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- ID:
- ivo://CDS.VizieR/J/AJ/108/2338
- Title:
- Photographic astrometry. VIII.
- Short Name:
- J/AJ/108/2338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 300 trigonometric parallaxes, 15 revised binary-star orbits, and 24 mass ratios are listed and annotated.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/4
- Title:
- Photometry of high proper motion objects from WISE
- Short Name:
- J/ApJ/781/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I have used multi-epoch astrometry from the Wide-field Infrared Survey Explorer to perform a search for a distant companion to the Sun via its parallactic motion. I have not found an object of this kind down to W2=14.5. This limit corresponds to analogs of Saturn and Jupiter at 28000 and 82000AU, respectively, according to models of the Jovian planets by Fortney and coworkers. Models of brown dwarfs by Burrows and coworkers predict fainter fluxes at a given mass for the age of the solar system, producing a closer distance limit of 26000 AU for a Jupiter-mass brown dwarf. These constraints exclude most combinations of mass and separation at which a solar companion has been suggested to exist by various studies over the years.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A141
- Title:
- Physical properties of AM CVn stars
- Short Name:
- J/A+A/620/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AM CVn binaries are hydrogen deficient compact binaries with an orbital period in the 5-65min range and are predicted to be strong sources of persistent gravitational wave radiation. Using Gaia, Data Release 2, we present the parallaxes and proper motions of 41 out of the 56 known systems. Compared to the parallax determined using the HST, Fine Guidance Sensor we find that the archetype star, AM CVn, is significantly closer than previously thought. This resolves the high luminosity and mass accretion rate which models had difficulty in explaining. Using Pan-STARRS1 data we determine the absolute magnitude of the AM CVn stars. There is some evidence that donor stars have a higher mass and radius than expected for white dwarfs or that the donors are not white dwarfs. Using the distances to the known AM CVn stars we find strong evidence that a large population of AM CVn stars has yet to be discovered. As this value sets the background to the gravitational wave signal of LISA, this is of wide interest. We determine the mass transfer rate for 15 AM CVn stars and find that the majority has a rate significantly greater than expected from standard models. This is further evidence that the donor star has a greater size than expected.
- ID:
- ivo://CDS.VizieR/J/AJ/154/134
- Title:
- Planetary-mass brown dwarfs in the Taurus SFR
- Short Name:
- J/AJ/154/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space- based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid-M to early-L, and they include the four faintest known members in extinction-corrected K_s_, which should have masses as low as ~4-5 M_Jup_ according to evolutionary models. Two of the coolest new members (M9.25, M9.5) have mid-IR excesses that indicate the presence of disks. Two fainter objects with types of M9-L2 and M9-L3 also have red mid-IR colors relative to photospheres at =<L0, but since the photospheric colors are poorly defined at >L0, it is unclear whether they have excesses from disks. We also have obtained spectra of candidate members of the IC 348 and NGC 1333 clusters in Perseus that were identified by Luhman et al. Eight candidates are found to be probable members, three of which are among the faintest and least-massive known members of the clusters (~5 M_Jup_).
