Beccari, G, Petr-Gotzens, MG, Boffin, HMJ, Romaniello, M, Fedele, D, Carraro, G, De Marchi, G, de Wit, W-J, Drew, JE, Kalari, VM, Manara, CF, Martin, EL, Mieske, S, Panagia, N, Testi, L, Vink, JS, Walsh, JR and Wright, NJ (2017) A tale of three cities - OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster. Astronomy and Astrophysics, 604. A22 - A22. ISSN 1432-0746

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As part of the accretion discs in Hα with OmegaCAM (ADHOC) survey, we imaged a region of 12 × 8 square degrees around the Orion Nebula Cluster in r, i and Hα. Thanks to the high-quality photometry obtained, we discovered three well-separated pre-main sequences in the color-magnitude diagram. The populations are all concentrated towards the cluster’s center. Although several explanations can be invoked to explain these sequences, we are left with two competitive but intriguing scenarios: a population of unresolved binaries with an exotic mass ratio distribution, or three populations with different ages. Independent high-resolution spectroscopy supports the presence of discrete episodes of star formation, each separated by about a million years. The stars from the two putative youngest populations rotate faster than the older ones, in agreement with the evolution of stellar rotation observed in pre-main sequence stars younger than 4 Myr in several star forming regions.  Whatever the final explanation, our results prompt a revised look at the formation mode and early evolution of stars in clusters.

Item Type: Article
Uncontrolled Keywords: stars: pre-main sequence, open clusters and associations: individual: Orion
Subjects: Q Science > QB Astronomy
Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Symplectic
Date Deposited: 31 Aug 2017 10:50
Last Modified: 09 Apr 2021 13:11

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