- ID:
- ivo://CDS.VizieR/J/AJ/162/150
- Title:
- Resolving circumstellar environment of MWC137 .II.
- Short Name:
- J/AJ/162/150
- Date:
- 14 Mar 2022 06:35:34
- Publisher:
- CDS
- Description:
- The Galactic B[e] supergiant MWC137 is surrounded by a large-scale optical nebula. To shed light on the physical conditions and kinematics of the nebula, we analyze the optical forbidden emission lines [NII] {lambda}{lambda}6548,6583 and [SII] {lambda}{lambda}6716,6731 in long-slit spectra taken with ALFOSC at the Nordic Optical Telescope. The radial velocities display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. The electron density shows strong variations across the nebula with values spreading from about zero to ~800cm^-3^. Higher densities are found closer to MWC137 and in regions of intense emission, whereas in regions with high radial velocities the density decreases significantly. We also observe the entire nebula in the two [SII] lines with the scanning Fabry-Perot interferometer attached to the 6m telescope of the Special Astrophysical Observatory. These data reveal a new bow-shaped feature at PA=225{deg}-245{deg} and a distance 80" from MWC137. A new H{alpha} image has been taken with the Danish 1.54m telescope on La Silla. No expansion or changes in the nebular morphology appear within 18.1yr. We derive a mass of 37_-5_^+9^M{sun} and an age of 4.7{+/-}0.8Myr for MWC137. Furthermore, we detect a period of 1.93d in the time series photometry collected with the TESS satellite, which could suggest stellar pulsations. Other, low-frequency variability is seen as well. Whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/150/41
- Title:
- Rotational velocities of 136 B stars from ALS
- Short Name:
- J/AJ/150/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined projected rotational velocities, vsini, from Magellan/MIKE echelle spectra for a sample of 136 early B-type stars having large Galactocentric distances. The target selection was done independently of their possible membership in clusters, associations or field stars. We subsequently examined the literature and assigned each star as Field, Association, or Cluster. Our vsini results are consistent with a difference in aggregate vsini with stellar density. We fit bimodal Maxwellian distributions to the Field, Association, and Cluster subsamples representing sharp-lined and broad-lined components. The first two distributions, in particular, for the Field and Association are consistent with strong bimodality in vsini. Radial velocities are also presented, which are useful for further studies of binarity in B-type stars, and we also identify a sample of possible new double-lined spectroscopic binaries. In addition, we find 18 candidate Be stars showing emission at H{alpha}.
- ID:
- ivo://CDS.VizieR/J/A+A/409/275
- Title:
- Rotation and magnetic field in omega Ori
- Short Name:
- J/A+A/409/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Omega Ori is a B2IIIe star for which rotational modulation and non-radial pulsations (NRP) have been recently investigated from two independent observational campaigns in 1998 and 1999. Putting the data of these 2 campaigns together, and adding data obtained in 2001, we search for multiperiodicity in the line profile variations and evidence for outbursts. From new spectropolarimetric data obtained at the Telescope Bernard Lyot (TBL, Pic du Midi, France) in 2001 we also measure the Stokes V parameter in the polarised light. We find evidence for the presence of a weak magnetic field in Omega Ori sinusoidally varying with a period of 1.29d. The equivalent widths (EW) of the wind sensitive UV resonance lines also show a variation with the same period, which we identify as the rotational period of the star. We propose an oblique rotator model and derive B_pol_=530+/-230G to explain the observations. Moreover, we carry out an abundance analysis and find the star to be N-enriched, a property which is shared with other magnetic stars. We propose Omega Ori as the first known classical Be star hosting a magnetic field.
- ID:
- ivo://CDS.VizieR/J/AJ/149/7
- Title:
- SDSS-III/APOGEE. I. Be stars
- Short Name:
- J/AJ/149/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has amassed the largest ever collection of multi-epoch, high-resolution (R~22500), H-band spectra for B-type emission line (Be) stars. These stars were targeted by APOGEE as telluric standard stars and subsequently identified via visual inspection as Be stars based on HI Brackett series emission or shell absorption in addition to otherwise smooth continua and occasionally non-hydrogen emission features. The 128/238 APOGEE Be stars for which emission had never previously been reported serve to increase the total number of known Be stars by ~6%. Because the H band is relatively unexplored compared to other wavelength regimes, we focus here on identification of the H-band lines and analysis of the emission peak velocity separations ({Delta}v_p_) and emission peak intensity ratios (V/R) of the usually double-peaked HI and non-hydrogen emission lines. HI Br11 emission is found to preferentially form in the circumstellar disks at an average distance of ~2.2 stellar radii. Increasing {Delta}v_p_ toward the weaker Br12-Br20 lines suggests these lines are formed interior to Br11. By contrast, the observed IR FeII emission lines present evidence of having significantly larger formation radii; distinctive phase lags between IR FeII and HI Brackett emission lines further supports that these species arise from different radii in Be disks. Several emission lines have been identified for the first time including CI 16895, a prominent feature in the spectra for almost a fifth of the sample and, as inferred from relatively large {Delta}v_p_ compared to the Br11-Br20, a tracer of the inner regions of Be disks. Emission lines at 15760{AA} and 16781{AA} remain unidentified, but usually appear along with and always have similar line profile morphology to FeII 16878. Unlike the typical metallic lines observed for Be stars in the optical, the H-band metallic lines, such as FeII 16878, never exhibit any evidence of shell absorption, even when the HI lines are clearly shell-dominated. The first known example of a quasi-triple-peaked Br11 line profile is reported for HD253659, one of several stars exhibiting intra- and/or extra-species V/R and radial velocity variation within individual spectra. Br11 profiles are presented for all discussed stars, as are full APOGEE spectra for a portion of the sample.
- ID:
- ivo://CDS.VizieR/J/AJ/153/174
- Title:
- SDSS-III/APOGEE. II. The multi-epoch ABE sample
- Short Name:
- J/AJ/153/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the H-band spectral variability of classical Be stars observed over the course of the Apache Point Galactic Evolution Experiment (APOGEE), one of four subsurveys comprising SDSS-III. As described in the first paper of this series, the APOGEE B-type emission-line (ABE) star sample was culled from the large number of blue stars observed as telluric standards during APOGEE observations. In this paper, we explore the multi-epoch ABE sample, consisting of 1100 spectra for 213 stars. These "snapshots" of the circumstellar disk activity have revealed a wealth of temporal variability including, but not limited to, gradual disappearance of the line emission and vice versa over both short and long timescales. Other forms of variability include variation in emission strength, emission peak intensity ratios, and emission peak separations. We also analyze radial velocities (RVs) of the emission lines for a subsample of 162 stars with sufficiently strong features, and we discuss on a case-by-case basis whether the RV variability exhibited by some stars is caused by binary motion versus dynamical processes in the circumstellar disks. Ten systems are identified as convincing candidates for binary Be stars with as of yet undetected companions.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A57
- Title:
- Six year spectroscopy of V2028 Cyg
- Short Name:
- J/A+A/542/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of nearly six years long spectroscopic observations of the B[e] star V2028 Cyg. The presence of the cold type absorption lines combined with the hot type spectrum indicate a binarity of this object. Since the B[e] stars are embedded in an extended envelope, the usage of common stellar atmosphere models for the analysis is not very appropriate. Therefore we focus on the analysis of the long term spectral line variations in order to determine the nature of this object. We present time dependencies of the equivalent width and radial velocities of the H{alpha} line, [OI] 6300{AA}, FeII 6427, 6433, and 6456{AA} lines. The bisector variations and line intensities are shown for the H{alpha} line. The radial velocities are also measured for the absorption lines of the K component. No periodic variation was found. The observed data show correlations between the measured quantities, which can be used for the future modelling.
- ID:
- ivo://CDS.VizieR/J/A+A/393/887
- Title:
- SMC Be stars candidates
- Short Name:
- J/A+A/393/887
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recently the OGLE experiment has provided accurate light curves and colours for about 2 millions stars in the Small Magellanic Cloud. We have examined this database for its content of Be stars, applying some selection criteria, and we have found a sample of ~1000 candidates. Some of these stars show beautiful light curves with amazing variations never observed in any Galactic variable. We find outbursts in 13% of the sample (type-1 stars), high and low states in 15%, periodic variations in 7%, and the usual variations seen in Galactic Be stars in 65% of the cases. The Galactic counterparts of type-1 objects could be the outbursting Be stars found by Hubert & Floquet (1998, Cat. J/A+A/335/565) after the analysis of Hipparcos photometry. We discuss the possibility that type-1 stars could correspond to Be stars with accreting white dwarf companions or alternatively, blue pre-main sequence stars surrounded by thermally unstable accretion disks. We provide coordinates and basic photometric information for these stars and some examples of light curves.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/252
- Title:
- Southern B and Be stars
- Short Name:
- J/MNRAS/371/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic monitoring of 141 southern field B-type stars, 114 of them known to exhibit the Be phenomenon, allowed the estimation of their projected rotational velocities, effective temperatures and superficial gravities from both line and equivalent width fitting procedures. Stellar ages, masses and bolometric luminosities were derived from internal structure models. Without taking into account the effects of gravity darkening, we note the occurrence of the Be phenomenon in later stages of main-sequence phase.
- ID:
- ivo://CDS.VizieR/J/PASP/126/219
- Title:
- Southern Galactic Be star candidates
- Short Name:
- J/PASP/126/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the result of a search for southern Galactic Be star candidates within the group of miscellaneous variables of the ASAS-2 catalog of variable stars, using statistical, morphological, photometric, and color criteria. This search lead us to obtain a catalog of 213 new Be star candidates. The I-band light curves of these candidates show outbursts (Type-1 stars) only in 9% of the sample, and stochastic variations (Type-4 stars) in 91% of the sample. We do not find stars showing clear high and low states (Type-2 stars) or showing outbursts and high and low states simultaneously (Type-1/Type-2 stars). Our sample of southern Galactic Be star candidates provide valuable new bright targets for high resolution spectroscopic studies with small/medium size telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A145
- Title:
- Space photometry of the Be stars nu Pup
- Short Name:
- J/A+A/620/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry of the bright Be star {nu} Puppis. The observations were obtained with the Solar Mass Ejection Imager (SMEI) and BRITE-Constellation satellites. Several closely but probably not perfectly evenly spaced frequencies are found that are attributed to nonradial pulsations.
