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41. Ages for stars in 19 clusters
ID:
ivo://CDS.VizieR/J/MNRAS/476/1213
Title:
Ages for stars in 19 clusters
Short Name:
J/MNRAS/476/1213
Date:
21 Oct 2021
Publisher:
CDS
Description:
The pace and pattern of star formation leading to rich young stellar clusters is quite uncertain. In this context, we analyse the spatial distribution of ages within 19 young (median t<=3Myr on the Siess et al. time-scale), morphologically simple, isolated, and relatively rich stellar clusters. Our analysis is based on young stellar object (YSO) samples from the Massive Young Star-Forming Complex Study in Infrared and X-ray and Star Formation in Nearby Clouds surveys, and a new estimator of pre-main sequence (PMS) stellar ages, Age_JX_, derived from X-ray and near-infrared photometric data. Median cluster ages are computed within four annular subregions of the clusters. We confirm and extend the earlier result of Getman et al. (2014ApJ...787..108G, Cat. J/ApJ/787/108; 2014ApJ...787..109G. Cat. J/ApJ/787/109): 80 per cent of the clusters show age trends where stars in cluster cores are younger than in outer regions. Our cluster stacking analyses establish the existence of an age gradient to high statistical significance in several ways. Time-scales vary with the choice of PMS evolutionary model; the inferred median age gradient across the studied clusters ranges from 0.75 to 1.5Myr/pc. The empirical finding reported in the present study - late or continuing formation of stars in the cores of star clusters with older stars dispersed in the outer regions - has a strong foundation with other observational studies and with the astrophysical models like the global hierarchical collapse model of Vazquez-Semadeni et al. (2017MNRAS.467.1313V).
42. Ages of star clusters in SMC
ID:
ivo://CDS.VizieR/J/ApJ/853/104
Title:
Ages of star clusters in SMC
Short Name:
J/ApJ/853/104
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis+ (2017, J/ApJ/845/56). Our code detects 1319 star clusters in the central 18deg^2^ of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (<=50Myr) clusters in both Magellanic Clouds, found where their bars join the HI arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.
43. ALMA observation of 152 1-11Myr aged stars
ID:
ivo://CDS.VizieR/J/ApJ/895/126
Title:
ALMA observation of 152 1-11Myr aged stars
Short Name:
J/ApJ/895/126
Date:
11 Mar 2022
Publisher:
CDS
Description:
We utilize ALMA archival data to estimate the dust disk size of 152 protoplanetary disks in Lupus (1-3Myr), Chamaeleon I (2-3Myr), and Upper-Sco (5-11Myr). We combine our sample with 47 disks from Tau/Aur and Oph whose dust disk radii were estimated, as here, through fitting radial profile models to visibility data. We use these 199 homogeneously derived disk sizes to identify empirical disk-disk and disk-host property relations as well as to search for evolutionary trends. In agreement with previous studies, we find that dust disk sizes and millimeter luminosities are correlated, but show for the first time that the relationship is not universal between regions. We find that disks in the 2-3Myr old ChaI are not smaller than disks in other regions of similar age, and confirm the Barenfeld et al. finding that the 5-10Myr USco disks are smaller than disks belonging to younger regions. Finally, we find that the outer edge of the solar system, as defined by the Kuiper Belt, is consistent with a population of dust disk sizes which have not experienced significant truncation.
44. Alpha Per cluster low-mass members. I.
ID:
ivo://CDS.VizieR/J/AN/319/201
Title:
Alpha Per cluster low-mass members. I.
Short Name:
J/AN/319/201
Date:
21 Oct 2021
Publisher:
CDS
Description:
Following the work of Randich et al. (1996A&A...305..785R) involving a ROSAT raster scan survey of the {alpha} Persei open cluster, we present here the results of a photometric/spectroscopic program examining the possible optical counterparts to a group of 73 X-ray sources in the raster survey which were not matched to catalogued stars. Of the 73 sources investigated, ~40 have an optical counterpart with photometry acceptable for cluster membership and ~20 of these also have radial velocities consistent with membership. We discuss the X-ray properties of these potential new members and why they may not have been identified in earlier membership surveys of this cluster.
45. Alpha Per cluster low-mass members. II.
ID:
ivo://CDS.VizieR/J/AN/319/215
Title:
Alpha Per cluster low-mass members. II.
Short Name:
J/AN/319/215
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present investigation examines possible optical counterparts to 130 X-ray sources in the region of the alpha Persei open cluster (d~170pc, age~50Myr) resulting from the analysis of three 22-25ksec ROSAT PSPC pointings. In the same manner as for 73 X-ray sources from a raster survey in alpha Per (Prosser & Randich, 1998, Cat. <J/AN/319/201>), CCD photometry is employed to obtain magnitudes and colors for stars/objects close to the X-ray positions, with additional echelle and low-dispersion Halpha spectra provided for some stars. For almost 60 X-ray sources, an optical counterpart with photometry acceptable for cluster membership is identified, some of which can be excluded from membership on the basis of discrepant radial velocity or X-ray characteristics. On the order of 30 new members or likely members associated with X-ray sources have been identified based on available data. A photometric rotation period has been obtained for one rapid rotator identified in X-rays.
46. {alpha} Per cluster members
ID:
ivo://CDS.VizieR/J/ApJ/752/58
Title:
{alpha} Per cluster members
Short Name:
J/ApJ/752/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
Because of its proximity to the Galactic plane, reliable identification of members of the {alpha} Persei cluster is often problematic. Based primarily on membership evaluations contained in six published papers, we constructed a mostly complete list of high-fidelity members of spectral type G and earlier that lie within 3 arc degrees of the cluster center. {alpha} Persei was the one nearby, rich, young open cluster not surveyed with the Spitzer Space Telescope. We examined the first and final data releases of the Wide-field Infrared Survey Explorer (WISE) and found 11, or perhaps 12, {alpha} Per cluster members that have excess mid-infrared emission above the stellar photosphere attributable to an orbiting dusty debris disk. The most unusual of these is V488 Per, a K-type star with an excess IR luminosity 16% (or more) of the stellar luminosity; this is a larger excess fraction than that of any other known dusty main-sequence star. Much of the dust that orbits V488 Per is at a temperature of ~800 K; if these grains radiate like blackbodies, then they lie only ~0.06 AU from the star. The dust is probably the aftermath of a collision of two planetary embryos or planets with small semimajor axes; such orbital radii are similar to those of many of the transiting planets discovered by the Kepler satellite.
47. alpha Per cluster possible members
ID:
ivo://CDS.VizieR/J/MNRAS/457/1028
Title:
alpha Per cluster possible members
Short Name:
J/MNRAS/457/1028
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained membership probabilities of stars within a field of from the centre of the open cluster alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of alpha Persei shows a turnover at m=0.62M_{sun}_ with low- and high-mass slopes of {alpha}_low_=0.50+/-0.09 (0.1<m/M_{sun}_<0.62) and {alpha}_high_=2.32+/-0.14 (0.62<=m/M_{sun}_<4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 110 to 2.63 outside 22, whereas the mean stellar mass decreases from 0.95 to 0.57M_{sun}_ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin=34+/-12 per cent for stars with 0.70<m/M_{sun}_<4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of {alpha}_low_=0.89+/-0.11 and {alpha}_high_=2.37+/-0.09 and a total cluster mass of 352M_{sun}_ for alpha Persei.
48. Alpha Per faint stars photometry
ID:
ivo://CDS.VizieR/J/A+A/395/813
Title:
Alpha Per faint stars photometry
Short Name:
J/A+A/395/813
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a deep, wide-field optical survey of the young stellar cluster Alpha Per, in which we have discovered a large population of candidate brown dwarfs. Subsequent infrared photometric follow-up shows that the majority of them are probable or possible members of the cluster, reaching to a minimum mass of 0.035M_{sun}_.
49. alpha Persei and Praesepe Clusters
ID:
ivo://CDS.VizieR/J/AJ/123/1570
Title:
alpha Persei and Praesepe Clusters
Short Name:
J/AJ/123/1570
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two hundred forty-two members of the Praesepe and alpha Persei clusters have been surveyed with high angular resolution 2.2{mu}m speckle imaging on the 3m Infrared Telescope Facility, the 5m Hale, and the 10m Keck telescopes, along with direct imaging using the near-infrared camera (NICMOS) aboard the Hubble Space Telescope. The observed stars range in spectral type from B (~5M_{sun}_) to early M (~0.5M_{sun}_), with the majority of the targets more massive than ~0.8M_{sun}_. The one quadruple and 39 binary systems detected encompass separations from 0.053" to 7.28"; 28 of the systems are new detections, and there are nine candidate substellar companions.
50. {alpha} Persei open cluster members
ID:
ivo://CDS.VizieR/J/AJ/131/2967
Title:
{alpha} Persei open cluster members
Short Name:
J/AJ/131/2967
Date:
21 Oct 2021
Publisher:
CDS
Description:
A kinematical study of the nearby open cluster {alpha} Persei is presented based on the astrometric proper motions and positions in the Tycho-2 catalog (Cat. I/259) and Second USNO CCD Astrographic Catalog (UCAC2, Cat. I/289). Using the astrometric data and photometry from the Tycho-2 and ground-based catalogs, 139 probable members of the cluster are selected, 18 of them new.

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