- ID:
- ivo://CDS.VizieR/J/A+A/626/A69
- Title:
- An old nova remnant in M22
- Short Name:
- J/A+A/626/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are expected to be overabundant in globular clusters (GCs) compared to the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extract the spectrum of the nebula and use the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios are used to determine the electron temperature and density. It is estimated to have a mass of 1 to 17x10^-5^ solar masses. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a 'guest star', an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extrasolar events recorded in human history.
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- ID:
- ivo://CDS.VizieR/J/ApJ/725/200
- Title:
- An updated catalog of M31 globular-like clusters
- Short Name:
- J/ApJ/725/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an updated UBVRI photometric catalog containing 970 objects in the field of M31, selected from the Revised Bologna Catalog (RBC v.4.0), including 965, 967, 965, 953, and 827 sources in the individual UBVRI bands, respectively, of which 205, 123, 14, 126, and 109 objects do not have previously published photometry. Photometry is performed using archival images from the Local Group Galaxies Survey, which covers 2.2deg^2^ along the major axis of M31. Detailed comparisons show that our photometry is fully consistent with previous measurements in all filters. We focus on 445 confirmed "globular-like" clusters and candidates, comprising typical globular and young massive clusters. The ages and masses of these objects are derived by comparing their observed spectral-energy distributions with simple stellar population synthesis. Approximately half of the clusters are younger than 2Gyr, suggesting that there has been significant recent active star formation in M31, which is consistent with previous results.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A49
- Title:
- ARGUS images of 6 Galactic globular clusters
- Short Name:
- J/A+A/552/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from ground based VLT/FLAMES spectroscopy in combination with HST data for six Galactic globular clusters. The aim of this work is to probe whether these massive clusters host an intermediate-mass black hole at their center using analytical Jeans models.
- ID:
- ivo://CDS.VizieR/J/AJ/136/614
- Title:
- Arp 2 and Ter 8 red giants equivalent widths
- Short Name:
- J/AJ/136/614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To compare the globular clusters (GCs) associated with the Sagittarius Galaxy (Sgr) we report the results obtained from new high-resolution spectra of red giant stars in Terzan 8 and Arp 2, collected with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at Las Campanas Observatory.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/12
- Title:
- A search for variable stars in M4 with K2 LCs
- Short Name:
- J/ApJS/244/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extract light curves for 4554 objects with 9<G<19 in the K2 superstamp observations of the globular cluster M4, including 3784 cluster members, and search for variability. Among cluster-member objects, we detect 66 variables, of which 52 are new discoveries. Among objects not belonging to the cluster, we detect 24 variables, of which 20 are new discoveries. We additionally discover 57 cluster-member suspected variables, 10 cluster-non-member suspected variables, and four variables with ambiguous cluster membership. Our light curves reach sub-millimagnitude precision for the cluster horizontal branch, permitting us to detect asteroseismic activity in six horizontal branch stars outside the instability strip and one inside the strip but with only ~1mmag amplitude variability. Nineteen additional stars along the red giant branch also have detected asteroseismic variability. Several eclipsing binaries are found in the cluster, including a 4.6 day detached eclipsing binary and an EW-class eclipsing binary, as well as an EW with uncertain cluster membership and three other candidate EWs. A 22 day detached eclipsing binary is also found outside the cluster. We identify a candidate X-ray binary that is a cluster member with quiescent and periodic ~20mmag optical variability. We also obtain high-precision light curves for 10 of the previously known RR Lyrae variables in the cluster and identify one as a candidate Blazhko variable with a Blazhko period in excess of 78d.
- ID:
- ivo://CDS.VizieR/J/A+AS/93/293
- Title:
- Astrometry of globular clusters (47 Tuc)
- Short Name:
- J/A+AS/93/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study determines relative proper motions for stars brighter than 17.0mag in a 1.5x1.5{deg} field centered on the globular cluster 47 Tuc (NGC 104). Proper motion and membership probabilities are tabulated for 3076 stars within 32 arcmin of the cluster center. A proper motion of 47 Tuc relative to the SMC is derived, which relies on the assumption that the mean proper motion of field stars is the same as that in the nearby field of NGC 362, and on the detection of SMC stars in that field. The resulting space motion confirms the membership of 47 Tuc in the rapidly rotating, flattened, metal-rich disk subgroup of the galactic cluster system. Relative proper motions for stars centered on the globular cluster NGC 362 are determined. NGC 362 is found to exhibit a highly eccentric orbit, typical for a member of the halo subgroup of the galactic globular cluster system. The perigalactic distance of NGC 362 is very small (less than about 1kpc).
- ID:
- ivo://CDS.VizieR/J/AcA/50/221
- Title:
- Astrometry of variable stars in M 3
- Short Name:
- J/AcA/50/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present identification and astrometry of all previously known or suspected variables along with the discovery of six new variables in the globular cluster M3. The number of the catalogued variables increased to 274 by including all the confirmed, previously known variables and the new discoveries. The precise and homogeneous astrometry, as well as the clarification of misapprehensions in the preceding identifications are done by using overlapping fields from a wide-field Schmidt-camera, 1-m RCC telescope, and HST archive observations from the center of the cluster. The astrometric positions can serve as a direct input to any photometry which needs the accurate centers of the variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/6
- Title:
- Astro-photometric catalog of the core of NGC 5139
- Short Name:
- J/ApJ/842/6
- Date:
- 16 Nov 2021 13:43:59
- Publisher:
- CDS
- Description:
- We have constructed the most comprehensive catalog of photometry and proper motions ever assembled for a globular cluster (GC). The core of {omega}Cen (NGC 5139) has been imaged over 650 times through WFC3's UVIS and IR channels for the purpose of detector calibration. There exist from 4 to over 60 exposures through each of 26 filters stretching continuously from F225W in the UV to F160W in the infrared. Furthermore, the 11yr baseline between these data and a 2002 ACS survey has allowed us to more than double the proper-motion accuracy and triple the number of well-measured stars compared to our previous groundbreaking effort. This totally unprecedented complete spectral coverage of over 470000 stars within the cluster's core, from the tip of the red giant branch down to the white dwarfs, provides the best astro-photometric observational database yet to understand the multiple-population phenomenon in any GC. In this first paper of the series, we describe in detail the data-reduction processes and deliver the astro-photometric catalog to the astronomical community.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/23
- Title:
- AstroSat/UVIT and Chandra X-ray sources in M31
- Short Name:
- J/ApJS/250/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An ultraviolet (UV) survey of M31 has been carried out during 2017-19 with the Ultra-Violet Imaging Telescope (UVIT) instrument on board the AstroSat Observatory. Here we match the M31 UVIT source catalog with the Chandra source catalog. We find 67 UVIT/Chandra sources detected in a varying number of UV and X-ray bands. The UV and X-ray photometry is analyzed using power-law and blackbody models. The X-ray types include 15 low-mass X-ray binaries (LMXBs) and five active galactic nuclei. Crossmatches with catalogs of stars, clusters, and other source types yield the following: 20 of the UVIT/Chandra sources match with M31 globular clusters, and nine with foreground stars. Three more globular clusters and two more foreground stars are consistent with the UVIT source positions although outside the Chandra match radius of 1". The UV emission of the UVIT/Chandra sources associated with globular clusters is consistent with emission from blue horizontal branch stars rather than from the X-ray source. The LMXBs in globular clusters are among the most luminous globular clusters in M31. Comparison with stellar evolutionary tracks shows that the UVIT/Chandra sources with high UV blackbody temperatures are consistent with massive (10-30M_{sun}_) stars in M31.
