- 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.
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- ID:
- ivo://CDS.VizieR/J/AJ/152/192
- Title:
- WOCS. LXXII. A uvbyCaHb study of NGC 2506
- Short Name:
- J/AJ/152/192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precision uvbyCaH{beta} photometry of the metal-deficient, old open cluster NGC2506 is presented. The survey covers an area of 20'*20' and extends to V~18 for b-y and H{beta} and to V~17.0 for c_1_ and hk. For V brighter than 16.0, photometric scatter among the indices leads to the recovery of six known variables within the cluster core and five new variables in the outer 5' of the survey field. Proper motions, radial velocities, and precise multicolor indices are used to isolate a highly probable sample of cluster members from the very rich color-magnitude diagram. From 257 highly probable members at the cluster turnoff, we derive a reddening estimate of E(b-y)=0.042+/-0.001 (E(B-V)=0.058+/-0.001), where the errors refer to the internal standard errors of the mean. [Fe/H] is derived from the A/F dwarf members using both m_1_ and hk, leading to [Fe/H]=-0.296+/-0.011 (sem) and -0.317+/-0.004 (sem), respectively. The weighted average, heavily dominated by hk, is [Fe/H]=-0.316+/-0.033. Based on red giant members, we place an upper limit of +/-0.010 on the variation in the reddening across the face of the cluster. We also identify two dozen potential red giant cluster members outside the cluster core. Victoria-Regina isochrones on the Stromgren system produce an excellent match to the cluster for an apparent modulus of (m-M)=12.75+/-0.1 and an age of 1.85+/-0.05Gyr.
- ID:
- ivo://CDS.VizieR/J/AJ/159/220
- Title:
- WOCS LXXIX. M48. I. WIYN/Hydra spectra for M48 stars
- Short Name:
- J/AJ/159/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectra (R~13500, signal-to-noise=50-1000/pixel) of a 400{AA} region around Li 6708{AA} are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our radial velocity (V_RAD_) measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of uncertain multiplicity, 56 as single nonmembers, 28 as single "likely" nonmembers, two as single "likely" members, one as a binary "likely" member, five as binary nonmembers, 10 as "likely" members of uncertain multiplicity, three as nonmembers of uncertain multiplicity, and three as "likely" nonmembers of uncertain multiplicity. From a subsample of 95 single members, we derive V_RAD_=8.512{+/-}0.087km/s ({sigma}_{mu}_, and {sigma}=0.848km/s). Using 16 isolated Fe I lines for a subsample of 99 single members (that have {sigma}_Teff_<75K (from 10 colors from UBVRI), vsini<25km/s, and well-behaved Fe I lines), [Fe/H]M48=-0.063{+/-}0.007dex ({sigma}_{mu}_). [Fe/H] is independent of Teff over an unprecedentedly large range of 2500K. The minimum cluster binary fraction is 11%-21%. M48 exhibits a clear but modest broadening of the main-sequence turnoff, and there is no correlation between color and vsini.
- ID:
- ivo://CDS.VizieR/J/AJ/153/128
- Title:
- WOCS. LXXV. Hyades&Praesepe stellar lithium data
- Short Name:
- J/AJ/153/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectroscopy (at R~15000) of the moderately metal-rich Praesepe and Hyades open clusters was used to study their main-sequence (MS) iron ([Fe/H]) and lithium (A(Li)) abundances. Self-consistent [Fe/H] and Li analyses of these clusters of consistent age, which we re-evaluate, confirms that they have consistent [Fe/H] and provides a foundation to investigate the poorly understood G-dwarf and F-dwarf Li-depletions. Neither phenomenon agrees with standard stellar evolution theory, but possible explanations abound. We supplement our A(Li) with previously published results placed on a uniform abundance scale. This creates the largest self-consistently analyzed sample of A(Li) in both the Hyades (90) and Praesepe (110). For each star, high-precision UBVRI photometry was used to determine a 10-color-based T_eff_ and then to test for photometric peculiarities indicated by a large {sigma}_Teff_ (>75 K). The stars that have large {sigma}_Teff_ were predominantly found to be binaries or stars with peculiar (apparent) A(Li). When considering only proper-motion members that have low {sigma}_Teff_ and are also photometrically consistent with the cluster MS fiducial, each cluster has a more tightly defined Li morphology than previously observed and the two clusters' A(Li) are indistinguishable. This suggests that clusters of consistent age and metallicity may have consistent Li-depletion trends across a broad range of T_eff_; no additional major parameters are required, at least for these two clusters. We propose that the combined Hyades and Praesepe data offer more rigorous constraints than does either cluster alone, and we discuss newly revealed features of the combined Li-T_eff_ trend.
- ID:
- ivo://CDS.VizieR/J/AJ/155/138
- Title:
- WOCS.LXXVI.Velocity & abundances in NGC2506
- Short Name:
- J/AJ/155/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HYDRA spectra of 287 stars in the field of NGC 2506 from the turnoff through the giant branch are analyzed. With previous data, 22 are identified as probable binaries; 90 more are classified as potential non-members. Spectroscopic analyses of ~60 red giants and slowly rotating turnoff stars using line equivalent widths and a neural network approach lead to [Fe/H]=-0.27+/-0.07 (s.d.) and [Fe/H]=-0.27+/-0.06 (s.d.), respectively. Li abundances are derived for 145 probable single-star members, 44 being upper limits. Among turnoff stars outside the Li-dip, A(Li)=3.04+/-0.16 (s.d.), with no trend with color, luminosity, or rotation speed. Evolving from the turnoff across the subgiant branch, there is a well-delineated decline to A(Li)~1.25 at the giant branch base, coupled with the rotational spindown from between ~20 and 70 km/s to less than 20 km/s for stars entering the subgiant branch and beyond. A(Li) remains effectively constant from the giant branch base to the red giant clump level. A new member above the clump redefines the path of the first-ascent red giant branch; its Li is 0.6 dex below the first-ascent red giants. With one exception, all post-He-flash stars have upper limits to A(Li), at or below the level of the brightest first-ascent red giant. The patterns are in excellent qualitative agreement with the model predictions for low/intermediate-mass stars which undergo rotation-induced mixing at the turnoff and subgiant branch, first dredge-up, and thermohaline mixing beyond the red giant bump.
- ID:
- ivo://CDS.VizieR/J/A+A/395/499
- Title:
- XMM observations in M8 and NGC6530
- Short Name:
- J/A+A/395/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/430/287
- Title:
- XMM observations of IC 2391 stars
- Short Name:
- J/A+A/430/287
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have been detected, from the early-types to the late-M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A150
- Title:
- XMM observations of {lambda} Ori cluster
- Short Name:
- J/A+A/530/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the X-ray properties of the young (~1-8Myr) open cluster around the hot (O8 III) star {lambda} Ori and compared them with those of the similarly-aged sigma Ori cluster to investigate possible effects of the different ambient environment. We analysed an XMM-Newton observation of the cluster using EPIC imaging and low-resolution spectral data. We studied the variability of detected sources, and performed a spectral analysis of the brightest sources in the field using multi-temperature models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/781
- Title:
- XMM observations of NGC 2547
- Short Name:
- J/MNRAS/367/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The following tables describe the results of a survey for X-ray (0.3-3 keV) sources in the young (30Myr) NGC 2547 open cluster using the XMM-Newton EPIC instrument. Table 1 lists the details of X-ray sources which are correlated with optical cluster members. Table 2 catalogues the cross-identifications with optical catalogues for the sources in Table 1 and derives their X-ray luminosities and X-ray to bolometric flux ratios. Table 3 lists the X-ray properties of sources which are uncorrelated with cluster members. Table 7 lists the correlations between cluster members detected by XMM-Newton and those detected 7 years earlier by the ROSAT HRI instrument, along with the X-ray luminosities and flux ratios as determined by the HRI.