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Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra

Ingleby, Laura and Calvet, Nuria and Herczeg, Gregory and Blaty, Alex and Walter, Frederick and Ardila, David and Alexander, Richard and Edwards, Suzan and Espaillat, Catherine and Gregory, Scott G. and Hillenbrand, Lynne and Brown, Alexander (2013) Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra. Astrophysical Journal, 767 (2). Art. No. 112. ISSN 0004-637X. doi:10.1088/0004-637X/767/2/112.

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We analyze the accretion properties of 21 low-mass T Tauri stars using a data set of contemporaneous near-UV (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph and the ground-based Small and Medium Aperture Research Telescope System, a unique data set because of the nearly simultaneous broad wavelength coverage. Our data set includes accreting T Tauri stars in Taurus, Chamaeleon I, η Chamaeleon, and the TW Hydra Association. For each source we calculate the accretion rate (Ṁ) by fitting the NUV and optical excesses above the photosphere, produced in the accretion shock, introducing multiple accretion components characterized by a range in energy flux (or density) for the first time. This treatment is motivated by models of the magnetospheric geometry and accretion footprints, which predict that high-density, low filling factor accretion spots coexist with low-density, high filling factor spots. By fitting the UV and optical spectra with multiple accretion components, we can explain excesses which have been observed in the near-IR. Comparing our estimates of Ṁ to previous estimates, we find some discrepancies; however, they may be accounted for when considering assumptions for the amount of extinction and variability in optical spectra. Therefore, we confirm many previous estimates of the accretion rate. Finally, we measure emission line luminosities from the same spectra used for the Ṁ estimates, to produce correlations between accretion indicators (Hβ, Ca II K, C II], and Mg II) and accretion properties obtained simultaneously.

Item Type:Article
Related URLs:
URLURL TypeDescription
Calvet, Nuria0000-0002-3950-5386
Herczeg, Gregory0000-0002-7154-6065
Brown, Alexander0000-0003-2631-3905
Additional Information:© 2013 American Astronomical Society. Received 2012 December 18; accepted 2013 March 3; published 2013 April 2. We thank Melissa McClure for valuable discussions regarding extinction estimates and veiling in the NIR and providing results prior to publication. We also thank Ted Bergin, Lee Hartmann, JonMiller, and Fred Adams for providing comments on an early version of this paper as part of L. Ingleby’s thesis. This work was supported by NASA grants for Guest Observer program 11616 to the University of Michigan, Caltech, and the University of Colorado. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute data archive. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA Contract NAS 5-26555. C.E. was supported by a Sagan Exoplanet Fellowship from NASA and administered by the NASA Exoplanet Science Institute. R.D.A. acknowledges support from the Science and Technology Facilities Council (STFC) through an Advanced Fellowship (ST/G00711X/1). S.G.G. acknowledges support from STFC via a Ernest Rutherford Fellowship (ST/J003255/1).
Funding AgencyGrant Number
NASANAS 5-26555
Science and Technology Facilities Council (STFC)ST/G00711X/1
Science and Technology Facilities Council (STFC)ST/J003255/1
Subject Keywords:accretion, accretion disks; stars: chromospheres; stars: pre-main sequence; ultraviolet: stars
Issue or Number:2
Record Number:CaltechAUTHORS:20130521-140050828
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Official Citation:Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra Laura Ingleby, Nuria Calvet, Gregory Herczeg, Alex Blaty, Frederick Walter, David Ardila, Richard Alexander, Suzan Edwards, Catherine Espaillat, Scott G. Gregory, Lynne Hillenbrand, and Alexander Brown doi:10.1088/0004-637X/767/2/112
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38615
Deposited By: Ruth Sustaita
Deposited On:21 May 2013 21:28
Last Modified:09 Nov 2021 23:38

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