We have derived new abundances of the rare earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other elements in individual stars, to produce internally consistent Ba, rare earth, and Hf(56<=Z<=72) element distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.
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.
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.
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.
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).
We report on the spectroscopic analysis of RAVE-J183013.5-455510, an extremely metal-poor star, highly enhanced in CNO, and with discernible contributions from the rapid neutron-capture process. There is no evidence of binarity for this object. At [Fe/H]=-3.57, this star has one of the lowest metallicities currently observed, with 18 measured abundances of neutron-capture elements. The presence of Ba, La, and Ce abundances above the solar system r-process predictions suggests that there must have been a non-standard source of r-process elements operating at such low metallicities. One plausible explanation is that this enhancement originates from material ejected at unusually high velocities in a neutron star merger event. We also explore the possibility that the neutron-capture elements were produced during the evolution and explosion of a rotating massive star. In addition, based on comparisons with yields from zero-metallicity faint supernova, we speculate that RAVE-J1830-4555 was formed from a gas cloud pre-enriched by both progenitor types. From analysis based on Gaia DR2 measurements, we show that this star has orbital properties similar to the Galactic metal-weak thick-disk stellar population.
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.
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.
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.
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.
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