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1391. r- and s- process elements in Milky Way disk
ID:
ivo://CDS.VizieR/J/A+A/586/A49
Title:
r- and s- process elements in Milky Way disk
Short Name:
J/A+A/586/A49
Date:
21 Oct 2021
Publisher:
CDS
Description:
Elements heavier than iron are produced through neutron-capture processes in the different phases of stellar evolution. Asymptotic giant branch (AGB) stars are believed to be mainly responsible for elements that form through the slow neutron-capture process, while the elements created in the rapid neutron-capture process have production sites that are less understood. Knowledge of abundance ratios as functions of metallicity can lead to insight into the origin and evolution of our Galaxy and its stellar populations. We aim to trace the chemical evolution of the neutron-capture elements Sr, Zr, La, Ce, Nd, Sm, and Eu in the Milky Way stellar disk. This will allow us to constrain the formation sites of these elements, as well as to probe the evolution of the Galactic thin and thick disks. Using spectra of high resolution (42000<=R<=65000) and high signal-to-noise (S/N>=200) obtained with the MIKE and the FEROS spectrographs, we determine Sr, Zr, La, Ce, Nd, Sm, and Eu abundances for a sample of 593 F and G dwarf stars in the solar neighborhood. The abundance analysis is based on spectral synthesis using one-dimensional, plane-parallel, local thermodynamic equilibrium (LTE) model stellar atmospheres calculated with the MARCS 2012 code.
1392. RASS AGN sample. II.
ID:
ivo://CDS.VizieR/J/ApJ/590/73
Title:
RASS AGN sample. II.
Short Name:
J/ApJ/590/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work studies the optical emission line properties of a sample of 155 low-redshift bright X-ray-selected ROSAT Seyfert 1-type active galactic nuclei for which adequate signal-to-noise ratio spectroscopic observations are available. We measured emission-line properties by performing multicomponent fits to the emission-line profiles, covering the effect of blended iron emission. We also obtained continuum parameters, including 250eV X-ray luminosities derived from the ROSAT database. In addition, the measured properties are gathered for a correlation analysis, which confirms the well-known relations between the strengths of Fe II, [O III] emission and the X-ray slope. We also detect striking correlations between H{beta} redshift (or blueshift) and flux ratios of Fe II to H{beta} broad component and [O III] to H{beta} narrow component. These trends are most likely driven by the Eddington ratio.
1393. RATAN observations of Galactic SNRs
ID:
ivo://CDS.VizieR/J/other/BSAO/46.62
Title:
RATAN observations of Galactic SNRs
Short Name:
J/other/BSAO/46.
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radio continuum spectra for 200 Galactic supernova remnants (SNRs) from 220 known and included in Green's (1998, Cat. VII/211) catalog. The spectra can be plotted only for 200 SNRs because about 20 remaining new and weak SNRs (Whiteoak and Green, 1996, Cat. J/A+AS/118/329; Gray, 1994MNRAS.270..847G) have only one-frequency flux density measurements. Spectrum plotting is an "on-line" procedure of the CATS database (Verkhodanov et al., 1997ASPCo.125..322V) created for some other multi-frequency catalogs. These spectra include most of the measurements available in literature, as well as multi-frequency measurements of nearly 120 SNRs with the RATAN-600 radio telescope in 1, 2 and 4 Galactic quadrants and from the Galactic plane survey at 960 and 3900MHz (Trushkin, 1986ATsir1453....4T, 1987AISAO..25...84T, 1989, Ph.D. Thesis. SAO, Nizhnij Arkhyz, 1996BSAO...41...64T, 1998BSAO...46...62T). The measurements have been placed on the same absolute flux density scale of Baars (1977A&A....61...99B) as in the paper by Kassim (1989ApJ...347..915K), using the correcting factor from the compiled catalog (Kuhr et al., 1981, Cat. VIII/5). The presented compilation has given a possibility of plotting quite accurate spectra with the thermal plasma free-free absorption in fitting the spectra accounted for.
1394. RATAN-600 radio sources spectra
ID:
ivo://CDS.VizieR/J/other/BSAO/40.128
Title:
RATAN-600 radio sources spectra
Short Name:
J/other/BSAO/40.
Date:
21 Oct 2021
Publisher:
CDS
Description:
In accordance with the program "Cold" in 1987-1988 and in 1996 deep surveys of the sky strip at the declination of the source SS 433 ({delta}~5{deg}+/-20') were made at the radio telescope RATAN-600. For the first time spectral characteristics of 400 sources from the RC catalog have been determined using only the data obtained with the RATAN-600. The maximum of the flux density distributions at the central wavelength {lambda}7.6cm is ~30mJy. The lower flux limit in the sample of the sources at the wavelengths 3.9, 7.6, 13.0, 31.0cm is 16, 9, 37, 61mJy, respectively. Spectra of 112 sources (28%) have been obtained for the first time, spectra of 90 (23%) sources have been made more accurate. For the first time the fluxes at the wavelengths 2.7, 3.9, 13.0 and 31.0cm (90% of data) have been measured. The maximum of the distribution of spectral indices for the entire sample of sources in the interval {lambda}{lambda}7.6-31.0cm falls at {alpha}=-0.86+/-0.04 (S_{nu}_{prop.to}{nu}^alpha^). About 20 (5%) sources of the sample have a maximum of radiation at a frequency of about 1GHz (GHz-Peaked-Spectrum radio sources), about 40 (10%) have a low-frequency cut off of the spectrum. About 70 (19%) sources have flat spectra ({alpha}>-0.5), 64 (18%) very steep ({alpha}<-1.1) spectra.
1395. RATAN-600 radio sources spectra
ID:
ivo://CDS.VizieR/J/AZh/74/42
Title:
RATAN-600 radio sources spectra
Short Name:
J/AZh/74/42
Date:
21 Oct 2021
Publisher:
CDS
Description:
A multifrequency deep survey of a band of sky with the declination of the source SS 433 ({delta}~5{deg}+/-20') was performed as part of the "Kholod" program on the RATAN-600 in 1987-1988. The right ascension intervals covered by the survey are 0h<{alpha}<14h and 18h<{alpha}<24h. The spectral properties of 400 sources from the RC catalog were determined for the first time by using only RATAN-600 data. The maximum in the flux density distribution for these sources at the central wavelength, {lambda}7.6cm, occurs at ~30mJy. The lower flux limits for the sample at wavelengths of 3.9, 7.6, 13.0, and 31.0cm are 16, 9, 37, and 61mJy, respectively. These observations provide the first flux estimates at 13.0 and 31.0cm for 90% of the sources. Spectra were measured for the first time for 112 sources (28%) and were revised for 90 sources (23%). The maximum in the spectral index distribution for the entire sample in the interval from {lambda}{lambda}7.6-31.0cm occurs at {alpha}=-0.86+/-0.04 (S_v_~{nu}^{alpha}^). The spectra of some 20 of the sample sources (5%) are peaked at roughly 1GHz, and about 40 spectra (10%) have low-frequency breaks. Roughly 70 sources (19%) have flat spectra ({alpha}>-0.5), and 64 (18%) have very steep spectra ({alpha}<-1.1).
1396. RAVE stellar elemental abundances (DR1)
ID:
ivo://CDS.VizieR/J/AJ/142/193
Title:
RAVE stellar elemental abundances (DR1)
Short Name:
J/AJ/142/193
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present chemical elemental abundances for 36561 stars observed by the RAdial Velocity Experiment (RAVE), an ambitious spectroscopic survey of our Galaxy at Galactic latitudes |b|>25{deg} and with magnitudes in the range 9<I_DENIS_<13. RAVE spectra cover the Ca-triplet region at 8410-8795{AA} with resolving power R~7500. This first data release of the RAVE chemical catalog is complementary to the third RAVE data release of radial velocities and stellar parameters, and it contains chemical abundances for the elements Mg, Al, Si, Ca, Ti, Fe, and Ni, with a mean error of ~0.2dex, as judged from accuracy tests performed on synthetic and real spectra. Abundances are estimated through a dedicated processing pipeline in which the curve of growth of individual lines is obtained from a library of absorption line equivalent widths to construct a model spectrum that is then matched to the observed spectrum via a {chi}^2^ minimization technique. We plan to extend this pipeline to include estimates for other elements, such as oxygen and sulfur, in future data releases.
1397. R-band spectra for 13 early-type supergiants
ID:
ivo://CDS.VizieR/J/A+A/439/1107
Title:
R-band spectra for 13 early-type supergiants
Short Name:
J/A+A/439/1107
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalogue contains R-band spectra for 13 early-type supergiants. Spectral types range from B0 to A6, all with luminosity classes Ia or Iab. Eight of the stars are classified as having emission. The wavelength range is 5846 to 7030{AA} at a spectral resolution of 1.2{AA}, and a signal-to-noise ratio of 400 or above. Identification of spectral lines in supergiant spectra can be found in Chentsov et al. (2003A&A...397.1035C). The reader should be aware of the blends of atmospheric telluric lines that contaminate the spectra in the ranges 5870-5995{AA}, 6270-6315{AA}, 6470-6500{AA}, and 6850{AA} onwards.
1398. Red clump stars selected from LAMOST and APOGEE
ID:
ivo://CDS.VizieR/J/ApJ/858/L7
Title:
Red clump stars selected from LAMOST and APOGEE
Short Name:
J/ApJ/858/L7
Date:
21 Oct 2021
Publisher:
CDS
Description:
Core helium-burning red clump (RC) stars are excellent standard candles in the Milky Way. These stars may have more precise distance estimates from spectrophotometry than from Gaia parallaxes beyond 3kpc. However, RC stars have values of Teff and logg that are very similar to some red giant branch (RGB) stars. Especially for low-resolution spectroscopic studies where Teff, logg, and [Fe/H] can only be estimated with limited precision, separating RC stars from RGB through established methods can incur ~20% contamination. Recently, Hawkins+ (2018ApJ...853...20H) demonstrated that the additional information in single-epoch spectra, such as the C/N ratio, can be exploited to cleanly differentiate RC and RGB stars. In this second paper of the series, we establish a data-driven mapping from spectral flux space to independently determined asteroseismic parameters, the frequency and the period spacing. From this, we identify 210371 RC stars from the publicly available LAMOST DR3 and APOGEE DR14 data, with ~9% of contamination. We provide an RC sample of 92249 stars with a contamination of only ~3%, by restricting the combined analysis to LAMOST stars with S/N_pix_>=75. This demonstrates that high-signal-to-noise ratio (S/N), low-resolution spectra covering a broad wavelength range can identify RC samples at least as pristine as their high- resolution counterparts. As coming and ongoing surveys such as TESS, DESI, and LAMOST will continue to improve the overlapping training spectroscopic-asteroseismic sample, the method presented in this study provides an efficient and straightforward way to derive a vast yet pristine sample of RC stars to reveal the three-dimensional (3D) structure of the Milky Way.
1399. Red giant Aluminium abundances in NGC 2808
ID:
ivo://CDS.VizieR/J/A+A/615/A17
Title:
Red giant Aluminium abundances in NGC 2808
Short Name:
J/A+A/615/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed a sample of 90 red giant branch (RGB) stars in NGC 2808 using FLAMES/GIRAFFE and the high resolution grating with the set up HR21. These stars have previous accurate atmospheric parameters and abundances of light elements. We derived aluminium abundances for them from the strong doublet AlI 8772-8773 Angstrom as in previous works of our group. In addition, we were able to estimate the relative CN abundances for 89 of the stars from the strength of a large number of CN features. When adding self consistent abundances from previous UVES spectra analysed by our team, we gathered [Al/Fe] ratios for a total of 108 RGB stars in NGC 2808. The full dataset of proton-capture elements is used to explore in details the five spectroscopically detected discrete components in this globular cluster. We found that different classes of polluters are required to reproduce the (anti)-correlations among all proton-capture elements in the populations P2, I1, and I2 with intermediate composition. This is in agreement with the detection of lithium in lower RGB second generation stars, requiring at least two kind of polluters. To have chemically homogeneous populations the best subdivision of our sample is into six components, as derived from statistical cluster analysis. By comparing different diagrams [element/Fe] vs [element/Fe] we show for the first time that a simple dilution model is not able to reproduce all the sub-populations in this cluster. Polluters of different masses are required. NGC 2808 is confirmed to be a tough challenge to any scenario for globular cluster formation.
1400. Red giants of NGC 1851
ID:
ivo://CDS.VizieR/J/A+A/658/A80
Title:
Red giants of NGC 1851
Short Name:
J/A+A/658/A80
Date:
22 Feb 2022
Publisher:
CDS
Description:
NGC 1851 is one of several globular clusters for which multiple stellar populations of the subgiant branch have been clearly identified and a difference in metallicity detected. A crucial piece of information on the formation history of this cluster can be provided by the sum of A(C+N+O) abundances. However, these values have lacked a general consensus thus far. The separation of the subgiant branch can be based on age and/or A(C+N+O) abundance differences. Our main aim was to determine carbon, nitrogen, and oxygen abundances for evolved giants in the globular cluster NGC 1851 in order to check whether or not the double populations of stars are coeval. High-resolution spectra, observed with the FLAMES-UVES spectrograph on the ESO VLT telescope, were analysed using a differential model atmosphere method. Abundances of carbon were derived using spectral synthesis of the C 2 band heads at 5135 and 5635.5{AA}. The wavelength interval 6470-6490{AA}, with CN features, was analysed to determine nitrogen abundances. Oxygen abundances were determined from the [OI] line at 6300{AA}. Abundances of other chemical elements were determined from equivalent widths or spectral syntheses of unblended spectral lines. We provide abundances of up to 29 chemical elements for a sample of 45 giants in NGC 1851. The investigated stars can be separated into two populations with a difference of 0.07dex in the mean metallicity, 0.3dex in the mean C/N, and 0.35 dex in the mean s-process dominated element-to-iron abundance ratios [s/Fe]. No significant difference was determined in the mean values of A(C+N+O) as well as in abundance to iron ratios of carbon, {alpha}- and iron-peak-elements, and of europium. As the averaged A(C+N+O) values between the two populations do not differ, additional evidence is given that NGC 1851 is composed of two clusters, the metal-rich cluster being by about 0.6Gyr older than the metal-poor one. A global overview of NGC 1851 properties and the detailed abundances of chemical elements favour its formation in a dwarf spheroidal galaxy that was accreted by the Milky Way.