Mon. Not. R. Astron. Soc., 430, 2910-2922 (2013/April-3)
A systematic survey for eruptive young stellar objects using mid-infrared photometry.
SCHOLZ A., FROEBRICH D. and WOOD K.
Abstract (from CDS):
Accretion in young stellar objects (YSOs) is at least partially episodic, i.e. periods with high accretion rates (`bursts') are interspersed by quiescent phases. These bursts manifest themselves as eruptive variability. Here we present a systematic survey for eruptive YSOs aiming to constrain the frequency of accretion bursts. We compare mid-infrared photometry from Spitzer and WISE separated by ∼ 5yr for two samples of YSOs, in nearby star-forming regions and in the Galactic plane, each comprising about 4000 young sources. All objects for which the brightness at 3.6 and 4.5µm is increased by at least 1 mag between the two epochs may be eruptive variables and burst candidates. For these objects, we carry out follow-up observations in the near-infrared. We discover two new eruptive variables in the Galactic plane which could be FU Ori-type objects, with K-band amplitudes of more than 1.5 mag. One object known to undergo an accretion burst, V2492 Cyg, is recovered by our search as well. In addition, the young star ISO-Oph-50, previously suspected to be an eruptive object, is found to be better explained by a disc with varying circumstellar obscuration. In total, the number of burst events in a sample of 4000 YSOs is 1-4. Assuming that all YSOs undergo episodic accretion, this constraint can be used to show that phases of strong accretion (>10-6M☉yr-1) occur in intervals of about 104yr, most likely between 5000 and 50 000yr. This is consistent with the dynamical time-scales for outflows, but not with the separations of emission knots in outflows, indicating that episodic accretion could either trigger or stop collimated large-scale outflows.
© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2013)
accretion, accretion discs - stars: activity - brown dwarfs - stars: pre-main-sequence
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