Violent environment of the inner disk of RW Aurigae A probed by the 2010 and 2015 dimming events

Abstract

Aims. The young binary system RW Aur shows strong signatures of a recent tidal encounter between the circumprimary disk and the secondary star. The primary star has recently undergone two major dimming events (∆mag ≈ 2 in V band) whose origin is still under debate. To shed light on the mechanism leading to the dimming events, we study the extinction properties, accretion variability, and gas kinematics using absorption lines from the material that is obscuring RW Aur A. Methods. We compared our moderate-resolution X-shooter spectra of the dim state of RW Aur A with other spectral observations. In particular, we analysed archival high-resolution UVES spectra obtained during the bright state of the system to track the evolution of the spectral properties across the second dimming event. Since the X-shooter spectrum is flux calibrated, we provide new synthetic photometry of RW Aur A during the dim state. Results. The spectrum obtained during the dim state shows narrow absorption lines in the Na and K optical doublets, where the former is saturated. With a velocity of −60 km s −1 , these lines indicate that during the dim state the disk wind is either enhanced or significantly displaced into the line of sight. The photometric evolution across the dimming event shows a grey extinction, and is correlated with a significant reduction of the EW of all photospheric lines. Emission lines that trace accretion do not vary significantly across the dimming. Conclusions. From comparing our observations with complementary results from the last years, we conclude that the dimming event is related to a major perturbation on the inner disk. We suggest that the inner disk is occulting (most of) the star and thus its photosphere, but does not occult the accretion regions within a few stellar radii. Since observations of the outer disk indicate that the disk is modestly inclined (45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60) • ), we propose that the inner disk might be warped by an as yet unseen (sub-) stellar companion, which may also explain the 2.77 day periodic variability of the spectral lines.

The Mysterious Dimmings of the T Tauri Star V1334 Tau

“…The sodium Na I D feature has a depth and width consistent with a stellar absorption line, along with a superimposed narrow feature due to the interstellar medium. Unlike RW Aur (Facchini et al 2016), we do not see a time varying P Cygni profile in the Na lines, which would suggest the existence of a strong disk wind. However, we do not have a spectroscopic observation of V1334 Tau prior to the large dimming, limiting our interpretation.…”

“…Although similar in duration, the dimming event in AA Tau shows a much larger depth of ∼2 mag. Other systems like V409 Tau, DM Ori, and RW Aur have shown similar dimmings (again at much larger depths), and are interpreted as either a periodically obscuring feature in the circumstellar disk, high disk winds, or inner disk instabilities (Rodriguez et al 2013(Rodriguez et al , 2015(Rodriguez et al , 2016b(Rodriguez et al , 2016cPetrov et al 2015;Facchini et al 2016). It is possible that the dimming mechanisms for all these systems are related.…”

“…Without a constraint on the inner disk inclination, we are unable to test the feasibility of this interpretation. However, this scenario has been proposed as the cause of the observed dimming events of RW Aur (Facchini et al 2016).…”

Star–Disk Interactions in Multiband Photometric Monitoring of the Classical T Tauri Star GI Tau

“…The disk interpretation is challenged in one case (J1604-2130) by the measurement of a face-on inclination of an outer disk (Ansdell et al 2016a). In a second case (RW Aur), the occultation source is uncertain and may be a dusty wind (Petrov et al 2015;Schneider et al 2015b), a tidal encounter of the secondary star (Dai et al 2015), the combination of occultation and time-variable accretion (Takami et al 2016), or partial occultation of the inner disk (Facchini et al 2016).…”

Inclined massive planets in a protoplanetary disc: gap opening, disc breaking, and observational signatures

“…At much longer wavelengths, ALMA detect twisted flow patterns in the disc, directly suggesting a warped inner disc (Rosenfeld et al 2014;Pineda et al 2014;Casassus et al 2015;Brinch et al 2016;Loomis et al 2017;Walsh et al 2017). Finally, the optical/near-IR light curves of some YSOs show dimming events, indicating blocking the stellar light by a warped inner disc (Alencar et al 2010;Bouvier et al 2013;Lodato & Facchini 2013;Cody et al 2014;Facchini et al 2016;Bodman et al 2017;Schneider et al 2018).…”