- ID:
- ivo://CDS.VizieR/J/A+A/352/600
- Title:
- O & B stars uvby-Hbeta photometry. I.
- Short Name:
- J/A+A/352/600
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stroemgren and H{beta} photometry of OB-stars generally brighter than 9.5mag in the Canis Major - Puppis - Vela region of Milky Way is reported. The observations are based on the Milky Way luminous-star (LS) identifications and are designed to create a complete, magnitude-limited sample of LS for this field. We present new uvby photometry for 127 LS and H{beta} photometry for 25 of them. These observations are part of an ongoing effort to improve the completeness of the existing uvby{beta} data-base for the bright OB-type stars in the Milky Way, with the aim to investigate the structure of selected star-forming regions.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/352/605
- Title:
- O & B stars uvby-Hbeta photometry. II.
- Short Name:
- J/A+A/352/605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stroemgren and H{beta} photometry of O and B type stars, generally brighter than 10mag is presented for the fields of the galactic OB associations Monoceros OB2, Canis Major OB1 and Collinder 121. The observations are based on the PPM catalogue identifications and are designed to improve the completeness of the existing uvby{beta} data for the bright early-type stars in these fields. We present new uvby photometry for 343 stars and H{beta} photometry for 213 of them. These observations are part of our effort to study the structure of selected star-forming regions in the Milky Way, utilizing uvby{beta} photometry.
- ID:
- ivo://CDS.VizieR/J/A+AS/146/365
- Title:
- O & B stars uvby-Hbeta photometry. III.
- Short Name:
- J/A+AS/146/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stroemgren and H{beta} photometry of O and B type stars, generally brighter than 9.5 mag is reported for the field of the Carina Spiral Feature. The observations are based on the PPM (Cat. <I/193>) catalogue identifications and are designed to improve the completeness of the existing uvby{beta} data for the bright early-type stars in the field. We present new uvby photometry for 283 stars and H{beta} photometry for 225 of them. These observations are part of an ongoing effort to study the structure of selected star-forming regions in the Milky Way by means of uvby{beta} photometry. A comparison of the new data to other uvby{beta} data sets for this field is presented.
- ID:
- ivo://CDS.VizieR/J/AN/331/349
- Title:
- O, B-type & red supergiant masses and luminosities
- Short Name:
- J/AN/331/349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars are of interest as progenitors of supernovae, i.e. neutron stars and black holes, which can be sources of gravitational waves. Recent population synthesis models can predict neutron star and gravitational wave observations but deal with a fixed supernova rate or an assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernova progenitors, i.e. with O- and early B-type stars, and also all supergiants within 3kpc. We restrict our sample to those massive stars detected both in 2MASS and observed by Hipparcos, i.e. only those stars with parallax and precise photometry. To determine the luminosities we calculated the extinctions from published multi-colour photometry, spectral types, luminosity class, all corrected for multiplicity and recently revised Hipparcos distances. We use luminosities and temperatures to estimate the masses and ages of these stars using different models from different authors.
- ID:
- ivo://CDS.VizieR/J/AJ/134/2385
- Title:
- Occulting galaxy pairs in SDSS
- Short Name:
- J/AJ/134/2385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spiral galaxy partially overlapping a more distant elliptical offers a unique opportunity to measure the dust extinction in the foreground spiral. From the Sloan Digital Sky Survey (SDSS) DR4 spectroscopic sample, we selected 83 occulting galaxy pairs and measured disk opacity over the redshift range z=0.0-0.2 with the goal of determining the recent evolution of disk dust opacity. The enrichment of the ISM changes over the lifetime of a disk, and it is reasonable to expect the dust extinction properties of spiral disks as a whole to change over their lifetime. When they do, the change will affect our measurements of galaxies over the observable universe. From the SDSS pairs we conclude that spiral disks show evidence of extinction to ~2 effective radii.
- ID:
- ivo://CDS.VizieR/J/AJ/161/46
- Title:
- (O-C) curve of the binary system KIC 06852488
- Short Name:
- J/AJ/161/46
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- The continuous and unbroken time-series photometry data of Kepler and the Transiting Exoplanet Survey Satellite (TESS) provide a good opportunity to study the continuous variations in the light curve of binary stars. This paper reports the discoveries of the correlation between the two maxima on the light curve of KIC06852488 and the correlation between the O'Connell effect and the O-C curve. The Max I and Max II vary with a same cycle length of ~2000days and a 180{deg} phase difference, and the variation of the Max II coincides with the O-C curve of the primary light minima. After analyzing the Kepler and TESS light curves, it is detected that this binary is a semi-detached system with a mass ratio of 0.4622({+/-}0.0036). The secondary component is filling its critical Roche lobe, while the primary component is only filling 12.25({+/-}0.10)% of the lobe volume that contributes more than 85% luminosity of the total system. The variation of the O'Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component. It is found that their positions are symmetrical with the inner Lagrange L1 point. After subtracting the binary brightness changes, six optical flares are detected that come from the cool secondary. We calculated the energy of flares and found that all of the flares are superflares. Both the flares and an evolving dark spot on the lobe-filling secondary component make the system a very interesting source to investigate the effects of binary interaction on the magnetic activities.
4607. OCSVM anomalies
- ID:
- ivo://CDS.VizieR/J/A+A/606/A39
- Title:
- OCSVM anomalies
- Short Name:
- J/A+A/606/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wide-angle photometric surveys of previously uncharted sky areas or wavelength regimes will always bring in unexpected sources - novelties or even anomalies - whose existence and properties cannot be easily predicted from earlier observations. Such objects can be efficiently located with novelty detection algorithms. Here we present an application of such a method, called one-class support vector machines (OCSVM), to search for anomalous patterns among sources preselected from the mid-infrared AllWISE catalogue covering the whole sky. To create a model of expected data we train the algorithm on a set of objects with spectroscopic identifications from the SDSS DR13 database, present also in AllWISE. The OCSVM method detects as anomalous those sources whose patterns - WISE photometric measurements in this case - are inconsistent with the model. Among the detected anomalies we find artefacts, such as objects with spurious photometry due to blending, but more importantly also real sources of genuine astrophysical interest. Among the latter, OCSVM has identified a sample of heavily reddened AGN/quasar candidates distributed uniformly over the sky and in a large part absent from other WISE-based AGN catalogues. It also allowed us to find a specific group of sources of mixed types, mostly stars and compact galaxies. By combining the semi-supervised OCSVM algorithm with standard classification methods it will be possible to improve the latter by accounting for sources which are not present in the training sample, but are otherwise well-represented in the target set. Anomaly detection adds flexibility to automated source separation procedures and helps verify the reliability and representativeness of the training samples. It should be thus considered as an essential step in supervised classification schemes to ensure completeness and purity of produced catalogues.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/L114
- Title:
- OGLE16aaa UVOT light curves
- Short Name:
- J/MNRAS/465/L114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery and first three months of follow-up observations of a currently on-going unusual transient detected by the Optical Gravitational Lensing Experiment (OGLE-IV) survey, located in the centre of a galaxy at redshift z=0.1655. The long rise to absolute magnitude of -20.5mag, slow decline, very broad He and H spectral features make OGLE16aaa similar to other optical/UV tidal disruption events (TDEs). Weak narrow emission lines in the spectrum and archival photometric observations suggest the host galaxy is a weak-line active galactic nucleus, which has been accreting at higher rate in the past. OGLE16aaa, along with SDSS J0748, seems to form a sub-class of TDEs by weakly or recently active supermassive black holes (SMBHs). This class might bridge the TDEs by quiescent SMBHs and flares observed as "changing-look quasars", if we interpret the latter as TDEs. If this picture is true, the previously applied requirement for identifying a flare as a TDE that it had to come from an inactive nucleus, could be leading to observational bias in TDE selection, thus affecting TDE-rate estimations.
- ID:
- ivo://CDS.VizieR/J/A+A/478/659
- Title:
- OGLE Be stars in Galactic Bulge
- Short Name:
- J/A+A/478/659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first systematic search for Be star candidates in the direction of the Galactic Bulge. We present the full catalogue, give a brief description of the stellar variability seen, and show some light curve examples. We searched for stars matching specific criteria of magnitude, color and variability in the I band. Our search was conducted on the 48 OGLE II fields of the Galactic Bulge.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/136
- Title:
- OGLE-2013-BLG-446 photometry
- Short Name:
- J/ApJ/812/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For all exoplanet candidates, the reliability of a claimed detection needs to be assessed through a careful study of systematic errors in the data to minimize the false positives rate. We present a method to investigate such systematics in microlensing data sets using the microlensing event OGLE-2013-BLG-0446 as a case study. The event was observed from multiple sites around the world and its high magnification (A_max_~3000) allowed us to investigate the effects of terrestrial and annual parallax. Real-time modeling of the event while it was still ongoing suggested the presence of an extremely low-mass companion (~3M_{Earth}_) to the lensing star, leading to substantial follow-up coverage of the light curve. We test and compare different models for the light curve and conclude that the data do not favor the planetary interpretation when systematic errors are taken into account.
