- ID:
- ivo://CDS.VizieR/J/A+A/623/A25
- Title:
- Photometric and astrometric study of NGC 6530
- Short Name:
- J/A+A/623/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6530 is a young cluster, with a complex morphology and star-formation history. We present a statistical study of its global properties, using a new, large list of candidate members down to masses of 0.2-0.4M_{sun}_ and Gaia DR2 astrometry. We consider a larger sky region compared to previous studies, to investigate the entire cluster until its periphery, including any diffuse population all around the main cluster. We study the distribution of extinction and age across the different regions, and obtain constraints on the star-formation history. We also study the dynamics of cluster members. Cluster membership was determined on the basis of literature X-ray data, H{alpha} emission, near-IR and UV excesses from the VPHAS+ and UKIDSS photometric surveys and published near-IR catalogs, and Gaia DR2 astrometry; moreover, we used a method for photometric selection of M-type pre-main-sequence cluster members, which we recently developed and used for other star-formation regions. The list of candidates includes nearly 3700 stars, of which we estimate approximately 2700 to be genuine NGC 6530 members. Using Gaia parallaxes, the cluster distance is found to be 1325pc, with errors of 0.5% (statistical) and 8.5% (systematic), in agreement with previous determinations. The cluster morphology and boundaries are established with great confidence, from the agreement between the subsamples of members selected using different criteria. There is no diffuse population of members around the cluster, but there are minor condensations of true members in addition to the two main groups in the cluster core and in the Hourglass nebula. Two such subgroups are spatially associated with the stars 7 Sgr (F2II-III) and HD 164536 (O7.5V). There is a definite pattern of sequential star formation across the cluster, within an age range from less than 0.5Myr to ~5Myr. Extinction is spatially non-uniform, with part of the population still embedded or obscured by thick dust. The precise Gaia proper motion data indicate that the NGC 6530 parent cloud collided with the Galactic plane around 4Myr ago, and we suggest that event as the trigger of the bulk of star formation in NGC 6530. The internal cluster dynamics is also partially resolved by the Gaia data, indicating expansion of the main cluster population with respect to its center.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/490/151
- Title:
- Photometric evolution of star clusters models
- Short Name:
- J/A+A/490/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To obtain an accurate description of broad-band photometric star cluster evolution, certain effects should be accounted for. Energy equipartition leads to mass segregation and the preferential loss of low-mass stars, while stellar remnants severely influence cluster mass-to-light ratios. Moreover, the stellar initial mass function and cluster metallicity affect photometry as well. Due to the continuous production of stellar remnants, their impact on cluster photometry is strongest for old systems like globular clusters. This, in combination with their low metallicities, evidence for mass segregation, and a possibly deviating stellar initial mass function, makes globular clusters interesting test cases for cluster models. In this paper we describe cluster models that include the effects of the preferential loss of low-mass stars, stellar remnants, choice of initial mass function and metallicity. The photometric evolution of clusters is predicted, and the results are applied to Galactic globular clusters. The cluster models presented in this paper represent an analytical description of the evolution of the underlying stellar mass function due to stellar evolution and dynamical cluster dissolution. Stellar remnants are included by using initial-remnant mass relations, while cluster photometry is computed from the Padova 1999 isochrones.
- ID:
- ivo://CDS.VizieR/V/140
- Title:
- Photometric rotation periods of stars in {alpha} Per
- Short Name:
- V/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a photometric monitoring program of primarily solar-type open cluster stars obtained during 1994 and 1995. Several members of the {alpha} Persei cluster have been monitored and the corresponding relation between coronal x-ray activity and rotation period derived. The relation among mid-G/K type members illustrates both the previously noticed downturn in L_X_/L_bol_ at high rotation rates and the sharp decrease in coronal activity at long rotation periods as seen among Pleiades stars. Intensive observation of one slowly rotating G-type member of IC 4665 has enabled a period determination of 8-10 days to be made and illustrates the need for (and limitations of) high quality observations.
- ID:
- ivo://CDS.VizieR/II/194A
- Title:
- Photometric study of IC 4665
- Short Name:
- II/194A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/152/75
- Title:
- Photometric survey of IC 2391, {eta} Cha, and USco
- Short Name:
- J/AJ/152/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The past two decades have seen a significant advancement in the detection, classification, and understanding of exoplanets and binaries. This is due, in large part, to the increase in use of small-aperture telescopes (<20cm) to survey large areas of the sky to milli-mag precision with rapid cadence. The vast majority of the planetary and binary systems studied to date consists of main-sequence or evolved objects, leading to a dearth of knowledge of properties at early times (<50Myr). Only a dozen binaries and one candidate transiting Hot Jupiter are known among pre-main-sequence objects, yet these are the systems that can provide the best constraints on stellar formation and planetary migration models. The deficiency in the number of well characterized systems is driven by the inherent and aperiodic variability found in pre-main-sequence objects, which can mask and mimic eclipse signals. Hence, a dramatic increase in the number of young systems with high-quality observations is highly desirable to guide further theoretical developments. We have recently completed a photometric survey of three nearby (<150pc) and young (<50Myr) moving groups with a small-aperture telescope. While our survey reached the requisite photometric precision, the temporal coverage was insufficient to detect Hot Jupiters. Nevertheless, we discovered 346 pre-main-sequence binary candidates, including 74 high-priority objects for further study.
- ID:
- ivo://CDS.VizieR/J/A+A/399/543
- Title:
- Photometry and Coravel observations of IC 2488
- Short Name:
- J/A+A/399/543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new UBV photoelectric observations of 119 stars in the field of the southern open cluster IC 2488, supplemented by DDO and Washington photometry and Coravel radial velocities for a sample of red giant candidates. Nearly 50% of the stars sampled - including three red giants and one blue straggler - are found to be probable cluster members. Photometric membership probabilities of the red giant candidates show good agreement with those obtained from Coravel data. A mean radial velocity of -2.63+/-0.06km/s is derived for the cluster giants. The reddening across the cluster is found to be uniform, the mean value being E(B-V)=0.24+/-0.04. IC 2488, located at a distance of (1250+/-120) pc from the Sun and 96 pc below the Galactic plane, is most probably not related to the planetary nebula ESO 166-PN21. A metal abundance [Fe/H]=0.10+/-0.06 relative to the Sun is determined from DDO data of the red giant members, in good agreement with the [Fe/H] values derived from five independent Washington abundance indices. An age of 180Myr is determined from the fitting of isochrones computed with convective overshooting for Z=0.019. The isochrone for logt=8.25 reproduces remarkably well not only the morphology of the upper main sequence but also the observed red giant pattern.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A4
- Title:
- Photometry and motions in Arches and Quintuplet
- Short Name:
- J/A+A/578/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the circumstellar disc fraction as determined from L-band excess observations of the young, massive Arches and Quintuplet clusters residing in the central molecular zone of the Milky Way. The Quintuplet cluster was searched for L-band excess sources for the first time. We find a total of 26 excess sources in the Quintuplet cluster, and 21 sources with L-band excesses in the Arches cluster, of which 13 are new detections. With the aid of proper motion membership samples, the disc fraction of the Quintuplet cluster could be derived for the first time to be 4.0+/-0.7. There is no evidence for a radially varying disc fraction in this cluster. In the case of the Arches cluster, a disc fraction of 9.2+/-1.2 approximately out to the cluster's predicted tidal radius, r<1.5pc (Habibi et al., 2013A&A...556A..26H, Cat. J/A+A/556/A26), is found. This excess fraction is consistent with our previously found disc fraction in the cluster in the radial range 0.3<r<0.8pc. In both clusters, the host star mass range covers late A to early B-type stars, 2<M<15M_{sun}, as derived from J-band photospheric magnitudes. We discuss the unexpected finding of dusty circumstellar discs in these UV intense environments in the context of primordial disc survival and formation scenarios of secondary discs. We consider the possibility that the L-band excess sources in the Arches and Quintuplet clusters could be the high-mass counterparts to T Tauri pre-transitional discs. As such a scenario requires a long pre-transitional disc lifetime in a UV intense environment, we suggest that mass transfer discs in binary systems are a likely formation mechanism for the B-star discs observed in these starburst clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A103
- Title:
- Photometry and proper motions in IC4665
- Short Name:
- J/A+A/532/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowledge of the mass function in open clusters constitutes one way to constrain the formation of low-mass stars and brown dwarfs along with the knowledge of the frequency of multiple systems and the properties of disks. The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes in the pre-main sequence (27Myr) cluster IC4665 located at 350pc from the Sun. We have cross-matched the near-infrared photometric data from the Eighth Data Release (DR8) of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS) with previous optical data obtained with the Canada-France-Hawaii (CFH) wide-field camera to improve the determination of the luminosity and mass functions in the low-mass and substellar regimes. The availability of i and z photometry taken with the CFH12K camera on the Canada France Hawaii Telescope added strong constraints to the UKIDSS photometric selection in this cluster located in a dense region of our Galaxy. We have derived the luminosity and mass functions of the cluster down to J=18.5mag, corresponding to masses of ~0.025M_{sun}_ at the distance and age of IC4665 according to theoretical models. In addition, we have extracted new candidate members down to ~20 Jupiter masses in a previously unstudied region of the cluster. We have derived the mass function over the 0.6-0.04M_{sun}_ mass range and found that it is best represented by a log-normal function with a peak at 0.25-0.16M_{sun}_, consistent with the determination in the Pleiades.
- ID:
- ivo://CDS.VizieR/V/52
- Title:
- Photometry and Proper Motions in M67
- Short Name:
- V/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Relative proper motions were determined for 1068 stars with limiting magnitude b=16.5 and located within an area 130'*130' centered at alpha=8h 47.7m,delta=+12 deg.00' and l=215.6deg.,b=+31.2deg.(1950.0). Five plate pairs taken with the Pulkovo normal astrograph with mean epoch difference of 62 years were used. The proper motions have a mean error of 0''.0020 per year and were measured relative to reference stars with 13.5<b<14.5. Photographic UBV magnitudes were determined using the photoelectric standards of Johnson, Sandage (1955ApJ...121..616J) and Eggen, Sandage (1964ApJ...140..130E). Three plates in each colour taken with the Schmidt telescope of the Radioastrophysical Observatory of the Latvian SSR were measured. In addition a plate taken with the Pulkovo 26inch telescope was used to determine v-magnitudes. The cluster members were selected on the basis of proper motion (vector point diagram) and photometric (V/B-V and U-B/B-V) criteria.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/57
- Title:
- Photometry and proper motions in Praesepe
- Short Name:
- J/ApJ/784/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Membership identification is the first step in determining the properties of a star cluster. Low-mass members in particular could be used to trace the dynamical history, such as mass segregation, stellar evaporation, or tidal stripping, of a star cluster in its Galactic environment. We identified member candidates of the intermediate-age Praesepe cluster (M44) with stellar masses ~0.11-2.4M_{sun}_, using Panoramic Survey Telescope And Rapid Response System and Two Micron All Sky Survey photometry, and PPMXL proper motions. Within a sky area of 3{deg} radius, 1040 candidates are identified, of which 96 are new inclusions. Using the same set of selection criteria on field stars, an estimated false positive rate of 16% was determined, suggesting that 872 of the candidates are true members. This most complete and reliable membership list allows us to favor the BT-Settl model over other stellar models. The cluster shows a distinct binary track above the main sequence, with a binary frequency of 20%-40%, and a high occurrence rate of similar mass pairs. The mass function is consistent with that of the disk population but shows a deficit of members below 0.3 solar masses. A clear mass segregation is evidenced, with the lowest-mass members in our sample being evaporated from this disintegrating cluster.
