- ID:
- ivo://CDS.VizieR/J/A+A/624/A129
- Title:
- 30 Dor red supergiant stars radial velocities
- Short Name:
- J/A+A/624/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The incidence of multiplicity in cool, luminous massive stars is relatively unknown compared to their hotter counterparts.Here we present radial velocity (RV) measurements and investigate the multiplicity properties of red supergiants (RSGs) in the 30~Doradus region of the Large Magellanic Cloud using multi-epoch visible spectroscopy from the VLT-FLAMES Tarantula Survey. Exploiting the high density of absorption features in visible spectra of cool stars, we use a novel slicing technique to estimate RVs of 17 candidate RSGs in 30 Doradus from cross-correlation of the observations with model spectra. We provide absolute RV measurements (precise to better than +/-1km/s) for our sample and estimate line-of-sight velocities for the Hodge 301 and SL 639 clusters, which agree well with those of hot stars in the same clusters. By combining results for the RSGs with those for nearby B-type stars, we estimate systemic velocities and line-of-sight velocity dispersions for the two clusters, obtaining estimates for their dynamical masses of log(M_dyn_/M_{sun}_)=~3.8+/-0.3 for Hodge 301, and an upper limit of log(M_dyn_/M_{sun}_)<~3.1+/-0.8 for SL 639, assuming Virial equilibrium. Analysis of the multi-epoch data reveals one RV-variable, potential binary candidate (VFTS 744), which is likely a semi-regular variable asymptotic giant branch star. Calculations of semi-amplitude velocities for a range of RSGs in model binary systems and literature examples of binary RSGs were used to guide our RV variability criteria. We estimate an upper limit on the observed binary fraction for our sample of 0.3, where we are sensitive to maximum periods for individual objects in the range of 1 to 10000-days and mass-ratios above 0.3 depending on the data quality. From simulations of the RV measurements from binary systems given the current data we conclude that systems within the parameter range q>0.3, logP[days]<3.5, would be detected by our variability criteria, at the 90% confidence level. The intrinsic binary fraction, accounting for observational biases, is estimated using simulations of binary systems with an empirically defined distribution of parameters where orbital periods are uniformly distributed in the 3.3<logP[days]<4.3 range. A range of intrinsic binary fractions are considered; a binary fraction of 0.3 is found to best reproduce the observed data. We demonstrate that RSGs are effective extragalactic kinematic tracers by estimating the kinematic properties, including the dynamical masses of two LMC young massive clusters. In the context of binary evolution models, we conclude that the large majority of our sample consists of currently effectively single stars (either single or in long period systems). Further observations at greater spectral resolution and/or over a longer baseline are required to search for such systems.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/501/297
- Title:
- Effective temperatures of B Supergiants
- Short Name:
- J/A+A/501/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Effective temperatures of early-type supergiants are important to test stellar atmosphere- and internal structure-models of massive and intermediate mass objects at different evolutionary phases. However, these Teff values are more or less discrepant depending on the method used to determine them. We aim to obtain a new calibration of the Teff parameter for early-type supergiants as a function of observational quantities that are: a) highly sensitive to the ionization balance in the photosphere and its gas pressure; b) independent of the interstellar extinction; c) as much as possible model-independent.
- ID:
- ivo://CDS.VizieR/J/A+A/364/237
- Title:
- Elemental abundances of Deneb
- Short Name:
- J/A+A/364/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study presents a detailed model atmosphere abundance analysis of Deneb which was performed using Kurucz LTE ATLAS9 model atmospheres. The atmospheric parameters were determined from Mg I/II and Fe I/II equilibrium, and by fitting the H{gamma} profile and optical region spectrophotometry. The compromise values which best satisfy these criteria are T_eff_ = 9000 K and log g = 1.45. The Mg I, Mg II, Si II, Ti II, Cr II, Fe I, and Fe II lines yield microturbulences of 3.60, 6.50, 8.50, 8.00, 11.90, 3.60, and 10.40 km/s, respectively. An average microturbulence of 7 km/s was used for the other atomic species.
- ID:
- ivo://CDS.VizieR/J/BaltA/14/51
- Title:
- Elemental abundances of 4 Lac and nu Cep
- Short Name:
- J/BaltA/14/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Elemental abundance analysis based on high S/N and high resolution Dominion Astrophysical Observatory spectrograms have been performed for two early type supergiants: 4 Lac (B9 Iab) and {nu} Cep (A2 Ia). Lines as weak as of order 5m{AA} are employed in this study. The projected rotational velocities of these stars are 14 and 26km/s, respectively. Both stars show similar radial velocity amplitudes, macroturbulent velocities and the same general elemental abundance trends. Their He, CNO and light element abundances are solar or overabundant while the iron peak and heavy element abundances are solar or underabundant. Detailed LTE model atmosphere abundance analysis shows that 4 Lac has nuclearly processed matter in its photosphere while {nu} Cep does not.
- ID:
- ivo://CDS.VizieR/J/AZh/77/619
- Title:
- Energy distributions in giants and supergiants
- Short Name:
- J/AZh/77/619
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Normal spectral energy distributions for early-type subgiants, giants and supergiants are derived.
- ID:
- ivo://CDS.VizieR/J/AJ/157/167
- Title:
- Equivalent widths for RSGs in the MW & LMC/SMC
- Short Name:
- J/AJ/157/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red supergiants (RSGs) are evolved massive stars that represent extremes, in both their physical sizes and their cool temperatures, of the massive star population. The effective temperature (T_eff_) is the most critical physical property needed to place an RSG on the Hertzsprung-Russell Diagram, due to the stars' cool temperatures and resulting large bolometric corrections. Several recent papers have examined the potential utility of atomic line equivalent widths (EWs) in cool supergiant (CSG) spectra for determining T_eff_ and other physical properties and found strong correlations between Ti I and Fe I spectral features and T_eff_ in earlier-type CSGs (G and early K) but poor correlations in M-type stars, a spectral subtype that makes up a significant fraction of RSGs. We have extended this work by measuring the EWs of Ti, Fe, and Ca lines in late K- and M-type RSGs in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud, and compared these results to the predictions of the theoretical stellar LTE atmosphere models (MARCS) stellar atmosphere models. Our analyses show a poor correlation between T_eff_ and the Fe I and Ti I lines in our observations (at odds with strong correlations predicted by stellar atmosphere models), but do find statistically significant correlations between T_eff_ and the Ca II triplet (CaT) features of Milky Way RSGs, suggesting that this could be a potential diagnostic tool for determining T_eff_ in M-type supergiants. We also examine correlations between these spectral features and other physical properties of RSGs (including metallicity, surface gravity, and bolometric magnitude), and consider the underlying physics driving the evolution of atomic line spectra in RSGs.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A106
- Title:
- eta Car velocity-resolved imaging
- Short Name:
- J/A+A/594/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass loss from massive stars is not understood well. eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. We want to investigate the structure and kinematics of eta Car's primary star wind and wind-wind collision zone with a high spatial resolution of ~6mas (~14au) and high spectral resolution of R=12000. Observations of eta Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/24
- Title:
- Evolved massive stars with TESS. II.
- Short Name:
- J/ApJ/902/24
- Date:
- 14 Mar 2022 07:45:17
- Publisher:
- CDS
- Description:
- Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the H-R diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sample of 76 cool supergiants observed by the Transiting Exoplanet Survey Satellite (TESS) at a two-minute cadence. These pulsating YSGs are concentrated in an H-R diagram region not previously associated with pulsations; we conclude that this is a genuine new class of pulsating star, fast yellow pulsating supergiants (FYPSs). For each FYPS, we extract frequencies via iterative prewhitening and conduct a time-frequency analysis. One FYPS has an extracted frequency that is split into a triplet, and the amplitude of that peak is modulated on the same timescale as the frequency spacing of the triplet; neither rotation nor binary effects are likely culprits. We discuss the evolutionary status of FYPS and conclude that they are candidate post-RSGs. All stars in our sample also show the same stochastic low-frequency variability found in hot OB stars and attributed to internal gravity waves. Finally, we find four {alpha} Cygni variables in our sample, of which three are newly discovered.
- ID:
- ivo://CDS.VizieR/J/A+A/392/491
- Title:
- Galactic abundance gradient. III.
- Short Name:
- J/A+A/392/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a continuation of our previous work, which concerned the radial abundance distribution in the galactic disc over the distances 4-10kpc this paper presents the first results on the metallicity in the outer disc (R_G_>10kpc). Based on high-resolution spectra obtained for 19 distant Cepheids we sampled galactocentric distances from 10 to 12 kpc. Combined with the results of our previous work on the inner and middle parts of the galactic disc, the present data enable one to study the structure of the radial abundance distribution over a large baseline. In particular, we find indications of a discontinuity in the radial abundance distribution for iron as well as a number of the other elements. The discontinuity is seen at a galactocentric distance R_G_=10kpc. This finding supports the results reported earlier by Twarog et al. (1997AJ....114.2556T).
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/3209
- Title:
- Galactic and MC O-AGBs and RSGs stars
- Short Name:
- J/MNRAS/427/3209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33{mu}m. We detect crystalline silicates in stars with dust mass-loss rates which span over 3dex, down to rates of ~10^-9^M_{sun}_/yr. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-{mu}m feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-{mu}m band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.
