- ID:
- ivo://CDS.VizieR/J/A+A/581/A52
- Title:
- Gaia-ESO Survey: H{alpha} emission stars catalogue
- Short Name:
- J/A+A/581/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the properties of H{alpha} emission stars across the sample of 22035 spectra from the Gaia-ESO Survey internal data release, observed with the GIRAFFE instrument and largely belonging to stars in young open clusters. Automated fits using two independent Gaussian profiles and a third component accounting for the nebular emission allow us to discern distinct morphological types of H{alpha} line profiles with the introduction of a simplified classification scheme. Altogether we find 3765 stars with intrinsic emission and sort their spectra into eight distinct morphological categories: single component emission, emission blend, sharp emission peaks, double emission, P-Cygni, inverted P-Cygni, self absorption, and emission in absorption. We have more than one observation for 1430 stars in our sample, thus allowing a quantitative discussion of the degree of variability of H{alpha} emission profiles, which is expected for young, active objects. We present a catalogue of stars with properties of their H{alpha} emission line profiles, morphological classification, analysis of variability with time and the supplementary information from SIMBAD, VizieR and ADS databases. The records in SIMBAD indicate the presence of H{alpha} emission for roughly 25% of all stars in our catalogue while at least 305 of them have already been more thoroughly investigated according to the references in ADS. The most frequently identified morphological categories in our sample of spectra are emission blend (23%), emission in absorption (22%), and self absorption (16%). Objects with repeated observations demonstrate that our classification into discrete categories is generally stable through time while seemingly less stable are categories P-Cygni and Self absorption, which is the consequence of discrete classification rules as well as of the fundamental change in profile shape. Such records of emission stars can be valuable for automatic pipelines in large surveys, where it may prove very useful to pinpoint outliers during calculation of general stellar properties and elemental abundances. They can find use in studies of star formation processes, interacting binaries and other fields of stellar physics.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/500/4849
- Title:
- GALAH emission-line stars
- Short Name:
- J/MNRAS/500/4849
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a neural network autoencoder structure that is able to extract essential latent spectral features from observed spectra and then reconstruct a spectrum from those features. Because of the training with a set of unpeculiar spectra, the network is able to reproduce a spectrum of high signal-to-noise ratio that does not show any spectral peculiarities, even if they are present in an observed spectrum. Spectra generated in this manner were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph at the Anglo-Australian telescope. Emission features were identified by a direct comparison of the observed and generated spectra. Using the described comparison procedure, we discovered 10364 candidate spectra with varying intensities (from partially filled-in to well above the continuum) of the H{alpha}/H{beta} emission component, produced by different physical mechanisms. A fraction of these spectra belong to the repeated observation that shows temporal variability in their emission profile. Among the emission spectra, we find objects that feature contributions from a nearby rarefied gas (identified through the emission of [NII] and [SII] lines) that was identified in 4004 spectra, which were not all identified as having H{alpha} emission. The positions of identified emission-line objects coincide with multiple known regions that harbour young stars. Similarly, detected nebular emission spectra coincide with visually prominent nebular clouds observable in the red all-sky photographic composites.
- ID:
- ivo://CDS.VizieR/J/MNRAS/491/3586
- Title:
- 611 {gamma} Doradus stars Kepler data
- Short Name:
- J/MNRAS/491/3586
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report our survey of {gamma} Dor stars from the 4-yr Kepler mission. These stars pulsate mainly in g modes and r modes, showing period-spacing patterns in the amplitude spectra. The period-spacing patterns are sensitive to the chemical composition gradients and the near-core rotation, hence they are essential for understanding the stellar interior. We identified period-spacing patterns in 611 {gamma} Dor stars. Almost every star pulsates in dipole g modes, while about 30 per cent of stars also show clear patterns for quadrupole g modes and 16 per cent of stars present r-mode patterns. We measure periods, period spacings, and the gradient of the period spacings. These three observables guide the mode identifications and can be used to estimate the near-core rotation rate. We find many stars are hotter and show longer period-spacing patterns than theory. Using the traditional approximation of rotation (TAR), we inferred the asymptotic spacings, the near-core rotation rates, and the radial orders of the g and r modes. Most stars have a near-core rotation rate around 1d^-1^ and an asymptotic spacing around 4000s. We also find that many stars rotate more slowly than predicted by theory for unclear reasons. 11 stars show rotational splittings with fast rotation rates. We compared the observed slope-rotation relation with the theory and find a large spread. We detected rotational modulations in 58 stars and used them to derive the core-to-surface rotation ratios. The interiors rotate faster than the cores in most stars, but by no more than 5 per cent.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/2307
- Title:
- gamma Dor stars spectroscopic survey
- Short Name:
- J/MNRAS/458/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of known and candidate {gamma} Doradus stars. The high-resolution, high signal-to-noise spectra of 52 objects were collected by five different spectrographs. The spectral classification, atmospheric parameters (T_eff_, logg, {xi}), vsini and chemical composition of the stars were derived. The stellar spectral and luminosity classes were found between G0-A7 and IV-V, respectively. The initial values for T_eff_ and logg were determined from the photometric indices and spectral energy distribution. Those parameters were improved by the analysis of hydrogen lines. The final values of T_eff_, logg and {xi} were derived from the iron lines analysis. The T_eff_ values were found between 6000K and 7900K, while log g values range from 3.8 to 4.5dex. Chemical abundances and vsin i values were derived by the spectrum synthesis method. The vsini values were found between 5 and 240km/s. The chemical abundance pattern of {gamma} Doradus stars were compared with the pattern of non-pulsating stars. It turned out that there is no significant difference in abundance patterns between these two groups. Additionally, the relations between the atmospheric parameters and the pulsation quantities were checked. A strong correlation between the vsini and the pulsation periods of {gamma} Doradus variables was obtained. The accurate positions of the analysed stars in the Hertzsprung-Russell diagram have been shown. Most of our objects are located inside or close to the blue edge of the theoretical instability strip of {gamma} Doradus.
- ID:
- ivo://CDS.VizieR/J/A+A/364/689
- Title:
- Geneva photometry of HDE 318107
- Short Name:
- J/A+A/364/689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rotation period of the Ap star HDE 318107 has been determined from magnetic and photometric observations obtained between August 1992 and September 1998
- ID:
- ivo://CDS.VizieR/J/A+A/458/569
- Title:
- H{alpha} equivalent widths of 36 Lyn (HD 79158)
- Short Name:
- J/A+A/458/569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports the photospheric, magnetic and circumstellar gas characteristics of the magnetic B8p star 36 Lyncis (HD 79158). Using archival data and new polarised and unpolarised high-resolution spectra, we redetermine the basic physical properties, the rotational period and the geometry of the magnetic field, and the photospheric abundances of various elements.
- ID:
- ivo://CDS.VizieR/J/A+AS/137/227
- Title:
- HD 133029 & HD 192913 elemental abundances
- Short Name:
- J/A+AS/137/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fine analyses of the silicon stars HD 133029 and HD 192913 are presented using ATLAS9 model atmospheres whose predictions fit the optical region spectrophotometry and H{gamma} profiles and have the same bulk metallicity as the deduced abundances. Both are very He poor stars. The light elements are mostly solar except for silicon, and all the heavier elements, except nickel in HD 133029 which is solar, are greatly overabundant. The iron peak elements are typically 10 times overabundant. SrYZr are of order of 100 times solar. The rare earths are 1000 or more times overabundant.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A85
- Title:
- HD 18078 uvby light curves
- Short Name:
- J/A+A/586/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Stromgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/4174
- Title:
- Heliocentric radial velocities of R CrB
- Short Name:
- J/MNRAS/482/4174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial-velocity observations made on more than a thousand nights are presented for the type star of the R Coronae Borealis (RCB) class. There are four principal sources: the Lick Observatory (1950 to 1953), the original Cambridge radial-velocity spectrometer (1968 to 1991), and the Haute-Provence and Cambridge Coravels (1986 to 1998 and 1997 to 2007, respectively). In the case of the last set the size (equivalent width) and width (expressed as if Vsin(i)) of the Coravel cross-correlation (dip) profiles are also given, and the variation and complexity of those profiles are discussed. Although there is often evidence of cyclical behaviour in radial velocity, no coherent periodicity is found in any of the series. From time to time, and especially over 100 days before the great decline of 2007, the atmosphere was highly disturbed, with evidence of high-velocity components. We suggest that those are associated with large turbulent elements and result in mass ejection to sufficient distances for the formation of soot and other solids and thus the initiation of RCB-type declines. We associate the changes in light and radial velocity near maximum light primarily with the combined effect of such turbulent elements, and not with coherent pulsation. There is some evidence for a variation in the mean radial velocity on a time scale of about ten thousand days.
- ID:
- ivo://CDS.VizieR/J/MNRAS/409/582
- Title:
- Helium-rich subluminous B stars abundances
- Short Name:
- J/MNRAS/409/582
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The connection between helium-rich hot subdwarfs of spectral types O and B (He-sdB) has been relatively unexplored since the latter were found in significant numbers in the 1980s. In order to explore this connection further, we have analysed the surface composition of six He-sdB stars, including LB 1766, LB 3229, SB 21 (= Ton-S 137 = BPS CS 29503-0009), BPS CS 22940-0009, BPS CS 29496-0010 and BPS CS 22956-0094.
