H-band de Boer et al. 2016 Searching for accreting protoplanets in transitional disks: SPHERE/ZIMPOL observations N. Huélamo (CAB, Spain), G. Chauvin, A. Lagarrigue, M. Benisty (U. Chile/IPAG), H.M. Schmidt, S. Quanz (ETH Zurich), E. Whelan (Maynooth Univ., Ireland), J. M. Alcalá (INAF, Italy), D. Barrado, B. Montesinos, I. Mendigutía (CAB, Spain) The project: When planets formed, they are surrounded by circumplanetary disks (CPDs). Different theories predict that magnetospheric accretion can occur from the CPD onto the planet. We aim at detecting accreting protoplanets within the gaps of transitional disks, using the Hα emission line as an accretion tracer. To achieve our goals, we have performed spectral angular differential imaging (ASDI) observations with SPHERE/ZIMPOL at the VLT. In this poster, we show our results for two transitional objects: the Herbig Ae star MWC758, and the T Tauri star RXJ1615.3-3255. RXJ1615.3-3255 RXJ1615.3−3255 0 100 200 300 400 distance to the star (mas) 12 10 8 6 4 2 0 Contrast−5σ (mag) CntHa NHa Diff Figure 3 – Left: SPHERE/IRDIS H-band image of RXJ1615 from de Boer et al. 2016, where several rings (R) and arcs (A), a gap (G), and an internal disk (I1) are detected. Right: SPHERE/ZIMPOL images of RXJ1615 in two individual filters (NHa & CntHa) and the difference image (NHa-CntHa). Figure 4: SPHERE/ZIMPOL 5σ contrast curves obtained in the two individual filters NHa and CntHa in ADI, and in the NHa- CntHa difference in ASDI. Preliminary curves obtained using Classical ADI. RXJ1615.3-3255: This T Tauri star (TTS) has been imaged by SPHERE/IRDIS in the near-IR (de Boer et al. 2016, Figure 3, left), and shows a disk with several structures: arcs, rings and a clear gap at 0.5 arcsec (79 au@158 pc). Our ZIMPOL ASDI dataset does not show any source within a 1” radius from the central star. Note that our preliminary analysis shows a contrast of 6 mag at 50 mas (8 au) in the ASDI image, and 8 mag at 200 mas (32 au) using classical ADI (cADI). (Huélamo et al., in prep.) SPHERE/ZIMPOL optical images Contrast curves Separation (mas/au*) Contrast NHa (mag) log LHα (L⦿) log Lacc (L⦿) log Macc (M⦿) 50 / 8 5.0 -5.0 -4.0 -8.4 100 / 16 7.6 -6.1 -5.3 -9.7 200 / 32 8.2 -6.3 -5.6 -10.0 Table 2: SPHERE/ZIMPOL Hα contrast, line and accretion luminosity at different separations from the star. We have also estimated the accretion rates (Macc) for a 1 MJup planet with 1 RJup radius. MWC758: This Herbig Ae star is surrounded by a disk with several spiral arms. Reggiani et al. (2017) reported the detection in the L’-band of a planet companion candidate at 111 mas (see Fig. 1, left). We do not detect it in the SPHERE/ZIMPOL images. Note that we reach a contrast of ~8 mag at 111 mas (see Fig. 2) in the ASDI image. MWC758 (Huélamo et al. 2018) Figure 1 – Left: L’-band image of MWC758 from Reggiani et al. 2017. The spiral arms in the disk (S1, S2 and S3), together with the protoplanet candidate (b), are marked. Right: SPHERE/ZIMPOL images of MWC758 in two individual filters centered in the Hα line (BHa) and the adjacent continuum (ContHa), and the differential image (BHa-ContHa). The red circle shows the position of the L’ source detected by Reggiani et al. 2017. L’-band SPHERE/ZIMPOL optical images Reggiani et al. 2017 0 100 200 300 400 12 10 8 6 4 2 0 0 100 200 300 400 distance to the star (mas) 12 10 8 6 4 2 0 Contrast 5σ (mag) 0 100 200 300 400 distance to the star (mas) 12 10 8 6 4 2 0 Contrast 5σ (mag) CntHα BHα BHα−CntHα Figure 2: SPHERE/ZIMPOL 5σ contrast curves obtained in CntHa, BHa in ADI, and in BHa-CntHa in ASDI. The grey area shows the separation of the companion candidate detected in L’. Contrast curves planet candidate separation * distance ～158 pc (GAIA DR2) NHa -400 -200 0 200 400 ∆ RA (mas) -400 -200 0 200 400 ∆ DEC (mas) CntHa -400 -200 0 200 400 ∆ RA (mas) -400 -200 0 200 400 NHa - CntHa -400 -200 0 200 400 ∆ RA (mas) -400 -200 0 200 400 Separation (mas/au*) Contrast BHa (mag) log LHα (L⦿) log Lacc (L⦿)