- ID:
- ivo://CDS.VizieR/J/MNRAS/477/3197
- Title:
- Radial velocities of Hyades members
- Short Name:
- J/MNRAS/477/3197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the membership of the Hyades open cluster, derive kinematically modelled parallaxes of its members, and study the colour-absolute magnitude diagram of the cluster. We use Gaia DR1 Tycho-Gaia Astrometric Solution (TGAS) data complemented by Hipparcos-2 data for bright stars not contained in TGAS. We supplement the astrometric data with radial velocities collected from a dozen literature sources. By assuming that all cluster members move with the mean cluster velocity to within the velocity dispersion, we use the observed and the expected motions of the stars to determine individual cluster membership probabilities. We subsequently derive improved parallaxes through maximum-likelihood kinematic modelling of the cluster. This method has an iterative component to deal with 'outliers', caused for instance by double stars or escaping members. Our method extends an existing method and supports the mixed presence of stars with and without radial velocities. We find 251 candidate members, 200 of which have a literature radial velocity, and 70 of which are new candidate members with TGAS astrometry. The cluster is roughly spherical in its centre but significantly flattened at larger radii. The observed colour-absolute magnitude diagram shows a clear binary sequence. The kinematically modelled parallaxes that we derive are a factor ~1.7/2.9 more precise than the TGAS/ Hipparcos-2 values and allow us to derive an extremely sharp main sequence. This sequence shows evidence for fine-detailed structure that is elegantly explained by the full spectrum turbulence model of convection.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/127/3579
- Title:
- Radial velocities of Hyades stars
- Short Name:
- J/AJ/127/3579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a radial velocity survey of a sample of Hyades stars and discuss the effects of stellar activity on radial velocity measurements. The level of radial velocity scatter due to rotational modulation of stellar surface features for the Hyades is in agreement with the 1997 predictions of Saar and Donahue (1997ApJ...485..319S) - the maximum radial velocity rms of up to ~50m/s, with an average rms of ~16m/s. In this sample of 93 stars we find one new binary, two stars with linear trends indicative of binary companions, and no close-in giant planets. We discuss the limits on extrasolar planet detection in the Hyades and the constraints imposed on radial velocity surveys of young stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/648/1090
- Title:
- Radial velocities of NGC 2264 stars
- Short Name:
- J/ApJ/648/1090
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from 1078 high-resolution spectra of 990 stars in the young open cluster NGC 2264, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5m MMT. We confirm 471 stars as members on the basis of their radial velocity and/or H{alpha} emission.
- ID:
- ivo://CDS.VizieR/J/A+A/354/881
- Title:
- Radial velocities of Praesepe & Hyades Am stars
- Short Name:
- J/A+A/354/881
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CORAVEL radial-velocity observations of Am stars in the Hyades and Praesepe have allowed the determination of orbital elements for 10 spectroscopic binaries, among which 3 are first determinations. One Am star (KW 40) is found to be a well hierarchised triple system. KW 538 has a rather long period (435 days) for an Am star. Orbits of systems with periods shorter than 8.5 days are circularized, or present eccentricities smaller than 0.04. For 19 Am stars, the number of quadruple-, triple-, double-, single systems is 1:2:14(10+4?):(2?). The Am stars in a ({beta}, B-V) diagram clearly stand away by 0.03mag from the sequence defined by normal main-sequence stars. This diagram could be a powerful method to identify Am stars in more distant open clusters, provided there is no differential reddening. In the colour-magnitude diagram (M_V_, {beta}), double-lined binaries are 0.6-0.7mag above the ZAMS as expected, while most single-lined are close to or on the ZAMS because the secondary does not contribute much light. The absence of X-ray detection of 4 systems in the Hyades is an argument for the presence of a white dwarf secondary.
- ID:
- ivo://CDS.VizieR/J/A+A/399/105
- Title:
- Radial velocities of red giants in NGC 1817
- Short Name:
- J/A+A/399/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial-velocity and BV CCD observations of 29 red-giant candidates in the central part of the intermediate-age open cluster NGC 1817 have confirmed the membership of 21 stars. In addition, we have used radial velocities and new UBVR photoelectric photometry to investigate the membership of 59 new candidates located in an outer corona surrounding NGC 1817, identified from the POSS plates. We have confirmed 18 new members out to a distance of 27' from the centre, thus doubling the previous cluster radius. Ten definite spectroscopic-binary members have been discovered, corresponding to a binary frequency of 25.6% and four orbits have been determined so far. Three additional stars have been identified as possible spectroscopic-binary members. We derive a cluster mean velocity of +65.33+/-0.09 (0.52 s.e.) km/s based on 29 members with no detected velocity variations plus the 3 binary members with orbital solutions.
- ID:
- ivo://CDS.VizieR/J/A+A/319/481
- Title:
- Radial velocities of 10 spectroscopic binaries
- Short Name:
- J/A+A/319/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new orbits for ten (single-lined) spectroscopic binaries in seven open clusters: NGC 2489, 2567, 3033, 5822, 6134, 6664 and IC 2488 based on 243 individual radial velocities obtained with the southern CORAVEL scanner. The orbital periods range from 98.5 to 3566 days. The shortest-period orbit is circular, as expected. Seven of the binaries are confirmed cluster members, one is a possible member, and two are clearly non-members. Maximum masses from photometric separation and minimum masses from the spectroscopic orbits define the mass of the secondaries within an interval of M_max_-M_min_=0.5M_{sun}_. NGC 6664 #54 seems to have a rather massive secondary (M>3M_{sun}_), but the UBV colours appear normal for a luminous red giant, while significantly bluer (B-V) and (U-B) colours would be expected. It could be a triple system, the secondary being itself a short period binary. This paper brings the number of orbits published in this programme to 53, 45 of which are confirmed red-giant cluster members and 8 are non-members
- ID:
- ivo://CDS.VizieR/J/AJ/149/119
- Title:
- Radial velocities of stars in NGC 2264
- Short Name:
- J/AJ/149/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an expanded kinematic study of the young cluster NGC 2264 based upon optical radial velocities measured using multi-fiber echelle spectroscopy at the 6.5m MMT and Magellan telescopes. We report radial velocities for 695 stars, of which approximately 407 stars are confirmed or very likely members. Our results more than double the number of members with radial velocities from Furesz et al., resulting in a much better defined kinematic relationship between the stellar population and the associated molecular gas. In particular, we find that there is a significant subset of stars that are systematically blueshifted with respect to the molecular (^13^CO) gas. The detection of Lithium absorption and/or infrared excesses in this blueshifted population suggests that at least some of these stars are cluster members; we suggest some speculative scenarios to explain their kinematics. Our results also more clearly define the redshifted population of stars in the northern end of the cluster; we suggest that the stellar and gas kinematics of this region are the result of a bubble driven by the wind from O7 star S Mon. Our results emphasize the complexity of the spatial and kinematic structure of NGC 2264, important for eventually building up a comprehensive picture of cluster formation.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A146
- Title:
- Radial velocities of stars in NGC 2546
- Short Name:
- J/A+A/633/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a broader project on the role of binary stars in clusters, we present a spectroscopic study of the open cluster NGC 2546, which is a large cluster lacking previous spectroscopic analysis. We report the finding of two open clusters in the region of NGC 2546. For the two star groups, we determine radial velocity, parallax, proper motion, reddening, distance modulus, and age, using our spectroscopic observations and available photometric and astrometric data, mainly from Gaia Data Release 2 (Gaia DR2). We also determine the orbit of four spectroscopic binaries in these open clusters. From mid-resolution spectroscopic observations for 28 stars in the NGC 2546 region, we determined radial velocities and evaluate velocity variability. To analyze double-lined spectroscopic binaries, we used a spectral separation technique and fit the spectroscopic orbits using a least-squares code. The presence of two stellar groups is suggested by the radial velocity distribution and confirmed by available photometric and astrometric data. We applied a multi-criteria analysis to determine cluster membership, and we obtained kinematic and physical parameters of the clusters. NGC 2546 is actually two clusters, NGC 2546A and NGC 2546B, the are not physically related to each other. NGC 2546A has an age of about 180Myr and a distance of 950pc. It has a half-number radius of 8pc and contains about 480 members brighter than G=18 mag. NGC 2546B is a very young cluster (<10Myr) located at a distance of 1450pc. It is a small cluster with 80 members and a half-number radius of 1.6pc. Stars less massive than 2.5 solar masses in this cluster would be pre- main-sequence objects. We detected four spectroscopic binaries and determined their orbits. The two binaries of NGC 2546A contain chemically peculiar components: HD 68693 is composed of two mercury- manganese stars and HD 68624 has a Bp silicon secondary. Among the most massive objects of NGC 2546B, there are two binary stars: HD 68572, with P=124.2d, and CD -37 4344 with P=10.4d.
- ID:
- ivo://CDS.VizieR/J/A+A/415/145
- Title:
- Radial velocities of 16 stars in NGC 6913
- Short Name:
- J/A+A/415/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Between 1996 and 2003 we obtained 226 high resolution spectra of 16 stars in the field of the young open cluster NGC 6913, to constrain its main properties and study its internal kinematics. Twelve of the program stars turned out to be members, one of them probably unbound. Nine are binaries (one eclipsing and another double lined) and for seven of them the observations allowed us to derive the orbital elements. All but two of the nine discovered binaries are cluster members. In spite of the young age (a few Myr), the cluster already shows signs that could be interpreted as evidence of dynamical relaxation and mass segregation. However, they may be also the result of an unconventional formation scenario. The dynamical (virial) mass as estimated from the radial velocity dispersion is larger than the cluster luminous mass, which may be explained by a combination of the optically thick interstellar cloud that occults part of the cluster, the unbound state or undetected very wide binary orbit of some of the members that inflate the velocity dispersion and a high inclination for the axis of possible cluster angular momentum. All the discovered binaries are hard enough to survive average close encounters within the cluster and do not yet show signs of relaxation of the orbital elements to values typical of field binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A4
- Title:
- Radial velocities of stars in NGC 2302 field
- Short Name:
- J/A+A/580/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spiral structure of the Milky Way (MW) is highly uncertain and is the subject of much discussion nowadays. Even the spiral structure close to the Sun and the real nature of the so-called Local or Orion arm are poorly known. We present the first result from a program that determines the properties of the Local (Orion) spiral arm (LOA), together with a full description of the program. In this context we have made a comprehensive study of the young LOA open cluster NGC 2302, which includes a UBVRI photometric analysis and determination of its kinematic properties - proper motion (PM) and radial velocity (RV) - and of its orbital parameters.
