Accretion dynamics of EX Lupi in quiescence: The star, the spot, and the accretion column

Aurora Sicilia-Aguilar, Min Fang, Veronica Roccatagliata, Andrew Collier Cameron, Ágnes Kóspál, Thomas Henning, P. Ábrahám, Nikoletta Sipos

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.

Original languageEnglish
Article numberA82
JournalAstronomy and Astrophysics
Volume580
DOIs
Publication statusPublished - Aug 1 2015

Fingerprint

accretion
stars
radial velocity
signatures
shock
velocity modulation
modulation
variable stars
excitation
proximity
contamination
prototypes
profiles

Keywords

  • Accretion, accretion disks
  • Protoplanetary disks
  • Stars: individual: EX Lupi
  • Stars: pre-main sequence
  • Stars: variables: T Tauri, Herbig Ae/Be
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Sicilia-Aguilar, A., Fang, M., Roccatagliata, V., Cameron, A. C., Kóspál, Á., Henning, T., ... Sipos, N. (2015). Accretion dynamics of EX Lupi in quiescence: The star, the spot, and the accretion column. Astronomy and Astrophysics, 580, [A82]. https://doi.org/10.1051/0004-6361/201525970

Accretion dynamics of EX Lupi in quiescence : The star, the spot, and the accretion column. / Sicilia-Aguilar, Aurora; Fang, Min; Roccatagliata, Veronica; Cameron, Andrew Collier; Kóspál, Ágnes; Henning, Thomas; Ábrahám, P.; Sipos, Nikoletta.

In: Astronomy and Astrophysics, Vol. 580, A82, 01.08.2015.

Research output: Contribution to journalArticle

Sicilia-Aguilar, A, Fang, M, Roccatagliata, V, Cameron, AC, Kóspál, Á, Henning, T, Ábrahám, P & Sipos, N 2015, 'Accretion dynamics of EX Lupi in quiescence: The star, the spot, and the accretion column', Astronomy and Astrophysics, vol. 580, A82. https://doi.org/10.1051/0004-6361/201525970
Sicilia-Aguilar A, Fang M, Roccatagliata V, Cameron AC, Kóspál Á, Henning T et al. Accretion dynamics of EX Lupi in quiescence: The star, the spot, and the accretion column. Astronomy and Astrophysics. 2015 Aug 1;580. A82. https://doi.org/10.1051/0004-6361/201525970
Sicilia-Aguilar, Aurora ; Fang, Min ; Roccatagliata, Veronica ; Cameron, Andrew Collier ; Kóspál, Ágnes ; Henning, Thomas ; Ábrahám, P. ; Sipos, Nikoletta. / Accretion dynamics of EX Lupi in quiescence : The star, the spot, and the accretion column. In: Astronomy and Astrophysics. 2015 ; Vol. 580.
@article{1fc1b14227b14159ad927a5783e8f04f,
title = "Accretion dynamics of EX Lupi in quiescence: The star, the spot, and the accretion column",
abstract = "Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.",
keywords = "Accretion, accretion disks, Protoplanetary disks, Stars: individual: EX Lupi, Stars: pre-main sequence, Stars: variables: T Tauri, Herbig Ae/Be, Techniques: spectroscopic",
author = "Aurora Sicilia-Aguilar and Min Fang and Veronica Roccatagliata and Cameron, {Andrew Collier} and {\'A}gnes K{\'o}sp{\'a}l and Thomas Henning and P. {\'A}brah{\'a}m and Nikoletta Sipos",
year = "2015",
month = "8",
day = "1",
doi = "10.1051/0004-6361/201525970",
language = "English",
volume = "580",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

TY - JOUR

T1 - Accretion dynamics of EX Lupi in quiescence

T2 - The star, the spot, and the accretion column

AU - Sicilia-Aguilar, Aurora

AU - Fang, Min

AU - Roccatagliata, Veronica

AU - Cameron, Andrew Collier

AU - Kóspál, Ágnes

AU - Henning, Thomas

AU - Ábrahám, P.

AU - Sipos, Nikoletta

PY - 2015/8/1

Y1 - 2015/8/1

N2 - Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.

AB - Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.

KW - Accretion, accretion disks

KW - Protoplanetary disks

KW - Stars: individual: EX Lupi

KW - Stars: pre-main sequence

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

KW - Techniques: spectroscopic

UR - http://www.scopus.com/inward/record.url?scp=84938807969&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84938807969&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201525970

DO - 10.1051/0004-6361/201525970

M3 - Article

AN - SCOPUS:84938807969

VL - 580

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A82

ER -