Search

Start Over Subject photometry
4611. OB stars extinction based in IR photometry
ID:
ivo://CDS.VizieR/J/AcA/43/209
Title:
OB stars extinction based in IR photometry
Short Name:
J/AcA/43/209
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents an extensive survey of interstellar extinction curves derived from the near IR photometric measurements of early type stars belonging to our Galaxy. This survey is more extensive and deeper than any other one, based on spectral data. The IR magnitudes of about 500 O and B type stars with E(B-V)>=0.05 were selected from literature. The IR color excesses are determined with the aid of "artificial standards". The results indicate that the extinction law changes from place to place. The mean galactic extinction curve in the near IR is very similar in different directions and changes very little from the value R=3.10+/-0.05 obtained in this paper.
4612. OB stars in NGC 6334 and NGC 6357
ID:
ivo://CDS.VizieR/J/A+A/538/A142
Title:
OB stars in NGC 6334 and NGC 6357
Short Name:
J/A+A/538/A142
Date:
21 Oct 2021
Publisher:
CDS
Description:
Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed HII regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases.
4613. O & B stars uvby-Hbeta photometry. I.
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.
4614. O & B stars uvby-Hbeta photometry. II.
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.
4615. O & B stars uvby-Hbeta photometry. III.
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.
4616. O, B-type & red supergiant masses and luminosities
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.
4617. Occulting galaxy pairs in SDSS
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.
4618. (O-C) curve of the binary system KIC 06852488
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.
4619. 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.
4620. OGLE16aaa UVOT light curves
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.