TY - JOUR
T1 - Stable accretion in young stars
T2 - the cases of EX Lupi and TW Hya
AU - Sicilia-Aguilar, A
AU - Campbell-White, J
AU - Roccatagliata, V
AU - Desira, J
AU - Gregory, S G
AU - Scholz, A
AU - Fang, M
AU - de Miera, F Cruz-Saenz
AU - Kóspál, Á
AU - Matsumura, S
AU - Ábrahám, P
N1 - Funding: ASA and JCW were supported by the STFC grant number ST/S000399/1 (‘The Planet-Disc Connection: Accretion, Disc Structure, and Planet Formation’).
JCWis Funded by the European Union (ERC,WANDA, 101039452). VR acknowledges the support of the Italian National Institute of Astrophysics (INAF) through the INAF GTO Grant ERIS & SHARK GTO data exploitation. AK and FCSM received funding
from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 716155 (SACCRED). JD was supported by a Summer Undergraduate Bursary Fellowship by the Royal Astronomical Society in summer 2020.
PY - 2023/12
Y1 - 2023/12
N2 - We examine the long-term spectroscopic and photometric variability of EX Lupi and TW Hya, studying the presence of stable accretion and the role it plays in the observed variability. Analysing the velocity modulations of the emission lines with STAR-MELT, we obtain information on the structure of the accretion columns and the disk-star connection. The emission line radial velocities reveal that TW Hya, like EX Lupi, has a remarkably stable or slow-varying accretion column footprint, locked to the star for several years. The line-emitting regions are non-polar for both EX Lupi and TW Hya, and species with different energies differ in position. In contrast, the continuum emission as observed in the photometry is very variable and can be modelled by hot spot(s) that change over time in phase, shape, temperature, size, and location with respect to the emission line region. The continuum emission region may not be limited to the stellar surface, especially during episodes of high accretion. The broad line emission observed in EX Lupi during episodes of increased accretion reveals a further structure, which can be fitted by non-axisymmetric disk in Keplerian rotation inwards of the corotation radius. Since the radial velocity modulation due to accretion footprints is so stable, we used it to search for further velocity modulations. While no residual modulation (other than caused by stellar rotation) is found in these objects, a similar analysis could help to identify young planets/companions. Therefore, determining whether stable accretion footprints are common among young stars is a key to detect young planets.
AB - We examine the long-term spectroscopic and photometric variability of EX Lupi and TW Hya, studying the presence of stable accretion and the role it plays in the observed variability. Analysing the velocity modulations of the emission lines with STAR-MELT, we obtain information on the structure of the accretion columns and the disk-star connection. The emission line radial velocities reveal that TW Hya, like EX Lupi, has a remarkably stable or slow-varying accretion column footprint, locked to the star for several years. The line-emitting regions are non-polar for both EX Lupi and TW Hya, and species with different energies differ in position. In contrast, the continuum emission as observed in the photometry is very variable and can be modelled by hot spot(s) that change over time in phase, shape, temperature, size, and location with respect to the emission line region. The continuum emission region may not be limited to the stellar surface, especially during episodes of high accretion. The broad line emission observed in EX Lupi during episodes of increased accretion reveals a further structure, which can be fitted by non-axisymmetric disk in Keplerian rotation inwards of the corotation radius. Since the radial velocity modulation due to accretion footprints is so stable, we used it to search for further velocity modulations. While no residual modulation (other than caused by stellar rotation) is found in these objects, a similar analysis could help to identify young planets/companions. Therefore, determining whether stable accretion footprints are common among young stars is a key to detect young planets.
KW - Circumstellar matter – stars: individual: EX Lupi, TW Hya
KW - Stars: pre-main sequence
KW - Stars: variables: T Tauri, Herbig Ae/Be
U2 - 10.1093/mnras/stad3029
DO - 10.1093/mnras/stad3029
M3 - Article
SN - 0035-8711
VL - 526
SP - 4885
EP - 4907
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -