Cahill, Eoin and Whelan, Emma and Huélamo, N. and Alcalá, J.M. (2019) UVES Spectroscopy of T Chamaeleontis: Line Variability, Mass Accretion Rate and Spectro-astrometric Analysis. Monthly Notices of the Royal Astronomical Society, 484 (3). pp. 4315-4324. ISSN 1365-2966

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Abstract

Although advances in exoplanet detection techniques have seen an increase in discoveries, observing a planet in the earliest stages of formation still remains a difficult task. Here four epochs of spectra of the transitional disk object T Cha are analysed to determine whether spectro-astrometry can be used to detect a signal from its proposed protoplanet, T Cha b. The unique properties of T Cha are also further constrained. H{\alpha} and [O I]{\lambda} 6300, the most prominent lines, were analysed using spectro-astrometry. H{\alpha} being a direct accretion tracer is the target for the T Cha b detection while [O I]{\lambda} 6300 is considered to be an indirect tracer of accretion. [O I]{\lambda} 6300 is classified as a broad low velocity component (BC LVC). The mass accretion rate was derived for all epochs using new [O I]{\lambda} 6300 LVC relationships and the H{\alpha} line luminosity. It is shown that a wind is the likely origin of the [O I]{\lambda} 6300 line and that the [O I]{\lambda} 6300 line serves as a better accretion tracer than H{\alpha} in this case. From the comparison between M acc([OI]) and M acc(H{\alpha}) it is concluded that T Cha is not an intrinsically weak accretor but rather that a significant proportion of the H{\alpha} emission tracing accretion is obscured. T Cha b is not detected in the spectro-astrometric analysis yet a detection limit of 0.5 mas is derived. The analysis in this case was hampered by spectro-astrometric artefacts and by the unique properties of T Cha. While it seems that spectro-astrometry as a means of detecting exoplanets in TDs can be challenging it can be used to put an limit on the strength of the H{\alpha} emission from accreting planetary companions and thus can have an important input into the planning of high angular resolution observations.

Item Type:	Article
Additional Information:	This is the preprint version of the published article available from arXiv:1902.01170 [astro-ph.SR]. The published version is available at: Eoin Cahill, Emma T Whelan, Nuria Huélamo, Juan Alcalá, UVES spectroscopy of T Chamaeleontis: line variability, mass accretion rate, and spectro-astrometric analysis, Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 3, April 2019, Pages 4315–4324, https://doi.org/10.1093/mnras/stz280
Keywords:	protoplanetary discs - planets and satellites; techniques: high angular resolution; techniques: spectroscopic; planets and satellites; individual: T Cha; stars: pre-main-sequence;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	13960
Identification Number:	https://doi.org/10.1093/mnras/stz280
Depositing User:	Emma Whelan
Date Deposited:	05 Feb 2021 15:29
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	The Royal Astronomical Society
Refereed:	Yes
URI:	Publisher Organisation
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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