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The Many-faceted Light Curves of Young Disk-bearing Stars in Upper Sco –– Oph Observed by K2 Campaign 2

Cody, Ann Marie and Hillenbrand, Lynne A. (2018) The Many-faceted Light Curves of Young Disk-bearing Stars in Upper Sco –– Oph Observed by K2 Campaign 2. Astronomical Journal, 156 (2). Art. No. 71. ISSN 1538-3881. doi:10.3847/1538-3881/aacead.

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The K2 Mission has photometrically monitored thousands of stars at high precision and cadence in a series of ~80-day campaigns focused on sections of the ecliptic plane. During its second campaign, K2 targeted over 1000 young stellar objects (YSOs) in the ~1–3 Myr ρ Ophiuchus and 5–10 Myr Upper Scorpius regions. From this set, we have carefully vetted photometry from WISE and Spitzer to identify those YSOs with infrared excess indicative of primordial circumstellar disks. We present here the resulting comprehensive sample of 288 young disk-bearing stars from B through M spectral types and analysis of their associated K2 light curves. Using statistics of periodicity and symmetry, we categorize each light curve into eight different variability classes, notably including "dippers" (fading events), "bursters" (brightening events), stochastic, and quasi-periodic types. Nearly all (96%) of disk-bearing YSOs are identified as variable at 30-minute cadence with the sub-1% precision of K2. Combining our variability classifications with (circum)stellar properties, we find that the bursters, stochastic sources, and the largest amplitude quasi-periodic stars have larger infrared colors, and hence stronger circumstellar disks. They also tend to have larger Hα equivalent widths, indicative of higher accretion rates. The dippers, on the other hand, cluster toward moderate infrared colors and low Hα. Using resolved disk observations, we further find that the latter favor high inclinations, except for a few notable exceptions with close to face-on disks. These observations support the idea that YSO time-domain properties are dependent on several factors, including accretion rate and view angle.

Item Type:Article
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URLURL TypeDescription Paper
Cody, Ann Marie0000-0002-3656-6706
Alternate Title:The many-faceted light curves of young disk-bearing stars in Upper Sco and ρ Oph observed by K2 Campaign 2
Additional Information:© 2018 The American Astronomical Society. Received 2018 February 18; revised 2018 June 6; accepted 2018 June 8; published 2018 July 27. We extend our appreciation to the referee for helpful comments. We thank Trevor David for help collecting and categorizing K2 light curves. We acknowledge John Carpenter for early conversations about ALMA samples in Upper Sco, as well as Luisa Rebull and John Stauffer for general discussions about young star variability, membership, and disk properties. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate.
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:accretion, accretion disks – circumstellar matter – protoplanetary disks – stars: pre-main sequence – stars: variables: T Tauri, Herbig Ae/Be – starspots
Issue or Number:2
Record Number:CaltechAUTHORS:20180808-133210304
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Official Citation:Ann Marie Cody and Lynne A. Hillenbrand 2018 AJ 156 71
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88663
Deposited By: Tony Diaz
Deposited On:08 Aug 2018 21:10
Last Modified:16 Nov 2021 00:28

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