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Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry

Venuti, L. and Bouvier, J. and Flaccomio, E. and Alencar, S. H. P. and Irwin, J. and Stauffer, J. R. and Cody, A. M. and Teixeira, P. S. and Sousa, A. P. and Micela, G. and Cuillandre, J.-C. and Peres, G. (2014) Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry. Astronomy and Astrophysics, 570 . Art. No. A82. ISSN 0004-6361.

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Context. The accretion process has a central role in the formation of stars and planets. Aims. We aim at characterizing the accretion properties of several hundred members of the star-forming cluster NGC 2264 (3 Myr). Methods. We performed a deep ugri mapping as well as a simultaneous u-band+r-band monitoring of the star-forming region with CFHT/MegaCam in order to directly probe the accretion process onto the star from UV excess measurements. Photometric properties and stellar parameters are determined homogeneously for about 750 monitored young objects, spanning the mass range ~0.1–2 M_⊙. About 40% of the sample are classical (accreting) T Tauri stars, based on various diagnostics (H_α, UV and IR excesses). The remaining non-accreting members define the (photospheric + chromospheric) reference UV emission level over which flux excess is detected and measured. Results. We revise the membership status of cluster members based on UV accretion signatures, and report a new population of 50 classical T Tauri star (CTTS) candidates. A large range of UV excess is measured for the CTTS population, varying from a few times 0.1 to ~3 mag. We convert these values to accretion luminosities and accretion rates, via a phenomenological description of the accretion shock emission. We thus obtain mass accretion rates ranging from a few 10^(-10) to ~10^(-7) M_⊙/yr. Taking into account a mass-dependent detection threshold for weakly accreting objects, we find a >6σ correlation between mass accretion rate and stellar mass. A power-law fit, properly accounting for censored data (upper limits), yields Ṁ_(acc) ∝ M_*^(1.4±0.3). At any given stellar mass, we find a large spread of accretion rates, extending over about 2 orders of magnitude. The monitoring of the UV excess on a timescale of a couple of weeks indicates that its variability typically amounts to 0.5 dex, i.e., much smaller than the observed spread in accretion rates. We suggest that a non-negligible age spread across the star-forming region may effectively contribute to the observed spread in accretion rates at a given mass. In addition, different accretion mechanisms (like, e.g., short-lived accretion bursts vs. more stable funnel-flow accretion) may be associated to different Ṁ_(acc) regimes. Conclusions. A huge variety of accretion properties is observed for young stellar objects in the NGC 2264 cluster. While a definite correlation seems to hold between mass accretion rate and stellar mass over the mass range probed here, the origin of the large intrinsic spread observed in mass accretion rates at any given mass remains to be explored.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Bouvier, J.0000-0002-7450-6712
Flaccomio, E.0000-0002-3638-5788
Stauffer, J. R.0000-0003-3595-7382
Cody, A. M.0000-0002-3656-6706
Micela, G.0000-0002-9900-4751
Additional Information:© 2014 ESO. Article published by EDP Sciences. Received 7 March 2014. Accepted 29 July 2014. Published online 21 October 2014. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. We would like to thank Christian Veillet, former director of CFHT, for granting discretionary time to perform the mapping survey in December 2010, and the Terapix center at Institut d’Astrophysique de Paris, and in particular Yannick Mellier, for the prompt processing of the MegaCam images obtained during this run.We also thank NadineManset and Jim Thomas at CFHT for efficient run scheduling and data retrieval procedures. We warmly thank Luisa Rebull for retrieving for us the L_(acc) values she derived for her 2002 paper on disk-bearing objects in NGC 2264. We thank Kevin Covey for discussions on SDSS dwarf sequences and Lynne Hillenbrand for discussions on bolometric corrections scales; we also acknowledge useful discussion on the M_(acc)–M_∗ relationship with Beate Stelzer. This publication makes use of data products from the Sloan Digital Sky Survey and the Two Micron All Sky Survey. This project was in part supported by the grant ANR 2011 Blanc SIMI5-6 020 01. S.H.P.A. and A.P.S. acknowledge support from CNPq, CAPES and Fapemig.
Funding AgencyGrant Number
Agence Nationale pour la Recherche (ANR)SIMI5-6 020 01
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)UNSPECIFIED
Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)UNSPECIFIED
Subject Keywords:accretion, accretion disks, stars: formation – stars: low-mass, stars: pre-main sequence, ultraviolet: stars, open clusters and associations: individual: NGC 2264
Record Number:CaltechAUTHORS:20141205-144045556
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Official Citation:Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry L. Venuti, J. Bouvier, E. Flaccomio, S. H. P. Alencar, J. Irwin, J. R. Stauffer, A. M. Cody, P. S. Teixeira, A. P. Sousa, G. Micela, J.-C. Cuillandre and G. Peres A&A 570 A82 (2014) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52443
Deposited By: Ruth Sustaita
Deposited On:05 Dec 2014 23:24
Last Modified:09 Mar 2020 13:19

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