- ID:
- ivo://CDS.VizieR/J/AJ/132/2665
- Title:
- QUEST2 BRI photometry of Taurus-Auriga PMS
- Short Name:
- J/AJ/132/2665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a drift-scan survey covering a ~5{deg}x5{deg} region toward the southern portion of the Taurus-Auriga molecular cloud. Data taken in the B,R,I filters with the Quest-2 camera on the Palomar 48 inch (1.2m) Samuel Oschin Telescope were combined with Two Micron All Sky Survey near-infrared photometry to select candidate young stars. Follow-up optical spectroscopy of 190 candidates led to the identification of 42 new low-mass pre-main-sequence stars with spectral types M4-M8, of which approximately half exhibit surface gravity signatures similar to known Taurus stars, while the other half exhibit surface gravity signatures similar to members of the somewhat older Upper Scorpius, TW Hya, and Pic associations.
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- ID:
- ivo://CDS.VizieR/J/A+A/618/A2
- Title:
- Quintuplet cluster updated stellar census
- Short Name:
- J/A+A/618/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Found within the central molecular zone, the Quintuplet is one of the most massive young clusters in the Galaxy. As a consequence it offers the prospect of constraining stellar formation and evolution in extreme environments. However, current observations suggest that it comprises a remarkably diverse stellar population that is difficult to reconcile with an instantaneous formation event. To better understand the nature of the cluster our aim is to improve observational constraints on the constituent stars. In order to accomplish this goal we present Hubble Space Telescope/NICMOS+WFC3 photometry and Very Large Telescope/SINFONI+KMOS spectroscopy for ~100 and 71 cluster members, respectively. Spectroscopy of the cluster members reveals the Quintuplet to be far more homogeneous than previously expected. All supergiants are classified as either O7-8 Ia or O9-B0 Ia, with only one object of earlier (O5 I-III) spectral type. These stars form a smooth morphological sequence with a cohort of seven early-B hypergiants and six luminous blue variables and WN9-11h stars, which comprise the richest population of such stars of any stellar aggregate known. In parallel, we identify a smaller population of late-O hypergiants and spectroscopically similar WN8-9ha stars. No further H-free Wolf-Rayet (WR) stars are identified, leaving an unexpectedly extreme ratio of 13:1 for WC/WN stars. A subset of the O9-B0 supergiants are unexpectedly faint, suggesting they are both less massive and older than the greater cluster population. Finally, no main sequence objects were identifiable. Due to uncertainties over which extinction law to apply, it was not possible to quantitatively determine a cluster age via isochrone fitting. Nevertheless, we find an impressive coincidence between the properties of cluster members preceding the H-free WR phase and the evolutionary predictions for a single, non-rotating 60M_{sun}_ star; in turn this implies an age of ~3.0-3.6Myr for the Quintuplet. Neither the late O-hypergiants nor the low luminosity supergiants are predicted by such a path; we suggest that the former either result from rapid rotators or are the products of binary driven mass-stripping, while the latter may be interlopers. The H-free WRs must evolve from stars with an initial mass in excess of 60M_{sun}_ but it appears difficult to reconcile their observational properties with theoretical expectations. This is important since one would expect the most massive stars within the Quintuplet to be undergoing core-collapse/SNe at this time; since the WRs represent an evolutionary phase directly preceding this event,their physical properties are crucial to understanding both this process and the nature of the resultant relativistic remnant. As such, the Quintuplet provides unique observational constraints on the evolution and death of the most massive stars forming in the local, high metallicity Universe.
813. RACE-OC project. II.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A10
- Title:
- RACE-OC project. II.
- Short Name:
- J/A+A/532/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotational properties of late-type low-mass members of associations of known age provide a fundamental source of information on stellar internal structure and its evolution. We aim at determining the rotational and magnetic-related activity properties of stars at different stages of evolution. We focus our attention primarily on members of young stellar associations of known ages. Specifically, we extend our previous analysis in Paper I (Messina et al., 2010, Cat. J/A+A/520/A15) to 3 additional young stellar associations beyond 100pc and with ages in the range 6-40Myr: {epsilon} Chamaeleontis (~6Myr), Octans (~20Myr), and Argus (~40Myr). Additional rotational data of {eta} Chamaeleontis and IC 2391 clusters are also considered. Rotational periods were determined by applying the Lomb-Scargle periodogram technique to photometric time-series data obtained by the All Sky Automated Survey (ASAS) and the Wide Angle Search for Planets (SuperWASP) archives. The magnetic activity level was derived from the amplitude of the V light curves.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A29
- Title:
- RACE-OC project: M11 (NGC6705)
- Short Name:
- J/A+A/513/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotation and magnetic activity are intimately linked in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on stellar rotation, and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the rotation/activity/age connection. The open cluster M11 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters with different ages. Photometric observations of the open cluster M11 were carried out in June 2004 using LOAO 1m telescope. The rotation periods of the cluster members are determined by Fourier analysis of photometric data time series. We further investigated the relations between the surface activity, characterized by the light curve amplitude, and rotation. We have discovered a total of 75 periodic variables in the M11 FoV, of which 38 are candidate cluster members. Specifically, among cluster members we discovered 6 early-type, 2 eclipsing binaries and 30 bona-fide single periodic late-type variables. Considering the rotation periods of 16 G-type members of the almost coeval 200-Myr M34 cluster, we could determine the rotation period distribution from a more numerous sample of 46 single G stars at an age of about 200-230 Myr and determine a median rotation period P=4.8d. A comparison with the younger M35 cluster (~150Myr) and with the older M37 cluster (~550Myr) shows that G stars rotate slower than younger M35 stars and faster than older M37 stars. The measured variation of the median rotation period is consistent with the scenario of rotational braking of main-sequence spotted stars as they age.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A15
- Title:
- RACE-OC project: YSOs within 100pc
- Short Name:
- J/A+A/520/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Examining the angular momentum of stars and its interplay with their magnetic fields represent a promising way to probe the stellar internal structure and evolution of low-mass stars. We attempt to determine the rotational and magnetic-related activity properties of stars at different stages of evolution.We focused our attention primarily on members of clusters and young stellar associations of known ages. In this study, our targets are 6 young loose stellar associations within 100pc and with ages in the range 8-70Myr: TW Hydrae (~8Myr), beta Pictoris (~10Myr), Tucana/Horologium, Columba, Carina (~30Myr), and AB Doradus (~70Myr). Additional rotational data for alpha Persei and the Pleiades from the literature are also considered.
- ID:
- ivo://CDS.VizieR/J/A+A/485/303
- Title:
- Radial velocities for 1309 stars and 166 OCl
- Short Name:
- J/A+A/485/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the final catalogues of a long term observing program performed with the two Coravel spectrovelocimeters for red giants in open clusters. The main aims were to detect spectroscopic binaries and determine their orbital parameters, determine the membership, and compute mean velocities for the stars and open clusters. We computed weighted mean radial velocities for 1309 stars from 10517 individual observations, including the systemic radial velocities from spectroscopic orbits and for Cepheids. The final results are contained in three catalogues collecting 10517 individual radial velocities, mean radial velocities for 1309 red giants, and mean radial velocities for 166 open clusters, among which 57 are new determinations. We identify 891 members and 418 non-members. We discovered a total of 288 spectroscopic binaries, among which 57 were classified as non-members. In addition 27 stars were judged to be variable in radial velocities, all of them being red supergiants.
- ID:
- ivo://CDS.VizieR/J/AJ/147/69
- Title:
- Radial velocities in Be 44, Be 81, and NGC 6802
- Short Name:
- J/AJ/147/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities for stars in the field of the open star clusters Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained using the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope. These clusters are of intermediate age (1-3Gyr), located within the solar Galactocentric radius, and have no previous radial velocity measurements. We find mean radial velocities of -9.6{+/-}3.0km/s, 48.1{+/-}2.0km/s, and 12.4{+/-}2.8km/s for Be 44, Be 81, and NGC 6802, respectively. We present an analysis of radial velocities of 134 open clusters of a wide range of ages using data obtained in this study and the literature. Assuming the system of clusters rotates about the Galactic center with a constant velocity, we find older clusters exhibit a slower rotation and larger line-of-sight (LOS) velocity dispersion than younger clusters. The gradual decrease in rotational velocity of the cluster system with age is accompanied by a smooth increase in LOS velocity dispersion, which we interpret as the effect of heating on the open cluster system over time.
- ID:
- ivo://CDS.VizieR/J/A+A/507/541
- Title:
- Radial velocities in cluster Blanco 1
- Short Name:
- J/A+A/507/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a part of our program on binaries in open clusters, we present a spectroscopic study of the bright stars of Blanco 1 aimed at detecting and characterizing spectroscopic binaries. Forty five stars previously mentioned as cluster candidates, plus another 24 stars in a wider region around the cluster were observed repeatedly during 6 years, with a spectral resolving power 13300. Radial velocities were measured by cross-correlations. We obtained a mean cluster velocity of 6.2+/-0.3km/s and determined kinematic membership. Eleven spectroscopic binaries were detected, and orbital solutions are presented for eight of them. Six binaries are confirmed to be members of the cluster. All of them are single-lined spectroscopic systems with periods in the range 1.9-1380 days. Considering all suspected binaries, the cluster binary frequency amounts to about 50%.
- ID:
- ivo://CDS.VizieR/J/A+A/386/187
- Title:
- Radial velocities in IC 4651
- Short Name:
- J/A+A/386/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radial-velocity observations were made during the years 1989-1997 with the photoelectric scanner CORAVEL (Mayor, 1985IAUCo..88...35M) on the Danish 1.54-m telescope at ESO, La Silla. The individual mean errors given are computed from the measured S/N ratio and the shape of the cross-correlation profile (see Sect. 2.2 of this paper).
- ID:
- ivo://CDS.VizieR/J/AJ/150/97
- Title:
- Radial velocities in M67. I. 1278 candidate members
- Short Name:
- J/AJ/150/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from 13776 radial-velocity (RV) measurements of 1278 candidate members of the old (4Gyr) open cluster M67 (NGC 2682). The measurements are the results of a long-term survey that includes data from seven telescopes with observations for some stars spanning over 40years. For narrow-lined stars, RVs are measured with precisions ranging from about 0.1 to 0.8km/s. The combined stellar sample reaches from the brightest giants in the cluster down to about 4mag below the main-sequence turnoff (V=16.5), covering a mass range of about 1.34M_{sun}_ to 0.76M_{sun}_. Spatially, the sample extends to a radius of 30arcmin (7.4pc in projection at a distance of 850pc or 6-7 core radii). We find M67 to have a mean radial velocity of +33.64km/s (with an internal precision of +/-0.03km/s) well separated from the mean velocity of the field. For stars with >=3 measurements, we derive RV membership probabilities and identify RV variables, finding 562 cluster members, 142 of which show significant RV variability. We use these cluster members to construct a color-magnitude diagram and identify a rich sample of stars that lie far from the standard single star isochrone, including the well-known blue stragglers, sub-subgiants and yellow giants. These exotic stars have a binary frequency of (at least) 80%, more than three times that detected for stars in the remainder of the sample. We confirm that the cluster is mass segregated, finding the binaries to be more centrally concentrated than the single stars in our sample at the 99.8% confidence level (and at the 98.7% confidence level when only considering main-sequence stars). The blue stragglers are centrally concentrated as compared to the solar-type main-sequence single stars in the cluster at the 99.7% confidence level. Accounting for measurement precision, we derive an RV dispersion in M67 of 0.80+/-0.04km/s for our sample of single main-sequence stars, subgiants and giants with V{<=}15.5. When corrected for undetected binaries, this sample yields a true RV dispersion of 0.59_-0.06_^+0.07^km/s. The radial distribution of the velocity dispersion is consistent with an isothermal distribution within our stellar sample. Using the cluster RV dispersion, we estimate a virial mass for the cluster of 2100_-550_^+610^M_{sun}_.
