NGC 4815 is an intermediate age cluster. Carraro and Ortolani determined the age of the cluster to be 500 million years, based on BVphotometry, which is nearly the same as theHyades,[5] while Sagar et al. determined its age at 400±50 million years[6] and Kharchenko et al. at 400 million years.[3] Friel at al. estimated its age to be between 500 and 630 million years.[7]
There are 69 probable member stars within the angular radius of the cluster and 39 within the central part of the cluster.[3] Fiveblue stragglers have been detected in the cluster,[8] and 15red giants are probable members of the cluster.[6] The earliestmain sequence stars are of type A0. One of the stars in the cluster region shows extremely red colour along with blueultraviolet colour and it could be an interactingbinary star.[6] Theturnoff point is at 2.6 ±0.1M☉.[7]
The members show small dispersions in abundance, with the exception of Mg, which is common for clusters of rather low mass, as NGC 4815.[7] The meanmetallicity of the cluster is [Fe/H] = +0.03 ± 0.05 dex (as estimated by Frieal et al.)[7] or −0.01 ± 0.04 (as estimated by Tautvaišienė et al.).[9]Alpha-elements [Ca/Fe] and [Si/Fe] show solar ratios, [Mg/Fe] is moderately enhanced, [Ti/Fe] is slightly subsolar, [Al/Fe] is enhanced, and [Na/Fe] is significantly enhanced.[7] THE CNO abundances in the cluster are [C/H] = −0.17 ± 0.08, [N/H] = 0.53 ± 0.07, [O/H] = 0.12 ± 0.09, and [C/N] = 0.79 ± 0.08.[9]
^Carraro, G.; Ortolani, S. (September 1994). "Deep CCD BV photometry of the poorly studied open cluster NGC 4815".Astronomy and Astrophysics Supplement.106:573–579.Bibcode:1994A&AS..106..573C.
^abcdeFriel, E. D.; Donati, P.; Bragaglia, A.; Jacobson, H. R.; Magrini, L.; Prisinzano, L.; Randich, S.; Tosi, M.; Cantat-Gaudin, T.; Vallenari, A.; Smiljanic, R.; Carraro, G.; Sordo, R.; Maiorca, E.; Tautvaišien*error*ė, G.; Sestito, P.; Zaggia, S.; Jiménez-Esteban, F. M.; Gilmore, G.; Jeffries, R. D.; Alfaro, E.; Bensby, T.; Koposov, S. E.; Korn, A. J.; Pancino, E.; Recio-Blanco, A.; Franciosini, E.; Hill, V.; Jackson, R. J.; de Laverny, P.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Hourihane, A.; Costado, M. T.; Jofré, P.;Lind, K. (19 March 2014). "Gaia -ESO Survey: Properties of the intermediate age open cluster NGC 4815".Astronomy & Astrophysics.563: A117.arXiv:1403.7451.Bibcode:2014A&A...563A.117F.doi:10.1051/0004-6361/201323215.S2CID119182955.
