Search

Start Over Subject b stars Content Level Research Capability Type Simple Cone Search
1. APOGEE2-N NIR spectra of B-type stars
ID:
ivo://CDS.VizieR/J/ApJ/894/5
Title:
APOGEE2-N NIR spectra of B-type stars
Short Name:
J/ApJ/894/5
Date:
19 Jan 2022 00:59:33
Publisher:
CDS
Description:
We present a semi-empirical spectral classification scheme for normal B-type stars using near-infrared (NIR) spectra (1.5-1.7{mu}m) from the Sloan Digital Sky Survey Apache Point Observatory Galaxy Evolution Experiment (APOGEE2)-N data release 14 (DR14) database. The main motivation for working with B-type stars is their importance in the evolution of young stellar clusters; however, we also take advantage of having a numerous sample (316 stars) of B-type star candidates in APOGEE2-N, for which we also have optical (3600-9100{AA}) counterparts from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. By first obtaining an accurate spectral classification of the sources using the LAMOST DR3 spectra and the canonical spectral classification scheme, we found a linear relation between optical spectral types and the equivalent widths of the hydrogen lines of the Brackett series in the APOGEE2-N NIR spectra. This relation extends smoothly from a similar relation for O and early B stars found by Roman-Lopes+ (2018, J/ApJ/855/68). This way, we obtain a catalog of B-type sources with features in both the optical and NIR and a classification scheme refined down to one spectral subclass.
2. A stellar rotation census of B stars
ID:
ivo://CDS.VizieR/J/ApJ/722/605
Title:
A stellar rotation census of B stars
Short Name:
J/ApJ/722/605
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two recent observing campaigns provide us with moderate dispersion spectra of more than 230 cluster and 370 field B stars. Combining them and the spectra of the B stars from our previous investigations (~430 cluster and ~100 field B stars) yields a large, homogeneous sample for studying the rotational properties of B stars. We derive the projected rotational velocity vsini, effective temperature, gravity, mass, and critical rotation speed V_crit_ for each star. We compare the evolutionary trends of rotation (measured according to the polar gravity of the star) with recent models that treat internal mixing.
3. Bayesian statistics for massive stars
ID:
ivo://CDS.VizieR/J/MNRAS/454/28
Title:
Bayesian statistics for massive stars
Short Name:
J/MNRAS/454/28
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectral analysis is a powerful tool to investigate stellar properties and it has been widely used for decades now. However, the methods considered to perform this kind of analysis are mostly based on iteration among a few diagnostic lines to determine the stellar parameters. While these methods are often simple and fast, they can lead to errors and large uncertainties due to the required assumptions. Here, we present a method based on Bayesian statistics to find simultaneously the best combination of effective temperature, surface gravity, projected rotational velocity, and microturbulence velocity, using all the available spectral lines. Different tests are discussed to demonstrate the strength of our method, which we apply to 54 mid-resolution spectra of field and cluster B stars obtained at the Observatoire du Mont-Megantic. We compare our results with those found in the literature. Differences are seen which are well explained by the different methods used. We conclude that the B-star microturbulence velocities are often underestimated. We also confirm the trend that B stars in clusters are on average faster rotators than field B stars.
4. B6-B9.5 stars abundance analysis
ID:
ivo://CDS.VizieR/J/A+A/506/213
Title:
B6-B9.5 stars abundance analysis
Short Name:
J/A+A/506/213
Date:
21 Oct 2021
Publisher:
CDS
Description:
The CoRoT satellite is collecting precise time-resolved photometry for tens of asteroseismology targets. To ensure a correct interpretation of the CoRoT data, the atmospheric parameters, chemical compositions, and rotational velocities of the stars must be determined. The main goal of the ground-based seismology support program for the CoRoT mission was to obtain photometric and spectroscopic data for stars in the fields monitored by the satellite. These ground-based observations were collected in the GAUDI archive. High-resolution spectra of more than 200 B-type stars are available in this database, and about 45% of them is analysed here. To derive the effective temperature of the stars, we used photometric indices. Surface gravities were obtained by comparing observed and theoretical Balmer line profiles. To determine the chemical abundances and rotational velocities, we used a spectrum synthesis method, which consisted of comparing the observed spectrum with theoretical ones based on the assumption of LTE. Atmospheric parameters, chemical abundances, and rotational velocities were determined for 89 late-B stars. The dominant species in their spectra are iron-peak elements. The average Fe abundance is 7.24+/-0.45dex. The average rotational velocity is 126km/s, but there are 13 and 20 stars with low and moderate Vsini values, respectively. The analysis of this sample of 89 late B-type stars reveals many chemically peculiar (CP) stars. Some of them were previously known, but at least 9 new CP candidates, among which at least two HgMn stars, are identified in our study. These CP stars as a group exhibit Vsini values lower than the stars with normal surface chemical composition.
5. 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.
6. Binary red supergiants. II. B-type companions
ID:
ivo://CDS.VizieR/J/ApJ/875/124
Title:
Binary red supergiants. II. B-type companions
Short Name:
J/ApJ/875/124
Date:
20 Jan 2022 11:13:46
Publisher:
CDS
Description:
The percentage of massive main-sequence OB stars in binary systems is thought to be as high as 100%. However, very few Galactic binary red supergiants (RSGs) have been identified, despite the fact that these stars are the evolved descendants of OB stars. As shown in our recent paper, binary RSGs will likely have B-type companions, as dictated by stellar evolution considerations. Such a system will have a very unique photometric signature due to the shape of the spectral energy distribution. Using photometric cutoffs, it should therefore be possible to detect candidate RSG+B star binary systems. Here we present our spectroscopic follow-up observations of such candidates. Out of our initial list of 280 candidates in M31 and M33, we observed 149 and confirmed 63 as newly discovered RSG+B star binary systems. Additional spectra of four candidate systems in the Small Magellanic Cloud confirmed all of them as new RSG+B star binaries including the first known RSG+Be star system. By fitting BSTAR06 and MARCS model atmospheres to the newly obtained spectra, we place estimates on the temperatures and subtypes of both the B stars and RSGs. Overall, we have found 87 new RSG+B star binary systems in M31, M33 and the Small and Large Magellanic Clouds. Our future studies are aimed at determining the binary fraction of RSGs.
7. Bright B-type variables in Scorpius
ID:
ivo://CDS.VizieR/J/A+A/557/A1
Title:
Bright B-type variables in Scorpius
Short Name:
J/A+A/557/A1
Date:
21 Oct 2021
Publisher:
CDS
Description:
The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. We acquired 117h of Stromgren uvy data during 19 nights. Our targets comprised the {beta} Cephei stars {kappa} and {lambda} Sco, the eclipsing binary {mu}^1^ Sco, and the variable super/hypergiant {zeta}^1^ Sco. For {kappa} Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l,m)=(1,-1) {beta} Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For {lambda} Sco, we recover the known dominant {beta} Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spectroscopic orbital ephemeris of the closer pair in this triple system is inconsistent with eclipse timings and propose a refined value for the orbital period of the closer pair of 5.95189+/-0.00003d. We also argue that the components of the {lambda} Sco system are some 30% more massive than previously thought. The binary light curve solution of {mu}^1^ Sco requires inclusion of the irradiation effect to explain the u light curve, and the system could show additional low amplitude variations on top of the orbital light changes. {zeta}^1^ Sco shows long-term variability on a time scale of at least two weeks that we prefer to interpret in terms of a variable wind or strange mode pulsations.
8. B-star rotational velocities in h and {chi} Persei
ID:
ivo://CDS.VizieR/J/AJ/129/809
Title:
B-star rotational velocities in h and {chi} Persei
Short Name:
J/AJ/129/809
Date:
21 Oct 2021
Publisher:
CDS
Description:
Projected rotational velocities (vsini) have been measured for 216 B0-B9 stars in the rich, dense h and {chi} Persei double cluster and compared with the distribution of rotational velocities for a sample of field stars having comparable ages (t~12-15Myr) and masses (M~4-15M_Sun_).
9. B stars in 4 open clusters
ID:
ivo://CDS.VizieR/J/A+A/610/A30
Title:
B stars in 4 open clusters
Short Name:
J/A+A/610/A30
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the H{alpha} region to confirm the Be nature of these stars. We provide Teff, logg, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC6087, NGC6250, NGC6383, and NGC6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (<40Myr). Another maximum of Be stars is observed at the spectral type B6-B8 in open clusters older than 40Myr, where the population of Bdd stars also becomes relevant. The Bdd stars seem to be in a passive emission phase. Our results support previous statements that the Be phenomenon is present along the whole main sequence band and occurs in very different evolutionary states.We find clear evidence of an increase of stars with circumstellar envelopes with cluster age. The Be phenomenon reaches its maximum in clusters of intermediate age (10-40Myr) and the number of B stars with circumstellar envelopes (Be plus Bdd stars) is also high for the older clusters (40-100Myr).
10. B stars UBV and SpType catalogue
ID:
ivo://CDS.VizieR/J/other/ApSS/203.53
Title:
B stars UBV and SpType catalogue
Short Name:
J/other/ApSS/203
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present work represents a catalogue of spectral classification and photometric data of 2047 B type stars using the {Delta}Q method.

Limit your search

more »

  • 262