WIYN OPEN CLUSTER STUDY. LXXII. A uvbyCaHβ CCD ANALYSIS OF THE METAL-DEFICIENT OPEN CLUSTER NGC 2506

Abstract

Precision uvbyCaHβ photometry of the metal-deficient, old open cluster, NGC 2506, is presented. The survey covers an area 20 × 20 and extends to V ∼ 18 for b − y and Hβ and to V ∼ 17.0 for c 1 and hk. For V brighter than 16.0, photometric scatter among the indices leads to the recovery of 6 known variables within the cluster core and 5 new variables in the outer 5 of the survey field. Proper motions, radial velocities, and precise multicolor indices are used to isolate a highly probable sample of cluster members from the very rich color-magnitude diagram (CMD). From 257 highly probable members at the cluster turnoff, we derive a reddening estimate of E(b − y) = 0.042 ± 0.001 (E(B − V ) = 0.058 ± 0.001), where the errors refer to the internal standard errors of the mean. [Fe/H] is derived from the A/F dwarf members using both m 1 and hk, leading to [Fe/H]= −0.296 ± 0.011 (sem) and −0.317 ± 0.004 (sem), respectively. The weighted average, heavily dominated by hk, is [Fe/H] = −0.316 ± 0.033. Based upon red giant members, we place an upper limit of ±0.010 on the variation in the reddening across the face of the cluster. We also identify two dozen potential red giant cluster members outside the cluster core. Victoria-Regina isochrones on the Strömgren system produce an excellent match to the cluster for an apparent modulus of (m − M ) = 12.75 ± 0.1 and an age of 1.85 ± 0.05 Gyr.

The Swift UVOT Stars Survey. III. Photometry and Color–Magnitude Diagrams of 103 Galactic Open Clusters

“…NGC 2506 is a third quadrant cluster located above the Galactic midplane. Previous studies have shown it to be an old (2 Gyr) metal-poor ([F e/H = −0.3) cluster (Reddy et al 2012b, Lee et al 2012. Anthony-Twarog et al 2016.…”

Li Evolution and the Open Cluster NGC 6819: A Correlation between Li Depletion and Spindown in Dwarfs More Massive Than the F-Dwarf Li-Dip*

“…Fig. 11 presents the rotational velocity distributions among the turnoff stars for four clusters processed and analyzed in the same way, NGC 6819 at 2.25 Gyr, NGC 3680 at 1.75 Gyr (Anthony- Twarog et al 2009), NGC 2506 at 1.85 Gyr (Anthony- Twarog et al 2016, and NGC 7789 at 1.5 Gyr (Brunker et al 2013;Rich et al 2013;Anthony-Twarog et al 2019). The spectroscopic samples for NGC 3680, NGC 2506, and NGC 7789 have all been matched with Gaia DR2 astrometry to eliminate probable nonmembers, following the same procedure adopted for NGC 6819.…”

“…With the goal of using atmospheric Li to probe stellar structure and evolution among low mass stars, the authors have undertaken an extensive spectroscopic program to survey members of a key set of open clusters from the tip of the giant branch to as far down the main sequence as the technology allows. Results have been published for the clusters NGC 3680 (age = 1.75 Gyr) (Anthony- Twarog et al 2009), NGC 6253 (3.0 Gyr) (Anthony- Twarog et al 2010;Cummings et al 2012), and, most recently, the metal-deficient open cluster NGC 2506 (1.85 Gyr) (Anthony- Twarog et al 2016. The current investigation reports on the analysis of over 330 stars in the older open cluster, NGC 6819 (2.3 Gyr).…”

WIYN Open Cluster Study. LXXVI. Li Evolution Among Stars of Low/Intermediate Mass: The Metal-deficient Open Cluster NGC 2506

“…This paper presents a spectroscopic complement to the intermediate-band photometric analysis of the old open cluster, NGC 2506 (Anthony- Twarog et al (2016), hereinafter AT16). The background history of this clusbjat@ku.edu donald@ku.edu cdeliyan@indiana.edu btwarog@ku.edu ter is explored in detail in AT16 and will not be repeated here except when required by the specifics of the analysis.…”