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- ID:
- ivo://CDS.VizieR/J/A+A/531/A141
- Title:
- Physical parameters of PMS in open clusters
- Short Name:
- J/A+A/531/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aims are twofold: To determine the physical parameters of PMS members in young open clusters (YOCs), and to check and compare the performances of different model isochrones. We compare UBVRI photometric observations of eleven YOCs to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for MS and PMS stars and estimates for the masses, ages, and spatial distribution of the candidate members. The relations found between the different cluster parameters show that the procedure applied to assign cluster membership, and to measure physical parameters for the selected members, is well founded.
- ID:
- ivo://CDS.VizieR/J/AJ/159/17
- Title:
- Physical properties of SFRs in NGC 3395/NGC 3396
- Short Name:
- J/AJ/159/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report long-slit spectroscopy of the early major merger galaxies NGC 3395/NGC 3396. The spectra are consistent with those for star-forming galaxies, but there is some indication of LINER-like active galactic nucleus activity in the center of NGC 3396. The total star formation rate in the regions observed is 2.83 M_{sun}_/yr, consistent with estimates for the entire galaxies. The highest abundances are in the centers of the galaxies, with the abundances decreasing with distance. There is a correlation between high abundance and high ionization parameter, both of which can be attributed to the presence of massive stars. Modeling with SB 99 indicates the star-forming regions are younger than 10 Myr. There are 1000-2000 WNL stars in the system, along with several thousand O stars, consistent with the ages of the star-forming regions. The highest electron densities are found in young regions with high star formation rates. The electron temperatures are higher than results for non-interacting galaxies, which is probably due to shock waves produced by the galaxy-galaxy interaction, the outflow of gas from massive stars, and/or collisions between gas clouds in the galaxies. There is star formation in the bridge of material between the galaxies. These regions are among the youngest in the system and have low abundances, suggesting the gas was pulled from the outer parts of the galaxies. X-ray point sources, probably high-mass X-ray binaries, are associated with several star-forming regions.
- ID:
- ivo://CDS.VizieR/J/AJ/153/101
- Title:
- Pleiades members stellar properties
- Short Name:
- J/AJ/153/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precise measurements of eclipsing binary parameters and statistical studies of young clusters have suggested that some magnetically active low-mass dwarfs possess radii inflated by ~5%-15% relative to theoretical expectations. If true, this effect should be pronounced in young open clusters, due to the rapid rotation and strong magnetic activity of their most extreme members. We explore this possibility by determining empirical radii for 83 members of the nearby Pleiades open cluster, using spectral energy distribution fitting to establish F_bol_ with a typical accuracy of ~3% together with color and spectro-photometric indices to determine T_eff_. We find several Pleiades members with radii inflated above radius-T_eff_ models from state-of-the-art calculations, and apparent dispersions in radii for the K-dwarfs of the cluster. Moreover, we demonstrate that this putative radius inflation correlates strongly with rotation rate, consistent with inflation of young stars by magnetic activity and/or starspots. We argue that this signal is not a consequence of starspot-induced color anomalies, binarity, or depth effects in the cluster, employing Gaia DR1 distances as a check. Finally, we consider the lithium abundances of these stars, demonstrating a triple correlation between rotation rate, radius inflation, and enhanced lithium abundance. Our result-already significant to ~99.99% confidence-provides strong support for a magnetic origin of the inflated radii and lithium dispersion observed in young, low-mass stars.
- ID:
- ivo://CDS.VizieR/I/300
- Title:
- PM2000 Bordeaux Proper Motion catalogue
- Short Name:
- I/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper motion catalogue of 2 670 974 stars, covering the declination zone +11{deg}<{delta}<+18{deg}. The catalogue has a limiting magnitude V=16.2 (Bordeaux CCD meridian circle magnitude) and is complete down to V=15.4. Depending on magnitude, the positional precision at mean epoch ranges from 50 to 70mas and the precision of proper motions varies from 1.5mas/yr to 6mas/yr. Meridian V magnitudes are provided for all objects together with additional photometry from the 2MASS catalogue when available (99.5% of objects). Positions and proper motions are on the ICRS (International Celestial Reference System). Proper motions are derived from the comparison of the positional M2000 catalogue (systematic observations of the Bordeaux Carte du Ciel Zone with the meridian circle, completed in 2000) with positions derived from the reduction of 512 Carte du Ciel plates of the Bordeaux zone (scanned at the APM Cambridge), the AC2000.2 catalogue, the USNO-A2.0 catalogue and the unpublished Yellow Sky (YS) USNO catalogue. Systematic offsets in 2MASS positions and in UCAC2 proper motions were revealed from comparisons with PM2000.
- ID:
- ivo://CDS.VizieR/J/A+A/467/1397
- Title:
- PMS stars in open clusters: the DAY-I Catalogue
- Short Name:
- J/A+A/467/1397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the basic ideas and first results from the project we are carrying out at present, the search for and characterisation of pre-main sequence (PMS) stars among the members of Galactic young clusters. The observations of 10 southern clusters, nine of them located in the Carina-Sagittarius spiral arm of the Milky Way are presented. We aim at listing candidate PMS member stars in young clusters. The catalogued stars will serve as a basis for future spectroscopic studies of individual objects to determine the properties of stellar formation in the last phases before the main sequence stage. Properties such as the presence of residual envelopes or disks, age spread among PMS members, and the possible presence of several episodes of star formation in the clusters, are to be addressed. Multicolour photometry in the UBVRcIc system has been obtained for 10 southern young clusters in the fourth Galactic quadrant, located between Galactic longitudes l=238 and l=310. For six clusters in the sample, the observations presented here provide the first published study based on CCD photometry. A quantitative comparison is performed with post-MS isochrones, and PMS isochrones from three different evolutionary models are used in the photometric membership analysis for possible PMS stars. The observations produce photometric indices in the Johnson-Cousins photometric systems for a total of 26962 stars. The matching of our pixel coordinates with corresponding fields in the 2MASS data base provides astrometric calibration for all catalogued stars and JHK 2MASS photometric indices for 60% of them. Post-MS cluster ages range from 4 to 60Myr, whereas the photometric membership analysis assigns PMS membership assignment to a total of 842 stars, covering an age range between 1 and 10Myr. This information on the PMS candidate members has been collected into a catalogue, named DAY-I, which contains 16 entries for 842 stars in the field of 10 southern clusters.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/451
- Title:
- PMS stars in the Cepheus flare region
- Short Name:
- J/ApJS/185/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of optical spectroscopic and BVR_C_I_C_ photometric observations of 77 pre-main-sequence (PMS) stars in the Cepheus flare region. A total of 64 of these are newly confirmed PMS stars, originally selected from various published candidate lists. We estimate effective temperatures and luminosities for the PMS stars, and comparing the results with PMS evolutionary models, we estimate stellar masses of 0.2-2.4M_{sun}_ and stellar ages of 0.1-15Myr. Among the PMS stars, we identify 15 visual binaries with separations of 2-10". From archival IRAS, Two Micron All Sky Survey, and Spitzer data, we construct their spectral energy distributions (SEDs) and classify 5% of the stars as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar objects. We identify 12 classical T Tauri stars and two weak-line T Tauri stars as members of NGC 7023, with a mean age of 1.6Myr. The 13 PMS stars associated with L1228 belong to three small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17 PMS stars associated with L1251 suggests that star formation has propagated with the expansion of the Cepheus flare shell. We detect sparse aggregates of ~6-7Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of ~400pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV Cep at a distance of 600pc. Our results confirm that the molecular complex in the Cepheus flare region contains clouds of various distances and star-forming histories.
- ID:
- ivo://CDS.VizieR/J/AJ/154/268
- Title:
- Point & compact H{alpha} sources in the inner of M33
- Short Name:
- J/AJ/154/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A variety of interesting objects such as Wolf-Rayet stars, tight OB associations, planetary nebulae, X-ray binaries, etc., can be discovered as point or compact sources in H{alpha} surveys. How these objects distribute through a galaxy sheds light on the galaxy star formation rate and history, mass distribution, and dynamics. The nearby galaxy M33 is an excellent place to study the distribution of H{alpha}-bright point sources in a flocculant spiral galaxy. We have reprocessed an archived WIYN continuum-subtracted H{alpha} image of the inner 6.5'x6.5' of M33 and, employing both eye and machine searches, have tabulated sources with a flux greater than approximately 10^-15^ erg/cm^2^/s. We have effectively recovered previously mapped H II regions and have identified 152 unresolved point sources and 122 marginally resolved compact sources, of which 39 have not been previously identified in any archive. An additional 99 H{alpha} sources were found to have sufficient archival flux values to generate a Spectral Energy Distribution. Using the SED, flux values, H{alpha} flux value, and compactness, we classified 67 of these sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1045
- Title:
- Polarimetry toward sightlines through ChaI
- Short Name:
- J/ApJ/720/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.
- ID:
- ivo://CDS.VizieR/J/AJ/160/256
- Title:
- Polarization of 125 stars in NGC 1817 open cluster
- Short Name:
- J/AJ/160/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiband linear polarimetric observations of 125 stars in the region of the cluster NGC1817 have been carried out intending to study properties of interstellar dust and grains in that direction. The polarization is found to be wavelength-dependent, being maximum in the V-band with an average value of 0.95%. The foreground interstellar dust grains appear to be the main source of linear polarization of starlight toward the direction of NGC1817. The average value of the position angle in the V-band of 119.2{deg} is found to be less than the direction of the Galactic parallel in the region, indicating that the dust grains in the direction are probably not yet relaxed. Spatial distribution of dust appears to be more diverse in the coronal region than the core region of the cluster. The maximum value of the degree of polarization is estimated to be 0.93% for members of the cluster using the Serkowski relation. The average value of wavelength corresponding to the maximum polarization of 0.54{+/-}0.02{mu}m indicates that the size distribution of dust grains in the line of sight is similar to that of the general interstellar medium. Several variable stars in the cluster were also observed polarimetrically and pulsating variables appear to have a slightly lower value of polarization from other nonvariable member stars of the cluster. There are indications of the existence of dust layers in front of those clusters which are located close to galactic plane while for clusters located away from galactic plane no major dust layers are observed.
