- ID:
- ivo://CDS.VizieR/III/243
- Title:
- Catalogue of neutral He lines of B-stars
- Short Name:
- III/243
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue of equivalent widths (EW) for neutral helium lines presented is based on numerous photographic spectral observations of B-stars made during 1978-1986 with the 6m telescope of Special Astrophysical Observatory of Russian Academy of Sciences. Original results of spectroscopy of B-stars inside the galactic open clusters and stellar associations were published by Klochkova and Panchuk in 1986PAZh...12..928K and 1987PAZh...13...56K. To make easier the procedure of EW reduction, several A- and O-stars were included in the Catalogue. All sequent steps of EW reduction were described in Klochkova and Panchuk (1987SoSAO..54....5K, Neutral Helium Lines in the Spectra of B-Stars - Part One - Catalogue). Due to profiles of HeI lines are essentially distinguished in spectra both of supergiants and normal stars, the procedure of EW reduction were made separately for these types of stars. After reduction to the common system of the published data and of observational data obtained by authors a homogeneous catalogue of equivalent widths EW for eight neutral helium lines (HeI, {lambda} 4009, 4026, 4121, 4144, 4387, 4471, 4713{AA}) for 524 stars is compiled. The catalogue is added by the mean values of EW for H{gamma} and H{delta} lines being also reduced to the common system of equivalent widths. The work is supported by the Russian Fondation for Basic Research (project 05-07-90087).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/472/111
- Title:
- Centaurus Compact Object Survey
- Short Name:
- J/A+A/472/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aim is to extend the investigations of ultra-compact dwarf galaxies (UCD) beyond the well studied Fornax and Virgo clusters. We measured spectroscopic redshifts of about 400 compact object candidates with 19.2<V<22.4mag in the central region of the Centaurus galaxy cluster (d=43Mpc), using 3 pointings with VIMOS@VLT. The luminosity range of the candidates covers the bright end of the globular cluster (GC) luminosity function and the luminosity regime of UCDs in Fornax and Virgo. Within the area surveyed, our completeness in terms of slit allocation is ~30%.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/120
- Title:
- CfA, CSP, BSP and LOSS spec. & phot. of SNe Ia
- Short Name:
- J/ApJ/882/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SNe Ia play key roles in revealing the accelerating expansion of the universe, but our knowledge of their progenitors is still very limited. Here we report the discovery of a rigid dichotomy in circumstellar (CS) environments around two subclasses of SNe Ia as defined by their distinct photospheric velocities. For the SNe Ia with high photospheric velocities (HVs), we found a significant excess flux in blue light 60-100 days past maximum, while this phenomenon is absent for SNe with normal photospheric velocity. This blue excess can be attributed to light echoes by circumstellar dust located at a distance of about (1-2)x10^17^cm from the HV subclass. Moreover, we also found that the HV SNe Ia show systematically evolving NaI absorption line by performing a systematic search of variable NaI absorption lines in spectra of all SNe Ia, whereas this evolution is rarely seen in normal ones. The evolving NaI absorption can be modeled in terms of photoionization model, with the location of the gas clouds at a distance of about 2x10^17^cm, in striking agreement with the location of CS dust inferred from B-band light-curve excess. These observations show clearly that the progenitors of HV subclass are likely from single-degenerate progenitor system (i.e., symbiotic binary), while the NV subclass may arise from double-degenerate system.
184. CF-HiZELS survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/2303
- Title:
- CF-HiZELS survey
- Short Name:
- J/MNRAS/451/2303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the largest contiguous narrow-band survey in the near-infrared. We have used the wide-field infrared camera/Canada-France-Hawaii Telescope and the lowOH2 filter (1.187+/-0.005{mu}m) to survey ~10deg^2^ of contiguous extragalactic sky in the SA22 field. A total of ~6000 candidate emission-line galaxies are found. We use deep ugrizJK data to obtain robust photometric redshifts. We combine our data with the High-redshift(Z) Emission Line Survey (HiZELS), explore spectroscopic surveys (VVDS, VIPERS) and obtain our own spectroscopic follow-up with KMOS, FMOS and MOSFIRE to derive large samples of high-redshift emission-line selected galaxies: 3471 H{alpha} emitters at z=0.8, 1343 [OIII] + H{beta} emitters at z=1.4 and 572 [OII] emitters at z=2.2. We probe comoving volumes of >10^6^Mpc^3^ and find significant overdensities, including an 8.5{sigma} (spectroscopically confirmed) overdensity of H{alpha} emitters at z=0.81. We derive H{alpha}, [OIII] + H{beta} and [OII] luminosity functions at z=0.8, 1.4, 2.2, respectively, and present implications for future surveys such as Euclid. Our uniquely large volumes/areas allow us to subdivide the samples in thousands of randomized combinations of areas and provide a robust empirical measurement of sample/cosmic variance. We show that surveys for star-forming/emission-line galaxies at a depth similar to ours can only overcome cosmic-variance (errors <10 percent) if they are based on volumes >5x10^5^Mpc^3^; errors on L* and {phi}* due to sample (cosmic) variance on surveys probing ~10^4^ and ~10^5^Mpc^3^ are typically very high: ~300 and ~40-60 percent, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/719
- Title:
- Chandra observations of 2106 radio-quiet QSOs
- Short Name:
- J/MNRAS/492/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<=z<=2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14, 2018ApJS..235...42A), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (large exposure time and small off-axis observation angle) X-ray observations, and analyze their X-ray properties (aox and daox) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >=99.99% level) between aox and these emission-line parameters, as well as between daox and CIV EW. Slight correlations are found between daox and CIV blueshift, MgII EW, and the ratio of CIV EW to MgII EW. The best-fit trend in each parameter space is used to compare the X-ray weakness (daox) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs clearly deviate from the expectation for every relationship, typically exhibiting much weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs with respect to our typical quasars can be explained by an X-ray shielding model.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A104
- Title:
- Chemical abundance analysis of HD 20
- Short Name:
- J/A+A/635/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metal-poor stars with available detailed information about their chemical inventory pose powerful empirical benchmarks for nuclear astrophysics. Here we present our spectroscopic chemical abundance investigation of the metal-poor ([Fe/H]=-1.60dex), r-process-enriched ([Eu/Fe]=0.73dex) halo star HD 20 using novel and archival high-resolution data at outstanding signal-to-noise ratios (up to 1000 per Angstroem). By combining one of the first asteroseismic gravity measurements in the metal-poor regime from a TESS light curve with the spectroscopic analysis of iron lines under non-local thermodynamic equilibrium conditions, we derive a set of highly accurate and precise stellar parameters. These allow us to delineate a reliable chemical pattern that is comprised of solid detections of 48 elements, including 28 neutron-capture elements. Hence, we establish HD 20 among the few benchmark stars that have almost complete patterns and possess low systematic dependencies on the stellar parameters. Our light-element (Z<30) abundances are representative of other, similarly metal-poor stars in the Galactic halo with contributions from core-collapse supernovae of type II. In the realm of the neutron-capture elements, our comparison to the scaled solar r-pattern shows that the lighter neutron-capture elements (Z<60) are poorly matched. In particular, we find imprints of the weak r-process acting at low metallicities. Nonetheless, by comparing our detailed abundances to the observed metal-poor star BD +17 3248, we find a persistent residual pattern involving mainly the elements Sr, Y, Zr, Ba, and La. These are indicative of enrichment contributions from the s-process and we show that mixing with material from predicted yields of massive, rotating AGB stars at low metallicity considerably improves the fit. Based on a solar ratio of heavy- to light-s elements -- at odds with model predictions for the i-process -- and a missing clear residual pattern with respect to other stars with claimed contributions from this process, we refute (strong) contributions from such astrophysical sites providing intermediate neutron densities. Finally, nuclear cosmochronology is used to tie our detection of the radioactive element Th to an age estimate for HD 20 of 11.0+/-3.8Gyr.
- ID:
- ivo://CDS.VizieR/J/ApJ/802/93
- Title:
- Chemical abundance analysis of 5 stars in Sculptor
- Short Name:
- J/ApJ/802/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous chemical abundance analysis of five of the most metal-poor stars in the Sculptor dwarf spheroidal galaxy. We analyze new and archival high resolution spectroscopy from Magellan/MIKE and VLT/UVES and determine stellar parameters and abundances in a consistent way for each star. Two of the stars in our sample, at [Fe/H]=-3.5 and [Fe/H]=-3.8, are new discoveries from our Ca K survey of Sculptor, while the other three were known in the literature. We confirm that Scl 07-50 is the lowest metallicity star identified in an external galaxy, at [Fe/H]=-4.1. The two most metal-poor stars both have very unusual abundance patterns, with striking deficiencies of the {alpha} elements, while the other three stars resemble typical extremely metal-poor Milky Way halo stars. We show that the star-to-star scatter for several elements in Sculptor is larger than that for halo stars in the same metallicity range. This scatter and the uncommon abundance patterns of the lowest metallicity stars indicate that the oldest surviving Sculptor stars were enriched by a small number of earlier supernovae, perhaps weighted toward high-mass progenitors from the first generation of stars the galaxy formed.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A30
- Title:
- Chemical abundance of 12 stars in open clusters
- Short Name:
- J/A+A/535/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are ideal test particles for studying the chemical evolution of the Galactic disc. However, the number and accuracy of existing high-resolution abundance determinations, not only of [Fe/H], but also of other key elements, remains largely insufficient. We attempt to increase the number of Galactic open clusters that have high quality abundance determinations, and to gather all the literature determinations published so far.
- ID:
- ivo://CDS.VizieR/J/AZh/79/909
- Title:
- Chemical abundances in barium stars
- Short Name:
- J/AZh/79/909
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used high-resolution spectra to compute model atmospheres to derive the atmospheric abundances of moderate barium stars. Comparing our results with analogous data for normal red giants, we find that the moderate barium stars appear to not differ systematically from normal red giants. Their chemical abundance anomalies show the same patterns and can be interpreted in terms of evolutionary effects: the evolutionary stage, mass, luminosity, and metallicity of the objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/378/318
- Title:
- Chemical abundances in Leo I and II dSph
- Short Name:
- J/MNRAS/378/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained calcium abundances and radial velocities for 102 red giant branch (RGB) stars in the Leo I dwarf spheroidal galaxy (dSph) and 74 RGB stars in the Leo II dSph using the low-resolution spectrograph (LRIS) on the Keck I 10-m telescope. We report on the calcium abundances [Ca/H] derived from the strengths of the Ca ii triplet absorption lines at 8498, 8542 and 8662{AA} in the stellar spectra using a new empirical Ca II triplet calibration to [Ca/H].
