Spirals inside the millimeter cavity of transition disk SR 21

Abstract

Context. Hydrodynamical simulations of planet-disk interactions suggest that planets may be responsible for a number of the substructures frequently observed in disks in both scattered light and dust thermal emission. Despite the ubiquity of these features, direct evidence of planets embedded in disks and of the specific interaction features like spiral arms within planetary gaps still remain rare. Aims. In this study we discuss recent observational results in the context of hydrodynamical simulations in order to infer the properties of a putative embedded planet in the cavity of a transition disk. Methods. We imaged the transition disk SR 21 in H-band in scattered light with SPHERE/IRDIS and in thermal dust emission with ALMA band 3 (3 mm) observations at a spatial resolution of 0.1 . We combine these datasets with existing band 9 (430 µm) and band 7 (870 µm) ALMA continuum data. Results. The Band 3 continuum data reveals a large cavity and a bright ring peaking at 53 au strongly suggestive of dust trapping. The ring shows a pronounced azimuthal asymmetry, with a bright region in the north-west that we interpret as a dust over-density. A similarly-asymmetric ring is revealed at the same location in polarized scattered light, in addition to a set of bright spirals inside the mm cavity and a fainter spiral bridging the gap to the outer ring. These features are consistent with a number of previous hydrodynamical models of planet-disk interactions, and suggest the presence of a ∼1 M Jup planet at 44 au and PA=11deg. This makes SR21 the first disk showing spiral arms inside the mm cavity, as well as one for which the location of a putative planet can be precisely inferred. Conclusions. SR 21's main features in both scattered light and thermal emission are consistent with hydrodynamical predictions of planet-disk interactions. With the location of a possible planet being well-constrained by observations, it is an ideal candidate for follow-up observations to search for direct evidence of a planetary companion still embedded in its disk.

Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk

“…We adopted L =5.8 mag, which is different from Muro-Arena et al (2020), for the SR 21 luminosity. For the plot of the previous data we checked the contrast limit presented in Figure A.1 of Muro-Arena et al (2020) and selected several points between 0. 2 − 0.…”

“…We reduce the public SPHERE observations of SR21 on UT 2018 March 1 (ESO GTO program 1100.C-0481(Q); PI: J.-L.Beuzit) using IRDAP (van Holstein et al 2017(van Holstein et al , 2020. The bright extended feature at the position angle (PA) between ∼170°and ∼270°is clearly colocated with the spiral detected by SPHERE (Spiral 1 in Muro-Arena et al 2020) and this detection is one of several cases that the spiral feature is clearly resolved in the L′ band (e.g., HD 142527, HD 100546, MWC 758, and CQ Tau; Rameau et al 2012;Currie et al 2015;Reggiani et al 2018;Uyama et al 2020b). To test the potential contamination of the disk feature around the reference stars in the L′ band, we checked the archival Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) H-band polarimetric data set of WaOph6 taken on UT 2018 June 22 (ESO GTO program 1100.C-0481(Q); PI: J.-L.Beuzit).…”

“…With the COND03 model (Baraffe et al 2003) assuming 10Myr overlaid in Figure 6, we set a constraint on ∼16 M Jup , 10 M Jup , and 5 M Jup at ∼40au, 55au, and 110au, respectively. We assumed 5.8 mag at the L′ band, which is different from Muro-Arena et al (2020).…”

“…Its spectral energy distribution (SED) shows strong infrared (IR) excess but lacks emission at ∼5 μm, which suggests a transitional disk with an inner gap (Brown et al 2007). High-angular resolution studies have shown a large cavity (e.g., van der Marel et al 2016), which together with complicated features such as gaps and spirals suggests possible planet formation within the disk (Sallum et al 2019;Muro-Arena et al 2020). This YSO is faint at optical wavelengths but bright at NIR wavelengths (e.g., V=14.1, H=7.5; Cutri et al 2003;Rebull et al 2018), making it a suitable testbed for high-contrast imaging with the PWFS to better explore its surrounding disk features and/or companions.…”

Dynamical Evidence of a Spiral Arm–driving Planet in the MWC 758 Protoplanetary Disk

“…Spiral arms, spanning from tens to hundreds of astronomical units, are found in more than a dozen protoplanetary disks in visible to near-infrared light with high-contrast imaging (e.g., Grady et al 1999Grady et al , 2013Muto et al 2012;Wagner et al 2015;Monnier et al 2019;Garufi et al 2020;Ménard et al 2020;Muro-Arena et al 2020). Their origin has profound implications for both planet formation and disk evolution (Dong et al 2018;Brittain et al 2020).…”