- ID:
- ivo://CDS.VizieR/J/ApJ/700/1216
- Title:
- Spectroscopy of Be stars in open clusters
- Short Name:
- J/ApJ/700/1216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We recently discovered a large number of highly active Be stars in the open cluster NGC 3766, making it an excellent location to study the formation mechanism of Be star disks. To explore whether similar disk appearances and/or disappearances are common among the Be stars in other open clusters, we present here multiple epochs of H{alpha} spectroscopy for 296 stars in eight open clusters. We identify 12 new transient Be stars and confirm 17 additional Be stars with relatively stable disks. By comparing the H{alpha} equivalent widths to the photometric y-H{alpha} colors, we present a method to estimate the strength of the H{alpha} emission when spectroscopy is not available. For a subset of 128 stars in four open clusters, we also use blue optical spectroscopy and available Stromgren photometry to measure their projected rotational velocities, effective temperatures, and polar surface gravities. We combine our Be star detections from these four clusters to investigate physical differences between the transient Be stars, stable Be stars, and normal B-type stars with no line emission. Both types of Be stars are faster rotating populations than normal B-type stars, and we find no significant physical differences between the transient and stable Be stars in our sample.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/BASI/39.517
- Title:
- Spectroscopy of classical Be stars
- Short Name:
- J/other/BASI/39.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800-9000{AA}. One-third of the sample (48 stars in 18 clusters) has been studied for the first time. All these candidates were identified from an extensive survey of emission stars in young open clusters using slitless spectroscopy (Mathew et al., 2008MNRAS.388.1879M). This large data set covers CBe stars of various spectral types and ages found in different cluster environments in largely northern open clusters, and is used to study the spectral characteristics of CBe stars in cluster environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/700/209
- Title:
- Spectroscopy of the B[e] star VES 695
- Short Name:
- J/ApJ/700/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- FS CMa type stars are a group of Galactic objects with the B[e] phenomenon. They exhibit strong emission-line spectra and infrared excesses, which are most likely due to recently formed circumstellar dust. The group content and identification criteria were described in the first two papers of the series. In this paper we report our spectroscopic and photometric observations of the optical counterpart of IRAS 00470+6429 obtained in 2003-2008. The optical spectrum is dominated by emission lines, most of which have P Cyg type profiles. We detected significant brightness variations, which may include a regular component, and variable spectral line profiles in both shape and position. The presence of a weak LiI6708{AA} line in the spectrum suggests that the object is most likely a binary system with a B2-B3 spectral-type primary companion of a luminosity logL/L_{sun}_=3.9+/-0.3 and a late-type secondary companion. We estimate a distance toward the object to be 2.0+/-0.3kpc from the Sun.
- ID:
- ivo://CDS.VizieR/J/BaltA/21/219
- Title:
- Spectroscopy of ups Sgr
- Short Name:
- J/BaltA/21/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high resolution spectra of hydrogen-deficient binary {upsilon} Sgr are analyzed. The atmospheric parameters are T_eff_= 12300+/-200K, logg=2.5+/-0.5 and {xi}_t_=5-15km/s depending on the element.
- ID:
- ivo://CDS.VizieR/J/AJ/157/159
- Title:
- Stellar parameters for 131 Herbig Ae/Be stars
- Short Name:
- J/AJ/157/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present study makes use of the unprecedented capability of the Gaia mission to obtain the stellar parameters such as distance, age, and mass of HAeBe stars. The accuracy of Gaia DR2 (Cat. I/345) astrometry is demonstrated from the comparison of the Gaia DR2 distances of 131 HAeBe stars with the previously estimated values from the literature. This is one of the initial studies to estimate the age and mass of a confirmed sample of HAeBe stars using both the photometry and distance from the Gaia mission. Mass accretion rates are calculated from H{alpha} line flux measurements of 106 HAeBe stars. Since we used distances and the stellar masses derived from the Gaia DR2 data in the calculation of the mass accretion rate, our estimates are more accurate than previous studies. The mass accretion rate is found to decay exponentially with age, from which we estimated a disk dissipation timescale of 1.9+/-0.1 Myr. The mass accretion rate and stellar mass exhibit a power-law relation of the form M_acc_{prop.to}M_*_^2.8+/-0.2^. From the distinct distribution in the values of the infrared spectral index, n_2-4.6_, we suggest the possibility of difference in the disk structure between Herbig Be and Herbig Ae stars.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A108
- Title:
- Stellar parameters of Be stars with X-shooter
- Short Name:
- J/A+A/609/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-shooter archive of several thousand telluric star spectra was skimmed for Be and Be-shell stars to derive the stellar fundamental parameters and statistical properties, in particular for the less investigated late type Be stars, and the extension of the Be phenomenon into early A stars. An adapted version of the BCD method is used, utilizing the Balmer discontinuity parameters to determine effective temperature and surface gravity. This method is optimally suited for late B stars. The projected rotational velocity was obtained by profile fitting to the Mgii lines of the targets, and the spectra were inspected visually for the presence of peculiar features such as the infrared Ca ii triplet or the presence of a double Balmer discontinuity. The Balmer line equivalent widths were measured, but due to uncertainties in determining the photospheric contribution are useful only in a subsample of Be stars for determining the pure emission contribution. A total of 78 Be stars, mostly late type ones, were identified in the X-shooter telluric standard star archive, out of which 48 had not been reported before. The general trend of late type Be stars having more tenuous disks and being less variable than early type ones is confirmed. The relatively large number (48) of relatively bright (V>8.5) additional Be stars casts some doubt on the statistics of late type Be stars; they are more common than currently thought: The Be/B star fraction may not strongly depend on spectral subtype.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/129
- Title:
- The Be phenomenon. V. MWC728
- Short Name:
- J/ApJ/809/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a long-term spectroscopic monitoring of the FS CMa type object MWC 728. We found that it is a binary system with a B5Ve (Teff=14000+/-1000K) primary and a G8III type (Teff~5000K) secondary. Absorption line positions of the secondary vary, with a semi-amplitude of ~20km/s and a period of 27.5 days. The system's mass function is 2.3x10^-2^M_{sun}_, and its orbital plane is ~13{deg}-15{deg} tilted from the plane of the sky. The primary's vsini~110km/s, combined with this tilt, implies that it rotates at a nearly breakup velocity. We detected strong variations of the Balmer and HeI emission-line profiles on timescales from days to years. This points to a variable stellar wind of the primary in addition to the presence of a circum-primary gaseous disk. The strength of the absorption-line spectrum, along with the optical and near infrared (IR) continuum, suggest that the primary contributes ~60% of the V-band flux, the disk contributes ~30%, and the secondary contributes ~10%. The system parameters, along with the interstellar extinction, suggest a distance of ~1kpc, that the secondary does not fill its Roche lobe, and that the companions' mass ratio is q~0.5. Overall, the observed spectral variability and the presence of a strong IR-excess are in agreement with a model of a close binary system that has undergone a non-conservative mass-transfer.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1695
- Title:
- The Chandra survey of the SMC "Bar". II.
- Short Name:
- J/ApJ/697/1695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the most likely optical counterparts of 113 X-ray sources detected in our Chandra survey of the central region of the Small Magellanic Cloud (SMC) based on the OGLE-II and Magellanic Clouds Photometric Survey catalogs. We estimate that the foreground contamination and chance coincidence probability are minimal for the bright optical counterparts (corresponding to OB type stars; 35 in total). We propose here for the first time 13 high-mass X-ray binaries, of which four are Be/X-ray binaries (Be-XRBs), and we confirm the previous classification of 18 Be-XRBs. We estimate that the new candidate Be-XRBs have an age of ~15-85Myr, consistent with the age of Be stars.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1249
- Title:
- The early spectra of eta Carinae
- Short Name:
- J/AJ/135/1249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observed behavior of {eta} Car from 1860 to 1940 has not been considered in most recent accounts, nor has it been explained in any quantitative model. We have used modern digital processing techniques to examine Harvard objective-prism spectra made from 1892 to 1941. Relatively high excitation HeI{lambda}4471 and [FeIII]4658 emission, conspicuous today, were weak and perhaps absent throughout those years. Feast et al. (2001MNRAS.322..741F) noted this qualitative fact for other pre-1920 spectra, but we quantify it and extend it to a time only three years before Gaviola (1953ApJ...118..234G)'s first observations of the high-excitation features. Evidently the supply of helium-ionizing photons ({lambda}<504{AA}) grew rapidly between 1941 and 1944. The apparent scarcity of such far-UV radiation before 1944 is difficult to explain in models that employ a hot massive secondary star, because no feasible dense wind or obscuration by dust would have hidden the photoionization caused by the proposed companion during most of its orbital period. We also discuss the qualitative near-constancy of the spectrum from 1900 to 1940, and {eta} Car's photometric and spectroscopic transition between 1940 and 1953.
- ID:
- ivo://CDS.VizieR/J/A+A/325/987
- Title:
- UBV magnitude of NGC 884 B-type pulsators
- Short Name:
- J/A+A/325/987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the photometric CCD search for B-type pulsators in the central region of Chi Persei (NGC 884) open cluster. In addition to the two newly-discovered Beta Cephei stars we found 11 other variables in the observed field. The photometric data for them are given in the file 'bmag' and 'vmag' for B and V-filter data, respectively. In addition, we present the new UBV magnitudes for stars in the observed field. This is Table 4 of the paper, available only in electronic form.