Optical spectroscopy of EX Lupi during quiescence and outburst: Infall, wind, and dynamics in the accretion flow

A. Sicilia-Aguilar, A. Kóspál, J. Setiawan, P. Ábrahám, C. Dullemond, C. Eiroa, M. Goto, Th Henning, A. Juhász

Research output: Article

26 Citations (Scopus)

Abstract

Context. EX Lupi is the prototype of EXor variables. After 50 years of mild variability and smaller outbursts, the object again experienced a large outburst in 2008. Aims. We explore the accretion mechanisms in EX Lupi during its pre-outburst, outburst, and post-outburst phases. Methods. We analyze 10 high-resolution optical spectra of EX Lupi, taken before, during, and after the 2008 outburst. In both quiescence and outburst, the star presents many permitted emission lines. These include lines typical of accreting T Tauri stars, plus a large number of neutral and ionized metallic lines (mostly Fe I and Fe II). During the outburst, the number of emission lines increases to about a thousand, and their structure shows a narrow and a broad component (NC and BC). We study the structure of the BC, which is highly variable on short timescales (24-72 h). Results. An active chromosphere can explain the metallic lines in quiescence and the outburst NC. The dynamics of the BC line profiles suggest that these profiles originate in a hot, dense, non-axisymmetric, and non-uniform accretion column that suffers velocity variations along the line-of-sight on timescales of days. Assuming Keplerian rotation, the emitting region would be located at ~0.1-0.2 AU, which is consistent with the location of the inner disk rim, but the velocity profiles of the lines reveal a combination of rotation and infall. Line ratios of ions and neutrals can be reproduced assuming a temperature of T ~ 6500 K for electron densities of a few times 10 12 cm -3 in the line-emitting region. The line profiles also indicate that there is an accretion-related inner disk wind. Conclusions. The data confirm that the 2008 outburst was an episode of increased accretion, albeit much stronger than previous EX Lupi and typical EXors outbursts. The line profiles are consistent with the infall/rotation of a non-axisymmetric structure that could be produced by clumpy accretion during the outburst phase. A strong inner disk wind appears in the epochs of higher accretion. The rapid recovery of the system after the outburst and the similarity between the pre-outburst and post-outburst states suggest that the accretion channels are similar during the whole period, and only the accretion rate varies, providing a superb environment for studying the accretion processes.

Original languageEnglish
Article numberA93
JournalAstronomy and Astrophysics
Volume544
DOIs
Publication statusPublished - 2012

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outburst
spectroscopy
accretion
profiles
T Tauri stars
chromosphere
rims
line of sight
optical spectrum
timescale
velocity distribution
recovery
prototypes
time measurement
stars
velocity profile
high resolution
electron density

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Optical spectroscopy of EX Lupi during quiescence and outburst : Infall, wind, and dynamics in the accretion flow. / Sicilia-Aguilar, A.; Kóspál, A.; Setiawan, J.; Ábrahám, P.; Dullemond, C.; Eiroa, C.; Goto, M.; Henning, Th; Juhász, A.

In: Astronomy and Astrophysics, Vol. 544, A93, 2012.

Research output: Article

Sicilia-Aguilar, A, Kóspál, A, Setiawan, J, Ábrahám, P, Dullemond, C, Eiroa, C, Goto, M, Henning, T & Juhász, A 2012, 'Optical spectroscopy of EX Lupi during quiescence and outburst: Infall, wind, and dynamics in the accretion flow', Astronomy and Astrophysics, vol. 544, A93. https://doi.org/10.1051/0004-6361/201118555
Sicilia-Aguilar, A. ; Kóspál, A. ; Setiawan, J. ; Ábrahám, P. ; Dullemond, C. ; Eiroa, C. ; Goto, M. ; Henning, Th ; Juhász, A. / Optical spectroscopy of EX Lupi during quiescence and outburst : Infall, wind, and dynamics in the accretion flow. In: Astronomy and Astrophysics. 2012 ; Vol. 544.
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abstract = "Context. EX Lupi is the prototype of EXor variables. After 50 years of mild variability and smaller outbursts, the object again experienced a large outburst in 2008. Aims. We explore the accretion mechanisms in EX Lupi during its pre-outburst, outburst, and post-outburst phases. Methods. We analyze 10 high-resolution optical spectra of EX Lupi, taken before, during, and after the 2008 outburst. In both quiescence and outburst, the star presents many permitted emission lines. These include lines typical of accreting T Tauri stars, plus a large number of neutral and ionized metallic lines (mostly Fe I and Fe II). During the outburst, the number of emission lines increases to about a thousand, and their structure shows a narrow and a broad component (NC and BC). We study the structure of the BC, which is highly variable on short timescales (24-72 h). Results. An active chromosphere can explain the metallic lines in quiescence and the outburst NC. The dynamics of the BC line profiles suggest that these profiles originate in a hot, dense, non-axisymmetric, and non-uniform accretion column that suffers velocity variations along the line-of-sight on timescales of days. Assuming Keplerian rotation, the emitting region would be located at ~0.1-0.2 AU, which is consistent with the location of the inner disk rim, but the velocity profiles of the lines reveal a combination of rotation and infall. Line ratios of ions and neutrals can be reproduced assuming a temperature of T ~ 6500 K for electron densities of a few times 10 12 cm -3 in the line-emitting region. The line profiles also indicate that there is an accretion-related inner disk wind. Conclusions. The data confirm that the 2008 outburst was an episode of increased accretion, albeit much stronger than previous EX Lupi and typical EXors outbursts. The line profiles are consistent with the infall/rotation of a non-axisymmetric structure that could be produced by clumpy accretion during the outburst phase. A strong inner disk wind appears in the epochs of higher accretion. The rapid recovery of the system after the outburst and the similarity between the pre-outburst and post-outburst states suggest that the accretion channels are similar during the whole period, and only the accretion rate varies, providing a superb environment for studying the accretion processes.",
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T1 - Optical spectroscopy of EX Lupi during quiescence and outburst

T2 - Infall, wind, and dynamics in the accretion flow

AU - Sicilia-Aguilar, A.

AU - Kóspál, A.

AU - Setiawan, J.

AU - Ábrahám, P.

AU - Dullemond, C.

AU - Eiroa, C.

AU - Goto, M.

AU - Henning, Th

AU - Juhász, A.

PY - 2012

Y1 - 2012

N2 - Context. EX Lupi is the prototype of EXor variables. After 50 years of mild variability and smaller outbursts, the object again experienced a large outburst in 2008. Aims. We explore the accretion mechanisms in EX Lupi during its pre-outburst, outburst, and post-outburst phases. Methods. We analyze 10 high-resolution optical spectra of EX Lupi, taken before, during, and after the 2008 outburst. In both quiescence and outburst, the star presents many permitted emission lines. These include lines typical of accreting T Tauri stars, plus a large number of neutral and ionized metallic lines (mostly Fe I and Fe II). During the outburst, the number of emission lines increases to about a thousand, and their structure shows a narrow and a broad component (NC and BC). We study the structure of the BC, which is highly variable on short timescales (24-72 h). Results. An active chromosphere can explain the metallic lines in quiescence and the outburst NC. The dynamics of the BC line profiles suggest that these profiles originate in a hot, dense, non-axisymmetric, and non-uniform accretion column that suffers velocity variations along the line-of-sight on timescales of days. Assuming Keplerian rotation, the emitting region would be located at ~0.1-0.2 AU, which is consistent with the location of the inner disk rim, but the velocity profiles of the lines reveal a combination of rotation and infall. Line ratios of ions and neutrals can be reproduced assuming a temperature of T ~ 6500 K for electron densities of a few times 10 12 cm -3 in the line-emitting region. The line profiles also indicate that there is an accretion-related inner disk wind. Conclusions. The data confirm that the 2008 outburst was an episode of increased accretion, albeit much stronger than previous EX Lupi and typical EXors outbursts. The line profiles are consistent with the infall/rotation of a non-axisymmetric structure that could be produced by clumpy accretion during the outburst phase. A strong inner disk wind appears in the epochs of higher accretion. The rapid recovery of the system after the outburst and the similarity between the pre-outburst and post-outburst states suggest that the accretion channels are similar during the whole period, and only the accretion rate varies, providing a superb environment for studying the accretion processes.

AB - Context. EX Lupi is the prototype of EXor variables. After 50 years of mild variability and smaller outbursts, the object again experienced a large outburst in 2008. Aims. We explore the accretion mechanisms in EX Lupi during its pre-outburst, outburst, and post-outburst phases. Methods. We analyze 10 high-resolution optical spectra of EX Lupi, taken before, during, and after the 2008 outburst. In both quiescence and outburst, the star presents many permitted emission lines. These include lines typical of accreting T Tauri stars, plus a large number of neutral and ionized metallic lines (mostly Fe I and Fe II). During the outburst, the number of emission lines increases to about a thousand, and their structure shows a narrow and a broad component (NC and BC). We study the structure of the BC, which is highly variable on short timescales (24-72 h). Results. An active chromosphere can explain the metallic lines in quiescence and the outburst NC. The dynamics of the BC line profiles suggest that these profiles originate in a hot, dense, non-axisymmetric, and non-uniform accretion column that suffers velocity variations along the line-of-sight on timescales of days. Assuming Keplerian rotation, the emitting region would be located at ~0.1-0.2 AU, which is consistent with the location of the inner disk rim, but the velocity profiles of the lines reveal a combination of rotation and infall. Line ratios of ions and neutrals can be reproduced assuming a temperature of T ~ 6500 K for electron densities of a few times 10 12 cm -3 in the line-emitting region. The line profiles also indicate that there is an accretion-related inner disk wind. Conclusions. The data confirm that the 2008 outburst was an episode of increased accretion, albeit much stronger than previous EX Lupi and typical EXors outbursts. The line profiles are consistent with the infall/rotation of a non-axisymmetric structure that could be produced by clumpy accretion during the outburst phase. A strong inner disk wind appears in the epochs of higher accretion. The rapid recovery of the system after the outburst and the similarity between the pre-outburst and post-outburst states suggest that the accretion channels are similar during the whole period, and only the accretion rate varies, providing a superb environment for studying the accretion processes.

KW - Line: profiles

KW - Protoplanetary disks

KW - Stars: individual: EX Lupi

KW - Stars: low-mass

KW - Stars: pre-main sequence

KW - Stars: variables: T Tauri, Herbig Ae/Be

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