The circumstellar environment of EX Lupi: SPHERE and SINFONI views

Abstract

Context. EX Lup is a well-studied T Tauri star that represents the prototype of young eruptive stars known as EXors. They are characterized by repetitive outbursts that are due to enhanced accretion from the circumstellar disk onto the star. In this paper, we analyze new adaptive optics imaging and spectroscopic observations to study EX Lup and its circumstellar environment in near-infrared in its quiescent phase. Aims. We aim to provide a comprehensive understanding of the circumstellar environment around EX Lup in quiescence, building upon the vast store of data provided by the literature. Methods. We observed EX Lup in quiescence with the high contrast imager SPHERE/IRDIS in the dual-beam polarimetric imaging mode to resolve the circumstellar environment in near-infrared scattered light. We complemented the data with earlier SINFONI spectroscopy, which was also taken in quiescence. Results. We resolve, for the first time in scattered light, a compact feature around EX Lup azimuthally extending from ~280° to ~360° and radially extending from ~0.3′′ to ~0.55′′ in the plane of the disk. We explore two different scenarios for the detected emission. The first one accounts for the emission as coming from the brightened walls of the cavity excavated by the outflow whose presence was suggested by ALMA observations in the J = 3−2 line of 12CO. The second attributes the emission to an inclined disk. In this latter case, we detect, for the first time, a more extended circumstellar disk in scattered light, which shows that a region between ~10 and ~30 au is depleted of μm-size grains. We compare the J-, H-, and K-band spectra obtained with SINFONI in quiescence with the spectra taken during the outburst, showing that all the emission lines result from the episodic accretion event. Conclusions. Based on the morphology analysis, we favor the scenario that assumes the scattered light is coming from a circumstellar disk rather than the outflow around EX Lup. We determine the origin of the observed feature as either coming from a continuous circumstellar disk with a cavity, from the illuminated wall of the outer disk, or from a shadowed disk. Moreover, we discuss the potential origins of the depleted region of μm-size grains, exploring the possibility that a sub-stellar companion may be the source of this feature.

V899 Mon: A Peculiar Eruptive Young Star Close to the End of Its Outburst

“…EXors also brighten by a few magnitudes, but unlike FUors, they remain in the high brightness stage for a few months to a few years. Observations of repetitive outbursts are almost the rule for the majority of EXors, e.g., EX Lup (Rigliaco et al 2020) and V1647 Ori (Ninan et al 2013). Another major difference between the two classifications is the rich emission line spectrum found in EXors (Herbig 2007;Aspin et al 2010;Kóspál et al 2011a;Audard et al 2014;Hodapp et al 2019Hodapp et al , 2020.…”

Polarimetric differential imaging with VLT/NACO

“…In this reduction of the NACO data, many of the nondetections are likely the result of small or faint disks, or the absence of polarised light. Notably, IM Lup, GQ Lup, and EX Lup do not show polarised light in the NACO data, despite their prominent detections with SPHERE/IRDIS (Avenhaus et al 2018;van Holstein et al 2021;Rigliaco et al 2020). The data of IM Lup and GQ Lup were not previously published, whereas Kóspál et al (2011)…”

Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct

“…The amplitude of 2019 brightening is higher than 4.8 mag, the largest burst in Gaia19fct, and is categorized as an outburst (ΔV = ∼ 2.5−6 mag; Fischer et al 2022). The high amplitude is similar to what is typical for FUors (Fischer et al 2022, and references therein), as well as the most powerful outbursts found in EXors (EX Lup, Ábrahám et al 2019;Rigliaco et al 2020;Gaia20eae, Cruz-Sáenz de Miera et al 2022a;Ghosh et al 2022). The peak brightness was reached in 2019 December within ∼70 days since the beginning of the outburst (2019 October), resulting in a steep rising rate of −0.072 mag day −1 .…”