- ID:
- ivo://CDS.VizieR/J/AJ/148/61
- Title:
- WIYN open cluster study. LIX. RVs of NGC 6791
- Short Name:
- J/AJ/148/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity (~8Gyr, [Fe/H]=+0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise ({sigma}=0.38km/s) radial velocities for proper motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to g' ~ 16.8, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitude limit, 93% have at least one radial velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper motion catalog includes 12 anomalous horizontal branch candidates blueward of the red clump, of which we find only 4 to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial velocity measurement distribution, we find the cluster's radial velocity dispersion to be {sigma}_c_=0.62+/-0.10km/s. This corresponds to a dynamical mass of ~4600M_{sun}_.
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- ID:
- ivo://CDS.VizieR/J/AJ/148/38
- Title:
- WIYN open cluster study. LX. RV survey of NGC 6819
- Short Name:
- J/AJ/148/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the current state of the WOCS radial-velocity (RV) survey for the rich open cluster NGC 6819 (2.5Gyr) including 93 spectroscopic binary orbits with periods ranging from 1.5 to 8000days. These results are the product of our ongoing RV survey of NGC 6819 using the Hydra Multi-Object Spectrograph on the WIYN 3.5m telescope. We also include a detailed analysis of multiple prior sets of optical photometry for NGC 6819. Within a 1{deg} field of view, our stellar sample includes the giant branch, the red clump, and blue straggler candidates, and extends to almost 2 mag below the main sequence (MS) turnoff. For each star observed in our survey we present all RV measurements, the average RV, and velocity variability information. Additionally, we discuss notable binaries from our sample, including eclipsing binaries (WOCS 23009, WOCS 24009, and WOCS 40007), stars noted in Kepler asteroseismology studies (WOCS 4008, WOCS 7009, and WOCS 8007), and potential descendants of past blue stragglers (WOCS 1006 and WOCS 6002). We find the incompleteness-corrected binary fraction for all MS binaries with periods less than 10^4^days to be 22%+/-3% and a tidal circularization period of 6.2^+1.1^_-1.1_days for NGC 6819.
- ID:
- ivo://CDS.VizieR/J/AJ/149/121
- Title:
- WOCS. LXV. Abundances in NGC 6819
- Short Name:
- J/AJ/149/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-dispersion spectra of 333 stars in the open cluster NGC 6819, obtained using the HYDRA spectrograph on the WIYN 3.5m telescope, have been analyzed to determine the abundances of iron and other metals from lines in the 400{AA} region surrounding the Li6708{AA} line. Our spectra, with signal-to-noise per pixel ranging from 60 to 300, span the luminosity range from the tip of the red giant branch to a point two magnitudes below the top of the cluster turnoff. We derive radial and rotational velocities for all stars, as well as [Fe/H] based on 17 iron lines, [Ca/H], [Si/H], and [Ni/H] in the 247 most probable, single members of the cluster. Input T_eff_ estimates for model atmosphere analysis are provided by (B-V) colors merged from several sources, with individual reddening corrections applied to each star relative to a cluster mean of E(B-V)=0.16. Extensive use is made of ROBOSPECT, an automatic equivalent width measurement program; its effectiveness on large spectroscopic samples is discussed. From the sample of likely single members, [Fe/H]=-0.03+/-0.06, where the error describes the median absolute deviation about the sample median value, leading to internal precision for the cluster below 0.01dex. The final uncertainty in the cluster abundance is therefore dominated by external systematics due to the temperature scale, surface gravity, and microturbulent velocity, leading to [Fe/H]=-0.02+/-0.02 for a sub-sample restricted to main sequence and turnoff stars. This result is consistent with our recent intermediate-band photometric determination of a slightly subsolar abundance for this cluster. [Ca/Fe], [Si/Fe], and [Ni/Fe] are determined to be solar within the uncertainties. NGC 6819 has an abundance distribution typical of solar metallicity thin disk stars in the solar neighborhood.
- ID:
- ivo://CDS.VizieR/J/AJ/150/10
- Title:
- WOCS. LXVI. Radial velocity survey in M35
- Short Name:
- J/AJ/150/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young (150Myr) open cluster M35 (NGC 2168) has been one of the core clusters of the WIYN Open Cluster Study since 1997. Over these 17years we have obtained approximately 8000 radial-velocity (RV) measurements of stars in the M35 field, which we provide here. Our target sample consists of 1355 photometrically selected stars in the field of M35 within the main sequence and binary sequence of the cluster and within 13<=V<=16.5 and (B-V)>=0.6. Using our RV measurements we cleanly separate likely cluster members from field stars. We calculate RV membership probabilities for over 1200 stars in our sample. 418 are probable cluster members, of which 64 are velocity-variable (binary) systems. Here we present 52 orbital solutions for binary members of M35. This sample defines the hard binary population of M35 that dynamically powers the cluster. We also present XMM-Newton X-ray detections within the cluster. We use our large binary sample to search for interacting binaries among the X-ray sources, investigate M35's period-eccentricity distribution, and determine binary frequency. We find a circularization period of 9.9+/-1.2days and a binary frequency of 24%+/-3% for main-sequence binaries with P<10^4^days. Determining these properties in a young cluster like M35 is key to defining the initial conditions used in models of cluster dynamical evolution.
- ID:
- ivo://CDS.VizieR/J/AJ/151/152
- Title:
- WOCS. LXXI. Spectroscopy of 5 stars in NGC 6791
- Short Name:
- J/AJ/151/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an optical color-magnitude diagram, sub-subgiants (SSGs) lie redward of the main sequence and fainter than the base of the red giant branch in a region not easily populated by standard stellar-evolution pathways. In this paper, we present multi-epoch radial velocities for five SSG candidates in the old and metal-rich open cluster NGC 6791 (8Gyr, [Fe/H]=+0.30). From these data, we are able to make three-dimensional kinematic membership determinations and confirm four SSG candidates as likely cluster members. We also identify three member SSGs as short-period binary systems and present their orbital solutions. These are the first SSGs with known three-dimensional kinematic membership, binary status, and orbital parameters since the two SSGs in M67 studied by Mathieu et al. We also remark on the other properties of these stars including photometric variability, H{alpha} emission, and X-ray luminosity. The membership confirmation of these SSGs in NGC 6791 strengthens the case that SSGs are a new class of nonstandard stellar evolution products, and that a physical mechanism must be found that explains the evolutionary paths of these stars.
- 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/AJ/160/169
- Title:
- WOCS. LXXXII. Orbital parameters & RVs in NGC 7789
- Short Name:
- J/AJ/160/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extensive time-series radial-velocity (RV) survey of stars in the rich open cluster NGC7789 (1.6Gyr, [Fe/H]=+0.02). The stellar sample lies within an 18' circular radius from the cluster center (10pc in projection, or about 2core radii), and includes giants, red clump stars, blue stragglers, red stragglers, sub-subgiants, and main-sequence stars down to 1mag below the turnoff. Our survey began in 2005 and comprises more than 9000 RV measurements from the Hydra Multi-Object Spectrograph on the WIYN 3.5m telescope. We identify 624 likely cluster members and present the orbital solutions for 81 cluster binary stars with periods between 1.45 and 4200days. From the main-sequence binary solutions we fit a circularization period of 7.2_-1.1_^+0.6^days. We calculate an incompleteness-corrected main- sequence binary frequency of 31%{+/-}4% for binaries with periods less than 104days, similar to other WIYN Open Cluster Survey (WOCS) open clusters of all ages. We detect a blue straggler binary frequency of 33%{+/-}17%, consistent with the similarly aged open cluster NGC6819. We also find one secure, rapidly rotating sub-subgiant and one red straggler candidate in our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/331/949
- Title:
- Wolf-Rayet and O-star runaways kinematics
- Short Name:
- J/A+A/331/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reliable systemic radial velocities are almost impossible to secure for Wolf-Rayet stars, difficult for O stars. Therefore, to study the motions - both systematic in the Galaxy and peculiar - of these two related types of hot, luminous star, we have examined the Hipparcos proper motions of some 70 stars of each type. We find that (a) both groups follow Galactic rotation in the same way, (b) both have a similar fraction of ``runaways'', (c) mean kinetic ages based on displacement and motion away from the Galactic plane tend to slightly favour the cluster ejection over the the binary supernova hypothesis for their formation, and (d) those with significant peculiar supersonic motion relative to the ambient ISM, tend to form bow shocks in the direction of the motion.
