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121. Census of Rho Oph candidate members from Gaia DR2
ID:
ivo://CDS.VizieR/J/A+A/626/A80
Title:
Census of Rho Oph candidate members from Gaia DR2
Short Name:
J/A+A/626/A80
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Ophiuchus cloud complex is one of the best laboratories to study the earlier stages of the stellar and protoplanetary disc evolution. We constructed a control sample composed of 188 bona fide Ophiuchus members. Using this sample as a reference we applied three different density-based machine learning clustering algorithms (DBSCAN, OPTICS, and HDBSCAN) to a sample drawn from the Gaia DR2 catalogue centred on the Ophiuchus cloud that contains 2300 sources covering a sky area of 38deg^2^. The clustering analysis was applied in the five astrometric dimensions defined by the three-dimensional Cartesian space and the proper motions in right ascension and declination. The three clustering algorithms systematically identify a similar set of candidate members in a main cluster with astrometric properties consistent with those of the control sample. We constructed a common sample containing 391 member candidates including 166 new objects, which have not yet been discussed in the literature. We built the SEDs for a subset of 48 objects and found a total of 41 discs.
122. Cepheids in open clusters
ID:
ivo://CDS.VizieR/J/MNRAS/434/2238
Title:
Cepheids in open clusters
Short Name:
J/MNRAS/434/2238
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cepheids in open clusters (cluster Cepheids: CCs) are of great importance as zero-point calibrators of the Galactic Cepheid period-luminosity relationship (PLR). We perform an 8-dimensional all-sky census that aims to identify new bona-fide CCs and provide a ranking of membership confidence for known CC candidates according to membership probabilities. The probabilities are computed for combinations of known Galactic open clusters and classical Cepheid candidates, based on spatial, kinematic, and population-specific membership constraints. Data employed in this analysis are taken largely from published literature and supplemented by a year-round observing program on both hemispheres dedicated to determining systemic radial velocities of Cepheids. In total, we find 23 bona-fide CCs, 5 of which are candidates identified for the first time, including an overtone-Cepheid member in NGC 129. We discuss a subset of CC candidates in detail, some of which have been previously mentioned in the literature. Our results indicate unlikely membership for 7 Cepheids that have been previously discussed in terms of cluster membership. We furthermore revisit the Galactic PLR using our bona fide CC sample and obtain a result consistent with the recent calibration by Turner (2010). However, our calibration remains limited mainly by cluster uncertainties and the small number of long-period calibrators. In the near future, Gaia will enable our study to be carried out in much greater detail and accuracy, thanks to data homogeneity and greater levels of completeness.
123. Chandra observations of NuSTAR sources
ID:
ivo://CDS.VizieR/J/ApJ/869/171
Title:
Chandra observations of NuSTAR sources
Short Name:
J/ApJ/869/171
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey has already uncovered a large number of active galactic nuclei (AGNs), providing new information about the composition of the cosmic X-ray background. For AGNs off the Galactic plane, it has been possible to use existing X-ray archival data to improve source localizations, identify optical counterparts, and classify the AGNs with optical spectroscopy. However, near the Galactic plane, better X-ray positions are necessary to achieve optical or near-IR identifications due to the higher levels of source crowding. Thus, we have used observations with the Chandra X-ray Observatory to obtain the best possible X-ray positions. With eight observations, we have obtained coverage for 19 NuSTAR serendips within 12{deg} of the plane. One or two Chandra sources are detected within the error circle of 15 of the serendips, and we report on these sources and search for optical counterparts. For one source (NuSTAR J202421+3350.9), we obtained a new optical spectrum and detected the presence of hydrogen emission lines. The source is Galactic, and we argue that it is likely a cataclysmic variable. For the other sources, the Chandra positions will enable future classifications in order to place limits on faint Galactic populations, including high-mass X-ray binaries and magnetars.
124. Close encounters to the Sun in Gaia DR1
ID:
ivo://CDS.VizieR/J/A+A/609/A8
Title:
Close encounters to the Sun in Gaia DR1
Short Name:
J/A+A/609/A8
Date:
21 Oct 2021
Publisher:
CDS
Description:
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which pass within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the Oort cloud. 16 stars are found to come within 2pc (although a few of these have dubious data). This is fewer than were found in a similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars with large radial velocity uncertainties (>10km/s), and partly because of missing stars in GDR1 (especially at the bright end). The closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3Myr. The Gaia astrometry predict a much closer passage than pre-Gaia estimates, however: just 16000AU (90% confidence interval: 10000-21000AU), which will bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars with implausibly large velocities), I estimate the rate of stellar encounters within 5pc averaged over the past and future 5Myr to be 545+/-59Myr^-1^. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds to 87+/-9Myr-1 within 2pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
125. Close encounters to the Sun in Gaia DR2
ID:
ivo://CDS.VizieR/J/A+A/616/A37
Title:
Close encounters to the Sun in Gaia DR2
Short Name:
J/A+A/616/A37
Date:
21 Oct 2021
Publisher:
CDS
Description:
Passing stars may play an important role in the evolution of our solar system. We search for close stellar encounters to the Sun among all 7.2 million stars in Gaia DR2 that have six-dimensional phase space data. We characterize encounters by integrating their orbits through a Galactic potential and propagating the correlated uncertainties via a Monte Carlo resampling. After filtering to remove spurious data, we find 694 stars that have median (over uncertainties) closest encounter distances within 5pc, all occurring within 15Myr from now. 26 of these have at least a 50% chance of coming closer than 1pc (and 7 within 0.5pc), all but one of which are newly discovered here. We confirm some and refute several other previously-identified encounters, confirming suspicions about their data. The closest encounter in the sample is Gl 710, which has a 95% probability of coming closer than 0.08pc (17000AU). Taking mass estimates obtained from Gaia astrometry and multiband photometry for essentially all encounters, we find that Gl 710 also has the largest impulse on the Oort cloud. Using a Galaxy model, we compute the completeness of the Gaia DR2 encountering sample as a function of perihelion time and distance. Only 15% of encounters within 5pc occurring within +/-5Myr of now have been identified, mostly due to the lack of radial velocities for faint and/or cool stars. Accounting for the incompleteness, we infer the present rate of encounters within 1pc to be 19.7+/-2.2 per Myr, a quantity expected to scale quadratically with the encounter distance out to at least several pc. Spuriously large parallaxes in our sample from imperfect filtering would tend to inflate both the number of encounters found and this inferred rate. The magnitude of this effect is hard to quantify.
126. Close star encounters
ID:
ivo://CDS.VizieR/J/A+A/575/A35
Title:
Close star encounters
Short Name:
J/A+A/575/A35
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stars which pass close to the Sun can perturb the Oort cloud, injecting comets into the inner solar system where they may collide with the Earth. Using van Leeuwen's re-reduction of the Hipparcos data complemented by the original Hipparcos and Tycho-2 catalogues, along with recent radial velocity surveys, I integrate the orbits of over 50000 stars through the Galaxy to look for close encounters. The search uses a Monte Carlo sampling of the covariance of the data in order to properly characterize the uncertainties in the times, distances, and speeds of the encounters.
127. Cluster SC2008-57(A3667)
ID:
ivo://CDS.VizieR/J/MNRAS/259/233
Title:
Cluster SC2008-57(A3667)
Short Name:
J/MNRAS/259/233
Date:
21 Oct 2021
Publisher:
CDS
Description:
(Abstract of the paper) We present the results of photometric and spectroscopic observations of the cluster of galaxies SC2008-57 (A3667). The observations have resulted in a catalogue with positions and magnitudes for 203 galaxies, complete at b_25 = 18.0, and radial velocities for 128 galaxies, 91 per cent complete at b_25 = 17.5. The cluster can be classified as type L because its galaxy distribution is highly flattened. It shows two strong concentrations: a main concentration, centred on the cluster brightest galaxy (a D galaxy) and coincident with the peak of X-ray emission, and a substructure around the second brightest galaxy (also a D galaxy). Most of the galaxies in this substructure seem to be bound to the second-brightest galaxy, forming a dynamical subunit inside the cluster. The extreme flattening of the cluster may at least partially be due to the presence of the substructure. The cluster also shows evidence for luminosity segregation, with the brightest galaxies being preferentially found in high galaxy density regions. Most of the luminosity segregation, however, is produced by galaxies associated with the two clumps around the D galaxies, suggesting that dynamical friction is effective in subclusters with low velocity dispersions and may be associated with the formation of D galaxies. The velocity dispersion of SC2008-57 is high, about 1200 km/s, but consistent with the observed X-ray luminosity. The cluster mass, derived using several estimators, is about 2.6 x 10^15 M_solar. Both the cluster mass and velocity dispersion may be overestimates due to the presence of the substructure.
128. CMC15, Carlsberg Meridian Catalogue
ID:
ivo://svo.cab/cmc15
Title:
CMC15, Carlsberg Meridian Catalogue
Short Name:
CMC15
Date:
03 Jun 2020 15:34:50
Publisher:
SVO CAB
Description:
CMC15 is an astrometric and photometric catalogue of more than 122.7 million stars in the magnitude range 9 < r' (SDSS) < 17. With a positional accuracy to about 35 mas, the catalogue covers the declination range -40deg to 50deg. The current release comprises all the observations made between March 1999 and March 2011. The catalogue fills the gap between 5h 30m and 10h 30m for declinations south of -15deg of the CMC14 and adds the bans -30deg to -40deg. Some zones north of -30deg have also been re-observed in order to improve their internal errors.
129. Color panorama image of the Milky Way
ID:
ivo://CDS.VizieR/J/PASP/121/1180
Title:
Color panorama image of the Milky Way
Short Name:
J/PASP/121/1180
Date:
21 Oct 2021
Publisher:
CDS
Description:
This article describes the assembly of an optical (RGB) all-sky mosaic image with an image scale of 36"/pix, a limiting magnitude of approximately 14mag, and an 18 bit dynamic range. Using a portable low-cost CCD camera system, 70 fields (each covering 40{deg}x27{deg}) were imaged over a time span of 22 months from dark-sky locations in South Africa, Texas, and Michigan. The fields were photometrically calibrated against standard catalog stars. Using sky background data from the Pioneer 10 and 11 space probes, gradients resulting from artificial light pollution, airglow, and zodiacal light were eliminated, while the large-scale galactic and extragalactic background resulting from unresolved sources was preserved. The 648 megapixel image is a valuable educational tool, being able to fully utilize the resolution and dynamic range of modern full-dome planetarium projection systems.
130. Coma Berenices astrometric catalogue
ID:
ivo://CDS.VizieR/J/A+AS/136/307
Title:
Coma Berenices astrometric catalogue
Short Name:
J/A+AS/136/307
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalogue of stellar positions and proper motions down to the 14th photographic magnitude in the area of the open cluster in Coma Berenices is compiled from data of 12 different sources. The accuracy of the proper motion data is comparable to that of the Hipparcos Catalogue (Cat. <I/239>).

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