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Magnetospheric Accretion in Close Pre-Main-Sequence Binaries

Ardila, David R. and Jonhs-Krull, Christopher and Herczeg, Gregory J. and Mathieu, Robert D. and Quijano-Vodniza, Alberto (2015) Magnetospheric Accretion in Close Pre-Main-Sequence Binaries. Astrophysical Journal, 811 (2). Art. No. 131. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20151119-131551500

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Abstract

The transfer of matter between a circumbinary disk and a young binary system remains poorly understood, obscuring the interpretation of accretion indicators. To explore the behavior of these indicators in multiple systems, we have performed the first systematic time-domain study of young binaries in the ultraviolet. We obtained far- and near-ultraviolet HST/COS spectra of the young spectroscopic binaries DQ Tau and UZ Tau E. Here we focus on the continuum from 2800 to 3200 Å and on the C iv doublet (λλ1548.19, 1550.77 Å) as accretion diagnostics. Each system was observed over three or four consecutive binary orbits, at phases ~0, 0.2, 0.5, and 0.7. Those observations are complemented by ground-based U-band measurements. Contrary to model predictions, we do not detect any clear correlation between accretion luminosity and phase. Further, we do not detect any correlation between C iv flux and phase. For both stars the appearance of the C iv line is similar to that of single Classical T Tauri Stars (CTTSs), despite the lack of stable long-lived circumstellar disks. However, unlike the case in single CTTSs, the narrow and broad components of the C iv lines are uncorrelated, and we argue that the narrow component is powered by processes other than accretion, such as flares in the stellar magnetospheres and/or enhanced activity in the upper atmosphere. We find that both stars contribute equally to the narrow component C iv flux in DQ Tau, but the primary dominates the narrow component C iv emission in UZ Tau E. The C iv broad component flux is correlated with other accretion indicators, suggesting an accretion origin. However, the line is blueshifted, which is inconsistent with its origin in an infall flow close to the star. It is possible that the complicated geometry of the region, as well as turbulence in the shock region, are responsible for the blueshifted line profiles.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/811/2/131DOIArticle
http://iopscience.iop.org/article/10.1088/0004-637X/811/2/131/metaPublisherArticle
ORCID:
AuthorORCID
Herczeg, Gregory J.0000-0002-7154-6065
Additional Information:© 2015 American Astronomical Society. Received 2015 April 2; accepted 2015 August 13; published 2015 September 29. This work is based on observations made with the NASA/ESA Hubble Space Telescope. Support for this work was provided by NASA through grant number xxx from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc (AURA) under NASA contract NAS 5-26555. Special thanks go to Steve Penton (STScI) and Kevin France (CASA-Colorado) for extensive discussions of the errors associated with COS pointing. Facility: HST - Hubble Space Telescope satellite (COS, STIS).
Funders:
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
NASANAS 5-26555
Subject Keywords:binaries: spectroscopic; stars: pre-main sequence; stars: variables: T Tauri, Herbig Ae/Be; techniques: spectroscopic; ultraviolet: stars
Issue or Number:2
Record Number:CaltechAUTHORS:20151119-131551500
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151119-131551500
Official Citation:David R. Ardila et al 2015 ApJ 811 131
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62244
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:19 Nov 2015 21:53
Last Modified:03 Oct 2019 09:16

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