- ID:
- ivo://CDS.VizieR/J/A+A/561/A94
- Title:
- Velocities and photometry in Trumpler 20
- Short Name:
- J/A+A/561/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Trumpler 20 is an old open cluster (OC) located toward the Galactic centre, at about 3kpc from the Sun and ~7kpc from the Galactic centre. Its position makes this cluster particularly interesting in the framework of the chemical properties of the Galactic disc because very few old OCs reside in the inner part of the disc. For this reason it has been selected as a cluster target of the Gaia-ESO Survey, and spectra of many stars in the main sequence and red clump phases are now available. Moreover, although it has been studied by several authors in the past, no consensus on the evolutionary status of Tr 20 has been reached. The heavy contamination of field stars (the line of sight of Tr 20 crosses the Carina spiral arm) complicates the correct interpretation. Another interesting aspect of the cluster is that it shows a broadened main sequence turn-off and a prominent and extended red clump, characteristics that are not easily explained by classical evolutionary models. Exploiting both spectroscopic information from the Gaia-ESO Survey (and the ESO archive) and literature photometry, we obtain a detailed and accurate analysis of the properties of the cluster. We make use of the first accurate metallicity measurement ever obtained from several spectra of red clump stars, and of cluster membership determination using radial velocities. According to the evolutionary models adopted, we find that Tr 20 has an age in the range 1.35-1.66Gyr, an average reddening E(B-V) in the range 0.31-0.35mag, a distance modulus (m-M)_0_ between 12.64 and 12.72mag. The spectroscopic metallicity is [Fe/H]=+0.17dex. We discuss the structural properties of the object and constrain possible hypotheses for its broadened upper main sequence, by estimating the effect of differential reddening, and its extended red clump.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/485/95
- Title:
- Velocities of F-G-K stars in Blanco 1
- Short Name:
- J/A+A/485/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby open cluster Blanco 1 is of considerable astrophysical interest for formation and evolution studies of open clusters because it is the third highest Galactic latitude cluster known. It has been observed often, but so far no definitive and comprehensive membership determination is readily available. An observing programme was carried out to study the stellar population of Blanco 1, and especially the membership and binary frequency of the F5-K0 dwarfs. We obtained radial-velocities with the CORAVEL spectrograph in the field of Blanco 1 for a sample of 148 F-G-K candidate stars in the magnitude range 10<V<14. New proper motions and UBVI CCD photometric data from two extensive surveys were obtained independently and are used to establish reliable cluster membership assignments in concert with radial-velocity data. The membership of 68 stars is confirmed on the basis of proper motion, radial velocity, and photometric criteria. Fourteen spectroscopic- and suspected binaries (2 SB2s, 9 SB1s, 3SB?) have been discovered among the confirmed members. Thirteen additional stars are located above the main sequence or close to the binary ridge, with radial velocities and proper motions supporting their membership. These are probable binaries with wide separations. Nine binaries (7 SB1 and 2 SB2) were detected among the field stars. The spectroscopic binary frequency among members is 20% (14/68); however, the overall binary rate reaches 40% (27/68) if one includes the photometric binaries. The cluster mean heliocentric radial velocity is +5.53+/-0.11km/s based on the most reliable 49 members. The Vsini distribution is similar to that of the Pleiades, confirming the age similarities between the two clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/346/390
- Title:
- VI and CMT1 photometry of NGC 2627
- Short Name:
- J/MNRAS/346/390
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Charge-coupled device (CCD) photometry in the Johnson V, Kron-Cousins I and Washington CMT1 systems is presented in the field of the poorly known open cluster NGC 2627.
- ID:
- ivo://CDS.VizieR/J/MNRAS/349/641
- Title:
- VIc, CT1 magnitudes in Trumpler 5
- Short Name:
- J/MNRAS/349/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in the Johnson V, Kron-Cousins I and the Washington system C and T_1_ passbands have been used to generate colour-magnitude diagrams (CMDs) reaching down to V~21.0mag and T_1_~19.0 for Trumpler 5, an old open cluster located towards the Galactic anticentre. Our data analysis confirms the existence of non-uniform extinction over the face of the cluster, the mean E(V-I) and E(C-T_1_) values being 0.80+/-0.05 and 1.17+/-0.15, respectively. Through comparison of the cluster CMDs with theoretical isochrones of the Geneva group, Washington Standard Giant Branches and measures of V and T_1_ indices, we derive the following values for the cluster apparent distance modulus, age, and metallicity: V-M_V_=13.80+/-0.30 (corresponding to a distance from the Sun of 2.4+/-0.5 kpc and 0.04kpc above the Galactic plane), t=5.0+/-0.5Gyr and [Fe/H]=-0.30+/-0.15. We estimate the cluster angular radius to be about 7.7 arcmin (=5.4pc) from star counts carried out within and outside the cluster field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3058
- Title:
- VIc photometry of IR-excess stars in NGC6611
- Short Name:
- J/MNRAS/435/3058
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Attention is given to a population of 110 stars in the NGC 6611 cluster of the Eagle nebula that have prominent near-infrared excess and optical colours typical of pre-main-sequence (PMS) stars older than 8Myr. At least half of those for which spectroscopy exists have a H{alpha} emission line profile revealing active accretion. In principle, the V-I colours of all these stars would be consistent with those of young PMS objects (<1Myr) whose radiation is heavily obscured by a circumstellar disc seen at high inclination and in small part scattered towards the observer by the back side of the disc. However, using theoretical models it is shown here that objects of this type can only account for a few percent of this population. In fact, the spatial distribution of these objects, their X-ray luminosities, their optical brightness, their positions in the colour-magnitude diagram and the weak Li absorption lines of the stars studied spectroscopically suggest that most of them are at least eight times older than the ~1Myr-old PMS stars already known in this cluster and could be as old as ~30Myr. This is the largest homogeneous sample to date of Galactic PMS stars considerably older than 8Myr that are still actively accreting from a circumstellar disc and it allows us to set a lower limit of 7 percent to the disc frequency at ~16Myr in NGC 6611. These values imply a characteristic exponential lifetime of ~6Myr for disc dissipation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/377/741
- Title:
- VIc photometry of NGC 2516
- Short Name:
- J/MNRAS/377/741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of an i-band time-series photometric survey of NGC2516 using the Cerro Tololo Inter-American Observatory (CTIO) 4-m Blanco telescope and 8k Mosaic-II detector, achieving better than 1 per cent photometric precision per data point over 15<~i<~19. Candidate cluster members were selected from a V versus V-I colour-magnitude diagram over 16<V<26 (covering masses from 0.7M_{sun}_ down to below the brown dwarf limit), finding 1685 candidates, of which we expect ~1000 to be real cluster members, taking into account contamination from the field (which is most severe at the extremes of our mass range). Searching for periodic variations in these gave 362 detections over the mass range 0.15<~M/M_{sun}_<~0.7. The rotation period distributions were found to show a remarkable morphology as a function of mass, with the fastest rotators bounded by P>0.25d, and the slowest rotators for M<~0.5M_{sun}_ bounded by a line of P~M3, with those for M>~0.5M_{sun}_ following a flatter relation closer to P ~ constant. Models of the rotational evolution were investigated, finding that the evolution of the fastest rotators was well reproduced by a conventional solid body model with a mass-dependent saturation velocity, whereas core-envelope decoupling was needed to reproduce the evolution of the slowest rotators. None of our models were able to simultaneously reproduce the behaviour of both populations.
- ID:
- ivo://CDS.VizieR/J/A+A/390/961
- Title:
- VI photometry in NGC 188
- Short Name:
- J/A+A/390/961
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used HST-WFPC2 to study the white dwarf luminosity function of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster (~5Gyr) by looking at the faint end of the cooling sequence (down to V~26.5).
- ID:
- ivo://CDS.VizieR/J/AJ/147/42
- Title:
- V light curves of EP Cep, ES Cep, and V369 Cep
- Short Name:
- J/AJ/147/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q=0.15, while ES Cep has a relatively high-mass ratio, q=0.69, indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2228
- Title:
- VRI photometry of PMS stars in NGC 2264 OB
- Short Name:
- J/AJ/127/2228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We summarize the results of an observing campaign to identify periodic pre-main-sequence (PMS) variables in the NGC 2264 OB association. We find 201 periodic candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/601/979
- Title:
- vsini of Orion low-mass stars
- Short Name:
- J/ApJ/601/979
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Projected rotational velocities (vsini) have been measured for a sample of 145 stars with masses between 0.4 and greater than 10M_{sun}_ (median mass 2.1M_{sun}_) located in the Orion star-forming complex. These measurements have been supplemented with data from the literature for Orion stars with masses as low as 0.1M_{sun}_.