- ID:
- ivo://CDS.VizieR/J/ApJ/671/781
- Title:
- Red supergiants in Sct-Cru Galactic arm
- Short Name:
- J/ApJ/671/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the unprecedented red supergiant (RSG) population of a massive young cluster, located at the base of the Scutum-Crux Galactic arm. We identify candidate cluster RSGs based on 2MASS photometry and medium-resolution spectroscopy. With follow-up high-resolution spectroscopy, we use CO band-head equivalent width and high-precision radial velocity measurements to identify a core grouping of 26 physically associated RSGs-the largest such cluster known to date.
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- ID:
- ivo://CDS.VizieR/J/A+AS/116/75
- Title:
- Region of the open cluster Tr 14
- Short Name:
- J/A+AS/116/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI CCD imaging photometry down to approximately V=19mag in the area of the very young open cluster Tr 14. Our results confirm the existence of an anomalous extinction law in the area if it is interpreted in terms of the UBVRI photometry. According to our analysis the cluster distance is d=3100 (V_0_-M_V_=12.50mag) and its age is 1.5+/-.5x10^6^y. We want to draw the attention on stars which, from the observed magnitude-spread at constant color, could be stars in an early stage of evolution. In that case, the observed spread leads to assume that the process of star formation in Tr 14 is continuous whereas, from pre-main sequence evolutionary tracks, a duration of about 5x10^6^y is deduced for it. The computation of the cluster initial mass function reveals a flat slop e even though it still compares to a Salpeter law. At the same time, we found a spatial variation of the cluster IMF, which could be explained by mass segregation in the star formation process. The cluster youth and its compact appearance seem to confirm that it is far from virial equilibrium. The observed tot al cluster mass is around 2000M_{sun}_ and its core contains about 40% of the total.
- ID:
- ivo://CDS.VizieR/J/PAZh/41/367
- Title:
- Relative proper motions in NGC 6800
- Short Name:
- J/PAZh/41/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a comprehensive study of the Galactic open cluster NGC 6800 are presented. The positions of stars to a limiting magnitude B<=16.5mag in an 80x80 arcmin field centered at the cluster were measured on eight plates from the Pulkovo normal astrograph with a maximum epoch difference of 57 years. The measurements were performed with the Pulkovo "Fantasy" automated measuring system. The corresponding field from the 2MASS catalogue was used as an additional plate. As a result, the relative proper motions of stars were obtained with a root-mean-square error of 3.0 mas/yr. A catalogue of BV and JHK magnitudes for objects in the investigated region was compiled from available published resources. The astrometric selection of cluster members was made by the maximum likelihood method. An individual cluster membership probability of a star P>=60% served as the first selection criterion. The position of a star on the photometric color-magnitude (V-(B-V)), J-(J-Ks)) diagrams was considered as the second selection criterion. On the basis of these criteria, it was established that 109 stars are members of NGC 6800. These data were used to refine the physical parameters of the cluster: the mean reddening E(B-V)=0.40mag, the true distance modulus (V-Mv)0=10.05mag, and the cluster age ~250Myr. The luminosity and mass functions were constructed. The position of the center of the cluster NGC 6800 was improved: RA=19:27:11.2 and DE=+25:07:24 (2000).
- ID:
- ivo://CDS.VizieR/J/A+A/597/A90
- Title:
- rho Oph proper motions and photometry
- Short Name:
- J/A+A/597/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim at performing a kinematic census of young stellar objects (YSOs) in the rho Ophiuchi F core and partially in the E core of the L1688 dark cloud. We run a proper motion program at the ESO New Technology Telescope (NTT) with the Son of ISAAC (SOFI) instrument over nine years in the near-infrared. We complemented these observations with various public image databases to enlarge the time base of observations and the field of investigation to 0.5{deg}x0.5{deg}. We derived positions and proper motions for 2213 objects. From these, 607 proper motions were derived from SOFI observations with a ~1.8mas/yr accuracy while the remaining objects were measured only from auxiliary data with a mean precision of about 3mas/yr. We performed a kinematic analysis of the most accurate proper motions derived in this work, which allowed us to separate cluster members from field stars and to derive the mean properties of the cluster. From the kinematic analysis we derived a list of 68 members and 14 candidate members, comprising 26 new objects with a high membership probability.
- ID:
- ivo://CDS.VizieR/J/AN/325/705
- Title:
- RIJHKs of low-mass stars in sigma Ori
- Short Name:
- J/AN/325/705
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an RI photometric survey covering an area of 430 arcmin^2^ around the multiple star sigma Orionis. The observations were conducted with the 0.8m IAC-80 Telescope at the Teide Observatory. The survey limiting R and I magnitudes are 22.5 and 21, and completeness magnitudes 21 and 20, respectively. We have selected 53 candidates from the I vs. R-I colour-magnitude diagram (I=14-20) that follow the previously known photometric sequence of the cluster. Adopting an age of 2-4 Myr for the cluster, we find that these objects span a mass range from 0.35M_{sun}_ to 0.015M_{sun}_. We have performed J-band photometry of 52 candidates and K_s photometry for 12 of them, with the result that 50 follow the expected infrared sequence for the cluster, thus confirming with great confidence that the majority of the candidates are bona fide members. JHK_s photometry from the Two Micron All Sky Survey (2MASS, Cat. <II/246>) is available for 50 of the candidates and are in good agreement with our data. Out of 48 candidates, which have photometric accuracies better than 0.1mag in all bands, only three appear to show near-infrared excesses.
- ID:
- ivo://CDS.VizieR/J/A+A/416/125
- Title:
- RI photometry in alpha Per and Pleiades
- Short Name:
- J/A+A/416/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photographic astrometry (proper motions and accurate positions), photometry (in the photographic R and I passbands) and membership probabilities for high probability proper motion members of the clusters Alpha Persei and The Pleiades are presented, along with cross-identifications with names from previously known members in the compilation of Prosser & Stauffer (The Stauffer & Prosser Open Cluster Catalogue, priv.comm.) and their corresponding proper motion membership probabilities according to our study. The SuperCOSMOS facility at the Royal Observatory Edinburgh has (using plates from the United Kingdom Schmidt Telescope) produced complete southern sky surveys in BJ, R and I with an additional second epoch R survey. These surveys are now publicly available (Hambly et al. 2001MNRAS.326.1279H). The scanning program has now moved on to the northern hemisphere, using film and glass copies of plates taken by the Oschin Schmidt Telescope on Mount Palomar, California. These data will soon be publicly available.
- ID:
- ivo://CDS.VizieR/J/A+A/509/A17
- Title:
- R light curves of NGC 6253 variables
- Short Name:
- J/A+A/509/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents the first high-precision variability survey in the field of the intermediate-age, metal-rich open cluster NGC 6253. We discovered 595 variables and we also characterized most of them providing their variability classes, periods and amplitudes. The sample is complete at short periods: we classified 20 pulsating variables, 225 contact systems, 99 eclipsing systems (22 Beta Lyr type, 59 Beta Per type, 18 RS CVn type), and 77 rotational variables. The time-baseline hampered the precise characterization of 173 variables with periods longer than 4-5days. Moreover, we found a cataclysmic system undergoing an outburst of about 2.5mag.
- ID:
- ivo://CDS.VizieR/J/AJ/155/51
- Title:
- Robo-AO binary star systems in 3 open clusters
- Short Name:
- J/AJ/155/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify and roughly characterize 66 candidate binary star systems in the Pleiades, Praesepe, and NGC 2264 star clusters, based on robotic adaptive optics imaging data obtained using Robo-AO at the Palomar 60" telescope. Only ~10% of our imaged pairs were previously known. We detect companions at red optical wavelengths, with physical separations ranging from a few tens to a few thousands of au. A three-sigma contrast curve generated for each final image provides upper limits to the brightness ratios for any undetected putative companions. The observations are sensitive to companions with a maximum contrast of ~6^m^ at larger separations. At smaller separations, the mean (best) raw contrast at 2" is 3.8^m^ (6^m^), at 1" is 3.0^m^ (4.5^m^), and at 0.5" is 1.9^m^ (3^m^). Point-spread function subtraction can recover nearly the full contrast in the closer separations. For detected candidate binary pairs, we report separations, position angles, and relative magnitudes. Theoretical isochrones appropriate to the Pleiades and Praesepe clusters are then used to determine the corresponding binary mass ratios, which range from 0.2 to 0.9 in q=m_2_/m_1_. For our sample of roughly solar-mass (FGK type) stars in NGC 2264 and sub-solar-mass (K and early M-type) primaries in the Pleiades and Praesepe, the overall binary frequency is measured at ~15.5%+/-2%. However, this value should be considered a lower limit to the true binary fraction within the specified separation and mass ratio ranges in these clusters, given that complex and uncertain corrections for sensitivity and completeness have not been applied.
- ID:
- ivo://CDS.VizieR/J/A+A/341/751
- Title:
- ROSAT HRI observations of the Pleiades
- Short Name:
- J/A+A/341/751
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a deep X-ray survey of the Pleiades open cluster, we use the ROSAT High Resolution Imager to explore a region of the cluster formerly surveyed with the PSPC. These new observations substantially improve upon both the sensitivity and the spatial resolution for this region of the Pleiades, allowing us to detect 18 cluster members not detected before and 16 members not included in the catalogs used in previous surveys. The high sensitivity of the present observations permits us to obtain more stringent upper limits for 72 additional members and also provides sufficient numbers of stars to enable us to explore the dependence of L_x_ on stellar rotation for the slow rotators of the Pleiades. Using the new high sensitivity X-ray observations and the recent rotational measurements we discuss the activity-rotation relationship in the Pleiades solar type stars. We also present new photometric observations of optical counterparts of a number of X-ray sources detected in previous surveys but not yet identified.
- ID:
- ivo://CDS.VizieR/J/ApJS/102/75
- Title:
- ROSAT Observations of the Pleiades
- Short Name:
- J/ApJS/102/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Of 214 stars in the core of the Pleiades, 99 were detected in X-rays with the ROSAT PSPC. This catalog lists the characteristics of the stars taken from the literature, in table1.dat and the rotational and X-ray characteristics in table5.dat.
