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  5. Exploring the dimming event of RW Aurigae A through multi-epoch VLT/X-shooter spectroscopy
 
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Exploring the dimming event of RW Aurigae A through multi-epoch VLT/X-shooter spectroscopy

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Author(s)
Koutoulaki, Maria-Kalliopi 
Facchini, S. 
Manara, C. F. 
Fedriani, Ruben 
Coffey, Deirdre 
et al. 
Uri
http://hdl.handle.net/10197/11139
Date Issued
08 May 2019
Date Available
10T09:24:38Z October 2019
Abstract
Context. RW Aur A is a classical T Tauri star that has suddenly undergone three major dimming events since 2010. The reason for these dimming events is still not clear. Aims. We aim to understand the dimming properties, examine accretion variability, and derive the physical properties of the inner disc traced by the CO ro-vibrational emission at near-infrared wavelengths (2.3 μm). Methods. We compared two epochs of X-shooter observations, during and after the dimming. We modelled the rarely detected CO bandhead emission in both epochs to examine whether the inner disc properties had changed. The spectral energy distribution was used to derive the extinction properties of the dimmed spectrum and compare the infrared excess between the two epochs. Lines tracing accretion were used to derive the mass accretion rate in both states. Results. The CO originates from a region with physical properties of T = 3000 K, NCO = 1 × 1021 cm−2 and vk sin i = 113 km s−1. The extinction properties of the dimming layer were derived with the effective optical depth ranging from τeff ~2.5−1.5 from the UV to the near-IR. The inferred mass accretion rate Ṁacc is ~1.5 × 10−8 M⊙ yr−1 and ~2 × 10−8 M⊙ yr−1 after and during the dimming respectively. By fitting the spectral energy distribution, additional emission is observed in the infrared during the dimming event from dust grains with temperatures of 500–700 K. Conclusions. The physical conditions traced by the CO are similar for both epochs, indicating that the inner gaseous disc properties do not change during the dimming events. The extinction curve is flatter than that of the interstellar medium, and large grains of a few hundred microns are thus required. When we correct for the observed extinction, the mass accretion rate is constant in the two epochs, suggesting that the accretion is stable and therefore does not cause the dimming. The additional hot emission in the near-IR is located at about 0.5 au from the star and is not consistent with an occulting body located in the outer regions of the disc. The dimming events could be due to a dust-laden wind, a severe puffing-up of the inner rim, or a perturbation caused by the recent star-disc encounter
Sponsorship
European Commission Horizon 2020
European Research Council
Irish Research Council
Science Foundation Ireland
Other Sponsorship
European Southern Observatory Fellowship
Type of Material
Journal Article
Publisher
EDP Sciences
Journal
Astronomy & Astrophysics
Volume
625
Copyright (Published Version)
2019 ESO
Keywords
  • Protoplanetary disks

  • Stars

  • RW Aurigae

  • T Tauri

  • Herbig Ae/Be

  • Dust

  • Extinction

  • Accretion

  • Accretion disks

  • Formation

DOI
10.1051/0004-6361/201834713
Language
English
Status of Item
Peer reviewed
ISSN
0004-6361
This item is made available under a Creative Commons License
https://creativecommons.org/licenses/by-nc-nd/3.0/ie/
Owning collection
Physics Research Collection
Scopus© citations
17
Acquisition Date
Jan 29, 2023
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