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- ID:
- ivo://CDS.VizieR/J/AJ/152/129
- Title:
- VR photometry for 914 stars in NGC 188
- Short Name:
- J/AJ/152/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the newly commissioned 50cm Binocular Network telescope at Qinghai Station of Purple Mountain Observatory (Chinese Academy of Sciences) to observe the old open cluster NGC188 in V and R as part of a search for variable objects. Our time-series data span a total of 36 days. Radial velocity and proper-motion selection resulted in a sample of 532 genuine cluster members. Isochrone fitting was applied to the cleaned cluster sequence, yielding a distance modulus of (m-M)_V_^0^=11.35+/-0.10mag and a total foreground reddening of E(V-R)=0.062+/-0.002mag. Light-curve solutions were obtained for eight W Ursae Majoris eclipsing binary systems (W UMas), and their orbital parameters were estimated. Using the latter parameters, we estimate a distance to the W UMas that is independent of the host cluster's physical properties. Based on combined fits to six of the W UMas (EP Cep, EQ Cep, ES Cep, V369 Cep, and-for the first time-V370 Cep and V782 Cep), we obtain an average distance modulus of (m-M)_V_^0^=11.31+/-0.08mag, which is comparable to that resulting from our isochrone fits. These six W UMas exhibit an obvious period-luminosity relation. We derive more accurate physical parameters for the W UMa systems and discuss their initial masses and ages. The former show that these W UMa systems have likely undergone angular momentum evolution within a convective envelope (W-type evolution). The ages of the W UMa systems agree well with the cluster's age.
- ID:
- ivo://CDS.VizieR/J/ApJ/601/979
- Title:
- vsini of Orion low-mass stars
- Short Name:
- J/ApJ/601/979
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Projected rotational velocities (vsini) have been measured for a sample of 145 stars with masses between 0.4 and greater than 10M_{sun}_ (median mass 2.1M_{sun}_) located in the Orion star-forming complex. These measurements have been supplemented with data from the literature for Orion stars with masses as low as 0.1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/466/137
- Title:
- Westerlund 2 JHKs photometry
- Short Name:
- J/A+A/466/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry for the stars detected with SOFI, NTT in J, H and Ks in the field containing the massive cluster Westerlund 2 (also know as RCW 49) associated with the HII region Gum29. For each star detected in all three bands the table contains the ID, equatorial coordinates, J, H and Ks magnitude and photometric errors. For the stars detected only in Ks or in H and Ks the magnitude and photometric error fields in the absent bands are filled with the values 99.99 and 9.999 respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3797
- Title:
- Westerlund 2 UBVIc photometry
- Short Name:
- J/MNRAS/446/3797
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep UBVI_c_ photometric data of the young open cluster Westerlund 2. An abnormal reddening law of R_V,cl_=4.14+/-0.08 was found for the highly reddened early-type members (E(B-V)>=1.45), whereas a fairly normal reddening law of R_V,fg_=3.33+/-0.03 was confirmed for the foreground early-type stars (E(B-V)_fg_<1.05). The distance modulus was determined from zero-age main-sequence fitting to the reddening-corrected colour-magnitude diagram of the early-type members to be V_0_-M_V_=13.9+/-0.14 (random error) _-0.1_^+0.4^ (the upper limit of systematic error) mag (d=6.0+/-0.4_-0.3_^+1.2^kpc). To obtain te initial mass function, pre-main-sequence (PMS) stars were selected by identifying the optical counterparts of Chandra X-ray sources and mid-infrared emission stars from the Spitzer GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) source catalogue. The initial mass function shows a shallow slope of {Gamma}=-1.1+/-0.1 down to log(m)=0.7. The total mass of Westerlund 2 is estimated to be at least 7400M_{sun}_. The age of Westerlund 2 from the main-sequence turn-on and PMS stars is estimated to be <~1.5Myr. We confirmed the existence of a clump of PMS stars located ~1-arcmin north of the core of Westerlund 2, but we could not find any clear evidence for an age difference between the core and the northern clump.
- ID:
- ivo://CDS.VizieR/J/AJ/155/50
- Title:
- WISE photometry of Be stars in young open clusters
- Short Name:
- J/AJ/155/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through the modeling of near-infrared photometry of star-plus disk systems with the codes BEDISK/BERAY, we successfully describe the Wide-Field Infrared Survey Explorer (WISE) photometric characteristics of Be stars in five young open clusters, NGC 663, NGC 869, NGC 884, NGC 3766, and NGC 4755, broadly studied in the literature. WISE photometry allows previously known Be stars to be detected and to find new Be candidates which could be confirmed spectroscopically. The location of Be stars in the WISE color-magnitude diagram, separates them in two groups; active (Be stars hosting a developed circumstellar disk) and quiescent objects (Be stars in a diskless phase), and this way, we can explore how often stars are observed in these different stages. The variability observed in most active variable Be stars is compatible with a disk dissipation phase. We find that 50% of Be stars in the studied open clusters are in an active phase. We can interpret this as Be stars having a developed circumstellar disk one-half of the time. The location of Be stars with a developed disk in the color-magnitude diagram require mass loss rates in agreement with values recently reported in the literature. For these objects, we expect to have a tight relation between the equivalent width of the H{alpha} line and the mass of the disk, if the inclination is known. Also, near-infrared photometry of Be stars in stellar clusters has the potential of being useful to test whether there is a preferential viewing angle.
- ID:
- ivo://CDS.VizieR/J/AJ/148/85
- Title:
- WIYN open cluster study. LXII. Photometry of M35
- Short Name:
- J/AJ/148/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The current generation of stellar isochrone models exhibits non-negligible discrepancies due to variations in the input physics. The success of each model is determined by how well it fits the observations, and this paper aims to disentangle contributions from the various physical inputs. New deep, wide-field optical and near-infrared photometry (UBVRIJHK_S_) of the cluster M35 is presented, against which several isochrone systems are compared: Padova, PARSEC, Dartmouth, and Y^2^. Two different atmosphere models are applied to each isochrone: ATLAS9 and BT-Settl. For any isochrone set and atmosphere model, observed data are accurately reproduced for all stars more massive than 0.7M_{sun}_. For stars less massive than 0.7M_{sun}_, Padova and PARSEC isochrones consistently produce higher temperatures than observed. Dartmouth and Y^2^ isochrones with BT-Settl atmospheres reproduce optical data accurately; however, they appear too blue in IR colors. It is speculated that molecular contributions to stellar spectra in the near-infrared may not be fully explored, and that future study may reconcile these differences.
- ID:
- ivo://CDS.VizieR/J/AJ/159/246
- Title:
- WIYN open cluster study. LXXX. Photometry of NGC 7142
- Short Name:
- J/AJ/159/246
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI photometry of 8702 stars in a 0.5x0.5{deg} field in the direction of NGC7142, taken with the Half Degree Imager at the WIYN 0.9m telescope, to improve knowledge of this cluster's basic parameters. Our photometry spans the ranges 10.6-20.4mag in U, 10.6-22.0mag in B, 10.0-21.8mag in V, 9.2-20.7mag in R, and 8.5-19.9mag in I. Using color-color diagrams that employ all four color combinations that include U, versus B-V, we derive a reddening-metallicity relation for the cluster, with preferred values E(B-V)=0.338{+/-}0.031mag for the left-edge fiducial of the main sequence and [Fe/H]=0.0{+/-}0.1dex, where the Hyades cluster has been used as an unreddened reference cluster, the extinction relations of Cardelli have been employed, and the metallicity dependence of the Yonsei-Yale (Y^2^) isochrones has been assumed. Comparison of our data to the Y^2^ isochrones in multiple color-magnitude diagrams (CMDs) yields distance-metallicity and age-metallicity relations, with preferred values of m-M=12.65{+/-}0.23 mag and age=4.0_+1.3_^-0.7^Gyr. Re-evaluation of the parameters of M67 using Stetson's UBVI photometry yields [Fe/H]=-0.02{+/-}0.05dex, E(B-V)=0.04{+/-}0.01mag, m-M=9.75{+/-}0.03mag, and age=3.85{+/-}0.17Gyr; we thus find the metallicity and age of the two clusters to be indistinguishable. A semi-independent analysis adopting the parameters of M67 and shifting the fiducials of the two clusters in six CMDs until they match strongly corroborates the values listed above. The differences between our inferred parallaxes and the Gaia DR2 values are 87{+/-}60{mu}as for NGC7142 and 48{+/-}15{mu}as for M67, consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A63
- Title:
- W51 OB stars NIR spectroscopy
- Short Name:
- J/A+A/624/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interplay between the formation of stars, stellar feedback and cloud properties strongly influences the star formation history of giant molecular clouds. The formation of massive stars leads to a variety of stellar clusters, ranging from low stellar density OB associations to dense, gravitationally bound starburst clusters. We aimed at identifying the massive stellar content and reconstructing the star formation history of the W51 giant molecular cloud. We performed near-infrared imaging and K-band spectroscopy of the massive stars in W51. We analysed the stellar populations using colour-magnitude and colour-colour diagrams and compared the properties of the spectroscopically identified stars with stellar evolution models. We derive the ages of the different sub-clusters in W51 and, based on our spectroscopy derive an age for W51 of 3Myrs or less. The age of the P Cygni star LS1 and the presence of two still forming proto- clusters suggests that the star formation history of W51 is more complex than a single burst. We did not find evidence for triggered star formation and we concluded that the star formation in W51 is multi seeded. We finally concluded that W51 is a OB association where different sub-clusters form over a time span of at least 3-5Myrs.
- ID:
- ivo://CDS.VizieR/J/AJ/145/143
- Title:
- XMM observations of {alpha} Per
- Short Name:
- J/AJ/145/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the analysis of an archival observation of part of the {alpha} Persei cluster obtained with XMM-Newton. We detected 102 X-ray sources in the band 0.3-8.0 keV, of which 39 of them are associated with the cluster as evidenced by appropriate magnitudes and colors from Two Micron All Sky Survey photometry. We extend the X-ray luminosity distribution (XLD) for M dwarfs, to add to the XLD found for hotter dwarfs from spatially extensive surveys of the whole cluster by ROSAT. Some of the hotter stars are identified as a background, possible slightly older group of stars at a distance of approximately 500 pc.