- ID:
- ivo://CDS.VizieR/J/AJ/159/50
- Title:
- Identifying multiple populations in M71 using CN
- Short Name:
- J/AJ/159/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed their cyanogen CN features at ∼3800 and 4120Å as well as the CH band at ∼4300Å for 145 evolved stars in the Galactic globular cluster M71 using the multi-object spectrograph, Hydra, on the Wisconsin-Indiana-Yale- NOAO-3.5 m telescope. We use these measurements to create two δCN indices finding that both distributions are best fit by two populations: a CN-enhanced and CN-normal. We find that 42%±4% of the red giant branch stars in our sample are CN-enhanced. The percentage of CN-enhanced is 40%±13% for the asymptotic giant branch and 33%±9% for the horizontal branch stars (HB stars), which suggests there are no missing second generation stars at these stages of stellar evolution. The two generations also separate in magnitude and color on the HB, which allows us to find the difference in He abundance between the two populations by fitting appropriate zero-age horizontal branches. The broad range of distances from the cluster's center covered by our sample allows us to study the dependence of the ratio of the number of first to second population stars on the distance from the cluster's center, and we find that this ratio does not vary radially and that the two populations are spatially mixed. Finally, we compare our identification of multiple populations with the classification based on the Na-O anti-correlation and the Hubble Space Telescope UV photometry, and we find good agreement with both methods.
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- ID:
- ivo://CDS.VizieR/J/ApJ/901/57
- Title:
- MAVERIC survey: Chandra X-ray sources in 38 GCs
- Short Name:
- J/ApJ/901/57
- Date:
- 17 Feb 2022 13:07:56
- Publisher:
- CDS
- Description:
- Globular clusters host a variety of lower-luminosity (L<SUB>X</SUB><10<SUP>35</SUP>erg/s) X-ray sources, including accreting neutron stars (NSs) and black holes (BHs), millisecond pulsars (MSPs), cataclysmic variables, and chromospherically active binaries. In this paper, we provide a comprehensive catalog of more than 1100 X-ray sources in 38 Galactic globular clusters (GCs) observed by the Chandra X-ray Observatory's Chandra/ACIS detector. The targets are selected to complement the MAVERIC survey's deep radio continuum maps of Galactic GCs. We perform photometry and spectral analysis for each source, determine a best-fit model, and assess the possibility of it being a foreground or background source based on its spectral properties and location in the cluster. We also provide basic assessments of variability. We discuss the distribution of X-ray binaries in GCs and their X-ray luminosity function, and we carefully analyze systems with L<SUB>X</SUB>>10<SUP>33</SUP>erg/s. Among these moderately bright systems, we discover a new source in NGC 6539 that may be a candidate accreting stellar-mass BH or a transitional MSP. We show that quiescent NS low-mass X-ray binaries in GCs may spend ∼2% of their lifetimes as transitional MSPs in their active (L<SUB>X</SUB>>10<SUP>33</SUP>erg/s) state. Finally, we identify a substantial underabundance of bright (L<SUB>X</SUB>>10<SUP>33</SUP>erg/s) intermediate polars in GCs compared to the Galactic field, in contrast with the literature of the past two decades.
