- ID:
- ivo://CDS.VizieR/J/MNRAS/298/753
- Title:
- Variables in Cygnus OB2
- Short Name:
- J/MNRAS/298/753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the photometric CCD search for B-type variables in the central region of the Cygnus OB2 association. We discover 29 new variables including two Beta Cephei stars. The photometric data in the Cousins I band are given in file photom.dat. In addition, we present BV(RI)c and H_{alpha}_ photometry for stars in the observed field. This is Table 4 of the paper, available only in electronic form.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/194/27
- Title:
- Variable stars in Cygnus OB2
- Short Name:
- J/ApJS/194/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of photometrically variable stars discovered within two 21.3'x21.3' fields centered on the Cygnus OB2 association (Cyg OB2). There have hitherto been no deep optical variability studies of Cyg OB2, despite it being replete with early-type massive stars, likely due to the high and variable extinction (up to A_V_~20) that permeates much of the region. Here, we provide results of the first variability study with this combination of spatial coverage (~0.5deg) and photometric depth (R~21mag). We find 121 stars to be variable in both R and I bands, 115 of them newly discovered. Of the 121 variables, we identify 27 eclipsing binaries and eclipsing-binary candidates, 52 pulsating variables, and 20 potential Herbig Ae/Be stars. Confirming both the status and the cluster membership of the Herbig Ae/Be stars would address the uncertainty regarding the age and star formation history of Cyg OB2. We match our catalog to known variables and binaries in the region, Two Micron All Sky Survey near-IR data, and Chandra X-ray observations to find counterparts to new variables in other wavelengths.
383. Vela OB2 members
- ID:
- ivo://CDS.VizieR/J/A+A/621/A115
- Title:
- Vela OB2 members
- Short Name:
- J/A+A/621/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Vela OB2 association is a group of 10Myr stars exhibiting a complex spatial and kinematic substructure. The all-sky Gaia DR2 catalogue contains proper motions, parallaxes (a proxy for distance) and photometry that allow us to separate the various components of Vela OB2. We characterise the distribution of the Vela OB2 stars on a large spatial scale, and study its internal kinematics and dynamic history. We make use of Gaia DR2 astrometry and published Gaia-ESO Survey data. We apply an unsupervised classification algorithm to determine groups of stars with common proper motions and parallaxes. We find that the association is made up of a number of small groups, with a total current mass over 2330M_{sun}_. The three-dimensional distribution of these young stars trace the edge of the gas and dust structure known as the IRAS Vela Shell across 180 pc and shows clear signs of expansion. We propose a common history for Vela OB2 and the IRAS Vela Shell. The event that caused the expansion of the shell happened before the Vela OB2 stars formed, imprinted the expansion in the gas the stars formed from, and most likely triggered star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A83
- Title:
- Velocities of interstellar lines in Sco-Cen
- Short Name:
- J/A+A/512/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to make a large-scale study of the morphology, kinematics, and origin of the HI, which surrounds the Sco-Cen association. We combine our high-sensitivity southern HI survey with the Leiden/Dwingeloo Survey, considering l=240{deg}-400{deg}, b=-60{deg} to +60{deg}, and radial velocities of V=-41.8 to +40.8km/s. We point out the main HI branches surrounding the association and derive their kinematics. Kinematical HI-maps were compared with spatial maps of interstellar (IS) NaI from the literature. Upper limits for distances d were derived from optical IS absorption components from the literature. Models of expanding spherical HI shells were fitted around each stellar subgroup.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/518
- Title:
- Velocity and proper motion of OB associations
- Short Name:
- J/MNRAS/400/518
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The proper motions of OB-associations computed using the old (1997, Cat. <I/239>) and new (2008, Cat. <I/311>) reductions of the Hipparcos data are in a good agreement with each other. The Galactic rotation curve derived from the analysis of line-of-sight velocities and proper motions of OB-associations is almost flat in the 3-kpc neighborhood of the Sun. The angular rotation velocity at the solar distance is Omega_0_=31(+/-1)km/s/kpc. The standard deviation of the velocities of OB-associations from the rotation curve is sigma=7.2km/s. The distance scale for OB associations by Blaha and Humpreys (1989AJ.....98.1598B) should be shortened by 10-20%. The residual velocities of OB-associations calculated for the new and old reductions differ, on average, by 3.5km/s. The mean residual velocities of OB-associations in the stellar-gas complexes depend slightly on the data reduction employed.
- ID:
- ivo://CDS.VizieR/J/other/BASI/29.519
- Title:
- VI CCD photometry in NGC 6631
- Short Name:
- J/other/BASI/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VI CCD photometric observations of about 5500 stars up to a limiting magnitude of V~20 in an area of ~16'x16' around the cluster NGC 6631. The cluster parameters determined for the first time by fitting the theoretical isochrones in the V, (V-I) diagram of the cluster stars are E(V-I)=0.60+/-0.05mag, distance=2.6+/-0.5kpc, age=400+/-100Myr and metallicity, Z=0.05. The cluster diameter determined from the radial density profile is 4.8+-0.5pc. The mass function of the cluster has a slope of 2.1+/-05.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A21
- Title:
- Vilnius photometry near Sh 2-205
- Short Name:
- J/A+A/590/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of CCD photometry in the seven-color Vilnius system for 302 stars in the 12x12 arcmin area in the vicinity of the dark cloud TGU H942 P7. Observational data were obtained in 2015-2016 with the 1.8m VATT telescope of the Vatican observatory on Mt Graham, Arizona. Using the Koenig & Leisawitz (2014ApJ...791..131K) classification scheme we identified 88 YSOs in this area. The majority of them are concentrated in dust clump P7 and the infrared cluster FSR 655. The other compact group of YSOs is located at RA=03:54:56, DEC=+53:45. These stars are probably members of small infrared cluster which we call SCB1.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/191
- Title:
- VI photometry and spectroscopy in h+{chi} Per
- Short Name:
- J/ApJS/186/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From photometric observations of ~47000 stars and spectroscopy of ~11000 stars, we describe the first extensive study of the stellar population of the famous Double Cluster, h and {chi} Persei, down to subsolar masses. By analyzing optical spectra and optical/infrared photometry, we constrain the distance moduli (dM), reddening (E(B-V)), and ages for h Persei, {chi} Persei, and the low-density halo population surrounding both cluster cores. With the exception of mass and spatial distribution, the clusters are nearly identical in every measurable way. From these data, we establish the first spectroscopic and photometric membership lists of cluster stars down to early/mid M dwarfs. At minimum, there are ~5000 members within 10' of the cluster centers, while the entire h and {chi} Persei region has at least ~13000 and as many as 20000 members. The Double Cluster contains ~8400M_{sun}_ of stars within 10' of the cluster centers. We estimate a total mass of at least 20000M_{sun}_. We conclude our study by outlining outstanding questions regarding the past and present properties of h and {chi} Persei. From comparing recent work, we compile a list of intrinsic colors and derive a new effective temperature scale for O-M dwarfs, giants, and supergiants.
- ID:
- ivo://CDS.VizieR/J/MNRAS/503/2265
- Title:
- VISTA and Subaru/HSC obs. of Upper Scorpius
- Short Name:
- J/MNRAS/503/2265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim at identifying very low-mass isolated planetary-mass member candidates in the nearest OB association to the Sun, Upper Scorpius (145pc; 5-10Myr), to constrain the form and shape of the luminosity function and mass spectrum in this regime. We conducted a deep multi-band (Y=21.2, J=20.5, Z=22.0mag) photometric survey of six square degrees in the central region of Upper Scorpius. We extend the current sequence of astrometric and spectroscopic members by about two magnitudes in Y and one magnitude in J, reaching potentially T-type free-floating members in the association with predicted masses below 5 Jupiter masses, well into the planetary-mass regime. We extracted a sample of 57 candidates in this area and present infrared spectroscopy confirming two of them as young L-type members with characteristic spectral features of 10Myr-old brown dwarfs. Among the 57 candidates, we highlight 10 new candidates fainter than the coolest members previously confirmed spectroscopically. We do not see any obvious sign of decrease in the mass spectrum of the association, suggesting that star processes can form substellar objects with masses down to 4-5 Jupiter masses.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A115
- Title:
- VVV: star formation and embedded clusters
- Short Name:
- J/A+A/562/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to locate previously unknown stellar clusters using the VISTA variables in the Via Lactea Survey (VVV) catalogue data. The method fits a mixture model of Gaussian densities and background noise and uses the expectation maximization algorithm to pre-filtered near-infrared survey stellar catalogue data; it was developed by the authors for the UKIDSS Galactic Plane Survey (GPS). The search located 88 previously unknown candidates, most of which are embedded stellar cluster candidates, and 39 previously unknown sites of star formation in the 562deg^2^ covered by VVV in the Galactic bulge and the southern disk.
