Journal Article

T Tauri candidates and accretion rates using IPHAS: method and application to IC 1396

Geert Barentsen, Jorick S. Vink, J. E. Drew, R. Greimel, N. J. Wright, J. J. Drake, E. L. Martin, L. Valdivielso and R. L. M. Corradi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 1, pages 103-132
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18674.x
T Tauri candidates and accretion rates using IPHAS: method and application to IC 1396

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The Isaac Newton Telescope (INT) Photometric H-Alpha Survey (IPHAS) is a 1800 deg2 survey of the Northern Galactic Plane, reaching down to r′∼ 21. We demonstrate how the survey can be used to (1) reliably select classical T Tauri star candidates and (2) constrain the mass accretion rates with an estimated relative uncertainty of 0.6 dex. IPHAS is a necessary addition to spectroscopic surveys because it allows large and uniform samples of accretion rates to be obtained with a precise handle on the selection effects.

We apply the method on a region of 7 deg2 towards the H ii region IC 1396 in Cepheus OB2 and identify 158 pre-main-sequence candidates with masses between 0.2 and 2.0 M and accretion rates between 10−9.2 and 10−7.0 M yr−1. We find a power-law dependency between the stellar mass and the accretion rates with a slope of α= 1.1 ± 0.2, which is less steep than indicated by previous studies. We discuss the influence of method-dependent systematic effects on the determination of this relationship.

The majority of our sample consists of faint, previously unknown, low-mass T Tauri candidates (56 per cent between 0.2 and 0.5 M). Many candidates are clustered in front of three bright-rimmed molecular clouds, which are being ionized by the massive star HD 206267 (O6.5V). We discover a spatio-temporal gradient of increasing accretion rates, increasing Spitzer infrared excess, and younger ages away from the ionizing star, providing a strong indication that the formation of these clusters has been sequentially triggered by HD 206267 during the last ∼1 Myr.

Keywords: accretion, accretion discs; stars: pre-main-sequence; stars: variables: T Tauri, Herbig Ae/Be; open clusters and associations: individual: IC 1396

Journal Article.  18756 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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