- ID:
- ivo://CDS.VizieR/J/other/JDSO/6.30
- Title:
- New Wide Common Proper Motion Binaries
- Short Name:
- J/other/JDSO/6.3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work we report the discovery of 150 new double stars of which 142 are wide common proper motion stellar systems. In addition to this, we report the study of 23 recently catalogued wide common proper motion binaries discovered by other observers. Spectral types, photometric distances, kinematics and ages were determined from data obtained consulting the literature. Several criteria were used to determine the nature of each double star. Orbital periods and the semimajor axes were calculated.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/106/1906
- Title:
- NGC 6611: A Cluster Caught in the Act
- Short Name:
- J/AJ/106/1906
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have combined optical CCD photometry and spectroscopy with infrared imaging photometry to study the young cluster NGC 6611. We use these data to derive improved values for the reddening law (R=3.75) and the distance modulus (m-M=11.5), and to construct a physical H-R diagram from which we can probe the ages, masses, and evolutionary states of this stellar ensemble. The H-R diagram shows a strong population of high-mass stars, the most massive of which has a mass of roughly 80 solar masses, similar to what we find in other Galactic and Magellanic Cloud clusters and associations. The age of the massive stellar population in NGC 6611 is approximately 2 million years, with an age spread of, perhaps, a million years, although the data are also consistent with there being no discernible age spread among the most massive stars. However, the H-R diagram does reveal that one star of somewhat lower mass (30 solar masses) must have formed approximately 6 million years ago. The upper end of the mass function of NGC 6611 is found to have a slope of Gamma=-1.1+/-0.3, indistinguishable from a Salpeter slope, and similar to what we have found in other Galactic associations, but shallower than what we have found in the Magellanic Clouds. Our most significant result, however, is that we catch this cluster in the act of forming intermediate mass (3-8 Solar masses) stars. This is the first well-established case where large numbers of intermediate-mass stars have been seen on their way to the zero-age main sequence. That intermediate mass pre-main sequence stars are indeed present is evidenced both by their location above the zero-age main sequence in the H-R diagram, and in some cases by their spectroscopic and infrared signatures of (possibly remnant protostellar) circumstellar material. The pre-main sequence population ranges from as young as 0.25 million years to at least 1 million years of age. We find an highly unusual number (27) of emission-line stars, which appear quite similar in their optical and infrared continuum and optical spectroscopic properties to "classical Be/Ae" stars (as opposed to Herbig Be/Ae stars). Our data are inconsistent with the traditional interpretation that these "classical Be/Ae" stars are slightly evolved stars undergoing mass loss. Instead, we offer the conjecture that these may be young stars whose circumstellar disks have become optically thin, and produce Balmer emission lines. The infrared data do indicate a number of stars, particularly amongst the embedded sample, whose colors are consistent with those of stars thought to be surrounded by optically thick circumstellar accretion disks. The identification of such disks around young massive stars continues to be rare, and implies that the disk survival times around intermediate and high mass stars are much shorter (< 0.5Myr) than those of disks surrounding lower mass stars.
- ID:
- ivo://CDS.VizieR/V/103
- Title:
- NGP G5-M stars RV, DDO and BV photometry
- Short Name:
- V/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities are given for some 900 stars within 15{deg} of the North Galactic Pole, including almost all such stars classified G5 or latter in the Henry-Draper Catalogue (Cat. <III/135>). Luminosities, two-dimensional spectral classes, composition indices, and distances are derived for the majority of the sample through DDO and BV photometry. The radial velocities come from several instruments (see the "Note(2)" section below) ; the BV and DDO photometries were obtained at Mount Laguna Observatory, with the San Diego State University 24-inch Schmidt reflector.
- ID:
- ivo://CDS.VizieR/J/AJ/138/466
- Title:
- NSVS variables automated classification
- Short Name:
- J/AJ/138/466
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 4659 variable objects in the Northern Sky Variability Survey. We have classified each of these objects into one of the five variable star classes: (1) Algol/alpha Lyr systems including semidetached, and detached eclipsing binaries, (2) W Ursae Majoris overcontact and ellipsoidal variables, (3) long-period variables such as Cepheid and Mira-type objects, (4) RR Lyr pulsating variables, and (5) short-period variables including delta Scuti stars. All the candidates have outside of eclipse magnitudes of ~10-13.
- ID:
- ivo://CDS.VizieR/J/ApJS/2/389
- Title:
- Observations of O and B stars
- Short Name:
- J/ApJS/2/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog of O and B stars contains magnitudes, colors, spectral types and polarization for 1259 stars. In addition to observations, the catalogue contains the derived absorption and distance modulus. A photoelectric photometer attached to the 82-inch (2m) reflector of the McDonald Observatory was used for the polarization observations. The photometric UBV observations were made over a period of 4 years with the 13-inch (33cm) and the 82-inch telescopes at McDonald. The spectroscopic classification was made with a new camera installed on the Cassegrain spectrograph, with a dispersion of 86{AA}/mm at H{delta}.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A101
- Title:
- OB stars in Cygnus OB2 association
- Short Name:
- J/A+A/543/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cygnus OB2 association and its surroundings display the richest collection of massive stars in our nearby Galactic environment and a wealth of signposts of the interaction between these stars and the interstellar gas. We perform a magnitude-limited, homogeneous census of O and early B-type stars with accurate spectral classifications in the blue, in a 6{deg}x4{deg} region centered on Cygnus OB2 that includes most of the Cygnus X complex, a sizeable fraction of the adjacent Cygnus OB9 association, and a large area of the field surrounding these complexes
- ID:
- ivo://CDS.VizieR/J/A+A/657/A62
- Title:
- OB stars spectral classification automated tool
- Short Name:
- J/A+A/657/A62
- Date:
- 17 Mar 2022 14:50:02
- Publisher:
- CDS
- Description:
- As an increasing number of spectroscopic surveys become available, an automated approach to spectral classification becomes necessary. Due to the significance of the massive stars, it is of great importance to identify the phenomenological parameters of these stars (e.g., the spectral type), which can be used as proxies to their physical parameters (e.g., mass and temperature). In this work, we aim to use the random forest (RF) algorithm to develop a tool for the automated spectral classification of OB-type stars according to their sub-types. We used the regular RF algorithm, the probabilistic RF (PRF), which is an extension of RF that incorporates uncertainties, and we introduced the KDE-RF method which is a combination of the kernel-density estimation and the RF algorithm. We trained the algorithms on the equivalent width (EW) of characteristic absorption lines measured in high-quality spectra (Signal-to-Noise (S/N)>50) from large Galactic (LAMOST, GOSSS) and extragalactic surveys (2dF, VFTS) with available spectral types and luminosity classes. By following an adaptive binning approach, we grouped the labels of these data in 11 spectral classes within the O2-B9 range. We examined which of the characteristic spectral lines (features) are more important for the classification based on a number of feature selection methods, and we searched for the optimal hyperparameters of the classifiers to achieve the best performance. From the feature-screening process, we find that the full set of 17 spectral lines is needed to reach the maximum performance per spectral class. We find that the overall accuracy score is ~70%, with similar results across all approaches. We apply our model in other observational data sets providing examples of the potential application of our classifier to real science cases. We find that it performs well for both single massive stars and for the companion massive stars in Be X-ray binaries, especially for data of similar quality to the training sample. In addition, we propose a reduced ten-features scheme that can be applied to large data sets with lower S/N~20-50. The similarity in the performances of our models indicates the robustness and the reliability of the RF algorithm when it is used for the spectral classification of early-type stars. The score of ~70% is high if we consider (a) the complexity of such multiclass classification problems (i.e., 11 classes), (b) the intrinsic scatter of the EW distributions within the examined spectral classes, and (c) the diversity of the training set since we use data obtained from different surveys with different observing strategies. In addition, the approach presented in this work is applicable to products from different surveys in terms of quality (e.g., different resolution) and different formats (e.g., absolute or normalized flux), while our classifier is agnostic to the luminosity class of a star, and, as much as possible, it is metallicity independent.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A7
- Title:
- Of-type stars in N206 in the LMC
- Short Name:
- J/A+A/609/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars severely influence their environment by their strong ionizing radiation and by the momentum and kinetic energy input provided by their stellar winds and supernovae. Quantitative analyses of massive stars are required to understand how their feedback creates and shapes large scale structures of the interstellar medium. The giant HII region N 206 in the Large Magellanic Cloud contains an OB association that powers a superbubble filled with hot X-ray emitting gas, serving as an ideal laboratory in this context. We aim to estimate stellar and wind parameters of all OB stars in N 206 by means of quantitative spectroscopic analyses. In this first paper, we focus on the nine Of-type stars located in this region. We determine their ionizing flux and wind mechanical energy. The analysis of nitrogen abundances in our sample probes rotational mixing. We obtained optical spectra with the multi-object spectrograph FLAMES at the ESO-VLT. When possible, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. Detailed spectral classifications are presented for our sample Of-type stars. For the quantitative spectroscopic analysis we used the Potsdam Wolf-Rayet model atmosphere code. We determined the physical parameters and nitrogen abundances of our sample stars by fitting synthetic spectra to the observations. The stellar and wind parameters of nine Of-type stars, which are largely derived from spectral analysis are used to construct wind momentum - luminosity relationship. We find that our sample follows a relation close to the theoretical prediction, assuming clumped winds. The most massive star in the N 206 association is an Of supergiant that has a very high mass-loss rate. Two objects in our sample reveal composite spectra, showing that the Of primaries have companions of late O subtype. All stars in our sample have an evolutionary age of less than 4 million yr, with the O2-type star being the youngest. All these stars show a systematic discrepancy between evolutionary and spectroscopic masses. All stars in our sample are nitrogen enriched. Nitrogen enrichment shows a clear correlation with increasing projected rotational velocities. The mechanical energy input from the Of stars alone is comparable to the energy stored in the N 206 superbubble as measured from the observed X-ray and H{alpha} emission.
- ID:
- ivo://CDS.VizieR/J/AJ/142/140
- Title:
- Optical spectroscopy of {rho} Oph stars. II.
- Short Name:
- J/AJ/142/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3deg^2^ of the {rho} Ophiuchi star-forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased toward particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function. We have obtained over 300 optical spectra to help identify 135 association members based on the presence of H{alpha} in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or extinction considerations.
- ID:
- ivo://CDS.VizieR/J/ApJS/119/141
- Title:
- Oxygen-rich dust shells IR spectral classification
- Short Name:
- J/ApJS/119/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents infrared spectral classifications for a flux-limited sample of 635 optically identified oxygen-rich variables including supergiants and sources on the asymptotic giant branch (AGB). Several classes of spectra from oxygen-rich dust exist, and these can be arranged in a smoothly varying sequence of spectral shapes known as the silicate dust sequence. Classification based on this sequence reveals several dependencies of the dust emission on the properties of the central star. Nearly all S stars show broad emission features from alumina dust, while most of the supergiants exhibit classic features from amorphous silicate dust. Mira variables with symmetric light curves generally show broad alumina emission, while those with more asymmetric light curves show classic silicate emission. These differences may arise from differences in the photospheric C/O ratio.
