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Start Over Subject open star clusters Publisher CDS
51. 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.
52. {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.
53. 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.
54. 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}_.
55. 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.
56. {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.
57. alpha Persei, Pleiades and Praesepe clusters
ID:
ivo://CDS.VizieR/J/A+A/628/A66
Title:
alpha Persei, Pleiades and Praesepe clusters
Short Name:
J/A+A/628/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our scientific goal is to provide revised membership lists of the alpha Per, Pleiades, and Praesepe clusters exploiting the second data release of Gaia and produce five-dimensional maps ({alpha}, {delta}, {pi}, {mu}_{alpha}_cos{delta}, {mu}_{delta}_) of these clusters. We implemented the kinematic method combined with the statistical treatment of parallaxes and proper motions to identify astrometric member candidates of three of the most nearby and best studied open clusters in the sky. We cross-correlated the Gaia catalogue with large-scale public surveys to complement the astrometry of Gaia with multi-band photometry from the optical to the mid-infrared. We identified 517, 1248, and 721 bona fide astrometric member candidates inside the tidal radius of alpha Per, the Pleiades, and Praesepe, respectively. We cross-matched our final samples with catalogues from previous surveys to address the level of completeness. We update the main physical properties of the clusters, including mean distance and velocity, as well as core, half-mass, and tidal radii. We infer updated ages from the white dwarf members of the Pleiades and Praesepe. We derive the luminosity and mass functions of the three clusters and compare them to the field mass function. We compute the positions in space of all member candidates in the three regions to investigate their distribution in space. We provide updated distances and kinematics for the three clusters. We identify a list of members in the alpha Per, Pleiades, and Praesepe clusters from the most massive stars all the way down to the hydrogen-burning limit with a higher confidence and better astrometry than previous studies. We produce complete 5D maps of stellar and substellar bona fide members in these three regions. The photometric sequences derived in several colour-magnitude diagrams represent benchmark cluster sequences at ages from 90 to 600Myr. We note the presence of a stream around the Pleiades cluster extending up to 40 pc from the cluster centre.
58. APOGEE and Gaia DR2 analysis of IC 166
ID:
ivo://CDS.VizieR/J/AJ/156/94
Title:
APOGEE and Gaia DR2 analysis of IC 166
Short Name:
J/AJ/156/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
IC 166 is an intermediate-age open cluster (OC) (~1 Gyr) that lies in the transition zone of the metallicity gradient in the outer disk. Its location, combined with our very limited knowledge of its salient features, make it an interesting object of study. We present the first high-resolution spectroscopic and precise kinematical analysis of IC 166, which lies in the outer disk with R_GC_~12.7 kpc. High-resolution H-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey. We made use of the Brussels Automatic Stellar Parameter code to provide chemical abundances based on a line-by-line approach for up to eight chemical elements (Mg, Si, Ca, Ti, Al, K, Mn, and Fe). The {alpha}-element (Mg, Si, Ca, and whenever available Ti) abundances, and their trends with Fe abundances have been analyzed for a total of 13 high-likelihood cluster members. No significant abundance scatter was found in any of the chemical species studied. Combining the positional, heliocentric distance, and kinematic information, we derive, for the first time, the probable orbit of IC 166 within a Galactic model including a rotating boxy bar, and found that it is likely that IC 166 formed in the Galactic disk, supporting its nature as an unremarkable Galactic OC with an orbit bound to the Galactic plane.
59. APOGEE parameters through 83 open clusters
ID:
ivo://CDS.VizieR/J/ApJ/903/55
Title:
APOGEE parameters through 83 open clusters
Short Name:
J/ApJ/903/55
Date:
15 Mar 2022
Publisher:
CDS
Description:
The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03dex level. Here we present (I) a new cluster member catalog based only on APOGEE radial velocities and Gaia-DR2 proper motions, (II) improved abundance uncertainties for APOGEE cluster members, and (III) the dependence of cluster homogeneity on Galactic and cluster properties, using abundances of eight elements from the APOGEE survey for 10 high-quality clusters. We find that cluster homogeneity is uncorrelated with Galactocentric distance, |Z|, age, and metallicity. However, velocity dispersion, which is a proxy for cluster mass, is positively correlated with intrinsic scatter at relatively high levels of significance for [Ca/Fe] and [Mg/Fe]. We also see a possible positive correlation at a low level of significance for [Ni/Fe], [Si/Fe], [Al/Fe], and [Fe/H], while [Cr/Fe] and [Mn/Fe] are uncorrelated. The elements that show a correlation with velocity dispersion are those that are predominantly produced by core-collapse supernovae (CCSNe). However, the small sample size and relatively low correlation significance highlight the need for follow-up studies. If borne out by future studies, these findings would suggest a quantitative difference between the correlation lengths of elements produced predominantly by Type Ia SNe versus CCSNe, which would have implications for Galactic chemical evolution models and the feasibility of chemical tagging.
60. APOGEE stars members of 35 star clusters
ID:
ivo://CDS.VizieR/J/A+A/629/A34
Title:
APOGEE stars members of 35 star clusters
Short Name:
J/A+A/629/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
The vast volume of data generated by modern astronomical surveys offer test beds for the application of machine learning. In these exploratory applications, it is important to evaluate potential existing tools and determine which ones are optimal to extract scientific knowledge from the available observations. This work aims to explore the possibility of using unsupervised clustering algorithms to separate stellar populations with distinct chemical patterns. Star clusters are likely the most chemically homogeneous populations in the Galaxy, and therefore any practical approach to identify distinct stellar populations should at least be able to separate clusters from each other. We have applied eight clustering algorithms combined with four dimensionality reduction strategies to discriminate automatically stellar clusters using chemical abundances of 13 elements. Our test-bed sample includes 18 stellar clusters with a total of 453 stars. We have applied statistical tests showing that some pairs of clusters (e.g., NGC 2458-NGC 2420) are indistinguishable from each other when using the Apache Point Galactic Evolution Experiment (APOGEE) chemical abundances. However, for most clusters we are able to automatically assign membership with metric scores similar to previous works. The confusion level of the automatically selected clusters is consistent with statistical tests that demonstrate the impossibility of perfectly discriminating all the clusters from each other. These statistical tests, and confusion levels establish a limit for the prospect of blindly identifying stars born in the same cluster based solely on chemical abundances. We find that some of the algorithms explored are capable of blindly identify stellar populations with similar ages and chemical distributions in the APOGEE data. Even though we are not able to fully separate the clusters from each other, the main confusion arises from clusters with similar ages. Since there are stellar clusters that are chemically indistinguishable, our study supports the notion of extending weak chemical tagging involving families of clusters instead of individual clusters.

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