- ID:
- ivo://CDS.VizieR/J/A+A/562/A135
- Title:
- Northern Galactic OB stars vsini
- Short Name:
- J/A+A/562/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation is an important parameter in the evolution of massive stars. Accurate and reliable measurements of projected rotational velocities in large samples of OB stars are crucial to confront the predictions of stellar evolutionary models with observational constraints. We reassess previous determinations of projected rotational velocities (vsini) in Galactic OB stars using a large, high-quality spectroscopic dataset and a strategy that accounts for other sources of line-broadening in addition to rotation. We present a versatile and user-friendly IDL tool - based on a combined Fourier transform (FT) + goodness-of-fit (GOF) methodology - for the line-broadening characterization in OB-type stars. We used this tool to (a) investigate the impact of macroturbulent and microturbulent broadenings on vsini measurements, and (b) determine vsini and the size of the macroturbulent broadening (v_m_) in a sample of ~200 Galactic OB-type stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/576/A89
- Title:
- O abundances from HARPS in F-G stars
- Short Name:
- J/A+A/576/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed and uniform study of oxygen abundance from two different oxygen lines at 6158{AA} and 6300{AA} in a large sample of solar-type stars. The results are used to check the behaviour of these spectral lines as oxygen abundance indicators and to study the evolution of oxygen in thick and thin disk populations of the Galaxy. Equivalent width measurements were carried out for the [OI]6158 and [OI]6300 lines. LTE abundances were obtained from these two lines in 610 and 535 stars, respectively. Careful error analysis has been performed.
- ID:
- ivo://CDS.VizieR/J/A+A/384/473
- Title:
- O, B and Be stars equivalent widths
- Short Name:
- J/A+A/384/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an atlas of spectra of O- and B-type stars, obtained with the Short Wavelength Spectrometer (SWS) during the Post-Helium program of the Infrared Space Observatory (ISO). This program is aimed at extending the Morgan & Keenan (1973ARA&A..11...29M) classification scheme into the near-infrared. Later type stars will be discussed in a separate publication. The observations consist of 57 SWS Post-Helium spectra from 2.4 to 4.1{mu}m, supplemented with 10 spectra acquired during the nominal mission with a similar observational setting. For B-type stars, this sample provides ample spectral coverage in terms of subtype and luminosity class. For O-type stars, the ISO sample is coarse and therefore is complemented with 8 UKIRT L'-band observations. In terms of the presence of diagnostic lines, the L'-band is likely the most promising of the near-infrared atmospheric windows for the study of the physical properties of B stars. Specifically, this wavelength interval contains the Br{alpha}, Pf{gamma}, and other Pfund lines which are probes of spectral type, luminosity class and mass loss. Here, we present simple empirical methods based on the lines present in the 2.4 to 4.1{mu}m interval that allow the determination of i) the spectral type of B dwarfs and giants to within two subtypes; ii) the luminosity class of B stars to within two classes; iii) the mass-loss rate of O stars and B supergiants to within 0.25dex.
- ID:
- ivo://CDS.VizieR/J/AJ/154/29
- Title:
- Observation of 148 young stars toward NGC 1980
- Short Name:
- J/AJ/154/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC1980 is a young cluster that is located about 0.5{deg} south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40pc. In this work, we present low-resolution spectra toward 148 young stars found toward the NGC1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction toward them. We determine that based on these observations, the age of the population of NGC1980 is indistinguishable from L1641, estimated to be ~3Myr, comparable with the study by Fang et al.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/L5
- Title:
- Observed red supergiants in the inner Galaxy
- Short Name:
- J/ApJ/822/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we present a search for Galactic red supergiant stars (RSGs) in the direction of the inner Galaxy. A total of 94 targets selected from the 2MASS (Cat. VII/233) and GLIMPSE I North (Benjamin et al. 2003, Cat. II/293; Churchwell et al. 2009PASP..121..213C) catalogs - via their blue extinction-free Q1 and Q2 colors - were spectroscopically observed at infrared wavelengths (in the H- and K-bands at R~1000), and an extraordinary high detection rate of RSGs (>61%) was found. We identified spectroscopically 58 RSGs, based on their flat continua and large equivalent widths of the CO-band at 2.293 {mu}m (EW>45 {AA}). This increase corresponds to about 25% of previously known RSGs in the Galactic region 10{deg}<l<60{deg}, -1.1{deg}<b<1.1{deg}. In order to confirm the location of the new RSGs in the inner Galaxy, distances were estimated for a subsample of 47 stars with the clump method and found to range from 3.6+/-0.4 to 8.6+/-0.7 kpc. The large new sample will allow us to investigate Galactic metallicity gradients as a function of galactocentric distances and azimuthal angles. Such information is currently an highly disputed issue to constrain models of Galaxy formation and evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/163
- Title:
- OI abs. search in Keck and VLT spectra of 199 QSOs
- Short Name:
- J/ApJ/883/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey for metal absorption systems traced by neutral oxygen over 3.2<z<6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000km/s. We use a maximum likelihood approach to fit the distribution of OI{lambda}1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W_1302_>0.05{AA}, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9<z<5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7<z<6.5, with a lower value at z<5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z~6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z~6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch.
- ID:
- ivo://CDS.VizieR/J/A+A/390/235
- Title:
- OI and FeII equivalent widths in metal-poor stars
- Short Name:
- J/A+A/390/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table gives equivalent widths (in m{AA}) of OI and FeII lines for 35 metal-poor main sequence and subgiant stars as measured from high resolution, high S/N spectra observed with the ESO VLT/UVES spectrograph, during three observing runs: April 8-12, 2000, July 22-24, 2000, and April 10-12, 2001.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/13
- Title:
- OI equivalent widths in Be stars
- Short Name:
- J/ApJ/753/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The possibility of the Ly{beta} fluorescence mechanism being operational in classical Be (CBe) stars and thereby contributing to the strength of the OI{lambda}8446 line has been recognized for long. However, this supposition needs to be quantified by comparing observed and predicted OI line ratios. In the present work, optical and near-infrared spectra of CBe stars are presented. We analyze the observed strengths of the OI{lambda}7774, {lambda}8446, {lambda}11287, and {lambda}13165 lines, which have been theoretically proposed as diagnostics for identifying the excitation mechanism. We have considered and examined the effects of Ly{beta} fluorescence, collisional excitation, recombination, and continuum fluorescence on these O I line strengths. From our analysis it appears that the Ly{beta} fluorescence process is indeed operative in Be stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/55
- Title:
- OI, GeII, KrI & H abundances from HST UV spectra
- Short Name:
- J/ApJ/872/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a survey of archived ultraviolet spectra of 100 stars recorded by the echelle spectrograph of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, we measure the strengths of the weak absorption features of OI, GeII, and KrI in the interstellar medium. Our objective is to undertake an investigation that goes beyond earlier abundance studies to see how these elements are influenced independently by three different environmental properties: (1) values of a generalized atomic depletion factor F_*_ due to condensations onto dust grains (revealed here by the abundances of Mg and Mn relative to H), (2) the fraction of H atoms in the form of H_2_/f(H_2_), and (3) the ambient intensity I of ultraviolet starlight relative to an average value in our part of the Galaxy I_0_. As expected, the gas-phase abundances of all three elements exhibit negative partial correlations with F*. The abundances of free O atoms show significant positive partial correlations with logf(H_2_) and log(I/I_0_), while Ge and Kr exhibit negative partial correlations with log(I/I_0_) at marginal levels of significance. After correcting for these trends, the abundances of O relative to H show no significant variations with location, except for the already-known radial gradient of light-element abundances in the Milky Way. A comparison of Ge and O abundances revealed no significant regional enhancements or deficiencies of neutron-capture elements relative to {alpha}-process ones.
- ID:
- ivo://CDS.VizieR/J/AJ/95/1629
- Title:
- [O III] emission in 2 field-galaxy surveys
- Short Name:
- J/AJ/95/1629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present emission-line strengths for 394 galaxies from the field-galaxy redshift surveys of Kirshner, Oemler, and Schechter (1978, Cat. <J/AJ/83/1549>, KOS) and Kirshner et al. (1983, Cat. <J/AJ/88/1285>, KOSS) as part of a study of the nature of field and void galaxies. These data are 95% complete in their coverage of the [O III]{lambda}{lambda}5007,4959 emission lines. We find that 8.8%+/-1.5% of a J magnitude-limited data set have [O III]{lambda}5007 emission equivalent widths greater than 10A. There is no evidence that the spatial distribution of emission-line galaxies in each field differs from that of galaxies without emission. However, there is a significant increase in the fraction of galaxies with strong [O III] emission in the southern fields of the Kirshner, Oemler, and Schechter (1978, Cat. <J/J/83/1549>) survey as compared with the other survey fields. Our results are consistent with the conclusion that the fraction of galaxies with emission is larger in the Bootes void than in the general field, but tighter constraints on the void normal galaxy population are needed to improve the statistics.
