Hedges, Christina, Hodgkin, Simon and Kennedy, Grant M. (2018) Discovery of new dipper stars with K2 : a window into the inner disc region of T Tauri stars. Monthly Notices of the Royal Astronomical Society, 476 (3). pp. 2968-2998. doi:10.1093/mnras/sty328

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Abstract

In recent years, a new class of young stellar object (YSO) has been defined, referred to as dippers, where large transient drops in flux are observed. These dips are too large to be attributed to stellar variability, last from hours to days and can reduce the flux of a star by 10-50 per cent. This variability has been attributed to occultations by warps or accretion columns near the inner edge of circumstellar discs. Here, we present 95 dippers in the Upper Scorpius association and ρ Ophiuchus cloud complex found in K2 Campaign 2 data using supervised machine learning with a random forest classifier. We also present 30 YSOs that exhibit brightening events on the order of days, known as bursters. Not all dippers and bursters are known members, but all exhibit infrared excesses and are consistent with belonging to either of the two young star-forming regions. We find 21.0 ± 5.5 per cent of stars with discs are dippers for both regions combined. Our entire dipper sample consists only of late-type (KM) stars, but we show that biases limit dipper discovery for earlier spectral types. Using the dipper properties as a proxy, we find that the temperature at the inner disc edge is consistent with interferometric results for similar and earlier type stars.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Accretion (Astrophysics), Circumstellar matter, Photometry, Machine learning
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Oxford University Press
ISSN:	1365-2966
Official Date:	9 February 2018
Dates:	Date Event 9 February 2018 Published 31 January 2018 Accepted
Date of first compliant deposit:	5 June 2018
Volume:	476
Number:	3
Page Range:	pp. 2968-2998
DOI:	10.1093/mnras/sty328
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
RIOXX Funder/Project Grant:	Project/Grant ID RIOXX Funder Name Funder ID UNSPECIFIED [STFC] Science and Technology Facilities Council http://dx.doi.org/10.13039/501100000271 Research Fellowship Royal Society http://dx.doi.org/10.13039/501100000288 UNSPECIFIED National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104
Open Access Version:	ArXiv

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