- ID:
- ivo://CDS.VizieR/J/ApJ/664/1102
- Title:
- Radial velocity survey of Cyg OB2 association
- Short Name:
- J/ApJ/664/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a radial velocity survey of the Cyg OB2 association over a 6yr (1999-2005) time interval to search for massive close binaries. During this time we obtained 1139 spectra on 146 OB stars to measure mean systemic radial velocities and radial velocity variations. We spectroscopically identify 73 new OB stars for the first time, the majority of which are likely to be association members.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/350/883
- Title:
- R CrA ISOCAM observations
- Short Name:
- J/A+A/350/883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of an ISOCAM survey of the R CrA star formation region are presented. The survey was carried out in two broad-band filters, LW2 (5-8.5{mu}m) and LW3 (12-18{mu}m). Although it was not possible to map the densest, central region due to saturation problems, 21 sources were identified which showed mid-IR excesses. Most of these sources have not previously been recognised as YSOs (Young Stellar Objects), mainly because they are relatively faint. We find evidence for a population of very low mass stars which are probably brown dwarfs in their early contraction phases.
- ID:
- ivo://CDS.VizieR/J/AJ/139/878
- Title:
- RGB stars in 8 LMC clusters
- Short Name:
- J/AJ/139/878
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we discuss the properties of color-magnitude diagrams, age, metallicity, and radial velocities of eight massive Large Magellanic Cloud (LMC) clusters using data taken from the FORS2 multiobject spectrograph at the 8.2m Very Large Telescope/Unit Telescope 1. The strong near-infrared CaII triplet lines of red giant branch stars obtained from the high signal-to-noise ratio spectra are used to determine the metallicity and radial velocity of cluster members.
- ID:
- ivo://CDS.VizieR/J/ApJS/112/109
- Title:
- Rho Oph Near-IR Positions and Photometry
- Short Name:
- J/ApJS/112/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the tabulated results from a three-color (JHK) near-Infrared imaging survey of the Rho Ophiuchi star-forming cloud core. The NIR imaging observations were acquired using the SQIID instrument on the Kitt Peak 1.3m telescope from June 4-10, 1993 and April 23-28, 1994. The survey covered one square degree (2.2pc by 2.2pc). The catalog contains 4495 sources with both J2000.0 and B1950.0 coordinates for each source and its J, H, and K magnitudes and/or upper their limits. The Rho Ophiuchi clouds are of great interest for star formation studies, since they include the nearest example of a currently forming star cluster. The absolute positions in RA and Dec were determined for each individual source by using a centering algorithm in the IRAF package APPHOT to obtain center positions in pixels which were then merged into a single common positional grid. Absolute stellar coordinates were determined by comparing the authors positional database with the positions of 36 HST Guide Star Catalog stars spread out over the survey field. These were used to determine a plate scale and rotation which was used to generate the final list of source positions. The position determination technique and the photometric data reduction and calibration is discussed in detail in the source reference.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1703
- Title:
- Ridgelines of six intermediate-age SMC clusters
- Short Name:
- J/AJ/136/1703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric analysis of the star clusters Lindsay 1, Kron 3, NGC 339, NGC 416, Lindsay 38, and NGC 419 in the Small Magellanic Cloud (SMC), observed with the Hubble Space Telescope Advanced Camera for Surveys (ACS) in the F555W and F814W filters. Our color-magnitude diagrams (CMDs) extend ~3.5mag deeper than the main-sequence turnoff points, deeper than any previous data. Cluster ages were derived using three different isochrone models: Padova, Teramo, and Dartmouth, which are all available in the ACS photometric system. Fitting observed ridgelines for each cluster, we provide a homogeneous and unique set of low-metallicity, single-age fiducial isochrones.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/19
- Title:
- riz photometry in Cyg OB2
- Short Name:
- J/ApJS/202/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to fully understand the gravitational collapse of molecular clouds, the star formation process, and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is a unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in the r, i, z filters with OSIRIS, mounted on the 10.4m Gran Telescopio CANARIAS telescope, which is the deepest optical catalog of CygOB2 to date. The catalog consists of 64,157 sources down to M=0.15M_{sun}_ at the adopted distance and age of Cyg OB2. A total of 38,300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r-i versus i-z diagram is compatible with an extinction of the optically selected cluster members in the 2.64m<A_V_<5.57m range. We derive an extinction map of the region, finding a median value of A_V_=4.33m in the center of the association, decreasing toward the northwest. In the color-magnitude diagrams, the shape of the distribution of main-sequence stars is compatible with the presence of an obscuring cloud in the foreground ~850+/-25pc from the Sun.
- ID:
- ivo://CDS.VizieR/J/A+A/419/249
- Title:
- RJHKs photometry of sigma Ori low-mass stars
- Short Name:
- J/A+A/419/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coordinates and photometry of probable cluster members in the sigma Ori cluster. Time series observations of this cluster were carried out using the CCD cameras at the 2m Schmidt telescope of the Thuringer Landessternwarte Tautenburg (TLS) and the 1.23m telescope on Calar Alto (CA). From these images, we derived coordinates (columns 2 and 3) as well as photometry in the R- and I-band (columns 5 and 6). Additional near- infrared photometry in J, H, K comes from the 2MASS database (columns 7-9). The cluster member selection is based on (I,I-J) colour magnitude diagrams. The R-I and J-H colours were used to reject contaminating field stars. The column 4 indicates whether the object was identified with the CA photometry (c), the TLS photometry (t), or both. The masses given in column 10 were estimated by comparing the near-infrared photometry with the evolutionary tracks of Baraffe et al. (1998A&A...337..403B). These tracks cover the mass range from 0.02 to 1.4 solar masses, for some objects with lower or higher masses we give upper or lower mass limits. The last two columns contain information about the results of the time series analysis. Column 10 gives the RMS of the CA lightcurve for targets No 1-52 and the RMS of the TLS lightcurve for all others. The last column indicates whether the target is classified as variable (v) and/or periodically variable (p). For a few objects, time series analysis was not possible, because they are either too faint or too bright in most of the images.
- ID:
- ivo://CDS.VizieR/J/AJ/143/80
- Title:
- R Low-mass stars of beta Pic and AB Dor groups
- Short Name:
- J/AJ/143/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our continuing effort to identify new, low-mass members of nearby, young moving groups (NYMGs), we present a list of young, low-mass candidates in the northern hemisphere. We used our proven proper-motion selection procedure and ROSAT X-ray and GALEX-UV activity indicators to identify 204 young stars as candidate members of the {beta} Pictoris and AB Doradus NYMGs. Definitive membership assignment of a given candidate will require a measurement of its radial velocity and distance. We present a simple system of indices to characterize the young candidates and help prioritize follow-up observations. New group members identified in this candidate list will be high priority targets for (1) exoplanet direct imaging searches, (2) the study of post-T-Tauri astrophysics, (3) understanding recent local star formation, and (4) the study of local galactic kinematics. Information available now allows us to identify eight likely new members in the list. Two of these, a late-K and an early-M dwarf, we find to be likely members of the {beta} Pic group. The other six stars are likely members of the AB Dor moving group. These include an M dwarf triple system, and three very cool objects that may be young brown dwarfs, making them the lowest-mass, isolated objects proposed in the AB Dor moving group to date.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A106
- Title:
- Rotational periods in Cygnus OB2
- Short Name:
- J/A+A/603/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a near-infrared time-series photometry study in the field of Cygnus OB2 association (RA~20.55h, DE~41.2{deg}). Observations were carried out in the JHK bands at the WFCAM/UKIRT telescope over 112 observed nights. We investigated the occurrence of periodicity in the time-series and we found reliable periods for 894 candidate members.
- ID:
- ivo://CDS.VizieR/J/AJ/134/1570
- Title:
- Rotational velocities of OB stars
- Short Name:
- J/AJ/134/1570
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive projected rotational velocities (vsini) for a sample of 156 Galactic OB star members of 35 clusters, HII regions, and associations. The HeI lines at 4026, 4388, and 4471{AA} were analyzed in order to define a calibration of the synthetic HeI full widths at half-maximum (FWHMs) versus stellar vsini. A grid of synthetic spectra of HeI line profiles was calculated in non-LTE using an extensive helium model atom and updated atomic data. The vsini values for all stars were derived using the HeI FWHM calibrations, but also, for those target stars with relatively sharp lines, vsini values were obtained from best-fit synthetic spectra of up to 40 lines of CII, NII, OII, AlIII, MgII, SiIII, and SIII. This calibration is a useful and efficient tool for estimating the projected rotational velocities of O9-B5 main-sequence stars. The distribution of vsini for an unbiased sample of early B stars in the unbound association Cep OB2 is consistent with the distribution reported elsewhere for other unbound associations.
