- 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.
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Search Results
- 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/A+A/570/A1
- Title:
- Cygnus-X CO and SiO outflows datacubes
- Short Name:
- J/A+A/570/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a PdBI study of six massive dense cores in Cygnus-X, with CO (2-1) and SiO (2-1) emission. We studied the outflows of the individual protostars with CO (Duarte-Cabral et al., 2013A&A...558A.125D), and investigated the interstellar shocks responsible for the SiO emission (in Duarte-Cabral et al. 2014A&A...570A...1D).
4146. Cygnus X-3 IR spectra
- ID:
- ivo://CDS.VizieR/J/MNRAS/308/473
- Title:
- Cygnus X-3 IR spectra
- Short Name:
- J/MNRAS/308/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four epochs, A, B, C and D, of resolution ({lambda}/{delta}{lambda}) = 1200, 2.12 micron spectroscopy of the peculiar X-ray binary Cygnus X-3. About a half dozen spectra taken with resolution 900, and at 1.62 micron are also included. These data were obtained using the FSpec near-infrared spectrometer (Williams, D., Thompson, C.L., Rieke, G.H., Montgomery, E. 1993, Proc. SPIE 1308, 482) on the Multiple Mirror Telescope (MMT). The MMT is located at an elevation of 2600 m at the top of Mt. Hopkins in southern Arizona and is jointly operated by the Smithsonian Astrophysics Observatory and the University of Arizona. The spectra are stored as ascii files, listing wavelength in Angstroms and relative flux. Each file contains a five line header, giving the UT, Heliocentric Julian date and phase of the X-ray system at the start of the integration, followed by the data points. Additional information about the spectra can be obtained in the paper.
4147. Cyg OB2 XMM observations
- ID:
- ivo://CDS.VizieR/J/A+A/536/A31
- Title:
- Cyg OB2 XMM observations
- Short Name:
- J/A+A/536/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cyg OB2 is one of the most massive associations of O-type stars in our Galaxy. Despite the large interstellar reddening towards Cyg OB2, many studies, spanning a wide range of wavelengths, have been conducted to more clearly understand this association. X-ray observations provide a powerful tool to overcome the effect of interstellar absorption and study the most energetic processes associated with the stars in Cyg OB2. We analyse XMM-Newton data to investigate the X-ray and UV properties of massive O-type stars as well as low-mass pre-main sequence stars in Cyg OB2.
4148. Cyg X-1 JK light curves
- ID:
- ivo://CDS.VizieR/J/other/PZ/28.7
- Title:
- Cyg X-1 JK light curves
- Short Name:
- J/other/PZ/28.7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our long-term (13 years) J and K photometry of the X-ray binary Cyg X-1. The object's JK variability amplitudes were less than 0.2mag. The J and K orbital light curves are appreciably asymmetric in quadratures. The secondary minimum is deeper, in comparison to the primary, and it is probable that the star becomes hotter at secondary minima.
- ID:
- ivo://CDS.VizieR/J/A+A/447/245
- Title:
- Cyg X-1 Spectral Evolution 1999-2004
- Short Name:
- J/A+A/447/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuing the observational campaign initiated by our group, we present the long term spectral evolution of the Galactic black hole candidate Cygnus X-1 in the X-rays and at 15GHz. We present about 200 pointed observations taken between early 1999 and late 2004 with the Rossi X-ray Timing Explorer and the Ryle radio telescope. The X-ray spectra are remarkably well described by a simple broken power law spectrum with an exponential cutoff. Physically motivated Comptonization models, e.g., by Titarchuk (1994ApJ...434..570T, compTT) and by Coppi (1999, eqpair), can reproduce this simplicity; however, the success of the phenomenological broken power law models cautions against ``over-parameterizing'' the more physical models. Broken power law models reveal a significant linear correlation between the photon index of the lower energy power law and the hardening of the power law at about 10keV. This phenomenological soft/hard power law correlation is partly attributable to correlations of broad band continuum components, rather than being dominated by the weak hardness/reflection fraction correlation present in the Comptonization model. Specifically, the Comptonization models show that the bolometric flux of a soft excess (e.g., disk component) is strongly correlated with the compactness ratio of the Comptonizing medium, with L_disk{propto}(l_h_/l_s_)^-0.19^. Over the course of our campaign, Cyg X-1 transited several times into the soft state, and exhibited a large number of ``failed state transitions''. The fraction of the time spent in such low radio emission/soft X-ray spectral states has increased from about 10% in 1996-2000 to about 34% since early 2000. We find that radio flares typically occur during state transitions and failed state transitions (at l_h_/l_s_~3), and that there is a strong correlation between the 10-50keV X-ray flux and the radio luminosity of the source. We demonstrate that rather than there being distinctly separated states, in contrast to the timing properties the spectrum of Cyg X-1 shows variations between extremes of properties, with clear cut examples of spectra at every intermediate point in the observed spectral correlations.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A49
- Title:
- CzeV404 Her light curves and spectra
- Short Name:
- J/A+A/652/A49
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a new study of the eclipsing cataclysmic variable CzeV404 Her (Porb=0.098d) located in the period gap. This report aims to determine the object's origin, system parameters and probe the system's accretion flow structure. We conducted simultaneous time-resolved photometric and spectroscopic observations of CzeV404 Her. We applied our light curve modeling techniques and the Doppler tomography method to determine the system parameters and analyse the structure of the accretion disk. We found that the system has a massive white dwarf M_WD_=1.00(2)M_{sun}_, a mass ratio of q=0.16, and a relatively hot secondary with an effective temperature T_2_=4100(50)K. The system inclination is 78{deg}. The accretion disk spreads out to the tidal limitation radius and has an extended hot spot/line region. The hot spot/line is hotter than the rest of the disk's outer part in quiescence or intermediate state but does not stand out completely from the disk flux in (super)outbursts. We claim that this object represents a link between two distinct classes of SU UMa-type and SW Sex-type cataclysmic variables. The accretion flow structure in the disk corresponds to the SW Sex systems, but the physical conditions inside the disk passed into behaviors of SU UMa-type objects.