- ID:
- ivo://CDS.VizieR/J/MNRAS/469/3125
- Title:
- Abundance ratio in gamma-ray burst
- Short Name:
- J/MNRAS/469/3125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distribution of the N/O element abundance ratios calculated by the detailed modelling of different galaxy spectra at z<4 is investigated. Supernova (SN) and long gamma-ray-burst (LGRB) host galaxies cover different redshift domains. N/O ratios in SN hosts increase due to secondary N production towards low z (0.01) accompanying the growing trend of active galaxies [active galactic nucleus (AGN), low-ionization nuclear emission-line region (LINER)]. N/O ratios in LGRB hosts decrease rapidly between z>1 and z~0.1 following the N/H trend and reach the characteristic N/O ratios calculated for the H II regions in local and nearby galaxies. The few short-period gamma-ray-burst (SGRB) hosts included in the galaxy sample show N/H<=0.04 solar and O/H solar. They seem to continue the low bound N/H trend of SN hosts at z<0.3. The distribution of N/O as a function of metallicity for SN and LGRB hosts is compared with star chemical evolution models. The results show that several LGRB hosts can be explained by star multibursting models when 12+log(O/H)<8.5, while some objects follow the trend of continuous star formation models. N/O in SN hosts at log(O/H)+12<8.5 are not well explained by stellar chemical evolution models calculated for starburst galaxies. At 12+log(O/H)>8.5 many different objects are nested close to O/H solar with N/O ranging between the maximum corresponding to starburst galaxies and AGN and the minimum corresponding to HII regions and SGRB.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/900/4
- Title:
- Abundances and ages of stars in the Milky Way bulge
- Short Name:
- J/ApJ/900/4
- Date:
- 14 Mar 2022 07:37:10
- Publisher:
- CDS
- Description:
- The age and chemical characteristics of the Galactic bulge link to the formation and evolutionary history of the Galaxy. Data-driven methods and large surveys enable stellar ages and precision chemical abundances to be determined for vast regions of the Milky Way, including the bulge. Here, we use the data-driven approach of The Cannon, to infer the ages and abundances for 125367 stars in the Milky Way, using spectra from Apache Point Observatory Galaxy Evolution Experiment (apogee) DR14. We examine the ages and metallicities of 1654 bulge stars within R_GAL_<3.5kpc. We focus on fields with b<12{deg}, and out to longitudes of l<15{deg}. We see that stars in the bulge are about twice as old ({tau}=8Gyr), on average, compared to those in the solar neighborhood ({tau}=4Gyr), with a larger dispersion in [Fe/H] (~0.38 compared to 0.23dex). This age gradient comes primarily from the low-{alpha} stars. Looking along the Galactic plane, the very central field in the bulge shows by far the largest dispersion in [Fe/H] ({sigma}[Fe/H]~0.4dex) and line-of- sight velocity ({sigma}vr~90km/s), and simultaneously the smallest dispersion in age. Moving out in longitude, the stars become kinematically colder and less dispersed in [Fe/H], but show a much broader range of ages. We see a signature of the X-shape within the bulge at a latitude of b=8{deg}, but not at b=12{deg}. Future apogee and other survey data, with larger sampling, affords the opportunity to extend our approach and study in more detail, to place stronger constraints on models of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A132
- Title:
- Abundances and distributions of CS and SiS
- Short Name:
- J/A+A/617/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sulphur has long been known to form different molecules depending on the chemical composition of its environment. More recently, the sulphur-bearing molecules SO and H2S have been shown to behave differently in oxygen-rich asymptotic giant branch (AGB) circumstellar envelopes of different densities. By surveying a diverse sample of AGB stars for CS and SiS emission, we aim to determine in which environments these sulphur-bearing molecules most readily occur. We include sources with a range of mass-loss rates and carbon-rich, oxygen-rich, and mixed S-type chemistries. Where these molecules are detected, we aim to determine their CS and SiS abundances. We surveyed 20 AGB stars of different chemical types using the APEX telescope, and combined this with an IRAM 30m and APEX survey of CS and SiS emission towards over 30 S-type stars. For those stars with detections, we performed radiative transfer modelling to determine abundances and abundance distributions. We detect CS towards all the surveyed carbon stars, some S-type stars, and the highest mass-loss rate oxygen-rich stars, (dM/dt>=5x10^-6^M_[sun}_/yr). SiS is detected towards the highest mass-loss rate sources of all chemical types (dM/dt>=8x10^-7^M_{sun}_/yr). We find CS peak fractional abundances ranging from ~4x10^-7^ to ~2x10^-5^ for the carbon stars, from ~3x10^-8^ to ~1x10^-7^ for the oxygen-rich stars, and from ~1x10^-7^ to ~8x10^-6^ for the S-type stars. We find SiS peak fractional abundances ranging from ~9x10^-6^ to ~2x10^-5^ for the carbon stars, from ~5x10^-7^ to ~2x10^-6^ for the oxygen-rich stars, and from ~2x10^-7^ to ~2x10^-^6 for the S-type stars. Overall, we find that wind density plays an important role in determining the chemical composition of AGB circumstellar envelopes. It is seen that for oxygen-rich AGB stars both CS and SiS are detected only in the highest density circumstellar envelopes and their abundances are generally lower than for carbon-rich AGB stars by around an order of magnitude. For carbon-rich and S-type stars SiS was also only detected in the highest density circumstellar envelopes, while CS was detected consistently in all surveyed carbon stars and sporadically among the S-type stars.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1766
- Title:
- Abundances and equivalent widths in NGC 2808
- Short Name:
- J/AJ/131/1766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the abundance analysis of stars from the tip of the red giant branch (RGB) to below the RGB bump in the globular cluster NGC 2808 based on high-resolution echelle spectra. We derive abundances of Al, {alpha}-process elements (SiI, CaI, TiI, and TiII), and Fe-group elements (ScII, VI, CrI, CrII, MnI, CoI, and NiI). Apart from Mg being somewhat reduced, likely because it has been depleted at the expense of Al in the MgAl cycle, the other {alpha}-element ratios show the overabundance typical of halo stars of similar metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/129/433
- Title:
- Abundances and equivalent widths of 14 Cepheids
- Short Name:
- J/AJ/129/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a detailed multiphase spectroscopic analysis of 14 classical Cepheids with pulsation periods longer than 10 days. For each star, we have derived phased values of effective temperature, surface gravity, microturbulent velocity, and elemental abundances. We show that the elemental abundance results for these Cepheids are consistent for all pulsational phases.
- ID:
- ivo://CDS.VizieR/J/AJ/120/1841
- Title:
- Abundances and Kinematics of Halo and Disk Stars
- Short Name:
- J/AJ/120/1841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table gives the equivalent widths of the 168 stars used in the abundance analyses. For stars that may have multiple observations the mean value of the measurements is given for each line. Only lines used in the final abundance analysis are provided.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/L38
- Title:
- Abundances and radial velocities of M13 giants
- Short Name:
- J/ApJ/754/L38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present O, Na, and Fe abundances, as well as radial velocities, for 113 red giant branch (RGB) and asymptotic giant branch (AGB) stars in the globular cluster M13. The abundances and velocities are based on spectra obtained with the WIYN-Hydra spectrograph, and the observations range in luminosity from the horizontal branch (HB) to RGB tip. The results are examined in the context of recent globular cluster formation scenarios. We find that M13 exhibits many key characteristics that suggest its formation and chemical enrichment are well described by current models. Some of these observations include the central concentration of O-poor stars, the notable decrease in [O/Fe] (but small increase in [Na/Fe]) with increasing luminosity that affects primarily the "extreme" population, the small fraction of stars with halo-like composition, and the paucity of O-poor AGB stars. In agreement with recent work, we conclude that the most O-poor M13 giants are likely He-enriched and that most (all?) O-poor RGB stars evolve to become extreme HB and AGB-manqu\'e stars. In contrast, the "primordial" and "intermediate" population stars appear to experience standard HB and AGB evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/511/L10
- Title:
- Abundances and space velocities of 94 stars
- Short Name:
- J/A+A/511/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precise abundance ratios are determined for 94 dwarf stars with 5200<Teff<6300K, -1.6<[Fe/H]<-0.4, and distances D<~335pc. Most of them have halo kinematics, but 16 thick-disk stars are included. Equivalent widths of atomic lines are measured from VLT/UVES and NOT/FIES spectra with resolutions R~55000 and R~40000, respectively. An LTE abundance analysis based on MARCS models is applied to derive precise differential abundance ratios of Na, Mg, Si, Ca, Ti, Cr, and Ni with respect to Fe.
- ID:
- ivo://CDS.VizieR/J/AJ/150/187
- Title:
- Abundances and stellar parameters of LAMOST stars
- Short Name:
- J/AJ/150/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe an application of the SEGUE Stellar Parameter Pipeline (SSPP) to medium-resolution stellar spectra obtained by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), in order to determine estimates of the stellar atmospheric parameters (T_eff_, logg, and [Fe/H]) and the abundance ratios ([{alpha}/Fe] and [C/Fe]). By performing a coordinate match with the LAMOST stellar database, we selected stars with LAMOST spectra in common with stars having available spectroscopy from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the RAdial Velocity Experiment (RAVE), and the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We ran the selected LAMOST stellar spectra from each survey through SSPP, and compared the stellar parameters down to signal-to-noise ratio (S/N) of 10 and chemical abundances down to S/N=20 derived by SSPP with those determined by the APOGEE, RAVE, and SEGUE software pipelines. Our results show that the derived stellar parameters generally agree quite well, even though there exist some small systematic offsets with small scatter in T_eff_, logg, and [Fe/H], due to the use of different temperature scales, abundance scales, and calibrations adopted by each survey. Comparison of the [{alpha}/Fe] determinations for LAMOST spectra suggests no sign of significant systematic offsets (< -0.04dex), with a small scatter (<0.08dex) relative to stars in common with APOGEE and SEGUE. The [C/Fe] estimates determined for the LAMOST spectra also exhibit good agreement, with a very small offset (~0.01dex) and scatter (~0.12dex) relative to the SEGUE stars, while there exists about a -0.19dex offset, with a small scatter of ~0.13dex, for the APOGEE sample. Due to the existence of small offsets in the stellar parameters and abundances among difference data sets, optimal results when combining the different data sets will be obtained by removing the offsets. Once accomplished, the stellar parameters and chemical abundances estimated by SSPP from the LAMOST stellar spectra should provide a reliable database for studies of the Galactic disk and halo systems.
- ID:
- ivo://CDS.VizieR/J/A+AS/113/299
- Title:
- Abundances and velocities for cluster giants
- Short Name:
- J/A+AS/113/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large dataset consisting of giants in the field, and in open and globular clusters. A total of 122 giants were observed in the fields of 8 open clusters. A total of 342 giants were observed in the fields of 25 globular clusters. A total of 36 field stars with well known abundances and luminosities were also observed. Table 8 lists the spectral indices measured for the giants observed with the Argus and Red Channel spectrographs during 1991 and 1992. The central and continuum passbands for these indices are defined in Table 6.
