- 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/AJ/159/27
- Title:
- LCs of the Manwe-Thorondor eclipsing system
- Short Name:
- J/AJ/159/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kuiper Belt Object (385446) Manwe-Thorondor is a multiobject system with mutual events predicted to occur from 2014 to 2019. To detect the events, we observed the system at 4 epochs (UT 2016 August 25 and 26, 2017 July 22 and 25, 2017 November 9, and 2018 October 6) in g, r, and VR bands using the 4m SOAR and the 8.1m Gemini South telescopes at Cerro Pachon, Chile, and Lowell Observatory's 4.3m Discovery Channel Telescope at Happy Jack, Arizona. These dates overlap the uncertainty range (±0.5 day) for four inferior events (Thorondor eclipsing Manwe). We clearly observe variability for the unresolved system with a double-peaked period 11.88190±0.00005hr and ∼0.5mag amplitude together with much longer-term variability. Using a multicomponent model, we simultaneously fit our observations and earlier photometry measured separately for Manwe and Thorondor with the Hubble Space Telescope. Our fit suggests Manwe is bilobed, close to the "barbell" shape expected for a strengthless body with density ∼0.8g/cm<SUP>3</SUP> in hydrostatic equilibrium. For Manwe, we thereby derive maximum width to length ratio ∼0.30, surface area equivalent to a sphere of diameter 190km, geometric albedo 0.06, mass 1.4x1018kg, and spin axis oriented ∼75deg from Earth's line of sight. Changes in Thorondor's brightness by ∼0.6mag with a ∼300day period may account for the system's long-term variability. Mutual events with unexpectedly shallow depth and short duration may account for residuals to the fit. The system is complex, providing a challenging puzzle for future modeling efforts.
