- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3879
- Title:
- Cygnus OB1 association stars radial velocities
- Short Name:
- J/MNRAS/465/3879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main objective of this study is the characterization of the velocity field in the Cygnus OB1 association using the radial velocity data currently available in the literature. This association is part of a larger star-forming complex located in the direction of the Cygnus region, but whose main subsystems may be distributed at different distances from the sun. We have collected radial velocity data for more than 300 stars in the area of 5x5 square degrees centred on the Cygnus OB1 association. We present the results of a kinematic clustering analysis in the subspace of the phase space formed by angular coordinates and radial velocity using two independent methodologies. We have found evidence of structure in the phase space with the detection of two main groups, corresponding to different radial velocity and distance values, belonging to the association, and associated with two main shells defined by the Halpha emission. A third grouping well separated from the other two in velocity appears to occupy the whole region associated with what has been called "common shell".
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/2593
- Title:
- Cygnus OB2 DANCe: Proper motion study
- Short Name:
- J/MNRAS/460/2593
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-precision proper motion study of 873 X-ray and spectroscopically selected stars in the massive OB association Cygnus OB2 as part of the DANCe project. These were calculated from images spanning a 15-year baseline and have typical precisions <1mas/yr. We calculate the velocity dispersion in the two axes to be 13.0^+0.8^_-0.7_ and 9.1^+0.5^_-0.5_km/s, using a 2-component, 2-dimensional model that takes into account the uncertainties on the measurements. This gives a 3-dimensional velocity dispersion of 17.8+/-0.6km/s implying a virial mass significantly larger than the observed stellar mass, confirming that the association is gravitationally unbound. The association appears to be dynamically unevolved, as evidenced by considerable kinematic substructure, non-isotropic velocity dispersions and a lack of energy equipartition. The proper motions show no evidence for a global expansion pattern, with approximately the same amount of kinetic energy in expansion as there is in contraction, which argues against the association being an expanded star cluster disrupted by process such as residual gas expulsion or tidal heating. The kinematic substructures, which appear to be close to virial equilibrium and have typical masses of 40-400M_{sun}_, also do not appear to have been affected by the expulsion of the residual gas. We conclude that Cyg OB2 was most likely born highly substructured and globally unbound, with the individual subgroups born in (or close to) virial equilibrium, and that the OB association has not experienced significant dynamical evolution since then.
- ID:
- ivo://CDS.VizieR/J/A+A/637/A64
- Title:
- Cygnus OB2 e-MERLIN 21cm survey (COBRaS)
- Short Name:
- J/A+A/637/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of massive stars is central to an understanding of galactic ecology. It is important to establish the details of how massive stars provide radiative, chemical, and mechanical feedback in galaxies. Central to these issues is an understanding of the evolution of massive stars, and the critical role of mass loss via strongly structured winds and stellar binarity. Ultimately, and acting collectively, massive stellar clusters shape the structure and energetics of galaxies. We aim to conduct high-resolution, deep field mapping at 21cm of the core of the massive Cygnus OB2 association and to characterise the properties of the massive stars and colliding winds at this waveband. We used seven stations of the e-MERLIN radio facility, with its upgraded bandwidth and enhanced sensitivity to conduct a 21cm census of Cygnus OB2. Based on 42 hours of observations, seven overlapping pointings were employed over multiple epochs during 2014 resulting in 1{sigma} sensitivities down to ~21{mu}Jy and a resolution of ~180mas. A total of 61 sources are detected at 21cm over a ~0.48{deg}x0.48{deg} region centred on the heart of the Cyg OB2 association. Of these 61 sources, 33 are detected for the first time. We detect a number of previously identified sources including four massive stellar binary systems, two YSOs, and several known X-ray and radio sources. We also detect the LBV candidate (possible binary system) and blue hypergiant star of Cyg OB2 #12. The 21cm observations secured in the COBRaS Legacy project provide data to constrain conditions in the outer wind regions of massive stars; determine the non-thermal properties of massive interacting binaries; examine evidence for transient sources, including those associated with young stellar objects; and provide unidentified sources that merit follow-up observations. The 21cm data are of lasting value and will serve in combination with other key surveys of Cyg OB2, including Chandra and Spitzer.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A27
- Title:
- Cygnus OB1-OB4 O stars radial velocities
- Short Name:
- J/A+A/550/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Establishing the multiplicity of O-type stars is the first step towards accurately determining their stellar parameters. Moreover, the distribution of the orbital parameters provides observational clues to the way that O-type stars form and to the interactions during their evolution. Our objective is to constrain the multiplicity of a sample of O-type stars belonging to poorly investigated OB associations in the Cygnus complex and for the first time to provide orbital parameters for binaries identified in our sample. Such information is relevant to addressing the issue of the binarity in the context of O-type star formation scenarios.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A168
- Title:
- Cygnus OB2 O stars spectroscopic analysis
- Short Name:
- J/A+A/642/A168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking. In this work, we created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that have not been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars with reliable Gaia astrometry, in addition to creating the Hertzsprung- Russell Diagram to interpret the evolutionary status of the association. This work has shown the improvement reached when using accurate spectroscopic parameters and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2, at least two star-forming bursts at ~3 and ~5Myr. We find an apparent deficit of very fast rotators in the distribution of rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in the region.
- ID:
- ivo://CDS.VizieR/J/A+A/472/557
- Title:
- Cygnus OB2 region 610MHz sources
- Short Name:
- J/A+A/472/557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The modern generation of Cherenkov telescopes has revealed a new population of gamma-ray sources in the Galaxy. Some of them have been identified with previously known X-ray binary systems while other remain without clear counterparts a lower energies. Our initial goal here was reporting on extensive radio observations of the first extended and yet unidentified source, namely TeV J2032+4130. This object was originally detected by the HEGRA telescope in the direction of the Cygnus OB2 region and its nature has been a matter of debate during the latest years. The situation has become more complex with the Whipple and MILAGRO telescopes new TeV detections in the same field which could be consistent with the historic HEGRA source, although a different origin cannot be ruled out. We aim to pursue our radio exploration of the TeV J2032+4130 position that we initiated in a previous paper but taking now into account the latest results from new Whipple and MILAGRO TeV telescopes. The data presented here are an extended follow up of our previous work.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1646
- Title:
- Debris disks in Upper Sco
- Short Name:
- J/ApJ/705/1646
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present MIPS 24um and 70um photometry for 205 members of the Upper Scorpius OB Association. These data are combined with published MIPS photometry for 15 additional association members to assess the frequency of circumstellar disks around 5Myr old stars with spectral types between B0 and M5. Twelve stars have a detectable 70um excess, each of which also has a detectable 24um excess. A total of 54 stars are identified with a 24um excess more than 32% above the stellar photosphere. The MIPS observations reveal 19 excess sources - 8 A/F/G stars and 11 K/M stars - that were not previously identified with an 8um or 16um excess. The lack of short-wavelength emission and the weak 24um excess suggests that these sources are debris systems or the remnants of optically thick primordial disks with inner holes. Despite the wide range of luminosities of the stars hosting apparent debris systems, the excess characteristics are consistent with all stars having dust at similar orbital radii after factoring in variations in the radiation blowout particle size with spectral type. The results for Upper Sco are compared to similar photometric surveys from the literature to re-evaluate the evolution of debris emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/19
- Title:
- DECam phot. of Gaia stars in Price-Whelan 1
- Short Name:
- J/ApJ/887/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a young ({tau}~117Myr), low-mass (M~1200M_{sun}_), metal-poor ([Fe/H]~-1.14) stellar association at a heliocentric distance D~28.7kpc, placing it far into the Milky Way (MW) halo. At its present Galactocentric position (R,z)~(23,15)kpc, the association is (on the sky) near the leading arm of the gas stream emanating from the Magellanic Cloud system, but is located ~60{deg} from the Large Magellanic Cloud center on the other side of the MW disk. If the cluster is colocated with HI gas in the stream, we directly measure the distance to the leading arm of the Magellanic stream. The measured distance is inconsistent with Magellanic stream model predictions that do not account for ram pressure and gas interaction with the MW disk. The estimated age of the cluster is consistent with the time of last passage of the leading arm gas through the Galactic midplane; we therefore speculate that this star formation event was triggered by its last disk midplane passage. Most details of this idea remain a puzzle: the Magellanic stream has low column density, the MW disk at large radii has low gas density, and the relative velocity of the leading arm and MW gas is large. However it formed, the discovery of a young stellar cluster in the MW halo presents an interesting opportunity for study. This cluster was discovered with Gaia astrometry and photometry alone, but follow-up DECam photometry was crucial for measuring its properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/64
- Title:
- Deep infrared photometry of {sigma} Ori cluster
- Short Name:
- J/ApJ/743/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep I, Z photometric survey covering a total area of 1.12deg^2^ of the {sigma} Orionis cluster and reaching completeness magnitudes of I=22 and Z=21.5mag. From I, I-Z color-magnitude diagrams we have selected 153 candidates that fit the previously known sequence of the cluster. They have magnitudes in the range I=16-23mag, which corresponds to a mass interval from 0.1 down to 0.008M_{sun}_ at the most probable age of {sigma} Orionis (2-4Myr). Using J-band photometry, we find that 124 of the 151 candidates within the completeness of the optical survey (82%) follow the previously known infrared photometric sequence of the cluster and are probably members. We have studied the spatial distribution of the very low mass stars and brown dwarf population of the cluster and found that there are objects located at distances greater than 30 arcmin to the north and west of {sigma} Orionis that probably belong to different populations of the Orion's Belt. For the 102 bona fide {sigma} Orionis cluster member candidates, we find that the radial surface density can be represented by a decreasing exponential function ({sigma}={sigma}_0_e^-r/r_0_^) with a central density of {sigma}_0_=0.23+/-0.03 objects arcmin^-2^ and a characteristic radius of r_0_=9.5+/-0.7 arcmin. Using near-infrared JHK-band data from Two Micron All Sky Survey and UKIRT Deep Infrared Sky Survey and mid-infrared data from Infrared Array Camera/Spitzer, we find that about 5%-9% of the brown dwarf candidates in the {sigma} Orionis cluster have K-band excesses and 30%+/-7% of them show mid-infrared excesses at wavelengths longer than 5.8um. These are probably related to the presence of disks, most of which are "transition disks".
- ID:
- ivo://CDS.VizieR/J/other/ChA+A/36.238
- Title:
- Dense parts of outflows toward massive cores
- Short Name:
- J/other/ChA+A/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A set of samples of 13 massive star-forming cores were observed in SiO (2-1), CH_3_OH (2-1) and C^34^S (2-1) thermal lines. Nine of these cores were detected in all three lines. Among the nine SiO detections, three were new detections, and relatively faint. Most of the lines have wide wings, which might be interpreted as the evidence of ongoing energetic outflows in the cores.
