- ID:
- ivo://CDS.VizieR/J/A+AS/137/113
- Title:
- Walraven photometry of OB stars
- Short Name:
- J/A+AS/137/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of OB-stars, made in 1959 and 1960 at the Leiden Southern Station near Hartebeespoortdam, South Africa, with the VBLUW photometer attached to th e 90 cm light-collector, are given in this paper. They are compared with photome try obtained by Graham (1968BANS....2..397G), Walraven & Walraven (1977BAN....15...67W), Lub & Pel (1977A&A....54..137L) and van Genderen et al. (1984A&AS...58..537V). Formulae for the transformation of the present observations to those of Walraven & Walraven (1977BAN....15...67W) and Lub & Pel (1977A&A....54..137L) are given. For a description of the VBLUW photometric system, see e.g. <GCPD/11>
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1741
- Title:
- Warped disks of YSOs in Galactic center
- Short Name:
- J/ApJ/697/1741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central parsec around the supermassive black hole in the Galactic center (GC) hosts more than 100 young and massive stars. Outside the central cusp (R~1") the majority of these O and Wolf-Rayet (W-R) stars reside in a main clockwise system, plus a second, less prominent disk or streamer system at large angles with respect to the main system. Here we present the results from new observations of the GC with the AO-assisted near-infrared imager NACO and the integral field spectrograph SINFONI on the ESO/VLT. These include the detection of 27 new reliably measured W-R/O stars in the central 12" and improved measurements of 63 previously detected stars, with proper motion uncertainties reduced by a factor of 4 compared to our earlier work. Based on the sample of 90 well measured W-R/O stars, we develop a detailed statistical analysis of their orbital properties and orientations. We show that half of the W-R/O stars are compatible with being members of a clockwise rotating system.
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/145
- Title:
- XMM observations of HD 191612 field
- Short Name:
- J/MNRAS/375/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the XMM-Newton observatory, we have observed the peculiar Of?p star HD 191612. The field contains a hundred individual X-ray sources. In this table we present the average X-ray count rates of these sources and their cross-identifications with several catalogues.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A45
- Title:
- X-ray detections in the {sigma} Ori cluster
- Short Name:
- J/A+A/521/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the X-ray emission from young stars and brown dwarfs in the {sigma} Orionis cluster ({tau}=~3Ma, d=~385pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory.
- ID:
- ivo://CDS.VizieR/J/ApJ/574/258
- Title:
- X-ray-emitting young stars in the Orion nebula
- Short Name:
- J/ApJ/574/258
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion Nebula Cluster (ONC) and the molecular cloud (OMC) in its vicinity have been observed with the ACIS-I detector on board the Chandra X-ray Observatory with 23hr exposure in two observations, on 1999 October 12 and 2000 April 1. We detect 1075 X-ray sources, most with sub-arcsecond positional accuracy. Ninety-one percent of the sources are spatially associated with known stellar members of the cluster, and an additional 7% are newly identified deeply embedded cloud members.
- ID:
- ivo://CDS.VizieR/J/A+A/477/593
- Title:
- X-ray properties of Carina OB1 association
- Short Name:
- J/A+A/477/593
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars. A timing and spectral analysis of five observations with XMM-Newton is performed using various statistical tests and thermal spectral models. 235 point sources have been detected within the field of view. Several of these sources are probably pre-main sequence stars with characteristic short-term variability. Seven sources are possible background AGNs. Spectral analysis of twenty three sources of type OB and WR 25 was performed. We derived spectral parameters of the sources and their fluxes in three energy bands. Estimating the interstellar absorption for every source and the distance to the nebula, we derived X-ray luminosities of these stars and compared them to their bolometric luminosities. We discuss possible reasons for the fact that, on average, the observed X-ray properties of binary and single early type stars are not very different, and give several possible explanations.
- ID:
- ivo://CDS.VizieR/J/ApJS/184/84
- Title:
- X-ray sources in Cyg OB2 region
- Short Name:
- J/ApJS/184/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 1696 X-ray sources detected in the massive star forming region (SFR) Cygnus OB2 and extracted from two archival Chandra observations of the center of the region. A deep source extraction routine, exploiting the low background rates of Chandra observations was employed to maximize the number of sources extracted. Observations at other wavelengths were used to identify low count-rate sources and remove likely spurious sources. Monte Carlo simulations were also used to assess the authenticity of these sources. X-ray spectra were fitted with thermal plasma models to characterize the objects and X-ray light curves were analyzed to determine their variability. We used a Bayesian technique to identify optical or near-IR counterparts for 1501 (89%) of our sources, using deep observations from the INT Photometric H-alpha Survey, the Two Micron All Sky Survey, and the UKIRT Infrared Deep Sky Survey-Galactic plane Survey. 755 (45%) of these objects have six-band r', H-alpha, i', J, H, and K optical and near-IR photometry. From an analysis of the Poisson false-source probabilities for each source we estimate that our X-ray catalogue includes <1% of false sources, and an even lower fraction when only sources with optical or near-IR associations are considered. A Monte Carlo simulation of the Bayesian matching scheme allows this method to be compared to more simplified matching techniques and enables the various sources of error to be quantified. The catalogue of 1696 objects presented here includes X-ray broad band fluxes, model fits, and optical and near-IR photometry in what is one of the largest X-ray catalogue of a single SFR to date. The high number of stellar X-ray sources detected from relatively shallow observations confirms the status and importance of Cygnus OB2 as one of our Galaxy's most massive SFRs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3089
- Title:
- Young clumps embedded in IRDC
- Short Name:
- J/MNRAS/451/3089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of starless and protostellar clumps associated with infrared dark clouds (IRDCs) in a 40 degrees wide region of the inner Galactic plane (|b|<=1). We have extracted the far-infrared (FIR) counterparts of 3493 IRDCs with known distance in the Galactic longitude range 15<=l<=55 and searched for the young clumps using Herschel infrared Galactic plane survey, the survey of the Galactic plane carried out with the Herschel satellite. Each clump is identified as a compact source detected at 160, 250 and 350um. The clumps have been classified as protostellar or starless, based on their emission (or lack of emission) at 70um. We identify 1723 clumps, 1056 (61%) of which are protostellar and 667 (39%) starless. These clumps are found within 764 different IRDCs, 375 (49%) of which are only associated with protostellar clumps, 178 (23%) only with starless clumps, and 211 (28%) with both categories of clumps. The clumps have a median mass of ~250M_{sun}_ and range up to >10^4^M_{sun}_ in mass and up to 10^5^L_{sun}_ in luminosity. The mass-radius distribution shows that almost 30% of the starless clumps identified in this survey could form high-mass stars; however these massive clumps are confined in only 4% of the IRDCs. Assuming a minimum mass surface density threshold for the formation of high-mass stars, the comparison of the numbers of massive starless clumps and those already containing embedded sources suggests an upper limit lifetime for the starless phase of ~10^5^yr for clumps with a mass M>500M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A57
- Title:
- Young, massive star candidates in Sgr A*
- Short Name:
- J/A+A/549/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nuclear star clusters (NSCs) are ubiquitous at the centers of galaxies. They show mixed stellar populations and the spectra of many NSCs indicate recent events of star formation. However, it is impossible to resolve external NSCs in order to examine the relevant processes. The Milky Way NSC, on the other hand, is close enough to be resolved into its individual stars and presents therefore a unique template for NSCs in general. Young, massive stars have been found by systematic spectroscopic studies at projected distances R<~0.5pc from the supermassive black hole, Sagittarius A* (Sgr A*). In recent years, increasing evidence has been found for the presence of young, massive stars also at R>0.5pc. Our goal in this work is a systematic search for young, massive star candidates throughout the entire region within R~2.5pc of the black hole.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A17
- Title:
- Young population in Vela-Puppis region
- Short Name:
- J/A+A/626/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Vela-Puppis region is known to host the Vela OB2 association as well as several young clusters featuring OB and pre-main-sequence stars. Several spatial and kinematic subgroups have been identified in recent years. By grouping stars based on their positions and velocity, we can address the question of the dynamical history of the region and the mechanisms that drove stellar formation. The Gaia DR2 astrometry and photometry enables us to characterise the 3D spatial and 3D kinematic distribution of young stars and to estimate the ages of the identified components. We used an unsupervised classification method to group stars based on their proper motions and parallax. We studied the expansion rates of the different identified groups based on 3D velocities and on corrected tangential velocities. We used theoretical isochrones to estimate ages. The young stars can be separated into seven main groups of different ages and kinematical distribution. All groups are found to be expanding, although the expansion is mostly not isotropic. The size of the region, the age substructure, and the anisotropic expansion rates are compatible with a prolonged period of star formation in a turbulent molecular cloud. The current kinematics of the stars cannot be explained by internal processes alone (such as gas expulsion).
