- ID:
- ivo://CDS.VizieR/J/AJ/132/749
- Title:
- Rotational velocities of O stars in clusters
- Short Name:
- J/AJ/132/749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study aimed at assessing whether low and high-mass stars form similarly. Our approach is (1) to examine the observed projected rotational velocities among a large sample of newly formed stars spanning a range in mass between 0.2 and 50M_{sun}_ and (2) to search for evidence of a discontinuity in rotational properties that might indicate a difference in the stellar formation process at some characteristic mass. Our database includes recently published values of vsini for young intermediate and low-mass stars in Orion, as well as new observations of O stars located in young clusters and OB associations.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/817
- Title:
- RV catalog of O-type stars in IC 2944 and Cen OB2
- Short Name:
- J/MNRAS/416/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an extended set of multi-epoch high resolution high signal-to-noise ratio optical spectra, we re-address the multiplicity properties of the O-type stars in IC 2944 and in the Cen OB2 association. We present new evidence of binarity for five objects and we confirm the multiple nature of another two. We derive the first orbital solutions for HD 100099, HD 101436 and HD 101190 and we provide additional support for HD 101205 being a quadruple system. The minimal spectroscopic binary fraction in our sample is f_min_=0.57. Using numerical simulations, we show that the detection rate of our observational campaign is close to 90%, leaving thus little room for undetected spectroscopic binary systems. The statistical properties of the O-star population in IC 2944 are similar, within the uncertainties, to the results obtained in the earlier papers in this series despite the fact that sample size effects limit the significance of the comparison. Using newly derived spectroscopic parallaxes, we reassess the distance to IC 2944 and obtained 2.3+/-0.3kpc, in agreement with previous studies. We also confirm that, as far as the O stars are concerned, the IC 2944 cluster is most likely a single entity.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A107
- Title:
- RV catalogue of O stars in 30 Doradus
- Short Name:
- J/A+A/550/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tarantula Nebula in the Large Magellanic Cloud is our closest view of a starburst region and is the ideal environment to investigate important questions regarding the formation, evolution and final fate of the most massive stars. We analyze the multiplicity properties of the massive O-type star population observed through multi-epoch spectroscopy in the framework of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. By modelling simultaneously the observed binary fraction, the distributions of the amplitudes of the radial velocity variations and the distribution of the time scales of these variations, we derive the intrinsic current binary fraction and period and mass-ratio distributions. We observe a spectroscopic binary fraction of 0.35+/-0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20km/s . We compute the intrinsic binary fraction to be 0.51+/-0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f(log_10_P/d)~(log_10_ P/d)^pi^ (with log_10_P/d in the range 0.15-3.5) and f(q)~q^kappa^ with 0.1<q=M2/M1< 1.0. The power-law indexes that best reproduce the observed quantities are pi=-0.45+/-0.30 and kappa=-1.0+/-0.4. The period distribution that we obtain thus favours shorter period systems compared to an Opik law (pi=0). The mass ratio distribution is slightly skewed towards low mass ratio systems but remains incompatible with a random sampling of a classical mass function (kappa=-2.35). The binary fraction seems mostly uniform across the field of view and independent of the spectral types and luminosity classes. The binary fraction in the outer region of the field of view (r>7.8 , i.e. ~117pc) and among the O9.7 I/II objects are however significantly lower than expected from statistical fluctuations. The observed and intrinsic binary fractions are also lower for the faintest objects in our sample (Ks>15.5mag), which results from observational effects and the fact that our O star sample is not magnitude-limited but is defined by a spectral-type cutoff. We also conclude that magnitude-limited investigations are biased towards larger binary fractions. Using the multiplicity properties of the O stars in the Tarantula region and simple evolutionary considerations, we estimate that over 50% of the current O star population will exchange mass with its companion within a binary system. This shows that binary interaction is greatly affecting the evolution and fate of massive stars, and must be taken into account to correctly interpret unresolved populations of massive stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/1479
- Title:
- RV catalogue of O-type stars in NGC 6611
- Short Name:
- J/MNRAS/400/1479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on a set of over 100 medium- to high-resolution optical spectra collected from 2003 to 2009, we investigate the properties of the O-type star population in NGC 6611 in the core of the Eagle Nebula (M16). Using a much more extended data set than previously available, we revise the spectral classification and multiplicity status of the nine O-type stars in our sample. We confirm two suspected binaries and derive the first SB2 orbital solutions for two systems. We further report that two other objects are displaying a composite spectrum, suggesting possible long- period binaries. Our analysis is supported by a set of Monte-Carlo simulations, allowing us to estimate the detection biases of our campaign and showing that the latter do not affect our conclusions. The absolute minimal binary fraction in our sample is f_min_=0.44 but could be as high as 0.67 if all the binary candidates are confirmed. As in NGC 6231 (see Paper I, Sana et al., Cat. J/MNRAS/386/447), up to 75% of the O star population in NGC 6611 are found in an O+OB system, thus implicitly excluding random pairing from a classical IMF as a process to describe the companion association in massive binaries. No statistical difference could be further identified in the binary fraction, mass-ratio and period distributions between NGC 6231 and NGC 6611, despite the difference in age and environment of the two clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/447
- Title:
- RV catalogue of O-type stars in NGC 6231
- Short Name:
- J/MNRAS/386/447
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star population. Almost three quarters of the O-type stars in the cluster are members of a binary system. The minimum binary fraction is 0.63, with half the O-type binaries having an orbital period of the order of a few days. The eccentricities of all the short-period binaries are revised downward, and henceforth match a normal period-eccentricity distribution. The mass-ratio distribution shows a large preference for O+OB binaries, ruling out the possibility that, in NGC 6231, the companion of an O-type star is randomly drawn from a standard IMF. Obtained from a complete and homogeneous population of O-type stars, our conclusions provide interesting observational constraints to be confronted with the formation and early-evolution theories of O stars.
- ID:
- ivo://CDS.VizieR/J/other/Sci/337.444
- Title:
- RV curves of Galactic massive O stars
- Short Name:
- J/other/Sci/337.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, X-ray binaries and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. Over seventy per cent of all massive stars will exchange mass with a companion, leading to a binary merger in one third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/2068
- Title:
- RV survey of the Carina Nebula's O stars
- Short Name:
- J/MNRAS/477/2068
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1-2 km/s precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6km/s. We calculate a velocity dispersion of <=9.1km/s, consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5km/s radial velocity offset from its neighbour Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10-15km/s, possibly triggering further massive star formation. The expansion of the surrounding H II region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/66
- Title:
- Search for extraterrestrial intelligence with ATA
- Short Name:
- J/ApJ/869/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a novel radio autocorrelation search for extraterrestrial intelligence. For selected frequencies across the terrestrial microwave window (1-10GHz), observations were conducted at the Allen Telescope Array to identify artificial non-sinusoidal periodic signals with radio bandwidths greater than 4Hz, which are capable of carrying substantial messages with symbol rates from 4 to 10^6^Hz. Out of 243 observations, about half (101) were directed toward sources with known continuum flux >~1Jy over the sampled bandwidth (quasars, pulsars, supernova remnants, and masers), based on the hypothesis that they might harbor heretofore undiscovered natural or artificial repetitive, phase or frequency modulation. The rest of the observations were directed mostly toward exoplanet stars with no previously discovered continuum flux. No signals attributable to extraterrestrial technology were found in this study. We conclude that the maximum probability that future observations like the ones described here will reveal repetitively modulated emissions is less than 5% for continuum sources and exoplanets alike. The paper concludes by describing a new approach to expanding this survey to many more targets and much greater sensitivity using archived data from interferometers all over the world.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/15
- Title:
- SMaSH+: observations and companion detection
- Short Name:
- J/ApJS/215/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 milliarcsec (mas) remain mostly unknown due to intrinsic observational limitations. At a typical distance of 2kpc, this corresponds to projected physical separations of 2-200AU. The Southern MAssive Stars at High angular resolution survey (SMaSH+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/Sparse Aperture Masking (SAM), probing the separation ranges 1-45 and 30-250mas and brightness contrasts of {Delta}H<4 and {Delta}H<5, respectively. Taking advantage of NACO's field of view, we further uniformly searched for visual companions in an 8" radius down to {Delta}H=8. This paper describes observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1mas to 8" and presents a catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample ({delta}<0{deg}; H<7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation {rho}<8" increases to f_m_=0.91+/-0.03. The nine non-thermal radio emitters observed by SMaSH+ are all resolved, including the newly discovered pairs HD 168112 and CPD-47{deg}2963.
- ID:
- ivo://CDS.VizieR/J/AJ/152/31
- Title:
- Spectral classification of O Vz stars from GOSSS
- Short Name:
- J/AJ/152/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the Galactic O Star Spectroscopic Survey (GOSSS), we present a detailed systematic investigation of the O Vz stars. The currently used spectral classification criteria are rediscussed, and the Vz phenomenon is recalibrated through the addition of a quantitative criterion based on the equivalent widths of the HeI{lambda}4471, HeII{lambda}4542, and HeII{lambda}4686 spectral lines. The GOSSS O Vz and O V populations resulting from the newly adopted spectral classification criteria are comparatively analyzed. The locations of the O Vz stars are probed, showing a concentration of the most extreme cases toward the youngest star-forming regions. The occurrence of the Vz spectral peculiarity in a solar-metallicity environment, as predicted by the FASTWIND code, is also investigated, confirming the importance of taking into account several processes for the correct interpretation of the phenomenon.
