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CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264. II. Photometric variability, magnetic activity, and rotation in class III objects and stars with transition disks

Guarcello, M. G. and Flaccomio, E. and Micela, G. and Argiroffi, C. and Sciortino, S. and Venuti, L. and Stauffer, J. and Rebull, L. and Cody, A. M. (2019) CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264. II. Photometric variability, magnetic activity, and rotation in class III objects and stars with transition disks. Astronomy and Astrophysics, 628 . Art. No. A74. ISSN 0004-6361. https://resolver.caltech.edu/CaltechAUTHORS:20190823-093802486

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Abstract

Context. Pre-main sequence stars are variable sources. In diskless stars this variability is mainly due to the rotational modulation of dark photospheric spots and active regions, as in main sequence stars even if associated with a stronger magnetic activity. Aims. We aim at analyzing the simultaneous optical and X-ray variability in these stars to unveil how the activity in the photosphere is connected with that in the corona, to identify the dominant surface magnetic activity, and to correlate our results with stellar properties, such as rotation and mass. Methods. We analyzed the simultaneous optical and X-ray variability in stars without inner disks (e.g., class III objects and stars with transition disks) in NGC 2264 from observations obtained with Chandra/ACIS-I and CoRoT as part of the Coordinated Synoptic Investigation of NGC 2264. We searched for those stars whose optical and X-ray variability is correlated, anti-correlated, or not correlated by sampling their optical and X-ray light curves in suitable time intervals and studying the correlation between the flux observed in optical and in X-rays. We then studied how this classification is related with stellar properties. Results. Starting from a sample of 74 class III/transition disk (TD) stars observed with CoRoT and detected with Chandra with more than 60 counts, we selected 16 stars whose optical and X-ray variability is anti-correlated, 11 correlated, and 17 where there is no correlation. The remaining stars did not fall in any of these groups. We interpreted the anti-correlated optical and X-ray variability as typical of spot-dominated sources, due to the rotational modulation of photospheric spots spatially coincident to coronal active regions, and correlated variability typical of faculae-dominated sources, where the brightening due to faculae is dominant over the darkening due to spots. Conclusions. Stars with “anti-correlated” variability rotate slower and are less massive than those with “correlated” variability. Furthermore, cool stars in our sample have larger u − r variability than hot stars. This suggests that there is a connection between stellar rotation, mass, and the dominant surface magnetic activity, which may be related with the topology of the large-scale magnetic field. We thus discuss this scenario in the framework of the complex magnetic properties of weak-line T Tauri stars observed as part of recent projects.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1051/0004-6361/201935466DOIArticle
https://arxiv.org/abs/1907.04030arXivDiscussion Paper
ORCID:
AuthorORCID
Guarcello, M. G.0000-0002-3010-2310
Flaccomio, E.0000-0002-3638-5788
Micela, G.0000-0002-9900-4751
Stauffer, J.0000-0003-3595-7382
Rebull, L.0000-0001-6381-515X
Cody, A. M.0000-0002-3656-6706
Additional Information:© 2019 ESO. Article published by EDP Sciences. Received 14 March 2019; Accepted 1 July 2019; Published online 08 August 2019. M. G. G. acknowledges partial support from the agreement ASI-INAF n. 2017-14-H.0. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory and the CoRoT satellite. The authors of this paper also made an extensive use of the Xspec and TOPCAT softwares and the NASA’s Astrophysics Data System. Finally, we wish to thank the anonymous reviewer for valuable insight into the paper and important suggestions.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)2017-14-H.0
Subject Keywords:stars: activity – stars: coronae – stars: variables: T Tauri, Herbig Ae/Be – stars: pre-main sequence – stars: rotation – starspots
Record Number:CaltechAUTHORS:20190823-093802486
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190823-093802486
Official Citation:CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264 - II. Photometric variability, magnetic activity, and rotation in class III objects and stars with transition disks. M. G. Guarcello, E. Flaccomio, G. Micela, C. Argiroffi, S. Sciortino, L. Venuti, J. Stauffer, L. Rebull and A. M. Cody. A&A, 628 (2019) A74. DOI: https://doi.org/10.1051/0004-6361/201935466
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98149
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:23 Aug 2019 16:45
Last Modified:03 Oct 2019 21:38

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