude diagram was considered. Using radial velocity and metallicity from Calcium triplet, we were able to select 83 bona fide cluster members. The addition of six previously known members leads to a total sample of 89 cluster giants with typical uncertainties <=1.0km/s in their radial velocity estimates. The sample covers a wide range of projected distances from the cluster centre, from ~0.2arcmin to 6.5arcmin =~23 half-light radii (r_h_). We find only very weak rotation, as typical of metal-poor globular clusters. The velocity dispersion gently declines from a central value of {sigma}=6.1km/s to {sigma}=~2.5km/s at ~2arcmin=~7.1r_h_, then it remains flat out to the next (and last) measured point of the dispersion profile, at ~4arcmin =~14.0r_h_, at odds with the predictions of isotropic King models. We show that both isotropic single-mass non-collisional models and multimass anisotropic models can reproduce the observed surface brightness and velocity dispersion profiles.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A148
- Title:
- NGC6397 red giants chemical composition
- Short Name:
- J/A+A/527/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical compositions of globular clusters provide important information on the star formation that occurred at very early times in the Galaxy. In particular the abundance patterns of elements with atomic number z<=13 may shed light on the properties of stars that early on enriched parts of the star-forming gas with the rest-products of hydrogen-burning at high temperatures. We analyse and discuss the chemical compositions of a large number of elements in 21 red giant branch stars in the metal-poor globular cluster NGC6397. We compare the derived abundance patterns with theoretical predictions in the framework of the "wind of fast rotating massive star"-scenario. High-resolution spectra were obtained with the FLAMES/UVES spectrograph on the VLT. We determined non-LTE abundances of Na, and LTE abundances for the remaining 21 elements, including O (from the [OI] line at 630nm), Mg, Al, alpha, iron-peak, and neutron-capture elements, many of which had not been previously analysed for this cluster. We also considered the influence of possible He enrichment in the analysis of stellar spectra. We find that the Na abundances of evolved, as well as unevolved, stars in NGC6397 show a distinct bimodality, which is indicative of two stellar populations: one primordial stellar generation of composition similar to field stars, and a second generation that is polluted with material processed during hydrogen-burning, i.e., enriched in Na and Al and depleted in O and Mg. The red giant branch exhibits a similar bimodal distribution in the Stroemgren colour index c_y_=c_1_-(b-y), implying that there are also large differences in the N abundance. The two populations have the same composition for all analysed elements heavier than Al, within the measurement uncertainty of the analysis, with the possible exception of [Y/Fe]. Using two stars with almost identical stellar parameters, one from each generation, we estimate the difference in He content, Delta-Y=0.01+/-0.06, given the assumption that the mass fraction of iron is the same for the stars. NGC6397 hosts two stellar populations that have different chemical compositions of N, O, Na, Mg, and probably Al. The cluster is dominated (75%) by the second generation. We show that massive stars of the first generation can be held responsible for the abundance patterns observed in the second generation long-lived stars of NGC6397. We estimate that the initial mass of this globular cluster is at least ten times higher than its present-day value.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A35
- Title:
- NGC104 RGB Na, Mg, and K abundances
- Short Name:
- J/A+A/604/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the abundances of Na, Mg, and K in the atmospheres of 32 red giant branch (RGB) stars in the Galactic globular cluster (GGC) 47 Tuc, with the goal to investigate the possible existence of Na-K and Mg-K correlations/anti-correlations, similar to those that were recently discovered in two other GGCs, NGC 2419 and 2808. The abundances of K, Na, and Mg were determined using high-resolution 2df spectra obtained with the Anglo-Australian Telescope (AAT). The 1D NLTE abundance estimates were obtained using 1D hydrostatic ATLAS9 model atmospheres and spectral line profiles synthesized with the MULTI package. We also used 3D hydrodynamical CO5BOLD and 1D hydrostatic LHD model atmospheres to compute 3D-1D LTE abundance corrections, Delta 3D-1D LTE, for the spectral lines of Na, Mg, and K used in our study. These abundance corrections were used to understand the role of convection in the formation of spectral lines, as well as to estimate the differences in the abundances obtained with the 3D hydrodynamical and 1D hydrostatic model atmospheres. The average element-to-iron abundance ratios and their RMS variations due to star-to-star abundance spreads determined in our sample of RGB stars were <[Na/Fe]>(1D-NLTE)=0.42+/-0.13, <[Mg/Fe]>(1D-NLTE)=0.41+/-0.11, and <[K/Fe]>(1D-NLTE)=0.05+/-0.14. We found no statistically significant relations between the abundances of the three elements studied here. Also, there were no abundance trends with the distance from the cluster center, nor any statistically significant relations between the abundance/abundance ratios and absolute radial velocities of individual stars. All these facts suggest the similarity of K abundance in stars that belong to different generations in 47 Tuc which, in turn, may hint that evolution of K in this particular cluster was unrelated to the nucleosynthesis of Na and/or Mg.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A104
- Title:
- NGC3278, SN2009bb host, ATCA and MUSE data
- Short Name:
- J/A+A/618/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The host galaxies of gamma-ray bursts (GRBs) have been claimed to have experienced a recent inflow of gas from the intergalactic medium. This is because their atomic gas distribution is not centred on their optical emission and because they are deficient in molecular gas given their high star-formation rates. Similar studies have not been conducted for host galaxies of relativistic supernovae (SNe), which may have similar progenitors. The potential similarity of the powering mechanisms of relativistic SNe and GRBs allowed us to make a prediction that relativistic SNe are born in environments similar to those of GRBs, i.e. rich in atomic gas. Here we embark on testing this hypothesis by analysing the properties of the host galaxy NGC 3278 of the relativistic SN 2009bb. This is the first time the atomic gas properties of a relativistic SN host is analysed and the first time resolved 21cm hydrogen line (HI) information is provided for a host of a SN of any type. We obtained radio observations with Australia Telescope Compact Array (ATCA) covering HI line; and optical integral field unit spectroscopy observations with Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). Moreover, we analysed archival carbon monoxide (CO) and broad-band data for this galaxy. The atomic gas distribution of NGC3278 is not centred on the optical galaxy centre, but instead around a third of atomic gas resides in the region close to the SN position. This galaxy has a few times lower atomic and molecular gas masses than predicted from its star formation rate (SFR). Its specific star formation rate (sSFR=SFR/M*) is ~2-3 times higher than the main-sequence value, placing it at the higher end of the main sequence towards starburst galaxies. SN 2009bb exploded close to the region with the highest SFR density and the lowest age, as evident from high Halpha EW, corresponding to the age of the stellar population of ~5.5Myr. Assuming this timescale was the lifetime of the progenitor star, its initial mass would have been close to ~36M_{sun}_. As for GRB hosts, the gas properties of NGC3278 are consistent with a recent inflow of gas from the intergalactic medium, which explains the concentration of atomic gas close to the SN position and the enhanced SFR. Super-solar metallicity at the position of the SN (unlike for most of GRBs) may mean that relativistic explosions signal a recent inflow of gas (and subsequent star-formation), and their type (GRBs or SNe) is determined by either i) the metallicity of the inflowing gas (metal-poor gas results in a GRB explosion and metal-rich gas in a relativistic SN explosion without an accompanying GRB), or ii) by the efficiency of gas mixing (efficient mixing for SN hosts leading to quick disappearance of metal-poor regions), or iii) by the type of the galaxy (more metal-rich galaxies would result in only a small fraction of star-formation to be fuelled by metal-poor gas).
1236. NGC 6067 stars
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/1330
- Title:
- NGC 6067 stars
- Short Name:
- J/MNRAS/469/1330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7M_{sun}_ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78+/-0.12 kpc, an age of 90+/-20Ma and a tidal radius of 14.8^+6.8^_-3.2_ arcmin. We estimate an initial mass above 5700M_{sun}_, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ~=6M_{sun}_. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H]=+0.19+/-0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li)=2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/139/2034
- Title:
- NGC 6253 stars equivalent widths
- Short Name:
- J/AJ/139/2034
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-dispersion spectra of 89 potential members of the old, super-metal-rich open cluster, NGC 6253, have been obtained with the HYDRA multi-object spectrograph. Based upon radial-velocity measurements alone, 47 stars at the turnoff of the cluster color-magnitude diagram (CMD) and 18 giants are identified as potential members.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A79
- Title:
- NGC 6121 turnoff and subgiant stars abundances
- Short Name:
- J/A+A/594/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar abundances observed in globular clusters show complex structures, currently not yet understood. The aim of this work is to investigate the relations between the abundances of different elements in the globular cluster M4, selected for its uniform deficiency of iron, to explore the best models explaining the pattern of these observed abundances. Moreover, in turnoff stars, the abundances of the elements are not suspected to be affected by internal mixing. In M4, using low and moderate resolution spectra obtained for 91 turnoff (and subgiant) stars with the ESO FLAMESGiraffe spectrograph, we have extended previous measurements of abundances (of Li, C and Na) to other elements (C, Si, Ca, Sr and Ba), using model atmosphere analysis. We have also studied the influence of the choice of the microturbulent velocity. Firstly, the peculiar turnoff star found to be very Li-rich in a previous paper does not show any other abundance anomalies relative to the other turnoff stars inM4. Secondly, an anti-correlation between C and Na has been detected, the slope being significative at more than 3{sigma}. This relation between C and Na is in perfect agreement with the relation found in giant stars selected below the RGB bump. Thirdly, the strong enrichment of Si and of the neutron-capture elements Sr and Ba, already observed in the giants in M4, is confirmed. Finally, the relations between Li, C, Na, Sr and Ba constrain the enrichment processes of the observed stars. The abundances of the elements in the turnoff stars appear to be compatible with production processes by massive AGBs, but are also compatible with the production of second generation elements (like Na) and low Li produced by, for example, fast rotating massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A78
- Title:
- NGC2264 weak-line T Tauri lithium abundances
- Short Name:
- J/A+A/590/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of lithium abundance in cool dwarfs provides a unique probe of non-standard processes in stellar evolution. Aims. We investigate here the lithium content of young low-mass stars in the 5 Myr-old star forming region NGC 2264 and its relationship with rotation. We combine lithium equivalent width measurements (EW(Li)) from the Gaia-ESO Survey with the determination of rotational periods from the CSI 2264 survey. We consider only bona fide non accreting cluster members in order to minimize uncertainties on EW(Li). We report the existence of a relationship between lithium content and rotation in NGC 2264 at an age of 5Myr. The Li-rotation connection is seen over a restricted temperature range (Teff=800-4400K) where fast rotators are Li-rich compared to slow ones. This correlation is similar to, albeit of lower amplitude than, the Li-rotation connection previously reported for K dwarfs in the 125Myr-old Pleiades cluster. We investigate whether the non-standard pre-main sequence models developed so far to explain the Pleiades results, which are based on episodic accretion, pre-main sequence core-envelope decoupling, and/or radius inflation due to enhanced magnetic activity, can account for an early development of the Li-rotation connection. While radius inflation appears to be the most promising possibility, each of these models has issues. We therefore also discuss external causes that might operate during the first few Myr of pre-main sequence evolution, such as planet engulfment and/or steady disk accretion, as possible candidates for the common origin for Li-excess and fast rotation in young low-mass pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/V/103
- Title:
- NGP G5-M stars RV, DDO and BV photometry
- Short Name:
- V/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities are given for some 900 stars within 15{deg} of the North Galactic Pole, including almost all such stars classified G5 or latter in the Henry-Draper Catalogue (Cat. <III/135>). Luminosities, two-dimensional spectral classes, composition indices, and distances are derived for the majority of the sample through DDO and BV photometry. The radial velocities come from several instruments (see the "Note(2)" section below) ; the BV and DDO photometries were obtained at Mount Laguna Observatory, with the San Diego State University 24-inch Schmidt reflector.
