HUBBLE SPACE TELESCOPE MEASURES OF MASS ACCRETION RATES IN THE ORION NEBULA CLUSTER
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Manara-2012-Hubble space telesco.pdf
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Author(s)
Manara, C. F.
Robberto, M.
Da Rio, N.
Lodato, G.
Hillenbrand, L. A.
Soderblom, D. R.
Stassun, Keivan
Date Issued
August 2012
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Manara, C. F., M. Robberto, N. Da Rio, G. Lodato, L. A. Hillenbrand, K. G. Stassun, and D. R. Soderblom. “HUBBLE SPACE TELESCOPE MEASURES OF MASS ACCRETION RATES IN THE ORION NEBULA CLUSTER.” The Astrophysical Journal 755, no. 2 (August 6, 2012): 154. © 2012 The American Astronomical Society
Version
Final published version
Abstract
The present observational understanding of the evolution of the mass accretion rates ([dot over M][subscript acc]) in pre-main-sequence stars is limited by the lack of accurate measurements of [dot over M][subscript acc] over homogeneous and large statistical samples of young stars. Such observational effort is needed to properly constrain the theory of star formation and disk evolution. Based on Hubble Space Telescope/WFPC2 observations, we present a study of [dot over M][subscript acc] for a sample of ~700 sources in the Orion Nebula Cluster, ranging from the hydrogen-burning limit to M [subscript *] ~ 2 M [subscript ☉]. We derive [dot over M][subscript acc] from both the U-band excess and the Hα luminosity (L [subscript Hα]), after determining empirically both the shape of the typical accretion spectrum across the Balmer jump and the relation between the accretion luminosity (L [subscript acc]) and L [subscript Hα], which is L [subscript acc]/L [subscript ☉] = (1.31 ± 0.03) · L [subscript Hα]/L [subscript ☉] + (2.63 ± 0.13). Given our large statistical sample, we are able to accurately investigate relations between [dot over M][subscript acc] and the parameters of the central star such as mass and age. We clearly find [dot over M][subscript acc] to increase with stellar mass and decrease over evolutionary time, but we also find strong evidence that the decay of [dot over M][subscript acc] with stellar age occurs over longer timescales for more massive PMS stars. Our best-fit relation between these parameters is given by log ([dot over M][subscript acc]/M [subscript ☉] yr) = (–5.12 ± 0.86) – (0.46 ± 0.13) · log (t/yr) – (5.75 ± 1.47) · log (M [subscript *]/M [subscript ☉]) + (1.17 ± 0.23) · log (t/yr) · log (M [subscript *]/M [subscript ☉]). These results also suggest that the similarity solution model could be revised for sources with M [subscript *] [> over ~] 0.5 M [subscript ☉]. Finally, we do not find a clear trend indicating environmental effects on the accretion properties of the sources.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1088/0004-637x/755/2/154
