- ID:
- ivo://CDS.VizieR/J/ApJ/733/115
- Title:
- Rotation periods and membership in M34
- Short Name:
- J/ApJ/733/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 5 month photometric time-series survey for stellar rotation periods combined with a 4 year radial-velocity survey for membership and binarity in the 220Myr open cluster M34. We report surface rotation periods for 120 stars, 83 of which are kinematic and photometric late-type cluster members. A comparison to previous work serves to illustrate the importance of high-cadence long baseline photometric observations and membership information. The new M34 periods are less biased against slow rotation and cleaned for non-members. The rotation periods of the cluster members span over more than an order of magnitude from 0.5 days up to 11.5 days, and trace two distinct rotational sequences -fast (C) and moderate-to-slow (I)- in the color-period diagram. The sequences represent two different states (fast and slow) in the rotational evolution of the late-type cluster members. We use the color-period diagrams for M34 and for younger and older clusters to estimate the timescale for the transition from the C to the I sequence and find <~150Myr, ~150-300Myr, and ~300-600 Myr for G, early-mid K, and late K dwarfs, respectively. The small number of stars in the gap between C and I suggests a quick transition. We determine a gyrochronology age of 240Myr for M34.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/879/49
- Title:
- Rotation periods for 171 Gaia members of NGC 6811
- Short Name:
- J/ApJ/879/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation was proposed as a potential age diagnostic that is precise, simple, and applicable to a broad range of low-mass stars (<=1M_{sun}_). Unfortunately, rotation period (P_rot_) measurements of low-mass members of open clusters have undermined the idea that stars spin down with a common age dependence (i.e., P_rot{propto}age^0.5^): K dwarfs appear to spin down more slowly than F and G dwarfs. Agueros+ (2018, J/ApJ/862/33) interpreted data for the ~1.4Gyr-old cluster NGC 752 differently, proposing that after having converged onto a slow-rotating sequence in their first 600-700Myr (by the age of Praesepe), K dwarf P_rot_ stall on that sequence for an extended period of time. We use data from Gaia DR2 to identify likely single-star members of the ~1Gyr-old cluster NGC 6811 with Kepler light curves. We measure P_rot_ for 171 members, more than doubling the sample relative to the existing catalog and extending the mass limit from ~0.8 to ~0.6M_{sun}_. We then apply a gyrochronology formula calibrated with Praesepe and the Sun to 27 single G dwarfs in NGC 6811 to derive a precise gyrochronological age for the cluster of 1.04+/-0.07Gyr. However, when our new low-mass rotators are included, NGC 6811's color-P_rot_ sequence deviates away from the naive 1Gyr projection down to T_eff_~4295K (K5V, 0.7M_{sun}), where it clearly overlaps with Praesepe's. Combining these data with P_rot_ for other clusters, we conclude that the assumption that mass and age are separable dependencies is invalid. Furthermore, the cluster data show definitively that stars experience a temporary epoch of reduced braking efficiency where P_rot_ stall, and that the duration of this epoch lasts longer for lower-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A60
- Title:
- Rotation periods for NGC 3532
- Short Name:
- J/A+A/652/A60
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- A very rich cluster intermediate in age between the Pleiades (150Myr) and the Hyades (600Myr) is needed to probe the rotational evolution, especially the transition between fast and slow rotation that occurs between the two ages. We study the rich 300Myr-old open cluster NGC 3532 to probe this important transition and to provide constraints on angular momentum loss. Measuring the rotation periods builds on our prior work of providing spectroscopic membership information for the cluster, and it supports the chromospheric activity measurements of cluster stars that we provide in a companion paper. Using 42d-long photometric time series observations obtained with the Yale 1m telescope at CTIO, we measured rotation periods for members of NGC 3532 and compared them with the predictions of angular momentum evolution models. We directly measured 176 photometric rotation periods for the cluster members. An additional 113 photometric rotation periods were identified using activity information, described fully in the companion paper, resulting in a total sample containing 279 rotation periods for FGKM stars in NGC 3532. The colour-period diagram constructed from this rich data set shows a well-populated and structured slow rotator sequence, and a fast rotator sequence evolved beyond zero-age main sequence age whose stars are in transition from fast to slow rotation. The slow rotator sequence itself is split into slightly slower and faster rotators, a feature we trace to photometric binary status. We also identify an extended slow rotator sequence extending to P~32d, apparently the analogue of the one we previously identified in NGC 2516. We compare our period distribution to rotational isochrones in colour-period space and find that all considered models have certain shortcomings. Using more detailed spin-down models, we evolve the rotation periods of the younger NGC 2516 forward in time and find that the spindown of the models is too aggressive with respect to the slow rotators. In contrast, stars on the evolved fast rotator sequence are not spun down strongly enough by these models. Our observations suggest a shorter crossing time for the rotational gap, one we estimate to be ~80Myr for early-K dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/417/557
- Title:
- Rotation & variability of PMS Stars in NGC 2264
- Short Name:
- J/A+A/417/557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 4 lists the 10554 stars in the area of NGC 2264 between I_C_=9.8mag and I_C_=21mag on which we did photometry. It contains information on the position, brightness, colours and the variability of these stars. It also lists the spectral type taken from the literature (if available) as well as the identification numbers of the stars in other studies. Table 6 lists the stars detected as periodic in this study and gives their brightness, periods determined by different periodogram techniques, and the period finally adopted as well as the estimated period error. Stars which passed the two adopted PMS tests are also indicated. Time series data were obtained in the I_C_ band in 44 nights between Dec. 2000 and March 2001 with the Wide Field Imager (WFI) on the MPG/ESO 2.2m telescope on La Silla (Chile).
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/1380
- Title:
- Rotation velocities in Pleiades and {alpha}Per
- Short Name:
- J/MNRAS/402/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate to what extent the spin axes of stars in young open clusters are aligned. Assuming that the spin vectors lie uniformly within a conical section, with an opening half-angle between {lambda}=0{deg} (perfectly aligned) and {lambda}=90{deg} (completely random), we describe a Monte Carlo modelling technique that returns a probability density for this opening angle given a set of measured sini values, where i is the unknown inclination angle between a stellar spin vector and the line of sight.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/14
- Title:
- ~17000 runaways stars from the Orion Nebula Cluster
- Short Name:
- J/ApJ/900/14
- Date:
- 14 Mar 2022 08:53:06
- Publisher:
- CDS
- Description:
- We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45{deg} around the ONC and out to 1 kpc to find sources that have overlapped in angular position with the cluster in the last ~10Myr. We find ~17000 runaway/walkaway candidates that satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and Wide-field Infrared Survey Explorer photometry; (3) having a high degree of optical variability; (4) having closest approach distances well-constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC, and discuss its implications for cluster formation theories via comparison with numerical simulations.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A115
- Title:
- Ruprecht 147 DANCe. I.
- Short Name:
- J/A+A/625/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ruprecht 147 is the oldest (2.5Gyr) open cluster in the solar vicinity (<300pc), making it an important target for stellar evolution studies and exoplanet searches. We aim to derive a census of members and the luminosity, mass, and spatial distributions of the cluster. We used an astro-photometric data set including all available information from the literature together with our own observations. We processed the data with an updated version of an existent membership selection methodology. We identify 259 high-probability candidate members, including 58 previously unreported. All these candidates cover the luminosity interval between G>6mag to i<21mag. The cluster luminosity and mass distributions are derived with an unprecedented level of details allowing us to recognize, among other features, the Wielen dip. The mass distribution in the low-mass regime drops sharply at 0.4M_{sun}_ even though our data are sensitive to stellar masses down to 0.1M_{sun}_, suggesting that most very-low-mass members left the cluster as the result of its dynamical evolution. In addition, the cluster is highly elongated (ellipticity~0.5) towards the galactic plane, and mass segregated. Our combined Gaia+DANCe data set allows us to obtain an extended list of cluster candidate members, and to derive luminosity, mass, and projected spatial distributions in the oldest open cluster of the solar vicinity.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A27
- Title:
- RV and [Fe/H] in 5 open clusters
- Short Name:
- J/A+A/578/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims. We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. We acquired medium-resolution spectra (R~8000) in the infrared region CaII triplet lines (~8500{AA}) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca ii lines and metallicity were also used to derive the metallicity for each cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/817
- Title:
- RV catalog of O-type stars in IC 2944 and Cen OB2
- Short Name:
- J/MNRAS/416/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an extended set of multi-epoch high resolution high signal-to-noise ratio optical spectra, we re-address the multiplicity properties of the O-type stars in IC 2944 and in the Cen OB2 association. We present new evidence of binarity for five objects and we confirm the multiple nature of another two. We derive the first orbital solutions for HD 100099, HD 101436 and HD 101190 and we provide additional support for HD 101205 being a quadruple system. The minimal spectroscopic binary fraction in our sample is f_min_=0.57. Using numerical simulations, we show that the detection rate of our observational campaign is close to 90%, leaving thus little room for undetected spectroscopic binary systems. The statistical properties of the O-star population in IC 2944 are similar, within the uncertainties, to the results obtained in the earlier papers in this series despite the fact that sample size effects limit the significance of the comparison. Using newly derived spectroscopic parallaxes, we reassess the distance to IC 2944 and obtained 2.3+/-0.3kpc, in agreement with previous studies. We also confirm that, as far as the O stars are concerned, the IC 2944 cluster is most likely a single entity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/1479
- Title:
- RV catalogue of O-type stars in NGC 6611
- Short Name:
- J/MNRAS/400/1479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on a set of over 100 medium- to high-resolution optical spectra collected from 2003 to 2009, we investigate the properties of the O-type star population in NGC 6611 in the core of the Eagle Nebula (M16). Using a much more extended data set than previously available, we revise the spectral classification and multiplicity status of the nine O-type stars in our sample. We confirm two suspected binaries and derive the first SB2 orbital solutions for two systems. We further report that two other objects are displaying a composite spectrum, suggesting possible long- period binaries. Our analysis is supported by a set of Monte-Carlo simulations, allowing us to estimate the detection biases of our campaign and showing that the latter do not affect our conclusions. The absolute minimal binary fraction in our sample is f_min_=0.44 but could be as high as 0.67 if all the binary candidates are confirmed. As in NGC 6231 (see Paper I, Sana et al., Cat. J/MNRAS/386/447), up to 75% of the O star population in NGC 6611 are found in an O+OB system, thus implicitly excluding random pairing from a classical IMF as a process to describe the companion association in massive binaries. No statistical difference could be further identified in the binary fraction, mass-ratio and period distributions between NGC 6231 and NGC 6611, despite the difference in age and environment of the two clusters.
