Data di Pubblicazione:
2012
Citazione:
Hubble Space Telescope measures of mass accretion rates in the Orion Nebula Cluster / C. F. Manara, M. Robberto, N. Da Rio, G. Lodato, L. A. Hillenbrand, K. G. Stassun, D. R. Soderblom. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 755:2(2012), pp. 154.154.1-154.154.16.
Abstract:
The present observational understanding of the evolution of the mass accretion rates ( ˙Macc) in pre-main-sequence
stars is limited by the lack of accurate measurements of ˙Macc 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 ˙Macc for a sample of
∼700 sources in the Orion Nebula Cluster, ranging from the hydrogen-burning limit to M∗ ∼ 2M . We derive
˙M
acc from both the U-band excess and the Hα luminosity (LHα), after determining empirically both the shape of
the typical accretion spectrum across the Balmer jump and the relation between the accretion luminosity (Lacc) and
LHα, which is Lacc/L = (1.31 ± 0.03) · LHα/L + (2.63 ± 0.13). Given our large statistical sample, we are able
to accurately investigate relations between ˙Macc and the parameters of the central star such as mass and age. We
clearly find ˙Macc to increase with stellar mass and decrease over evolutionary time, but we also find strong evidence
that the decay of ˙Macc with stellar age occurs over longer timescales for more massive PMS stars. Our best-fit
relation between these parameters is given by log( ˙Macc/M yr) = (−5.12 ± 0.86) − (0.46 ± 0.13) · log(t/yr) −
(5.75±1.47) · log(M∗/M ) + (1.17±0.23) · log(t/yr) · log(M∗/M ). These results also suggest that the similarity
solution model could be revised for sources with M∗ 0.5M . Finally, we do not find a clear trend indicating
environmental effects on the accretion properties of the sources.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
accretion, accretion disks; protoplanetary disks; stars: formation; stars: pre-main sequence
Elenco autori:
C. F. Manara, M. Robberto, N. Da Rio, G. Lodato, L. A. Hillenbrand, K. G. Stassun, D. R. Soderblom
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