- ID:
- ivo://CDS.VizieR/J/A+A/634/A18
- Title:
- Be and Bn stars Balmer discontinuity
- Short Name:
- J/A+A/634/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A significant number of Be stars show a second Balmer discontinuity (sBD) attributed to an extended circumstellar envelope (CE). The fast rotational velocity of Be stars undoubtedly plays a significant role in the formation of the CE. However, Bn stars, which are also B-type rapidly rotating stars, do not all present clear evidence of being surrounded by circumstellar material. We aim to characterize the populations of Be and Bn stars, and discuss the appearance of the sBD as a function of the stellar parameters. We expect to find new indices characterizing the properties of CEs in Be stars and properties relating Be and Bn stars. We obtained low- and high-resolution spectra of a sample of Be and Bn stars, derived stellar parameters, characterized the sBD, and measured the emission in the H{alpha} line. Results. Correlations of the aspect and intensity of the sBD and the emission in the H{alpha} line with the stellar parameters and the Vsini are presented. Some Bn stars exhibit the sBD in absorption, which may indicate the presence of rather dense CEs. Six Bn stars show emission in the H{alpha} line, so they are reclassified as Be stars. The sBD in emission appears in Be stars with Vsini<=250km/s, and in absorption in both Be and Bn stars with Vsini>=50km/s Low-mass Be and Bn stars share the same region in the Hertzsprung-Russell diagram. The distributions of rotational to critical velocity ratios of Be and Bn stars corresponding to the current stellar evolutionary stage are similar, while distributions inferred for the zero-age main sequence have different skewness. We found emission in the H{alpha} line and signs of a CE in some Bn stars, which motivated us to think that Bn and Be stars probably belong to the same population. It should be noted that some of the most massive Bn stars could display the Be phenomenon at any time. The similarities found among Be and Bn stars deserve to be more deeply pursued.
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Search Results
1712. BEAST sample properties
- ID:
- ivo://CDS.VizieR/J/A+A/646/A164
- Title:
- BEAST sample properties
- Short Name:
- J/A+A/646/A164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While the occurrence rate of wide giant planets appears to increase with stellar mass at least up through the A-type regime, B-type stars have so far not been systematically studied in large scale surveys. It therefore remains unclear up to what stellar mass this occurrence trend continues. The B-star Exoplanet Abundance Study (BEAST) is a direct imaging survey with the Extreme Adaptive Optics instrument SPHERE, targeting 85 B-type stars in the young Scorpius-Centaurus (Sco-Cen) region with the aim of detecting giant planets at wide separations and constraining their occurrence rate and physical properties. The statistical outcome of the survey will help determining if and where an upper stellar mass limit for planet formation occurs. Here, we describe the selection and characterization of the BEAST target sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/L33
- Title:
- Be-B concentrations in rare CB/CH chondrite
- Short Name:
- J/ApJ/763/L33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A search for short-lived ^10^Be in 21 calcium-aluminum-rich inclusions (CAIs) from Isheyevo, a rare CB/CH chondrite, showed that only 5 CAIs had ^10^B/^11^B ratios higher than chondritic correlating with the elemental ratio ^9^Be/^11^B, suggestive of in situ decay of this key short-lived radionuclide. The initial (^10^Be/^9^Be)_0_ ratios vary between ~10^-3^ and ~10^-2^ for CAI 411. The initial ratio of CAI 411 is one order of magnitude higher than the highest ratio found in CV3 CAIs, suggesting that the more likely origin of CAI 411 ^10^Be is early solar system irradiation. The low (^26^Al/^27^Al)_0_ [<=8.9x10^-7^] with which CAI 411 formed indicates that it was exposed to gradual flares with a proton fluence of a few 10^19^protons/cm2, during the earliest phases of the solar system, possibly the infrared class 0. The irradiation conditions for other CAIs are less well constrained, with calculated fluences ranging between a few 10^19^ and 10^20^protons/cm2. The variable and extreme value of the initial ^10^Be/^9^Be ratios in carbonaceous chondrite CAIs is the reflection of the variable and extreme magnetic activity in young stars observed in the X-ray domain.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A21
- Title:
- BEER analysis of CoRoT light curves
- Short Name:
- J/A+A/580/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The BEER algorithm, introduced by Faigler & Mazeh (2011MNRAS.415.3921F), searches stellar lightcurves for the BEaming, Ellipsoidal, and Reflection (BEER) photometric modulations that are caused by a short-period companion. These three effects are typically of very low amplitude, and can mainly be detected in lightcurves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. Applying the algorithm to wide-field photometric surveys such as CoRoT and Kepler offers an opportunity to better understand the statistical properties of short-period binaries. It also widens the window for detecting intrinsically rare systems, like short-period brown-dwarf and massive- planetary companions to main-sequence stars. Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiber-allocations with dedicated softwares, we acquired 6-7 medium-resolution spectra of 281 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842{AA}, yielded a radial-velocity precision of ~1 km/s. Spectra containing lines of more than one star were analyzed with the two- dimensional correlation algorithm TODCOR. The measured radial velocities confirmed the binarity of seventy of the BEER candidates, 45 single-line binaries, 18 double-line binaries, and 7 diluted binaries. We show that red giants introduce a major source of false candidates and demonstrate a way to improve BEER's performance in extracting higher fidelity samples from future searches of CoRoT lightcurves. The periods of the confirmed binaries span a range of 0.3-10days and show a rise in the number of binaries per logP bin toward longer periods. The estimated mass ratios of the double-line binaries and the mass ratios assigned to the single-line binaries, assuming an isotropic inclination distribution, span a range of 0.03-1. On the low-mass end we have detected two brown-dwarf candidates on a ~1day period orbit. This is the first time non-eclipsing beaming binaries are detected in CoRoT data, and we estimate that ~300 such binaries can be detected in the CoRoT long-run lightcurves.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/14
- Title:
- Behavior of heavy elements in H-He-Z mixtures
- Short Name:
- J/ApJ/829/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The core-accretion model for giant planet formation suggests a two-layer picture for the initial structure of Jovian planets, with heavy elements in a dense core and a thick H-He envelope. Late planetesimal accretion and core erosion could potentially enrich the H-He envelope in heavy elements, which is supported by the threefold solar metallicity that was measured in Jupiter's atmosphere by the Galileo entry probe. In order to reproduce the observed gravitational moments of Jupiter and Saturn, models for their interiors include heavy elements, Z, in various proportions. However, their effect on the equation of state of the hydrogen-helium mixtures has not been investigated beyond the ideal mixing approximation. In this article, we report results from ab initio simulations of fully interacting H-He-Z mixtures in order to characterize their equation of state and to analyze possible consequences for the interior structure and evolution of giant planets. Considering C, N, O, Si, Fe, MgO, and SiO_2_, we show that the behavior of heavy elements in H-He mixtures may still be represented by an ideal mixture if the effective volumes and internal energies are chosen appropriately. In the case of oxygen, we also compute the effect on the entropy. We find the resulting changes in the temperature-pressure profile to be small. A homogeneous distribution of 2% oxygen by mass changes the temperature in Jupiter's interior by only 80K.
- ID:
- ivo://CDS.VizieR/J/AJ/112/2769
- Title:
- Behlen Observatory Survey. IV.
- Short Name:
- J/AJ/112/2769
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Finding charts, accurate coordinates, and light curves are presented for 106 variable stars including 6 which are newly discovered. Parameters descriptive of the light curves are tabulated including periods for 16 stars which lacked them. The periods from the General Catalog of Variable Stars for ten stars were found to be seriously in error. The classification of the stars is discussed. Revisions or refinements of the classifications from the General Catalogue of Variable Stars are suggested for 20 stars and classifications are given for 7 which were previously unclassified. 15%-23% of the Bailey type ab RR Lyrae stars show scatter in their light curves which is suggestive of the Blazhko effect.
- ID:
- ivo://CDS.VizieR/J/AJ/106/2429
- Title:
- Behlen Obs. variables stars survey
- Short Name:
- J/AJ/106/2429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a previous paper, photometry for the first ninety-three stars in a photometric survey of variable stars was discussed. Finding charts, accurate coordinates, and light curves for those stars are presented here. The reliability of the coordinates from the General Catalogue of Variable Stars is discussed. The magnitude scale of the present photometry is compared with that of the Hubble Space Telescope Guide Star Catalogue.
- ID:
- ivo://CDS.VizieR/J/other/BOBeo/155.3
- Title:
- Belgrade meridian circle catalog
- Short Name:
- J/other/BOBeo/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The authors present an observational catalogue containing the positions of 351 stars situated in the vicinity of radio sources (RRS2, Tel'nyuk-Adamchuk & Kumkova, 1991, IAU Colloq. 127, 363) worked out by differential method in the FK5 system. The (O-C) corrections to the positions of 267 fundamental stars used in the determination of the instrument parameters are also presented. The star positions are derived from the observations with the Belgrade Large Meridian Circle during 1991-1993.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/40
- Title:
- Be-like ions from BII to NeVII transition data
- Short Name:
- J/ApJS/234/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Large-scale self-consistent multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations are reported for the n<=6 levels in Be-like ions from BII to NeVII. Effects from electron correlation are taken into account by means of large expansions in terms of a basis of configuration state functions, and a complete and accurate data set of excitation energies; lifetimes; wavelengths; electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole line strengths; transition rates; and oscillator strengths for these levels is provided for each ion. Comparisons are made with available experimental and theoretical results. The uncertainty of excitation energies is assessed to be 0.01% on average, which makes it possible to find and rule out misidentifications and aid new line identifications involving high-lying levels in astrophysical spectra. The complete data set is also useful for modeling and diagnosing astrophysical plasmas.
- ID:
- ivo://CDS.VizieR/J/ApJS/79/77
- Title:
- Bell Lab. H I Survey - High Velocity Clouds
- Short Name:
- J/ApJS/79/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sky north of declination -40 deg. was observed in the 21 cm line of atomic hydrogen with the FWHM = 2 deg. beam of the 20 foot horn reflector at AT&T Bell Laboratories, Crawford Hill. The survey covers a velocity range of 654 km/s centered on the Galactic standard of rest, with 5.3 km/s wide filters. This survey is distinguished by its sensitivity to low surface brightness features (antenna temperature about 50 mK) and relative freedom from sidelobe contamination. The high-velocity cloud list was extracted and catalogued automatically from the survey data.
